Enhancing Manufacturing Planning and Control Systems Through Artificial Intelligence Techniques

Manufacturing planning and control systems are currently dominated by systems based upon Material Requirements Planning (MRP). MRP systems have a number of fundamental flaws. A potential alternative to MRP systems is suggested after research into the economic batch scheduling problem. Based on the ideas of economic batch scheduling, and enhanced through artificial intelligence techniques, an alternative approach to manufacturing planning and control is developed. A framework for future research on this alternative to MRP is presented

Constraint Programming for Scheduling

Our goal is to introduce the constraint programming (CP) approach within the context of scheduling. We start with an introduction to CP and its distinct technical vocabulary. We then present and illustrate a general algorithm for solving a CP problem with a simple scheduling example. Next, we review several published studies where CP has been used in scheduling problems so as to provide a feel for its applicability. We discuss the advantages of CP in modeling and solving certain types of scheduling problems. We then provide an illustration of the use of a commercial CP tool (OPL Studio) in modeling and designing a solution procedure for a classic problem in scheduling. We conclude with our speculations about the future of scheduling research using this approach

IS Journal Quality Assessment Using the Author Affiliation Index

Research productivity is one means by which academic units attain legitimacy within their institutional milieu and make their case for resources. Journal quality assessment is an important component for assessing faculty research productivity. We introduce the Author Affiliation Index (AAI), a simple method for assessing journal quality, to the IS domain. Essentially, the AAI of a journal is the percentage of academic authors publishing in that journal who are affiliated with a base set of high-quality academic institutions. Besides explaining the AAI, we demonstrate its use with a set of well-known IS journals, discuss its rankings vis-à-vis those resulting from other methods, and provide an example of how the basic AAI approach can be modified by changing the base school set that is used to define journal quality. The AAI has a number of advantages. First, it is a simple, low cost and transparent method for assessing any journal given a base school set. Second, it provides a consistent ranking of journals, particularly of those beyond the top consensus journals where less consistency is achieved with other measures. Third, it enables new journals to be rapidly assessed against more established ones without the lags or costs of other measures. The AAI provides another indicator of journal quality that is different from surveys and citation analyses

Mean Flowtime and Inventory in Production Systems: A Finite Time Analogue to Little’s Law

One of the most important results regarding flows in production systems is the well-known formula L=λW, commonly referred to as “Little\u27s Law”. Whereas the formula pertains to steady state averages, we show here that it has a finite analogue, i.e., there is another “law” for the case of a finite time interval. The analogue has practical economic value as it provides a precise reconciliation of average inventory and time-in-system over a finite time interval—sometimes more relevant than “steady state” averages. Examples of the usefulness of the law in practical managerial situations are provided. An additional result is to show how the analogue leads to a straightforward proof of Little\u27s Law that requires minimal assumptions

New Precedence Theorems for One-Machine Weighted Tardiness

In an earlier paper by Emmons [Emmons, H. 1969. One-machine sequencing to minimize certain functions of job tardiness. Oper. Res. 17 701–715], the problem of sequencing jobs on a single machine in order to minimize total tardiness was analyzed. Emmons provided three theorems for specifying precedence relations for pairs of jobs. His theorems apply when the tardiness penalty for each job grows at the same rate. Rinnooy Kan et al. [Rinnooy Kan, A. H. G., B. J. Lageweg, J. K. Lenstra. 1975. Minimizing total costs in one-machine scheduling. Oper. Res. 23 908–927] later extended Emmons’s theorems to the case when job tardiness penalties can grow at different rates for different jobs. Provided here is a set of theorems, stronger than those of Rinnooy Kan et al., that more fully exploits the special properties of the weighted tardiness function, allowing for greater reduction of the solution space

Note---On Anomalies in Dynamic Ratio Type Scheduling Rules: A Clarifying Analysis

Previous authors have shown that dynamic ratio scheduling rules do not always behave as intended. A recent proposal by Adam and Surkis (Adam, N. R., J. Surkis. 1980. Priority update intervals and anomalies in dynamic ratio type job shop scheduling rules. Management Sci. 26 (12, December) 1227--1237.) to correct such anomalies is shown to be in error. The reason why such anomalies occur is clarified and a rule which prevents such anomalies is presented.simulation: applications, production/scheduling: job shop, deterministic, queues: priority

Weighted Tardiness for the Single Machine Scheduling Problem: An Examination of Precedence Theorem Productivity

Earlier research by Kanet [11] has provided a number of new theorems for deciding precedence between pairs of jobs for 1∣∣ΣwjTj. The theorems supplant those of Rinnooy Kan, Lageweg, and Lenstra [16]. Presented here are the results of an analysis of the marginal benefit these new theorems provide over the earlier versions of Rinnooy Kan et al. Results show that the new theorems can provide noteworthy improvements in the ability to discover precedence relations between job pairs. For a large set of problem instances the new theorems uncovered up to 8% more precedence relations than the original theorems of Rinnooy Kan et al. The improvement in the productivity in discovering precedence relations shows to be dependent on the coefficient of variation of the distribution of job weights. Logical application of the theorems is to include them in search procedures and/or heuristic approaches to 1||ΣwjTj. One such heuristic based on the theorems is provided here in which the solutions to a large set of sample problems are within 8–12% of the optimum