• 한국정밀공학회지
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• 제28권5호
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• pp.623-631
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• 2011

Metallic sandwich panels based on a truss core structure have been developed for a wide range of potential applications with their lightweight and multi-functionality. Structural performance of sandwich panels can be predicted from the studies on mechanical behavior of a unit cell of truss core structures. Analytical investigations on the unit cell provide approximated guidelines for the design of overall core structures for a specific application in short time. In this study, the effects of geometrical parameters on mechanical behavior of a pyramidal shape of unit cell were investigated with analytical models. The unit cell with truss member angle of 45 degree was considered as reference model and other models were designed to have the same weight and projected area but different truss member angle. All truss members were assumed to be connected with pin joint in analytical models. Under the assumptions, the equivalent strength and stiffness of the unit cell under compressive and shear loads were predicted and compared. And finally, the optimum core member angle to have maximum mechanical property could be calculated and verified with FE analysis results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.30-32
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• 2001

Switched reluctance motors have the advantage a high torque/weight ratio, as the large reluctance torque is made by salient poles of both start and rotor, and a high reliability. On the other hand, the switched reluctance motors have the disadvantage of a large ripple torque which is made by salient poles. So the application for the industrial fields have been limited to special cases. Geometric significant parameters are ${\beta}_r$ and ${\beta}_s$ respectively the rotor and stator pole arc while the significant electric parameters are the angles where the drive switches are turned on and off. It can be simulated that ${\beta}_r$ and ${\beta}_s$ must be chosen in a particular region of the plane (${\beta}_r,\;{\beta}_s$) called the feasible triangle. The aim of this paper is to simulate the minimum of the torque ripple by using finite element method and to determine the best choice of the rotor and stator pole arc.

• 대한화학회지
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• 제38권3호
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• pp.214-220
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• 1994

금속시료를 직접분석하기 위하여 원자흡수법에 의한 글로우방전시스템을 구성하였다. 방전이 일어나는 양극과 음극은 가공성 세라믹을 이용한 arrestor에 의해 분리하였으며, 방전에 영향을 미치는 전류 및 전압, arrestor의 형태, 가스 압력 그리고 가스 흐름 등을 개인용 컴퓨터와 ADC/DAC board 및 RS-232를 사용하여 자동적으로 제어될 수 있도록 하였다. 여러가지 방전에 미치는 실험변수들을 변화시키면서 시료손실속도, 원자흡광도 등의 변화를 측정하였으며, sputtering 된 후의 시료 표면을 주사형 전자현미경으로 관찰하였다.

• 설비공학논문집
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• 제27권12호
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• pp.620-625
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• 2015

The summer climate is very hot and humid in Korea. Humidity is an important factor in determining thermal comfort. Recently, research on dehumidification device development has been attempted to save the energy required for operating the dehumidifier. Existing dehumidification systems have disadvantages such as wasting energy to drive the compressor. Meanwhile, dehumidification systems with membranes can dehumidify humid air without increasing the dry bulb temperature. Therefore. they don't have to consume cooling energy. In this paper, the installation conditions for a membrane system were analyzed to improve the shape and optimum performance of the system. The results showed that the distance between elements was the critical system design factor, and that a distance of 20 mm was the optimal condition for the pressure drop and flow characteristics of the internal air flow.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제3B권4호
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• pp.165-172
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• 2003

Low voltage circuit breakers are widely used in power distribution systems to interrupt fault current rapidly and to assure the reliability of the power supply. This paper is focused on understanding the interrupting capability, more specifically of the contacts and the arc runner, based on the shape of the contact system in the current molded case circuit breaker (hereafter MCCB). Moreover, in order to improve the interrupting capability of the circuit breaker, the estimation and analysis of the interrupting capability, based on the 3-D magnetic flux analysis, were developed. Furthermore, this paper also presents results of the estimation and analysis of the interrupting capability when applied to different model breakers. In addition, this paper analyzes the efficiency of the interrupting tests by forming false current paths consisting of a three-division cascade arc runner in the contact system. With regards to the interrupting test, there is a need to assure that the optimum design required to analyze the electromagnetic forces of the contact system generated by the current and flux density be present. Based on the results of this study, this paper presents both computational analysis and test results for the newly developed MCCB 460V/225A/50㎄ contact system.

• 한국표면공학회지
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• 제36권1호
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• pp.69-73
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• 2003

The atmospheric pressure plasma is regarded as an effective method for surface treatments because it can reduce the period of process and doesn't need expensive vacuum apparatus. The performance of non-transferred plasma torches is significantly depended on jet flow characteristics out of the nozzle. In order to produce the high performance of a torch, the maximum discharge velocity near an annular gap in the torch should be maintained. Also, the compulsory swirl is being produced to gain the shape that can concentrate the plasma at the center of gas flow. In this work, the distribution of gas flow that goes out to atmosphere through a plenum chamber and nozzle is analyzed to evaluate the performance of atmospheric pressure plasma torch which can present the optimum design of the torch. Numerical analysis is carried out with various angles of an inlet flow velocity. Especially, three-dimensional model of the torch is investigated to estimate swirl effect. We also investigate the stabilization of plasma distribution. For analyzing the swirl in the plenum chamber and the flow distribution, FVM (finite volume method) and SIMPLE algorithm are used for solving the governing equations. The standard k-model is used for simulating the turbulence.

• 조명전기설비학회논문지
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• 제16권6호
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• pp.137-144
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• 2002

배선용 차단기(MCCB)는 신속한 고장전류 차단과 전원시스템의 안정성을 확보하기 위해 배전시스템에 폭넓게 사용되고 있다. 본 논문에서는 MCCB의 소호부 형상에 따른 차단성능을 파악하고 이를 통해 성능향상을 꾀하고자 3차원 자계해석을 이용한 차단성능 평가해석기법을 개발하고, 개발한 평가해석기법을 각 모델 차단기에 적용한 바를 기술하였다. 또한, 소호부내 3분할 다단형 아크런너을 구성하여 불연속 통전경로를 형성함으로 해서 차단성능에 미치는 영향을 살펴보았다. 끝으로, 이상의 연구내용을 토대로 새로운 소호부 형상을 고안하여 국내 최초로 460［V］/225［A］/50［kA］ 대전력 단락시험에 성공한 결과를 제시하였다.

• 한국정밀공학회지
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• 제14권12호
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• pp.73-85
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• 1997

The rolling force and roll deformation behavior in the twin roll type strip continuous casting process has been computed to estimate the thermal charcteristics of a caster roll. To calculation of rolling force, the relationship between flow stress and strain for a roll material and casting alloy are assumed as a function of strain-rate and temperature because mechanical properties of a casting materials depends on tempera- ture. The three dimensional thermal dlastic-plastic analysis of a cooling roll has also been carried out to obtain a roll stress and plastic strain distributions with the commercial finite element analysis package of ANSYS. Temperature fields data of caster roll which are provided by authors were used to estimated of roll deformation. Roll life considering thermal cycle is calculated by using thermal elastic-plastic analysis results. Roll life is proposed as a terms of a roll revolution in the caster roll with and without fine failure model on the roll surface. To obtain of plastic strain distributions of caster roll, thermomechan- ical properties of roll sleeve with a copper alloy is obtained by uniaxial tensile test for variation of temperature.

• 한국구조물진단유지관리공학회 논문집
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• 제11권2호
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• pp.93-102
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• 2007

FRP바닥판은 경량이기 때문에 신속한 시공이 가능하고, 고정하중을 경감시킬 수 있다는 장점이 있어 전 세계적으로 시공 실적이 점차 증가하고 있다. 본 논문에서는 효과적인 FRP바닥판의 적용을 위하여 유한요소해석을 통하여 FRP바닥판을 구성하는 부재별 적정 형상비를 결정하였으며, 향후 FRP바닥판 설계시 기초자료로 활용할 수 있도록 하고자 하였다. 또한, FRP의 이방적 재료 특성과 복잡한 제약조건을 고려한 FRP바닥판의 최적설계를 수행하였으며, 그 결과를 토대로 제안된 FRP바닥판의 기본 단면 형상에 대한 검증을 수행하였다.

• 한국산학기술학회논문지
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• 제19권10호
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• pp.24-30
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• 2018

지하공간의 수요가 증가되면서 지중구조물의 기능을 저하시키는 상재하중 및 토피증가에 대한 구조물의 안정성 문제를 해결하기 위해 많은 연구자들이 고압축성 물질을 이용한 하중저감방법 연구를 진행해왔다. 본 논문은 하수관거에 작용하는 하중을 EPS Geofoam을 활용하여 경감시키는 하중저감공법을 아치구조물에 적용하고 그 효과를 증가시키기 위한 최적의 Soft Zone 적용방법에 대해 기술하고 있다. 지반구조 상호작용을 고려한 ABAQUS 유한요소해석을 통해 아치구조물의 거동 특성을 파악하고 4가지 EPS Geofoam 형식을 해석적으로 분석하여 최적의 적용형상을 확인하였다. 해석 결과를 토대로 선정된 최적 단면 형상에 대해 아치구조물의 라이즈비, 지간길이 변화를 해석변수로 고려하여 발생하는 토압감소율을 비교하여 적용성을 분석하였다. 수치해석에서 선정한 최적 Soft Zone를 적용한 아치구조물에 발생하는 토압이 평균 78% 감소되는 것을 확인하였다. 본 연구 결과에서 EPS Geofoam의 토압 경량화 효과와 이에 대한 지중아치구조물의 적용성 평가는 지중구조물 설계 시 경제적이고 합리적인 방법을 제공해 줄 것이며, 향후 심층 지하공간에 대한 활용성 증가에 도움이 될 것이다.