5,844 research outputs found
A multi-domain hybrid method for head-on collision of black holes in particle limit
A hybrid method is developed based on the spectral and finite-difference
methods for solving the inhomogeneous Zerilli equation in time-domain. The
developed hybrid method decomposes the domain into the spectral and
finite-difference domains. The singular source term is located in the spectral
domain while the solution in the region without the singular term is
approximated by the higher-order finite-difference method.
The spectral domain is also split into multi-domains and the
finite-difference domain is placed as the boundary domain. Due to the global
nature of the spectral method, a multi-domain method composed of the spectral
domains only does not yield the proper power-law decay unless the range of the
computational domain is large. The finite-difference domain helps reduce
boundary effects due to the truncation of the computational domain. The
multi-domain approach with the finite-difference boundary domain method reduces
the computational costs significantly and also yields the proper power-law
decay.
Stable and accurate interface conditions between the finite-difference and
spectral domains and the spectral and spectral domains are derived. For the
singular source term, we use both the Gaussian model with various values of
full width at half maximum and a localized discrete -function. The
discrete -function was generalized to adopt the Gauss-Lobatto
collocation points of the spectral domain.
The gravitational waveforms are measured. Numerical results show that the
developed hybrid method accurately yields the quasi-normal modes and the
power-law decay profile. The numerical results also show that the power-law
decay profile is less sensitive to the shape of the regularized
-function for the Gaussian model than expected. The Gaussian model also
yields better results than the localized discrete -function.Comment: 25 pages; published version (IJMPC
Telerobotic controller development
To meet NASA's space station's needs and growth, a modular and generic approach to robotic control which provides near-term implementation with low development cost and capability for growth into more autonomous systems was developed. The method uses a vision based robotic controller and compliant hand integrated with the Remote Manipulator System arm on the Orbiter. A description of the hardware and its system integration is presented
Ground Water Monitoring Project for Arkansas, Phase III
This report is composed of two parts. The first part is an interpretation of the pesticide and nitrate data collected in Woodruff County based on samples collected during 1994. Because there is an indication that there were hydrological differences between 1994 and 1995, and because most of the pesticide data is from 1994, this interpretive portion is restricted to 1994 data. Six wells initially sampled in 1994 that contained pesticides had continuing contamination in re-sampling in 1994 and 1995. Part II lists a seventh well in Woodruff County that contained pesticides in February and May of 199
Dietary control of the renal reabsorption and excretion of α2u-globulin
Dietary protein supply is a factor in controlling the excretion of proteins in the urine. As early as 1926, Addis, Mackay, and Mackay observed that male rats on a 69% protein diet excreted more urinary proteins than did those on a 17% diet [1]. Protein deficiency had the opposite effect, resulting in a suppression of the proteinuria [2]. Of the total urinary proteins excreted by the adult male rat, approximately 30% is a sex-dependent globulin called α2u [3,4], which is synthesized by the liver [5] and controlled synergistically by androgens and glucocorticoids [6]. Dietary protein supply also had a profound influence on the excretion of α2u [4]. On a 0% casein diet, the excretion was reduced to approximately 1 mg/24 hours compared with a normal of 10 to 15mg. On a 50% casein diet, rats excreted 30 to 50 mg/24 hours, an increase of more than 100% above the normal [4].Early studies also suggested that high protein diets exaggerated the leakage of plasma proteins caused by a spontaneous nephrotic syndrome observed in male rats [7, 8]. Rats previously castrated did not exhibit an increased excretion of urinary protein on a 50% casein diet, whereas supplementation with testosterone restored the augmented proteinuria [9]. This suggested that the elevated excretion of urinary protein was dependent on the presence of androgens. It is now known that a high-protein diet caused an increased excretion of α2u without at the same time leading to a compensatory, stimulated hepatic biosynthesis. Conceivably, the increased excretion of α2u was the consequence of an altered state of renal reabsorption [4]. The purpose of the present communication was to compare the degree of renal reabsorption under three different dietary conditions and to determine whether the kidneys controlled the urinary excretion of α2u by altering its reabsorption
Muting the noise cone in near-surface reflection data: An example from southeastern Kansas
This is the publisher's version, also available electronically from "http://library.seg.org".A 300-m nearâsurface seismic reflection profile was collected in southeastern Kansas to locate a fault(s) associated with a recognized stratigraphic offset on either side of a region of unexposed bedrock. A substantial increase in the S/N ratio of the final stacked section was achieved by muting all data arriving in time after the airwave. Methods of applying traditional seismic data processing techniques to nearâsurface data (200 ms of data or less) often differ notably from hydrocarbon explorationâscale processing (3â4 s of data or more). The example of noise cone muting used is contrary to normal explorationâscale seismic data processing philosophy, which is to include all data containing signal. The noise cone mute applied to the data removed more than oneâthird of the total data volume, some of which contains signal. In this case, however, the severe muting resulted in a higher S/N ratio in the final stacked section, even though some signal could be identified within the muted data. This example supports the suggestion that nontraditional techniques sometimes need to be considered when processing nearâsurface seismic data
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High-altitude migration of Heteroptera in Britain
Heteroptera caught during day and night sampling at a height of 200 m above ground at Cardington, Bedfordshire, UK, during eight summers (1999, 2000, and 2002-2007) were compared to high-altitude catches made over the UK and North Sea from the 1930s to the 1950s. The height of these captures indicates that individuals were engaged in windborne migration over distances of at least several kilometres and probably tens of kilometres. This conclusion is generally supported by what is known of the species' ecologies, which reflect the view that the level of dispersiveness is associated with the exploitation of temporary habitats or resources. The seasonal timing of the heteropteran migrations is interpreted in terms of the breeding/overwintering cycles of the species concerned
Quantum Approach to a Derivation of the Second Law of Thermodynamics
We re-interprete the microcanonical conditions in the quantum domain as
constraints for the interaction of the "gas-subsystem" under consideration and
its environment ("container"). The time-average of a purity-measure is found to
equal the average over the respective path in Hilbert-space. We then show that
for typical (degenerate or non-degenerate) thermodynamical systems almost all
states within the allowed region of Hilbert-space have a local von
Neumann-entropy S close to the maximum and a purity P close to its minimum,
respectively. Typically thermodynamical systems should therefore obey the
second law.Comment: 4 pages. Accepted for publication in Phys. Rev. Let
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