• Journal of the Ergonomics Society of Korea
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• v.33 no.2
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• pp.155-165
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• 2014

Objective: The aim of this study is to develop an office chair enabling to keep working at reclined sitting posture. Background: Sedentary workers are supposed to change the posture frequently during long hours of sitting. A reclined sitting position has been recommended to reduce disc pressure. But slumped sitting posture caused by the buttock sliding forward without any adjustment of back reclining is commonly observed. The worker seems to have tendency to change the sitting posture maintaining working condition. We assumed the reason to be their hands movement away from the working space when tilting backward. Method: Slide mechanism allowing seat to move forward was designed to maintain the hand position in working space during reclining. A prototype was manufactured and tilting motion was analyzed using motion capture system. Four experiment chairs were tested including the manufactured prototype chair and three other commercial chairs. Results: A backward movements of the hand position were 13.0mm, 101.7mm, 156.1mm and 139.3mm at the prototype chair, compared to chair B, chair C and chair D, respectively. And the movement was remarkably small at the prototype chair. Conclusion: The developed seat sliding chair allows back tilting maintaining hand position at working space. We expect the user tilting back more often than normal tilting chair during seated work. But further investigation is required to figure out the effectiveness of the developed chair using prolonged working hours. Application: The developed office chair directly affects commercialization.

• Journal of the Ergonomics Society of Korea
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• v.30 no.3
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• pp.395-401
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• 2011

Objective: This study examined the effects of working chair that was developed for farmers who work in grapevine's cluster thinning. Background: Agricultural work involves some of the nation's highest occupational risk exposures. Fruit cultivation has been recognized as one of the most hazardous crops in which to work. Grapevine cluster thinning task involve activities related to the main risk factors associated with upper limb work-related musculoskeletal disorders. Method: An experiment was designed to test the working chair. Six healthy male($25.8{\pm}4.9years$) were selected as the subjects for this study. Electromyography(EMG) was used to monitor the muscles activity, and Electro-goniometer was used to measure the ranges of motions of the elbow, trunk and knee. Subjective test was also carried out to examine discomfort body parts and their pain intensity. A grapevine's working space was built for the experiment and working chair was installed on it. In order to examine the muscle activity and range of motion, subjects used to the working chair for 30 minutes for each experimental condition. Another test without working chair was also performed for comparison. %MVC was used to quantify the level of muscle activity. Results: Decreases of muscle activity was found in all leg muscles and significant decrease of muscle activity was found in left Gastrocnemius. The range of motion of the trunk and knee also decreased when working chair used. Discomfort in lower back, thigh and shank region were reduced significantly. However, in upper limbs muscle activity tended to increase in working chair compared with conventional task. Conclusion: Improvement for cushion in seat back and pan required to reduce discomfort in buttocks. Application: Overall findings verified that the working chair might help to prevent upper limb and lower back MSDs based on the current study. These results can be practically used for work improvement for the grapevine growers to prevent MSDs.

• International Journal of Safety
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• v.7 no.1
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• pp.35-38
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• 2008

The purpose of this study is to extract typical body shape of Korean VDT workers based on the three-dimensional Korean shape data and recommendation supported by Korea Occupational Safety & Health Agency during VDT task. Desirable desk heights and chair heights for the selection of the VDT working posture is proposed by analyzing moment, compression and joint shear for lumbar and spine of Korean adult(male and female). The desirable heights for desk and chair can be selected by the least load method during VDT tasks. In the current work the figures of Korean 50th percentile offered by CATIA-HUMAN are used as the average body type of the grown-ups and this research is accomplished with the recommended size of all working attitude such as the height of a monitor except for the height of desk and chair and the degree of watching the monitor.

• Journal of the Ergonomics Society of Korea
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• v.33 no.2
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• pp.167-174
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• 2014

Objective: This research focuses on the working environment of office workers and aims to propose an ideal seating posture and chair design. Background: Generally, office workers having to seat in a fixed posture for long periods of time tend to suffer from an increased rate of musculoskeletal disorders. Method: The measurement and survey of 123 office workers on their working conditions and literature survey will lead to a suggestion of an ideal seating posture and workstation design theory. Results: Work environment satisfaction appeared low for chair and desks. Work-related pain over the last year was experienced among 47.2% of the respondents in shoulder (34.2%), neck (30.9%). Observation of working posture revealed that only 27.6% of workers utilize backrest during work. Conclusion: Office work embodies many situations where risks of musculoskeletal disorders may be high. Thus, the seated workplace must be set up to allow proper seating posture for workers. Application: The results of this study can be applied as baseline data for preventing musculoskeletal disorders of office workers.

• IE interfaces
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• v.15 no.1
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• pp.82-88
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• 2002

A study was conducted to develop user-centered kitchen furniture and workspace to reduce fatigue and to prevent housewives's disorders such as low back pain and musculoskeletal disorders from housekeeping activities. A questionnaire survey and interview were performed on 150 households those live in 32Pyung-type($105m^2$) apartment in Seoul vicinity. Also actual housekeeping activities for 24 hours were video-taped for further motion analysis. Results of the study revealed that housewives complained the inconvenience and small size of storage space, and worksurface height as the most important problems to be considered for redesign. And they responded, if feasible, sitting is preferred over standing while they are working. After adapting a sit/stand chair in the kitchen, a physiological experiment measuring heart rate(HR) and oxygen consumption($VO_2$) as response variables was conducted to examine the effects of sit/stand chair in reducing physiological demand during housekeeping activities. The results showed that working on sit/stand chair reduced energy expenditures by maximum of 30% and 31.0% in terms of HR and $VO_2$, respectively. Also rearrangement of kitchen structure based on motion analysis showed that walking distance during daily housekeeping activities can be reduced by 5.5% on the average. Hence, it is concluded that adapting a sit/stand chair in the kitchen could reduce fatigue and occupational disorders of housewives from extended housekeeping activities.

• Journal of the Ergonomics Society of Korea
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• v.29 no.1
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• pp.139-144
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• 2010

Grape weeding work requires Ergonomics improvement, because it performs motion likely to cause Musculoskeletal disorders (MSDs) repeatedly and continuously. The object of this study was to reject workload in Grape weeding works raised MSDs with the Moving Rail-chair and Electromotive Scissors. As objective method of analysis, we used heart rate, EMG, RULA, REBA. As subjective method of analysis, we used questionnaire that indicate lethargy area of body, pain of muscle and bone. As a result, working with Moving Rail-Chair and Electromotive Scissors is lower heart rate and EMG than typical working. Also for the subjective evaluation, reducing of neck and shoulder movement makes improve workload.

• Journal of the Ergonomics Society of Korea
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• v.33 no.4
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• pp.267-279
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• 2014

Objective: The objective of this study was to define the Dynamic Sitting (DS) through trend analysis and research on the Dynamic Chair (DC) and applied technologies. Background: The effects of changing posture on the human body have been studied to find out healthy sitting postures. It is believed that changing posture is effective in reducing disc pressure on spinal cord and preventing back pain and musculoskeletal disease. But, the definition of DS and trends of DC have not been researched yet. Therefore, trend analysis of DC and its applied technologies are required to define dynamic sitting posture. Method: We researched the type of occupant postures from previous studies. And then, sitting behaviors were classified into three types; (1) sitting and standing, (2) working and studying, (3) taking a rest. Results: Variety shapes of DC and applied technologies were found out. From the result, the trend of DC and applied technology were summarized from three perspectives. ; (1) changing the chair functions according to user's intention, (2) conversion of dynamic chair technologies to office chair mechanism, (3) enables the user to change their sitting posture without operating control device. Conclusion: From this study, we defined dynamic sitting posture and analyzed the trend of DC and its applied technologies. This result might be used to develop an office chair for healthy sitting. But further investigation is required to figure out the technologies and functions for development of healthy chair. Application: The results of the publishing trend analysis might help to determine design concept of office chair.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.403-408
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• 2006

We have developed a four mask LTPS TFT p-channel process and fabricated active matrix backplanes based on a pixel circuit with three TFTs and one storage capacitor. Top emitting AMOLED displays have been produced to prove the working principle of the active matrix.

• Korean Journal of Occupational Health Nursing
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• v.7 no.1
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• pp.55-64
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• 1998

In order to investigate and compare the health risk factors of nurses in the operating room(OR nurse) and ward (WARD nurse), the questionnaire survey for subjective symptoms was carried out on 553 nurses(132 OR nurses and 421 WARD nurses) who were employed at seven hospital. The self-administered questionnaries were composed of low back pain, subjective fatigue symptoms, musculo-skeletal symptoms, psychological stress and reproductive function. The results were as follows : 1. In the type of working posture and working environment, there were significant difference between two groups for working posture, waist form, height of working table, satisfaction of chair, lifting & carring. 2. Job satisfaction, duration of work, height of working table, satisfaction of chair, lifting & carring were significantly associated the low back pain. 3. In the complaints of subjective fatigue symptoms, the total mean score was higher in OR nurse than WARD nurse, but there was not significant. The items that the mean score of OR nurse was significantly higher than WARD nurse were 'head feels muddled', 'apt to forget', 'feel choky'. 4. In the complaints of musculo-skeletal syrrptoms, the total mean score was higher in OR nurse than WARD nurse, but there was not significant. The item that the mean score of OR nurse was significantly higher WARD nurse was 'wrist discomfort or pain'. 5. The comparison of spontatenous abortion in married nurses who had the experience of pregnancy were significantly associated the stress risk group. 6. In all of OR and Ward nurses, the job satisfaction is associated with subjective fatigue symptoms, musculo-skeletal symptoms, and stress. In conclusion, it suggested that working posture, working environment, stress, and job satisfaction were health risk factors of nurses working in the operating room. Further prospective intervention studies should be conducted to educate right working posture, improve of working environment, decrease of stress, and increase of job satisfaction.

• Journal of Drive and Control
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• v.20 no.4
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• pp.35-44
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• 2023

This study aimed to analyze the performance of hydraulic systems for dental chair when long working hours makes the temperature of hydraulic fluid rise. The study was carried out in the following manner. First, 'cylinder's clearance' was reflected in the three kinds of hydraulic circuits, which were developed through the preceding study, in order to analyze oil leak. Second, 12 cases of simulations comprised of the up and down of cylinders were carried out. Third, it was determined whether the cylinder velocity of dental chair surpasses 1cm/s required in the development even in the hydraulic fluid temperature of 60℃. In conclusion, this study used SimulationX to verify the performance stability at high temperatures using three types of hydraulic circuits designed to develop a Korean unit chair.