• 경영과학
• /
• 제17권2호
• /
• pp.39-54
• /
• 2000

This paper presents a causal forecasting model using guided genetic algorithm in continuous manufacturing process. The guide genetic algorithm(GGA) is an extended genetic algorithm(GA) using penalty function and population diversity index to increase forecasting accuracy. GGA adds to the canonical GA the concept of a penalty function to avoid selecting the unproductive chromosomes and to make a proper searching direction. Also, GGA modifies the current population using the similarity of chromosomes to avoid falling into the trap of local optimal solution. For investigation GGA performance, we used a set of real data that was collected in local glass melting processes, and experimental results show the proposed model results in the better forecasting accuracy than linear regression model and canonical GA.

• 한국경영과학회:학술대회논문집
• /
• 한국경영과학회 1996년도 추계학술대회발표논문집; 고려대학교, 서울; 26 Oct. 1996
• /
• pp.135-138
• /
• 1996

In solving the Travel Salesman Problem(TSP), we easily reach local optimal solutions with the existing methods such as TWO-OPT, THREE-OPT, and Lin-Kernighen. Tabu search, as a meta heuristic, is a good mechanism to get an optimal or a near optimal solution escaping from the local optimal. By utilizing AI concepts, tabu search continues to search for improved solutions. In this study, we focus on developing a new neighborhood structure that maintains the feasibility of the tours created by exchange operations in TSP. Intelligent methods are discussed, which keeps feasible tour routes even after exchanging several edges continuously. An extended tabu search model, performing cycle detection and diversification with memory structure, is applied to TSP. The model uses effectively the information gathered during the search process. Finally, the results of tabu search and simulated annealing are compared based on the TSP problems in the prior literatures.

• 한국안전학회지
• /
• 제12권3호
• /
• pp.120-131
• /
• 1997

This paper presents an approximate reanalysis methods of structures based on substructuring for an effective optimization of large-scale structural systems. In most optimal design procedures the analysis of the structure must be repeated many times. In particular, one of the main obstacles in the optimization of structural systems are involved high computational cost and expended long time in the optimization of large-scale structures. The purpose of this paper is to evaluate efficiently the structural behavior of new designs using information from previous ones, without solving basic equations for successive modification in the optimal design. The proposed reanalysis procedure is combined Taylor series expansions which is a local approximation and reduced basis method which is a global approximation based on substructuring. This technique is to choose each of the terms of Taylor series expansions as the basis vector of reduced basis method in substructuring system which is one of the most effective analysis of large -scale structures. Several numerical examples illustrate the effectiveness of the solution process.

• 대한전기학회논문지
• /
• 제40권3호
• /
• pp.243-249
• /
• 1991

Adaptive mesh refinement scheme is incorporated with the boundary element analysis in order to get accurate solution with relatively fewer unnowns for magnetostatic field analysis. A new andsimple posteriori local error estimate is also presented. The local error is defined as an integraktion over the element of the difference between solutions from quadratic interpolation functions and linear interpolation functions and is used as the criterion for mesh refinement. Case study with a singular point reveals that adaptive meshes are more efficient in accuracy of solutions than uniform meshs generated by dividing al the elements evenly. The adaptive meshes give much better rate of convergence in global errors than the uniform meshes.

• 정보처리학회논문지B
• /
• 제14B권7호
• /
• pp.523-530
• /
• 2007

본 논문에서는 자동 독순(automatic lipreading)의 인식기로 쓰이는 은닉 마르코프 모델(HMM: hidden Markov model)의 새로운 확률적 최적화 기법을 제안한다. 제안하는 기법은 전역 최적화가 가능한 확률적 기법인 모의 담금질과 지역 최적화 기법을 결합하는 것으로써, 알고리즘의 빠른 수렴과 좋은 해로의 수렴을 가능하게 한다. 제안하는 알고리즘이 전역 최적해로 수렴함을 수학적으로 보인다. 제안하는 기법을 통해 HMM을 학습함으로써 기존의 알고리즘이 지역해만을 찾는 단점을 개선함으로써 향상된 독순 성능을 나타냄을 실험으로 보인다.

• The Journal of the Acoustical Society of Korea
• /
• 제25권3E호
• /
• pp.131-136
• /
• 2006

The PML developed for the radio wave propagation is a powerful numerical domain truncation technique. We perform an analytic study on the reflection from the PML inserted in the ocean bottom. In the ocean bottom, we show the PML to have the improved performance but simultaneously the degeneration below the critical angle of the fast ocean bottom. The degeneration of the PML can be simply relaxed by stretching the thickness of the PML or putting the attenuation coefficient to the ocean bottom. As a better solution, we propose the improved truncation technique based on the PML and the non-local boundary condition. Finally, we apply the PML to the acoustic wave propagation using split-step Pade PE solver. For the problems of the ocean waveguide, the numerical efficiency of the PML is examined and the usefulness of the PML is confirmed.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2002년도 하계종합학술대회 논문집(2)
• /
• pp.109-112
• /
• 2002

This paper presents relationship between the dynamic behavior of an asynchronous linear pipeline (ALP) and the performance of the ALP as buffers are allocated. Then the relationship is used in order to characterize a local optimum situation on the buffer design space of the ALP. Using the characterization we propose an efficient algorithm optimizing buffer allocation on an ALP in order to achieve its average case performance. Without the loss of optimality, our algorithm works in linear time complexity so it achieves fast buffer-configuration optimization. This paper makes two contributions. First, it describes relationship between the performance characteristics of an ALP and a local optimum on the buffer design space of the ALP. Second, it devises a buffer allocation algorithm finding an optimum solution in linear time complexity.

• ETRI Journal
• /
• 제31권1호
• /
• pp.42-50
• /
• 2009

A new method for simulating voltage and current distributions in transmission lines is described. It gives the time domain solution of the terminal voltage and current as well as their line distributions. This is achieved by treating voltage and current distributions as distributed state variables (DSVs) and turning the transmission line equation into an ordinary differential equation. Thus the transmission line is treated like other lumped dynamic components, such as capacitors. Using backward differentiation formulae for time discretization, the DSV transmission line component is converted to a simple time domain companion model, from which its local truncation error can be derived. As the voltage and current distributions get more complicated with time, a new piecewise exponential with controllable accuracy is invented. A segmentation algorithm is also devised so that the line is dynamically bisected to guarantee that the total piecewise exponential error is a small fraction of the local truncation error. Using this approach, the user can see the line voltage and current at any point and time freely without explicitly segmenting the line before starting the simulation.

• 대한기계학회논문집
• /
• 제19권8호
• /
• pp.1982-1988
• /
• 1995

Methane/Air premixed flames are studied numerically, using a detailed chemical model, to investigate the flame strech effects on the extinction in a counterflow. The finite difference method, time integration and modified Newton iteration are used, and adaptive grid technique and grid smoothing have been employed to adjust the grid system according to the spatial steepness of the solution profiles. Results show that the flame stretch, or the conventional nondimensionalized stretch having the tangential flow characteristics of the stretched flame alone cannot adequately describes the extinction phenomena. On the other hand, the local flame stretch having both the normal and tangential flow characteristics of the stretched flame can give a proper explanation to the extinction of the symmetric planar premixed flames stabilized in a counter flow. The extinction condition were found to be a constant local stretch regardless of the equivalence ratio.

• Journal of Advanced Marine Engineering and Technology
• /
• 제19권2호
• /
• pp.10-19
• /
• 1995

Heat trnasfer for absorbing and emitting media in laminar layer along the cylinders has been analyzed. Governing equation are transformed to local nonsimilarity equations by the dimensional analysis. The effects of the Stark number, Prandtl number, Optical radius and wall emissivity are mainly investigated. For the formal solution a numerical integration is performed and the results are compared with those obtained by P-1 and P-3 approximation. The results show that boundary layers consist of conduction-convection-radiation layer near the wall and convection-radiation layer far from the wall. As the Stark number of wall emissivity increases the local radiative heat flux is increased. The Pradtl number or curvature variations do not affect the radiative heat flux from the wall, but The Prandtl number or wall emissivity variations affect the conduction heat flux. Consequently the total heat flux from the wall are affected by the Prandtl number or wall emissivity variation.