444 research outputs found
Numerical Comparison of 2-satisfiability algorithms
No full textSono riportati i risultati di uno studio sperimentale nel quale si sono confrontati i comportamenti di 4 algoritmi per la 2-soddisfacibilita
Local search algorithms for political districting
No full textElectoral district planning plays an important role in a political election, especially when a majority voting rule is adopted, because it interferes in the translation of votes into seats. The practice of gerrymandering can easily take place if the shape of electoral districts is not controlled. In this paper we consider the following formulation of the political districting problem: given a connected graph (territory) with n nodes (territorial units), partition its set of nodes into k classes such that the subgraph induced by each class (district) is connected and a given vector of functions of the partition is minimized. The nonlinearity of such functions and the connectivity constraints make this network optimization problem a very hard one. Thus, the use of local search heuristics is justified. Experimentation on a sample of medium-large real-life instances has been carried out in order to compare the performance of four local search metaheuristics, i.e., Descent, Tabu Search, Simulated Annealing, and Old Bachelor Acceptance. Our experiments with Italian political districting provided strong evidence in favor of the use of automatic procedures. Actually, except for Descent, all local search algorithms showed a very good performance for this problem. In particular, in our sample of regions, Old Bachelor Acceptance produced the best results in the majority of the cases, especially when the objective function was compactness. Moreover, the district maps generated by this heuristic dominate the institutional district plan with respect to all the districting criteria under consideration. When properly designed, automatic procedures tend to be impartial and yield good districting alternatives. Moreover, they are remarkably fast, and thus they allow for the exploration of a large number of scenarios. (c) 2007 Elsevier B.V. All rights reserved
The give-up problem for blocked regional lists with multi-winners
No full textThe current electoral law for the Italian Parliament prescribes blocked, linearly ordered lists of candidates for each party within each constituency. The peculiarity of the Italian electoral system is that a party can present the same candidate in different constituencies. There are several seats at stake in each constituency; these seats are allocated to the parties proportionally to the total number of votes they get. If the blocked list mechanism-which assigns the seats obtained by a party in a constituency to the first candidates of the corresponding ordered list-causes some candidates to win in more than one constituency, they may retain only one of the seats, giving up all the remaining ones. Thus, the problem arises for a party to find a suitable schedule of give-ups that produces the final set of winners for that party. In order to do this, we assume that such decision is centralized and based on some models of global (inter-regional) preferences over the set of candidates. In this paper, we introduce two classes of models to formulate the give-up problem, i.e., utility and ordinal models, and we show that for both of them some natural formulations of the problem can be efficiently solved by network flows techniques. © 2011 Elsevier B.V
Political districting: from classical models to recent approaches
No full textThe political districting problem has been studied since the 60's and many different models and techniques have been proposed with the aim of preventing districts' manipulation which may favor some specific political party (gerrymandering). A variety of political districting models and procedures was provided in the Operations Research literature, based on single- or multiple-objective optimization. Starting from the forerunning papers published in the 60's, this article reviews some selected optimization models and algorithms for political districting which gave rise to the main lines of research on this topic in the Operartions Research literature of the last five decades
Multiple resistance to primary pests of grain sorghum hybrids: Spodoptera frugiperda (Lepidoptera: Noctuidae), Diatraea saccharalis (Lepidoptera: Crambidae), and Diceraeus melacanthus (Hemiptera: Pentatomidae)
No full textSouza, Camila da Silva Fernandes, Souza, Bruno Henrique Sardinha de, Menezes, Cícero Bezerra de, Simeone, Maria Lúcia Ferreira, Nascimento, Priscilla Tavares, França, Josélia Carvalho Oliveira, Mendes, Simone Martins (2023): Multiple resistance to primary pests of grain sorghum hybrids: Spodoptera frugiperda (Lepidoptera: Noctuidae), Diatraea saccharalis (Lepidoptera: Crambidae), and Diceraeus melacanthus (Hemiptera: Pentatomidae). Revista Brasileira de Entomologia (e20210118) 67: 1-9, DOI: 10.1590/1806-9665-RBENT-2021-011
Giornata di studio in Memoria di Bruno Simeone, Dip. di Scienze Statistiche, Sapienza Università di Roma
No full textGeomechanical modelling and stability analysis of the shallow underground water reservoir ‘Palombaro Lungo’ (Matera-Italy)
No full textThe city of Matera, as several other ancient historical cities and towns, is recovering a large part of its ancient parts developing a policy of urban regeneration. In the early 90s, during the restoration works of the main square, Piazza Vittorio Veneto, it was re-discovered a huge underground space used as water reservoir named Palombaro Lungo. It was built linking ancient pre-existing smaller caves and completed at the end of the nineteenth century making it impermeable with the cocciopesto (opus signinum) technique. The hypogeum is dug in a Plio-Pleistocene rock called Gravina Calcarenite. It is a calcareous sandstone weak rock with good mechanical properties, low permeability and easy to be dug. The internal geometry of the hypogeum and the rock thicknesses above the caves was reconstructed by the integration of topographic and GPR surveys. The paper presents a geo-mechanical model of Palombaro Lungo underground reservoir and evaluation about the stability of this structure. The stability analysis were developed using the numerical code UDEC for several transect of Palombaro Lungo assuming the calcareous sandstone blocks as deformable, trying to address the evolution of the stress-strain conditions. The case study can be considered as an example of general interest for the study of rupestrian underground reservoir of a longed form, where one planimetric dimension strictly prevails over the other. Numerical simulations showed a stress-strain state compatible with the fractures detected in situ and confirmed the absence of instability problems in the groundwater reservoir
Political Districting: From classical models to recent approaches
No full textThe Political Districting problem has been studied since the 60's and many different models and techniques have been proposed with the aim of preventing districts' manipulation which may favor some specific political party (gerrymandering). A variety of Political Districting models and procedures was provided in the Operations Research literature, based on single- or multiple-objective optimization. Starting from the forerunning papers published in the 60's, this article reviews some selected optimization models and algorithms for Political Districting which gave rise to the main lines of research on this topic in the Operations Research literature of the last five decades. © 2012 Springer Science+Business Media New York
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