• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2137-2142
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• 2003

One of the important performance metrics of the World Wide Web is how fast and precise a request from users will be serviced successfully. Shared Web Caching (SWC) is one of the techniques to improve the performance of the network system. In Shared Web Caching Systems, the key issue is on deciding when and where an item is cached, and also how to transfer the correct and reliable information to the users quickly. Such SWC distributes the items to the proxies which have sufficient capacity such as the processing time and the cache sizes. In this study, the Hot Spot Prediction Algorithm (HSPA) has been suggested to improve the consistent hashing algorithm in the point of the load balancing, hit rate with a shorter response time. This method predicts the popular hot spots using a prediction model. The hot spots have been patched to the proper proxies according to the load-balancing algorithm. Also a simulator is developed to utilize the suggested algorithm using PERL language. The computer simulation result proves the performance of the suggested algorithm. The suggested algorithm is tested using the consistent hashing in the point of the load balancing and the hit rate.

• 한국정보과학회논문지:정보통신
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• 제34권3호
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• pp.193-202
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• 2007

본 논문에서는, $a{\times}a$ 출력 버퍼 스위치로 구성되며 핫스팟이 발생하는 다단 연결 망 (Multistage Interconnection Network， MIN)의 성능 예측 모형을 제안하고, 스위치에 장착된 버퍼의 개수 증가에 따른 성능 향상 추이를 분석하였다. 제안한 성능 예측 모형은 먼저 네트워크 내부의 임의 스위치 입력 단에 유입되는 데이타 패킷이 스위치 내부에서 전송되는 유형을 확률적으로 분석하여 수립되었다. 성능분석 모형은 스위치에 장착된 버퍼의 개수와 무관하게 버퍼를 장착한 $a{\times}a$ 스위치의 성능, 네트워크 정상상태 처리율(Normalized Throughput, NT)과 네트워크 지연시간(Network Delay)의 예측이 가능하고, 나아가서 이들로 구성된 모든 종류의 다단 연결망 성능 분석에 적용이 용이하다. 제안한 수학적 성능 분석 연구의 실효성 검증을 위하여 병행된 시abf레이션 결과는 상호 미세한 오차 범위 내에서 모형의 예측 데이타와 일치하는 결과를 보여 분석 모형의 타당성을 입증하였다.

• 대한기계학회논문집B
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• 제33권10호
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• pp.820-826
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• 2009

The anisotropic phonon conductions with varying Joule heating rate of the silicon film in Silicon-on-Insulator devices are examined using the electron-phonon interaction model. It is found that the phonon heat transfer rate at each boundary of Si-layer has a strong dependence on the heating power rate. And the phonon flow decreases when the temperature gradient has a sharp change within extremely short length scales such as phonon mean free path. Thus the heat generated in the hot spot region is removed primarily by heat conduction through Si-layer at the higher Joule heating level and the phonon nonlocality is mainly attributed to lower group velocity phonons as remarkably dissimilar to the case of electrons in laser heated plasmas. To validate these observations the modified phonon nonlocal model considering complete phonon dispersion relations is introduced as a correct form of the conventional theory. We also reveal that the relation between the phonon heat deposition time from the hot spot region and the relaxation time in Si-layer can be used to estimate the intrinsic thermal resistance in the parallel heat flow direction as Joule heating level varies.

• 한국기계가공학회지
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• 제20권7호
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• pp.48-57
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• 2021

The main research content of this paper is to evaluate the structural integrity and the cooling performance of 4250 kVA power transformer with ONAN(Oil Natural and Air Natural) mode. The dynamic analysis is used to verify the structural safety of the transformer by seismic loading. The transformer structure is simplified and NX software is used to build a three-dimensional model, and ANSYS commercial software is used to calculate the stress and deformation by applying corresponding load. The analysis result was evaluated whether it satisfies the design requirements according to the IEEE Std 693 standard. In terms of thermal analysis to evaluate the cooling performance, the thermal physical model is used to calculate the heat exchange between the radiator and the tank in the steady state, and the result is input into the Fluent software to calculate the internal temperature field of the transformer tank, which reduces the calculation cost of thermal fluid. Comparing the simulated hot spot temperature and top oil temperature of the transformer with the calculation results of the IEC60076 classic model, it is found that the error is only 1.9%.

• 전기학회논문지P
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• 제62권1호
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• pp.6-11
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• 2013

In this paper, the temperature characteristics of mold transformer for the distribution power system have been analyzed by using computational fluid dynamics(CFD). The model has been modeled by coil, cores, insulating materials and frames about 3MVA grade mold transformer and analyzed the temperature distribution of the structure with a heat fluid. The fluid, which is incompressible ideal gas, is analyzed as a turbulent flow phenomenon on the assumption that it is natural cooling of transformer cooling system. Through this study, by examining the temperature distribution and hot-spot of the structure field of the mold transformer, cooling design and temperature distribution information, which are demanded for designing are estimated.

• 한국산학기술학회논문지
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• 제13권12호
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• pp.6081-6088
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• 2012

불균형 클러스터링은 클러스터의 크기를 서로 다른 크기로 나누는 방법으로 균형 클러스터링에 비해 핫스팟 문제를 어느 정도 해결할 수 있으므로 전체 네트워크의 에너지 소모량을 줄인다. 본 논문에서는 불균형 클러스터링 모델을 이용하여 계층 기반의 동적 불균형 클러스터링을 제안한다. 이는 라운드별로 최적의 클러스터 수 및 클러스터 헤드 위치를 제공함으로써 전체 네트워크에 대한 에너지 소모를 균형 있게 하고 또한 네트워크 수명을 연장시킨다. 실험을 통하여 제안된 기법이 이전 클러스터링 기법보다 네트워크 수명이 연장되었음을 보였다.

• 한국초전도ㆍ저온공학회논문지
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• 제7권4호
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• pp.14-19
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• 2005

A transient numerical simulation was conducted to have variation of temperature on an element of resistive Superconducting Fault Current Limiter (SFCL) under quench condition. It is very important engineering information for an optimum design of cryogenic system for cooling of a resistive SFCL element. A bifilar coil for resistive SFCL for 10 MVA system was incorporated as a model in this numerical study. From the numerical simulation result, it was found that the averaged temperature on the shunt and Bi-2212 element at 500 kW, 100 ms was 711.1 K and 198.4 K respectively. The temperature variation with the change of the hot-spot size and time is also obtained. The maximum temperature was continuously increased in all cases until the hot-spot stops at 100ms and it was going down after then. Such as, the details of temperature distribution on the SFCL element obtained from this numerical study and it should be very valuable information on the decision of the cooling capacity of cryogenic system.

• 연구논문집
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• 통권34호
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• pp.59-68
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• 2004

The hot spot stress approach and the notch strain approach are discussed with some results of them. And a stress model that can be applicable to several types of weld joints with single S-N curve of the base material. The stress model uses the geometric characteristics of the stress distribution vicinity of weld joints. The model was applied to five different weld joins(the base material is SM490B). By the representative stress, the experimental fatigue data are plotted very closely to the S-N curve of the base material.

• 한국자동차공학회논문집
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• 제11권6호
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• pp.93-100
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• 2003

This paper describes the thermoelastic instability arising from friction heat generation in braking and proposes the finite element methods to predict the variation of temperature and thermal deformation. In a conventional disc brake analysis, heat generation is only related with wheel speed and friction material and the interface pressure between disc and pad is assumed constant. But under dynamic braking conditions, the frictional heat causes the thermoelastic distortion that leads to more concentrated contact pressure distribution and hence more and more non-uniform temperature. In this paper, to complete the solution of the thermomechanically coupled problem, the linear relation model between pressure and temperature is proposed and demonstrated in examples of a simple two dimensional contact problem. And the two dimensional model has been extended to an annular three dimensional disc model in order to consider more realistic geometry and to provide a more accurate critical speed for automotive brake systems.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.263-267
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• 2011

본 연구는 에틸렌-공기 혼합물로 채워져 있는 굽은 관에서의 충격파와 화염의 상호 작용, 화염 가속, 연소폭발천이 현상을 수치적으로 살펴보았다. 여기서 사용되는 모델은 지배방정식으로 Navier-Stokes 방정식과 경계조건 처리 방법으로 ghost fluid 기법을 사용하였다. 굽은 관에서 여러 충격파 강도를 이용한 모델링을 통하여 화염과 강한 충격파의 충돌에 의한 열점 생성과 화염 전파의 가속 현상을 확인하였으며 추가적으로 평균 화학적 열 발생률이 대략 20 MJ/($g{\cdot}s$)이 되는 지점에서 최초 폭굉이 발생한다는 것을 확인하였다. 즉, 우리는 복잡한 형상에 의한 효과를 포함하는 수치적 계산 결과를 기반으로 관에서의 강한 충격파, 충격파와 화염의 상호 작용, 열점, 연소폭발천이 현상 등의 발생을 확인하였다.