Knowledge that Transforms

This paper proposes new concepts and new results which could lead to a more realistic preference modeling than in classical decision theory. Sections 1–3 present four fundamental situations of preferences, their combinations and the concept of relational system of preferences. In §4, a particular case of relational system of preference is studied. It is associated with the concept of pseudo-criterion derived from the classical concept of criterion by adjunction of two thresholds. Some results are given, generalizing the properties of such well-known structures as complete preorders and semiorders. Sections 5 and 6 emphasize the possibilities given by the preceding concepts to take the imprecisions, irresolutions and incomparabilities appearing in every concrete problem where several criteria must be considered into account.

We provide worst case error bounds for several approximation methods (heuristics, product aggregation, and partitioning of the planning horizon) for the uncapacitated dynamic lot size problem. We propose two managerially oriented heuristics and show that they have a relative wont case error bound equal to two, and develop similar analyses for methods known as the least cost per unit heuristic, the part period balancing heuristic, and an economic order quantity heuristic (expressed in terms of a time supply of demand). We also show how errors introduced by partitioning of the planning horizon in multi-product multi-facility problems are bounded by product set-up costs, and how errors introduced by product aggregation are bounded by set-up costs, holding costs, and demands. The latter results suggest methods for product aggregation that minimize the worst case error bounds.

This paper seeks to get behind specific contextual referents of risky situations to consider characteristics of risk that apply to many situations. It is guided by previous theoretical and empirical research in perceived risk, and focuses on the joint effects on risk of loss probability and the distribution of losses. The approach taken follows modern axiomatic theory by proposing conditions on a relation “is at least as risky as” between pairs of probability distributions over an outcome variable. Several sets of axioms for risk that characterize different forms for risk measurement are presented.

The factored transportation problem is one having cost coefficients of the form c ij = u i v j . The main result proven in this paper is that if rows are arranged according to nonincreasing u i and columns by nondecreasing v j , then the northwest corner rule provides an optimal solution. Applications to stock location in a warehouse and information storage and retrieval policies are presented. For the stock location problem, this verifies that a previously advocated heuristic is optimal.

In this Note, we address the issue of safety stock considerations in an MRP environment through the use of a single identical component as a replacement for a set of multiple components. We indicate where the results reported by Collier (Collier, David A. 1982. Aggregate safety stock levels and component part commonality. Management Sci. 28 (11, November) 1296–1303.) may prove to be misleading.

Hazard management of the risks of human injury and death related to the automobile are described and exemplified by the Swedish car manufacturer Volvo. The study presents the Volvo units engaged in accident hazard management and their roles in the elaborate system of feedbacks (information, penalties and rewards) created by the company and society for maintaining a high level of automobile safety. Improvements are suggested although the overall quality of the accident hazard management process is considered quite good. Although the study is focused on the automobile industry, it should be regarded as part of a much-needed wider perspective on hazard management applying to other technologies and industries as well. In general, the following factors are considered important to high quality accident hazard management by companies and society: (1) Public concern about safety issues, (2) technological capacity and organizational tradition of safety engineering in the manufacturing company, (3) routines for announcing future proposed safety standards, e.g., US Federal Register, (4) laws enforcing a recall system, (5) annual vehicle inspections and (6) effective product liability laws.

Recent research studies of job shop scheduling have begun to examine the interaction between sequencing priorities and the method of assigning due-dates. This paper surveys the tactical aspects of this interaction, focusing primarily on average tardiness as a measure of scheduling effectiveness. The discussion highlights several factors that can affect the performance of dispatching rules, such as the average flow allowance, the due-date assignment method, and the use of progress milestones. A set of simulation experiments illuminates how these factors interact with the dispatching rule, and the experimental results suggest which combinations are most effective in a scheduling system.

This paper deals with the M/G/m queueing system with group arrivals. Using a diffusion approximation, we present approximate formulae for the steady-state distribution of the number of customers in the system. From this distribution, approximate formulae for some queueing characteristics such as the delay probability and the mean queue length are derived. In order to check the accuracy of the approximate formulae, they are numerically tested on some special cases.

We consider the problem of minimizing the expected makespan of n jobs with independent exponentially distributed processing times on two parallel machines, under resource constraints. Job j has expected processing time 1/μ j and requires throughout its processing an amount r j of a resource; the total amount of resource available is r. In the case where 1/μ 1 < ⋯ < 1/μ n and r 1 < ⋯ < r n , we characterize all the optimal policies in the class of preemptive schedules, and show that the following nonpreemptive policy is optimal: Find the largest k for which r k + r k−1 < r, and start processing jobs k − 1, k. Thereafter, at any job completion, start processing on the machine that is freed, the longest job compatible with the job running on the other machine.

The purpose of this paper is to apply a generalized version of the Farrell measure of technical efficiency to a sample of Illinois strip mines. We disaggregate the original Farrell measure (which was designed to measure lost output or wasted inputs due to underutilization of inputs) into three mutually exclusive and exhaustive components: (1) a measure of purely technical efficiency, (2) a measure of input congestion (overutilization of some input(s)) and (3) a measure of scale efficiency. This approach has the advantage that it provides additional information on the sources of inefficiency of production, which should be useful to managers, in general, not only in strip mining. Simple linear programming techniques are derived and used in calculating these efficiency measures for our sample. We find that Illinois strip mines are fairly efficient (relative to each other). The major source of inefficiency was due to deviations from the optimal scale of production. We also find suggestive evidence that inefficient mines tend to have relatively high stripping ratios, high labor-output ratios, single rather than multiple coal seams, and lower earth-moving capacity.