The effect of MRP lot sizing on actual cumulative lead times in multi-level systems

This study investigates how different lot sizing techniques influence the cumulative lead time for multi-level production-inventory systems controlled by material requirements planning (MRP). Theoretical approaches, a numerical example, as well as simulation are used to analyse and illustrate the combined effect of lot sizing at different product structure levels. It is shown that lot-sizing requirements for more than a single period, such as fixed period requirements, period under quantity, Silver Meal algorithm, as well as economic order quantity will lead to longer actual cumulative lead times than would be expected, when taking the item lead times along the critical path through the product structure into account. Consequently, MRP will underestimate the cumulative lead time and will require a longer planning horizon. We show that the extension of the cumulative lead techniques covering the time is a lot-sizing related phenomenon and cannot be accounted for by, e.g. using safety lead time. Lot-sizing techniques with multi-period coverage will only occasionally provide the 'expected' cumulative lead time. We also show that average and maximum throughput times, as well as throughput time variability increases with increasing time-period coverage of lots.     

A chain game for distributed trading and negotiation

This position paper introduces a simulation gaming environment for enacting a production network. The environment aims to be an integrative laboratory for investigating supply networks, as well as being a versatile training tool. The primary focus is on food production networks. The environment enables a number of teams of participants, each representing one actor in a food chain, to conduct business together. The teams can have the role of auction, co-operation, wholesaler, factory, retail chain, and retail outlet. Producers and consumers are either enacted or simulated. The game leaders freely determine the products and production methods in each run of the game. The gaming environment takes performance, process and institutional aspects of chains into account. It is particularly suited for investigating issues of sustainability and trust. Currently the gaming environment is under development. The paper presents version 1B. This version can be found at http://www.chaingame.org. It runs on the Web, enabling to model distributed chains.     

Supply chain management: A just-in-time perspective

Just-in-time (JIT) has been a widely recognized production philosophy alternative since the early 1980s. JIT principles and techniques have been widely adopted in many manufacturing firms. More recently, supply chain management has evolved as a discipline focusing on the design, planning and control of processes linking the initial raw materials to the ultimate consumption of the finished product. Supply chain efficiency is dependent on the efficiencies of the individual manufacturing organizations and the ability to connect along the supply chain. In this paper supply chain management from a JIT perspective is investigated, focusing on the linking mechanisms between successive companies and the collective efficiency of the supply chain.     

Inhospitable workplaces? International students and paid work in food services

Most international students in Australia take up paid work during their studies, generally as part‐time employees in low‐wage, low‐skill labour markets. Though little is known about the detail of their work experiences, scattered reports suggest that wages and working conditions are often poor and pose significant issues of social justice. This article examines the characteristics of jobs held by one group of international students, drawing on in‐depth qualitative interviews that form part of a case study of Melbourne's café, restaurant and takeaway food services sector. The evidence indicates that precariousness in employment is widespread in this sector and that it centres on underpayment and non‐payment of wages, in breach of labour regulation. The article suggests that such illegal employer practices are facilitated by use of undeclared casual work. Underpayments are most severe in what are typically regarded as ethnic cafes and restaurants, which concentrate on employment of international students, but they are also widespread in mainstream cafes and restaurants, where international students share precarious work conditions with other workers. The findings underline the case for more concerted research and new policy initiatives.     

Measuring underemployment and inequality in the work force

In a recent article in this journal, Tipps and Gordon (1985) presented new indicators of underemployment and compared them to indicators obtained from the Labor Utilization Framework (LUF) of Hauser, Sullivan, Clogg, and others. In this note the Tipps-Gordon criticisms of LUF are reviewed, the Tipps-Gordon framework is criticized, and both LUF and the Tipps-Gordon approach are compared empirically as well as conceptually. An extension of LUF is also presented.     

Investigating the Level of End‐User Development and Involvement Among Time‐Based Competitors

As global markets and technology change, time‐based competitors create product development and manufacturing practices that reduce response time and enhance customization capabilities. These practices require an information‐rich internal environment that is capable of flexible resource deployment and direct and continuous feedback. To build this environment, time‐based competitors are developing end‐user capabilities and involving them in information systems (IS) activities. Data collected from 265 manufacturers were used to determine if firms with high levels of time‐based product development and time‐based manufacturing practices also have high levels of end‐user involvement in IS‐related activities, end‐user training effectiveness, and end‐user computing skills. The results of this study support that contention.     

A MODEL FOR BATCH ADVANCED AVAILABLE‐TO‐PROMISE

The available‐to‐promise (atp) function is becoming increasingly important in supply chain management since it directly links production resources with customer orders. In this paper, a mixed integer programming (mip) ATP model is presented. This model can provide an order‐promising and ‐fulfillment solution for a batch of orders that arrive within a predefined batching interval. A variety of constraints, such as raw material availability, production capacity, material compatibility, and customer preferences, are considered. Simulation experiments using the model investigate the sensitivity of supply chain performance to changes in certain parameters, such as batching interval size and customer order flexibility.     

An Empirical Model for Managing Quality in the Electronics Industry

Much of the empirical research in the past two decades has suggested that quality management (QM) is context dependent. This research develops an empirical QM model in a technology‐based sector—electronics manufacturing. Based on quantitative and qualitative investigations of 225 electronics firms in Hong Kong and the Pearl River Delta (PRD) region of China, a path analytic model is developed. The empirical model shows that a typical quality management system (QMS) in the electronics industry is composed of four major modules, namely leadership, cultural elements, operational support systems, and process management. These modules create a series of chain effects on organizational performance, rather than acting as parallel elements with an equal impact. By quantifying their effects on organizational performance and comparing the model to others in the literature, we identify those QM constructs that are context dependent. In electronics manufacturing, process management and customer focus are more important than other elements (e.g., cultural factors) for garnering business results. This study contributes to contingency theory and research by identifying the key constructs and their relationships in a competitive, volatile, and technology‐based industry with complex supply networks.     

How Leaders Affect Followers’ Work Engagement and Performance: Integrating Leader−Member Exchange and Crossover Theory

Drawing on leader?member exchange and crossover theory, this study examines how leaders’ work engagement can spread to followers, highlighting the role of leader?member exchange as an underlying explanatory process. Specifically, we investigate if leaders who are highly engaged in their work have better relationships with their followers, which in turn can explain elevated employee engagement. For this purpose, we surveyed 511 employees nested in 88 teams and their team leaders in a large service organization. Employees and supervisors provided data in this multi‐source design. Furthermore, we asked the employees to report their annual performance assessment. We tested our model using multilevel path analyses in Mplus. As hypothesized, leaders’ work engagement enhanced leader?member exchange quality, which in turn boosted employee engagement (mediation model). Moreover, employee engagement was positively linked to performance and negatively linked to turnover intentions. As such, our multilevel field study connects the dots between work engagement research and the leadership literature. We identify leaders’ work engagement as a key to positive leader?follower relationships and a means for promoting employee engagement and performance. Promoting work engagement at the managerial level may be a fruitful starting point for fostering an organizational culture of engagement.     

Nuclear Waste Management under Approaching Disaster: A Comparison of Decommissioning Strategies for the German Repository Asse II

This article compares different strategies for handling low‐ and medium‐level nuclear waste buried in a retired potassium mine in Germany (Asse II) that faces significant risk of uncontrollable brine intrusion and, hence, long‐term groundwater contamination. We survey the policy process that has resulted in the identification of three possible so‐called decommissioning options: complete backfilling, relocation of the waste to deeper levels in the mine, and retrieval. The selection of a decommissioning strategy must compare expected investment costs with expected social damage costs (economic, environmental, and health damage costs) caused by flooding and subsequent groundwater contamination. We apply a cost minimization approach that accounts for the uncertainty regarding the stability of the rock formation and the risk of an uncontrollable brine intrusion. Since economic and health impacts stretch out into the far future, we examine the impact of different discounting methods and rates. Due to parameter uncertainty, we conduct a sensitivity analysis concerning key assumptions. We find that retrieval, the currently preferred option by policymakers, has the lowest expected social damage costs for low discount rates. However, this advantage is overcompensated by higher expected investment costs. Considering all costs, backfilling is the best option for all discounting scenarios considered.