• Journal of Biomedical Engineering Research
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• v.34 no.1
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• pp.1-7
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• 2013

According to the frequent use of mobile devices, risk of repetitive strain injury for the finger joints was increasing recently. The purpose of this study was to investigate the difference of muscular endurance limit of the thumb between adults and children. A total of thirty subjects (15 adults: $41.0{\pm}7.9$ years and 15 children: $9.5{\pm}2.7$ years) was recruited for this experiment. Maximum voluntary contraction (MVC) of the thumb was measured for 100 trials for each subject by using a push-pull gauge. From the maximum peak value obtained, three main factors (MVC, endurance limit, and fatigue index) were defined to quantify fatigue characteristics of the thumb flexor muscle. The experimental results showed that the mean of MVC, endurance limit, and fatigue index of the children were approximately 50% compared to the adults (p < 0.001). From the results of Pearson correlation test, the endurance limit was highly correlated with weight, age, hand length rather than height. Based on this study, children are more vulnerable to repetitive task using the thumb such as text/SNS messaging, gaming, and scrolling.

• Korean Journal of Occupational Health Nursing
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• v.24 no.3
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• pp.162-172
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• 2015

Purpose: This study was to explore factors affecting musculoskeletal symptoms of the child care centers' teachers in Korea. Methods: This study was a descriptive research, using a cross-sectional survey. Convenience samples of 230 child care centers' teachers aged 20 to 65 were selected. A self-administered questionnaire was used to measure general characteristics, job-related characteristics, exercise habit, fatigue and musculoskeletal symptoms of the body parts. The data were analyzed with the SPSS/WIN 21.0 program. Results: Shoulder pain (73.5%), low back pain (72.6%) and wrist/hand pain (57.8%) were the most common musculoskeletal symptoms. Shoulder pain significantly differed depending on the age of children in charge at the child care center (p<.047). The exercise habit was related to low back pain (p<.028) and the career was linked to wrist/hand pain (p<.046). The logistic regression analysis revealed exercise habit and fatigue were the risk factors on musculoskeletal symptoms of many body parts. Conclusion: These results suggest that interventions targeting the child care centers' teachers should be considered job-related characteristics and fatigue in order to prevent musculoskeletal disorder. Thus, there continues to be a need to develop exercise program for the child care centers' teachers.

• Journal of the Ergonomics Society of Korea
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• v.20 no.2
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• pp.71-82
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• 2001

Twisting posture in lifting tasks has been identified as a risk factor of low back pain. However, it has been usually estimated in terms of compressive stress or muscular activity. Thus, this study was conducted to predict the influence on muscular fatigue during lifting simulation. Fifteen young and healthy subjects were recruited and performed isometric trunk exertions during upright standing, two-level flexions and five-level asymmetric twisting conditions. EMG signals from five primary trunk muscles in right part of body were collected during 20sec for 45 different lifting conditions. RMS(root mean square) and MPF(mean power frequency) parameters were used to analyze the EMG signals. Twisting postures were significant in right erector spinae(ERSR), right latissimus dorsi(LATR), right internal oblique(INOR) for muscular activities. Especially, when trunk was $30^{\circ}$ CCW twisting posture. ERSR and INOR activities increased respectively by 11% and 3%. Regarding the trunk muscle fatigue, we found that MPF shifts in twisting posture increased 2.3 and 2.6 times for ERSR and INOR muscles respectively. Therefore, It is probable for workers to suffer from low back disorders when they were exposed to a extreme twisting posture during prolonged lifting. This study suggests NIOSH(National Institute for Occupational Safety and Health) lifting equation needs the time-duration multiplier in addition to asymmetric multiplier.

• Environmental Analysis Health and Toxicology
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• v.27
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• pp.7.1-7.7
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• 2012

Objectives: Modafinil is a waking drug prescribed to narcolepsy patients, but its usage among healthy individuals is increasing to enhance their alertness or to mitigate fatigue. This study was conducted to investigate practical use and toxic effects on neuro-immune interaction of modafinil. Methods: This study reviewed the significance of psychoactive drugs, and discussed the benefits and risks of the application of modafinil, which seems to be ideal as an anti-psychotic or anti-fatigue agent. Results: Modafinil is known to have less or no adverse effects than those found in traditional psychostimulants such as amphetamine, methylphenidate or cocaine. It can be applied as an anti-psychotic or anti-fatigue agent. However, the waking mechanism of modafinil is yet to be fully revealed. Recent studies reported that modafinil may be subject to abuse and addiction. In addition prolonged sleeplessness induces stress responses and impairs immune function. Conclusions: Modafinil can be used by anyone, who wishes to work late, stay awake, enhance their cognitive reactions, or brighten their moods. Users may already be under a great level of stress, i.e. cancer patients or soldiers in a battle field. A psychoneuroimmunological approach is thus needed to investigate the multi-functional effects of modafinil.

• Korean Journal of Health Education and Promotion
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• v.7 no.1
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• pp.54-63
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• 1990

This study aims to find out the prevalence of smoking, and to analyze the effect of smoking for health status, and then to emphasize the necessity of stop smoking. The data used in this study are obtained from periodic health care programe at Health Care Center in a suburban hospital, and selected 435 males who have occupation. The independent varibles chosen for the analysis are general charactersitic variables and smoking habit. The dependent variables are designed to cover the health status of individual cases, and include blood pressure, blood cholesterol level with HDL-cholesterol and blood triglyceride level, recent symptoms and recently being managed diseases. The result of this study are summarized as follows. 1) Percentage of smoker by the age groups is highest in 4th decade, being 71.1%. The second and third ranks are 6th and 7th decades, being 53.5% and 44.4%, respectively. 2) In the view of socio-economic levels, smoking rate is higher in the groups who live at rural area and whoes occupation is labor or merchant. Smoking rate is significantly higher in the heavy drinking group. 3) Among the atherosclerotic risk factors, which include hypertension, HDL-cholesterol by total cholesterol ratio lower than 0.2 and triglyceride level higher than 200gm/dl, hypertension was not statistically associated with smoking, but others revealed statistically high association with smoking. 4) The groups who have the symptoms of severe fatigue, gastrointestinal symptoms, pulmonary symptoms, palpitation and chest tightness havepositive association with smoking. 5) The groups who have hypertension with cardiovascular diseases and gastrointestinal diseases showed highly significant association with non-smoking. 6) In relation of the smoking habit to the atherosclerotic risk factor index, smokers have more atherosclerotic risk factors, but that is not statistically significant. 7) In relation of the smoking habit to the recent symptom index, smokers have more symptoms than non-smokers with statistical significance. In conclusion, smokers have worse health status than non-smokers especially in the atherosclerotic risk factors such as hypertension or abnormal blood lipid status and have more symptoms such as severe fatigue, gastrointestinal symptoms, pulmonary symptoms, palpitation and chest tightness. And the campaingn against smoking should direct for the male in 4th decade because they have highest smoking rate.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.965-966
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• 2010

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.781-785
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• 2015

In this study, a newly developed ultrasonic fatigue test was performed for durability assessment of polyoxymethylene engineering plastic, which has a high crystallization rate and degree of crystallization. Fatigue strength of POM (polyoxymethylene) was performed on a piezoelectric UFT developed by Mbrosia Co., Ltd(1), operating at a high frequency of 20 kHz. The test results showed a fatigue limit of 5.0~6.0 MPa under fatigue testing at R = -1, 20kHz; and, electron microscopy revealed the size effect by risk volume and fractured dimple structure after the coalescence of micro-voids through the crazing effect, which occurs during the failure of a polymer.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.703-708
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• 2020

As the risk of earthquakes increases recently, earthquake-resistant designs were getting interest. For this reason, this study applies that Friction pendulum-type seismic isolator is a device that attenuates seismic energy by friction and pendulum motion. The friction pendulum-type seismic isolator of this study is very easy to transport, install and maintain with light weight of metal by applying the slider using high strength engineering plastic. In addition, there is an advantage that the corrosion resistance is very excellent compared to the existing metal parts. However, there is concern about long-term durability by replacing metal materials. In this study, the frictional pendulum-type seismic isolator with EP was applied to compressive-shear test, repeated fatigue test, and ultimate load test after fatigue test, and analyzed the deformation and shear or properties after the test. As the results, the adequacy of long term fatigue durability was experimentally proven.

• Journal of the Ergonomics Society of Korea
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• v.29 no.2
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• pp.211-216
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• 2010

Fire service personnel and ambulance paramedics suffer musculoskeletal disorders as they lift and carry patients while performing Emergency Medical Services (EMS). The objective of the current study was performed to examine the association between working environment and musculoskeletal disorders of 119 paramedics and to analysis the EMS activities for them through basic survey (including task characteristics, risk factors, symptoms and illnesses). Observational job analysis of EMS activities indicated the squatting posture during first-aid performed on floor and the abrupt use of force during carrying heavy load including stretcher with patients on as hazard factors, and excessive low back twisting and bending during stairway transfer was observed. In addition, work-physiological assessment revealed various but rather high lumbar muscle usage rate among the study subjects, being 14.6~32.8% compared with Maximum Voluntary Contraction (MVC) during patients transfer work. Resting heart rate showed 65/min, on the other hand, heart rate on mobilization indicated maximum 124~156/min. Therefore, the results of analysis to the EMS activities, rescuer activities and medical tasks were accompanied with high possibility of accident and musculoskeletal disorders. Also, EMS activities indicated high muscle fatigue and energy consumption, and accumulated muscle fatigue with during continued work.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.2
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• pp.226-235
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• 2019

Objectives: The purpose of this study was to investigate whether there were differences in manufacturing industry worker's health issues depending on job stress, fatigue, and health and safety services. Methods: The purpose of the questionnaire survey and its contents were explained to manufacturing industry health personnel, and the questionnaires were collected from 666 workers from 17 manufacturing workplaces. Questionnaires with missing data were excluded from the analysis so a total of 632 questionnaires were included. Results: Overall, 74.1% of the respondents had experienced health issues during the preceding month. The factors affecting worker health were number of workers(OR=1.000034, p=.013), job demand(OR=1.82, p=.009), MFS(OR=1.85, p=.003), provision of safety & health information(OR=1.85, p=.048), wearing protector(OR=2.58, p=.021). Conclusion: It is necessary to strengthen the safety and health education to mitigate hazardous and risk factors. Employers should provide health managers in charge of safety and health education to control workplace risk factors. In case of small businesses, it may be necessary to strengthen safety and health education in existing worker health centers and government support projects.