• 산업경영시스템학회지
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• 제45권1호
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• pp.31-40
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• 2022

Six Sigma is a philosophy and systematic methodology for quality improvement. It encourages continuous quality improvement efforts to achieve the ideal goal of 6σ. Sigma(σ) is a statistic representing the standard deviation of the normal distribution, and 6σ level means a level where the tolerance of the specification is six times the standard deviation of the process distribution. In terms of the defective rate, the 6σ level achieves the 0.002 defectives per one million units. However, in the field, the 6σ level is used in the sense of achieving 3.4 defects per one million opportunities, which shows a large gap from the 6σ level in the statistical viewpoint. This is because field practitioners accept a 1.5σ shift of the mean of process when calculating the defective rate under sigma level. It said that the acceptance of 1.5σ shift of the mean is from experience, but there is no research or theoretical explanation to support it logically. Although it is a non-scientific explanation based on experience, considering that there has been no objection to the 1.5σ shift for a long time and it is rather accepted, it is judged that there is a reasonable basis for the 1.5σ shift. Therefore, this study tries to find a reasonable explanation through detective power of control chart via the run-rules to the 1.5σ shift empirically recognized by practitioners.

• Safety and Health at Work
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• 제6권3호
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• pp.240-248
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• 2015

Background: Recovery from fatigue is important in maintaining night workers' health. This study compared the course of self-reported recovery after 2-week 12-hour schedules consisting of either night shifts or swing shifts (i.e., 7 night shifts followed by 7 day shifts) to such schedules consisting of only day work. Methods: Sixty-one male offshore employees-20 night workers, 16 swing shift workers, and 25 day workers-rated six questions on fatigue (sleep quality, feeling rested, physical and mental fatigue, and energy levels; scale 1-11) for 14 days after an offshore tour. After the two night-work schedules, differences on the $1^{st}$ day (main effects) and differences during the follow-up (interaction effects) were compared to day work with generalized estimating equations analysis. Results: After adjustment for confounders, significant main effects were found for sleep quality for night workers (1.41, 95% confidence interval 1.05-1.89) and swing shift workers (1.42, 95% confidence interval 1.03-1.94) when compared to day workers; their interaction terms were not statistically significant. For the remaining fatigue outcomes, no statistically significant main or interaction effects were found. Conclusion: After 2-week 12-hour night and swing shifts, only the course for sleep quality differed from that of day work. Sleep quality was poorer for night and swing shift workers on the $1^{st}$ day off and remained poorer for the 14-day follow-up. This showed that while working at night had no effect on feeling rested, tiredness, and energy levels, it had a relatively long-lasting effect on sleep quality.

• 한국직업건강간호학회지
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• 제32권2호
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• pp.49-57
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• 2023

Purpose: This study aimed to explore the meaning of job experiences of fixed night shift nurses participating in a pilot project by a tertiary hospital, and to provide basic information for improving their night shift working environment. Methods: A descriptive qualitative study was conducted using individual interviews in September 2022. Three female nurses who worked fixed night shifts were recruited from a tertiary hospital. Data were analyzed using content analysis. Results: By analyzing the meaning of job experience as a fixed night shift nurse, four categories and nine subcategories were identified. The four categories of job experience of fixed night shift nurses were: expecting an improvement physical health due to predictable working hours, enjoying leisure time due to long off-duty hours, regretting for loosened relationships, and considering a successful settlement of fixed night shift nursing. Conclusion: As night shift work is essential for nurses to provide continuous nursing to patients, it is necessary to develop various strategies to improve the physical health of night shift nurses through fatigue management and good sleep quality, mental health through work-life harmony, and social health through intimate relationships between patients and coworkers.

• 대한간호학회지
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• 제50권5호
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• pp.646-657
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• 2020

Purpose: The purpose of this study was to identify the quality of sleep in novice and experienced shift work nurses and compare the factors associated with their quality of sleep. Methods: We analyzed the data of 192 and 256 novice and experienced nurses, respectively. The quality of sleep, sleep hygiene, job stress, and fatigue were measured using Insomnia Severity Index, Sleep Hygiene Practice Scale, the Korean Occupational Stress Scale, and Fatigue Severity Scale. Data were analyzed using SPSS 25.0 to calculate descriptive statistics and logistic regression. Results: Sleep quality was lower in experienced nurses (12.55 ± 5.71) than in novice nurses (11.18 ± 5.78). Fatigue was more severe in experienced nurses (4.47 ± 1.13) than in novice nurses (4.23 ± 1.12). In the logistic regression, factors related to sleep quality in novice nurses were sleep hygiene (odds ratio; OR = 1.06, p < .001) and fatigue (OR = 2.49, p < .001). Factors related to sleep quality in the experienced nurses were also sleep hygiene (OR = 1.04, p = .001) and fatigue (OR = 1.53, p = .012). Conclusion: Sleep quality of experienced nurses is lower than those of novice nurses. Factors associated with sleep quality in novice and experienced nurses are equally identified as sleep hygiene and fatigue. Therefore, personal efforts to improve sleep hygiene, such as providing comfortable sleep environment, are needed. Furthermore, organized efforts to decrease fatigue, such as constructing a working environment with a bright light at night and providing a fatigue-decreasing program that includes meditation, are required.

• 전기전자학회논문지
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• 제22권3호
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• pp.539-547
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• 2018

계통 연계형 인버터는 단독운전 조건에서 반드시 전력 공급을 차단해야 한다. 이러한 이유로 분산 발전 시스템은 단독운전을 검출 기능을 반드시 가지고 있어야 한다. 분산 발전용 인버터에 적용되는 일반적인 방법 중에는 Slip-Mode frequency Shift (SMS) 단독운전 검출 기법이 있다. SMS 기법은 계통 전압의 주파수에 따라 무효 전력을 공급하여 단독운전 조건에서 계통 주파수를 허용 범위 밖으로 이동시키는 방법이다. SMS 기법은 안정적으로 단독운전을 검출할 수 있으며, 계통 전류에 고주파를 인가하지 않는다는 장점이 있으나, 무효 전류를 인가하기 때문에 계통 역률이 나빠져서 전력 품질의 저하를 가져온다. 본 논문에서는 계통 전원이 연결되어 있는 정상 조건에서 전력 품질 저하가 없는 수정된 SMS 기법을 제안한다. 600W 단상 인버터 실험을 통해 제안된 방법의 유효성을 검증한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.263-266
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• 2001

The performance of the powertrain can be analyzed using dynamic models including transient characteristics, and the equations of motion can also be derived from the dynamic models of the powertrain. In this study, the shift transient characteristics of the vehicle equipped with Ravigneaux type planetary gears automatic transmission has been investigated.

• 정신신체의학
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• 제29권2호
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• pp.111-120
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• 2021

연구목적 이전 연구에 따르면 교대근무는 인간의 자연적인 일주기 리듬에 적응하기 어렵게 만들어 각종 건강문제를 일으킨다. 특히 교대근무자는 근무 일정과 연관된 수면의 어려움을 호소하는 경향이 있으며, 알코올을 수면유도를 위한 자가약으로 사용하는 경우가 있다. 현재까지 교대근무와 수면 및 음주와의 관련성에 관한 명확한 기전이 밝혀지지 않고 있는 상태이다. 따라서 이 연구에서는 교대근무와 수면과의 관련성을 확인하고, 교대근무로 인한 수면의 변화가 음주를 유발하는지에 대해 분석하고자 한다. 방 법 이 연구는 국민건강영양조사 제6기, 제7기 자료 중 2014, 2016, 2018년도를 분석대상으로 하였으며 총 11360명(남성 5704명, 여성 5656명)을 연구대상인원으로 포함시켰다. 6 am-6 pm사이의 근무형태를 주간근무, 이외의 근무형태를 교대근무로 정의하였으며 로지스틱 회귀분석을 통하여 교대근무와 수면의 질, 교대근무와 고위험 음주, 음주량 및 음주 횟수의 관계를 분석하였다. 또한 매개분석을 통하여 수면이 교대근무와 음주의 관계를 매개하는지 여부를 분석하였다. 결 과 교대근무는 남성과 여성에서 수면 질과 유의한 음의 관계를 보였다(남성 OR=1.37, 95% CI=1.11-1.70, 여성 OR=1.26, 95% CI=1.05-1.50). 교대근무와 음주와의 관계에서는 남성의 경우 유의한 관계가 나타나지 않았으나, 여성의 경우 교대근무와 음주횟수에서 유의한 양의 관계를 보였다(OR=1.34, 95% CI=1.04-1.72). 매개분석 시행 시 여성의 수면 질은 교대근무와 음주횟수의 관계를 부분매개하는 것으로 나타났다. 결 론 이 연구의 결과는 교대근무가 수면의 어려움을 유발하며, 여성의 경우에서는 수면의 부분매개효과를 통해 음주를 유발할 수 있음을 시사한다. 여성이 수면장애에 대한 대처방안으로 음주를 선택할 가능성이 높은 점을 고려할 때, 여성 교대근무자에 대한 보다 적극적인 중재방안이 마련된 필요가 있다.

• 한국지능시스템학회논문지
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• 제4권3호
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• pp.32-48
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• 1994

This paper proposes the compensation algorithm of conventional shift pattern using fuzzy reasoning in automatic transmission vehicles. Recently, automatic transimssion vehicles are continually increasing because of theire ease to drive. Also users require the high performance which includes the smooth shift quality and shift scheduling that matches driver;s intentions. So the shift scheduling has been inproved significantly through the application of electronic control. But, in spite of this development, vehicles using conventional shift pattern are sometimes in discord with driver's intention on roads. In this paper, the paper, the proposed compensation algorithm makes a automatic transmission vehicle be able to select an optimal gear shifting time and position using fuzzy reasoning and make a vehicle driver feel confortable even when the vehicle runs on roads which is extremely changed. Therefore, a vehicle driver can expect to reduce the nimber of unnecessary gear shifting and expect the fuel efficiency high. To show usefulness of the proposed method, some simulation are made to compared with conventional gear shifting. Paper prosposes the compensation mehtod of conventional shift pattern using fuzzy reasoning for the purpose that a vehicle can select an optimal gerar shifting time and position in automatic vehicle. Though the conventional shift pattern has no pliability, vehicle driver can feel comfortable and can reduce the number of unnecessary gear shifting using the proposed method on variable road condition. Therefore, it can be expected the fuel efficiency.

• International Journal of Internet, Broadcasting and Communication
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• 제4권1호
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• pp.8-12
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• 2012

The purpose of this study is to review the possible effect of the learning paradigm shift from traditional method to ubiquitous learning. What are the societal issues that need to be address in order to design a new pedagogical platform trending from e-learning to m-learning and now the u-learning? That without the proper study of how learning environment may affect the learning process of an individual will lead to poor quality of education. This new era of learning environment offer a big opportunity for "anytime, anywhere" learning. Thus, Lifelong learning is at hand of everyone. Maximizing the benefit of new trend will be a great help and addressing the limitations will lead to quality education.

• 한국정밀공학회지
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• 제14권12호
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• pp.95-104
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• 1997

We consider controller design problem to enhance shift quality for automatic transmission. A dynamic modeling related to shifting (mainly 2-3 up-shift) is constructed and nonlinear robust controllers are designed to reduce output torque during shifting. Suggesting a new hydraulic circuit enabling the direct clutch drive, the control activity is extended and more implementable than the conventional design. The designed robust controllers overcome the unmodeled dynamics and the uncertainty embending in the system. Moreover, the dynamic effect between the clutch pressure and the PWM valve duty is considered via singular perturbation technique.