Operations and Supply Chain Management Commons^™

Have We Taught Our Students The Right Stuff?, Jaydeep Balakrishnan, Kum Khiong Yang

Research Collection Lee Kong Chian School Of Business

Operations Management involves managing the resources that are required to convert inputs to outputs. These resources include materials, capital and people which requires decision making within the operations function to be cross functional (Schroeder, 2000). The resulting impact is that whenever an operations manager makes a decision, he or she should be cognizant of its impact on other areas within the firm, such as finance, marketing and human resources, as well as the external partners such as suppliers and customers. Our question is whether Production and Operations Management (POM) educators are training students adequately to make the necessary cross functional …

The Effect Of Remanufacturing On Procurement Decisions For Resellers In Secondary Markets, Andreas Robotis, Shantanu Bhattacharya, Luk N. Van Wassenhove

Research Collection Lee Kong Chian School Of Business

The role of remanufacturing as a competitive tool for firms has been reflected in a number of studies to show that remanufacturing can reduce the unit cost of production by reusing components. However, the fact that remanufacturing can be used as a strategic tool for serving secondary markets as well has not been acknowledged in the literature. In this paper, we study the use of remanufacturing as a tool to serve secondary markets. Specifically, we model the case of a reseller who procures used products based on an older generation of technology from an advanced market and then uses one …

Interaction Of Technology Choice And Financial Risk Management Under Costly External Financing, Onur Boyabatli, L. Beril Toktay

Research Collection Lee Kong Chian School Of Business

This paper analyzes the integrated operational and financial risk management portfolio of a firm that determines whether to use flexible or dedicated technology and whether to undertake financial risk management or not. The risk management value of flexible technology is due to its risk pooling benefit under demand uncertainty. The financial risk management motivation comes from the existence of deadweight costs of external financing due to capital market imperfections. Financial risk management has a fixed cost, while technology investment incurs both fixed and variable costs. The firm's limited budget, which depends partly on a tradable asset, can be increased by …

K-Center Problems With Minimum Coverage, Andrew Lim, Brian Rodrigues, Fan Wang, Zhou Xu

Research Collection Lee Kong Chian School Of Business

In this work, we study an extension of the k-center facility location problem, where centers are required to service a minimum of clients. This problem is motivated by requirements to balance the workload of centers while allowing each center to cater to a spread of clients. We study three variants of this problem, all of which are shown to be -hard. In-approximation hardness and approximation algorithms with factors equal or close to the best lower bounds are provided. Generalizations, including vertex costs and vertex weights, are also studied.

Managing Learning Resources For Consecutive Product Generations, Lieven Demeester, Mei Qi

Research Collection Lee Kong Chian School Of Business

In this paper, we study how a firm should allocate its learning resources when it is concurrently producing two consecutive generations of one product. We define learning resources as scarce firm-specific resources that a firm allocates towards the improvement of the cost, quality or timeliness of its existing products and processes. We use empirically tested models for demand substitution and learning curves to formulate this problem, and we present our results as propositions with regard to the optimal time at which a firm should direct all its learning resources to the newer product generation, depending on the substitution rate of …

Logistics Network Design With Differentiated Delivery Lead Time: A Chemical Industry Case Study, Michelle Lee Fong Cheong, Rohit Bhatnagar, Stephen C. Graves

Research Collection School Of Computing and Information Systems

Most logistics network design models assume exogenous customer demand that is independent of the service time or level. This paper examines the benefits of segmenting demand according to lead-time sensitivity of customers. To capture lead-time sensitivity in the network design model, we use a facility grouping method to ensure that the different demand classes are satisfied on time. In addition, we perform a series of computational experiments to develop a set of managerial insights for the network design decision making process.

The Role Of Manufacturing Flexibility On Product Platform Development, Soumen Ghosh, Byung Joon Park

Research Collection Lee Kong Chian School Of Business

In recent years firms from a range of industries have responded to growing market uncertainty by investing heavily in manufacturing flexibility. Manufacturing Flexibility is understood as process flexibility, that is a process that results from being able to build different types of products on the same production line at the same time. One benefit of manufacturing flexibility is the reduction of change over cost from building one product to another. Flexible manufacturing also relieves the problem of overcapacity, since excessive overcapacity could be avoided through the introduction of flexible manufacturing plants. Recently, firms have examined a new concept of enabling …

Port Yard Storage Optimization, Ping Chen, Zhaohui Fu, Andrew Lim, Brian Rodrigues

Research Collection Lee Kong Chian School Of Business

The port yard storage optimization problem (PYSOP) originates from space allocation needs at the Port of Singapore. Space allocated to cargo is to be minimized in a designated yard within a time interval. The problem is akin to a packing problem in space and time, but where shapes packed and constraints are particular to port operations. Further, space requests can change within the time interval in which it is requested. This basic problem is generic to port operations and may find applications elsewhere. The PYSOP is NP-hard, but we propose a number of metaheuristics. Extensive experiments were conducted and good …

Organic Production Systems: What The Biological Cell Can Teach Us About Manufacturing, Lieven Demeester, Knut Eichler, Christoph H. Loch

Research Collection Lee Kong Chian School Of Business

Biological cells run complicated and sophisticated production systems. The study of the cell's production technology provides us with insights that are potentially useful in industrial manufacturing. When comparing cell metabolism with manufacturing techniques in industry, we find some striking commonalities, but also some important differences. Like today's well-run factories, the cell operates a very lean production system, assures quality at the source, and uses component commonality to simplify production. While we can certainly learn from how the cell accomplishes these parallels, it is even more interesting to look at how the cell operates differently. In biological cells, all products and …

Solving Hierarchical Constraints Over Finite Domains With Local Search, Martin Henz, Roland H.C. Yap, Yun Fong Lim, Seet Chong Lua, J. Paul Walser, Xiao Ping Shi

Research Collection Lee Kong Chian School Of Business

Many real world problems have requirements and constraints which conflict with each other. One approach for dealing with such over-constrained problems is with constraint hierarchies. In the constraint hierarchy framework, constraints are classified into ranks, and appropriate solutions are selected using a comparator which takes into account the constraints and their ranks. In this paper, we present a local search solution to solving hierarchical constraint problems over finite domains (HCPs). This is an extension of local search for over-constrained integer programs WSAT(OIP) to constraint hierarchies and general finite domain constraints.The motivation for this work arose from solving large airport gate …

Closed-Loop Supply Chain Models With Product Remanufacturing, R. Canan Savaskan, Shantanu Bhattacharya, Luk N. Van Wassenhove

Research Collection Lee Kong Chian School Of Business

The importance of remanufacturing used products into new ones has been widely recognized in the literature and in practice. In this paper, we address the problem of choosing the appropriate reverse channel structure for the collection of used products from customers. Specifically, we consider a manufacturer who has three options for collecting such products: (1) she can collect them herself directly from the customers, (2) she can provide suitable incentives to an existing retailer (who already has a distribution channel) to induce the collection, or (3) she can subcontract the collection activity to a third party. Based on our observations …

Metaheuristics With Local Search Techniques For Retail Shelf-Space Optimization, Andrew Lim, Brian Rodrigues, Xingwen Zhang

Research Collection Lee Kong Chian School Of Business

Efficient shelf-space allocation can provide retailers with a competitive edge. While there has been little study on this subject, there is great interest in improving product allocation in the retail industry. This paper examines a practicable linear allocation model for optimizing shelf-space allocation. It extends the model to address other requirements such as product groupings and nonlinear profit functions. Besides providing a network flow solution, we put forward a strategy that combines a strong local search with a metaheuristic approach to space allocation. This strategy is flexible and efficient, as it can address both linear and nonlinear problems of realistic …

Operational Hedging: A Review With Discussion, Onur Boyabatli, L. Beril Toktay

Research Collection Lee Kong Chian School Of Business

Motivated by the increasing prevalence of operational hedging in corporate-level risk management programs, this paper provides an extensive overview and synthesis of the existing literature on operational hedging. In particular, we focus on the treatment of operational hedging in the operations management literature. We then explore how the concept of operational hedging is studied in the fields of finance, strategy and international business. Finally, we discuss and critique the approaches adopted in the operations management literature in the context of the broader literature on the topic.

Heuristics For A Brokering Set Packing Problem, Yunso Guo, Andrew Lim, Brian Rodrigues, Yi Zhu

Research Collection Lee Kong Chian School Of Business

In this paper we formulate the combinatorial auction brokering problem as a Set Packing Problem (SPP) and apply a simulated annealing heuristic to solve SPP. Experimental results are compared with a recent heuristic algorithm and also with the CPLEX Integer Programming solver where we found that the simulated annealing approach outperforms the previous heuristic method and CPLEX obtaining results within smaller timescales.

Nurse Rostering Problems: A Bibliographic Survey, Brenda Cheang, Haibing Li, Andrew Lim, Brian Rodrigues

Research Collection Lee Kong Chian School Of Business

Hospitals need to repeatedly produce duty rosters for its nursing staff. The good scheduling of nurses has impact on the quality of health care, the recruitment of nurses, the development of budgets and other nursing functions. The nurse rostering problem (NRP) has been the subject of much study. This paper presents a brief overview, in the form of a bibliographic survey, of the many models and methodologies available to solve the NRP.

Manpower Allocation With Time Windows And Job Teaming Constraints, Xi Li, Yan Zhi Li, Andrew Lim, Brian Rodrigues

Research Collection Lee Kong Chian School Of Business

In the Manpower Allocation Problem with Time Windows and Job-Teaming Constraints (MAPTWTC), we have a set of jobs located at various locations where each job requires a team of workers. Each job has a time window and a job duration, during which everyone on the team has to be present. The job requirement is satisfied if and only if the required composite team works for long enough duration within the job's time window. The objective of the problem is find a schedule to minimize a weighted sum of the total number of workers, the total travelling distances of all workers …

Broadcast Scheduling For Mobile Advertising, Bert De Reyck, Zeger Degraeve

Research Collection Lee Kong Chian School Of Business

We describe a broadcast scheduling system developed for a precision marketing firm specialized in location-sensitive permission-based mobile advertising using SMS (Short Message Service) text messaging. Text messages containing advertisements were sent to registered customers when they were shopping in one of two shopping centers in the vicinity of London. The ads typically contained a limited-time promotional offer. The company's problem was deciding which ads to send out to which customers at what particular time, given a limited capacity of broadcast time slots, while maximizing customer response and revenues from retailers paying for each ad broadcast. We solved the problem using …

A New Node Centroid Algorithm For Bandwidth Minimization, Brian Rodrigues, F. Xiao, A. Lim

Research Collection Lee Kong Chian School Of Business

We propose a Node Centroid method with Hill-Climbing to solve the well-known matrix band-width minimization problem, which is to permute rows and columns of the matrix to minimize its bandwidth. Many heuristics have been developed for this NP-complete problem including the Cuthill-McKee (CM) and the Gibbs, Poole and Stockmeyer (GPS) algorithms. Recently, heuristics such as Simulated Annealing, Tabu Search and GRASP have been used, where Tabu Search and the GRASP with Path Relinking have achieved significantly better solution quality than the CM and GPS algorithms. Experimentation shows that the Node Centroid method achieves the best solution quality when compared with …

Managing Project Uncertainty: From Variation To Chaos, Arnoud De Meyer, Christoph H. Loch, Michael T. Pich

Research Collection Lee Kong Chian School Of Business

The article cites a study finding that accurately gauging the degree of uncertainty inherent in the projects can help project managers quickly adapt to it. Researchers studied 16 projects in areas including personal-computer development, telecommunications, Internet startups, pharmaceutical development, iron-ore processing, airship development, and building construction, to examine risk management and project outcomes. They found that most managers failed to recognize that there are different types of uncertainty, each requiring a different management approach. This paper explores uncertainty-based management, which derives planning, monitoring and management style from an uncertainty profile comprising four types of uncertainty: variation, foreseen uncertainty, unforeseen uncertainty, …

On Uncertainty, Ambiguity, And Complexity In Project Management, Michael T. Pich, Christoph H. Loch, Arnoud De Meyer

Research Collection Lee Kong Chian School Of Business

This article develops a model of a project as a payoff function that depends on the state of the world and the choice of a sequence of actions. A causal mapping, which may be incompletely known by the project team, represents the impact of possible actions on the states of the world. An underlying probability space represents available information about the state of the world. Interactions among actions and states of the world determine the complexity of the payoff function. Activities are endogenous, in that they are the result of a policy that maximizes the expected project payoff.

A key …

Solving The Pickup And Delivery Problem With Time Windows Using "Squeaky Wheel" Optimization With Local Search, Hongping Lim, Andrew Lim, Brian Rodrigues

Research Collection Lee Kong Chian School Of Business

The Pickup and Delivery Problem with Time Windows (PDPTW) is an important problem in fleet planning where decisions can involve not only dispatching company fleets but also the selection of carriers on certain routes. In this problem, vehicles travel to a variety of locations to deliver or pick up goods and to provide services. The increasing costs for additional vehicles motivate managers to optimize fleet usage. Managers also seek to achieve economical use of fuel, maintenance and overtime costs by minimizing travel distance and duration. As such, PDPTW impacts the interface of supplier-customer relationship management in the supply chain process …

Combining Two Heuristics To Solve A Supply Chain Optimization Problem, Hoong Chuin Lau, Yuyue Song

Research Collection School Of Computing and Information Systems

In this paper, we consider a real-life supply chain optimization problem concerned with supplying a product from multiple warehouses to multiple geographically dispersed retailers. Each retailer faces a deterministic and period-dependent demand over some finite planning horizon. The demand of each retailer is satisfied by the supply from some predetermined warehouse through a fleet of vehicles which are only available within certain time windows at each period. Our goal is to identify a combined inventory and routing schedule such that the system-wide total cost over the planning horizon is minimised. This problem in essence is an amalgamation of two classical …

Exchanging Preliminary Information In Concurrent Engineering: Alternative Coordination Strategies, Christian Terwiesch, Christoph H. Loch, Arnoud De Meyer

Research Collection Lee Kong Chian School Of Business

Successful application of concurrent development processes (concurrent engineering) requires tight coordination. To speed development, tasks often proceed in parallel by relying on preliminary information from other tasks, information that has not yet been finalized. This frequently causes substantial rework using as much as 50% of total engineering capacity. Previous studies have either described coordination as a complex social process, or have focused on the frequency, but not the content, of information exchanges. Through extensive fieldwork in a high-end German automotive manufacturer, we develop a framework of preliminary information that distinguishes information precision and information stability. Information precision refers to the …

Mobile Commerce Applications In Supply Chain Management, Keng Siau, Zixing Shen

Research Collection School Of Computing and Information Systems

As wireless technologies evolve, the coming mobile revolution will bring dramatic and fundamental changes to supply chain management. When complete, the revolution will impact numerous facets of organizational life. It will provide important data in real time to assist decision makers, exert great influence on the ways businesses communicate and develop relationships with consumers and suppliers, and ultimately transform the way we manage the supply chain. This paper examines issues in integrating mobile commerce and supply chain management. The paper discusses issues such as the absence of killer applications, mobile device limitations, networking problems, infrastructure constraints, security concerns, and user …

Scale-Invariant Behavior In A Spatial Game Of Prisoners’ Dilemma, Yun Fong Lim, Kan Chen, Ciriyam Jayaprakash

Research Collection Lee Kong Chian School Of Business

A spatially extended version of the game of prisoner’s dilemma, originally proposed by Nowak and May, is modified to include stochastic updating and found to exhibit scale-invariant behavior. Two critical regimes with different scaling behaviors are found; the corresponding exponents have been determined numerically. Spatially, the critical states are characterized by the existence of delicately balanced networks of defectors separating domains of cooperators; temporally, the evolution of the critical states following local perturbations is characterized by avalanches of various magnitudes, which cause restructuring of the networks of defectors on all scales.

Collaborative Model And Algorithms For Supporting Real-Time Distribution Logistics Systems, Hoong Chuin Lau, Qi Zhang Liu

Research Collection School Of Computing and Information Systems

We study a complex optimization problem that arises due to an emerging trend in distribution logistics. The problem involves the integration of an inventory management problem and the vehicle routing problem with time windows, both of which are known to be NP-hard. We describe a collaborative approach to solve this problem in real-time. The novelty of our approach lies in the tight algorithmic integration between two sub-problems, and suggests an elegant scheme to deal with other integrated optimization problems of the same nature. For first sub-problem, we will present two algorithms: a complete mathematical model integrating integer programming with constraint …

Managing A Flow Line With Single-Kanban, Dual-Kanban Or Conwip, Kum Khiong Yang

Research Collection Lee Kong Chian School Of Business

To control the production of different parts on a single flow line, managers can choose between the Single-kanban, Dual-kanban, and Conwip. This paper therefore compares the three different systems. The results show that Conwip consistently produces the shortest mean customer wait time and lowest total work-in-process. Our results also contradict the finding of a previous study, which showed that Dual-kanban performed better than Single-kanban. The different findings can, however, be attributed to the use of a material transfer policy, which favors the Dual-kanban modeled in the previous study. Our study shows that transferring replenished containers immediately to downstream stations, increasing …

Solving A Supply Chain Optimization Problem Collaboratively, Hoong Chuin Lau, A. L. C. Lim, Q Liu

Research Collection School Of Computing and Information Systems

We propose a novel algorithmic framework to solve an integrated planning and scheduling problem in supply chain management. This problem involves the integration of an inventory management problem and the vehicle routing problem with time windows, both of which are known to be NP-hard. Under this framework, algorithms that solve the underlying sub-problems collaborate rigorously yet in a computationally efficient manner to arrive at a good solution. We will then present two algorithms to solve the inventory management problem: a complete mathematical model integrating integer programming with constraint programming, and an incomplete algorithm based on tabu search. We present experimental …

The Empirical Determinants Of Inventory Levels In High-Volume Manufacturing, Marvin B. Lieberman, Susan Helper, Lieven Demeester

Research Collection Lee Kong Chian School Of Business

This study uses survey data on several hundred automotive suppliers in North America to evaluate the determinants of inventory levels in high-volume discrete parts manufacturing. We assess the magnitude of raw materials, work-in-process, and finished goods inventories held at automotive supply plants. Inventories are shown to be jointly determined by technological and managerial factors in a manner roughly consistent with classical inventory theory. Several categories of managerial practices are found to be important. Low inventories are linked to employee problem solving and frequent communication with customers. More unexpectedly, we find the absence of inventory differences between U.S.-owned and Japanese-owned plants …

Inventory Reduction And Productivity Growth: Linkages In The Japanese Automotive Industry, Marvin B. Lieberman, Lieven Demeester

Research Collection Lee Kong Chian School Of Business

The literature on JIT production suggests a causal link between work-in-progress inventory and manufacturing productivity. Such a connection has been described in numerous case studies but never tested statistically. Historical data for 52 Japanese automotive companies are used to evaluate the inventory-productivity relationship. It is found that firms increased their productivity rank during periods of substantial inventory reduction. More detailed tests suggest that inventory reductions stimulated gains in productivity. On average, each 10% reduction in inventory led to about a 1% gain in labor productivity, with a lag of about one year. Such effects were more immediate for Toyota affiliates, …