About Me +86 17822011900 daniel0623@tju.edu.cn English & Mandarin
Employment
Activities 2021 MIT City Science Summit (virtual) I discussed and generated a range of ideas on issues such as urban-rural planning strategies with other city science lab members through TJ-MIT CSL-SH invitation access.
01
02
03
A series of stress toys
A small house hold sterilizer
Community waste reuse plan
Product Design Graduation project 2020.11-2021.06
Product Design Coures assignment 2020.03-2020.05
Service Design Course assignment 2020.05-2020.10
Tetrapods
cleaner-o
Com-Compost
07/2021-01/2022 School of Mechanical Engineering, Tianjin University, Tianjin, China Research Assistant-Industrial Design
Research 07/2021-01/2022 Research Group Leader
Education
White Paper Research on Current Status of Industrial Design in Pharmaceutical Industry (CR Sanjiu-Tianjin University project)
09/2017-07/2021 School of Mechanical Engineering, Tianjin University, Tianjin, China BEng-Industrial Design
07/2021-01/2022 Research Group Leader Electric Bicycle User Experience Research (Xinri-Tianjin University project)
Honor & Prize 2021
‘Excellent graduation project for undergraduates of Tianjin University’
2020
1st Prize of ‘National College Students Industrial Design Competition, Tianjin division’
2019
2nd Prize of ‘Tianjin Industry and Art Design Competition’
2019
2nd Prize of ‘China Renewable Energy Society College Students' Excellent Scientific and Technological Works Competition’
2019
2nd Prize of ‘Tianjin University Social Practice and Science and Technology Competition on Energy Conservation and Emission Reduction’
2021 UNNC Youth Researcher Leadership Summit I conducted research with other three members on green materials and co-wrote the final report. Our report won the third place in this summint. 2021 Machine’s Gaze Workshop In this workshop, I participated in three stages of fictional, object-centered ideation, and led the group to finish the report for the first stage. 2018 That Hill Growth Camp I visited each subsidized family in Mianyang city during the 15-day practice as the practice team leader of TJU and summarized the home visit report pertinently. 2018 TEDxTJU As a new member of TEDxTJU, I successfully completed all the conference work on site on the day of the activity. 2016 TEDxYinzhouSeniorSchool As the head of the selection committee, I had invited all the speakers of this event. And I successfully presided over the whole activity.
01
Background
Tetrapods
The frequency of reading mental health related information
66.99% Rest 66.40%
A series of stress toys Product Design
‘2021 Excellent graduation project for undergraduates of Tianjin University’
Ways for people to deal with mental health problems Self adjustment (top 4)
58.75%
Chat with a friend
47.12%
Leisure activities
Only 0.73% of the respondents paid no attention to mental health.
Eat something
Professional resource support (top 4)
66.99%
Find information online
INTRO COVID-19 has prompted the psychological pressure problem a common phenomenon. People need to find some ways to get rid of it in the pressure environment. Playing toys is a way to decompress, but the mechanism and mode of decompression need to be defined and redesigned.
The top 10 mental health topics people pay attention to
66.40% Read books on psychology
23.13%
Go to the hospital
In October 2020, 2153 people committed suicide in Japan, which even exceeded the number of deaths caused by the epidemic.
83%
The female suicide rate in that month increased by 83% over the same period last year.
Anxiety Meaninglessness Aimlessness Depression
The design methods and rules of decompression toys being studied and verified, a decompression toy is to be designed for young groups through empathic ways.
Chart: Top 4 psychological problems brought by study or work
Empathic Research Strategies Pre survey The first five psychological distress are more emotional related problems, and the last five are more related to relationship.
Individual Project
3
28.15%
Find a psychologist
2153
Target User: college students
GOAL
2020.11 - 2021.06
Facts in Japan
Undergraduate
Interview
Probes
Generative symposium
Time: Goal: Participants: About 30 days total Obtain specific elements for design Students close to researcher There are two generative symposiums. The first one aims to generate some ideas about the final product, and the second one is about verifying the prototype.
Data source: anonymous questionnaire on public mental health awareness jointly sponsored by Simple Psychology and Nutshell, sample size n = 11031 Chart source: Simple Psychology 2020 public mental health insight Report
4
generative research Pre Survey
Semi Structured Interview (two out of ten respondents) Job: Student
Age: 19-22
This persona is only used for probes.
Fake Target User
Name
Coping strategy
Stress toys are...
Liang
I would like to lie in bed, playing with my cell phone, and go out for a walk. Lying in bed is the most helpful way, because I can get rid of stress caused by studying.
Less social attributes
Name
Coping strategy
Stress toys are...
Toys I would like to buy
Yihe
I might eat, read novels or some essays, sleep, and also deal directly with stressors. Some activities make me happy, while others make me feel meaningful.
I think some stress toys may have the same effect as cats, which are fluffy, soft, silent companions and reward people for their efforts.
I might buy a stuffed toy, like Teddy Bear. Beautiful things make me feel happy. I won't buy barbie dolls. It would be too childish.
I feel pressure because of course study and of job searching. And the more pressure I feel, the less willingness I have to face it.
Probes Stress Card Record all your stories and objects related to stress.
The time, place, environment and weather of the story. How does something trigger your stress? What actions do you want to take? Finally, what is your response (including emotional and behavioral)? Why? What is the actual result? What do you think of the final result? What specific and subtle emotions did you generate throughout the story? Has your attention being shifted? What do you think of the change?
Positive Emotion Card Record all your stories and objects related to positive emotion. The time, place, environment and weather of the story. How does something trigger your positive emotions? Did you seek it or did you encounter it? Is your emotional change related to your previous experience? What exactly are your emotions in the whole story? What do you think of the role of these emotional changes in your life?
Camera Record: Record everything in your life.
A2
A3 A4
B3:
Work & living space
I think toys work better when the toys stay alone, and they should be reassuring.
Slightly recognizable Different styles
Work & living space
Categorize Existing Stress Toys
B1 B2
B3 C1
C2 C3
Picture: I bought 10 kinds of stress toys on the market for users to experience
Best sound & appearance
Toys I would like to buy
High-quality craft
Products For Test
A1
Experience Report
A3:
Best in playing
Common Interactions
Emotional
Destructive behavior, such as pulling.
Behavioral
Splicing, installation, etc.
Cognitive
Finger flicking, palm grasping/pan moving, etc
Chart: A summary of all the stress relief toys on the shopping website Taobao
Best weight
Color
Weight (g)
Material
Interaction
Style
Other factors
A1
74.5
plastic
spin
cheap looking
a little noisy
A2
97.8
metal
spin
high-quality
really quiet
A3
86.0
metal & plastic
spin
cheap looking
good feeling when play it
A4
94.4
metal
spin
a little puzzling
really quiet
B1
134.0
metal
flip
boring
nice sound
B2
62.5
plastic
flip
light
too light and too small
B3
155.7
metal
flip
shining
nice sound and is cold
C1
110.3
plastic
multi
boring
not sure how to use
C2
100.2
plastic
multi
cheap looking
bad surface
C3
98.9
plastic
multi
fashionable
bad sound
Chart: Different characteristics of the toys tested
Type
A2:
Name
B type:
Best shopping option
You need to answer these questions. You can also fill out your answers with emojis. Which product do you use most often? When is it usually used? What functions do these products have? How do you implement these features? Is the experience of using the product what you expect? What is your desired outcome/experience? From a visual perspective, which product fits into the workspace better? Which one doesn't? From a tactile point of view, which product bothers you? Which product gives you pleasure? Why? What else influences your perception of the product? How do they all work? Which product is sitting on your desk? Has it made a difference in your daily life and behavior? Given the choice of one product to clear from your desktop, which one would you choose? The products experience report includes not only some superficial perception questions, but also questions that can only be answered by user who have deep experience. The users are required to use each product over a period of time. Products experience report is an alternative method of empathic design for the questionnaire survey.
Picture: The result of probes (generated by target users)
5
6
generative symposium 1
Sketch
Participant Selection Based on the results of previous user interviews, probes and product experience report, four senior undergraduates were selected to participate in the generative symposium. The purpose of the first symposium was to define the form of stress toys.
Name
Gender
Research area
Type
Ruihong
Male
Industrial design
Host
Yonghao
Male
Visual art and design
Expert user
Yihe
Female
Internal combustion engine
Ordinary user
Haiyun
Female
Chinese literature
Ordinary user
Mingya
Female
Interaction design
Expert user
Chart: An overview of symposium participants
Picture: Before the symposium (photographed by Geng Ruihong)
Mood Board: balanced and unbalanced
Introduction Discussion 1 What are the downsides of current toys?
If you were to add a toy or a ornament to your desktop, what qualities would it have?
What makes a good toy?
If a toy needs to be operated by yourself, what qualities should it have? Define: What are the qualities of a good toy on the table? Discussion 2
Waves and stress can both be thought of as a state of imbalance. So tetrapods have some characteristics in common with stress toys.
7
What are the better alternatives? What should it look like?
What are the disadvantages and advantages of the current scheme?
Summary: What other actions can be taken to define and optimize the current solution? The workshop was held on May 8, 2020 and was divided into two sessions, each lasting 1.5 hours.
8
Prototype
generative symposium 1
Clay Model
Participant Selection
Assembly & Painting
Suggetions
The second symposium focused on evaluation and discussion of existing prototypes. The participants of the second generative symposium are all fourth-year industrial design undergraduates. The participants and the host discussed and evaluated the prototype from visual, tactile and auditory perspectives.
Name
Gender
Type
Ruihong
Male
Host
Yonghao
Male
Expert user
Shuixin
Male
Expert user
Jingyue
Female
Expert user
Mingya
Female
Expert user
Defects in one-handed operation Altough the elongated shape makes it easier for fingers to slip through the gaps between the rotating bodies, and therefore easier to grip with one hand. But the elongated shape is less spaceefficient, reducing the volume of the flat rotating body to make it easier to operate with one hand. Longer rotation The current prototype rotates with a lot of vibration, so the rotation time is not very long compared to similar fidget spinner. The persistent rotation may have something to do with the craft.
Chart: An overview of symposium participants
Picture: Before the symposium (photographed by Geng Ruihong)
Theoretical Support: the role of stress toys in GAS. Users can divert their attention and then relieve their emotional stress during the operation.
B1
S1
B2
Operation The M-series prototype, shown at left, uses six opposite rubidium magnets to hold each other in place. The prototype S-series, by contrast, uses an open deep groove ball shaft fixed with an end cap. The diagram below shows four possible prototypes, S for one-handed operation and B for both hands. Among them, type B1 operation mode can only be applied to the M series prototype.
9
The painting process was carried out outdoors with a mask, glasses and gloves.
S2
Stress toys serve as an avenue or aid to psychological and physical therapy to help users return to the original state.
Introduction Discussion Which product do you think you use most? Do you think the experience of using the product is what you expect?
Users shift their attention while playing, and also change their cognitive assessment of stressors and trigger positive emotions to offset the negative emotions.
M Series Graph: General Adaptation Syndrome [GAS], identified by Han Selye
Can you think of any scenes or objects from watching and manipulating the current prototype? Can you think of scenes, objects and stories when talking about your peaceful state of yourself? Define
Which product is more likely to make you want to use for fun and relaxation?
What can be improved in the styling?
Which product is more likely to make you want to use in an anxious, stressed state? Why?
What should the product look like in touch and color?
10
Test
Photography
Quantitative Test Experimental objective Test the effect of operating the prototype on the stress level of the subjects (psychological significance). By comparing the time consumption of the experimental group and the control group, the influence of the stress toy on the stress state can be obtained. Control group While the researcher was delivering 32 questions of 2-digit additional and subtraction to all the subjects, they were required to calculate the number as quick as possible and try to keep the accuracy at the same time.
Experimental group While the researcher was delivering 32 questions of 2-digit additional and subtraction to all the subjects, they were required to calculate the number while playing the prototype with the normal rate.
600 500
Picture: Experiments in progress
The impact of operating prototypes on computing
Rate of Chage 50 40
400
30 20
300
10 0 -10
200
1
3
5
7
9 11 13 15 17 19 21 23 25 27 29
-100 Control group
11
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
-20
100 0
1
Experimental group
Rate of change
Results analysis Since mindfulness is also a stressful state, it makes sense that the control group would take slightly less time than the experimental group. Out of the 30 sample results, only one sample showed that the control group took longer time than the experimental group, which might be caused by the subjects being too nervous. Although the time spent by different subjects fluctuated greatly, the change rate was relatively constant at about 20%, with an average change rate of 19.25%. This means that operating the prototype reduced stress levels, but only up to a point. This slight effect is also one of the expectations of stress toys, toys with too much fun may have a negative effect on the user's daily life.
Picture: M series and S series prototypes photographed in the studio (photographed by Geng Ruihong)
12
Scenario
02
define Market Research
Cleaner-o
Quick
Flexible placement
A small household sterilizer Product Design
Prompt
Stable Market
Sterilizers can also be hung on walls to save space, but not all Spaces have vertical planes to use.
Not everyone is interested in disinfection, so the sterilizer must have some prompt functions, such as voice prompt or sound and light prompt.
INTRO The COVID-19 pandemic has made ever yone pay attention to hygiene in our daily lives. Disinfecting small household items, such as watches and headphones, has become a new requirement for many spaces.
Design opportunities
Control of ozone Disinfectors are designed to disinfect objects that are difficult to clean, so high temperatures and ultraviolet light are reasonable.
GOAL
Portable
Fixed
Grey as the main color. In order to adapt to the desktop space, the color of the sterilizer is best gray, and there are some eye-catching colors as an ornament to remind users to use.
Design a sanitary and suitable for everyone to operate disinfection machine.
Small size Individual Project 2020.03 - 2020.05
Undergraduate
Desktop space is often limited, so sterilizers should be as compact as possible to reduce volume.
Slow By studying the scenario we can identify some design elements of the sterilizer.
13
The products come from taobao shopping website, where different types of products are summarized in a comprehensive order.
14
define
analysis
UVC Disinfection
Mood Board
concept Placement strategy
**Facade**
+
=
+
=
+
=
+
=
+
=
+
=
+
=
+
=
Structures
Frequency
Picture: How ultraviolet disinfection works (source: Stanley Electric website)
Advantages of ultraviolet disinfection
01 02 03
15
Serious product homogenization.
There is no need to wipe and clean the area after use as is the case with chemicals.
It may cause health problems to humans and living things (acute and chronic ultraviolet radiation induced damage).
02
Some UVC lamps generate ozone. Ozone inhalation can be irritating to the airway.
03
Places in shadow or where light does not reach cannot be disinfected using this method.
Information is integrated on the U.S. Food and Drug Administration website and Stanley Electric's website
• Reduce the size of existing products as much as possible.
• Try to avoid the common "square box" appearance.
This method does not create bacteria that is resistant to ultraviolet disinfection.
01
O
• Enterprises can produce small and efficient disinfection machine.
Ultraviolet is also effective against microorganisms that are resistant to chlorine, when chlorine disinfection does not work.
Risks of UVC
Required Structure
SWOT Analysis
• Enrich product functions.
S
W The production line is not mature.
UVC disinfection technology is mature.
• Keep focus on competitive products and ensure the innovation of our sterilizers.
• Make detailed positioning of target users and scenarios. • Ensure that the product meets the needs of the target users.
• Emerging technologies during the pandemic may be better suited for disinfecting machines.
T
Fierce market competition.
1
Exhaust fans and vents
2
UVC lamp bead
3
The lithium battery
4
Charging mouth
5
Stents
6
Confined space
7
A small UVC transmitter
8
Interactive panel
**Plane**
Eliminate possible ozone in time.
Emit ultraviolet light to disinfect.
In this way, the sterilizer can be used in space with limited power supply.
**Board**
Charge the battery or support the sterilizer.
This allows the object to be exposed to a larger area of uvc light.
Prevent ultraviolet radiation from causing harm to human body.
**Grid plate**
It can be placed inside the sterilized item to disinfect the inner wall.
Users can operate on the panel and check the working status.
Plane is the most common space in the desktop environment. Compared with products hung on the wall, objects on the plane have better mobility.
Cube can be well placed in various types of spaces.
Although square shape is ideal, considering the influence of homogenization, simple square shape also needs to be avoided.
16
users Persona (During pandemic)
Sketch for Hardware Ideation User goals Experience goals
User tasks
• Can easily operate the disinfection machine, a "high-tech" product.
• Disinfect daily carryings. • Store small sterilizer. • Tidy up the desk.
End goals • Stay away from viruses. • Save time.
Daily Routine The picture shows the disinfection work Jiaqi will need when she gets home. Using a small sterilizer to disinfect small objects such as mobile phones is the last and most important joint on a daily basis.
Door
001 Back to home
Preference
Life goals • Enjoy a clean, uncluttered life and keep family members and friends healthy.
• Clean feel. • Pure color. • Simple function.
The shoes also need to be disinfected 003 Pull the chair
Name: Jiaqi Age: 22 Gender: Female
Desk, a typical scenario
Profession: Student
**Grid plate**
Status: Primary user
Window
Desk: Pretty clean
Prepare items that need to be disinfected
Daily Carrying: Glasses, mask, cellphone, watch, earphones
004 Use the sterilizer on the desk
Activities in front of desk: Reading and using laptop
002 Disinfect clothes with alcohol
Need to take off the clothes and hang them on the wall
**Facade** **Hair band**
“
I would like to simply disinfect my everyday carryings, but some are too cumbersome to disinfect with alcohol.
“
17
Window
Start the sterilizer and remove the item after disinfection
Closet
**A power outlet** **Mask**
Window
Bed
**Plane** 18
ineraction Control Panel
Function Realization User flow
Time
Structure Electrified connection
Control panel
Ventilation system
Cover
Baffle
Connected by plastic snap
Touch panel
Sieve
Direction of air flow
LED array
Exhaust fan
Key component
Group
PCB
Status
Bottom of cover Ozone detection chip Gold plated contacts
Rubidium magnet
Disinfection bin
Display area Size: 80*60mm
Display color: White
Time area: 80*40mm Function: • Show disinfection progress bar. • Show the remaining time of disinfection. • Set the working time of the sterilizer. Interaction: by finger touch.
Upper part Glass cover UVC beads Portable UVC emitter.
Status area: 80*15mm Function: Show the working status. Language: 简体中文
19
Sieve
UVC beads Lithium battery Gold plated contacts
Segmentation
Sterilized air
Air inlet
Lithium battery Bottom
Air
Drying can only play an auxiliary role in disinfection, and the heater has safety risks, so the heating component is not shown in the drawing.
20
exploded view
prototype
The shape of the sterilizer comes from race cars and ships.
Gold plated contacts UVC lights The mobile transmitter has three rings of UVC light to provide adequate illumination.
rendering
The method of addition finally distinguishes the shape of the sterilizer from the common heavy cube appearance.
The battery is charged by contacts.
Lithium battery The battery is placed inside the mobile transmitter.
Container The inside of the container is coated with teflon.
Rb magnet The inside of the container is coated with teflon.
UVC beads
Control panel The panel contains LED lamp beads, PCB and other parts.
Exhaust fan
Each UVC bead is placed in a concentrating groove to provide greater intensity of exposure.
Handle Ecofriendly rubber
Snap Fix the exhaust fan to the panel.
21
Baffle
Ecofriendly PP
The scale of the clay model is 1:1.
22
Background
02
The relationship between the residents lacks stability
Kitchen waste and fallen leaves are not effectively recycled
Com-compost Community waste reuse plan Service Design
1st Prize of ‘2020 National College Students Industrial Design Competition, Tianjin division’
Plants that are maintained in the community often use inorganic fertilizers, and the falling leaves, treated as a kind of garbage, are totally burned. This kind of waste disposal method of mass incineration or landfill is difficult to improve from the upstream industry in a short time.
Problems and Solutions: through sticky notes.
INTRO A large amount of garbage is produced in urban communities every day. It is not only produced, but also needs to be sorted, transported and disposed of. In these processes, many resources are consumed and wasted, making it difficult for resources to flow effectively within the community.
Children lack opportunities for playing with others.
To create a way of life that makes use of residents' free time resources and reduces the waste of human and material resources in the recycling process.
The leaves inside the community need to be cleared.
Not all games and competitions are suitable for children. Children's role in garbage sorting can be really limited.
Old people who live alone find it difficult to fit in community.
Interface Design: group work Other part: individual work
23
Undergraduate
Families are more likely to play with their own family members.
A lot of garbage is produced in the community.
Reduce the burden of garbage disposal in the community and promote communication among children by designing games and small competitions to get children interested in collecting leaves and sorting household and kitchen waste.
GOAL
2020.05 - 2020.10
The change of population structure not only changes the existing living and social pattern of urban community residents, but also exerts a subtle influence on the psychological state of urban population.
Parents have less free time.
The number of plants is not enough in communities. Residens can plant vegetables in family units, with parents doing most of hard work, while the elderly can provide guidance. The elderly can also perform maintenance work such as watering. Not all families have a lot of free time, and keeping everyone motivated can be a challenge.
Community plants maintenance.
Elderly people from different families can take care of community plants by working together to maintain the functions and services of community. The health status of the elderly varies greatly in different ages, and not all the elderly have the ability to take care of plants
Neighborhood committees are usually reluctant to get involved in the organization of activities. Low waste utilization. There is a need to introduce new products and systems to help reuse resources within the community. Composting of fallen leaves and kitchen waste is a good way to reduce the cost of community sanitation. After the compostable material is collected, it needs to go through a second screening and treatment to produce the material for composting.
The brown cards represent pain points related to the environment, while the green cards are more interpersonal traits. New concerns and issues may arise in addressing these environmental and human-computer relationship issues, and these emerging issues are presented with white letters.
24
ecology map
Service Blueprint
Possibility Residents' strong social needs The expansion of cities and the strengthening of community population mobility have restricted the communication of residents. Residents need a way to socialize offline, such as having parties, collaborative community services, salons, and so on.
Sustainable communities Due to China's carbon peaking and carbon emission reduction goals, communities also need to save energy and reduce emissions. Obviously, community managers need to fully mobilize the power of residents.
Distributive solutions The distributed solution within the community should be based on the grouping and division of labor. Different groups support each other to achieve a common goal of energy conservation and emission reduction.
From garbage to compost material A lot of organic waste is produced within the community every day. In addition to centralized incineration or landfill treatment, the waste can also be used as compost materials. And the composting process can be dealt with the residents themselves.
25
26
persona
System map
Interface Main Function
Goals:
Jianguo Age: 65 Male Widowed Job: Cook (retired) Hobby: Jogging
• • • •
Get help with physically tasks. To keep fit. Start a new relationship. Find friends at his age.
Register Online
Grouping
Grouping Users can post new grouping requests or join other published invatations. Different teams have different responsibilities, which include watering, fertilizing and collecting compost materials. Administrators can also specify groups in order to increase the success rate of grouping.
Pain points: • His own plants have a low survival rate. • Make friends in the community. • There is no suitable place in the community to grow his own plants.
Recording
Assign Tasks
Interact with other residents Users within the community compare their contributions to each other through ranking list. There is a similar competition between different communities. Users speak freely, either to share pictures or to comment on the work of others.
Trim
Goals:
Yifan Age: 40 Female Married Job: Engineer Hobby: Yoga
Register Offline
• Participate in more community activities such as barbecue party. • Have more opportunities to play with her own children.
Sharing Check composting plan Users can check the completion of their work and the corresponding plan on the app. Then the users make plans for the next phase. Users who have spare time can also sign up to help other users with their composting and planting.
Pain points: • Long term high-pressure work makes it difficult for her to balance work and family. • Not much exercise during these days leads to her poor physical quality.
Collect Materials
Goals:
Zihao Age: 14 Male Single Job: Student Hobbies: Soccer
27
• Attend some social activities during holidays. • Hang out with friends. • Make friends in the community.
Pain points: • Meaningless entertainments such as video games occupy a lot of free time. • There is always a feeling of idleness after finishing the course work.
Fertilize Ranking Irrigation Expert Guidance
Compost
Reward
The waste from the distributed plants will be recycled again through the "compost collection" process.
28
sketch
exploded view
hardware
Size
Flowerbox handle Aluminum alloy tube
Flowerbox High density PP
Delivery hose Environmentally friendly rubber
Compost Box The compost box consists of two parts: the upper part is for flower box for planting green plants, and the lower part is for placing compost materials. Two hoses with peristaltic pumps are arranged at the bottom of the box to make it easier for the liquid fertilizer produced at the bottom to be transported to the upper part and to prevent composting failure due to liquid fertilizer.
Fixed frame at the waist High density PP
Back package board Biodegradable plastics (PP)
Liquid fertilizer filter
Front package board Biodegradable plastics (PP)
Biodegradable plastics (PP)
Liquid fertilizer storage area Peristaltic pumps were installed
Compost part handle Aluminum alloy tube
Base High density PP
29
PP materials are widely used because of their lightness and stability.
30