19,412 research outputs found
Microlensing path parametrization for Earth-like Exoplanet detection around solar mass stars
We propose a new parametrization of the impact parameter u0 and impact angle
{\alpha} for microlensing systems composed by an Earth-like Exoplanet around a
Solar mass Star at 1 AU. We present the caustic topology of such system, as
well as the related light curves generated by using such a new parametrization.
Based on the same density of points and accuracy of regular methods, we obtain
results 5 times faster for discovering Earth-like exoplanet. In this big data
revolution of photometric astronomy, our method will impact future missions
like WFIRST (NASA) and Euclid (ESA) and they data pipelines, providing a rapid
and deep detection of exoplanets for this specific class of microlensing event
that might otherwise be lost.Comment: 8 pages, 7 figures, accepted to be published in The Astronomical
Journa
The radiation of a uniformly accelerated charge is beyond the horizon: a simple derivation
We show, by exploring some elementary consequences of the covariance of
Maxwell's equations under general coordinate transformations, that, despite
inertial observers can indeed detect electromagnetic radiation emitted from a
uniformly accelerated charge, comoving observers will see only a static
electric field. This simple analysis can help understanding one of the most
celebrated paradoxes of last century.Comment: Revtex, 6 pages, 2 figures. v2: Some small corrections. v3: Citation
of a earlier paper included. v4: Some stylistic changes. v5: Final version to
appear in AJ
Evolution of microstructure, texture and grain boundary character distribution of potassium doped tungsten fibers annealed at variable temperatures
The effect of the annealing temperature on the microstructure and grain boundary character distribution of potassium doped tungsten fibers made of drawn wire was investigated by Electron Backscatter Diffraction. Samples, with a diameter of 148.7 μm, in the as-received condition and annealed at 1300, 1600, 1900, 2100 and 2300 °C were analyzed at the center of the transversal sections. Up to 1900 °C, a uniform microstructural coarsening and primary recrystallization followed by normal grain growth was observed. Between 1900 and 2100 °C abnormal grain growth took place. The strong texture (<110> parallel to the drawing axis) remained present in all conditions. With increasing the annealing temperature, the low angle grain boundary fraction increased at the expense of high angle grain boundaries while the amount of coincidence site lattice boundaries reached its maximum at 1600 °C. At this temperature, the most resistant configuration of triple junctions against intergranular crack propagation was obtained
A theoretical analysis of the fluid-solid interactions governing the removal of woody debris jams from cylindrical bridge piers
This is the author accepted manuscript. The final version is avaialble from Cambridge University Press via the DOI in this recordThis paper proposes a theoretical model to describe previous laboratory observations
of the dynamics of debris accumulations around bridge piers of cylindrical shape. The
model is based on the assumption that the observed dynamics is mainly governed by
dynamic changes of the point of application of the drag force exerted on the solid body
formed by debris accumulated around the pier. A phase plane analysis of the resulting
non-linear system of ODEs shows that the model captures the main patterns observed
in previous laboratory experiments, including an oscillatory motion and the removal
of debris from the pier by the flow. The model provides a theoretical basis for the
analysis of the conditions required for debris jams to remain stable over long periods
of exposure to impinging flow. Namely, the model indicates that stability of debris
accumulations primarily depends on geometrical asymmetry and on the length of the
extension downstream of the pier. The former induces the torque required to rotate the
jam about the pier, while the latter produces a stabilising effect after the body rotates.Engineering and Physical Sciences Research Council (EPSRC
Decoherence of tripartite states - a trapped ion coupled to an optical cavity
We investigate the non-dissipative decoherence of three qubit system obtained
by manipulating the state of a trapped two-level ion coupled to an optical
cavity. Modelling the environment as a set of noninteracting harmonic
oscillators, analytical expressions for the state operator of tripartite
composite system, the probability of generating maximally entangled GHZ state,
and the population inversion have been obtained. The pointer observable is the
energy of the isolated quantum system. Coupling to environment results in
exponential decay of off diagonal matrix elements of the state operator with
time as well as a phase decoherence of the component states.
Numerical calculations to examine the time evolution of GHZ state generation
probability and population inversion for different system environment coupling
strengths are performed. Using negativity as an entanglement measure and linear
entropy as a measure of mixedness, the entanglement dynamics of the tripartite
system in the presence of decoherence is analysed.Comment: Revised version, errors corrected and references added. 12 pages, 6
figures, Presented at ICSSUR May 2005, Besancon, Franc
Periodic orbit bifurcations and scattering time delay fluctuations
We study fluctuations of the Wigner time delay for open (scattering) systems
which exhibit mixed dynamics in the classical limit. It is shown that in the
semiclassical limit the time delay fluctuations have a distribution that
differs markedly from those which describe fully chaotic (or strongly
disordered) systems: their moments have a power law dependence on a
semiclassical parameter, with exponents that are rational fractions. These
exponents are obtained from bifurcating periodic orbits trapped in the system.
They are universal in situations where sufficiently long orbits contribute. We
illustrate the influence of bifurcations on the time delay numerically using an
open quantum map.Comment: 9 pages, 3 figures, contribution to QMC200
Avaliação das características agronômicas de sete adubos verdes de inverno no município de Paty do Alferes(RJ).
Adubação verde. Cobertura do solo, produção e fitomassa e acúmulo de macronutrientes.bitstream/CNPAB-2010/27145/1/cot020.pd
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