• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 1998년도 The 12th Asia Quality Management Symposium* Total Quality Management for Restoring Competitiveness
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• pp.680-695
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• 1998

The objective of this study is to optimize the responses of the creep feed ceramic grinding process simultaneously by an off-1ine multicriteria optimization methodology. The responses considered as objectives are material removal rate, flexural strength, normal grinding force, workpiece surface roughness and grinder power. Alumina material was ground by the creep feed grinding mode using superabrasive grinding wheels. The process variables optimized for the above objectives include grinding wheel specification, such as bond type, mesh size, and grit concentration, and grinding process parameters, such as depth of cut and feed rate. A weighting method transforms the multi-objective problem into a single-objective programming format and then, by parametric variation of weights, the set of non-dominated optimum solutions are obtained. Finally, the multi-objective optimization methodology was tested by a sensitivity analysis to check the stability of the model.

• Structural Engineering and Mechanics
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• 제29권4호
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• pp.391-410
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• 2008

In this article, a harmony search algorithm is presented for optimum design of steel frame structures. Harmony search is a meta-heuristic search method which has been developed recently. It is based on the analogy between the performance process of natural music and searching for solutions of optimization problems. The design algorithms obtain minimum weight frames by selecting suitable sections from a standard set of steel sections such as American Institute of Steel Construction (AISC) wide-flange (W) shapes. Stress constraints of AISC Load and Resistance Factor Design (LRFD) and AISC Allowable Stress Design (ASD) specifications, maximum (lateral displacement) and interstorey drift constraints, and also size constraint for columns were imposed on frames. The results of harmony search algorithm were compared to those of the other optimization algorithms such as genetic algorithm, optimality criterion and simulated annealing for two planar and two space frame structures taken from the literature. The comparisons showed that the harmony search algorithm yielded lighter designs for the design examples presented.

• 대한기계학회논문집A
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• 제30권10호
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• pp.1249-1254
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• 2006

Existing adaptive observers may cause the parameter drifts due to disturbances even if state estimation errors remain small. To avoid the drift phenomena in the presence of bounded disturbances, several robust adaptive observers have been introduced addressing bounds in state and parameter estimates. However, it is not easy for these observers to manipulate the size of the bounds with the selection of the observer gain. In order to reduce estimation errors, this paper introduces the (equation omitted) gain minimization problem in the adaptive observer structure, which minimizes the (equation omitted) gain between disturbances and estimation errors. The stability condition of the adaptive observer is reformulated as a linear matrix inequality, and the observer gain is optimally chosen by solving the convex optimization problem. The estimation performance is demonstrated through a numerical example.

• 정보저장시스템학회논문집
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• 제5권2호
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• pp.53-57
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• 2009

This study is concerned with the design of a camera iris-shutter device for producing force. The camera iris-shutter with yoke should have a smaller size and a bigger magnetic force than the previous model. Since the induced magnetic force operates shutter movement, the magnetic force maximization for a given input current is an important issue. To achieve the goal, new system is designed by the topology optimization method. The design is refined through the design of experiments to find the detail camera iris shutter design satisfying design constraints.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.352-355
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• 2004

The objective of this work is to develop a new design method to find optimal coils, especially the optimal coil configuration of an optical pickup actuator. In designing actuator coils, the developed Lorenz force in the coils along the desired direction should be made as large as possible while forces and torques in other directions should be made as small as possible. The design methodology we are developing is a systematic approach that can generate optimal coil configurations for given permanent magnet configurations. To consider the best coil configuration among all feasible coil configurations, we formulate the design problem as a topology optimization of a coil. The present formulation for coil design is noble in the sense that the existing topology optimization is mainly concerned with the design of yokes and permanent magnets and that the optimization of actuator coils is so far limited within shape or size optimization. Though the present design methodology applies to any problem, the specific design example considered is the design of fine-pattern tracking and focusing coils.

• 한국정보통신학회논문지
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• 제14권5호
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• pp.1085-1092
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• 2010

본 논문에서는 최적화 알고리즘인 PSO를 이용하여 한국인의 생활자계 노출실태 조사 시 확보한 16세 이하의 미취학 아동, 초등학생, 중학생 실측 데이터베이스를 활용하여, 자계노출의 정도를 실측에 의하지 않고 추정할 수 있는 '24시간 소아고노출 생활자계 추정식'을 개발하였다. 24시간 개인자계 노출량 추정식의 입력 데이터는 성, 연령, 주거형태, 주거지 크기, 선로이격거리 및 송전전압을 사용하였다. 그리고 16세 이하에 대해서 24시간 고노출 개인자계 노출분포, 자계노출의 특성, 특정 조건별 자계노출특성 등을 분석하였다.

• 한국컴퓨터정보학회논문지
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• 제26권1호
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• pp.111-118
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• 2021

본 논문에서는 디바이스 캐싱 네트워크에서 다양한 퀄리티의 콘텐츠를 캐싱하는 기술을 제안한다. 하나의 파일을 온전히 캐싱하는 기존 기술들과 다르게, 저자는 콘텐츠의 일부 조각을 캐싱하는 것을 허용하였고, 사용자가 스스로 캐시 히트를 달성할 수 있는 경우를 고려하였다. 캐싱하는 콘텐츠의 퀄리티와 캐시 히트율 간의 트레이드오프를 분석하고, 사용자가 소비하는 콘텐츠의 기대 퀄리티를 최대화하는 디바이스 캐싱 기법을 제안한다. 퀄리티와 파일 크기의 관계 파라미터에 따라 볼록 최적화 문제와 DC programming 문제 두 가지 방식으로 나누어서 캐싱 문제를 풀어냈다. 퀄리티 증가 폭에 비해 파일 크기가 더 빠르게 증가하면, 인기도에 따라 캐싱할 콘텐츠의 부분 조각이 점차 증가하는 반면, 파일 크기가 더 느리게 증가하면, 일부 인기도가 높은 콘텐츠는 전체를 캐싱하고 그렇지 않은 콘텐츠는 아예 캐싱하지 않는 결과를 낸다.

• 제어로봇시스템학회논문지
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• 제6권8호
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• pp.623-628
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• 2000

Video-on-demand system in which users can request any video through the network at any time is made possible by rapid increase in network bandwidth and capacity of the media server. However true video-on-demand system cannot support all requests since bandwidth requirement is still too demanding. Therefore efficient bandwidth reduction algorithm is necessary. both the piggybacking method and the batching method are novel solutions that can provide more logical number of streams than the physical system can support. Of course each of them has its pros and cons. hence piggybacking with batching-by-size can take advantage of both the schemes. Some parameters such as the size of batch and the size of the catch-up window should be adjusted and order to maximize the bandwidth reduction for piggybacking with batching-by-size method. One of the most important parameters is decided optimally in this paper. Simulation shows that the optimized parameter can achieve considerable reductionand consequently remarkable enhancement in performance.

• 대한기계학회논문집A
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• 제36권11호
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• pp.1335-1343
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• 2012

논문은 위상최적화와 치수최적화 해석기법을 이용한 샌드위치 복합재와 알루미늄 압출재로 구성되는 하이브리드 철도차량 차체 구조물의 경량 모듈화 설계에 관한 연구이다. 위상최적설계는 초기설계단계에 차체 구조물의 최적의 재료적용부위를 선정하기 위해 사용되었으며, 치수최적화설계는 하이브리드 차체 구조물의 최적 설계 변수를 찾기 위해 사용되었다. 이때, 최적화해석은 일계법과 부분문제근사법을 사용하였다. 위상최적설계해석을 통해 차체 구조물의 강성 및 제작성을 향상시키기 위한 언더프레임, 로우 사이드 패널 모듈에 1차 부재인 알루미늄 압출재의 적용이 적절하고, 샌드위치 복합재는 무게를 최소화하기 위한 2차 부재로서 루프 및 미들 사이드 패널 모듈에 적용이 적합하다는 결론을 얻었다. 또한, 알루미늄 압출재와 샌드위치 복합재로 구성되는 하이브리드 차체 구조물의 무게는 샌드위치 복합재로만 만들어진 차체 구조물과 비교하여 최대 17.7%까지의 경량화 효과를 얻을 수 있음을 확인하였다.

• 대한기계학회논문집A
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• 제25권12호
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• pp.1950-1959
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• 2001

An active control of the vibration transmitted by longitudinal load in flight control system is investigated numerically. The flight control system is modeled as a finite, thin shell cylinder with constant thickness. A vibration source is generated by exterior monopole source. Distributed piezoelectric actuator is used to control of the vibration. Thin shell theory is used to formulate the numerical models. The amplitude of vibration at discrete location and power transmission are minimized by analytical optimization method. Genetic algorithm is used as numerical optimization method to search optimal actuator position and size which amplitude of vibration is minimized.