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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

Silva, André Luis Bonfim Bathista e
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 PT
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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...

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

Oscar Samuel Cajahuaringa Macollunco
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/07/2011 PT
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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...

Agent based models and opinion dynamics as Markov chains

Banisch, Sven; Lima, Ricardo; Araújo, Tanya
Fonte: ISEG - Departamento de Economia Publicador: ISEG - Departamento de Economia
Tipo: Outros
Publicado em //2012 ENG
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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...

Cluster dynamics transcending chemical dynamics toward nuclear fusion

Heidenreich, Andreas; Jortner, Joshua; Last, Isidore
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
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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...

Dynamics of Choice: A Tutorial

Baum, William M
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 EN
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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...

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

Hansen, Anders Sejr; O’Shea, Erin K
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica
EN_US
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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.

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

Heiser, Gernot A.
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
ENG
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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...

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

de Majo, María Sol; Fischer, Sylvia Cristina; Otero, Marcelo Javier; Schweigmann, Nicolas Joaquin
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
ENG
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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...

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

O'Connor, Rory V.
Fonte: University of Limerick Publicador: University of Limerick
Tipo: info:eu-repo/semantics/conferenceObject; all_ul_research; ul_published_reviewed
ENG
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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...

Nonlinear Dynamics of Coiling in Viscoelastic Jets

Majmudar, Trushant; Varagnat, Matthieu; Hartt, William; McKinley, Gareth
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/12/2010
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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...

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

Constantinou, Navid C.; Lozano-Durán, Adrian; Nikolaidis, Marios-Andreas; Farrell, Brian F.; Ioannou, Petros J.; Jiménez, Javier
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...

Lagrangian dynamics of incompressible thermofluids

Tessarotto, Marco; Cremaschini, Claudio; Nicolini, Piero; Tessarotto, Massimo
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)

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

Kupervasser, Oleg
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

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

Skardal, Per Sebastian; Restrepo, Juan G.
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.

Lie algebras in vortex dynamics and celestial mechanics - IV

Bolsinov, A. V.; Borisov, A. V.; Mamaev, I. S.
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

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

Jalan, Sarika; Jost, Juergen; Atay, Fatihcan
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...

Lyapunov Mode Dynamics in Hard-Disk Systems

Robinson, D. J.; Morriss, G. P.
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.

On finding the relevant dynamics for model based controlling walking robots

García Armada, Elena; Gálvez, J. A; González de Santos, Pablo
Fonte: Kluwer Academic Publishers Publicador: Kluwer Academic Publishers
Tipo: Artículo Formato: 434882 bytes; application/pdf
ENG
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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

Projected single-spin-flip dynamics in the Ising model

Ferreira, António L. C.; Toral, Raúl
Fonte: American Physical Society Publicador: American Physical Society
Tipo: Artículo Formato: 2373 bytes; 253402 bytes; 250607 bytes; text/plain; application/pdf; application/pdf
ENG
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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.

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

Rodríguez-Velásquez,Javier; Prieto,Signed; Domínguez,Darío; Correa,Catalina; Melo,Martha; Pardo,Juan; Mendoza,Fernán; Victoria Rodríguez,Ligia; Cardona,Diana Margarita; Méndez,Laura
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 EN
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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.