286,539 research outputs found
OL-Transformer: A Fast and Universal Surrogate Simulator for Optical Multilayer Thin Film Structures
Deep learning-based methods have recently been established as fast and
accurate surrogate simulators for optical multilayer thin film structures.
However, existing methods only work for limited types of structures with
different material arrangements, preventing their applications towards diverse
and universal structures. Here, we propose the Opto-Layer (OL) Transformer to
act as a universal surrogate simulator for enormous types of structures.
Combined with the technique of structure serialization, our model can predict
accurate reflection and transmission spectra for up to different
multilayer structures, while still achieving a six-fold degradation in
simulation time compared to physical solvers. Further investigation reveals
that the general learning ability comes from the fact that our model first
learns the physical embeddings and then uses the self-attention mechanism to
capture the hidden relationship of light-matter interaction between each layer.Comment: 4 pages, 4 figure
ELLC - a fast, flexible light curve model for detached eclipsing binary stars and transiting exoplanets
Very high quality light curves are now available for thousands of detached
eclipsing binary stars and transiting exoplanet systems as a result of surveys
for transiting exoplanets and other large-scale photometric surveys. I have
developed a binary star model (ELLC) that can be used to analyse the light
curves of detached eclipsing binary stars and transiting exoplanet systems that
is fast and accurate, and that can include the effects of star spots, Doppler
boosting and light-travel time within binaries with eccentric orbits. The model
represents the stars as triaxial ellipsoids. The apparent flux from the binary
is calculated using Gauss-Legendre integration over the ellipses that are the
projection of these ellipsoids on the sky. The model can also be used to
calculate the flux-weighted radial velocity of the stars during an eclipse
(Rossiter-McLaughlin effect). The main features of the model have been tested
by comparison to observed data and other light curve models. The model is found
to be accurate enough to analyse the very high quality photometry that is now
available from space-spaced instruments, flexible enough to model a wide range
of eclipsing binary stars and extrasolar planetary systems, and fast enough to
enable the use of modern Monte Carlo methods for data analysis and model
testing.Comment: Accepted for publication in A&A. Source code available from
pypi.python.org/pypi/ellc. Definition of "third-light" changed from version
ellc-1.0.0 to ellc-1.1.0 - this preprint describes the definition used in the
later versio
Analytical modeling of light transport in scattering materials with strong absorption
We have investigated the transport of light through slabs that both scatter
and strongly absorb, a situation that occurs in diverse application fields
ranging from biomedical optics, powder technology, to solid-state lighting. In
particular, we study the transport of light in the visible wavelength range
between and nm through silicone plates filled with YAG:Ce
phosphor particles, that even re-emit absorbed light at different wavelengths.
We measure the total transmission, the total reflection, and the ballistic
transmission of light through these plates. We obtain average single particle
properties namely the scattering cross-section , the absorption
cross-section , and the anisotropy factor using an analytical
approach, namely the P3 approximation to the radiative transfer equation. We
verify the extracted transport parameters using Monte-Carlo simulations of the
light transport. Our approach fully describes the light propagation in phosphor
diffuser plates that are used in white LEDs and that reveal a strong absorption
() up to , where is the
slab thickness, is the absorption mean free path. In
contrast, the widely used diffusion theory fails to describe this parameter
range. Our approach is a suitable analytical tool for industry, since it
provides a fast yet accurate determination of key transport parameters, and
since it introduces predictive power into the design process of white light
emitting diodes
Accretion, ejection and reprocessing in supermassive black holes
This is a White Paper in support of the mission concept of the Large
Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We
discuss the potential of LOFT for the study of active galactic nuclei. For a
summary, we refer to the paper.Comment: White Paper in Support of the Mission Concept of the Large
Observatory for X-ray Timin
Wind from the black-hole accretion disk driving a molecular outflow in an active galaxy
Powerful winds driven by active galactic nuclei (AGN) are often invoked to
play a fundamental role in the evolution of both supermassive black holes
(SMBHs) and their host galaxies, quenching star formation and explaining the
tight SMBH-galaxy relations. Recent observations of large-scale molecular
outflows in ultra-luminous infrared galaxies (ULIRGs) have provided the
evidence to support these studies, as they directly trace the gas out of which
stars form. Theoretical models suggest an origin of these outflows as
energy-conserving flows driven by fast AGN accretion disk winds. Previous
claims of a connection between large-scale molecular outflows and AGN activity
in ULIRGs were incomplete because they were lacking the detection of the
putative inner wind. Conversely, studies of powerful AGN accretion disk winds
to date have focused only on X-ray observations of local Seyferts and a few
higher redshift quasars. Here we show the clear detection of a powerful AGN
accretion disk wind with a mildly relativistic velocity of 0.25c in the X-ray
spectrum of IRAS F11119+3257, a nearby (z = 0.189) optically classified type 1
ULIRG hosting a powerful molecular outflow. The AGN is responsible for ~80% of
the emission, with a quasar-like luminosity of L_AGN = 1.5x10^46 erg/s. The
energetics of these winds are consistent with the energy-conserving mechanism,
which is the basis of the quasar mode feedback in AGN lacking powerful radio
jets.Comment: Revised file including the letter, methods and supplementary
information. Published in the March 26th 2015 issue of Natur
Fast simulation method for parameter reconstruction in optical metrology
A method for automatic computation of parameter derivatives of numerically
computed light scattering signals is demonstrated. The finite-element based
method is validated in a numerical convergence study, and it is applied to
investigate the sensitivity of a scatterometric setup with respect to
geometrical parameters of the scattering target. The method can significantly
improve numerical performance of design optimization, parameter reconstruction,
sensitivity analysis, and other applications
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