• 한국정보통신학회논문지
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• 제18권1호
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• pp.135-141
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• 2014

본 연구에서는 무접합 MuGFET의 핀 폭에 따른 문턱전압의 변화를 줄이기 위한 소자 설계 가이드라인을 제시하였다. 제작된 무접합 MuGFET으로부터 핀 폭이 증가할수록 문턱전압의 변화가 증가하는 것을 알 수 있었다. 무접합 MuGFET의 핀 폭에 따른 문턱전압의 변화를 줄이기 위한 소자 설계가이드라인으로 게이트 유전체, 실리콘박막의 두께, 핀 수를 최적화 하는 연구를 3차원 소자 시뮬레이션을 통해 수행하였다. 고 유전율을 갖는 $La_2O_3$ 유전체를 게이트 절연층으로 사용하거나 실리콘 박막을 최대한 얇게 하므로 핀 폭이 증가해도 문턱전압의 변화율을 줄일 수 있음을 알 수 있었다. 특히 유효 채널 폭을 같게 하면서 핀 수를 많게 하므로 문턱전압 변화율과 문턱전압 아래 기울기를 작게 하는 것이 무접합 MuGFET의 최적의 소자 설계 가이드라인임을 알 수 있었다.

• 설비공학논문집
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• 제15권9호
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• pp.711-717
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• 2003

This paper presents the effects of the fin array and pitch on the frost layer growth of a heat exchanger. The numerical results are compared with experimental data of a cold plate to validate the present model, and agree well with experimental data within a maximum error of 8%. The frost behaviors of the staggered fin array are somewhat different from those of in-line array. The frost layer formed on the first fin of the in-line array grows rapidly, compared to second fin, whereas the difference of the frost layer growth between the fins of the staggered array is small. For fin pitch below 10 m, the frost layer growth of second fin in the staggered array is affected by that of first fin. The thickness of the frost layer and heat transfer of single fin are reduced with decreasing fin pitch regardless of fin array. However, the thermal performance of a heat exchanger is enhanced due to the increase of heat transfer surface area.

• 환경생물
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• 제38권1호
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• pp.137-145
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• 2020

The sectioned-body morphometric characteristics of the diploid and triploid marine medaka, Oryzias dancena, of both sexes were examined to collect basic data on the significant differences between the diploid and triploid fish. Significant differences between the diploid and triploid fish in both sexes were observed in the body circumference anterior to the base of the pelvic fin, the body circumference anterior to the base of the anal fin, the body circumference anterior to the base of the dorsal fin, the area anterior to the base of the pelvic fin, the area anterior to the base of the anal fin, the area anterior to the base of the dorsal fin, the total height anterior to the base of the pelvic fin, the total height anterior to the base of the anal fin, the height anterior to the base of the pelvic fin, the height anterior to the base of the anal fin, the width anterior to the base of the anal fin, the belly thickness II anterior to the base of the anal fin, section shape 2-1, and section shape 4-1 (p<0.05). These measurements were greater in the triploid marine medaka of both sexes than those in the diploid marine medaka of both sexes, and they were also greater in the male diploid and triploid marine medaka than those in the corresponding female fish. Therefore, the sectioned-body morphometric dimensions were greater in the triploid males than those in the triploid females and the diploid fish in this study.

• 대한전자공학회논문지
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• 제22권6호
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• pp.63-70
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• 1985

Unilateral Fin-Line 구조와 I-평면 구조를 Rayleigh-Ritt의 변분법으로 해석하는 방법을 제시하고, Cohn의 여파기 설계 이론에 의해 대역통과 멸파기를 설계하는 CAD프로그램을 개각했다. 관내 재역폭이 5%∼24.6%인 Unilateral Fin-Line 여파기를 제작하여 수험과 이론이 일치함을보였다. 시험 결과, 삽입손실이 0.17∼0.2545의 저손실 여파특성을 얻었으며 중심주파교에 대한 오차는 0.2%이 내였다.

• 대한기계학회논문집B
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• 제32권4호
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• pp.307-316
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• 2008

The objective of this study is to provide numerical and experimental data that can be used to investigate the performance characteristics of a flat plate fin-tube evaporator in household and commercial refrigerators under frosting conditions. Computer simulations with variations of operating conditions such as air inlet temperature, relative humidity, and geometries were performed to find out optimal design parameters of a fin-tube evaporator for household and commercial refrigerators. The tube-by-tube method was used in the simulation and the frost growth model was considered under frosting conditions. The developed analytical model predicted the decreasing rates of heat transfer capacity and air flow rate ratio within ${\pm}$10% compared to the experimental results for a refrigerator under real operating conditions. As a result, the frost thickness at $3^{\circ}C$ & 80% is increased 40% than that of $-3^{\circ}C$ & 80%, and the frost thickness at $3^{\circ}C$ & 90% is increased 30% than that of $3^{\circ}C$ & 60%. Accordingly, the operating time of the evaporator in the refrigerator was reduced with the increase of the decreasing rate of air flow rate ratio at each condition.

• 설비공학논문집
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• 제25권12호
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• pp.654-659
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• 2013

This paper presents a numerical optimization of louvered fins to enhance the JF factor in terms of the design parameters, including the fin pitch, the number of louvers, the louver angle, the fin thickness, and the re-direction louver length. We carried out a parametric study to select the three most important parameters affecting the JF factor, which were the fin pitch, number of louvers, and the louver angle. We optimally designed the louvered fin by using 3rd-order full factorial design, the kriging method, and a micro genetic algorithm. Consequently, the JF factor of the optimum model increased by 16% compared to that of the base model. Moreover, the optimum model reduced the pressure drop by 17% with a comparable heat transfer rate.

• 태양에너지
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• 제10권1호
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• pp.14-21
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• 1990

단일 핀-관열교환기와 관련된 열역학적 최적설계법을 기준하여 핀-관열교환기의 엔트로피 생성율을 조사하였다. 엔트로피 생성율(비가역성)해석법을 사용하여 최적설계조건을 구하였고 설계조건의 변화에 따른 총엔트로피 생성율과 핀의 길이, 관의 안지름과 바깥지름 및 핀간거리를 조사하였다. 이 연구의 결과에 따르면 바깥지름이 클수록 최적핀간거리와 핀높이는 커지고 엔트로피 생성율과 최적안지름은 작아진다. 또한 핀 두께를 증가시키면 계의 엔트로피 생성율과 최적핀간거리는 증가하고 핀높이를 증가시키면 엔트로피 생성율과 최적바깥지름은 증가한다.

• 대한기계학회논문집
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• 제6권3호
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• pp.247-255
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• 1982

The heat diffusion equation for an annular fin is analyzed by Laplace transformation. The fin has a uniform thickness, with its end insulated, and three different temperature profiles at the base such as step change, harmonic and exponential functions. The exact solutions for the temperature and heat flux of the fins are obtained with the infinite series. The series solutions converge rapidly for large values of dimensionless time, but slowly for small values. Therefore some approximate solutions are presented here to fine the temperature distribution and heat flux for small values of dimensionless time. Furthermore a simple approximate heat flux, .OMEGA.=1.13c.tau.$^{1}$2/ is found in the range of .tau. .leg. o.1/c for the exponential function at the base.

• 설비공학논문집
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• 제1권1호
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• pp.64-72
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• 1989

Laminar natural convection heat transfer from a horizontal heat exchanger tube with one infinitely long vertical plate fin has been studied by a finite-difference numerical procedure. In predicting convective heat transfer from a circular tube, the thermal boundary condition at solid fluid interface is usually assumed to be isothermal. However, in reality, the thermal boundary condition is not isothermal, and the tube has the thickness and the conductivity. So the temperature at the interface is not known a priori to the calculation. This problem has the conjugate phenomena which occur between the tube conduction and external natural convection, and between the fin conduction and external natural convection. Numerical results are obtained to determine the effects of the conductivity of solid wall and the thickness of tube wall on heat transfer. It is found that the conduction causes significant influence on the natural convection heat transfer at low K and high ${\delta}$.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.256-261
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• 2008

In this study, frost behavior on two dimensional fins of a heat exchanger was experimentally investigated. Temperature distribution on a 2-D fin surface and frost properties were measured in the directions perpendicular to and parallel to airflow. The results indicated that the temperature gradient in the direction perpendicular to airflow was large because of fin heat conduction, while that in the direction parallel to airflow was very small. Frost thickness in the airflow direction decreased from the leading edge towards the trailing edge of the fin due to leading edge effect. The reduction rate of frost thickness in the airflow direction, however, was very small compared with that in the direction perpendicular to the airflow, as affected by the temperature distribution.