International Journal of Integrated Supply Management, 2007
ABSTRACT The research reported in this article is part of a larger project involving Enterprise R... more ABSTRACT The research reported in this article is part of a larger project involving Enterprise Resource Planning (ERP) adoption in Greece aiming at the investigation of the criteria that affect actual implementation. A structured questionnaire has been developed based on a combination of two frameworks: the first one is an extension proposed to the Markus and Tanis model, and the second one is based on a previously developed methodology (the six imperatives) for ERP evaluation, selection, and implementation. The paper discusses the frameworks, methodology, and preliminary findings from 40 companies of various industries. The results indicate a number of factors affecting ERP implementation and some differences in choices and activities between Small and Medium Sized Enterprises (SMEs) and larger companies concerning ERP adoption. One important finding is that many SMEs do not follow a structured methodology for ERP system implementation and they are not familiar with techniques such as business process reengineering and change management.
The 'European Paradox' encapsulates concerns that although European research institutions play a ... more The 'European Paradox' encapsulates concerns that although European research institutions play a leading role in terms of top-level scientific output, they lag behind in their ability to convert this strength into successful innovations in the market. This paradox and the related intriguing problematic aspects of European research institutions have inspired a significant number of research papers, reports and studies by academics, innovation think tanks and the European Commission itself. In this position paper, we review the literature on the European paradox, identify gaps and contradictions in the understanding of the actual situation and discuss possible ways of moving forward towards a European research and innovation system that taps into diversity and complementarity of resources as a competitive innovation advantage.
We consider inventory management decisions when manufacturing and warehousing are controlled by i... more We consider inventory management decisions when manufacturing and warehousing are controlled by independent entities. The latter possess private information that affects their choices and are allowed to communicate via a mediator who attempts to streamline their decisions without restricting their freedom. The mediator designs a mechanism based on quantity discounts to minimize the overall system costs, attempting to reach a win-win situation for both entities. Using the Revelation Principle we show that it is in the entities' self-interest to reveal their information and we prove that coordination is attainable even under bilateral information asymmetry. The acceptable cost allocation is not unique, providing adequate flexibility to the mediator during mechanism design; the flexibility may reflect the relative power of the entities and is quantified in our work by a series of computational experiments. Our approach is motivated by inventory management practices in a manufacturing group and, thus, it is directly applicable to real-life cases.
We are concerned with the interaction and integration between demand forecasting and inventory co... more We are concerned with the interaction and integration between demand forecasting and inventory control, in the context of supply chain operations. The majority of the literature is fragmented. Forecasting research more often than not assumes forecasting to be an end in itself, disregarding any subsequent stages of computation that are needed to transform forecasts into replenishment decisions. Conversely, most contributions in inventory theory assume that demand (and its parameters) are known, in effect disregarding any preceding stages of computation. Explicit recognition of these shortcomings is an important step towards more realistic theoretical developments, but still not particularly helpful unless they are somehow addressed. Even then, forecasts often constitute exogenous variables that serially feed into a stock control model. Finally, there is a small but growing stream of research that is explicitly built around jointly tackling the inventory forecasting question. We introduce a framework to define four levels of integration: from disregarding, to acknowledging, to partly addressing, to fully understanding the interactions. Focusing on the last two, we conduct a structured review of relevant (integrated) academic contributions in the area of forecasting and inventory control and argue for their classification with regard to integration. We show that the development from one level to another is in many cases chronological in order, but also associated with specific schools of thought. We also argue that although movement from one level to another adds realism, it also adds complexity in terms of actual implementations, and thus a trade-off exists. The article makes a contribution into an area that has always been fragmented despite the importance of bringing the forecasting and inventory communities together to solve problems of common interest. We close with an indicative agenda for further research and a call for more theoretical contributions, but also more work that would help to expand the empirical knowledge base in this area.
In this paper we consider the operational planning problem of physical distribution via a fleet o... more In this paper we consider the operational planning problem of physical distribution via a fleet of hired vehicles, for which the travelling cost is solely a function of the sequence of locations visited within all open delivery routes, while vehicle fixed cost is inexistent. The problem is a special class of vehicle routing and is encountered in the literature as the Open Vehicle Routing Problem (OVRP), since vehicles are not required to return to the depot. The goal is to distribute in an optimal way finished goods from a central facility to geographically dispersed customers, which pose daily demand for items produced in the facility and act as sales points for consumers. To solve the problem, we employ an annealing-based method that utilizes a backtracking policy of the threshold value when no acceptances of feasible solutions occur during the search process. Computational results on a set of benchmark problems show that the proposed method consistently outperforms previous algorithms for solving the OVRP. The approach can serve as the means for effective fleet planning in real-life problems.
... approximately two thousand customers, is presented and solved by our heuristic, using an inte... more ... approximately two thousand customers, is presented and solved by our heuristic, using an interface to ... One can solve with success any of the two underlying sub-problems of the ... 20 Thus, a key determinant factor for obtaining good solutions for vehicle routing problems with tight ...
International Journal of Production Economics, 2008
The tendency of companies to expand their control through the entire supply chain is a significan... more The tendency of companies to expand their control through the entire supply chain is a significant managerial driver. On the other hand, large manufacturing and distribution firms have developed competences that do not cover all levels of the supply chain. In order to confront the lack of knowledge and expertise, enterprises can either outsource a specific operation or acquire a company that is specialized in the specific field. In this paper we focus on warehousing decisions and investigate three different warehousing policies and ownership structures of the warehousing facilities. The approach is based on game theory and an industrial example provides insight on the results reached.
ABSTRACT Increased competition and uncertainty characterise the new economy, introducing signific... more ABSTRACT Increased competition and uncertainty characterise the new economy, introducing significant pressures to supply chain participants, calling for capital investments only in value adding/revenue-generating assets. The tendency of companies to expand their control through the entire supply chain seems to attract significant managerial attention. On the other hand, large manufacturer and distributor firms have developed specific competences that do not expand to all the levels of the supply chain. In order to confront the lack of knowledge and expertise companies can either outsource the specific operation or acquire a company that is specialized in the specific field. In this paper we focus on warehousing decisions and investigate three different warehousing policies and ownership structures of the warehousing facilities.
We develop a model for lead-time quotation in a Markovian make-to-order production or service sys... more We develop a model for lead-time quotation in a Markovian make-to-order production or service system with strategic customers who exhibit risk aversion. Based on a CARA utility function of their net benefit, customers make individual decisions to join the system or balk by observing the state of the queue. The decisions of arriving customers result in a symmetric join/balk game. Regarding the firm's strategy, the provider announces a lead-time quotation for each state and a respective balking threshold. There is also a fixed entrance fee and compensation rate for the part of a customer' delay exceeding the quoted lead-time. Moreover, we consider the problem from the point of view of a social optimizer who maximizes the total net benefit of the system. We analyze the provider's and social optimizer's maximization problems and we consider two cases regarding the class of lead-time quotation policies, i.e., dynamic and single. We identify the optimal entrance thresholds...
We develop a model for lead-time quotation in a Markovian Make-To-Order production or service sys... more We develop a model for lead-time quotation in a Markovian Make-To-Order production or service system with strategic customers who exhibit risk aversion. Based on a CARA utility function of their net benefit, customers make individual decisions to join the system or balk by observing the state of the queue. The decisions of arriving customers result in a symmetric join/balk game. Regarding the firm’s strategy, the provider announces a lead-time quotation for each state and a respective balking threshold. There is also a fixed entrance fee and compensation rate for the part of a customer’ delay exceeding the quoted lead-time. Moreover, we consider the problem from the point of view of a social optimizer who maximizes the total net benefit of the system. We analyze the provider’s and social optimizer’s maximization problems and we consider two cases regarding the class of lead-time quotation policies, i.e., dynamic and single. We identify the optimal entrance thresholds in each case. F...
The plant layout project has been the mainstay of industrial engineering curriculum for many year... more The plant layout project has been the mainstay of industrial engineering curriculum for many years. Yet, even today, some schools miss the educational opportunities offered by these projects. While working through the steps of the layout design process, students can be exposed to exercises in open ended problem solving, business communications, computer modeling and team participation. All of these facets of the process occur naturally. However, unless proper design of the project and its evaluation mechanisms are considered, the full benefits of the assignments will not be realized. This paper presents the plant layout project as a tool for experimental learning on a broader frontfrom communications through engineering design. Opportunities for exercises of various kinds are explored. Throughout the paper, the Virginia Tech layout project is discussed to provide a contextual framework for the presentation.
We develop and validate a model of the micro-level dynamics underlying the formation of macro-lev... more We develop and validate a model of the micro-level dynamics underlying the formation of macro-level information propagation patterns in online social networks. In particular, we address the dynamics at the level of the mechanism regulating a user's participation in an online information propagation process. We demonstrate that this mechanism can be realistically described by the dynamics of noisy spiking neurons driven by endogenous and exogenous, deterministic and stochastic stimuli representing the influence modulating one's intention to be an information spreader. Depending on the dynamically changing influence characteristics, time-varying propagation patterns emerge reflecting the temporal structure, strength, and signal-to-noise ratio characteristics of the stimulation driving the online users' information sharing activity. The proposed model constitutes an overarching, novel, and flexible approach to the modeling of the micro-level mechanisms whereby information propagates in online social networks. As such, it can be used for a comprehensive understanding of the online transmission of information, a process integral to the sociocultural evolution of modern societies. The proposed model is highly adaptable and suitable for the study of the propagation patterns of behavior, opinions, and innovations among others.
International Journal of Production Research, 2016
The Resource Constrained Project Scheduling Problem (RCPSP) is one of the most intractable combin... more The Resource Constrained Project Scheduling Problem (RCPSP) is one of the most intractable combinatorial optimisation problems that combines a set of constraints and objectives met in a vast variety of applications and industries. Its solution raises major theoretical challenges due to its complexity, yet presenting numerous practical dimensions. Adaptive Memory Programming (AMP) is one of the most successful frameworks for solving hard combinatorial optimisation problems (e.g., vehicle routing and scheduling). Its success stems from the use of learning mechanisms that capture favourable solution elements found in high quality solutions. This paper challenges the efficiency of AMP for solving the RCPSP, to our knowledge, for the first time in the up-to-date literature. Computational experiments on well known benchmark RCPSP instances show that the proposed AMP consistently produces high-quality solutions in reasonable computational times.
The management of supply chains is the current focus of corporate strategies. Currently, we note ... more The management of supply chains is the current focus of corporate strategies. Currently, we note that it is not businesses that compete but supply chains that compete. In order to lead in the corporate race, organisations take advantage of information and communication technologies for e-business. An executive level of strategic management of the supply chain is a requirement of which, one of the major ingredient is information that is passed among supply chain constituents. The information is generated, distributed, received and stored in supply chain management information systems of heterogeneous architectures and/or platforms. This poses a challenge in the sharing and understanding of the bits of information. In this paper we present an artificial intelligence approach for supply chain information systems that have heterogeneous architectures to share information through a common ontology. The supply chain ontology structures a shared formal specification of concepts and the rel...
The main objective of this paper is to propose a two-phase solution algorithm for solving the Inv... more The main objective of this paper is to propose a two-phase solution algorithm for solving the Inventory Routing Problem with Time Windows (IRPTW), which has not been excessively researched in the literature. The solution approach is based on (a) a simple simulation for the planning phase (Phase I) and (b) the Variable Neighborhood Search Algorithm (VNS) for the routing phase (Phase II). Testing instances are established to investigate algorithmic performance, and the computational results are then reported. The computational study underscores the importance of integrating the inventory and vehicle routing decisions. Graphical presentation formats are provided to convey meaningful insights into the problem.
In this paper, we consider the open vehicle routeing problem (OVRP), in which routes are not sequ... more In this paper, we consider the open vehicle routeing problem (OVRP), in which routes are not sequences of locations starting and ending at the depot but open paths. The problem is of particular importance for planning fleets of hired vehicles, a common practice in the distribution and service industry. In such cases, the travelling cost is a function of the vehicle open paths. To solve the problem, we employ a single-parameter metaheuristic method that exploits a list of threshold values to guide intelligently an advanced local search. Computational results on a set of benchmark problems show that the proposed method consistently outperforms previous approaches for the OVRP. A real-world example demonstrates the applicability of the method in practice, demonstrating that the approach can be used to solve actual problems of routing large vehicle fleets.
International Journal of Integrated Supply Management, 2007
ABSTRACT The research reported in this article is part of a larger project involving Enterprise R... more ABSTRACT The research reported in this article is part of a larger project involving Enterprise Resource Planning (ERP) adoption in Greece aiming at the investigation of the criteria that affect actual implementation. A structured questionnaire has been developed based on a combination of two frameworks: the first one is an extension proposed to the Markus and Tanis model, and the second one is based on a previously developed methodology (the six imperatives) for ERP evaluation, selection, and implementation. The paper discusses the frameworks, methodology, and preliminary findings from 40 companies of various industries. The results indicate a number of factors affecting ERP implementation and some differences in choices and activities between Small and Medium Sized Enterprises (SMEs) and larger companies concerning ERP adoption. One important finding is that many SMEs do not follow a structured methodology for ERP system implementation and they are not familiar with techniques such as business process reengineering and change management.
The 'European Paradox' encapsulates concerns that although European research institutions play a ... more The 'European Paradox' encapsulates concerns that although European research institutions play a leading role in terms of top-level scientific output, they lag behind in their ability to convert this strength into successful innovations in the market. This paradox and the related intriguing problematic aspects of European research institutions have inspired a significant number of research papers, reports and studies by academics, innovation think tanks and the European Commission itself. In this position paper, we review the literature on the European paradox, identify gaps and contradictions in the understanding of the actual situation and discuss possible ways of moving forward towards a European research and innovation system that taps into diversity and complementarity of resources as a competitive innovation advantage.
We consider inventory management decisions when manufacturing and warehousing are controlled by i... more We consider inventory management decisions when manufacturing and warehousing are controlled by independent entities. The latter possess private information that affects their choices and are allowed to communicate via a mediator who attempts to streamline their decisions without restricting their freedom. The mediator designs a mechanism based on quantity discounts to minimize the overall system costs, attempting to reach a win-win situation for both entities. Using the Revelation Principle we show that it is in the entities' self-interest to reveal their information and we prove that coordination is attainable even under bilateral information asymmetry. The acceptable cost allocation is not unique, providing adequate flexibility to the mediator during mechanism design; the flexibility may reflect the relative power of the entities and is quantified in our work by a series of computational experiments. Our approach is motivated by inventory management practices in a manufacturing group and, thus, it is directly applicable to real-life cases.
We are concerned with the interaction and integration between demand forecasting and inventory co... more We are concerned with the interaction and integration between demand forecasting and inventory control, in the context of supply chain operations. The majority of the literature is fragmented. Forecasting research more often than not assumes forecasting to be an end in itself, disregarding any subsequent stages of computation that are needed to transform forecasts into replenishment decisions. Conversely, most contributions in inventory theory assume that demand (and its parameters) are known, in effect disregarding any preceding stages of computation. Explicit recognition of these shortcomings is an important step towards more realistic theoretical developments, but still not particularly helpful unless they are somehow addressed. Even then, forecasts often constitute exogenous variables that serially feed into a stock control model. Finally, there is a small but growing stream of research that is explicitly built around jointly tackling the inventory forecasting question. We introduce a framework to define four levels of integration: from disregarding, to acknowledging, to partly addressing, to fully understanding the interactions. Focusing on the last two, we conduct a structured review of relevant (integrated) academic contributions in the area of forecasting and inventory control and argue for their classification with regard to integration. We show that the development from one level to another is in many cases chronological in order, but also associated with specific schools of thought. We also argue that although movement from one level to another adds realism, it also adds complexity in terms of actual implementations, and thus a trade-off exists. The article makes a contribution into an area that has always been fragmented despite the importance of bringing the forecasting and inventory communities together to solve problems of common interest. We close with an indicative agenda for further research and a call for more theoretical contributions, but also more work that would help to expand the empirical knowledge base in this area.
In this paper we consider the operational planning problem of physical distribution via a fleet o... more In this paper we consider the operational planning problem of physical distribution via a fleet of hired vehicles, for which the travelling cost is solely a function of the sequence of locations visited within all open delivery routes, while vehicle fixed cost is inexistent. The problem is a special class of vehicle routing and is encountered in the literature as the Open Vehicle Routing Problem (OVRP), since vehicles are not required to return to the depot. The goal is to distribute in an optimal way finished goods from a central facility to geographically dispersed customers, which pose daily demand for items produced in the facility and act as sales points for consumers. To solve the problem, we employ an annealing-based method that utilizes a backtracking policy of the threshold value when no acceptances of feasible solutions occur during the search process. Computational results on a set of benchmark problems show that the proposed method consistently outperforms previous algorithms for solving the OVRP. The approach can serve as the means for effective fleet planning in real-life problems.
... approximately two thousand customers, is presented and solved by our heuristic, using an inte... more ... approximately two thousand customers, is presented and solved by our heuristic, using an interface to ... One can solve with success any of the two underlying sub-problems of the ... 20 Thus, a key determinant factor for obtaining good solutions for vehicle routing problems with tight ...
International Journal of Production Economics, 2008
The tendency of companies to expand their control through the entire supply chain is a significan... more The tendency of companies to expand their control through the entire supply chain is a significant managerial driver. On the other hand, large manufacturing and distribution firms have developed competences that do not cover all levels of the supply chain. In order to confront the lack of knowledge and expertise, enterprises can either outsource a specific operation or acquire a company that is specialized in the specific field. In this paper we focus on warehousing decisions and investigate three different warehousing policies and ownership structures of the warehousing facilities. The approach is based on game theory and an industrial example provides insight on the results reached.
ABSTRACT Increased competition and uncertainty characterise the new economy, introducing signific... more ABSTRACT Increased competition and uncertainty characterise the new economy, introducing significant pressures to supply chain participants, calling for capital investments only in value adding/revenue-generating assets. The tendency of companies to expand their control through the entire supply chain seems to attract significant managerial attention. On the other hand, large manufacturer and distributor firms have developed specific competences that do not expand to all the levels of the supply chain. In order to confront the lack of knowledge and expertise companies can either outsource the specific operation or acquire a company that is specialized in the specific field. In this paper we focus on warehousing decisions and investigate three different warehousing policies and ownership structures of the warehousing facilities.
We develop a model for lead-time quotation in a Markovian make-to-order production or service sys... more We develop a model for lead-time quotation in a Markovian make-to-order production or service system with strategic customers who exhibit risk aversion. Based on a CARA utility function of their net benefit, customers make individual decisions to join the system or balk by observing the state of the queue. The decisions of arriving customers result in a symmetric join/balk game. Regarding the firm's strategy, the provider announces a lead-time quotation for each state and a respective balking threshold. There is also a fixed entrance fee and compensation rate for the part of a customer' delay exceeding the quoted lead-time. Moreover, we consider the problem from the point of view of a social optimizer who maximizes the total net benefit of the system. We analyze the provider's and social optimizer's maximization problems and we consider two cases regarding the class of lead-time quotation policies, i.e., dynamic and single. We identify the optimal entrance thresholds...
We develop a model for lead-time quotation in a Markovian Make-To-Order production or service sys... more We develop a model for lead-time quotation in a Markovian Make-To-Order production or service system with strategic customers who exhibit risk aversion. Based on a CARA utility function of their net benefit, customers make individual decisions to join the system or balk by observing the state of the queue. The decisions of arriving customers result in a symmetric join/balk game. Regarding the firm’s strategy, the provider announces a lead-time quotation for each state and a respective balking threshold. There is also a fixed entrance fee and compensation rate for the part of a customer’ delay exceeding the quoted lead-time. Moreover, we consider the problem from the point of view of a social optimizer who maximizes the total net benefit of the system. We analyze the provider’s and social optimizer’s maximization problems and we consider two cases regarding the class of lead-time quotation policies, i.e., dynamic and single. We identify the optimal entrance thresholds in each case. F...
The plant layout project has been the mainstay of industrial engineering curriculum for many year... more The plant layout project has been the mainstay of industrial engineering curriculum for many years. Yet, even today, some schools miss the educational opportunities offered by these projects. While working through the steps of the layout design process, students can be exposed to exercises in open ended problem solving, business communications, computer modeling and team participation. All of these facets of the process occur naturally. However, unless proper design of the project and its evaluation mechanisms are considered, the full benefits of the assignments will not be realized. This paper presents the plant layout project as a tool for experimental learning on a broader frontfrom communications through engineering design. Opportunities for exercises of various kinds are explored. Throughout the paper, the Virginia Tech layout project is discussed to provide a contextual framework for the presentation.
We develop and validate a model of the micro-level dynamics underlying the formation of macro-lev... more We develop and validate a model of the micro-level dynamics underlying the formation of macro-level information propagation patterns in online social networks. In particular, we address the dynamics at the level of the mechanism regulating a user's participation in an online information propagation process. We demonstrate that this mechanism can be realistically described by the dynamics of noisy spiking neurons driven by endogenous and exogenous, deterministic and stochastic stimuli representing the influence modulating one's intention to be an information spreader. Depending on the dynamically changing influence characteristics, time-varying propagation patterns emerge reflecting the temporal structure, strength, and signal-to-noise ratio characteristics of the stimulation driving the online users' information sharing activity. The proposed model constitutes an overarching, novel, and flexible approach to the modeling of the micro-level mechanisms whereby information propagates in online social networks. As such, it can be used for a comprehensive understanding of the online transmission of information, a process integral to the sociocultural evolution of modern societies. The proposed model is highly adaptable and suitable for the study of the propagation patterns of behavior, opinions, and innovations among others.
International Journal of Production Research, 2016
The Resource Constrained Project Scheduling Problem (RCPSP) is one of the most intractable combin... more The Resource Constrained Project Scheduling Problem (RCPSP) is one of the most intractable combinatorial optimisation problems that combines a set of constraints and objectives met in a vast variety of applications and industries. Its solution raises major theoretical challenges due to its complexity, yet presenting numerous practical dimensions. Adaptive Memory Programming (AMP) is one of the most successful frameworks for solving hard combinatorial optimisation problems (e.g., vehicle routing and scheduling). Its success stems from the use of learning mechanisms that capture favourable solution elements found in high quality solutions. This paper challenges the efficiency of AMP for solving the RCPSP, to our knowledge, for the first time in the up-to-date literature. Computational experiments on well known benchmark RCPSP instances show that the proposed AMP consistently produces high-quality solutions in reasonable computational times.
The management of supply chains is the current focus of corporate strategies. Currently, we note ... more The management of supply chains is the current focus of corporate strategies. Currently, we note that it is not businesses that compete but supply chains that compete. In order to lead in the corporate race, organisations take advantage of information and communication technologies for e-business. An executive level of strategic management of the supply chain is a requirement of which, one of the major ingredient is information that is passed among supply chain constituents. The information is generated, distributed, received and stored in supply chain management information systems of heterogeneous architectures and/or platforms. This poses a challenge in the sharing and understanding of the bits of information. In this paper we present an artificial intelligence approach for supply chain information systems that have heterogeneous architectures to share information through a common ontology. The supply chain ontology structures a shared formal specification of concepts and the rel...
The main objective of this paper is to propose a two-phase solution algorithm for solving the Inv... more The main objective of this paper is to propose a two-phase solution algorithm for solving the Inventory Routing Problem with Time Windows (IRPTW), which has not been excessively researched in the literature. The solution approach is based on (a) a simple simulation for the planning phase (Phase I) and (b) the Variable Neighborhood Search Algorithm (VNS) for the routing phase (Phase II). Testing instances are established to investigate algorithmic performance, and the computational results are then reported. The computational study underscores the importance of integrating the inventory and vehicle routing decisions. Graphical presentation formats are provided to convey meaningful insights into the problem.
In this paper, we consider the open vehicle routeing problem (OVRP), in which routes are not sequ... more In this paper, we consider the open vehicle routeing problem (OVRP), in which routes are not sequences of locations starting and ending at the depot but open paths. The problem is of particular importance for planning fleets of hired vehicles, a common practice in the distribution and service industry. In such cases, the travelling cost is a function of the vehicle open paths. To solve the problem, we employ a single-parameter metaheuristic method that exploits a list of threshold values to guide intelligently an advanced local search. Computational results on a set of benchmark problems show that the proposed method consistently outperforms previous approaches for the OVRP. A real-world example demonstrates the applicability of the method in practice, demonstrating that the approach can be used to solve actual problems of routing large vehicle fleets.
Increased competition and uncertainty characterise the new economy, introducing significant press... more Increased competition and uncertainty characterise the new economy, introducing significant pressures to supply chain participants, calling for capital investments only in value adding/revenue-generating assets. The tendency of companies to expand their control through the entire supply chain seems to attract significant managerial attention. On the other hand, large manufacturer and distributor firms have developed specific competences that do not expand to all the levels of the supply chain. In order to confront the lack of knowledge and expertise companies can either outsource the specific operation or acquire a company that is specialized in the specific field. In this paper we focus on warehousing decisions and investigate three different warehousing policies and ownership structures of the warehousing facilities. INTRODUCTION The new economy is characterised by increased uncertainty and intense competition. The continuously changing market needs and the increased competition in the global markets introduce significant pressures to supply chain participants. The tendency of companies to expand their control through the entire supply chain seems to attract significant managerial attention. On the other hand flexibility associated to the ability to respond to the challenges of the changing and dynamic economic environment is highlighted as the key feature in coping successfully with the uncertainty of the new economy. In this paper, under the above mentioned perspective, we focus on inventory and warehousing decisions and operations and investigate alternative warehousing policies accompanied with different ownership structures of the warehousing facilities. Since the seminal papers of Arrow et al. (1951) and Dvoretzky et al. (1952) inventory theory has been an active area of research attracting the interest of both academics and professionals. Significant research effort has been conducted to determine the optimal inventory policies. For example, Toktay and Wein (2001) focused on the base-stock policy incorporating forecast information to determine the base-stock level that minimizes the expected steady-state inventory holding and backorders costs, assuming stationary demand. Graves (1999) and Graves and Willems (2000) developed a framework for modeling strategic safety stock incorporating non-stationary demand. Meca et al. (2004) analysed situations where a collective of firms minimizes its joint inventory by means of information sharing and cooperation. Inventory theory has also been of great importance in supply chain management. Giannoccaro et al. (2003) defined a supply chain inventory management policy utilising fuzzy set theory to model uncertainty of demand and costs. Belvaux and Wolsey (2001) used mixed-integer programming in order to handle safety stocks in multilevel supply chains. Furthermore, in the context of supply chain, procedures that combine
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Papers by George Ioannou