• Journal of Power Electronics
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• 제2권1호
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• pp.19-24
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• 2002

The torque of SRM depends on a phase current and the inductance of the motor. But the inductance is saturated nonlinearly according to the position and current. To drive the motor effectively, the control scheme should take into account the nonlinear characteristics of the magnetic material. This paper proposes an optimal control scheme for high efficiency drive of SRM by adjusting both the turn-on and turn-off angle. The high efficiency drive points are simulated and searched by using GA-Neural Network The switching angles are nonlinearly varied with rotor speed and load.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.772-774
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• 2000

The objective of a cathodic protection system (CP) is to protect the buried metallic structure against the corrosion caused by chemical reaction between the buried structure and the surrounding medium, such as soil. This paper presents a boundary element application to determine the optimal impressed current densities in a cathodic protection system. The potential within the electrolyte is described by the Laplace's equation with nonlinear boundary conditions which are enforced based on experimentally determined electrochemical polarization curves. The optimal impressed current densities are determined in order to minimize the power supply for protection. The solution is obtained by using the conjugate gradient method in which the governing equations and the protecting conditions are taken into account by the penalty function method. Numerical example are presented to demonstrate the practical applicability of the proposed method.

• Transactions on Electrical and Electronic Materials
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• 제7권6호
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• pp.319-323
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• 2006

The problem of the partial discharge (PD) extinction is investigated. The transient process takes place in a small spherical inclusion which is located in the dielectric. Both the losses caused by polarization and ohmic losses as the dielectric parameters are taken into account. From the inclusion standpoint the dielectric is considered as an active two-pole element (equivalent generator) and inclusion represents by own current-voltage curve. PD extinction voltage was shown to depend on the polarization loss tangent.

• Transactions on Electrical and Electronic Materials
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• 제16권3호
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• pp.107-111
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• 2015

Our work is based on the development of a numerical model to develop a methodology for predicting the aging and breakdown in insulation due to the dynamics of space charge packets. The model of bipolar charge transports is proposed to simulate space charge dynamic for high DC voltage in law-density polyethylene (LDPE), taking into account the trapping and detrapping of recombination phenomena, this model has been developed and experimentally validation. Theoretical formulation of the physical problem is based on the Poisson, the continuity and the transport equations as well as on the appropriate models for injection. Numerical results provide temporal and local distributions of the electric field, the space charge density for the different kinds of charges, conduction and displacement current densities, and the external current.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.20-27
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• 1998

In the current seismic design codes design earthquake is usually defined as the earthquake with the 90 percent probability of not being exceeded in the life time of a structure which is assumed as 50 years equivalent to the earthquake with 475 year recurrence period. However the life time of tall building structures may be much longer than 50 yers. The current seismic design code requires the modal analysis or dynamic time history analysis for the buildings with the height exceeding a certain height limit. The objective of this study is to collect the earthquake ground motion(EQGM) which can be used for dynamic time history analysis for tall buildings. For this purpose linear elastic design response spectrum (LEDRS) in the code is scaled to account for the recurrence period of the design earthquake. The earthquake ground motions which has been recorded are calibrated to fit the scaled LEDRS. The set of calibrated EQGM can be treated as design EQGM for the design of tall building with longer lifetime than ordinary building.

• 설비공학논문집
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• 제23권2호
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• pp.147-152
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• 2011

The cryogenic cooling load from the top plate of cryostat to liquid helium surface, including wall conduction, thermal radiation and current leads, is investigated in a closed cryostat system for superconducting magnet. In general methods of load estimation, individual load is calculated separately, however they are actually coupled each other because of natural convection of helium vapor. Using relevant heat transfer analysis, we calculate cryogenic load with taking into account the effect of natural convection. Cryogenic load is under-estimated approximately 1% when the natural convection is ignored. The difference between actual cooling load and cooling load by individual calculation increases with supplying current.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.797-800
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• 2004

Some test results indicated that the current ASTM grip adapter of GFRP rebar was not successful in developing the design tensile strength of GFRP rebar with reasonable accuracy. It is because the current ASTM grip adapter of GFRP rebar does not take into account the various geometric characteristics of GFRP rebar such as surface treatment, shape of bar cross section, bar deformation as well as physical characteristics such as poisson effect, elastic modulus in the transverse direction and so on. The research reported in this paper is to provide how to proportion an adequate grip adapter to develop design tensile properties of GFRP rebar. The proposed grip adapter is derived from the equilibrium or compatibility equations. From the preliminary test results for rounded GFRP rebar, it was found that the grip adapter with specific size proportioned by proposed method shows the highest tensile strength among them.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2003년도 가을 학술발표논문집 Vol.30 No.2 (2)
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• pp.43-45
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• 2003

Nowadays, with numerous emerging applications (e.g., traffic control, meteorology monitoring, mobile computing, etc.), access methods to process current and future queries for moving objects are becoming increasingly important. Among these methods, the time-parameterized R-tree (TPR-tree) seems likely the most flexible method in one, two, or three-dimensional space. A key point of TPR-tree is that the (conservative) bounding rectangles are expressed by functions of time. In this paper, we propose a new method, which takes into account positions of its moving objects against the rectangle's bounds. In proposed method, the size of bounding rectangle is significantly smaller than the traditional bounding rectangle in many cases. By this approach, we believe that the TPR-tree can improve query performance considerably.

• 한국통신학회논문지
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• 제22권8호
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• pp.1740-1746
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• 1997

본 논문에서는 도파관 슬롯 결합 마이크로스트림 안테나를 마이크로스트림 안테나의 개선된 급전 구조로서 제안하고 해석을 수행하였다. 해석 과정에서 스트립과 슬롯 사이의 유전체 기판의 존재가 충분히 고려되었따. 안테나 특성 파악을 위해 스트립의 전류 분포와 슬롯의 자류 분포를 알아내기 위한 수치해석 방법으로 모멘트법과 공간 주파수 영역법이 사용되었다. 해석 결과, 제안된 구조는 개선된 특성과 대량 생산의 용이함으로 인하여 배열 안테나의 설계시 우수한 단위요소로 쓰일 수 있음을 확인하였다.

• 조명전기설비학회논문지
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• 제28권7호
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• pp.69-74
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• 2014

Recently, IEC published new standards about the requirements and tests for lightning protection system(LPS) components. If components are used for LPS, they should comply with the IEC standards. This paper, we collected six specimens for the metallic connection components using in domestic, and it tested for withstand lightning current which according to the IEC 62561-1. As a result, only one specimen meet this performance requirement. The specimen is the metallic connection component with four bolts fixed. Therefor, when designing of LPS in domestic, the metallic connection components shall be taken into account for the selection of the withstand lightning current. In addition, we need to develop for LPS components product and the national standards.