Elective Course Allocation with numerical preferences

In Universities, students have to select a specified number of elective courses to be included in their curriculum. Elective courses are a good way to increase students motivation and improve their academic success. At HEC- Management School of the University of Liège, each student has to set a preference value for each course offered and taking a number of courses is mandatory to fulfill his curriculum. The Elective Course Allocation with Numerical Preferences (ECANP) is the problem of assigning to each student the requested number of courses such as to maximize the total preference score (i.e. the overall sum of preference values associated by each student to the courses he has been granted). The course assignment problem often comes along with the course time tabling problem. This issue is not considered in this work as a complete course schedule is available at the time of registration. Each student provides his own schedule availability and can only attend one course at a time. An additional constraint is that a course cannot be granted to a student if his preference value for this course is null. We present the set of rules defined to ensure that a feasible assignment can be obtained for each student. The ECANP problem is modeled as a mixed integer programming model and we use CPLEX to obtain optimal solutions for a set of realistic instances. The ECANP problem is compared to the Elective Course Planning problem solved with heuristic methods in [2], to the course Allocation problem for which a bidding mechanism is described in [1] and to the College Admission (CA) problem as presented in [3]. In particular in the CA each student provides a preference order instead of numerical values and each student must be granted only one college. We discuss the differences between the mathematical formulations of theses problems and the ECANP problem, and their properties

A mixed-integer heuristic for the structural optimization of a cruise ship

peer reviewedA heuristic approach is proposed to solve the structural optimization problem of a cruise ship. The challenge of optimization is to define the scantling of the structure of a ship in order to minimize the weight or the production cost. The variables are the dimensions and positions of the constitutive elements of the structure: they are discrete by nature. The objective functions are nonlinear functions. The structure is submitted to geometric constraints and to structural constraints. The geometric constraints are linear functions and the structural constraints are implicit functions requiring a high computation cost. The problem belongs to the class of mixed-integer nonlinear problems (MINLP). A local heuristic of the type “dive and fix” is combined with a solver based on approximation methods. The solver is used as a black-box tool to perform the structural analysis and solve the nonlinear optimization problems (NLP) defined by the heuristic. The heuristic is designed to always provide a discrete feasible solution. Experiments on a real-size structure demonstrate that the optimal value of the mixed-integer problem is of the same magnitude as the optimal value of the optimization problem for which all the variables can take continuous values

Multicriterion Scantling Optimization of the Midship Section of a Passenger Vessel considering IACS Requirements

peer reviewedIn the scantling design of a passenger ship, minimum production cost, minimum weight and maximum moment of inertia (stiffness) are conflicting objectives. For that purpose, recent improvements were made to the LBR-5 software (French acronym of “Stiffened Panels Software”, version 5.0) to optimize the scantling of ship sections by considering production cost, weight and moment of inertia in the optimization objective function. Moreover, IACS requirements regarding bending, shearing and buckling strength are currently available in LBR-5. Until now, only raw scantling optimizations were performed with LBR-5. Thanks to new developments using heuristics, it is now possible to realize discrete optimization so that a standardized and “ready to use” set of optimum scantlings can be obtained

Outcome after allogeneic stem cell transplantation with haploidentical versus HLA-matched donors in patients with higher-risk MDS.

peer reviewedAllogeneic hematopoietic stem cell transplantation remains the best curative option for higher-risk myelodysplastic syndrome. The presence of monosomal karyotype and/or complex karyotype abnormalities predicts inferior survival after allo-SCT in MDS patients. Haploidentical allo-SCT has been increasingly used in acute leukemia (AL) and has similar results as using HLA-matched donors, but data on higher-risk MDS is sparse. We compared outcomes in 266 patients with higher-risk MDS after HLA-matched sibling donor (MSD, n = 79), HLA-matched unrelated donor (MUD, n = 139) and HLA haploidentical donor (HID, n = 48) from 2010 to 2019. Median donor age differed between the three groups (p < 0.001). The overall survival was significantly different between the three groups with a better OS observed in the MUD group (p = 0.014). This observation could be explained by a higher progression-free survival with MUD (p = 0.014). The cumulative incidence of grade 2-4 acute GvHD was significantly higher in the HID group (p = 0.051). However, in multivariable analysis, patients transplanted using an HID had comparable mortality to patients transplanted using a MUD (subdistribution hazard ratio [sHR]: 0.58 [0.32-1.07]; p = 0.080) and a MSD ([sHR]: 0.56 [0.28-1.11]; p = 0.094). MUD do not remain a significant positive predictor of survival, suggesting that beyond the donor-recipient HLA matching, the donor age might impact recipient outcome

Méthodes d'optimisation pour la conception et le production de structures navales

In the past decades the marine industry has undergone significant evolution and the production of large passenger ships faced dramatic changes. The size, the complexity and the security standards of the ships have increased and the ship-owners have become less and less willing to wait once the order is placed. In the meantime, due to growing intense competition, the shipyards have had to improve their efficiency and master their production costs: they progressively moved from manufacture to automated production processes. As a consequence, the shipyards have now to meet this difficult challenge: produce more complex ships, cheaper and faster. In the first part of the thesis we consider the structural optimization problem that arises in the early design phase of a project. Given a vessel overall dimensions and form, structural optimization consists in defining the scantling of the structure’s constitutive elements so as to minimize its total weight or cost, while taking weight, robustness and security issues into account. Designers have to make the most adequate choices within a very short period of time. The decisions made during the design phase have a major impact on the final structure and on its production cost. We propose new algorithms to compute near-optimal solutions of the discrete structural optimization problem. In the second part of the thesis, we turn to the building process of large ships and we present new methods to improve production facility management of shipyards. The ship building process requires the production and the assembly of tens, or even hundreds of thousands of steel elements. We define a space and time allocation problem that arises in assembly halls producing large building blocks and we develop algorithms for its solution. A successful implementation of a flexible and robust application is nowadays in use at a shipyard

Une approche "Branch and Bound" appliquée à l'optimisation des structures navales

Naval structure optimization consists of defining the optimum scantling of the constitutive elements of a structure with given general dimensions and form of the hull. Amathematical formulation leads to non linear problem with mixed (discrete continuos) variables and implicit constraints that are evaluated with a "black-box" software. The evaluation of the constraints is vry expensive in computation time. A non-linear branch and bound framework is presented to solve this problem. The method is first tested on a small example to set up the parameters of the algorithm and then is applied to a real size structures. It performs very well to provide good solutions in a reasonable time

Avoir le véhicule vert

L'argument est séduisant d'acquérir un nouveau véhicule, plus propre en émission de CO2, mais il faut aussi se débarrasser de son ancien. Attention au bilan CO2 total de l'opération ! [...] De plus en plus d'entreprises s'emparent des problématiques environnementales pour vanter leurs produits "plus écologiques". Il faut bien avouer que, suite au film d'Al Gore sur le réchauffement climatique et aux interventions très médiatisées de Nicolas Hulot sur l'urgence écologique, le sujet est très à la mode dans notre pays. D'autant plus qu'au cours des trois dernières années de divers constructeurs automobiles devenues très "vertes" nous incitent à remplacer notre ancien véhicule "polluant" par un nouveau, plus économe en carburant et donc plus propre également en émissions de CO2. Certes l'argument est séduisant. Il faut cependant prendre garde de ne pas oublier que la production, le transport, le marketing et le démantèlement d'un nouveau véhicule émettent aussi beaucoup de CO2 et doivent donc être pris en compte dans le "bilan CO2" total de l'opération. [...

Alimentation durable : De la promotion des filières courtes à la promotion d’emplois durables

Consommation durable ? Le thème de la consommation durable est relativement neuf. Il trouve ses origines au Sommet de la Terre qui s’est tenu en 1992 à Rio de Janeiro. Ce thème part du constat que les politiques publiques ne peuvent plus seulement se contenter d’agir sur la production ; infléchir également les modes de consommation écologiquement et socialement non soutenables étant devenu indispensable pour parvenir à un développement durable. Mais cela pose une série de questions. Quelles sont actuellement les spécificités des modes de consommation des ménages ? Quelles sont leurs capacités à évoluer vers la prise en compte des critères du développement durable ? Quels sont les rôles que doivent jouer les pouvoirs publics, les acteurs économiques et associatifs dans la consommation durable