John J. Bernardo

Developing and validating a decision support system for locating emergency medical vehicles in Louisville, Kentucky

Abstract Decreasing the elapsed time to respond to an emergency is a goal of Emergency Medical Services (EMS). The size of the ambulance fleet and the location of ambulances within the service area are two factors that the EMS planners can control; these two factors directly affect the systems response time and contribute to the attainment of this goal. In this paper, a maximal expected coverage location model with time variation (TIMEXCLP) is developed and integrated into a decision support system (DSS) to aid EMS planners to allocate vehicles within their service area. In applying TIMEXCLP to the Louisville, Kentucky, EMS system, response time was decreased by 36%.

The measurement and use of operational flexibility in the loading of Flexible Manufacturing Systems

Abstract Flexibility has been recognized as a key aspect of a firms response to competitive markets. However, no accepted measures of flexibility exist that would allow firms to evaluate FMS planning policies. In this paper, three measures of operational flexibility are derived to represent the ability of an FMS to respond to external and internal disturbances given a production plan. These flexibility measures are then used to evaluate tool loading and part routing decisions. A minimum-cost tool loading and part routing policy is derived, modeled, and statistically tested against a maximum-production-rate policy. The minimum-cost policy resulted in inventory levels being lowered by as much as 43% while routing flexibility increases by as much as 11% without statistically affecting capacity flexibility or the planned makespan.

Tool planning models for flexible manufacturing systems

Although the tool loading problem for Flexible Manufacturing Systems (FMSs) has been analyzed in the past, the tool planning problem, the basis of tool management, has largely been ignored. In this paper, the interface between tool planning and the FMS loading and routing decisions is analyzed. It is shown that tool policy has a pronounced effect on the flexibility and the planned makespan of an FMS. A tool planning model is developed and integrated into an overall FMS detailed tool loading and part routing procedure. This model while considerably reducing the number of tools required (by 55%) matches the performance of a policy that equips each machine with all tools in terms makespan, routing flexibility, and tool productivity.

A comparison of interactive multiple-objective decision making procedures

Abstract Many algorithms have been developed for the multiple objective decision making (MODM) problem. Unfortunately, there is a lack of empirical testing of these algorithms. From a managerial point of view, it is desirable to conduct a multi-model evaluation so that decision-makers can determine which method would be best in a given situation. This study compares the applicability of two computerized interactive MODM procedures: the Steuer Method and the Franz Method. Experimentation is designed to determine how effectively the two procedures arrive at a solution based upon interaction with a simulated decision-maker. Non-parametric statistical analysis is performed on the results of randomly generated problems. Both linear and nonlinear utility functions are examined. The experimentation also determines the efficiency by which the procedures derive solutions as measured by the number of iterations necessary for convergence. The results of the study recommend the use of the Steuer procedure when (1) the accuracy of the solution is the critical factor in selecting an interactive MODM algorithm, and/or (2) the objectives under consideration are of relatively equal importance to the decision maker. It is also recommended that the Franz procedure be used when (1) the number of iterations necessary for convergence is the critical factor in the algorithm selection, and/or (2) there is one main objective that the decision maker wishes to accomplish and the remaining objectives are of diminishing importance.

An interactive procedure for bi-criteria production scheduling

Abstract In this paper, a scheduling problem is analysed in which the scheduler desires to minimize both the tardiness of the jobs and the incurred set-up costs. Unlike existing bi-criteria scheduling formulations, the approach developed in this paper does not utilize a weighted objective function. Because the application studied is dynamic in that the importance of each criteria varies over time, an interactive approach is developed that allows the decision maker to evaluate the job assignments. By analysing simulations of the application, the procedure is shown to be efficient in that the elapsed time between the decision makers input and the systems response was within 5.3 sec. Furthermore, the system was able to reduce the number of feasible sequences by an average of 55% which allowed a decision to be made in six or fewer iterations.

The effect of inventory and production costs on the optimal planning horizon

Production planning mid smoothing models have been analysed in the operational research literature for some time. Application of these models in industry is growing, mid they have proved to be economically beneficial. Still, we find there exist many questions concerning the length of time over which production should lx) planned: (1) Does an optimal planning horizon exist? (2) If it does, is it of reasonable length as to be useful to the practitioner? (3) What factors affect the length of the planning horizon? In this paper, we show that an optimal planning horizon does exist and that it can easily be found in any application. Furthermore, the length of time over which production should be planned is acceptable for reasonable values of production costs, inventory costs and fluctuations in demand.

Scheduling independent jobs on nonuniform, unequal processors

Abstract The problem of scheduling n independent jobs on a single processor to minimize the total tardiness of the assignment has attracted much attention. Solution algorithms, both exact and approximate, have been reported, but no polynomial time exact algorithm has yet been found, nor has the problem been proven NP-complete. In this paper we consider the more general case of scheduling n independent jobs on m unequal processors to minimize total tardiness. Since this problem is more complex than the corresponding single-processor problem, no polynomial-time algorithm is in sight. For problems of this nature, approximate algorithms may be more valuable than exact algorithms in terms of applications. A heuristic algorithm is developed to solve the multiple-processor problem. Computational experiments show that the heuristic algorithm is efficient, fast, and easy to implement.

Stochastic preference and randomized strategies for consumer choice

Abstract In this article a stochastic model of choice is developed that is based on game theory. The model is developed to demonstrate that a basic stochastic model can yield results similar to phenomena discovered in consumer behavior. In particular, a definition of brand loyalty is developed along with a basis for rational intransitivity of preferences, which is noted by brand switching. A measurement approach is also presented along with an example. The basic intent is to demonstrate that stochastic approaches to choice do have a foundation in both theoretical development beside observations in empirical studies.

The cost advantage of hysteretic controls for bi-level production systems

Frequently, production systems can be designed to be flexible in that the output rate of the system can be changed depending upon the demand requirements that the system faces. In such systems, the problem is considered to be the determination of the optimal point at which the system switches between its output levels. Simple control has one switching point between adjacent output levels. In this paper, it is shown that hysteretic control, the determination of two switching points, always provides for a lower operating cost than simple control. Based upon the characteristics of the performance measures, a procedure is developed that easily finds the optimal switching points. The procedure, when applied to a small midwest job shop, resulted in a cost savings of 9-97%.

Multiple Criteria Trajectory Decision Support Using Polyscreen Workstations: A Production Planning Illustration

This paper demonstrates how the Combined Tchebycheff/Reference Point Procedure [8] can be installed in a decision support system for solving multiple criteria trajectory optimization problems. With such problems often presenting difficult modeling and solution procedure challenges, the Combined Procedure is employed because it gives good direction while providing substantial user control. The approach of this paper is futuristic in that it explores the use of polyscreen workstations (up to six screens) in order to facilitate man/machine communications at each iteration. A multiple criteria multi-time period production planning problem is used to illustrate the decision making approach.