• Korean Management Science Review
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• v.20 no.2
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• pp.33-43
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• 2003

In this paper we applied dynamic programming to determining work schedule type. In dynamic programming formulation, each day during a planning horizon represents a stage for which a decision is made. The alternatives are given by work schedule types that combine regular time, overtime, additional shift, and so on. In this case, their associated return function is labor cost. The state is defined as the amount of work time allocated to stage 1, stage 2,…, and current stage. A case study for a real manufacturing company was performed to apply dynamic programming to scheduling daily work hours during a week. The case study showed that total cost of our solution derived from dynamic programming decreased by about 6％ as compared with the solution obtained from the previous method.

• Korean Journal of Occupational Health Nursing
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• v.9 no.2
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• pp.110-120
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• 2000

The purpose of this study was to examine which factors affected the job stress of workers in the manufacturing industry. The subjects were 128 workers in automobile component manufacturing companies located in Kyonggi-do province. Data were collected through self-reporting technique for 8 days, October 24-31, 2000. The instrument to test the work related truss was NIOSH's Work-related Stress Inventory revised by Korea Occupational Safety and Health Association(KOSHA) in 1999. The collected data were analysed with SAS. and frequency, percentage, mean value, standard deviation, t-test, ANOVA. Scheffe's post hoc test and Pearson's Correlation Coefficients. The major findings were as follows: 1. Mean job stress score for the job-related stress was $2.6{\pm}0.5$ on the basis of 5.0 points. Job stress was significantly different according to gender. The stress by role conflict showed higher score than the stress by role ambiguity. 2. Discretionary power(freedom to determine) of workers was scored $2.6{\pm}0.7$ on the basis of 5.0 points. And it was significantly different according to gender, duration of work and shift experience. 3. The work environment scored $2.2{\pm}0.3$ on the basis of 3.0 points and significant difference according to gender, age, marital status, type of employment, type of service, and shift work. 4. Role ambiguity showed significant negatively correlate with job control(r=-.32, P=.000) and decision making(r=-.31, P=.000). And decision making showed positively correlated with job control(r=.62, P=.000), and role conflict(r=.26, P=.003).

• Journal of the Ergonomics Society of Korea
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• v.26 no.2
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• pp.157-165
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• 2007

The Work-Related Musculoskeletal Disorders (WMSDs) can be occurred by various factors such as repetition, forceful exertions and awkward postures. Especially, occurrences of the WMSDs on the waist and lower limb are reported in workplaces, demanded standing postures for a long time, in service and manufacturing industry. The static and standing postures without movement for a long time increase work loads to the lower limb and the waist. Accordingly, anti-fatigue mat or anti-fatigue insole is used as a preventing device of the WMSDs. However anti-fatigue mats are limited in space and movement. In this study, multi-elastic insoles are designed and shown the effects of the workload reduction for a long time under the standing work. The foot pressures and EMG (Electromyography) are measured at 0 hour and after 2 hours by 6 health students in their twenties. The 6 prototype insoles are designed with three elastic (Low, Medium and High). These insoles are compared with no insole (insole type 7) as control group. The EMG measurement was conducted to waist (erector spinae muscle), thigh (vastus lateralis muscle) and calf (gastrocnemius muscle). The foot pressure is analyzed by mean pressure value and the EMG analysis is investigated through MF (Median Frequency), MPF (Mean Power Frequency) and ZCR (Zero Crossing Rate). The results of the foot pressure show that the multi-elastic insoles had smaller foot pressure value than that of no-insole. Moreover, Insole 2 and Insole 3 have the smallest increasing rate in foot pressure. The EMG results show that the multi-elastic insoles had smaller EMG shift value than that of no-insole in 2 hour, and then shift value shows the smallest value in Insole 2. Therefore, this study presents that the multi-elastic insoles have reducing effects of the work load for a long time standing work in both side of foot pressure and EMG.

• Nuclear Engineering and Technology
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• v.52 no.8
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• pp.1764-1770
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• 2020

The present work was mainly concerned with studying the operation of RC-phase shift oscillator based on MOSFET type 2N6660 under the influence of different temperature levels ranging from room temperature (25 ℃) up-to135 ℃ and gamma-irradiation up-to 3.5 kGy. In this concern, both the static (I-V) characteristic curves of MOSFET devices and the output signal of the proposed oscillator were recorded under ascending levels of both temperature and gamma-irradiation. From which, it is clearly shown that the drain current was decreased from 0.22 A, measured at 25 ℃, down to 0.163 A, at 135 ℃. On the other hand, its value was increased up-to 0.49 A, whenever the device was exposed to gamma-rays dose of 3.5 kGy. Considering RC-phase shift oscillator, the oscillation frequency and output pk-pk voltage were decreased whenever MOSFET device exposed to gamma radiation by ratio 54.9 and 91%, respectively. While, whenever MOSFET device exposed to temperature the previously mentioned parameters were shown to be decreased by ratio 2.07 and 46.2%.

• Journal of the Optical Society of Korea
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• v.18 no.4
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• pp.301-306
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• 2014

A porous silicon microcavity (PSMC) sensor has been made for vapors of solvent solutions, and a method has been developed in order to obtain simultaneous determination of two volatile substances with different concentrations. In our work, the temperature of the solution and the velocity of the air stream flowing through the solution have been used to control the response of the sensor for ethanol and acetone solutions. We study the dependence of the cavity-resonant wavelength shift on solvent concentration, velocity of the airflow and solution temperature. The wavelength shift depends linearly on concentration and increases with solution temperature and velocity of the airflow. The dependence of the wavelength shift on the solution temperature in the measurement contains properties of the temperature dependence of the solvent vapor pressure, which characterizes each solvent. As a result, the dependence of the wavelength shift on the solution temperature discriminates between solutions of ethanol and acetone with different concentrations. This suggests a possibility for the simultaneous determination of the volatile substances and their concentrations.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.30 no.3
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• pp.93-110
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• 2019

This study surveyed 129 librarians of public libraries in the northwestern region of Seoul to identify harmful factors under the assumption that the work and environmental factors of them would burden their musculoskeletal system and influence their work satisfaction. The results of this study showed that the musculoskeletal symptoms in the shoulder, one of the general items, were more frequently observed in women than in men. Secondly, the musculoskeletal symptoms in the arms and elbows, one of the working environment characteristics, were most frequently reported when they worked more than one year and less than three years. The musculoskeletal symptoms in the waist were influenced by the operation method; the librarians of public libraries entrusted to the Office of Education or a local government showed symptoms more frequently. The musculoskeletal symptoms in the neck were affected by working hours; librarians working in the day shift showed neck symptoms more frequently than those working in the night shift. Thirdly, when the characteristics of the work environment were examined, the musculoskeletal symptoms in the hands, wrists, and fingers were highly frequent under all characteristics of the work environment, the musculoskeletal symptoms in the waist were highly frequent under all characteristics of the work environment except for work satisfaction, and the musculoskeletal symptoms in the legs and feet were highly frequent according to the proficiency, work intensity, and physical burden. Fourthly, this study evaluated the differences in musculoskeletal symptoms according to the work satisfaction of individuals. The results revealed that the occurrence frequency of musculoskeletal symptoms for all body parts decreased as work satisfaction increased. Therefore, it will be necessary for the main body of public library operation to improve the work and working environments and enhance the work satisfaction of individuals by reducing the physical burden of the librarian of public libraries through adjusting the work intensity in order for the health of the librarian of public libraries.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.18 no.3
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• pp.216-223
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• 2008

Objectives : To investigate the effect of overtime work on fatigue symptoms among Korean female workers. Methods : A total of 1,875 subjects were analyzed using the structured questionnaire, which was composed of overtime work, fatigue symptom, and background characteristics. Data analysis included multiple regression to test for a relationship of overtime work with fatigue symptom while statistically controlling for demographic and occupational variables. Results : Overtime work was more common in those with shorter work years of 3 or less than in those with longer work years. Overtime work was more popular in day workers than in shift workers. No significant difference of smoking and drinking state was observed between two groups. Subjective fatigue symptoms were significantly higher in overtime workers than in workers without overtime work. In a multiple regression analysis with significant control variables, overtime work was associated with 0.31 more fatigue symptom(p<0.001). Conclusion : Our findings suggest that overtime work may increase risks for fatigue symptom. Therefore, preventive strategies will be needed to control the negative effect of overtime work on health status of female workers.

• Journal of Korean Biological Nursing Science
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• v.24 no.4
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• pp.209-218
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• 2022

Purpose: This study aimed to investigate the relationships between the characteristics of nurses' work schedules, health outcomes, and work-life balance. Methods: This was a secondary data analysis that included 422 nurses in Korean hospitals. Descriptive analysis, independent sample t-test, one-way ANOVA, Pearson correlation analysis, and multiple linear regression analysis were used to identify the associated factors. Results: Multiple linear regression analysis showed that work-life balance was lower when atypical work was performed (β=-.14, p=.010). Nurses who did not work overtime showed a higher level of work-life balance than those who worked overtime infrequently (β=-.11, p=.002) or frequently (β=-.28, p<.001). The work-life balance level increased when nurses had better subjective health status (β=.16, p<.001) or higher sleep quality (β=.29, p<.001). It was verified that the work-life balance level was higher for single-person households than for households with two (β=-.18, p=.003), three to four (β=-.16, p=.022), or five or more (β=-.21, p<.001) persons. Conclusion: This study suggests that government and hospital organizations should provide high-quality care and consideration to nurses who do atypical or overtime work as well as their subjective health status and sleep quality. Further research should focus on the development of a policy that improves the work-life balance of nurses, especially for those who work during atypical hours.

• Journal of Nutrition and Health
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• v.53 no.5
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• pp.488-502
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• 2020

Purpose: This study examined the factors influencing Nutrition Quotient for adults (NQ-A), focusing on workers in the manufacturing industry. Methods: The participants were 738 industrial workers in Gwangju. Their dietary information was analyzed using a questionnaire of NQ-A, which consisted of 21 checklist items and the general characteristics of the subjects. The scores of NQ-A and its 4 factors (balance, moderation, diversity, and dietary behavior) were calculated according to the general characteristics of subjects. The data were analyzed using a χ² test, t-test, correlation, and multiple regression using SPSS 21.0 program. Results: The mean NQ-A score was 45.3 for the total subjects, indicating a low grade. Non-shift workers showed significantly higher scores for balance, diversity, and moderation factors than shift workers. Forty-three (8.7%) shift workers and 123 (50.8%) non-shift workers had good NQ-A scores, whereas 453 (91.3%) shift workers and 119 (49.2%) non-shift workers required monitoring for nutrition. The significant influencing factors of NQ-A were the working pattern (p < 0.001), gender (p < 0.001), family composition (p < 0.001), age (p < 0.001), and household income (p < 0.001). As a result of multiple regression analysis, there was a significant difference in the NQ-A score for moderation (F = 141.930, p < 0.001), diversity (F = 98.998, p < 0.001), balance (F = 52.329, p < 0.001), and dietary behavior (F = 12.895, p < 0.001). As a result, shift work and gender had the greatest influence on the balance (β = -0.372, p < 0.001), diversity (β = -0.316, p < 0.001), and moderation (β = -0.507, p < 0.001) factors in NQ-A. Gender had the most influence on the dietary behavior in NQ-A. Conclusion: Shift work and gender were significant factors affecting NQ-A. To manage workers' health better, it will be necessary to prepare a nutrition education program according to the type of working pattern and gender.

• Safety and Health at Work
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• v.12 no.3
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• pp.351-358
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• 2021

Backgrounds: Irregular and unpredictable work schedules have become more common in most societies. The purpose of this study was to investigate the association between unpredictable work schedules and depressive symptoms in Korea. Methods: Data from 34,486 workers who participated in the Korean Working Condition Survey in 2017 were used. Unpredictable work schedules were measured by questions about the frequency of changes in work schedule and limited advanced notice. Depressive symptoms were assessed by a single item asking if the participants had depressive symptoms over the last 12 months. Multivariable-adjusted logistic regression analysis was used to calculate odds ratios (ORs) for high depressive symptoms. Results: The OR for depressive symptoms was significantly higher in the workers with unpredictable work schedules compared to those with predictable work schedules after controlling for age, sex, education, salary, marital status, occupation, contract period, full-time versus part-time, shift work, weekly working hours, and having a child under the age of 18 years (OR = 2.43, 95% confidence interval 1.93-3.07). Conclusion: Unpredictable work schedules were associated with depressive symptoms controlling for the other dimensions of precarious employment in a representative working population in Korea.