Página 1 dos resultados de 45697 itens digitais encontrados em 0.057 segundos

Second-order negative-curvature methods for box-constrained and general constrained optimization

ANDREANI, R.; BIRGIN, E. G.; MARTINEZ, J. M.; SCHUVERDT, M. L.
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
65.85%
A Nonlinear Programming algorithm that converges to second-order stationary points is introduced in this paper. The main tool is a second-order negative-curvature method for box-constrained minimization of a certain class of functions that do not possess continuous second derivatives. This method is used to define an Augmented Lagrangian algorithm of PHR (Powell-Hestenes-Rockafellar) type. Convergence proofs under weak constraint qualifications are given. Numerical examples showing that the new method converges to second-order stationary points in situations in which first-order methods fail are exhibited.

Solução Numérica de escoamentos viscoelásticos tridimensionais com superfícies livres: fluidos de segunda ordem; Numerical solution of three-dimensional viscoelastic flows with free surfaces: second order fluids

Revoredo, Igor Feliciano Simplicio
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 26/03/2010 PT
Relevância na Pesquisa
65.82%
Este trabalho apresenta uma técnica de diferenças finitas para resolver a equação constitutiva Fluido de Segunda Ordem para escoamentos tridimensionais com superfície livre. As equações governantes são resolvidas pelo método de diferenças finitas em uma malha deslocada 3D. A superfície livre é modelada por células marcadoras (Marker-and-Cell) e as condições de contorno a superfície livre são empregadas. O método numérico apresentado neste trabalho foi validado pela comparação entre as soluções numéricas obtidas para o escoamento em um tubo com a solução analítica correspondente para Fluidos de Segunda Ordem. Ao fazer refinamento de malha, a convergência do método numérico foi verificada. Resultados numéricos da simulação do problema do inchamento do extrudado para números de Deborah De '< OU =' 0:3 são apresentados; This work presents a finite difference method to simulate three-dimensional viscoelastic flow with free surfaces governed by the constitutive equation Second Order Fluid. The governing equations are solved by the finite difference method in a three-dimensional shifted mesh. The free surface of fluid is modeled by the Marker-and-Cell method which allows for the visualization and the location of the free surface of fluid. The full free surface stress conditions are employed. The numerical method developed in this work is validated by comparing the numerical and analytic solutions for the steady state flow of a Second Order Fluid in a pipe. By using mesh refinement convergence results are given. Numerical results of the simulation of the transient extrudate swell of a Second Order Fluid of the Deborah number De '< OR =' 0:3 are presented

Análise de segunda ordem global em edifícios com estrutura de concreto armado; Overall second-order analysis in buildings with reinforced concrete structure

Zumaeta Moncayo, Winston Junior
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 15/03/2011 PT
Relevância na Pesquisa
65.84%
A análise de segunda ordem global de edifícios é indispensável nos dias atuais, em que as estruturas são cada vez mais esbeltas. No mercado, há diversos sistemas computacionais que realizam essa análise, e alguns dos novos engenheiros estruturais podem não saber os conceitos em que ela se baseia. Portanto, este trabalho pretende: avaliar os efeitos de segunda ordem em edifícios por meio dos coeficientes 'gama'z e FAVt, este desenvolvido pela TQS, e por meio do processo P-Delta; mostrar como este processo P-Delta funciona e como o sistema computacional CAD/TQS o considera; e analisar também os esforços de segunda ordem calculados a partir dos de primeira ordem multiplicados por O,95 'gama'z. Em relação à avaliação da estabilidade global, serão comparados os resultados obtidos com os parâmetros 'alfa', 'gama'z, FAVt e RM2M1, este último gerado a partir do processo P-Delta. Pretende-se, assim, fornecer subsídios para que os novos engenheiros tenham condições de atuar com base conceitual bem fundamentada, tanto na escolha do método quanto na análise dos resultados.; The overall second-order analysis of buildings is essential nowadays, in which the structures are each time more slender. In the market, there are several computer systems that perform this analysis...

Saddle Point and Second Order Optimality in Nondifferentiable Nonlinear Abstract Multiobjective Optimization

Santos, Lucelina Batista dos; Rojas-Medar, Marko Antonio; Oliveira, Valeriano Antunes de
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 179-191
ENG
Relevância na Pesquisa
65.82%
This article deals with a vector optimization problem with cone constraints in a Banach space setting. By making use of a real-valued Lagrangian and the concept of generalized subconvex-like functions, weakly efficient solutions are characterized through saddle point type conditions. The results, jointly with the notion of generalized Hessian (introduced in [Cominetti, R., Correa, R.: A generalized second-order derivative in nonsmooth optimization. SIAM J. Control Optim. 28, 789–809 (1990)]), are applied to achieve second order necessary and sufficient optimality conditions (without requiring twice differentiability for the objective and constraining functions) for the particular case when the functionals involved are defined on a general Banach space into finite dimensional ones.; O artigo trata de um problema de otimização vetorial entre espaços de Banach com restrições envolvendo cones. Usando-se uma lagrangiana que toma valores escalares e o conceito de funções subconvexas generalizadas, soluções fracamente eficientes são caracterizadas por condições do tipo ponto de sela. Os resultados, em conjunto com a noção de Hessiana generalizada (introduzida em [R. Cominetti, R. Correa, A generalized second-order derivative in nonsmooth optimization...

Second-order negative-curvature methods for box-constrained and general constrained optimization

ANDREANI, R.; BIRGIN, E. G.; MARTINEZ, J. M.; SCHUVERDT, M. L.
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
65.85%
A Nonlinear Programming algorithm that converges to second-order stationary points is introduced in this paper. The main tool is a second-order negative-curvature method for box-constrained minimization of a certain class of functions that do not possess continuous second derivatives. This method is used to define an Augmented Lagrangian algorithm of PHR (Powell-Hestenes-Rockafellar) type. Convergence proofs under weak constraint qualifications are given. Numerical examples showing that the new method converges to second-order stationary points in situations in which first-order methods fail are exhibited.

η5-Monocyclopentadienylruthenium(II) Complexes For Second-Order NLO Purposes

Mendes, Paulo J.
Fonte: XXI Encontro Nacional SPQ, Book of Abstracts Publicador: XXI Encontro Nacional SPQ, Book of Abstracts
Tipo: Aula
ENG
Relevância na Pesquisa
65.84%
Organometallic compounds have given rise to a great deal of interest owing to their application in the field of nonlinear optics (NLO) [1]. For second-order nonlinear optics (SONLO), strongly asymmetric systems are needed, which led to the development of typical push–pull systems in which the metal centre, bound to a highly polarizable conjugated backbone, acts as an electron releasing or withdrawing group. Among the organometallic compounds presenting this donor–π-system–acceptor feature, η5-monocyclopentadienyliron and ruthenium moieties were found to be much more efficient donor groups for second-order NLO purposes than the traditional organic donor groups, leading to higher first hyperpolarizabilities (β) [2]. Recent results on η5-monocyclopentadienyliron complexes presenting thiophene nitrile chromophores showed an enhanced SONLO performance when compared to that observed on analogue benzenoid structures. Also, the first hyperpolarizability of these complexes was found to be influenced by a compromise between the conjugation length of the chromophores and the metal-to-ligand charge-transfer [3]. In our continuous effort to understand the role played by the organometallic fragment on the SONLO properties and to establish detailed structure–NLO activity correlations...

Swirling motion of a second-order viscous fluid in a straight tube

Carapau, Fernando; Sequeira, Adélia
Fonte: Carapau, F., Sequeira, A., "Swirling motion of a second-order viscous fluid in a straight tube", Proceedings of the International Conference on Topical Problems of Fluid Mechanics, Institute of Thermomechanics AS CR, Prague, Czech Republic, February 28 – March 2, 2007, pp. 21-24. Publicador: Carapau, F., Sequeira, A., "Swirling motion of a second-order viscous fluid in a straight tube", Proceedings of the International Conference on Topical Problems of Fluid Mechanics, Institute of Thermomechanics AS CR, Prague, Czech Republic, February 28 – March 2, 2007, pp. 21-24.
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
85.78%
We consider a second-order viscous fluid with swirling motion flowing in a circular straight tube with constant radius. Integrating the equation of conservation of linear momentum over the tube cross section with the velocity field approximated by the Cosserat theory, we obtain a one-dimensional system depending only on time and on a single spatial variable. From this 1D model, we derive the relationship between mean pressure gradient and volume flow rate over a finite section of the tube as well the wall shear stress.

A modified parametric iteration method for solving nonlinear second order BVPs

Ghorbani,Asghar; Gachpazan,Morteza; Saberi-Nadjafi,Jafar
Fonte: Sociedade Brasileira de Matemática Aplicada e Computacional Publicador: Sociedade Brasileira de Matemática Aplicada e Computacional
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 EN
Relevância na Pesquisa
65.85%
The original parametric iteration method (PIM) provides the solution of a nonlinear second order boundary value problem (BVP) as a sequence of iterations. Since the successive iterations of the PIM may be very complex so that the resulting integrals in its iterative relation may not be performed analytically. Also, the implementation of the PIM generally leads to calculation of unneeded terms, which more time is consumed in repeated calculations for series solutions. In order to overcome these difficulties, in this paper, a useful improvement of the PIM is proposed. The implementation of the modified method is demonstrated by solving several nonlinear second order BVPs. The results reveal that the new developed method is a promising analytical tool to solve the nonlinear second order BVPs and more promising because it can further be applied easily to solve nonlinear higher order BVPs with highly accurate. Mathematical subject classification: Primary: 34B15; Secondary: 41A10.

Evaluation of second order moments in reinforced concrete structures using the γz and B2 coefficients

Oliveira,D. M.; Silva,N. A.; Oliveira,P. M.; Ribeiro,C. C.
Fonte: IBRACON - Instituto Brasileiro do Concreto Publicador: IBRACON - Instituto Brasileiro do Concreto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2014 EN
Relevância na Pesquisa
65.86%
This paper presents an alternative to estimate the magnifier of first order moments to be applied on each storey of reinforced concrete structures, from the values obtained for the γz and B2 coefficients, used to evaluate second order effects in reinforced concrete structures and in steel structures, respectively. In order to develop the study, initially several reinforced concrete buildings of medium height are processed, in first order and in second order, using the ANSYS software. Next, γz, B2 and the increase in first order moments, when considering the second order effects along the height of the buildings, are calculated. Finally, from the results obtained, the magnifier of the first order moments, differentiated for each storey of the structure and calculated from both γz and B2 coefficients, is estimated and the efficiency of the simplified method of obtaining final moments using the magnifier proposed is evaluated.

Global stereo reconstruction under second order smoothness priors

Woodford, O.; Torr, P.; Reid, I.; Fitzgibbon, A.
Fonte: IEEE Computer Soc Publicador: IEEE Computer Soc
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
Relevância na Pesquisa
65.8%
Second-order priors on the smoothness of 3D surfaces are a better model of typical scenes than first-order priors. However, stereo reconstruction using global inference algorithms, such as graph cuts, has not been able to incorporate second-order priors because the triple cliques needed to express them yield intractable (nonsubmodular) optimization problems. This paper shows that inference with triple cliques can be effectively performed. Our optimization strategy is a development of recent extensions to alpha-expansion, based on the ldquo QPBOrdquo algorithm. The strategy is to repeatedly merge proposal depth maps using a novel extension of QPBO. Proposal depth maps can come from any source, for example, frontoparallel planes as in alpha-expansion, or indeed any existing stereo algorithm, with arbitrary parameter settings.; Oliver Woodford, Philip Torr, Ian Reid and Andrew Fitzgibbon

Campaign Effects and Second-Order Cycles - A Top-Down Approach to European Parliament Elections

WEBER, Till
Fonte: Sage Publications Ltd Publicador: Sage Publications Ltd
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
65.87%
Second-order elections theory explains cyclical losses by national government parties in elections to the European Parliament (EP) through strategic protest voting owing to performance deficits in policy- making. This paper confronts the conventional bottom-up view with a top-down approach to second-order elections. Ultimately, the electoral cycle is driven not by instrumental voting behaviour but by party strategies oriented towards governmental power in the member states of the European Union. Based on survey data from the European Election Studies of 1999 and 2004, first-order campaign mobilization is shown to determine the prospects of government parties in second-order elections. Mobilization itself depends on the quality of spatial representation in terms of distinct programmatic alternatives, which governments are unable to provide during the midterm. Although this process can be traced on the left-right dimension, parties prevent it with regard to integration issues by systematic demobilization. After all, EP elections are still second order, but first-order politics exert their influence through cyclical campaign mobilization and not through strategic protest voting.

Sufficient second-order optimality conditions for semilinear control problems with pointwise state constraints

Casas Rentería, Eduardo; Reyes, Juan Carlos de los; Tröltzsch, Fredi
Fonte: Society for Industrial and Applied Mathematics Publicador: Society for Industrial and Applied Mathematics
Tipo: info:eu-repo/semantics/article; publishedVersion
ENG
Relevância na Pesquisa
65.82%
Second-order sufficient optimality conditions are established for the optimal control of semilinear elliptic and parabolic equations with pointwise constraints on the control and the state. In contrast to former publications on this subject, the cone of critical directions is the smallest possible in the sense that the second-order sufficient conditions are the closest to the associated necessary ones. The theory is developed for elliptic distributed controls in domains up to dimension three. Moreover, problems of elliptic boundary control and parabolic distributed control are discussed in spatial domains of dimension two and one, respectively.

Families of two-step fourth order P-stable methods for second order differential equations

Chawla, M.M.; Neta, Beny
Fonte: Escola de Pós-Graduação Naval Publicador: Escola de Pós-Graduação Naval
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
65.82%
This paper deals with a class of symmetric (hybrid) two-step fourth order P-stable methods for the numerical solution of special second order initial value problems. Such methods were proposed independently by Cash and Chawla and normally require three function evaluations per step. The purpose of this paper is to point out that there are some values of the (free) parameters available in the methods proposed which can reduce this work; we study two classes of such methods. This first is the class of 'economical' methods (see Definition 3.1) which reduce this work to two function evaluations per step, and the second is the class of 'efficient' methods (see Definition 3.2) which reduce this work with respect to implementation for nonlinear problems. We report numerical experiments to illustrate the order, acuracy and implementational aspects of these two classes of methods.

Real Second-Order Freeness and Fluctuations of Random Matrices

REDELMEIER, CATHERINE EMILY ISKA
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
65.85%
We introduce real second-order freeness in second-order noncommutative probability spaces. We demonstrate that under this definition, independent ensembles of the three real models of random matrices which we consider, namely real Ginibre matrices, Gaussian orthogonal matrices, and real Wishart matrices, are asymptotically second-order free. These ensembles do not satisfy the complex definition of second-order freeness satisfied by their complex analogues. This definition may be used to calculate the asymptotic fluctuations of products of matrices in terms of the fluctuations of each ensemble. We use a combinatorial approach to the matrix calculations similar to genus expansion, but in which nonorientable surfaces appear, demonstrating the commonality between the real ensembles and the distinction from their complex analogues, motivating this distinct definition. We generalize the description of graphs on surfaces in terms of the symmetric group to the nonorientable case. In the real case we find, in addition to the terms appearing in the complex case corresponding to annular spoke diagrams, an extra set of terms corresponding to annular spoke diagrams in which the two circles of the annulus are oppositely oriented, and in which the matrix transpose appears.; Thesis (Ph.D...

A Second-Order Scheme for Integration of One-Dimensional Dynamic Analysis

Ma, Hang; Qin, Qing Hua
Fonte: Pergamon-Elsevier Ltd Publicador: Pergamon-Elsevier Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
65.88%
This paper proposes a second-order scheme of precision integration for dynamic analysis with respect to long-term integration. Rather than transforming into first-order equations, a recursive scheme is presented in detail for direct solution of the homogeneous part of second-order algebraic and differential equations. The sine and cosine matrices involved in the scheme are calculated using the so-called 2N algorithm. Numerical tests show that both the efficiency and the accuracy of homogeneous equations can be improved considerably with the second-order scheme. The corresponding particular solution is also presented, incorporated with the second-order scheme where the excitation vector is approximated by the truncated Taylor series.

Uncertainty Levels of Second-Order Probability

Sundgren,David; Karlsson,Alexander
Fonte: Instituto Politécnico Nacional, Centro de Innovación y Desarrollo Tecnológico en Cómputo Publicador: Instituto Politécnico Nacional, Centro de Innovación y Desarrollo Tecnológico en Cómputo
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2013 EN
Relevância na Pesquisa
65.85%
Since second-order probability distributions assign probabilities to probabilities there is uncertainty on two levels. Although different types of uncertainty have been distinguished before and corresponding measures suggested, the distinction made here between first- and second-order levels of uncertainty has not been considered before. In this paper previously existing measures are considered from the perspective of first- and second-order uncertainty and new measures are introduced. We conclude that the concepts of uncertainty and informativeness needs to be qualified if used in a second-order probability context and suggest that from a certain point of view information can not be minimized, just shifted from one level to another.

Symbolic sensitivity analysis of the new second-order IIR structure

Jovanovic-Dolecek,G; Mitra,S.K
Fonte: Facultad de Ingeniería, UNAM Publicador: Facultad de Ingeniería, UNAM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2008 EN
Relevância na Pesquisa
65.84%
An high-order IIR (In fi nite im pulse response) filter is usually realized in the form of a cas cade or in the form of a parallel connection of second-order sections. Consequently, it is of in ter est to study properties of a second-order digital filter structures. To this end, in this paper we propose a new second-order IIR filter structure. The effect of multiplier coefficient quantization of the proposed structure is analyzed using the MATLAB-based symbolic analysis. The sensitivity matrix of the structure is computed in a symbolic form and its pole sensitivities are compared with that of other known structures.

Expected Utility from Multinomial Second-order Probability Distributions

Sundgren,David
Fonte: Instituto Politécnico Nacional, Centro de Innovación y Desarrollo Tecnológico en Cómputo Publicador: Instituto Politécnico Nacional, Centro de Innovación y Desarrollo Tecnológico en Cómputo
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2010 EN
Relevância na Pesquisa
65.8%
We consider the problem of maximizing expected utility when utilities and probabilities are given by discrete probability distributions so that expected utility is a discrete stochastic variable. As for discrete second-order distributions, that is probability distributions where the variables are themselves probabilities, the multinomial family is a reasonable choice at least if first-order probabilities are interpreted as relative frequencies. We suggest a decision rule that reflects the uncertainty present in distribution-based probabilities and utilities and we show an example of this rule in action with multinomial second-order distributions.

Evaluation of a second order simulation for Sterling engine design and optimisation

Strauss,Johannes M; Dobson,Robert T
Fonte: Journal of Energy in Southern Africa Publicador: Journal of Energy in Southern Africa
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 EN
Relevância na Pesquisa
65.86%
This paper reports on the investigation of the simulation accuracy of a second order Stirling cycle simulation tool as developed by Urieli (2001) and improvements thereof against the known performance of the GPU-3 Stirling engine. The objective of this investigation is to establish a simulation tool to perform preliminary engine design and optimisation. The second order formulation under investigation simulates the engine based on the ideal adiabatic cycle, and parasitic losses are only accounted for afterwards. This approach differs from third order formulations that simulate the engine in a coupled manner incorporating non-idealities during cyclic simulation. While the second order approach is less accurate, it holds the advantage that the degradation of the ideal performance due to the various losses is more clearly defined and offers insight into improving engine performance. It is therefore particularly suitable for preliminary design of engines. Two methods to calculate the performance and efficiency of the data obtained from the ideal adia-batic cycle and the parasitic losses were applied, namely the method used by Urieli and a proposed alternative method. These two methods differ essentially in how the regenerator and pumping losses are accounted for. The overall accuracy of the simulations...

LOGICAL TRUTH AND SECOND-ORDER LOGIC: RESPONSE TO GUILLERMO ROSADO-HADDOCK

Chateaubriand, Oswaldo
Fonte: UNICAMP-CLE-Publicações Publicador: UNICAMP-CLE-Publicações
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Artigo Avaliado pelos Pares; Formato: application/pdf
Publicado em 11/12/2015 POR
Relevância na Pesquisa
65.81%
In my response to Guillermo Rosado-Haddock I discuss the two main issues raised in his paper. The first is that by allowing Henkin’s general models as a legitimate model-theoretic interpretation of second-order logic, I undermine my defense of second-order logic against Quine’s views concerning the primacy of firstorder logic. The second is that my treatment of logical truth and logical properties does not take into account various systems of logic and properties of systems of logic such as the Löwenheim-Skolem property. Resumo: Em minha réplica à Guillermo Rosado-Haddock discuto as duas questões centrais levantadas em seu artigo. A primeira é que ao permitir modelos gerais de Henkin como uma interpretação legítima da lógica de segunda ordem, desvirtuo minha defesa da lógica de segunda ordem contra a visão de Quine respeito à primazia da lógica de primeira ordem. A segunda é que meu tratamento da verdade lógica e das propriedades lógicas não leva em consideração diversos sistemas de lógica e propriedades de sistemas de lógica tais como a propriedade de Löwenheim-Skolem.Palavras chave: Verdade lógica. Propriedade lógica. Lógica de segunda ordem. Modelos gerais.