• Economic and Environmental Geology
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• v.28 no.3
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• pp.305-309
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• 1995

There is a deep and useful connection between thermodynamics (the behavior of systems with many degrees of freedom in thermal equilibrium at a finite temperature) and combinational or continuous optimization (finding the minimum of a given multiparameter function). At the heart of the method of simulated annealing is an analogy with the way that liquids freeze and crystallize, or metals cool and anneal. This paper provides a detailed description of simulated annealing. Although computationaly intensive, when it is carefully implemented, simulated annealing is found to give superior results to more traditional methods of nonlinear optimization.

• Journal of Korea Multimedia Society
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• v.17 no.9
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• pp.1084-1091
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• 2014

When demand for transmitting multimedia data increases, network congestion is more likely to occur and users will suffer high loss rate as well as high delay. In order to enhance quality-of-service (QoS) of video multicasting, we need to raise transmission reliability and reduce end-to-end delay. This paper proposes a routing mechanism for a OpenFlow-based small-scale network in order to multicast video reliably with low delay. In our method, multipath routing will be applied to Multiple Description (MD) Coded video to exploit its multi-description property. Through performance evaluation, our method shows improvement on loss rate, delay and video distortion.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.644-646
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• 2003

물류 공급 관리 시스템과 같은 정보 통합 시스템은 분산되어 있는 데이터베이스들에 대해서 정보를 통합하여 사용자에게 보여준다. 이러한 정보 통합 시스템은 전역 질의를 생성하고 지역 질의로 변환하여 실행하기 전에 질의를 최적화할 필요성이 있다. 그런데, 단일데이터 베이스 시스템에서의 질의 최적화 기법은 멀티데이터베이스 시스템에서 사용하기에는 부적절하다. 이는 분산된 데이터베이스 환경에서 오는 높은 연결 오버헤드, 높은 계산 시간, 데이터의 중복성 뿐만 아니라 의미 이질성 문제 때문에 기존의 최적화 방법은 사용하기가 어렵다. 이를 해결하기 위해서 의미상 질의 최적화 방법이 연구되어 왔다. 의미상 질의 최적화는 전역 질의보다 더 효과적으로 응답하고 의미상으로 동등한 질의로 변환하기 위해서 의미상 지식을 사용한다. 본 논문에서는 정보 통합 시스템에서 Description Logic(DL)을 이용하여 의미상 지식으로 사용할 지식 기반을 표현하고 이를 바탕으로 추론화된 지식을 이용하는 의미상 질의 최적화 방식을 제시한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2003.11a
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• pp.27-30
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• 2003

본 논문에서는 하이브리드 다중 표현(hybrid multiple description) 개념을 이용하여 에러가 발생하기 쉬운 환경에서 사용될 수 있는 강인한 동영상 압축 알고리듬을 제안한다. 다중 표현 압축은 단일 표현 압축(single description coding. SDC) 보다 패킷 손실 율(packet loss rate, PLR)이 높은 환경에서 에러에 더 강인성을 갖는다. 그러나 PLR 이 낮은 환경에서는 과도한 중복량(redundancy) 때문에 성능이 저하되는 문제가 발생한다 이러한 MDC 의 문제를 해결하기 위해서 채널 환경에 따라 SD/MID 를 전환할 수 있는 방법을 제안한다. 좀더 자세히 설명하면, 낮은 PLR 에서는 압축 효율을 위하여 SDC 를 사용하고 높은 PLR 환경에서는 에러에 대한 강인성을 위해 MDC 를 사용한다. SD/MD 전환을 최적화시키기 위해 비트율-왜곡 최적화 프레임웍(rate-distortion optimization framework)을 사용한다. 부호화시에 복호기에서의 왜곡(distortion)을 정확히 예측하기 위해서 ROPE(recursive optimal per-pixel estimate) 방법을 사용한다. 모의 실험 견과 제안된 SD/MD 전환 방법이 기존의 SDC-ROPE 와 MDC-ROPE 보다 모든 에러 환경에서 더 효과적임을 알 수 있다.

• Korean Journal of Computational Design and Engineering
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• v.21 no.4
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• pp.443-452
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• 2016

This paper proposes a method for expensive black box optimization using radial basis functions (RBFs). The proposed algorithm is a computational strategy that uses a RBF model approximating the expensive black box function to predict an optimum. First, a RBF-based approximation technique is introduced and a sampling plan for estimation of the black box function is described. Then the proposed algorithm is explained, which presents the pseudo-codes for implementation and the detailed description of each step performed in the optimization process. In addition, numerical experiments will be given to analyze the performance of the proposed algorithm, by investigating computation accuracy, number of function evaluations, and convergence history. Finally, geometric distance problem as application example will be also presented for showing the algorithm applicability to different engineering problems.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.8
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• pp.790-797
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• 2007

This paper proposes a new measure of cost function ruggedness in local optimization with DEAS. DEAS is a computational optimization method developed since 2002 and has been applied to various engineering fields with success. Since DEAS is a recent optimization method which is rarely introduced in Korean, this paper first provides a brief overview and description of DEAS. In minimizing cost function with this non-gradient method, information on function shape measured automatically will enhance search capability. Considering the search strategies of DEAS are well designed with binary matrix structures, analysis of search behaviors will produce beneficial shape information. This paper deals with a simple quadratic function contained with various magnitudes of noise, and DEAS finds local minimum yielding ruggedness measure of given cost function. The proposed shape information will be directly used in improving DEAS performance in future work.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.917-920
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• 2005

This paper introduces an optimal design technique for a 250-watt isolation transformer using a recently developed optimization method, dynamic encoding algorithm for searches(DRAS). Although the optimal design technique for transformers dates back to 1970s and local optimization is often undertaken using FEM nowadays, literature concerning global optimization of transformer cores is rarely found against its importance. In this paper, a small isolation transformer is used as a model to be optimized with application of DEAS to corresponding mathematical description. The optimization result confirms that DEAS can be successfully employed to design transformer cores for various design specifications only by changing cost functions.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.69.5-69
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• 2002

1. Introduction 2. System Description 3. Hybrid Modeling of SM Reactor 4. Simulation Results 5. Optimization of Operating Condition 6. Conculsion

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.54.6-54
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• 2002

1. Introduction 2. The Netwoked Control System Description 2.1 A close-loop system with the network induced delay 2.2 Discretization and State Augmentation of NCS 3. Delay-dependent H_infinity Controller Design for NCS 4. Numerical Example 5. Conclusion

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.4
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• pp.54-62
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• 2010

Semantic Web programming is such an immature area that it is yet based on API calls, and does not provide high productivity in compiler time and sufficient efficiency in runtime. To get over this limitation, some efforts have been devoted on dedicated programming languages for Semantic Web. In this paper, we introduce a sophisticated cashing technique to enhance the runtime efficiency of RDF (Resource Description Framework) processing programs with SPARQL queries. We use static program analysis on those programs to determine what to be cashed, so as to decrease the cash miss ratio. Our method is implemented on programs in 'Jey' language, which is one of the programming languages devised for RDF data processing.