References of "Crama, Yves"
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See detailA Rich Vehicle Routing Problem with Multiple Trips and Driver Shifts
Arda, Yasemin ULg; Crama, Yves ULg; Kucukaydin, Hande ULg et al

Conference (2012)

This study is concerned with a rich vehicle routing problem (RVRP) encountered at a Belgian transportation company in charge of servicing supermarkets and hypermarkets belonging to a franchise. The ... [more ▼]

This study is concerned with a rich vehicle routing problem (RVRP) encountered at a Belgian transportation company in charge of servicing supermarkets and hypermarkets belonging to a franchise. The studied problem can be classified as a one-to-many-to-one pick-up and delivery problem, where there is a single depot from which all delivery customers are served and to which every pick-up demand must be carried back (Gutiérrez-Jarpa et al., 2010). The delivery and backhaul customers are considered to be two disjoint sets, where on a given route backhaul customers can be visited only after all delivery customers are served. Split deliveries and pick-ups are not allowed. The service at a customer must start within the given time window of the customer. However, it is not possible to serve a customer with every available vehicle, since the vehicles at the company’s disposal are of different types according to which the capacity changes. Therefore, our problem can be classified also as a heterogeneous fleet vehicle routing problem with customer-vehicle incompatibilities (Ceselli et al., 2009). The problem at hand requires that the same vehicle may be assigned to several routes, which leads to a multiple-trip RVRP. Furthermore, driver shifts are taken into account so that each vehicle of the fleet starts servicing the customers when the shift of the assigned driver starts. The shift duration is the same for all drivers. If the service of the vehicle exceeds SH, an overtime cost incurs to the transportation company. In such a case, a vehicle can be used during at most a fixed length of time. In addition to the vehicles of the company’s own fleet (i.e. internal vehicles), there is a possibility to request external vehicles for servicing some customers. External vehicles can be used for a fixed maximum amount of time and can start servicing customers at any desired time. A fixed reservation cost and distance and time based variable costs are incurred in the case of an external vehicle, while only distance based variable costs are incurred in the case of an internal vehicle. We employ a binary integer linear programming formulation in order to model our problem. The first constraint set ensures that each customer is visited at least once by either an internal or external vehicle. With the second constraint set, it is guaranteed that each internal vehicle is assigned to at most one tour. The last two constraint sets are the binary restrictions on the assignment variables. In order to solve the problem, we first relax the binary restrictions on the assignment variables and develop a column generation procedure, where we obtain two pricing problems, one for internal vehicles and the other one for external vehicles. The pricing problem of each internal vehicle can be formulated as an elementary shortest path problem with resource constraints, which can be solved using a dynamic programming algorithm based on a bounded bi-directional search (Righini and Salani, 2008). However, since an external vehicle can start the service at any point in time and is paid based on its total travel time, the second pricing algorithm has to take into account an infinite number of Pareto-optimal states (Liberatore et al., 2011). We discuss the efficient solution of the pricing subproblems and present preliminary computational results. [less ▲]

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See detailBoolean methods in operations research and related areas
Crama, Yves ULg

Conference (2011, November)

These are the slides of the "IFORS Distinguished Lecture" that I delivered at the INFORMS Annual meeting in November 2011. The title of the lecture is the title of a monograph co-authored by Peter L ... [more ▼]

These are the slides of the "IFORS Distinguished Lecture" that I delivered at the INFORMS Annual meeting in November 2011. The title of the lecture is the title of a monograph co-authored by Peter L. Hammer and Sergiu Rudeanu, which appeared in 1968. Their pioneering work has stimulated a large amount of research and has been very frequently cited. Over the last year, the late Peter Hammer and myself have published two distant follow-ups to this classical book: a monograph entitled Boolean Functions: Theory, Algorithms, and Applications (700 pages, Cambridge University Press, 2011), and a collection of survey papers on Boolean Models and Methods in Mathematics, Computer Science and Engineering (780 pages, Cambridge University Press, 2010). The size of these two volumes and of their bibliographic sections are witnesses of the vitality of the field and of its impressive development. Boolean functions are actually among the most fundamental objects investigated in mathematics, and provide the basic building blocks for many models arising in operations research, computer science, artificial intelligence, economics, engineering, cryptography, biology, and other fields of application. In this lecture, I propose a brief overview of some fundamental Boolean models, I discuss applications in corporate governance (modeling of shareholders’ power) and in classification (Logical Analysis of Data), and I mention a few challenging research problems. [less ▲]

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See detailPower indices and the measurement of control in corporate structures
Crama, Yves ULg; Leruth, Luc ULg

E-print/Working paper (2011)

This paper proposes a review of the use of power indices in the corporate governance literature. It places the emphasis on the game-theoretic aspects of this research, but it also addresses some of the ... [more ▼]

This paper proposes a review of the use of power indices in the corporate governance literature. It places the emphasis on the game-theoretic aspects of this research, but it also addresses some of the key issues linked to the specific field of application. [less ▲]

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See detailControl and Voting Power in Complex Shareholding Networks
Crama, Yves ULg; Leruth, Luc ULg; Su Wang

Conference (2011, June)

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See detailMultiperiod vehicle loading optimization with stochastic supply
Amand, Guillaume ULg; Arda, Yasemin ULg; Crama, Yves ULg et al

Scientific conference (2011, April 07)

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See detailThe Mathematics of Peter L. Hammer (1936-2006): Graphs, Optimization, and Boolean Models
Boros, Endre; Crama, Yves ULg; De Werra, Dominique et al

in Boros, Endre; Crama, Yves; De Werra, Dominique (Eds.) et al The Mathematics of Peter L. Hammer (1936-2006): Graphs, Optimization, and Boolean Models (2011)

This volume of the Annals of Operations Research, contains a collection of papers published in memory of Peter L. Hammer. As we recall further down, Peter made substantial contributions to several areas ... [more ▼]

This volume of the Annals of Operations Research, contains a collection of papers published in memory of Peter L. Hammer. As we recall further down, Peter made substantial contributions to several areas of operations research and discretemathematics, including, in particular, mathematical programming (linear and quadratic 0–1 programming, pseudo-Boolean optimization, knapsack problems, etc.), combinatorial optimization (transportation problems, network flows, MAXSAT, simple plant location, etc.), graph theory (special classes of graphs, stability problems, and their applications), data mining and classification (Logical Analysis of Data), and, last but not least, Boolean theory (satisfiability, duality, Horn functions, threshold functions, and their applications). [less ▲]

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See detailThe Mathematics of Peter L. Hammer (1936-2006): Graphs, Optimization, and Boolean Models
Boros, Endre; Crama, Yves ULg; de Werra, Dominique et al

in Annals of Operations Research (2011), 188

This volume contains a collection of papers published in memory of Peter L. Hammer (1936-2006). Peter Hammer made substantial contributions to several areas of operations research and discrete mathematics ... [more ▼]

This volume contains a collection of papers published in memory of Peter L. Hammer (1936-2006). Peter Hammer made substantial contributions to several areas of operations research and discrete mathematics, including, in particular, mathematical programming (linear and quadratic 0--1 programming, pseudo-Boolean optimization, knapsack problems, etc.), combinatorial optimization (transportation problems, network flows, MAXSAT, simple plant location, etc.), graph theory (special classes of graphs, stability problems, and their applications), data mining and classification (Logical Analysis of Data), and, last but not least, Boolean theory (satisfiability, duality, Horn functions, threshold functions, and their applications). The volume contains 23 contributed papers along these lines. [less ▲]

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See detailLogical Analysis of Data: Classification with justification
Boros, Endre; Crama, Yves ULg; Hammer, Peter L. et al

in Annals of Operations Research (2011), 188

Learning from examples is a frequently arising challenge, with a large number of algorithms proposed in the classification, data mining and machine learning literature. The evaluation of the quality of ... [more ▼]

Learning from examples is a frequently arising challenge, with a large number of algorithms proposed in the classification, data mining and machine learning literature. The evaluation of the quality of such algorithms is frequently carried out ex post, on an experimental basis: their performance is measured either by cross validation on benchmark data sets, or by clinical trials. Few of these approaches evaluate the learning process ex ante, on its own merits. In this paper, we dis- cuss a property of rule-based classifiers which we call "justifiability", and which focuses on the type of information extracted from the given training set in order to classify new observations. We investigate some interesting mathematical properties of justifiable classifiers. In partic- ular, we establish the existence of justifiable classifiers, and we show that several well-known learning approaches, such as decision trees or nearest neighbor based methods, automatically provide justifiable clas- sifiers. We also identify maximal subsets of observations which must be classified in the same way by every justifiable classifier. Finally, we illustrate by a numerical example that using classifiers based on "most justifiable" rules does not seem to lead to over fitting, even though it involves an element of optimization. [less ▲]

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See detailBoolean Functions: Theory, Algorithms, and Applications
Crama, Yves ULg; Hammer, Peter L.

Book published by Cambridge University Press (2011)

This monograph provides the first comprehensive presentation of the theoretical, algorithmic and applied aspects of Boolean functions, i.e., {0,1}-valued functions of a finite number of {0,1}-valued ... [more ▼]

This monograph provides the first comprehensive presentation of the theoretical, algorithmic and applied aspects of Boolean functions, i.e., {0,1}-valued functions of a finite number of {0,1}-valued variables. The book focuses on algebraic representations of Boolean functions, especially normal form representations. It presents the fundamental elements of the theory (Boolean equations and satisfiability problems, prime implicants and associated representations, dualization, etc.), an in-depth study of special classes of Boolean functions (quadratic, Horn, shellable, regular, threshold, read-once, etc.), and two fruitful generalizations of the concept of Boolean functions (partially defined and pseudo-Boolean functions). It features a rich bibliography of about one thousand items. Prominent among the disciplines in which Boolean methods play a significant role are propositional logic, combinatorics, graph and hypergraph theory, complexity theory, integer programming, combinatorial optimization, game theory, reliability theory, electrical and computer engineering, artificial intelligence, etc. The book contains applications of Boolean functions in all these areas. [less ▲]

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See detailModèles mathématiques en gestion
Bair, Jacques ULg; Crama, Yves ULg; Henry, Valérie ULg et al

Book published by Cassini et POLE (2011)

Mis au point notamment pour la gestion de très grands projets industriels, les modèles mathématiques se sont imposés à tous les niveaux de l’activité économique : production, distribution et transports ... [more ▼]

Mis au point notamment pour la gestion de très grands projets industriels, les modèles mathématiques se sont imposés à tous les niveaux de l’activité économique : production, distribution et transports, marketing, finance... Des logiciels du commerce permettent aujourd’hui aux entreprises dépourvues d’un service de recherche d’en faire usage mais, même si ces logiciels se présentent comme des « boîtes noires », il est évident que la compréhension des principes mobilisés doit permettre au décideur de poser intelligemment le problème à résoudre et d’interpréter correctement les résultats obtenus. L’un des buts de ce livre est de les y aider. "Modèles mathématiques en gestion" est le fruit de la longue expérience de quatre professeurs qui, dans plusieurs universités et grandes écoles de Belgique, enseignent la statistique, la recherche opérationnelle, la gestion de la production et la mathématique financière à de futurs gestionnaires, économistes ou mathématiciens. L’originalité de l’ouvrage réside dans les liens établis entre ces diverses matières et dans le projet des auteurs d’établir un passage progressif des théories mathématiques couramment enseignées à des applications réfléchies de modèles mathématiques dans des situations réelles. Autant dire qu’on est loin d’un livre de recettes. Qu’il s’agisse des diverses façons de représenter des données réelles par une fonction mathématique, d’ordonnancement de projets complexes, d’optimisation de la production, de gestion de stocks, de problèmes de files d’attente, de modélisation d’obligations ou de valorisation d’options, les auteurs ont toujours le souci d’éveiller l’esprit critique de leur lecteur. Ce livre s’adresse donc aux étudiants en économie et en gestion, mais il devrait également intéresser les futurs ingénieurs, concernés par les problèmes quantitatifs rencontrés dans l’industrie, et les praticiens désireux de réfléchir aux fondements de leur activité professionnelle. [less ▲]

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See detailOperations Research for the steel industry : the art of combining science and knowledge
Crama, Yves ULg; Chevalier, Philippe

Conference (2010, October)

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See detailSpace and time allocation in a shipyard assembly hall
Bay, Maud ULg; Crama, Yves ULg; Langer, Yves et al

in Annals of Operations Research (2010), 179(1), 57-76

We present a space and time allocation problem that arises in assembly halls producing large building blocks (namely, a shipyard which assembles prefabricated keel elements). The building blocks are very ... [more ▼]

We present a space and time allocation problem that arises in assembly halls producing large building blocks (namely, a shipyard which assembles prefabricated keel elements). The building blocks are very large, and, once a block is placed in the hall, it cannot be moved until all assembly operations on this block are complete. Each block must be processed during a predetermined time window. The objective is to maximize the number of building blocks produced in the hall. The problem is modeled as a 3-dimensional bin packing problem (3D-BPP) and is handled by a Guided Local Search heuristic initially developed for the 3D-BPP. Our com- putational experiments with this heuristic demonstrate that excellent results can be found within minutes on a workstation, and that the heuristic outperforms a standard constraint programming approach. We also describe some additional real-life constraints arising in the industrial application and show how these constraints can be conveniently integrated in the model. [less ▲]

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See detailThroughput optimization in two-machine flowshops with flexible operations
Crama, Yves ULg; Gultekin, Hakan

in Journal of Scheduling (2010), 13(3), 227-243

In this study, a two-machine flowshop producing identical parts is considered. Each of the identical parts is assumed to require a number of manufacturing operations, and the machines are assumed to be ... [more ▼]

In this study, a two-machine flowshop producing identical parts is considered. Each of the identical parts is assumed to require a number of manufacturing operations, and the machines are assumed to be flexible enough to perform different operations. Due to economical or technological constraints, some specific operations are preassigned to one of the machines. The remaining operations, called flexible operations, can be performed on either one of the machines, so that the same flexible operation can be performed on different machines for different parts. The problem is to determine the assignment of the flexible operations to the machines for each part, with the objective of maximizing the throughput rate. We consider various cases regarding the number of parts to be produced and the capacity of the buffer between the machines. We present solution methods for each variant of the problem. [less ▲]

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See detailChallenging Combinatorial Problems
Crama, Yves ULg

Conference (2010, May 06)

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See detailFunctions of Binary Variables and Nonlinear 0-1 Optimization
Crama, Yves ULg

Conference (2010, April 29)

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See detailHigh Multiplicity Scheduling Problems and Just-In-Time Scheduling
Crama, Yves ULg

Conference (2010, April 22)

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See detailCombinatorial Optimization Models in Automated Manufacturing
Crama, Yves ULg

Conference (2010, April 01)

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See detailLogical Analysis of Data and Classification
Crama, Yves ULg

Conference (2010, March 25)

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See detailControl and Voting Power in Shareholding Networks
Crama, Yves ULg

Conference (2010, March 18)

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See detailModels for Decision Making: From Applications to Mathematics... and Back
Crama, Yves ULg

Conference (2010, March 15)

In this inaugural lecture, I describe some facets of the interplay between mathematics and management science, economics, or engineering, as they come together in operations research models. I intend to ... [more ▼]

In this inaugural lecture, I describe some facets of the interplay between mathematics and management science, economics, or engineering, as they come together in operations research models. I intend to illustrate, in particular, the complex and fruitful process through which fundamental combinatorial models find applications in management science, which in turn foster the development of new and challenging mathematical questions. [less ▲]

Detailed reference viewed: 13 (0 ULg)