An approach for the detection of point-sources in very high resolution microwave maps

This paper deals with the detection problem of extragalactic point-sources in multi-frequency, microwave sky maps that will be obtainable in future cosmic microwave background radiation (CMB) experiments with instruments capable of very high spatial resolution. With spatial resolutions that can be of order of 0.1-1.0 arcsec or better, the extragalactic point-sources will appear isolated. The same holds also for the compact structures due to the Sunyaev-Zeldovich (SZ) effect (both thermal and kinetic). This situation is different from the maps obtainable with instruments as WMAP or PLANCK where, because of the smaller spatial resolution (approximately 5-30 arcmin), the point-sources and the compact structures due to the SZ effect form a uniform noisy background (the "confusion noise"). Hence, the point-source detection techniques developed in the past are based on the assumption that all the emissions that contribute to the microwave background can be modeled with homogeneous and isotropic (often Gaussian) random fields and make use of the corresponding spatial power-spectra. In the case of very high resolution observations such an assumption cannot be adopted since it still holds only for the CMB. Here, we propose an approach based on the assumption that the diffuse emissions that contribute to the microwave background can be locally approximated by two-dimensional low order polynomials. In particular, two sets of numerical techniques are presented containing two different algorithms each. The performance of the algorithms is tested with numerical experiments that mimic the physical scenario expected for high Galactic latitude observations with the Atacama Large Millimeter/Submillimeter Array (ALMA).Comment: Accepted for publication on "Astronomy & Astrophysics". arXiv admin note: substantial text overlap with arXiv:1206.4536 Replaced version is the accepted one and published in A&

Characterizing Weak Chaos using Time Series of Lyapunov Exponents

We investigate chaos in mixed-phase-space Hamiltonian systems using time series of the finite- time Lyapunov exponents. The methodology we propose uses the number of Lyapunov exponents close to zero to define regimes of ordered (stickiness), semi-ordered (or semi-chaotic), and strongly chaotic motion. The dynamics is then investigated looking at the consecutive time spent in each regime, the transition between different regimes, and the regions in the phase-space associated to them. Applying our methodology to a chain of coupled standard maps we obtain: (i) that it allows for an improved numerical characterization of stickiness in high-dimensional Hamiltonian systems, when compared to the previous analyses based on the distribution of recurrence times; (ii) that the transition probabilities between different regimes are determined by the phase-space volume associated to the corresponding regions; (iii) the dependence of the Lyapunov exponents with the coupling strength.Comment: 8 pages, 6 figure

Desenvolvimento de um ceifador enleirador de plantas de feijoeiro.

Este trabalho teve o objetivo de desenvolver um ceifador enleirador de plantas de feijoeiro simplificado, de pequeno porte para ser acionado por um trator médio e com capacidade de ceifar as plantas rente ao solo.CONAFE

Zoneamento agroclimático da cultura do feijoeiro para o Estado de Alagoas.

Neste estudo foi utilizado o modelo SARRA (Sistema de Análise Regional dos Riscos Agroclimáticos).bitstream/CNPAF/25034/1/comt_122.pd

Zoneamento agroclimático da cultura do feijoeiro para o Estado de Pernambuco.

Neste estudo foi utilizado o modelo SARRA (Sistema de Análise Regional dos Riscos Agroclimáticos).bitstream/CNPAF/25035/1/comt_123.pd