• 전자공학회논문지B
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• 제28B권12호
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• pp.75-82
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• 1991

We proposed an optimal parallel implementation of an optimization neural network with linear increase of speedup by using multicomputer system and presented performance analysis model of the system. We extracted the temporal-and the spatial-parallelism from the optimization neural network and constructed a parallel pipeline processing model using the parallelism in order to achieve the maximum speedup and efficiency on the CSP architecture. The results of the experiments for the TSP using the Transputer system, show that the proposed system gives linear increase of speedup proportional to the size of the optimization neural network for more than 140 neurons, and we can have more than 98% of effeciency upto 16-node system.

• 물과 미래
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• 제27권3호
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• pp.135-143
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• 1994

본 논문에서는 분기형 관수로 설계방법의 모델을 제시하기 위하여 선형계획법(LP)을 도입한 설계를 연구하였다. 실제 사업지구인 전남해남군 간척사업지구의 자료를 토대로 LP 수식화에 필요한 자료를 수집하여 파이프 관경과 펌프마력설계를 최적화하였다. 연구결과 기존의 관망설계와 비교해 보았을 때 파이프 관경과 펌프마력등에서 더 경제적인 결과를 얻을 수 있었고, 수리모의모형을 사용한 기존의 설계방법보다 객관적이고 효율적인 설계가 가능했다. 이러한 결과를 바탕으로 본 논문에서 연구된 선형계획법을 이용한 분기형 관망설게의 모형이 실무에서도 효율적으로 적용될 수 있음을 알 수 있었다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권2호
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• pp.53-59
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• 2005

In this paper, optimum shape design of permanent magnet in slotted type Permanent Magnet Linear Synchronous Motor(PMLSM) is progressed for minimization of detent force owing to structure of slot-teeth and thrust ripple by harmonic magnetic flux of permanent magnet. In order to reduce remodeling time as changing design parameter for Permanent Magnet shape optimization, the moving model node technique was applied. The characteristics of thrust and detent force computed by finite element analysis are acquired equal effect both skewed basic model and optimum model which is optimization of permanent magnet shape. In addition to, thrust per unit volume is improved 4.l2[%] in optimum model.

• 대한토목학회논문집
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• 제5권4호
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• pp.57-64
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• 1985

유출 특성이 정상이라는 가정하에 침투능식의 매개 변수들을 추정하기 위해 다음의 절차를 고안하였다 : (1) 최적화기법에 의하여 유출모형의 제 매개변수를 추정한다. (2) 추정된 매개 변수들이 정상이라는 가정하의 기간 동안에 발생한 호우들에 대해 적합성을 보이도록 유효우량을 제어한다. (3) (1)~(2)의 절차를 반복하여 모든 매개 변수들이 평형상태에이르면 최적 제어된 손실우량을 수식으로 표현하기 위하여 비선형 fitting 을 적용한다. 이때 손실우량은 강우심도를 반영하도록 한다. 횡성 유역의 연속된 3개의 호우에 대해 위 기법을 적용한 결과, 선정된 얼개와 고안된 절차는 관측치에 충분한 적합성을 보였고 과거 연구와도 비교하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.216-221
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• 2008

Shape design optimization for linear elasticity problem is performed using isogeometric analysis method. In many design optimization problems for real engineering models, initial raw data usually comes from CAD modeler. Then designer should convert this CAD data into finite element mesh data because conventional design optimization tools are generally based on finite element analysis. During this conversion there is some numerical error due to a geometry approximation, which causes accuracy problems in not only response analysis but also design sensitivity analysis. As a remedy of this phenomenon, the isogeometric analysis method is one of the promising approaches of shape design optimization. The main idea of isogeometric analysis is that the basis functions used in analysis is exactly same as ones which represent the geometry, and this geometrically exact model can be used shape sensitivity analysis and design optimization as well. In shape design sensitivity point of view, precise shape sensitivity is very essential for gradient-based optimization. In conventional finite element based optimization, higher order information such as normal vector and curvature term is inaccurate or even missing due to the use of linear interpolation functions. On the other hands, B-spline basis functions have sufficient continuity and their derivatives are smooth enough. Therefore normal vector and curvature terms can be exactly evaluated, which eventually yields precise optimal shapes. In this article, isogeometric analysis method is utilized for the shape design optimization. By virtue of B-spline basis function, an exact geometry can be handled without finite element meshes. Moreover, initial CAD data are used throughout the optimization process, including response analysis, shape sensitivity analysis, design parameterization and shape optimization, without subsequent communication with CAD description.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1512-1519
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• 2002

Most of mechanical failures are caused by repeated loadings and therefore they are strongly related to fatigue. To avoid the failures caused by fatigue, determination of an optimal shape of a structure is one of the very important factors in the initial design stage. Shape optimization fer two types of specimens, which are very typical ones in opening mode in fracture mechanics, was accomplished by the linear elastic fracture mechanics and the growth-strain method in this study. Also shape optimization for a cantilever beam in mixed mode was carried out by the same techniques. The linear elastic fracture mechanics was used to estimate stress intensity factors and fatigue lives. And the growth-strain method was used to optimize the shape of the initial shape of the specimens. From the results of the shape optimization, it was found that shapes of two types of specimens and a cantilever beam optimized by the growth-strain method prolong their fatigue lives significantly. Therefore, it was verified that the growth-strain method is an appropriate technique for shape optimization of a structure having a crack.

• Nuclear Engineering and Technology
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• 제33권5호
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• pp.547-555
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• 2001

In pressurized light water reactor fuel assembly, spacer grids support nuclear fuel rods both laterally and vertically. The fuel rods are supported by spacer grid springs and grid dimples that are located in the grid cell. The support system allows for some thermal expansion and imbalance of the fuel rods. The imbalance is absorbed by elastic energy to prevent coolant flow- induced vibration damage. Design requirements are defined and a design process is established. The design process includes mathematical optimization as well as practical design method. The shape of the grid spring is designed to maintain its function during the lifetime of the fuel assembly. A structural optimization method is employed for the shape design. Since the optimization is carried out in the linear range of finite element analysis, the optimum solution is verified by nonlinear analysis. A good design is found and the final design is compared with the initial conceptual design. Commercial codes are utilized for structural analysis and optimization.

• Structural Engineering and Mechanics
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• 제7권1호
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• pp.19-33
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• 1999

The critical buckling loads of unsymmetrically laminated rectangular plates with a given material system and subjected to combined lateral and inplane loads are maximized with respect to fiber orientations by using a sequential linear programming method together with a simple move-limit strategy. Significant influence of plate aspect ratios, central circular cutouts, lateral loads and end conditions on the optimal fiber orientations and the associated optimal buckling loads of unsymmetrically laminated plates has been shown through this investigation.

• 대한산업공학회지
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• 제17권2호
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• pp.131-142
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• 1991

The concept of criterion function is proposed as a framework for comparing the geometric and computational characteristics of various nonlinear programming approaches to linear programming such as the method of centers, Karmakar's algorithm and the gravitational method. Also, we discuss various computational issues involved in obtaining an efficient parallel implementation of these methods. Clearly, the most time consuming part in solving a linear programming problem is the direction finding procedure, where we obtain an improving direction. In most cases, finding an improving direction is equivalent to solving a simple optimization problem defined at the current feasible solution. Again, this simple optimization problem can be seen as a least squares problem, and the computational effort in solving the least squares problem is, in fact, same as the effort as in solving a system of linear equations. Hence, getting a solution to a system of linear equations fast is very important in solving a linear programming problem efficiently. For solving system of linear equations on parallel computing machines, an iterative method seems more adequate than direct methods. Therefore, we propose one possible strategy for getting an efficient parallel implementation of an iterative method for solving a system of equations and present the summary of computational experiment performed on transputer based parallel computing board installed on IBM PC.

• 제어로봇시스템학회논문지
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• 제13권11호
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• pp.1048-1052
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• 2007

This paper presents a rank-constrained linear matrix inequality(LMI) approach to simultaneous linear-quadratic(LQ) optimal control by static output feedback. Simultaneous LQ optimal control is formulated as an LMI optimization problem with a nonconvex rank condition. An iterative penalty method recently developed is applied to solve this rank-constrained LMI optimization problem. Numerical experiments are performed to illustrate the proposed method, and the results are compared with those of previous work.