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Self-organised systems: fundamental properties

Correia, Luís
Fonte: Universidade Aberta Publicador: Universidade Aberta
Tipo: Artigo de Revista Científica
Publicado em //2006 ENG
Relevância na Pesquisa
27.29%
Abstract: A set of fundamental properties of self-organised systems is identified. Asynchronism is here proposed as one of these properties. It is shown that, by overlooking it, the concept of self-organisation is not fulfilled. Implications of this property to the study of selforganisation are discussed. Further, two other salient aspects are identified: minimisation of local conflicts produces optimal evolutionarily stable self-organisation; and the hypothesis that complexity variations may distinguish living from non-living self-organised systems. Conclusions and further research bring the document to an end.; Resumo: Neste artigo identifica-se um conjunto de propriedades fundamentais que caracterizam os sistemas auto-organizados. Propõe-se o assincronismo como uma dessas propriedades. Mostra-se que sistemas sem assincronismo não se podem considerar autoorganizados. Discutem-se as implicações desta propriedade para o estudo da autoorganização. Para além disso, identificam-se dois outros aspectos notáveis: a minimização de conflitos locais produz auto-organização óptima e evolucionariamente estável; e a hipótese de que as variações de complexidade permitem distinguir sistemas auto-organizados vivos dos não vivos. O documento termina com as principais conclusões e perspectivas de investigação futura.

The influence of the update dynamics on the evolution of cooperation

Grilo, Carlos Fernando Almeida; Correia, Luís
Fonte: Atlantis Press Publicador: Atlantis Press
Tipo: Artigo de Revista Científica
Publicado em //2009 ENG
Relevância na Pesquisa
16.67%
We investigate the influence of the update dynamics on the evolution of cooperation. Three of the most studied games in this area are used: Prisoner’s Dilemma, Snowdrift and the Stag Hunt. Previous studies with the Prisoner’s Dilemma game reported that less cooperators survive with the asynchronous version of the game than with the synchronous one. On the other side, studies with the Snowdrift game are not conclusive about this subject. Based on simulations with these three games, played on different types of networks and using different levels of noise in the choice of the next strategy to be adopted by the agents, we conclude that, in general, an asynchronous dynamics favors the evolution of cooperation. Results concerning the monotonicity of these models and their sensitivity to small changes in the synchrony rate are also reported. This work is a contribution to a better understanding of the conditions under which cooperation can emerge and how different parameters may influence this emergence.

Update dynamics, strategy exchanges and the evolution of cooperation in the snowdrift game

Grilo, Carlos; Correia, Luís
Fonte: Instituto Politécnico de Leiria Publicador: Instituto Politécnico de Leiria
Tipo: Conferência ou Objeto de Conferência
Publicado em //2009 ENG
Relevância na Pesquisa
16.67%
We verify through numerical simulations that the influence of the update dynamics on the evolution of cooperation in the Snowdrift game is closely related to the number of strategy exchanges between agents. The results show that strategy exchanges contribute to the destruction of compact clusters favorable to cooperator agents. In general, strategy exchanges decrease as the synchrony rate decreases. This explains why smaller synchrony rates are beneficial to cooperators in situations where a large number of exchanges occur with synchronous updating. On the other hand, this is coherent with the fact that the Snowdrift game is completely insensitive to the synchrony rate when the replicator dynamics transition rule is used: there are almost no strategy exchanges when this rule is used.

Respostas ecofisiológicas de Andropogon lateralis Nees subsp. lateralis (capim-caninha) : variação ecotípica ou plasticidade fenotípica?; Ecophysiological responses of andropogon lateralis nees Subsp. Lateralis (caninha grass) : ecotypic variation or Phenotypicplasticity?

Porto, Claudia Beltrame
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
16.67%
Plasticidade fenotípica é a capacidade de um organismo alterar sua fisiologia e/ou morfologia em decorrência de suas interações com o meio, podendo resultar em uma maior tolerância às modificações ambientais. Tendo em vista que a seleção natural age sobre o fenótipo, a plasticidade fenotípica se caracteriza como um importante mecanismo gerador de variabilidade populacional. Em populações com grande potencial plástico pode ocorrer a formação de ecótipos, gerando populações geneticamente adaptadas às condições do seu local de origem. Este estudo teve como objetivo principal verificar a ocorrência de variações fenotípicas e a formação de ecótipos em duas populações de Andropogon lateralis subsp. lateralis do Rio Grande do Sul, provenientes de duas regiões fisiográficas, Depressão Central e Campos de Cima da Serra. As plantas foram cultivadas em casa de vegetação e avaliadas quanto a seus padrões de respostas fisiológicas, morfológicas e fenológicas a três níveis de adubação nitrogenada e a dois regimes hídricos. As populações apresentaram o mesmo padrão de resposta fotossintética, mas mostraram diferentes respostas quanto a atributos morfológicos, demonstrando diferenças em sua habilidade de responder às influências ambientais. Observou-se também uma assincronia temporal na floração das populações das duas regiões. Os resultados obtidos indicam a formação de ecótipos morfológicos para a espécie e a importância da variabilidade genética nos processos adaptativos e evolutivos nas regiões fisiográficas do Rio Grande do Sul.; Phenotypic plasticity is the capacity of an organism to modify its physiology andJor morphology as the result of interaction with the environment...

Fases do desenvolvimento e diferenciação testicular em cutias (Dasyprocta aguti) criadas em cativeiros

Assis-Neto, Antônio Chaves de; Carvalho, Maria Acelina Martins de; Melo, Maria Isabel Vaz de; Miglino, Maria Angélica; Oliveira, Moacir Franco de; Mariana, Arani Nanci Bomfim
Fonte: Universidade de São Paulo (USP), Faculdade de Medicina Veterinária e Zootecnia (FMVZ) Publicador: Universidade de São Paulo (USP), Faculdade de Medicina Veterinária e Zootecnia (FMVZ)
Tipo: Artigo de Revista Científica Formato: 71-79
POR
Relevância na Pesquisa
16.67%
A cutia (Dasyprocta aguti) é um roedor silvestre encontrado amplamente na região Nordeste do Brasil. É uma espécie muito utilizada pela população humana de baixa renda como fonte alternativa de proteína na alimentação. Foram utilizadas 31 cutias, machos, provenientes da Universidade Federal do Piauí (FUFPI), Estado do Piauí e da Escola Superior de Agricultura de Mossoró Estado do Rio Grande do Norte. Os animais foram divididos em grupos etários desde o nascimento até os 14 meses de idade. O diâmetro nuclear médio foi obtido pela medida de 10 núcleos do tipo celular estudado em cada testículo, no estágio 1 do ciclo do epitélio seminífero. Nos animais que não apresentaram o epitélio organizado em estágios bem definidos em virtude da idade, foram feitas medidas em secções transversais escolhidas somente pelo contorno circular. O início da assincronia do processo espermatogênico foi observado a partir dos seis meses de idade. A puberdade, na cutia Dasyprocta aguti, foi definitivamente estabelecida a partir dos nove meses de idade, pois estavam presentes todos os tipos celulares e espermatozóides liberados no lume tubular em grande parte do parênquima testicular.; The Agouti (Dasyprocta aguti) is a wild rodent that...

Quantitative aspects of the migration and evolutive asynchronism of Schistosoma mansoni in mice

Barbosa, M. A.; Pellegrino, J.; Coelho, P. M. Z.; Sampaio, I. B. M.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 121-132
ENG
Relevância na Pesquisa
27.29%
Two groups of white mice (Mus musculus) were infected with 65 and 440 cercariae transcutaneously. Migration of Schistosoma mansoni from skin to the lungs and to the portal system thereafter was studied through fitting mathematical equations. Six evolutive stages previously defined were used to determine the asynchronic development of parasites in the portal system. Equations the moment of maximum schistosomula recovery in skin and lungs. In the portal system the equations lead to different days of maximum recovery according to each stage. These differences measure quantitatively the asynchronism of S. mansoni.

Influência da dinâmica de actualização na evolução da cooperação

Grilo, Carlos Fernando Almeida, 1972-
Fonte: Universidade de Lisboa Publicador: Universidade de Lisboa
Tipo: Tese de Doutorado
Publicado em //2011 POR
Relevância na Pesquisa
17.29%
Tese de doutoramento, Informática (Engenharia Informática), Universidade de Lisboa, Faculdade de Ciências, 2011; A identificação dos mecanismos que permitem promover a emergência e a manutenção de comportamentos de cooperação é um problema com relevância em diversas disciplinas científicas tais como a Biologia, a Sociologia, a Economia e a Informática. Numa população de indivíduos que interagem entre si, estes decidem, de vez em quando, alterar a forma como agem nas interacções em que participam. Potencialmente, a relação temporal entre os processos de actualização que ocorrem na população pode influenciar a proliferação de comportamentos cooperativos uma vez que condiciona a informação disponível da qual estes processos dependem. Esta relação estabelece uma dinâmica que denominamos por dinâmica de actualização. A actualização diz-se síncrona se os agentes actualizam a sua estratégia em simultâneo e assíncrona em caso contrário. Neste trabalho investigamos a influência da dinâmica de actualização na evolução da cooperação utilizando como plataforma de trabalho a Teoria dos Jogos Evolucionária. Os resultados mostram que, em geral, quando a dinâmica de actualização tem alguma influência...

Ser ou não ser, eis a questão: o processo de construção da identidade na pessoa com altas habilidades/superdotação adulta

Pérez, Susana Graciela Pérez Barrera
Fonte: Pontifícia Universidade Católica do Rio Grande do Sul; Porto Alegre Publicador: Pontifícia Universidade Católica do Rio Grande do Sul; Porto Alegre
Tipo: Tese de Doutorado
PORTUGUêS
Relevância na Pesquisa
17.29%
A pesquisa científica na área de Altas Habilidades/Superdotação (AH/SD) tem se focado na compreensão de diferentes aspectos da identificação e atendimento de crianças e adolescentes. A presente tese de Doutorado é um estudo de caso qualitativo que teve como objetivo geral compreender a forma como a Pessoa com Altas Habilidades/Superdotação (PAH/SD) adulta constrói sua identidade como tal, propondo estratégias educacionais para uma construção sadia dessa identidade e para seu desenvolvimento. O referencial teórico está alicerçado nos conceitos de inteligência de Gardner (1993, 2000) e de superdotação de Renzulli (1975, 1986), buscando também autores como Erikson (1987), Woodward (2002) e Silva (2000), Gross (1998) e Silverman (1995, 1998), para auxiliar na elaboração relativa à identidade e autores que discutem o desenvolvimento humano ao longo de toda a vida, como Papalia, Olds e Feldman (2006), Schaie e Willis (2000) e Mosquera (1987), entre outros. A investigação teve como participantes 10 adultos (5 formalmente identificados e 5 que apresentavam indicadores claros de AH/SD, não identificados formalmente antes desta pesquisa), atualmente residentes em 4 estados brasileiros e 2 países estrangeiros que...

Asynchronous stochastic dynamics and the spatial prisioner's dilemma game

Grilo, Carlos Fernando Almeida; Correia, Luís
Fonte: Springer Publicador: Springer
Tipo: Conferência ou Objeto de Conferência
Publicado em //2007 ENG
Relevância na Pesquisa
17.62%
We argue that intermediate levels of asynchronism should be explored when one uses evolutionary games to model biological and sociological systems. Usually, only perfect synchronism and continuous asynchronism are used, assuming that it is enough to test the model under these two opposite update methods. We believe that biological and social systems lie somewhere between these two extremes and that we should inquire how the models used in these situations behave when the update method allows more than one element to be active at the same time but not necessarily all of them. Here, we use an update method called Asynchronous Stochastic Dynamics which allows us to explore intermediate levels of asynchronism and we apply it to the Spatial Prisoner’s Dilemma game. We report some results concerning the way the system changes its behaviour as the synchrony rate of the update method varies.

The influence of asynchronous dynamics in the spatial prisioner's dilemma game

Grilo, Carlos Fernando Almeida; Correia, Luís
Fonte: Springer Publicador: Springer
Tipo: Conferência ou Objeto de Conferência
Publicado em //2008 ENG
Relevância na Pesquisa
27.62%
We examine the influence of asynchronism in the Spatial Prisoner’s Dilemma game. Previous studies reported that less cooperation is achieved with the asynchronous version of the game than with the synchronous one. Here, we show that, in general, the opposite is the most common outcome. This conclusion is only possible because a larger number of scenarios was tested, namely, different interaction topologies, a transition rule that can be tuned to emulate different levels of determinism in the choice of the next strategy to be adopted and different rates of asynchronism. The influence of stochastic and deterministic periodic updating in the outcome of the system is also compared. We found that these two update disciplines lead basically to the same result. This is an important issue in the simulation of social and biological behavior.

Optimal Sequential Frame Synchronization

Chandar, Venkat; Tchamkerten, Aslan; Wornell, Gregory
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/08/2007
Relevância na Pesquisa
17.29%
We consider the `one-shot frame synchronization problem' where a decoder wants to locate a sync pattern at the output of a channel on the basis of sequential observations. We assume that the sync pattern of length N starts being emitted at a random time within some interval of size A, that characterizes the asynchronism level between the transmitter and the receiver. We show that a sequential decoder can optimally locate the sync pattern, i.e., exactly, without delay, and with probability approaching one as N tends to infinity, if and only if the asynchronism level grows as O(exp(N*k)), with k below the `synchronization threshold,' a constant that admits a simple expression depending on the channel. This constant is the same as the one that characterizes the limit for reliable asynchronous communication, as was recently reported by the authors. If k exceeds the synchronization threshold, any decoder, sequential or non-sequential, locates the sync pattern with an error that tends to one as N tends to infinity. Hence, a sequential decoder can locate a sync pattern as well as the (non-sequential) maximum likelihood decoder that operates on the basis of output sequences of maximum length A+N-1, but with much fewer observations.; Comment: 6 pages

Constraining white dwarf viscosity through tidal heating in detached binary systems

Dall'Osso, Simone; Rossi, Elena Maria
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 07/08/2013
Relevância na Pesquisa
17.29%
Although the internal structure of white dwarfs is considered to be generally well understood, the source and entity of viscosity is still very uncertain. We propose here to study white dwarf viscous properties using short period (< 1 hr), detached white dwarf binaries, such as the newly discovered ~12.8 min system. These binaries are wide enough that mass transfer has not yet started but close enough that the least massive component is subject to a measurable tidal deformation. The associated tidal torque transfers orbital energy, which is partially converted into heat by the action of viscosity within the deformed star. As a consequence, its outer non-degenerate layers expand, and the star puffs up. We self-consistently calculate the fractional change in radius, and the degree of asynchronism (ratio of stellar to orbital spin) as a function of the viscous time. Specializing our calculations to J0651, we find that the discrepancy between the measured radius of the secondary star and He white dwarf model predictions can be interpreted as tidal inflation if the viscous timescale is either ~2 10^5 yr or ~10^4 yr. Such values point to a non-microscopic viscosity, possibly given by tidally induced turbulence, or by magnetic field stresses with a magnetic field strength of 10-100 Gauss. Fortunately...

Asynchronous Communication: Capacity Bounds and Suboptimality of Training

Tchamkerten, Aslan; Chandar, Venkat; Wornell, Gregory
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
17.29%
Several aspects of the problem of asynchronous point-to-point communication without feedback are developed when the source is highly intermittent. In the system model of interest, the codeword is transmitted at a random time within a prescribed window whose length corresponds to the level of asynchronism between the transmitter and the receiver. The decoder operates sequentially and communication rate is defined as the ratio between the message size and the elapsed time between when transmission commences and when the decoder makes a decision. For such systems, general upper and lower bounds on capacity as a function of the level of asynchronism are established, and are shown to coincide in some nontrivial cases. From these bounds, several properties of this asynchronous capacity are derived. In addition, the performance of training-based schemes is investigated. It is shown that such schemes, which implement synchronization and information transmission on separate degrees of freedom in the encoding, cannot achieve the asynchronous capacity in general, and that the penalty is particularly significant in the high-rate regime.; Comment: 27 pages, 8 figures, submitted to the IEEE Transactions on Information Theory

Synchronism vs Asynchronism in Boolean networks

Noual, Mathilde
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.29%
We show that synchronism can significantly impact on network behaviours, in particular by filtering unstable attractors induced by a constraint of asynchronism. We investigate and classify the different possible impacts that an addition of synchronism may have on the behaviour of a Boolean automata network. We show how these relate to some strong specific structural properties, thus supporting the idea that for most networks, synchronism only shortcuts asynchronous trajectories. We end with a discussion on the close relation that apparently exists between sensitivity to synchronism and non-monotony.

Progresses in the Analysis of Stochastic 2D Cellular Automata: a Study of Asynchronous 2D Minority

Regnault, Damien; Schabanel, Nicolas; Thierry, Éric
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/06/2007
Relevância na Pesquisa
17.29%
Cellular automata are often used to model systems in physics, social sciences, biology that are inherently asynchronous. Over the past 20 years, studies have demonstrated that the behavior of cellular automata drastically changed under asynchronous updates. Still, the few mathematical analyses of asynchronism focus on one-dimensional probabilistic cellular automata, either on single examples or on specific classes. As for other classic dynamical systems in physics, extending known methods from one- to two-dimensional systems is a long lasting challenging problem. In this paper, we address the problem of analysing an apparently simple 2D asynchronous cellular automaton: 2D Minority where each cell, when fired, updates to the minority state of its neighborhood. Our experiments reveal that in spite of its simplicity, the minority rule exhibits a quite complex response to asynchronism. By focusing on the fully asynchronous regime, we are however able to describe completely the asymptotic behavior of this dynamics as long as the initial configuration satisfies some natural constraints. Besides these technical results, we have strong reasons to believe that our techniques relying on defining an energy function from the transition table of the automaton may be extended to the wider class of threshold automata.

Communication under Strong Asynchronism

Tchamkerten, Aslan; Chandar, Venkat; Wornell, Gregory
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 31/07/2007
Relevância na Pesquisa
27.83%
We consider asynchronous communication over point-to-point discrete memoryless channels. The transmitter starts sending one block codeword at an instant that is uniformly distributed within a certain time period, which represents the level of asynchronism. The receiver, by means of a sequential decoder, must isolate the message without knowing when the codeword transmission starts but being cognizant of the asynchronism level A. We are interested in how quickly can the receiver isolate the sent message, particularly in the regime where A is exponentially larger than the codeword length N, which we refer to as `strong asynchronism.' This model of sparse communication may represent the situation of a sensor that remains idle most of the time and, only occasionally, transmits information to a remote base station which needs to quickly take action. The first result shows that vanishing error probability can be guaranteed as N tends to infinity while A grows as Exp(N*k) if and only if k does not exceed the `synchronization threshold,' a constant that admits a simple closed form expression, and is at least as large as the capacity of the synchronized channel. The second result is the characterization of a set of achievable strictly positive rates in the regime where A is exponential in N...

Coal Enterprise Management and Asynchronism of Return

Qiao, Kenan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/11/2012
Relevância na Pesquisa
27.29%
For researching the association between coal enterprise management and return in financial market, this paper applies the method of time difference relevance and PageRank method to seek the leader-index of a stock set containing 21 coal enterprises in A-share market and score those stocks. Based on the return in 2011, the asynchronism of the return series is revealed and presents a hierarchical structure of our stock set. Finally, we compare the result with the firm-level variables and discuss the relation between them. The results show that those large coal enterprises with a good management condition always present an antecedence of stock return; there is a significant positive association between company scale and the score given by PageRank method.

Modified CRB for Location and Velocity Estimation using Signals of Opportunity

Leng, Mei; Tay, Wee Peng; See, Chong Meng Samson; Razul, Sirajudeen Gulam; Win, Moe Z.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
17.29%
We consider the problem of localizing two sensors using signals of opportunity from beacons with known positions. Beacons and sensors have asynchronous local clocks or oscillators with unknown clock skews and offsets. We model clock skews as random, and analyze the biases introduced by clock asynchronism in the received signals. By deriving the equivalent Fisher information matrix for the modified Bayesian Cram\'er-Rao lower bound (CRLB) of sensor position and velocity estimation, we quantify the errors caused by clock asynchronism.

Stochastic Minority on Graphs

Rouquier, Jean-Baptiste; Regnault, Damien; Thierry1, Eric
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/11/2010
Relevância na Pesquisa
17.62%
Cellular automata have been mainly studied on very regular graphs carrying the vertices (like lines or grids) and under synchronous dynamics (all vertices update simultaneously). In this paper, we study how the asynchronism and the graph act upon the dynamics of the classical Minority rule. Minority has been well-studied for synchronous updates and is thus a reasonable choice to begin with. Yet, beyond its apparent simplicity, this rule yields complex behaviors when asynchronism is introduced. We investigate the transitory part as well as the asymptotic behavior of the dynamics under full asynchronism (also called sequential: only one random vertex updates at each time step) for several types of graphs. Such a comparative study is a first step in understanding how the asynchronous dynamics is linked to the topology (the graph). Previous analyses on the grid [1,2] have observed that Minority seems to induce fast stabilization. We investigate here this property on arbitrary graphs using tools such as energy, particles and random walks. We show that the worst case convergence time is, in fact, strongly dependent on the topology. In particular, we observe that the case of trees is non trivial.

Astrophysical Unipolar Inductors Powered by Gravitational Wave Emission

Dall'Osso, Simone; Israel, Gian Luca; Stella, Luigi
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/07/2005
Relevância na Pesquisa
17.29%
We consider the Unipolar Inductor Model (Goldreich & Lynden-Bell 1969) applied to Double Degenerate Binaries (DDBs) with ultrashort periods (Wu et al. 2002). In this model a magnetized primary white dwarf has a slight asynchronism between its spin and orbital motion, so that the (non-magnetic) secondary experiences a motional electric field when moving through the primary field lines. This induces a current flow between the two stars and provides an electric spin-orbit coupling mechanism for the primary. We study the combined effect of Gravitational Wave emission and electric spin-orbit coupling on the evolution of the primary degree of asynchronism and the associated rate of electric current dissipation in such systems, assuming that the primary's spin is not affected by any other mechanisms. In particular, we show that in ultrashort period binaries the emission of GW pumps energy in the electric circuit as to keep it steadily active. This happens despite the fact that spin-orbit coupling can rapidly synchronize the primary, because GW represent a slow desynchronizing mechanism steadily substracting orbital angular momentum to the system. A slightly asynchronous steady-state is thus achieved, determined by the balance between these two competing effects. This can be shown to correspond to a condition where the total available electric energy is conserved...