• 한국국방경영분석학회지
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• 제33권2호
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• pp.31-47
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• 2007

본 연구는 엄격한 시간제약 차량경로문제에 대하여 유전자알고리즘과 휴리스틱 기법을 이용하여 최적해를 산출하는 것이다. 문제해결을 위해 수리적 모형을 구성하고, ILOG-CPLEX를 이용하여 최적해를 산출하였다. 임의 생성방법과 세이빙 휴리스틱을 적용한 초기해 생성, 실행불가능해의 교정과 유전자 알고리즘 종료 후 2-opt, Or-opt 등 해교정 및 해개선을 위한 과정이 추가된 하이브리드 유전자 알고리즘을 구축하여 엄격한 시간제약이 있는 차량경로 문제에 적용하여 솔로몬 예제와 비교하고, 제안한 알고리즘의 해공간탐색능력, 수렴성, 휴리스틱 기법의 효과를 확인하였다.

• 전자공학회논문지
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• 제50권8호
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• pp.67-75
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• 2013

OFDM (Orthogonal Frequency Division Multiplexing) 전송방식의 장점은 높은 주파수 효율, RF 간섭에 대한 강인성, 낮은 다중경로 왜곡 등을 들 수 있다. 다중 사용자 OFDM의 채널용량을 확대하기 위해서는 사용자간의 부채널과 비트할당을 위한 효율적인 알고리즘을 개발하여야 한다. 본 연구에서는 다중 사용자 OFDM 시스템에서 총전송전력을 최소화하는 부채널 및 비트 할당을 위한 0-1 정수계획법문제의 선형계획법 dual 문제의 특성을 기존의 볼록최적화기법 접근법과 비교하고 선형계획법 dual 해를 이용한 primal 휴리스틱 알고리즘을 제안한다. MQAM (M-ary Quadrature Amplitude Modulation)을 사용하고 3개의 독립적인 Rayleigh 다중 경로로 구성된 주파수 선택적 채널을 가정한 경우 MATLAB을 사용한 모의실험에서 제안된 휴리스틱 해의 성능을 기존의 MAO, ESA 휴리스틱 해 및 정수계획법 최적해와 성능을 비교하였다.

• 경영과학
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• 제23권2호
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• pp.161-174
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• 2006

In this paper, we consider a network optimization problem arising from the deployment of BcN access network. BcN convergence services requires that access networks satisfy QoS meausres. BcN services have two types of traffics : stream traffic and elastic traffic. Stream traffic uses blocking probability as a QoS measure, while elastic traffic uses delay factor as a QoS measure. Incorporating the QoS requirements, we formulate the problem as a nonlinear mixed-integer Programming model. The Proposed model seeks to find a minimum cost dimensioning solution, while satisfying the QoS requirement. We propose two local search heuristic algorithms for solving the problem, and develop a network design system that implements the developed heuristic algorithms. We demonstrate the computational efficacy of the proposed algorithm by solving a realistic network design problem.

• 산업공학
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• 제11권1호
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• pp.183-190
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• 1998

This paper is concerned with the bicriteria vehicle routing problems with time window constraints(BVRPTW). The BVRPTW is to determine the most favorable vehicle routes that minimize the total vehicle travel time and the total customer wait time which are, more often than not, conflicting. We construct a linear goal programming (GP) model for the BVRPTW and propose a heuristic algorithm to relieve a computational burden inherent to the application of the GP model. The heuristic algorithm consists of a parallel insertion method for clustering and a sequential linear goal programming procedure for routing. The results of computational experiments showed that the proposed algorithm finds successfully more favorable solutions than the Potvin an Rousseau's method that is known as a very good heuristic for the VRPs with time window constraints, through the change of target values and the decision maker's goal priority structure.

• 한국IT서비스학회지
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• 제10권1호
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• pp.117-133
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• 2011

In this paper, we present a frequency reassignment problem (FRP) arising from the reconfiguration of radio networks such as adding new base stations (BSs) and changing the number of frequencies assigned to BSs. For this problem, we develop an integer programming (IP) model that minimizes the sum of frequency reassignment cost and the cost for unsatisfied frequency demands, while avoiding interference among frequencies. To obtain tight lower bounds, we develop some valid inequalities and devise an objective function relaxation scheme. Also, we develop a simple but efficient heuristic procedure to solve large size problems. Computational results show that the developed valid inequalities are effective for improving lower bounds. Also, the proposed tabu search heuristic finds tight upper bounds with average optimality gap of 2.3%.

• 한국경영과학회지
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• 제12권2호
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• pp.36-41
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• 1987

This paper presents a heuristic algorithm for solving the simple facility location problem. Its main procedure is essentially of 'add' type, which progressively selects facilities to open according to a certain criterion derived from the analysis of the linear programming dual. Computational experience with test problem from the literature is presented.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.329-337
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• 2016

With the increasing deployment of distributed generators in the distribution system, a very large search space is required when dynamic programming (DP) is applied for the optimized dispatch schedules of voltage and reactive power controllers such as on-load tap changers, distributed generators, and shunt capacitors. This study proposes a new optimal voltage and reactive power scheduling method based on dynamic programming with a heuristic searching space reduction approach to reduce the computational burden. This algorithm is designed to determine optimum dispatch schedules based on power system day-ahead scheduling, with new control objectives that consider the reduction of active power losses and maintain the receiving power factor. In this work, to reduce the computational burden, an advanced voltage sensitivity index (AVSI) is adopted to reduce the number of load-flow calculations by estimating bus voltages. Moreover, the accumulated switching operation number up to the current stage is applied prior to the load-flow calculation module. The computational burden can be greatly reduced by using dynamic programming. Case studies were conducted using the IEEE 30-bus test systems and the simulation results indicate that the proposed method is more effective in terms of saving electric charges and improving the voltage profile than loss minimization.

• 산업공학
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• 제7권2호
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• pp.75-85
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• 1994

This paper presents a production scheduling model in a block assembly shop in shipbuilding industry. In a block assembly shop, the most important performance criterion is load leveling, which balances manpower and work area utilization through the planning horizon. The problem is formulated as a mixed-integer nonlinear programming(MINLP) problem of which objective function is to optimize load leveling. The developed MINLP problem can not be solvable due to computational complexity. The MINLP problem is decomposed into two stage mixed-integer linear programming (MILP) problems to obtain a good solution, but the decomposed MILP problems are still computationally intractable because of combinatorial complexity. Therfore, a heuristic method using linear programming is proposed to solve two stage MILP problems sequentially. The proposed heuristic generates a good production schedule within a reasonable computation time, and it is easily applicable for establishing the production schedule in a block assembly shop in shipbuilding industry.

• 산업경영시스템학회지
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• 제35권2호
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• pp.57-63
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• 2012

소프트웨어 개발에 있어서 소프트웨어를 시장에 출시하는 계획을 수립하는 것은 소프트웨어를 이루고 있는 기능들을 구현하는 데 제약이 되는 조건들(기술, 자원, 위험, 예산 등)을 만족하면서 계획된 출시기간에 이들 기능들을 할당하는 일이다. 이와 같이 소프트웨어 출시를 계획하는 것은 소프트웨어 제품라인에 대해서 고려할 때 더욱 복잡해진다. 본 연구에서는 소프트웨어 제품라인에 있어서 소프트웨어 출시 계획을 수립하기 위한 문제를 우선순위 제약하의 다수 0-1 배낭문제로 수리 모형화하고, 이를 풀기 위한 최적해법이 개발된다. 최적해법은 동적 계획법이 주가 되고, 문제의 크기를 줄이기 위하여 휴리스틱과 축소방법이 이용된다.

• 대한산업공학회지
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• 제33권3호
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• pp.373-380
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• 2007

In this paper, we consider a new lot-sizing and scheduling problem (LSSP) that minimizes the sum of production cost, setup cost and inventory cost. Setup carry-over and overlapping as well as demand splitting are considered. Also, maximum number of setups for each time period is not limited. For this LSSP, we have formulated a mixed integer programming (MIP) model, of which the size does not increase even if we divide a time period into a number of micro time periods. Also, we have developed an efficient heuristic algorithm by combining decomposition scheme with local search procedure. Test results show that the developed heuristic algorithm finds good quality (in practice, even better) feasible solutions using far less computation time compared with the CPLEX, a competitive MIP solver.