• 한국시뮬레이션학회논문지
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• 제21권2호
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• pp.41-50
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• 2012

본 연구에서는 반도체 제조공정 및 클러스터 장비에 대한 상세히 설명하고 현 팹 레이아웃 및 클러스터 장비 아키텍처상의 문제점을 제시하였다. 또한 현 아키텍처상의 대안으로서 클러스터 장비간의 웨이퍼 이동이 상호 연결된 인라인 EFEM(Equipment Front End Module) 을 통해 이루어지는 ILE (In-Line EFEM) 아키텍처의 개념을 제시하였다. 마지막으로 해당 아키텍처를 실제 적용하여 구현된 파일럿 시스템을 시뮬레이션 을 통해 사이클 타임 관점에서 비교 분석하였다.

• 한국자동차공학회논문집
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• 제15권1호
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• pp.139-145
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• 2007

This paper presents the low cycle thermal fatigue of the engine exhaust manifold subject to thermomechanical cyclic loadings. The analysis includes the FE model of the exhaust system, temperature dependent material properties, and thermal loadings. The result shows that at an elevated temperature, large compressive plastic deformations are generated, and at a cold condition, tensile stresses are remained in several critical zones of the exhaust manifold. From the repetitions of thermal shock cycles, plastic strain ranges could be estimated by the stabilized stress-strain hysteresis loops. The method was applied to assess the low cycle thermal fatigue for the engine exhaust manifold. It shows a good agreement between numerical and experimental results.

• Journal of Power Electronics
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• 제10권6호
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• pp.667-672
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• 2010

A way how to teach a general understanding of switched mode power supplies (SMPS) is shown. A fourth order PWM DC-to-DC converter with limited duty cycle range is treated as an example and a survey over important data (maximum voltage and current ratings for the elements, rms- values for the semiconductor devices and a rough approximation of the losses) of the circuit is given. Furthermore, a converter model based on duty ratio averaging is established. Continuous mode of operation is used. The results make it possible to estimate the applicability of the given converter structure and offer sufficient material for the calculation, design, and analysis and give a better insight into switched mode energy conversion.

• 한국과학교육학회지
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• 제12권3호
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• pp.61-76
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• 1992

The purpose of this study was to develop the instructional model and teaching material to change the middle school students'conceptions of electric current into the scientific ones and to investigate the effects of the model in actual classrooms. We identified the students' ideas and their misunderstanding about the concept of eIectic current through reviewing the literatures and our in this study. Based on the above results, we developed the instructional model and designed the teaching sequence and prepare the learning materials about the unit of the electric current in middle school Our instructional model was based on 'learning cycle' developed by Lawson, but the new stage called "exploration through qualitative questions" to elicit the students' own conceptions was inserted to it. To investigate the effects or the new teaching model, the pre- and post-test using the POE type were administered to experimental group(52 students) taught with learning cycles and control group(52 students) taught with traditional styles. The results are as follows; 1) The rates of correct. predictions was varying according to the kinds of problems. And the rates of the correct. reasons of their predictions were lower than those of the predictions. 2) The mean scores of the post-test of both groups were significantly higher than those of the pre-test. We could not find statistically significant difference in theme an score between experimental group and control group after implementation of the model. But the experimental group gained higher scores than those of the control group on two problem. Therefore, although we cannot show the prominent effects of our teaching model based on learning cycles, there are some effects of our model on changing the middle school students' conceptions of electric current.

• Journal of Welding and Joining
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• 제23권4호
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• pp.17-26
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• 2005

HAZ (Heat Affected Zone) which occurs during welding thermal cycle has an important effect on the mechanical properties of the weld metal. So there were many efforts to develop the model which is able to predict the microstructure and mechanical properties in weld HAZ and lots of metallurgical models have reported since early 1940. These models are justifiable based on the reasonable assumption and analytical approach, but they also have limitation by interesting alloying system and assumption in each literature. Therefore, this study summaries the previous models for prediction of properties in weld HAZ. Then several issues to solve for developing the more reliable model were proposed.

• 대한안전경영과학회지
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• 제12권4호
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• pp.61-66
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• 2010

Organic light emitting diode(OLED) has been developed fast from 1963 when electric light emitting phenomenon was discovered. PMOLED(passive matrix OLED) is producted earlier than AMOLED(active matrix OLED). PMOLED is mainly mounted at sub display, but AMOLED is mounted at main display. Nowadays AMOLED is expanded to PMP(portable multimedia players), navigation and TV market. Even thought OLED's market is opening to many applications, OLED's life is worried until now. If we know about OLED's real life, we need time to test so much time over 20,000hrs. Realistically, there is difficult to test such as long time with products from the information-technology sector having a short life cycle. In this paper, we study about OLED's accelerated test to reduce life test by current. We can design OLED's accelerated life model by the result of test. The model consists of design variables like ratio of light emitting, organic material structure, condition of aging, etc. In conclusion, this model can be applied to study about organic material, machine and manufacturing process etc, and also it's possible to develop a method of manufacturing process & materials, so we need to study on the subject of this paper continuously.

• 대한토목학회논문집
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• 제10권4호
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• pp.113-122
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• 1990

도로(道路)의 노반(路盤)에 교통하중(交通荷重)이 반복해서 가해질 경우 흙 구조물의 설계기준을 얻기 위해 현장시험이 행해지고 있으나, 본 연구는 지금까지 잘 알려지지 않은 흙의 동력학적(動力學的) 성질(性質), 특히 반복응력(反復應力)을 받을 때의 성질을 규명한 것으로 유변학적(流變學的) 모델 해석에 의해 흙의 항복응력(降伏應力) 탄성계수(彈性係數)를 구하고 이에 대한 반복응력재하의 영향에 대해서 고찰(考察)한 것이다. 항복응력(降伏應力)은 재하횟수가 많을 수록 경화(硬化) 효과(效果)가 현저하므로 그 값이 크고, 어느 재하횟수에 달하면 한계치에 접근한다. 또한 탄성계수(彈性係數)는 반복응력이 작은 경우에는 재하횟수가 많을수록 현저하게 증가하고, 반복응력이 커지면 반대로 감소한다.

• 항공우주기술
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• 제9권1호
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• pp.93-97
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• 2010

액체산소/케로신을 사용하는 가스발생기 사이클 액체로켓엔진의 비추력 해석을 수행하였다. 본 해석 방법으로 재연한 300톤급 엔진의 시스템 성능은 문헌에 보고된 결과와 비교하여 비추력 0.1%, 최적 연소압 12%의 오차를 보였다. 오차의 주요 원인은 문헌에 공개되지 않은 서브시스템의 성능모델 차이와 가스발생기 생성물의 물성 모델 차이로 판단된다. 막냉각이 적용되는 30톤급 1단용 엔진의 경우, 연소압 68 bar에서 혼합비 2.2가 최적 비추력 조건인 것으로 평가되었으며 최적 조건은 주어진 성능 모델에 따라 달라질 수 있다.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.351-359
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• 2016

The Korean Prototype Gen-IV sodium-cooled fast reactor (PGSFR) is supposed to be loaded with a relatively-costly low-enriched U fuel, while its envisaged transuranic fuels are not available for transmutation. In this work, the U-enrichment reduction by improving the neutron economy is pursued to save the fuel cost. To improve the neutron economy of the core, a new reflector material, PbO, has been introduced to replace the conventional HT9 reflector in the current PGSFR core. Two types of PbO reflectors are considered: one is the conventional pin-type and the other one is an inverted configuration. The inverted PbO reflector design is intended to maximize the PbO volume fraction in the reflector assembly. In addition, the core radial configuration is also modified to maximize the performance of the PbO reflector. For the baseline PGSFR core with several reflector options, the U enrichment requirement has been analyzed and the fuel depletion analysis is performed to derive the equilibrium cycle parameters. The linear reactivity model is used to determine the equilibrium cycle performances of the core. Impacts of the new PbO reflectors are characterized in terms of the cycle length, neutron leakage, radial power distribution, and operational fuel cost.

• Advances in Energy Research
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• 제4권4호
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• pp.285-297
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• 2016

Fundamental understanding of vanadium ion transport and the detrimental effects of cross-contamination on vanadium redox flow battery (VRFB) performance is critical for developing low-cost, robust, and highly selective proton-conducting membranes for VRFBs. The objective of this work is to examine the effect of conductivity and diffusivity, two key membrane parameters, on long-cycle performance of a VRFB at different operating conditions using a transient 2D multi-component model. This single-channel model combines the transport of vanadium ions, chemical reactions between permeated ions, and electrochemical reactions. It has been discovered that membrane selecting criterion for long cycles depends critically on current density and operating voltage range of the cell. The conducted simulation work is also designed to study the synergistic effects of the membrane properties on dynamics of VRFBs as well as to provide general guidelines for future membrane material development.