Richard A. Dudek

The Lessons of Flowshop Scheduling Research

This paper reviews the flowshop-sequencing research since 1954 that has been devoted to the static deterministic case in which n jobs are to be processed through a shop in which the processing times at each stage are fixed. The paper then comments on NP-completeness, the selection of criteria for optimization, and the lack of applications of this work in industry. Finally, it draws some conclusions about the possible future of sequencing research and the lessons that this areas work has to teach the rest of operations research.

Sequencing Research and the Industrial Scheduling Problem

Types of industrial scheduling problems were investigated by personal visits to plants and by questionnaires mailed to scheduling departments. Information on problem sizes, job flow, optimization criteria and job similarity was obtained. Results indicate that most of the present procedures in theoretical research cannot handle average industrial problems. Also most commonly used objective criteria differ from industrial goals. There is a definite need for better communication between sequencing researchers and scheduling practioners.

Increasing the production rate of a just-in-time production system with variable operation times

Abstract This paper examines a just-in-time (JIT) system with kanbans with three subassembly lines feeding a final assembly station. Variability in operation times exists and variability effects are reduced by increasing work in process levels or by unbalancing the subassembly lines through assignment of work content at each station. Of the several unbalancing methods that were analysed in this study, only the high-medium-low showed a consistent improvement in the output rate of the JIT production system. The output rates with unbalanced stations were always superior to the output rate of the perfectly balanced configurations used as controls. The extent of improvement over the output rate of balanced systems increased directly with the variability in operation times in final assembly and subassembly stations and inversely with the interstage buffer capacity allowed in the system.

Optimality Criteria for Flowshop Schedules

Abstract This article considers the problem of scheduling n jobs on M machines in a flowshop and examines the present formulation of the problem. To understand the true nature of the problem, this article provides economic interpretations of various optimality criteria which are being used for solving the scheduling problem. A general optimization criterion, called minimization of opportunity cost, is proposed for flow-shop scheduling problems and the results of the sensitivity analysis of various optimality criteria are reported which indicate the need to reformulate the scheduling problem.

A categorized survey of the JIT literature

Abstract The Just-In-Time production system is considered by many (o be a solution for Western manufacturers who desperately need to improve productivity. A great number of papers dealing with Just-In-Timc have been published in conference proceedings, technical journals and other periodicals. In this paper, an extensive survey of 266 Just-In-Time articles appearing in 38 major English journals is presented. A classification of the literature is proposed. An analysis of article characteristics and apparent trends in the literature is provided.

Heart Rate Recovery during a College Basketball Game

Abstract This paper investigated the relationships between brief rest intervals and physiological recovery during intensive physical activity; namely, a basketball game. Heart rate was monitored for two university basketball players during a regularly scheduled game by means of telemetry. Brief rest intervals, as short as 40- to 60-sec. in duration, provided opportunity for physiological recovery in terms of significant decreases in heart rate response. Such rest intervals occurred during time-out periods and when some other player was taking a foul shot. Those foul shots in which the player himself was involved, however, did not show a decrease in heart response. Neither the game score nor any particular type of player activity was directly reflected in the players heart rate.

The dependent shop sequencing algorithm A general algorithm for solving flow shop, job shop, and dependent shop sequencing problems

This article describes a heuristic algorithm which will yield an optimal or near optimal minimal makespan solution to a specific type of sequencing/scheduling problem defined as the dependent sequencing problem which includes the pure job-shop and flow-shop sequencing problems. The name ‘ dependent sequencing ’ was selected for this model since it reflects the possibility of interdependence between activities of the technological processing order graph (GTPO) not present in ‘ pure ’ job -shop or f low-shop sequencing models. There are some approaches to this class of problem which provide optimal solutions, but their time to solutions and/or theoretical approaches make them difficult to understand and apply. Recent articles in the literature have recommended that research in the sequencing/ scheduling area be directed toward developing practical approaches which can be easily understood and applied. The dependent shop algorithm utilizes extensions of PERT/CPM techniques which are widely known and therefor...

A Study of JIT Application under Stochastic Demand and Supply Arrival

A simulation and analysis of variance study was conducted of a production line system operating in a near Just-In-Time (JIT) mode. The objective was to investigate the effect of four system parameters on the production line idle time and the carrying time of inventory. The system consisted of a production line producing one unit of product each production cycle to a JIT demand, each cycle was defined as one unit of time. The demand arrived stochastically during each cycle. The system was supplied by a supplier delivering materials with a stochastic arrival time of up to two cycles. The four system parameters were (1) operating inventory order quantity, representing a policy of ordering which permitted supply arrival for more than one cycle of production requirement, (2) stochastic demand arrival of up to one cycle, (3) safety stock of up to 3 units (Kanbans) of production, and (4) stochastic arrival of supply of up to three cycles.