Models and methods for capacitated lot-sizing problems

This is a summary of the author’s PhD thesis supervised by Philippe Chrétienne and Safia Kedad-Sidhoum and defended in December 2005 at the Université Pierre et Marie Curie (Paris VI). The thesis is written in French and is available from . This work mainly deals with multi-item capacitated lot-sizing problems with setup times, shortages on demand and safety stock deficit costs. We propose a new mathematical model that includes these new constraints. Three solution approaches are considered: branch-and-cut, Lagrangean relaxation and MIP-based heuristics approaches. Experimental results showing the effectiveness and the limit of each approach are presented. This work was financed by the ANRT and DynaSys S.A.     

Metaheuristic algorithms for combinatorial optimization problems

We present the main results in the author’s Ph.D. thesis (Iori 2004), defended at the University of Bologna in April 2004 and supervised by S. Martello. The thesis is written in English and is available from the author upon request. It proposes exact and metaheuristic algorithms for solving some relevant combinatorial optimization problems, with particular emphasis on scheduling, two-dimensional cutting and packing and capacitated vehicle routing. The performance of each algorithm is tested through extensive computational experiments and comparison with other approaches in the literature.Received: 21 September 2004, AMS classification: 90-08, 90C27, 90C59     

A new stochastic Petri net model and its applications to logistics systems

This is a summary of the author’s PhD thesis supervised by Lionel Amodeo and Hoaxun Chen and defended on 29 November 2005 at the Université de Technologie de Troyes (France). The thesis is written in French and is available from the author upon request. This work deals with a new stochastic Petri net model and its applications for modeling and studying logistics systems and more generally discrete event dynamic systems.      

Coordination of production planning and distribution

This is a summary of the main results presented in the author’s Ph.D thesis, supervised by C. Prins and defended at the Université de Technologie de Troyes in October 2006. The thesis, written in French, is available from the author upon request. It deals with the integrated optimization of production planning and distribution in supply chains. A single product case and a multiproduct case are investigated. Integer linear programming models are proposed and different approaches based on heuristics, metaheuristics and cooperative methods are developed. Significant savings are obtained, compared to classical decoupled methods. These results confirm both the interest of integrating production and distribution decisions and of using metaheuristics for the largest instances.      

Personnel scheduling in the Call Center industry

We discuss the main results of the author’s PhD thesis (Canon 2005) presented in December 2005 at the Université François-Rabelais de Tours and supervised by J.-C. Billaut and J.-L. Bouquard. This thesis is written in French and is available from the author upon request. It deals with three different problems arising in the call center industry: the problem of dimensioning a call center, the annualisation problem and finally the Shift Design Problem.     

Solving scheduling problems from high-level models

This is the summary of the author??s PhD thesis supervised by Yves Deville and Pascal Van Hentenryck, and defended on 25 May 2010?at the Université catholique de Louvain in Louvain-la-Neuve. The thesis is written in English and is available from the author, or downloadable from http://becool.info.ucl.ac.be/files2/thesis-monette.pdf. This work is about the gap between high-level modelling of scheduling problems and its efficient resolution. We propose to automatically classify models of scheduling problems, and to apply an appropriate search algorithm. Thanks to the strong separation between model and search, we propose also a simple way to create hybrid algorithms. A second part of the thesis deals with Constraint Programming approaches for two scheduling problems: The one-machine non-preemptive problem and the Just-In-Time Job-Shop problem. All parts are accompanied by experimental results showing their practicality.     

Methods to solve multi-skill project scheduling problem

This is a summary of the author’s PhD thesis supervised by P. Martineau and E. Néron and defended on 28 November 2006 at the Université François-Rabelais de Tours. The thesis is written in French, and is available upon request from the author. This work deals with the problem of scheduling a project. The activities of this project requires skills that may not be mastered by all persons involved. First of all, the problem is defined in the introduction part. Then we propose different methods to solve it: lower bounds in part 2, different heuristics and meta-heuristics in part 3, and finally a branch-and-bound procedure in the last part.     

Models and algorithms for the reconfiguration of distributed wireless switching systems

This paper is a summary of the author’s PhD thesis entitled “Models and algorithms for the reconfiguration of wireless switching systems”. The thesis deals with the study of a strongly NP-hard resource-constrained scheduling problem arising from the telecommunication industry. This work was supervised by Jacques Carlier and Dritan Nace, both from Université de Technologie de Compiègne, and carried out while the author was a System Architect within Nortel GSM Access R&D organization. The thesis, which is written in both French and English, has been defended on 29 March 2007 and is available by email request to the author. This research was supported in part by Association Nationale de la Recherche Technique grant CIFRE-121/2004.     

A branch-and-cut algorithm for solving the Non-Preemptive Capacitated Swapping Problem

This paper models and solves a capacitated version of the Non-Preemptive Swapping Problem. This problem is defined on a complete digraph G=(V,A), at every vertex of which there may be one unit of supply of an item, one unit of demand, or both. The objective is to determine a minimum cost capacitated vehicle route for transporting the items in such a way that all demands are satisfied. The vehicle can carry more than one item at a time. Three mathematical programming formulations of the problem are provided. Several classes of valid inequalities are derived and incorporated within a branch-and-cut algorithm, and extensive computational experiments are performed on instances adapted from TSPLIB.     

Mutual exclusion scheduling with interval graphs or related classes: Complexity and algorithms

This note summarizes the main results presented in the author's Ph.D. thesis, supervised by Professor Michel Van Caneghem and defended on 14th June 2005 at University of Aix-Marseille II, France. The thesis, written in French, is available at http: //www.lif-sud.univ-mrs.fr/Rapports/25-2005.html. The mutual exclusion scheduling problem has an elegant graph-theoretic formulation: given an undirected graph G and an integer k, find a minimum coloring of G such that each color appears at most k times. When G is an interval graph, this problem has some applications in workforce planning. Then, the object of the thesis is to study the complexity of mutual exclusion scheduling problem for interval graphs and related classes. Received: August 2005 / Revised version: September 2005 Frédéric Gardi: On leave from Laboratoire d'Informatique Fondamentale - CNRS UMR 6166, Parc Scientifique et Technologique de Luminy, Marseille, France.     

Practical aspects associated with location planning for maternal and perinatal assistance in Brazil

A study has been carried out aimed at reducing perinatal mortality in the municipality of Rio de Janeiro through a better distribution of health care facilities. The algorithmic aspects are detailed elsewhere and here the emphasis is on practical issues and difficulties encountered. A 3-level hierarchical model was developed. Both uncapacitated and capacitated versions are briefly described together with some results based on actual data. The project brought to light many contradictions between OR theory and practice in developing countries and, unfortunately, the models developed were not implemented by the municipality health authorities. Possible reasons for this outcome are analysed.     

Efficient Solution of the Single-item,Capacitated Lot-sizing Problem with Start-up and Reservation Costs

A capacitated dynamic lot-sizing model, where the costs incurred are a start-up cost for switching the production facility on and another reservation cost for keeping the facility on, whether or not it is producing, is considered. The resulting scheduling problem is NP-hard. An efficient shortest path model of the uncapacitated version of the problem is developed. This model is then included, via a redefinition of variables, into a tight capacitated model; tight in the sense that sharp lower bounds can be produced from it. The lower bound problems are solved efficiently by recovering the shortest path structure through column generation, and effective upper bounds are generated by solving a small capacitated trans-shipment problem. The results of computational tests to verify the computational efficiency of the resulting solution scheme are presented.     

Optimization of the capacity of wireless mesh networks

This is a summary of the authors PhD thesis supervised by Hervé Rivano and defended on 29 October 2009 at the Université de Nice-Sophia Antipolis. The thesis is written in French and is available from . This work deals with the optimization of the capacity of wireless mesh networks, defined as the throughput offered to each flow. We develop optimization models integrating the cross-layer characteristics of radio communications. The joint routing and scheduling is studied and solved using column generation. A linear formulation focusing on the transport capacity available on the network cuts is derived. We prove the equivalence of the models, and adapt the resolution method into a cross line and column generation process. Thorough tests, a contention area located around the gateways which constraints the capacity is highlighted. These results are applied to a quantitative study of the effects of acknowledgments on the capacity. Finally, a stability study of a protocol routing a traffic injected arbitrarily is investigated.     

Progressive methods in multiple criteria decision analysis

This is a summary of the author’s Ph.D. thesis, defended on 8 October 2007 at the University of Luxembourg and the Faculté Polytechnique de Mons, under the joint supervision of Raymond Bisdorff and Marc Pirlot. The thesis is written in English and is available from the author upon request. The work is situated in the field of multiple criteria decision analysis. It mostly deals with what we call progressive methods, i.e., iterative procedures presenting partial conclusions to the decision maker that can be refined at further steps of the analysis. Such progressive methods have been studied in the context of multiattribute value theory and outranking methods.      

A multicriteria perspective on reverse auctions

This is a summary of the main contributions of the author’s PhD thesis. The thesis is written in English. It was supervised by Philippe Vincke and was defended on 20 December 2005 at the Université Libre de Bruxelles. A copy is available from the author upon request. The aim of this work is to investigate the use of a partial relations for bids’ comparisons in the context of multi-attribute auctions. At first a theoretical framework is developed. Then a specific model referred to as the butterfly model is presented. Finally the concept of bidding niches is formalized and related to the aforementioned model.      

Internal transport in automated semiconductor manufacturing systems

This paper summarizes the main results presented by the author in his PhD thesis (Montoya-Torres 2005), supervised by Stéphane Dauzèere-Pérés, Jean-Pierre Campagne and Hélène Marian, and defended on 29 November 2005 at the école des Mines de Saint-étienne and Université Jean-Monnet. The thesis is written in French and is available upon request from the author. This work deals with a real-life transportation problem in the semiconductor industry. It proposes a new approach by integrating tactical and operational decisions for the control of the automated transport system. At the tactical level, the problem is modeled using integer linear programming models inspired from Location Theory. At the operational level, the solution obtained from the tactical optimization is coupled with a discrete-event computer simulation program and some policies for transportation operations are implemented and compared.     

An interior-point Benders based branch-and-cut algorithm for mixed integer programs

We present an interior-point branch-and-cut algorithm for structured integer programs based on Benders decomposition and the analytic center cutting plane method (ACCPM). We show that the ACCPM based Benders cuts are both pareto-optimal and valid for any node of the branch-and-bound tree. The valid cuts are added to a pool of cuts that is used to warm-start the solution of the nodes after branching. The algorithm is tested on two classes of problems: the capacitated facility location problem and the multicommodity capacitated fixed charge network design problem. For the capacitated facility location problem, the proposed approach was on average 2.5 times faster than Benders-branch-and-cut and 11 times faster than classical Benders decomposition. For the multicommodity capacitated fixed charge network design problem, the proposed approach was 4 times faster than Benders-branch-and-cut while classical Benders decomposition failed to solve the majority of the tested instances.     

Dynamic management of a portfolio of orders

We survey the main results of the PhD Thesis presented by the author in December 2003 at The Institut National Polytechnique de Grenoble. This work was supervised by Prof. Lionel Dupont and assistant professor Christophe Rapine. The thesis is written in French and is available at http: //gilco.inpg.fr. In this work, we present results on the problem of selection and scheduling of orders in a make to order production environment. We proposed exact methods and heuristic approaches for the resolution of the problem in a static context and a static iterative algorithm for a dynamic context.Received: November 2004, AMS classification: 90C27, 90B35