Página 1 dos resultados de 6269 itens digitais encontrados em 0.028 segundos

## Métodos para diagnóstico e integração de sistemas de gestão; Management system diagnostic and integration methods

Bonato, Samuel Vinícius
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
45.99%

## Comparison of methodologies for degree-day estimation using numerical methods

Souza, Adilson Pacheco de; Ramos, Clóvis Manoel Carvalho; Lima, Adriano Dawison de; Florentino, Helenice de Oliveira; Escobedo, João Francisco
Tipo: Artigo de Revista Científica Formato: 391-400
ENG
Relevância na Pesquisa
55.96%

## Symplectic integration methods in molecular and spin dynamics simulations

Tsai,Shan-Ho; Krech,M.; Landau,D.P.
Tipo: Artigo de Revista Científica Formato: text/html
Relevância na Pesquisa
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We review recently developed decomposition algorithms for molecular dynamics and spin dynamics simulations of many-body systems. These methods are time reversible, symplectic, and the error in the total energy thus generated is bounded. In general, these techniques are accurate for much larger time steps than more standard integration methods. Illustrations of decomposition algorithms performance are shown for spin dynamics simulations of a Heisenberg ferromagnet.

## Comparison of methodologies for degree-day estimation using numerical methods

Souza,Adilson Pacheco de; Ramos,Clóvis Manoel Carvalho; Lima,Adriano Dawison de; Florentino,Helenice de Oliveira; Escobedo,João Francisco
Tipo: Artigo de Revista Científica Formato: text/html
Relevância na Pesquisa
55.96%
The development of projects related to the yield of various crops has been greatly enhanced with the incorporation of mathematical models as well as essential and more consistent equations which enable a prediction and greater approximation to their actual behavior, thus reducing error in estimate. Among the operations requiring further investigation are those related to crop growth, characterized by the ideal temperature for addition of dry matter. Due to the wide use of mathematical methods for representing, analyzing and attaining degree-day estimation as well as the great importance of sugarcane in the Brazilian economy, we carried out an evaluation of the mathematical models and numerical integration methods commonly used for estimating the availability of degrees-day for this crop in the region of Botucatu, in São Paulo State, Brazil. Integration models with discretization every 6 hours have shown satisfactory results in degree-day estimation. Conventional methodologies have shown satisfactory results when the estimation of degrees-day was based on the time-temperature curve for each day and for groups of 3, 7, 15 and 30 days. Through numerical integration method, the region of Botucatu showed a annual thermal availability average from 1...

## Integration of DNA into bacterial chromosomes from plasmids without a counter-selection marker

Heap, John T.; Ehsaan, Muhammad; Cooksley, Clare M.; Ng, Yen-Kuan; Cartman, Stephen T.; Winzer, Klaus; Minton, Nigel P.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
45.92%
Most bacteria can only be transformed with circular plasmids, so robust DNA integration methods for these rely upon selection of single-crossover clones followed by counter-selection of double-crossover clones. To overcome the limited availability of heterologous counter-selection markers, here we explore novel DNA integration strategies that do not employ them, and instead exploit (i) activation or inactivation of genes leading to a selectable phenotype, and (ii) asymmetrical regions of homology to control the order of recombination events. We focus here on the industrial biofuel-producing bacterium Clostridium acetobutylicum, which previously lacked robust integration tools, but the approach we have developed is broadly applicable. Large sequences can be delivered in a series of steps, as we demonstrate by inserting the chromosome of phage lambda (minus a region apparently unstable in Escherichia coli in our cloning context) into the chromosome of C. acetobutylicum in three steps. This work should open the way to reliable integration of DNA including large synthetic constructs in diverse microorganisms.

## Health Systems Integration of Sexual and Reproductive Health and HIV Services in Sub-Saharan Africa: A Scoping Study

Hope, Rebecca; Kendall, Tamil; Langer, Ana; Bärnighausen, Till
Fonte: JAIDS Journal of Acquired Immune Deficiency Syndromes Publicador: JAIDS Journal of Acquired Immune Deficiency Syndromes
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
45.91%
Objective: Both sexual and reproductive health (SRH) services and HIV programs in sub-Saharan Africa are typically delivered vertically, operating parallel to national health systems. The objective of this study was to map the evidence on national and international strategies for integration of SRH and HIV services in sub-Saharan Africa and to develop a research agenda for future health systems integration. Methods: We examined the literature on national and international strategies to integrate SRH and HIV services using a scoping study methodology. Current policy frameworks, national HIV strategies and research, and gray literature on integration were mapped. Five countries in sub-Saharan Africa with experience of integrating SRH and HIV services were purposively sampled for detailed thematic analysis, according to the health systems functions of governance, policy and planning, financing, health workforce organization, service organization, and monitoring and evaluation. Results: The major international health policies and donor guidance now support integration. Most integration research has focused on linkages of SRH and HIV front-line services. Yet, the common problems with implementation are related to delayed or incomplete integration of higher level health systems functions: lack of coordinated leadership and unified national integration policies; separate financing streams for SRH and HIV services and inadequate health worker training...

## Uma estratégia de adaptação no tempo baseada na curvatura do histórico de deslocamentos; A time adaptive strategy based on displacement history curvature

Cintra, Diogo Tenório
Fonte: Universidade Federal de Alagoas; BR; Estruturas; Programa de Pós-Graduação em Engenharia Civil; UFAL Publicador: Universidade Federal de Alagoas; BR; Estruturas; Programa de Pós-Graduação em Engenharia Civil; UFAL
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
45.99%

## Characterization of virtual nano-structures through the use of Monte Carlo integration

Herrera, L.F.; Do, D.D.; Birkett, G.R.
Fonte: Trans Tech Publications Publicador: Trans Tech Publications
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.85%
The determination of the properties of porous solids remains an integral element to the understanding of adsorption, transport and reaction processes in new and novel materials. The advent of molecular simulation has led to an improved understanding and prediction of adsorption processes using molecular models. These molecular models have removed the constraints of traditional adsorption theories, which require rigid assumptions about the structure of a material. However, even if we possess a full molecular model of a solid, it is still desirable to define the properties of this solid in a standard manner with quantities such as the accessible volume, surface area and pore size distribution. This talk will present Monte Carlo integration methods for calculating these quantities in a physically meaningful and unambiguous way. The proposed methods for calculating the surface area and pore size distribution were tested on an array of idealised solid configurations including cylindrical and cubic pores. The method presented is adequate for all configurations tested giving confidence to its applicability to disordered solids. The method is further tested by using several different noble gas probe molecules. Finally, the results of this technique are compared against those obtained by applying the BET equation for a range of novel materials.; Luis F. Herrera...

## Functional determinants by contour integration methods

Kirsten, Klaus; McKane, Alan
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.78%
We present a simple and accessible method which uses contour integration methods to derive formulae for functional determinants. To make the presentation as clear as possible, the general idea is first illustrated on the simplest case: a second order differential operator with Dirichlet boundary conditions. The method is applicable to more general situations, and we discuss the way in which the formalism has to be developed to cover these cases. In particular, we also show that simple and elegant formulae exist for the physically important case of determinants where zero modes exist, but have been excluded.; Comment: 29 pages

## On the impact of explicit or semi-implicit integration methods over the stability of real-time numerical simulations

Cioaca, Teodor; Caramizaru, Horea
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.96%
Physics-based animation of soft or rigid bodies for real-time applications often suffers from numerical instabilities. We analyse one of the most common sources of unwanted behaviour: the numerical integration strategy. To assess the impact of popular integration methods, we consider a scenario where soft and hard constraints are added to a custom designed deformable linear object. Since the goal for this class of simulation methods is to attain interactive frame-rates, we present the drawbacks of using explicit integration methods over inherently stable, implicit integrators. To help numerical solver designers better understand the impact of an integrator on a certain simulated world, we have conceived a method of benchmarking the efficiency of an integrator with respect to its speed, stability and symplecticity.; Comment: Submitted to the ROMAI Journal of Applied Mathematics. Presented at the CAIM 2013 Conference on Applied and Industrial Mathematics

## Hamiltonian integration methods for Vlasov-Maxwell equations

He, Yang; Qin, Hong; Sun, Yajuan; Xiao, Jianyuan; Zhang, Ruili; Liu, Jian
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.89%
Hamiltonian integration methods for the Vlasov-Maxwell equations are developed by a Hamiltonian splitting technique. The Hamiltonian functional is split into five parts, i.e., the electrical energy, the magnetic energy, and the kinetic energy in three Cartesian components. Each of the subsystems is a Hamiltonian system with respect to the Morrison-Marsden-Weinstein Poisson bracket and can be solved exactly. Compositions of the exact solutions yield Poisson structure preserving, or Hamiltonian, integration methods for the Vlasov-Maxwell equations, which have superior long-term fidelity and accuracy.

## Elementary Integration Methods for Velocity Excitations in Displacement Digital Waveguides

Essl, Georg
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.94%
Elementary integration methods for waveguides are compared. One using non-local loading rules based on Heaviside step functions, one using input side integration and one using integration of the output of traveling velocity waves. We show that most approaches can be made consistent with the wave equation in principle, under proper circumstances. Of all methods studied the Heaviside method is the only method shown to not suffer from undesirable numerical difficulties and amendable to standard waveguide loop filtering practices, yet it gives incorrect results for Neumann boundary conditions. We also discuss localized velocity excitations, time-limited input-side excitations and the relation of loop filters to wave variable type.; Comment: 8 pages, no figures (yet), draft, comments are very welcome

Hayes, A. P.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.92%
We present a generalization of the Adams-Bashforth-Moulton predictor-corrector numerical integration methods to an adaptive grid. The step size may be chosen dynamically in order to maintain a desired relative magnitude of error in each step. We demonstrate that the methods remain convergent to the expected degree, and apply various methods to the famous problem of determining the maximum possible mass of a neutron star supported by pure fermionic exclusion pressure. We reproduce the Tolman-Oppenheimer-Volkoff result of 0.71 solar masses using only 23 integration steps, and reproducing both mass and radius within 1% requires 27. We also present various optimizations and features of our implementation.; Comment: 8 figures, one table included as png image or eps file

## Energy conservation and dissipation properties of time-integration methods for the nonsmooth elastodynamics with contact

Acary, Vincent
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.85%
This research report is devoted to the study of the conservation and the dissipation properties of the mechanical energy of several time--integration methods dedicated to the elasto--dynamics with unilateral contact. Given that the direct application of the standard schemes as the Newmark schemes or the generalized--$\alpha$ schemes leads to energy blow-up, we study two schemes dedicated to the time--integration of nonsmooth systems with contact: the Moreau--Jean scheme and the nonsmooth generalized--$\alpha$ scheme. The energy conservation and dissipation properties of the Moreau--Jean is firstly shown. In a second step, the nonsmooth generalized--$\alpha$ scheme is studied by adapting the previous works of Krenk and H{\o}gsberg in the context of unilateral contact. Finally, the known properties of the Newmark and the Hilber--Hughes--Taylor (HHT) scheme in the unconstrained case are extended without any further assumptions to the case with contact.; Comment: 29 pages

## Numerical integration methods for large-scale biophysical simulations

Chignola, Roberto; Del Fabbro, Alessio; Milotti, Edoardo
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.78%
Simulations of biophysical systems inevitably include steps that correspond to time integrations of ordinary differential equations. These equations are often related to enzyme action in the synthesis and destruction of molecular species, and in the regulation of transport of molecules into and out of the cell or cellular compartments. Enzyme action is almost invariably modeled with the quasi-steady-state Michaelis-Menten formula or its close relative, the Hill formula: this description leads to systems of equations that may be stiff and hard to integrate, and poses unusual computational challenges in simulations where a smooth evolution is interrupted by the discrete events that mark the cells' lives. This is the case of a numerical model (Virtual Biophysics Lab - VBL) that we are developing to simulate the growth of three-dimensional tumor cell aggregates (spheroids). The program must be robust and stable, and must be able to accept frequent changes in the underlying theoretical model: here we study the applicability of known integration methods to this unusual context and we describe the results of numerical tests in situations similar to those found in actual simulations.; Comment: 11 figures, submitted to Computer Physics Communications

## An introduction to particle integration methods: with applications to risk and insurance

Del Moral, P.; Peters, G. W.; Vergé, Ch.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.92%
Interacting particle methods are increasingly used to sample from complex and high-dimensional distributions. These stochastic particle integration techniques can be interpreted as an universal acceptance-rejection sequential particle sampler equipped with adaptive and interacting recycling mechanisms. Practically, the particles evolve randomly around the space independently and to each particle is associated a positive potential function. Periodically, particles with high potentials duplicate at the expense of low potential particle which die. This natural genetic type selection scheme appears in numerous applications in applied probability, physics, Bayesian statistics, signal processing, biology, and information engineering. It is the intention of this paper to introduce them to risk modeling. From a purely mathematical point of view, these stochastic samplers can be interpreted as Feynman-Kac particle integration methods. These functional models are natural mathematical extensions of the traditional change of probability measures, commonly used to design an importance sampling strategy. In this article, we provide a brief introduction to the stochastic modeling and the theoretical analysis of these particle algorithms. Then we conclude with an illustration of a subset of such methods to resolve important risk measure and capital estimation in risk and insurance modelling.

## On the minimal accuracy required for simulating self-gravitating systems by means of direct N-body methods

Zwart, Simon Portegies; Boekholt, Tjarda
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.89%
The conservation of energy, linear momentum and angular momentum are important drivers for our physical understanding of the evolution of the Universe. These quantities are also conserved in Newton's laws of motion under gravity \citep{Newton:1687}. Numerical integration of the associated equations of motion is extremely challenging, in particular due to the steady growth of numerical errors (by round-off and discrete time-stepping, \cite{1981PAZh....7..752B,1993ApJ...415..715G,1993ApJ...402L..85H,1994LNP...430..131M}) and the exponential divergence \citep{1964ApJ...140..250M,2009MNRAS.392.1051U} between two nearby solution. As a result, numerical solutions to the general N-body problem are intrinsically questionable \citep{2003gmbp.book.....H,1994JAM....61..226L}. Using brute force integrations to arbitrary numerical precision we demonstrate empirically that ensembles of different realizations of resonant 3-body interactions produce statistically indistinguishable results. Although individual solutions using common integration methods are notoriously unreliable, we conjecture that an ensemble of approximate 3-body solutions accurately represents an ensemble of true solutions, so long as the energy during integration is conserved to better than 1/10. We therefore provide an independent confirmation that previous work on self-gravitating systems can actually be trusted...

## Efficient time integration methods based on operator splitting and application to the Westervelt equation

Kaltenbacher, Barbara; Nikolic, Vanja; Thalhammer, Mechthild
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.78%
Efficient time integration methods based on operator splitting are introduced for the Westervelt equation, a nonlinear damped wave equation that arises in nonlinear acoustics as mathematical model for the propagation of sound waves in high intensity ultrasound applications. For the first-order Lie-Trotter splitting method a global error estimate is deduced, confirming that the splitting method remains stable and that the nonstiff convergence order is retained in situations where the problem data are sufficiently regular. Fundamental ingredients in the stability and error analysis are regularity results for the Westervelt equation and related linear evolution equations of hyperbolic and parabolic type. Numerical examples illustrate and complement the theoretical investigations.

## Representation of transmission lines: comparison of models and parameters distributed discrete parameters

Araujo, Anderson Ricardo Justo de; Silva, Rodrigo Cleber da; Kurokawa, Sergio
Fonte: Institute of Electrical and Electronics Engineers (IEEE) Publicador: Institute of Electrical and Electronics Engineers (IEEE)
Tipo: Artigo de Revista Científica Formato: 1047-1052
ENG
Relevância na Pesquisa
45.96%
A transmission line is characterized by the fact that its parameters are distributed along its length. This fact makes the voltages and currents along the line to behave like waves and these are described by differential equations. In general, the differential equations mentioned are difficult to solve in the time domain, due to the convolution integral, but in the frequency domain these equations become simpler and their solutions are known. The transmission line can be represented by a cascade of π circuits. This model has the advantage of being developed directly in the time domain, but there is a need to apply numerical integration methods. In this work a comparison of the model that considers the fact that the parameters are distributed (Universal Line Model) and the fact that the parameters considered concentrated along the line (π circuit model) using the trapezoidal integration method, and Simpson's rule Runge-Kutta in a single-phase transmission line length of 100 km subjected to an operation power. © 2003-2012 IEEE.

## Linearly implicit discrete event methods for stiff ODE's.

Migoni,G.; Kofman,E.
Fonte: Latin American applied research Publicador: Latin American applied research
Tipo: Artigo de Revista Científica Formato: text/html