5,071 research outputs found
The Trick Simulation Toolkit: A NASA/Open source Framework for Running Time Based Physics Models
This paper describes the design and use at of the Trick Simulation Toolkit, a simulation development environment for creating high fidelity training and engineering simulations at the NASA Johnson Space Center and many other NASA facilities. It describes Trick's design goals and how the development environment attempts to achieve those goals. It describes how Trick is used in some of the many training and engineering simulations at NASA. Finally it describes the Trick NASA/Open source project on Github
Trick Simulation Environment 07
The Trick Simulation Environment is a generic simulation toolkit used for constructing and running simulations. This release includes a Monte Carlo analysis simulation framework and a data analysis package. It produces all auto documentation in XML. Also, the software is capable of inserting a malfunction at any point during the simulation. Trick 07 adds variable server output options and error messaging and is capable of using and manipulating wide characters for international support. Wide character strings are available as a fundamental type for variables processed by Trick. A Trick Monte Carlo simulation uses a statistically generated, or predetermined, set of inputs to iteratively drive the simulation. Also, there is a framework in place for optimization and solution finding where developers may iteratively modify the inputs per run based on some analysis of the outputs. The data analysis package is capable of reading data from external simulation packages such as MATLAB and Octave, as well as the common comma-separated values (CSV) format used by Excel, without the use of external converters. The file formats for MATLAB and Octave were obtained from their documentation sets, and Trick maintains generic file readers for each format. XML tags store the fields in the Trick header comments. For header files, XML tags for structures and enumerations, and the members within are stored in the auto documentation. For source code files, XML tags for each function and the calling arguments are stored in the auto documentation. When a simulation is built, a top level XML file, which includes all of the header and source code XML auto documentation files, is created in the simulation directory. Trick 07 provides an XML to TeX converter. The converter reads in header and source code XML documentation files and converts the data to TeX labels and tables suitable for inclusion in TeX documents. A malfunction insertion capability allows users to override the value of any simulation variable, or call a malfunction job, at any time during the simulation. Users may specify conditions, use the return value of a malfunction trigger job, or manually activate a malfunction. The malfunction action may consist of executing a block of input file statements in an action block, setting simulation variable values, call a malfunction job, or turn on/off simulation jobs
Parametric instabilities in the LCGT arm cavity
We evaluated the parametric instabilities of LCGT (Japanese interferometric
gravitational wave detector project) arm cavity. The number of unstable modes
of LCGT is 10-times smaller than that of Advanced LIGO (U.S.A.). Since the
strength of the instabilities of LCGT depends on the mirror curvature more
weakly than that of Advanced LIGO, the requirement of the mirror curvature
accuracy is easier to be achieved. The difference in the parametric
instabilities between LCGT and Advanced LIGO is because of the thermal noise
reduction methods (LCGT, cooling sapphire mirrors; Advanced LIGO, fused silica
mirrors with larger laser beams), which are the main strategies of the
projects. Elastic Q reduction by the barrel surface (0.2 mm thickness
TaO) coating is effective to suppress instabilities in the LCGT arm
cavity. Therefore, the cryogenic interferometer is a smart solution for the
parametric instabilities in addition to thermal noise and thermal lensing.Comment: 6 pages,3 figures. Amaldi7 proceedings, J. Phys.: Conf. Ser.
(accepted
Transport and Spectra in the Half-filled Hubbard Model: A Dynamical Mean Field Study
We study the issues of scaling and universality in spectral and transport
properties of the infinite dimensional particle--hole symmetric (half-filled)
Hubbard model within dynamical mean field theory. One of the simplest and
extensively used impurity solvers, namely the iterated perturbation theory
approach is reformulated to avoid problems such as analytic continuation of
Matsubara frequency quantities or calculating multi-dimensional integrals,
while taking full account of the very sharp structures in the Green's functions
that arise close to the Mott transitions and in the Mott insulator regime. We
demonstrate its viability for the half-filled Hubbard model. Previous known
results are reproduced within the present approach. The universal behavior of
the spectral functions in the Fermi liquid regime is emphasized, and adiabatic
continuity to the non-interacting limit is demonstrated. The dc resistivity in
the metallic regime is known to be a non-monotonic function of temperature with
a `coherence peak'. This feature is shown to be a universal feature occurring
at a temperature roughly equal to the low energy scale of the system. A
comparison to pressure dependent dc resistivity experiments on Selenium doped
NiS yields qualitatively good agreement. Resistivity hysteresis across the
Mott transition is shown to be described qualitatively within the present
framework. A direct comparison of the thermal hysteresis observed in VO
with our theoretical results yields a value of the hopping integral, which we
find to be in the range estimated through first-principle methods. Finally, a
systematic study of optical conductivity is carried out and the changes in
absorption as a result of varying interaction strength and temperature are
identified.Comment: 19 pages, 12 figure
Thermoelastic dissipation in inhomogeneous media: loss measurements and displacement noise in coated test masses for interferometric gravitational wave detectors
The displacement noise in the test mass mirrors of interferometric
gravitational wave detectors is proportional to their elastic dissipation at
the observation frequencies. In this paper, we analyze one fundamental source
of dissipation in thin coatings, thermoelastic damping associated with the
dissimilar thermal and elastic properties of the film and the substrate. We
obtain expressions for the thermoelastic dissipation factor necessary to
interpret resonant loss measurements, and for the spectral density of
displacement noise imposed on a Gaussian beam reflected from the face of a
coated mass. The predicted size of these effects is large enough to affect the
interpretation of loss measurements, and to influence design choices in
advanced gravitational wave detectors.Comment: 42 pages, 7 figures, uses REVTeX
Effect of heat treatment on mechanical dissipation in TaO coatings
Thermal noise arising from mechanical dissipation in dielectric reflective
coatings is expected to critically limit the sensitivity of precision
measurement systems such as high-resolution optical spectroscopy, optical
frequency standards and future generations of interferometric gravitational
wave detectors. We present measurements of the effect of post-deposition heat
treatment on the temperature dependence of the mechanical dissipation in
ion-beam sputtered tantalum pentoxide between 11\,K and 300\,K. We find the
temperature dependence of the dissipation is strongly dependent on the
temperature at which the heat treatment was carried out, and we have identified
three dissipation peaks occurring at different heat treatment temperatures. At
temperatures below 200\,K, the magnitude of the loss was found to increase with
higher heat treatment temperatures, indicating that heat treatment is a
significant factor in determining the level of coating thermal noise.Comment: accepted Classical and Quantum Gravity 201
Towards low-carbon conferencing : acceptance of virtual conferencing solutions and other sustainability measures in the ALIFE community
The latest report from the Intergovernmental Panel on Climate Change (IPCC) estimated that humanity has a time window of about 12 years in order to prevent anthropogenic climate change of catastrophic magnitude. Green house gas emission from air travel, which is currently rising, is possibly one of the factors that can be most readily reduced. Within this context, we advocate for the re-design of academic conferences in order to decrease their environmental footprint. Today, virtual technologies hold the promise to substitute many forms of physical interactions and increasingly make their way into conferences to reduce the number of travelling delegates. Here, we present the results of a survey in which we gathered the opinion on this topic of academics worldwide. Results suggest there is ample room for challenging the (dangerous) business-as-usual inertia of scientific lifestyle
Measurements of a low temperature mechanical dissipation peak in a single layer of Ta2O5 doped with TiO2
Thermal noise arising from mechanical dissipation in oxide coatings is a
major limitation to many precision measurement systems, including optical
frequency standards, high resolution optical spectroscopy and interferometric
gravity wave detectors. Presented here are measurements of dissipation as a
function of temperature between 7 K and 290 K in ion-beam sputtered Ta2O5 doped
with TiO2, showing a loss peak at 20 K. Analysis of the peak provides the first
evidence of the source of dissipation in doped Ta2O5 coatings, leading to
possibilities for the reduction of thermal noise effects
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