Página 1 dos resultados de 20350 itens digitais encontrados em 0.024 segundos

Branch and bound based coordinate search filter algorithm for nonsmooth nonconvex mixed-integer nonlinear programming problems

Fernandes, Florbela P.; Costa, Fernanda P.M.; Fernandes, Edite M.G.P.
Fonte: Springer Publicador: Springer
Tipo: Parte de Livro
ENG
Relevância na Pesquisa
36.44%
A mixed-integer nonlinear programming problem (MINLP) is a problem with continuous and integer variables and at least, one nonlinear function. This kind of problem appears in a wide range of real applications and is very difficult to solve. The difficulties are due to the nonlinearities of the functions in the problem and the integrality restrictions on some variables. When they are nonconvex then they are the most difficult to solve above all. We present a methodology to solve nonsmooth nonconvex MINLP problems based on a branch and bound paradigm and a stochastic strategy. To solve the relaxed subproblems at each node of the branch and bound tree search, an algorithm based on a multistart strategy with a coordinate search filter methodology is implemented. The produced numerical results show the robustness of the proposed methodology.

U-curve: A branch-and-bound optimization algorithm for U-shaped cost functions on Boolean lattices applied to the feature selection problem

RIS, Marcelo; BARRERA, Junior; MARTINS JR., David C.
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.51%
This paper presents the formulation of a combinatorial optimization problem with the following characteristics: (i) the search space is the power set of a finite set structured as a Boolean lattice; (ii) the cost function forms a U-shaped curve when applied to any lattice chain. This formulation applies for feature selection in the context of pattern recognition. The known approaches for this problem are branch-and-bound algorithms and heuristics that explore partially the search space. Branch-and-bound algorithms are equivalent to the full search, while heuristics are not. This paper presents a branch-and-bound algorithm that differs from the others known by exploring the lattice structure and the U-shaped chain curves of the search space. The main contribution of this paper is the architecture of this algorithm that is based on the representation and exploration of the search space by new lattice properties proven here. Several experiments, with well known public data, indicate the superiority of the proposed method to the sequential floating forward selection (SFFS), which is a popular heuristic that gives good results in very short computational time. In all experiments, the proposed method got better or equal results in similar or even smaller computational time. (C) 2009 Elsevier Ltd. All rights reserved.; BZG; BZG

Uma nova abordagem branch and cut aplicada ao problema de planejamento da expansão de redes de transmissão de grande porte; A new branch and cut approach applied to the long-term transmission expansion planning problem

Sousa, Aldir Silva; Asada, Eduardo Nobuhiro
Fonte: Sociedade Brasileira de Automática Publicador: Sociedade Brasileira de Automática
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
36.51%
Neste artigo propomos um algoritmo branch and cut com novas inequações específicas ao problema de planejamento da expansão de redes de transmissão de energia elétrica. Todas as inequações propostas neste trabalho são válidas tanto para os modelos lineares como para os modelos não lineares do problema. Os testes computacionais têm mostrado a eficiência do método proposto neste trabalho quando aplicado a subsistemas reais brasileiros e ao sistema colombiano.

Aplicação do método branch-and-bound na programação de tarefas em uma única máquina com data de entrega comum sob penalidades de adiantamento e atraso.; Branch-and-bound method application in a single machine earliness/tardiness scheduling problem with a common due date.

Kawamura, Márcio Seiti
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 07/04/2006 PT
Relevância na Pesquisa
36.51%
O objetivo desse trabalho é o de estudar o problema de programação de tarefas num ambiente produtivo com uma única máquina com data comum de entrega. Nesse caso, as tarefas, depois de processadas uma única vez na máquina, devem ser entregues em uma data comum e sofrem penalidades de adiantamento e de atraso conforme o instante em que são completadas. Na prática, esse problema é encontrado em casos de pedidos de lotes de produtos com data de entrega comum préespecificada, embarques para exportação e material químico ou misturas que têm vida média de curta duração. Problemas desse tipo são NP-hard (Hall, Kubiak & Sethi, 1991; Hoogeven & van de Velde, 1991), sendo comumente tratados na literatura através de heurísticas e meta-heurísticas. Visto não ser de nosso conhecimento a existência na literatura de tratamento desse problema através de métodos exatos, propôs-se a utilização de um algoritmo do tipo branch-and-bound para obtenção da solução ótima do problema que minimize a soma das penalidades de adiantamento e de atraso. No desenvolvimento do algoritmo, a utilização de propriedades do problema foi importante na elaboração de limitantes inferiores e regras de dominância que melhoraram a eficiência do modelo. Os experimentos realizados avaliaram o desempenho de diferentes critérios elaborados...

Estudo comparativo do diagnóstico de edema macular secundário a oclusão de ramo da veia central da retina pela biomicroscopia de mácula, angiofluoresceinografia e tomografia de coerência óptica; Comparison of optic coherence tomography, macular biomicroscopy and fluorescein angiography for macular edema secondary to branch retinal vein occlusion

Pinheiro, Alexandre Grobberio
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 04/10/2007 PT
Relevância na Pesquisa
36.44%
As Oclusões Venosas da Retina são complicações do sistema vascular retiniano com grande potencial de impacto no sentido da visão. As oclusões Venosas são classificadas de acordo com a anatomia da região acometida e podem ser divididas em oclusão de ramo e da veia central da retina. O edema macular é a principal causa de baixa acuidade visual na Oclusão de Ramo da Veia Central da Retina (OVR). Sua detecção, localização e classificação são cruciais para a prevenção e tratamento da perda visual na OVR. A Biomicrospia Macular e a Angiofluoresceinografia são os métodos tradicionais de avaliação do edema macular na OVR, a Tomografia de Coerência Óptica (TCO) é uma tecnologia nova, que permite uma avaliação objetiva da morfologia macular. O objetivo primário do presente estudo foi avaliar, em uma mesma população, a acurácia dos métodos de diagnóstico do edema macular na OVR através da análise de três quesitos, aumento da espessura macular e da sua localização, presença de cistos intra-retinianos e a presença de descolamento seroso macular (DSM). Indivíduos com OVR foram selecionados com base nos achados fundoscópicos da doença e com tempo de história da doença entre três e vinte quatro meses. Todos os sujeitos foram submetidos a exames com o Stratus OCT (TCO)...

Efeito de métodos químicos de indução de copa no desenvolvimento da seringueira (Hevea brasiliensis Muell. Arg. cv. RRIM 600); Effect of chemical methods of branch induction on growth of rubber tree (Hevea brasiliensis Muell. Arg. cv. RRIM 600)

Bernardes, Marcos Silveira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/03/1990 PT
Relevância na Pesquisa
36.56%
Objetivando-se estudar o efeito de métodos químicos de indução de copa no desenvolvimento da seringueira, realizou-se experimento em condições de campo, em Casa Branca-SP, aplicando-se reguladores vegetais de crescimento em plantas enxertadas do cultivar RRIM 600 com 20 meses de idade, com 1,70 a 3,00 m de altura e último lançamento foliar maduro. O experimento foi delineado em Blocos ao Acaso com quatro repetições, utilizando-se como tratamentos, a aplicação de hidrazida maléica a 500, 750 e 1. 000 ppm, chlormequat a 1.000, 1.500 e 2.000 ppm, daminozide a 2.000, 3.000 e 4.000 ppm e a testemunha. Durante a realização do experimento efetuaram-se avaliações das seguintes variáveis: perímetro do tronco, espessura de casca, altura da árvore, altura do tronco, comprimento da copa, diâmetro da copa, número e porcentual de árvores ramificadas, número de ramos, concentração de ramos, ângulo de inserção dos ramos, índice de área foliar, coeficiente de absorção de radiação e danos por vento. Estudos de correlação foram feitos para analisar a influência das características da copa sobre o desenvolvimento das árvores. Nas condições em que foi conduzido o experimento, os resultados obtidos permitiam concluir que a indução de copa por métodos químicos pode incrementar o crescimento do perímetro do tronco...

A new Branch and Bound method for a discrete truss topology design problem

Cerveira, Adelaide; Agra, Agostinho; Bastos, Fernando; Gromicho, Joaquim
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.56%
Our paper considers a classic problem in the field of Truss Topology Design, the goal of which is to determine the stiffest truss, under a given load, with a bound on the total volume and discrete requirements in the cross-sectional areas of the bars. To solve this problem we propose a new two-stage Branch and Bound algorithm. In the first stage we perform a Branch and Bound algorithm on the nodes of the structure. This is based on the following dichotomy study: either a node is in the final structure or not. In the second stage, a Branch and Bound on the bar areas is conducted. The existence or otherwise of a node in this structure is ensured by adding constraints on the cross-sectional areas of its incident bars. In practice, for reasons of stability, free bars linked at free nodes should be avoided. Therefore, if a node exists in the structure, then there must be at least two incident bars on it, unless it is a supported node. Thus, a new constraint is added, which lower bounds the sum of the cross-sectional areas of bars incident to the node. Otherwise, if a free node does not belong to the final structure, then all the bar area variables corresponding to bars incident to this node may be set to zero. These constraints are added during the first stage and lead to a tight model. We report the computational experiments conducted to test the effectiveness of this two-stage approach...

Bundle branch and atrioventricular block as complications of acute myocardial infarction in the thrombolytic era

Escosteguy,Claudia Caminha; Carvalho,Marciano de Almeida; Medronho,Roberto de Andrade; Abreu,Luiz Maurino; Monteiro Filho,Mario Ypiranga
Fonte: Sociedade Brasileira de Cardiologia - SBC Publicador: Sociedade Brasileira de Cardiologia - SBC
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2001 EN
Relevância na Pesquisa
36.51%
OBJECTIVE: To analyze the incidence of intraventricular and atrioventricular conduction defects associated with acute myocardial infarction and the degree of in hospital mortality resulting from this condition during the era of thrombolytic therapy. METHODS: Observational study of a cohort of 929 consecutive patients with acute myocardial infarction. Multivariate analysis by logistic regression. Was used. RESULTS: Logistic regression showed a greater incidence of bundle branch block in male sex (odds ratio = 1.87, 95% CI = 1.02-3.42), age over 70 years (odds ratio = 2.31, 95% CI = 1.68-5.00), anterior localization of the infarction (odds ratio = 1.93, 95% CI = 1.03-3.65). There was a greater incidence of complete atrioventricular block in inferior infarcts (odds ratio = 2.59, 95% CI 1.30-5.18) and the presence of cardiogenic shock (odds ratio = 3.90, 95% CI = 1.43-10.65). Use of a thrombolytic agent was associated with a tendency toward a lower occurrence of bundle branch block (odds ratio = 0.68) and a greater occurrence of complete atrioventricular block (odds ratio = 1.44). The presence of bundle branch block (odds ratio = 2.45 95% , CI = 1.14-5.28) and of complete atrioventricular block (odds ratio = 13.59, 95% CI = 5.43-33.98) was associated with a high and independent probability of inhospital death. CONCLUSION: During the current era of thrombolytic therapy and in this population...

Anatomosurgical study of the marginal mandibular branch of the facial nerve for submandibular surgical approach

Woltmann,Marcus; Faveri,Ricardo de; Sgrott,Emerson Alexandre
Fonte: Fundação Odontológica de Ribeirão Preto Publicador: Fundação Odontológica de Ribeirão Preto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2006 EN
Relevância na Pesquisa
36.51%
The purpose of this study was to estimate the distance from the mandibular marginal branch of the facial nerve to the inferior margin of the mandible in order to determine the best and safest location to approach the posterior mandibular region. Forty-five hemi-faces of 27 Brazilian adult cadavers were dissected and the distance between the mandibular marginal branch and the inferior margin of the mandible was measured. The number of marginal branches and anastomoses with other branches of the facial nerve was also recorded. The evaluation of the anatomic pieces showed 1 to 3 branches of the marginal mandibular branch, anastomoses with the buccal and cervical branches of the facial nerve and distances between 1.3 cm to +1.2 cm from the inferior margin of the mandible. In 57.7% of the cases, the nerve passed superiorly and along the length of the inferior margin of the mandible. Based on the findings of the present anatomosurgical study, it may be recommended an incision 3 cm below the inferior margin of the mandible associated to a careful dissection in planes and flap retraction. This is expected to reduce the risk of neuropraxia of the marginal mandibular nerve making the submandibular incision a safe approach.

Carlot shipments of fresh fruits and vegetables by commodities, states and months

United States -- Dept. of Agriculture. -- Production and Marketing Administration. -- Fruit and Vegetable Branch; United States -- Dept. of Agriculture. -- Production and Marketing Administration. -- Fruit and Vegetable Branch. -- Market News Division; Un
Fonte: Fruit and Vegetable Branch; Fruit and Vegetable Branch ( Washington, D.C ) Publicador: Fruit and Vegetable Branch; Fruit and Vegetable Branch ( Washington, D.C )
Tipo: Artigo de Revista Científica Formato: 7 v. : ; 27 cm.
Publicado em // ENGLISH
Relevância na Pesquisa
36.6%
(Statement of Responsibility) United States Department of Agriculture, Production and Marketing Administraion, Fruit and Vegetable Branch.; (Dates or Sequential Designation) Calendar year 1947-calendar year 1953.; (Issuing Body) Issued by: Production and Marketing Administration, Fruit and Vegetable Branch, Market News Division, 1948-1952; Agricultural Marketing Service, Fruit and Vegetable Division, Market News Branch, 1953.

Predictors of long-term benefit of cardiac resynchronization therapy in patients with right bundle branch block

Leong, D.; Hoke, U.; Delgado, V.; Auger, D.; Thijssen, J.; Van Erven, L.; Bax, J.; Schalij, M.; Marsan, N.
Fonte: W B Saunders Co Ltd Publicador: W B Saunders Co Ltd
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
36.51%
Aims: The aims of this study were: (i) to characterize consecutive cardiac resynchronization therapy (CRT) recipients with right bundle branch block (RBBB) in comparison with left bundle branch block (LBBB) and (ii) to identify independent predictors of long-term outcome among CRT recipients with RBBB. The presence of RBBB has been associated with poorer prognosis after CRT compared with LBBB; however, little is known about the differences in cardiac mechanics between RBBB and LBBB patients. Furthermore, predictors of favourable outcome after CRT in patients with RBBB have not been identified. Methods and results: Five hundred and sixty-one consecutive CRT recipients (89 with RBBB and 472 with LBBB) underwent echocardiography before and 6 months after CRT to determine left ventricular (LV) size and function, and interventricular and LV dyssynchrony (as measured by tissue Doppler imaging). Long-term follow-up to identify a composite endpoint of all-cause mortality or heart failure hospitalization was available. Right bundle branch block patients exhibited a higher prevalence of male gender, ischaemic heart disease, atrial fibrillation, and lower exercise capacity when compared with LBBB patients, despite smaller LV volumes. In addition...

Interessenverbände in der IT-Branche - erste empirische Ergebnisse zur Organisationsfähigkeit von Arbeitgeberverbänden; Interest federations in the IT branch - the first empiric results to the organization ability of employers' associations

Menez, Raphael
Fonte: Universität Tübingen Publicador: Universität Tübingen
Tipo: ResearchPaper; info:eu-repo/semantics/other
DE_DE
Relevância na Pesquisa
36.56%
Gegenstand des Forschungsprojektes „Interessenverbände in der IT-Branche“ ist die Organisationsfähigkeit von Arbeitgeberverbänden und Gewerkschaften in dieser Querschnittsbranche. Die vorliegende Studie markiert das erste Teilprojekt in diesem Rahmen und beschäftigt sich mit den Organisationsbedingungen von Arbeitgeberverbänden in der IT-Branche. Folgende Ergebnisse werden in dem Bericht präsentiert: Arbeitgeberverbände schätzen den Organisationsbedarf von IT-Unternehmen als eher gering ein, da erstens die Nachfrage nach tariflicher Regulierung gering ist und zweitens die Gewerkschaften noch keine hinreichende Mitgliederbasis in den IT-Unternehmen aufgebaut haben. Als Reaktion darauf verstärken einige der untersuchten Verbände den Ausbau von Beratungs- und Serviceleistungen und die Einrichtung von OT-Strukturen. Die OT-Strukturen führen bei den Arbeitgeberverbänden allerdings zu einer Entkopplung von Tariforientierung und Dienstleistungsorientierung und einer Redefinition des verbandlichen Selbstverständnisses in Richtung Arbeitgeberdienstleistungsverband. Dabei scheint die Etablierung einer verbandlichen Ordnung in der IT-Branche in der aktuellen Situation aus zwei Gründen eher unwahrscheinlich zu sein: Weil erstens diejenigen Verbände...

Refined MDP-based branch-and-fix algorithm for the Hamiltonian cycle problem

Ejov, V.; Filar, J.A.; Haythorpe, M.; Nguyen, G.T.
Fonte: Informs Publicador: Informs
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
Relevância na Pesquisa
36.51%
We consider the famous Hamiltonian cycle problem (HCP) embedded in a Markov decision process (MDP). More specifically, we consider the HCP as an optimisation problem over the space of occupation measures induced by the MDP's stationary policies. In recent years, this approach to the HCP has led to a number of alternative formulations and algorithmic approaches. In this paper, we focus on a specific embedding, because of the work of Feinberg. We present a “branch-and-fix” type algorithm that solves the HCP. At each branch of the algorithm, only a linear program needs to be solved and the dimensions of the successive linear programs are shrinking rather than expanding. Because the nodes of the branch-and-fix tree correspond to specially structured 1-randomised policies, we characterise the latter. This characterisation indicates that the total number of such policies is significantly smaller than the subset of all 1-randomised policies. Finally, we present some numerical results.; Vladimir Ejov, Jerzy A. Filar, Michael Haythorpe, Giang T. Nguyen

Colonel John Butler (Niagara)/St. Catharines District Branch of the United Empire Loyalists fonds

Adams, Anne
Fonte: Brock University Publicador: Brock University
Tipo: Outros
EN
Relevância na Pesquisa
36.71%
United Empire Loyalist is an honour given to American Loyalists who came to British North America and the British Colonies to show their loyalty to King George III after the British defeat in the American Revolution. The Loyalists settled in Quebec, Ontario, Nova Scotia and modern day New Brunswick. The Colonel John Butler (Niagara) Branch (formerly the St. Catharines and District Branch) has origins which date as far back as 1898. A branch was organized in Virgil by Captain John D. Servos, but was unsuccessful. In 1905 there was another attempt to form a branch, but the war of 1914-1918 resulted in this branch becoming inactive. In 1914, an Act of Parliament incorporated the United Empire Loyalists’ Association of Canada. The St. Catharines and District Branch was formed in 1921. This branch remained active, and in 1992 they changed their name to The Colonel John Butler (Niagara) Branch. The Loyalists also have a strong focus on genealogy. All descendants are eligible to use UE (which stands for Unity of the Empire) after their names. source: http://www.coljohnbutleruel.com; The fonds contains materials relating to the Colonel John Butler (Niagara)/ St. Catharines District Branch. The materials included are minutes, correspondence...

L'algorithme de Branch and Price and Cut pour le problème de conception de réseaux avec coûts fixes et sans capacité

Grainia, Sameh
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
Relevância na Pesquisa
36.63%
Le problème de conception de réseaux est un problème qui a été beaucoup étudié dans le domaine de la recherche opérationnelle pour ses caractéristiques, et ses applications dans des nombreux domaines tels que le transport, les communications, et la logistique. Nous nous intéressons en particulier dans ce mémoire à résoudre le problème de conception de réseaux avec coûts fixes et sans capacité, en satisfaisant les demandes de tous les produits tout en minimisant la somme des coûts de transport de ces produits et des coûts fixes de conception du réseau. Ce problème se modélise généralement sous la forme d’un programme linéaire en nombres entiers incluant des variables continues. Pour le résoudre, nous avons appliqué la méthode exacte de Branch-and-Bound basée sur une relaxation linéaire du problème avec un critère d’arrêt, tout en exploitant les méthodes de génération de colonnes et de génération de coupes. Nous avons testé la méthode de Branch-and-Price-and-Cut sur 156 instances divisées en cinq groupes de différentes tailles, et nous l’avons comparée à Cplex, l’un des meilleurs solveurs d’optimisation mathématique, ainsi qu’à la méthode de Branch-and- Cut. Notre méthode est compétitive et plus performante sur les instances de grande taille ayant un grand nombre de produits.; The network design problem has been studied extensively in the field of operational research given its characteristics and applications in many areas such as transportation...

Développement d’un algorithme de branch-and-price-and-cut pour le problème de conception de réseau avec coûts fixes et capacités

Larose, Mathieu
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
Relevância na Pesquisa
36.56%
De nombreux problèmes en transport et en logistique peuvent être formulés comme des modèles de conception de réseau. Ils requièrent généralement de transporter des produits, des passagers ou encore des données dans un réseau afin de satisfaire une certaine demande tout en minimisant les coûts. Dans ce mémoire, nous nous intéressons au problème de conception de réseau avec coûts fixes et capacités. Ce problème consiste à ouvrir un sous-ensemble des liens dans un réseau afin de satisfaire la demande, tout en respectant les contraintes de capacités sur les liens. L'objectif est de minimiser les coûts fixes associés à l'ouverture des liens et les coûts de transport des produits. Nous présentons une méthode exacte pour résoudre ce problème basée sur des techniques utilisées en programmation linéaire en nombres entiers. Notre méthode est une variante de l'algorithme de branch-and-bound, appelée branch-and-price-and-cut, dans laquelle nous exploitons à la fois la génération de colonnes et de coupes pour la résolution d'instances de grande taille, en particulier, celles ayant un grand nombre de produits. En nous comparant à CPLEX, actuellement l'un des meilleurs logiciels d'optimisation mathématique...

Estudio poliedral y algoritmo branch-and-cut para el problema de coloreo equitativo en grafos; A polyhedral study and a Branch-and-Cut algorithm for the equitable graph coloring problem

Severin, Daniel E.
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: info:eu-repo/semantics/doctoralThesis; tesis doctoral; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2012 SPA
Relevância na Pesquisa
36.63%
Los problemas de coloreo de grafos constituyen una familia de problemas de una gran relevancia tanto teórica como práctica. Todos ellos son variaciones del problema del coloreo clásico, cuyo estudio se inició en el Siglo XIX. El origen de estas variaciones radica en las restricciones adicionales que imponen las aplicaciones a problemas de la vida real. En esta tesis abordamos en particular el Problema de Coloreo Equitativo en Grafos. Como muchos problemas de Optimización Combinatoria, el Problema de Coloreo Equitativo es un problema NP-difícil. Los algoritmos Branch-and-Cut basados en el estudio poliedral de una formulación del problema como programa lineal entero, son la herramienta más efectiva que se conoce para la resolución exacta de problemas NP-difíciles. En esta tesis se propone un modelo de programación lineal entera para el Problema del Coloreo Equitativo y se estudia el poliedro asociado. Se derivan varias familias de desigualdades validas y se prueba que siempre definen caras de alta dimensión, lo cual es un buen indicador para la utilización de las mismas como planos de corte. Finalmente, se desarrolla e implementa un algoritmo Branch-and-Cut para el Problema de Coloreo Equitativo que resulta altamente competitivo con los algoritmos exactos conocidos.; The graph coloring problems constitute a family of problems of great theoretical and practical relevance. All of them are variations of the classical coloring problem...

Estudio poliedral y algoritmo branch-and-cut para el problema de coloreo equitativo en grafos; A polyhedral study and a Branch-and-Cut algorithm for the equitable graph coloring problem

Severin, Daniel E.
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: Tesis Doctoral Formato: text; pdf
Publicado em //2012 ESPAñOL
Relevância na Pesquisa
36.51%
Los problemas de coloreo de grafos constituyen una familia de problemas de una gran relevancia tanto teórica como práctica. Todos ellos son variaciones del problema del coloreo clásico, cuyo estudio se inició en el Siglo XIX. El origen de estas variaciones radica en las restricciones adicionales que imponen las aplicaciones a problemas de la vida real. En esta tesis abordamos en particular el Problema de Coloreo Equitativo en Grafos. Como muchos problemas de Optimización Combinatoria, el Problema de Coloreo Equitativo es un problema NP-difícil. Los algoritmos Branch-and-Cut basados en el estudio poliedral de una formulación del problema como programa lineal entero, son la herramienta más efectiva que se conoce para la resolución exacta de problemas NP-difíciles. En esta tesis se propone un modelo de programación lineal entera para el Problema del Coloreo Equitativo y se estudia el poliedro asociado. Se derivan varias familias de desigualdades validas y se prueba que siempre definen caras de alta dimensión, lo cual es un buen indicador para la utilización de las mismas como planos de corte. Finalmente, se desarrolla e implementa un algoritmo Branch-and-Cut para el Problema de Coloreo Equitativo que resulta altamente competitivo con los algoritmos exactos conocidos.

Features of the secondary xylem that facilitate branch abscission in juvenile Wollemia Nobili

Heady, Roger; Burrows, G E
Fonte: National Herbarium and Botanic Gardens Publicador: National Herbarium and Botanic Gardens
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.51%
Wollemi pine (Wollemia nobilis) does not shed individual leaves but instead cleanly self-prunes the whole first-order branch with all the leaves still attached. A zone of stranded xylem at the branch base, the site of branch abscission, is described here

In-hospital outcome in patients with ST elevation myocardial infarction and right bundle branch block: A sub-study from RENASICA II, a national multicenter registry

Juárez-Herrera,Úrsulo; Jerjes Sánchez,Carlos; González-Pacheco,Héctor; Martínez-Sánchez,Carlos
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2010 EN
Relevância na Pesquisa
36.68%
Objective: Compare in-hospital outcome in patients with ST-elevation myocardial infarction with right versus left bundle branch block. Methods: RENASICA II, a national mexican registry enrolled 8098 patients with final diagnosis of acute coronary syndrome secondary to ischemic heart disease. In 4555 STEMI patients, 545 had bundle branch block, 318 (58.3%) with right and 225 patients with left (41.6%). Both groups were compared in terms of in-hospital outcome through major cardiovascular adverse events; (cardiovascular death, recurrent ischemia and reinfarction). Multivariable analysis was performed to identify in-hospital mortality risk among right and left bundle branch block patients. Results: There were not statistical differences in both groups regarding baseline characteristics, time of ischemia, myocardial infarction location, ventricular dysfunction and reperfusion strategies. In-hospital outcome in bundle branch block group was characterized by a high incidence of major cardiovascular adverse events with a trend to higher mortality in patients with right bundle branch block (OR 1.70, CI 1.19 - 2.42, p < 0.003), compared to left bundle branch block patients. Conclusion: In this sub-study right bundle branch block accompanying ST-elevation myocardial infarction of any location at emergency room presentation was an independent predictor of high in-hospital mortality.