Journal of Applied Engineering Science 10(2012)4 by JAES

IMPRESSUM J O U R N A L O F A P P L I E D E N G I N E E R I N G S C I E N C E (J A E S) The journal publishes original and review articles covering the concept of technical science, energy and environment, industrial engineering, quality management and other related sciences. JAES is Open-Access Journal that follows new trends and progress proven practice in listed fields, thus creating a unique forum for interdisciplinary or multidisciplinary dialogue. JAES is part of the electronic journal editing with a transparent editorial and review policy. Provided are: • Online paper submission and tracking of review process with communication between editors, authors and reviewers • CrossRef: assignment of numerical identifiers (DOI) to assure greater visibility and accessibility of journal articles • CrossCheck: control for originality of submitted papers, to prevent plagiarism and duplicate publications • KWASS: automatic extraction of keywords from disciplinary thesaurus • Online-first publishing • Automatic transfer of metadata to SCIndeks that support international protocols for data transfer All published articles are indexed by international abstract base Elsevier Bibliographic Databases through service SCOPUS since 2006 and through service SCImago Journal Rank since 2011. Serbian Ministry of Science admitted the Journal of Applied Engineering Science in a list of reference journals. Same Ministry financially supports journal’s publication. Publisher Institute for Research and Design in Commerce and Industry - IIPP; www.iipp.rs For publisher: Prof. dr Branko Vasić Copublishers Faculty of Mechanical Engineering - Belgrade University; www.mas.bg.ac.rs For copublisher: Prof. dr Milorad Milovančević Faculty of Transport and Traffic Engineering – Belgrade University; www.sf.bg.ac.rs For copublisher: Prof. dr Branimir Stanić Editor in Chief Prof. dr Jovan Todorović Faculty of Mechanical Engineering, Belgrade; Assistant Editor Dr Predrag Uskoković, IIPP Editorial Board Prof. dr Gradimir Danon, Faculty of Forestry, Belgrade; Doc. dr Dušan Milutinović, Institute for Transport and Traffic CIP, Belgrade; Mr Đorđe Milosavljević, CPI - Process Engineering Center, Belgrade; Prof. dr Miodrag Zec, Faculty of Philosophy, Belgrade; Prof. dr Nenad Đajić, Mining and Geology Faculty, Belgrade; Prof. dr Vlastimir Dedović, Faculty of Transport and Traffic Engeneering, Belgrade; Prof. dr Mirko Vujošević, Faculty of organizational sciences, Belgrade; Doc. dr Vladimir Popović, Faculty of Mechanical Engineering, Belgrade; Doc. dr Vesna Spasojević Brkić, Faculty of Mechanical Engineering, Belgrade. ISSN 1451-4117 UDC 33 Papers are indexed by SCOPUS

International Editorial Board Prof. dr Vukan Vučić, University of Pennsylvania, USA; Prof. dr Robert Bjeković, Hochschule Ravensburg-Weingarten, Germany; Prof. dr Jozef Aronov, Research Institute for Certification JSC, Russia; Prof. dr Jezdimir Knežević, MIRCE Akademy, England; Dr Nebojša Kovačević, Geotechnical consulting group, England; Adam Zielinski, Solaris Bus & Coach, Poland; Prof. dr Miloš Knežević, Faculty for Civil Engineering, Montenegro; MSc Siniša Vidović, Energy Testing & Balance Inc, USA; Dr Zdravko Milovanović, Faculty of Mechanical Engineering, Banja Luka. Publishing Council Milutin Ignjatović, Institute for Transport and Traffic CIP, Belgrade; Dragan Belić, Transport Company “Lasta”, Belgrade; Dr Deda Đelović, Port of Bar, Bar; Dr Drago Šerović, Adriatic Shipyard, Bijela; Cvijo Babić, Belgrade Waterworks and Sewerage, Belgrade; Nenad Jankov, Power Plant Kostolac B, Kostolac; Miroslav Vuković, Mercator Business System, Belgrade; Dušan Đurašević, Euro Sumar, Belgrade. Editorial Office Nada Stanojević, Miloš Vasić, Darko Stanojević, Miloš Dimitrijević, Ivana Spasojević, IIPP, Belgrade; Journal of Applied Engineeering Science is available at: www.engineeringscience.rs http://scindeks-eur.ceon.rs/index.php/jaes http://www.singipedia.com/content/1166-naucni-casopisi Printed by: Sigrastar, Beograd Journal of Applied Engineering Science 10(2012)4

CONTENTS

Dr Miroslav Demić, Dr Đorđe Diligenski A CONTRIBUTION TO RESEARCH OF DEGRADATION OF CHARACTERISTIC 185 - 190 OF VIBRATION PARAMETERS OF VIBRATION ASPECT OF VEHICLE COMFORT Dr Nikola Dondur, Dr Vesna Spasojević-Brkić, Mr Aleksandar Brkić CRANE CABINS WITH INTEGRATED VISUAL SYSTEMS FOR DETECTION 191 - 196 AND INTERPRETATION OF ENVIRONMENT - ECONOMIC APPRAISAL Zoran Petrović, Dr Uglješa Bugarić, Dr Dušan Petrović USING ARIMA MODELS FOR TURNOVER PREDICTION IN INVESTMENT 197 - 200 PROJECT APPRAISAL Dr Radoljub Tomić, Dr Predrag Petrović, Marija Petrović CONTRIBUTION TO THE EVALUATION OF THE COMPLIANCE FOR NEW 201 - 208 PRODUCTS WITH ASPECT RELIABILITY AND MAINTENANCE Dimić-Mišić Katarina, Dr Paltakari Jouni FIBRILLAR MATERIAL AS A COBINDER IN COATING COLORS FORMULATIONS 209 - 220 Dr Vesna Spasojević-Brkić, Dr Slobodan Pokrajac, Dr Nikola Dondur, MSc Sonja Josipović 221 - 225 ALLOCATIVE EFFIENCY AND QM FACTORS COVARIATE IN SERBIAN INDUSTRY MSc Marija Savić, MSc Predrag Đorđević, Dr Đorđe Nikolić, Dr Ivan Mihajlović, Dr Živan Živković 227 - 233 COMBINATION OF KNOWLEDGE IN SYSTEM SUPPLIERS - MSP - CUSTOMERS IN TRANSITIONAL ECONOMY ENVIRONMENT IN SERBIA EVENTS REVIEW

234

ANNOUNCEMENT OF EVENTS 235 - 236 BOOK RECOMMENDATION

237

EDITORIAL AND ABSTRACTS IN SERBIAN LANGUAGE 238 - 242

Journal of Applied Engineering Science 10(2012)4

EDITORIAL

ALTERNATIVE FUELS AND RENEWABLE ENERGY

Prof. dr Jovan TodoroviÄ&#x2021;

The intensive development of world economy and transportation in particularly, caused two big problems: a fast depletion of fossil fuels resources and a severe pollution of the environment. Providing alternative fuels and renewable energy resources make, therefore, the main challenges for engineers over the world.

Alternative fuels, known as non-conventional or advanced fuels, are any materials or substances that can be used as fuels, other than conventional fossil fuels (petroleum, coal, propane, and natural gas), as well as nuclear materials. Some well-known alternative fuels are biodiesel, bioalcohol (methanol, ethanol, butanol), chemically stored electricity (batteries and fuel cells), vegetable oil and other biomass sources. One of the best is hydrogen which is practically emission free. The usage of hydrogen as a fuel needs large investment and it is nowadays considered as a fuel for future. Natural gas is another fuel that burns cleanly; cleaner than both gasoline and diesel engines. Renewable energy is energy that comes from natural resources such as hydropower, sunlight, wind, tides, waves and geothermal heat, which are renewable because they are naturally replenished at a constant rate. Biofuels are also considered a renewable source. Biodiesel is made from animal fats or vegetable oils and from plants such as soybean, sunflowers, sugar cane, corn, etc. Biodiesel will release a smaller number of its pollutants; it burns both cleaner and more efficiently. Methanol and Ethanol fuel are primary sources of energy; they are convenient fuels for storing and transporting energy. These alcohols can be used in internal combustion engines as alternative fuels. Sunlight is used by photovoltaic cells made from silicon alloys. These cells can convert sunlight into other forms of energy, such as heat and electricity. Geothermal energy is another perspective chance. Technologies used in geothermal production have much in common with those for oil and gas. Wind power is considered the most economical form of electrical power, particularly during night. Fuel cells, a solution to store electricity, are nowadays one of the most realistic perspectives for motorization, particularly with hydrogen as a fuel. In many countries there are already very important improvements in developments of alternative fuels and renewable energy sources. Renewable energy covers in many countries 15 to 20% of all demands (in Norway almost 100%). The most important is hydropower, but there are many wind and sunlight power plants over world, some of them with high power capacity. Biofuels, natural gas and electricity fuels millions of motor vehicles. The development of alternative fuels and renewable energy sources makes a priority task for Serbian economy as well. Taking in account our economical and engineering possibilities and natural sources, it is obvious that a priority should be given to further development of hydro powerplatns (rivers Drina, Ibar, Danube and a large number of small water flows) and to development of new energy sources, such as wind farms, sunlight and geothermal power plants. An attention should be paid to oil shale resources and to an improvement of coal mining sector, regarding capacities and environmental protection. In the transportation sector, very important is transfer to natural gas and various types of biofuels that will improve country economy and decrease the environment pollution. Sincerely yours, Prof.dr Jovan TodoroviÄ&#x2021;

Journal of Applied Engineering Science 10(2012)4

Paper number: 10(2012)4, 236, 185- 190

doi:10.5937/jaes10-2244

A CONTRIBUTION TO RESEARCH OF DEGRADATION OF CHARACTERISTICS OF VIBRATION PARAMETERS ON VIBRATION ASPECT OF VEHICLE COMFORT Dr Miroslav Demić * University of Kragujevac, Faculty of Engineering Science, Kragujevac, Serbia Dr Đorđe Diligenski Vinča Institute of Nuclear Sciences, Department of Motor Vehicles and IC engines, Belgrade, Serbia Dynamic simulation, based on modeling, has a significant role in vehicle development, especially in the early stages of design process, when relevant parameters are being defined. In praxis it is usually assumed that vibration parameters are unchangeable, what is basically wrong. All researches indicate that vibration parameters degrade in time of vehicle service, consequently leading to a variation of its dynamic characteristics. This paper, based on preliminary research results, attempts to point out the necessity of taking into consideration this variation in the earliest phases of vehicle design by its implementation in the vehicle simulation model. Key words: Vehicle, Vibration parameters, Degradation, Vibration comfort INTRODUCTION

Z=Z(A,U,L,t)

Dynamic simulation has important role in development of motor vehicles, based on modeling, by use of application of numerous vehicle models [05-16,22,24-26,28,29]. It can be assumed that the mechanical model, in the general form, is described by the equation [05, 06]:

The simplest case is when there does is no control function (U=0) and when variation of vibration parameters of a vehicle in service is not taken into account (L=0), i.e.:

(1) where: • Z - vector of generalized coordinates of the vibration system, • A - vector of vehicle vibration parameters, • U - vector of control functions, • Q – time function of excitation (coming from road microprofile, engine function, unbalanced masses, tire nonuniformities, etc.), • L – function that takes into account stochastic variation of characteristics of vibration parameters during the vehicle service life, and • t - time. General solution of vector differential equation (1) can be written in the form [05-06]:

Z=Z(A,t)

(2)

(3)

In practice, a simplification given by expression (3) is commonly used, which neglects the influence of duration of service time on variation of vehicle vibration parameters. However, it represents a major simplification, according to [23], where the existence of the mentioned variation is shown. Therefore, this problem will be considered in details by application of the appropriate vehicle vibration model. SELECTION OF VEHICLE VIBRATION MODEL The structure of a vehicle model is chosen with regard to the variables supposed to be analyzed [04, 05]. Therefore, vibration model of various structure and complexity [05-16,20-22,24-31]. The vehicle model should be chosen to be as simple as possible, and to enable simulation of the desired value [05,06]. A vehicle vibration model, often regarded in literature as quarter

* University of Kragujevac, Faculty of Engineering Science, Sestre Janjić 6, 34000 Kragujevac, Serbia; demic@kg.ac.rs

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Dr Miroslav Demić - A contribution to research of degradation of characteristics of vibration parameters on vibration aspect of vehicle comfort

model [21,22,24,26,28,29], given in Figure 1, has been estimated to be optimal for the observation, bearing in mind that the aim of this research was to introduce degradation of vibration parameters in the model.

of motion, for model with two or more degrees of freedom of motion. Besides, it appears that the acceleration is of minor influence on the force than displacement and velocity, so for further analyses a model [01, 16] has been adopted, where the force is described with the expression:

(5) where: •

and - relative displacement and velocity, respectively, and • x1, x2,3, x4, x5 and x6 – parameters of shock absorber model. Radial force in the tire is also nonlinear [20,21,23,25], and therefore the following expression is used: (6) where: • -radial deformation of the tire, and • c3, c4 and c5 – parameters of tire radial stiffness.

Figure 1: The equivalent vehicle model

Where the following signs were applied: • m1, m2 –unsprung and sprung mass of quarter vehicle model, respectively (in this case 27.5 and 250 kg), • Fs – force in the spring, • Fsh – force in the shock absorber, and • Ft – force in the tire. Force in the tire can be represented by the polynomial equation of the third degree [05-15, 20,21,23,25]: (4) where: • c1 and c2 – stiffness parameters, and • – spring relative deformation. Force in the shock absorber depends not only on the relative speed but on the relative motion and acceleration [01, 16]. The analyses have shown that the model defined in [01, 16], which applies transcendent functions of acceleration, can hardly be used in modeling of vehicles with more than one degree of freedom. That comes from the fact that the acceleration is covered by the function tangens hyperbolicus, in which case problems of decoupling of differential equations 186

As it is well known, vertical vehicle vibration depend on type of road, velocity and the number of passengers riding in the vehicle. Having that in mind, the analysis is performed for the case that there are two passengers in the vehicle, riding with the characteristic velocity of 30 m/s [32] on a good asphalt road, whose time excitation function is shown in Figure 2 [16]. To be more precise, a polyharmonic excitation function is applied because the analyses have shown that it represents a good approximation of real road microprofile, for the applied vehicle velocity of 30 m/s. Bearing in mind the observed vehicle vibration model, by use of Newton’s law [27,31], the following differential equations of vibration motion of vehicle are obtained: (7) (8) where: •

•

, -accelerations of unsprung and sprung mass measured from the equilibrium position, respectively, Fs – force in the spring given by expression (4), Journal of Applied Engineering Science 10(2012)4, 236

Dr Miroslav Demić - A contribution to research of degadation of characteristics of vibration parameters on vibration aspect of vehicle comfort

• •

Fsh – force in the shock absorber given by expression (5), and Ft – radial force in the tire given by expression (6).

METHOD Parameters of elasto-damping elements are variable values during the service life. To be more precise, their values tend to descend. For the illustration, Figure 3 shows a typical example of that variation [23], where it is assumed that values of parameters descend linearly with the duration of service, expressed in km. Data from Figure 3 enable analysis of the influence of vibration parameters variation on vehicle dynamic characteristics.

Figure 2: The applied function of road microprofile excitation for the velocity of 30 m/s

Bearing in mind nonlinear and very complex structure of expressions (4,5,6), even in case of such a simple vehicle model, as well as quasistochastic character of the excitation function, it appears to be obvious that the vehicle model described by equations (8,9) is complex and cannot be solved in finite form. The analyses have shown that the argument of the tangens hyperbolicus function in the expression (5) – displacement divided with the triple variation – lies in the domain -1.8 to +1.8 (established on the basis of the experimental results [01, 15]. It can be noted that the argument of the observed function is usually in the interval -1 to +1, and the relative error of approximation of the mentioned function with the Maclaurin polynomial of third degree is approx. 9% [01,16], which is found acceptable. During the simulation, parameters of the passenger car “Zastava 1100” were utilized, provided by the manufacturer [32], and shown in Table 1. Table 1: Vehicle parameters c1, N/m

c2, N/m3

c3, N/m c4, N/m2

c5,N/m3

50000

10000

5000

500000

x1, 1/N

x2,/x3, s/s

x4, s2/m

x5, N/m

x6, N/m

20.25

0.008/0.02

-9.51

-2.091

0.0015

It should be pointed out that dimensions of the coefficients in Table 1 are within SI unit system. Journal of Applied Engineering Science 10(2012)4, 236

Figure 3: Variation of vibration parameters in service

For the analysis of the influence of vehicle dynamic cahracteristics due to variation of parameters of elasto-damping elements in service, two groups of parameters were utilized, taking into account these variations. To be more precise, having in mind Figure 3, after approximation with streight line, any variation is described by the expression: (9) where: • vibpar – value of vibration parameter after service of kilometers, • vibpar0 - value of vibration parameter at the beginning of vehicle service, and • ki – factor that takes into account degradation of vibration parameters during service. In order to take into account the influence of aging on vehicle dynamic characteristics, on the basis of the data given in Figure 3, corrective parameters are adopted and given in Table 2. It should be pointed out that factor k1 refers to 187

Dr Miroslav Demić - A contribution to research of degradation of characteristics of vibration parameters on vibration aspect of vehicle comfort

springs, k2 to shock absorbers and k3 to tires, and there were two groups of factors observed: at the beginning of service (group 1) and after 200000 kilometers of service (group 2). As it has already been pointed out, differential equations (7,8) are solved numerically, by use of method Runge-Kutta, with the sample of increment 0.01s, in 1024 points, which enabled reliability of the results within the domain 0.1–50 Hz, what is regarded acceptable for this kind of analysis [02-04, 13-15]. On the basis of [02-04], statistical values of errors were calculated. For the signal of 1024 points with the sample of increment 0.01, number of averaging 256, bias errors were obtained 0.003, stochastic error for a single signal 0.10, and for two signals 0.118, for spectra. Such small values of errors indicate that these results enable reliable analyses. Table 2: Corrective factors k1

Group 1

Group 2

0,95

0,83

0,70

ANALYSIS OF THE RESULTS On the basis of the calculated time series of vertical vibration of sprung mass, ordinary coherence functions, cross-correlation functions and transfer functions for the initial state were calculated, and also for the state of vibration parameters after 200000 km of service, by use of software [17, 18], and presented in Figures 4-7.

Figure 4: Ordinary coherence function

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Figure 5: Cross-correlation function

The analysis of the data from the Figure 4 may lead to the conclusion that ordinary coherence function is subject to variation within the interval 0.65 – 1, what indicates that the vehicle model is nonlinear [02-04]. Degradation of vibration parameters also influences the value of ordinary coherence function. Figure 5 presents the variation of cross-correlation function with the increment of time duration. To be more precise, it descends with the time increment and gravitates towards zero value, and also indicates that the process of vibration is stationary, what is understandable when the applied function of excitation is stationary value [02-04]. As in previous case, degradation of vibration parameters influences forced vibration of vehicle sprung mass.

Figure 6: Modulus of transfer function

Journal of Applied Engineering Science 10(2012)4, 236

Dr Miroslav Demić - A contribution to research of degadation of characteristics of vibration parameters on vibration aspect of vehicle comfort

The analysis of data from the Figure 6 shows the resonance of sprung mass at approx. 2.5 Hz, and unsprung mass at approx. 7.5 Hz, which confirms the fact that vehicle parameters are well chosen [21]. It is obvious that degradation of vibration parameters leads to a variation of parameters of resonance of sprung and unsprung masses. I.e., since spring and shock absorber cahracteristics descend with the duration of service, it is clear that reduced damping leads to a variation of transfer function amplitude [26]. Variation of vibration parameters also influences the variation of phase angle, Figure 7.

Figure 7: Phase angle of transfer function

It should be noticed that the variation of parameters of resonant point strongly influences parameters of vibration comfort of the vehicle, and degradation of these parameters may lead to a distraction of the vehicle due to unconfortable ride [12-14, 18]. This effect is often noticed in service when shock absorbers are worn, or suspension characteristics degrade to the extent that makes the vehicle unsafe to use. Therefore, it appears to be a need to introduce a degree of the allowed degradation of vibration parameters, what is not the subject of this paper. It is important to point out that the influence of degradation of vibration parameters should be taken into consideration in the process of creating a vehicle model in the early phase of vehicle design.

Journal of Applied Engineering Science 10(2012)4, 236

CONCLUSIONS Performed research enabled following conclusions: •

•

Degradation of vibration parameters during the service influences the variation of characteristics relevant for vehicle vibration comfort. The influence of degradation of vibration parameters should be taken into account in vehicle model in the early phase of vehicle design

REFERENCES 1) Belingardi, G., Demić, M. (2009), A possible model for shock absorber by using the „Black Box“ method, Istraživanja i projektovanja za privredu, VII/4, pp. 45-53. 2) Bendat, J. and Piersol, A. (1980), Engineering applications of correlation and spectral analysis, John Wiley and Sons, New York. 3) Bendat, J. and Piersol, A. (2000), Random data analysis and measurement, John Wiley and Sons, London. 4) Bendat, J. (1998), Nonlinear Systems - Techniques and Applications, John Wiley and Sons, London. 5) Demić, M. (2011), Scientific Methods and Technical Development (in Serbian), Mechanical Engineering Faculty, Kragujevac. 6) Demić, M. (1997), The Optimization of Vehicle Vibration Systems (in Serbian), Mechanical Engineering Faculty, Kragujevac. 7) Demić, M. (2004), Design of Passenger Cars (in Serbian), Mechanical Engineering Faculty, Kragujevac. 8) Demić, M. et al. (1984), A Suplement to Standardization of Nonuniformity of Passenger Car Tires with Respect to Oscillatory Comfort and Handling, ISATA, Milan. 9) Demić, M. (1999), The definition of the tires limit of admissible nonuniformity by using the vehicle vibratory model, Vehicle System Dynamics 31 (3), pp. 183-211 10) Demić, M. (1994), Optimization of Vehicles Elasto-Damping Element Characteristics from the Aspect of Ride Comfort, Vehicle System Dynamics, Vol. 23, pp.351-377. 11) Demić, M. (1996), Optimization of Characteristics of Elasto-Damping Elements from the Aspect of Oscillatory Comfort and Vehicle Handling, Int. J. of Vehicle Design, Vol. 17, No 1. 189

Dr Miroslav Demić - A contribution to research of degradation of characteristics of vibration parameters on vibration aspect of vehicle comfort

12) Demić, M., Diligenski, Đ., Demić, I., Demić, M. (2006), A Method of Vehicle Active Suspension Design, Forschung im Ingenieurwessen. 5, 70: DOI 10.1007/s10010-06-0025-, pp 145-158. 13) Demić, M. and Lukić, J. (2008), Human Body Under Two-Directional Random Vibration, Journal of Low Frequency Noise, Vibration and Active Control, 3, pp. 185-201. 14) Demić, M. and Lukić, J. (2009), Investigation of the transmission of fore and aft vibration trough the human body, Applied Ergonomics, XXX, 1-8. 15) Demić, M., Lukić, J. and Milić, Ž. (2002), Some aspects of the investigation of random vibration influence on ride comfort, Journal of Sound and Vibration, 1, pp. 109 – 129. 16) Demić, M., Belingardi, G. (2010), A Contribution to shock absorber modelling and Analysis of their Influence on Vehicle ride Characteristics, Journal of Middle European Construction and Design of Cars (MECCA), 01, pp 6-17. 17) Demić, M. (2003), Analsigdem: Software for signal analysis, www.ptt.yu/korisnici/i/m/imizm034/index.swf. 18) Demić, M. (2003), Demparcoh Software, www.ptt.yu/korisnici/i/m/imizm034/index.swf 19) Griffin, M. J. (1990), Handbook of Human Vibration, Academic Press, London. 20) Featherstone, R. (2008), Rigid Body Dynamics, Springer. 21) Genta A. (2003), Motor Vehicle Dynamics. Politecniko di Torino. 22) Gillespie T. (1992), Fundamentals of Vehicle Dynamics. SAE, Warrendale, 1992.

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23) Magneti Marelli (2012), Informations. 24) Miliken W.F, Miliken D.L. (1995), Race Car Vehicle Dynamics. SAE, Warrendale. 25) Miloradović, D. (2012), Research of Mechanical and Functional Couplings of Vehicle Dynamic System from the Aspect of Required Performances (in Serbian), PhD Thesis. Faculty of Engineering Sciences, Kragujevac. 26) Rajamani, R. (2005), Vehicle Dynamics and Control, University of Minesota. 27) Rašković, D. (1974), Analytical Mechanics- A Brief Course (in Serbian). Mechanical Engineering Faculty, Kragujevac. 28) Sekulić, D., Dedović, V. (2008), Simulation of oscillatory behavior of buses with conventional and active suspension systems. Journal of Applied Engineering Science, Vol. 6, No. 20, pp. 23-32 29) Sekulić, D., Dedović, V.(2011), Effects of vibration on user comfort intercity buses using oscillatory model with seven degrees of freedom using ADAMS / View software. Journal of Applied Engineering Science, Vol. 9, No. 3, pp. 401-410 30) Simić, S., S. (2006), Analytical Mechanics: Dynamics, Stability, Bifurcations (in Serbian). FTN Editions, Novi Sad. 31) Fabien, B. (2009), Analitical System Dynamics – Modeling and Simulation, Springer. 32) Zastava Informations (in Serbian) (19772010) Kragujevac. Paper sent to revision: 24.09.2012. Paper ready for publication: 03.12.2012.

Journal of Applied Engineering Science 10(2012)4, 236

doi:10.5937/jaes10-2516

Paper number: 10(2012)4, 237, 191-196

CRANE CABINS WITH INTEGRATED VISUAL SYSTEMS FOR THE DETECTION AND INTERPRETATION OF ENVIRONMENT - ECONOMIC APPRAISAL Dr Nikola Dondur * University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia Dr Vesna Spasojević-Brkić University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia Mr Aleksandar Brkić University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia This paper analyses the economic feasibility of production and use of the new generation crane cabins of considerably lighter weight and stiff structure whose interior space necessary for the operator will be developed by using the methods of physical, cognitive and organizational ergonomics with the solved problem of visibility and which will allow higher productivity due to reduction of physical and psychological stress of the operator, as well as greater safety and security due to the integrated visual system. It is proved that the total economic benefit of the exploitation of the cabin in the overall exploitation period is significantly higher than the purchase price of the cabin, as well as that the internal rate of return is above the relevant average weighted interest rate and the payback period is less than three years. The analysed project of production and use of crane cabins with integrated visual systems for the detection and interpretation of environment is the project with low economic risk. Key words: Economic feasibility, Cranes, Cabin, Integrity, Products, Operator INTRODUCTION As a result of the complicated and constantly changing nature of industrial and construction work, there are very high injury and fatality rates, where cranes contribute to as many as one-third of all fatalities and injuries resulting in permanent disability [01]. The Crane and Hoist Safety report - OSHA reported a death rate of 1.4 deaths per 1000 operators [06]. Human error is the cause of almost 60% of lifting operation related accidents [01]. It is not surprising since crane operators still work in ergonomically unadjusted surrounding with very high visual tension in stressful working conditions due to both physical stress (shocks, vibrations and accelerations), and psychological stress (the sway of the load, extremely low visibility of cranes, etc.). Additionally, the ever growing competitiveness in the international and/or national market makes further improvement in the management, effectiveness and efficiency of crane operations and crane systems absolutely essential. According to previous research results

[01,06, 05] a new solution for crane cabins is needed to solve the aforementioned problems is needed. The goal is to develop crane cabin as ergonomically adjusted, light weight and integrated visual systems for the detection and interpretation of environment. TECHNICAL DESCRIPTION AND FEASIBILITY We propose the following: 1) To develop smaller and lighter ergonomically adjusted crane cabins with appropriate safety features using physical, cognitive and organizational ergonomics and modelling, and static and dynamic calculations using the finite element method; 2) To develop well designed integrated visual systems for the detection and interpretation of environment which will solve the operator’s visibility problems; 3) To develop a simulation crane cabin, based on Virtual Reality technology, to replicate a real crane cabin together with the instrumentation and control of crane operations for the purposes of training and enhancing the cognitive abilities

* University of Belgrade, Faculty of Mechanical Engineering, Kraljice Marije 16, 11000 Belgrade, Serbia; ndondur@mas.bg.ac.rs Paper presented at SIE 2012

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Dr Nikola Dondur - Crane cabins with integrated visual systems for the detection and interpretation of environment - economic appraisal

necessary for the effective and efficient use of integrated vision systems, and 4) To develop a prototype remote control for cranes which will include a remote control console and associated tracking (sensory) and management information systems. The main innovative idea behind this project consists of synergetic contributions from the following entities as the main fields of development: a) The development of a model with the minimal dimensions of the cabin where the operator will be accommodated in an ergonomically adjusted way based on an anthropometric study; b) The development of a model for the cabin interior including well-designed controls and the control station layout according to the principles of ergonomics and biomechanics which will ensure good safety features, c) The further optimization of the cabin by designing a light weight cab supporting structure with the application of the finite element method (FEM) for the analysis of load distribution, membrane and bending stresses, strain energy and the distribution of kinetic and potential energy to groups of elements of cab structure; d) The development of integrated visual systems for the detection and interpretation of environment which will solve visibility problems; e) A Virtual Reality based simulation cabin, and f) A crane remote control prototype setup. The benefits of this project lie in offering solutions to the following problems: (i) lower productivity due to human-machine interface problems; (ii) large financial and other losses resulting from the direct and indirect costs of the accidents caused;(iii) damage to the materials as well as to the material handling equipment; (iv) the unnecessary cost of frequent repairs and consequent loss of production; (v) disturbance in material handling schedules and (vi) an increased work-load on the other equipment and their consequent quicker downtime and break down. ECONOMIC APPRAISAL METHODOLOGY According to the Global Cranes, Lifting and Handling Equipment â&#x20AC;&#x201C; Market Opportunities and Business Environment, Analyses and Forecasts to 2015 document produced by World Market Intelligence during the period 2006-2010, the consumption value of the global crane, lifting and handling equipment market grew at a CAGR of 2.76%. After witnessing a year of production and consumption decline due to low demand, the market recovered in 2010 to record production growth of 5.9% and consumption growth of 4.7%. 192

Whilst South America experienced the fastest growth in consumption value during the review period, Asia-Pacific and Europe made the highest contributions to market consumption value in 2010. In terms of construction equipment from emerging nations to support infrastructural and mining investments, global cranes, lifting and handling equipment consumption is expected to record a CAGR of 10.75% in the forecast period - 2015. The European market has experienced a constant and the largest growth, amounting to 46% in 2000, in contrast to 15% in America and 11% in the rest of the world. A European crane cabins market is envisaged in this project as this is the area with the lowest transportation costs, thus the highest market growth is expected in this region. For the assessment of economic feasibility of development, production and use of crane cabins, in practice the most commonly used approach is costbenefit (CB) framework. Economic feasibility assessment through the cost-benefit framework can generally be used in the two assumed scenarios: â&#x20AC;˘ development, production and sale of a new generation of crane cabins (producer point of view) â&#x20AC;˘ use /purchase of the above type of crane cabins by the crane owners /lessors. Economic and financial feasibility in the first assumed scenario foresees defining the standard parameters of the assessment from the aspect of a cabin producer (owner of the crane cabin factory, shareholders, potential creditors) and the overall economy [3]. This approach requires developing complete tables of financial and economic flows, necessary for the calculation of the selection criteria (FNPV, FIRR, ENPV, EIRR, pay-back period, BCR). The second approach refers to an assessment of economic feasibility of investing into acquisition of a new generation of crane cabins and/or comparison of such investments (initial investment costs) and discounted additional effects (savings) in the crane exploitation over the entire (remaining) lifetime. Thus developed net flow serves as a basis for developing the quantitative parameters for the justification of investment and/or purchase of the new generation crane cabins from the aspect of the crane owner or user and from the aspect of the entire economy (NPV, IRR, BCR, pay-back period). For creating an economic net flow related to a new crane cabin, it is necessary to identify and quantify relevant costs and effects. [08, 03]. Journal of Applied Engineering Science 10(2012)4, 237

Dr Nikola Dondur - Crane cabins with intergrated visual systems for the detection and interpretation of environment - economic appraisal

Costs In the standard terminology that refers to project analysis, acquisition (purchase price) of the new generation of crane cabin can be seen as an initial investment cost. In the competitive circumstances, purchase price is nearly equal to the marginal production cost, increased by transport, insurance and trade margin. The cost of manufacturing a cabin should include materials, labour and energy costs, as well as a portion of dependent fixed costs. In addition to the costs included in the purchase price (I0 ), it is necessary to assemble and test the crane cabin, ensure training for a crane operator, but also disassemble the existing cabin if it is already existed on the crane (I1). Initial investment costs, required for the economic assessment of the project of using the new generation crane cabins, would represent a sum of the above-mentioned costs (I0 + I1). Benefits The exploitation of the new generation of crane cabins has direct and indirect positive effects from the aspect of the owner or user of the crane, but also positive effects on the overall economy. Direct positive effects from the point of view of the crane owner are primarily appeared through increase in productivity of the crane use. The cabin with integrated visual systems for the detection and interpretation of environment allows the crane operator to perform work operations faster. Savings of time at one duty allows the crane owner to engage the crane at another job without any additional exploitation costs. Reduction of the annual crane exploitation costs due to the assembly of the new crane cabin, which allows saving of time in performing work operations (Δt) represents benefit from the aspect of the crane owner. As the exploitation costs depend on the time of the crane operation (t), for the calculation purposes the positive effect for the crane owner represents a product of the sum of all exploitation costs and weight of the average time saving in performing operations (∑CEt· ρt). The annual crane exploitation costs can be decomposed to the costs of depreciation (capital recovery), costs of maintenance and repairs, as well as insurance and registration costs. Formally, these costs can be presented as follows: (1)

Journal of Applied Engineering Science 10(2012)4, 237

where PC represents a purchase value of the crane, stands for capital recovery factor for the specific exploitation lifespan of the crane (n) and interest rate (i). Depreciation of the crane is observed as depreciation of debt and/or future value of equal annual repayments of the amount invested in the purchase of the crane. Weight of the average time saving is determined as a relative ratio of the sum of differences in time of the operations performed by the crane without the new generation cabin and the time of operations with the new cabin and the total time of operations without the cabin with the integrated visual crane management system:

(2)

where represents weight of the average reduction in time of operation of the crane with the new cabin, time of operation (j) without the cabin with the integrated visual system for detection and stands for time of operation (j) with the new generation crane cabin. The following direct benefit of installing the new generation crane cabins is reduction in labour costs. If we assume that the number of workers and labour cost per hour remain the same, operation time reduction allows the worker to perform in such time reduction an additional work that is beneficial for the crane owner. Accordingly, time reduction of the operations (ρt) which the crane achieves due to the use of the new generation cabins represents a weight for calculation of the annual savings in labour costs (LSCt) as a product of the number of workers, cost of labour per hour and number of working hours of the crane: (3) where represents savings of labour costs in a year (t), stands for a number of crane operators, number of effective working hours of the crane in a year (t), average value of the working hour and is a weight of average savings of time of the crane operation in a year (t). By installing the new generation crane cabin, incidence of professional diseases and injuries of crane operators is reduced. This positive effect can be quantified through reduction of number of 193

Dr Nikola Dondur - Crane cabins with integrated visual systems for the detection and interpretation of environment - economic appraisal

working hours which the crane operator spends on a sick leave, during which period a new worker must be hired. This saving can be quantified as a product of the number of workers, number of hours lost due to the crane operatorâ&#x20AC;&#x2122;s absence, labour cost per hour and average weight of time reduction of the crane operations: (4) where represents annual savings in labour costs while the crane operator is on a sick leave, n a number of crane operators, number of working hours lost due to sick leaves, represents a cost of the working hour and weight of average time saving of the crane operation in a year (t). Thanks to a better visibility, the use of the new crane cabin reduces a number of breakdowns and slows down wear and tear of the crane mobile parts and/or reduces the costs of crane maintenance and repairs. This positive effect is determined as a product of the crane value and difference in the relative annual maintenance and repair costs:

where represents annual savings on depreciation write-offs, purchase value of the crane, capital recovery factor with the assumed exploitation lifespan without the new crane cabin (n) with appropriate interest rate (i), whereas represents a capital recovery factor with the extended exploitation lifespan (n+m) due to the use of the new crane cabin with appropriate interest rate (i). ECONOMIC APPRAISAL CRITERIA For the assessment of economic feasibility of the crane cabin with integrated visual systems for the detection and interpretation of environment, the following standard cost benefit criteria are defined: net present value, internal rate of return, cost - benefit ratio and payback period on investment. Net present value (NPV) of an investment in the new generation crane cabin represents the difference between the sum of initial investment costs and the sum of discounted savings over the entire lifetime of the crane, whereby such savings are resulting from the use of the new crane cabin: (7)

(5) where represents savings on the annual costs for maintenance and repairs of the crane , is a purchase value of the crane, is the value of the annual costs for maintenance and repairs of the crane without crane cabin with visual system and is a value of the annual costs for maintenance and repairs of the crane with the new generation crane cabin. Through a more efficient use of the crane, the new generation crane cabin is supposed to exend the assumed crane exploitation lifespan. Extension of the crane exploitation lifespan brings additional benefits through reduction of annual depreciation (recapitalisation) costs of the crane which is quantitatively determined as the difference between recapitalised annual write-offs and the lifetime of the crane (n) without the new generation crane cabin and recapitalised annual write-offs with the extended crane exploitation lifespan (n+m): (6)

194

where NPV represents net present value of savings on costs of the crane exploitation achieved by the crane cabin with the integrated visual system over the crane lifetime (n+m) and (i) represents relevant discount rate. Based on this criterion, use of the new crane cabin is acceptable if the net present value is positive. Internal rate of return (IRR) of the investment in acquisition of the new crane cabin is the value of discount rate which equalize the difference of the initial purchase costs of the new crane cabin and the present value of the total savings in operating costs with zero. For a project to be economically justified, this rate should be above the average weighted interest rate. [02, 07]. Cost benefit ratio is a quotient of the total net savings of the crane exploitation and the purchase costs, assembly costs and training costs for the work in that cabin. According to this criterion, purchase of the crane cabin will be economically acceptable if this ratio is greater than one. ECONOMIC APPRAISAL RESULTS For the assessment of the economic feasibility of the new generation crane cabin purchase, we Journal of Applied Engineering Science 10(2012)4, 237

Dr Nikola Dondur - Crane cabins with intergrated visual systems for the detection and interpretation of environment - economic appraisal

used the data referring to the bridge crane cabin. Table 1. provides the estimated data and, by using equtions from (1) to (7), calculated values referring to the costs of purchase and savings during the exploitation of the new crane cabin. Table 1: Economic cost - benefit appraisal inputs Variables

20000 Eur

Costs of assembly, testing, crane operator training and disassembly of the existing cabin if it is already fitted on the crane (I1)

1500 Eur

Benefits ( Savings)

Purchase price of the crane

Table 2: Sensitivity analysis

Values (Euros, %,)

Cabin manufacturing costs (costs of materials, labour, energy - I0)

Savings in time of operations /cycle reduction / ( )

that the payback period is slightly less than three years. As these are estimated input values applied in the calculation of the relevant criteria for the assessment of acceptability, we used sensitivity and risk analysis to test the robustness of the obtained results.

10 % (8-12%) 268000 Eur (20000-500000)

Annual savings on labour costs (LSCt)

1440 Eur

Annual savings due to reduced incidence of professional diseases and injuries of crane operators (LSCt)

400 Eur

Reduction of the crane maintenance and repair costs (LSDCt)

4025 Eur

Savings due to the extended exploitation lifespan (from 15 to 18 years) (ELSCt)

1828 Eur

By using the expression (7), we estimated empirically net present value of the net effect of the purchase and use of the new generation crane cabin. Net present value as a synthetic measure of absolute economic viability is in the first step calculated on the basis of the best estimates values of variables. Those values are given in Table 1. Net present value is, at the discount rate of 10%, Eur 68350. The total economic benefit of the exploitation of the cabin in the overall exploitation period is higher than the purchase price of the cabin and according to this criterion, the project of installing the new generation cabin is economically viable. Internal rate of return as a relative measure of economic acceptability of the purchase and exploitation of the new crane cabin is significantly above the relevant average weighted interest rate and is equal to 34.30%, which implies high economic profitability of the investment. Annual savings which are made in the operation of the crane managed from the new generation cabin are Eur 13770 which shows Journal of Applied Engineering Science 10(2012)4, 237

NPV Change (%)

+10

IRR(%) -10

+10

-10

Purchase value 77415 of the crane

59273

37.31

31.26

Cabin price

64708

71980

31.11

38.17

Dh (savings in working hours )

68648

68040

34.4

34.19

Sensitivity analysis shows relative stability of results as the change of the selected critical variables in the range (Âą10%) does not significantly influence the value of the criteria for the assessment of the economic viability of purchase and use of the new generation crane cabin. In risk analysis, we modelled five critical uncertain variables (cycle reduction, purchase price of the crane, cabin price, price of the working hour of a crane operator, number of working hours lost due to sick leaves and crane maintenance costs) by triangle probability distribution. Figure 1. gives an overview of simulation results (Hypercube sampling).

Figure 1: Distribution of the results

195

Dr Nikola Dondur - Crane cabins with integrated visual systems for the detection and interpretation of environment - economic appraisal

Net present value varies in the range from 16123,6 Eur to 162144 Eur and the internal rate of return ranges from 3% to 72.4%. Probabilities for negative net present values and for internal rates of return below average weighted reference interest rate (10%) are very low. The results of the analysis show that the project of purchase and use of the crane cabin with integrated visual systems for the detection and interpretation of environment is the project with low economic risk. CONCLUSION Techno-economic analysis of the project shows that the total economic benefit in the overall exploitation period is significantly higher than the purchase price of the cabin and according to this criterion the project of installing the new generation cabin is economically viable. Internal rate of return is above the average weighted interest rate, which implies high economic profitability of the investment. Annual savings made in the operation of the crane which is managed from the new generation cabin have the payback period of less than 3 years. The analyzed project of production and use of crane cabins with integrated visual systems for the detection and interpretation of environment is the project with low economic risk. Acknowledgement The authors wish to acknowledge the financial support from the Ministry of Education and Science Republic of Serbia through project E!6761.

REFERENCES 1) Beavers J. E., Moore J. R., Rinehart R., Schriver W. R., (2006), Crane-Related Fatalities in the Construction Industry, Journal of Construction Engineering and Management, Vol. 132, No. 9, , pp. 901-910 2) Curry, S. And Weiss, J. (2000). Project Analysis in Developing Countries, MacMillan Press. London 3) Dobrojević, M., Rakin, M., Medo, B., Omić, S., Sedmak, A.: INTERNET APLIKACIJA ZA UPRAVLJANJE PROJEKTIMA U INDUSTRIJSKIM SISTEMIMA, (2010), Journal of Applied Engineering Science (Istraživanja i projektovanja u privredi), no. 28, pp. 73-82 4) Dondur, N., (2002). Economic Analysis of Projects, Faculty of Mechanical Engineering, Belgrade (in Serbian) 5) Global Cranes, Lifting and Handling Equipment - Market Opportunities and Business Environment, Analyses and Forecasts to 2015, World Market Intelligence,(March20 11). (http://www.researchandmarkets.com/ reports/1579090/global_cranes_lifting_and_ handling_equipment) 6) Neitzel, R. L., Seixas, N. S., and Ren, K. K., (2001), A review of crane safety in the construction industry, Appl. Occup. Environ. Hyg., Vol. 16 No.12, pp. 1106–1117. 7) Potts, D. (2002). Project Planning and Analysis for Development, Lynne Rienner Publishers, Inc. London 8) Rosenfeld, Y. and Shapira, A. (1998). Automation of existing tower cranes: economic and technological feasibility, Automation in Construction, vol. 7. pp. 285-298 Paper sent to revision: 15.10.2012. Paper ready for publication: 03.12.2012.

196

Journal of Applied Engineering Science 10(2012)4, 237

doi:10.5937/jaes10-2617

Paper number: 10(2012)4, 238, 197-200

USING ARIMA MODELS FOR TURNOVER PREDICTION IN INVESTMENT PROJECT APPRAISAL Zoran Petrović * Tecon System d.o.o, Belgrade, Serbia Dr Uglješa Bugarić University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia Dr Dušan Petrović University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia In the contemporary investment project analyses, most critical point is how to estimate daily turnover of production, or service, based system. In order to make prediction, for investment in certain type of equipment more accurate, daily turnover in the system for automated car wash was observed, along with weather conditions. According to observation, ARIMA model for daily turnover and weather condition is created, according to Box-Jenkins procedure. Conclusion was made that daily turnover can be analytically expressed through daily weather conditions. Validity of observation is checked on second system that is installed in different town in Serbia. According to compared results, conclusion was made that ARIMA model of system daily turnover, predicted by dependent variable, can be generally used as good predictor in investment analyses, or selective criteria for investment decisions. Key words: Arima, Box-Jenkins, Investments, Predictions, Turnover INTRODUCTION Life cycle of project is determined by, at least four phases. In the first phase, also called initial phase, feasibility study is performed and decision for continuing or cancelation of the project, (if not feasible), is made. In the production systems if project is evaluated as feasible, other phases can be carried out (planning and construction, production and final operational phase), Figure 1. From the Figure 1, it is hard to conclude that first phase of the project is most important one. Conclusions from the first phase will have vital influence to the project successful finishing [03].

Considering risk distribution across project life cycle, beginning of the project is bearing most of the risk, since in the beginning number of available information is relatively small.

Figure 2: Diagram of project life cycle considering project expenditure and risk [03]

Usually, in investment analyses average daily turnover, measured on existing system is used to estimate turnover for system that is analyzed from the point of investment appraisal. Problem in such approximation is that fluctuation of average daily turnover of the system that is analyzed as potential investment, can differ significantly from any other, previously installed system. Figure 1: Project cycle phases [04] * Tecon System d.o.o, Antifašističke borbe 21b, 11000 Belgrade, Serbia; office@tecon.rs Paper presented at SIE 2012

197

Zoran PetroviÄ&#x2021; - Using arima models for turnover prediction in investment project appraisal

In order to predict daily turnover, two variables were measured on existing system. First variable is Daily turnover and second one is Daily weather condition. HYPOTHESIS Hypothesis 1.: H0: Daily turnover is dependent from Daily weather condition. Hypothesis 2.: H0: Measure of dependence can be expressed in analytical form. Hypothesis 3.: H0: Daily weather condition can be used as predictor for estimation of daily turnover in investment analyses.

Data for both variables were tested against Hypothesis that they can fit to the Normal distribution. Goodness of fit for both variables was tested with Kolmogorov-Smirnov test, with significance level =0,05. Students T test was used in order to test both variables against Hypothesis 3, that there is no significant differences between distribution of two samples. RESULTS According to proposed methodology time series of daily turnover is given on the Figure 3:

METHODOLOGY Automated car wash was observed in such way that daily records of turnovers and weather conditions were registered in research protocol. Case study was created from daily records taken from 25.05.2009. until 21.5.2010. During mentioned time 362 data records were taken. From research protocol two variables were created â&#x20AC;&#x201C; Daily turnover and Daily weather condition. Daily turnovers are represented as values in RSD and Daily weather conditions are represented as one of four different, weather conditions. If weather during most of the day was sunny, number 1 was assigned for Daily weather condition. If weather during most of the day was cloudy, number 2 was assigned. To mostly cloudy with rainy period was assigned number 3 and to the rainy, or snowy, day was assigned number 4. Variables defined in research were modeled as ARIMA time series according to Box-Jenkins modeling strategy [01]. Such variables are used for forecasting of turnover on the system [02]. All calculations were done in statistical software IBM SPSS Statistics 20. Dependency between those variables was examined in order to check if daily turnover depends from daily weather condition. In the results, after confirmation of the Hypothesis 1, analytical model of dependency was created and Hypothesis 2 was confirmed. For confirming Hypothesis 3, new system in different town was observed. Observation period was defined as 100 days, on which both variables (Daily turnovers and Daily weather conditions) were recorded and registered in research protocol. Based on the analytic expression of the dependency between variables in first case, daily turnover on second system was modeled, using daily weather conditions as predictor. 198

Figure 3: Observed daily turnover

Time series of measured data compared to time series of modeled data using ARIMA methodology is given on the Figure 4.

Figure 4: Observed and modeled daily turnover

According to the calculated data best fitted model that describes analytical relationship between Daily turnover and Daily weather condition was: ARIMA (1,0,14). Parameters of ARIMA (1,0,14) model are given in the Table 1. Analytical expression for relationship between variables is given as:

Journal of Applied Engineering Science 10(2012)4, 238

Zoran PetroviÄ&#x2021; - Using arima models for turnover prediction in investment project appraisal

where:

Wc is daily weather condition on observed day as categorical variable that can take value 1-4.

is average turnover for past 14 days. n is number of observation n 1.

Table 1: ARIMA model paramters ARIMA Model Parameters

VA02Model_1

VAR02

No Transf.

VAR01

No Transf.

Constant

Estimate

Sig.

8447,649

557,341

15,157

,000

Lag 1

,696

,041

17,070

,000

Lag 14

-,265

,055

-5,431

,000

Num.

Lag 0

-1789,317

115,705

-15,464

,000

According to Ljung-Box procedure, statistical model is good fitted to observed data. Significance of the test was 0,081, so difference be-

tween fitted and measured values are not statistically significant. Values of the Ljung â&#x20AC;&#x201C;Box test for goodness of fit are given in the Table 2.

Table 2: Model goodnes of fit Model VAR02Model_1

Number of Predictors 1

Model Fit statistics

Number of Outliers

Ljung-Box Q(18)

Stationary R-squared

Statistics

Sig.

R-squared

,609

23,158

,081

Table 3: Extreme values (outliers)

VAR02Model_1

Estimate

Sig.

Additive

7889,826

2094,530

3,767

,000

182

Additive

10126,487

1996,093

5,073

,000

300

Additive

10890,786

2045,844

5,323

,000

335

Additive

13578,128

2011,825

6,749

,000

341

Additive

10432,565

2030,952

5,137

,000

Number of extreme cases (outliers) is 6, which is less than 2%, of all observed cases. Extreme values (outliers) are given in the Table 3. In order to validate results, newly installed system was observed in different town. Average turnover form first model was used as starting value for modeling. Rest of time series was modeled from analytical expression for relationship between variables, based on weather variable that was recorded on the system, as predictor. Data sets from observed real system were tested against Hypothesis that they can be described with Normal distribution. Data sets from model, were tested against Hypothesis that they can be described with Log Normal distribution. In the first case results are distributed according to Normal distribution N (2671,4912) and in the second, results were distributed according to Log Normal distribution LogN (0.77,8.2). Histograms for both variables are presented on Figures 5 and 6. Journal of Applied Engineering Science 10(2012)4, 238

Figure 5: Histogram of data observed from real system

Figure 6: Histogram of data predicted with ARIMA model

199

Zoran Petrović - Using arima models for turnover prediction in investment project appraisal

Goodness of fit was tested with KolmogorovSmirnov test, for same significance level =0,05. In the first case, where data on real system were tested against Hypothesis of Normal distribution, critical value for Kolmogorov –Smirnov test was 0,13403 for 100 recorder data sets and value of the test was 0,086. In the second case, where modeled data were tested against Hypothesis of Log Normal distribution, critical value for Kolmogorov –Smirnov test was 0,13403 for 100 recorder data sets and value of the test was 0,078. Student’s T test was accomplished in order to test Hypothesis 3, that there is no significant difference between means on two independent samples. According to calculated values of Student’s T test, for significance level of = 0,05 and degrees of freedom df=198, value of the test was t=0,553. There is no significant difference between means on two variables. DISCUSION Hypothesis 1 was tested and results confirmed stated Hypothesis that variable Daily turnover can be predicted by variable Daily weather condition. From the model fit it can be seen that goodness of the fit is 60,9%, which is considered as good model fit [06]. Number of outliers in fitted model was significantly small (below 2%), which also indicates goodness of the fit. Hypothesis 2 was also confirmed. Analytical formulation of dependency was made, which also established mathematical model for next Hypothesis. Hypothesis 3 was also confirmed. Based on proposed methodology, record sets of measurements from real system and record sets from modeled values were analyzed. Measured values were fitted to Normal distribution and modeled values were fitted to Log Normal distribution. Reason for this is in the fact that modeled values are dependent from previous record sets, so sudden changes from one weather condition to completely opposite one (from sunny weather to snow for example) can’t be described completely by model. Never the less model is in the end, for mentioned number of record sets giving good predictive results, with no statistically significant differences between two samples.

200

CONCLUSION As described in the paper Daily turnover of automated car wash system depends from observed variable Daily weather condition. Measure of this dependence is calculated through ARIMA time series model. Results from modeling were compared to observed values got from another system. According to these results there is no statistically significant difference between two data sets, which implies that proposed ARIMA method can be used for prediction of daily turnover of car wash facilities. Similar model can be used for estimation of daily turnover in other industry fields. Future analyses will be in the direction of finding one or more variables that can be used for prediction of daily turnovers in other technical systems and comparing results with one published in this paper. REFERENCES 1) Box, G.E.P., Jenkins, G.M., 1987. Time Series Analyses, Forecasting and Control. 2nd ur. San Francisco: Holden-Day. 2) Ho, S.L., 1998. The use of ARIMA models for reliability forecasting and analyses. Computers and industrial engineering, 35 (1-2), 213-216 3) Jiang, B., Heise, D.R., 2004. The Eye Diagram: New Perspective on the Project Life Cycle. Journal of education for Business, pp. 10-16 4) Morris, P. W., 1998. Managing Project interfaces: Key Points for Project Success. Englewood Cliffs, New Jersey: Prentice-Hall. 5) Newell, M.W., Grashina, M.N., 2004. The Project Management Question and Answer Book. New York: AMACOM. 6) Tabachnik, B.G., Fidell, L.S., 2007. Using multivariate statistics (5th edn.). Boston: Pearson Education Paper sent to revision: 10.09.2012. Paper ready for publication: 04.12.2012.

Journal of Applied Engineering Science 10(2012)4, 238

doi:10.5937/jaes10-1688

Paper number: 10(2012)4, 239, 201-208

CONTRIBUTION TO THE EVALUATION OF THE COMPLIANCE FOR NEW PRODUCTS WITH ASPECT RELIABILITY AND MAINTENANCE Dr Radoljub Tomić * Alfa University, Faculty for Strategic and Operating Management , Belgrade, Serbia Dr Predrag Petrović Institute Kirilo Savić, Belgrade, Serbia Marija Petrović Institute Kirilo Savić, Belgrade, Serbia Development and promotion of the principles of harmonization of new products, it is very important, especially in technical systems and their components, which are applied and exploited in a transport vehicle. Quality and reliability of these products have to be high to make the product, and thus the system, first of all was safe, yet competitive in the global market. On the other hand, one of the conditions for the promotion of local products is increasing product competitiveness, while meeting the technical regulations, product quality, reliability and maintenance. When it comes to the proper functioning of the brake system of railway vehicles is a significant benefit to system maintenance. Bearing in mind that the braking system must fulfill a series of conditions in terms of quality of legislation, safety and reliability in all operating and other conditions, this paper describes the dynamics of maintaining a technical system, with special emphasis on the share of costs in relation to the price of the brake system of railway equipment vehicles. It is a new domestic product of IHP “First five” Trstenik-(PPT), with special reference to the component relating to the sealing element, the most sensitive part of the device in the brake system of railway vehicles. Key words: Maintenance, Braking, Availability, Reliable, Railway, Compliance, New product, Costs INTRODUCTION When it comes to existing products, but the concept of project solutions, the successful operation of the brake system is significantly affected by the maintenance system. The very concept of product design solution, must include all aspects relating to benefits for its maintenance. This attitude almost always have to be aware of the concept of establishing a complex new product configuration [16,06]. Technical system has the design and manufacture to be adjusted given environmental conditions and system reliability is treated as its internal (inherent) property, which can improve the structural and technological measures. Cancellations technical system represents each event after which the system is unable to perform the required functions. Readiness or availability of a technical system is the probability that the system will successfully take effect and achieve the projected size of the output in minimum re-

quired time period and the circumstances surrounding. Reliability theory is the science which deals with the legality of the failures of technical systems and their functional units (system, subsystem, assembly, subassembly, element). From a practical viewpoint term reliability of the easiest and most complete to be considered as a property of the technical system to operate without failures in certain conditions and time periods. Reliability analysis involves analyzing continuous technical failure of the system and its functional units, as well as all the factors, which in some way influence the occurrence of failures. [01] System maintenance management system is very complex, which applies to the brake system of railway vehicles, and will in this paper only indicate maintenance subsystem elements related to the brakes. The theoretical aspects of this problem are considered in and widely considered in the very knowen books and monographies [16,10,02,15,18].

* Alfa University, Faculty for Strategic and Operating Management, Staro Sajmište 29, Belgrade, Serbia; mpm@eunet.rs

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Dr Radoljub TomiÄ&#x2021; - Contribution to the evaluation of the compliance for new products with aspect reliability and maintenance

System reliability is the probability that the system by entering in areas tolerances, successfully serve as criteria in the territory of a given, and given the projected weather conditions. It is based on the comparison of the criteria set functions and actual working capacity of the system functions. Brake systems must comply with numerous quality demands, law regulations about safety issues and high reliability in all sorts of work regimes; the logic of maintenance has been described with special review on the share of expenses to the price of brake systems. The sealing system, as the most sensitive assembly of the brake devices and system /epecially for this paper, which is produced by Industry of hydraulics and pneumatics ÂťPrva PetoletkaÂŤTrstenik (PPT), will be particularly considered. Analysis of this problem are based on the standards and the system of documentation and production programme of PPT [18,12,05]. BASIC MAINTENANCE ASPECTS Main objective technical systems of the railway (MS), refers to the provision of uninterrupted functioning of the system as a whole, provided that its subsystems are functioning properly (PS), and elements (EL). In order to fulfill the logical requirements that determine the overall goal, it is necessary to provide an adequate supply of spare parts (RD), and supplies. The level and quality of spare parts and causes the cost to the user invests in procurement, storage and controlled storage reserves [16,06].

Availability of the system is a measure of the state of the system in terms of efficiency of entry into effect of the realization of output values of the system-level deviations allowed areas set of criteria in a given function, given the time and conditions of use. Size components, availability, caused a number of influences, defines the different parameters of the function linking no cancellation work and maintainability of the system functions on the basis of: operational, planned and built-in readiness. Operational availability is by definition the probability that the system successfully take effect and go in areas tolerances set of criteria function at a given time in the given environmental conditions, as determined by the ratio of total time in the system and the total duration (total time in service and cancellation ), as will be shown further on. Planned availability is the time in which it is not required and the efficient operation of the system, which is a function of operating conditions and operational levels of the organization and maintenance of the system is dependent on the structural characteristics of the system. Built-availability is determined by structural measures benefits and minimum time necessary maintenance procedures. Availability of the system is determined for certain parts of the system as a whole, based on the ratio of total working time (tr), the sum of the total time in service (tu), and the time of failure (to). [08]

Figure 1: Concept of Maintenance Mechanical Systems (MS)

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Dr Radoljub Tomić - Contribution to the evaluation of the compliance for new products with aspect reliability and maintenance

Current standards ISO 9004 provides event fulfillment costs in managing the quality of products and mechanical systems, with most of the technical and production-control demands in terms of efficient operation of mechanical systems. Proper maintenance is achieved by an efficient level of reliability and a high level of operational system. Possible concepts maintenance of mechanical systems are defined in Figure 1. [04] Important to maintain the brakes on rail cars are the following: • estimate, measure and record the frequency of the need for spare parts; • determination of cases in which it is possible to apply the law of probability, as well as cases where you need permanent removal specific groups of causes; • minimizing the costs of holding reserves, reserve reconstruction costs and expenses caused by not having a reservation. Optimization of a new product in terms of technical and economic feasibility of this case is necessary for the railway company as a precondition of competitiveness in the market traffic with other transportation companies. To realize these goals requires research policies, standards, models and tools in the field of Reliability, Availability, Maintainability and Safety (RAMS) and Life Cycle Cost (LCC). Functionality models and tools and their continuous improvement in certain areas allow for effective incorporation into the design stages. Standard EN 50126 defines the underlying processes in the field of railway RAMS is based on the life cycle of the system and the cost (LCCLife Cycle Cost), and the basic principles of management. When defining the parameters of rail systems in the area of RAMS and LCC’s, the standard defines the correctness of the factors that may divide into three categories: sources of failure (system requirements), imposed factors during operation (operational requirements), undesirable, and the real phenomenon of a factor during maintenance (maintenance requirements). All these factors should be identified and assessed qualitatively, to the effect when operating in the life of the system was as efficient as possible. Definition of the system over the RAMS and identify potential risks dangers that need to be analyzed and displayed for example. Frequency or through the matrix to the estimation of a simJournal of Applied Engineering Science 10(2012)4, 239

pler and more efficient at different levels (undesirable, intolerable, unbearable, negligible-(eg undesirable, intolerable, tolerable, negligible). Standard EN 50126 defines the system life cycle as a series of stages that cover the overall lifetime systems and provide conditions for the planning, management, control and monitoring of all aspects of the system including the RAMS. These stages are: Concept, system definition and application Conditions, Risk Analysis, System Requirements, Apportionment of system requirements, Design and implementation, Manufacturing, Installation, System Acceptance, Operation and Maintenance, Performance Monitoring. Annex A gives a principal outline of RAMS specifications for rolling stock, identifying operating and environmental conditions, reliability targets, system failure modes and mean time between failures, maintenance and repair requirements (e.g. mean time to repair), safety targets, hazardous conditions, safety-related functions and failures, safety hazards severity levels, system availability. Annex B gives an outline procedure for a basic RAMS programme and lists some appropriate methods and tools for conducting and managing a RAMS programme. In particular, it refers to some procedures for performing deductive (top-down) and inductive (bottom-up) preliminary, worst case and in-depth RAMS analysis, which are included in separate standards. The most relevant procedures listed are: diagnostic testing, (FMEA-Failure Modes and Effect Analysis), (FTA-Fault Tree Analysis), (FMECA– Failure Mode, Effects and Criticality Analysis), reliability block diagram method and Markov techniques.[18] SPECIAL ASPECTS OF BRAKE MAINTENANCE Only small parts of theoretical models, for understanding of the problem, will be discussed in this paper. Successful definition and realization of the brake design should prevent problems that may occur during its exploitation. It is clear that constructor should have in mind product features that will provide easy maintenance for the final user. Therefore, constructors have great responsibility to trace the reliability level (Rd), to define maintenance programme and to establish methodology for analysis of causes for improper functioning of brakes. Afterwards, based on observing concrete brake system, dur-

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ing some period of normal use, constructor has to perform revision of (Rd) and to define control system for the real level of reliability (Rs), Fig. 2, in adequate period of time (three month period, semiannual, annual), that depends of importance of the groups (PS) (subsystems) and

Figure 2: Model maintenance elements, method POPS-KNP

Maintaining of some elements using method (POPS–KNP - Preventive Maintenance by Condition with the Control Level of Reliability), can be applied in maintenance of (EL) which don’t have essential importance in brake system, but have importance in aspect of economy (cost minimization), for finding out possibilities of selective application. Such an approach in the literature is generally referred to as POPS-KNP (Preventive Maintenance by Condition with the Control Level of Reliability). Preventive maintenance is a series of actions necessary to prevent it fails, or the maintenance of the criterion function within the permissible deviations in the long term. It is performed on the basis of speculation fails it is studying the weather conditions of the previous period of the same or similar systems Which are based on time intervals prescribed maintenance procedures implementation. Depending on the characteristics of emergence and implementation of time are adjusted structure and running time of the procedure, Which Enables the adaptive system for preventive maintenance. This approach is typical of the new systems that do not have enough information from weather conditions or exploitation process. [08] Costs of reserve possession are related, in the first place, on purchase costs of reserve, costs of storage, securing, keeping and maintaining. Costs of reserve renewal are related with the costs of ordering, communication, transport, checking and storage.

(EL) (elements) for the safety and quality work of brake system. If the value of (RS) is below (Rd), an analysis of causes has to be carried out, and some measures for increasing reliability have to be taken.[16, 05]

Figure 3: Relation of Cu and Crd costs, as a function of allowed reliability level Rd

Costs of non-possessing reserves are related to interruption of device or brake system function, profit loss, risk of major damage and costs of emergency delivery, price increase etc. Relation between spare parts costs (Crd) and total costs (Cu), for allowed reliability level (Rd) is presented on Figure 3. Optimization of guaranteed reserve is for each part separately; expenses level particularly depends on: • type of brakes, • life cycle of devices and systems, • quality system of handling and maintaining, • presence of manufacturer of (RD=SP) (spare parts) on the market. The aim is to accomplish appropriate or wanted reliability level with minimal total maintenance expenses. For the reason of limited size of this paper, only usual functioning scheme of specialized workshops for maintenance of vital brake devices will be presented, Figure 4.

Figure 4: Functioning scheme of specialized work shops: tu-time of use, tv-idle time, to-repairing time, ts-free time, ID-correct part, ND-incorrect part

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RESERVE OPTIMIZATION When a system successfully performs the function of set criteria, it is said that the system meets the and is in operation. Otherwise, when the system does not satisfy, or does not function successfully set of criteria, indicates that the system is in failure and determined that it violated the interdependence of the elements and the relationships between them and their features, and it is necessary to take measures to return the system to work. [08] In practice, two of the most frequently used systems for the renewal of the reserves are [16, 02]: • system of periodic renewal, • system of renewal according to quantity level of reserve. System of periodical renewal means renewal of reserve in equal time intervals and the renewed quantities are different. Purchased quantity depends of (Rd), i.e. of reserve achieved by it, Figure 5. This system is applied on the reserves spent in large scale and evenly. Time elapsed from ordering moment (RD) to their delivery in warehouse

is marked with Tp=T1+T2+T3. Therefore, time of vulcanization and entry time of sealing material in warehouse should be considered (Table 1). What defines a probability distribution law of distribution according to (Equation 1) is called a Poisson distribution, introduced by Simeon Denis Poisson (1781-1840) as a limiting case of binomial distribution provided a large number of experiments, and the probability (p) of occurrence of event (A) in each experiment small. [14] Poisson distribution law defines the boundary layer binomial model, when the volume of samples of part mechanical system tends to infinity, provided that the product of the sample size and the probability of the observed events remain limited. So Poisson, the model used to describe the probability of rare mutually independent (requirement for binomial law) events such as failures of individual components of mechanical systems. Random variable is the realization of a rare event in a given time interval weight. Random variable (r = 0,1,2,3, .......), a Poisson distribution if in equation (1), value (λ) a positive number.

Figure 5: System of periodic renewal of the reserve

Figure 6: System of renewal according to the quantity level of wanted reserve

System of renewal according to quantity level of reserve is shown on the Fig.6. Application of both systems ensures control of costs and provides proper safety of brake system. Managing reserves can be observed as few random values, where rule of distribution is properly described by Poisson’s distribution. In this case reliability can be easily calculated according to equation (1).

• - frequency of reserve usage, • t – time unit. User should form nomograph based on experience and analysis, which ensures that determination of guaranteed reserves relies on factors as: ordering time and establishing (RD), costs of reserve elements and expenses of non-possessing reserve. Experienced by the example of the same-type elements of the complex technical system with approximately constant intensity of failure, (POPS-KNP -Preventive Maintenance by Condition with the Control Level of Reliability) conception is recommended, also based on Poisson’s distribution, equation (2) [16]:

(1) Where: • P – reliability achieved with “r” complete sets of elements in reserve, • r – number of complete sets in reserve, Journal of Applied Engineering Science 10(2012)4, 239

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(2) Where: N – number of (sub)systems observed a – number of the same-type elements in (sub)system tsr – average time in element exploitation n – number of element failures during observed period of exploitation nggr – upper regulation limit If n nggr, then usage of (POPS-KNP) model is prolonged. Otherwise steps should be taken to increase reliability of elements by testing for causes of failure, revising project, change of exploitation conditions or change scale and frequency of control. If reliability could not be increased by these parameters, some other models of maintenance should be considered [16, 05]. SEALING ELEMENTS APPLIED IN BRAKE SYSTEM DEVICES Sealing elements must be replaced in devices whether it is planned or not planned intervention on device. Constructor has great responsibility to choose proper sealing system. Influence of high temperature, aggressive medium, light and ozone, are criteria

for acceptability of construction solution. Also, hardness, tensile strength, extensibility, plastic deformation due to pressure, brittleness etc. are pointing to elastomers as adequate sealing material. Elastomers used in brake system devices are based on NBR–caoutchouc, hardness from 45 to 80Sh. Determination of the temperature–time boundary is according to DIN 53546 (temperatures 100 0C to 160 0C and time from 4h to 672h). Artificial aging of standard samples takes place in the stream of hot air according to DIN 53508 [18]. Selected physical properties observed during the testing are: • breakdown dilatation, • plastic deformation due to pressure, • tensile strength. Considering the request of the constructor that exploitation temperature varies from -40 0C to 80 0C, used methods of selection and testing are guarantee for sealing system to work properly. EXPLOITATION LIFE TIME Under normal conditions for storage of sealing elements made of elastomers on NBR basis, maximal recommended intervals of time from their production to entry in warehouse, exit from warehouse to mounting, and their exploitation life time, are presented in the table 1. If the time interval to reduce the installation, service life for so extended and vice versa.

Table 1: Number of three month period

Element type

Maximal period of time from the quarterly period that follows quarterly period in which vulcanization has been accom- Exploitation life time, plished counted from the mounting Before entry in Before exit from Before mounting warehouse warehouse

O–ring, Cuff, Wiper membrane

4quartal/3months 10quartal/3months 16quartal/3 months 20quartal/3 months

With more severe exploitation conditions exploitation life time must be shorter then shown in the table 1. For example, when the parameter values from table 1, are assigned to equation (1) and requested reliability is defined at Pd 0.98 (Pd 98%), the results are below mentioned indexes for required complete sets of sealing elements, as guaranteed reserves for reliable exploitation of the brake system [08]. 206

1) For = 0.200 (reserve is used once in tcr =5 year period) P(r=0) = 0.819, P(r=1) = 0.983, P(r=2) = 0.998 2) For = 0.111 (reserve is used once in tcr=9 year period) P(r=0) = 0.895, P(r=1) = 0.994, P(r=2) = 0.999 3) For = 0.087 (reserve is used once in tcr =11.5 year period) P(r=0) = 0.917, P(r=1) = 0.996, P(r=2) = 0.999 Journal of Applied Engineering Science 10(2012)4, 239

Dr Radoljub Tomić - Contribution to the evaluation of the compliance for new products with aspect reliability and maintenance

4) For = 0.080 (reserve is used once in tcr =12.5 year period) P(r=0) = 0.923, P(r=1) = 0.997, P(r=2) = 0.999 Relation between P ( , r, t) based on the above mentioned results is shown in the Figure 7. Practically, with the reserve of one sealing elements complete set, Pd=98 can be accomplished; in the case when mounting is performed immediately after the material left the warehouse, achieved reliability would be at level P Pd, i.e. P=0.99 (P=99%).

Figure 7: Relation between P (λ, r, t)

The conclusion is that it is possible to increase system reliability with minimal reserve only in well– equipped market with spare sealing elements, i.e. with high competition level of reliable producers, and other relevant preconditions for the existence of reliable extern reserves. We have been observing that case, so it is obvious that costs of reserve possessing can be minimized. SOME INTERNATIONAL EXPERIENCE IN RAILWAY VEHICLES BRAKE The braking system is a very important aspect of the security subsystem rolling stock. The process of applied technology on the brakes and other systems is very important to the rail service. In China, a group of authors conducted a reliability analysis method using FMEA and BCEU (Brake Control Execution Unit) and in doing so revealed some weaknesses in the components of the braking system to the application statistical analysis of stochastic processes significantly improve system reliability evaluation. [11] In order to improve the reliability and scheduled maintenance brake system of railway vehicles, using the relevant techniques, from classic to new models introduced. Some methods and if Journal of Applied Engineering Science 10(2012)4, 239

they are present for several years, though in practice many are not available because of the extra costs and are increasingly using sophisticated control algorithms and the use of special sensors to detect errors in braking systems, and can be used on other mechanical systems. [07] As for the braking systems of railway vehicles, the introduction of the so-called interesting. vortex electric brakes, which are essentially based on eddy currents. It is a system ECB (Eddu Current Brake), which is mainly used for High-Speed Railway Train (HSRT). The system is suitable because it is independent of the point and the conditions of adhesion, whose coefficients may be variable, changing atmospheric conditions. Such a system reduces maintenance time, increases reliability, without additional electricity demands, as supplied from its own regenerative agregata. was donenumerous simulations regarding the design of the system and the control algorithm of the system uses a linear variation depending on the speed (ECB). Experimental studies have shown that achieving a constant torque on the wheel in the entire operating speed range, with a high degree of reliability. [03,09,01] CONCLUSION Theory base of maintenance of the technical systems and DIN 53000 series standard was used for analysis of a model for providing guaranteed reserve of sealing elements for the brake systems of the railway vehicles. [6]. For assigned reliability level Pd 0.98 (Pd 98%), with application of equation (1), the results have been gathered by identification of the guaranteed reserves of the sealing material and adequate reliability. Practically, with the reserve of one sealing elements complete set, in the case when mounting is performed immediately after the material left the warehouse, achieved reliability would be at level P 0.99 (P 99%). The conclusion is that it is possible to increase system reliability with minimal reserve only in well–equipped market with spare sealing elements, i.e. with high competition level of reliable producers, and other relevant preconditions for the existence of reliable extern reserves. We have been observing that case, so it is obvious that costs of reserve possessing can be minimized. Considering application of sealing elements, in same category as in table 1, we can conclude that if the period of time before mounting decreases, exploitation life time increases for the

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same value and opposite. With more severe exploitation conditions exploitation life time must be shorter then shown in the table 1, so in that case intensity of failures would change, i.e. the number of reserves usage in unit of time would increase, which would affect to guaranteed reserve increase and appropriate expenses. Presented results confirm adequacy of theoretical base and accessibility of the shown concept for identification of model and quantification of indications relevant for referring guaranteed reserves of the brake system sealing elements for railway vehicles. Acknowledgment This work was created as a result of the project, the number of TR 35 031, entitled “Development and application of methods and laboratory equipment for conformity assessment of technical products,” co-financed by the Ministry of Education and Science of Serbia, 2012. REFERENCES 1) Basim Al-Najjar: „Just in time dynamic & cost-efective maintenance (JIT DMAINT) for more reliable production: a case study“, Journal of Applied Engineering Science (JAES), No. 2, 2012, Vol.10, ISSN 1451-4117, doi:10.5937/jaes 10-2132, UDC 33, p.107-115. 2) Čatić D., Tomić R., Pantić R.: „Steering of the light industrial vehicle”, Third International Conference Heavy Machinery – HM ’99, Kraljevo, 27-30. October, 1999., p.4.32-4.37. 3) Daley, S., Newton, D.A., Bennett, S.M., Patton, R.J.:“ Methods for fault Diagnosis in Rail Vehicle Traction and Braking Systems“, Mech. Eng. Centre, Eur. Gas Turbines Ltd., Leicester, Conference Publications, Qualitative and Quantitative Modelling Methods for Fault Diagnosis, IEE, 5/1-513, 1995. 4) Hong-Je Ryoo, Jong-Soo Kim, Do-Hyun Kang, Geun-Hie Rim,Yong-Ju Kim, ChungYuen Won: „Design and Analysis of an Eddy Current Brake for a High-Speed Railway Train with Constant Torque Control“, Centre of Ind. Application, Korea Electrotechnol. Res. Inst., Changwon, Conference Publications, Industry Applications Conference, Conference Record of the 2000 IEEE, p. 277-281. 5) Internal documents, Industry of Hydraulics and Pneumatics »Prva petoletka«-Trstenik, (regulations, procedures, guidelines, software testing, reports, catalogs )

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6) Jovančić M., Tomić R., Pantić R., „Basic aspects of maintaining the vacuum system for heat treating furnaces“, 2 DQM Conference maintenance management’’ ‘99’’, Čačak, 1999., p.174-178. 7) Luo Min, Wu Meng-lin; Wang Xiao-yan: „Study On Reliability Test For Brake Control Execution Unit Of Rail Transit Vehicle“, Railway &Urban Transit Inst., Tongji Univ., Shanghai, China, Conference Publications, p. 1-4, 2010. 8) Marković Z., Petrović P.:”Primena metode statističke kontrole procesa (SPC) sa aspekta kvaliteta proizvoda’’, Journal JUSK-a, No. 2, Vol.26, 1998.,p. 143-147. 9) Pacaiova H., Glatz J., Kacvinsky S., „Pozitive and negative aspect in application of maintenance management philosophy“, Journal of Applied Engineering Science (JAES), No. 2, 2012, Vol.10, , ISSN 1451-4117, doi:10.5937/jaes 102132, UDC 33, p.99-105. 10) Popović P.: „Technical diagnostics and maintenance technology “- Analysis of reliability and maintainability engineering systems, University Singidunum, Excerpts lectures, 2010 11) S.Vukadinović: „Elementi teorije verovatnoće i matematičke statistike“, drugo izdanje,1978., Privredni pregled. 12) Series of standards ISO 9000 and DIN 53 000. 13) Standard EN 50126. 14) Todorović J., Zelenović D.: „Efektivnost sistema u mašinstvu“, Naučna knjiga, Beograd, 1981. 15) Tomić R., Đurđević Ž.: „Key issues in the maintenance of hydraulic systems based on components and devices of the IHP program’’ ,“PPT’’ Hip-2000, Vrnjačka Banja, p.199–207. 16) Tomić R.,Bijelić S.,Tonić M.:“Basic principles on the quality of maintenance of mechanical systems in terms of optimal management of spare parts“. (special topics, review), OMO, XXV, No. 2-3, Belgrade, 1996., p.101-108. 17) Tomić R.,Jovančić M., Radovanović M., „Contribution to maintenance of brakes of the railway vehicle based on products made in IHP“, “Prva petoletka”, RaDMI 2002.,Vrnjačka Banja, p.1443-1452. 18) Tomić R.:„Appendix objectification of domestic developments in relation to the quality system ISO 9000“, 5 DQM Conference “Dependability and Quality Management”, 2002., Belgrade, p.267–273.

Paper sent to revision: 13.03.2012. Paper ready for publication: 05.12.2012.

Journal of Applied Engineering Science 10(2012)4, 239

doi:10.5937/jaes10-2526

Paper number: 10(2012)4, 240, 209-220

FIBRILLAR MATERIAL AS A COBINDER IN COATING COLORS FORMULATIONS DimiÄ&#x2021;-MiĹĄiÄ&#x2021; Katarina* Aalto University, Helsinki, Finland Dr Paltakari Jouni Aalto University, Helsinki, Finland The micro-fibrillated cellulose (MFC) is a potential material which will at least partly substitute the synthetic co- binders, such as carboxymethyl cellulose (CMC), in paper coating color formulations. Co-binders play an important role in controlling both the flow properties and the dewatering rate of coating colors during the application process as well as during the subsequent film immobilization [25, 19, 02]. In this study, MFC fibers are used to substitute standard, synthetic co-binder material, CMC, affecting both dewatering and rheological properties of coating colors. This study was partly attempting to establish standard measurement procedures that can give overall picture of complex rheological behavior of MFC coating colors. Elastic effects of coating color in low shear rate influence both the flow and blade load [23]. By influencing leveling, elasticity, substitution of CMC with MFC influences coating color application and immobilization process, as well as the uniformity and optical properties of the coating film [06] . It has been demonstrated that coating colors which contained MFC fibers as a co-binder had pronounced shear-thinning characteristics which is a desirable property for paper coatings. However, a complete substitution of CMC with MFC fibers in paper coatings induced low retention properties, longer shearrecovery time and fast immobilization of coating colors, which can have a negative influence on leveling and final coating layer uniformity.Coating suspension rheology of the coating influences the coating performance at high speeds. The quality of the coated and printed papers is also affected by the rheology of the suspension [06,26]. Co-binders play an important role in controlling both the flow properties and the dewatering rate of coating colors during the application process as well as during the subsequent film immobilization [23,06]. The micro fibrillated cellulose (MFC) is a potential material which will at least partly substitute the synthetic co- binders, such as carboxymethyl cellulose (CMC), in paper coating color formulations [08,22]. It was expected that the introduction of the MFC material into the coating formulation affects the coating color rheology since the MFC fibers are highly flocculated and have reactive groups on their surface [08].Micro-fibrillated cellulose material (MFC), can beproduced through several pre-treatment and refining routes, each giving products with very differentmorphological and chemical properties [18].It is expected that refining and treatment route of MFC influence traditional coating layer properties as those designed for special purposes [18]. The observation that MFC could be used in paper coating formulations, as a co-binder, since it is biodegradable and has good shear thinning properties, raises a question about the processability of MFC coatings in a high speed coating process(above 1000m/min) [12]. This work focuses on determining general rheological and dewatering behavior of coating colors that contain MFC fibers used as co-binders. A thickener is added to prevent an excessive loss of water from coating color into the base paper and to adjust the rheological properties of the color, a thickener is usually added [03,28]. The physical and chemical properties of the thickeners differ, and they can be roughly divided into synthetic and natural polymers [01]. Water retention and immobilization are the key properties for successful paper coating formulations [21,05]. The task of research is to evaluate how the replacement of CMC co-binder with MFC material influences the viscoelastic and dewatering properties of the coating color [07]. Correlation of the data matrix obtained from dewatering, low-shear viscoelastic and immobilization time measurements show that there is a pattern providing general understanding of the MFC fiber performance in coating suspensions. It is important to understand what the typical behavioral pattern of all MFC coatings would be once they are in the coating process. A key characteristic of the response of a viscoelastic material, as are coating colors, to its deformation during dynamic process, is its ability to recover after cessation of the force which causes deformation [13,04]. * Aalto University, PO Box 110000 Aalto, Finland; katarina.dimic.misic@aalto.fi Paper presented at SIE 2012

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Pigment reactivity with binders and co binders has an important effect in viscoelastic behavior of coating color.It has been proved through many previous research papers that more elastic structures of clay coatings yield larger elastic moduli than the carbonate coatings [05,14]. Key words: Property, Fiber, Coloration, Coatings, CMC OBJECTIVES As micro-fibrillated materials are known to be highly flocculated gel emulsions, it was necessary to examine what kind of reactivity they have with coating pigments and other chemicals in coating formulations. The possible differences in this reactivity with respect to the fiber fineness, and pigments types were also to be determined. In order to get a deeper understanding of MFC fibers used as co-binders and such coating colors rheology, this study aim to give in-depth investigation of the rheological behavior of such coatings in shear rates of industrial interest. Reference, standardly used coating formulations having co-binder CMC, were rheologically and in dewatering terms compared with the MFC-containing coatings. Two different pigments were used, and coating colors made from carbonate, kaolin, and 50% mixture of kaolin and carbonate. Reactivity of differently charged kaolin(anionic– cationic)) and calcium carbonate (all sides cationic) with MFC fibers is expected to increase viscoelasticity though interaction with highly reactive hydroxyl groups of MFC fibers and charges on particles. Bridging mechanismis expected to link MFC fibers and pigments together. After data analysiscorrelationfactorswere calculated between the coating color recipe properties (i.e. solid content, relative amount of nano-fibers per amount of pigment) and coating performance responses. Static dewatering, viscoelastic and low-shear oscillation rheological measurements were accompanied with an immobilization cell, which uses dynamic dewatering data to measure final immobilization time of the coating layer [09,11]. These measuring techniques make connection between the microscopic state of coating suspensions and their macroscopic behavior in process flows. EXPERIMENTAL MATERIALS MFC fibers specification Micro fibrillated cellulose was obtained from UPM –Kymmene Corporation. It was prepared from never dried birch pulp by different pretreatment and refining methods. Masuko was prepared 210

as pulp was passed once through a Voith refiner (Voith AG, Germany) and then seven times through Fluidizer M7115 (microfluidics corp.)The first pass was through a chamber with diameter of 500 μm and 200 μm and the rest through chambers with diameters of 500 and 100 μm at a pressure 1,850 bar.The final solid content of suspension was 3 wt%, and the fibers contained about 25 wt % xylene. Tempo mediated cellulose was obtained as well from UPM –KymmeneCorporation. It was prepared using tempo-mediated oxidation of native cellulose followed by disintegration of the oxidized cellulose fibers in water using a Warning blender.Transmission electron microscope (TEM)observation of the dispersions showed that mostly individualized cellulose fibrils 3-5 nm in width were obtained, Table 1. Swelling and dispersion behavior of the cellulose in water were studied in detail in terms of carboxylate content by spectroscopic microscopic and viscosity analysis, data property of UPM –Kymmene. Pigments specification Two types of pigments were used for both reference (CMC-binder) and MFC coating colors, Tab.1.Coating colors with different pigment packing abilities (Capim RO kaolin and two different carbonate pigments HC-60 and HC-90) were compared in relation to different co-binders. Table 1: Pigments specification Tt

Tempo- mediated with 2% pretreatment chemicals

Tempo-mediated with 4% pretreatment chemical

Masuko treated, 15% carboxymethylated pretreatment l

Tempo-mediated ethanol- dried with pretreatment chemical

Tempo-mediated, dried

Cmd

Masuko treaded, carboxymethylated pretreatment and drying prior refining

Tfs

Tempo-mediated, carboxymethilated and dried

Cme

Masuko treaded, carboxymethilated prior to refining

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Pigments were obtained as pigment slurries in cases, carbonate HC-60 , of 35% consistency and HC-90 37% consistency (HC-60 /HC-90 with 60% /90% less 2μm particle size). Kaolin Capim RO was obtained as slurry, 35% consistency.

Water retention value WRV The wet Tempo-mediated cellulose (Td) and MFC (Mf) were centrifuged at 4500 gravity for 20 min in mixture with reference birch pulp , with different relative consistency, Figure.1

Figure 1: Apparent WRV for MFc fibers

Relative water retention value calculated by interpolation method is presented in Table 2. It is obvious that water retention value for tempo fibers is much higher as generally this fibers are having more reactive groups on fiber surface and have more swollen cell wall. It is more difficult for water to flow through such highly swollen fibers network and go through easily sealed opening of filter cake. Rheological measurements Viscoelastic properties of the suspensions were measured with a stress controlled MCR 300 PaarPhysicaRheometer rotational rheometer, plate-plate geometry with anPeltier element temperature control, temperature during measurements was 23ºC. The gap between plates was 1mm.

0,01-100%). Critical strain of MFC fibers suspensions was determined for consistency of fibers (1, 1.5, 2 and 2.3%) as a point of the breakage of structure in fiber suspension, and can be calculated as τ =G0c, were G0 is storage modulus for liner viscoelastic region, Figure 2. Masuko fibers have higher yield stress as they have less reactive fiber surfaces, less swollen fiber walls and there is more friction between fibers during shearing, which shows as higher storage moduli.

Table 2: Relative water retention value calculated by interpolation method consistency of MFC fibers in filter cake suspention w/w %

WRV, g water/g dry fiber

Masuko 3

9,68

Tempo UPM

24,024

Apparent yield stress were determined using amplitude sweep of 1Hz frequency and strain of Journal of Applied Engineering Science 10(2012)4, 240

Figure 2: Apparent yield stress of MFC fibers

211

212

Tempo 2% Consistency

Carboxymethylated and Dried

Tempo Ethanol pretreated

MFC (Masuko) 5 passes

Carboxymethylated and Dried

Dry Tempo

Tfs

Cme

Cmd

Tempo 4% Consistency

Coating starch

Starch

CMC (Finnfix 10)

100

Latex (Dow 966)

100% Kaolin

Miragloss90

Covercarb 75

Dry solids %

Treatment/Unit

100

100% Kaolin

50% Carb 0% Kaolin

100

pph

100

100% 100% 100% Carbonate Carbonate Carbonate

Reference Coating color

Table 2: Structure of coating colors

Tfs

8,5 8,5 8,5

Cme

Cmd

8,5 8,5 8,5 8,5

MFC Coating Color

Dimić-Mišić Katarina - Fibrillar material as a cobinder in coating colors formulations

Journal of Applied Engineering Science 10(2012)4, 240

Dimić-Mišić Katarina - Fibrillar material as a cobinder in coating colors formulations

COATING COLORS Reference coating colors were made in thjree different solid content (50,55 and 60%) and pigment types (kaolin, carbonate, blend of 50%kaolin and 50 % carbonate), Table.2. Carboxymethyl cellulose (CMC) was chosen as water soluble thickener in the reference coating colors, making the suspensions susceptible to depletion flocculation. In addition, the pH of each coating material mixture was adjusted to approximately 9.5 using NaOH. For MFC coating color preparation for thickener was used Finnfix-10, purified low viscous carboxymethyl cellulose, with degree of substitution of 0.60-0.95, and FF-10 is usually used in coating colors as thickener. MFC coatings were made with blend of 50% kaolin and 50% carbonate pigments. Solid content of MFC coatings was adjusted, so that their Brookfiled100 viscosity stayed within coating color viscosity window, recommended for coating colors, 3000 Pas. Coating colors were prepared following the next order; pigments, OBA, NFC /CMC, with half an hour mixing and then Latex. Testing of the coating colors was first done according to quick test procedure, dry solid content oven drying, Brookfield viscosity 50 and 100 RPM and ÅA-GWR(ÅboAkademi Gravimetric Water Retention Device). Additional dynamical low-shear measurements were performed on a MCR 300 PaarPhysicaRheometer, plate-plate geometry, gap 1mm. The immobilization cell accompanied on rheometer IMC enables the recording of the time to immobilization, i.e. the time for complete build-up of filter cake .The immobilization cell enables monitoring of the dewatering process of applied layers and controlled shear forces through increase in elastic moduli G` and G`` of suspension [14, 09].

Figure 3: Gravimetric dewatering of reference coating colors

It is obvious that kaolin pigment coating color has a more pronounced shear thinning behavior as kaolin with CMC forms three dimensional structure in a coating dispersion (“house of cards” structure) which brakes when shear is applied, only to be again reconstructed after shear ceases [24].Decrease in apparent viscosity measured with increase in spindle rotation rate, from 50 to 100 RPM is shown in Figure 2.

RESULTS Reference coating colors-carboxymethilated cellulose as co-binder As can be seen from Figure 3, the gravimetric dewatering of reference coating colors increases in the order: kaolin<CaCO3 , and at the same time decreases with increase in solid content. This is due to the shape and electric charge of carbonate and kaolin pigments [06, 26, 14], as water passes easily through carbonate pigments but platy kaolin pigments make this passage more difficult. Journal of Applied Engineering Science 10(2012)4, 240

Figure 4: Brookfield viscosity of the reference coating colors

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Dimić-Mišić Katarina - Fibrillar material as a cobinder in coating colors formulations

When measured apparent viscosity on Brookfield viscometer, it is obvious that kaolin pigment coating color has a more pronounced shear thinning behavior as kaolin,through molecular bridging with long CMC chains forms three dimensional structure in a coating dispersion (“house of cards” structure) which brakes when shear is applied, only to be again reconstructed after shear ceases [11, 24]. Decrease in apparent viscosity measured with increase in spindle rotation rate, from 50 to 100 RPM is shown in Figure 4. Within the frequency sweep test( 0,01-100 Hz)

within the linear viscoelastic region ( 1% strain), elastic modulus of clays is higher than that for carbonate coatings, Figure 5. Particle flocks induced by hydrodynamic and surface interactions group together into a macro scale three-dimensional network which comprises the elastic structure of the coating dispersions [20]. Same figure shows that elasticity expressed as storage modulus G`, is higher for kaolin based than carbonate-based coating colors, for all three consistencies, and elasticity is increasing with solid content with more dense packaging of material.

Figure 5.a

Figure 5.b

214

Journal of Applied Engineering Science 10(2012)4, 240

Dimić-Mišić Katarina - Fibrillar material as a cobinder in coating colors formulations

MFC coating colors-micro fibrillated cellulose material (masuko and Tempo based) as a co-binder

trix under the coating layer, but in the case of MFC faster immobilization is achieved with lower solids than in conventional coatings.

As a reference coating for this evaluations was used blend of 50%kaolin 50% carbonate coating color, with 55% consistency, and dewatering band rheological behavior of this particular reference coating color was compared with behavior of MFC coatings. Since MFC fibers have very high water retention as presented at Figure 2, the gravimetric dewatering of MFC based coating colors show higher retention values than for reference coatings, Figure 6. Pretreatment and production route of MFC fibers has as a product fibers with different swelling of fiber wall and surface reactivity and thus some fibers as Mf and Td induced as co-binders drastically increase water retention, while some decrease, as with sample Te.

Figure 7: Brookfield viscosities for MFC coating colors

Figure 6. ÅA-GWR Water retention values for MFC coating colors

For some MFC coatings (Tf, Tt, Cme) apparent (Brookfield viscosity at 50 and 100 RPM) is much higher for MFC coatings than for reference one , as a product of reactivity between pigment particles and highly reactive MFC fibers, while for others (Mf, Td, Tfcs viscosity is lower, Figure 5.a and 5.b. It is important that the coating color immobilizes quickly after metering, and therefore too long immobilization times are not desirable [17, 16]. High solid content normally means a faster immobilization of the coating layer, which reduces the structural changes of the paper maJournal of Applied Engineering Science 10(2012)4, 240

Flow behavior of coatings prior to metering and after the exit from the blade nip depend, to a certain extent, on the viscoelastic parameters, as viscoelasticity influences consolidation on the wet coatings [11, 27]. Wet paper coatings demonstrate a fading memory of recent shearing. The magnitude and rate of recovery after application are defined by the formulation and process speed [13]. Rheological measurements done in frequency sweep mode ( 0,01-100 Hz) at temperature 23º C on MCR 300 rheometer show complex viscosity development for coating colors when samples go from low to high shear, in linear viscoelastic region. The double logarithmic plot in Figure 8 depicts the power law shear thinning behavior of the complex viscosity of MFC coatings, typical for a gel like structures. For some MFC coatings (Tf, Tt, Cme) maximal complex viscosity is much higher than for reference coating, while for others(Mf, Td, Tfcs) maximal complex viscosity is lower, Figure 8. Ratio of maximum and minimum complex viscosity within a defined frequency sweep was calculated and is presented in Figure 9. Shear thinning behavior, desirable in coating process is obtained when MFC fibers are replacing traditional CMC co-binder.

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Dimić-Mišić Katarina - Fibrillar material as a cobinder in coating colors formulations

Figure 8. Complex viscosity curves for NFC and reference (50%. kaolin and 50% carbonate) coating colors; frequency sweep

Figure 9: Shear thinning, ratio of Max/Min complex viscosity for MFC coating colors within a frequency sweep of 0.1- 100 s-1

During frequency sweep measurements MFC coatings have much higher increase on elastic moduli G` at the beginning of measurement, at even very low frequencies, which is because 216

of their high elasticity, which causes immediate response of coating colors to deformation, as Weissenberg effect as shown in Figure10.

Journal of Applied Engineering Science 10(2012)4, 240

Dimić-Mišić Katarina - Fibrillar material as a cobinder in coating colors formulations

Figure 10: Amplitude sweep ,storage and loss moduli- two different MFC coatings(Tfcs and Cme), compared with reference coating ( 50% carbonate 50% kaolin, solid content 55%)

It is important that the coating color immobilizes quickly after metering, and therefore too long immobilization times are not desirable [13]. Inter-

estingly, MFC coating colors immobilize faster although they have a lower solid content than the reference CMC coatings, Figure 11.

Figure 11: Immobilization time for MFC coating colors

A correlation matrix was made comprising data from static, ÅAGWR and dynamical low-shear dewatering with IMC results. Data obtained from these two measurements show a strong corJournal of Applied Engineering Science 10(2012)4, 240

relation, proving the hypothesis that those two measurements correlate [14, 09] as presented in Figure 12.

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Dimić-Mišić Katarina - Fibrillar material as a cobinder in coating colors formulations

Figure 12: Correlation diagram ÅAGWR vs. Immo time, MFC coatings

Figure 13: First and Second Immobilization time vs. final Storage modulus; MFC coatings

218

Journal of Applied Engineering Science 10(2012)4, 240

Dimić-Mišić Katarina - Fibrillar material as a cobinder in coating colors formulations

High solid content normally means a faster immobilization of the coating layer [13], which reduces the structural changes of the paper matrix under the coating layer, but in the case of MFC faster immobilization is achieved with lower solids than in conventional coatings. Even though faster immobilization is desirable in drying process, high elasticity of MFC coatings filter cake can cause problems at leveling and metering nip. In several

types of coating units, a more extended dwell time between application and metering leads to the formation of an immobilized coating color prior to leveling. It is evident from Figure 13 and 14 that for some types of MFC fibers, like for those carboxymethylated prior to refining (Cmd, Cme), both immobilization time and storage modulus of immobilized layer cake are in better range, more similar to those of reference coating colors.

Figure 14: Immobilization diagrams; MFC coatings vs. 50% carbonate 50% kaolin reference coating color

CONCLUSION At low frequencies, elasticity of carbonate coatings increases with replacement of CMC with MFC fibers, while shear thinning is higher for MFC coatings which have kaolin inside. Lowshear frequency sweep oscillation measurements showed that MFC coating colors have astronger” memory effect” after shear from standard CMC coatings, as having higher elastic modulus. Results show that fiber finesse, hence pre-treatment and refining route of MFC fibers determines consolidation, low shear rheology and immobilization time of coating color, as well as there is different reactivity of fibers in respect to pigment types. MFC samples had different amount of fibrous material depending on the type of pretreatments, with less fibrous material indicating a better refining result, higher shear thinning effect, better dewatering /higher Journal of Applied Engineering Science 10(2012)4, 240

immobilization time with lower filter cake elasticity. Generally all MFC coatings had lower water retention and much faster immobilization, than reference CMC coating colors. Acknowledgement This data is from Author`s Licentiate thesis “ Influence of fibrillar cellulose on pigment coating formulation`s rheology”, supervising professor PaltakariJouni,published at Aalto University, Helsinki, 2012. REFERENCES 1) Adams P. D andKuszewskiJ., Crystallography and NMR system: a new software suite for macromolecular structure determination, ActaCrystallogr, 1988, p. 18 2) Åkerholm J., Berg C. and Kirstilä V., An experimental evaluation of the governing mois-

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ture movement phenomena in the paper coating process, Part II, ÅboAkademi University, Finland 3) BackfolkK., Methods for controlling surface contact area of a paper or board structure, Doctoral Thesis, ÅBO Academy, Finland, 2002 4) BarnessH. A., Hutton J. F., WaltersK., An Introduction to Rheology, Coating Conference proceedings, Amsterdam, 1998 5) BourneP. andWeissigH., Structural bioinformatics A John Wiley & Sons Publication, Figures. 15, 18, 34, 2003 6) BruunS-E., Pigment Coating and Surface sizing of Paper, Totally updated version, Paltakari J. ed., Ch. 14, PaperijaPuuOy, Finland, 2009 7) BruunS-E., Pigment Coating and Surface sizing of Paper, Totally updated version, Paltakari J. ed., Ch. 6, PaperijaPuuOy, Finland, 2009 8) DreiffenbergI., Lohmander S., Effects of the air content on the rheological properties of coating colors, Advanced Coating Fundamentals Symposium, 1999 9) Eklund D, Grankvist T., Salahetdin R., Theinfluence of viscosity and water retention on blade forces, PTS Coating Symposium, 21stpaper, Munich, Germany 10) EngströmD. and Ridahl, On the transition from linear to non-linear viscoelastic behavior of CMC /Latex coating colors, Nordic Pulp Paper, 1991 11) EngströmD. and Ridahl, The effect of some polymer dispersions on the rheological properties of coating colors, Tappi press, 1989 12) GrovesR., Ruggles C., Paper Coating Structure – The Role of Latex, PITACoating Conference Proceedings, 1993 13) Jäder J. and JärnströmL., Calculation of filter cake thickness under conditions of dewatering under shear, Annual transactions of the Nordic Rheological Society, vol. 9, p. 113-117, 2001 14) Jäder J., Engström G, and Järnström L., Extensional Viscosity of paper coating Suspensions studies by converging Channel-flow and filament stretching, Annual transactions of the Nordic Rheology Society, vol. 12, 2004

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15) JäderJ., Consolidation and Rheology at High Solid Content, Dissertation; Karlstad University Studies, 2004 16) Kugge C., Consolidation and structure of paper coating and fiber systems, Doctoral dissertation, Stockholm, 2003 17) Kugge C., DaicicJ. and Furo, Compressional rheology of model paper coatings, fundamental research paper symposium, Pira international, Oxford, 2001 18) Leino M., VeikkolaT., A New Board Coating Method, TappiCoating Conference Proceedings, 1998 19) Lepoutre P., Coating structure and surface coverage, Symposium on Surface Coverage, Helsinki, Finland, 1999 20) Lepoutre P., Substrate Absorbency and Coating StructureTappi Journal, 61[5], 1978 21) Li J., Tanguy P., Carreau J., Moan M., Effect of thickener structure on paper-coating color properties, Colloid Polymer Sci. 2001 22) Paltakari J., Puu-21. 3060 Pigment Coating Technology, Aalto University, Finland 23) Pigment Coating and Surface sizing of Paper, Totally updated version, Paltakari J. ed., Ch. 5, PaperijaPuuOy, Finland, 2009 24) Triantafillopoulos N., Paper coating Viscoelasticity, Tappi press, 1996 25) Watanabe J. andLepoutre P., A Mechanism for the Consolidation of the Structure of Claylatex Coatings Appl. Polym. Sci., 1982 26) Willenbacher N., Wagner H., High Shear Rheology of Paper Coating colors-More than just viscosity , Chem. Eng. Technol. 20, 1997 27) Young T, Fu E., Associative behavior of cellulose thickeners and its implementation on coating structure and rheology, Coating Conference Proceedings Tappi press 28) Zeyringer E. and EichingerR., A new method to determine the water retention of coating colours and its impact on mottling of coated paperTappi Advanced Coating Symposium, October, 2010 Paper sent to revision: 07.09.2012. Paper ready for publication: 05.12.2012.

Journal of Applied Engineering Science 10(2012)4, 240

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ALLOCATIVE EFFICIENCY AND QM FACTORS COVARIATE IN SERBIAN INDUSTRY Dr Vesna Spasojević-Brkić* University of Belgrade, Faculty of Mecahical Engineering, Belgrade, Serbia Dr Slobodan Pokrajac University of Belgrade, Faculty of Mecahical Engineering, Belgrade, Serbia Dr Nikola Dondur University of Belgrade, Faculty of Mecahical Engineering, Belgrade, Serbia MSc Sonja Josipović University of Belgrade, Faculty of Mecahical Engineering, Belgrade, Serbia Trends of allocative efficiency and covariate of firm size and efficiency of quality management(QM) factors in the Serbian industry were tested on the unbalanced panel sample of 48 industrial firms from 12 industrial sectors in the period 2004-2009. The obtained results show that 10 of 12 sectors have a positive covariate of participation in the output market and multi-factor productivity. Covariates of firm size and efficiency of all QM factors record the same direction in the chemicals sector (positive) and motor vehicles (negative), which means that in those two sectors larger companies had above-average and/or below-average efficient TQM. The same (positive) trend of allocative efficiency and covariates of all QM factors was recorded in manufacture of chemical industry. Key words: Allocation, Allocative efficiency, Covariation, Industry, QM INTRODUCTION The more recent literature brings a limited number of studies which analyse the relationship between firm performances and quality management. [01], [05], [12]. Results are mixed and often do not support the hypothesis on positive correlation between productivity and efficiency of some critical QM factors [13]. Reallocation of resources significantly influences the level of aggregate productivity of industry from less productive to more productive firms. In this type of studies, aggregate industry productivity is determined as weighted average of firm level total (multi-factor) productivity with market share in industry output as a weight. This method of defining productivity allows decomposition of industry productivity on average productivity and covariate part as sum of cross product of firm size and firm productivity. Such decomposition gives insight into correlation of firm size (market share) and firm level productivity. If the sum of cross product positive industry productivity is improved, the sector resources are allocated towards more productive firms and industry is allocative efficient.

Concurrently, deregulation and market liberalisation may have positive impact on QM practice as companies are trying, in the conditions of increased competition, to have more effective QM. Therefore, thanks to reallocation of resources, more productive firms can be expected to grow bigger and at the same time have more effective QM. Average QM efficiency may be, similarly to productivity, decomposed to average efficiency of critical QM factors and a sum of cross product of firm size and firm QM effectiveness (QM factors covariate). If a covariate is positive, QM effectiveness of the industry is improved. The aim of this research is to examine the trend of allocative efficiency and QM factors covariate. METHODOLOGY Allocative efficiency Market reallocation of resources represents one of key channels for identifying the change in productivity at the level of an industry. [02],[07],[11]. Aggregate multi-factor productivity in industry is average weighted productivity of firms, whereby a weight is share of a firm in the output market:

* Faculty of Mechanical Engineering, Kraljice Marije 16, 11000 Belgrade; vspasojevic@mas.bg.ac.rs Paper presented at the SIE 2012

(1)

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Dr Vesna SpasojeviÄ&#x2021;-BrkiÄ&#x2021; - Allocative efficiency and QM factors covariate in Serbian industry

but also through contributions entering and exiting firms [10]. Contribution of resource reallocation to the change in aggregate productivity can be captured through decomposition of productivity of industry to the product of the deviation of market share of plant from the average market share and firm productivity from average unweighted productivity at the level of the industry:

where represents aggregate productivity in industry (j) in time (t), is market share of plant (i), in industry (j) in time (t), firm level productivity and N represents a number of firms in the sector (j). Industry productivity may vary through changes in allocation of productivity and market share reallocation between incumbent (surviving) firms,

(2) or (3) where represents average unweighted productivity, average unweighted sales participation, difference between participation in company sales and average sales participation and difference between company productivity and average productivity at the level of the industry .Sum of cross product represents productivity covariate (covprod) and contains contribution of resource reallocation to the change in aggregate productivity. If it is positive, industry has a positive allocative efficiency where resources in the industry follow more productive incumbent (surviving) firms. QM factors covariate The covariate of efficiency of QM and firm size comes down to a question whether firms with above-average scale of dimensions of the specific critical QM factor have bigger output market participation. QM efficiency is measured as an average value of the dimension scale for specific critical QM factor. Efficiency of the specific QM factor at the industry level is a weighted average of firm-level efficiency (scale of QM factor at firm level) with market share of industry as weights: (4) where represents a weighted scale of the factor (n), sector (j) in time (t), represents a market share of the firm (i), in the market of the sector (j) and time (t), scale of the factor (n) of the firm (i) sector (j) in time (t) and N represents a number of firms in the sector (j). 222

Weighted efficiency of the specific QM factor in the sector (j) can be decomposed to average unweighted efficiency of factor (n) and the sum of cross product deviation of firm size (i) and efficiency (scale) of the factor (n) in a firm (i): (5) where represents average unweighted efficiency of factor (n), sector (j) in time (t), whereas represents average unweighted market share as a measure of average size of a company in the sector (j) in time (t). If covariate of QM factor (QM cov) and firm size is positive, efficiency of QM factor at the industry level increases. Companies with higher market share (larger companies) had in the observed time a more efficient QM factor. Analysis procedure and results The sample is a stratified random sample drawn from the population of Serbian industrial firms certified according to ISO 9000. The information referring to the determination of MFP and efficiency of QM factor cover the period 2004-2009. The information on company productivity comes from the official financial reports and information about QM practice comes from a questionnaire. Quality management elements or critical QM factors, as the components that will lead to the successful application of the QM concept, were considered for the first time by [03] and the number of available works reported to date is not negligible. Following an analysis of frequency incidence in available literature the QM critical factors shown in Table 1. can be segregated. Journal of Applied Engineering Science 10(2012)4, 241

Dr Vesna Spasojević-Brkić - Allocative efficiency and QM factors covariate in Serbian industry

Table 1: The dimensions of critical QM factors after factor and reliability analysis [13] CRITICAL QM FACTORS

DIMENSIONS FOR CRITICAL QM FACTORS

Leadership and management support for quality program (LID)

L2: Care of Department manager for quality L3: Efforts of company management to improve quality L4: Goal setting and quality policy L5: Establishing regulation for quality

Training and involvement of employees (OB)

OB2: Employees training as priority of the company OB3: Existence of financial resources for employees training OB4: Employees training to apply methods and techniques (tools) for quality improvement

Systemic approach and documentary evidence for quality system (SIST)

SIST1: Availability of data on quality to each employee SIST2: Analysis of collected data on quality in order to improve it SIST3: Existence of Department of quality SIST4: Possession of documents for quality system

Process approach (PROC)

PROC1: Differentiation and description of each process in the company PROC2: Continuous monitoring of key processes in the company and their improvement PROC3: Determination of quality measure for each process in the company PROC4: Participation of machine operator in maintenance

Beneficial interaction with suppliers (ISP)

ISP1: Relying upon a small number of reliable suppliers ISP2: Selection of certified suppliers ISP3: Participation of supplier in program development ISP4: Participation in employees training in quality field at supplier’s firm

Permanent quality improvement (PK)

PK1: Permanent tendency to eliminate internal process leading to waste of time or money PK3: Application of advanced IT to better analyze data and determining priorities to improve quality PK4: Revision of documents for quality system if necessary PK5: Application of methods and techniques to improve quality

Product design according to user demands (PP)

PP1: Coordination of employees from different organizational units in product development process PP2: New product quality as priority in its design and manufacture PP3: Analysis of possibility for manufacture and cooperation in product development

The research instrument proposed initially contains 7 factors with 31 dimensions (Table 1.), which is substantially the lowest of all offered to date. Using recommendations by [13] to recode 25 – 50% of the questions (posed in reverse order relative to other questions), 45.88% of the questions were recorded. All questions had a five-level Likert scale. The majority of questions in the research instrument were taken from or designed using previous research (which is of critical importance in research of this kind as stated in [12, 14]. The information from financial statements is used for the determination of MFP at the indusJournal of Applied Engineering Science 10(2012)4, 241

try level through neoclassical production function, whereby LP algorithm is applied in order to avoid simultaneity. [04]. The data due to QM practice were exposed to factorial analysis to ensure that they constituted reliable indicators of QM constructs. [13]. Based on the determined MFP and selected reliable QM factors by applying algorithms (2),(3),(4) and (5), allocative efficiency and QM covariate of all 12 industrial sectors were determined.

223

Dr Vesna SpasojeviÄ&#x2021;-BrkiÄ&#x2021; - Allocative efficiency and QM factors covariate in Serbian industry

Figure 1: Allocative efficiency and QM factors covariate

The results show that 10 of 12 sectors have positive covariate of output market participation and multi-factor productivity and in those sectors market allocates most resources towards companies with factor productivity above average productivity of the sector. Allocative efficiency in these sectors is increasing in the observed period. Covariates of firm size and efficiency of all QM factors show the same trend in the sector of chemical industry (positive) and motor vehicles (negative), which means that in these two sectors larger companies had QM efficiency above average. In other sectors, the trends of covariate of firm size and scale of QM factor are different. In food-manufacturing industry, an increase of quality with negative covariate is visible, which means that larger companies had efficiency of quality increase below sector average. Training of employees has positive covariate in leather sector, while it is negative in non-metal industry. Metal sector shows a positive covariate of product design, while the sector of machine manu224

facturing has positive covariate of training and negative covariate of quality improvement. In the production of TV sets, values of covariate are very low. In the electrical sector, there is a positive covariate of suppliers, whereas in the construction sector a positive covariate of systemic approach should be noted. In the transport sector, there is a very negative covariate of leadership. If a covariate of firm size and efficiency of all analysed QM factors and a covariate of firm size and MFP are observed only in the sector of manufacture of chemicals and chemical products, the same trends are recorded. It is only in that sector that larger firms record a higher factor productivity and more efficient TQM as well. CONCLUSIONS The chemical industryâ&#x20AC;&#x2122;s predominant use of batch manufacturing processes is in sharp contrast to the use of assembly line production in automotive or computer industries, so it can be expected that these differences influence the reJournal of Applied Engineering Science 10(2012)4, 241

Dr Vesna Spasojević-Brkić - Allocative efficiency and QM factors covariate in Serbian industry

lationship between QM implementation [6]. According to the same authors the strongest contributor to variation in total effects of QM across groups was industry type, followed by size and then QM duration. Typical risks associated with the work in chemical industry require high level of organisation, documented, transparent and effective management systems and therefore, greater attention is given to the standardisation of various management systems. On the other hand, motor vehicles industry in Serbia is in most cases only learning about ISO/TS 16949: 2009, whereby larger manufacturers are for many years in the phase of restructuring and production programme adjustment. Therefore, our result is expected. Work thus offers managers the possibility to allocate available resources subject to the type of industry and size of the company. An important result of this research is also a fact that majority of the sectors have positive covariate of output market participation and multi-factor productivity so that in those sectors the market directs most of the resources towards companies that have factor productivity above average productivity of the relevant industrial sector. REFERENCES 1) Agus A., Ahmad M.S., Muhammad J., (2009) An Empirical Investigation on the Impact of Quality Management on Productivity and Profitability: Associations and Mediating Effect, Contemporary Management Research, Vol. 5, No. 1, pp. 77-92. 2) Baily, M., Hulten, C., and Campbell, D. (1992). Productivity dynamics in manufacturing plants. In Brookings Papers on Economic Activity: Microeconomics, Brookings Institute. Vol. 4, pp. 187-267. 3) Benson G, Saraph J, Schroeder R (1991). The effects of oranizational context on quality management: An Empirical Investigation. Manag. Sci. 37(9): pp. 107-1124. 4) Dondur, N., Pokrajac, S., Spasojevic Brkic, V., and Grbic, S. (2011) Decompisition of Productivity and Allocative Efficiency in Serbian Industry, FME Transactions, Vol. 39, N0 2, pp.73-78. 5) Feng M., Terziovski M., Samson D., (2008) Relationship of ISO 9001:2000 quality system certification with operational and business performance - A survey in Australia Journal of Applied Engineering Science 10(2012)4, 241

and New Zealand-based manufacturing and service companies, Journal of Manufacturing Technology, Management, Vol. 19. No. 1, pp. 22-37. 6) Grandzol JR, M Gershon, 1997. “Which TQM Practices Really Matter: An Empirical Investigation”, Quality Management Journal, Vol 4 No 4, pp. 43-59. 7) Griliches, Z. and Regev, H. (1995). Firm productivity in Israeli Industry: 1979-1988. Journal of Econometrics, 65, pp. 175-203. 8) Jayaram J., Ahire S.L., Dreyfus P., (2010) Contingency relationships of firm size, TQM duration, unionization, and industry context on TQM implementation - A focus on total effects, Journal of Operations Management 28. pp. 345–356. 9) Madu, C., (1998). An Empirical Assessment of Quality: Research Consideration, International Journal of Quality Science, 3(4). pp.348-355. 10) Melitz, M. and Polanec, S. (2009). Dynamic Oley-Pakes Decomposition with Entry and Exit, manuscript. 11) Olley, S. and Pakes, A. (1996) The Dynamics of Productivity in the Telecommunications Industry. Econometrica, 64(6), pp. 12631298. 12) Spasojevic Brkic, V,. Djurdjevic T,. Omic, S,. Klarin, M,. and Dondur, N., (2011). An Empirical Examination of Quality Tools Impact on Financial Performances: Evidence from Serbia, Serbian journal of Business Management, 7(1), pp.77-88. 13) Spasojevic Brkic, V., Dondur, N., Klarin, M., Komatina, M., & Curovic, D. (2011). Effectiveness of quality management and total factor productivity. African Journal of Business Management, 5(22), pp. 9200–9213. 14) Spasojevic-Brkic, V., Klarin, M., Curovic, D. (2009): Dimenzije menadžmenta kvalitetom isporučioca u industrijskim preduzećima Srbije. Journal of Applied Engineering Science (Istraživanja i projektovanja za privredu), no. 23/24, pp. 67-70 Paper sent to revision: 10.08.2012 Paper ready for publication: 06.12.2012.

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doi:10.5937/jaes10-2522

Paper number: 10(2012)4, 242, 227-233

COMBINATION OF KNOWLEDGE IN THE SYSTEM SUPPLIERS - MSP - CUSTOMERS IN THE TRANSITIONAL ECONOMY ENVIRONMENT IN SERBIA MSc Marija Savić* University of Belgrade, Tehnical Faculty in Bor, Bor, Serbia MSc Predrag Đorđević University of Belgrade, Tehnical Faculty in Bor, Bor, Serbia Dr Đorđe Nikolić University of Belgrade, Tehnical Faculty in Bor, Bor, Serbia Dr Ivan Mihajlović University of Belgrade, Tehnical Faculty in Bor, Bor, Serbia Dr Živan Živković University of Belgrade, Tehnical Faculty in Bor, Bor, Serbia The paper presents the results of research of the combination of knowledge in the system: suppliers - SMEs - consumers in case of SMEs in Eastern Serbia. A theoretical model of a combination of knowledge was established in the investigated system. By using the statistical analysis of the results a satisfactory statistical significance of acquired results was determined, which allowed the testing of the defined model using LISREL software package. The results show the importance of the established hypotheses for the impact of the cooperation with suppliers on a combination of knowledge, as well as the combination of knowledge of customers and suppliers on the creation of the new knowledge in SMEs. The hypothesis about the positive influence of the sharing of knowledge with customers on the combination of the knowledge in SMEs has not been proven. These facts suggest that SMEs in Serbia do not collaborate with their customers. The cause of such a situation is the lack of system quality (SQ) in the SME sector in Serbia, as well as not applying the principles of TQM practices, which provides the best explanation of the short life cycle of SMEs in Serbia and the inability of their internationalization. Key words: SMEs, Customers, Suppliers, Knowledge, Combination, LISREL INTRODUCTION The concept of small and medium enterprises (SMEs) is particularly developed in the U.S., and has recently been experiencing an expansion in Europe [01].The development of SMEs in Europe is slower because of the barriers in the process of starting a new business and the fear of failure [02, 17]. SMEs in developed economies are complementary to large companies, which provides them with safety in their work, growth and development [10, 02]. In transition economies in post-communist countries (countries of the former USSR, the countries of the former Warsaw Pact, countries that emerged from the disintegration of Yugoslavia....) there is a great desire, among entrepreneurs, to create

their own businesses and to start new SMEs, but many attempts have been unsuccessful. Unsuccessful attempts were usually caused by a lack of knowledge of entrepreneurs, who gained their experience in the state-owned companies. In the educational systems in these countries, until recently, there were no elements pertinent to the field of private enterprise, therefore the knowledge to start and run a private business was obviously lacking among entrepreneurs [03, 04]. In Serbia, which has been going through the transitional process for a long period of time, the expansion of the starting SMEs actually takes place after the year 2000. The motivation for the creation and development of SMEs is growing during 2009 and onwards, due to the global economic crisis and high unemployment.

* Tehnical Faculty in Bor, Vojske Jugoslavije 12, 19210 Bor, Serbia; msavic@tf.bor.ac.rs Paper presented at the SIE 2012

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In such conditions, the survival of SMEs during the period of economic crisis is becoming more difficult, which causes many SMEs to fail. Development Strategy for SMEs can be defined as the creation of knowledge and the concepts of utilizations and adaptation of knowledge artifacts (knowledge artifact) which are necessary for the key elements of the SMEs functioning (Jarzabkowski and Wilson, 2006). Many studies show that the knowledge is transferable in certain organizational systems such as TQM [18]. According to the theory of entrepreneurship, SMEs innovative behavior is conditioned by a combination of knowledge that is widespread, which means that different individuals know different things [26]. Science has established networks of knowledge [05] through the various concepts, such as learning through a network, relationship memory [07, 22]. Within the concept of entrepreneurial activities, innovative behavior is caused by a combination of knowledge which can be created within the concept of knowledge networks of SMEs with their customers and suppliers [23], which in many cases can lead to the creation of the new knowledge [22] In terms of globalization of the market, many SMEs become more international [28, 17] and the terms of the concept of creating a network of development produce good results, leading to the emergence of entrepreneurial firms with high technological performance as a consequence of the accumulation of knowledge in the process of combining knowledge [26]. The system suppliers - SMEs - customers, if the activity of SMEs is internationalized, creates good opportunities for the creation of a network of different knowledge whose combination can create a new knowledge which presents a basis for growth and development of SMEs (Street and Cameron, 2007). In terms of transitional economy in Serbia, with high entropy in the system suppliers - SMEs - customers, the creation of the new knowledge, by combining existing knowledge in certain areas of the defined system, can be a good starting point for improving the performance of SMEs in Serbia. THEORETICAL BACKGROUND AND HYPOTHESES Many SMEs have a problem with limited resources, which limits their business activity on the market, where they operate in one way in activities on domestic market, and in different way 228

in the process of internationalization of business. Very often the missing resources cannot be provided through the proprietary possession, therefore SMEs become dependent on the resources they utilize from the network with customers and suppliers [28] In accordance with the substantive arguments of this study, SMEs are dependent on the knowledge network of clients and the knowledge networks of suppliers, because these categories provide different knowledge which is the instrument for combining the knowledge [27]. Knowledge derived from these networks, in the case of SMEs, may consist mainly of market knowledge (consumer preferences, market conditions) and technological innovation [25]. Market knowledge is usually associated with a network of consumers, but may be associated with the network of suppliers. Technological knowledge is usually associated with a network of suppliers, but may be also connected to the network of consumers. Knowledge within the networks of SMEs with customers and suppliers can be acquired by reacting to exogenous situations, as well as through conscious and planned efforts by SMEs [26]. Modern SMEs should be actively operating in the network capabilities of customers and suppliers, which implies that they must work to change the existing combination of knowledge and to find new ones. These findings enable definition of the following hypotheses: H1 Supplier knowledge positively affects the combination of the knowledge in SMEs. H2 Customer knowledge positively affects the combination of the knowledge in SMEs. Research suggests that knowledge-based view serves as an important tool for understanding the spread of entrepreneurial firms [21] Current knowledge is not sufficient and requires constant accumulation regardless of whether SME operates at the local level or the international level [16].Therefore, SME performance depends on its ability to create knowledge, to combine it order to achieve the objectives required by the market [28]. It was determined that the business opportunities are improving more rapidly and developing more innovatively with the knowledge that is being actively developed as opposed to the knowledge gained by experience over time [08]. Activities that take place through a combination of knowledge adjusted dynamics of the SMEs with the dynamics of the market. Therefore, the combination of knowledge will enhance the acJournal of Applied Engineering Science 10(2012)4, 242

MSc Marija Savić - Combination of knowledge in the system suppliers - MSP - customers in the transitional economy environment in Serbia

cumulation of knowledge which will enhance the performance of SMEs. These facts allow the definition of the following hypotheses: H3 Combining knowledge of suppliers and customers has a positive impact on the creation of the knowledge in the SMEs. Based on the defined hypothesis it is possible to define a theoretical model of a combination of knowledge in the system suppliers-SME-customers to increase the knowledge, in order to increase the performance of SMEs, Figure 1. DISCUSSION OF RESULTS The studies presented in this paper were carried out through a questionnaire given in Appendix A [28]. Studies were conducted in the Eastern Serbia in a total of 536 SMEs, by surveying entrepreneurs during the visit to their firms. The questionnaire was administered in a way that the interviewer conducted an interview with the entrepreneur. The questionnaire has four groups of dependent variables (DV) supplier knowledge (DV-1), customer knowledge (DV-2), knowledge combination (DV-3) and the creation of knowledge (DV-4), within which 10 independent variables are contained.

Figure 1: The theoretical model of the combination of knowledge in the system: suppliers - SMEs – customers

The demographic structure of the sample is as follows: with the sample of entrepreneurs, in the most devastated part of Serbia, 71% were men and 29% were women entrepreneurs. Most of the SMEs were as follows: 75% had up to 10 employees, 22% had 10-30 employees and 3% had 50-250 employees. Time from starting a business: 11% up to 1 year; 18% 1-3 years; 25% 3-5 years; 24% 5 – 10 years and 22% over 10 years. Investigated SMEs belong to the sector of: agriculture - 11%; transport - 24%; industry - 5%; tourism - 7%; service sector - 45% and healtservice - 8%. Demographic characteristics of the sample indicate that the dominant strucJournal of Applied Engineering Science 10(2012)4, 242

ture in the SMEs belongs to the service sector, the existence of most companies was noted to be up to five years and that the dominant structure of entrepreneurs male. Likert’s five-point scale (1 - completely disagree, 2 - disagree, 3 - undecided, 4 - agree and 5 completely agree) was used for testing, with results presented in this paper. This methodology has been used in numerous previous studies [18, 14, 24, 15], which justifies the validity of the utilized methodology. A statistical analysis of the results obtained in our research and validation of theoretical models defined in Figure 1. were performed by using the software packages SPSS v18 and LISREL (Linear Structural Relationship) v16. For the empirical validation of the hypothetical model, Figure 1., a SEM [22]. In the statistical analysis of the validation of the defined models, firstly one-dimensionality was confirmed, using factor analysis (PCA), across all 10 groups of latent variables in the considered model. The values obtained by factor analysis are shown in Table 1. To ensure the reliability and validity of the research model a control measurement model was defined on which confirmatory factor analysis (CFA) was performed. CFA analysis confirmed the good fit of the control model, which practically verifies that 10 defined variables describe, in a reliable way, the four latent class variables, defined in the research model, Figure 1. Consistency of variables, defined in the framework of latent classes in the investigated model, was measured by the size of the Crombach’s alpha [09]. Acquired values of the Crombach’s alpha > 0.7, Table 1, show good consistency of certain variables within the four defined latent groups of variables in the investigated models. Crombac’h alpha value for the whole population is 0.98, so the obtained data can be considered reliable for the testing of the proposed model [06]. The values of the t-tests are used to test the hypothesis that the sample does not differ from the population, which shows the tendency of the normal Gaussian distribution; t values should be greater than 2. Results obtained in Table 1 show that in all cases t - values are greater than 2, with the significance level of p < 0.05, which indicates that values in the tested model, are statistically reliable [12]. To study the discriminant validity of various groups of questions the Structural Equation Modeling (SEM) was performed, by comparing pairs of latent class-

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defined questions on the principle of two by two. Table 2 shows the results of discriminative validity and the correlation between the four groups of questions. Positive values of Pearson’s coefficient were obtained

with statistical significance of p < 0.05, which indicates that the correlation of random pairs of groups of latent variables are true [19].

Table 1: The results of the factor analysis and CFA analysis of the investigated model Factor analysis (EFA) Groups of questions

Considered variable

Confirmatory factor analysis (CFA)

PCA

Convergent validity

Reliability

% of variance explained by one-dimensional factor

Factor loading

Cronbach`s alpha

Factor loading

t -statistics

Supplier knowledge: ZV-1

L1 L2

67.343

0.911 0.804

0.891

0.830 0.703

4.13*

Client knowledge: DV-2

L1 L2

82.392

0.861 0.906

0.942

0.836 0.932

6..56* 6.14*

Knowledge combination: DV - 3

L1 L2 L3 L4

49.937

0.718 0.842 0.872 0.975

0.956

0.631 0.775 0.769 0.845

6.53* 4.04* 5.10* 6.74*

Knowledge creation DV - 4

L1 L2

89.236

0.881 0.801

0.956

0.887 0.775

8.02* 4.75*

8.19*

* p < 0.05 Correlations between pairs of latent classes of variables, associated to the defined model, Figure 1. have values of Pearson’s coefficients generally above 0.12 (coefficients marked bold in Table 2). The highest value of correlation exists between knowledge of suppliers and knowledge combinations (0.44 with p < 0.05), indicating that entrepreneurs perceive the dominant influence on customer knowledge on the knowledge combination in SMEs. The lowest correlation with the value of Pearson’s coefficient of 0.12 with p < 0.05 refers to the influence of a combination of knowledge of customers and suppliers on the creation of the new knowledge, indicating a poorly developed mechanisms for combining knowledge with the goal to create new knowledge in terms of SMEs operation under the conditions of transitional economy in Serbia. Table 2: Analysis of the discriminant validity correlation of the latent class-defined questions Groups of variables DV- 1 DV- 2 DV- 3 DV-4

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DV- 1

DV- 2

0.39*

DV- 3

0.14*

0.44*

DV- 4

0.31*

0.33*

0.12*

To test the validity of the model defined in Figure 1. software package LISREL v16 was used for statistical data analysis, considering that the statistical reliability of the data for the model validation is satisfactory. Firstly, the values of indicators were determined, which determine whether the proposed model adequately fits the input data. The results of the analyzed fitting indicators are shown in Table 3. Goodness-of-fit index (GFI) is the extent to which the model is applicable in comparison with the case where a model does not exist. Good fitting is indicated with GFI value above 0.90 [18]. In this case the value of GFI of 0.96 is above the threshold. V Indicator Root Mean Square Error of Approximation (RMSE) shows the errors that occur during the approximate connection of populations. Good value of the RMSA indicators is within the limits of 0.08 – 0.10. The obtained value of this indicator 0.081 shows, together with the GFI indicator, a satisfactory coincidence. In addition to GFI and RMSA indicators for assessing the quality of fitting the following indicators are also being used: Normed fit index (NFI), Comparative fit index (CFI), Incremental Fit InJournal of Applied Engineering Science 10(2012)4, 242

MSc Marija Savić - Combination of knowledge in the system suppliers - MSP - customers in the transitional economy environment in Serbia

dex (IFI) Relative Fit Index (RFI). Following values were obtained in the tested model : 0.92, 0.92, 0.93 and 0.92, respectively. The values were above 0.9 therefore they can be regarded as absolutely satisfactory. Also, an indicator of Minimum Fit Function Chi-Square/Degre of Frededom X2/d.f. should be considered, which in this case has a value of 1.93, where the required value should be less than 3.

positive effect on the entrepreneurial combining of knowledge of firms and the creation of new knowledge, which in accordance with the results of the investigation of SMEs in Sweden [26].

Table 3: Summary values for the fitting indicators Indicators of the Values obtained Recommended fitting statistics in the model values X2/d.f.

59.97/31 = 1.93

< 3.0

RMSEA

0.081

0.08 – 1.0

GFI

0.96

> 0.9

NFI

0.92

> 0.9

CFI

0.92

> 0.9

IFI

0.93

> 0.9

RFI

0.92

> 0.9

The obtained values of the considered fitting indicators of indicate a satisfactory level of fitting in the suggested model which suggests that the regression coefficients of the paths can be calculated in the defined theoretical model in Figure 1. By using LISREL v16 the path-regression coefficients were determined (correlations between the latent class variables defined in the model which is shown in Figure 1) and the obtained results are shown in Figure 2. The results in Figure 2. indicate that the hypotheses H1 and H3 in the defined model have positive values of path coefficients with the values for t above 2 and the statistical significance of p < 0.05, indicating that these hypotheses are confirmed. The obtained value of - 0.10 for the path coefficient of the H3 hypothesis is negative and t = - 0.29, indicating that H3 is not proven. CONCLUSION Bearing in mind the proposed hypothetical model of knowledge creation by combining knowledge in the system suppliers - SME - customers in SMEs in the transition economy in Serbia, Figure 1., and obtained results in Figure 2., hypothesis H1 and H2 were confirmed while the hypothesis H3 is not confirmed. Hence, it was confirmed that knowledge has a positive effect on the combination of entrepreneurial skills of a company, as well as on developing the dependence on supplier knowledge networks which have a Journal of Applied Engineering Science 10(2012)4, 242

Figure 2: Structural model of the combination of knowledge in the system: suppliers - SMEs – customers in Serbia (t - values in parenthesis) Level of significance: * < 0.05

Our research has shown that information obtained from clients do not have a positive effect on the combinations of entrepreneurial firms knowledge, which means that manufacturers do not rely on knowledge of clients (consumers) because it does not contribute to new knowledge in entrepreneurial firms. This result can be explained by under-developed marketing function in the investigated SMEs in Serbia, which indicates a low level of compliance with the requirements of clients, including the lack of TQM practices in investigated SMEs. Transitional conditions in Serbia: the reforms, restructuring, price liberalization, the establishment of a strong private sector and the fulfillment of the EU requests, still holds Serbian borders closed for major business projects, which is slowing down the internationalization of Serbian SMEs. Due to the confusing situation in the market customers have lost their vision of what they want in the market, and suppliers use this as an opportunity to sell to the market what they have, by providing favorable terms of payment of purchased goods. Most entrepreneurs are determined to purchase goods offered by suppliers, while not being informed if customers have a demand for it or not. Due to the organizational and business culture in Serbia overloaded with transitional restrictions, client’s culture, and primarily due to a lack of quality standards, most of the SMEs are

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confident that they will sell on the Serbian market whatever they offer. APPENDIX A QUESTIONNAIRE DV-1 (Supplier knowledge) 1. Your relationships with key suppliers depend on information, knowledge and experience you acquire from them. 2. Your relationships with other suppliers in the market depend on information, knowledge and experience you acquire from them. DV - 2 (Client knowledge) 1. Your relationships with key clients depend on information, knowledge and experience you get from them. 2. Your relationships with other clients in the market depend on information, knowledge and experience you get from them. DV-3 (combination of knowledge) 1. Business partners (customers and suppliers) are a source of information, knowledge and experience to you. 2. The relationship with your business partners (customers and suppliers) is characterized by mutual adjustments 3. The relationship with your business partners (customers and suppliers) is characterized by an exchange of information, knowledge and experience. 4. How familiar are you with the business partner’s (customers and suppliers) information, knowledge and experience? DV-4 (Knowledge creation) 1. The relationship with your business partners (customers and suppliers) result in the creation of new products/new services. 2. The relationship with your business partners (customers and suppliers) result in new procedures, practices of the organizational details etc. in your company. REFERENCES 1) Acs., Z.J., Dana, L.P., Jones, M., (2003) Toward new horizons: The internationalization of entrepreneurship, Journal of International Entrepreneurship, 1:5-10. 2) Audretsch, D.B., Thurik, A.R., (2000) Capitalism and democracy in the 21st centry: from 232

the managed to the enterpreneurial economy, Journal of Evolytionary Economics, 10: 17-34. 3) Benzing, C., Chou, H.M., Shabo, B., (2005) Hungarian and Romanian enterpreneurs in Romania – motivation, problems and differences, Journal of Global Busines, 16: 77-87. 4) Benzing, C., Chu, H.M., Kara, O., ( 2009) Journal of Small Business Management, Enterpreneurs in Turkey: A factor analysis of motivations, Success factors and problems, Journal of Small Business Management 47(1): 58-91. 5) Bolomstermo, A., Eriksson, K., Lindstard, A., Sharma, D., (2004) The percieved usefulness of network experimental knowledge in the internationalizing firm, Journal of International Management , 10(3): 355-374. 6) Bou-Luslar, J.C., Escrig – Tena, A.B., RocaPuig, V., Beltran – Martin, I., (2009) An 7) Cegerra – Navarro, J., (2007) Linking exploration with exploration through relationship memory, Journal of Small Business Management, 45(3): 333- 354. 8) Crick, D., Jones, M.V., (2000) Small hightechnology firms and international high – technology markets, Journal of International Marketing, 8(2): 63-85. 9) Crombach, J.I., (1951) Coefficien aplha and the ingternal structure in tests, Psychometrica , 16: 297 – 334. 10) Dyer, J.H., Nobeoka, K., (2000) Creating and managing a high –performance knowledge – sharing network : the Toyota case, Strategic Management Journal, 21(3):345-368. 11) Empiriical assessment of the EFQM excellence model: Evaluation as a TQM framework relative to the MBNQA model, Journal of Operations Management, 27 : 1 – 22. 12) Ho, R., (2006) Handbook univariante and multivariante data analysis and interpretation with SPSS, Central Queensland University Rockhampton, Australia 13) Jarzabkovski, P. And Wilson, D.C., (2006) Actionable strategy knowledge: A practice perspective, European Management Journal, 24(5): 348-367. 14) Kale, P., Singh, H., Perlmutter, H., (2000) Learning and protection of proprietary assets in strategic alliances: bulding relational capital, Strategic Management Journal, 21, 217- 237. Journal of Applied Engineering Science 10(2012)4, 242

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15) Kayank, H., (2003) The relationship betwen total quality management practices and their effects on firm performance, Journal of Operations Management 21(4), 405 – 435. 16) Knight G.A., Cavusgil, T., (2004) Innovation organizational capabilities and the Bornglobal firm, Journal of International Business Studies, 35(1): 124-141. 17) Moen, O., (2002) The born globals: A new generation of small European exporters, International Marketing Review, 19: 156 – 175. 18) Molina, L.M., Montes, L.J., Moreno, A.R., Relathionship betwen quality management practices and knowledge transfer, Journal of Operations Management, 25: 682-701. 19) Moris, H. DeGroot, Mark S. Schervish (2002) Probabiolity and Statistics, Addison – Wesley, p.485. 20) Omerzel, G.D., Antončič, B., (2008) Critical enterpreneur knowledge dimensions for SME performance, Industrial Management & Data systems, 108(9): 1182 – 1199. 21) Rialp, A., Rialp, J., Knight, G.A., (2005) The phenomenon of early internationalizing firms: what do we know after decade (1993-2003) of scientific linquiry , International Business Review, 14(2):147-166. 22) Soda, G., Usai, A., Zaheer, A., (2004) Network memory: the influence of past and current networks on performance, Academy of Management Journal, 47(6): 893-906.

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23) Street, C.T., Cameron, A.F., (2007) External relationchips and the small business: a review of small business alliance and network research, Journal of Small Business Management, 45(2): 239 - 266. 24) Tari, J.J., Molina, J.F., Castejon, J.L., (2007) The realatonship between quality management practices and their effects on quality outcomes, European Journal of Operational Research, 183: 483- 501. 25) Thorpe, R., Holt, R., Macpherson, A., Pittaway, L., (2005) Using knowledge within small and medium-sized firms : a sistematic review of the evidence, International Journal of Management Reviews, 7(4): 257-281 26) Tolstoy, D., (2009) Knowledge combination in a foreign-market network, Journal of Small Business Management, 47(2):202-220. 27) Uzzi, B., Lancaster, R., (2003) Relational emeddedness and learning: the case of bank Loan Managers and thier clients, Management Science, 49(4): 383-399. 28) Zahra, S.,Matherne, B., Carleton, J., (2003) Technological resource leveraging and the internalisation of new ventture, Journal of International Enterpreneurship, 1(2): 163- 186. Paper sent to revision: 14.09.2012. Paper ready for publication: 07.12.2012.

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EVENTS REVIEW

ENERGY DAYS 23rd-25th October 2012 The Province Secretariat for Energy and Mineral Resources for many years focus its activities to the promotion of the energy sector, particularly renewable energy, energy efficiency improvement and cooperation with potential investors who wants to direct their resources in the energy sector. Therefore, Secretariat actively participated in both the exhibition and the congress event INVESTEXPO, which is traditionally held in late October at the Novi Sad Fair. During the mentioned event ENERGY DAYS, that were held from 23-25. October 2012 in the Master Center of Novi Sad Fair, following conferences has been held: • Conference “The potential of investments in the energy” (23.10.2012.) that presented possibilities for realization of projects in renewable energy and energy efficiency sector, as well as examples of good practice of investing in various forms of renewable energy, with special focus to models of public-private partnership and potential investors. • Scientific Conference “Natural Gas” (24.10.2012.) that discussed the current issues: ensuring supply security, investment opportunities and increase potential of the natural gas consumption over other fuels, natural gas quality, the new legislation, the protection of fire in the field of natural gas, possibilities of natural gas use in combination with renewable energy sources, as well as the possibility of using compressed natural gas, especially as fuel for motor vehicles. • Scientific Conference “Energy and agro-processing” (24.10.2012.) that presented topics related to the use of all forms of biomass for energy purposes such as solid biomass, liquid (bio-diesel) and gaseous (biogas). In cooperation with the Ministry responsible for the Diaspora, this event provided a video conference with the presentations of international experience in the field of biomass. • 6th International Forum on Renewable Energy “Serbian Energy Challenge 2020-30-50” (24-25.10.2012.). The subject of the Forum was future of energy in Europe and in Serbia. Partner of the Forum was the Republic of Finland that presented the best practices of the use of various forms of renewable energy. First year of the use of photovoltaic power plant at FTS building was presented, as well as a new program for renewable energy in schools. The event ENERGY DAYS gathered large number of representatives of energy companies, local governments, businesses, citizens and all interested to hear the positive case studies due to the fact that future investment in the energy sector could be best implemented through available technical, production, implementation and financial capacity.

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ANNOUNCEMENT OF EVENTS IIPP QUALITY MANAGEMENT SCHOOL Considering business conditions of European market, quality has a significant role, not only in providing new markets, but also in maintaining the existing ones. Nowadays, customers do not only expect a quality product, but they require a proof that the company is capable to produce high quality products and provide quality services. Obtaining of this evidence should be the first goal for each company that has high aspirations when it comes to new markets but also standard’s procedure in order to maintain its reputation. Implementation is not complete if employees are not familiar with standards. With the aim to closer inform the employees of the meaning and significance of ISO standards, Institute for research and design in commerce & industry – IIPP organize training “School of Quality”. During the training participants will: • expend their knowledge about implementation of ISO standards, • learn how to maintain and improve quality level of companies • learne how to verify and improve business performance of companies Training will be held during four days in two locations. First lectures will be held at the Faculty of Mechanical Engineering in Belgrade, while the final lecture and the test will take place in attractive location in Serbia - Zlatibor. Programme • Fundamentals of quality concepts, definitions, approaches • Standards, review and interpretation • Management Responsibility • System and process approach • Data management, information system • Statistical methods (engineering methods, quality management methods) • RISK, FMEA, FTA • Supply and storage, evaluation of supplier • Maintenance • Evaluation, audit, certification • Examples, practice, Deming management experiment • PAS 99 - Integrated Management Systems Result After implemented training, Qiipp consultant is able to assume responsibility for independent work in the following fields of activity: • Implementation of quality standards • Maintaining a high level of quality • Constant improvement of the quality system • Assessment and audits of own companies and their suppliers Candidates who passe the test will get a diploma “Qiipp consultant for implementation, maintenance, analysis, evaluation and testing, design and improvement of the quality system”. Time and location: March 2013, Belgrade, Faculty of Mechanical Engineering info: www.iipp.rs Institute for research and design in commerce & industry Phone: 011/6300750; Fax: 011/6300751; E-mail: office@iipp.rs; web: www.iipp.rs

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ANNOUNCEMENT OF EVENTS IIPP MAINTENANCE MANAGEMENT SCHOOL Maintenance Management School presents practical experience in combination with adopted theoretical knowledge, thus creating maintenance management experts capable to perform and coordinate the maintenance of complex technical systems. Use unique opportunity to expand knowledge in the field of technical systems maintenance. During fourdays training focus will give to the following topics: • Maintenance Objectives and Policies • Corporate/Company Environment • Maintenance Concepts • Work Planning • Maintenance Terminology • Team Working and Communications • Laws and Regulations • Information Technology • Condition Monitoring • Quality Assurance (Systems) • Fault Finding Techniques • Environment and Occupational Health and Safety • Spare Part Management The school program merges best local knowledge and experience modernized and harmonized with the recommendations of European Federation of National Maintenance Societies. Since Maintenance Management School connected and unified local tradition and experience in the maintenance process with the European norms and requirements, it’s result is thus twofold - to all who signed up gives a chance to gain national certificate ’’Expert for maintenance management” and to those who can and want more, Maintenance management school opens the possibility of obtaining the International certificate “European maintenance manager”. Result: More than 240 national certificates and 16 internationally recognized certificates: European Maintenance Manager. Time and location: March 2013, Belgrade, Faculty of Mechanical Engineering Info: www.dots.rs

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BOOK RECOMMENDATION Recommended by prof. dr Slobodan Vujić METODE OPTIMIZACIJE U INŽENJERSKOM MENADŽMENTU OPTIMIZATION METHODS IN ENGINEERING MANAGEMENT Author: prof. dr Mirko Vujošević, University of Belgrade, Faculty of organizational sciences This book is devoted to engineering problems in decision-making and management. It is a result of the author’s long time research in the area of optimization methods and their application in engineering practice. The accent is put on planning and decision problems. The operations research and system engineering methodology is used. The monograph is designed to professionals, practitioners who use or should use contemporary scientific methods in studying and solving management problems in complex systems. Some parts of the text might be useful for students of academic master and doctoral studies in the area of management, engineering, economy, artificial intelligence and applied mathematics. It consists of five chapters: Introduction to optimization (28 pages), Integer programming (37 pages), Constraint programming (42 pages), Multi-criteria optimization (20 pages), and Computational complexity (30 pages). The text is written in clear style and simple examples are used as illustration of main optimization and solving ideas. Language: Serbian Format B5, 165 pages, ISBN 978-86-87035-06-5 (AINS) Publishers: Serbien Academy of Engineering Science and Faculty of Organizational Sciences (2012)

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SADRŽAJ

OD UREĐIVAČKOG ODBORA Prof. dr Jovan Todorović UVODNIK

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REZIMEI RADOVA Dr Miroslav Demić, Dr Đorđe Diligenski PRILOG ISTRAŽIVANJU DEGRADACIJE KARAKTERISTIKA OSCILATORNIH PARAMETARA NA OSCILATORNU UDOBNOST VOZILA

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Dr Nikola Dondur, Dr Vesna Spasojević-Brkić, Mr Aleksandar Brkić KABINE KRANA SA INTEGRISANIM VIZUELNIM SISTEMOM ZA DETEKCIJU I INTERPRENTACIJU EKONOMSKE PROCENE SREDINE

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Zoran Petrović, Dr Uglješa Bugarić, Dr Dušan Petrović UPOTREBA “ARIMA” MODELA ZA PROMET PREDVIĐANJA U PROCENI INVESTICIONOG PROJEKTA

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Dr Radoljub Tomić, Dr Predrag Petrović, Marija Petrović PRIlOG OCENI USAGLAŠAVANJA NOVIH PROIZVODA SA ASPEKTA POUZDANOSTI I ODRŽAVANJA

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Dimić-Mišić Katarina, Dr Paltakari Jouni FIBRILARNI MATERIJAL KAO ZAMENA KO-VEZIVU U BOJI ZA KOTIRANJE PAPIRA

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Dr Vesna Spasojević-Brkić, Dr Slobodan Pokrajac, Dr Nikola Dondur, MSc Sonja Josipović ALOKATIVNA EFIKASNOST I KOVARIJANTNI FAKTORI MENADŽMENTA KVALITETA U SRPSKOJ INDUSTRIJI

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MSc Marija Savić, MSc Predrag Đorđević, Dr Đorđe Nikolić, Dr Ivan Mihajlović, Dr Živan Živković KOMBINACIJA ZNANJA U SISTEMU DOBAVLJAČI-MSP-KUPCI U USLOVIMA TRANZICIONE EKONOMIJE U SRBIJI

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Journal of Applied Engineering Science 10(2012)4

OD UREĐIVAČKOG ODBORA

ALTERNATIVNA GORIVA I OBNOVLJIVI IZVORI ENERGIJE Intenzivan razvoj svetske privrede, a posebno sektora transporta, stvorio je dva velika problema: sve veće iskorišćavanje rezervi fosilnih goriva i velika zagađenja okoline. Stoga su razvoj alternativnih goriva i obnovljivih izvora energije glavni izazovi za inženjera u celom svetu. Alternativna goriva, poznata još i kao nekonvencionalna ili napredna goriva, predstavljaju materijale ili supstance koje mogu da se koriste da goriva, pored konvencionalnih fosilnih goriva (nafta, ugalj, propan, prirodni gas), kao i nuklearni materijali. Najpoznatija alternativna goriva su biodizel, bioalkohol (metanol, etanol, butanol), elektricitet hemijski uskladišten (akumulatori i gorivne ćelije), biljna ulja i drugi oblici biomasa. Jedan od najboljih je vodonik, koji sagoreva praktično bez emisije štetnih gasova. Primena vodonika zahteva velike investicije i zato se danas još uvek smatra gorivom budućnosti. I prirodni gas je takodje gorivo koje sagoreva čisto, sa manjim emisijama od benzina i dizel goriva. Obnovljiva energija se dobija iz prirodnih izvora, kao što su hidroelektrane, sunčeva energije, vetar, plima, talasi i geotermijska energija. Ova energija je obnovljiva pošto se prirodno stalno obnavlja. Biogoriva su takodje obnovljivi izvori energije. Biodizel se dobija iz životinjskih masti ili biljnog ulja, kao i od biljaka, kao što su soja, suncokret, kukuruz, šećerna trska, itd. Biodizel ima manju emisiju zagađivača i sagoreva čistije i ekonomičnije. Metanol i etanol su primarni izvori energije i pogodni su za skladištenje i primenu u transportu. Ovi alkoholi mogu da se koriste i za motore sa unutrašnjim sagorevanjem. Sunčeva energije se koristi pomoću fotoćelija koje se izrađuju od legura silikona. Ove ćelije pretvaraju sunčevu energiju u toplotu ili elektricitet. Geotermalna energija je druga mogućnost. Tehnologije koje se koriste u proizvodnji geotermalne energije slične su onima koje se koriste za naftu i gas. Energija vetra se smatra najekonomičnijim vidom proizvodnje električne energije, posebno preko noći. Gorivne ćelije, kao vid akumuliranja elektriciteta, danas su jedna od najperspektivnijih alternativa za motorna vozila, posebno sa vodonikom kao gorivom. U mnogim zemljama već su ostvareni značajni rezultati u razvoju alternativnih goriva i obnovljivih izvora energije. Obnovljiva energija danas zadovoljava 15 do 20% ukupnih poteba (u Norveškoj skoro 100%). Najvažnija je energija koja se dobija iz hidroelektrana, ali ima sve više i postrojenja koja energiju proizvode pomoću vetra i solarnih ćelija, ponekad sa velikim instalisanim snagama. Danas su u svetu milioni vozila koja rade na biogoriva, prirodni gas i elektopogon. Razvoj alternativnih goriva i obnovljivih izvora energije predstavlja primarni zadatak i za srpsku ekonomiju. Uzimajući u obzir naše privredne i tehničke mogućnosti i prirodne resurse, očigledno je da prednost treba da se da gradnji novih hidroelektrana (na Drini, Ibru, Dunavu i brojnij manjim vodenim tokovima), a i razvoju novih izvora energije, vetro i solarnim postrojenjima, kao i korišćenju geotermalne energije. Pažnja treba da se usmeri i na uljne škriljce, kao i na dalje unapređenje rudnika uglja, u pogledu kapaciteta i zaštite okoline. U sektoru transporta veoma važno je veće korišćenje prirodnog gasa i različitih vrsta biogoriva, što može da doprinese poboljšanju ekonomije i većoj zaštiti okoline. S poštovanjem, Prof.dr Jovan Todorović

Journal of Applied Engineering Science 10(2012)4

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REZIMEI RADOVA doi:10.5937/jaes10-2244

Broj rada: 10(2012)4, 236

PRILOG ISTRAŽIVANJU DEGRADACIJE KARAKTERISTIKA OSCILATORNIH PARAMETARA NA OSCILATORNU UDOBNOST VOZILA Dr Miroslav Demić-Univerzitet u Kragujevcu, Fakultet inženjerskih nauka, Kragujevac, Srbija Dr Đorđe Diligenski-Institut Vinča, Centar za motorna vozila i motore, Beograd, Srbija Tokom razvoja motornih vozila, značajnu ulogu ima dinamička simulacija, koja je zasnovana na modeliranju. Uloga modeliranja je veoma značajna u prvim fazama projektovanja, tokom definisanja opredeljujućih parametara. U praksi se obično pretpostavlja da su oscilatorni parametri vozila tokom eksploatacije nepromenljivi, što u osnovi nije tačno. Naime, sva istraživanja pokazuju da tokom eksploatacije dolazi do degradacije oscilatornih parametara i, zbog toga, promene dinamičkih karakteristika motornih vozila. U ovom radu će biti učinjen pokušaj da se, na osnovu preliminarnih rezultata, ukaže na neophodnost da se i u najranijim fazama projektovanja te promene uključe u razmatranje tokom modeliranja vozila. Ključne reči: Vozilo, Vibracioni parametri, Degradacija, Vibraciona udobnost doi:10.5937/jaes10-2516

Broj rada: 10(2012)4, 237

KABINE KRANA SA INTEGRISANIM VIZUELNIM SISTEMOM ZA DETEKCIJU I INTERPRENTACIJU EKONOMSKE PROCENE SREDINE

Dr Nikola Dondur-Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija Dr Vesna Spasojević-Brkić-Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija Mr Aleksandar Brkić-Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija Rad analizira ekonomsku opravdanost i upotrebu nove generacije kabina krana znatno manje težine i krutosti čiji će unutrašnji prostor neophodan za rukovaoca biti razvijen korišćenjem metode fizičkog, kognitivnog i ergonomskog organizovanja sa rešenim problemom vidljivosti i koji će omogućiti veću produktivnost, usled smanjenja fizičkog i psihičkog stresa rukovaoca, kao i veću bezbednost i sigurnost usled integrisanja vizuelnog sistema. Dokazano je da ukupna ekonomska prednost eksploatacije kabine u ukupnom eksploatacijskom period značajno veća, nego upotrebna cena kabine, kao i da je interna stopa prinosa iznad prosečne ponderisane kamatne stope i da je vreme povratka uloženog manje od 3 godine. Analizirani proizvodni projekat i upotreba kabine krana sa integrisanim vizuelnim sistemom za detekciju i interpretaciju sredine je projekat niskog ekonomskog rizika. Ključne reči: Ekonomska opravdanost, Kran, Kabina, Integritet, Proizvodi, Operator doi:10.5937/jaes10-2617

Paper number: 10(2012)4, 238

UPOTREBA “ARIMA” MODELA ZA PROMET PREDVIĐANJA U PROCENI INVESTICIONOG PROJEKTA

Zoran Petrović-Tecon Sistem d.o.o, Beograd, Srbija Dr Uglješa Bugarić-Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija Dr Dušan Petrović-Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija U savremenim analizama investicionih projekata, najkritičnija tačka je kako proceniti dnevni promet proizvodnje, ili usluga, na bazi sistema. Da bi ostvarili predviđanje, za precizno ulaganje u određenu vrstu opreme analiziran je dnevni promet za automatko pranje vozila u skadu sa vremenskim uslovima. Prema analizama, napravaljen je ARIMA model i vremensko stanje u skladu sa “Box-Jenkins” procedurom. Zaključak je da se dnevni promet može analitički izraziti kroz dnevne vremenske uslove. Ispravnost sistema je proverena na drugom sistemu koji je postavljen u drugom gradu Srbije. Prema upoređenim rezultatima,zaključak je da se ARIMA model za sistem dnevnog prometa, predviđen zavisnom promenljivom, generalno može koristiti kao dobar za predviđanje u analizama investicija ili za kriterijum izbora u investicionim odlukama. Ključne reči: Arima, Box-Jenkins, Investicije, Predviđanja, Promet Journal of Applied Engineering Science 10(2012)4 240

REZIMEI RADOVA Paper number: 10(2012)4, 239

doi:10.5937/jaes10-1688

PRIlOG OCENI USAGLAŠAVANJA NOVIH PROIZVODA SA ASPEKTA POUZDANOSTI I ODRŽAVANJA

Dr Radoljub Tomić-Alfa Univerzitet, Fakultet za strateški i operativni menadžment , Beograd, Srbija Dr Predrag Petrović-Institut Kirilo Savić, Beograd, Srbija Marija Petrović-Institut Kirilo Savić, Beograd Srbija Razvoj i unapređenje principa usaglašavanja novih proizvoda, je veoma bitno, posebno kod tehničkih sistema i njihovih komponenata, koje se primenjuju i eksploatišu u saobraćajnim sredstvima.Nivo kvaliteta i pouzdanosti takvih proizvoda, mora biti visok, kako bi proizvod, a time i sistem, pre svega bio bezbedan, a istovremeno konkurentan na globalnom tržištu. S druge strane, jedan od uslova za promociju izvoza domaćih proizvoda je povećanje konkurentnosti proizvoda, uzistovremeno ispunjavanje tehničkih propisa, kvaliteta proizvoda, pouzdanosti i održavanja. Kada je u pitanju pravilno funkcionisanje kočionog sistema železničkih vozila značajna je pogodnost održavanja sistema. Imajući u vidu da kočioni sistem mora da ispuni niz kvalitativnih uslova sa aspekta zakonodavstva, bezbednosti, pouzdanosti rada na svim režimima i drugih uslova, ovaj rad opisuje dinamiku održavanja jednog tehničkog sistema, sa posebnim osvrtom na učešće troškova u odnosu na cenu uređaja kočionog sistem železničkih vozila. Radi se o domaćemnovom proizvodu Industrije hidraulike i pneumatike „Prva petoletka” Trstenik-(PPT), sa posebnim osvrtom na komponentu koja se odnosi na zaptivnielement, kao najosetljivijem delu uređaja na kočionom sistemu železničkih vozila Ključne reči: Održavanje, Kočenje, Raspoloživost, Pouzdanost, Železnica, Usaglašenost, Novi proizvod, Troškovi doi:10.5937/jaes10-2517

Paper number: 10(2012)4, 241

ALOKATIVNA EFIKASNOST I KOVARIJANTNI FAKTORI MENADŽMENTA KVALITETA U SRPSKOJ INDUSTRIJI Dr Vesna Spasojević-Brkić-Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija Dr Slobodan Pokrajac-Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija Dr Nikola Dondur-Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija MSc Sonja Josipović-Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija Trendovi alokativne efikasnosti i kovarijati veličine preduzeća i efikasnosti faktora menadžmenta kvlitetom u srpskoj industriji su testirani na nebalansiranom panel uzorku od 48 industrijskih preduzeća iz 12 industrijskih sektora u periodu 2004-2009. Dobijeni rezultati pokazuju da 10 od 12 sektora ima pozitivan kovarijat učešća u outputu tržišta i multi-faktorskoj produktivnosti. Kovarijat veličine preduzeća i efikasnosti svih faktora menadžmenta kvalitetom pokazuju isti smer u hemijskom sektoru (pozitivno) i sektoru motornih vozila (negativno), što znači da u ta dva sektora veće kompanije imaju natprosečnu i/ili ispodprosečnu efikasnost menadžmenta kvalitetom. Isti (pozitivan) trend alokativne efikasnosti i kovarijata svih faktora menadžmenta kvalitetom je zabeležen u hemijskoj industriji. Ključne reči: Raspodela, Alokativna efikasnost, Kovarijantnost, Industrija, QM

Journal of Applied Engineering Science 10(2012)4

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REZIMEI RADOVA Paper number: 10(2012)4, 242

doi:10.5937/jaes10-2522 KOMBINACIJA ZNANJA U SISTEMU DOBAVLJAČI-MSP-KUPCI U USLOVIMA TRANZICIONE EKONOMIJE U SRBIJI

MSc Marija Savić, University of Belgrade, Tehnical Faculty in Bor, Bor, Srbija MSc Predrag Đorđević, University of Belgrade, Tehnical Faculty in Bor, Bor, Srbija Dr Đorđe Nikolić, University of Belgrade, Tehnical Faculty in Bor, Bor, Srbija Dr Ivan Mihajlović, University of Belgrade, Tehnical Faculty in Bor, Bor, Srbija Dr Živan Živković, University of Belgrade, Tehnical Faculty in Bor, Bor, Srbija U radu se prezentuju rezultati istraživanja kombinacije znanja u sistemu: Dobavljači – MSP – Kupci za slučaj MSP u Istočnoj Srbiji. Uspostavljen je teorijski model kombinacije znanja u ispitivanom sistemu. Statističkom obradom dobijenih rezultata utvrđena je zadovoljavajuća statistička značajnost dobijenih rezultata, što je omogućilo testiranje definisanog modela korišćenjem LISREL softverskog paketa. Dobijeni rezultati pokazali su važnost postavljenih hipoteza za uticaj saradnje sa dobavljačima na kombinaciju znanja, kao i kombinacije znanja kupaca i dobavljača na stvaranje novog znanja u MSP. Hipoteza o pozitivnom uticaju razmene znanja sa kupcima na kombinaciju znanja u MSP nije dokazana. Ove činjenice ukazuju da MSP u Srbiji nemaju saradnju sa svojim klijentima. Uzrok ovom stanju je nepostojanje sistema kvaliteta (SQ) u MSP u Srbiji, kao ni primene principa TQM prakse, što na najbolji način objašnjava činjenicu kratkog životnog ciklusa MSP u Srbiji i nemogućnost njihove internacionalizacije. Ključne reči: SMEs, Potrošači, Snabdevači, Znanje, Kombinacija, LISREL Paper number: 10(2012)4, 240

doi:10.5937/jaes10-2526

FIBRILARNI MATERIJAL KAO ZAMENA KO-VEZIVU U BOJI ZA KOTIRANJE PAPIRA Dimić-Mišić Katarina, Aalto University, Helsinki, Finland Dr Paltakari Jouni, Aalto University, Helsinki, Finland Mikrofibrilarna celuloza (MFC) je novi materijal koji ima tendenciju da se koristi u formulaciji boja za kotiranje papira, kao delimična substitucija sintetičkim ko-vezivima, kao što je karboksimetil celuloza (CMC). Ko vezivo je važan sastojak u smeši boja za kotiranje papira jer kontroliše fluidnost i brzinu kojom voda ističe na papirnu podlogu, neposredno posle primene ove suspenzije na papir koji se kotira. U ovoj studiji, MFC vlakna su se koristila da zamene uobičajno ko-vezivo CMC, u suspenziji boja za kotiranje papira i na taj način uticala na promenu reoloških karakteristika smeše i brzine oticanja vode iz smeše nakon primene. Ova studija pokušava da bar delimično utvrdi standardnu metodologiju kojom bi reološka ispitivanja ovakvih boja za kotiranje papira bilo moguće. Veoma izražen elasticitet ovih suspenzija pri niskim naponima utiče na fuidnost istih i napon samog noža zaravnjanja pri upotrebi. Raznim reološkim metodama je pokazano da boje za kotiranje papira koje sadrže MFC vlakna imaju izraženu osobinu smanjenja viskoziteta kada su izložene naponima, što je željeno ponašanje u proizvodnji istih. Ovim radom je pokazano da u slučaju kompletne zamene ko-vezivnim vlaknima suspenzija bi imala veoma nizak nivo retencije vode, mnogo duže vreme povratka viskoziteta i to po prestanku delovanja napona i veoma brzu imobilizaciju, osobine koje negativno utiču na sam mehanizam primene. S obzirom da reologija boje za kotiranje papira utiče na fluiditet pri velikim brzinam a pri primeni, i sam kvalitet kotiranog sloja zavisi od istih parametara. Zamena ko-veziva MFC vlaknima bi uticala na viskozitet i reologiju preko mehanizma visoke flokulacije ovih vlakana i velike reaktivnosti hidroksilnih grupa na površini MFC. Postoje razne metode za proizvodnju MFC vlakana, u zavisnosti od kojih se hemijske osobine vlakana veoma razlikuju. Njihova primena kao sastojka kotiranog sloja treba da bude najrasprostranjenija za one vrste kotiranja papira koje se koriste u specijalne namene. Naravno, postavlja se pitanje da li i pored njihovih povoljnih osobina,jer su prirodnog porekla, njihov uticaj na fluiditet i reologiju može da izađe u susret visokim zahtevima koje sam proces primene postavlja (sa brzinama primene preko 1000 m/min). Ključne reči: Svojstva, Vlakno, Bojenje, Premazi, CMC 242

Journal of Applied Engineering Science 10(2012)4