Istraživanja i projektovanja za privredu - Applied Engineering Science 9(2011)4 by JAES

CONTENTS

Mr Dragan Komarov, Dr Slobodan Stupar, Zorana Posteljnik REVIEW OF THE CURRENT WIND ENERGY TECHNOLOGIES 437 - 448 AND GLOBAL MARKET Dr Dragan Ćoćkalo, Dr Dejan Đorđević, Dr Zvonko Sajfert, Dr Srđan Bogetić 449 - 456 SMES IN THE REPUBLIC OF SERBIA: THE DEVELOPING CAPACITIES Dragan Stamenković, Dr Vladimir Popović, Dr Vesna Spasojević Brkić, Jovan Radivojević 457 - 464 COMBINATION FREE REPLACEMENT AND PRO-RATA WARRANTY POLICY OPTIMIZATION MODEL Dr Gradimir Danon, Miloš Petrović 465 - 472 PROACTIVE TIRE MAINTENANCE Dr Časlav Mitrović, Dr Slobodan Radojević, Milan Srećković, Mr Zoran Milanović FROM IDEA TO IMPLEMENTATION IN PROTECTION 473 - 479 OF ELECTRONIC EDITIONS (BOOK)

EVENTS REVIEW 481 - 483

ANNOUNCEMENT OF EVENTS 484 - 486

BOOK RECOMMENDATION

487

INSTRUCTIONS FOR AUTHORS 488 - 489

EDITORIAL AND ABSTRACTS IN SERBIAN LANGUAGE 491 - 495

Journal of Applied Engineering Science 9(2011)4

IMPRESSUM Journal of Applied Engineering Science The journal publishes original and review articles covering the concept of technical science, energy and environment, industrial engineering, quality management and other related sciences. The Journal follows new trends and progress proven practice in listed fields, thus creating a unique forum for interdisciplinary or multidisciplinary dialogue. 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 Education and Science admitted the Journal of Applied Engineering Science in a list of reference journals. Same Ministry financially supports journal’s publication.

Assistant Editor Dr Predrag Uskoković Institute for Research and Design in Commerce and Industry, Belgrade;

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.

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.

Publishing Council Prof. dr Milorad Milovančević, Faculty of Mechanical Engineering, Belgrade; 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.

ISSN 1451-4117 UDC 33 Papers are indexed by SCOPUS

Editorial Office Nada Stanojević, Miloš Vasić, Darko Stanojević, Miloš Dimitrijević, Mirjana Solunac, Ivana Spasojević, Andrija Đurašević, Institute IIPP, Belgrade; Bojan Mančić, Faculty of Mechanical Engineering, Belgrade.

Publisher Institute for Research and Design in Commerce and Industry www.iipp.rs For publisher: Prof. dr Branko Vasić Copublisher Faculty of Transport and Traffic Engineering – Belgrade University www.sf.bg.ac.rs For copublisher: Prof. dr Slobodan Gvozdenović Editor in Chief Prof. dr Jovan Todorović Faculty of Mechanical Engineering, Belgrade;

Journal of Applied Engineeering Science is also available on www.engineeringscience.rs and http://scindeks-eur.ceon.rs/index.php/jaes Designed and prepress: IIPP

Printed by: Beografika, Beograd Journal of Applied Engineering Science 9(2011)4

EDITORIAL Vehicles which are sold and put into service in a country have to meet the regulations and standards of that country. The registration procedure of that country requires the approval of the vehicle and/ or its components. The existence of separate national regulations and approval procedures in the different countries requires expensive design modifications, additional tests and duplicating approvals. Thus, there is the need to harmonize the different national technical requirements for vehicles and to elaborate a unique international regulation. Once the vehicle or its equipment and parts are manufactured and approved according to that regulation, they can be internationally traded without further tests or approvals. Furthermore, these regulations have to be continuously adapted to the technical progDoc. dr Vladimir Popović ress and to the new requirements regarding safety, environmental protection and energy efficiency. Currently, in the European vehicle market, there are two key, parallel system for vehicle type approval, which practically define the criteria and conditions for trading vehicles, through: • UNECE Regulations, that is regulations of United Nations Economic Commission for Eu rope (UNECE), passed by The World Forum for Harmonization of Vehicles Regulations WP.29, within the 1958 Agreement, and • EU Directives, that is regulations of The European Union (EU). The Republic of Serbia is a Contracting Party of the 1958 Agreement and it actively participates in the work of WP.29, while the application of EU regulations depends on the status of our country in the process of joining the EU, which is at this point rather uncertain. The main principle of WP.29 is “Certified once, accepted everywhere”. If we consider the key challenges the UNECE Transport Department is to face in the future, we can see the importance the territory of Southeast Europe is attributed with respect to them. The region in question has significant position because of two, out of six challenges previously mentioned: • Insufficient and inadequate infrastructures, particularly in Eastern Europe, the Caucasus and Central Asia; • Old, unsafe and highly polluting road vehicle fleets, particularly in Eastern and South-Eastern Europe, as well as in the Caucasus and Central Asia, which result in higher accident rates and environmental impacts. The best preventive, regarding the second challenge in particular, is harmonizing regulations to do with vehicles, with the purpose of enhancing their safety and environmental performance. Harmonizing certainly leads to market expansion and overcoming certain obstacles. In the last few years, it has become evident that harmonizing regulations connected to vehicle type approval is heading towards substituting EU Directives by UNECE Regulations. This is accounted for by the increasing importance of the 1958 Agreement. It is obvious that, in WVTAs themselves, numerous vehicle manufacturers from the EU include an increasing number of individual type approvals according to UNECE Regulations, compared to EU Directives. Among other things, the reason for this is the fact that, apart from all the countries which have signed the Agreement, USA, China, EU (Contracting Party to the Agreement) and India, whose importance in automobile industry is indisputable, actively participate in the WP.29, together with numerous non-governmental international organizations, interested in this matter (International Organization for Standardization - ISO; International Organization of Motor Vehicle Manufacturers - OICA; International Motorcycle Manufacturers Association – IMMA…). Furthermore, it is very important to point out that one of the informal working parties of WP.29 is in charge of the development and implementation of The International Vehicle Type Approval System (IWVTA), to be applied as from 2016, which should, in the long run, replace WVTA, which is the basis of today’s system of type approval in the EU. This trend will most certainly continue in the future, since it would complete the process of regulation harmonization on the world level, which is an inevitable consequence of globalization, particularly evident in automobile industry. Institute for research and design in commerce & industry, Belgrade. All rights reserved.

Journal of Applied Engineering Science 9(2011)4

Speaking of our region, all countries have signed the 1958 Agreement, except for Albania. Perhaps the key indicator for the development of regulations to do with vehicles on the territory of Southeast Europe is a more or less expressed wish of all the countries and territories of this region to be members of the EU. However, each country individually, regardless of the fact whether it is a member of the EU or not, has to sign the 1958 Agreement in case it wants to apply it. On the other hand, many countries which have not signed the 1958 Agreement, recognize it unilaterally, and apply UNECE Regulations as equivalent to national regulations, which resulted in the fact that type-approved vehicles represent a harmonized level of quality on the international market of vehicles, equipment and components. Still, this entire process of joining the EU implies two conflicting aspects when it comes to vehicle market. On the one hand, the EU will most certainly require compliance of all regulations of the countries which want to join it with its own, including regulations to do with vehicles. On the other hand, the used vehicles from EU countries must find their own markets where they can be sold, but in practice, a big difference between regulations for importing new and used vehicles in the same country is impossible and economically speaking, unsustainable. Although regulations on vehicle type approval, formally speaking, have technical nature, it is evident that their change is rather a consequence of global and political trends, since automobile industry is a vital factor of any economy. Therefore, it is important to emphasize that the general political and economic circumstances in the Balkans have always been turbulent and prone to fundamental changes. For that reason, it is very difficult to make more accurate predictions regarding the development of any regulations, those related to vehicle type approval and importing included, for a longterm period, despite the current situation. However, this problem must be addressed with a degree of optimism, and a belief in market stability and economic prosperity of this region.

Doc. dr Vladimir PopoviÄ&#x2021;

Journal of Applied Engineering Science 9(2011)4

DOI: 10.5937/JAES9 - 1120 Paper number: 9(2011)4, 208, 437 - 448

REVIEW OF THE CURRENT WIND ENERGY TECHNOLOGIES AND GLOBAL MARKET Mr Dragan Komarov * University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia Dr Slobodan Stupar University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia MSc Zorana Posteljnik University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia The modern wind energy technologies and recent global wind energy market trends are reviewed in the paper. Basic principles of conversion of wind energy to electricity are described with brief overview of the state-of-the-art technologies for subassemblies such as wind turbine blades and drivetrains. Global wind energy market was reviewed in order to attain notion of wind power market developments in the future. The most developed countries in terms of wind energy utilization such as Denmark, Germany, Spain and USA were identified as the key drivers of wind energy technology advances. After the long leadership of European Union in built annual wind power capacities, China and USA have overtook leading positions for the last several years. Wind energy costs per unit of electricity produced after gradual decrease until 2005 have recorded slight increase until the present due to high demand and higher raw materials price. It was predicted that the trend of the wind energy cost will decrease in the future. Steady growth of wind energy capacities was predicted in the next years, with forecast that present global installed capacities of nearly 200 GW should grow to almost one terawatt by the 2020. Key words: capacity, energy use, globalization, markets, technology, wind turbine, wind energy, winds INTRODUCTION Energy demand had rapid growth in the last century. The gross energy needs were supplied by conventional energy resources such as coal and oil, as well as newer technologies such as nuclear power plants. High demand and limited resources had influence on the price growth of the produced electricity. Environmental issues, economy and political factors have influenced on renewable energy growth in the last thirty years. Due to large quantity of CO2 emissions from power and heavy industries, as well as traffic, the social awareness have risen of induced climate change. After the oil crisis in 1970s, the interest in renewable energy was growing. Relatively simple design and existing technologies developed mainly for aeronautical and power-generation purposes made wind energy industry one of the fastest growing in the following decades [09]. As technology has matured, wind energy grew to substantial capacity [19], [23]. Although this capacity is still

incomparable to the total installed power in the world [12], wind energy presents industry that should not be neglected in the recent period and in the future. After the brief introduction, the review of the current wind turbine technologies was given with emphasis on commercial design. Technology trends and novel concepts of some assemblies were also given in this section. Overview of global wind energy capacities was given with brief summary of the most developed markets as well as emerging ones in the next section. Wind energy costs were described in the following section with breakdown of the costs due to initial investment, operation and maintenance and other costs. Short conclusions were given at the end of the paper. WIND TURBINE DESIGN CONCEPTS Wind turbine design has been changing over the years, from being convention-driven to being optimized-driven. As well as becoming larger (the generators in the largest modern wind turbines are 100 times the size of those in 1980),

* Faculty of Mechanical Engineering, Kraljice Marije 16, 11000 Beograd, Serbia; dkomarov@mas.bg.ac.rs

437

Mr Dragan Komarov etc. - Review of the current wind energy technologies and global market

wind turbine designs have been progressing from fixed-speed, stall-controlled to pitch-controlled, variable speed, with or without gearboxes. Other improvements include the use of different combinations of composite materials to manufacture blades, especially to ensure that their weight is kept to a minimum, as well as modern control system for better compatibility with the grid connection. Some of the design drivers for current wind turbine technology are reliability, grid compatibility, maximum efficiency, noise reduction, high productivity for low wind speeds, aerodynamic performance, etc. Even though much time and resources are continuously spent on improving the wind technology since its commercial beginnings in the early 1980s, the basic architecture of the mainstream design has maintained its original topology. Wind power technologies can be grouped in three applications: • • •

Large grid connected wind turbines, Small “stand-alone” wind turbines for water pumping, battery charging, heating, etc. Hybrid energy systems – wind turbines in combination with other energy sources.

Generally, wind turbines can be classified, according to the axis of rotation of main shaft, as

horizontal axis wind turbines (HAWT) and vertical axis wind turbines (VAWT), the first being dominate in wind power large-scale utilization, figure 1. HAWTs are usually classified according to the rotor orientation relative to wind direction (upwind or downwind), hub design (rigid or teetering), rotor control (pitch vs. stall), rotor speed (fixed or variable), number of blades, their alignment with the wind direction (active or passive yaw). HAWTs can use different number of blades, depending on the purpose of the wind turbine. The determination of the number of blades involves design considerations of aerodynamic efficiency, component costs and system reliability, as well as aesthetics. The loads on wind turbine rotor are cyclic depending on blade position during the operation. Cyclic loads when combined together at the drivetrain shaft are symmetrically balanced for three blades, [06]. Modern utility-scale wind turbines usually have three-bladed upwind rotor and are actively yawed to preserve alignment with the wind direction. Although the length of the blade can be as long as 60m, blades of the rotor are commonly manufactured as one part using different techniques for composite manufacturing. Still, one of the world’s largest wind turbines, the Enercon E126, adopts a jointed blade design. In the E-126

Figure 1. Main components of a horizontal axis wind turbine [13]

438

Journal of Applied Engineering Science 9(2011)4 , 208

Mr Dragan Komarov and etc. - Review of the current wind energy technologies and global market

blade, an outer blade section with a conventional blade root attachment is bolted to a steel inner blade spar. The trailing edge of the inner blade is a separate composite structure. Gamesa has also developed a jointed blade design for the G10X wind turbine. The rotor size will increase in the future, as the trend of manufacturing of the larger multi-megawatt wind turbines will not cease. Beside the reason for the manufacturing of larger blades due to demand for megawatt machines in the range between 3 and 7 megawatts, larger rotors would enable higher energy yield at sites with lower wind speeds. For example, Nordex has revealed the wind turbine with 117 meter rotor diameter with 2.4 MW rated power. It is claimed that this wind turbine could achieve 3500 full-load hours at typical inland locations, which corresponds to capacity factor around 40 percent, which makes it feasible for construction in lower wind speed sites. In order to attain technology necessary for manufacturing and operation of wind turbines with very long blades (longer than 100 m) it is necessary to develop stronger and lighter materials, to reduce loads using advanced flexible materials and novel concepts of blade operation control, to use innovative technologies for wind speed measurements

etc. With these innovations, it is believed that 20 MW wind turbine will be feasible in the future [08]. The rotation of the blades is transferred through the drivetrain on to the generator, creating electricity. At the wind speeds between 10 and 15 m/s, the power output of wind turbine rotor usually reaches its rated capacity. If the rated wind speed is exceeded the power has to be limited, to prevent wind turbine from overloading and to ensure that it has constant output. There are two principal means of limiting rotor power in high operating wind speeds â&#x20AC;&#x201C; stall regulation and pitch regulation. Stall-regulated machines require a constant rotational speed which can be achieved with a grid-connected induction generator. As wind speed increases and the rotor speed is held constant, flow angles over the blade sections increase. The blades become increasingly stalled and this limits power to acceptable levels, without any additional active control. On the other hand, using pitch regulation the blades have additional degree of freedom around their longitudinal axis so that the aerodynamic characteristics of the blade - and the rotor - can be controlled. In contrast to stall regulation, pitch regulation requires changes of rotor geometry by pitching the blades. This involves an active control

Figure 2. Direct drive of Enercon E-48 [17]

Journal of Applied Engineering Science 9(2011)4, 208

439

Mr Dragan Komarov etc. - Review of the current wind energy technologies and global market

system, which senses blade position, measures output power and instructs appropriate changes of blade pitch [01]. Modern large-scale wind turbines are almost exclusively pitch-regulated. As it was mentioned, the drivetrain contains the rotor attached to a main shaft driving the generator through the optional gearbox. However,

there are many significant variations in structural support, in rotor bearing system and in general layout. Vestas adopted the large single front bearing arrangement in the V90 3 MW design, which contributed to a very compact and lightweight nacelle system. Also, there has been a significant trend towards innovative drivetrain

Figure 3. Savonius and Darrieus type of VAWT

systems. There are companies that use directly driven variable speed synchronous generators with large-diameter synchronous ring generator (figure 2.), but majority of wind turbine manufacturers still use six-pole induction (asynchronous) generators connected through a gearbox to a rotor. Induction generators have a softer connection to the network frequency than synchronous generators, which reduce the loads between rotor and generator during wind gusts. Low overall efficiency during low speed winds can be overcome using two induction generators, smaller and larger one. The motivation for direct drive application is to simplify the nacelle systems, increase reliability, increase efficiency and avoid gearbox issues. Enercon and Siemens established the direct drive system, as well as some other manufacturers like Vensys, whose wind turbines are based on the generator concept of a synchronous machine with permanent magnet excitation [15]. There are also a number of hybrid systems. Clipper Windpower (after research into systems with multiple induction generators) developed a system with an in-

440

novative gearbox with ouputs to four permanent magnet generators (PMGs). Northern Power Systems (after initially adopting a wound rotor direct drive design) and GE Energy in their 2.5 XL series, have all adopted PMG systems. Generator and gearbox of the vertical axis wind turbines can be placed near the ground, hence avoiding the need of a tower and improving accessibility for maintenance, figure 3. Wind turbines of this type have low rotational speed with a consequential higher torque and higher cost of the drivetrain, lower power coefficient, but they donâ&#x20AC;&#x2122;t need to be pointed into wind to be effective. There are several subtypes of vertical axis wind turbine such as Darrieus, Savonius wind turbine and giromill. Regarding offshore wind energy, currently, Europe is the world leader. As of 2010, there are no offshore wind farms in the United States. However, there are some projects under development. Siemens and Vestas are the leading turbine suppliers for offshore wind energy. Commercialscale offshore wind farms currently are similar to the onshore wind farms, but with modifications Journal of Applied Engineering Science 9(2011)4, 208

Mr Dragan Komarov and etc. - Review of the current wind energy technologies and global market

Figure 4. World wind energy capacities (1990-2010)

to withstand higher wind loads, prevent corrosion and protect against wave and wind interactions. Offshore wind turbines are bottom founded (driven monopiles or conventional concrete gravity bases as foundations) or of the floating type. For large water depths and soft seabeds, floating wind turbines may be attractive due to a cheaper anchor installation than the cost of a fixed foundation. These floating foundations are mainly in research phase. Some of the proposed solutions are: spar-buoy, tension-leg platform, semi-submersible (column stabilized) and pontoon (barge) type [21]. The first grid-connected deep water floating wind turbine in the world is an Siemens Wind Power 2.3 called Hywind [14]. GLOBAL WIND ENERGY MARKET In the last two decades the growth of the installed wind power capacities in the world was rapid. At the beginning of the 1990s there were 1742 MW of installed wind turbines globally. In the early period of commercial utilization of wind power, wind turbines were mainly installed in Denmark and USA as the result of research efforts in these countries. USA expeJournal of Applied Engineering Science 9(2011)4, 208

rienced a wind power expansion from 1982 to 1986 when thousands of Danish and American wind turbines were installed in massive arrays. As the wind power technology matured and awareness of renewable energy sources (RES) utilization grew, Europe overtook the leading role as the wind power market with the highest growth from the mid-nineties, figure 4. Denmark, Germany and Spain may be attributed as main drivers of high annual growth of wind power capacities during the period from 1990 until 2007. Denmark was one of the key countries for wind power technology development. The knowledge acquired during the eighties based on commercially developed wind turbines up to 100 kW of rated power presented excellent basis for further research and development of megawatt wind turbines, which was implemented by strong collaboration between research institutions and interested companies with lasting support from the society. The main driver of the swift technology development was learning-by-doing, i.e. construction of demonstration and commercial wind farms. As early as 1999, Denmark had 1749 MW of total wind energy capacities with more than 6000 wind turbines erected, which

441

Mr Dragan Komarov etc. - Review of the current wind energy technologies and global market

have presented 50% of capacities in 2010. Onshore wind power capacities in Denmark from 1739 MW in 1999 grew to 2600 MW in 2003 and are in stagnation until present. In the same time, number of wind turbines has been reduced to 5000 in 2009. Future development of wind energy market in Denmark is oriented towards off-shore wind power utilization. Installed wind energy capacities in Denmark (3479 MW) can attribute roughly 20 % of national electric energy

consumption. Market maturity and high share of wind energy in overall energy capacities present good basis for transfer of the best practices from Denmark in terms of operation and maintenance of wind turbines, as well as wind power integration in national power system. Despite relatively small overall installed capacities comparing to other wind energy markets, Denmark remained one of the key countries in terms of exporting of wind power technologies and had great sig-

Figure 5. Countries with the largest cumulative wind power capacities (MW) [24]

Figure 6. Countries with the highest growth of installed wind power capacities (%) [24]

442

Journal of Applied Engineering Science 9(2011)4, 208

Mr Dragan Komarov and etc. - Review of the current wind energy technologies and global market

nificance and impact on development of other national markets. Germany and Spain also had high wind power growth during the period between 1997 and 2008. In the early nineties several wind power companies emerged in Germany that had driven research and development efforts in order to commercialize wind power which later had impact on the global market. Wind energy in Germany in 1997 accounted for roughly 3000 MW, and at the end of 2008 there were 23903 MW of installed wind power with 21164 wind tur-

bines. In the same period in Spain was installed 15906 MW for total capacity of 16740 MW. Early development of the wind power market in Spain during mid-nineties is due to wind turbine import and technology transfer from Denmark. In the following years domestic companies overtook larger part of the market until the present. At the end of 2010 Spain had a total capacity of 20676 MW and Germany 27215 MW which accounted for 55 % of European installed wind power capacities. It should be mentioned that

Table 1. Market share of top ten wind turbine manufacturers for period 2005-2010 [5] Wind turbine manufacturer

2005 (11471MW)

2006 (12042MW)

2007 (23590MW)

2008 (26180MW)

2009 (38863MW)

2010 (36864MW)

Vestas

27.9

Sinovel

N/A

27.4

17.8

12.5

14.8

N/A

3.4

4.5

9.2

11.1

GE Wind

17.7

15.3

16.7

12.4

9.6

Goldwind

1.2

2.9

4.2

3.6

7.2

9.5

Enercon

14.2

14.5

9.0

8.5

7.2

Suzlon

6.1

7.5

10.5

8.1

6.4

6.9

Dongfang

N/A

3.4

6.5

6.7

Gamesa

12.9

15.5

15.4

10.8

6.7

6.6

Siemens

5.5

7.1

6.2

5.9

Nordex

2.6

3.3

3.4

N/A

Other

11.9

6.5

16.5

24.7

21.7

annual electricity generation in Germany in 2009 and 2010 was 38000 GWh and 36500 GWh respectfully, while in Spain 42976 GWh has been produced by wind power capacities in 2010. After US government adopted tax incentives for wind energy in 2004, substantial capacities were to be built in USA in the following years. From initial 9147 MW of installed wind power in 2005, the capacities were enlarged to 34863 MW at the end of 2009 making USA country with the largest total wind power capacity in the world. In 2010 annual growth rate in USA was 15.25 % which is the lowest growth rate since 2004, resulted in total wind power capacities of 40180 MW at the end of 2010. Intensive wind power market growth was seen in China between 2005 and 2010, with annual growth around 100%. Total installed wind power was increased from 1260 MW in 2005 to 41800 MW at the end of 2010, which made China the world largest wind energy market in 2010, figure 5. [24]. Journal of Applied Engineering Science 9(2011)4, 208

The markets in surrounding countries showed the signs of huge investments made in wind power for the last two years. Romania had total installed capacity of 591 MW in 2010, with added 577 MW in the previous year, figure 6. During the 2010 in Bulgaria was installed 198 MW of wind power for total capacity of 347.5 MW. Hungary has added 94 MW during 2010, with total capacity of 295 MW at the end of 2010. It has been erected 43 MW of new capacities in Croatia, for the total capacity of 69.8 MW [24]. World market annual share of the leading wind turbine manufacturers has been shown for period between 2005 and 2010 in table 1. It can be noticed that eight largest wind turbine manufacturers were involved in production of at least 80% of the worldâ&#x20AC;&#x2122;s wind power capacities until 2009. The individual manufacturers have chosen different ways to market success [02]. Vestas has been one of the worldâ&#x20AC;&#x2122;s leading manu-

443

Mr Dragan Komarov etc. - Review of the current wind energy technologies and global market

facturers of wind turbines. Vestas technology is generally particularly lightweight. Their innovation in nacelle systems design has contributed to this characteristic. Currently, Vestas is working on the development of a 7MW wind turbine. Siemens (along with Vestas) is among a few companies increasingly successful in the offshore wind energy market. Its 3.6 MW SWT turbines of 107 m diameter are now figuring prominently in offshore projects. The advanced technology used in Gamesa G1284.5 MW wind turbine makes for a more reliable system. Technological developments applied to improve reliability include load-reducing multivariable control, powertrain without the high-

speed rotating components and modular electric power system which isolates the mechanical train from loads caused by voltage drops. Gamesa ranks among the world leaders in the market, having installed 20,834 MW until 2010 [11]. The Enercon E 40/500kW horizontal-axis turbine was the first system with a direct-drive generator to establish itself in the market with great success in a very short time. Today, Enercon has dominated supply of direct drive turbines [10]. Nordex is developing new control techniques and has a condition monitoring system, which monitors component wear, also incorporating ice sensors and an automatic fire extinguishing system.

Figure 7. Breakdown of the capital costs

Manufacturers from EU have been dominating the world market for years, although with the expansion of markets in China during the last several years their shares were in decline as several local Chinese companies has developed own well established positions at national level, table 1. This was a consequence of the strong support for wind power from government with high incentives for wind power manufacturing related activities. Despite lower relative shares of well established wind turbine manufacturers such as Vestas, GE Wind, Enercon and Gamesa during 2009 and 2010, all of these companies had rapid growth in the production due to the growth of the worldâ&#x20AC;&#x2122;s wind power capacities (11471 MW were installed in 2005, while 36864

444

MW were installed during 2010). The forecasts are made that until 2020 the global capacity will be close to one terawatt, and present capacities of the leading manufacturers will be in expansion, as well as newly established manufacturing companies. One of the indicators of intensified activities in the wind power manufacturing sector is the growth of the market share that was held by smaller and emerging wind power companies. Almost one quarter of the world market was held by such manufacturers in 2009 which is more than double comparing to 2005.

WIND ENERGY COSTS Journal of Applied Engineering Science 9(2011)4, 208

Mr Dragan Komarov and etc. - Review of the current wind energy technologies and global market

The cost of electricity produced by wind turbines consist of investment (capital) costs and cost due to operating and maintenance. The investment costs include initial costs of the project such as feasibility study cost, the cost of project management including acquiring all necessary permits, wind turbines procurement, civil works, electrical infrastructure, grid connection, installation and other costs (insurance cost, bank fees etc.). Breakdown of the capital costs according to [7] is shown in fig. 7.Although there are variations in the capital cost structure introduced in the existing literature, there are certain trends that are widely confirmed. Capital costs account for more than 80% of all costs for a wind farm during lifetime. The larger part of the capital cost is due to wind turbine procurement. According to several sources [03], [18] at least 70% of capital cost is due to wind turbine procurement excluding works (transportation is included in the price). Other capital costs such as grid connection, civil works and installation costs are highly dependent on location of the wind farm. Factors such as the local legislative framework for obtaining operating permits, grid connection availability and type (distributive or transmission grid), soil structure, availability and the cost of local labor and machinery influence on other capital costs. The capital costs vary from 1200 euros per kW of rated power to 1850 euros per kW for onshore wind farms. The unit price for off-shore wind power plants can be substantially higher.

After the steady decay of wind turbine costs from 1980s until 2000s, from 2005 the growth of investment costs has been observed. It should be pointed out that the capital costs in Europe (more specifically in European Union), USA and China and other markets in Asia are notably different, as well as wind turbine procurement costs. Operation and maintenance (O&M) costs are variable costs that are usually expressed in term of the fraction of the produced electricity price. They comprise of costs for regular maintenance, repair, spare parts, insurance, taxes, management, administration, land rental and grid integration costs. According to [07] O&M costs could have share of 20-25% of total levelised costs per produced kWh over the lifetime of the turbine. Based on the experience in the leading European markets, O&M costs are generally estimated to be between 1.2 and 1.5 c€/kWh of power produced over the total lifetime of wind farm (wind turbine). Usually, wind turbines have warranty period for two to three years. In this period the maintenance cost can be as low as 0.3-0.4 c€/kWh. For older turbines it is reported that this cost can be between 0.6 and 0.7 c€/kWh. It has been reported that average O&M costs could vary from 1.5 c€/kWh to 2.6 c€/ kWh [16]. It must be pointed out that this mentioned values are based on the data mainly consisted of wind turbines that are no more than ten years in operation. This variable cost is augmented during the operating lifetime. Some means of

Figure 8. Wind energy costs per kWh of produced electricity Journal of Applied Engineering Science 9(2011)4, 208

445

Mr Dragan Komarov etc. - Review of the current wind energy technologies and global market

reducing O&M costs through wind turbine condition monitoring system were described in [20]. On contrary to conventional fossil fuel-fired power plants, where 40-60% of total costs are related to the fuel and O&M costs, wind energy is capital intensive with more than 70% of production costs, as mentioned, accounted to initial investment, i.e. capital costs. Therefore, the cost of capital (interest rate) is an important factor that influences the overall cost of wind-generated power. The total cost per kWh produced is usually calculated by discounting and levelising investment and O&M costs over the lifetime of the turbine. In order to obtain the price per kWh of produced electricity it is necessary to predict annual electricity production. One of the methods is to estimate capacity factor of a wind turbine according to available wind resource which is considered to be representative over the wind turbine lifetime. Capacity factor is defined as the ratio of the calculated annual energy production and energy that would be produced if the wind turbine would operate at rated power over the whole year. System operators are faced with the challenges in order to maintain system stability, as wind energy share increase in overall energy portfolio of energy systems and emerging balancing costs. Although there are options for balancing of wind power plants output, which are highly variable but predictable to certain extent, practical solutions are the field of wide research in which must be included wind project owners, system operators and other utility companies [22]. European wind energy association (EWEA) published [7] that calculated costs per kWh of wind-generated electricity range from 8 to 11 c€/kWh at sites with low average wind speeds (with capacity factor lower than 18%) to approximately 5-7 c€/kWh at windy coastal sites with capacity factor between 30 and 33%. The average cost of electricity produced from wind energy is 7 c€/kWh according to EWEA, which should be related to capacity factor around 25%. Wind energy costs per unit of electricity produced gradually decreased from mid-eighties until 2000s, fig. 8. The average total cost has decreased from 9.5 c€/kWh to around 5 c€/kWh. Cost decrease can be attributed to gradually increase in wind turbine capacity (from average 50 kW machines at the beginning of 1980s to average 1500 kW wind turbines in 2000s), acquired know-how and innovations in wind turbine 446

design, gained experience by the wind turbine manufacturers, owners and grid operators and economy of scale. The trend of cost decrease lasted until early 2000s. Gradual cost increase that was observed after the 2005 in the world (or 2002. in USA according to [04]) led to approximately 20% costs rise. Some of the identified reasons for higher costs are due to a continual high demand for new wind turbines, constraints in the supply chain in the delivery of turbine components, the price growth of raw materials and even higher profit share of manufacturers. The gradual cost decrease trend is expected to continue in 2012, but with lower rate than the previous trend at the end of 20th century. CONCLUSION Wind power industry had high growth in the last decade. Steady growth during the next ten years is anticipated. Current installed capacities of nearly 200 GW should grow to almost one terawatt until 2020. Rapid technology development was initiated by researches led by several institutions in Europe and USA, such as Risoe – Danish Technical University (Risoe DTU), Energy research Centre of Netherlands (ECN), Fraunhofer, Deutches Windenergie Institut (DEWI) and National Renewable Energy Laboratory (NREL) during the eighties and nineties of the twentieth century. With commercialization of the wind power technologies during early nineties, manufacturers significantly contributed to industry development as the reduction of the price of produced energy was the main driver of research activities. Modern on-shore wind turbines became large structures with good reliability tailored to specific wind sites and operating conditions. Current research trends are oriented towards manufacturing of even larger wind turbines with more than 7 MW of rated power. This trend corresponds to exploitation of off-shore wind resources, for which there are still many barriers that remain to be overcome in the future. Nevertheless, there is a space for further improvement of current mainstream on-shore technologies, such as rotor load alleviation using novel materials and load control methods, further improvements of reliability and availability, mass reduction, integration in power systems etc. Dynamic global wind power market is mainly driven by utilization of the best available wind sites and government incentives both for manJournal of Applied Engineering Science 9(2011)4, 208

Mr Dragan Komarov and etc. - Review of the current wind energy technologies and global market

ufacturing and installation of wind turbines and wind farms. EU remained the biggest wind power market during early 2000s (particularly markets in Germany and Spain). With adoption of wind power incentives in China and steady development of national manufacturers and wind farms between 2005 and 2010, the new market expanded taking leading role in annual installed capacities in 2010. During the same period the wind power industry regained momentum in USA. With all mentioned above, installed capacities were more than doubled in four years: from 2007 until 2010 wind power capacities grew from 94104 MW to 196630 MW. After the steady price reduction of electricity produced by wind power from 1980s until early 2000s, the price has began to increase due to high demand for wind turbines and price growth of base materials. It is expected that the wind turbine price will gradually be reduced to the level from 2002 until 2013. Wind power technology improvements and better grid integration should attribute to the costs reduction. High wind turbine demand predictions, rapid technology and market growths are some of the indicators that should alert the public and private sector for broader involvement of available capacities in order to acquire necessary skills for wind power utilization and manufacturing, including participation in supply chains of large wind turbine manufacturers. ACKNOWLEDGEMENT This paper is a contribution to the research TR 35035 â&#x20AC;&#x153;Research and Development of Advanced Design Approaches for High Performance Composite Rotor Bladesâ&#x20AC;?, that has been funded by Ministry of Education and Science of Republic Serbia. REFERENCES 1) Ackermann T, Lennart S. (2000) Wind energy technology and current status: a review, Renewable and Sustainable Energy Reviews 4 (4), 315-374. 2) Avis M., Maegaard P. (2008), Worldwide Wind Turbine Market and Manufacturing Trends, Denmark: Folkecenter. 3) Blanco M. (2009), The economics of wind energy, Renewable and Sustainable Energy Reviews 13 (6-7),1372-1382. Journal of Applied Engineering Science 9(2011)4, 208

4) Bolinger M., Wiser R., (2009). Wind power price trends in the United States: Struggling to remain competitive in the face of strong growth. Energy Policy 37 (3), 1060-1071. 5) BTM Consult (2011), International Wind Energy Development: World Market Update 2010, Denmark: BTM 6) Det Norske Veritas and Wind Energy Department, Risoe National Laboratory (2002), Guidelines for Design of Wind Turbines, Second Edition, Denmark: Jydsk Centraltrykkeri 7) European Wind Energy Association (2009), Wind Energy-The Facts, UK: EWEA 8) European Wind Energy Association (2011), Upwind: Design limits and solutions for very large wind turbines, Brussels: EWEA 9) Global Wind Energy Council (2011), Global wind energy report 2010, Brussels: GWEC 10) http://www.enercon.de/en-en/767.htm retrieved on July 2nd, 2011 11) http://www.gamesa.es/en/gamesaen/, retrieved on July 2nd, 2011 12) http://www.iea.org/statist/index.htm, retrieved on June 20th , 2011 13) http://www.nordex-online.com/en/productsservices/wind-turbines/n80-25-mw/technical-drawing.html?type=98&%3BL=2, retrieved on June 2nd , 2011 14) http://www.powermag.com/renewables/ wind/Top-Plants-Hywind-Floating-WindTurbine-North-Sea-Norway_2305.html, retrieved on June 22nd, 2011 15) http://www.vensys.de/energy-en/technologie/generator-pm-technologie.php retrieved on June 15th, 2011 16) h t t p : / / w w w. w i n d p o w e r m o n t h l y. c o m / news/1010136/Breaking-down-cost-wind-turbine-maintenance/, retrieved on July 2nd , 2011 17) http://www.wwindea.org/technology/ch01/en/1_ 2_3_2.html, retrieved on July 15nd, 2011 18) Junginger M. (2007), Learning in onshore and offshore wind energy technology development, International workshop on technology learning and deployment, International Energy Agency 19) Klaassen G., Miketa A., Larsen K., Sundqvist

447

Mr Dragan Komarov etc. - Review of the current wind energy technologies and global market

T. (2005), The impact of R&D on innovation for wind energy in Denmark, Germany and the United Kingdom, Ecological Economics, 54 (2-3), 1227-1240.

22) Weigt H. (2009), Germany’s wind energy: The potential for fossil capacity replacement and cost saving, Applied Energy 86 (10), 1857-1863.

20) Milovančević M., Anđelković B. (2010), Modern techniques of wind turbine condition monitoring. Applied Engineering Science, 8 (1), 33-38.

23) Welch J. B., Venkateswaran A. (2009) The dual sustainability of wind energy, Renewable and Sustainable Energy Reviews, 13 (5), 1121-1126.

21) Wang C.M., Utsunomiya T., Wee S.C., Choo Y.S. (2010) Research on floating wind turbines: a literature survey, The IES Journal Part A: Civil &Structural Engineering; 3(4), 267-277.

24) World Wind Energy Association (2011), World Wind Energy Report 2010, Bonn: WWEA Head Office

448

Paper sent to revision: 19.10.2011. Paper ready for publication: 23.11.2011.

Journal of Applied Engineering Science 9(2011)4, 208

DOI: 10.5937/JAES9 - 1131 Paper number: 9(2011)4, 209, 449 - 456

SMES IN THE REPUBLIC OF SERBIA: THE DEVELOPING CAPACITIES Dr Dragan Ćoćkalo * University of Novi Sad, Technical faculty “Mihajlo Pupin”, Zrenjanin, Serbia Dr Dejan Đorđević University of Novi Sad, Technical faculty “Mihajlo Pupin”, Zrenjanin, Serbia Dr Zvonko Sajfert University of Novi Sad, Technical faculty “Mihajlo Pupin”, Zrenjanin, Serbia Dr Srđan Bogetić Belgrade Business School, Belgrade, Serbia Small and mid-sized enterprises (SMEs) represent one of the main generators of economic development in every market economy. In the last thirty years the SME sector has been successful all over the world, especially in newly industrialized and transitional countries. The management process in SMEs is specific because their business activities are performed in conditions of insufficient resources. The development of SMEs is one of the crucial developmental priorities in the Republic of Serbia. This paper represents a review and recommendations for further developmenti of the developing capacities of SMEs in the Republic of Serbia. Key words: SMEs, economy, development, Serbia. INTRODUCTION One of the important trends in the last 15 years has been a decrease in the average size of enterprises. Even at the beginning of the 1990s the strategic significance of the SME sector for the development of the economy and the process of economic flux internationalization was noted. According to Drucker [08], a step ahead from a big company to a mid-sized one which represents the centre of an economy is, in fact, a radical turn in the ruling trend of developed countries. This trend has been dominant in developed countries for more than a century. It is Drucker’s belief that in the future it will no longer be desirable to be “big”. Achieving successful results will be in direct relation to the size of a company – a mid-sized company will be an imperative. SMEs are of special importance for the successful development of transitional countries. In this regard “market orientation and entrepreneurial orientation are correlated, but distinct constructs. market orientation reflects the degree to which firms’ strategic market planning is driven by customer and competitor intelligence. Entrepreneurial orientation reflects the degree to which firms’

growth objectives are driven by the identification and exploitation of untapped market opportunities.” [01]. The development of the SME sector is of vital significance for privatisation because it facilitates its acceleration – SMEs represent an autochthonous private sector and they enable the development of domestic private capital [06]. Mahajan [16] says: “The state does not create business opportunities. Entrepreneurs are those who create them. Whatever the state does, it must stimulate entrepreneurship. On this exceptionally competitive market the entrepreneur who has better ideas and who knows how to realize them better than the others is important. Entrepreneurship is not the monopoly of the French, Germans, Americans, Chinese or Indians. The Region of the West Balkans is full of entrepreneurs. The problem is in the small size of West Balkan countries. They are faced with a challenge – how to grow further? For further development they should have a global vision, they should turn around and search for opportunities on a global level”. The development of the SME sector is a vital priority for our economy. The Serbian Government has adopted the strategy for developing competitiveness and innovations of SMEs for the period

* University of Novi Sad, Technical faculty “Mihajlo Pupin”, Djure Djakovića bb, 23000 Zrenjanjin, Serbia; cole@tfzr.uns.ac.rs

449

Dr Dragan Ä&#x2020;oÄ&#x2021;kalo and etc. - SMEs in the Republic of Serbia: The developing capacities

from 2008-2013. This strategy should contribute to increasing competitiveness and exports, the further strengthening of the innovative capacity of companies, a dynamic increase in employment and more equal regional development [14]. SMEs: THE BASIC CHARACTERISTICS For many years SMEs have represented the generators of economic development, both in developed and newly developed countries â&#x20AC;&#x201C; especially in transitional ones. The development of enterprising initiative enables the formation of autochthonous private capital and the development of the SME sector creates the conditions for faster local development, the strengthening of private property and solutions to certain macroeconomic problems, such as unemployment [11]. SMEs play a significant role in all OECD countries: they represent over 95% of the total number of all active companies and participate with 60-70% in total employment [04]. Between 30% and 60% of SMEs can be called innovative and 10% of them are high- technological companies. It is obvious that SMEs represent a segment which considerably determines the development of national economies. The development of SMEs is certainly the fastest and cheapest way to achieve the overall development of national economies. There are several reasons for this: the risk of SMEs business is mostly on the side of entrepreneurs, SMEs are more flexible in comparison with big companies, they are better adjusted to market requirements, they have low business expenses and lower prices for services/products, they offer greater reliability and efficiency, they have greater possibilities for specialization, they introduce innovations faster, they introduce IT more easily and cheaply. The most significant values of SMEs are market and technological flexibility, an innovative approach and their ability to take risks more easily. THE ROLE AND POSITION OF SMEs IN THE REPUBLIC OF SERBIA As in other countries which have begun the transitional process, SMEs in the Republic of Serbia have shown a constant growth in the last ten years. According to data from 2000, there were 60,552 active companies in the Republic of Serbia and the majority of them were small

450

companies - 56,993, while mid-sized companies numbered 2,573, and big companies 986. At the same time, out of the total number of registered companies (50.041) 82.6% were private and they mostly belonged to the group of SMEs [03]. In 2000, the most favourable financial results were on the side of small companies in which income exceeded expenses by 0.5%, while in midsized and big companies the total income covered 98.4% or 97.8% of expenses. Small companies made 33.9% of the profit and they recorded 16.8% of the total deficit, in other words, 8.8% of the whole deficit from the previous and current years. These results were achieved by small companies with 9.3% participation in the total capital of all domestic companies from the Republic of Serbia and with 22% participation in the total number of employed persons in Serbian companies. There were 367,367 employed people in 2001, which represents a slight fall in comparison with the previous year. Big companies employed 777,059 people, or 1.4% more than the previous year. It is also obvious that the number of employed persons in small companies increased to a total of 314,894 (23%), (compared with 309,710 the year before). However, the number of employees in mid-sized companies decreased. Therefore, in mid-sized companies in 2000 there were 313.303 (22.4%) employees compared with 275,414 or 20.1% in 2001 [13]. In the last few years the state administration has facilitated the establishment of certain institutional mechanisms for the development of the SME sector and the promotion of entrepreneurship. 1. The Central Agency for the Development of SMEs and Entrepreneurship was established (by the Serbian Government), whose aim is the stimulation of entrepreneurship, the development of an enterprising climate and IT support in the SME sector. This agency works as a consistuent part of the Agency for Regional Development. 2. An independent network of agencies for the development of the SME sector was also organized. The main financier of this activity was EAR together with the local administration. 3. The National Employment Office and Agency for the Development of SMEs worked together on the implementation of the concept of entrepreneurship centres at local level.

Journal of Applied Engineering Science 9(2011)4 , 209

Dr Dragan Ćoćkalo and etc. - SMEs in the Republic of Sebia: The developing capacities

SMEs participate in the total number of companies in the Republic of Serbia with 99.8%, in employment with 65.5%, with 67.6% in turnover and approximately 36% in the GNP (Table 1). As regards exports, the SME sector participates with

50.2%, in imports the percentage is 64% and in investments in the nonfinancial sector 51.2%. Micro companies are dominant in the SME sector, making up 95.6% of the total number and employing almost 50% of all employees [14].

Table 1. The number of companies according to size and employment [05] Size

Number of companies

Number of employees

Up to 50 employees

88.264

300.000

Up to 250 employees

2.218

280.000

Over 250 employees

503

420.000

In 2009 the number of SMEs and entrepreneurship companies increased by 9,337, which is 45% less than in the previous year. According to data from the Agency for Economic Records, in the first nine months of 2010 the number of newly established companies and shops was only 3,196 bigger than those which closed business in the same period. This drastic fall in the number of potential entrepreneurs who see a chance for new employment in starting a new business points to the considerably more difficult conditions for starting and maintaining a new business and the consequences of the global economic crisis are also a contributing factor. During 2009 the SME sector could use EUR 369 million. About EUR 318.1 million was from public sources. Out of EUR 252.8 million which was available only EUR 50.8 million was used from foreign sources. The main problems in the development of SMEs on the national market are the following [04]: 1. There is no systemic base which could create favourable conditions for the development of the SME sector. The institutions are not connected and the required level of coordination does not exist. 2. Lack of financial means (although they exist). Namely, financial resources for the development of SMEs are distributed selectively and are not available to all companies and entrepreneurs. This is especially related to state bodies which finance the development of SMEs. 3. Realization of financial means – When commercial banks are in question, both domestic and foreign, the procedure of obtaining loans is very long (minimum three months). The issue is even more complex with those state institutions which give financial support to Journal of Applied Engineering Science 9(2011)4, 209

SMEs – approximately 3-6 months is needed for funds to be approved. Most analysis dealing with the attitudes of entrepreneurs and SME owners show that it is very difficult to obtain loans despite several credit lines which state institutions and a considerable number of commercial banks offer. 4. The current chamber system is bureaucratic and is not coordinated with the needs of SMEs. Moreover, it is mostly oriented towards big state systems in the process of privatization. The chamber system mainly deals with issues of international regional cooperation. It is focused on big companies and fails to support the requirements of the SME sector, especially the private sector. Regional chambers of commerce are somewhat more flexible but this depends exclusively on the given local economic structure. 5. The owners of SMEs and entrepreneurs are not well enough informed. Despite the existence of numerous economic journals and programmes there is no one who deals with the problems of SMEs especially in the sphere of permanent and current information. 6. The majority of SME directors and owners lack the relevant knowledge and skills from the field of management necessary for the successful management of their companies (such as making business plans or investment studies). Although courses and seminars from this field are organized in regional development centres and regional chambers, they are usually too expensive for the owners of small shops and companies. There are a number of studies dealing with motivation, and intentions – the elements which in-

451

Dr Dragan Ä&#x2020;oÄ&#x2021;kalo and etc. - SMEs in the Republic of Serbia: The developing capacities

fluence enterprising behaviour and starting-up businesses in different ways, in other words, enterprising behaviour of the young and students and self-employment. This trend is expanding, depending on time (historical) and space (geographical) dimensions [06], [05]. POSSIBILITIES FOR IMPROVING THE COMPETITIVENESS OF SMEs IN SERBIA Competitive capacity of Serbian companies According to the Strategy for the Development of Competitiveness and Innovations of SMEs from 2008-2013, the basic pillars of development policy related to SMEs are: encouraging the opening of new companies, improving the management skills of employees, improving financing and taxation, promoting exports and innova-

tions, and improving legislation and the business environment. On the other hand, the competitive position of Serbian companies is unfavourable because they have failed to focus on business efforts in their development. According to the global index of competitiveness issued by the World Economic Forum in 2009 Serbia finished in 93rd place out of 133 countries. In one year alone Serbia fell eight places according to the same index. Slovenia, Montenegro, Croatia, Macedonia, Hungary, Romania and Bulgaria are all ahead of Serbia as are countries such as Panama and Kazakhstan. In our region only Bosnia and Herzegovina is behind Serbia, in 109th place. Table 2 presents the review of West Balkan countries according to the global index of competitiveness issued by the World Economic Forum in 2010.

Table 2. Ranking West Balkan countries according to competitiveness in 2010 [11]

Country Slovenia

Montenegro

Croatia

Macedonia

Serbia

BandH

102

Out of date technology, poor quality, unattractive packaging and high prices are the main reasons for Serbiaâ&#x20AC;&#x2122;s poor competitive position. The manufacturing industry is the least competitive, followed by the metal industry and electronics in which there have been no investments in technology for many years. Businessmen are of the opinion that tax and customs relief are necessary in order to increase competitiveness, accompanied by a reduction in state taxes, as well as lower prices of electrical energy, gas and fuel. Increasing the level of technological equipment is of major significance because the average age of machinery in Serbia is 30 years. Compared to other countries in the region it is lagging behind by 12 years. In terms of technology the Serbian economy is 29.5 years behind the EU as determined by a representative sample of 154 small, midsized and big companies in six economic branches with similar production programmes [17]. The research results dealing with the competitive index of Serbian companies show that as

452

Place

regards the competitive capacity of our companies, 47.93% of those interviewed think that it partially satisfies international requirements, 43.28% of them think that domestic companies do not satisfy these requirements while only 5.69% of interviewees consider these conditions competitive enough for the international market. The most important factors which Serbian companies lack concerning the development of competitiveness are presented in the figure 1. When asked about the level of innovations in domestic companies the majority of those interviewed, 60.17%, think that our companies partially satisfy this factor, 30.52% are of the opinion that our companies are not innovative, while only 6.55% consider domestic companies innovative. It is their view that the necessary elements for the development of the competitive capacity of our companies are presented in the figure 2.[07]

Journal of Applied Engineering Science 9(2011)4, 209

Dr Dragan Ä&#x2020;oÄ&#x2021;kalo and etc. - SMEs in the Republic of Sebia: The developing capacities

Figure 1. The most important factors which Serbian companies lack concerning the development of competitiveness /13/

Figure 2. The necessary elements for the development of the competitive capacity of Serbian companies [13]

Forms of improvements in performing business activities in the SME sector The principles which should be applied in performing business activities in the SME sector are as follows [11], [12]: 1. A small business does not mean small investments. It only means smaller investments in relation to capacity and the number of employees. A small business means a small number of employees who achieve a high degree of work productivity, the use of modJournal of Applied Engineering Science 9(2011)4, 209

ern technology achievements and the realization of development aims (a companyâ&#x20AC;&#x2122;s profit and growth). 2. A small business requires the implementation of high technologies but, first of all, it requires knowledge application and the permanent improvement of knowledge productivity. 3. Money does not come easily and quickly. Running a small business requires hard work, competence and diligence from all employees so that productivity of knowledge and work can be achieved.

453

Dr Dragan Ćoćkalo and etc. - SMEs in the Republic of Serbia: The developing capacities

4. The market is everything. Getting to know the market, buyers and customers, but competitors as well, establishes the conditions for successful business. 5. The modern market does not tolerate badquality business. Products and services of poor quality cannot be sold on global markets because high technologies are available to all nowadays. 6. The global aim of SMEs is a permanent increase in business productivity. This increase in productivity influences the quality of products which in turn serves to increase productivity. Finally, this results in market expansion and higher employment. 7. Marketing is not advertising. Marketing is not sales. Marketing is a management process which should create the conditions for permanent business performance along with fulfilling a company’s development aims. 8. Profit is not the only aim in a modern economy. Profit is a result of well created and realized business. Customer interests and society’s welfare are always priorities. Profit comes as a result of satisfied customers who ensure the development of the organization by their loyalty. 9. Small programmes can be stimulated only if they are profitable. 10. Small companies are founded in great numbers but they are also often closed in great numbers because they are not competitive on the market. Not everybody can be successful. Only those firms which can accept the fact that knowledge represents the base of business and increased productivity of work the imperative of modern business will be successful. In addition, such companies should constantly strive to improve quality and satisfy market requirements. SMEs are leaders in development in relation to innovations and mid-sized organizations are becoming the best options for achieving business success. Reducing the average size of companies creates the necessity for different forms of associations and cooperation between companies which enter the international market – they should achieve a synergic effect. Finally, this assumes the need to form associations and alliances not only for SMEs but for big companies as well. Small and mid-sized enterprises real-

454

ize this through different forms of associations based on common interests, such as agreement on common investment, associations for the realization of innovations, joint appearance on the market, and overcross licensing. Clusters represent one of the significant forms of associating SMEs. The notion of clusters was introduced by the American economist Michael Porter. Clusters represent the geographically limited concentration of similar or complementary businesses with active channels for business transactions, communications and cooperation. Regional clusters represent the concentration of mutually dependent companies in one geographical region. They are limited to one geographical region and consist of a great number of companies and employees within a small number of related industrial sectors. The organization of SMEs is certainly a question of entrepreneurship initiative – entrepreneurs have to find their own interest in associating but they should not be destimulated in the realization of their interests. Although it is up to administrative bodies to establish an institutional framework that will facilitate free entrepreneur associations, the problem of their organization should be the problem of the entrepreneurs themselves. Entrepreneurs should be organized on the basis of private initiative in order to ensure a successful appearance on the market, especially on the international market. These issues are not adequately represented on the Serbian market. According to the Strategy for the Development of Competitiveness and Innovations of SMEs for the period from 2008-2013 clusters are considered as instruments for increasing competitiveness on international markets [14]. Nowadays, there are 22 clusters in the Republic of Serbia, and in 2008, 14 clusters were financially supported by the state – the Ministry for the Economy and Regional Development provided a grant in the amount of RSD 52 million for the start-up and development of clusters (31 million were budget funds and 21 million a donation from Norway) [15]. Four out of 14 clusters were in the process of establishment – the medical tourism cluster, the tourist cluster in Srem, the association for the development of business and manifestation tourism and computers cluster. Only two out of 22 clusters are national – the car industry cluster and the wood industry cluster, while the remaining 19 clusters are regional ones. Clusters are organized as associations of citizens. Journal of Applied Engineering Science 9(2011)4, 209

Dr Dragan Ćoćkalo and etc. - SMEs in the Republic of Sebia: The developing capacities

Education for entrepreneurship

CONCLUSIONS

Knowledge is becoming a decisive factor for the development of entrepreneurship in transitional economies. One of the possible options for the improvement of entrepreneurship is the educational process in the field of entrepreneurship. This is related to the training of professionals and company executives, regardless of the ownership type, because of the identical principles of entrepreneurial business. The basic task of this type of education is achieving the knowledge necessary for the successful management of businesses and/or companies so as to increase productivity of work and knowledge. The final aim is business literacy for appropriate business management. Education for entrepreneurship must create the conditions and climate that ensure that newly acquired knowledge can be applied to both work and knowledge (the emphasis is not only on what but also on how something should be done). This means that the total result of education for entrepreneurship should be a manager and an entrepreneur – the generally accepted definition “the one who is responsible for the application and practical use of knowledge” must be applied to him/her. Education for entrepreneurship also includes the following issues: [10]:

SME-s facilitate the development of an entrepreneurial climate, especially in transitional countries. The main role of entrepreneurship in modern economies is reflected in innovative actions which create the conditions for technological development, flexible organizations and new employment. The development of SMEs and private entrepreneurship in transitional countries serve to boost employment in the whole economy. According to the Strategy for the Development of Competitiveness and Innovations of SMEs for the period from 2008-2013 [14], the economic progress and development of the Republic of Serbia require the development of a competitive economy based on knowledge, new technologies and innovations. Entrepreneurship is expected to make an important contribution to economic and social development. In addition, the readiness of SMEs to enter EU markets, adopt necessary standards and reduce differences concerning the level of development is of special significance. The hope of the global economy is in enabling regions to bring wealth from the rest of the world. In order to accomplish this task regions have to be equipped with highly educated and disciplined people led by visionary leaders able to communicate with the rest of the world [09]. Some of these regions are Hainan island (South China, Guandong Province), Vancouver and British Columbia (Canada), Estonia, Cho Shi Minn (Vietnam), Coastal and Sahalin island (Russia), Sao Paolo (Brazil), and Kiu-shiu (Japan). Serbia has all the preconditions to become one such region in the near future under one condition – our businessmen must change their business philosophy as quickly as possible. Serbia has all the preconditions to become one of these regions in the near future, under one condition – our businessmen must change their business philosophy as quickly as possible. Capital owners and executive management should establish new elements of competitiveness in our companies [02]. Old policies and management techniques must be abandoned in favour of new ones, and we need to learn from the experiences of global leaders and companies from newly industrialized countries which are successful on the global market. Small and mid-sized enterprises can only survive on the global market if they are associated in clusters. However, the state also has a crucial role to play in cluster formation. Cluster

1. Acquiring knowledge and the development of creative, problem solving abilities, the development of entrepreneurial style in the population of youth and adults within formal education. 2. Building-up the business management knowledge and abilities of current entrepreneurs and executives (financial and low business, informatics, management, marketing, business communication). 3. Training the unemployed and redundant for the start-up of their own businesses.Special attention must be paid to the implementation of new management approaches, both in a conceptual and organizational sense. Enterprises, including a great number of those organizations which do not belong to enterprises (universities, institutes, etc.), should begin with experiments related to new corporative forms and they should carry out pilot studies especially in cooperation with partners or associations – they should define common tasks, structures and activities.

Journal of Applied Engineering Science 9(2011)4, 209

455

Dr Dragan Ćoćkalo and etc. - SMES in the Republic of Serbia: The developing capacities

policy assumes an initiative on the part of the state in the process of their formation, as well as in improving business contacts and relations among associates which is based on commercial and innovation links, knowledge flow and the provision of specialized infrastructural support. Clusters provide SMEs with the following advantages: greater access to new knowledge and skills, common services, partnership support, branding products, the development of marketing strategies, joint work on innovations, more efficient implementation of QMS, and the co-financing of private and state organizations. Economic growth and development of the Republic of Serbia requires the development of such an economy which is competitive and based on knowledge, new technologies and innovations. In order to achieve this objective it is expected from entrepreneurship to give a significant contribution to social and economic development. Besides, it is of special importance the readiness of SME sector to enter and win EU market together with applying necessary standards and reducing differences concerning the level of development. REFERENCES 1) Baker, W.A., & Sinkula, J.M. (2009). “The Complementary Effects of Market Orientation and Entrepreneurial Orientation on Profitability in Small Businesses,” in Journal of Small Business Management 47(4), 443–464. 2) Ćockalo, D., Đorđević, D., & Đurin, S. (2011). Business Strategy of Providing Customer Satisfaction: An Exploratory Study in QM Certified Serbian Companies. Journal of Applied Engineering Science, 9(2), 339-348. 3) Đorđević, D. (2001). Mala i srednja preduzeća [in Serbian]. Belgrade: KAS. 4) Đorđević, D. (2005). “The Situation of SMEs Regarding Financing in Serbia and Montenegro,” in International Workshop “Financing of SMEs”. Belgrade: Organization of the Black Sea Economic Cooperation, Konrad Adenaure Stiftung Belgrade and Chamber of Commerce of Serbia. 5) Đorđević, D., Bogetić, S., Ćoćkalo, D., & Bešić, C. (2009) Analiza preduzetničkog ponašanja kod mladih u Republici Srbiji, Megatrend revija, 6(1), 221-234. 6) Đorđević, D., D. Ćoćkalo, & Bogetić S. (2010). “Preduzetničko ponašanje kod mladih – rezultati istrživanja u Srbiji (The Youth’s Enter-

456

prising Behaviour –The Research Results From Serbia),“ in Ekonomske teme (Economic Themes) 3/2010, 467-479. 7) Đorđević, D., D. Ćoćkalo, & Bogetić, S. (2011). “The Role of Knowledge in Improving the Quality of Business within Serbian Companies,” in VI International working conference Total Quality Management – Advanced and intelligent approaches. Belgrade: UASQ, 265-270. 8) Drucker, P. (1996). Menadžment za budućnost [in Serbian]. Belgrade: PS Grmeč-Privredni pregled. 9) Ohmae, K. (2007). Nova Globalna Pozornica [in Croatian]. Zagreb: Mate. 10) Sajfert, Z., C. Besic, & Petrovic, N. (2008). “The Role of Corporate Entrepreneurship in the Process of Improving the Quality of the Business of Domestic Companies,” [in Serbian] in International convention on quality “Quality for European and World Integrations”. Belgrade: UASQ, 259-260. 11) Sajfert, Z., D. Đorđević, & Bešić, C. (2006). Menadžment Trendovi [in Serbian]. Zrenjanin: Tehnički fakultet “Mihajlo Pupin”. 12) Spasojević-Brkić, V., Klarin, M., & Curović, D. (2009). Dimenzije menadžmenta kvalitetom isporučioca u industrijskim preduzećima Srbije. Istraživanja i projektovanja za privredu, 7(23-24), pp. 67-71. 13) *** (September 2002). “Twenty Percent of the Capital With a Fifty Percent Obtain,” [in Serbian] in SME’s News. Belgrade. 14) *** (2008). “Strategy for the Development of SMEs Competitiveness and Innovation for 2008-2013,” [in Serbian] in Službeni glasnik RS, br.55/05, 71/05-ispravka, 101/07 i 65/08. Belgrade: Official Gazette RS. 15) *** (04.10.2008). “With Clusters in the Hunt For Markets,” [in Serbian] in Novac. Belgrade: Ringier. 16) *** (11.07.2009). “Developing Countries A New Marketing Eldorado,” in Novac. Belgrade: Ringier. 17) *** (16.07.2009). “Serbia Technologically Lags Three Decades Behind EU,” [in Serbian] in Blic. Belgrade: Ringier. 18) *** (2010). “The Global Competitiveness Report 2010-2011,” World Economic Forum. Paper sent to revision: 27.10.2011. Paper ready for publication: 21.11.2011. Journal of Applied Engineering Science 9(2011)4, 209

DOI: 10.5937/JAES9 - 1202 Paper number: 9(2011)4, 210, 456 - 464

COMBINATION FREE REPLACEMENT AND PRO-RATA WARRANTY POLICY OPTIMIZATION MODEL MSc Dragan Stamenković University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia Dr Vladimir Popović University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia Dr Vesna Spasojević-Brkić University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia MSc Jovan Radivojević University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia Product development risk increases more and more every day. One of the factors that affect this risk is product warranty. Warranty is a powerful marketing instrument for the manufacturer and a good protection for both the manufacturer and the customer, but it always involves additional costs to the manufacturer. These costs depend on the product reliability and the warranty parameters. This paper deals with the optimization of these parameters for known product failure distribution to reduce the warranty costs to the manufacturer while retaining the promotional function of the warranty. Combination free replacement and pro-rata warranty policy is chosen as a model and the length of free replacement and pro-rata policy periods are varied, as well as the coefficients that define the pro-rata cost function. Warranty costs are obtained by using analytical equations and by simulation. The obtained results are shown and discussed and some concluding remarks are given. Key words: free replacement warranty, pro-rata warranty, combination, costs, optimization INTRODUCTION More and more increasing product development risk is affected by the competition, schedule pressure, short deadlines, failure costs, rapid development of new materials, methods and complex systems, need for product cost reduction and safety issues [11]. Figure 1 shows the effects on an overall risk perception [09]. These effects are: customer requirements, safety, development risks, market pressure, legal and statutory regulations, management emphasis, warranty and service costs, competition, public liability and many more. Successful control of these risk factors is the main goal of reliability engineering development [10]. The focus of this paper is on the reduction of the effects warranty has on the product risk by choosing the best warranty policy. Product unavailability depends on its reliability,

Figure 1. Risk perception [2]

maintainability and logistic support [06,12]. Product may become unavailable due to a hardware or software failure, human error or preventive maintenance (which requires the product to be excluded from service). When product or service becomes unavailable, a number of consequential costs can arise. These costs are called unavailability costs and may include [11]: • warranty costs; • liability costs;

* Faculty of Mechanical Engineering, Kraljice Marije 16, 11000 Belgrade, Serbia, dstamenkovic@mas.bg.ac.rs

457

MSc Dragan Stamenković and etc. - Combination free replacement and pro-rata warranty policy optimization model

• •

costs caused by the decrease of the production function output; costs of providing the alternative services.

Unavailability costs should be identified by using the risk analysis techniques to determine the costs caused by the negative publicity which could eventually lead to customer loss. Costs of recovery from the negative effects that such publicity has on the company image, reputation and respectability and costs of reducing these risks are also unavailability costs. In many cases these costs are hard to asses, but it is sometimes possible to quantify them. For example, they can be assessed as a public campaign and marketing costs, or costs of compensation in order to keep the customers. These costs should be calculated whenever possible. One of the key factors in the customer’s decision-making process is product warranty. When choosing between several products with similar characteristics, customer will usually buy the product that provides a better warranty. A warranty is a contract or an agreement between the manufacturer and the customer. Under this agreement the manufacturer is obligated to repair, replace or provide service when the product fails to perform its function before the end of the warranty period. From the customer’s point of view warranty has two functions – protective and informative. Warranty performs its protective function by assuring the customer that faulty products will either be repaired or replaced at no cost or at a reduced cost. Informative function of warranty means that it indirectly gives the customer the information about the product quality. From the manufacturer’s point of view warranty also has two functions – protective and promotional. Protective function is reflected in warranty terms that specify the use of the product and limited coverage or no coverage at all in the case of misuse of the product. Promotional function from the manufacturer’s point of view is associated with the informative function from the customer’s point of view. As said before, when choosing between similar products, customer tends to buy the product with better warranty. This led to the competition between the manufacturers in offering the better warranty to attract more customers. Warranty costs are usually borne by the manufacturer, depending on the reliability characteristics, maintainability and the performance of the product logistic support. The manufacturer could

458

take important measures to control these characteristics during the design, development and manufacturing process and lower the warranty costs. Warranties are defined by their terms and are usually time limited. Rarely they include consumer protection against unavailability costs due to the product unavailability. Warranties could be supplemented or replaced by a service agreement according to which the manufacturer performs complete preventive and corrective maintenance during the specific period of time, which could be extended to a limited period, or even to the end of the product life-cycle. There are three commonly used types of warranty policies [03,04]: Free replacement warranty (FRW) – under this warranty, if a product fails before the end of the warranty period, the manufacturer is required to either repair the product or provide a new product at no cost to the customer. This type of policy is usually offered for repairable products. There are two types of free replacement warranty policy: a) ordinary free replacement warranty – under this warranty, the repaired product is covered by the same type of warranty policy as it was before the failure. Warranty length for the repaired product is equal to the remaining length of the original warranty. This type of warranty is usually used for products such as home appliances, computers and vehicles; b) unlimited free replacement warranty – under this warranty, the repaired product is covered by a new unlimited free replacement warranty. The length of the new warranty is equal to the original warranty length. This type of warranty policy is used for small electronic appliances with high early failure rates. The length of the unlimited free replacement warranty is usually short; Pro-rata warranty (PRW) – under this warranty, if a product fails before the end of the warranty period, the manufacturer is required to replace the product at a cost, which is called pro-rata cost, that depends on the age of the product at the time of failure, and can be either a linear or non linear function of the remaining time in the warranty length. The replacement product is then covered by an identical new warranty. This type of warranty is usually offered with non-repairable products such as tyres, bulbs and batteries;

Journal of Applied Engineering Science 9(2011)4, 210

MSc Dragan Stamenković and etc. - Combination free replacement and pro-rata warranty policy optimization model

Combination free replacement and pro rata warranty (FRW/PRW) – this type of policy is often used as a compromise, since the FRW policy is the most favourable to the customer and the PRW policy is the most favourable to the manufacturer. This type of warranty is comprised of two periods – a period of free replacement followed by a period of pro rata policy. Such combination has a significant promotional value to the manufacturer and at the same time provides adequate cost control for both manufacturer and customer in most cases [02,07]. Like the pro-rata warranty policy, combination warranty policy is usually offered with non repairable products. A more comprehensive study on the types of warranty policies can be found in [03,04]. Warranty cost calculation is covered in [01,08,13]. In this paper a fully renewing combination free replacement and pro-rata policy will be considered with the objective to find the optimal warranty parameters. The optimal warranty parameters are those which lower the warranty costs, but still attract the customers. Parameters considered for optimization are: total warranty length, free replacement period length and two coefficients that define the pro-rata cost function, which will be defined later in the text. WARRANTY MODEL Fully renewing combination free replacement and pro-rata policy specifies two warranty periods, denoted w’ and w. The manufacturer agrees to replace the product with a new product at no cost to the customer if it fails before w’ (w’ < w) expires. If a failure occurs in the time interval from w’ to w the product is replaced by the manufacturer at a fraction of the replacement cost (pro-rata cost) to the customer. Warranty analysis in this paper is done for one type of passenger car batteries. This type of batteries has been on the market for 16 years and the manufacturer wanted to launch the new warranty policy along with the start of a new marketing campaign. According to the collected data from a 16 year long exploitation it is determined that life of this type of battery follows Weibull distribution with a shape parameter = 1.63 and a scale parameter η = 4380 days. The price per battery unit excluding the warranty cost is = 82 €. It is assumed that every failure results in a warranty claim, all warranty claims are valid and all failures are statistically independent. Journal of Applied Engineering Science 9(2011)4, 210

In this warranty model the pro-rata cost is a linear function of time. Replacement cost to the manufacturer is calculated by the following equation [02,07]:

(1)

Figure 2. FRW/PRW policies with different values of proportionality coefficients

For w’ = 0 FRW/PRW policy becomes PRW policy, and for w’ = w FRW/PRW policy becomes FRW policy. Figure 2 illustrates how different values of proportionality coefficients k and affect the FRW/PRW policy. Probability density function for a Weibull distribution is given by: (2)

and the cumulative distribution function is: (3) The number of failures for one battery unit by time t has a geometric distribution, so the expected number of failures for one battery unit by time t is: (4) The expected number of failures for the whole lot by time t can be calculated by multiplying the

459

MSc Dragan Stamenković and etc. - Combination free replacement and pro-rata warranty policy optimization model

expected number of failures for one battery by the product lot size: (5) (10)

The total number of failures for the whole lot in the interval from t to t+dt is: (6)

where N1 and N2 are the numbers of failures in the free replacement period and pro-rata warranty period, respectively. After dividing the both sides by the lot size L equation (10) becomes:

and the expected total cost to the manufacturer for the failures from t to t+dt is: (7)

(11)

The warranty cost to the manufacturer per unit then can be calculated as:

where C(t) is the replacement cost to the manufacturer at time t. Total expected cost to the manufacturer for the whole warranty period is then calculated by the following equation: (12)

(8)

Warranty cost to the manufacturer per unit is obtained by dividing the total cost with the lot size L:

Warranty costs are calculated and simulated for the warranty period length w ranging from 1 to 6 years and the free replacement period length w’ ranging from 0 to w for three different polices: the first policy with proportionality coefficients k = 1 and = 1, the second with k = 0.5 and , = 1 and finally, the third with k = 1 and = 0.5. DISCUSSION OF RESULTS

(9)

For the purpose of this paper, analytical equations (8) and (9) are solved numerically using MATLAB. Warranty cost can also be obtained by performing the simulation in order to compare the simulated results with those obtained using the analytical equations. The life-cycle of every battery unit in a lot is simulated using MATLAB. Lot size for the simulation is set to 10 000 units. If one battery unit fails, simulation of life-cycle of the replacement battery starts from the beginning. This process is repeated until one of the replacement batteries reaches full warranty period without a failure for every battery in the lot. Total expected cost to the manufacturer then can be calculated using the equation:

460

Tables 1 to 3 show unit prices after adding the warranty cost for different warranty and free replacement period length for all three policies considered. In these tables cs and ca denote the price values obtained by simulation and by using analytical equations, respectively. For equal values of w an w’ FRW/PRW becomes FRW policy, so the analytical price values for these cases are identical for all three policies. Because of this, unit price curves start at the same points on all three diagrams. Displayed results also show that simulated price values follow analytical ones closely. Figures 3 to 5 show the analytical unit price values after adding the warranty cost as a function of warranty period length w and free replacement period length w’ for all three policies. These diagrams show the effects that change of the proportionality coefficients k and and free replaceJournal of Applied Engineering Science 9(2011)4, 210

MSc Dragan Stamenković and etc. - Combination free replacement and pro-rata warranty policy optimization model

ment period length w’ has on the unit price–warranty length relation. By reducing the proportionality coefficient k price curve slope decreases, while reduction of proportionality coefficient has the opposite effect. Table 1. Simulated and analytical unit price values after adding the warranty cost for k = 1 and =1 w’ 0

82.57

82.55

83.26

83.47

83.66

83.74

85.13

85.53

85.51

88.52

5 6

84.98

86.98

86.81

87.14

87.06

89.41

87.87

90.44

89.80

92.05

90.95

94.55

96.99

94.92

99.37

89.26

91.94

92.14

93.58

92.43

95.82

93.33

98.65

96.49

97.85

104.33

101.71

95.83

100.69

100.19

102.38

100.56

106.55

110.11

106.66

116.79

105.78

112.54

112.53

113.05

123.92

121.39

131.73

132.55

Table 2. Simulated and analytical unit price values after adding the warranty cost for k = 0.5 and =1 w’ 0

82.32

82.27

83.45

83.47

82.95

83.47

84.20

83.59

83.72

85.01

5 6

84.21

87.19

86.81

85.65

85.23

88.38

84.83

86.87

86.52

86.68

86.24

89.17

88.87

87.99

91.41

88.02

92.22

92.14

90.45

89.53

94.38

88.12

92.46

91.39

90.09

95.89

93.67

Journal of Applied Engineering Science 9(2011)4, 210

93.95

100.43

100.19

97.84

96.17

105.54

102.74

98.87

111.37

102.91

111.75

112.53

106.23

120.42

116.79

133.12

132.55

461

MSc Dragan Stamenković and etc. - Combination free replacement and pro-rata warranty policy optimization model

Table 3. Simulated and analytical unit price values after adding the warranty cost for k = 1 and = 0.5 w’ 0

83.07

83.00

83.46

83.47

85.04

85.25

85.48

89.03

88.70

94.37

5 6

85.88

86.97

86.89

88.94

89.53

91.02

93.63

95.37

94.71

100.78

100.60

103.25

111.73

110.62

114.30

90.68

92.45

92.14

95.67

96.15

98.09

102.03

103.65

103.89

112.59

116.58

115.10

97.96

99.25

100.19

107.13

106.21

109.03

117.83

118.21

124.51

109.05

112.64

112.53

122.03

127.88

126.73

Figure 3. Analytical unit price values after adding the warranty cost for k = 1 and

Beside the costs to the manufacturer, the promotional effect needs to be considered for every warranty policy variant. For example, for the warranty policy defined by k = 0.5 and = 1 (Figure 4), analytical unit price value after adding the warranty cost for w = 5 and w’ = 0 (ca = 86.245) is less than the price value for w = 2 and

462

131.56

132.55

w’ = 2 (ca = 86.808). Although longer, and thus potentially having greater promotional value, the first of two variants is characterised by less cost to the manufacturer. The analysis of promotional value of warranty policies is not the subject of this paper and should by acquired through market research. Journal of Applied Engineering Science 9(2011)4, 210

MSc Dragan StamenkoviÄ&#x2021; and etc. - Combination free replacement and pro-rata warranty policy optimization model

Figure 4. Analytical unit price values after adding the warranty cost for k = 0.5 and

Figure 5. Analytical unit price values after adding the warranty cost for k = 1 and

= 0.5

CONCLUSION Product warranty is one of the key factors that affect the risk involved with product development. By choosing the best warranty policy manufacturer can reduce this risk. The best policy is one having the best ratio of warranty cost to the manufacturer to promotional value to the buyer. In Journal of Applied Engineering Science 9(2011)4 , 210

the present paper the effects that change of parameters k and that define warranty has on its cost to the manufacturer was considered. It was done by both calculating and simulating the warranty costs for three different FRW/PRW policy variants and different length of warranty period and free replacement period. It is also important to notice that conducted simulation proved

463

MSc Dragan Stamenković and etc. - Combination free replacement and pro-rata warranty policy optimization model

useful in the determination of warranty costs. Shown results define the relation between the proportionality coefficients k and and warranty cost to the manufacturer that is depicted through the change of unit price after adding the warranty cost. These results, after conducting the market research and obtaining the promotional value for all of three warranty variants, enable the manufacturer to conduct cost-benefit analysis and choose the best warranty policy. ACKNOWLEDGEMENTS This paper is a part of two important projects of The Ministry of Science and Technological Development of Serbia (project number TR 35045 – “Scientific-Technological Support to Enhancing the Safety of Special Road and Rail Vehicles” and TR 35040 – “Developed New Methods for Diagnosis and Examination Mechanical Structures”). The authors wish to express their gratitude to the investors in these projects, and to all persons who helped making this paper better. NOTATIONS - Weibull distribution shape parameter η - Weibull distribution scale parameter c’ - battery unit price before adding the warranty cost r - expected warranty cost per battery unit c - unit price after adding the warranty cost, c = c’ + r k - proportionality coefficient of c - proportionality coefficient of time of failure in the warranty interval N(t) - number of failures at time t L - battery lot size for warranty cost determination w - warranty period length w’ - free replacement period length C(t) - replacement cost to the manufacturer at time t TC - total warranty cost of a lot of size L. Most of the notations are taken from [5]. REFERENCES 1) Balcer, Y., Sahin, I., (1986) Replacement Costs Under Warranty: Cost Moments and Time Variability, Operations Research, 34(4), 554–559.

464

2) Blischke, W.R., Murthy, D.N.P., (1996) Product Warranty Handbook, New York: Marcel Dekker. 3) Blischke, W.R., Rezaul, M.K., Murthy, D.N.P., (2011) Warranty Data Collection and Analysis, London: Springer Verlag. 4) Guangbin, Y., (2007) Life Cycle Reliability Engineering, Hoboken: John Wiley & Sons. 5) http://www.weibull.com/hotwire/issue100/ relbasics100.htm, consulted 7 September 2011. 6) Mitic, S., Rakicevic, B., Stamenkovic, D., Popovic, V., (2011) Advanced Theoretical–Experimental Method for Optimization of Dynamic Behaviour of Firefighting Vehicle Modular Superstructure, Journal of Applied Engineering Science, 9(1), 267–275. 7) Mitra, A., Patankar, J.G., (1997) Market Share and Warranty Costs for Renewable Warranty Programs, International Journal of Production Economics, 50(2–3), 155–168. 8) Nguyen, D.G., Murthy, D.N.P., (1984) Cost Analysis of Warranty Policies, Naval Research Logistics Quarterly, 31(4), 525–541. 9) O’Connor, P., (2002) Practical Reliability Engineering (4th edn), Hoboken: John Wiley & Sons. 10) Popovic, V., Vasic, B., (2008) Review of Hazard Analysis Methods and Their Basic Characteristics, FME Transactions, 36(4), 181–187. 11) Popovic, V., Vasic, B., Petrovic, V., (2010) The Possibility for FMEA Method Improvement and Its Implementation into Bus Life Cycle, Strojniski vestnik – Journal of Mechanical Engineering, 56(3), 179–185. 12) Popovic, V., Vasic, B., Rakicevic, B., Vorotovic, G., (in press) Optimization of Maintenance Concept Choice Using Risk Decision Factor – a Case Study, International Journal of Systems Science (Accepted for publication April 2011, doi: 10.1080/00207721.2011 .563868). 13) Ritchken, P.H., (1985) Warranty Policies for Non-Repairable Items under Risk Aversion, IEEE Transactions on Reliability, 34(2), 147– 150. Paper sent revision: 21.11.2011. Paper ready for publication: 13.12.2011. Journal of Applied Engineering Science 9(2011)4, 210

DOI: 10.5937/JAES9 - 1267 Paper number: 9(2011)4, 211, 465 - 472

PROACTIVE TIRE MAINTENANCE Dr Gradimir Danon * University of Belgrade, Faculty of Forestry, Belgrade, Serbia Miloš Petrović Institute for research and design in commerce and industry, Belgrade, Serbia Objective of the paper is to promote the proactive approach in tire maintenance for commercial vehicles and application of the Tire Pressure Monitoring System (TPMS). Researches have confirmed that the installation of TPMS on commercial vehicles is technically and economically justified, namely traffic safety and comfort of passengers would thus be significantly improved and operating costs would be decreased. Example of articulated city bus shows that the investment in the Tire Pressure Monitoring System would be recovered in the second year of operation. Key words: tire, pressure control, traffic accident, costs INTRODUCTION From the end of the 1980’s a lot of attention has been paid in professional and scientific journals to the problems connected with tire use and maintenance and potential dangers if the tires are not controlled and/or maintained regularly. It was determined that tires are very frequent cause of vehicle stopping. For example, in 2002 AAA (The American Automobile Association, Inc.) received 2.4 million calls from drivers who stayed on the roads because of deflated tires [15]. It was more than 50% of the total number of calls, namely almost 0.5 of tire failures per million vehicle/kilometres in the USA in the same year (2002). Number of failures is probably higher as it can be assumed that a significant number of drivers solved the “problem” and replaced the deflated tire with a spare one. The stated researches did not confirm usual statements that tire failures during driving were mostly the consequence of tire punctures. On the contrary, it was determined that more frequently these are failures as a consequence of thermal-mechanic loads of insufficiently inflated or overloaded tires, i.e. accelerated fatigue of material the tires were made of. Researches conducted in the USA showed that tires, beside the large number of failures, are not frequent cause of traffic accidents (only 0.5% of 6.3 million accidents that occurred in the USA in 2003) [01], however they have a high participation in “technical” accidents i.e. the accidents the cause of which was a vehicle system. For

example, tire failures compose 21% of all technical accidents of trucks [15] or even 50% according to the data from Germany [07]. Figure 1 shows the structure of tire failures (causes of accidents with casualties or fatalities) in Germany.

Figure 1: Causes of tire failures causing accidents with casualties or fatalities in Germany [11]

On the Figure it can be seen that negligence and poor maintenance of tires are the most frequent cause of accidents for which tires are marked as the main cause (43%). Insufficient maintenance, or negligence, primarily implies insufficiently frequent control of tire pressure. According to the researches of the National Highway Traffic Safety Administration (NHTSA) on over 10,000 passenger and light trucks conducted in 2001 [15], 36% of the tested passenger vehicles and 40% of light trucks were found to have one or more tires under-inflated (by more than 20%). The situation was not better among commer-

* Faculty of Forestry, Kneza Višeslava 1, 11000 Belgrade, Serbia, gradimir.danon@sfb.bg.ac.rs

465

Dr Gradimir Danon and etc. - Proactive tire maintenance

cial vehicles. According to the study [02], almost 44% of tires on trucks and buses had the pressure ranging about 0.4 bar of the recommended pressure, and about 7% of tires had the pressure lower by more than 1.5 bar than the recommended pressure. Researchers in Serbia reached similar results as well [14, 05]. The situation is especially worrying regarding the pressure maintenance of dual tires for which (Figure 2) air pressure control could not be performed due to the lack of valve stem extender [05].

Figure 2: Results of air pressure control on city busses /16/

Common conclusion that can be made based on these researches is that the present maintenance of tires on passenger and commercial vehicles is not on adequate level, users do not pay sufficient attention to tires and they do not realize the importance of tires for safe driving. Also, it can be concluded that a large number of failures with happy ending was found which could act as a reminder that luck can be changeable and that lack of tire maintenance can significantly jeopardize traffic safety. One of the available opportunities for solving the problem of monitoring air pressure in tires is wider application of the Tire Pressure Monitoring System (TPMS) on cars and commercial vehicles. This idea is not new. More than fifteen years ago (in 1996) an article on TPMS for passenger and freight vehicles was published in “Commercial Carrier” journal [06]. The article analyzed devices used for monitoring air pressure in tires available at that time, as well as devices that enable pressure equalization in dual tires or pressure regulation, i.e. air inflation in tires. Based on this article and the information obtained from the companies that developed or sold these devices, an impression could be reached that these were already developed systems already commercially applied [09]. Unfortunately, the situation was not such. Lack of legislation (which appeared much later, first in the USA) and their price at

466

that time limited the application of these devices to luxury passenger cars equipped with run-flat tires. Only after Ford – Firestone scandal [10] did the extensive researches start in the USA regarding the justification of using these devices [13]. These researches resulted with the TREAD regulation [11] that forbids the sale of new passenger cars without a TPMS device in the USA after 2006. The European Community adopted a similar regulation in 2009 with obligatory application for new vehicles from November 2014. Based on positive experience with passenger cars, the introduction of obligatory installation of TPMS also on trucks and busses is expected as the next step. To that effect, adequate researches have been conducted for several years already focused on the quantification of the impact of maintaining proper air pressure in tires of commercial vehicles in busses on safety and operating costs. Conclusion of these studies [02, 04] is that the realized savings in tire and fuel costs for commercial vehicles would pay off the investment in installing TPMS already in the second year of operation. TIRE PRESSURE MONITORING SYSTEM (TPMS) DEVICES Drivers traditionally avoid their obligations regarding tire maintenance. Despite various educational activities, no special advancement has been done and producers of tires and vehicles have searched for solutions which would “make the drivers’ life easier” eliminating at the same time the main cause of tire failures, namely (instantaneous or gradual) loss of air pressure in tire. The simplest way is the sealants injected in the tire through the valve stem. The advancement in this area was made by Goodyear which offered tires with built-in sealants between two tire layers several years ago [12]. The best solution, however for passenger vehicles only, is the so called “run flat” tires. Run-flat tires are always accompanied with TPMS devices. These devices are, as previously mentioned, obligatory for all new vehicles sold in the USA from 2008 and from 2014 similar law will be in force in the European Community countries. Today, there are two types of these devices on the market, namely the ones that indirectly measure air pressure in tires by calculating the change of wheel radius from extensive tire speed and the others that directly measure the pressure (usually the temperature as well) and send the data to the driver’s cab. Journal of Applied Engineering Science 9(2011)4, 211

Dr Gradimir Danon and etc. - Proactive tire maintenance

Indirect systems – use the speed sensors of anti-lock braking systems. These sensors measure angular velocity of each wheel and based on this the computer calculates rolling radius which is in correlation with tire pressure among other things. Smaller rolling radius on a wheel means lower tire pressure. Too large differences in the calculated rolling radii activate alert signals in the driver’s cab. Advantage of this system is that additional costs of installation are small if the vehicle is already equipped with ABS system. Disadvantages of these devices are numerous: • Proper functioning of the system requires reset after each inflation and set-up of the new condition. If the device is not set on the recommended pressure, calculation of rolling diameter will not be correct and the system will not react timely; • Current indirect systems have different reactions for different speeds usually reacting only when the pressure drops to 30% lower value than the recommended pressure; • Tires of different producers can have different elasticity characteristics and different rolling diameters (for the same load and air pressure), which can also impact the moment of system reaction; • Insufficient pressure on all four wheels at the same time (which is a frequent case) is difficult to detect because of the manner of device operation. • If the vehicle is not already equipped with ABS system, installation costs for indirect TPMS are significantly higher. Direct systems – TPMS measures actual (over)inflation and temperature of air in tires. Sensors can be placed in the deepest groove on the wheel rim interior (in tubeless tires) or integrated with tire valve stem. Device in the cab receives signals from the transmitter and compares them with the previously given limit values for pressure and temperature. If the measured pressure or temperature exceeds the set limits, sound and/ or light alert is activated in the driver’s cab. Advantages of these systems are: • Sensors are factory calibrated and do not have to be recalibrated; • They operate with all usual tire types; • They can also be used as measuring devices of air pressure in tires if the driver does not have it; Journal of Applied Engineering Science 9(2011)4 , 211

•

It alerts the driver when the pressure drops below the set limit (which the driver can also change) and identifies the wheel where it occurred.

Disadvantage of direct TPMS systems is costs of procurement and installation in new and existing vehicles. Regulations in the USA and Europe so far give preference to direct systems, therefore only these systems will be discussed hereafter. The set consists of a certain number of sensors (depending on the number of wheels on a vehicle) and receiver installed in the driver’s cab. Example of the system for monitoring air pressure in truck tires is given on Figure 3.

Figure 3: Example of tire pressure monitoring system for freight vehicles Appropriate sensors (5) are installed on each wheel. Sensors measure air (over)inflation and temperature in tires. Signal from the sensors is transmitted via antennas (6) to the receiver (3 and 4) and finally to the display in the driver’s cab (1). The measured (over)pressure is recalculated in the receiver for standard conditions (20oC) and compared with the set limit values. Many devices with sensors can be found on the market which are mounted on wheel rim by means of steel belt (see Figure 4). Sensors for passenger cars, light trucks and heavy trucks are developed. The second group consists of the sensors installed on the interior of the valve stem of tubeless tires (see Figure 5). These sensors and valve stems are specially developed for the installation on the wheels of commercial vehicles. The sensor is installed on a standard valve stem and does not hinder

467

Dr Gradimir Danon and etc. - Proactive tire maintenance

Sensor for passenger vehicles

Transmitter installed on wheel rim

Sensor for passenger vehicles

Figure 4: Devices installed on wheel rim

Figure 5: Sensor installed on valve stem

inflation and manual pressure control. There are two types of valve stems: the one made for steel and the other made for aluminium wheels. The advantage of these systems is that they are tougher, they have low profile, they are not easily damaged when mounting/dismounting tires and there is no need for a special antenna because the valve stem itself acts as one.

Disadvantage of these sensors is that they have to be removed during inflation and they could become the target of inquisitive persons. Technical solutions allowing manual control or inflation of tires to their proper pressure without taking off the sensors can also be found on the market (Figure 7). These are the so called “Flow–Through” sensors which can be dismantled by means of special tools only.

The third group consists of TPMS installed as valve caps. They are a simple and cheap do-ityourself solution, which can be used for passenger and freight vehicles (Figure 6).

The simplest solutions do not have this option. Sensors act as valve caps at the same time. Air pressure control in tires is done in various ways depending on the applied technical solution:

a) for passenger vehicles

b) for freight vehicles

Figure 6: Valve caps – sensors for monitoring tire pressure

•

In the driver’s cab – most existing technical solutions also have adequate display in the driver’s cab where it is possible to read temperatures and pressures in each tire separately. Driver can react on time and inflate

468

the tire on the first petrol station or in the garage. Also, the system should react with sound or light signal if the pressure in one of the tires is lower than the set threshold (usually 80% of the recommended pressure); Journal of Applied Engineering Science 9(2011)4, 211

Dr Gradimir Danon and etc. - Proactive tire maintenance

Figure 7: „Flow–Through“ sensors for external installation

In the garage – a stationary device is mounted which controls tire pressure on vehicles that enter or leaving the facility provided that they have adequate transmitters installed on wheels (see Figure 8). These way vehicles with deflated tires can be prevented from leaving. The system is primarily intended for garages with a lot of vehicles whose daily movement radius and daily kilometres are relatively low. • By means of a handheld device – maintenance worker has a personal digital assistant (PDA) and adequate software by means of which it can read air pressures in tires and record air pressure in tires in contact-less manner. If RFID (Radio frequency identification) is also installed in the tire, this device can also be used to read other data about tires. •

Figure 8: Control point for remote control of air pressure in tires

All text paragraphs should be single spaced, with first line intended by 10 mm. Double spacing should only be used before and after headings and subheadings as shown in this example. Position and style of headings and subheadings should follow this example. No spaces should be placed between paragraphs.

Journal of Applied Engineering Science 9(2011)4 , 211

JUSTIFICATION OF USING TPMS ON COMMERCIAL VEHICLES In the last several years, a lot of researches have been done with the objective to reject or confirm economic justification for applying TPMS devices [02, 08, 12]. Frequency of tire failures on passenger and freight vehicles, causes and consequences of these failures were researched. Objective of these researches was to determine if the realized savings would be higher than the costs of procurement, installation and maintenance of this equipment. Results of these and many other researches unambiguously indicate that improper air pressure in tires reduces the safety of passengers and vehicles and increases total operating costs. To quantify the effects of improper tire inflation, it was necessary to use “impact profile curves,” which describe the correlation between the amounts a tire is under-inflated or over-inflated and the percentage impact on tire life, tread wear, and/or fuel economy [02]. Reduced tire life (total useable kilometres including all retreads - Inadequate tire inflation, specifically underinflation, causes a reduction in the useable life of a tire because the tire is running in an overloaded condition. Overloading causes the sidewall of the tire to extend and contract, causing heat generation inside the tire. Excessive heat leads to fatigue of the rubber and cords thus further exacerbating the sidewall flexing. The weakened structure increases the likelihood of punctures and cuts, and the increased temperature leads to premature separation between the tire cords and the rubber. In effect, the increased heat and motion reduces the number of times that a tire could be safely retreaded (see Figure 10). A common rule is that a constant 20% under-inflated condition will reduce the life of a tire by 30% and 40% under-inflation will reduce tire life by 50%.

469

Dr Gradimir Danon and etc. - Proactive tire maintenance

•

Increased tire wear (miles between retreading) - In addition to impacting the usable life of a tire, improper tire inflation also affects tread wear. Both over and under-inflation change a tire’s footprint thus affecting tire traction and leading to irregular wear (see Figure 11). Under-inflation causes many types of irregular and accelerated wear patterns including shoulder wear, block-pumping wear, spot wear, diagonal wear, rib wear, and block-edge wear. Over-inflation also can cause shoulder and block-edge wear, and accelerates heel and toe wear.

A common principle is that a constant 20% underinflation will increase tread wear by 25%. • Reduced fuel economy - Fuel economy is also impacted by inadequate tire inflation. Increased flexing and the irregular footprint caused by underinflation, yields increased rolling resistance which leads to increased fuel consumption as more power is required to move the vehicle. In fact, for every 1 bar underinflation there is a 0.75% reduction in fuel economy. Figure 12 shows the impact profile of underinflation on fuel economy.

Figure 10: Underinflation impact of tire life [8]

•

Tire failures from sudden loss of tire tread and blow-outs, leading to an out-of-service condition (road calls) - Under-inflation causes excessive deformation of the sidewalls and heat built up, which weakens adhesion between the rubber and steel cords. Improper tire inflation also increases the potential for

tire failures from sudden loss of tire. Over-inflated tires also can lead to major tire failures since they are more vulnerable to tread surface cutting, impact breaks, punctures, and shock damage. Based on the data from the same source [02], impact of under-inflated tires on operating costs

Figure 11: Inflation pressure versus tread wear [8]

470

Journal of Applied Engineering Science 9(2011)4, 211

Dr Gradimir Danon and etc. - Proactive tire maintenance

is calculated using a city bus in Belgrade as an example (see table 1). Due to the reduction of tire life, the average of 7.67% of the price of a new tire is lost. Tire wear is 6.89% higher, which impacts the reduction of life of a new or renewed protector. Regarding fuel

consumption, it is about 0.2% higher due to negligence in tire maintenance. Table 2 gives the required data for the calculation of possible savings. For this example, based on the assumed input data (given in table 3) and on the assumption that effects amounting to 80% of the expect-

Figure 12: Underinflation impact on fuel economy

ed effects are realized with the introduction of TPMS, savings for one articulated bus in the amount of 471 EUR annually would be obtained. Vehicle with installed TPMS does not require frequent controls of air pressure in tires; how-

ever, they are needed for occasional controls of proper functioning of the installed devices. Taking into consideration all these points and assuming that it will be possible to realize only 80% of the expected benefits, a bit reduced amount of savings is obtained (see table 4).

Table 1: Impact of improperly inflated tires of an articulated bus on operating costs [02] Reduction of tire life

Increase of protector wear

Increased fuel consumption

-7.67%

+6.89%

+0.19%

Table 2: Input data required for the calculation [03] Number of wheels on articulated bus

Number

Average annual kilometres

70,000

Average tire life

54,000

l/100km

0.11

Price of a new tire

EUR

300

Price of diesel

EUR

Average price of retreading

EUR

150

Price of intervention in the field for 1 tire

EUR

Number of interventions

Average consumption for articulated buses Coefficient of tire retreading â&#x20AC;&#x201C; average number of retreading in tire life

Number of interventions per vehicle annually

Journal of Applied Engineering Science 9(2011)4 , 211

471

Dr Gradimir Danon and etc. - Proactive tire maintenance

Calculated savings should be compared with the costs of the user. These are the costs of procuring receivers and sensors (table 5). Table 3: Possible savings that would be realized by installing TPMS on articulated bus [14] New tires EUR

298

Retreaded tires EUR

Fuel EUR

Interventions on the road

Total

471

Table 4: Possible savings that can be achieved by installing TPMS on articulated bus [02, 08] Reduced amount of savings for tires and fuel (80% of 471 EUR)

377

Retreaded tires EUR

TPMS maintenance for one year EUR

-50

Possible savings EUR

407

Table 5: Costs of installing TPMS on articulated city bus Receiver EUR

300

Sensors (10*40) EUR

400

Total* EUR

700

Table 6: Comparison of costs and benefits Item

Amount

Costs of installing TPMS on articulated city bus EUR

700

Possible annual savings EUR

407

CBR (Cost-Benefit Ratio)

1.72

* Costs of installation are included in the price of a new bus. Now possible costs and possible benefits of installing TPMS on city buses can be determined (table 6). It arises from the analysis that the funds invested in the installation of the system for controlling and monitoring air pressure and temperature in tires would be returned in less than two years or 21 month, i.e. by installing these systems the traffic would become safer, more comfortable and cost-effective. REFERENCES 1) Anon. 2003. National Highway Traffic Safety Administration. Traffic Safety Facts 2003, DOT HS 809 775.

472

2) Commercial Vehicle Tire Condition Sensors, Final Report, Booz Allen Hamilton Inc., Commercial Vehicle Safety Technology Diagnostics and Performance Enhancement Program Contract Number: DTFH61-99-C00025, 2003, p 97. 3) Cross R. Tire Pressure Monitors, Commercial Carrier Journal, No 64, 1996, pp 7 – 16. 4) Danon G, Mitrović Č. Opravdanost primene TMPS na gradskim autobusima GSP Beograd. Istraživanja i projektovanja za privredu, 6 (21), 2008, pp. 35-44. 5) Danon G, Petković M. Propisi i nove tendencije u proizvodnji i korišćenju pneumatika, u knjizi „Ka održivom razvoju“, Papić, V, Manojlović A, Univerzitet u Beogradu, Saobraćajni Fakultet 2011, pp 97-107. 6) Danon G. Važnost održavanja pritiska u pneumaticima komercijalnih vozila i mogućnosti njegove kontrole, XX Majski skup održavalaca, 1998. godina, pp 132 – 145. 7) Federal Statistical Office Germany, (Statistisches Bundesamt Deutschland), Accident reports by police at the accident location. 8) Gavrić P, Danon G, Momčilović V, Bunčić S. “Eksploatacija i održavanje pneumatika komercijalnih vozila”, Istraživanja i projektovanja za privredu, 2009, vol. 7, no. 25, pp. 1-10. 9) Govindjee S. Firestone Tire Failure Analysis, Confidential Bridgestone/Firestone Document, 2001, p 73. 10) Grygier P, Garrott R, Mazzae E. An Evaluation of Existing Tire Pressure Monitoring Systems, DOT HS 809 297, National Highway Traffic Safety Administration, p 161. 11) http://www.bartecautoid.com/tyre_pressure_ monitoring_system.html 12) http://www.goodyear.com/cfmx/web/truck/ line.cfm?prodline=160926 13) http://www.tireindustry.org/pdf/TREAD_ ACT_Summary.pdf. 14) Lipovac K, Vukašinović M. Analiza stanja pneumatika na putničkim vozilima u Beogradu, Naučno- stručni skup “Pneumatici 2000”, Vrnjačka Banja 1. - 3. juna 2000, Zbornik radova, OMO Beograd, pp 120 - 128. 15) Winsor J. 2003. Breakdown: 10 Top Reasons. Heavy Duty Trucking• January 2003, 38. Paper sent to revision: 14.11.2011. Paper ready for publication: 16.12.2011. Journal of Applied Engineering Science 9(2011)4, 211

DOI: 10.5937/JAES9 - 1194 Paper number: 9(2011)4, 212, 471 - 479

FROM IDEA TO IMPLEMENTATION IN PROTECTION OF ELECTRONIC EDITIONS (BOOK) Dr Časlav Mitrović * University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia Dr Slobodan Radojević University of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia Milan Srećković Academy of criminalistic and police studies, Belgrade, Serbia Mr Zoran Milanović Academy of criminalistic and police studies, Belgrade, Serbia This paper presents a study of electronic editions protection on optical discs (CD/DVD) based on basic principles of logic and côde protection. The design of this solution is rather simple, but it is mainly similar to complex methods used nowadays in protection of great number of commercial electronic editions. The implementation and usage are adapted to users (students/professors) who are interested in electronic editions that are published on Criminal-Police Academy in Belgrade. Key words: CD, DVD, data, protective, editing, electrons, implementation, logics. INTRODUCTION Ensuring protection of data, information and knowledge is one of the most important and most delicate issue encountered by all social and information systems. The need for data, information and knowledge is vast, as well as the possibility of their abuse. In order to prevent their abuse and to provide system protection, different social, legal, technical, organizational and other measures are taken.

Figure 1. – Preliminary design

Nowadays the greatly accepted opinion is that the protection of information systems in information environment is something that shouldn’t be foreign but domestic product. Although there is a great number of software manufactures that offer commecial solutions (Multimedia Protector [01], CD FrontEnd [02], DeployLX [03] , SerialShield [04] , CopyMinder [05] ), as well as a number of websites that offer free ideas, solutions and parts of the open côde (The Côde Project [06]), we chose an example of the study in which a preliminary design of the process of logic and côde protection is given. Namely, the process can be described in few steps. The first step is provision of an electronic edition (hereinafter book) on a media, usually CD-ROM. Then there is an attempt of opening the book on user’s computer. What follows is the introducing screen on which the user has choice of starting the book or the installation of the required the appropriate software for starting the book. If the user chooses to open the book, the next step is the dialogue for activation where the unique number of this computer is displayed to user, contact phone or e-mail address of the publisher or responsible person for contacting in order to

* Faculty of Mechanical Engineering, Kraljice Marije 16, 11000 Belgrade, Serbia; cmitrovic@mas.bg.ac.rs

473

Dr Časlav Mitrović and etc. - From idea to implementation in protection of electronic editions (book)

get the activation côde as well as the field where the user enters the given côde. If the côde is correct, further access to the book is allowed to user. Technically, the solution is performed in the following procedure (Figure 1). The project is set in VisualStudio 2008 [7] (the language used is VisualBasic.NET) which manages of the book review. The book itself is in PDF format and put in Resource file of the project. By compiling, the book is integrated in EXE file together with the executable côde from where it is later called. During program execution the book is temporarily unpacked into temp directory from where it is taken over by the PDF file reading control which is integrated into the program. After closing the program the book is erased from the temporary location. PROGRAM FUNCTIONS DESCRIPTION

Figure 3. – Dialogue for entering the activation côde

record that number in Registry base and open the window for reading the book itself (Figure 4).

When starting the program from the disc, the first thing seen on the screen is a menu with three options (Figure 2). It offers the book

Figure 2. – Appearance of the first window when starting media with book

opening, installation of the accompanying package and the exit from the program. The accompanying package is actually .NET Framework 2.0 [08] a set of libraries for running the programs written on VisualStudio.NET platform. This component is necessary for starting the book and the information about it can be obtained by placing the pointer over the .NET 2 button. By clicking the exit button is the path to leaving the application.In order to start the book, it is necessary to choose the first option - “Otvori knjigu”. Once the book is started, the next what appears on the screen is the dialogue for entering the activation côde (Figure 3). The explanation is here provided to the user about which phone to contact so that the activation côde could be assigned to him based on his unique number, thus enabling the starting of the book. After entering the correct activation côde, clicking the button «Aktiviraj kopiju» will make the program

474

Figure 4. – View of the book

BOOK PROTECTION Electronic book is protected on several levels. As mentioned above, PDF file is integrated into the executable EXE file. In this way, the book is not only protected from simple copying of the file, but its isolation in an independent file is made more complex. Dotsfucator [09] supplement is used during the compiling whose task is to further encrypt the EXE file and thus protects it from reverse engineering. This is another step in protecting the PDF within the program, but, what is more important, it is a very strong protection from atJournal of Applied Engineering Science 9(2011)4, 212

Dr Časlav Mitrović and etc. - From idea to implementation in protection of electronic editions (book)

tempts of hacking into the program in order to avoid the activation procedure and try to find out the algorithm for computing the activation côde. After a successful activation, the côde is recorded in Registry database, in the section of the active user. It is thus enabled that only that user canopen the book. In multiuser systems, if the user is not in the administrator group, his right of access to write into the database is limited to only his section and that is where it is only possible to record the data. If it is necessary to write something in the section that applies to all users, the user would then be required to call the system administrator in order to start the book [10]. Furthermore, from that moment on, all the users of that computer would have the access to the book, which may not be the intention of the person who purchased it. Once the côde is recorded, it is no more necessary to enter it through the mask, yet each time when starting the program it is being checked in order to avoid the attempt of using someone else’s côde by simple reconstructing the tree of Registry database from another computer. The côde itself is calculated according to the serial number of the processor on which the program is installed. Each produced processor has it own unique serial number that is added to it. That basically means that the book will be run on a certain computer until its processor is changed. A corresponding activation côde generator is on the publisher or distributor of the edition side which helps in making the côde necessary for the program activation on user’s computer.

•

• •

GhostScriptLib – a set of functions that manage the library gsdll32.dll which contains the functions necessary for the access to PDF database and interpretation of PDF descriptive language ImageUtil – a set of functions for the conversion of image; manages the libraries FreeImage.dll and FreeImageNET.dll iTextSharpUtil – a set of functions used for accurate text rendering in the picture; it manages the library itextsharp.dll PrinterUtil – a set of functions for page printing PDFViewer – the central form that contains the control loos and which combines all the functions of this sub-project.[11]

When compiling, the sub-project PDFView is compiled in the independent library PDFView.dll which contains ready-made control that can be used in other projects and not only in this one.

PROGRAM OPERATION PRINCIPLE-SOURCE CÔDE The project itself consists of two sub-projects: 1. Book.Worm – program that protects the book, activates it, checks the activation côde and its recording in Registry database 2. PDFView – a set of routines, functions and libraries that perform the conversion from PDF file to TIFF image and display it in the graphics PDFView is the part that is mostly taken from the Internet database of open côde and embedded in the unit which is used for conversion of pages from PDF files to images in TIFF format which a re drawn in a given frame (Figure 5). In this way the control is made which is later used in the main program to display the PDF file. PDFView

contains

the

following

modules:

Journal of Applied Engineering Science 9(2011)4,, 212

Figure 5. – Project tree structure Book.Worm is the main project and it manages the protection logic. It contains two forms: • fProvera – the form that verifies the activa-

475

Dr Časlav Mitrović and etc. - From idea to implementation in protection of electronic editions (book)

•

tion côde if it exists, and if it does not or if it is incorrect, it requests its entering, and fWorm.Book – the form that contains the control which displays the book.

Beside these two forms, Worm.Book also conImports System.Management Public ISBN As String = “123456789”

tains the module mFunctions held by functions used in the program and Skladiste.resx resurs file where the book itself is located. Module mFunctions starts with the following two lines:

A set of functions is introduced in the program in the first line which will enable to read the serial number of the processor. They are the integral part of .NET 2 environment. The second line initializes the variable ISBN string type in a value. This value is important because it is the identifier of the book. Each book has its unique ISBN number. It is useful for the data recording in Registry, because it is the way to know that the activation côde is entered for a certain book and it is impossible that two books have the same activation côde. The module function follow. Public Function fRacunajAktivacioni() As Integer Dim A, B, C, D As Integer A = fSaberiClanove() * 1.2 B = A * 34 + 56 C = B / 0.78 D = C - 9 Return D End Function The function fRacunajAktivacioni takes the value that fSaberiClanove function returned and transforms it through a series of arithmetic operations with the values for that book which are randomly selected in advance. Public Function fGetProcessorID() As String Dim objMOS As ManagementObjectSearcher Dim objMOC As Management.ManagementObjectCollection Dim objMO As New Management.ManagementObject Dim ProcID As String = “” objMOS = New ManagementObjectSearcher(“Select * From Win32_Processor”) objMOC = objMOS.Get For Each objMO In objMOC ProcID = objMO(“ProcessorID”) Next objMOS.Dispose () objMOS = Nothing objMO.Dispose() objMO = Nothing Return ProcID End Function

476

Journal of Applied Engineering Science 9(2011)4, 212

Dr Časlav Mitrović and etc. - From idea to implementation in protection of electronic editions (book)

The function fGetProcessorID reads the serial number of the processor from the sister by means of Windows Management Instrumentation set of instructions that are embedded in Windows operating systems and forwards that number. Public Function fSaberiClanove() As Integer Dim Brojac As Integer Dim Rez1 As Integer Dim Rez2 As Integer = 0 Dim ProcID As String ProcID = fGetProcessorID() For Brojac = 1 To Len(ProcID) Rez1 = AscW(Mid(ProcID, Brojac, 1)) Rez2 = Rez2 + Rez1 Next Return Rez2 * 28 End Function The function fSaberiClanove converts each individual symbol from the processor serial number in the ASCII value, then adds them and in the end multiplies the sum with the value for that book which is randomly selected in advance. Public Function fSnimiAktivacioni(ByVal Broj As String) SaveSetting(“Knjiga”, ISBN, “Aktivacioni”, Broj) Return 0 End Function The function fSnimiAktivacioni puts the correct activation côde in Registry. Public Function fProcitajAktivacioni() As Integer Dim SSer As String Dim ISer As Integer SSer = GetSetting(“Knjiga”, ISBN, “Aktivacioni”) ISer = Int(Val(SSer)) Return ISer End Function The function fProcitajAktivacioni reads the activation côde from Registry database and forwards it. These are the main functions that are performed either by calling each other or by being called from other places during the execution of the program. The first place encountered when the program starts is the event fProveraLoad(). It contains the following instructions. Me.Visible = False If fRacunajAktivacioni() = fProcitajAktivacioni() Then fWormBook.Show() Else Me.Visible = True lJedinstveniBroj.Text = fSaberiClanove() End If

Journal of Applied Engineering Science 9(2011)4 , 212

477

Dr Časlav Mitrović and etc. - From idea to implementation in protection of electronic editions (book)

The form is hidden from the user in the first line. Then the comparison of the calculated activation côde and the one read from the database is performed. If the database does not contain any data, the function fProcitajAktivacioni will return the value 0. If it is determined by comparing that those two numbers are the same, the program will open the next form for viewing the book. Otherwise, a dialogue with the information necessary for activation will be displayed. After contacting the technical support and obtaining the activation côde, the user is expected to press the button “Aktiviraj kopiju”. It is covered by the event bAktiviraj_Click(). If tAktivacioniKod.Text = fRacunajAktivacioni() Then fSnimiAktivacioni(tAktivacioniKod.Text) fWormBook.Show() Else MsgBox(“Uneti broj nije ispravan!” + Chr(13) + “Pokušajte ponovo.”, MsgBoxStyle.Exclamation) End If This event starts with confirming the activation côde that the user entered. If the côde is correct, the program will call the function that records it in Registry, and then the book will open. Otherwise, the user will receive the message about error. The form that opens the book contains three events: fWormBook_Load(), fWormBook_Resize() and fWormBook_FormClosing; and one function – PrilagodiVelicinu. Private Sub PrilagodiVelicinu() PdfViewer1.Location = New Point(0, 0) PdfViewer1.Width = Me.Width - 15 PdfViewer1.Height = Me.Height - 40 End Sub The function PrilagodiVelicinu serves for adopting the size of the container PDFView control to the size of the form so as to touch its edges from the inside. fProvera.Close() PutanjaFajla = IO.Path.GetTempPath & “B.pdf” IO.File.WriteAllBytes(PutanjaFajla, My.Resources.Skladiste. Lorem) PdfViewer1.FileName = PutanjaFajla PrilagodiVelicinu() This is the body of the event fWorkBook_Load(). In the first line the program closes the previous form. Then the value of the variable PutanjaFajla is formed which contains the path to the file where the book will be temporarily unpacked. This location in within the implied Windows Temp directory, and the name of the file is b.pdf. In Windows operating systems that are based on NT technology, the implied temporary directory is formed for each user separately and is usually located on the path: c:\documents and settings\user\local settings\temp. What follows is the drawing the book in user’s control and adopting its size to the dimensions of the form.

478

CONCLUSION When estimating the degree of protection accomplished, one should bear in mind that the absolute protection cannot be achieved, but it is necessary to strive for maximum safety at any time. In that sense any real protection system requires continuous upgrading and improvement, regardless of the quality achieved so far. Corrective actions should be focused to modifications of the solutions with noticed weaknesses to the acceptable satisfactory solutions, or their elimination from the system in case of impossible modification; as well as finding, deJournal of Applied Engineering Science 9(2011)4, 212

Dr Časlav Mitrović and etc. - From idea to implementation in protection of electronic editions (book)

veloping and applying of individual original solutions for protecting, as it is shown in this work. The practical contribution of the paper is reflected in the design and implementation of new technical solutions to protect electronic books, which is now increasingly used in scientific research and educational institutions. This solution is not prevented from copying a physical media on which the issue is, but it is practically difficult to use it without the appropriate activation procedures. This type of protection is more interesting and „rigid“ than the physical protection of media. Naimely, nowadays it is easy to find tools that very proficiently emulate different mechanisms for media protection, and the procedure with the activation of software is still difficult to avoid, partly because it is unique for each edition and partly because of its complex procedure. The solution shown in this paper is only the example of protection technology used. For producing it, it is necessary to introduce some more improvements. Another possible way of improving it to introduce the serial numbers. In this way the monitoring of each individual edition would be enabled as well as the number of activation performed. The second way is to introduce more complex algorithm for côde calculation. The third way is to provide the activation over the Internet, but the implementation of serial numbers is necessary for this step. In more advanced stage of development, a cross-platform solution could be an option, that is a software that could run on multiple systems (Windows, Linux, OSX,…).

REFERENCES 1) Mirage systems: All-In-One Protector (http://www.mirage-systems.info/download/ mp/ marketing/ flyer-multimedia-protectoren.pdf) 2) http://www.cdfrontend.com/cd_dvd_presentation_brochure_00002e.htm 3) http://xheo.com/products/copy-protection?g clid=CJvszfqdq6YCFY0r3wodg2w8pA 4) http://www.ionworx.com/serialshield.html?gc lid=CNnw06KNoaYCFYUw3wod9G-goQ 5) http://www.microcosm.co.uk/copyminder.ph p?gclid=CLj8j8KSoaYCFUco3wodBVQ9oA 6) http://www.côdeproject.com/KB/applications/opensrcprot_part2.aspx 7) Visual Studio 2008, http://msdn.microsoft. com/en-us/vstudio/default.aspx 8) .NET Framework 2.0, http://msdn.microsoft. com/en-us/netframework/aa731542.aspx 9) Dot Fuscator, http://www.preemptive.com/ products/dotfuscator/overview 10) Mitrović, Č., Vorotović, G. Modeliranje informacionog sistema za praćenje sastava i načina eksploatacije pneumatika u vazduhoplovstvu. Journal of Applied Engineering Science, 1 (2003) 2, 35-52.), 11) PDF Viewer Control Without Acrobat Reader Installed, (http://www.côdeproject. com/KB/ applications/PDFViewerControl. aspx?msg=3127440) Paper sent to revision: 15.11.2011. Paper ready for publication: 01.12.2011.

Journal of Applied Engineering Science 9(2011)4,, 212

479

480

Journal of Applied Engineering Science 9(2011)4

EVENTS REVIEW

6TH DUBROVNIK CONFERENCE ON SUSTAINABLE DEVELOPMENT OF ENERGY WATER AND ENVIRONMENT SYSTEMS The Conference on Sustainable Development of Energy, Water and Environment Systems (SDEWES), was held for its 6th consecutive time, on September 25 - 29, 2011 in Dubrovnik in Croatia. VI SDEWES was successfully organized by the University of Zagreb with the help of research and academic institutions partners from Europe and America. Institute of Nuclear Sciences “Vinča” from Belgrade is one of them. The Conference was dedicated to the improvement and dissemination of knowledge on methods, policies and technologies for increasing the sustainability of development by de-coupling growth from natural resources and replacing them with knowledge based economy, taking into account its economic, environmental and social pillars, as well as methods for assessing and measuring sustainability of development, regarding energy, transport, water, environment and food production systems and their many combinations. Conference was attended by about 450 participants from all continents. Large number of papers was presented. Sustainability being also a perfect field for interdisciplinary and multi-cultural evaluation of complex system, the Dubrovnik Conference has during the first decade of the 21st century become a significant venue for researchers in those areas to meet, and originate, discuss, share, and disseminate new ideas. In parallel with the main program a special section dedicated to various topical issues took place: • • • • • • •

Future Sustainable Electricity Supply Grids mesh with Supplies for Heat, Cold and Transport Energy and Buildings Efficiency for Sustainable Future: from smart buildings to sustainable behaviors Energy and Water Efficiency for Sustainable Future Utilization of industrial byproducts towards sustainability Biofuels sustainability Understanding environment- society interactions for sustainable development Research and Governance for Sustainability and etc.

The conference was also attended by researchers from Serbia. They were from “Vinča”, the University of Belgrade and the University of Niš.

Journal of Applied Engineering Science 9(2011)4

481

EVENTS REVIEW

Conference “TOWARDS SUSTAINABLE TRANSPORT 2011” For the second time, Faculty of Transport and Traffic Engineering from Belgrade and Transportlog, have organized a Conference “Toward Sustainable Transport 2011”. This conference was held on October 20th and 21st 2011 at Hotel Park in Ivanjica, supported by the Ministry of Education and Science, the Public Enterprise Electric Power Industry of Serbia and the Ministry of Environment, Mining and Spatial Planning. The conference program was conceived in four thematic sections with eighteen papers that were presented by the most relevant experts in their corresponding areas of expertise. These papers were related to: • vehicles and environment, • vehicle fleet insurance, • vehicle inspection, • vehicle fleets organization, operation and maintenance. The presentations were dealing with contemporary issues and everyday challenges of the road transport industry practices. Besides their initial meaning, they were very useful in improving the knowledge-base of road transport experts and engineers, as well as giving them necessary guidelines and best practices for further development in all of the presented areas. At the end of each daily presentation sections, round tables were organized meant to open discussion regarding the presentations and problems in transport industry and profession in general. From fruitful discussions some guidelines were drawn for the selection of themes and issues that will be considered at the next conference “Towards Sustainable Transport 2013”. Further dialogue and informal discussion of participants continued in a more pleasant atmosphere at the Conference dinner held at the end of the first conference day. More than 150 participants attended the conference from the field of transport, vehicle insurance, public authorities (Ministries, Cities, and Municipalities), secondary and higher education, vehicle dealers, spare parts and materials suppliers (including tires, fuels, lubricants, etc.), managers of vehicle inspection, maintenance and repair centres, recycling centres and others. The organization of the conference and presentations were held at a high professional level. From an extremely positive feedback from the majority of participants, the organizers remain convinced that the objectives of this conference were fully accomplished by assembling relevant road transport and associated experts.

482

Journal of Applied Engineering Science 9(2011)4

EVENTS REVIEW

SCHOOL OF MAINTENANCE IH-HOUSE TRAINING FOR BELGRADE AIRPORT COMPANY

During first half of December 2011, In-house training on most relevant aspects of maintenance of technical systems was realized for the Belgrade Airport Company. In-house training was organized in line with specific request of the Client and from December 1st till December 14th was held in the premises of the Belgrade Airport. Training was organized for the senior managers of the Technical Maintenance Department, including Electrical, Termotechnical, ICT, Technical, Safety and Quality division. In its program, training included the best local knowledge and experience, modernized and harmonized with the recommendations EFNMS (European Federation of National Maintenance Societies). Through this in-house School of Maintenance participants had the opportunity to hear and learn about: Concepts, Organization and Technology of maintenance, Systems theory, Information theory, Outsourcing concepts in maintenance, Risk, Life Cycle Cost, Resources, Methods of failure analysis, Maintenance facilities design, Project management, Key Performance Indicators in maintenance, Structural analysis of the system, Re-engineering concepts, Benchmarking, Quality Management Systems, Inventory management, etc. Training was conducted as combination of theoretical lectures and practical examples, performed by prof. dr Jovan Todorović, prof. dr Branko Vasić and Nada Stanojević. At the last day of the training the participants did the test. Achieved test results were at very high level, and therefore all participants were promoted at National Experts in Maintenance Management. Since training connected and unified the local tradition and experience in the maintenance process with the European norms and requirements, its result is thus multiple. It is quite certain that this kind of training and certification brings recognition to the people and profession, but apart of the fact that Belgrade Airport now has certified Maintenance experts in national level with high competences, this training and certificates opens a way toward the International recognized European Maintenance Manager certificates and contributes to further regional development of Belgrade Airport .

Journal of Applied Engineering Science 9(2011)4

483

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: 17.03.2012. - Belgrade, Faculty of Mechanical Engineering 19 - 21.03.2012. - Zlatibor, Hotel Dunav Institute for research and design in commerce & industry Phone: 011/6300750; Fax: 011/6300751; E-mail: office@iipp.rs; web: www.iipp.rs

484

Journal of Applied Engineering Science 9(2011)4

ANNOUNCEMENT OF EVENTS

Belgrade, Serbia on June 14-15, 2012 organized by INDUSTRIAL ENGINEERING DEPARTMENT, FACULTY OF MECHANICAL ENGINEERING UNIVERSITY OF BELGRADE, SERBIA and STEINBEIS ADVANCED RISK TECHNOLOGIES, STUTTGART, GERMANY Venue Faculty of Mechanical Engineering, University of Belgrade Kraljice Marije 16, 11120 Belgrade,Serbia http://ie.mas.bg.ac.rs http://www.sie2012.risk-technologies.com/ e-mail: sie2012@mas.bg.ac.rs The aim of the 5th International Symposium of Industrial Engineering – SIE 2012 is to contribute to a better comprehension of the role and importance of Industrial Engineering and to mark the twentieth anniversary of the Industrial Engineering program in Serbia, established at FME, Belgrade. The Symposium is expected to foster networking, collaboration and joint effort among the conference participants to advance the theory and practice as well as to identify major trends in Industrial Engineering today. CALL FOR PAPERS Topics covering industrial issues/applications and academic research include, but are not limited to: • • • • • • • • • • • • • •

Decision Analysis and Methods E-Business and E-Commerce Engineering Economy and Cost Analysis Engineering Education and Training Enterprise Information Systems Entrepreneurship Engineering Economy Engineering Management Systems Facilities Planning and Management Global Manufacturing and Management Human Factors Intelligent Manufacturing Systems Inventory Management Logistics and Supply Chain Managemen

• • • • • • • • • • •

Manufacturing Systems Operations Research Production Planning and Control Project Management Quality Control and Management Reliability and Maintenance Engineering Service Innovation and Management Systems Modelling and Simulation Operations Management Service Engineering Safety, Security and Risk Management including special topic “ Risks and Opportunities of New Industrial Technologies “

SUBMISSIONS AND DATES • • • • • •

April 15, 2012 - Deadline for paper and registration form submission online on addresss http://www.sie2012.risk-technologies.com or http://ie.mas.bg.ac.rs April 25, 2012 - Notification of acceptation April 25-May 20, 2012 - Early Registration fee payment May 20, 2012 - June 14, 2012 – Registration fee payment June 14-15, 2012- Symposium

Journal of Applied Engineering Science 9(2011)4

485

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: 17.03.2012. - Belgrade, Faculty of Mechanical Engineering 19 - 21.03.2012. - Zlatibor, Hotel Dunav

486

Journal of Applied Engineering Science 9(2011)4

BOOK RECOMMENDATION Recommended by: Prof. dr Branko Vasić QUALITY MANAGEMENT SYSTEM AND BUSINESS PERFORMANCES By: Vesna Spasojević Brkić, Dragan Milanović, Snežana Knežević, Danijela Lazić and Tanja Milanović In the Serbian business context, there is not enough knowledge about quality management organizational aspects, support systems and its impact on effectiveness and efficiency of enterprises. In order to overcome these uncertainties and aimed by the acquisition of new knowledge, in this monograph, after theoretical examination, three independent studies were experimentally conducted considering the following aspects of quality management: 1. Quality management and its correlation with business performances in Serbian companies. 2. The issue of structuring quality management system and resistances caused by this change. 3. The information system as a support system of integrated management systems and their interactions with business performances. The first study identified critical factors of quality management that can lead to improvements in key performance areas. Measurement instrument is developed, followed by choice of QM critical factors and performance measures and association measurement within these factors on a representative sample of Serbian companies. Theme of the second study examined the mutual interaction of the process, culture, structure and distribution of power changes in structuring QMS. The third research dealing with the determination of the interdependence of information systems, integrated systems and business performance management provides solution for building competitive advantage in today’s business world. The monograph is written on around 250 pages and is divided into 8 chapters. The conceptual contribution of the monograph is that quality management is not as universally applicable, but is considered in the light of theories of organization. The methodological contribution of the monograph lies in the application of the method of “field studies”, with the statistical modeling methods applied. The empirical contribution of the monograph is pointed by large number of companies in survey. The practical contribution of the monograph is reflected in usefulness for: a) researchers in the field and b) experts in business and c) consultants engaged in the implementation of quality management systems. The importance of the monograph “Quality management system and business performance” is reflected in the attractive research topics on a global scale, in the multi-causal understanding of interaction between quality management and business performances, with special emphasis on organizational change and integrated management systems, and with modern mathematical methods and models applied in describing the phenomena discussed on representative samples of local companies, so monograph is a significant contribution to the spread of knowledge limits and possibilities of solving the problems of competitiveness of domestic enterprises. Prof.dr Miroslav Radojičić Publisher: Faculty of Mechanical Engineering, University of Belgrade, Serbia Forthcoming: 2012; Format B5; Pages 254; ISBN: 978-86-7083-741-6

Journal of Applied Engineering Science 9(2011)4

487

INSTRUCTIONS

FOR

AUTHORS

The benefits of publishing in Journal for Applied Engineering Science are: • No page charges • World wide exposure of your work • Accelerate publication times • Online author service • Automatic transfer of metacontent in SCOPUS, SJR, SCIndeks and other bases supporting international protocols for data transfer • Assignment of numerical identifiers DOI • Fair, constructive and able to follow reviewing process • Dedicated team to manage the publication process and to deal with your needs Submission of the papers has to be done online, trough journal e-service at http://scindeks-eur.ceon.rs/index.php/jaes. For assistance during the process of submission and publication, please contact graphical editor Mr. Darko Stanojevic at dstanojevic@iipp.rs or +381 116300750 Every manuscript submitted to JAES will be considered only if the results contained in the paper were not already published, that are not currently in the process of publishing and not to be published in another journal. Each paper is sent to a review by two independent experts and the authors are obligated to adopt the observations and comments of the reviewers. Articles presented at conferences may also be submitted, provided these articles do not appear in substantially the same form in published conference proceedings. All articles are treated as confidential until they are published. Manuscripts must be in English free of typing errors. The maximum length of contributions is 10 pages. THE FORMAT OF THE MANUSCRIPT The manuscript should be written in the following format: • A Title, which adequately describes the content of the manuscript. • An Abstract should not exceed 250 words. The Abstract should state the principal objectives and the scope of the investigation, as well as the methodology employed. It should summarize the results and state the principal conclusions. • Not more than 10 significant key words should follow the abstract to aid indexing. • An Introduction, which should provide a review of recent literature and sufficient background information to allow the results of the article to be understood and evaluated. • A Theory or experimental methods used. • An Experimental section, which should provide details of the experimental set-up and the methods used for obtaining the results. • A Results section, which should clearly and concisely present the data using figures and tables where appropriate. • A Discussion section, which should describe the relationships and generalizations shown by the results and discuss the significance of the results making comparisons with previously published work. (It may be appropriate to combine the Results and Discussion sections into a single section to improve the clarity). • Conclusions, which should present one or more conclusions that have been drawn from the results and subsequent discussion and do not duplicate the Abstract. • References, which must be cited consecutively in the text using brackets [1] and collected together in a reference list at the end of the manuscript and in alphabetic order.

488

Journal of Applied Engineering Science 9(2011)4

INSTRUCTIONS

FOR

AUTHORS

Units - standard SI symbols and abbreviations should be used. Abbreviations should be spelt out in full on first appearance, e.g., variable time geometry (VTG). Meaning of symbols and units belonging to symbols should be explained in each case or quoted in a special table at the end of the manuscript before References. Figures must be cited in a consecutive numerical order in the text and referred to in both the text and the caption as Fig. 1, Fig. 2, etc. Figures should be prepared without borders and on white grounding and should be sent separately in their original formats. Pictures may be saved in resolution good enough for printing in any common format, e.g. BMP, GIF or JPG. Tables should carry separate titles and must be numbered in consecutive numerical order in the text and referred to in both the text and the caption as Table 1, Table 2, etc. The tables should each have a heading. Tables should not duplicate data found elsewhere in the manuscript. Acknowledgement of collaboration or preparation assistance may be included before References. Please note the source of funding for the research. REFERENCES must be written in alphabetical order and in the following form: Journal: /Number/ (must match number in the text), Last name, Initial of the authors name, (Year of publication). Article title: secondary title. Title of the Journal (italic), volume number (number of the journal), page number. // Petrović, G., Petrović, N., Marinković, Z. (2008). Primena teorije Markova u mrežnim sistemima masovnog opsluživanja. FACTA UNIVERSITATIS Series Mechanical Engineering, 6 (1), 45 – 56. Book: /Number/ (must match number in the text), Last name, Initial of the authors name, (Year of publication) Book title: secondary title, Place of publishing: Publisher. /2/ Vasić, B., Popović, V. (2007) Inženjerske metode menadžmenta, Beograd: Institut za istraživanja i projektovanja u privredi. Book chapter: /Number/ (must match number in the text), Last name, Initial of the authors name, (Year of publication) Chapter title: secondary title, Book title: secondary title, Place of publishing: Publisher, page numbers. /3/ Vasić, B. (2004) Model Hardverskog resursa, Menadžment i inženjering u održavanju, Beograd: Institut za istraživanja i projektovanja u privredi, 95 – 97. Internet source: /Number/ (must match number in the text), link to the page from which the text is taken, retrieved on (state the date) /4/ http://www.autogume.net/veleprodaje/kelena/, retrieved on November 7th, 2010

Journal of Applied Engineering Science 9(2011)4

489

SADRŽAJ

OD UREĐIVAČKOG ODBORA

491 - 492

Doc. dr Vladimir Popović UVODNIK

REZIMEI RADOVA

493

Mr Dragan Komarov, Dr Slobodan Stupar, Zorana Posteljnik PREGLED STANJA VETROENERGETSKIH TEHNOLOGIJA I TRŽIŠTA VETROTURBINA U SVETU

493

Dr Dragan Ćoćkalo, Dr Dejan Đorđević, Dr Zvonko Sajfert, Dr Srđan Bogetić SMEs U REPUBLICI SRBIJI: RAZVOJ KAPACITETA

494

Dragan Stamenković, Dr Vladimir Popović, Dr Vesna Spasojević Brkić, Jovan Radivojević MODEL OPTIMIZACIJE KOMBINACIJE GARANCIJE BESPLATNE ZAMENE I PARCIJALNE GARANCIJE

494

Dr Gradimir Danon, Miloš Petrović PROAKTIVNO ODRŽAVANJE PNEUMATIKA

495

Dr Časlav Mitrović, Dr Slobodan Radojević, Milan Srećković, Mr Zoran Milanović OD IDEJE DO IMPLEMENTACIJE U ZAŠTITI ELEKTRONSKIH IZDANJA

490

Journal of Applied Engineering Science 9(2011)4

OD UREĐIVAČKOG ODBORA Vozila koja se prodaju i učestvuju u saobraćaju u bilo kojoj državi moraju da ispunjavaju propise i standarde te države. Postupak registracije vozila u većini država uglavnom zahteva homologaciju vozila i/ili njegovih komponenti. Postojanje posebnih nacionalnih propisa i homologacionih procedura u različitim zemljama zahteva skupe promene konstrukcije, dodatne testove i dupliranje homologacija. Stoga, postoji potreba da se harmonizuju različiti nacionalni tehnički zahtevi za vozila i da se razrade jedinstveni međunarodni propisi. Jednom kada su vozila ili njihova oprema i delovi proizvedeni i odobreni u skladu sa tim propisima, njima se može trgovati u međunarodnoj razmeni, bez ikakvog daljeg ispitivanja ili odobrenja. Osim toga, ovi propisi treba da budu stalno Doc. dr Vladimir Popović prilagođavani tehničkom progresu i novim zahtevima u pogledu bezbednosti, zaštite životne sredine i energetske efikasnosti. Trenutno na tržištu vozila u Evropi funkcionišu dva ključna, paralelna sistema za homologaciju vozila, koji praktično definišu i uslove i kriterijume za promet vozilima, i to kroz: • UNECE Pravilnike, odnosno propise Ekonomske komisije za Evropu Ujedinjenih nacija (UNECE), koje donosi Svetski forum za harmonizaciju Pravilnika za vozila - WP.29, u okviru Sporazuma iz 1958., i • EU Direktive, odnosno propise Evropske unije (EU). Republika Srbija je potpisnik Sporazuma iz 1958. i veoma aktivno učestvuje u radu WP.29, dok primena propisa EU zavisi i od statusa naše države u procesu pristupanja EU, koji je za sada prilično neizvestan. Osnovni moto WP.29 je “Certifikovano jednom, prihvaćeno bilo gde”. Ako pogledamo ključne izazove sa kojima će se suočiti sektor transporta UNECE-a u budućnosti, možemo videti koliki se značaj u istim pridaje regionu jugoistočne Evrope. Naš region se u dva od tih šest izazova eksplicitno pominje: • Nedovoljna i neadekvatna infrastruktura, posebno u istočnoj Evropi, regionu Kavkaza i centralnoj Aziji; • Stari, nebezbedni i ekološki neprihvatljivi vozni parkovi, posebno u istočnoj i jugoistočnoj Evropi, kao i u regionu Kavkaza i centralnoj Aziji, što rezultuje velikim brojem saobraćajnih incidenata i aerozagađenjem. Najbolja preventiva, posebno u pogledu ovog drugog izazova, je harmonizacija propisa u oblasti vozila, u cilju podizanja nivoa njihovih bezbedonosnih i ekoloških performansi. Ona svakako vodi ka proširenju tržišta i oslobađanju od određenih barijera. Poslednjih godina je očigledno da se harmonizacija propisa odvija u pravcu zamene EU Direktiva sa UNECE Pravilnicima. Ovo se objašnjava sve većim značajem koji ima Sporazum iz 1958. Evidentno je da veliki broj proizvođača vozila iz EU, u okviru homologacije tipa vozila (WVTA), ima sve više pojedinačnih saopštenja prema UNECE Pravilnicima, a sve manje prema EU Direktivama. Razlog za to je i činjenica da u radu WP.29, pored svih država potpisnica Sporazuma, aktivno učestvuju i SAD, Kina, EU (koja je potpisnik Sporazuma) i Indija, o čijem značaju u autoindustriji ne treba posebno govoriti, kao i brojne zainteresovane nevladine međunarodne organizacije (International Organization for Standardization - ISO; International Organization of Motor Vehicle Manufacturers - OICA; International Motorcycle Manufacturers Association - IMMA…). Nadalje, jako je bitno naglasiti da je jedna od neformalnih radnih grupa pri WP.29 zadužena za razvoj i implementaciju Međunarodnog sistema homologacije tipa vozila (IWVTA), koji bi trebao da se primenjuje od 2016. godine, i koji bi trebalo da u dogledno vreme zameni WVTA, na kome se danas bazira sistem homologacije vozila u EU. U tom pravcu će se sigurno ići i nadalje, jer se na taj način kompletira proces harmonizacije propisa na svetskom nivou, što je neminovna posledica i sveopšte globalizacije, koja je naročito izražena u automobilskoj industriji.

Journal of Applied Engineering Science 9(2011)4

491

OD UREĐIVAČKOG ODBORA Kada je reč o našem regionu, sve države su potpisnice Sporazuma iz 1958., osim Albanije. Možda i ključni pokazatelj za razvoj propisa u oblasti vozila u regionu jugoistočne Evrope je, više ili manje izražena, želja svih država i teritorija ovog regiona da budu članice EU. Međutim, svaka država za sebe, bez obzira da li je član EU ili ne, mora da potpiše Sporazum iz 1958., ako želi da primenjuje isti. Sa druge strane, mnoge države koje nisu potpisnice Sporazuma iz 1958., isti unilateralno priznaju, i primenjuju UNECE Pravilnike kao ekvivalente nacionalnim propisima, što je dovelo do toga da homologovana vozila predstavljaju harmonizovani nivo kvaliteta na međunarodnom tržištu vozila, opreme i delova. Ipak, ceo ovaj proces pridruživanja EU sadrži u sebi dve suprotnosti, kada je reč o tržištu vozila. Sa jedne strane, EU će sigurno zahtevati usklađivanje svih propisa država koje žele da joj pristupe, sa svojim propisima, uključujući i propise u oblasti vozila. Sa druge strane, korišćena vozila iz zemalja EU moraju da nađu tržišta na kojima će se prodavati, a u praksi je nemoguća i ekonomski gledano neodrživa velika razlika u propisima za uvoz novih i korišćenih vozila u jednoj državi. Iako su propisi o homologaciji vozila, formalno gledano, tehničke prirode, evidentno je da na promenu istih itekako utiču globalna i regionalna politička kretanja, jer je autoindustrija veoma bitan činilac svake ekonomije. Zbog toga je važno naglasiti i to da su opšte političke i ekonomske prilike na Balkanskom poluostrvu uvek bile turbulentne i sa velikim zaokretima, pa je na duži rok gledano, bez obzira na sadašnju situaciju, jako teško dati preciznija predviđanja u pogledu razvoja bilo kojih propisa, pa i onih vezanih za uvoz i homologaciju vozila. Ipak, ovom problemu se mora pristupiti i sa određenom dozom optimizma, i verovati u stabilizaciju tržišta i ekonomski prosperitet ovih prostora.

Doc. dr Vladimir Popović

492

Journal of Applied Engineering Science 9(2011)4

REZIMEI RADOVA DOI: 10.5937/JAES9 - 1120 Broj rada: 9(2011)4, 208

PREGLED STANJA VETROENERGETSKIH TEHNOLOGIJA I TRŽIŠTA VETROTURBINA U SVETU Mr Dragan Komarov Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija Dr Slobodan Stupar Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija MSc Zorana Posteljnik Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija U radu je dat pregled modernih vetroenergetskih tehnologija i trendova razvoja tržišta. Ukratko su opisani osnovni principi koverzije energije vetra u električnu energiju sa kratkim osvrtom na moderne konstrukcije podsklopova kao što su lopatice vetroturbina i agregati. Izvršen je pregled stanja vetroenergetike u svetu u cilju dobijanja predstave o budućem razvoju tržišta. Najrazvijenije države u pogledu iskorišćenja energije vetra, kao što su Danska, Nemačka, Španija i SAD identifikovane su kao glavni pokretači daljeg napredovanja vetroenergetike. Nakon dugog vođstva Evropske Unije u pogledu izgradnje vetroenergetskih kapaciteta na godišnjem nivou, Kina i SAD su preuzele vodeće pozicije u poslednjih nekoliko godina. Troškovi proizvodnje električne energije korišćenjem energije vetra su posle postepenog opadanja do 2005. godine zabeležile blagi rast usled visoke tražnje i viših cena repromaterijala. Procenjeno je da će troškovi proizvodnje električne energije iz energije vetra u budućnosti imati trend opadanja. U narednim godinama predviđa se stabilan rast vetroenergetskih kapaciteta, uz očekivanja da će sadašnji instalisani kapaciteti u svetu od oko 200 GW porasti do skoro 1 TW do 2020. godine. Ključne reči: kapacitet, energija, globalizacija, tržište, tehnologija, vetroturbine, vetroenergija, vetar DOI: 10.5937/JAES9 - 1131 Broj rada: 9(2011)4, 209

SMEs U REPUBLICI SRBIJI: RAZVOJ KAPACITETA Dr Dragan Ćoćkalo Univerzitet u Novom Sadu, Tehnički fakultet “Mihajlo Pupin”,Zrenjanin, Srbija Dr Dejan Đorđević Univerzitet u Novom Sadu, Tehnički fakultet “Mihajlo Pupin”,Zrenjanin, Srbija Dr Zvonko Sajfert Univerzitet u Novom Sadu, Tehnički fakultet “Mihajlo Pupin”,Zrenjanin, Srbija Dr Srđan Bogetić Beogradska poslovna škola, Beograd, Srbija Mala i srednja preduzeća (SMEs) predstavljaju jedan od glavnih generatora ekonomskog razvoja u svakoj tržišnoj ekonomiji. U poslednjih trideset godina sektor (SMEs) je bio uspešan u celom svetu, posebno u novo industrijalizovanim zemljama u tranziciji. Proces upravljanja SMEs je specifičan jer se poslovne aktivnosti obavljaju u uslovima nedovoljnih resursa. Razvoj srdnjih i malih preduzeća je jedan od ključnih razvojnih prioriteta u Republici Srbiji. Ovaj rad predstavlja pregled i preporuke za dalji razvoj kapaciteta malih i srednjih preduzećau Republici Srbiji. Ključne reči: SMEs, ekonomija, razvoj, Srbija

Journal of Applied Engineering Science 9(2011)4

493

REZIMEI RADOVA DOI: 10.5937/JAES9 - 1202 Broj rada: 9(2011)4, 210

MODEL OPTIMIZACIJE KOMBINACIJE GARANCIJE BESPLATNE ZAMENE I PARCIJALNE GARANCIJE MSc Dragan Stamenkovic Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija Dr Vladimir Popovic Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija Dr Vesna Spasojevic-Brkic Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija MSc Jovan Radivojevic Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija Rizik koji prati razvoj proizvoda raste iz dana u dan. Jedan od faktora koji utiču na ovaj rizik je garancija proizvoda. Garancija je moćno marketinško oružje za proizvođača i istovremeno dobra zaštita za proizvođača i kupca, ali uvek podrazumeva dodatne troškove za proizvođača. Ovi troškovi zavise od karakteristika pouzdanosti proizvoda i parametara garancije. Ovaj rad se bavi optimizacijom ovih parametara za poznatu raspodelu otkaza proizvoda u cilju smanjivanja troškova garancije i istovremenog zadržavanja njene promotivne funkcije. Kombinacija garancije besplatne zamene i parcijalne garancije je izabrana kao model, pri čemu su varirane dužine perioda besplatne zamene i perioda parcijalne garancije, kao i koeficijenti koji definišu funkciju parcijalnih troškova. Vrednosti troškova garancije dobijene su pomoću analitičkih jednačina i simulacije. Dobijeni rezultati su prikazani i razmotreni i izneta su zaključna opažanja. Ključne reči:garancija besplatne zamene, parcijalna garancija, kombinacija, troškovi, optimizacija DOI: 10.5937/JAES9 - 1267 Broj rada: 9(2011)4, 211

PROAKTIVNO ODRŽAVANJE PNEUMATIKA Dr Gradimir Danon Univerzitet u Beogradu, Šumarski fakultet, Beograd, Srbija Miloš Petrović Institut za istraživanja i projektovanja u privredi, Beograd, Srbija Cilj rada je da promoviše proaktivan pristup u održavanju pneumatika za komercijalna vozila i primenu sistema za kontrolu pritiska guma (TPMS). Istraživanja su potvrdila da instalacija TPMS sistema na komercijalnim vozilima je tehnički i ekonomski opravdano, odnosno bezbednost saobraćaja i udobnost putnika bi na taj način bila značajno poboljšana i cena operativnih troškova znatno samnjena. Primer artikulisanog gradskog autobusa pokazuje da ulaganje u sistem za kontrolu pritiska u pneumaticima je pokriveno u drugoj godini eksploatacije. Ključne reči: pneumatic, kontrola pritiska, saobraćajna nezgoda, troškovi;

494

Journal of Applied Engineering Science 9(2011)4

REZIMEI RADOVA DOI: 10.5937/JAES9 - 1194 Broj rada: 9(2011)4, 212

OD IDEJE DO IMPLEMENTACIJE U ZAŠTITI ELEKTRONSKIH IZDANJA Dr Časlav Mitrović Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija Dr Slobodan Radojević Univerzitet u Beogradu, Mašinski fakultet, Beograd, Srbija Milan Srećković Kriminalističko policijska akademija, Beograd, Srbija Mr Zoran Milanović Kriminalističko policijska akademija, Beograd, Srbija Ovaj rad predstavlja studiju zaštite elektronskih izdanja na optičkim diskovima (CD/DVD), na osnovu osnovnih principa logike i kodne zaštite. Dizajn ovog rešenja je prilično jednostavan, ali je uglavnom sličan kompleksu metoda koje se danas koriste u zaštiti velikog broja komercijalnih elektronskih izdanja. Implementacija i upotreba je prilagođena korsnicima (studentima/profesorima) koji se interesuju za elektronska izdanja objavljenja na kriminalističko - policijskoj akademiji u Beogradu. Ključne reči: CD, DVD, podaci, zaštita, prikazivanje, elektroni, implementacija, logika

Slika 1. – Idejni projekat

Journal of Applied Engineering Science 9(2011)4

Slika 2. – Dijalog za ulazak u aktivacioni kod

495

GENERAL INFORMATION INDEXING Starting from 2006th, only three years since the launch of the journal Istraživanja i projektovanja za privredu (Journal of Applied Engineering Science), all published articles are indexed in international ELSEVIER database through SCOPUS service. In this way, the work and results of the local scientiest are widely available as the SCOPUS is the largest database of abstracts and citations in terms of scientific publications and quality web sources which, above all, give the results of research in various fields.This database provides excellent information necessary for further work and scientists training with extensive search capabilities.

Recognizing professional and business results of your company, Journal offers the possibility for advertising of your products or services to the wide circle of experts engaged in the in the different fields of technical science. The journal is published four times a year. Annual institutional subscription price is 50€. Price is exclusive of tax. Delivery is included in the price. The recipient is responsible for any import duties or taxes. To order the Journal please complete the form on our website: www.engineeringscience.rs You can advertise to the inner pages of the Journal as well as to the cover pages. For the subscription and advertisement and any other information please visit: www.engineeringscience.rs We would like to thank the reviewers who have taken part in the peer-review process.

496

CIP - Katalogizacija u publikaciji Narodna biblioteka Srbije, Beograd 33 Istraživanja i projektovanja za privredu = Journal of Applied Engineering Science: naučno-stručni časopis / glavni urednik Jovan Todorović; odgovorni urednik Predrag Uskoković. - God. 1, br. 1 (2003) Beograd (Vatroslava Lisinskog 12a): Institut za istraživanja i projektovanja u privredi, 2003 - (Beograd: Beografika). - 29 cm Tromesečno Drugo izdanje na drugom medijumu: Istraživanja i projektovanja za privredu (Online) = ISSN 1821-3197 ISSN 1451-4117 = Istraživanja i projektovanja za privredu COBISS.SR-ID 108368396 Journal of Applied Engineering Science 9(2011)4