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.     

Solving the capacitated location-routing problem

This is a summary of the main results presented in the author’s Ph.D thesis, available at http://prodhonc.free.fr/homepage. This thesis, written in French, was supervised by Christian Prins and Roberto Wolfler-Calvo, and defended on 16 October 2006 at the Université de Technologie de Troyes. Several new approaches are proposed to solve the capacitated location-routing problem (CLRP): heuristic, cooperative and exact methods. Their performances are tested on various kinds of instances with capacitated vehicles and capacitated or uncapacitated depots.      

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.      

Effects of a low frequency parametric excitation

The effects of a slowly varying parametric excitation on a shallow arch model are investigated. The delay bifurcation and the sequence of visited equilibria are analyzed. The method of Melnikov and a method proposed by Berglund [Adiabatic dynamical systems and hysteresis, Ph.D. thesis, Institut de Physique Théorique EPRFL, Lausanne, Switzerland, 1998] are used to determine chaotic regions.     

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.     

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.     

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.      

Optimization via simulation for logistic systems planning and control

This text summarizes the author’s PhD thesis, presented in February 2007 at the University of Calabria and supervised by Roberto Musmanno and Pasquale Legato. The work deals with the field of optimization via simulation. A special emphasis is put on problems with discrete decision variables because they are especially relevant in engineering applications (e.g., in the design of logistic systems). In particular, the thesis focuses on a critical decision problem at marine container terminals. For tackling the problem, an optimization via simulation procedure is presented. Computational results are obtained by using high performance computing systems. The thesis is written in Italian and is available from the author upon request.      

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.      

Optimization of modular machining lines

The paper summarizes the main results of the author’s Ph.D. thesis presented in December 2006 at the école des Mines de Saint étienne. The work was supervised by Alexandre Dolgui and Xavier Delorme. The thesis is written in French and is available upon request from the author. Its purpose is to provide decision support in the design and reconfiguration of modular machining lines with multi-spindle units. This design problem is defined as the selection of spindle units to perform a set of operations needed to produce the parts and subsequently their assignment to workstations. The corresponding optimization problem is solved using different models based on integer and constraint programming.      

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.     

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.     

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.     

An eigenvalue comparison theorem for second order self-adjoint differential equations

Summary This paper is concerned with a comparison of the eigenvalues for pairs of self-adjoint differential systems which arise from a single ordinary second-order differential equation. The sistems differ in the boundary conditions which are imposed, and it is these boundary conditions which will draw most of the attention. The principal results obtained deal with predicting alternation of the eigenvalues for two such systems from the boundary conditions alone, without special consideration of the differential equation. This paper is part of a thesis submitted to Carnegie Institute of Technology in partial fulfillment of the requirements for the degree of Doctor of Philosophy. The author wishes to express his thanks to the thesis director, ProfessorAllan D. Martin Jr. Presented to the American Mathematical Society November 17, 1962.     

Planning in tourism and public transportation

This is a summary of the author’s Ph.D. thesis supervised by Dirk Van Oudheusden and Willy Herroelen and defended in May 2008 at the Katholieke Universiteit Leuven. The thesis is written in English and is available from the author upon request. In this work different operations research techniques are applied to solve several scheduling problems in two different domains. The first domain deals with improved passenger service in railway systems. The second domain deals with the automated selection of the most interesting tourist attractions by means of a hand-held personalised electronic tourist guide.     

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.     

Stochastic hybrid simulation

This is a summary of the author’s PhD thesis supervised by Bart Scheers and Antoine Van de Capelle and defended on 20 November 2009 at the Royal Military Academy, Brussels. The thesis () is written in English and is available from the author upon request. This work deals with an extension to the hybrid simulation paradigm, i.e. the combination of event-driven simulation and analytical modelling, applied to packet telecommunication networks. In order to speed up the simulation only a small part of all packets, the foreground traffic, is processed in an event-driven way. On each arrival of a foreground packet, the waiting time of the packet is sampled from the virtual waiting time distribution function of the combined foreground and background traffic. This distribution function is stochastically modelled by the exact large deviations asymptotic of the virtual waiting time in a many sources regime. This novel methodology is not only valid for wired point-to-point queueing networks having a fixed transmission capacity, but it can also be applied to queueing networks for which the transmission capacity varies with the traffic load of all the elements in the network. The results obtained by the stochastic hybrid simulator are compared to full-blown event-driven simulations. An important reduction in simulation run-time is gained without sacrificing accuracy.     

A new implementation of the CMRH method for solving dense linear systems

The CMRH method [H. Sadok, Méthodes de projections pour les systèmes linéaires et non linéaires, Habilitation thesis, University of Lille1, Lille, France, 1994; H. Sadok, CMRH: A new method for solving nonsymmetric linear systems based on the Hessenberg reduction algorithm, Numer. Algorithms 20 (1999) 303–321] is an algorithm for solving nonsymmetric linear systems in which the Arnoldi component of GMRES is replaced by the Hessenberg process, which generates Krylov basis vectors which are orthogonal to standard unit basis vectors rather than mutually orthogonal. The iterate is formed from these vectors by solving a small least squares problem involving a Hessenberg matrix. Like GMRES, this method requires one matrix–vector product per iteration. However, it can be implemented to require half as much arithmetic work and less storage. Moreover, numerical experiments show that this method performs accurately and reduces the residual about as fast as GMRES. With this new implementation, we show that the CMRH method is the only method with long-term recurrence which requires not storing at the same time the entire Krylov vectors basis and the original matrix as in the GMRES algorithm. A comparison with Gaussian elimination is provided.