• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2736-2738
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• 1999

Power electronic loads inject harmonic currents into the utility system. The large increase of power consumption will inevitably lead to deteriorating power quality due to the popularization of switch-mode power electronic equipment. In this paper, a periodic voltage is injected in the control circuit to vary duty cycle of the rectifier switch within a line cycle so that the fifth-order harmonic of the input current is reduced to meet the IEC 61000-3-2 requirement. Experimental results are presented to confirm the validity of this method.

• Proceedings of the Korea Society for Simulation Conference
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• 2002.11a
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• pp.47-51
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• 2002

전 규모에서 소규모에 이르는 MMIS(Man Machine Interface System) 모사설비는 실제의 원자력발전소에 사용될 MMIS를 응용 소프트웨어로 구동되는 모사환경을 통하여 사전에 시험 및 검증할 목적으로 사용된다. 기존의 MMIS 모사설비 개발은 잘 정의된 개발 프로세스에 기반을 두지 않고 프로젝트 관리자 또는 개발 담당자의 경험과 직관에 의존하여 수행되었다. 이로 인하여 MMIS 모사설비의 개발 일정이 지연되거나 개발의 결과가 초기목표를 만족하지 못하는 불만족 사항이 나타났다. 본 연구는 MMIS 모사설비의 응용 소프트웨어 개발을 위한 프로세스를 정의하고 이에 따라 설비개발을 진행하였다. 개발 프로세서는 계획 단계, 설계 및 구현단계, 시험단계의 세 부분으로 구성하였다. 본 논문에서는 MMIS 모사설비에 요구되는 일반적인 성능특성요건과 개발공정요건을 살펴보고, 본 연구가 정립한 응용 소프트웨어 개발의 프로세스 및 각 프로세서에서의 공정활동을 제시한다.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.6
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• pp.683-687
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• 2010

In this paper, we propose an anycast routing scheme for large-scale wireless mesh networks, which requires only one-hop local information with no flooding overhead. We develop an analytical model for anycast mesh networks based on an electrostatic theory. A finite difference method contributes to achieving gateway load balancing with constant control overheads. We verify the performance of the proposed scheme by simulations.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.257-260
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• 1990

Monte Carlo simulations of electron impact ionization in silicon utilizing simple spherical band approximation including L valley are presented. The mean energy of electron at high electric field is lowered and the threshold energy of electron impact ionizaiotn is smeared out to $E_x$ by including L valley. This work also presents the importance of the modeling of L valley by calculating the electron population rate of it over the threshold energy of eletron impact ionization, which is higher than 10%

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.6
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• pp.61-71
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• 2008

An advanced model for assessing life cycle cost of the facility containing several subdivisions has been proposed with systems engineering approach. This model evaluates the maintenance cost in the sphere of the safety as well as in that of its functionality. The proposed approach has been shown to be more reasonable and practical than existing models. The serviceability and reasonability have been proved through evaluating life cycle cost of the reservoir which is a representative agricultural facility. In addition, the proposed method is helpful to make a maintenance strategy using the survival probability in the point of safety and functionality.

• Environmental and Resource Economics Review
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• v.9 no.4
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• pp.773-799
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• 2000

The purpose of this paper is to measure the benefits of conservation of the green belt in the Greater Seoul area by CVM using dichotomous choice with a follow-up elicitation method. According to the government's plan, part of the green belt in the Greater Seoul area is to be freed from green belt designation. The mean willingness-topay(WTP) to conserve the green belt in the current state turns out to be about 7,430 won(95% confidence interval 6,220 - 8,640 won) per household, which amounts to 308 billion won per year for entire population of Seoul. This WTP figure is found to be significantly influenced by level of education, sex, and the variables related to the perception and attitudes of respondents.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.135-138
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• 2005

This study began to establish a risk evaluation method for irrigation reservoirs under the overtopping failure mode. To define the risk, reliability analysis was performed using time series of reservoir flood inflow and spillway outflow. The former was defined as a load and the latter was the resistance component. The method results in failure probability, which is calculated by convolution multiplication between probability distribution functions of both components. The proposed method was applied to 3 reservoir sites and each failure probability was determined as 0.0012, 0.00001, and 0.000001 respectively.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.365-372
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• 2001

This study is concerned with the application of an analytical model of cyclic crack growth that includes the effects of crack closure. The crack closure model is based on the Dugdale model and the strip model, considering the plasticity-induced closure which is caused by residual plastic deformation remaining in the wake of an advancing crack. This study is performed to get the relation between crack growth and crack opening stress with the constant stress ratio, and the relation between stress ratio and crack opening stress with the constant maximum stress under constant-amplitude loading. Under constant-amplitude loading, the crack opening stress is conversed the constant value as a crack grows and is proportion to both the stress ratio and the maximum stress. The crack closure effect, however, is decreased in the positive stress ratio and disappeared at about 0.7. The crack growth analysis using the crack closure model shows that the influence of stress ratio is minimized in the relation between crack growth ratio and effective stress intensity range specially at the negative stress ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.177-185
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• 1997

The purpose of this study is to investigate the mechanical properties of super-workable concrete using O.P.C., blast-furnace slag, and fly ash respectively. For this purpose, after determining the optimum mix proportion of super-workable concrete according to unit weight of binder and percentage of fine aggregate respectively, mechanical properties of super-workable concrete such as compressive, tensile and flexural strength as well as elastic modules were tested and analyzed. Also, the mechanical performances of super-workable concrete were compared with those of high-strength concrete with equal mix proportion of concrete. As a result, super-workable concrete have an excellent mobility, placeability, and segregation-resistance, but the strength of super-workable concrete was shown to be somewhat lower than that of high-strength concrete with equal mix proportion of concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.289-292
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• 2005

It is not feasible for agricultural facility managers to estimate how severe damages are and what are causes of them when agricultural hydraulic facilities get damaged for some reasons. Moreover, it is nearly impossible for agricultural facility managers to take immediate actions to repair and reinforce the damaged structures. Thus, there have been needs for well-established systems to help agricultural facility managers understand its severity and causes, and take proper actions to reduce speed of deterioration and to repair/reinforce them. Thus repairing and reinforcing systems of agricultural hydraulic structures based on agricultural facility management policies, developed in this study, can be efficiently used in field works to determine top priority location and the budget of repairing and reinforcing projects if detailed information of damages in concrete structures and damage types are well compiled and classified with standardized image data complemented.