• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2552-2557
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• 2007

Shape optimization of an internal cooling passage with staggered dimples on single surface is performed and performances of surrogates are evaluated in this paper. Optimizations are performed so that turbulent heat transfer can be enhanced compromising with pressure loss due to friction. The three-dimensional governing differential equations have been solved to find the overall Nusselt number and friction factor which are related to the objective functions of this problem. Three design variables were selected among the dimensionless geometric variables. Basic surrogate models such as second order polynomial response surface approximation (RSA), Kriging meta-modeling technique, radial basis neural network (RBNN), and derived press based averaged (PBA) surrogate model are constructed. The optimal points are searched from the above constructed surrogates by sequential quadratic programming (SQP). It is shown that use of multiple surrogates can increase the robustness in prediction of better design with minimum computational cost.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.9
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• pp.733-740
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• 2007

Microchannel heat sink shape optimization is performed using Kriging method. Design variables relating to microchannel width, depth and fin width are selected, and thermal resistance has been taken as objective function. Design points are selected through a three-level fractional factorial design of sampling method. Navier-Stokes and energy equations for laminar flow and conjugate heat transfer are solved at these design points using a finite volume solver. Solutions are carefully validated with experimental results. Using the numerically evaluated objective function, a surrogate model (Kriging) is constructed and optimum point is searched by sequential quadratic programming. The process of shape optimization greatly improves the thermal performance of microchannel heat sink under constant pumping power.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.187-194
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• 2010

Shape optimization of an upper plenum of PBMR type gas cooled nuclear reactor has been performed by using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) analysis and surrogate modeling technique. The objective function is defined as a linear combination of uniformity of flow distribution in the core and pressure drop in the upper plenum and the core. The ratio of thickness of slot to diameter of rising channels, ratio of height of upper plenum to diameter of rising channels, and ratio of eight of the slot at inlet to outlet, are used as design variables for optimization. Design points are selected through Latin-hypercube sampling. The optimal point is determined through surrogate-based optimization method which uses 3-D RANS analyses at design points. The results show that the optimum shape represent remarkably improved performance in flow uniformity and friction loss than the reference shape.

• Journal of computational fluids engineering
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• v.15 no.3
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• pp.16-23
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• 2010

Shape optimization of an upper plenum of a PBMR type gas cooled nuclear reactor has been performed by using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) analysis and surrogate modeling technique. The objective function is defined as a linear combination of uniformity of flow distribution in the core and pressure drop in the upper plenum and the core. The ratio of thickness of slot to diameter of rising channels, ratio of height of upper plenum to diameter of rising channels, and ratio of height of the slot at inlet to outlet, are used as design variables for optimization. Design points are selected through Latin-hypercube sampling. The optimal point is determined through surrogate-based optimization method which uses 3-D RANS analyses at design points. The results show that the optimum shape represent remarkably improved performance in flow uniformity and friction loss than the reference shape.

• Journal of the Korea Society for Simulation
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• v.16 no.3
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• pp.39-48
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• 2007

This study suggests a method of command and control in modeling a combat situation. In particular, it presents the structure of an intelligent agent that may substitute for the current system of decision making in the military operation to lead a troop. Today the Korean military war game simulations emphasize on engagements, instead of command and control. This suggested principle will be a good foundation for the today and the future Korean warfare.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.1
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• pp.163-173
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• 1999

The CORBA provides a object-oriented middleware that lets applications extend their range across networks, languages, component boundaries, and operating systems. Java can provide a potable object that works in any operating system. Mapping Java into CORBA helps large scale information system operate through the Web by using the mobile code property of Java and object component technique of CORBA. This development environment is called the Object Web. This paper proposes an architecture of OSI network management with a CORBA manager using Object Web and an CORBA/CMIS gateway which apply a CMIS-level gateway model to gateway. In this architecture, CORBA manager is based on Object Web and can manage MOs in the OSI domain. The gateway has a role to translate CORBA IDLs into CMIS services and vice versa. In addition, an OSI agent is abstracted into a CORBA agent.

• Journal of the Korea Society of Computer and Information
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• v.27 no.1
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• pp.193-200
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• 2022

In this paper, we examined the causes of privacy concerns and related factors in social log-in services. On the basis of the 'principal-agent theory,' we established factors such as perceived information asymmetry and fear of seller opportunism affecting information privacy concern of social log-in services users. In addition, we analyzed the relationship between the information privacy concern and intention to use on the basis of the 'privacy calculus theory'. The results of the study showed that (1) fear of seller opportunism had the significant effect on information privacy concerns, (2) information privacy concerns had the significant effect on perceived risk, (3) in accordance with the privacy calculus theory, perceived risk had the negative effect on intention to use, while perceived benefit had the positive effect on intention to use. The findings of the study are expected to help to improve the social log-in service firms' understanding for customers' information privacy protection behaviors.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.91-91
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• 2020

IPCC (Intergovernmental Panel on Climate Change) 5차 평가보고서에 의하면 최근 배출 온실가스의 양은 관측 이래 최고 수준이며 온실가스로 인한 기후변화는 인간계와 자연계에 광범위한 영향을 주고 있다고 보고하였다. 기후변화의 영향은 국제적으로 빙하 감소, 사막화, 해수면 상승 등 뚜렷하게 나타나고 있다. 이러한 기후변화에 대응하기 위해 온실가스 완화 정책과 동시에 새로운 기후변화 환경에 적응하는 것이 필요하다. 기후변화 적응이란 현재 나타나고 있거나 미래에 나타날 것으로 예상되는 기후변화의 파급효과와 영향에 대응할 수 있도록 하는 모든 행동이며 이를 위해서는 기후변화 영향분석이 수반되어야 한다. MOTIVE 연구단에서는 기후변화 적응대책 수립의 지원을 목표로 7개 부문(건강, 물관리, 농업, 산림, 생태, 해양, 수산)에서 "한국형 통합평가 모형"을 개발하고 있다. 각 부문에서 개발하는 프로세스 모델은 시스템에 대한 지식을 가진 상황에서 사용하면 신뢰할 수 있는 예측 결과를 얻을 수 있지만, 부문별 통합을 통한 영향 분석 시 타 분야에 대한 지식이 수반되어야 하는 어려움을 가진다. 이를 위해 본 연구에서는 시스템 내의 물리적 프로세스에 대한 요구 없이 입출력 데이터만을 이용하여 결과를 신속하게 추정하는 데이터 모델링(기계학습)을 이용하였다. 데이터 모델링을 위한 데이터는 다양한 자연 현상에 대한 BANPOL(수질 프로세스 모델) 분석을 통한 자료를 이용하여 학습 자료를 구축하였다. 즉, 데이터 모델링은 BANPOL 모델을 대리하는 메타모델이며, 낙동강 표준유역에 대한 유량 및 수질을 높은 상관성으로 추정하였다. 원 모델보다 정확도는 낮을 수 있으나 메타모델의 개발을 통한 웹 시스템을 개발하여 비전문가의 구동 및 신속한 기후 시나리오를 적용할 수 있는 환경을 개발하였다.

• The Korean Journal of Financial Management
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• v.16 no.2
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• pp.179-213
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• 1999

본 연구에서는 국내 주식시장에서 주식수익률의 횡단면 차이에 유의적인 설명력을 가지는 것으로 나타난 기본적 변수가 시장지수 베타에서는 측정되지 않은 또 다른 가격화된 위험에 대해 유용한 대용변수인지를 규명하였다. 기본적 변수들 중에서 기업규모와 장부/시장가치 비율은 주식수익률의 횡단면 차이를 설명함에 있어 독립적인 효과를 갖는 가장 유의적인 변수였다. 주식수익률의 횡단면 차이에 매우 유의적인 설명력을 가지는 깃으로 나타난 거시경제요인의 요인민감도는 기업규모, 장부/시장가치 비율을 포함시 더 이상 유의적인 설명력을 가지지 못하였다. 소규모, 높은 장부/시장가치 기업은 매우 지속적인 수익성 악화를 겪고 있는 곤경기업이며, 역시 배당감소위험, 레버리지위험 및 미래 현금흐름의 불확실성으로 측정된 기업특성적 위험이 보다 큰 곤경기업이었다. 따라서 이러한 실증결과는 소규모, 높은 장부/시장가치 주식이 대규모, 낮은 장부/시장가치 주식에 비해 높은 수익률을 보이는 원인이 보다 높은 위험에 따른 보상의 결과이며, 규모변수와 장부/시장 가치 비율은 이들 위험에 대한 유용한 대용치라는 '위험에 기초한 가설'을 지지하는 증거로 주장될 수 있다. 기업규모와 장부/시장가치 비율이 시장베타로는 측정되지 않는 주식가격결정에 있어 가격화 된 또 다른 위험을 대리한다면 수익률에 나타난 SIZE, B/M효과는 합리적 가격결정하 APT나 ICAPM과 같은 확장된 CAPM과 모순되지 않는 하나의 증거로 볼 수 있으며, 비록 이들 변수들이 관찰 불가능한 진정한 시장베타에 대한 보다 나은 대용치라고 할지라도 이들 두 변수와 관련된 요인을 포함한 다요인 가격결정모델이 시장지수만을 포함한 단일요인모델에 비해 보다 유용한 모형임을 기대할 수 있다.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2666-2671
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• 2007

This work presents microchannel heat sink shape optimization procedure using Kriging method. Design variables relating to microchannel width, depth and fin width are selected, and thermal resistance has been taken as objective function. Design points are selected through a three-level fractional factorial design of sampling method. Navier-Stokes and energy equations for laminar flow and conjugate heat transfer are solved at these design points using a finite volume solver. Solutions are carefully validated with experimental results. Using the numerically evaluated objective function, a surrogate model (Kriging) is constructed and optimum point is searched by sequential quadratic programming. The process of shape optimization greatly improves the thermal performance of microchannel heat sink under constant pumping power.