• 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.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.11 no.1
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• pp.5-16
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• 2003

The present study was carried out to develop highly efficient RC ornithopter 'Songgolmae' powered by motor and battery. Designed electric ornithopter, which has the dimension of O.88m(W)${\times}$0.56m(L)${\times}$0.15m(H), is smaller than a conventional ornithopter. This ornithopter weighs 277 grams and has 3 channels radio control. It runs on an electric motor by a lithium polymer battery and has a gear ratio of about 75${\sim}$95 to 1 to flap its 88 cm wingspan. The aerodynamic performance of the ornithopter, applied to a flapping motion only, was validated by flight tests. Flight times have exceeded 23 minutes until the battery was used up. The flight test results indicate that the ornithopter developed here has sufficient thrust to propel itself in a forward flight. From the economical point of view and the handling of the RC ornithopter, it can be said that the developed robot ornithopter is an effective RC ornithopter. This robot ornithopter flies its way high into the sky just like a real bird flies. The robot ornithopter is used for a wide range of missions.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.82-85
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• 1987

The objective of this paper is to develop computer programs to aid in the design and analysis of control systems in which nonlinear characteristics exist. Control systems are dynamic systems, which can be described using various mathematical models. A convenient model for digital computer simulation is the state model in which described using a set of linear and non linear first order differential equations. The digital simulation was performed on a IBM PC/XT personal computer, and the computer language was BASIC. There are four possible configurations from which a user may choose. When running a program, the user is asked to enter the system parameters according to a specified control system configurations are; 1. A control system with a nonlinear element followed by a plant in a feedback configurations(NLSVF1). 2. A control system with a nonlinear device situated between two plants in a feedback configurations(NLSVF2). 3. A control system with a nonlinear element followed by a plant, followed by a the dealy in feedback configurations(TLAG). 4. A motor and load with a backlash nonlinearity between dynamic portions of the motor/load configurations (BACKLASH). The matrix from state equations are integrated using combination the trapezoidal method and fixed point iteration. Several cases which have nonlinearity were implemented on the computer and the results were discussed.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.150-152
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• 1994

In this paper, the optimum shape design of stator slot of induction motors for iron loss reduction is proposed. To obtain the flux distribution in induction motors, 2-D finite element method with voltage source is employed. The iron loss is calculated from the iron loss data given by the iron manufacturer. To calculate the sensitivity of iron loss to shape variation, the sensitivity analysis of discrete approach is used. The proposed algorithm is applied to a 3-phase squirrel cage induction motor. The nodes at stator slot boundary of the induction motor are defined as design parameters. By controlling these parameters under the constant volume of iron, we can minimize the iron loss. Furthermore, the stator copper loss is reduced by increasing the slot area. So the stator slot area is determined at the point that the summation of iron loss and copper loss of stator is minimized. Since the constraint of constant volume of iron is nonlinear to the design parameters, the Gradient Projection method is used as an optimization algorithm.

• Journal of Power Electronics
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• v.11 no.6
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• pp.856-863
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• 2011

In this paper a novel method of the Ant Colony Optimization algorithm for rotor position estimation in Switched Reluctance Motors is presented. The data provided by the initial assumptions is one of the important aspects used to solve the problems relative to an Ant Colony algorithm. Considering the nature of a real ant colony, it was found that the ants have no primary data for deducing which is the shortest path in their initial iteration. They also do not have the ability to see the food sources at a distance. According to this point of view, a novel method is presented in which the rotor pole position relative to the corresponding stator pole in a switched reluctance motor is estimated with high accuracy using the active and inactive phase parameters. This new method gives acceptable results such as a desirable convergence together with an optimized and stable response. To the best knowledge of the authors, such an analysis has not been carried out previously.

• Fashion & Textile Research Journal
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• v.11 no.1
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• pp.121-129
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• 2009

Nowadays, global interest is being placed on research and development of smart clothing which is expected to create a high added-value industry in the future. The purpose of this research is to develop smart pants with vibrating massage functions that have excellent outer appearances and provide comfort to wearers and assess outer appearance, comfort, and massaging effects of smart pants. As the results of this research, smart pants where vibrating devices which are mainly composed of vibrating motor, controller, and switch are attached were completed. Vibrating motors were fixed on a thin and light non-woven fabric material, covered with a mesh material, and attached by snaps to the experiment pants. Switch was attached to the inside of a pocket, and batteries were positioned inside of pockets. Ten subjects marked their satisfaction of wearing smart pants on a 5-point scale. Noticeable changes in outer appearance when vibrating motors operate turned out to be low. Wearer's comfort in back waist and front thigh parts where vibrating motors were attached turned out to be high-satisfied. Massaging effects of smart pants turned out to be high. Attaching and detaching vibrating devices turned out to be convenient. Lining materials used for smart paints were effective in blocking electromagnetic waves generated from vibrating devices.

• Journal of the Korean Magnetics Society
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• v.8 no.3
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• pp.169-177
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• 1998

In the case of an induction motor efficiency optimal design for electric vehicle which is a real world problem, several different designs are almost equal in terms of efficiency. But these designs may have the differences in terms of other characteristics such as power factor, temperature rise, material cost, and ease of manufacture. Therefore it is necessary that an optimization routine suggests various possible solution alternatives and a designer selects optimal solution among them using other characteristics, his experience and judgment. In this paper new niching genetic algorithm and the rating function method to select the optimal point among possible optimal solution alternatives are presented.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.4
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• pp.16-23
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• 2008

Theoretical and numerical approaches were conducted in order to study supersonic exhaust diffusers to simulate high altitude performance of rockets on the ground. A physical model of concern includes a rocket motor, vacuum chamber, and diffuser, which have axisymmetric configurations. An analysis was conducted to investigate operation characteristics of supersonic exhaust diffusers from a flow-development point of view. Emphasis was placed on theoretical formulation to predict the starting pressure of diffusers, the effect of the vacuum chamber size, and the minimum starting pressure of the rocket motor to start the diffuser.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.5
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• pp.711-716
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• 2012

To assess the insulation deterioration of stator windings, diagnostic and AC breakdown tests were performed on the eleven high voltage (HV) motors rated at 6kV. After completing the diagnostic tests, the AC overvoltage test was performed by gradually increasing the voltage applied to the stator windings until electrical insulation failure occurred, to obtain the breakdown voltage. Stator winding of motors 1, 3, and 8 failed at above rated voltage at 14 kV, 13.8kV, and 16.4kV, respectively. The breakdown voltage of three motors was higher than expected for good quality windings in 6kV motors. Based on deterioration evaluation criteria, the stator winding insulation of eleven HV motors are confirmed to be in good condition. The turning point of the current, $P_{i2}$, in the AC current vs. voltage characteristics occurred between 5kV and 6kV, and the breakdown voltage was low between 13.8kV and 16.4kV. There was a strong correlation between the breakdown voltage and various electrical characteristics in diagnostic tests including Pi2.

• Journal of Electrical Engineering and Technology
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• v.3 no.2
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• pp.152-161
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• 2008

This paper deals with a new wave shaping technique for cost effective harmonic mitigation in ac-dc converter feeding Vector Controlled Induction Motor Drives(VCIMD's) for improving power quality at the point of common coupling(PCC). The proposed harmonic mitigator consists of a polygon connected autotransformer based twelve-pulse ac-dc converter and a small rating passive shunt filter tuned for $11^{th}$ harmonic frequency. This ac-dc converter eliminates the most dominant $5^{th},\;7^{th},\;and\;11^{th}$ harmonics and imposes the reduction of other higher order harmonics from the ac main current, thereby improving the power quality at ac mains. The design of autotransformer is carried out for the proposed ac-dc converter to make it suitable for retrofit applications, where presently a 6-pulse ac-dc converter is used. The effect of load variation on VCIMD is also studied to demonstrate the effectiveness of the proposed ac-dc converter in a wide operating range of the drive. Experimental results obtained on the developed laboratory prototype of the proposed harmonic mitigator are used to validate the model and design of the ac-dc converter.