4,551 research outputs found
The application of interactive graphics to large time-dependent hydrodynamics problems
A written companion of a movie entitled "Interactive Graphics at Los Alamos Scientific Laboratory" was presented. While the movie presents the actual graphics terminal and the functions performed on it, the paper attempts to put in perspective the complexity of the application code and the complexity of the interaction that is possible
On the Sensitivity of a Hollow Sphere as a Multi-modal Resonant Gravitational Wave Detector
We present a numerical analysis to simulate the response of a spherical
resonant gravitational wave detector and to compute its sensitivity. Under the
assump- tion of optimal filtering, we work out the sensitivity curve for a
sphere first taking into account only a single transducer, and then using a
coherent analysis of the whole set of transducers.Comment: 24 pages, 11 figures, published versio
Deconvolving the information from an imperfect spherical gravitational wave antenna
We have studied the effects of imperfections in spherical gravitational wave
antenna on our ability to properly interpret the data it will produce. The
results of a numerical simulation are reported that quantitatively describe the
systematic errors resulting from imperfections in various components of the
antenna. In addition, the results of measurements on a room-temperature
prototype are presented that verify it is possible to accurately deconvolve the
data in practice.Comment: 5 pages, 2 figures, to be published in Europhysics Letter
Thermal diagnostic of the Optical Window on board LISA Pathfinder
Vacuum conditions inside the LTP Gravitational Reference Sensor must comply
with rather demanding requirements. The Optical Window (OW) is an interface
which seals the vacuum enclosure and, at the same time, lets the laser beam go
through for interferometric Metrology with the test masses. The OW is a
plane-parallel plate clamped in a Titanium flange, and is considerably
sensitive to thermal and stress fluctuations. It is critical for the required
precision measurements, hence its temperature will be carefully monitored in
flight. This paper reports on the results of a series of OW characterisation
laboratory runs, intended to study its response to selected thermal signals, as
well as their fit to numerical models, and the meaning of the latter. We find
that a single pole ARMA transfer function provides a consistent approximation
to the OW response to thermal excitations, and derive a relationship with the
physical processes taking place in the OW. We also show how system noise
reduction can be accomplished by means of that transfer function.Comment: 20 pages, 14 figures; accepted for publication in Class. Quantum Gra
An anti-Schwarzshild solution: wormholes and scalar-tensor solutions
We investigate a static solution with an hyperbolic nature, characterised by
a pseudo-spherical foliation of space. This space-time metric can be perceived
as an anti-Schwarzschild solution, and exhibits repulsive features. It belongs
to the class of static vacuum solutions termed "a degenerate static solution of
class A". In the present work we review its fundamental features, discuss the
existence of generalised wormholes, and derive its extension to scalar-tensor
gravity theories in general.Comment: 3 pages, contribution to the proceedings of the Spanish Relativity
Meeting-ERE200
Exploratory data analysis and clustering of multivariate spatial hydrogeological data by means of GEO3DSOM, a variant of Kohonen's Self-Organizing Map
International audienceThe use of unsupervised artificial neural network techniques like the self-organizing map (SOM) algorithm has proven to be a useful tool in exploratory data analysis and clustering of multivariate data sets. In this study a variant of the SOM-algorithm is proposed, the GEO3DSOM, capable of explicitly incorporating three-dimensional spatial knowledge into the algorithm. The performance of the GEO3DSOM is compared to the performance of the standard SOM in analyzing an artificial data set and a hydrochemical data set. The hydrochemical data set consists of 141 groundwater samples collected in two detritic, phreatic, Cenozoic aquifers in Central Belgium. The standard SOM proves to be more adequate in representing the structure of the data set and to explore relationships between variables. The GEO3DSOM on the other hand performs better in creating spatially coherent groups based on the data
Thermal and back-action noises in dual-sphere gravitational-waves detectors
We study the sensitivity limits of a broadband gravitational-waves detector
based on dual resonators such as nested spheres. We determine both the thermal
and back-action noises when the resonators displacements are read-out with an
optomechanical sensor. We analyze the contributions of all mechanical modes,
using a new method to deal with the force-displacement transfer functions in
the intermediate frequency domain between the two gravitational-waves sensitive
modes associated with each resonator. This method gives an accurate estimate of
the mechanical response, together with an evaluation of the estimate error. We
show that very high sensitivities can be reached on a wide frequency band for
realistic parameters in the case of a dual-sphere detector.Comment: 10 pages, 7 figure
Cabras mestiças: opção para a produção de leite no Nordeste do Brasil.
bitstream/item/51983/1/Midia-Cabras-mesticas.pd
Combinações de isolados de Trichoderma spp. para o controle do mofo branco em feijão comum.
Sabendo do potencial antagônico do gênero Trichoderma (Pers.), este trabalho objetivou testar em campo combinações de isolados deste gênero, da coleção de microrganismos da Embrapa Arroz e Feijão, para o controle do mofo branco (Sclerotinia sclerotiorum) na cultura do feijão comum
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