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유호선 대한기계학회 1993 대한기계학회논문집 Vol.17 No.6
This paper deals with the analysis method of regenerator characteristics for designing a vuilleumier heat pump. First, models for evaluating the reheat and the flow losses are established by the comparative study between already proposed ones. Calculations based on the second-order method are performed for the well-known schulz heat pump. Results show that operating conditions as well as design parameters significantly affect the regenerator performances. The effects of operating conditions on the reheat and the flow losses appear to be similar in trends in both the hot-warm and the cold-warm regenerators. However, the losses in the one regenerator vary oppositely to those in the other with specific design parameters such as the phase angle and the swept volume ratio being changed. Also, it is confirmed that there is an optimum aspect ratio(D/L) which minimizes total loss for each regenerator. 본 연구는 VM열펌프를 구성하는 2개 재생기의 특성을 동시에 고려하여 해석하 고자 시도되었다. 먼저, 기존의 유동 및 열전달모델들을 비교, 검토하여 VM열펌프용 재생기 특성에 부합되는 해석모델을 선정한다. 선정된 해석모델을 2차해석법(second -order method)의 개념에 의거, 실제 열펌프에 적용하여 작동조건 및 설계인자에 따른 재생기의 성능변화를 고찰한다. 여기서 2차해석법의 개념은 이상화된 전체시스템에 대한 해석결과로부터 압력, 질량유량 등 필요한 기본변수를 구하여 이들을 재생기특성 해석에 적용하는 접근방법으로서 재생기특성과 작동유체거동 사이의 상호작용은 고려 되지 않는다. 해석과정에서의 구체적인 계산은 각 구성요소에 대한 제원이 비교적 상세히 공개된 Schulz열펌프를 대상으로 수행하며 전술한 기본변수는 이미 발표된 VM사이클에 대한 단열해석법으로부터 구한다.
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수직환상주형내 Al-Cu합금의 응고과정 및 냉각속도의 조대편석에 대한 영향
유호선 대한기계학회 1994 대한기계학회논문집 Vol.18 No.7
Transport process during solidification of an AI-CU alloy in a vertical annular mold of which inner wall is cooled is numerically simulated. A model which can take account of local density dependence on the solute concentration is established and incorperated in the analysis. Results show that thermally and solutally induced convections are developed in sequence, so that there is little interaction between them. Thermal convection effectively removes the initial superheat from the melt and vanishes as solidification proceeds from the cooling wall. On the other hand, solutal convection which is developed later over the meshy and the pure liquid regions leads to large-scale redistribution of the consituents. The degree of the initial superheating hardly affects overall solidification behavior except the early stage of the process, when the cooling rate is kept constant. Macrosegregation is reduced remarkably with increasing cooling rate, because not only the liquidus interface advances so quickly that time available for the solute transport is not enough, but also the interdendritic flow is strongly damped by rapid crystal growth within the mushy region.
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등온모델에 의한 자유행정 Vuilleumier열펌프의 동특성 해석
유호선 대한기계학회 1994 대한기계학회논문집 Vol.18 No.2
This paper deals with dynamic behaviors of a free-piston Vuilleumier heat pump system, which are characterized by stroke of each diplacer/stroke ratio, operating frequency and phase angle. Based on the Isothermal Model, basic equations of motion are derived and linearized. In particular, dependence of damping coefficients of the dynamic parameters are taken into account in the formulation, which does not bring additional difficulties in the analysis. In order to investigate effects of design conditions on the dynamic parameters are taken into account in the formulation, which does not bring additional difficulties in the analysis. In order to investigate effects of design conditions on the dynamic characteristics, calculations are performed for the prototype made by Schulz and Thomas and results are qualitatively compared with their data obtained from the analysis as well as the experiment. It appears that they made a mistake in evaluating the hysteresis loss of the gas spring in their analysis. And, the present results show a better agreement with their experimental data than those by their own analysis. Although there are some unresolved aspects such as frequency variations with respect to the mean pressure and the hot space temperature, it is expected that the present analysis may be an effective tool for prediction of dynamics of a free- pistion VM machine at the preliminary design stage.
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柳好宣 (사)한국인물사연구회 2013 한국인물사연구 Vol.19 No.-
From late 19th century to early 20th century, Choseon Dynasty has experienced the political upheavals and government-reforms a few times. The people in that time went through a period of turbulence. Choseon Dynasty(1392~1910) was feudal society, so it had hierarchical classes as example aristocrat, peasant, tradesman, commoner. Although Ji Ku-sik(池圭植:1850∼?) was the lower class, unusually he left the poetry that monopolized by aristocrats. Ji, Ku-sik was a supplier who supplied the royal ceramics to the palace and the government office(司饔院). He wrote the diary Hajeilki(荷齋日記) for 20 years, from 1882 to 1911. It includes his daily lives, business, cash book, friendship and a lot of poetry. This article is about his poetry. His works revealed the world of spirit that he supported. They were mostly divided into two categories. The first part is the worry about the current station of his country and the second part is the aim for the unworld and seclusion. They tends to have a style of Tang-Dynasty poetry such as metaphor and rhyming couplets. And their descriptions are mostly realistic ones. The peculiar thing is that he wrote the poetry for the time that business hour was over and in the place that was away from his daily life. Nevertheless he was the lower classes, he left 439 poems. That is due to his various amounts of reading. In short, his poetry keeps itself in existence of the classics in Chinese fallen behind with the literature in Korean in the early 20th century, therefore they represent much to the history of Korean literature.
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