• Advances in Computational Design
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• 제2권4호
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• pp.313-331
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• 2017

In this study, teaching-learning based optimization (TLBO) is improved by incorporating model of multiple teachers, adaptive teaching factor, self-motivated learning, and learning through tutorial. Modified TLBO (MTLBO) is applied for simultaneous topology, shape, and size optimization of space and planar trusses to study its effectiveness. All the benchmark problems are subjected to stress, displacement, and kinematic stability constraints while design variables are discrete and continuous. Analyses of unacceptable and singular topologies are prohibited by seeing element connectivity through Grubler's criterion and the positive definiteness. Performance of MTLBO is compared to TLBO and state-of-the-art algorithms available in literature, such as a genetic algorithm (GA), improved GA, force method and GA, ant colony optimization, adaptive multi-population differential evolution, a firefly algorithm, group search optimization (GSO), improved GSO, and intelligent garbage can decision-making model evolution algorithm. It is observed that MTLBO has performed better or found nearly the same optimum solutions.

• 한국CDE학회논문집
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• 제17권5호
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• pp.375-386
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• 2012

Most engineering design problems require analyses or simulations to evaluate objective functions. However, a single simulation can take many hours or even days to finish for many real world problems. As a result, design optimization becomes impossible since they require hundreds or thousands of simulation evaluations. The surrogate-based optimization (SBO) strategy became a remedy for such computationally expensive analyses and simulations. A surrogate-based optimization strategy has been developed in this study in order to improve global optimization performance. The strategy is a heuristic algorithm and it exploits not only multiple surrogates, but also multiple optimizers. Multiple optimizations of multiple surrogate models yield multiple candidate design points of optima. During the sequential sampling process, the algorithm ranks candidate design points, selects the points as many as specified, and builds the improved surrogate model. Various mathematical functions with different numbers of design variables are chosen to compare the proposed method with the other most recent algorithm, MSEGO. The proposed method shows superior performance to the other method.

• Journal of the Korean Data and Information Science Society
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• 제23권6호
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• pp.1103-1115
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• 2012

본 연구는 고지혈증에 대해 양파추출물을 투여한 무작위 대조군 전-후 실험설계 연구 12편을 대상으로 체중, 간 무게, 신장 무게, 심장 무게, 혈당, 총콜레스테롤, 트리글리세리드, HDL-콜레스테롤, LDL-콜레스테롤의 평균비교를 통해 양파의 효능에 대해 알아보았다. 고정효과모형을 적용시킨 결과 체중과 심장 무게를 제외한 간 무게, 신장 무게, 혈당, 총콜레스테롤 농도, 트리글리세리드 농도, LDL-콜레스테롤 농도는 유의한 감소를 보였고, HDL-콜레스테롤 농도는 유의하게 증가하였다. 갈브레스 그림으로 동질성 여부를 알아보았고 동질성을 만족하지 않은 변수에 대해 랜덤효과모형을 적용시킨 결과 간 무게와 혈당, 총 콜레스테롤 농도, 트리글리세리드 농도의 감소에 대해 유의한 효과를 나타냈고, HDL-콜레스테롤 농도는 유의하게 증가하였다. 각 변수에 대해 출판편의의 존재를 알아보았고, 출판편의의 존재를 확인 후 절단과 보충 방법으로 대체값을 추정하였다.

• Asia pacific journal of information systems
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• 제9권3호
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• pp.1-23
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• 1999

The objective of this study is to examine the media richness theory and the social information processing model by analyzing the effect of media experience on media perception and communication process. To accomplish this objective, a laboratory experiment was conducted. The independent variable was text medium experience and a face-to-face medium was added as a control group. The dependent variables were medium perception and communication process. Medium perception includes perceived richness, medium feeling, task satisfaction, and communication satisfaction. Communication processes were also analyzed to compare each treatment group. The results can be summarized into two facts. First, face-to-face group showed higher perceived richness than text medium group. And experienced text medium group perceived their text medium richer than inexperienced text medium group. Second, experienced text medium groups showed more interactions between subjects than inexperienced text medium group. Experienced text medium group also showed more agreements and meta-communication which could be found in face-to-face group. The result of this study supported media richness theory by finding that face-to-face medium was perceived richer than text medium, And the results also proved social information processing model by comparing experienced text medium group and inexperienced text medium group. The text medium, although thought to be the leanest one, could be perceived richer if users had lots of experience on it.

• 자원환경지질
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• 제30권2호
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• pp.153-161
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• 1997

Diagrams of $^{87}Sr/^{86}Sr$ versus Ba/Nb and MgO/FeO are scattered, and $^{87}Sr/^{86}Sr$ variation with the increase of $SiO_2$ are scattered in Gwangju granitoid. Diagrams of $(^{87}Sr/^{86}Sr)$i versus $(^{143}Nd/^{144}Nd)$i and ${\varepsilon}Nd$ versus 1/Nd variation are also scattered in Gwangju granitoid. It shows that the source magma of Gwangju granitoid are derived from partial melting materials of heterogeneous upper crust. Very low ${\varepsilon}Nd$ values (-15.19~-19.49) and very high ${\varepsilon}Sr$ values (92.72~308.85) mean that the source magma of Gwangju granitoid is derived from sedimentary substance melting. According to $(^{87}Sr/^{86}Sr)$ 180Ma, and the plot of ${\varepsilon}Sr$ versus ${\varepsilon}Nd$, the Gwangju granitoid shows that the source magma is derived from upper crust materials. Nd model ages of Gwangju granitoid (1.82~2.42G.A.) are older than meta-sediments of Okcheon formation (1.15~1.60G.A.) and similar or close to Pre-Cambrian gneiss complex of Ryoungnam massif (2.17~2.47G.A.or 2.11~2.38G.A.).Therefore, the source magma of the Gwangju granitoid could be derived from the partial melting of Pre-Cambrian gneiss complex of Ryoungnam massif.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 제5회 압연심포지엄 신 시장 개척을 위한 압연기술
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• pp.297-306
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• 2004

This study investigated Austenite Grain Size (AGS) distribution in Low-Speed Round-Oval Rolling. Rolling experiments were done along with the AGS numerical modeling to characterize the final AGS distribution and its kinetics behavior. For bar rolling experiment, we utilized the pilot rolling mill, operating at 34 fixed rpm, at POSCO Technical Research Laboratories. To investigate the microstructural observation, the rigid-viscoplastic finite element analysis was combined with Hodgson's AGS evolution model. To consider the transient thermal history in the integrative AGS modeling, additivity rule was introduced. The integrated analysis revealed that static or meta-dynamic recrystallization is responsible for the AGS difference in the inner or outer region of rolled bar. Comparative study showed that the current AGS modeling approach can be used to model the overall AGS distribution in bar rolling processes. For more accurate AGS prediction, the AGS modeling method should be verified under the various rolling conditions such as different rolling speeds and different deformations.

• 한국공간구조학회논문집
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• 제15권2호
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• pp.87-94
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• 2015

This paper aimed at modeling a fine triangular grid for network dome by using Harmony Search (HS) algorithm. For this purpose, an optimization process to find a fine regular triangular mesh on the curved surface was proposed and the analysis program was developed. An objective function was consist of areas and edge's length of each triangular and its standard deviations, and design variables were subject to the upper and lower boundary which was calculated on the nodal connectivity. Triangular network dome model, which was initially consist of randomly irregular triangular mesh, was selected for the target example and the numerical result was analyzed in accordance with the HS parameters. From the analysis results of adopted model, the fitness function has been converged and the optimized triangular grid could be obtained from the initially distorted network dome example.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2007년도 가을 학술발표논문집 Vol.34 No.2 (C)
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• pp.66-71
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• 2007

멀티미디어 데이터에 대한 효율적인 검색을 지원하기 위해 제정된 MPEG7이나 TV-AnyTime 등의 표준들은 XML을 사용하여 Metadata를 효과적으로 표현할 수 방법을 제시하고 있다. 플랫폼에 독립적으로 사용가능하다는 XML의 강점에도 불구하고 Text 방식으로 데이터를 저장하기 때문에 보안에 취약할 수밖에 없으며, 대용량의 자료 처리에도 문제점을 드러낸다. 이를 보완하기 위하여 XML 문서를 RDBMS에 저장하는 방법들이 제안되고 있는데, 기존의 Model Mapping이나 Structure Mapping의 경우 노드 검색을 위해 Traversing을 할 경우 많은 조인이 필요하기 때문에 한정된 메모리와 낮은 처리능력을 갖춘 임베디드 멀티미디어 플랫폼에서는 비효율적일 수밖에 없다. 본 논문에서는 MPEG7 Metadata를 RDBMS에 저장하고, 이를 검색할 때, 조인의 횟수를 최소화할 수 있는 저장 모델을 제안하고 있다. 부모, 자식, 형제간의 노드를 효율적으로 검색할 수 있도록 path MetaSchema를 제안함으로써, 최소 1번의 검색으로 필요한 노드 정보들을 추출할 수 있도록 하였다. 그리고 Annotation 작성시에 XML의 Attribute와 Element로 삽입하였기에, 기존의 방법에서 Annotation을 분석하기 위해 필요했던 Annotation 파싱을 제거하고, SAX나 DOM을 사용할 수 있도록 제안함으로써, Annotation의 정보에 대한 접근이 효율적으로 개선되었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.263-270
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• 2008

The capillary tube/suction line heat exchanger (SLHX) is widely used in small refrigeration systems. The refrigerant flowing in the SLHX experiences frictional and accelerational head losses, flashing, and heat transfer simultaneously. The simulation of refrigerant flow through SLHX is important since this will help engineers analyze and optimize the SLHX incorporated in a refrigeration system. The present SLHX model is based on conservation equations of mass, momentum and energy. Also a meta-stable model is included. All these equations are solved simultaneously. In this paper, HFC-134a refrigerant flow through a non-adiabatic capillary tube is simulated. The simulation results are discussed but not validated against experimental measurements yet.

• 산업경영시스템학회지
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• 제33권2호
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• pp.48-55
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• 2010

Reliability has been considered as a one of the major design measures in various industrial and military systems. The main objective is to suggest a mathematical programming model and a hybrid parallel genetic algorithm(HPGA) for the problem that determines the optimal component reliability to maximize the system reliability under cost constraint in this study. Reliability optimization problem has been known as a NP-hard problem and normally formulated as a mixed binary integer programming model. Component structure, reliability, and cost were computed by using HPGA and compared with the results of existing meta-heuristic such as Ant Colony Optimization(ACO), Simulated Annealing(SA), Tabu Search(TS) and Reoptimization Procedure. The global optimal solutions of each problem are obtained by using CPLEX 11.1. The results of suggested algorithm give the same or better solutions than existing algorithms, because the suggested algorithm could paratactically evolved by operating several sub-populations and improving solution through swap and 2-opt processes.