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‣ SYNCHRONIZATION OF A CLASS OF SECOND-ORDER NONLINEAR SYSTEMS

MIJOLARO, A. P.; ABERTO, L. F. C.; BRETAS, N. G.
Fonte: WORLD SCIENTIFIC PUBL CO PTE LTD Publicador: WORLD SCIENTIFIC PUBL CO PTE LTD
Tipo: Artigo de Revista Científica
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The asymptotic behavior of a class of coupled second-order nonlinear dynamical systems is studied in this paper. Using very mild assumptions on the vector-field, conditions on the coupling parameters that guarantee synchronization are provided. The proposed result does not require solutions to be ultimately bounded in order to prove synchronization, therefore it can be used to study coupled systems that do not globally synchronize, including synchronization of unbounded solutions. In this case, estimates of the synchronization region are obtained. Synchronization of two-coupled nonlinear pendulums and two-coupled Duffing systems are studied to illustrate the application of the proposed theory.; Brazilian research foundation FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo)[04/06660-3]

‣ Avaliação da eficiência de métodos de coordenação semafórica em vias arteriais; Performance analysis of traffic signal synchronization methods for arterial streets

Dutra, Cristiane Biazzono
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 05/08/2005 Português
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Os planos de coordenação semafórica são reconhecidamente eficientes para promover a fluidez das correntes de tráfego e melhorar a qualidade operacional do sistema viário. Portanto, os técnicos responsáveis pela gestão do tráfego deveriam, sempre que possível, adotar métodos para a definição adequada das defasagens, utilizando ferramentas que auxiliem na decisão das operações. Porém, uma pesquisa realizada em cidades das regiões Sul e Sudeste sobre as estratégias de coordenação empregadas, demonstrou especialmente para municípios de porte médio que somente 13% utilizam ferramentas computacionais para prover planos de coordenação nos semáforos monitorados por centrais. Para os demais corredores semaforizados, cerca de 27% utilizam o diagrama espaço-tempo, 36% realizam ajustes locais através da observação do tráfego, 14% utilizam veículo-teste e 23% não adotam esquemas de coordenação. O objetivo desta dissertação é avaliar a eficiência de dois programas de coordenação semafórica que poderiam ser utilizados em cidades que não dispõem de técnicas mais eficientes para definir os planos semafóricos. Uma revisão bibliográfica sobre os métodos mais conhecidos foi realizada, identificando que os programas disponíveis seguem três critérios distintos: a maximização da largura da banda verde; a minimização dos atrasos e paradas; e a combinação das vantagens de ambos os critérios. O primeiro programa...

‣ Sincronização de uma classe de sistemas não-lineares acoplados com aplicações em sistemas elétricos de potência; Synchronization of a class of coupled non-linear systems with applications in electric power systems

Mijolaro, Ana Paula
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 11/08/2008 Português
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Neste trabalho, estudou-se a sincronização de uma classe de sistemas dinâmicos não-lineares acoplados. Do ponto de vista teórico, apresentam-se resultados que fornecem condições suficientes sobre o campo vetorial e estimativas dos parâmetros de acoplamentos que garantem sincronização de um conjunto de soluções de uma classe de sistemas não-lineares acoplados. Diferentemente da grande maioria dos resultados existentes na literatura de sincronização de sistemas não-lineares acoplados, os resultados propostos nesta tese podem ser aplicados para demonstrar sincronização em sistemas que não possuem atratores globais, incluindo casos instáveis, onde as soluções são não-limitadas. Quando o sistema não possui atrator global, foi utilizado um resultado, também proposto nesta tese, que fornece estimativas uniformes de atratores, para estimar conjuntos positivamente invariantes contidos na região de sincronização do sistema. Os resultados teóricos propostos foram empregados para demonstrar sincronização em um sistema formado por dois pêndulos acoplados e também por dois sistemas de Duffing acoplados. Do ponto de vista aplicado, estuda-se o problema de coerência de geradores em sistemas elétricos de potência. Valendo-se dos resultados teóricos desta tese...

‣ Bifurcações, controle e sincronização do caos nos circuitos de Matsumoto-Chua; Bifurcations, Control and Synchronization of Chaos in Matsumoto-Chua Circuits

Santos, Elinei Pinto dos
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 05/04/2001 Português
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Neste trabalho utilizamos técnicas de controle e sincronização de sistemas caóticos, visando o uso delas para comunicação com caos. Aplicamos tais técnicas no circuito elétrico de Matsumoto-Chua. Inicialmente, mostramos a sensibilidade dos atratores deste circuito quando variamos os seus parâmetros. Determinamos as suas bacias de atração. Através da análise biespectral, verificamos que o acoplamento quadrático é alto para o atrator tipo Rössler, e quase nulo para o atrator Espiral-Dupla. Para a caracterização global do circuito, apresentamos diagramas, no espaço de parâmetros, com os valores dos expoentes de Lyapunov ou autocorrelação. A seguir estudamos esse circuito com uma perturbação senoidal. Com isto, identificamos novos cenários para a transição para o caos a partir da quase periodicidade. Duas destas transições foram identificados pela primeira vez nesse circuito. Aplicamos ao circuito cinco métodos de controle de caos: supressão de caos por sincronização de freqüências, controle de órbitas periódicas instáveis pelos métodos OGY e de realitnentação , estabilização no ponto ele equilíbrio (método de Hwang), migração e arraste (método OPCL). Finalmente, consideramos dois circuitos de Matsumo-Chua acoplados e determinamos as suas bacias de sincronização. Mostramos que a sincronização dos circuitos acoplados pode não depender das condições iniciais (fronteira das bacias contínua) ou ser extremamente sensível às condições iniciais (fronteira elas bacias elo tipo crivada ou intercrivada).; In this work we use control and synchronization of chaos techniques aiming their implementation in communicating with chaos. These techniques are applied into the electric circuit of Matsumoto-Chua. Initialty...

‣ Symbolic Dynamics and chaotic synchronization

Gracio, Clara; Caneco, Acilina; Rocha, José
Fonte: World Scientific Publicador: World Scientific
Tipo: Parte de Livro
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Chaotic communications schemes based on synchronization aim to provide security over the conventional communication schemes. Symbolic dynamics based on synchronization methods has provided high quality synchronization [5]. Symbolic dynamics is a rigorous way to investigate chaotic behavior with finite precision and can be used combined with information theory [13]. In previous works we have studied the kneading theory analysis of the Duffing equation [3] and the symbolic dynamics and chaotic synchronization in coupled Duffing oscillators [2] and [4]. In this work we consider the complete synchronization of two identical coupled unimodal and bimodal maps. We relate the synchronization with the symbolic dynamics, namely, defining a distance between the kneading sequences generated by the map iterates in its critical points and defining n-symbolic synchronization. We establish the synchronization in terms of the topological entropy of two unidirectional or bidirectional coupled piecewise linear unimodal and bimodal maps. We also give numerical simulations with coupled Duffing oscillators that exhibit numerical evidence of the n-symbolic synchronization.

‣ Synchronization and basins of Synchronized States in Two-Dimensional piecewise Maps via Coupling Three Pieces of One-Dimensional Maps

Fournier-Prunaret, Daniele; Rocha, José; Caneco, Acilina; Fernandes, Sara; Grácio, Clara
Fonte: World Scientific Publicador: World Scientific
Tipo: Artigo de Revista Científica
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This paper is devoted to the synchronization of a dynamical system defined by two different coupling versions of two identical piecewise linear bimodal maps. We consider both local and global studies, using different tools as natural transversal Lyapunov exponent, Lyapunov functions, eigenvalues and eigenvectors and numerical simulations. We obtain theoretical results for the existence of synchronization on coupling parameter range. We characterize the synchronization manifold as an attractor and measure the synchronization speed. In one coupling version, we give a necessary and sufficient condition for the synchronization. We study the basins of synchronization and show that, depending upon the type of coupling, they can have very different shapes and are not necessarily constituted by the whole phase space; in some cases, they can be riddled.

‣ Complete synchronization and delayed synchronization in couplings

Lopes, Luís Mário; Fernandes, Sara; Grácio, Clara
Fonte: Nonlinear Dynamics Publicador: Nonlinear Dynamics
Tipo: Artigo de Revista Científica
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We consider a general coupling of two identical chaotic dynamical systems, and we obtain the conditions for synchronization. We consider two types of synchronization: complete synchronization and delayed synchronization. Then, we consider four different couplings having different behaviors regard- ing their ability to synchronize either completely or with delay: Symmetric Linear Coupled System, Com- manded Linear Coupled System, Commanded Cou- pled System with delay and symmetric coupled sys- tem with delay. The values of the coupling strength for which a coupling synchronizes define its Window of synchronization. We obtain analytically the Windows of complete synchronization, and we apply it for the considered couplings that admit complete synchroniza- tion. We also obtain analytically the Window of chaotic delayed synchronization for the only considered cou- pling that admits a chaotic delayed synchronization, the commanded coupled system with delay. At last, we use four different free chaotic dynamics (based in tent map, logistic map, three-piecewise linear map and cubic-like map) in order to observe numerically the analytically predicted windows.

‣ Scheduler-Conscious Synchronization

Kontothanassis, Leonidas I. ; Wisniewski, Robert W. (1968 - ); Scott, Michael L. (1959 - )
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Relatório
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Efficient synchronization is important for achieving good performance in parallel programs, especially on large-scale multiprocessors. Most synchronization algorithms have been designed to run on a dedicated machine, with one application process per processor, and can suffer serious performance degradation in the presence of multiprogramming. Problems arise when running processes block or, worse, busy-wait for action on the part of a process that the scheduler has chosen not to run. In this paper we describe and evaluate a set of scheduler-conscious synchronization algorithms that perform well in the presence of multiprogramming while maintaining good performance on dedicated machines. We consider both large and small machines, with a particular focus on scalability, and examine mutual-exclusion locks, reader-writer locks, and barriers. The algorithms we study fall into two classes: those that heuristically determine appropriate behavior and those that use scheduler information to guide their behavior. We show that while in some cases either method is sufficient, in general sharing information across the kernel-user interface both eases the design of synchronization algorithms and improves their performance.

‣ Algorithms for Scalable Synchronization on Shared-Memory Multiprocessors

Mellor-Crummey, John M. (1962 - ); Scott, Michael L. (1959 - )
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Relatório
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Busy-wait techniques are heavily used for mutual exclusion and barrier synchronization in shared-memory parallel programs. Unfortunately, typical implementations of busy-waiting tend to produce large amounts of memory and interconnect contention, introducing performance bottlenecks that become markedly more pronounced as applications scale. We argue in this paper that this problem is not fundamental, and that one can in fact construct busy-wait synchronization algorithms that induce no memory or interconnect contention. The key to these algorithms is for every processor to spin on a separate location in local memory, and for some other processor to terminate the spin with a single remote write operation at an appropriate time. Locations on which to spin may be local as a result of coherent caching, or by virtue of static allocation in the local portion of physically distributed shared memory. We present a new scalable algorithm for spin locks that generates O(1) remote references per lock acquisition, independent of the number of processors attempting to acquire the lock. Our algorithm provides reasonable latency in the absence of contention, requires only a constant amount of space per lock, and requires no hardware support other than a swap-with-memory instruction. We also present a new scalable barrier algorithm that generates O(1) remote references per processor reaching the barrier...

‣ Timing synchronization for cooperative wireless communications

Hossain, Md Tofazzal
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
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In this work the effect of perfect and imperfect synchronization on the performance of single-link and cooperative communication is investigated. A feedforward non- data-aided near maximum likelihood (NDA-NML) timing estimator which is effective for an additive white Gaussian noise (AWGN) channel and also for a flat-fading channel, is developed. The Cramer Rao bound (CRB) and modified Cramer Rao bound (MCRB) for the estimator for a single-link transmission over an AWGN channel is derived. A closed form expression for the probability distribution of the timing estimator is also derived. The bit-error-rate (BER) degradation of the NDA-NML timing estimator with raised cosine pulse shaping for static timing errors over an AWGN channel is characterized. A closed form expression is derived for the conditional bit error probability (BEP) with static timing errors of binary phase shift keying modulation over a Rayleigh fading channel using rectangular pulse shaping. The NDA-NML timing estimator is applied to a cooperative communication system with a source, a relay and a destination. A CRB for the estimator for asymptotically low signal-to-noise-ratio case is derived. The timing complexity of the NDA-NML estimator is derived and compared with a feedforward correlation based data-aided maximum likelihood (DA-ML) estimator. The BER performance of this system operating with a detect-and-forward relaying is studied...

‣ Relationship between motor unit short-term synchronization and common drive in human first dorsal interosseous muscle

Semmler, J.; Nordstrom, M.; Wallace, C.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
Publicado em //1997 Português
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We assessed the strength of motor unit (MU) short-term synchronization and common fluctuations in mean firing rate (common drive) in the same pairs of MUs in order to evaluate whether these features of voluntary MU discharge arise from a common mechanism. Shared, branched-axon inputs, with the most important being widely divergent monosynaptic projections to motoneurons from motor cortical cells, are regarded as the principal determinants of MU short-term synchronization. It is not known to what extent these synaptic inputs are responsible for common drive behaviour of MUs. MU spike trains from 77 pairs of concurrently active MUs in first dorsal interosseous muscle of 17 subjects were discriminated with the high reliability needed for common drive analysis. For each MU pair, the data used for comparison of the two analyses of correlated MU discharge came from a single trial (1-5 min duration) of isometric abduction of the index finger. Linear regression revealed a weak, significant positive correlation between the strength of MU short-term synchronization and the strength of common drive in the MU pairs (r2 = 0.06, P < 0.05, n = 77), which was slightly stronger when MU pairs with broad synchronous peaks (> 20 ms) were excluded (r2 = 0.09...

‣ Synchronization enhancement via an oscillatory bath in a network of self-excited cells

Nbendjo, B. R. Nana; Kadji, H. G. Enjieu; Cerdeira, Hilda A.
Fonte: Indian Acad Sciences Publicador: Indian Acad Sciences
Tipo: Artigo de Revista Científica Formato: 257-272
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); The possibility of using a dynamic environment to achieve and optimize phase synchronization in a network of self-excited cells with free-end boundary conditions is addressed in this paper. The dynamic environment is an oscillatory bath coupled linearly to a network of four cells. The boundaries of the stable solutions of the dynamical states as well as the ranges of coupling parameters leading to stability and instability of synchronization are determined. Numerical simulations are used to check the accuracy and to complement the result obtained from analytical treatment. The robustness of synchronization strategy is tested using a local and global injection of Gaussian white noise in the network. The control gain parameter of the bath coupling can modulate the occurrence of synchronization in the network without prior requirement of direct coupling among all the cells. The process of synchronization obtained through local injection is independent of the node at which noise is injected into the system. As compared to local injection, the global injection scheme increases the range of noise amplitude for which synchronization occurs in the network.

‣ Adaptive synchronization for neutral-type neural networks with stochastic perturbation and Markovian switching parameters

Zhou, W.; Zhu, Q.; Shi, P.; Su, H.; Fang, J.; Zhou, L.
Fonte: IEEE Publicador: IEEE
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
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In this paper, the problem of adaptive synchronization is investigated for stochastic neural networks of neutral-type with Markovian switching parameters. Using the M-matrix approach and the stochastic analysis method, some sufficient conditions are obtained to ensure three kinds of adaptive synchronization for the stochastic neutral-type neural networks. These three kinds of adaptive synchronization include the almost sure asymptotical synchronization, exponential synchronization in p th moment and almost sure exponential synchronization. Some numerical examples are provided to illustrate the effectiveness and potential of the proposed design techniques.; Wuneng Zhou, Qingyu Zhu, Peng Shi, Hongye Su, Jian’an Fang, and Liuwei Zhou

‣ On the outer synchronization of complex dynamical networks

Asheghan, Mohammad Mostafa
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: Tese de Doutorado
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Complex network models have become a major tool in the modeling and analysis of many physical, biological and social phenomena. A complex network exhibits behaviors which emerge as a consequence of interactions between its constituent elements, that is, remarkably, not the same as individual components. One particular topic that has attracted the researchers' attention is the analysis of how synchronization occurs in this class of models, with the expectation of gaining new insights of the interactions taking place in real-world complex systems. Most of the work in the literature so far has been focused on the synchronization of a collection of interconnected nodes (forming one single network), where each node is a dynamical system governed by a set of nonlinear differential equations, possibly displaying chaotic dynamics. In this thesis, we study an extended version of this problem. In particular, we consider a setup consisting of two complex networks which are coupled unidirectionally, in such a way that a set of signals from the master network are injected into the response network, and then investigate how synchronization is attained. Our analysis is fairly general. We impose few conditions on the network structure and do not assume that the nodes in a single network are synchronized. This work can be divided into two main parts; outer synchronization in fractional-order networks...

‣ Synchronization in Cooperative Communication Systems

Nasir, Ali Arshad
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
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Cooperative communication is an attractive solution to combat fading in wireless communication systems. Achieving synchronization is a fundamental requirement in such systems. In cooperative networks, multiple single antenna relay terminals receive and cooperatively transmit the source information to the destination. The multiple distributed nodes, each with its own local oscillator, give rise to multiple timing offsets (MTOs) and multiple carrier frequency offsets (MCFOs). Particularly, the received signal at the destination is the superposition of the relays' transmitted signals that are attenuated differently, are no longer aligned with each other in time, and experience phase rotations at different rates due to different channels, MTOs, and MCFOs, respectively. The loss of synchronization due to the presence of MTOs and MCFOs sets up the recovery of the source signal at the destination to be a very challenging task. This thesis seeks to develop estimation and compensation algorithms that can achieve synchronization and enable cooperative communication for both decode-and-forward (DF) and amplify-and-forward (AF) relaying networks in the presence of multiple impairments, i.e., unknown channel gains, MTOs, and MCFOs. In the first part of the thesis...

‣ Anticipated Synchronization: Numerical and Theoretical Study

Ciszak, Marzena
Fonte: Universidad de las Islas Baleares Publicador: Universidad de las Islas Baleares
Tipo: Tesis Formato: 2373 bytes; 10703488 bytes; text/plain; application/pdf
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Tesis doctoral de la Universidad de las Islas Baleares, Facultad de Física y del Instituto Mediterráneo de Estudios Avanzados (IMEDEA-CSIC/UIB).-- Texto en inglés, introducción en inglés y castellano.-- Fecha de lectura: 30-06-2006.; [EN] In this thesis we study the phenomena of synchronization between two or more constituents coupled in an unidirectional way. The coupling is designed in a way which permits the occurrence of achronal synchronization, more specifically anticipated synchronization. Anticipated synchronization refers to the situation in which one system synchronizes to the future dynamics of other system.; The framework of this thesis touches many problems related to dynamical systems, for which we characterize the occurrence of anticipated synchronization with a special interest in excitable and spatiotemporal ones. We provide a theoretical description of the phenomenon, mostly through numerical simulations, but also in the particular case of excitable systems, through experimental results. Moreover we model the anticipation of the chemical reaction consisting on the oxidation of the CO on the platinum surface and provide the study from a point of view of the experimental requisites and limitations.; We show that spatially separated and coupled excitable cells with the anticipated synchronization scheme under particular conditions may contribute to zero-lag synchronization. We relate this result to the experimental observation of zero-lag synchronization between spatially separated brain areas. Considering further spatiotemporal dynamics we demonstrate on the example of coupled cellular automata the equivalence between the coupling based on time-delayed and on space-delayed variables. We relate this finding to the previous study on the spatial properties of time-delayed systems.; We uncover the dynamical mechanism of anticipated synchronization in excitable systems showing that the anticipation is due to the lowering of the excitability threshold of the slave by the delayed coupling term. Also we try to answer the question about the dynamical mechanism of anticipated synchronization in chaotic systems in terms of a modified system approach.; Finally we estimate the practical usage of anticipated synchronization. We present a new control method which we call predict-prevent control method for excitable systems. We also compare the prediction capacity of the anticipated synchronization scheme implemented in neural networks modules with the standard prediction methods given by neural networks.; [ES] En esta tesis estudiamos el fenómeno de sincronización entre dos o más sistemas acoplados unidireccionalmente. El acoplamiento esta diseñado de tal manera que permite que ocurra sincronización ácrona...

‣ Coupling and feedback effects in excitable systems: anticipated synchronization (Review paper)

Ciszak, Marzena; Toral, Raúl; Mirasso, Claudio R.
Fonte: World Scientific Publishing Publicador: World Scientific Publishing
Tipo: Artículo Formato: 2373 bytes; 8138290 bytes; text/plain; application/pdf
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20 pages, 19 figures.; This paper reviews our recent work on the synchronization of excitable systems in a master–slave configuration and when the slave system includes a delayed self-coupling term. Particularly, we address the existence of the so-called anticipated synchronization, i.e. a dynamical regime in which the slave system is able to reproduce in advance the evolution of the master. This is most remarkable since the anticipated synchronization appears even when the excitable spikes are induced by random terms, such as white noise. After providing a short review of the general theory of synchronization as well as the main features of excitable systems, we present numerical and experimental results in coupled excitable systems of the FitzHugh–Nagumo type driven by different types of noise. The experiments have been done in electronic implementations of the model equations. We present the conditions (values of the coupling intensity and delay time) for which the anticipated synchronization regime is a stable one and show that it is possible to increase the anticipation time by using a cascade of several coupled systems. We use a particular limit of the FitzHugh–Nagumo system, as well as a simple excitable model, to give evidence that the physical reason for the existence of anticipated synchronization is the lowering of the excitability threshold of the slave due to the coupling. Finally...

‣ Zero-lag long-range synchronization of Hodgkin-Huxley neurons is enhanced by dynamical relaying

Vicente, Raúl; Pipa, Gordon; Fischer, Ingo; Mirasso, Claudio R.
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Póster Formato: 206822 bytes; application/pdf
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Poster presentation, Sixteenth Annual Computational Neuroscience Meeting: CNS*2007 Toronto, Canada. 7–12 July 2007.-- Meeting proceedings published in BMC Neuroscience supplement: "Sixteenth Annual Computational Neuroscience Meeting: CNS*2007", http://www.biomedcentral.com/bmcneurosci/8?issue=S2.; [Background] The synchrony hypothesis postulates that precise temporal synchronization of different pools of neurons conveys information that is not contained in their firing rates. The synchrony hypothesis had been supported by experimental findings demonstrating that millisecond precise synchrony of neuronal oscillations across well separated brain regions plays an essential role in visual perception and other higher cognitive tasks. Albeit, more evidence is being accumulated in favour of its role as a binding mechanism of distributed neural responses, the physical and anatomical substrate for such a dynamic and precise synchrony, especially zero-lag even in the presence of non-negligible delays, remains unclear.; Here we propose a simple network motif that naturally accounts for zero-lag synchronization for a wide range of temporal delays [3]. We demonstrate that zero-lag synchronization between two distant neurons or neural populations can be achieved by relaying the dynamics via a third mediating single neuron or population.; [Methods] We simulated the dynamics of two Hodgkin-Huxley neurons that interact with each other via an intermediate third neuron. The synaptic coupling was mediated through α-functions. Individual temporal delays of the arrival of pre-synaptic potentials were modelled by a gamma distribution. The strength of the synchronization and the phase-difference between each individual pairs were derived by cross-correlation of the membrane potentials.; [Results] In the regular spiking regime the two outer neurons consistently synchronize with zero phase lag irrespective of the initial conditions. This robust zero-lag synchronization naturally arises as a consequence of the relay and redistribution of the dynamics performed by the central neuron. This result is independent on whether the coupling is excitatory or inhibitory and can be maintained for arbitrarily long time delays (see Fig 1).; [Conclusion] We have presented a simple and extremely robust network motif able to account for the isochronous synchronization of distant neural elements in a natural way. As opposed to other possible mechanisms of neural synchronization...

‣ A clustering approach in sensor network time synchronization

Krishnaram, Ramesh
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
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In recent years tremendous technological advances have led to the development of low-cost sensors capable of data processing activities. These sensor nodes are organized in to a network typically called wireless Sensor Network. WSN's are based on the principle of "Data Fusion" where the data collected from each sensor node is condensed into one meaningful result: Data Fusion is achieved by exchanging messages between the sensors. These messages are time stamped by each sensor node's local clock fuse reading. As noted in various references, Time Synchronization is a common feature used in networking in order to give the nodes a common time reference. Time Synchronization is an important middleware service in Wireless Sensor Networks, as physical time is needed to relate events to the physical world. WSN's require a great deal of synchronization accuracy so that information from many nodes can be cohesively integrated without creating time skews in the data. State-of-the-art research has been investigating the sources of error in attempting to synchronize the nodes in a network. The objective of this thesis is to define a Time Synchronization protocol for a Hierarchical Cluster Head based Wireless Sensor Network. Thus, the goals of this thesis are three fold: We first analyze the shortcomings of existing time synchronization protocols and propose a novel time synchronization protocol based on cluster tree based routing. We perform hardware-based simulation using Mica motes...

‣ Tapestry: weaving execution and synchronization models

Landwehr, Joshua
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
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Gao, Guang R.; With the advent of the many-core era of computing, finding parallelism has become a key battleground to the performance of computer algorithms. Traditional methods focused on providing users with synchronization primitives, standard threading models, and shared memory models. However, it was clear that these models were limited in performance. Thus, many new forms of synchronization and parallel models were designed focusing on the big three types of parallelism: data, task, and dataflow. Nevertheless, all these models (1) only solve a particular subset of problems, (2) provide limited extendability for addressing new forms of parallelism, (3) and require a new languages with poor fine-grain performance. As an approach to find a unified solution to these problems, Tapestry is an easily extendable portable compiler-free runtime. It is designed to quickly explore new or traditional synchronization and execution models for multi-core and many-core architectures by separating synchronization and threading models. The main contributions of this thesis are: 1. Design of the Tapestry runtime and model to explore synchronization features or execution models that supports the mixing of all of the big three types of parallelism. 2. Proposal of extendable threaded dependency model of execution that expands traditional threads...