• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2000.04a
• /
• pp.613-616
• /
• 2000

This paper considers the problem of subway crew scheduling. Crew scheduling is concerned with finding a minimum number of assignments of crews to a given timetable satisfying various restrictions. Traditionally, crew scheduling problem has been formulated as a set covering or set partitioning problem possessing exponentially many variables, but even the LP relaxation of the problem is hard to solve due to the exponential number of variables. In this paper, we propose two basic techniques that solve the problem in a reasonable time, though the optimality of the solution is not guaranteed. To reduce the number of variables, we adopt column-generation technique. We could develop an algorithm that solves column-generation problem in polynomial time. In addition, the integrality of the solution is accomplished by variable-fixing technique. Computational results show column-generation makes the problem of treatable size, and variable fixing enables us to solve LP relaxation in shorter time without a considerable increase in the optimal value. Finally, we were able to obtain an integer optimal solution of a real instance within a reasonable time.

• International conference on construction engineering and project management
• /
• 2015.10a
• /
• pp.114-116
• /
• 2015

This paper presents a Stochastic Time-Cost Tradeoff analysis system (STCT) that identifies optimal construction methods for activities, hence reducing the project completion time and cost simultaneously. It makes use of schedule information obtained from critical path method (CPM), applies alternative construction methods data obtained from estimators to respective activities, computes an optimal set of genetic algorithm (GA) parameters, executes simulation based GA experiments, and identifies near optimal solution(s). A test case verifies the usability of STCT.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.31A no.3
• /
• pp.77-86
• /
• 1994

A New environment SENSATION for circuit optimization and statistical analysis has been developed. It provides real time simulation and includes automatic algorithms to assist for reaching optimal solution. Furthermore, statistical analysis environment is presented which aids in Monte Carlo analysis. worst case corner analysis, and sensitivity analysis. These capabilities faciliate the characterization of the effects of several operating conditions and manufacture process paramenters on the design performances. We verify that the proposed methods can obtain the optimal solution of the objective function through several experimental results.

• Communications for Statistical Applications and Methods
• /
• v.7 no.1
• /
• pp.357-370
• /
• 2000

This study has adapted a genetic algorithm for an optimal design for the first time. the models that was used a simulation are the first and second order response surfaces model, Using an genetic algorithm in D-opimal it is more efficient than previous algorithms to get an object function. Not like other algorithm without any restrictions like troublesome about the initial solution not falling into a local optimal solution it's the most suitable algorithm.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.23 no.2
• /
• pp.83-101
• /
• 1998

Assembly U-lines are increasingly accepted in industry, especially just-in-time production systems, for the efficient utilization of workforce. In this paper, we present an integer programming formulation and a branch-and-bound method for balancing the U-line with the objective of minimizing the number of workstations with a fixed cycle time. In the mathematical model, we provide the method that can reduce the number of variables and constraints. The proposed branch-and-bound method searches the optimal solution based on a depth-first-search. To efficiently search for the optimal solutions to the problems, an assignment rule is used in the method. Bounding strategies and dominance rules are also utilized. Some problems require a large amount of computation time to find the optimal solutions. For this reason. some heuristic fathoming rules are also proposed. Extensive experiments with test-bed problems in the literature are carried out to show the performance of the proposed method. The computational results show that our method is promising in solution quality.

• Journal of the military operations research society of Korea
• /
• v.24 no.2
• /
• pp.117-129
• /
• 1998

This study is concerned with developing a heuristic for a web-based vehicle routing problem using mixed genetic algorithm(VRPMGA) which determines each vehicle route in order to minimize the transportation costs, subject to meeting the demands of all delivery points. VRP is known to be NP-hard, and it needs a lot of computing time to get the optimal solution, so that heuristics are more frequently developed than optimal algorithms. This study aims to develop a mixed genetic algorithm by partitioned strategy which can give a good solution in comparatively brief time. The good features of the VRPMGA are, fristly, the ability of early convergence and, secondly, the capability of producing multiple, alternative, and near-optimal solutions. The VRPMGA is a useful algorithm that can be appliable to VRP and TSP. Finally, the computational test were performed using the benchmark problems and the proposed heuristic is compared with the other existing algorithms (COSA). The result of computational tests shows that proposed heuristic gives good solutions, in much shorter time, which are same as the best known solutions in the pervious research.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.36 no.8
• /
• pp.529-538
• /
• 1987

The time optimal position control scheme based on the Pontryagin's minimum principle is proposed in the current source inverter(CSI) fed induction motor system. The field oriented induction motor system is modelled with a second order plant and a switching curve is obtained by solving Hamiltonian equation. The validity of time optimal control solution has been verified by experimental tests carried out with a prototype MC68000 based microcomputer system, and 5Hp induction motor. Experimental results are in a close agreement with those the digital simulation ones.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.26 no.10
• /
• pp.1471-1478
• /
• 1989

The optimal-time control of the coordinated motion of two robot manipulators may be of consequence in the industrial automation. In this paper two robot manipulators garsping a common object are assumed to travel a specified Cartesian path and the method how to derive the optimal-time solution is explained. This approach is based on parameterizing the corresponding patn and utilizing the phase-plame technique in the trajectory planning. Also the torques supplied by the actuators are assumed to have some constant bounds. The effectiveness of this approach is demonstrated by a computer simulation using a PUMA 560 manipulator.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.22 no.52
• /
• pp.109-116
• /
• 1999

Flow Shop with Multiple Processors(FSMP) scheduling involves sequencing jobs in a flow shop where, at any processing stage, there exists one or more identical processors. Any methodology to determine the optimal mean flow time for this type of problem is NP-complete. This necessitates the use of sub-optimal heuristic methods to address problems of moderate to large scale. This paper presents global lower bounds on FSMP mean flow time problems which may be used to assess the quality of heuristic solutions when the optimal solution is unknown.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.92.2-92
• /
• 2001

This paper presents the time optimal reorientation solution of three-axis spacecraft which has only three magnetic torquers. It has been very difficult problem because the magnetic torquer generates only perpendicular to Earth magnetic field vector. In this paper, minimum-time solution using only magnetic torquer is solved using collocation method and nonlinear programming solver NPSOL. IGRF Earth magnetic field model used to simulate magnetic field. The result is verified by comparing to the result of numerical integration. The solution is obtained for the various reorientation maneuver of three axes rigid spacecraft. And the results show that all three axes of rigid spacecraft are controlled effectively only by magnetic torqure.