7,730 research outputs found
C4.5: um recurso para geração de árvores de decisão.
O Sistema de Indução C4.5. Requerimentos-chave para a utilização do software. Um exemplo ilustrativo. Algumas dicas de uso.bitstream/CNPTIA/9200/1/INSTRTECNICAS7int.pdfAcesso em: 30 maio 2008
Probing quantum fluctuation theorems in engineered reservoirs
Fluctuation Theorems are central in stochastic thermodynamics, as they allow
for quantifying the irreversibility of single trajectories. Although they have
been experimentally checked in the classical regime, a practical demonstration
in the framework of quantum open systems is still to come. Here we propose a
realistic platform to probe fluctuation theorems in the quantum regime. It is
based on an effective two-level system coupled to an engineered reservoir, that
enables the detection of the photons emitted and absorbed by the system. When
the system is coherently driven, a measurable quantum component in the entropy
production is evidenced. We quantify the error due to photon detection
inefficiency, and show that the missing information can be efficiently
corrected, based solely on the detected events. Our findings provide new
insights into how the quantum character of a physical system impacts its
thermodynamic evolution.Comment: 9 pages, 4 figure
Expansivity and Shadowing in Linear Dynamics
In the early 1970's Eisenberg and Hedlund investigated relationships between
expansivity and spectrum of operators on Banach spaces. In this paper we
establish relationships between notions of expansivity and hypercyclicity,
supercyclicity, Li-Yorke chaos and shadowing. In the case that the Banach space
is or (), we give complete characterizations
of weighted shifts which satisfy various notions of expansivity. We also
establish new relationships between notions of expansivity and spectrum.
Moreover, we study various notions of shadowing for operators on Banach spaces.
In particular, we solve a basic problem in linear dynamics by proving the
existence of nonhyperbolic invertible operators with the shadowing property.
This also contrasts with the expected results for nonlinear dynamics on compact
manifolds, illuminating the richness of dynamics of infinite dimensional linear
operators
Emergence of Hierarchy on a Network of Complementary Agents
Complementarity is one of the main features underlying the interactions in
biological and biochemical systems. Inspired by those systems we propose a
model for the dynamical evolution of a system composed by agents that interact
due to their complementary attributes rather than their similarities. Each
agent is represented by a bit-string and has an activity associated to it; the
coupling among complementary peers depends on their activity. The connectivity
of the system changes in time respecting the constraint of complementarity. We
observe the formation of a network of active agents whose stability depends on
the rate at which activity diffuses in the system. The model exhibits a
non-equilibrium phase transition between the ordered phase, where a stable
network is generated, and a disordered phase characterized by the absence of
correlation among the agents. The ordered phase exhibits multi-modal
distributions of connectivity and activity, indicating a hierarchy of
interaction among different populations characterized by different degrees of
activity. This model may be used to study the hierarchy observed in social
organizations as well as in business and other networks.Comment: 13 pages, 4 figures, submitte
Coleta de material de cromossomos utilizando microscópio de força atômica.
bitstream/CNPDIA-2009-09/11835/1/CT75_2006.pd
Imagem por ressonância magnética nuclear: aplicações em amostras de carne.
bitstream/CNPDIA-2010/12629/1/CT103-2009.pd
Tecnologias sociais, TICs e educação: pilares para a construção da Tecnopedia Social Rural - TeSoRu.
O artigo apresenta uma proposta de modelo conceitual para formar uma rede de conhecimento integrada à pesquisa, extensão e ensino visando atender aos agricultores familiares, denominada de Tecnopedia Social Rural (TeSoRu) usando as Tecnologias da Informação e Comunicação (TICs) como instrumento mediador. A partir da ênfase na construção, aperfeiçoamento, captura e disseminação de experiências, saberes, informações e conhecimentos, inerentes às diversas coletividades que integram a rede e das potencialidades inseridas nas TICs, espera-se que a TeSoRu sirva como um canal dinâmico de comunicação e institucionalização de novas inteligibilidades subsidiando a inclusão social e digital no espaço rural .SBIE 2010
Reflexões sobre a implantação de um programa de TI-Verde para a Embrapa: bases conceituais e metodológicas.
A Embrapa Informática Agropecuária, neste documento, oferece sua contribuição trazendo à tona uma reflexão sobre a implementação de um Programa de TI-Verde coorporativo. A ideia central é introduzir essa problemática no escopo das iniciativas de gestão ambiental que vêm sendo exercitadas pela empresa de maneira que sirva como um ponto de partida para se ampliar discussões sobre como a empresa pode produzir uma gestão sustentável dos recursos tecnológicos da informação.bitstream/item/11848/1/doc86.pd
Immunization and Aging: a Learning Process in the Immune Network
The immune system can be thought as a complex network of different
interacting elements. A cellular automaton, defined in shape-space, was
recently shown to exhibit self-regulation and complex behavior and is,
therefore, a good candidate to model the immune system. Using this model to
simulate a real immune system we find good agreement with recent experiments on
mice. The model exhibits the experimentally observed refractory behavior of the
immune system under multiple antigen presentations as well as loss of its
plasticity caused by aging.Comment: 4 latex pages, 3 postscript figures attached. To be published in
Physical Review Letters (Tentatively scheduled for 5th Oct. issue
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