Ue-Pyng Wen

Algorithms for solving the mixed integer two-level linear programming problem

Abstract Several algorithms have been developed to solve the two-level linear programming problem during the past years. In this paper, we will formulate the mixed integer two-level linear programming problem and develop both the exact and heuristic solution procedures based on the branch-and-bound technique for solving the problem. Computational experience and comparisons will be presented.

The impact of acceleration/deceleration on travel-time models for automated storage/retrieval systems

In this note we propose a travel-time model of automated storage/retrieval (S/R) machines by considering the speed profiles that exist in real-world applications. Compact forms of expected travel-times under randomized storage conditions have been determined for both single and dual command cycles.

The hybrid algorithm for solving the three-level linear programming problem

Abstract Several algorithms have been developed to solve two-level programming problem during the past years. In this paper, we will develop an algorithm for solving three-level programming problem. The hybrid algorithm is coded and used to test a group of problems. Computational experience and comparisons will be presented.

The impact of acceleration/deceleration on travel-time models in class-based automated S/R systems

The travel time models of Automated Storage and Retrieval systems (AS/RS) machines under randomized storage proposed by Chang et al. (IIE Transactions, 27(1), 108–111, 1995), which consider the speed profiles in real-world applications, are extended in this paper. In the present study, travel time models are proposed that consider various travel speeds with known acceleration and deceleration rates. Compact forms of expected travel times under the class-based storage assignment and full-turnover-based storage assignment have been determined. The results show that both the proposed exponential travel time model and the adjusted exponential model perform satisfactorily and could be useful tools for designing an AS/RS in real-world applications.

A note on a linear bilevel programming algorithm based on bicriteria programming

Abstract In this note the relationship between linear bilevel and bicriteria programming problems is clarified. This paper points out that the bicriteria programming algorithm is not suitable for all bilevel programming problems in searching for optimal solutions. A counterexample is given to demonstrate the shortcomings of the results by Unlu [1, Comput. Opns Res . 14 , 173–179 (1987)] and Bard [2, Opns Res . 31 , 670–684 (1983)]. We also propose a sufficient condition to use the bicriteria programming algorithm for solving a bilevel programming problem.

The impact on rack configuration on the speed profile of the storage and retrieval machine

The travel-time models of automated storage/retrieval machines, proposed by Chang, Wen and Lin (IIE Transactions, 27 (1), 108--111(1995)), which consider the speed profiles in real world applications, have been extended in this paper to investigate the impact on the rack configuration. The results demonstrate that the optimal rack configuration of the single-command cycle is square-in-time whereas the dual-command cycle may not be. Furthermore, the travel times for both single- and dual-command cycles are quite insensitive to the deviation in the length of the rack configuration.

Applying tabu search to spare capacity planning for network restoration

Abstract This paper employs tabu search to solve the network spare capacity planning problem. Our study involves the determination of the necessary spare capacity on each link of a network required to achieve a certain desired level of restoration at minimum cost during network failure. We have developed here a procedure based on tabu search. The computational results show that the proposed tabu search algorithm offers an effective and efficient way for handling this network restoration problem. Scope and purpose Telecommunication network plays a crucial role in modern communication. An ever increasing number of end users are completely relying on telecommunication in their business activities today. The use and integration of computers with telecommunication have created a new information era. In order to provide the much desired broadband services, high capacity transport systems are widely adopted in the transmission network. While these systems offer great economic advantages through multiplexing and sharing of transmission facilities, they also increase the vulnerability of the telecommunication services dependent on them. If a failure occurs on a high speed facility of such a network, all the related services get affected. Network survivability has, therefore, become a major concern in broadband network planning. One of the methods to improve network survivability is to keep redundant or spare capacity for Digital Cross-Connect System (DCS) to restore failed services. However, the problem of spare capacity deployment on the links of a restorable network is NP-hard, implying exponential growth in execution time with network size for an exact solution. In this paper, an algorithm based on tabu search is proposed to find an approximate optimal solution for this problem.

Algorithms for sequencing robot activities in a robot-centered parallel-processor workcell

Abstract This paper deals with the problem of sequencing robot activities for a robot-centered parallel-processor workcell where n jobs and m identical processors exist in the cell, and a robot is responsible for both loading and unloading activities. The objective of this paper is to determine the sequence of robot activities for minimizing the sum of completion times. A modified shortest processing time procedure based on the traditional shortest processing time sequencing rule in order to determine an upper bound has been proposed. A branch and bound algorithm to find an optimal sequence of robot activities has then been presented. A numerical example is illustrated and the computational results have been given.

TABU SEARCH METHODS FOR THE FLOW SHOP SEQUENCING PROBLEM

ABSTRACT The Tabu search method is currently used in research to solve a range of scheduling problems. The method achieves superior results compared to the other heuristic methods for solving the same problem. In this paper, we compare the solution procedures of the flow shop sequencing problems that have been studied in the literature based on Tabu search. We investigate the algorithms using two heuristic rules to find the starting solution and two kinds of neighborhood structures. The computational results of the different combinations demonstrate some of the desirable characteristics of the Tabu search approach.

Travel time estimation for the order picking problem in automated warehousing systems

Abstract The order picking problem is an important issue in the operation of an Automatic Storage/Retrieval System (AS/RS). An area propagation‐based model designed to estimate the expected travel time required to pick an order is presented in this paper. The estimation model of the Nearest Neighbor (NN) heuristic was derived and Monte Carlo Sampling was adopted to show the accuracy of the estimation model. The model can be applied to a carousel system with some slight modifications.