• 대한기계학회논문집
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• 제16권12호
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• pp.2358-2367
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• 1992

본 연구에서는 그 기초단계로서 작동유체의 실제상태변화에 근접하면서 간편 한 근사적인 단열해석법을 적용하여 VM사이클의 구체적인 예비설계조건을 제시하고자 한다.

• Journal of Biosystems Engineering
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• 제28권5호
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• pp.421-428
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• 2003

This study was conducted to determine the optimum blade shape for peeling Altari radish. To figure out the required peeling force according to various angles of blade and rakes of peeling cutter, two peeling tests such as circumferential peeling and longitudinal peeling of Altari radish were carried out. Based on the pretest results, which performed to investigate the applicability of the optimum shape of cutter and to find out the cutting pattern according to the lapse of days after harvesting the radish, the peeling depth and width of the blade were fixed at 2 mm and 10 mm. From two methods of circumferential and longitudinal peeling test, the angles of rake and blade as cutter shape factors were affected on peeling force. But the peeling speed was not affected on it under the safety speed as 0.2 m/s, without blade vibrating on peeling operation. The rake angle was more effective factor than the blade angle, and the optimum angles of blade and rake were 10$^{\circ}$ and 55$^{\circ}$ respectively. The cutting surface by the longitudinal peeling was more smooth than that by the circumferential peeling. There was no problem in peeling work during 4 days after harvest because the freshness of the Altari radish was maintained.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3050-3055
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• 2007

A wind turbine is one of the most popular energy conversion systems to generate electricity from the natural renewable energy source and an axial-flow type wind turbine is the most popular system for the electricity generation in the wind farm nowadays. In this study, a cross-flow type turbine has been studied for the application of wind turbine for electricity generation. The target capacity of electric power generation of the model wind turbine developing on the project is 12 volts, 130A/H (about 1.56kW). The important design parameters of the model turbine impeller are the inlet and exit angle of the turbine blade, number of blade, hub/tip ratio and the exit flow angle of the casing. In this study, the radial equilibrium theorem was used to decide the inlet and exit angle of the impller blade and CFD technique was used to have the performance analysis of the designed model power turbine to find out the optimum geometry of the CPT impeller and casing. The designed CPT with 24 impeller blades at ${\alpha}=82^{\circ}$, ${\beta}=40^{\circ}$ of turbine blade angle was estimated to generate 284.6 N.m of indicated torque and 2.14kW of indicated power.

• Journal of Mechanical Science and Technology
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• 제16권9호
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• pp.1102-1111
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• 2002

The study focuses on the heat transfer performance of two-phase closed thermosyphons with plain copper tube and tubes having 50, 60, 70, 80, 90 internal grooves. Three different working fluids(distilled water, methanol, ethanol) are used with various volumetric liquid fill charge ratio from 10 to 40%. Additional experimental parameters such as operating temperature and inclination angle of zero to 90 degrees are used for the comparison of heat transfer performance of the thermosyphon. Condensation and boiling heat transfer coefficients, heat flux are obtained using experimental data for each case of specific parameter. The experimental results are assessed and compared with existing correlations. The results show that working fluids, liquid fill charge ratio, number of grooves and inclination angle are very important factors for the operation of thermosyphons. The relatively high rate of heat transfer is achieved when the thermosyphon with internal grooves is used compared to that with plain tube. The optimum liquid fill charge ratio for the best heat transfer performance lies between 25% and 30%. The range of the optimum inclination angle for this study is 20$^{\circ}$～30$^{\circ}$ from the horizontal position.

• 한국강구조학회 논문집
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• 제23권3호
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• pp.349-356
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• 2011

본 논문에서는 파라메트릭 기법을 이용한 최적설계 알고리즘을 사용하여 최근 들어 다양한 형태를 지니고 있는 비정형 초고층 구조물의 최적 다이아그리드 각도를 찾는 것에 대해 연구하였다. 다이아그리드는 비정형 초고층 구조물을 구성하는 대각방향의 부재로 수직하중과 수평하중에 대해 효과적으로 대응할 수 있는 구조 시스템으로써 다이아그리드의 각도를 최적화 하여 비정형 초고층 구조물의 최대강성을 찾는 것에 목적을 두었다. 본 연구에서 검증예제로 비정형 형상인 원통형 구조물과 테이퍼드 원형 구조물에 다이아그리드 최적설계 알고리즘을 적용하여 변위를 효과적으로 제어하는 다이아그리드의 최적각도를 검토하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.414-417
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• 2003

A copper-clad aluminium composite bar is lighter and less expressive than a commercial copper alloy bar. Copper-clad aluminium composite bar can be fabricated by hot hydrostatic extrusion process. In this work, the effect of die angle on the compressive properties of copper-clad aluminium composites fabricated using hydrostatic extrusion process was investigated experimentally. The results showed that optimum half die angle was in the range of 40$^{\circ}$ to 50$^{\circ}$ for an extrusion ratio of 19. The results also showed that the half die angle had little influence on the compressive strength of copper-clad aluminium composites. A diffusion layer increased with increasing die angle.

• 대한기계학회논문집B
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• 제26권9호
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• pp.1292-1301
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• 2002

An experimental study of turbine performance is conducted with various incidence angles on a rotating turbine rotor. 5 different incidence angles are applied from -17$^{\circ}$to 13$^{\circ}$with 7.5$^{\circ}$gaps. In order to precisely set up the incidence angles at the rotor inlet, 5 turbine discs are manufactured with the different fir tree section. Total-to-total efficiencies are obtained on the several off-design points with considering the exit total pressure, which is meas fred at 12 locations between the hub and casing using a pressure rake. The degree of reaction is 0.373 at the mean radius, and Reynolds number based on the rotor chord is 0.86$\times$10$^{5}$ at the turbine inlet on the design point experiment. The experiment on a single-stage turbine is conducted at the low-pressure and low-speed state, but it is sufficient to consider the blade loading effect due to the rotating apparatus even though the total pressure loss at the exit is increased proportionally to the turbine output power. The experimental results recommend 6$^{\circ}$as an optimum incidence angle on the turbine blade design. The total-to-total efficiency is steeply decreased when the incidence angle is over $\pm$9$^{\circ}$ from the optimum incidence angle. In the range of less than -10$^{\circ}$incidence angle, 7.5$^{\circ}$ reduction of incidence angle generates 15% decrease of total-to-total efficiency. This result is obtained on the same rotor blade by changing only the rotational speed to minimize the effect of profile and secondary flow loss in the passage. Experimental results show that the change rate of total-to-total efficiency according to the incidence angle change is unchanged although the turbine operates at the off-design condition.

• 전력전자학회논문지
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• 제5권4호
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• pp.309-317
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• 2000

이 논문은 4상 6극 SRM의 최대토크/효율 및 최소토크맥동 운전을 위한 적정 전압과 스위칭각에 관한 연구이다. SRM은 비선형적인 특성이강하여 해석적인 방법으로 특성을 고찰하거나 속도/토크 제어가 어려운 단점이 있다. 이 논문에서는 최대토크/효율 및 최소토크맥동의 운전이 가능한 최적의 스위칭각과 전압을 SIMULINKK를 이용하여 구하였다. 시뮬레이션 결과 최대토크운전에서는 속도는 스위칭각에 의존되고, 토크는 전압에 의존됨을 알 수 있었다. 뿐 만 아니라 최대효율, 최소토크리플운전에서는 전압보디는 속도와 스위칭각에 의해서 최대효율과 최소토크 리플이 발생되는 것을 알 수 있었다. 시뮬레이션에 의해서 구해진 최적각들을 ROM 데이터형식으로 참조 테이블을 만들어 마이크로 프로세서를 이용하여 구동하여 최대토크/효율, 최소토크리플 운전의 타당성을 보였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2006년도 전력전자학술대회 논문집
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• pp.122-124
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• 2006

ADD is under development for the high speed motor. This paper describes simulation and test results for obtaining the maximum output by leading angle of encoder. So we carried out the test for obtaining the optimum leading angle of encoder. Test results on the motor of 7 phases 6 poles were showed the validity of proposed methods and phase-leading angle.

• 생물환경조절학회지
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• 제7권4호
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• pp.290-297
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• 1998

겨울철 온실의 기본적인 열에너지원인 일사를 최대한 확보하도록 하는 은실의 지붕형상을 결정하기 위해 유전알고리즘 및 광투과율 전산모델을 이용한 최적화기법을 이용하여 설치지역, 피복재료특성, 온실의 기본치수등이 주어졌을 때 지붕경사각, 경간폭비의 최적조합을 결정할 수 있도록 하는 최적설계를 수행하였다. 수원지방에 위치한 경간폭 6m의 2연동 동서동 온실 및 단동 온실을 가정하여 최적화를 수행한 결과 경사각, 폭비 순으로 2연동, 단동 온실에 대해 각각 40.861≒40 $_。 / , 0.4806≒0.5, 37.490≒37 $_。 / , 0.7748≒0.78의 결과를 얻을 수 있었다. 광투과율 문제를 예로 적용해 본 결과 직접 전산모델을 호출하여 최적화를 수행하는 유전알고리즘의 기법은 온실환경의 해석을 위해 연구되어온 다양한 분야의 전산모델들을 종합적인 온실의 최적설계에 활용하도록 하는데 유용한 기법이 될 것으로 판단되었다.판단되었다.