615 research outputs found
Rational approximation and arithmetic progressions
A reasonably complete theory of the approximation of an irrational by
rational fractions whose numerators and denominators lie in prescribed
arithmetic progressions is developed in this paper. Results are both, on the
one hand, from a metrical and a non-metrical point of view and, on the other
hand, from an asymptotic and also a uniform point of view. The principal
novelty is a Khintchine type theorem for uniform approximation in this context.
Some applications of this theory are also discussed
The motion of stars near the Galactic center: A comparison of the black hole and fermion ball scenarios
After a discussion of the properties of degenerate fermion balls, we analyze
the orbits of the stars S0-1 and S0-2, which have the smallest projected
distances to Sgr A*, in the supermassive black hole as well as in the fermion
ball scenarios of the Galactic center. It is shown that both scenarios are
consistent with the data, as measured during the last six years by Genzel et
al. and Ghez et al. The free parameters of the projected orbit of a star are
the unknown components of its velocity v_z and distance z to Sgr A* in 1995.4,
with the z-axis being in the line of sight. We show, in the case of S0-1 and
S0-2, that the z-v_z phase-space which fits the data, is much larger for the
fermion ball than for the black hole scenario. Future measurements of the
positions or radial velocities of S0-1 and S0-2 could reduce this allowed
phase-space and eventually rule out one of the currently acceptable scenarios.
This may shed some light into the nature of the supermassive compact dark
object, or dark matter in general at the center of our Galaxy.Comment: 30 pages, 12 figures, Latex, aasms4 styl
Sistema automatizado para monitoramento de parâmetros abióticos em tempo real e aplicações na Agricultura de Precisão.
Neste artigo é apresentado o desenvolvimento de um sistema automatizado para análise espaço-temporal de seqüências de parâmetros abióticos de curto termo com dados coletados em tempo real por uma rede de sensores fixos inteligentes. Esse sistema pode ser dividido basicamente em duas partes: uma base de dados e uma interface que oferece aos usuários a possibilidade de acesso remoto aos dados armazenados através da Internet, utilizando um navegador. O sistema possibilita a visualização desses dados na forma de relatórios e na forma gráfica. O trabalho foi dirigido para ser uma ferramenta de auxílio na tomada de decisões em agricultura de precisão. Uma das aplicações previstas é o controle da irrigação espacialmente diferenciada.bitstream/CNPDIA/8731/1/BPD05_2003.pd
Recent advances in ICRF heating of mixture plasmas : survey of JET and AUG experiments and extrapolation to JET-DT and ITER
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