Sabah U. Randhawa

Resource-constrained project scheduling with renewable and non-renewable resources and time-resource tradeoffs

The resource-constraint project scheduling problem is modeled as a zero-one integer programming model. The model considers many important characteristics of project scheduling including activity preemption, renewable and non-renewable resources, time-resource tradeoffs, and multiple objectives. Solution algorithms are developed for three single objective problems (time minimization, cost minimization, and resource leveling) and for the preemptive goal programming model that includes time, cost and resource leveling objectives.

A multi-attribute dispatching rule for automated guided vehicle systems

This paper considers the dispatching problem associated with operations of automated guided vehicles (AGVs). A multi-attribute dispatching rule for dispatching of an AGV is developed and evaluated. The multi-attribute rule, using the additive weighting method, considers three system attributes concurrently: the remaining space in the outgoing buffer of a workstation, the distance between an idle AGV and a workstation with a job waiting for the vehicle to be serviced, and the remaining space in the input buffer of the destination workstation of a job. A neural network approach is used to obtain dynamically adjusting attribute weights based on the current status of the manufacturing system. Simulation analysis of a job shop is used to compare the multi-attribute dispatching rule with dynamically adjusting attribute weights to the same dispatching rule with fixed attribute weights and to several single attribute rules. Results show that the multi-attribute dispatching rule with the ability to adapt attribute weights to job shop operational conditions provides a better balance among the performance measures used in the study.

Factors in capital decisions involving advanced manufacturing technologies

This paper presents an integrated framework for the selection of attributes used in the evaluation of advanced manufacturing systems. The primary focus in the development of this framework is the modularity of the framework so that it is applicable to a wide range of advanced manufacturing systems with differing process configurations and technologies. Based on data collected from industry and the current body of knowledge, decision attributes were identified and ranked relatively against each other, forming a hierarchy of decision attributes. To simplify the hierarchy, making it more user‐friendly in real‐world applications, each decision attribute was also evaluated relative to the strength of its relationships to other decision attributes. Several decision attributes were found to be highly correlated with others, resulting in a new, single decision attribute. The final decision attribute hierarchy provides managers responsible for making capital decisions involving advanced manufacturing technologies with a framework for their decision making.

A Discrete-Event Object-Oriented Modeling Environment For Sawmill Simulation

The paper presents a simulation modeling environment developed for sawmill design and analysis in the forest products industry. The design facilitates flexibility in modeling different sawmill configurations and production scenarios. The system represents a library of objects developed in an object-oriented framework. These include structures required to develop simulation models, to execute discrete event simulation, and for system-user interface.

An integer programming application to solve sequencer mix problems in printed circuit board production

The production of printed circuit board in the electronics industry requires that the taped components at the insertion machines input be in a predetermined order or sequence. The sequencing operation is performed on a microcomputer-controlled sequencing machine which represents a substantial proportion of both the initial capital and direct costs. The sequencing costs are affected by two sequential decisions: sequencer mix or the size and the number of sequencers required to meet the production requirements, and the processing schedule at each sequencer. An integer programming approach is presented for determining the optimum sequencer mix and is illustrated by means of an industrial case study example.

Simulation-based design evaluation of unit load automated storage/retrieval systems

Abstract The focus of this paper is unit load automated storage/retrieval (AS/R) systems. Two of the more important factors affecting the design of AS/R systems are system configuration and policies used for storing and retrieving items to and from the warehouse. Simulation results are obtained for six different single-dock layouts using three different scheduling policies. The results are compared using system throughput as the primary criterion; other performance measures investigated are storage and retrieval waiting times, and rejects due to the rack or input/output queues being fully utilized.

An integrated approach to facility location problems

Abstract An integrated analysis approach to facility location problems is described. The approach is based on integrating analytical location models and a multicriteria decision model.

Evaluation of scheduling rules for single- and dual-dock automated storage/retrieval system

Abstract The effect of the number of pick-up delivery stations (or docks or input/output points) is analyzed and compared for three different unit load automated storage and retrieval (AS/R) systems operating under dual command cycle. The AS/R system layouts differ in the number of docks per aisle, and the relationship between the storage and retrieval sources. A simulation model was used to evaluate the systems on three performance criteria—system throughput, mean waiting time and maximum waiting time. The efficiency of the AS/R system can be improved by the introduction of two docks per aisle with the input/output pallets for each dock being independent of each other, the input pallet storage based on closest open location policy, and output pallet withdrawal based on a nearest neighbour policy (or its variant, with a maximum waiting time limit).

Computerized container-ship load planning: a methodology and evaluation

Abstract A heuristic is developed to plan loads for containerized cargo ships. It is designed to serve a port which uses gantry cranes (transtainers) and trucks to handle containers. The model recognizes constraints on ship stability, placing containers in a bay with the proper length, limits on stack height in under-deck bays, limits on stack weight in on-deck bays, refrigerated containers, and the need for support under a container. Provisions are made for the operator to handle overstowage of cargo for different ports and placement of oversize cargo. The model uses minimization of transtainer movement time and minimization of rehandles in the yard as an objective. The heuristic uses strategies for container placement similar to those used in manual load planning. A test of two ships and four voyages at the Port of Portland produced feasible load plans for each voyage. Transtainer movement and rehandling time varied for the four voyages; but on the average, the heuristic reduced a composite material handling measure by 4.8%.

A case study assessment of performance measurement in distribution centers

Managing supply‐chain operations is critical to any company’s ability to compete effectively. Success in today’s markets depends on the ability to balance a stream of products and processes to stay competitive. Companies are constantly evaluating every area of operations to ensure that productivity and cost objectives are realistic and attainable. Research has been carried out to investigate the measurement systems used in today’s distribution centers. Five distribution centers in the Pacific Northwest were selected for this study. The characteristics of these five distribution centers and their measurement systems are discussed in this paper. A cross‐case analysis is provided, which gives a view of a typical measurement system used in today’s distribution centers.