• 대한조선학회논문집
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• 제31권1호
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• pp.50-62
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• 1994

본 논문에서는 비대선형에서 구상선수의 형상변화가 저항성능에 미치는 영향을 조사해 보기 위하여 구상선수 계열들을 창안하고 이들의 모형시험 결과를 비교 분석한 내용이 기술되었다. 구상선수의 형상을 결정짓는 7가지의 변수를 생각하고 이들을 체계적으로 변화시켜 구상선수 형상변화의 영향을 실험적으로 조사하도록 계획하였다. 총 23개 선형의 모형선을 제작하였으며, 각 선형에 대하여 저항시험, 유선조사시험 및 선측파고 계측시험이 수행되었다. 구상선수의 형상변화와 모형시험 결과와를 상호 비교 분석하기 위하여 유사한 특성의 구상선수들을 모아서 9개 그룹으로 분류하였으며 각 그룹 별 저항성분의 변화 경향을 분석해 본 결과 비대선에서는 형상저항이 전저항에 지배적인 영향이 있음을 확인하였다. 또한 모형시험 결과 및 이의 통계적 분석 자료로부터 비대선에서는 구상선수 주위의 유선의 방향이 저항성분들과 밀접한 관계가 있으며 저항성분들 중에서도 형상저항과 더욱 밀접한 관계가 있다는 사실을 발견하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제21권1호
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• pp.31-35
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• 2019

The lumped-parameter circuit model for a no- insulation (NI) high temperature superconductor (HTS) magnet has been well understood after many experimental and analytic studies over a decade. It successfully explains the non-linear charging behaviors of NI magnets. Yet, recently, multiple groups reported that the post-quench electromechanical behaviors of an NI HTS magnet may not be well explained by the lumped circuit model. The characteristic resistance of an NI magnet is one of the key parameters to characterize the so-called "NI behaviors" of an NI magnet and recently a few groups reported a potential that the characteristic resistance of an NI magnet may substantially vary during a quench. This paper deals with this issue, the increment of contact resistance of the no-insulation (NI) REBCO magnet during a quench and its impact on the post-quench behaviors. A 7 T 78 mm NI REBCO magnet that was previously built by the MIT Francis Bitter Magnet Laboratory was chosen for our simulation to investigate the increment of contact resistance to better duplicate the post-quench coil voltages in the simulation. The simulation results showed that using the contact resistance value measured in the liquid nitrogen test, the magnitude of the current through the coil must be much greater than the critical current. This indicates that the value of the contact resistance should increase sharply after the quench occurs, depending on the lumped circuit model.

• 한국기계가공학회지
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• 제12권3호
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• pp.21-27
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• 2013

This study is investigated on flow analysis according to grill configuration of radiator. The stream of flow which pass through radiator grill in car body and the contour of pressure distribution are estimated by the basis. As the magnitude of resistance force which flow affects the car body is investigated so that the power reduction can be reduced. As the pressure inside radiator grill is assessed, more efficiency can be investigated in order that the flow rate inside car body can be increased. Model 2 has the most air resistance and model 1 has the least among model 1, 2 and 3. Model 1 has the most air flow rate at inside. There are model 3 and 2 simulated according to flow rate. As the curved surface at radiator grill configuration increases in number, air flow rate becomes distributed uniformly. By considering the effect on air resistance and air flow rate at radiator grill, model 3 becomes the most effective configuration.

• 한국환경과학회지
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• 제4권2호
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• pp.151-158
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• 1995

A numerical model has been developed to predict the deposition of air pollutants considering canopy effect. In this model, the deposition velocity is calculated using the deposition resistances(aerodynamic resistance, viscosity resistance, surface resistance). Using the results, a comparative study was made between the model calculation and observation results. The calculated daily variation of deposition resistances and in daytime most of the model cases are well agreed with observation results, and a slight difference was found in nighttime. From the results, it is suggested that the present model is capable of estimating the deposition velocity of air Pollutants considering characteristics of canopy layer.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권4호
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• pp.381-386
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• 2013

A new resistance model for a Schottky Barrier Diode (SBD) in CMOS technology is proposed in this paper. The proposed model includes the n-well thickness as a variable to explain the operational behavior of a planar SBD which is firstly introduced in this paper. The model is verified using the simulation methodology ATLAS. For verification of the analyzed model and the ATLAS simulation results, SBD prototypes are fabricated using a $0.13{\mu}m$ CMOS process. It is demonstrated that the model and simulation results are consistent with measurement results of fabricated SBD.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1611-1613
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• 2000

In this study in order to find out the trends and the residual lifetime for electric connections/contacts using infrared image camera, "lifetime temperature rise model" is theoretically proposed on the base of "lifetime resistance model" and to prove this theory, experiments have been performed for various kinds of electric connections/contacts. Two suggestions have been builded up or the "lifetime temperature rise model" ; one is the linear relationship between the temperature rise $\Delta K$ and contact resistance, and the other is the functional relationship between the temperature of electric connections/contacts and the operating time which ascribed in the "lifetime resistance model". From the experimental results, measured values were quite similar to the theoretical value so that two suggestions in "lifetime temperature rise model" were appeared to be correct.

• 한국기계가공학회지
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• 제9권1호
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• pp.55-60
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• 2010

The air resistance about automotive body is studied by the flow analysis in this study. Maximum air flow velocity is shown with 28 to 30 m/s on the upper roof of automotive body. The air flow becomes most regular at automotive body model 3 but the model of 2 or 3 becomes irregular in comparison with the model 1. The maximum air resistance pressure is shown with 413 to 420 Pa at the front bumper of automotive body. The flow velocity at inlet or middle plane of automotive body is shown as the contour same with the model of 1, 2, or 3. But the velocity at outlet plane at model 1 is shown as the contour different with the model of 2 or 3.

• 한국기계기술학회지
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• 제13권1호
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• pp.41-47
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• 2011

In this study, the structural analysis of cooling fan is combined with 3-D flow analysis by using CFD on fluid domain. The smoothly cooling flow with optimum design of cooling parts is essential at automotive combustion engine. The fan shape is modeled with three kinds of shape by varying the radius of the fan blade. By the results of analysis, the flow at Model I is more uniform than Model II or III. And the displacement at Model I is less than Model II or III. As the flow resistance of cooling fan at Model I decreases more than Model II or III, the efficiency becomes better.

• 대한조선학회논문집
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• 제55권4호
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• pp.313-320
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• 2018

As ships operating on the Arctic route are exposed to various ice environments such as level ice, pre-swan, pack ice, ice ridge and brash ice, it is essential to estimate the ice resistance according to the ice environment. Methods for estimating the ice resistance include a method using mathematical model, numerical simulation, and a method using empirical formula. In this study, empirical formulas are used to estimate the ice resistance. The purpose of this study is to develop the ice resistance and attainable speed estimation program(I-RES) for brash ice. To develop the Brash ice attainable speed estimation algorithm, the environmental characteristics of the brash ice were analyzed, and the results of I-RES were evaluated by comparing the model test results of brash ice. The accuracy of I-RES for brash ice is around 20% in this study but it will be more developed near future with accumulating more model test results and calculation results.

• 동력기계공학회지
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• 제16권4호
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• pp.17-23
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• 2012

In this study, the numerical simulation and basin model test have been performed to evaluate sea worthiness and resistance performance for a small pre-planning three type of leisure boats which are U, V, Y shapes of hull forms. As a well known commercial CFD code, Maxsurf, was applied for modeling hull forms used as the solver of motion analysis. Also the model resistance test was carried out to estimate the effective power of boat in the basin tank. Numerical simulation and model test results show that Y-shaped hull is better than the other types in terms of heave and pitch motion, having a key effect on a boat sea worthiness. But V-type hull is more efficiency than others cases in resistance performance.