Exploiting Resolution-based Representations for MaxSAT Solving

Most recent MaxSAT algorithms rely on a succession of calls to a SAT solver in order to find an optimal solution. In particular, several algorithms take advantage of the ability of SAT solvers to identify unsatisfiable subformulas. Usually, these MaxSAT algorithms perform better when small unsatisfiable subformulas are found early. However, this is not the case in many problem instances, since the whole formula is given to the SAT solver in each call. In this paper, we propose to partition the MaxSAT formula using a resolution-based graph representation. Partitions are then iteratively joined by using a proximity measure extracted from the graph representation of the formula. The algorithm ends when only one partition remains and the optimal solution is found. Experimental results show that this new approach further enhances a state of the art MaxSAT solver to optimally solve a larger set of industrial problem instances

The first analytical expression to estimate photometric redshifts suggested by a machine

We report the first analytical expression purely constructed by a machine to determine photometric redshifts ($z_{\rm phot}$) of galaxies. A simple and reliable functional form is derived using $41,214$ galaxies from the Sloan Digital Sky Survey Data Release 10 (SDSS-DR10) spectroscopic sample. The method automatically dropped the $u$ and $z$ bands, relying only on $g$, $r$ and $i$ for the final solution. Applying this expression to other $1,417,181$ SDSS-DR10 galaxies, with measured spectroscopic redshifts ($z_{\rm spec}$), we achieved a mean $\langle (z_{\rm phot} - z_{\rm spec})/(1+z_{\rm spec})\rangle\lesssim 0.0086$ and a scatter $\sigma_{(z_{\rm phot} - z_{\rm spec})/(1+z_{\rm spec})}\lesssim 0.045$ when averaged up to $z \lesssim 1.0$. The method was also applied to the PHAT0 dataset, confirming the competitiveness of our results when faced with other methods from the literature. This is the first use of symbolic regression in cosmology, representing a leap forward in astronomy-data-mining connection.Comment: 6 pages, 4 figures. Accepted for publication in MNRAS Letter

Controlled Shock Shells and Intracluster Fusion Reactions in the Explosion of Large Clusters

The ion phase-space dynamics in the Coulomb explosion of very large ($\sim 10^6 - 10^7$ atoms) deuterium clusters can be tailored using two consecutive laser pulses with different intensities and an appropriate time delay. For suitable sets of laser parameters (intensities and delay), large-scale shock shells form during the explosion, thus highly increasing the probability of fusion reactions within the single exploding clusters. In order to analyze the ion dynamics and evaluate the intracluster reaction rate, a one-dimensional theory is used, which approximately accounts for the electron expulsion from the clusters. It is found that, for very large clusters (initial radius $\sim$ 100 nm), and optimal laser parameters, the intracluster fusion yield becomes comparable to the intercluster fusion yield. The validity of the results is confirmed with three-dimensional particle-in-cell simulations.Comment: 25 pages, 11 figures, to appear in Physical Review

BRESEX: On board supervision, basic architecture and preliminary aspects for payload and space shuttle interface

Data relative to the on board supervision subsystem are presented which were considered in a conference between INPE and NASA personnel, with the purpose of initiating a joint effort leading to the implementation of the Brazilian remote sensing experiment - (BRESEX). The BRESEX should consist, basically, of a multispectral camera for Earth observation, to be tested in a future space shuttle flight

Modelling radiation emission in the transition from the classical to the quantum regime

An emissivity formula is derived using the generalised Fermi-Weizacker-Williams method of virtual photons which accounts for the recoil the charged particle experiences as it emits radiation. It is found that through this derivation the formula obtained by Sokolov et al using QED perturbation theory is recovered. The corrected emissivity formula is applied to nonlinear Thomson scattering scenarios in the transition from the classical to the quantum regime, for small values of the nonlinear quantum parameter \chi. Good agreement is found between this method and a QED probabilistic approach for scenarios where both are valid. In addition, signatures of the quantum corrections are identified and explored.Comment: 11 pages, 4 figures, submitted for publicatio

Análise do desempenho reprodutivo de cinco grupos genéticos Holandês x Gir no Brasil.

Tendo em vista a grande importância dos mestiços Holandês x Gir (HxG) no contexto dos sistemas de produção de leite no Brasil e a íntima relação entre reprodução e a produtividade destes sistemas, foram obtidos registros de partos e datas de nascimento junto à Associação Brasileira de Criadores de Girolando, no intuito de avaliar o desempenho reprodutivo de vários grupos genéticos HxG. Foram analisados 2.630 registros de idade ao primeiro parto (IPP) e 3.853 intervalos entre partos (IEP). Os dados foram analisados através do procedimento GLM do pacote estatístico SAS (2000). As comparações do desempenho dos grupos genéticos foram feitas através de modelos classificatórios incluindo o efeito de grupo genético. Foram feitas estimativas dos efeitos genéticos (diferença aditiva entre Holandês e Gir, dominância e epistático aditivo x aditivo) através de modelos de regressão simplificados. As médias para IPP e IEP foram 1.014,74 ± 2,94 dias e 407,51 ± 1,32 dias, respectivamente. O grupo meio-sangue apresentou desempenho superior (menores IPP e IEP). Foi observada uma tendência de elevação do IEP com a elevação da proporção de genes da raça Holandesa. O efeito de dominância influenciou significativamente as duas características estudadas, enquanto que o efeito de interação epistática do tipo aditivo x aditivo influenciou significativamente apenas a IPP. Os resultados indicaram que a perda por recombinação contribuiu para a alta IPP no grupo 5/8 holandês. ANALYSIS OF REPRODUCTIVE PERFORMANCE OF FIVE HOLSTEIN X GIR GENETIC GROUPS IN BRAZIL. ABSTRACT: Because of importance of Holstein x Gir crosses to milk production systems in Brazil and the close relation between reproduction and productivity in these systems, data of calving and birth date were obtained from Brazilian Association of Girolando Breeders with objective to evaluate the reproductive performance of some grades of Holstein x Gir crosses. 2,630 records of age at first calving (IPP) and 3,853 calving intervals (IEP) were analyzed. Data were analyzed through GLM procedure from the SAS (2000). Classification models including the genetic group effect were used for the comparison of breed group?s performance. Estimates of genetics effects (additive difference between Holstein and Gir, dominance and additive x additive epistatic effects) were made through simplified regression models. The means for age at first calving and calving interval were 1,014.74 ± 2.94 days and 407.51 ± 1.32 days, respectively. The group 1/2 show better performance (smaller IPP and IEP). A tendency of elevation of IEP was observed with the elevation of Holstein genes proportion. The dominance effect influenced significantly both traits analyzed, while the additive x additive epistatic effects significantly influenced only IPP. The results indicated that loss due to recombination contributed to the high IPP in 5/8 group

Using gamma regression for photometric redshifts of survey galaxies

Machine learning techniques offer a plethora of opportunities in tackling big data within the astronomical community. We present the set of Generalized Linear Models as a fast alternative for determining photometric redshifts of galaxies, a set of tools not commonly applied within astronomy, despite being widely used in other professions. With this technique, we achieve catastrophic outlier rates of the order of ~1%, that can be achieved in a matter of seconds on large datasets of size ~1,000,000. To make these techniques easily accessible to the astronomical community, we developed a set of libraries and tools that are publicly available.Comment: Refereed Proceeding of "The Universe of Digital Sky Surveys" conference held at the INAF - Observatory of Capodimonte, Naples, on 25th-28th November 2014, to be published in the Astrophysics and Space Science Proceedings, edited by Longo, Napolitano, Marconi, Paolillo, Iodice, 6 pages, and 1 figur

Dynamics and control of the expansion of finite-size plasmas produced in ultraintense laser-matter interactions

The strong influence of the electron dynamics provides the possibility of controlling the expansion of laser-produced plasmas by appropriately shaping the laser pulse. A simple irradiation scheme is proposed to tailor the explosion of large deuterium clusters, inducing the formation of shock structures, capable of driving nuclear fusion reactions. Such a scenario has been thoroughly investigated, resorting to two- and three-dimensional particle-in-cell simulations. Furthermore, the intricate dynamics of ions and electrons during the collisionless expansion of spherical nanoplasmas has been analyzed in detail using a self-consistent ergodic-kinetic model. This study clarifies the transition from hydrodynamic-like to Coulomb-explosion regimes