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- Biblioteca Digitais de Teses e Dissertações da USP
- Biblioteca Digital da Unicamp
- ISEG - Departamento de Economia
- National Academy of Sciences
- Society for the Experimental Analysis of Behavior, Inc
- Wiley-Blackwell
- Brock University
- Entomological Society of America
- University of Limerick
- Universidade Cornell
- Kluwer Academic Publishers
- American Physical Society
- Revista de la Facultad de Medicina
- Mais Publicadores...

## Estudo da dinâmica molecular em copolímeros em bloco compostos de poli(metacrilato de metila), poli(ácido acrílico) e poli(acrilato de chumbo) por técnicas de ressonância magnética nuclear e análise térmica; Study of Molecular Dynamics in Copolymers of Poly (methyl methacrylate), poly (acrylic acid) and Poly (acrylate lead) by nuclear magnetic resonance and thermal analyses

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 07/07/2009
Português

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#Beta relaxation#Blindagem aos raios-x#Dinâmica molecular#DMTA#DMTA#DSC#DSC#Glass transition#Lentes ópticas#Molecular dynamics#Optical lenses

Esta tese envolveu o estudo da dinâmica molecular em copolímeros em bloco compostos de poli(metacrilato de metila) (PMMA), poli(ácido acrílico) (PAA) e Poli(acrilato de chumbo) (PAPb) por técnicas de Ressonância Magnética Nuclear e de análise térmica (DSC e DMTA). Estes copolímeros em bloco foram sintetizados visando a obtenção de compostos para serem utilizados, tanto como lentes oftálmicas com maiores índices de refração, como materiais dedicados à proteção radiológica, sendo estas duas propriedades de emprego individual ou integrado. Para o estudo destes materiais, as amostras foram confeccionadas com várias composições, incluindo aquelas nas formas puras contendo apenas um bloco, resultantes da combinação de dois blocos, e as triblocos, com diferentes quantidades relativas de PAPb, variando de 1 a 40%. Para o caso do PMMA, a dinâmica molecular é bem conhecida, sendo caracterizada por uma relaxação β, que envolve mais especificamente movimentos de seus ramos laterais e que ocorre dentro de um amplo intervalo de temperatura centrado em torno da ambiente, e pela transição vítrea, que envolve, predominantemente, movimentos da cadeia principal que ocorrem para temperaturas em torno de 100oC. Devido à extensão destes dois eventos em grandes intervalos de temperatura...

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## Estudo das propriedades dinâmicas e estruturais do gálio líquido super-resfriado através de simulações atomísticas; Study of dynamics and structural properties of supercooled liquid gallium through atomistic simulations

Fonte: Biblioteca Digital da Unicamp
Publicador: Biblioteca Digital da Unicamp

Tipo: Dissertação de Mestrado
Formato: application/pdf

Publicado em 26/07/2011
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#Dinâmica molecular#Líquidos super-resfriados#Transição de fase líquido-líquido#Dinâmica espacialmente heterogênea#Molecular dynamics#Supercooled liquids#Liquid-liquid phase transition#Spatially heterogeneous dynamics

A física dos líquidos super-resfriados é um dos problemas para o qual ainda não existe uma única teoria que tenha capturado com sucesso todas as características destes materiais, principalmente a origem da dinâmica complexa, e também a possível ocorrência de transições líquido-líquido nesse regime. Nosso trabalho está focado nas propriedades dinâmicas do gálio, que é evidenciada pelas funções de correlação temporais antes e depois da transição de fase líquido-líquido. Primeiro, foram feitas simulações atomísticas no gálio através de dinâmica molecular usando o modied embedded atom model (MEAM) e condições periódicas de contorno em uma super-célula contendo 1152 átomos, com o propósito de mostrar a transição de fase líquido-líquido obtida em recentes pesquisas teóricas. Para estudar a dinâmica do sistema como um todo, calculamos o deslocamento quadrático médio, que revela o platô em tempos intermediários, o qual se torna mais notório após a transição líquido-líquido. Esse comportamento pode ser originado por uma dinâmica espacialmente homogênea ou uma dinâmica espacialmente heterogênea. Para saber qual das duas hipóteses é mais relevante foi medido o parâmetro não-gaussiano de ordem 2...

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## Agent based models and opinion dynamics as Markov chains

Fonte: ISEG - Departamento de Economia
Publicador: ISEG - Departamento de Economia

Tipo: Outros

Publicado em //2012
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This paper introduces a Markov chain approach that allows a rigorous analysis of agent based opinion dynamics as well as other related agent based models (ABM). By viewing the ABM dynamics as a micro description of the process, we show how the corresponding macro description is
obtained by a projection construction. Then, well known conditions for lumpability make it possible to establish the cases where the macro model is stillMarkov. In this case we obtain a complete picture of the dynamics including the transient stage, the most interesting phase in applications. For such
a purpose a crucial role is played by the type of probability distribution used to implement the stochastic part of the model which defines the updating rule and governs the dynamics. In addition, we show how restrictions in communication leading to the co–existence of different opinions follow
from the emergence of new absorbing states. We describe our analysis in detail with some specific models of opinion dynamics. Generalizations concerning different opinion representations as well as opinion models with other interaction mechanisms are also discussed. We find that our method may be an attractive alternative to mean–field approaches and that this approach provides new perspectives on the modeling of opinion exchange dynamics...

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## Cluster dynamics transcending chemical dynamics toward nuclear fusion

Fonte: National Academy of Sciences
Publicador: National Academy of Sciences

Tipo: Artigo de Revista Científica

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Ultrafast cluster dynamics encompasses femtosecond nuclear dynamics, attosecond electron dynamics, and electron-nuclear dynamics in ultraintense laser fields (peak intensities 1015–1020 W·cm−2). Extreme cluster multielectron ionization produces highly charged cluster ions, e.g., (C4+(D+)4)n and (D+I22+)n at IM = 1018 W·cm−2, that undergo Coulomb explosion (CE) with the production of high-energy (5 keV to 1 MeV) ions, which can trigger nuclear reactions in an assembly of exploding clusters. The laser intensity and the cluster size dependence of the dynamics and energetics of CE of (D2)n, (HT)n, (CD4)n, (DI)n, (CD3I)n, and (CH3I)n clusters were explored by electrostatic models and molecular dynamics simulations, quantifying energetic driving effects, and kinematic run-over effects. The optimization of table-top dd nuclear fusion driven by CE of deuterium containing heteroclusters is realized for light-heavy heteroclusters of the largest size, which allows for the prevalence of cluster vertical ionization at the highest intensity of the laser field. We demonstrate a 7-orders-of-magnitude enhancement of the yield of dd nuclear fusion driven by CE of light-heavy heteroclusters as compared with (D2)n clusters of the same size. Prospective applications for the attainment of table-top nucleosynthesis reactions...

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## Dynamics of Choice: A Tutorial

Fonte: Society for the Experimental Analysis of Behavior, Inc
Publicador: Society for the Experimental Analysis of Behavior, Inc

Tipo: Artigo de Revista Científica

Publicado em /09/2010
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Choice may be defined as the allocation of behavior among activities. Since all activities take up time, choice is conveniently thought of as the allocation of time among activities, even if activities like pecking are most easily measured by counting. Since dynamics refers to change through time, the dynamics of choice refers to change of allocation through time. In the dynamics of choice, as in other dynamical systems that include feedback, change is away from perturbation and toward a steady state. Steady state or equilibrium is assessed on a longer time scale than change because change is only visible on a smaller time scale. When we compare laws of equilibrium, such as the matching law with laws of dynamics, two possibilities emerge. Self-similarity occurs when the same law can be seen across smaller time scales, with the result that the law at longer time scales may be understood as the expression of its application at smaller time scales. Reduction occurs when the dynamics at a small time scale are incommensurate with the dynamics at longer time scales. Then the process at the longer time scale is reduced to a qualitatively different process at the smaller time scale, as when choice is reduced to switching patterns. When reduction occurs...

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## Promoter decoding of transcription factor dynamics involves a trade-off between noise and control of gene expression

Fonte: Wiley-Blackwell
Publicador: Wiley-Blackwell

Tipo: Artigo de Revista Científica

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Numerous transcription factors (TFs) encode information about upstream signals in the dynamics of their activation, but how downstream genes decode these dynamics remains poorly understood. Using microfluidics to control the nucleocytoplasmic translocation dynamics of the budding yeast TF Msn2, we elucidate the principles that govern how different promoters convert dynamical Msn2 input into gene expression output in single cells. Combining modeling and experiments, we classify promoters according to their signal-processing behavior and reveal that multiple, distinct gene expression programs can be encoded in the dynamics of Msn2. We show that both oscillatory TF dynamics and slow promoter kinetics lead to higher noise in gene expression. Furthermore, we show that the promoter activation timescale is related to nucleosome remodeling. Our findings imply a fundamental trade-off: although the cell can exploit different promoter classes to differentially control gene expression using TF dynamics, gene expression noise fundamentally limits how much information can be encoded in the dynamics of a single TF and reliably decoded by promoters.

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## Molecular dynamics calculation of mean square displacement in alkali metals and rare gas solids and comparison with lattice dynamics

Fonte: Brock University
Publicador: Brock University

Tipo: Electronic Thesis or Dissertation

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Molec ul ar dynamics calculations of the mean sq ua re
displacement have been carried out for the alkali metals Na, K
and Cs and for an fcc nearest neighbour Lennard-Jones model
applicable to rare gas solids. The computations for the alkalis
were done for several temperatures for
temperature vol ume a swell as for
the
the
ze r 0 pressure ze ro
zero pressure volume
corresponding to each temperature. In the fcc case, results were
obtained for a wide range of both the temperature and density.
Lattice dynamics calculations of the harmonic and the lowe s t
order anharmonic (cubic and quartic) contributions to the mean
square displacement were performed for the same potential models
as in the molecular dynamics calculations. The Brillouin zone
sums arising in the harmonic and the quartic terms were computed
for very large numbers of points in q-space, and were
extrapolated to obtain results ful converged with respect to
the number of points in the Brillouin zone.An excellent agreement between the
lattice dynamics results was observed
molecular dynamics and
in the case of all the
alkali metals, e~ept for the zero pressure case of CSt where the
difference is about 15 % near the melting temperature. It was
concluded that for the alkalis...

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## Effects of Thermal Heterogeneity and Egg Mortality on Differences in the Population Dynamics of Aedes aegypti (Diptera: Culicidae) Over Short Distances in Temperate Argentina

Fonte: Entomological Society of America
Publicador: Entomological Society of America

Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion
Formato: application/pdf

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#SPATIAL DISTRIBUTION#OVIPOSITION#SEASONAL DYNAMICS#TEMPERATE REGION#STOCHASTIC MODEL#Zoología, Ornitología, Entomología, Etología#Ciencias Biológicas#CIENCIAS NATURALES Y EXACTAS#Ecología#Ciencias Biológicas#CIENCIAS NATURALES Y EXACTAS

In temperate regions, the seasonal dynamics of Aedes aegypti (L.) (Diptera: Culicidae) is mainly influenced by temperature, whereas the probability of local extinction depends on the egg mortality during the cold season. The aim of the current study was to assess the importance of temperature and egg mortality in determining the differences in the oviposition dynamics of Ae. aegypti between favorable and less favorable areas in Buenos Aires City (Argentina). Year-round temperature dynamics were monitored, and oviposition dynamics were experimentally studied with ovitraps at two sites. Daily egg mortality values were calculated from a previous study performed at the same sites. The relative contribution of the differences in temperature and egg mortality between sites to the oviposition dynamics was assessed by means of a mathematical stochastic population dynamics model for Ae. aegypti. The results showed higher temperature and lower daily egg mortality at the site where higher oviposition activity was recorded. A larger influence of temperature than of egg mortality on population abundance during most of the activity season was detected in the results of the simulations. Our results showed a temperature gradient that relates to the distance to the Río de la Plata river and contributes to explaining the spatial heterogeneity in Ae. aegypti population abundances previously reported. The hypothesis of local extinctions because of egg mortality during the winter was not supported by the present analysis. The differences between field oviposition dynamics and simulation results suggest that rainfall might also be an important variable under extremely dry conditions.; Fil: de Majo...

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## Software project team dynamics a study of enablers and barriers to successful teams

Fonte: University of Limerick
Publicador: University of Limerick

Tipo: info:eu-repo/semantics/conferenceObject; all_ul_research; ul_published_reviewed

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peer-reviewed; Team dynamics is the term used to define how people work and interact together in teams. Positive team dynamics are those that enable and contribute to high performing successful teams. Negative team dynamics are the dynamics that create barriers preventing teams from achieving their full potential. Teamwork is more effective with the existence of positive team dynamics and will encourage a better working environment with
satisfied, fulfilled employees, who will in turn be more productive. Participation in a team should be of benefit to team members on both a personal and professional level.
The absence of the positive dynamics can lead to a decrease in performance, preventing teams from achieving their full potential. If team members feel that being part of the team is not meeting their personal development needs or that their contribution to the team’s success is not relevant, then this will lead to a decrease in their level of motivation and commitment, which will in turn lead to a reduction in their level of productivity. When the
individual roles of the team have not been clearly defined, this will lead to confusion and a sense of aimlessness.
The objective of this research was to identify the positive and negative team dynamics...

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## Nonlinear Dynamics of Coiling in Viscoelastic Jets

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 09/12/2010
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#Physics - Fluid Dynamics#Condensed Matter - Soft Condensed Matter#Nonlinear Sciences - Chaotic Dynamics

Instabilities in free surface continuous jets of non-Newtonian fluids,
although relevant for many industrial processes, remain less well understood in
terms of fundamental fluid dynamics. Inviscid, and viscous Newtonian jets have
been studied in great detail; buckling instability in viscous jets leads to
regular periodic coiling of the jet that exhibits a non-trivial frequency
dependence with the height of the fall. Very few experimental or theoretical
studies exist for continuous viscoelastic jets beyond the onset of the first
instability. Here, we present a systematic study of the effects of
viscoelasticity on the dynamics of free surface continuous jets of surfactant
solutions that form worm-like micelles. We observe complex nonlinear
spatio-temporal dynamics of the jet and uncover a transition from periodic to
doubly-periodic or quasi-periodic to a multi-frequency, possibly chaotic
dynamics. Beyond this regime, the jet dynamics smoothly crosses over to exhibit
the "leaping shampoo effect" or the Kaye effect. This enables us to view
seemingly disparate jetting dynamics as one coherent picture of successive
instabilities and transitions between them. We identify the relevant scaling
variables as the dimensionless height, flow rate...

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## Turbulence in the highly restricted dynamics of a closure at second order: comparison with DNS

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 30/01/2014
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S3T (Stochastic Structural Stability Theory) employs a closure at second
order to obtain the dynamics of the statistical mean turbulent state. When S3T
is implemented as a coupled set of equations for the streamwise mean and
perturbation states, nonlinearity in the dynamics is restricted to interaction
between the mean and perturbations. The S3T statistical mean state dynamics can
be approximately implemented by similarly restricting the dynamics used in a
direct numerical simulation (DNS) of the full Navier-Stokes equations (referred
to as the NS system). Although this restricted nonlinear system (referred to as
the RNL system) is greatly simplified in its dynamics in comparison to the
associated NS, it nevertheless self-sustains a turbulent state in wall-bounded
shear flow with structures and dynamics comparable to that in observed
turbulence. Moreover, RNL turbulence can be analyzed effectively using
theoretical methods developed to study the closely related S3T system. In order
to better understand RNL turbulence and its relation to NS turbulence, an
extensive comparison is made of diagnostics of structure and dynamics in these
systems. Although quantitative differences are found, the results show that
turbulence in the RNL system closely parallels that in NS and suggest that the
S3T/RNL system provides a promising reduced complexity model for studying
turbulence in wall-bounded shear flows.; Comment: 18 pages...

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## Lagrangian dynamics of incompressible thermofluids

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 30/06/2008
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A key aspect of fluid dynamics is the correct definition of the \textit{%
phase-space} Lagrangian dynamics which characterizes arbitrary fluid elements
of an incompressible fluid. Apart being an unsolved theoretical problem of
fundamental importance, the issue is relevant to exhibit the connection between
fluid dynamics and the classical dynamical systems underlying incompressible
and non-isothermal fluid, typically founded either on: a) a
\textit{configuration-space} Lagrangian description of the dynamics of fluid
elements; b) a kinetic description of the molecular dynamics, based on a
discrete representation of the fluid. The goal of this paper is to show that
the exact Lagrangian dynamics can be established based on the inverse kinetic
theory (IKT) for incompressible fluids recently pointed out (Ellero \textit{et
al.}, 2004-2006, \cite{Ellero2004}). The result is reached by adopting an IKT
approach based on a \textit{restricted phase-space representation} of the
fluid, in which the configuration space coincides with the physical fluid
domain. The result appears of potential importance in applied fluid dynamics
and CFD.; Comment: Contributed paper at RGD26 (Kyoto, Japan, July 2008)

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## Base of nonlinear dynamics or Real Dynamics, Ideal Dynamics, Unpredictable Dynamics and "Schrodinger cat"

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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In the paper paradoxes underlying thermodynamics and a quantum mechanics are
discussed. Their solution is given from the point of view of influence of the
exterior observer (surrounding medium) destroying correlations of system, or
boundedness of self-knowledge of system in a case when both the observer, and a
surrounding medium are included in system. Concepts Real Dynamics, Ideal
Dynamics and Unpredictable Dynamics are entered. Consideration an appearance of
a life is given from the point of view of these three Dynamics.; Comment: 47 pages paper is written in two languages: English and Russian. This
paper is the previous version of arXiv:nlin/0508025 and arXiv:0911.2076

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## Coexisting chaotic and multi-periodic dynamics in a model of cardiac alternans

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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The spatiotemporal dynamics of cardiac tissue is an active area of research
for biologists, physicists, and mathematicians. Of particular interest is the
study of period-doubling bifurcations and chaos due to their link with cardiac
arrhythmogenesis. In this paper we study the spatiotemporal dynamics of a
recently developed model for calcium-driven alternans in a one dimensional
cable of tissue. In particular, we observe in the cable coexistence of regions
with chaotic and multi-periodic dynamics over wide ranges of parameters. We
study these dynamics using global and local Lyapunov exponents and spatial
trajectory correlations. Interestingly, near nodes -- or phase reversals --
low-periodic dynamics prevail, while away from the nodes the dynamics tend to
be higher-periodic and eventually chaotic. Finally, we show that similar
coexisting multi-periodic and chaotic dynamics can also be observed in a
detailed ionic model.

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## Lie algebras in vortex dynamics and celestial mechanics - IV

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 30/03/2005
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The work of A.V. Borisov, A.E. Pavlov, Dynamics and Statics of Vortices on a
Plane and a Sphere - I (Reg. & Ch. Dynamics, 1998, Vol. 3, No 1, p.28-39)
introduces a naive description of dynamics of point vortices on a plane in
terms of variables of distances and areas which generate Lie-Poisson structure.
Using this approach a qualitative description of dynamics of point vortices on
a plane and a sphere is obtained in the works Dynamics of Three Vortices on a
Plane and a Sphere - II. General compact case by A.V. Borisov, V.G. Lebedev
(Reg. & Ch. Dynamics, 1998, Vol. 3, No 2, p.99-114), Dynamics of three vortices
on a plane and a sphere - III. Noncompact case. Problem of collaps and
scattering by A.V. Borisov, V.G. Lebedev (Reg. & Ch. Dynamics, 1998, Vol. 3, No
4, p.76-90). In this paper we consider more formal constructions of the general
problem of n vortices on a plane and a sphere. The developed methods of
algebraization are also applied to the classical problem of the reduction in
the three-body problem.; Comment: 41 pages, 17 figures

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## Symbolic Synchronization and the Detection of Global Properties of Coupled Dynamics from Local Information

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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We study coupled dynamics on networks using symbolic dynamics. The symbolic
dynamics is defined by dividing the state space into a small number of regions
(typically 2), and considering the relative frequencies of the transitions
between those regions. It turns out that the global qualitative properties of
the coupled dynamics can be classified into three different phases based on the
synchronization of the variables and the homogeneity of the symbolic dynamics.
Of particular interest is the {\it homogeneous unsynchronized phase} where the
coupled dynamics is in a chaotic unsynchronized state, but exhibits (almost)
identical symbolic dynamics at all the nodes in the network. We refer to this
dynamical behaviour as {\it symbolic synchronization}. In this phase, the local
symbolic dynamics of any arbitrarily selected node reflects global properties
of the coupled dynamics, such as qualitative behaviour of the largest Lyapunov
exponent and phase synchronization. This phase depends mainly on the network
architecture, and only to a smaller extent on the local chaotic dynamical
function. We present results for two model dynamics, iterations of the
one-dimensional logistic map and the two-dimensional H\'enon map, as local
dynamical function.; Comment: 21 pages...

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## Lyapunov Mode Dynamics in Hard-Disk Systems

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 20/09/2007
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The tangent dynamics of the Lyapunov modes and their dynamics as generated
numerically - {\it the numerical dynamics} - is considered. We present a new
phenomenological description of the numerical dynamical structure that
accurately reproduces the experimental data for the quasi-one-dimensional
hard-disk system, and shows that the Lyapunov mode numerical dynamics is linear
and separate from the rest of the tangent space. Moreover, we propose a new,
detailed structure for the Lyapunov mode tangent dynamics, which implies that
the Lyapunov modes have well-defined (in)stability in either direction of time.
We test this tangent dynamics and its derivative properties numerically with
partial success. The phenomenological description involves a time-modal linear
combination of all other Lyapunov modes on the same polarization branch and our
proposed Lyapunov mode tangent dynamics is based upon the form of the tangent
dynamics for the zero modes.

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## On finding the relevant dynamics for model based controlling walking robots

Fonte: Kluwer Academic Publishers
Publicador: Kluwer Academic Publishers

Tipo: Artículo
Formato: 434882 bytes; application/pdf

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Leg dynamics are often ignored in the real-time control of walking
robots because of the high gearing used in leg transmissions. However, the use of a
gear reduction high enough to discount Coriolis and centripetal components yields
additional non-desired dynamics, which are friction, backlash and elasticity. In such
cases, simplifying robot dynamics without considering the effect of gear dynamics
leads to unavoidable errors. In order to make dynamic equations reflect the reality
of the physical system, it is of paramount importance to model the most significant
effects acting on the system. Robot dynamics could then be analyzed and related
to trajectory parameters for motion-control purposes. In this paper, a method to
derive the dynamics of a robot leg as a function of leg-trajectory parameters is
proposed. The method experimentally finds the simplified equations of motion that
reflect the reality of the physical system. The resulting model is an accurate and
simple representation of the system dynamics, taking into account the most relevant
dynamics affecting the system. The simplification of the model allows it to be used
in a real-time dynamic-control system.; Peer reviewed

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## Projected single-spin-flip dynamics in the Ising model

Fonte: American Physical Society
Publicador: American Physical Society

Tipo: Artículo
Formato: 2373 bytes; 253402 bytes; 250607 bytes; text/plain; application/pdf; application/pdf

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#Complex systems#Monte Carlo simulations#Ising model#Critical dynamics#Spin dynamics#Matrix algebra#Magnetisation

10 pages.-- PACS numbers: 02.50.-r, 02.70.Tt, 05.10.Ln, 64.60.Ht.-- Final full-text version of the paper available at: http://dx.doi.org/10.1103/PhysRevE.76.011117.; We study transition matrices for projected dynamics in the energy-magnetization, magnetization, and energy spaces. Several single-spin-flip dynamics are considered, such as the Glauber and Metropolis canonical ensemble dynamics, and the Metropolis dynamics for three multicanonical ensembles: the flat energy-magnetization, the flat energy, and the flat magnetization histograms. From the numerical diagonalization of the matrices for the projected dynamics we obtain the subdominant eigenvalues and the largest relaxation times for systems of varying size. Although the projected dynamics is an approximation to the full state space dynamics, comparison with some available results, obtained by other authors, shows that projection in the magnetization space is a reasonably accurate method to study the scaling of relaxation times with system size. For each system size, the transition matrices for arbitrary single-spin-flip dynamics are obtained from a single Monte Carlo estimate of the infinite-temperature transition matrix. This makes the method an efficient tool for evaluating the relative performance of any arbitrary local spin-flip dynamics. We also present results for appropriately defined average tunneling times of magnetization and compare their finite-size scaling exponents with results of energy tunneling exponents available for the flat energy histogram multicanonical ensemble.; We acknowledge financial support by the MEC (Spain) and FEDER (EU) through Projects No. FIS2006-09966 and No. FIS2007-60327. A.L.C.F. thanks the Portuguese Fundação para a Ciência e Tecnologia (FCT) for financial support.

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## Application of the chaotic power law to the study of cardiac dynamics in patients with arrhythmias

Fonte: Revista de la Facultad de Medicina
Publicador: Revista de la Facultad de Medicina

Tipo: Artigo de Revista Científica
Formato: text/html

Publicado em 01/10/2014
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Background. An exponential law for chaotic cardiac dynamics, found previously, allows the quantification of the differences between normal cardiac dynamics and those with acute diseases, as well as the cardiac dynamics of the evolution between these states. Objective. To confirm the clinical applicability of the developed methodology through the mathematical law for cardiac dynamics in dynamics with arrhythmias. Materials and methods. 60 Holter electrocardiograms were analyzed, 10 corresponded to normal subjects, and 50 to subjects with different arrhythmias. For each Holter, an attractor was performed, and its fractal dimension and spatial occupancy were measured. A mathematical evaluation was applied in order to differentiate normal dynamics from pathological ones. Sensitivity, specificity and the Kappa coefficient were calculated. Results. The mathematical evaluation differentiated occupation spaces, normal dynamics, acute illness dynamics, and evolution between these states. The sensitivity and specificity values were 100%, and the Kappa coefficient was 1. Conclusions. The clinical applicability of the methodology for cases with arrhythmia was shown. It is also applicable for the detection of changes in dynamics that are not classified clinically as pathological.

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