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David Robb

The University of Auckland, Graduate School of Management, Faculty Member

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David is Professor of Operations and Supply Chain Management, and Deputy Director of the Graduate School of Management at the University of Auckland Business School. He co-directs the Consortium for Operational Excellence in Retailing – Greater China. He was Associate Professor for 5 years, Visiting Professor for 5 years, and is now Research Fellow, at Tsinghua University School of Economics and Management in Beijing. He has MBA and PhD degrees in Operations Management from The University of Calgary, where he also served as Assistant Professor (1992-1994).

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Chung Yuan Christian University

Bucks New University

Cristobal Miralles

Universitat Politècnica de València

Alexandru Constangioara

University of Oradea

Jatinder N.d Gupta

ManMohan S Sodhi

City, University of London

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Papers by David Robb

Erratum: Inventory management under date-terms supplier trade credit with stochastic demand and leadtime

Journal of the Operational Research Society, May 10, 2006

Decision support for serials deselection and acquisition: A case study

Journal of the American Society for Information Science, Mar 1, 1997

Assessing Forecast Model Performance in an ERP Environment

Social Science Research Network, Jun 23, 2008

PurposeThe paper aims to describe and apply a commercially oriented method of forecast performanc... more PurposeThe paper aims to describe and apply a commercially oriented method of forecast performance measurement (cost of forecast error – CFE) and to compare the results with commonly adopted statistical measures of forecast accuracy in an enterprise resource planning (ERP) environment.Design/methodology/approachThe study adopts a quantitative methodology to evaluate the nine forecasting models (two moving average and seven exponential smoothing) of SAP®'s ERP system. Event management adjustment and fitted smoothing parameters are also assessed. SAP®is the largest European software enterprise and the third largest in the world, with headquarters in Walldorf, Germany.FindingsThe findings of the study support the adoption of CFE as a more relevant commercial decision‐making measure than commonly applied statistical forecast measures.Practical implicationsThe findings of the study provide forecast model selection guidance to SAP®'s 12+ million worldwide users. However, the CFE metric can be adopted in any commercial forecasting situation.Originality/valueThis study is the first published cost assessment of SAP®'s forecasting models.

The “More for Less” Paradox in Distribution Models: An Intuitive Explanation

Iie Transactions, Dec 1, 1990

An evaluation of scheduling heuristics for dynamic single-processor scheduling with early/tardy costs

Naval Research Logistics, Apr 1, 1996

In an endeavor to broaden the application of scheduling models to decisions involving the use of ... more In an endeavor to broaden the application of scheduling models to decisions involving the use of a manager's time we use simulation to investigate the performance of a number of simple algorithms (including eight priority rules and a construction heuristic) in a dynamic setting with tasks amving (randomly) and scheduling decisions being made, over time. We compare these simple methods relative to a bound that uses an adjacent pairwise interchange algorithm. We model uncertainty in task durations, and costs being incurred for early and tardy task completion (representative of JIT settings). In addition to evaluating the efficacy of the scheduling rules and various preemption strategies (using ANOVA), we highlight the managerial implications of the effects of eight environmental parameters.

Quality disclosure strategy in a decentralized supply chain with consumer returns

International Transactions in Operational Research, Sep 16, 2019

We study the quality disclosure strategy of a manufacturer/retailer in a supply chain with consum... more We study the quality disclosure strategy of a manufacturer/retailer in a supply chain with consumer returns for new products. In particular, we explicitly model the effect of quality disclosure on the reduction of the returns rate. We identify the condition in which the manufacturer/retailer should reveal product quality in the presence of consumer returns. We find that (1) the manufacturer/retailer has an incentive to choose quality disclosure strategy when the disclosure quality is above a lower bound; (2) if the returns rate of new products is low, the retailer-disclosure scenario leads to reveal more quality information than that of the manufacturerdisclosure scenario; otherwise, the manufacturer-disclosure scenario leads to reveal more quality information; and (3) the manufacturer prefers to reveal a higher level of product quality in the supply chain with a higher refund amount or a lower salvage value per unit of returned product.

An In-Class Competition Introducing Inventory Management Concepts

Informs Transactions on Education, May 1, 2010

E ncouraging interest in inventory management necessitates that instructors overcome concerns tha... more E ncouraging interest in inventory management necessitates that instructors overcome concerns that the subject is too abstract or conceptual. To aid in this process, we describe a competition engaging students in concepts, including demand estimation, demand uncertainty, and costs of inventory and shortages. The competition simulates a multi-item newsvendor problem employing participant-generated data. We present results from use of the exercise in multiple class settings over the past decade. A number of possible extensions of the basic competition are discussed. Data collection and analysis materials are available to interested readers.

A Survey of Manufacturing Strategy and Technology in the Chinese Furniture Industry

European Management Journal, Aug 1, 2003

Analysis and Management of Periodic Review, Order-Up-To Level Inventory Systems with Order Crossover

Production and Operations Management, Sep 6, 2013

In this paper we investigate the (R, S) periodic review, order-up-to level inventory control syst... more In this paper we investigate the (R, S) periodic review, order-up-to level inventory control system with stochastic demand and variable leadtimes. Variable leadtimes can lead to order crossover, in which some orders arrive out of sequence. Most theoretical studies of order-up-to inventory systems under variable leadtimes assume that crossovers do not occur and, in so doing, overestimate the standard deviation of the realized leadtime distribution and prescribe policies that can inflate inventory costs. We develop a new analytic model of the expected costs associated with this system, making use of a novel approximation of the realized (reduced) leadtime standard deviation resulting from order crossovers. Extensive experimentation through simulation shows that our model closely approximates the true expected cost and can be used to find values of R and S that provide an expected cost close to the minimum cost. Taking account of, as opposed to ignoring, crossovers leads, on average, to substantial improvements in accuracy and significant cost reductions. Our results are particularly useful for managers seeking to reduce inventory costs in supply chains with variable leadtimes.

Sharing shipment quantity information in the supply chain

Omega, Oct 1, 2006

This paper evaluates the benefit of a strategy of sharing shipment information, where one stage i... more This paper evaluates the benefit of a strategy of sharing shipment information, where one stage in a supply chain shares shipment quantity information with its immediate downstream customers-a practice also known as advanced shipping notice. Under a periodic review inventory policy, one supply-chain member places an order on its supplier every period. However, due to supplier's imperfect service, the supplier cannot always exactly satisfy what the customer orders on time. In particular, shipment quantities arriving at the customer, after a given lead-time, may be less (possibly more) than what the customer expects-we define this phenomenon as shipment quantity uncertainty. Where shipment quantity information is not shared with customers, the only way to respond is through safety stock. However, if the supplier shares such information, i.e. customers are informed every period of the shipment quantity dispatched, the customer may have enough time to adapt and resolve this uncertainty by adjusting its future order decisions. Our results indicate that in most circumstances this strategy, enabled by information technologies, helps supply-chain members resolve shipment quantity uncertainty well. This study provides an approach to quantify the value of shared shipment information and to help supply-chain members evaluate the cost-benefit trade-off during information system construction. Numerical examples are provided to indicate the impact of demand/shipment parameters on strategy implementation. While previous studies mainly focus on the information receiver's perspective, we evaluate a more general three-tier linear supply chain model via simulation, studying how this strategy affects the whole supply chain: the information sender, the information receiver and the subsequent downstream tier.

Production Scheduling Theory: Just Where Is It Applicable?

Interfaces, Dec 1, 2000

A proliferation of scheduling research has done little to improve production planning practice, d... more A proliferation of scheduling research has done little to improve production planning practice, despite calls for more comprehensive models. Using a four-factor classification of planning environments (planning level, production type, production strategy, and production cycle time) we show scheduling theory is relevant in few settings. For example, in increasingly common short-cycle environments, where production cycle times are shorter than the planning period, the order in which one processes jobs is seldom important. Moreover, even in long-cycle environments, capacity is seldom fixed, with managers often negotiating for enough capacity to make scheduling fairly easy. Based on extensive consulting experience in Australasia, we call for caution in applying scheduling theory. While complex models are pertinent in some cases, more benefit often arises from establishing appropriate performance measures, planning periods, capacity negotiation processes, and uncertainty reduction measures.

Manufacturing and Supply Chain Management in China: A Survey of State-, Collective-, and Privately-Owned Enterprises

Social Science Research Network, Jun 8, 2000

Because of the booming economy, interest in China has soared in recent years. The government has ... more Because of the booming economy, interest in China has soared in recent years. The government has decided to privatize many state-owned enterprises (SOEs), so foreigners can much more easily invest in existing firms than ever before. Is it wise to consider investing in these SOEs? Certainly, many have major problems. How sophisticated are Chinese manufacturing firms? Do they understand modern principles of manufacturing strategy and supply chain management? What is the level of installed technology, from traditional production planning systems, like MRP, to robotics? This paper attempts to answer these questions based on a survey of 100 firms in the Shanghai area. We surveyed state-owned enterprises, collective-owned enterprises and privately held firms, and we discovered some fascinating insights about their differences and their similarities. We discovered that the differences among the ownership types are generally insignificant, suggesting that our results are quite general. We find that these firms are far more advanced using explicit manufacturing strategies than we had expected. However, they are not as advanced in supply chain management as many Western firms. They report significant communication with customers and suppliers-more with customers than suppliers-but the nature of the communication is often limited to one dimension, particularly on the downstream side. Firms that communicate with customers tend to do so with suppliers as well.

Service failure, recovery and improvement: the case of a Chinese restaurant

International Journal of Services and Operations Management, 2008

218 Int. J. Services and Operations Management, Vol. 4, No. 2, 2008 ... Service failure, recovery... more

Some insights regarding the optimal reorder period in periodic review inventory systems

International Journal of Production Economics, Mar 1, 2008

The periodic review inventory system is not only pervasive, but also has an extensive literature ... more The periodic review inventory system is not only pervasive, but also has an extensive literature dealing with various aspects, from its theoretical underpinnings through to its performance. However, the selection of the best review period and its behaviour with respect to basic inventory parameters such as demand and supply variability appears to be poorly understood. In this paper we treat

Accident rates and the impact of daylight saving time transitions

Accident Analysis & Prevention, Feb 1, 2018

One-third of nations have adopted some form of Daylight Saving Time (DST). Associated costs and b... more One-third of nations have adopted some form of Daylight Saving Time (DST). Associated costs and benefits include impacts on accident rates. Using data from 12.6 million accident claims in New Zealand during 2005-2016, we model accident rates as a function of various date-based predictors including days before/after the start and end of DST, holidays, day of week, and month of year. This is the first study to consider multiple accident categories (Road, Work, Falls and Home & Community), and the first in the southern hemisphere. The start of DST is associated with significantly higher rates of road accidents (first day +16% and second day +12%). Evidence that accident rates for Falls and Home & Community decline (increase) prior to the start (end) of DST suggest potential behavioural adaption from anticipating the change. While Work accidents show limited impact from DST changes, they exhibit a significant decline over the course of the week (Friday 13% lower than Monday), whereas Road accidents exhibit a significant increase (Friday 19% higher than Monday). Our results have implications for both DST implementation and policy.

Probability Density Functions of Task-processing Times for Deterministic, Time-varying Processor Efficiency

Journal of the Operational Research Society, Nov 1, 1990

Page 1. J. Opl Res. Soc. Vol. 41, No. 11, pp. 1049-1052, 1990 0160-5682/90 $3.50 + 0.00 Printed i... more

Appropriate manufacturing strategy in China: a case study

International Journal of Manufacturing Technology and Management, 2000

... This high-tech machine had been acquired from Siemens in Germany for DM 300,000 and was expec... more

Digitalization and omnichannel retailing: Innovative OR approaches for retail operations

European Journal of Operational Research, Nov 1, 2021

Abstract Omnichannel retailing and digitalization result in considerable challenges for the manag... more Abstract Omnichannel retailing and digitalization result in considerable challenges for the management and optimization of retail operations. The continued demand of quantitative insights, their practical need, and the growing availability of data motivates an increasing number of scientists and practitioners to intensify research on demand and supply-related issues in retailing. This featured cluster provides the state-of-the art literature on forecasting and digitalization technologies, channel structures and delivery concepts as well as logistics in omnichannel and online retailing. The featured cluster contains 17 articles that deal with such topics.

Scheduling in a Management Context: Uncertain Processing Times and Non-Regular Performance Measures

Decision Sciences, Nov 1, 1993

Decision makers often face scheduling problems in which processing times are not known with Certa... more Decision makers often face scheduling problems in which processing times are not known with Certainty. Non-regular performance measures, in which both earliness and tardiness are penalii, are also becoming more common in both manufacturing and service operations. We model a managerial environment with task processing times (which include sequenceindependent setup times) prescribed by three-parameter lognormal distributions. Upon completion, each task &rives a reward given by a particular piecewise-linear reward function. The objective is to select a sequence of tasks maximizing the expected total reward. The relative generality of the problem tenders many enumerative methods inapplicable or computationally intractable. To overcome such difficulties we develop efficient priorityinduced construction (PIC) heuristics which build up a complete schedule by inserting tasks (singly from a list) into a partial sequence of tasks. In each partial and complete sequence a period of idle time is permitted prior to the first task. Performance on realistic-sized problems is very encouraging, with cost penalties averaging less than one percent.

Inventory performance under pack size constraints and spatially-correlated demand

International Journal of Production Economics, Feb 1, 2009

Motivated by a problem facing a large retailer, we consider the impact of pack size on the perfor... more

Erratum: Inventory management under date-terms supplier trade credit with stochastic demand and leadtime

Journal of the Operational Research Society, May 10, 2006

Decision support for serials deselection and acquisition: A case study

Journal of the American Society for Information Science, Mar 1, 1997

Assessing Forecast Model Performance in an ERP Environment

Social Science Research Network, Jun 23, 2008

PurposeThe paper aims to describe and apply a commercially oriented method of forecast performanc... more PurposeThe paper aims to describe and apply a commercially oriented method of forecast performance measurement (cost of forecast error – CFE) and to compare the results with commonly adopted statistical measures of forecast accuracy in an enterprise resource planning (ERP) environment.Design/methodology/approachThe study adopts a quantitative methodology to evaluate the nine forecasting models (two moving average and seven exponential smoothing) of SAP®'s ERP system. Event management adjustment and fitted smoothing parameters are also assessed. SAP®is the largest European software enterprise and the third largest in the world, with headquarters in Walldorf, Germany.FindingsThe findings of the study support the adoption of CFE as a more relevant commercial decision‐making measure than commonly applied statistical forecast measures.Practical implicationsThe findings of the study provide forecast model selection guidance to SAP®'s 12+ million worldwide users. However, the CFE metric can be adopted in any commercial forecasting situation.Originality/valueThis study is the first published cost assessment of SAP®'s forecasting models.

The “More for Less” Paradox in Distribution Models: An Intuitive Explanation

Iie Transactions, Dec 1, 1990

An evaluation of scheduling heuristics for dynamic single-processor scheduling with early/tardy costs

Naval Research Logistics, Apr 1, 1996

In an endeavor to broaden the application of scheduling models to decisions involving the use of ... more In an endeavor to broaden the application of scheduling models to decisions involving the use of a manager's time we use simulation to investigate the performance of a number of simple algorithms (including eight priority rules and a construction heuristic) in a dynamic setting with tasks amving (randomly) and scheduling decisions being made, over time. We compare these simple methods relative to a bound that uses an adjacent pairwise interchange algorithm. We model uncertainty in task durations, and costs being incurred for early and tardy task completion (representative of JIT settings). In addition to evaluating the efficacy of the scheduling rules and various preemption strategies (using ANOVA), we highlight the managerial implications of the effects of eight environmental parameters.

Quality disclosure strategy in a decentralized supply chain with consumer returns

International Transactions in Operational Research, Sep 16, 2019

We study the quality disclosure strategy of a manufacturer/retailer in a supply chain with consum... more We study the quality disclosure strategy of a manufacturer/retailer in a supply chain with consumer returns for new products. In particular, we explicitly model the effect of quality disclosure on the reduction of the returns rate. We identify the condition in which the manufacturer/retailer should reveal product quality in the presence of consumer returns. We find that (1) the manufacturer/retailer has an incentive to choose quality disclosure strategy when the disclosure quality is above a lower bound; (2) if the returns rate of new products is low, the retailer-disclosure scenario leads to reveal more quality information than that of the manufacturerdisclosure scenario; otherwise, the manufacturer-disclosure scenario leads to reveal more quality information; and (3) the manufacturer prefers to reveal a higher level of product quality in the supply chain with a higher refund amount or a lower salvage value per unit of returned product.

An In-Class Competition Introducing Inventory Management Concepts

Informs Transactions on Education, May 1, 2010

E ncouraging interest in inventory management necessitates that instructors overcome concerns tha... more E ncouraging interest in inventory management necessitates that instructors overcome concerns that the subject is too abstract or conceptual. To aid in this process, we describe a competition engaging students in concepts, including demand estimation, demand uncertainty, and costs of inventory and shortages. The competition simulates a multi-item newsvendor problem employing participant-generated data. We present results from use of the exercise in multiple class settings over the past decade. A number of possible extensions of the basic competition are discussed. Data collection and analysis materials are available to interested readers.

A Survey of Manufacturing Strategy and Technology in the Chinese Furniture Industry

European Management Journal, Aug 1, 2003

Analysis and Management of Periodic Review, Order-Up-To Level Inventory Systems with Order Crossover

Production and Operations Management, Sep 6, 2013

In this paper we investigate the (R, S) periodic review, order-up-to level inventory control syst... more In this paper we investigate the (R, S) periodic review, order-up-to level inventory control system with stochastic demand and variable leadtimes. Variable leadtimes can lead to order crossover, in which some orders arrive out of sequence. Most theoretical studies of order-up-to inventory systems under variable leadtimes assume that crossovers do not occur and, in so doing, overestimate the standard deviation of the realized leadtime distribution and prescribe policies that can inflate inventory costs. We develop a new analytic model of the expected costs associated with this system, making use of a novel approximation of the realized (reduced) leadtime standard deviation resulting from order crossovers. Extensive experimentation through simulation shows that our model closely approximates the true expected cost and can be used to find values of R and S that provide an expected cost close to the minimum cost. Taking account of, as opposed to ignoring, crossovers leads, on average, to substantial improvements in accuracy and significant cost reductions. Our results are particularly useful for managers seeking to reduce inventory costs in supply chains with variable leadtimes.

Sharing shipment quantity information in the supply chain

Omega, Oct 1, 2006

This paper evaluates the benefit of a strategy of sharing shipment information, where one stage i... more This paper evaluates the benefit of a strategy of sharing shipment information, where one stage in a supply chain shares shipment quantity information with its immediate downstream customers-a practice also known as advanced shipping notice. Under a periodic review inventory policy, one supply-chain member places an order on its supplier every period. However, due to supplier's imperfect service, the supplier cannot always exactly satisfy what the customer orders on time. In particular, shipment quantities arriving at the customer, after a given lead-time, may be less (possibly more) than what the customer expects-we define this phenomenon as shipment quantity uncertainty. Where shipment quantity information is not shared with customers, the only way to respond is through safety stock. However, if the supplier shares such information, i.e. customers are informed every period of the shipment quantity dispatched, the customer may have enough time to adapt and resolve this uncertainty by adjusting its future order decisions. Our results indicate that in most circumstances this strategy, enabled by information technologies, helps supply-chain members resolve shipment quantity uncertainty well. This study provides an approach to quantify the value of shared shipment information and to help supply-chain members evaluate the cost-benefit trade-off during information system construction. Numerical examples are provided to indicate the impact of demand/shipment parameters on strategy implementation. While previous studies mainly focus on the information receiver's perspective, we evaluate a more general three-tier linear supply chain model via simulation, studying how this strategy affects the whole supply chain: the information sender, the information receiver and the subsequent downstream tier.

Production Scheduling Theory: Just Where Is It Applicable?

Interfaces, Dec 1, 2000

A proliferation of scheduling research has done little to improve production planning practice, d... more A proliferation of scheduling research has done little to improve production planning practice, despite calls for more comprehensive models. Using a four-factor classification of planning environments (planning level, production type, production strategy, and production cycle time) we show scheduling theory is relevant in few settings. For example, in increasingly common short-cycle environments, where production cycle times are shorter than the planning period, the order in which one processes jobs is seldom important. Moreover, even in long-cycle environments, capacity is seldom fixed, with managers often negotiating for enough capacity to make scheduling fairly easy. Based on extensive consulting experience in Australasia, we call for caution in applying scheduling theory. While complex models are pertinent in some cases, more benefit often arises from establishing appropriate performance measures, planning periods, capacity negotiation processes, and uncertainty reduction measures.

Manufacturing and Supply Chain Management in China: A Survey of State-, Collective-, and Privately-Owned Enterprises

Social Science Research Network, Jun 8, 2000

Because of the booming economy, interest in China has soared in recent years. The government has ... more Because of the booming economy, interest in China has soared in recent years. The government has decided to privatize many state-owned enterprises (SOEs), so foreigners can much more easily invest in existing firms than ever before. Is it wise to consider investing in these SOEs? Certainly, many have major problems. How sophisticated are Chinese manufacturing firms? Do they understand modern principles of manufacturing strategy and supply chain management? What is the level of installed technology, from traditional production planning systems, like MRP, to robotics? This paper attempts to answer these questions based on a survey of 100 firms in the Shanghai area. We surveyed state-owned enterprises, collective-owned enterprises and privately held firms, and we discovered some fascinating insights about their differences and their similarities. We discovered that the differences among the ownership types are generally insignificant, suggesting that our results are quite general. We find that these firms are far more advanced using explicit manufacturing strategies than we had expected. However, they are not as advanced in supply chain management as many Western firms. They report significant communication with customers and suppliers-more with customers than suppliers-but the nature of the communication is often limited to one dimension, particularly on the downstream side. Firms that communicate with customers tend to do so with suppliers as well.

Service failure, recovery and improvement: the case of a Chinese restaurant

International Journal of Services and Operations Management, 2008

218 Int. J. Services and Operations Management, Vol. 4, No. 2, 2008 ... Service failure, recovery... more

Some insights regarding the optimal reorder period in periodic review inventory systems

International Journal of Production Economics, Mar 1, 2008

The periodic review inventory system is not only pervasive, but also has an extensive literature ... more The periodic review inventory system is not only pervasive, but also has an extensive literature dealing with various aspects, from its theoretical underpinnings through to its performance. However, the selection of the best review period and its behaviour with respect to basic inventory parameters such as demand and supply variability appears to be poorly understood. In this paper we treat

Accident rates and the impact of daylight saving time transitions

Accident Analysis & Prevention, Feb 1, 2018

One-third of nations have adopted some form of Daylight Saving Time (DST). Associated costs and b... more One-third of nations have adopted some form of Daylight Saving Time (DST). Associated costs and benefits include impacts on accident rates. Using data from 12.6 million accident claims in New Zealand during 2005-2016, we model accident rates as a function of various date-based predictors including days before/after the start and end of DST, holidays, day of week, and month of year. This is the first study to consider multiple accident categories (Road, Work, Falls and Home & Community), and the first in the southern hemisphere. The start of DST is associated with significantly higher rates of road accidents (first day +16% and second day +12%). Evidence that accident rates for Falls and Home & Community decline (increase) prior to the start (end) of DST suggest potential behavioural adaption from anticipating the change. While Work accidents show limited impact from DST changes, they exhibit a significant decline over the course of the week (Friday 13% lower than Monday), whereas Road accidents exhibit a significant increase (Friday 19% higher than Monday). Our results have implications for both DST implementation and policy.

Probability Density Functions of Task-processing Times for Deterministic, Time-varying Processor Efficiency

Journal of the Operational Research Society, Nov 1, 1990

Page 1. J. Opl Res. Soc. Vol. 41, No. 11, pp. 1049-1052, 1990 0160-5682/90 $3.50 + 0.00 Printed i... more

Appropriate manufacturing strategy in China: a case study

International Journal of Manufacturing Technology and Management, 2000

... This high-tech machine had been acquired from Siemens in Germany for DM 300,000 and was expec... more

Digitalization and omnichannel retailing: Innovative OR approaches for retail operations

European Journal of Operational Research, Nov 1, 2021

Abstract Omnichannel retailing and digitalization result in considerable challenges for the manag... more Abstract Omnichannel retailing and digitalization result in considerable challenges for the management and optimization of retail operations. The continued demand of quantitative insights, their practical need, and the growing availability of data motivates an increasing number of scientists and practitioners to intensify research on demand and supply-related issues in retailing. This featured cluster provides the state-of-the art literature on forecasting and digitalization technologies, channel structures and delivery concepts as well as logistics in omnichannel and online retailing. The featured cluster contains 17 articles that deal with such topics.

Scheduling in a Management Context: Uncertain Processing Times and Non-Regular Performance Measures

Decision Sciences, Nov 1, 1993

Decision makers often face scheduling problems in which processing times are not known with Certa... more Decision makers often face scheduling problems in which processing times are not known with Certainty. Non-regular performance measures, in which both earliness and tardiness are penalii, are also becoming more common in both manufacturing and service operations. We model a managerial environment with task processing times (which include sequenceindependent setup times) prescribed by three-parameter lognormal distributions. Upon completion, each task &rives a reward given by a particular piecewise-linear reward function. The objective is to select a sequence of tasks maximizing the expected total reward. The relative generality of the problem tenders many enumerative methods inapplicable or computationally intractable. To overcome such difficulties we develop efficient priorityinduced construction (PIC) heuristics which build up a complete schedule by inserting tasks (singly from a list) into a partial sequence of tasks. In each partial and complete sequence a period of idle time is permitted prior to the first task. Performance on realistic-sized problems is very encouraging, with cost penalties averaging less than one percent.

Inventory performance under pack size constraints and spatially-correlated demand

International Journal of Production Economics, Feb 1, 2009

Motivated by a problem facing a large retailer, we consider the impact of pack size on the perfor... more