• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.651-654
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• 2002

We carried out 2-dimensional numerical calculations of electrostatic potential for triode field emitters with planar cathodes using the finite element method. As it turned out, the conventional triode structure with a planar cathode suffered from large gate current and wide spreading of emitted electrons. To circumvent these shortcomings, we proposed a new triode structure. By simply inserting a conducting layer of proper thickness on top of the cathode layer, we were able to modify the electric field distribution on the cathode surface so that low gate current and electron-focusing effect were achieved, simultaneously.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.513-516
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• 2002

In electrical impedance tomography(EIT), various image reconstruction algorithms have been used in order to compute the internal resistivity distribution of the unknown object with its electric potential data at the boundary. Mathematically the EIT image reconstruction algorithm is a nonlinear ill-posed inverse problem. This paper presents two intelligent optimization algorithm techniques such as genetic algorithm and simulated annealing for the solution of the static EIT inverse problem. We summarize the simulation results for the three algorithm forms: modified Newton-Raphson, genetic algorithm, and simulated annealing.

• 한국표면공학회지
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• 제44권1호
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• pp.26-31
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• 2011

Numerical modeling is used to investigate the perturbation of a single Langmuir probe (0.2 mm diameter shielded with 6 mm insulator) inserted along the center axis of a cylindrical inductively coupled plasma chamber filled with Ar at 10 mTorr and driven by 13 MHz. The probe was driven by a sine wave. When the probe tip is close to a substrate by 24.5 mm, the probe characteristics was unperturbed. At 10 mm above the substrate, the time averaged electric potential distribution around the tip was severly distorted making a normal probe analysis impossible.

• 한국전기전자재료학회논문지
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• 제11권7호
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• pp.571-580
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• 1998

The numerical model that can describe the ignition of pseudospark discharge using hybrid fluid-particle(Monte Carlo )method has been developed. This model consists of the fluid expression for transport of electrons and ions and Poisson's equation in the electric field. The fluid equation determines the spatiotemporal dependence of charged particle densities and the ionization source term is computed using the Monte carlo method. This model has been used to study the evolution of a discharge in Argon at 0.5 torr, with an applied voltage if 1kV. The evolution process of the discharge has been divided into four phases along the potential distribution : (1) Townsend discharge, (2) plasma formation, (3) onset of hollow cathode effect, (4) plasma expansion. From the numerical results, the physical mechanisms that lead to the rapid rise in current associated with the onset of pseudospark could be identified.

• Structural Engineering and Mechanics
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• 제8권1호
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• pp.73-84
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• 1999

This paper is concerned with shape optimization problems by the boundary element method (BEM) emphasizing the use of a reduced basis reanalysis technique proposed recently by the author. Problems of this class are conventionally carried out iteratively through an optimizer; a sequential quadratic programming-based optimizer is used in this study. The iterative process produces a succession of intermediate designs. Repeated analyses for the systems associated with these intermediate designs using an exact approach such as the LU decomposition method are time consuming if the order of the systems is large. The newly developed reanalysis technique devised for boundary element systems is utilized to enhance the computational efficiency in the repeated system solvings. Presented numerical examples on optimal shape design problems in electric potential distribution and elasticity show that the new reanalysis technique is capable of speeding up the design process without sacrificing the accuracy of the optimal solutions.

• 대한전기학회논문지:시스템및제어부문D
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• 제52권2호
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• pp.120-127
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• 2003

In electrical impedance tomography(EIT), various image reconstruction algorithms have been used in order to compute the internal resistivity distribution of the unknown object with its electric potential data at the boundary. Mathematically the EIT image reconstruction algorithm is a nonlinear ill-posed inverse problem. This paper presents a simulated annealing technique as a statistical reconstruction algorithm for the solution of the static EIT inverse problem. Computer simulations with the 32 channels synthetic data show that the spatial resolution of reconstructed images by the proposed scheme is improved as compared to that of the mNR algorithm or genetic algorithm at the expense of increased computational burden.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.811-813
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• 1996

High impedance fault can not be easily detected by conventional method. But if it would not be detected and cleared quickly, it can result in fires, and electric shock. In this paper, neural network, which has learning capability, is used for high impedance fault detector. The potential of the neural network approach is demonstrated by simulation using KEPCO's measured data. The instantaneous values and frequency spectrum of current are respectively used as the inputs of neural networks. Also, the methods using combined data to exploit the advantage of each data are proposed. In this paper, back-propagation network(BPN) is used for high impedance fault detector and can use for high speed relay because it detects faults within 1 cycle.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 추계학술대회 논문집
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• pp.270-274
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• 1997

The numerical model that can describe the ignition of the pseudospark discharge using hybrid fluid-particle method has been developed. The evolution process of the discharge has been divided into four phases along the potential distribution. After the plasma enters in the hollow cathode, the confining effect which is one of hollow cathode properties occurs and the electron current on anode rises rapidly. As the plasma expands successively, the sheath contracts and as the electric field in the sheath increases, the field-enhanced thermionic emission(Schottky emission) occurs. From numerical results, the physical mechanism that causes the rapid current rise in the ignition of the pseudospark discharge could be identified.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.2074-2075
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• 2007

본 연구에서는 침수된 저압 지중함에서 발생될 수 있는 누전 사고시 지중함내의 접지조건이 주변의 대지전위분포에 미치는 영향을 고찰하였다. 저압 지중함 실증실험장을 설계 구축하였으며 3가지 접지조건의 경우에 대해 대지전위 측정 실험을 실시하였다. case 1과 case2와 같은 실증실험을 통해 저압 지중함에 설치되어 있는 접지선은 저압 지중함에서 대지전위 분포에 거의 영향이 없음을 확인하였으며, case 3과 같은 실증실험을 통해 저압 지중함 철재틀에 접지단자를 본딩 할 경우 저압 지중함 주변의 대지전위 상승이 거의 발생되지 않음을 확인하였다. 따라서 저압 지중함 철재틀에 접지단자를 본딩 할 경우 혹시 발생될 수 있는 지중함의 누전에 의한 감전사고를 매우 효과적으로 방지할 수 있을 것이다.

• Journal of Mechanical Science and Technology
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• 제17권8호
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• pp.1120-1132
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• 2003

A problem of a circular elastic inhomogeneity interacting with a crack under uniform loadings (mechanical tension and heat flux at infinity) is solved. The singular. integral equations for edge and temperature dislocation distribution functions are constructed and solved numeric-ally, to obtain the stress intensity factors. The effects of the material property ratio on the stress intensity factor (SIF) are investigated. The computed SIFs are used to predict the kink angle of the crack when the crack grows.