The effect of the asymmetry of road transportation networks on the traveling salesman problem

The routing of vehicles on road transportation networks is an area of great importance to transportation planners within scientific literature. This field includes well known and studied problems like traveling salesman problems or TSP or the more realistic asymmetric variant or ATSP, whose applications extend to other areas of transport and operations research. This work studies the effect that the asymmetry of road transportation networks, geographical location and territory have over TSP and ATSP methods. We conduct comprehensive experiments in order to assess the effects that these factors have on some of the best known algorithms for the TSP/ATSP. We demonstrate that all these factors have a significant influence in solution time and quality. Furthermore, we show that the solutions obtained with Euclidean matrices and those obtained with real distance matrices differ significantly. © 2011 Elsevier Ltd. All rights reserved.The authors would like to warmly thank Prof. Keld Helsgaun, Prof. Yuichi Nagata, Profs. Boris Goldengorin and Gerold Jager, and especially Prof. Matteo Fischetti, for facilitating the code of their great algorithms. This work is partially funded by the Spanish Ministry of Science and Innovation, under the project "SMPA Advanced Parallel Multiobjective Sequencing: Practical and Theoretical Advances" with reference DPI2008-03511/DPI. The authors should also thank the IMPIVA-Institute for the Small and Medium Valencian Enterprise, for the project OSC with references IMIDIC/2008/137, IMIDIC/2009/198 and 175 and the Polytechnic University of Valencia, for the project PPAR with reference 3147.Rodríguez Villalobos, A.; Ruiz García, R. (2012). The effect of the asymmetry of road transportation networks on the traveling salesman problem. Computers and Operations Research. 39(7):1566-1576. https://doi.org/10.1016/j.cor.2011.09.005S1566157639

Pareto Autonomous Local Search

This paper presents a study for the dynamic selection of operators in a local search process. The main purpose is to propose a generic autonomous local search method which manages operator selection from a set of available operators, built on neighborhood relations and neighbor selection functions, using the concept of Pareto dominance with respect to quality and diversity. The latter is measured using two different metrics. This control method is implemented using the Comet language in order to be easily introduced in various constraint local search algorithms. Focusing on permutation-based problems, experimental results are provided for the QAP and ATSP to assess the method’s effectiveness

Ownership and control in a competitive industry

We study a differentiated product market in which an investor initially owns a controlling stake in one of two competing firms and may acquire a non-controlling or a controlling stake in a competitor, either directly using her own assets, or indirectly via the controlled firm. While industry profits are maximized within a symmetric two product monopoly, the investor attains this only in exceptional cases. Instead, she sometimes acquires a noncontrolling stake. Or she invests asymmetrically rather than pursuing a full takeover if she acquires a controlling one. Generally, she invests indirectly if she only wants to affect the product market outcome, and directly if acquiring shares is profitable per se. --differentiated products,separation of ownership and control,private benefits of control

Local search for the surgery admission planning problem

We present a model for the surgery admission planning problem, and a meta-heuristic algorithm for solving it. The problem involves assigning operating rooms and dates to a set of elective surgeries, as well as scheduling the surgeries of each day and room. Simultaneously, a schedule is created for each surgeon to avoid double bookings. The presented algorithm uses simple Relocate and Two-Exchange neighbourhoods, governed by an iterated local search framework. The problem's search space associated with these move operators is analysed for three typical fitness surfaces, representing different compromises between patient waiting time, surgeon overtime, and waiting time for children in the morning on the day of surgery. The analysis shows that for the same problem instances, the different objectives give fitness surfaces with quite different characteristics. We present computational results for a set of benchmarks that are based on the admission planning problem in a chosen Norwegian hospital

Biostratigraphy of large benthic foraminifera from Hole U1468A (Maldives): A CT-scan taxonomic approach

Large benthic foraminifera are important components of tropical shallow water carbonates. Their structure, developed to host algal symbionts, can be extremely elaborate and presents stratigraphically-significant evolutionary patterns. Therefore their distribution is important in biostratigraphy, especially in the Indo-Pacific area. To provide a reliable age model for two intervals of IODP Hole U1468A from the Maldives Inner-Sea, large benthic foraminifera have been studied with computed tomography. This technique provided 3D models ideal for biometric-based identifications, allowing the upper interval to be placed in the late middle-Miocene and the lower interval in the late Oligocene

Analisi dinamica e sviluppo dell'assetto della vettura FSAE MG 13.18

Il lavoro all'interno di questa tesi verte sull'analisi della dinamica della vettura MG 13.18 del team RaceUP dell'Università di Padova. Nei primi capitoli sono esposte le caratteristiche tecniche principali della vettura e la procedura per calcolare e misurare la posizione del baricentro del veicolo, mentre nella seconda parte ci si addentra nelle fasi di modellazione e simulazione attraverso il software Dymola; inoltre vengono introdotte delle linee guida per lo sviluppo dei set-up