13,131 research outputs found
Constrained Interpolation And Shape Preserving Approximation By Space Curves [QA297.6. K82 2006 f rb].
Dua jenis masalah rekabentuk lengkung telah ipertimbangkan. Terlebih dahulu kami mempertimbangkan interpolasi satu set titik data ruang yang bertertib dengan satu lengkung licin tertakluk kepada satu set satah kekangan yang berbentuk terhingga atau tak terhingga di mana garis cebis demi cebis yang menyambung titik data secara berturutan tidak bersilang dengan satah kekangan.
Two types of curve designing problem have been considered. We first consider the interpolation of a given set of ordered spatial data points by a smooth curve in the
presence of a set of finite or infinite constraint planes, where the polyline joining consecutive data points does not intersect with the constraint planes
Constraint-preserving Sommerfeld conditions for the harmonic Einstein equations
The principle part of Einstein equations in the harmonic gauge consists of a
constrained system of 10 curved space wave equations for the components of the
space-time metric. A new formulation of constraint-preserving boundary
conditions of the Sommerfeld type for such systems has recently been proposed.
We implement these boundary conditions in a nonlinear 3D evolution code and
test their accuracy.Comment: 16 pages, 17 figures, submitted to Phys. Rev.
SModelS: a tool for interpreting simplified-model results from the LHC and its application to supersymmetry
We present a general procedure to decompose Beyond the Standard Model (BSM)
collider signatures presenting a Z2 symmetry into Simplified Model Spectrum
(SMS) topologies. Our method provides a way to cast BSM predictions for the LHC
in a model independent framework, which can be directly confronted with the
relevant experimental constraints. Our concrete implementation currently
focusses on supersymmetry searches with missing energy, for which a large
variety of SMS results from ATLAS and CMS are available. As show-case examples
we apply our procedure to two scans of the minimal supersymmetric standard
model. We discuss how the SMS limits constrain various particle masses and
which regions of parameter space remain unchallenged by the current SMS
interpretations of the LHC results.Comment: v3: Version published in EPJ
Combining weak and strong lensing in cluster potential reconstruction
We propose a method for recovering the two-dimensional gravitational
potential of galaxy clusters which combines data from weak and strong
gravitational lensing. A first estimate of the potential from weak lensing is
improved at the approximate locations of critical curves. The method can be
fully linearised and does not rely on the existence and identification of
multiple images. We use simulations to show that it recovers the surface-mass
density profiles and distributions very accurately, even if critical curves are
only partially known and if their location is realistically uncertain. We
further describe how arcs at different redshifts can be combined, and how
deviations from weak lensing can be included.Comment: 9 pages, 5 figures, A&A in press, changes to match the accepted
versio
Optimization of starshades: focal plane versus pupil plane
We search for the best possible transmission for an external occulter
coronagraph that is dedicated to the direct observation of terrestrial
exoplanets. We show that better observation conditions are obtained when the
flux in the focal plane is minimized in the zone in which the exoplanet is
observed, instead of the total flux received by the telescope. We describe the
transmission of the occulter as a sum of basis functions. For each element of
the basis, we numerically computed the Fresnel diffraction at the aperture of
the telescope and the complex amplitude at its focus. The basis functions are
circular disks that are linearly apodized over a few centimeters (truncated
cones). We complemented the numerical calculation of the Fresnel diffraction
for these functions by a comparison with pure circular discs (cylinder) for
which an analytical expression, based on a decomposition in Lommel series, is
available. The technique of deriving the optimal transmission for a given
spectral bandwidth is a classical regularized quadratic minimization of
intensities, but linear optimizations can be used as well. Minimizing the
integrated intensity on the aperture of the telescope or for selected regions
of the focal plane leads to slightly different transmissions for the occulter.
For the focal plane optimization, the resulting residual intensity is
concentrated behind the geometrical image of the occulter, in a blind region
for the observation of an exoplanet, and the level of background residual
starlight becomes very low outside this image. Finally, we provide a tolerance
analysis for the alignment of the occulter to the telescope which also favors
the focal plane optimization.This means that telescope offsets of a few
decimeters do not strongly reduce the efficiency of the occulter
The Optical, Ultraviolet, and X-ray Structure of the Quasar HE 0435-1223
Microlensing has proven an effective probe of the structure of the innermost
regions of quasars, and an important test of accretion disk models. We present
light curves of the lensed quasar HE 0435-1223 in the R band and in the
ultraviolet, and consider them together with X-ray light curves in two energy
bands that are presented in a companion paper. Using a Bayesian Monte Carlo
method, we constrain the size of the accretion disk in the rest-frame near- and
far-UV, and constrain for the first time the size of the X-ray emission regions
in two X-ray energy bands. The R-band scale size of the accretion disk is about
10^15.23 cm (~23 r_g), slightly smaller than previous estimates, but larger
than would be predicted from the quasar flux. In the UV, the source size is
weakly constrained, with a strong prior dependence. The UV to R-band size ratio
is consistent with the thin disk model prediction, with large error bars. In
soft and hard X-rays, the source size is smaller than ~10^14.8 cm (~10 r_g) at
95% confidence. We do not find evidence of structure in the X-ray emission
region, as the most likely value for the ratio of the hard X-ray size to the
soft X-ray size is unity. Finally, we find that the most likely value for the
mean mass of stars in the lens galaxy is ~0.3 M_sun, consistent with other
studies.Comment: 13 pages, 7 figures. Replaced with version accepted to Ap
High-resolution ab initio three-dimensional X-ray diffraction microscopy
Coherent X-ray diffraction microscopy is a method of imaging non-periodic
isolated objects at resolutions only limited, in principle, by the largest
scattering angles recorded. We demonstrate X-ray diffraction imaging with high
resolution in all three dimensions, as determined by a quantitative analysis of
the reconstructed volume images. These images are retrieved from the 3D
diffraction data using no a priori knowledge about the shape or composition of
the object, which has never before been demonstrated on a non-periodic object.
We also construct 2D images of thick objects with infinite depth of focus
(without loss of transverse spatial resolution). These methods can be used to
image biological and materials science samples at high resolution using X-ray
undulator radiation, and establishes the techniques to be used in
atomic-resolution ultrafast imaging at X-ray free-electron laser sources.Comment: 22 pages, 11 figures, submitte
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