• Bulletin of the Society of Naval Architects of Korea
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• v.12 no.2
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• pp.13-34
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• 1975

Analytical solutions for the transient temperature distribution and quasi-static thermal stresses which arise in a thin circular disk of finite radius subjected to an instantaneous point source acting in its interior have been obtained. And the solutions have been extended to the case of a moving heat source with the aid of the Duhamel's superposition integral. The solutions given are in the form of double infinite serieses, and their numerical results have been compared with the experimental temperature histories. It can be found out that the theoretical histories of thermal stresses show a good agreement with the experimental results and the theoretical histories of thermal stresses show a good qualitative agreement with a physical phenomena. The solutions can be applied to the problems such as a flame hardening of the cylindrical machine elements and a circular patch welding or a circular cutting of the structural member.

• Proceedings of the Korean Society of Computer Information Conference
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• 2016.01a
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• pp.9-10
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• 2016

본 논문에서는 멀티 스레드 기반 병렬 프로그램의 동적 분석을 통한 자료경합 탐지를 위해 효율적인 감시 필터링 기술을 제시한다. 제시하는 감시 필터링 기술은 자료경합과 같은 동시성 오류를 탐지하기 위해 프로그램의 수행 중에 발생하는 공유 메모리에 대한 스레드들의 접근 분석 시에 동일한 코드영역을 단순 반복하는 스레드들을 감시대상에서 제외시킴으로써 동적 분석을 위한 추가적인 오버헤드를 최소화한다. 제시하는 필터링 기술을 수행 중 자료경합 탐지 도구에 적용한 실험적 평가를 통해 개선된 수행시간 오버헤드의 제공이 가능함을 보인다.

• Korean Journal of Materials Research
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• v.18 no.4
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• pp.181-186
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• 2008

In this study, tantalum (Ta) compacts were fabricated in a spark plasma sintering (SPS) process and their microstructure and mechanical properties were investigated. Ta compacts with a density of 99% were successfully fabricated by controlling the sintering conditions of the current and the temperature. The density and hardness were increased as the sintering temperature increased. The $Ta_2C$ compound was observed at the surface of the compacts due to the contact between the Ta powder and graphite mold during the sintering process. The main fracture mode showed a mixed type with intergranular and transgranular modes having some roughness.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.6
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• pp.509-514
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• 2012

In this research, a heat pump system with a heat source network is suggested which utilizes solar heat and ground heat as heat source for cooling and heating. This paper describes the summary of the suggested system and the results of the annual energy simulation. The heating and cooling loads, the electric consumption and the COP were calculated by TRNSYS 16 and evaluated in the cases of different local conditions and different system compositions. In the results, the superiority of the suggested system has been quantitatively evaluated comparing with the conventional heat pump system using one heat source. Furthermore, it was more significant in cold climate, in which the heating COP was 146% increased compared the air source heat pump system, than it in subtropical climate, 119% increased.

• Journal of the Korean Solar Energy Society
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• v.22 no.4
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• pp.51-61
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• 2002

Analysis of thermodynamic design data of double effect solar absorption heat pump system for heating has been done to find the property of Libr-water + ethylene Glycol mixture for working fluid by computer simulation. Derived thermodynamic design data. enthalpy based coefficient of performance and flow ratio for possible combinations of operating temperature for water - LiBr and Ethylene Glycol mixture (H2O: CHO ratio 10:1 by mole) by computer simulation. The obtained results, COP and mass flow ratio of the water-lithium bromide-ethylene glycol system, are compared with data for the water-Libr pair solution.

• Solar Energy
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• v.19 no.1
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• pp.77-86
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• 1999

The optimal thermal design of a single heat source on one wall of a vertical open top cavity was studied experimentally. The temperature and flow fields in the cavity were visualized. The objectives of this study is to obtain the best location of the single heat source and to examine the effects of heat source protrusion, substrate thermal conductivity and cavity aspect ratio on the natural convection cooling due to a single heat source. As the results, the cooling effect for the copper substrate is superior to that of the epoxy-resin substrate and is improved with increasing cavity width. For the epoxy-resin substrate of lower conductivity, the protrusion of the heaters plays a role in decreasing the cooling effect. The best location was the mid-height of the substrate.

• Journal of the Korean Solar Energy Society
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• v.24 no.3
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• pp.39-46
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• 2004

In this paper, thermodynamic design data for heating of double-effect absorption system using LiCl-water for evaporator heating source of sofar energy are investigated for the water-LiCl pair and a comparative study of the water-LiCl pair with the water-LiBr pair is given used for the computer simulation. The computer simulation is based on mass, material and heat balance equations for each part of the system. Coefficients of performance and flow ratios for effects of different operating temperatures are investigated. It is found that the heating COP is higher for the water -LiCl pair than for the water-LiBr pair, and FR is lower for the water-LiCl pair than for the water LiBr pair.

• Journal of the KSME
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• v.21 no.1
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• pp.6-9
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• 1981

최근의 공작기계에서는 수치제어등에 의한 자동화가 활발히 연구, 실용화되어 우리나라에서도 이미 상당한 양의 NC 공작기계가 가동되고 있다. (1979년까지 도입대수 669대) 이러한 공작기 계에서는 그 생산성과 아울러 정밀도가 요구되며 따라서 이전에는 문제시되지 않았던 열변형에 대한 문제가 정적 및 동적강성도 문제와 함께 공작정도를 향상시키기 위한 중요한 문제로 되고 있다. 최근에는 대형전자계산기가 발달함에 따라 유항요소법은 물론이고 그 제어방법에 대한 연구가 활발히 이루어지고 있다. 그 가운데 Okushima와 Kakino는 열변형을 정상상태에서의 열 변형 내부열원에 의한 열변형, 액체의 순환에 의한 열변형으로 나누어 여기에 유한요소법을 적 용한 연구결과를 발표하고 있다. 이외에도 외기온도의 변화에 의한 공작기계의 열변형에 관한 실험적인 연구도 상당히 이루어지고 있다.

• Journal of Hydrogen and New Energy
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• v.27 no.5
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• pp.597-603
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• 2016

In this paper a comparative thermodynamics analysis is carried out for organic Rankine cycle (ORC) and ammonia-water Rankine cycle (AWRC) utilizing low-grade heat sources. Effects of the working fluid, ammonia concentration, and turbine inlet pressure are systematically investigated on the system performance such as mass flow rate, pressure ratio, turbine-exit volume flow, and net power production as well as the thermal efficiency. Results show that ORC with a proper working fluid shows higher thermal efficiency than AWRC, however, AWRC shows lower mass flow rate of working fluid and lower pressure ratio of expander than ORC.

• KIEAE Journal
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• v.5 no.3
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• pp.25-31
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• 2005

Computer simulations were performed for Heating Ventilating and Air-Conditioning (HVAC) systems to figure out more efficient maintenance methods for the building used for adolescent trainees. This study aims at suggesting design alternatives for optimum operation and performing life cycle cost (LCC) for each alternative. First, the capacity of the heat source equipment was determined using annual maximum heating and cooling loads. Annual loads were calculated and applied to the alternative for the purpose of calculating annual energy cost. Second, several types of data were collected to predict energy cost. Finally, the pay back period for each alternative was calculated using total cost estimation during standard duration period. This study indicates that the absorption chiller that does not occupy most part of a mechanical room, and does not need much operation cost was most economical.