Top-down segmentation of non-rigid visual objects using derivative-based search on sparse manifolds

The solution for the top-down segmentation of non rigid visual objects using machine learning techniques is generally regarded as too complex to be solved in its full generality given the large dimensionality of the search space of the explicit representation of the segmentation contour. In order to reduce this complexity, the problem is usually divided into two stages: rigid detection and non-rigid segmentation. The rationale is based on the fact that the rigid detection can be run in a lower dimensionality space (i.e., less complex and faster) than the original contour space, and its result is then used to constrain the non-rigid segmentation. In this paper, we propose the use of sparse manifolds to reduce the dimensionality of the rigid detection search space of current state-of-the-art top-down segmentation methodologies. The main goals targeted by this smaller dimensionality search space are the decrease of the search running time complexity and the reduction of the training complexity of the rigid detector. These goals are attainable given that both the search and training complexities are function of the dimensionality of the rigid search space. We test our approach in the segmentation of the left ventricle from ultrasound images and lips from frontal face images. Compared to the performance of state-of-the-art non-rigid segmentation system, our experiments show that the use of sparse manifolds for the rigid detection leads to the two goals mentioned above. © 2013 IEEE.Jacinto C. Nascimento, Gustavo Carneirohttp://www.pamitc.org/cvpr13

Quasi-Topological Field Theories in Two Dimensions as Soluble Models

We study a class of lattice field theories in two dimensions that includes gauge theories. Given a two dimensional orientable surface of genus $g$, the partition function $Z$ is defined for a triangulation consisting of $n$ triangles of area $\epsilon$. The reason these models are called quasi-topological is that $Z$ depends on $g$, $n$ and $\epsilon$ but not on the details of the triangulation. They are also soluble in the sense that the computation of their partition functions can be reduced to a soluble one dimensional problem. We show that the continuum limit is well defined if the model approaches a topological field theory in the zero area limit, i.e., $\epsilon \to 0$ with finite $n$. We also show that the universality classes of such quasi-topological lattice field theories can be easily classified. Yang-Mills and generalized Yang-Mills theories appear as particular examples of such continuum limits.Comment: 23 pages, 16 figures, uses psbox.te

Equality of opportunity and educational achievement in Portugal

Portugal has one of the highest levels of income inequality in Europe, and low wages and unemployment are concentrated among low skill individuals. Education is an important determinant of inequality. However, there are large differences in the educational attainment of different individuals in the population, and the sources of these differences emerge early in the life-cycle when families play a central role in individual development. We estimate that most of the variance of school achievement at age 15 is explained by family characteristics. Observed school inputs explain very little of adolescent performance. Children from highly educated parents benefit of rich cultural environments in the home and become highly educated adults. Education policy needs to be innovative: (1) it needs to explicitly recognize the fundamental long run role of families on child development; (2) it needs to acknowledge the failure of traditional input based policies

Evidence of Two Distinct Dynamic Critical Exponents in Connection with Vortex Physics

The dynamic critical exponent $z$ is determined from numerical simulations for the three-dimensional (3D) lattice Coulomb gas (LCG) and the 3D XY models with relaxational dynamics. It is suggested that the dynamics is characterized by two distinct dynamic critical indices $z_0$ and $z$ related to the divergence of the relaxation time $\tau$ by $\tau\propto \xi^{z_0}$ and $\tau\propto k^{-z}$, where $\xi$ is the correlation length and $k$ the wavevector. The values determined are $z_0\approx 1.5$ and $z\approx 1$ for the 3D LCG and $z_0\approx 1.5$ and $z\approx 2$ for the 3D XY model. It is argued that the nonlinear $IV$ exponent relates to $z_0$, whereas the usual Hohenberg-Halperin classification relates to $z$. Possible implications for the interpretation of experiments are pointed out. Comparisons with other existing results are discussed.Comment: to appear in PR

Evolution of density perturbations in decaying vacuum cosmology: The case of non-zero perturbations in the cosmological term

We extend the results of a previous paper where a model of interacting dark energy, with a cosmological term decaying linearly with the Hubble parameter, is tested against the observed mass power spectrum. In spite of the agreement with observations of type Ia supernovas, baryonic acoustic oscillations and the cosmic microwave background, we had shown previously that no good concordance is achieved if we include the mass power spectrum. However, our analysis was based on the ad hoc assumption that the interacting cosmological term is strictly homogeneous. Now we perform a more complete analysis, by perturbing such a term. Although our conclusions are still based on a particular, scale invariant choice of the primordial spectrum of dark energy perturbations, we show that a cosmological term decaying linearly with the Hubble parameter is indeed disfavored as compared to the standard model.Comment: Version accepted for publication in Physical Review

Non-singular inflation with vacuum decay

On the basis of a semi-classical analysis of vacuum energy in an expanding spacetime, we describe a non-singular cosmological model in which the vacuum density decays with time, with a concomitant production of matter. During an infinitely long period we have an empty, inflationary universe, with H \approx 1. This primordial era ends in a fast phase transition, during which H and \Lambda decrease to nearly zero in a few Planck times, with release of a huge amount of radiation. The late-time scenario is similar to the standard model, with the radiation phase followed by a long dust era, which tends asymptotically to a de Sitter universe, with vacuum dominating again. An analysis of the redshift-distance relation for supernovas Ia leads to cosmological parameters in agreement with other current estimations.Comment: Work presented at IRGAC 2006, Barcelona, July 11-15 2006. To appear in a special issue of Journal of Physics

Host status of different crops for Meloidogyne ethiopica control.

Made available in DSpace on 2011-04-09T16:14:48Z (GMT). No. of bitstreams: 1 limahost.pdf: 955558 bytes, checksum: 19e5536e1387456bbe042fef85951be0 (MD5) Previous issue date: 2009-10-2

Single-phase series active conditioner for the compensation of voltage harmonics, sags, swell and flicker

Simulation and experimental results shown on this paper describes the performance of a developed Single-Phase Series Active Conditioner that regulates the voltage being delivered to a load. This Custom Power device is a solution for power quality issues related with voltage amplitude variations, which are responsible for innumerous flaws in industrial processes which brings with it high financial losses. The Single-Phase Series Active Conditioner is a back-to-back converter, composed by two power converters sharing a common DC link. One of the converters is series connected to the electrical grid, whereas the other one is shunt connected. The first is used to compensate load voltage, and the second to regulate the DC link voltage. This paper shows the results obtained with the Series Active Conditioner in Sag, Swell and Flicker events, and also Voltage Harmonics compensation, in order to deliver to the load a sinusoidal voltage, at nominal amplitude.Fundação para a Ciência e Tecnologia (FCT

Produção e composição bromatológica do capim sudão e de seus híbridos (BRS 800 e AG 2501) com 42 E 56 dias.

Um experimento foi conduzido com o objetivo de avaliar a produtividade e composicao bromatologica do capim Sudao e os seus hibridos com o sorgo (BRS 800 e Ag 2501) colhidos aos 42 e 56 dias de crescimento. O delineamento foi blocos casualizados com tres repeticoes. Aos 42 dias todas plantas estavam no estadio vegetativo e aos 56 dias observou-se 38,5; 78,3 e 46,8% de floracao do capim Sudao, BRS 800 e Ag 2501, respectivamente. A producao (kg) de materia seca por hectare para o capim Sudao, BRS 800 e AG 2501 foram: 3,56; 4,18 e 4,43; respectivamente, sendo a do AG 2501 superior (P0,05) a do BRS 800. Os teores (%) de materia seca, FDN e FDA foram semelhantes (P>0,05) para os tres cultivares , sendo 13,49; 70,26 e 40,72 respectivamente. O teor de proteina bruta do BRS 800 (11,00%) foi superior (P0,05) ao do capim Sudao. A producao de materia seca (t/ha), teores (%) de materia seca, proteina bruta e FDN foram diferentes (P0,05)

Host status of fruit plants to meloidogyne enterolobii.

Edição dos Proceedings do 6th International Congress of Nematology, Cape Town, South Africa, May 2014