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This is a summary of the author’s PhD thesis supervised by Manlio Gaudioso and Maria Flavia Monaco and defended on 21 February 2008 at the Università della Calabria. The thesis is a survey on nonsmooth optimization methods for both convex and nonconvex functions. The main contribution of the dissertation is the presentation of a new bundle type method. The thesis is written in English and is available...
We survey the main results of the PhD Thesis presented by the author in January 2009 at the University of Padova. This work was supervised by Giacomo Zambelli. The thesis is written in English and is available from the author upon request. In this work we consider the Edmonds–Johnson property and we survey some related results. Next we present our contributions, that consist into two classes of matrices...
This survey is concerned with the size of perfect formulations for combinatorial optimization problems. By “perfect formulation”, we mean a system of linear inequalities that describes the convex hull of feasible solutions, viewed as vectors. Natural perfect formulations often have a number of inequalities that is exponential in the size of the data needed to describe the problem. Here we are particularly...
This text summarizes the PhD dissertation that was defended by the author in January 2009 under the supervision of Erik Demeulemeester at the Katholieke Universiteit Leuven (Belgium). The text is written in English and is available from the author upon request. The PhD dissertation is situated within the health care services domain and studies the impact of planning and scheduling procedures in the...
We extend the reduced games introduced by Davis and Maschler (Naval Res Log Q 12:223–259, 1965) and Moulin (J Econ Theory 36:120–148, 1985) to multi-choice non-transferable utility games and define two related properties of consistency. We also show that the core proposed by Hwang and Li (Math Methods Oper Res 61:33–40, 2005) violates these two consistency properties. In order to investigate how seriously...
In this paper, we deal with the two-machine flow shop scheduling problem having an unavailability interval on the first machine, and nonresumable jobs. We first present an enhancement procedure that, once applied to any arbitrary solution, produces a schedule that is at most equal 2 times the optimal makespan. We then develop an improved heuristic, with a relative worst-case error of 3/2.
The team orienteering problem (TOP) is a generalization of the orienteering problem. A limited number of vehicles is available to visit customers from a potential set. Each vehicle has a predefined running-time limit, and each customer has a fixed associated profit. The aim of the TOP is to maximize the total collected profit. In this paper we propose a simple hybrid genetic algorithm using new algorithms...
We bring some concepts from market segmentation, which is a fundamental topic of marketing theory and practice, into the statement of an advertising and production problem for a seasonal product with Nerlove–Arrow’s linear goodwill dynamics. We consider two kinds of situations. In the first one, the advertising process can reach selectively each segment. In the second one, one advertising medium is...
This is a summary of the author’s PhD thesis supervised by Edoardo Amaldi and defended on 3 April 2009 at the Politecnico di Milano. The thesis is written in English and is available from the author upon request. In this work, we extensively study two challenging variants of the general problem of clustering a given set of data points with respect to hyperplanes so as to extract collinearity between...
Empirical evidence demonstrates that when the same local search operator is used, variable neighborhood search consistently outperforms random multistart local search on all types of combinatorial and global optimization problems tested. In this paper we suggest that this superiority in performance may be explained by the distribution of the attraction basins around a current solution as a function...
Many financial optimization problems involve future values of security prices, interest rates and exchange rates which are not known in advance, but can only be forecast or estimated. Several methodologies have therefore, been proposed to handle the uncertainty in financial optimization problems. One such methodology is Robust Statistics, which addresses the problem of making estimates of the uncertain...
An automated negotiation mechanism for decentralized production coordination is presented and evaluated. The coordination problem contains a set of self-interested software agents, representing the production facilities of a supply chain, searching for a mutually agreeable production plan, while taking private information into account. The negotiation mechanism is applied and evaluated using a multi-facility...
The small world phenomenon, Milgram (1967) has inspired the study of real networks such as cellular networks, telephone call networks, citation networks, power and neural networks, etc. The present work is about the study of the graphs produced by efficient solutions of the bi-objective {0,1}-knapsack problem. The experiments show that these graphs exhibit properties of small world networks. The importance...
We survey the main results obtained by the author in his PhD dissertation supervised by Anass Nagih and Lucas Létocart. It was defended in December 2008 at The Computer Science lab of the Paris-Nord University (L.I.P.N.), Villetaneuse, France. The thesis is written in French and is available from http://www-lipn.univ-paris13.fr/~touati/TM_Thesis.pdf . Column generation algorithms are instrumental...
In this paper, we compute the probability generating functions (PGF’s) of the customer delay for two batch-service queueing models with batch arrivals. In the first model, the available server starts a new service whenever the system is not empty (without waiting to fill the capacity), while the server waits until he can serve at full capacity in the second model. Moments can then be obtained from...
The purpose of this article is to investigate a stochastic integrated supplier-retailer inventory problem. The model analyzed in this article explores the problem of the protection interval, the backorder price discount, the lead time, and the numbers of shipments from the supplier to the retailer in one production run as control variables to widen applications for an integrated periodic review inventory...
Flight delays (such as early or late arrivals and late departures) are a frequent occurrence in actual day to day airport operations and it is often not possible to assign such flights to their original gates. Flight delay information may also vary with time. As a consequence, the airport authority needs to reassign flights to different gates in real-time. The traditional manual flight reassignment...
This paper describes a Diversification-Driven Tabu Search (D2TS) algorithm for solving unconstrained binary quadratic problems. D2TS is distinguished by the introduction of a perturbation-based diversification strategy guided by long-term memory. The performance of the proposed algorithm is assessed on the largest instances from the ORLIB library (up to 2500 variables) as well as still larger instances...
This is a summary of the author’s PhD thesis supervised by Andrea Lodi and defended on 16 April 2009 at the University of Bologna. The thesis is written in English and available for download at http://www.or.deis.unibo.it/staff_pages/dambrosio/Phd_Th_DAmbrosio.tar.gz . The main topic of the thesis is Mixed Integer Non-Linear Programming, with focus on non-convex problems (i.e., problems for which...
This a summary of the author’s PhD thesis supervised by Leo Liberti, Philippe Baptiste and Daniel Krob and defended on 18 June 2009 at Ecole Polytechnique, Palaiseau, France. The thesis is written in English and is available at http://pastel.paristech.org/5275/ . The computation of point-to-point shortest paths in road networks has many practical applications that require very fast solution times,...
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