Zied Bahroun

Multi-agent modelling for replenishment policies simulation in supply chains

In recent days, the industrial sector is characterised by saturated worldwide target markets and high expectations of the consumers. This new context subjects the company to a great deal of pressure. Therefore, companies try to optimise their supply chains in order to improve their competitiveness. Many approaches and techniques were developed over the last decades to help the design, control, synchronisation, and collaboration within supply chains. In this work, we propose, based on multi-agent systems, a generic model of software agent to model supply chains in order to simulate and evaluate replenishment policies within these chains. To validate the proposed model, we present an implementation of the supply chain based on the beer game, and we simulate some replenishment policies. [Received 30 September 2008; Revised 25 May 2009; Accepted 6 December 2009]

Decentralised decision-making with information sharing vs. centralised decision-making in supply chains

In recent years, implementing coordination mechanisms in decentralised supply chains to reduce the well-known negative effects of decentralisation, such as the ‘bullwhip effect’, has become a considerable challenge. Furthermore, with the dramatic developments in information and communication technologies, real-time information sharing has become increasingly easier to implement. In this work, we study a mono-product divergent supply chain composed of a supplier, a warehouse, retailers and customers in the context of decentralised and centralised decisions. The main objective of this study is to compare a decentralised supply chain combined with different scenarios of simultaneous upstream and downstream information sharing vs. a centralised supply chain. A mathematical model is developed to compare the logistics costs in the two decision contexts. The experimental results clearly show that the simultaneous sharing of customer demand and supplier-warehouse lead time information in a decentralised supply chain yields nearly equivalent logistics costs as the centralised supply chain context. However, the main beneficiary of the sharing is the warehouse, which receives approximately two-thirds of the benefit. Thus, incentives and revenue sharing contracts should be implemented to motivate and balance the benefits between supply chain partners.

Assessing the value of information sharing and its impact on the performance of the various partners in supply chains

We study the influence of sharing perturbed information on a serial supply chain.We evaluate the gains of sharing different types of information for each partner.We estimate the cumulative impact of simultaneously sharing different information.The gains are not cumulative when we simultaneously share different information.Incentive cooperation mechanisms should be established between partners. With major developments in information and communication technologies, real-time information sharing becomes a significant challenge and has a considerable impact on the overall performance of supply chains. Here, we study the influence of information sharing for a monoproduct serial supply chain consisting of a supplier, warehouse, retailer and customers in the context of a decentralized decision. The objectives of this study are twofold: (1) to estimate the gains from sharing different types of information on each elementary cost and for each partner of the supply chain in detail and (2) to determine the cumulative impact of simultaneously sharing different types of information.A mathematical model is developed to assess the value of information sharing in terms of logistic costs and for different combinations related to the sharing or non-sharing of three types of upstream and downstream information: the customer demand and the supplier-warehouse and warehouse-retailer lead times. A perturbation is also injected to consider the intended or unintended distortion in the communicated information.Our study clearly showed that the gains are not cumulative when we simultaneously share different types of information. The results also highlighted the necessity to establish incentive cooperation mechanisms between the different links in the supply chain in many scenarios where the gains are not balanced. A distortion in the communicated information can also have a significant effect on the gains from sharing.

Internet of things and supply chain management: a literature review

This paper explores the role of Internet of Things (IoT) and its impact on supply chain management (SCM) through an extensive literature review. Important aspects of IoT in SCM are covered including IoT definition, main IoT technology enablers and various SCM processes and applications. We offer several categorisation of the extant literature, such as based on methodology, industry sector and focus on a classification based on major supply chain processes. In addition, a bibliometric analysis of the literature is also presented. We find that most studies have focused on conceptualising the impact of IoT with limited analytical models and empirical studies. In addition, most studies have focused on the delivery supply chain process and the food and manufacturing supply chains. Areas of future SCM research that can support IoT implementation are also identified.

Production planning and scheduling in the context of cyclic delivery schedules

Abstract This paper considers a factory which produce n items on a single facility and which is confronted to a cyclic demand: each item is ordered relatively to a cyclic delivery schedule with a mean quantity for each delivery. This kind of « contract-order a is found very frequently, especially in the big distribution and the automotive sectors. So, the long-term information becomes the due date and the exact quantity that will be delivered is only known in the short term. This work aims at defining a new production management model and especially determining cyclic production schedules in this context. The proposed approaches are based on generating, evaluating and selecting the best production sequences and phases.

Job-shop production scheduling with reverse flows

In this paper, we present a modeling approach for the NP-hard scheduling problem Job-shop with reverse flows. This problem is characterized by two flows that cover the same machines but in opposite senses. The objective is to minimize the maximum completion time of the jobs. We start by providing a mathematical formulation and we analyze the complexity and some particular cases of the problem. Then, we propose a heuristic method for solving the NP-hard 3-machine case, which we evaluate by conducting tests on Taillards benchmark. These tests give satisfying results and show that the heuristic ensures good performance when the two flows have close numbers of jobs.

A dichotomic algorithm for an operating room scheduling problem

In this paper, we study an NP-hard operating room scheduling problem, consisting in a set of operations which have to be scheduled on identical operating rooms. In this problem, the operations are divided in groups; each one should be achieved by a single surgeon. The objective is to minimize the global completion time of the operations. We start by providing a mathematical model inspired from the two-dimensional Strip Packing problems and we compare its performances to the classical formulation. Then we introduce a dichotomic algorithm that we use to solve some larger instances of the problem.

Medium Term Production Management for Cyclic Deliveries

The growing quality and delay requirements have catalyzed the emergence of new commercial paradigms, which have strongly modified the customer–supplier relationship. Customers and suppliers become more and more linked with contracts or global orders spanned over a relatively important period. This paper, examines a type of contract which specifies a fixed and cyclic delivery dates with delivery quantities varying between a min and a max values. The exact delivery quantities are usually known only few days before the delivery. A company which produces n items on a bottleneck facility is considered; each item is confronted to a cyclic demand and has an important holding cost in comparison to set-up costs. We propose heuristic approaches, to build, in a medium term level, cyclic production schedules. These schedules face the demand and minimize a total cost function composed of holding and set-up costs. An experiment is proposed in order to prove the effectiveness of our approaches.

A method to evaluate downstream and upstream information sharing using the genetic algorithm

This paper deals with four scenarios of sharing upstream and downstream information simultaneously in supply chains. Replenishment leadtime is the upstream information studied in this work and demand information is the downstream one. We propose a system cost formulation for two-echelon (a depot and several retailers) and multi-products supply chain. We focused our study on a centralized system case. In our formulation, we consider holding, ordering, penalty and transportation costs. Then, we use a Genetic Algorithm in order to approximate the optimal echelon inventory position at depot which minimizes the system cost. Our approach is illustrated by some numerical experiments.

A NEW APPROACH OF FLEXIBILITY PLANNING A REALITY OR A SEARCH OF THE HOLY GRAIL

Abstract In the new context of “contract-order”, companies are engaged with their customers on a global program of delivery orders. Each order concerns the deliver of quantities (varying between a minimum and a maximum value) of products at precise moments. The exact quantities are known only few days before the delivery. This variability of delivery quantities needs the management in an efficient way of some flexibility levers in order to guarantee the service engagement and minimize the costs. In this paper, a new approach of flexibility planning will be presented. This approach tends to satisfy these goals and takes into account internal and external constraints of these companies. The most important internal constraint is the evidence presence of a bottleneck resource. An external constraint must be obviously satisfied which is the imposed regulations.