• Journal of Korean Institute of Industrial Engineers
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• v.27 no.4
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• pp.406-412
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• 2001

IP address lookup is to determine the next hop destination of an incoming packet in the router. The address lookup is a major bottleneck in high performance router due to the increased routing table sizes, increased traffic, higher speed links, and the migration to 128 bits IPv6 addresses. IP lookup time is dependent on data structure of lookup table and search scheme. In this paper, we propose a new approach to build a lookup table that satisfies the memory constraint. The design of lookup table is formulated as an optimization problem. The objective is to minimize average depth from the root node for lookup. We assume that the frequencies with which prefixes are accessed are known and the data structure is level compressed trie with branching factor $\kappa$ at the root and binary at all other nodes. Thus, the problem is to determine the branching factor k at the root node such that the average depth is minimized. A heuristic procedure is proposed to solve the problem. Experimental results show that the lookup table based on the proposed heuristic has better average and the worst-case depth for lookup.

• Journal of Information Technology Applications and Management
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• v.12 no.1
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• pp.49-68
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• 2005

It is one of the crucial components of electronic logistics systems to manage logistics information of cargos and transportation companies and to mediate appropriate brokerage between them. Due to the advance of e-Commerce technologies many kinds of logistics transactions can be handled by means of EDI or XML/EDI applications. but the brokering processing relies mostly on the traditional processes and the research in this field is still at the initial stage. In this paper we study a logistics brokering system for ships and cargos and describe the design and implementation of the system. We analyze the brokering constraints for logistics of cargos and ships and construct an optimization model for their brokering. We also suggest a brokering procedure and a simple heuristic algorithm with respect to the proposed matching criteria. The experimental result shows that the proposed greedy-based heuristic algorithm performs very well. In its response time the proposed algorithm executed within a couple of seconds independently of the number of cargos and the container capacities of ships. The output of the algorithm is very close to that of the optimal solution. showing higher than 95% of approximation. The proposed system is implemented for the Web environment using JSP and PL/SQL.

• Journal of Computational Design and Engineering
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• v.2 no.4
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• pp.253-260
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• 2015

Feature-based NC machining, which requires high quality of 3D CAD model, is widely used in machining aircraft structural part. However, there has been little research on how to automatically detect the CAD model errors. As a result, the user has to manually check the errors with great effort before NC programming. This paper proposes an automatic CAD model errors detection approach for aircraft structural part. First, the base faces are identified based on the reference directions corresponding to machining coordinate systems. Then, the CAD models are partitioned into multiple local regions based on the base faces. Finally, the CAD model error types are evaluated based on the heuristic rules. A prototype system based on CATIA has been developed to verify the effectiveness of the proposed approach.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.10a
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• pp.375-388
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• 2004

As today's business environment has become more and more competitive, forward as well as backward flows of products among members belonging to a supply chain have been increased. The backward flows of products, which are common in most industries, result from increasing amount of products that are returned, recalled, or need to be repaired. Effective management for these backward flows of products has become an important issue for businesses because of opportunities for simultaneously enhancing profitability and customer satisfaction from returned products. Since third party logistics service providers (3PLs) are playing an important role in reverse logistics operations, the 3PLs should perform two simultaneous logistics operations for a number of different clients who want to improve their logistics operations for both forward and reverse flows. In this case, distribution networks have been independently designed with respect to either forward or backward flows so far. This paper proposes a mixed integer programming model for the design of network integrating both forward and reverse logistics. Since this network design problem belongs to a class of NP-hard problems, we present an efficient heuristic based on Lagrangean relaxation and apply it to numerical examples to test the validity of proposed heuristic.

• Korean Journal of Computational Design and Engineering
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• v.15 no.1
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• pp.1-10
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• 2010

Recently, a shipyard is making every effort to efficiently manage equipments of resources such as a gantry crane, transporter, and so on. So far block lifting scheduling of a gantry crane has been manually performed by a manager of the shipyard, and thus it took much time to get scheduling results and moreover the quality of them was not optimal. To improve this, a block lifting scheduling system of the gantry crane using optimization techniques was developed in this study. First, a block lifting scheduling problem was mathematically formulated as a multi-objective optimization problem, considering the minimization of travel distance at an idle state and wire replacement during block lifting. Then, to solve the problem, a meta-heuristic optimization algorithm based on the genetic algorithm was proposed. To evaluate the efficiency and applicability of the developed system, it was applied to an actual block lifting scheduling problem of the shipyard. The result shows that blocks can be efficiently lifted by the gantry crane using the developed system, compared to manual scheduling by a manager.

• The Journal of Information Systems
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• v.25 no.1
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• pp.159-182
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• 2016

Purpose This paper aims to develop a novel tabu search algorithm for solving the sequencing problems with precedence constraints. Due to constraints, the traditional meta heuristic methods can generate infeasible solutions during search procedure, which must be carefully dealt with. On the contrary, the candidate order based tabu search (COTS) is based on a novel neighborhood structure that guarantees the feasibility of solutions, and can dealt with a wide range of sequencing problems in flexible manner. Design/methodology/approach Candidate order scheme is a strategy for constructing a feasible sequence by iteratively appending an item at a time, and it has been successfully applied to genetic algorithm. The primary benefit of the candidate order scheme is that it can effectively deal with the additional constraints of sequencing problems and always generates the feasible solutions. In this paper, the candidate order scheme is used to design the neighborhood structure, tabu list and diversification operation of tabu search. Findings The COTS has been applied to the single machine job sequencing problems, and we can see that COTS can find the good solutions whether additional constraints exist or not. Especially, the experiment results reveal that the COTS is a promising approach for solving the sequencing problems with precedence constraints. In addition, the operations of COTS are intuitive and easy to understand, and it is expected that this paper will provide useful insights into the sequencing problems to the practitioners.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11B
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• pp.663-672
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• 2007

This paper proposes an algorithm for design of a multiple ring network that can be applied to an arbitrary topology in the WDM optical transport networks. Especially, we suggest an integer linear program(ILP) formulation with the objective of minimizing the total cost of nodes based on the reconfigurable OADM(ROADM) architecture and propose a heuristic algorithm to reduce computational complexity of the exact problem formulation. To evaluate the performance and validity of this scheme, we applied it to an NSFnet topology assuming the dynamic or static traffic condition and compared it with a mesh methodology about capacity of connection requests and the total cost of the nodes.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.11a
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• pp.259-262
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• 2003

Group technology(GT) is a manufacturing philosophy which identifies and exploits the similarity of parts and processes in design and manufacturing. A specific application of GT is cellular manufacturing. the first step in the preliminary stage of cellular manufacturing system design is cell formation, generally known as a machine-part cell formation(MPCF). This paper presents and tests a grouping gentic algorithm(GGA) for solving the MPCF problem and uses the measurements of e(ficacy. GGA's replacement heuristic used similarity coefficients is presented.

• Journal of the Korean Operations Research and Management Science Society
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• v.6 no.1
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• pp.25-32
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• 1981

The optimum design problem of a proposed oil pipeline network has been formulated as a zero-one programming model to determine the optimum sizes of pipe and pump which minimize the sum of material costs and operating costs during the 20 years of life span. Applying to a real situation, the problem constitutes an assignment type zero-one programming with 372 zero-one variables and 13 constraints. A heuristic algorithm has been developed based on the modified Petersen algorithm utilizing the special form of the activity matrix. The results showed impressive cost savings of 37 percent of the total cost from the original proposal.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.4
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• pp.106-115
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• 1994

This paper presents the design of a technology mapping system for optimizing delays of combinational and synchronous sequential logic circuits. The proposed system performs delay optimization for combinational logic circuits by remapping, buffering, and gate merging methods through the correct delay calculation in which the loading values are considered. To get time optimized synchronous sequential circuits, heuristic algorithms are proposed. The proposed algorithms reallocate registers by considering the critical path characteristics. Experimental results show that the proposed system produces a more optimized technology mapping for MCNC benchmarks compared with mis-II.