• Journal of the Korea Safety Management & Science
• /
• v.15 no.2
• /
• pp.1-7
• /
• 2013

Based on a literature review regarding shift work, it is recognized that it has an adverse effect on workers' health. Especially, the night shift rather than the day shift imposes severe disorders on workers, which are indicated to dyssomnia, maladaptation to social life, and health problems such as gastroenteric trouble, cardiovascular diseases and depression. As the shift work can be explainable by using workers' labor ability necessarily to maintain company business consistently, it does not consider biorhythm, active mass and health condition of workers Actually duration of shit work would deprive workers of fundamental life rights by causing physical and mental effects. As a result of reviewing previous case studies related to effect of work pattern (day shift and night shift) on workers' health, an incidence of physical diseases like dyssomnia, gastroenteric trouble, cardiovascular diseases and premature delivery was higher in shift workers than normal workers. Additionally the incidence of mental disorders such as busy brain, social isolation, depression and work stress was also higher in shift workers than normal workers. These adverse physical and mental problems were intensified to night shift workers compared to day shift workers. Considering current various reports and study results, it is recommended that the shift work, especially the night work pattern, should not apply to contemporary work situation for sustaining workers' health condition constantly.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.1767-1772
• /
• 2008

A microcantilever is a well-known MEMS structure for sensing bio-chemical molecules. When bio-chemical molecules are adsorbed on the microcantilever's surface, resonance frequency shift is generated. There are two issues in this phenomena. The first one is which one between mass change and surface stress change effects is more dominant on the resonance frequency shift. The second one is what will be the performance change when the boundary condition is changed from cantilevers to double clamped beams. We have studied the effect of surface stress change and compared it with that of mass change by using FEM analysis. Furthermore, for microstructures having different boundary conditions, we have studied Q-factor, which determines the detection limit of micro/nano mechanical sensors.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.3 no.1
• /
• pp.15-18
• /
• 1998

The entanol productivity of superoxide dismutase (SOD)-deficient mutants of Saccharo-Myces cerevisiae was examined under the oxidative stress by Paraquat. It was observed that MnSOD-deficient mutant of S. cerevisiae had higher ethanol productivity than wild type or CuZnSOD-deficient yeast both in aerobic and in anaerobic culture condition. Pyruvated dehydrogenase activity decreased by 35% and alcohol dehydrogenase activity increased by 32% were observed in MnSOD-deficient yeast grown aerobically. When generating oxygen radicals by Paraquat, the ehanol productivity was increased by 40% in CuZnSOD-deficient or wild strain, resulting from increased activity of alcohol dehydrogenase and decreased a activity of pyruvate dehydrogenase. However, the addition of ascorbic acid with Paraquat returned the enzyme activities at the level of control. These results imply that SOD-deficiency in yeast strains may cause the metabolic flux to shift into anaerobic ethanol fermentation in order to avoid their oxidative damages by Paraquat.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.5
• /
• pp.291-299
• /
• 2003

The effect of temperature and soil confining stress on geosyntheic creep behaviour was studied by performing the temperature dependent confined creep tests for HDPE geogrid and geomembrane specimen. The visco-elastic creep coefficients of the geosynthetics were evaluated by the test results and it was proposed that the simple expressions for the instantaneous and limit creep strain of geosynthetics was considered as a function of temperature and confining stress on geosynthetics. Based on the time-temperature superposition principle, a master curve has been drawn for extrapolating tensile creep strains to longer time intervals(1$\times$10 $^7$min.∼1$\times$10$^{10}$min.). By using this master curves, the shift factors which can be used in establishing master curve considering confining stress on geosynthetics were carried out. Each tests was performed during 8,000∼12,000 min., with temperature ranging between 5$^{\circ}C$ and 4$0^{\circ}C$ and with confining stress ranging between 0 t/$m^2$ and 9 t/$m^2$.

• Journal of the Korean Home Economics Association
• /
• v.27 no.1
• /
• pp.47-58
• /
• 1989

This study was undertaken to investigate whether the stress caused by day/night shifts on industrial workers can be affected through nutritional status. A sample of 573 female industrial workers, aged 17 through 23 years, from 4 different industries (2 in normal, 2 in 3 shift work pattern) were surveyed by questionaire examining their nutritional status, food intake, dietary habit, sleep complaint, performance of digestive organs, and degree of fatigue. Shift workers were surveyed during night work. The results are summarized as follows: 1. Sleep complaints and degree of fatigue in shift workers were higher than normal workers, whereas the performance of digestive organs were as lower than normal workers. These results showed that shift workers were more stressed than normal workers. 2. The workers who were surveyed were all poor in nutritional status. The intakes of calorie, protein, Ca, riboflavin, and ascorbic acid were lower than Korean Recommanded Dietary Allowences (RDA). Dietary habit of the shift workers was irregular. 3. There was a negative correlation between nutritional status and degrss of fatigue. The intakes of energy nutrients, ascorbic acid, and niain were significantly related to the degree of fatigue in which protein intake was found to be most influential. Among workers with the same level of protein intake, shift workers showed higher degree of fatigue. When the protein intake of shift workers was 100-125% of R.D.A., they showed the same degree of fatigue to the average normal workers.

• Journal of the Korean Society of Safety
• /
• v.38 no.4
• /
• pp.32-38
• /
• 2023

Job stress factors are factors that induce biological, psychological, and behavioral responses in individuals when they encounter mental and physical stimuli in the workplace. According to occupational safety and health standards, employers are responsible for the health consequences of job stress when workers engage in activities that result in high levels of physical fatigue and mental stress. Such activities include long working hours, shift work (including night shifts), driving vehicles, and operating precision machinery. Therefore, precautionary measures should be implemented. Following the COVID-19 epidemic, the logistics industry in Korea has experienced rapid growth owing to the shift from offline to online platforms facilitated by advanced digital infrastructure. Consequently, this study conducted a survey to analyze job stress factors among delivery workers. The survey utilized a Korean job stress factor assessment tool comprising 43 items and analyzed job stress factors considering the work characteristics of the courier business field obtained from responses provided by 421 courier workers nationwide. The survey analysis revealed that the physical environment, job demands, and job autonomy exhibited higher stress indices among Korean workers. Furthermore, the younger the age, the higher the stress on job demands, whereas the higher the age, the higher the stress on relationship conflict, job instability, and workplace culture. In addition, daytime delivery work was associated with higher stress levels in job demands and job instability compared with nighttime delivery work. These findings can serve as foundational data for reducing and preventing job stress among courier workers, whose workload has increased owing to the growth of the logistics industry.

• Korean Journal of Occupational Health Nursing
• /
• v.31 no.3
• /
• pp.125-136
• /
• 2022

Purpose: The aim of this systematic literature review was to synthesize and investigate the effects of shift workers' sleep in Korea. Methods: A search was conducted through three electronic databases using keywords such as "shift work" or "rotation work" and "sleep", with sleep as the independent variable, and 17 papers were reviewed. Results: The design of those 17 studies was analyzed in a cross-sectional analysis. The most commonly measured characteristic was quality of sleep, whereas the others were sleep disturbance, sleep efficiency, and sleepiness. The study outcome variables were job-related factors, mental health, wellness, stress, fatigue, and metabolic syndrome. Conclusion: The results inform sleep and health-promoting behaviors and improvement in shift workers' working condition.

• Korean Journal of Food Science and Technology
• /
• v.27 no.2
• /
• pp.193-198
• /
• 1995

The changes in the rheological properties of soybean curd upon the various storage temperatures ($5{\sim}25^{\circ}C$) were measured by the stress-relaxation test and analysed by time-temperature superposition theory. As the storage temperature was lower, higher initial and equilibrium stress of soybean curd were observed. When the stress-relaxation curves were moved horizontally by using the shift-factor on the basis of reference temperature, the master curve was obtained. By applying master curve and shift-factor to the WLF (Williams-Landel-Ferry) equation, activation energy (30kcal/mol) was calculated and storage time at the specific temperature could be predicted, suggesting the equivalent shelf-life of soybean curd texture.

• Safety and Health at Work
• /
• v.13 no.1
• /
• pp.3-8
• /
• 2022

Background: This study aims to allow the development of efficient measures to improve occupational health of shift-working nurses focusing on job stress, health promotion behavior, resilience, and sleep disturbance. Methods: It was conducted on a subject panel of 137 nurses who were aware of the purpose of the study and agreed to participate. They worked three shifts at a tertiary hospital or a general hospital located in metropolitan city B. The collected data were analyzed by the independent t test and one-way analysis of variance and post-tested by Scheffe's test, Pearson's correlation coefficients, and multiple linear regression analysis using SPSS/WIN 25.0. Results: The significant influencing factors on sleep disturbance were of those whose subjective health status was 'normal' (b = 0.29, p < .001), 'not healthy' (β = .40, p < .001), who have job stress (β = .22, p = .003), and who have health promotion behavior (β = -0.17, p = .023). The overall explanatory power was 31.1% (F = 16.31, p < .001). Conclusion: Through this study, nurses' subjective health status and job stress of working shifts were found to be important factors influencing the sleep disturbance level, and the most influencing factor was identified as the subjective health status.

• Journal of the Korean Society for Heat Treatment
• /
• v.24 no.6
• /
• pp.311-317
• /
• 2011

The effect of strain rate on the yield stress of an Al-Li alloy has been investigated at temperatures between 77 and 523 K and over the strain rate range from $1.77{\times}10^{-4}s^{-1}$ to $1.77{\times}10^{-2}s^{-1}$. At testing temperatures below 373 K, the yield stress is almost independent of strain rate at any aging stage. At testing temperatures above 373 K, the yield stress increases linearly with the logarithm of strain rate, and the strain rate dependence increases with increasing testing temperature. The yield stresses of under-aged alloy at temperatures between 373 and 473 K at high strain rates are greater than the yield stress at 77 K. For the alloy under-aged or aged nearly to its peak strength, the temperature range within which the positive temperature dependence of yield stress appears expands to the higher temperature side with increasing strain rate. The strain rate dependence of the yield stress is slightly negative at this aging stage. The yield stress of the over-aged alloy decreases monotonically with decreasing strain rate and with increasing testing temperature above 373 K. The modulus normalized yield stress is nearly constant at testing temperatures below 373 K at any strain rate investigated. And, strength depends largely both on the aging conditions and on the testing temperature. The peak positions in strength vs. aging time curves shift to the side of shorter aging time with increasing testing temperature. For the specimens aged nearly to the peak strength, the positive temperature dependence of yield stress is observed in the temperature range. The shift of peak positions in the aging curves are explained in terms of the positive temperature dependence of cutting stress and the negative temperature dependence of by-passing stress.