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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    International journal of flexible manufacturing systems 6 (1994), S. 5-31 
    ISSN: 1572-9370
    Keywords: printed circuit board assembly ; surface mount technology ; quadratic integer programming ; dynamic programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Populating printed circuit boards is one of the most costly and time-consuming steps in electronics assembly. At the beginning of each work order, three decisions are required: (1) a sequence must be specified for placing the individual components on the board; (2) tape reels must be assigned to positions on the magazine rack; and (3) a retrieval plan must be determined should the same component type be assigned to more than one magazine slot. Collectively, these problems can be modeled as a nonlinear integer program. In this paper, we develop a series of algorithms for solving each using an iterative two step approach. Initially, a placement sequence is generated with a weighted, nearest neighbor traveling salesman problem (TSP) heuristic; the two remaining problems are then formulated as a quadratic integer program and solved with a Lagrangian relaxation scheme. As a final step, the current magazine assignments are used to update the placement sequence, and the entire process is repeated. Our ability to deal, at least in part, with simultaneous machine operations represents the major contribution of this work. The methodology was simulated for a set of boards obtained from Texas Instruments and theoretically compared with a heuristic currently in use.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Annals of operations research 34 (1992), S. 149-162 
    ISSN: 1572-9338
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract The bilevel programming problem (BLPP) is a two-person nonzero sum game in which play is sequential and cooperation is not permitted. In this paper, we examine a class of BLPPs where the leader controls a set of continuous and discrete variables and tries to minimize a convex nonlinear objective function. The follower's objective function is a convex quadratic in a continuous decision space. All constraints are assumed to be linear. A branch and bound algorithm is developed that finds global optima. The main purpose of this paper is to identify efficient branching rules, and to determine the computational burden of the numeric procedures. Extensive test results are reported. We close by showing that it is not readily possible to extend the algorithm to the more general case involving integer follower variables.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of heuristics 5 (1999), S. 53-70 
    ISSN: 1572-9397
    Keywords: flow shop scheduling ; sequence-dependent setup times ; heuristics ; traveling salesman problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper presents an enhanced heuristic for minimizing the makespan of the flow shop scheduling problem with sequence-dependent setup times. The procedure transforms an instance of the problem into an instance of the traveling salesman problem by introducing a cost function that penalizes for both large setup times and bad fitness of schedule. This hybrid cost function is an improvement over earlier approaches that penalized for setup times only, ignoring the flow shop aspect of the problem. To establish good parameter values, each component of the heuristic was evaluated computationally over a wide range of problem instances. In the testing stage, an experimental comparison with a greedy randomized adaptive search procedure revealed the conditions and data attributes where the proposed procedure works best.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of flexible manufacturing systems 9 (1997), S. 251-272 
    ISSN: 1572-9370
    Keywords: approximation ; assembly lines ; NP-completeness ; product sequencing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Mixed-model assembly lines are becoming increasingly interesting as the use of just-in-time principles in manufacturing continues to expand. This paper presents, for the first time, complexity results for the underlying problem of product sequencing. It is shown that the problem is intractable for both the single station and the multiple station case. Nevertheless, efficient 1.5-approximation algorithms are developed for the early- and late-start models associated with the former case. Empirical results demonstrate that these algorithms perform extremely well in practice.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    IIE transactions 32 (2000), S. 181-193 
    ISSN: 1573-9724
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper, the irregular operations problem is approached for the first time in a way that allows an airline to provide for schedule recovery with minimal deviations from the original aircraft routings. A network model with side constraints is presented in which delays and cancellations are used to deal with aircraft shortages in a way that ensures a significant portion of the original aircraft routings remain intact. The model is flexible, allowing user preferences in the objective, and thereby reflecting the immediate concerns of the decision-maker in the recovery schedule. The model can be tailored by airline operations personnel to emphasize differing solution characteristics. Fleet data provided by Continental Airlines are used to demonstrate the approach. Extensive testing indicates that optimal or near-optimal solutions are routinely obtained from the LP relaxation of the network formulation. When integrality is not achieved, a rounding heuristic is provided that finds feasible solutions within a small fraction of the optimum.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of combinatorial optimization 1 (1997), S. 211-228 
    ISSN: 1573-2886
    Keywords: GRASP ; airline scheduling ; real-time control ; irregular operations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper presents a greedy randomized adaptive search procedure (GRASP) to reconstruct aircraft routings in response to groundings and delays experienced over the course of the day. Whenever the schedule is disrupted, the immediate objective of the airlines is to minimize the cost of reassigning aircraft to flights taking into account available resources and other system constraints. Associated costs are measured by flight delays and cancellations. In the procedure, the neighbors of an incumbent solution are generated and evaluated, and the most desirable are placed on a restricted candidate list. One is selected randomly and becomes the incumbent. The heuristic is polynomial with respect to the number of flights and aircraft. This is reflected in our computational experience with data provided by Continental Airlines. Empirical results demonstrate the ability of the GRASP to quickly explore a wide range of scenarios and, in most cases, to produce an optimal or near-optimal solution.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of global optimization 3 (1993), S. 289-309 
    ISSN: 1573-2916
    Keywords: Single machine scheduling ; dynamic programming ; greedy heuristics ; bicriteria optimization ; branch and bound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper considers the problem of schedulingn jobs on a single machine to minimize the total cost incurred by their respective flow time and earliness penalties. It is assumed that each job has a due date that must be met, and that preemptions are not allowed. The problem is formulated as a dynamic program (DP) and solved with a reaching algorithm that exploits a series of dominance properties and efficiently generated bounds. A major factor underlying the effectiveness of the approach is the use of a greedy randomized adaptive search procedure (GRASP) to construct high quality feasible solutions. These solutions serve as upper bounds on the optimum, and permit a predominant portion of the state space to be fathomed during the DP recursion. To evaluate the performance of the algorithm, an experimental design involving over 240 randomly generated problems was followed. The test results indicate that problems with up to 30 jobs can be readily solved on a microcomputer in less than 12 minutes. This represents a significant improvement over previously reported results for both dynamic programming and mixed integer linear programming approaches.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical programming 40 (1988), S. 15-27 
    ISSN: 1436-4646
    Keywords: Bilevel programming ; Stackelberg games ; branch and bound ; active set strategy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper a model for a two-level planning problem is presented in the form of a static Stackelberg game. By assumption, play is sequential and noncooperative; however, the leader can influence the actions of the followers through a set of coordination variables while the followers' responses may partly determine the leader's payoff. Under certain convexity assumptions, it is shown that the feasible region induced by the leader is continuous in the original problem variables. This observation, coupled with two corollary results, are used as a basis for a hybrid algorithm which clings to the inducible region until a local optimum is found. A branching scheme is then employed to located other segments of the region, eventually terminating with the global optimum. A number of examples are given to highlight the results, while the algorithm's performance is tested in a comparison with two other procedures.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    IIE transactions 30 (1998), S. 821-834 
    ISSN: 1573-9724
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An important aspect of the vehicle routing problem (VRP) that has been largely overlooked is the use of satellite facilities to replenish vehicles during a route. When possible, satellite replenishment allows the drivers to continue making deliveries until the close of their shift without necessarily returning to the central depot. This situation arises primarily in the distribution of fuels and certain retail items. When demand is random, optimizing customer routes a priori may result in significant additional costs for a particular realization of demand. Satellite facilities are one way of safeguarding against unexpected demand. This paper presents a branch and cut methodology for solving the VRP with satellite facilities subject to capacity and route time constraints. We begin with a mixed-integer linear programming formulation and then describe a series of valid inequalities that can be used to cut off solutions to the linear programming relaxation. Several separation heuristics are then outlined that are used to generate the cuts. Embedded in the methodology is a VRP heuristic for finding good feasible solutions at each stage of the computations. Results are presented for a set of problems derived from our experience with a leading propane distributor.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    IIE transactions 31 (1999), S. 721-731 
    ISSN: 1573-9724
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper presents a branch-and-bound enumeration scheme for the makespan minimization of the permutation flow shop scheduling problem with sequence-dependent setup times. The algorithm includes the implementation of both lower and upper bounding procedures, a dominance elimination criterion, and special features such as a partial enumeration strategy. A computational evaluation of the overall scheme demonstrates the effectiveness of each component. Test results are provided for a wide range of problem instances.
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