摘要:

To keep abreast of the ever-tightening robustness standards of communication services, we consider the topological design of the two-level network where a sufficient level of structural redundancy is imposed: the embedded backbone subnet is fully meshed and each user node is connected to two different backbone nodes. This complicated design problem for the dual homing full-mesh network is formulated as a 0-1 integer problem so that the key structural characteristics of the single homing network design model are carried over. By applying the usual dual-based solution procedure, we develop ours, which consists of three dual and one primal subprocedures. The computational experiments conducted with a variety of test problems illustrate the effectiveness of the proposed solution approach.

ISSN:0740-817X    

DOI:10.1080/07408179508936771

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In this paper we study lot-sizing and changeover decisions in production schedules that are implemented on a rolling-horizon basis. The study is carried out by comparing production schedules for the packaging operations of a pharmaceutical company that produces various products on several capacitated production lines. The schedules are obtained by solving a mixed-integer programming formulation by using a heuristic procedure. We examine the effects of the number of periods in the planning horizon, the starting inventory and the demand fluctuation on the schedules. We show empirically that the saving in annual production cost diminishes rapidly as more demand periods are added to the planning horizon. Computational results are reported.

ISSN:0740-817X    

DOI:10.1080/07408179508936772

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In this paper, research on the resource-constrained project scheduling problem is classified according to specified objectives and constraints. Each classified area is extensively surveyed, and special emphasis is given to trends in recent research. Specific papers involving nonrenewable resource constraints and time/cost-based objectives are discussed in detail because they present models that are close representations of real-world problems. The difficulty of solving such complex models by optimization techniques is noted. For the purposes of this survey, a set of 78 optimally solved test problems from the literature and a second set of 110 benchmark problems have been subjected to analysis with some well-known dispatching rules and a scheduling algorithm that consists of a decision-making process utilizing the problem constraints as a base of selection. The computational results are reported and discussed in the text. Constructive scheduling algorithms that are directly based on the problem constraints and whose performances are independent of problem characteristics are identified as a promising area for future research.

ISSN:0740-817X    

DOI:10.1080/07408179508936773

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper examines scheduling problems in which individual tasks require several resources concurrently. We analyze the situation where, in addition to the need to schedule resources concurrently, it is possible to choose the batch sizes of the tasks. Although such situations arise in both manufacturing and service firms, the likely application of these results will be to repetitive batch manufacturing situations. Several formulations for this problem are presented. Both a lagrangian relaxation and a surrogate relaxation are developed. Heuristics based on these relaxations as well as extensive computational experiments are discussed. The simultaneous resource scheduling problem without batching is quite difficult because jobs need to be synchronized so that individual jobs can capture their required simultaneous resources. Nevertheless, if batch size is introduced as an additional variable, we show that the resulting problem is in some sense easier because of the added flexibility provided by the ability to adjust production batch sizes, which allows us to eliminate ‘gaps’ in the schedule.

ISSN:0740-817X    

DOI:10.1080/07408179508936774

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A real-time algorithm is developed for scheduling single-part-type production lines with work-in-process inventory buffers. We consider three classes of activities: operations, failures and repairs, and starvation and blockage. The scheduling objectives are to keep the actual production close to the demand, the work-in-process (WIP) inventory level low, and the cycle time short. A three-level hierardhical controller is constructed to regulate the production. At the top level, we determine the desirable buffer sizes and the target production level for each operation. At the middle level is a production flow rate controller that recalculates the production rates whenever a machine fails or is starved or blocked. The loading times for individual parts are determined at the bottom level of the hierarchy. The production scheduling algorithm is evaluated by using computer simulations for a variety of cases. Compared with a transfer line policy, a significant improvement in system performance is observed.

ISSN:0740-817X    

DOI:10.1080/07408179508936775

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A real-time algorithm is developed for scheduling single-part-type production lines with work-in-process inventory buffers. We consider three classes of activities: operations, failures and repairs, and starvation and blockage. The scheduling objectives are to keep the actual production close to the demand, the work-in-process (WIP) inventory level low, and the cycle time short. A three-level hierardhical controller is constructed to regulate the production. At the top level, we determine the desirable buffer sizes and the target production level for each operation. At the middle level is a production flow rate controller that recalculates the production rates whenever a machine fails or is starved or blocked. The loading times for individual parts are determined at the bottom level of the hierarchy. The production scheduling algorithm is evaluated by using computer simulations for a variety of cases. Compared with a transfer line policy, a significant improvement in system performance is observed.

ISSN:0740-817X    

DOI:10.1080/07408179508936776

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Inventory clearing sales, especially in the case of highly competitive, established products, are sometimes accompanied by temporary discounts in the purchase price, to encourage customers to place orders larger than usual. This paper presents a generalized model of this temporary price discount problem in which explicit recognition is given to widely used variations (i) in the length of the grace period within which prospective buyers may place the discounted order; (ii) in the size of the order needed to qualify for the discounts; and (iii) in the portion of the order eligible for the discount.

ISSN:0740-817X    

DOI:10.1080/07408179508936777

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We consider the lot-sizing discrete problem of a single machine whose yield is uniformly distributed. We assume that the customers' demand is rigid, i.e. all demand must be satisfied. The costs involved are a setup cost paid each time a run is initiated plus a unit variable cost per unit produced. No salvage cost is associated with extra or defective units. We prove that there exists an optimal sequence of lot-sizes that is strictly increasing in the demand levels and therefore an optimal lot-size that is at least as large as the demand level. These properties have been proved in the literature only for binomial yields. We also provide an extremely simple algorithm to compute the optimal lot-sizes. Moreover, we show that the cost function is strongly robust in the lot-size: for any ϵ > 0 we develop a procedure that generates a (usually large) class of policies whose relative error is bounded by ϵ.

ISSN:0740-817X    

DOI:10.1080/07408179508936778

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In a recent paper, Hopp and Spearman (1993) presented a model to determine optimal lead-times for purchasing components where the only manufacturing operation is the final assembly. It is assumed that delivery times of the different components are normal variates. An approximate iterative solution procedure is presented that facilitates derivation of the optimal lead-times.

ISSN:0740-817X    

DOI:10.1080/07408179508936779

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper investigates a two-echelon (warehouse-retailer) inventory system with stochastic demand and a pull system of inventory allocation. We assume that ordering costs are charged at the warehouse for procuring the item from a supplier. However, the internal costs of ordering the item from the warehouse by the retailers are considered negligible. For this problem, the lower echelon uses a single critical number, an order-up-to-level policy, whereas a (s,S) inventory system is followed at the upper echelon. We develop a cost model for this problem and provide a simple algorithm for estimating the optimal policy. Simulation is used to test the accuracy of the model.

ISSN:0740-817X    

DOI:10.1080/07408179508936780

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor