• 대한기계학회논문집B
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• 제27권5호
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• pp.644-654
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• 2003

An analytical solution for a vertically stratified viscous flow in a microchannel with a rectangular cross-section is constructed, assuming fully developed laminar flow where the interfaces between the fluid layers are flat. Although the solution is for n-layer flow, restricted results to symmetrical three-layer flow are presented to investigate the effects of the viscosity and thickness ratios of the fluid layers and the aspect ratio of the microchannel on the flow field. Relations between the flow rate and thickness ratios of the fluid layers with varying viscosity distributions are found, considering the cross -sectional velocity profiles which vary noticeably with the three parameters and differ significantly from the velocity profiles of the flow between infinite parallel plates. Interfacial instability induced by the viscosity stratification in the microchannel is discussed referring to previous studies on the instability analysis for plane multilayer flow. Exact solution derived in the present study can be used for examining a diffusion process and three -dimensional stability analysis. More works are needed to formulate the equations including the effects of interfacial' tension between immiscible liquids and surface wettability which are important in microscale transport phenomena.

• 전자공학회논문지C
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• 제36C권1호
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• pp.12-21
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• 1999

휴대용 통신장비를 비롯한 각종 전자기기는 고집적화 및 소형화 되고 있으며, 이러한 전자기기는 무수히 많은 원하지 않은 전자파를 발생시키고 있다. 이에 따라 EMI 영향을 최소화 하기 위한 연구가 요구되며, 본 연구에서는 전자기기를 구성하는 각 회로들의 반도체 설계 단계에서의 EMI발생 원인을 분석하여 병렬 버퍼의 출력 구동회로와 decoupling 커페시터를 이용하여 EMI를 최소화하는 회로를 제안한다. 이를 i8052에 적용하여 칩을 제작하고 측정한 결과 delta 전류는 1/3으로 감소하였고 EMI는 10dBuV 이상 개선된 결과를 얻었다.

• 전기학회논문지
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• 제58권1호
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• pp.100-106
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• 2009

A novel 8 V DC power source with an external series-parallel connection of 50 Dye-sensitized Solar Cells (DSCs) has been proposed. One DSC has the optimized length to width ratio of $5.2{\times}2.6\;cm$ and an active area $8\;cm^2$ ($4.62{\times}1.73\;cm$) which attained a conversion efficiency of 4.02%. From the electrochemical impedance spectroscopic analysis, it was found that the resistance elements related to the Pt electrode and electrolyte interface behave like that of diode and the series resistance corresponds to the sum of the other resistance elements. Surface morphology and sheet resistance of Pt counter electrode did not degrade the performance of the cell. This novel 8V-0.33A DC power source shows stable performance with an energy conversion efficiency of 4.24% under 1 sun illumination (AM 1.5, Pin of $100\;mW/cm^2$).

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1025-1034
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• 2015

This paper presented an improved analytical method for calculating the open-circuit magnetic field in the surface-mounted permanent magnet machines accounting for slots and eccentric magnet pole. Magnetic field produced by radial and parallel permanent magnet is equivalent to that produced by surface current according to equivalent surface-current method of permanent magnet. The model is divided into two types of subdomains. The field solution of each subdomain is obtained by applying the interface and boundary conditions. The magnet field produced by equivalent surface current is superposed according to superposition principle of vector potential. The investigation shows harmonic contents of radial flux density can be reduced a lot by changing eccentric distance of eccentric magnet poles compared with conventional surface-mounted permanent-magnet machines with concentric magnet poles. The FE(finite element) results confirm the validity of the analytical results with the proposed model.

• 대한기계학회논문집A
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• 제32권12호
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• pp.1072-1087
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• 2008

A mixed volume and boundary integral equation method (Mixed VIEM-BIEM) is used to calculate the plane elastostatic field in an isotropic elastic half-plane containing an isotropic or anisotropic inclusion and a void subject to remote loading parallel to the traction-free boundary. A detailed analysis of stress field at the interface between the isotropic matrix and the isotropic or orthotropic inclusion is carried out for different values of the distance between the center of the inclusion and the traction-free surface boundary in an isotropic elastic half-plane containing three different geometries of an isotropic or orthotropic inclusion and a void. The method is shown to be very accurate and effective for investigating the local stresses in an isotropic elastic half-plane containing multiple isotropic or anisotropic inclusions and multiple voids.

• 한국통신학회논문지
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• 제21권8호
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• pp.1937-1947
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• 1996

객체 지향 개발 방법을 이용하여 실시간 시스템을 개발할 경우에는 반드시 시간제약 문제를 고려해야 한다. 본 논문에서는 사건의 발생에 따른 시스템의 상태 변이를 상태도로 나타내는 동적 모델에 대한 실시간 규격화로서, OMT와 SDL을 이용한 객체 지향 실시간 시스템 모델링 방법을 제안하였다. 현재 가장 널리 활용되고 있는 OMT방법론의 분석과정에서 생성되는 동적 모델에 실시간 시스템의 시간제약을 반영함으로써 예상시간 도표를 작성하였고, 실시간 예측이 가능하도록 순차 수행, 반복 수행, 병렬 수행에 대한 최대 및 최소 실시간 예측 공식을 제시하였다. 또한, 제안된 방법론을 이용하여 ATM 시스템의 최대 수행 시간을 예측해 보았고 객체 상호 작용 그래프와 SDL의 구문적 표현을 이용하여 ATM 시스템의 사용자 인터페이스에 대한 기능 명세서를 기술하였다.

• 전력전자학회논문지
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• 제22권4호
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• pp.336-344
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• 2017

This paper presents the three-port DC-DC converter modeling and controller design procedure, which is part of the solid-state transformer (SST) to interface medium voltage AC grid to bipolar DC distribution network. Due to the high primary side DC link voltage, the proposed converter employs the three-level neutral point clamped (NPC) topology at the primary side and 2-two level half bridge circuits for each DC distribution network. For the proposed converter particular structure, this paper conducts modeling the three winding transformer and the power transfer between each port. A decoupling method is adopted to simplify the power transfer model. The voltage controller design procedure is presented. In addition, the output current sharing controller is employed for current balancing between the parallel-connected secondary output ports. The proposed circuit and controller performance are verified by experimental results using a 30 kW prototype SST system.

• Applied Microscopy
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• 제27권4호
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• pp.483-488
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• 1997

A misfit dislocation generation in InAs epilayers grown on (001) InP substrates (oriented $2^{\circ}$ off (001) toward the [110] direction) using metalorganic chemical-vapor deposition was studied. The InAs film of 17 nm thickness grown at $405^{\circ}C$ showed the three different arrays of dislocations: a straight orthogonal array to the <110> direction, an array to the >100> direction, and an array tilted by a degree of $5\sim45^{\circ}$ from the [110] direction. All of the dislocations had a/2<101> Burgers vectors inclined $45^{\circ}$ to the interface. Upon annealing at $660^{\circ}C$ the InAs films with 60, 140 and 220 nm thicknesses, most of the misfit dislocations became the Lomer type $(\sim100%)$ oriented exactly along the >110> direction. These misfit dislocation spacings were decreased with increasing the InAs thickness up to 220 nm thickness. This phenomena was interpreted by the relationship between the dislocation interaction energy among parallel misfit dislocations and the opposite remnant InAs epilayer strain energy. The distance between misfit dislocations was measured by transmission electron microscopy.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제8권6호
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• pp.639-646
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• 2002

본 논문에서는 리눅스 클러스터 시스템 통합 관리 도구인 CATS-i'(Cluster Administration ToolS on the Internet)의 시스템 구성과 디자인 문제들을 논한다. CATS-i'는 리눅스 클러스터 시스템을 쉽고 빠르고 안전하게 설치하고 관리하기 위하여 개발된 도구이다. 클러스터의 운영체제 설치에서부터 응용 프로그램 패키지 설치, 클러스터 노드들의 자원들을 실시간으로 모니터링하고 관리할 수 있는 기능, 배치 작업 제출 및 관리 기능들이 통합되어 사용자에게 단일 시스템 이미지를 제공한다. 또한 사용자가 플랫폼에 관계없이 쉽고 편리하게 클러스터의 상태를 파악하고 관리할 수 있는 자바 기반의 강력한 그래픽 사용자 인터페이스를 제공한다.

• 한국유체기계학회 논문집
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• 제10권5호
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• pp.20-26
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• 2007

Some gate valves are susceptible to pressure locking and thermal binding which prevent the safety function. The safety related gate valves susceptible to pressure locking and thermal binding shall be identified and taken preventive actions to ensure the safety function. The identification of the gate valves susceptible to pressure locking and thermal binding needs the evaluation of system design, valve and piping arrangement, test requirements, and operating conditions. Application of preventive methods should consider the system safety function, applicability, effectiveness, interface with system design, and cost. The selection procedure of valves susceptible to pressure locking and thermal binding can be effectively used in industry including nuclear power plants. In order to prevent the pressure locking, the hole can be drilled through the one disc of upstream side or down stream and the external equalizing line can be installed from bonnet to downstream or upstream. The double disc parallel seat valve type can be used instead of flexible wedge gate valve to prevent the thermal binding. The identification of gate valves susceptible to pressure locking and thermal binding, and preventive actions will meet the regulatory requirements and enhance the availability and safety of plants.