• 한국기계가공학회지
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• 제7권3호
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• pp.17-24
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• 2008

Rail clamps are mechanical components installed to fix the container crane to its lower members against wind blast or slip. According to rail clamps should be designed to survive harsh wind loading conditions. In this study, a jaw structure, which is a part of a wedge-typed rail clamp, is optimized with respect to its strength under a severe wind loading condition. According to the classification of structural optimization, the structural optimization of a jaw is included in the category of shape optimization. Conventional structural optimization methods have difficulties in defining complex shape design variables and preventing mesh distortions. To overcome the difficulties, the metamodel using Kriging interpolation method is introduced to replace the true response by an approximate one. This research presents the shape optimization of a jaw using iterative Kriging interpolation models and a simulated annealing algorithm. The new Kriging models are iteratively constructed by refining the former Kriging models. This process is continued until the convergence criteria are satisfied. The optimum results obtained by the suggested method are compared with those obtained by the DOE (design of experiments) and VT (variation technology) methods built in ANSYS WORKBENCH.

• 한국소음진동공학회논문집
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• 제19권11호
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• pp.1151-1157
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• 2009

Ensuring both product quality and reducing material cost are important issue for the design of the piping system of an air conditioner outdoor unit. This paper describes a shape optimization that achieves mass reduction of an air conditioner piping system while satisfying two design constraints on resonance avoidance and the maximum stress in the pipes. In order to obtain optimized design results with various analysis fields considered simultaneously, an automated multidisciplinary analysis system was constructed using PIAnO v.2.4, a commercial process integration and design optimization(PIDO) tool. As the first step of the automated analysis system, a finite element model is automatically generated corresponding to the specified shape of the pipes using a morphing technique included in HyperMesh. Then, the performance indices representing various design requirements (e.g. natural frequency, maximum stress and pipe mass) are obtained from the finite element analyses using appropriate computer-aided engineering(CAE) tools. A sequential approximate optimization(SAO) method was employed to effectively obtain the optimum design. As a result, the pipe mass was reduced by 18 % compared with that of an initial design while all the constraints were satisfied.

• Composites Research
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• 제27권6호
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• pp.207-212
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• 2014

The shape optimization of composite flexbeam sections of a bearingless helicopter rotor is studied using a finite element (FE) sectional analysis integrated with an efficient evolutionary optimization algorithm called particle swarm assisted genetic algorithm (PSGA). The sectional optimization framework is developed by automating the processes for geometry and mesh generation, and the sectional analysis to compute the elastic and inertial properties. Several section shapes are explored, modeled using quadratic B-splines with control points as design variables, through a multiobjective design optimization aiming minimum torsional stiffness, lag bending stiffness, and sectional mass while maximizing the critical strength ratio. The constraints are imposed on the mass, stiffnesses, and critical strength ratio corresponding to multiple design load cases. The optimal results reveal a simpler and better feasible section with double-H shape compared to the triple-H shape of the baseline where reductions of 9.46%, 67.44% and 30% each are reported in torsional stiffness, lag bending stiffness, and sectional mass, respectively, with critical strength ratio greater than 1.5.

• 한국전산구조공학회논문집
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• 제15권4호
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• pp.599-607
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• 2002

형상 최적설계 중에 발생하는 절점의 과도한 이동은 요소망을 왜곡하고, 결국 최적해의 저하를 유발한다. 이러한 문제를 개선한 형상 최적설계 기법을 개발하였다. 이 방법은 구조물의 형상이 변해 갈 수 있는 충분한 공간의 설계 영역을 정하여, 균일하고 세밀한 요소망을 미리 생성한다. 각각의 최적화 단계마다 모든 요소들과 구조물의 위치 관계를 검사하여, 내부의 요소에는 실제의 물성치를 부여하고, 외부에 존재하는 요소는 0에 가까운 물성치를 부여한다. 변위와 고유 진동수의 제한조건을 가진 두 개의 예제를 통해 이 방법의 특징을 살펴보았다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.329-334
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• 2006

Rail clamps are mechanical components installed to fix the container crane to its bottoms from wind blast or slip. Rail clamps should be designed to survive the harsh wind loading condition. In this study, the jaw structure that is one part of wedge-typed rail clamp is optimized, considering strength under the severe wind loading condition. According to the classification of structural optimization, the structural optimization of a jaw belongs to shape optimization. In the conventional structural optimization methods, they have difficulties in defining complex shape design variables and preventing mesh distortions. To overcome the difficulties, the metamodel using kriging interpolation method is introduced, replacing true response by approximate one. This research presents the shape optimization of a jaw using iterative kriging interpolation models and simulated annealing algorithm. The new kriging models are iteratively constructed by refining the former kriging models. This process is continued until the convergence criteria are satisfied. The optimum results obtained by the suggested method are compared with those obtained by the DOE (design of experiments) and VT (variation technology) methods built in ANSYS WORKBENCH.

• 한국정보과학회논문지:시스템및이론
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• 제33권10호
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• pp.759-767
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• 2006

컴퓨터 그래픽스 분야에 활용되는 단순화 기법(LoD)은 실시간 렌더링을 위해 메쉬(mesh)의 다각형 수를 줄이는 방법으로 널리 알려져 있다. 본 논문에서는 이러한 단순화 기법의 기본적인 개념이 가상 캐릭터의 동작 단순화에 적용된 새로운 방법론을 제안한다. 가상 캐릭터의 구성요소 중 하나인 관절은 동작을 생성하는 기본 단위로서 메쉬와 연계되어 캐릭터의 움직임을 생성한다. 동작 단순화의 기본과정은 이러한 캐릭터의 관절 수를 줄이고 남은 관절들의 움직임을 기존동작과 가장 유사하도록 최적화 하는 방법이다. 동작의 최적화를 위해 기존 동작과 단순화 된 동작 간의 오차를 측정하는 방법론을 제시하고, 최적화 문제를 빠르게 풀기 위해 동작 간 오차 식을 선형시스템으로 재구성한다. 본 논문에 제시한 동작 단순화 방법은 동작편집 또는 군중 애니메이션의 성능향상 둥 캐릭터 애니메이션의 여러 분야에 유용하게 활용 될 수 있다.

• 산업융합연구
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• 제17권4호
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• pp.131-137
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• 2019

전통적으로 예상 전송 시간 메트릭을 라우팅으로 사용하는 인프라스트럭처 무선 메쉬 네트워크는 모바일 유저에게 심각한 지연을 발생한다. 캐시를 갖는 메쉬 라우터를 통해 성능 향상을 기대할 수 있지만, 콘텐츠 인기도, 캐시 비용 및 다운로드 지연을 고려한 캐싱 할당 기법에 대한 연구는 부족하다. 이러한 문제점을 해결하고자 모바일 유저 수의 증가에 따라 성능을 극대화할 수 있는 최적화 기반 사용자 중심의 캐싱 기법을 제안한다. 또한 메타 휴리스틱 기법인 유전 알고리즘 (일정 교차/변이)을 적용하여 예상 지연 시간을 줄이며 캐시 적중률에 만족하는 최적의 모바일 유저 수를 찾는다. 이는 인프라스트럭처 무선 메쉬 네트워크를 운영하는 통신 사업자가 다양한 캐싱 비용, 라우터 속도, 콘텐츠 인기도를 고려한 목표 캐시 적중률을 만족할 뿐만 아니라 성능 향상을 기대할 수 있다.

• 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.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.111-118
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• 2004

For the precise analysis of high velocity impact problem though FEM with element erosive method, the adequate mesh size and critical equivalent plastic strain(EQPS) is chosen prior to the simulation. In this research, it is strongly required from a standpoint that critical EQPS is used to decide whether perforation occurs or not. The optimization of dual armor plate consisting of 4340 steel and 2024 aluminium against a die steel sphere with high-velocity has been suggested using Lagrangian explicit time-integration code, NET2D. The response surface method based on the design of experiment is utilized for the size optimization. The optimized thickness of each layer, in which perforation does not occur, the strength of multi-layer is maximized and total weight is minimized, is obtained at a constant velocity of a pellet with a designated total thickness.

• Journal of Power Electronics
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• 제18권4호
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• pp.1037-1050
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• 2018

This paper presents a novel reconfigurable selective harmonic elimination technique to control harmonics over a wide range of Modulation Indexes (MI) in Multi-Level Inverter (MLI). In the proposed method, the region of the MI is divided into various sectors and expressions are formulated with different switching patterns for each of the sectors. A memetic BBO-MAS (Biogeography Based Optimization - Mesh Adaptive direct Search) optimization algorithm is proposed for solving the Selective Harmonic Elimination - Pulse Width Modulation (SHE-PWM) technique. An experimental prototype is developed using a Field Programmable Gate Array (FPGA) and their FFT spectrums are analyzed over a wide range of MI using a fluke power logger. Simulation and experimental results have validated the performance of the proposed optimization algorithms and the reconfigurable SHE-PWM technique. Further, the sensitivity of the harmonics has been analyzed considering non-integer variations in the magnitude of the input DC sources.