• Journal of Korean Institute of Industrial Engineers
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• v.22 no.3
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• pp.325-336
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• 1996

This study is concerned with developing a heuristic for the vehicle routing problem(VRP) which determines each vehicle route in order to minimize the transportation costs, subject to meeting the demands of all delivery points. VRP is known 10 be NP-hard, and it needs a lot of computing time to get the optimal solution, so that heuristic are more frequently developed than optimal algorithms. This study aims to develop a heuristic which can give a good solution in comparatively brief time. Finally, the computational tests were performed using the benchmark problems and the proposed heuristic is compared with the other existing algorithms. The result of computational tests shows that the proposed heuristic gives good solutions, in much shorter time, which are not 1% more expensive than the best known solutions, which are same as the best known solutions in the previous researches.

• Industrial Engineering and Management Systems
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• v.8 no.1
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• pp.29-36
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• 2009

We present two local-search based metaheuristics for the multi-source capacitated facility location problem. In such a problem, each customer's demand can be supplied by one or more facilities. The problem is NP-hard and the number of locations in the optimal solution is unknown. To keep the search process effective, the proposed methods adopt the following features: (1) a multi-exchange neighborhood structure, (2) a tabu list that keeps track of recently visited solutions, and (3) a multi-start to enhance the diversified search paths. The transportation simplex method is applied in an efficient manner to obtain the optimal solutions to neighbors of the current solution under the algorithm framework. Two in-and-out selection rules are also proposed in the algorithms with the purpose of finding promising solutions in a short computational time. Our computational results for some of the benchmark instances, as well as some instances generated using a method in the literature, have demonstrated the effectiveness of this approach.

• IE interfaces
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• v.17 no.spc
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• pp.97-102
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• 2004

AGV flowpath layout design is one of the most important steps for efficient AGV systems design. Since it was formulated by Gaskins & Tanchoco (1987), a unidirectional AGV flowpath layout design problem has been tackled by many researchers. However, the solution methods were traded off between the solution quality and the computational time. In this paper, a tabu search technique is applied to obtain a good solution for a relatively large problem in reasonable computational time. Specifically, fast construction algorithm for feasible initial solutions, long-term memory structure and neighbor solutions generation are adapted to the problem characteristics and embedded in the tabu search algorithm. Also, sets of computational experiments show that the proposed tabu search algorithm outperforms to the Ko and Egbelu's algorithm (2003).

• Industrial Engineering and Management Systems
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• v.14 no.1
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• pp.11-21
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• 2015

The purpose of this research is to develop algorithms using the Differential Evolution Algorithm (DE) to solve a multi-objective, sources and stages location-allocation problem. The development process starts from the design of a standard DE, then modifies the recombination process of the DE in order improve the efficiency of the standard DE. The modified algorithm is called modified DE. The proposed algorithms have been tested with one real case study (large size problem) and 2 randomly selected data sets (small and medium size problems). The computational results show that the modified DE gives better solutions and uses less computational time than the standard DE. The proposed heuristics can find solutions 0 to 3.56% different from the optimal solution in small test instances, while differences are 1.4-3.5% higher than that of the lower bound generated by optimization software in medium and large test instances, while using more than 99% less computational time than the optimization software.

• Journal of Welding and Joining
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• v.8 no.2
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• pp.53-57
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• 1990

Analytic solutions of heat conduction during welding which were first found by Resenthal have some restrictions. One of these is that models to which analytic solutions can be applied must have simple geometric shape, and another is that quasi-stationary state must be created. On the other hand, computational methods developed recently with the aid of the computer can overcome these shortcomings, but the methods raise problems from economic point of view when they are applied to 3 dimensional problems. Taking account of these problems, a new method combinig the analytic method with the computational one is proposed. This method can be ued in weldments with complicated geometric shape in non-stationary state, but with the aid of the analytic method can reduce the computing time.

• Computational Structural Engineering
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• v.7 no.2
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• pp.69-75
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• 1994

The procedure for the stress and displacement analysis of realistic viscoelastic materials by time domain boundary element method(BEM) has been discussed. The fundamental solutions and stress kernels have been obtained using the elastic-viscoelastic correspondence principle. The relaxation function is expanded in a sum of exponentials and the transformed fundamental solutions and stress kernels are inverted numerically into real time space. The proposed procedure requires a small computational effort and it is applicable in time domain boundary element analysis of realistic viscoelastic problems. Numerical results of example problem show the effectiveness and applicability of the proposed method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.53-60
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• 2001

Meshfree methods have been attracting issue as computational methods during past a few years. Nowadays, various meshfree methods such as EFGM, RKPM h-p cloud method and etc. were developed and applied in engineering problems. But, most of them were not truly meshless method because background mesh of cell was required for the spatial integration of a weak form. A nodal integration is required for truly meshless methods but it is known that this method gives a little unstable and incorrect solutions. In this paper, an improvement scheme of the existed nodal integration which the weak form can be simply integrated without any stabilization term is proposed. Numerical tests show that the proposed method is more convenient and gives more correct solutions than the previous method.

• Korean Journal of Computational Design and Engineering
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• v.6 no.3
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• pp.174-183
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• 2001

This study proposes an improved genetic algorithm (GA) to derive solutions for facility layout problems having inner walls and passages. The proposed algorithm models the layout of facilities on a flour-segmented chromosome. Improved solutions are produced by employing genetic operations known as selection, crossover, inversion, mutation, and refinement of these genes for successive generations. All relationships between the facilities and passages are represented as an adjacency graph. The shortest path and distance between two facilities are calculated using Dijkstra's algorithm of graph theory. Comparative testing shows that the proposed algorithm performs better than other existing algorithm for the optimal facility layout design. Finally, the proposed algorithm is applied to ship compartment layout problems with the computational results compared to an actual ship compartment layout.

• Journal of applied mathematics & informatics
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• v.25 no.1_2
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• pp.353-361
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• 2007

In this paper, we prove the existence of multiple solutions for Neumann and periodic problems. Our main tools are recent general multiplicity theorems proposed by B. Ricceri.

• Journal of applied mathematics & informatics
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• v.33 no.5_6
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• pp.531-543
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• 2015

We determine interval of two eigenvalues for which there existence and nonexistence of positive solution for a system of even-order dynamic equation on time scales subject to Sturm-Liouville boundary conditions.