Overlapping operations in material requirements planning

Material requirements planning (MRP) is a planning and information system that has widespread application in discrete-parts manufacturing. The purpose of this article is to introduce ideas that can improve the flow of material through complex manufacturing systems operating under MRP, and that can increase the applicability of MRP within diverse manufacturing environments.MRP models the flow of material by assuming that items flow from work station to work station in the same batches that are used in production. That is, once work starts on a batch of a certain item at a certain work station, the entire batch will be produced before any part of the batch will be transported to the next work station on its routing plan. Clearly, efficiency can be increased if some parallelism can be introduced. The form of parallelism investigated here is overlapping operations.Overlapping operations occurs when the transportation of partial batches to a downstream work station is allowed while work proceeds to complete the batch at the upstream work station. The potential efficiencies to be gained are the following:

• Reduced work-in-process inventory

• Reduced floor space requirements

• Reduced size of transfer vehicles

Additional costs may accrue through additional cost of transportation of partial batches and through additional costs of control.Some MRP software vendors provide the data processing capability for overlapping operations. However, the user is given little or no guidance on overlapping percentages or amounts. It is our intent to provide a simple, robust technique to MRP users who would like to overlap operations and gain some or all of the above efficiencies.An optimal lot-sizing technique is derived by considering a generic two work station segment of a manufacturing system. Under the assumptions of constant demand and identical production rates, a cost function that considers setup costs, inventory holding costs and transportation costs is derived. This cost function is minimized subject to the constraint that the production batch is an integer multiple of the transfer batch. We solve for the optimal production batch, the optimal transfer batch, and the integer number relating them. Solutions are obtained as closed form, easy to-evaluate formulas.By introducing more parallelism, overlapping operations can reduce lead time. However, this will not happen without modification of MRP logic to accommodate such reduced lead time. We derive a formula that shows how a significant lead time compression can easily be obtained and implemented in MRP.We consider an example to illustrate the application of the technique on typical data from the electronics industry. The outcome showed a cost savings of approximately 22.5% over the standard MRP approach.Overlapping operations allows the applicability of MRP to an increasing number of situations that are not modeled faithfully by conventional MRP logic. Three such situations that occur often are the following:

• Limited size of transfer vehicles dictate that several transfers should be planned.

• Lead time requirements prohibit nonoverlapped operations.

Our analysis suggests how to accommodate these difficult practical situations into MRP.Overlapping operations in material requirements planning provides an enhancement that allows wider applicability, shortened lead times, and lower total costs. It may be applied selectively to any two work stations where it is deemed appropriate. Due to the structure of the cost function, it is possible to make the transfer lot-sizing decisions independent of the production lot-sizing decisions. Therefore, significant improvements can be made through overlapping with minimum disruption to the existing MRP system machinery. It is our conviction that overlapping operations is an important concept that can and will impact MRP. We suggest the approach presented here as a systematic way to implement overlapping.     

Otra Empanada en la Parilla: Examining the Role of Culture and Information Sharing in Chile and Australia

One of the biggest assets of a firm is its information base. Included in this information base is a knowledge of prior errors and failures. Extant research suggests that while the propensity to share “bad news” (i.e. a prior error) is dependent on the cost of sharing, the perceived value of that cost may be culturally dependent. One area of interest that has received substantial attention in the prior literature has been cross‐cultural differences in negative information sharing in general, as well as the particular context in which the individual's superior is either present or absent during the information‐sharing process. Our study examines the role of the two cultural values (individualism/collectivism and to a lesser extent power distance) in explaining national differences in information sharing. By focusing on a sample from Chile and Australia, we were able to remove the regional cultural dimension of face, which has been inherent in prior studies that used Greater China as the representative of a collectivist society. Results from our quasi experiment show that when a supervisor is present during information sharing, collectivist Chilean decision‐makers are more willing to share negative information with their colleagues than their counterpart and individualist Australian decision‐makers. Our results also show that when a supervisor is absent, both Australian and Chilean decision‐makers are willing to share more negative information but the increase in the Australian propensity is significantly greater than that of the Chileans.     

Postschool education and training: Accessible to all?

This article examines knowledge and skill development during early adulthood when the individual has severed ties with formal education and entered the world of work. Focusing on a cohort of young men from the National Longitudinal Surveys, the paper examines the economic and social forces influencing participation in various forms of postschool education and training. A recursive model is used to explore skill development patterns over the lifecycle. Attention is focused on the role of early human capital development and its influence on the cost and incentives for subsequent skill development in the adult working years. The findings point to the cumulative nature of skill development over the lifecycle with some important implications for efforts to reduce economic and social inequalities for blacks and whites.     

Changes in european defence procurement and industrial capabilities

The impact of defence procurement on a country's industrial and technological base can be considerable—among NATO countries, the USA, Britain and France stand out in this regard. Equally, concern is also often expressed about how to safeguard the civil technology base as a necessary foundation for security, broadly conceived. This article examines the changes taking place in the UK, and more broadly in Europe, regarding defence procurement: first, by examining arguments and events regarding defence R&D; and second, through analysing procurement issues relating especially to industrial structures and strategies. Much strategic repositioning by firms is currently taking place, often encouraged by governments, who seem to lack adequate means of regulating the restructuring, thereby creating unintended problems.     

The Educational Choice Anomaly for Principles Students: Using Ordinary Supply and Demand Rather than Indifference Curves

The surprise value of many economic observations makes the economics discipline quite interesting for many students. One such anomaly is that providing “free” education in an effort to reduce the number of dropouts can often result in a lower level of educational quality purchased. This result is easy to show with indifference curves, but many instructors of introductory courses do not introduce this analytical technique. As a consequence, a result that many students find quite interesting is seldom presented. The authors show that it is easy to clarify the educational choice anomaly with ordinary supply and demand curves. Moreover, the exercise of doing so provides students with a greater understanding of benefit/cost analysis as well as consumer and producer surplus.     

Do citizenship behaviors matter more for managers than for salespeople?

This research was designed to investigate the effects of organizational citizenship behaviors (OCBs) and objective sales productivity on sales managers’ evaluations of their sales personnel’s performance and to examine whether the impact of OCBs on performance evaluations is greater at higher levels of the sales organization hierarchy. Two samples were obtained from the same organization: a sample of 987 multiline insurance agents and a sample of 161 agency managers. Objective measures of sales productivity were obtained for both samples along with evaluations of three dimensions of OCBs and an assessment of overall performance. The results indicate that managers’ evaluations are determined at least as much by OCBs as they are by objective measures of performance. After partialing out common method variance, the results also indicate that OCBs account for a greater proportion of a sales manager’s evaluation than of a sales representative’s evaluation. The implications of these findings are discussed. Scott B. MacKenzie (Ph.D., UCLA, 1983) is a professor of marketing and the Edgar G. Williams Faculty Fellow at the Kelley School of Business at Indiana University. His research on advertising effectiveness, organizational citizenship behavior, and leadership issues can be found in theJournal of marketing Research, Journal of Marketing, Journal of Consumer Research, Journal of Applied Psychology, Organizational Behavior and Human Decision Processes, Personnel Psychology, Journal of Management, andThe Leadership Quarterly. Currently, he serves on the editorial boards of theJournal of Marketing Research, Journal of Marketing, Journal of Consumer Research, andJournal of Consumer Psychology. Philip M. Podsakoff (D.B.A., Indiana University, 1980) is the John F. Mee Professor of Organizational Behavior and Human Resources at the Kelley School of Business at Indiana University. He is the author or coauthor of more than 60 articles and/or scholarly book chapters that have appeared in such journals as theJournal of Marketing, Journal of Marketing Research, Academy of Management Journal, Psychological Bulletin, Organizational Behavior and Human Decision Processes, Journal of Applied Psychology, The Leadership Quarterly, Organizational Dynamics, Research in Organizational Behavior, Journal of International Business Studies, andJournal of Occupational and Organizational Psychology. He serves on the Board of Editors of theJournal of Applied Psychology, Organizational Behavior and Human Decision Processes, andThe Leadership Quarterly. Julie Beth Paine is a doctoral student in management at the Kelley School of Business at Indiana University. Her research interests include competence in performance, performance evaluation processes, and reward systems.