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Search Results: 1 - 10 of 22878 matches for " Eduardo Uchoa Barboza "
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New Lower Bounds for the Vehicle Routing Problem with Simultaneous Pickup and Delivery
Anand Subramanian,Eduardo Uchoa Barboza,Luiz Satoru Ochi
Relatórios de Pesquisa em Engenharia de Produ??o , 2010,
Abstract: The present work deals with the Vehicle Routing Problem with SimultaneousPickup and Delivery (VRPSPD). In this problem, the customershave both delivery and pickup demands. We propose undirectedand directed two-commodity flow formulations, which are based on theone developed by Baldacci, Hadjiconstantinou and Mingozzi for the CapacitatedVehicle Routing Problem. These new formulations are theoreticallycompared with the one-commodity flow formulation proposedby Dell’Amico, Righini and Salani. The three formulations were testedwithin a branch-and-cut scheme and their practical performance was measuredin well-known benchmark problems available in the literature. Theundirected two-commodity flow formulation obtained consistently betterresults. We also ran the three formulations in a particular case of theVRPSPD, namely the Vehicle Routing Problem with Mixed Pickup andDelivery (VRPMPD). Several optimal solutions to open problems with upto 100 customers and new improved lower bounds for instances with upto 200 customers were found.
FORMULA ES COM VARIáVEIS CONTENDO íNDICE DE TEMPO PARA O PROBLEMA DO FLOW SHOP EM DUAS MáQUINAS COM PENALIDADES POR ATRASO NAS TAREFAS
José Mauricio Brasil Gon?alves,Eduardo Uchoa Barboza
Relatórios de Pesquisa em Engenharia de Produ??o , 2010,
Abstract: Muitos dos problemas de escalonamento situam-se na classe de complexidade NP - dificil, sendo o caso do problema deste estudo. Este trabalho tem por objetivo propor formulacoes de programacao inteira com variaveis contendo indice de tempo t para o problema de escalonamento deterministico Flow shop com duas maquinas onde existem penalidades por atraso nas tarefas, na notacao de tres campos tem-se: F2 | | ......... Sao apresentadas formulacoes com variaveis binarias ........ (que assumem valor unitario se a tarefa j finaliza seu processamento na maquina i no tempo t) e variaveis binarias ...... (que assumem valor unitario se a tarefa j tem seu processamento finalizado na segunda maquina no tempo t). Em testes elaborados com instancias de ate cinquenta tarefas, observou-se que a primeira formulacao obteve limites duais iniciais mais proximos do valor otimo da funcao objetivo, enquanto a segunda formulacao, mais compacta, obteve melhores tempos de resolucao.
A Robust and Scalable Algorithm for the Steiner Problem in Graphs
Thomas Pajor,Eduardo Uchoa,Renato F. Werneck
Computer Science , 2014,
Abstract: We present an effective heuristic for the Steiner Problem in Graphs. Its main elements are a multistart algorithm coupled with aggressive combination of elite solutions, both leveraging recently-proposed fast local searches. We also propose a fast implementation of a well-known dual ascent algorithm that not only makes our heuristics more robust (by quickly dealing with easier cases), but can also be used as a building block of an exact (branch-and-bound) algorithm that is quite effective for some inputs. On all graph classes we consider, our heuristic is competitive with (and sometimes more effective than) any previous approach with similar running times. It is also scalable: with long runs, we could improve or match the best published results for most open instances in the literature.
A column generation approach for power-aware optimization of virtualized heterogeneous server clusters
Hugo Harry Kramer,Vinicius Petrucci,Anand Subramanian,Eduardo Uchoa
Relatórios de Pesquisa em Engenharia de Produ??o , 2011,
Abstract: Increasingly, clusters of servers have been deployed in large data centersto support the development and implementation of many kinds of services,having distinct workload demands that vary over time, in a scalableand ecient computing environment. Emerging trends are utility/cloudcomputing platforms, where many network services, implemented andsupported using server virtualization techniques, are hosted on a sharedcluster infrastructure of physical servers. The energy consumed to maintainthese large server clusters became a very important concern, which inturn, requires major investigation of optimization techniques to improvethe energy eciency of their computing infrastructure.In this work, we present a novel optimization approach that simultaneouslydeals with (1) CPU power-saving techniques combined with serverswitching on/o mechanisms, (2) the case of server heterogeneity, (3) virtualizedserver environments, (4) an ecient optimization method basedon column generation techniques. The key aspects of our approach arethe basis on rigorous and robust optimization techniques, given by highquality solutions in short amount of processing time, and experimentalresults on the cluster conguration problem for large-scale heterogeneous server clusters that can make use of virtualization techniques.
Autonomia e conhecimento – algumas aproxima es possíveis entre Ant nio Gramsci e Paulo Freire a partir da análise de práticas pedagógicas emancipatórias
Cleoni Maria Barboza Fernandes,Solon Eduardo Viola
Educa??o : Revista do Centro de Educa??o UFSM , 2004,
Abstract: Este texto nasce como uma síntese da reuni o de dois pensadores do século XX, Ant nio Gramsci e Paulo Freire, dois homens de tempos e lugares distintos, mas relacionados por sentimentos e constru es teóricas, que em muitos pontos se afastam e em muitos se aproximam, mas mediam as rela es humanas na dire o de outra sociedade, justa e solidária. A escolha intencional e arbitrária dos pontos de aproxima o entre esses autores foi resultante da discuss o das práticas pedagógicas e da forma o de professores com um grupo de alunos do Programa de Pós-gradua o em Educa o da Universidade do Vale do Rio dos Sinos. A origem dessa possibilidade está situada em uma disciplina, em que foi discutido o livro: "Medo e ousadia: o cotidiano do professor", no qual Paulo Freire dialoga com Ira Shor, sendo constatado a presen a muito forte de Antonio Gramsci. A busca com a rigorosidade metódica que caracteriza a curiosidade epistemológica do sujeito, da leitura desse autor anunciado pelo próprio Freire como de grande influência nos seus estudos sobre cultura, tornou-se um grande desafio. A proposta de uma leitura dirigida foi realizada em parceria com uma professora do PPGEDU e um professor da Pedagogia. A tematiza o da obra de Gramsci, baseada especialmente nos três volumes de Cadernos do Cárcere, com os questionamentos trazidos pelos alunos, contribuiu para a síntese aqui apresentada. Palavras-chave: Autonomia. Conhecimento. Práticas Pedagógicas.
Accomplishments in Learning Self-Regulation in Personal Environments  [PDF]
Eduardo Chaves-Barboza, Juan M. Trujillo-Torres, Juan A. López-Nú?ez
Creative Education (CE) , 2015, DOI: 10.4236/ce.2015.611109
Abstract: This article aims to analyze the accomplishments in learning self-regulation from a student popu-lation in personal learning environments. A Likert scale-like questionnaire is applied to a random cluster sample of students from the Pedagogy, Social Education and Psychopedagogy degrees from the University of Granada, Spain. Descriptive or inferential analyses are carried out along the research in order to characterize the population. Additionally, Kendall’s correlation coefficients are calculated and interpreted to define the relations among students’ accomplishments. Finally, Kruskal-Wallis H tests are performed to ascertain through analysis of variance if the variable degree influences such accomplishments. The results show that the students from these three degrees set goals, perform tasks in an organized manner, accomplish extra work on time, meet the deadlines to hand in the class-work, and reflect on their learning. Pedagogy presents the highest relation between achieving an appropriate period of time to perform the tasks and carrying out their extra work on time. Social Education shows a smaller number of students and less intensity when meeting the deadlines to hand in the classwork. The students from Psychopedagogy have the highest accomplishments in reading the whole material suggested by the teacher. The research concludes that, although there are some variations among these three degrees, they are homo-geneous in the majority of the variables studied here. The students succeeded in learning self-regulation; however, it is necessary to reinforce the time planning, the reading of the material suggested by the teacher, enhancement of knowledge, and complementary research. One student subgroup is distinguished for its accomplishments in task organization and performance, while other groups excel for deepening their understanding of the units and metacognition.
Laser Doppler Imaging para quantifica??o do fluxo sanguíneo de polpa digital em condi??es basais e após estímulo frio em pacientes com esclerose sistêmica
Corrêa, Marcelo José Uchoa;Perazzio, Sandro F;Andrade, Luís Eduardo Coelho;Kayser, Cristiane;
Revista Brasileira de Reumatologia , 2010, DOI: 10.1590/S0482-50042010000200003
Abstract: objectives: the objective of this study was to investigate the dynamic behavior of the blood flow of the microvascular circulation of the fingertips before and after two cold stimuli (cs), using laser doppler imaging with different intensities in patients with systemic sclerosis (ssc) and in healthy individuals. patients and methods: fourteen ssc patients (51.2 ± 5.5 years) with raynaud's phenomenon and 12 healthy controls (44.8 ± 9.0 years) were included in this study. two cs protocols (submersion of the hands in water at 10 oc or 15 oc for 1 minute) were performed on the same day. mean fingertip blood flow (fbf) of four digits of the left hand was measured using ldi (moor ldi-vr, moor instruments) at baseline and at 1, 4, 10, 25, and 40 minutes after cs. results: baseline blood flow was significantly lower in both cs protocols in ssc patients when compared to controls (312.9 ± 102.7 vs 465.4 ± 135.4 pu, p = 0.006 at 15 oc; 305.2 ± 121.0 vs 437.9 ± 119.8 pu; p = 0.01 at 10 oc). in the control group, a significant decrease in fbf after cs, when compared to baseline, was observed 1 minute (p = 0.001) after cs at 15 oc and at 1 (p = 0.005) and 25 minutes (p = 0.001) after cs at 10 oc. in ssc patients, a significant decrease in fbf was observed in both cs protocols at 1, 4, and 10 minutes (p < 0.000; p = 0.002; p = 0.014, after cs at 15 oc; p < 0.000; p = 0.004; p = 0.001, after cs at 10 oc). conclusions: laser doppler imaging showed lower baseline fingertip perfusion and further reduction after cs in ssc patients compared to controls. quantification of fingertip blood flow by ldi may be useful in the longitudinal monitoring of the disease status and therapeutic interventions in ssc.
The electron many-body problem in graphene
Bruno Uchoa,James P. Reed,Yu Gan,Young Il Joe,Diego Casa,Eduardo Fradkin,Peter Abbamonte
Physics , 2011, DOI: 10.1088/0031-8949/2012/T146/014014
Abstract: We give a brief summary of the current status of the electron many-body problem in graphene. We claim that graphene has intrinsic dielectric properties which should dress the interactions among the quasiparticles, and may explain why the observation of electron-electron renormalization effects has been so elusive in the recent experiments. We argue that the strength of Coulomb interactions in graphene may be characterized by an effective fine structure constant given by $\alpha^{\star}(\mathbf{k},\omega)\equiv2.2/\epsilon(\mathbf{k},\omega)$, where $\epsilon(\mathbf{k},\omega)$ is the dynamical dielectric function. At long wavelengths, $\alpha^{\star}(\mathbf{k},\omega)$ appears to have its smallest value in the static regime, where $\alpha^{\star}(\mathbf{k}\to0,0)\approx1/7$ according to recent inelastic x-ray measurements, and the largest value in the optical limit, where $\alpha^{\star}(0,\omega)\approx2.6$. We conclude that the strength of Coulomb interactions in graphene is not universal, but depends highly on the scale of the phenomenon of interest. We propose a prescription in order to reconcile different experiments.
The effective fine structure constant of freestanding graphene measured in graphite
James P. Reed,Bruno Uchoa,Young Il Joe,Yu Gan,Diego Casa,Eduardo Fradkin,Peter Abbamonte
Physics , 2010, DOI: 10.1126/science.1190920
Abstract: Electrons in graphene behave like Dirac fermions, permitting phenomena from high energy physics to be studied in a solid state setting. A key question is whether or not these Fermions are critically influenced by Coulomb correlations. We performed inelastic x-ray scattering experiments on crystals of graphite, and applied reconstruction algorithms to image the dynamical screening of charge in a freestanding, graphene sheet. We found that the polarizability of the Dirac fermions is amplified by excitonic effects, improving screening of interactions between quasiparticles. The strength of interactions is characterized by a scale-dependent, effective fine structure constant, \alpha *(k,\omega), whose value approaches \alpha * ~ 1/7 at low energy and large distances. This value is substantially smaller than the nominal \alpha = 2.2, suggesting that, on the whole, graphene is more weakly interacting than previously believed.
Itinerários da loucura em territórios Dogon
Uchoa Elizabeth
Cadernos de Saúde Pública , 2005,
Abstract:
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