• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.5
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• pp.334-339
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• 2012

A study on electrical and electronic equipment will occur in the atmosphere, which is essential to cut the power to prevent the waste of power by power measurement technology development and to develop the technology to do this operation is the main core of standby power to detect and block it and return the configured for software and hardware, while the actual construction to ensure stability through field testing and debugging of problems improved accordingly, as well as ease of installation and so it could be done while the test. In addition, in terms of basic hardware switching of standby power when blocking, reducing stress and ensure stable operation and circuit design, power off and back to ensure stable operation even when a protection circuit is applied.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.9
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• pp.1597-1604
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• 2016

The speed at which the SRM (Switched Reluctance Motor) makes a transition from chopping control to single pulse operation. (i.e., low speed to high speed operation). It is unsatisfied with performance at all operational regimes. In this paper, the operational performance of SRM can be improved by using current hysteresis control method. This method maintains a generally flat current waveform. At the high speed, the current chopping capability is lost due to the development of the back-EMF. Therefore SRM operates in single pulse mode. By using zero-current switching and zero-voltage switching technique, the stress of power switches can be reduce in chopping mode. When the commutation from one phase winding to another phase winding, the current can be zero as fast as possible in this period because several times negative voltage of DC-source voltage produce in phase winding. This paper is compared to performance based on energy efficient C-dump converter topology and the proposed resonant C-dump converter topology. Simulation and experimental results are presented to verify the effectiveness of the proposed circuit.

• Journal of Korean Institute of Industrial Engineers
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• v.24 no.2
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• pp.167-173
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• 1998

Many workers like welders work in squatting postures with the object on the ground during an entire work shift. It is suspected that such prolonged squatting without any supporting stool would gradually cause musculoskeletal injuries to workers. This study is to examine the physical stress caused by the prolonged squatting and to recommend a safe work/rest schedule for a welding task with squatting posture based on the lab experiments. In this study, 8 healthy student subjects participated in the experiment. They maintained a squatting work posture for 16 minutes with 4 different stool height conditions: no stool; 10cm height; 15cm height; and 20cm height. Every 2 minutes, the discomfort was subjectively assessed with the magnitude estimation method for the whole body, lower back, upper leg and lower leg. Based on discomfort ratings, we found that a 10cm height stool relieved the workload most. Discomfort rating results also indicated that a 20cm height stool showed the highest workload, and the there were no difference in workload between a 15cm height stool and no stool. We recommend to use low height stools and to maintain such working postures no longer than 6 minutes for prolonged squatting tasks.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.134-140
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• 2018

This paper describes the design and fabrication of an automatic alignment and loading system for workpieces. To move a workpiece to a chucking position of a machine tool using a gantry robot, an automatic aligning device is required to load the workpiece before machining and automatically align them. The automatic alignment system was conceptually designed, and the structural analysis was performed for the main parts such as the top plate, center support, front and back support, and support shaft. Based on the structural analysis results, the size of these structures was determined. The automatic alignment system was manufactured, and the vertical movement characteristics of the workpiece up-and-down movement device and the rotation characteristics of the workpiece rotation device were experimentally examined. The result has confirmed that they operate normally.

• Structural Engineering and Mechanics
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• v.56 no.1
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• pp.49-56
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• 2015

Dynamic compaction (DC) is a useful method for improvement of granular soils. The method is based on falling a tamper (weighting 5 to 40 ton) from the height of 15 to 30 meters on loose soil that results in stress distribution, vibration of soil particles and desirable compaction of the soil. Propagation of the waves during tamping affects adjacent structures and causes structural damage or loss of performance. Therefore, determination of the safe or critical distance from tamping point to prevent structural hazards is necessary. According to FHWA, the critical distance is defined as the limit of a particle velocity of 76 mm/s. In present study, the ABAQUS software was used for numerical modeling of DC process and determination of the safe distance based on particle velocity criterion. Different variables like alluvium depth, relative density, and impact energy were considered in finite element modeling. It was concluded that for alluvium depths less than 10 m, reflection of the body waves from lower boundaries back to the soil and resonance phenomenon increases the critical distance. However, the critical distance decreases for alluvium depths more than 10 m. Moreover, it was observed that relative density of the alluvium does not significantly influence the critical distance value.

• Korean Journal of Adult Nursing
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• v.27 no.2
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• pp.198-210
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• 2015

Purpose: This study was to develop a health promotion program for marriage immigrant women and to evaluate its efficacy. Methods: The health promotion program was comprised of eight 100-minute weekly sessions. Each session included understanding of health responsibility, nutrition, physical activity, interpersonal relations, stress management, and self actualization. The research was conducted under the principles of nonequivalent control group pretest-post test design. The outcome variables were health promoting behavior, health status, acculturation, self efficacy, and perceived barrier. The participants were 15 immigrant women in the experimental group and 16 in the control group. Data was analyzed using ${\chi}^2$ test, Fisher's exact test, Mann Whitney U-test and Wilcoxon signed rank test. Results: There was a significant improvement in health promoting behaviors (U=-3.08, p=.002), left shoulder flexibility (U=-3.02, p=.003), right shoulder flexibility (U=-3.02, p=.003), low back flexibility (U=-3.37, p=.001), social health status (U=-3.38 p=.001) and subjective health status (U=-2.17 p=.030) in the experimental group compared to the control group. Conclusion: The health promotion program for marriage immigrant women was an effective intervention for improving health promoting behavior, physical health status, social health, and subjective health status. Therefore, the developed health promotion program needs to be applied to married immigrant women in other kinds nursing care settings in future research.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.28-32
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• 2004

In this paper, the operational performance of SRM can be improved by using current hysteresis control method. This method maintains a generally flat current waveform. At the high speed, the current chopping capability is lost due to the development of the back-EMF. Therefore SRM operates in single pulse mode. By using zero-current switching and zero-voltage switching technique, the stress of power switches can be reduce in chopping mode. When the commutation from one phase winding to another phase winding, the current can be zero as fast as possible in this period because several times negative voltage of DC-source voltage produce in phase winding. This paper is compared to performance based on conventional C-dump converter topology and the proposed resonant C-dump converter topology Simulation and experimental results are presented to verify the effectiveness of the proposed circuit.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.840-842
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• 2001

The cogging torque and torque ripple in motor which cause noise and vibration are an inevitable phenomenon and they give a bad effect to motor performance. So we are required to reduce the cogging torque and torque ripple not by electrical controlling but by changing the inner mechanical structure and we focused on the permanent magnet. In this research, we calculated current, torque, Back-EMF(electromotive force) and cogging torque according to the change of the magnet shape using two dimensional FEM(Finite Element Method). Maxwell stress tensor and time-stepping method. From the results, we present an appropriate model that can satisfy both low cogging torque, low torque ripple and high efficiency.

• Safety and Health at Work
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• v.6 no.3
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• pp.233-239
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• 2015

Background: The Job Content Questionnaire (JCQ), which is based on the Demand-Control-Support model, is designed to measure the psychosocial characteristics of the respondent's work, and has been identified to predict health and psychological outcomes. The purpose of this study was to investigate the psychometric properties of this instrument and the subsequent adaptation of its scales to the population of Greek health workers. Methods: The Greek version of the JCQ was developed by using forward- and back-translation in accordance with the JCQ policy. The reliability and validity of the measure were investigated in a sample of health workers working in a hospital in Athens, Greece. The internal consistency of the scales was examined based on Cronbach ${\alpha}$ coefficients, and the validity was evaluated subjecting the items of the three main scales of the JCQ (decision latitude, psychological job demands, and social support) to exploratory and confirmatory factor analysis. Results: The reliability of the scales was found to be acceptable for all the scales, except for the skill discretion subscale. Confirmatory factor analysis confirmed a slightly modified version of the original construct including several items to more than one factor. Conclusion: Our findings suggest that the Greek JCQ is reliable and valid for investigating psychosocial job characteristics among Greek health workers.

• Journal of the Ergonomics Society of Korea
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• v.34 no.2
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• pp.135-143
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• 2015

Objective: The purposes of this study are to investigate ergonomic problems and to propose their improving measures in office environment of big general hospitals. Background: Office tasks have varying risk factors of work-related musculoskeletal disorders (WMSDs). The first symptom resulted from the office work was recognized as an occupational disease in Korea in 1986. Although the symptoms have increased since its first recognition, there has been few study on the effect of office work environment settings. Method: First, the author took pictures of working scenes performed in three big university hospitals. Next, the pictures were analyzed in view point of ergonomics. Based on the analysis, their improving measures were proposed for reducing work stress. Results: The results showed that most physical office environment settings such as dimensions of tables/desks and chairs, leg room, thigh, knee and foot clearances, and chairs used did not satisfy the ergonomically recommended design guidelines. In addition, some clerks placed personal belongings under their desks, put monitors in high position and did not lean against the backrest of chairs in seated tasks, which resulted in poor working postures of leg, back, neck etc. It is recommended that the hospital management should provide their clerks with ergonomically designed office furniture and continuously perform ergonomics training program for raising clerks' recognition for office ergonomics. Conclusion: Most office environment settings investigated in this study were not in good condition in view point of ergonomic design for the settings. Application: It would be useful as basic data for establishing ergonomically good office environment in hospitals.