Optimizing Connectivity through Network Gradients for the Restricted Boltzmann Machine

Leveraging sparse networks to connect successive layers in deep neural networks has recently been shown to provide benefits to large scale state-of-the-art models. However, network connectivity also plays a significant role on the learning performance of shallow networks, such as the classic Restricted Boltzmann Machines (RBM). Efficiently finding sparse connectivity patterns that improve the learning performance of shallow networks is a fundamental problem. While recent principled approaches explicitly include network connections as model parameters that must be optimized, they often rely on explicit penalization or have network sparsity as a hyperparameter. This work presents a method to find optimal connectivity patterns for RBMs based on the idea of network gradients (NCG): computing the gradient of every possible connection, given a specific connection pattern, and using the gradient to drive a continuous connection strength parameter that in turn is used to determine the connection pattern. Thus, learning RBM parameters and learning network connections is truly jointly performed, albeit with different learning rates, and without changes to the objective function. The method is applied to the MNIST and other datasets showing that better RBM models are found for the benchmark tasks of sample generation and input classification. Results also show that NCG is robust to network initialization, both adding and removing network connections while learning

Spillover and diffraction sidelobe contamination in a double-shielded experiment for mapping Galactic synchrotron emission

We have analyzed observations from a radioastronomical experiment to survey the sky at decimetric wavelengths along with feed pattern measurements in order to account for the level of ground contamination entering the sidelobes. A major asset of the experiment is the use of a wire mesh fence around the rim-halo shielded antenna with the purpose of levelling out and reducing this source of stray radiation for zenith-centered 1-rpm circular scans. We investigate the shielding performance of the experiment by means of a geometric diffraction model in order to predict the level of the spillover and diffraction sidelobes in the direction of the ground. Using 408 MHz and 1465 MHz feed measurements, the model shows how a weakly-diffracting and unshielded antenna configuration becomes strongly-diffracting and double-shielded as far-field diffraction effects give way to near-field ones. Due to the asymmetric response of the feeds, the orientation of their radiation fields with respect to the secondary must be known a priori before comparing model predictions with observational data. By adjusting the attenuation coefficient of the wire mesh the model is able to reproduce the amount of differential ground pick-up observed during test measurements at 1465 MHz.Comment: 14 pages, 17 eps + 1 gif figures and 4 Tables. Accepted for publication in A&AS. Fig.7 available at full resolution from http://www.das.inpe.br/~tello/publications.ht

Massive binaries and the enrichment of the interstellar medium in globular clusters

Abundance anomalies observed in globular cluster stars indicate pollution with material processed by hydrogen burning. Two main sources have been suggested: asymptotic giant branch stars and massive stars rotating near the break-up limit. We discuss the potential of massive binaries as an interesting alternative source of processed material. We discuss observational evidence for mass shedding from interacting binaries. In contrast to the fast, radiatively driven winds of massive stars, this material is typically ejected with low velocity. We expect that it remains inside the potential well of a globular cluster and becomes available for the formation or pollution of a second generation of stars. We estimate that the amount of processed low-velocity material that can be ejected by massive binaries is larger than the contribution of two previously suggested sources combined.Comment: 6 pages, 2 figures, to appear in the proceedings of IAU Symposium 266, "Star Clusters - Basic Galactic Building Blocks throughout Time and Space", 10-14 August 2009, at the general assembly in Rio de Janeiro, Brazi

Water quality-quantity evaluation of the Ribeirão das Posses Watershed, Brazil, applying the AgES-W model.

Southeastern Brazil is under a period of drought that has impacted the conservation of watersheds and the management of water quality and quantity for agricultural and urban demands. In this context agro-hydrological modeling tools can generate information of water response over time in response to climate and landuse changes. A 12-km2 watershed which has suffered from anthropogenic activities is the Ribeirão das Posses watershed that is located in the extreme south of Minas Gerais State and is a headwater catchment of the Jaguari river, one of the contributing rivers of the Cantareira Reservoir Complex in the state of São Paulo. This watershed had its landscape changed over the last century from native forests to more homogeneous vegetation for pastures and small crops and some forest plantations fragments with eucalyptus. Currently, the Conservative Waters project has planted some small areas with vegetation of native species, especially where there are springs and at the top of the hills, in order to recover degraded areas and improve the hydrogeochemistry in this study basin. In this context, the AgroEcoSystem-Watershed (AgES-W) model is presented to simulate the water movement and storage in agricultural watersheds with different spatial resolutions of land areas or hydrological responses units. The objectives are to evaluate the quality and quantity of water in Ribeirão das Posses Basin using measured data, then simulate these responses in space and time to test the AgES-W model. The period chosen for research was from 2011 to 2015, because the water quality data were collected during this period. The answers that we hope to find out are: How well does the AgES-W model simulate this Brazilian watershed in the tropics? What are the future prospects of the quality and quantity of water in this basin? The results will help to guide hydrological simulations in similar tropical environments in Brazil in this and other agricultural watersheds with AgES-W

Níveis de fósforo, potássio e calcario para o cultivo de soja em solos de campos cerrados do Amapá.

O Amapá possui cerca de um milhão de hectares de áreas de cerrado. Essas áreas, embora sejam potencialmente capazes de serem aproveitadas para produzir alimentos, apresentam limitações de fertilidade, especialmente daqueles elementos indispensaveis ao desenvolvimento das plantas. Assim, para que essas áreas sejam ocupadas de forma racional, e de fundamental importância o desenvolvimento de pesquisas que possam tornar esse ecossistema viavel, bem como a seleção de espécies potencialmente capazes de se adaptarem a essas condições edafo-climáticas. Nesse aspecto a soja aparece como uma provavel alternativa agroeconomica.bitstream/item/65027/1/AP-1984-niveis-fosforo-potassio-calcario.pd

Comportamento produtivo de cultivares de soja em área de cerrado do Amapá.

A agricultura amapaense, voltada para a produção de alimentos, vem sendo desenvolvida, predominantemente, em solos de área de mata e de capoeira de terra firme e, em menor escala, em áreas de várzeas. Por outro lado, os campos cerrados do território, que representam cerca de um milhão de hectares, tem sido aproveitados basicamente para florestamento e com pecuária extensiva, apesar de apresentarem condições físicas favoraveis a implantação de cultivos com espécies produtoras de alimentos.bitstream/item/65017/1/AP-1984-comportamento-produtivo-cultivares-soja.pd

Características agroclimáticas do município de Paragominas.

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Aspectos biológicos do parasitóide Campolus flavicincta (Ashmead) criados em lagartas de Spodoptera frugiperda (Smith).

Estudou-se em laboratorio, aspectos biologicos do parasitoide Campoletis flavicincta (Ashmead) utilizando como hospedeiro larvas de Spodoptera frugiperda (Smith). Dez casais recem-nascidos de C. flavicincta foram individualizados no interior de vidros transparentes, (9,5 cm de diametro x 22 cm de altura) cobertos com um tecido fino, com solucao acucarada enriquecida com acido ascorbico. Sob condicoes de temperatura de 25 +/_ 2oC, umidade relativa de 70 +/- 10% e fotofase de 12 horas, cada casal recebeu diariamente cerca de 50 lagartas de tres dias de idade da especie S. frugiperda. Apos cada periodo de parasitismo as larvas foram individualizadas em copos plasticos contendo dieta artificial. O ciclo biologico total do parasitoide foi de 19,3 dias, sendo de 12,1 dias o periodo de ovo-larva e 7,2 dias o periodo de pupa. O peso medio da pupas foi de 8,3mg. A longevidade dos adultos foi em media 29,3 dias para os machos e 23,3 para as femeas. O periodo de parasitismo foi de 25 dias, com uma media de 18 lagartas parasitadas por dia. Houve predominancia de machos, com uma razao sexual de 0,15