• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.323-329
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• 2020

The aim of this study was to investigate the level of depression among female hospital nurses and the influence of rotating shift work and quality of sleep on depression. A total of 295 nurses in Seoul were recruited and the data were analyzed using descriptive statistics and multiple regression analysis. The number of depressed nurses was 71.2%(CES-D total score ≥ 16) and factors influenced on nurses' depression were quality of sleep, rotating shift work, and work experience in nursing(1-2.9 years, more than 10 years). Based on the result of this study, nurse managers and hospital organization should use appropriate interventions to improve quality of sleep and negative effects of rotating shift work for nurses.

• Journal of Korean Society for Quality Management
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• v.46 no.2
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• pp.193-210
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• 2018

Purpose: The purpose of this study is to escape from the existing defense quality policy focused on government-led quality assurance for mass-produced items and to secure quality reliability of weapon systems through a defense quality policy paradigm shift based on designing a verification systems anchored on reliability through the enhancement of military supply quality control in the development stage, the enhancement of quality responsibility of the manufacturing contractor and other methods. Methods: For the shift to the quality-based defense quality policy, the status and the problems of the status quo are analyzed and the direction of future defense quality policy is suggested based on literature review of the concept of reliability and reliability in the field of defense, on case studies of global corporations and their quality policies, on the background on quality assurance in defense, and on case studies of quality policies in other government organizations, Results: Based on the case studies of quality policies in global corporations and other government agencies, the importance of preventive quality control from the early development stages, quality control based on the reliability of the materials and parts, and shift of the quality policy to a certification system to achieve these objectives were highlighted. Conclusion: To secure reliability of weapon system quality, the quality policy must be shifted to a system focused on reliability-based design and verification and there is a further need to enhance the operational efficiency and capacity of DTaQ based on studies and evaluation of weapon system reliability.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.1
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• pp.165-172
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• 2017

Machines are physically or chemically degenerated by continuous usage. One of the results of this degeneration is the process mean shift. Under the process mean shift, production cost, failure cost and quality loss function cost are increasing continuously. Therefore a periodic preventive resetting the process is necessary. We suppose that the wear level is observable. In this case, process mean shift problem has similar characteristics to the maintenance policy model. In the previous studies, process mean shift problem has been studied in several fields such as 'Tool wear limit', 'Canning Process' and 'Quality Loss Function' separately or partially integrated form. This paper proposes an integrated cost model which involves production cost by the material, failure cost by the nonconforming items, quality loss function cost by the deviation between the quality characteristics from the target value and resetting the process cost. We expand this process mean shift problem a little more by dealing the process variance as a function, not a constant value. We suggested a multiplier function model to the process variance according to the analysis result with practical data. We adopted two-side specification to our model. The initial process mean is generally set somewhat above the lower specification. The objective function is total integrated costs per unit wear and independent variables are wear limit and initial setting process mean. The optimum is derived from numerical analysis because the integral form of the objective function is not possible. A numerical example is presented.

• Journal of Mechanical Science and Technology
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• v.14 no.12
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• pp.1348-1357
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• 2000

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.639-645
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• 2011

Wheel-loader is a construction vehicle for uploading soil or sand into truck and transportation of materials, which requires large driving power and high rotational speed. To improve the working efficiency, the operator has to shift gears and control levers for bucket & boom simultaneously. Therefore, the automatic transmission has been introduced to enhance operator's convenience and enable effective operation. To develop the automatic transmission for the wheel-loader, technologies such as gears and a clutch-pack design and shift algorithm are required for improvement of shift quality. In this paper, the shift algorithm for the wheel-loader was developed and its shift pattern was analyzed. As the shift control is affected by the pressure profile for the clutch control, the shift quality depending on the pressure profile has been evaluated using experiment and simulation model analysis.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.361-364
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• 2008

In this paper, several fields for improving shift quality and mode conversion quality are presented and considered. For a series type hybrid vehicle, improving mode conversion quality is important because it changes its speed with its own motors. A parallel type hybrid vehicle usually has AT or AMT, and its motor and engine can work independently. Therefore, improving both of two qualities is equally important in this case. For a power split type hybrid vehicle, improving mode conversion quality is more important due to the existence of planetary gears which change vehicle's speed.

• Journal of Korean Academy of Nursing
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• v.50 no.4
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• pp.631-640
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• 2020

Purpose: This study aimed to examine premenstrual symptoms (PMS) of shift nurses and identify the association between PMS, sleep, and occupational stress. Methods: This study was conducted with a secondary data analysis that used data from the Shift Work Nurse's Health and Turnover study. The participants were 258 nurses who were working in shifts including night shifts. PMS, sleep patterns (sleep time and sleep time variability), sleep quality, and the occupational stress of each participant were measured using the Moos Menstrual Distress Questionnaire, a sleep diary, an actigraph, the Insomnia Severity Index, and the Korean Occupational Stress Scale, respectively. Data were analyzed using SPSS 23 and STATA 15.1 to obtain descriptive statistics, Pearson's correlation coefficients, multiple linear regression with generalized estimating equations (GEE) and Baron and Kenny's mediating analysis. Results: The average PMS score, average sleep time, average sleep time variability, average sleep quality score, and average occupational stress score of the participants was 53.95 ± 40.45, 7.52 ± 0.89 hours, 32.84 ± 8.43%, 12.34 ± 5.95, and 49.89 ± 8.98, respectively. A multiple linear regression analysis with GEE indicated that sleep time variability (B = 0.86, p = .001), and sleep quality (B = 2.36, p < .001) had negative effects on nurses' PMS. We also found that sleep quality had a complete mediating effect in the relationship between occupational stress and PMS. Conclusion: These findings indicate that both sleep time variability and sleep quality are important factors associated with PMS among shift work nurses. To improve shift nurses' PMS status, strategies are urgently needed to decrease sleep time variability and increase sleep quality.

• Journal of Korean Biological Nursing Science
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• v.21 no.4
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• pp.266-274
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• 2019

Purpose: The aim of this research was to identify the mediating effect of sleep quality on the relationship between job stress and stress response of shift-working nurses. Methods: The participants in this study were 150 nurses who had more than 6 months of shift-working experience. A survey was conducted from May to June 2017 in a hospital in Gyeonggi-do, South Korea. The data were collected through self-report questionnaires. The collected data were analyzed using SAS 9.4 program. The analysis was based on Baron and Kenny's model to examine the mediating effects of sleep quality on the relationship between job stress and stress response of shift-working nurses. Results: In the first and second steps, job stress was identified as a significant predictor of sleep quality (β= .29, p= .001) and stress response (β = .24, p= .004). In the third step, sleep (B = .55, p< .001) was observed as a significant predictor of stress response, and the direct relationship between job stress and stress response was not significant (β= .07, p= .291). Sleep quality was found to exhibit complete mediating effect on the relationship between job stress and stress response. Conclusion: The results of this study suggest that strategies for managing the stress of shift-working nurses should include effective ways to ensure sleep quality.

• Journal of Power Electronics
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• v.12 no.4
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• pp.664-676
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• 2012

A phase shift algorithm based on the closed-loop control of dc-link voltage implemented on a series active voltage quality regulator (AVQR) is proposed in this paper. To avoid pumping-up the dc-link voltage, a general phase shift compensation strategy is applied. The relationships among the operation variables are discussed in detail, which is very important for guiding the design of both the main circuit and the control system. Then on the basis of an investigation of the dc-link voltage pumping-up from viewpoint of the active power flow, a novel phase shift control method based on the closed-loop of the dc-link voltage is proposed. This method can adjust the phase of the output voltage gradually and automatically according to the dc-link voltage variation without introducing a phase jump. The effectiveness of the proposed strategy is verified through simulations of a single-phase 5kVA prototype and laboratory experiments on both a single-phase 5kVA and a three-phase 15kVA prototype.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.26 no.4
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• pp.426-435
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• 2016

Objectives: The major objective of this study was to analyze stress response after a change to consecutive day shifts from day and night shifts in a motor assembly factory. Methods: Using a survey conducted by a labor union, we collected data on stress response index(SRI), lifestyle factors, work-family conflict and job stress before and after a shift system change. We analyzed the transition on the SRI among 222 workers. The cut-off point for the SRI was a T-score over 60. Results: The high risk stress response group was 20.3% of the population before the shift system change. After the shift system change it decreased to 11.3%. After the shift system change, social support improved, leisure time became more sufficient, work-family conflict declined, and sleep quality in the night shift week improved. In multivariable linear regression, among workers under 40 years old sleep quality on night shift, leisure time sufficiency, social support and work-family conflict contributed to the improvement of stress response. Among workers over 40, work-family conflict contributed to the improvement of stress response. Conclusions: The change to consecutive day shifts improved stress response and mediated with improved nighttime sleep, decreased work-family conflict, increased leisure time and improved work-family conflict.