• 한국공작기계학회논문집
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• 제14권6호
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• pp.45-51
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• 2005

Braking performance of a vehicle can be significantly affected by the temperature increment in the brake system. Therefore, the important problem in brake system is to reduce the thermal effect by friction heat. Recently, many studies have been performed and good results have been reported on the prediction of the brake disk temperature. However, the study on the pad, piston and brake fluid temperature is rarely found despite of its importance. In this study, the temperature distribution of the disc brake system is studied according to the material properties of brake piston. Vehicle deceleration, weight distribution by deceleration, disc-pad heat division and the cooling of brake components are considered in the analysis of heat transfer. Unsteady state temperature distributions are analyzed by using the finite element method and the numerical results are compared with the experimental data.

• 한국지구과학회지
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• 제29권7호
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• pp.579-585
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• 2008

열적으로 불안정한 강착원반의 비선형 유체역학적 모형에 기초하여 블랙홀 마이크로케이사의 광폭발 한계 순환주기에 대한 원반 질량의 시간적 진화 모형을 계산하였다. 블랙홀의 질량, 원반 크기 및 질량 유입률과 같은 물리적인 매개변수들은 블랙홀 X선 신성의 원형인 A0620-00에서 관측된 역사적인 1975 광폭발을 재현하도록 선택되었다. 중심부에서 원반으로 쪼여지는 조사(照射)의 시간에 따른 효과는 직접 조사와 원반위의 뜨거운 강착 흐름으로부터 굴절되어 원반에 쪼여지는 간접조사의 두 가지 방법이 고려되었다. 우리의 강착원반 열적 불안정성 모형은 광폭발의 순환과정 전반에 걸쳐 X-선 변광체들에서 관측된 광도의 전형적인 복사 광도를 설명할 수 있다. 강착원반의 최대질량 ${\sim}4.03{\times}10^{24}g$은 광폭발의 점화 때에 얻어지며, 최소질량 ${\sim}8.54{\times}10^{23}g$은 차가운 쇠퇴기와 정지기(靜止期) 때에 이루어진다. 원반의 질량은 광폭발 한계 순환주기에 걸쳐 약 5배 정도 변한다.

• 정보저장시스템학회논문집
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• 제11권1호
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• pp.16-21
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• 2015

An archive system is designed to store data for a long time without loss. However, many important factors such as temperature, dust, vibration, and humidity must be considered to design a successful archive system. Read/write devices, for example optical disk drives(ODDs), in an archive system generate heat while they are in operation. Fans are usually used to remove heat but the air flow accompanies dust into the system result in system failure. In this study, an archive system with six ODDs is chosen as an analysis model and flow together with temperature distributions are computed using a CFD simulation package. Flow analysis is focused on four cooling fans at the rear panel and temperature distribution is studied for various cases of fan operation. From the temperature point of view, fans give significant effects on $4^{th}$ to $6^{th}$ ODDs compared to the $1^{st}$ to $3^{rd}$ ODDs. Also, it is noticed which fan is the most important as far as cooling is concerned.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.124-124
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• 2009

We observed the changes of crystal structure of Rubrene (5,6,11,12-tetraphenylnaphthacene) polycrystal thin films at various in situ substrate temperature and process by scanning electron microscope(SEM), x-ray diffraction (XRD) and near-field microwave microprobe (NFMM). Amorphous rubrene thin film was initially obtained on 200 nm thick $SiO_2/Si$ substrate at 35 $^{\circ}C$ in a vacuum evaporation but in situ long time postannealing at the temperature 80 $^{\circ}C$ transformed the amorphous phase into crystalline. Four heating conditions are followed : (a) preheating (b) annealing (c) preheating, annealing (d) preheating, cooling(35 $^{\circ}C$), annealing. We have obtained the largest polycrystal disk in sample (c). But the highest crytallity and conductivity of the rubrene thin films were obtained in sample (d).

• 전기학회논문지
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• 제57권1호
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• pp.78-81
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• 2008

A hollow cathode which has extremely stable discharge characteristic has been developed. This is composed of the two separated lanthanum hexaboride(LaB6) of a disk type in the tube as the electron emitters. The way of design is of great advantage to extend the surface discharge area of the LaB6, which is also useful for optimal fixing of the LaB6. The hollow cathode is capable of producing 30 kW(100 V, 300 A) of power continuously. Because the generated plasma beam with the high temperature(above $3000^{\circ}C$) from the hollow cathode passes through the center hole of the two intermediate electrodes, it is designed with the high temperature material of the tungsten and the suitable structure of the water cooling. The combinations of the hollow cathode and the two intermediate electrodes are practically useful for the ion plating plasma beam source.

• 천문학회보
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• 제41권2호
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• pp.55.2-55.2
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• 2016

In this talk, I will present a theoretical and numerical framework for self-regulation of the star formation rates (SFRs) in disk galaxies. The theory assumes (1) force balance between pressure support and the weight of the interstellar medum (ISM), (2) thermal balance between radiative cooling in the ISM and heating via FUV radiation from massive young stars, and (3) turbulent energy balance between dissipation in the ISM and driving by momentum injection of SNe. Numerical simulations show vigorous dynamics in the ISM at all times, but with proper temporal and spatial averages, all the expected balances hold. This leads to a scaling relation between mean SFRs and galactic gas and stellar properties, arising from the fundamental relationship between SFR surface density and the total midplane pressure.

• 천문학회보
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• 제35권1호
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• pp.66.1-66.1
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• 2010

Using two-dimensional numerical hydrodynamic simulations, we investigate the star formation rate (SFR) in turbulent, multiphase, galactic gaseous disks. Our simulation domain is axisymmetric, and local in the radial direction and global in the vertical direction. Our models include galactic rotation, vertical density stratification, self-gravity, radiative heating and cooling, and thermal conduction, but do not include spiral-arm features. Turbulence in our models is driven by momentum feedback from supernova explosion events occurring in localized dense regions formed by thermal and gravitational instabilities. Self-consistent radiative heating, representing enhanced/reduced FUV photons from the star formation, is also taken into account. By controlling three parameters (the gas surface density, the stellar disk density, and the angular rotation rate) that characterize local galactic disks, we explore how the SFR depends on the background environmental state. We also discuss the relation between the SFR and the gas surface density found in our numerical models in comparison with observations.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제30회 추계학술대회
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• pp.57-61
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• 1999

The effect of the microstructure of gray cast iron on friction properties was investigated by using a pad-on-disk type friction tester. Cast iron samples used in this investigation were obtained from "step block" castings, which were designed to produce microstructure with different graphite flake morphologies from different cooling rate and solidification rate. Results of this work showed that the gray cast iron disks with long graphite flakes showed less fading. The rotors containing smaller amounts of ferrite showed higher friction coefficient and better fade resistance than others.an others.

• 한국재료학회지
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• 제16권2호
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• pp.111-115
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• 2006

High-finned tubes have good thermal conductivity and have better cooling efficiency than plain tubes or low-fined tubes due to bigger air contact area. During high-fined tubes are manufactured by roll forming, the main technique is illustrated to optimizing primary material(copper pipe), optimized die matrix designing technique for roll forming, control manufacturing speed to develop productivity etc. In this study, a roll forming system was developed in oder to produce high-finned tube. Also a multi-step roll forming die was designed & built to produce high-finned tube that has over 10 mm fin height. And then, roll forming test using copper pipe was performed to produce high-finned tube. Roll forming process for producing highfinned tube was optimized by analyzing and adjusting misrostructure, hardness, and surface roughness of roll formed high-fined tube.

• 천문학회보
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• 제36권2호
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• pp.57.2-57.2
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• 2011

To study the formation and evolution of sub-galactic scale structures, we have added SPH (Smoothed Particle Hydrodynamics) method into an existing cosmological PMTree code, GOTPM. To follow the evolution of gas particles, we consider heating/cooling processes, star formation, and energy & metal feedback by supernova explosion. We have performed various tests for the new code and found that the results reproduce observed quantities or follow the known analytic solutions. We present a test simulation of isolated disk galaxy with a focus on whether the star formation reproduces the observed features.