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Search Results: 1 - 10 of 298661 matches for " J. Avila "
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Wavelet Supersede FFT in MB-OFDM: an Effective Cognitive Spectrum Sensing
J. Avila,K. Thenmozhi
Journal of Artificial Intelligence , 2012,
Abstract: The curiosity of human on wireless devices is expanding exorbitantly, emphasizing high data rates and band width requirements. Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) is the technique that victuals high data rate. Studies manifests that most of the licensed bands are not exercised in an efficient way thereby leading to the progression of cognitive radio which allows the secondary users to access and activate the free band of primary users. Moreover, sensing the free holes is the prior concern in CR cycle. With the existence of diverse spectrum sensing methods each with its own pros and cons, this study is mainly subjected about the enhancement of energy detection method owing to its ease, simplicity and monotony. The Fast Fourier Transform (FFT) block of the above method is replaced with Discrete Wavelet Transform (DWT) as it can operate in both time and frequency domains. Four wavelet families are discussed in this study. The results are perceived from the probability of detection (pd) versus Signal to Noise Ratio (SNR) graph.
Reptilia, Squamata, Dipsadidae, Pseudotomodon trigonatus (Leybold, 1873): Distribution extension
Avila, L. J.
Check List , 2009,
Abstract:
Reptilia, Squamata, Colubridae, Liophis sagittifer sagittifer: Distribution extension
Avila, L. J.
Check List , 2009,
Abstract:
Cosmological/Black-Hole Unified Theory as a Constrained System
J. A. Nieto,G. Avila
Physics , 2014,
Abstract: Using a Lagrangian formalism we unify the cosmology and black-hole concepts. Specifically, we identify these two physical scenarios as part of a 2-dimensional metric, which arises from a Lagrangian (with constraints) derived from the Einstein-Hilbert action. In particular, we show that the Friedman-Robertson-Walker cosmological model and the Schwarzschild black-hole solution are both a consequence of a such Lagrangian.
Técnica de Necropsia, Interpretación de Hallazgos Macroscópicos y Toma de Muestras en Mamíferos Silvestres
Jahnier Caicedo,J C Ospina,J Avila
Memorias de la Conferencia Interna en Medicina y Aprovechamiento de Fauna Silvestre, Exótica y no Convencional , 2012,
Abstract: La correcta realización de necropsias y toma de muestras en los animales silvestres de los diferentes sistemas de conservación del país es una herramienta de alta importancia en el manejo epidemiológico de muchas enfermedades. La falta de entrenamiento en las técnicas de necropsia de estos animales dificulta la elaboración de propuestas diagnósticas y de control que repercutan en los problemas sanitarios; por lo cual, se presenta una guía de técnica de necropsia general para mamíferos silvestres con algunas lesiones comunes y la adecuada recolección de muestras para diferentes laboratorios de diagnóstico.
Low $Q^2$ wave-functions of pions and kaons and their parton distribution functions
C. Avila,J. Magnin,J. C. Sanabria
Physics , 2000, DOI: 10.1103/PhysRevD.66.034016
Abstract: We study the low $Q^2$ wave-functions of pions and kaons as an expansion in terms of hadron-like Fock state fluctuations. In this formalism, pion and kaon wave-functions are related one another. Consequently, the knowledge of the pion structure allows the determination of parton distributions in kaons. In addition, we show that the intrinsic (low $Q^2$) sea of pions and kaons are different due to their different valence quark structure. Finally, we analize the feasibility of a method to extract kaon's parton distribution functions within this approach and compare with available experimental data.
Virulence markers and antimicrobial susceptibility of bacteria of the Bacteroides fragilis group isolated from stool of children with diarrhea in S?o Paulo, Brazil
Nakano, Viviane;Avila-Campos, Mario J;
Memórias do Instituto Oswaldo Cruz , 2004, DOI: 10.1590/S0074-02762004000300012
Abstract: bacteroides fragilis has been isolated from several human and non-human monomicrobial and mixed infections. in this study, some virulence markers and the antimicrobial susceptibility of bacteria of the b. fragilis group isolated from children's stools were evaluated. all the 64 isolates showed the following characteristics: capsulated, b-hemolytic, hydrophilic, and serum-resistant. only, 24 (37.5%) strains were resistant at 60oc, for 30 min, and among them, 12 (18.75%) were resistant at 60oc, for 60 min. also, none strain was resistant at 100oc. four strains were able to hemagglutinate erythrocytes and d-mannose, d-galactose, d-arabinose, and d-xylose inhibited hemagglutination in 2 b. fragilis strains (p76a, p76b). the hemagglutination in the strain b. uniformis p3-2 was inhibited by d-xylose and d-galactose. the bft gene detection and the enterotoxin production were observed only in 13 ef-enterotoxigenic species. fragilysin activity was confirmed on ht-29 cells. the antimicrobial determination confirmed that both imipenem and metronidazole were efficient against b. fragilis species; all the strains were resistant to lead and nickel. plasmids of 2.9, 4.4, 4.8, and 8.9 kb were observed in 6 tested strains. these results show the values of the species identification from clinical infections, as well as of the periodic evaluation of the resistance patterns of the b. fragilis group at brazilian medical institutions.
Eikonal zeros in the momentum transfer space from proton-proton scattering: An empirical analysis
R. F. Avila,M. J. Menon
Physics , 2007, DOI: 10.1140/epjc/s10052-008-0542-5
Abstract: By means of improved empirical fits to the differential cross section data on $pp$ elastic scattering at $19.4 \le\sqrt{s}\le 62.5$ GeV and making use of a semi-analytical method, we determine the eikonal in the momentum transfer space (the inverse scattering problem). This method allows the propagation of the uncertainties from the fit parameters up to the extracted eikonal, providing statistical evidence that the imaginary part of the eikonal (real part of the opacity function) presents a zero (change of signal) in the momentum space, at $q^2 \approx 7 \pm 1$ GeV$^2$. We discuss the implication of this change of signal in the phenomenological context, showing that eikonal models with one zero provide good descriptions of the differential cross sections in the full momentum transfer range, but that is not the case for models without zero. Empirical connections between the extracted eikonal and results from a recent global analysis on the proton electric form factor are also discussed, in special the Wu-Yang conjecture. In addition, we present a critical review on the $pp$ differential cross section data presently available at high energies.
Derivative dispersion relations above the physical threshold
R. F. Avila,M. J. Menon
Physics , 2005, DOI: 10.1590/S0103-97332007000300006
Abstract: We discuss some formal and practical aspects related to the replacement of Integral Dispersion Relations (IDR) by derivative forms, without high-energy approximations. We first demonstrate that, for a class of functions with physical interest as forward scattering amplitudes, this replacement can be analytically performed, leading to novel Extended Derivative Dispersion Relations (EDDR), which, in principle, are valid for any energy above the physical threshold. We then verify the equivalence between the IDR and EDDR by means of a popular parametrization for total cross sections from proton-proton and antiproton-proton scattering and compare the results with those obtained through other representations for the derivative relations. Critical aspects on the limitations of the whole analysis, from both formal and practical points of view, are also discussed in some detail.
Critical analysis of derivative dispersion relations at high energies
R. F. Avila,M. J. Menon
Physics , 2003, DOI: 10.1016/j.nuclphysa.2004.08.014
Abstract: We discuss some formal and fundamental aspects related with the replacement of integral dispersion relations by derivative forms, and their practical uses in high energy elastic hadron scattering, in particular $pp$ and $\bar{p}p$ scattering. Starting with integral relations with one subtraction and considering parametrizations for the total cross sections belonging to the class of entire functions in the logarithm of the energy, a series of results is deduced and our main conclusions are the following: (1) except for the subtraction constant, the derivative forms do not depend on any additional free parameter; (2) the only approximation in going from integral to derivative relations (at high energies) concerns to assume as zero the lower limit in the integral form; (3) the previous approximation and the subtraction constant affect the fit results at both low and high energies and therefore, the subtraction constant can not be disregarded; (4) from a practical point of view, for single-pole Pomeron and secondary reggeons parametrizations and center-of-mass energies above 5 GeV, the derivative relations with the subtraction constant as a free fit parameter are completely equivalent to the integral forms with finite (non-zero) lower limit. A detailed review on the conditions of validity and assumptions related with the replacement of integral by derivative relations is also presented and discussed.
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