HAL (Le Centre pour la Communication Scientifique Directe), Feb 19, 2018
A plethora of methods have been developed in the last decades to deal with the inventory forecast... more A plethora of methods have been developed in the last decades to deal with the inventory forecasting of intermittent demand items. These methods belong to the parametric and non-parametric approaches, the artificial neural networks approach and the fuzzy logicbased techniques among others. Most of the parametric methods represent variations of the Croston method and the non-parametric ones are based on bootstrapping. When the inventory performance is considered, these methods often result in an under-achievement of the target service level. A study by Teunter and Duncan (2009) has shown that when the lead-time demand forecast is adjusted by assuming that the first period in the lead-time bucket corresponds to a non-zero demand, the service performance improves considerably. The study has been conducted by considering two Croston type methods and a parametric (with Normal distribution) bootstrapping method. However, the study has not included two well performing bootstrapping methods that are commonly considered in the literature to deal particularly with the inventory forecasting of intermittent demand items. A first method that samples demand data by using a Markov chain to switch between no demand and demand periods and a second method that samples separately demand intervals and demand sizes. In this paper, we propose variations of the two bootstrapping methods where the lead-time demand is adjusted by considering that a demand occurs in the first period of each lead-time bucket. A service driven inventory system is considered to evaluate the performance of the proposed forecasting methods with two objective service measures: the cycle service level and the fill rate. Through an empirical investigation based on the spare parts demand of more than 9000 stock keeping units, we show that the proposed adjusted methods result in a higher service-cost efficiency compared to the original methods.
This paper considers the continuous review can-order (s,c,S) policy for coordinating the replenis... more This paper considers the continuous review can-order (s,c,S) policy for coordinating the replenishment of multiple perishable items with random lifetimes. For zero lead time, we model this inventory system as a Markov process. An iterative procedure is proposed to solve the joint replenishment problem for perishable items under positive lead time. We investigate the impact of perishability and cost parameters on the performance of the can-order policy and compare it to the optimal periodic review (s,S) policy.
HAL (Le Centre pour la Communication Scientifique Directe), May 3, 2009
This paper analyzes the impact of perishability on the well known (r, Q) review policy. We first ... more This paper analyzes the impact of perishability on the well known (r, Q) review policy. We first formulate an (r, Q) inventory model for perishables with fixed lifetime. The expected quantity of perished products, the expected shortage and the expected inventory level are derived and a closed form expression of the average total cost per unit time is obtained. Then, we develop a numerical analysis to illustrate the advantages of using the proposed policy compared to the classical (r, Q) policy which ignores the perishability of products. Finally, we study the benefits of using a Time Temperature Integrator which is a new technology that enables to increase the lifetime of such products.
HAL (Le Centre pour la Communication Scientifique Directe), Aug 24, 2014
Earlier papers on the newsboy problem considered the determination of optimal price and quantity ... more Earlier papers on the newsboy problem considered the determination of optimal price and quantity when the demand is price-dependent or there are multiple discounts. In the real world, price dependence and multiple discount can both happen. But no complete work was done for the joint determination of the order quantity and initial price. In this paper, we present a solution procedure for this problem with general demand distributions in two cases of price-dependent demand: additional case and multiplicative case. We provide some insights by using numerical examples and show the influence of the number of discounts on the expected profit.
HAL (Le Centre pour la Communication Scientifique Directe), May 27, 2006
In this paper, we develop a general two-stage newsboy model. Each period decision induces specifi... more In this paper, we develop a general two-stage newsboy model. Each period decision induces specific costs. In addition to the usual decision variables for such models, we consider that, at the beginning of the decision process, an initial inventory is available and some preliminary fixed orders are to be delivered at each period. The unsatisfied demands during a period are backlogged to be satisfied in the future. The model is solved by a dynamic programming approach. We then provide insight regarding this type of two-stage inventory decision process with the help of numerical examples.
HAL (Le Centre pour la Communication Scientifique Directe), Mar 31, 2008
This paper deals with the inventory control of perishable products having a fixed lifetime. In th... more This paper deals with the inventory control of perishable products having a fixed lifetime. In the first part of the paper, we review the relevant literature on the problem of determining appropriate ordering policies for fixed life perishable inventory. Then, we propose a continuous review inventory policy; i.e. an (r, Q) policy, extending an earlier investigation (i.e. Chiu, 1995). Expressions of the different components of the expected total cost are derived and the problem of finding the optimal replenishment level r and the optimal incoming quantity Q is formulated. A comparative numerical study shows that the model we propose significantly outperforms the classical (r, Q) policy and Chiu's model.
DOI to the publisher's website. • The final author version and the galley proof are versions of t... more DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:
13th IFAC Symposium on Information Control Problems in Manufacturing, Jun 3, 2009
We propose a new method for approximating the optimal order-up-to level in inventory systems with... more We propose a new method for approximating the optimal order-up-to level in inventory systems with compound Poisson demand process and stochastic lead-time. The approximations are derived for cost oriented inventory systems where unfilled demands are backordered. The condition under which the system behaves like a Make-To-Order system is also discussed. By means of a numerical investigation, we show that our method provides "good" approximations of the optimal orderup-to level. Furthermore, a numerical comparison of these approximations with an approximation provided in the literature for fast moving items is also conducted. Our works allows insights to be gained on the stock control of fast and slow moving items related issues.
Abstract Supply chain can be a powerful source of competitive differentiation for today’s compani... more Abstract Supply chain can be a powerful source of competitive differentiation for today’s companies. For this purpose, a measurement and management system of supply chain performance is paramount. However, companies often failed in this endeavour. The present article examines this area by means of a benchmarking approach analysing eleven large companies’ performance systems and complemented by two brainstorming workshops. The responses of these companies to this need are categorized to form a framework for addressing this critical topic and as a basis for further research.
in today’s extremely changing economic landscape, agility, defined as the ability to respond rapi... more in today’s extremely changing economic landscape, agility, defined as the ability to respond rapidly and effectively to internal and external variations, become a vital competence for supply chains. A first step to understand supply chain agility is to study the environment in which the supply chain evolves and the internal and external drivers that force supply chain to acquire agile capabilities. Secondly, agility manifests itself through a number of agility enablers allowing the supply chain to respond to sudden disturbances. In this paper, we present a framework for agility drivers and agility enablers, based on expert opinions and findings from literature.
In this article, we emphasize on one hand the importance of quantifying the shortage cost in orde... more In this article, we emphasize on one hand the importance of quantifying the shortage cost in order to measure the optimal parameters for any selected inventory policy and thus enhance the performance of the supply chain and on the other hand the complexity of doing so. Then, we provide a detailed literature review of the existing various models for quantifying the shortage cost in an inventory management context along with a classification of this literature under three categories: Theoretical descriptive models, empirical approaches and simulation based models. Finally, we point out some gaps in this literature such as the lack of continuity of research in this field and the absence of generic fairly easy to apply but accurate methods and we suggest a few future perspectives.
We study the cost-sharing problem among independent service providers in a service capacity pooli... more We study the cost-sharing problem among independent service providers in a service capacity pooling system. The effective improvement of such pooling system can be achieved by reducing the resource idleness in case of congestion. In this paper, we model both the service provider and the cooperative coalition as a single server queue. We attempt to answer the following questions: (i) which coalition strategy should be used; and (ii) which allocation rule should be selected in order to maintain the stability of the coalition? In particular, we consider the service pooling with a fixed service capacity for M/G/1 service systems. The benefit of the pooling system is due to the shortened waiting queue in the overall system. We develop the corresponding cooperative game with transferable utility, and analyze the core allocations. Although it is difficult to express a core allocation explicitly for the game, we prove the nonemptiness of the core. We give a reasonable expression of Equal Profit Method to distribute the cost for our game, and investigate a number of cost allocation rules under three typical situations to evaluate the gain of the service pooling strategy for each service provider. The numerical results show that the cost allocation rule proposed gives a reasonable cost-sharing result considering the contribution of each participant.
HAL (Le Centre pour la Communication Scientifique Directe), Oct 11, 2010
ABSTRACT This paper aims at evaluating the performance of distribution supply chains (DSCs) in te... more ABSTRACT This paper aims at evaluating the performance of distribution supply chains (DSCs) in terms of sustainability. Addressing the challenge of sustainable DSCs requires an appropriate set of key performance indicators (KPIs) to support assessment. In our literature review, we did not identify any framework that perfectly evaluates sustainable DSCs. Our contribution is thus twofold. We propose a new insight in the literature suggesting a new classification of the existing KPIs sets for sustainability. Secondly, we present a new methodology for KPIs set building in the context of sustainable DSCs.
We consider an order up to level policy for perishable items with random lifetime. We investigate... more We consider an order up to level policy for perishable items with random lifetime. We investigate two cases: the first one is the case where excess demand is completely lost and the second one deals with full backorders. Demands arrive according to a Poisson process. The lifetime of each item is assumed to be exponentially distributed and the procurement lead time is constant. We also assume that there is at most one outstanding order at any time. We model this inventory system as a Markov process in which stationary regime can be characterised. This model allows us to get insights on the impact of the model parameters on the overall system performance in terms of costs.
ECMS 2023 Proceedings edited by Enrico Vicario, Romeo Bandinelli, Virginia Fani, Michele Mastroianni
The growing complexity of worldwide supply chain networks, together with the increased occurrence... more The growing complexity of worldwide supply chain networks, together with the increased occurrence of disruptive events stress the need for a focused introduction of digital support tools. Digital twins have encountered an increased interest from both industry and research for their capability to provide useful services in the short term. The number of contributions on digital twin-based methodologies for system design and production planning and control experienced a significant increase, while applications to supply chain management remain scarce. However, the recent investments in digitization and the concrete need for short-term planning capabilities mean digital twins can effectively aid enterprises in the management of their value chains. This paper provides an overview of the existing contributions regarding digital twins for supply chains, and gathers useful insights on both the current level of development and the future research challenges.
HAL (Le Centre pour la Communication Scientifique Directe), Feb 19, 2018
A plethora of methods have been developed in the last decades to deal with the inventory forecast... more A plethora of methods have been developed in the last decades to deal with the inventory forecasting of intermittent demand items. These methods belong to the parametric and non-parametric approaches, the artificial neural networks approach and the fuzzy logicbased techniques among others. Most of the parametric methods represent variations of the Croston method and the non-parametric ones are based on bootstrapping. When the inventory performance is considered, these methods often result in an under-achievement of the target service level. A study by Teunter and Duncan (2009) has shown that when the lead-time demand forecast is adjusted by assuming that the first period in the lead-time bucket corresponds to a non-zero demand, the service performance improves considerably. The study has been conducted by considering two Croston type methods and a parametric (with Normal distribution) bootstrapping method. However, the study has not included two well performing bootstrapping methods that are commonly considered in the literature to deal particularly with the inventory forecasting of intermittent demand items. A first method that samples demand data by using a Markov chain to switch between no demand and demand periods and a second method that samples separately demand intervals and demand sizes. In this paper, we propose variations of the two bootstrapping methods where the lead-time demand is adjusted by considering that a demand occurs in the first period of each lead-time bucket. A service driven inventory system is considered to evaluate the performance of the proposed forecasting methods with two objective service measures: the cycle service level and the fill rate. Through an empirical investigation based on the spare parts demand of more than 9000 stock keeping units, we show that the proposed adjusted methods result in a higher service-cost efficiency compared to the original methods.
This paper considers the continuous review can-order (s,c,S) policy for coordinating the replenis... more This paper considers the continuous review can-order (s,c,S) policy for coordinating the replenishment of multiple perishable items with random lifetimes. For zero lead time, we model this inventory system as a Markov process. An iterative procedure is proposed to solve the joint replenishment problem for perishable items under positive lead time. We investigate the impact of perishability and cost parameters on the performance of the can-order policy and compare it to the optimal periodic review (s,S) policy.
HAL (Le Centre pour la Communication Scientifique Directe), May 3, 2009
This paper analyzes the impact of perishability on the well known (r, Q) review policy. We first ... more This paper analyzes the impact of perishability on the well known (r, Q) review policy. We first formulate an (r, Q) inventory model for perishables with fixed lifetime. The expected quantity of perished products, the expected shortage and the expected inventory level are derived and a closed form expression of the average total cost per unit time is obtained. Then, we develop a numerical analysis to illustrate the advantages of using the proposed policy compared to the classical (r, Q) policy which ignores the perishability of products. Finally, we study the benefits of using a Time Temperature Integrator which is a new technology that enables to increase the lifetime of such products.
HAL (Le Centre pour la Communication Scientifique Directe), Aug 24, 2014
Earlier papers on the newsboy problem considered the determination of optimal price and quantity ... more Earlier papers on the newsboy problem considered the determination of optimal price and quantity when the demand is price-dependent or there are multiple discounts. In the real world, price dependence and multiple discount can both happen. But no complete work was done for the joint determination of the order quantity and initial price. In this paper, we present a solution procedure for this problem with general demand distributions in two cases of price-dependent demand: additional case and multiplicative case. We provide some insights by using numerical examples and show the influence of the number of discounts on the expected profit.
HAL (Le Centre pour la Communication Scientifique Directe), May 27, 2006
In this paper, we develop a general two-stage newsboy model. Each period decision induces specifi... more In this paper, we develop a general two-stage newsboy model. Each period decision induces specific costs. In addition to the usual decision variables for such models, we consider that, at the beginning of the decision process, an initial inventory is available and some preliminary fixed orders are to be delivered at each period. The unsatisfied demands during a period are backlogged to be satisfied in the future. The model is solved by a dynamic programming approach. We then provide insight regarding this type of two-stage inventory decision process with the help of numerical examples.
HAL (Le Centre pour la Communication Scientifique Directe), Mar 31, 2008
This paper deals with the inventory control of perishable products having a fixed lifetime. In th... more This paper deals with the inventory control of perishable products having a fixed lifetime. In the first part of the paper, we review the relevant literature on the problem of determining appropriate ordering policies for fixed life perishable inventory. Then, we propose a continuous review inventory policy; i.e. an (r, Q) policy, extending an earlier investigation (i.e. Chiu, 1995). Expressions of the different components of the expected total cost are derived and the problem of finding the optimal replenishment level r and the optimal incoming quantity Q is formulated. A comparative numerical study shows that the model we propose significantly outperforms the classical (r, Q) policy and Chiu's model.
DOI to the publisher's website. • The final author version and the galley proof are versions of t... more DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:
13th IFAC Symposium on Information Control Problems in Manufacturing, Jun 3, 2009
We propose a new method for approximating the optimal order-up-to level in inventory systems with... more We propose a new method for approximating the optimal order-up-to level in inventory systems with compound Poisson demand process and stochastic lead-time. The approximations are derived for cost oriented inventory systems where unfilled demands are backordered. The condition under which the system behaves like a Make-To-Order system is also discussed. By means of a numerical investigation, we show that our method provides "good" approximations of the optimal orderup-to level. Furthermore, a numerical comparison of these approximations with an approximation provided in the literature for fast moving items is also conducted. Our works allows insights to be gained on the stock control of fast and slow moving items related issues.
Abstract Supply chain can be a powerful source of competitive differentiation for today’s compani... more Abstract Supply chain can be a powerful source of competitive differentiation for today’s companies. For this purpose, a measurement and management system of supply chain performance is paramount. However, companies often failed in this endeavour. The present article examines this area by means of a benchmarking approach analysing eleven large companies’ performance systems and complemented by two brainstorming workshops. The responses of these companies to this need are categorized to form a framework for addressing this critical topic and as a basis for further research.
in today’s extremely changing economic landscape, agility, defined as the ability to respond rapi... more in today’s extremely changing economic landscape, agility, defined as the ability to respond rapidly and effectively to internal and external variations, become a vital competence for supply chains. A first step to understand supply chain agility is to study the environment in which the supply chain evolves and the internal and external drivers that force supply chain to acquire agile capabilities. Secondly, agility manifests itself through a number of agility enablers allowing the supply chain to respond to sudden disturbances. In this paper, we present a framework for agility drivers and agility enablers, based on expert opinions and findings from literature.
In this article, we emphasize on one hand the importance of quantifying the shortage cost in orde... more In this article, we emphasize on one hand the importance of quantifying the shortage cost in order to measure the optimal parameters for any selected inventory policy and thus enhance the performance of the supply chain and on the other hand the complexity of doing so. Then, we provide a detailed literature review of the existing various models for quantifying the shortage cost in an inventory management context along with a classification of this literature under three categories: Theoretical descriptive models, empirical approaches and simulation based models. Finally, we point out some gaps in this literature such as the lack of continuity of research in this field and the absence of generic fairly easy to apply but accurate methods and we suggest a few future perspectives.
We study the cost-sharing problem among independent service providers in a service capacity pooli... more We study the cost-sharing problem among independent service providers in a service capacity pooling system. The effective improvement of such pooling system can be achieved by reducing the resource idleness in case of congestion. In this paper, we model both the service provider and the cooperative coalition as a single server queue. We attempt to answer the following questions: (i) which coalition strategy should be used; and (ii) which allocation rule should be selected in order to maintain the stability of the coalition? In particular, we consider the service pooling with a fixed service capacity for M/G/1 service systems. The benefit of the pooling system is due to the shortened waiting queue in the overall system. We develop the corresponding cooperative game with transferable utility, and analyze the core allocations. Although it is difficult to express a core allocation explicitly for the game, we prove the nonemptiness of the core. We give a reasonable expression of Equal Profit Method to distribute the cost for our game, and investigate a number of cost allocation rules under three typical situations to evaluate the gain of the service pooling strategy for each service provider. The numerical results show that the cost allocation rule proposed gives a reasonable cost-sharing result considering the contribution of each participant.
HAL (Le Centre pour la Communication Scientifique Directe), Oct 11, 2010
ABSTRACT This paper aims at evaluating the performance of distribution supply chains (DSCs) in te... more ABSTRACT This paper aims at evaluating the performance of distribution supply chains (DSCs) in terms of sustainability. Addressing the challenge of sustainable DSCs requires an appropriate set of key performance indicators (KPIs) to support assessment. In our literature review, we did not identify any framework that perfectly evaluates sustainable DSCs. Our contribution is thus twofold. We propose a new insight in the literature suggesting a new classification of the existing KPIs sets for sustainability. Secondly, we present a new methodology for KPIs set building in the context of sustainable DSCs.
We consider an order up to level policy for perishable items with random lifetime. We investigate... more We consider an order up to level policy for perishable items with random lifetime. We investigate two cases: the first one is the case where excess demand is completely lost and the second one deals with full backorders. Demands arrive according to a Poisson process. The lifetime of each item is assumed to be exponentially distributed and the procurement lead time is constant. We also assume that there is at most one outstanding order at any time. We model this inventory system as a Markov process in which stationary regime can be characterised. This model allows us to get insights on the impact of the model parameters on the overall system performance in terms of costs.
ECMS 2023 Proceedings edited by Enrico Vicario, Romeo Bandinelli, Virginia Fani, Michele Mastroianni
The growing complexity of worldwide supply chain networks, together with the increased occurrence... more The growing complexity of worldwide supply chain networks, together with the increased occurrence of disruptive events stress the need for a focused introduction of digital support tools. Digital twins have encountered an increased interest from both industry and research for their capability to provide useful services in the short term. The number of contributions on digital twin-based methodologies for system design and production planning and control experienced a significant increase, while applications to supply chain management remain scarce. However, the recent investments in digitization and the concrete need for short-term planning capabilities mean digital twins can effectively aid enterprises in the management of their value chains. This paper provides an overview of the existing contributions regarding digital twins for supply chains, and gathers useful insights on both the current level of development and the future research challenges.
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