Towards an inclusion driven learning of Bayesian Networks

Two or more Bayesian Networks are Markov equivalent when their corresponding acyclic digraphs encode the same set of conditional independence (= CI) restrictions. Therefore, the search space of Bayesian Networks may be organized in classes of equivalence, where each of them consists of a particular set of CI restrictions. The collection of sets of CI restrictions obeys a partial order, the graphical Markov model inclusion partial order, or inclusion order for short. This paper discusses in depth the role that inclusion order plays in learning the structure of Bayesian networks. We prove that under very special conditions the traditional hill-climber always recovers the right structure. Moreover, we extend the recent experimental results presented in (Kocka and Castelo, 2001). We show how learning algorithms for Bayesian Networks, that take the inclusion order into account, perform better than those that do not, and we introduce two new ones in the context of heuristic search and the MCMC method

Integration of touch attention mechanisms to improve the robotic haptic exploration of surfaces

This text presents the integration of touch attention mechanisms to improve the efficiency of the action-perception loop, typically involved in active haptic exploration tasks of surfaces by robotic hands. The progressive inference of regions of the workspace that should be probed by the robotic system uses information related with haptic saliency extracted from the perceived haptic stimulus map (exploitation) and a “curiosity”-inducing prioritisation based on the reconstruction's inherent uncertainty and inhibition-of-return mechanisms (exploration), modulated by top-down influences stemming from current task objectives, updated at each exploration iteration. This work also extends the scope of the top-down modulation of information presented in a previous work, by integrating in the decision process the influence of shape cues of the current exploration path. The Bayesian framework proposed in this work was tested in a simulation environment. A scenario made of three different materials was explored autonomously by a robotic system. The experimental results show that the system was able to perform three different haptic discontinuity following tasks with a good structural accuracy, demonstrating the selectivity and generalization capability of the attention mechanisms. These experiments confirmed the fundamental contribution of the haptic saliency cues to the success and accuracy of the execution of the tasks

Influência de diferentes sítios de crescimento sobre a qualidade da madeira de Pinus taeda.

O presente trabalho analisa os efeitos de diferentes sítios de crescimento na qualidade da madeira de Pinus taeda, além de testar a técnica não-destrutiva de aplicação de ondas de tensão para estimativa das características da madeira. Foram analisados três sítios com árvores de 14, 16 e 18 anos de idade. Para a caracterização do sítio, foram coletadas amostras de solo indeformadas e compostas. Em cada sítio foram selecionadas cinco árvores. Com elas ainda em pé, foram realizadas medições do tempo de propagação de ondas de tensão. Também foram medidos a altura total e comercial e o diâmetro à altura do peito, e retirados discos em cinco posições ao longo do fuste. Posteriormente, nas toras recém-abatidas, efetuaram-se novamente as medições do tempo de propagação das ondas de tensão, além de serem coletadas acículas do terço médio da copa de cada árvore. De maneira geral, as madeiras provenientes de sítios com taxa de crescimento elevado apresentaram maiores valores para massa específica, fibras mais curtas, mais largas, com diâmetros maiores e paredes mais espessas ? conseqüentemente, maiores valores para índice de Runkel e fração parede e menores valores para coeficiente de flexibilidade e índice de enfeltramento. Correlações significativas foram detectadas, indicando que a técnica não-destrutiva pode ser empregada para determinação indireta dessas características

Out-of-phase oscillation between superfluid and thermal components for a trapped Bose condensate under oscillatory excitation

The vortex nucleation and the emergence of quantum turbulence induced by oscillating magnetic fields, introduced by Henn E A L, et al. 2009 (Phys. Rev. A 79, 043619) and Henn E A L, et al. 2009 (Phys. Rev. Lett. 103, 045301), left a few open questions concerning the basic mechanisms causing those interesting phenomena. Here, we report the experimental observation of the slosh dynamics of a magnetically trapped $^{87}$Rb Bose-Einstein condensate (BEC) under the influence of a time-varying magnetic field. We observed a clear relative displacement in between the condensed and the thermal fraction center-of-mass. We have identified this relative counter move as an out-of-phase oscillation mode, which is able to produce ripples on the condensed/thermal fractions interface. The out-of-phase mode can be included as a possible mechanism involved in the vortex nucleation and further evolution when excited by time dependent magnetic fields.Comment: 5 pages, 5 figures, 25 reference

Perfil dos consumidores de hortaliças da cidade de Santo Antônio do Descoberto - GO.

Made available in DSpace on 2011-04-09T16:13:21Z (GMT). No. of bitstreams: 1 castelobrancoperfil.pdf: 583251 bytes, checksum: 6323d57fe63330e5c4179f9b4cdaf008 (MD5) Previous issue date: 2006-11-1

Three-vortex configurations in trapped Bose-Einstein condensates

We report on the creation of three-vortex clusters in a $^{87}Rb$ Bose-Einstein condensate by oscillatory excitation of the condensate. This procedure can create vortices of both circulation, so that we are able to create several types of vortex clusters using the same mechanism. The three-vortex configurations are dominated by two types, namely, an equilateral-triangle arrangement and a linear arrangement. We interpret these most stable configurations respectively as three vortices with the same circulation, and as a vortex-antivortex-vortex cluster. The linear configurations are very likely the first experimental signatures of predicted stationary vortex clusters.Comment: 4 pages, 4 figure