603 research outputs found
POGO Instabilities Suppression Evaluation
A dynamic (frequency response) analysis was made of a liquid oxygen feed system consisting of a low-speed inducer, a high-speed main pump and a positive displacement pulser utilized for simulating pogo induced pressure oscillations. Based on the results of the analysis, an active control system for suppression of pulser generated pressure oscillations was designed, fabricated and tested. The test results verified that the suppressor was effective in attenuating the generated pressure oscillations over the frequency range from 10 to 30 Hz
Digital program for dynamics of non-rigid gravity gradient satellites
Digital program for dynamics of nonrigid gravity gradient satellite
The transient performance of a hydraulic turbine driven inducer - Computer predictions and test verification Final report
Analog and digital computer programs for predicting transient performance of inducer driven by hydraulic turbin
Germanium Detector with Internal Amplification for Investigation of Rare Processes
Device of new type is suggested - germanium detector with internal
amplification. Such detector having effective threshold about 10 eV opens up
fresh opportunity for investigation of dark matter, measurement of neutrino
magnetic moment, of neutrino coherent scattering at nuclei and for study of
solar neutrino problem. Construction of germanium detector with internal
amplification and perspectives of its use are described.Comment: 13 pages, latex, 3 figures, report at NANP-99, International
Conference on Non-Accelerator Physics, Dubna, Russia, June 29- July 3, 1999.
To be published in the Proceeding
Performance of AAOmega: the AAT multi-purpose fibre-fed spectrograph
AAOmega is the new spectrograph for the 2dF fibre-positioning system on the
Anglo-Australian Telescope. It is a bench-mounted, double-beamed design, using
volume phase holographic (VPH) gratings and articulating cameras. It is fed by
392 fibres from either of the two 2dF field plates, or by the 512 fibre SPIRAL
integral field unit (IFU) at Cassegrain focus. Wavelength coverage is 370 to
950nm and spectral resolution 1,000-8,000 in multi-Object mode, or 1,500-10,000
in IFU mode. Multi-object mode was commissioned in January 2006 and the IFU
system will be commissioned in June 2006.
The spectrograph is located off the telescope in a thermally isolated room
and the 2dF fibres have been replaced by new 38m broadband fibres. Despite the
increased fibre length, we have achieved a large increase in throughput by use
of VPH gratings, more efficient coatings and new detectors - amounting to a
factor of at least 2 in the red. The number of spectral resolution elements and
the maximum resolution are both more than doubled, and the stability is an
order of magnitude better.
The spectrograph comprises: an f/3.15 Schmidt collimator, incorporating a
dichroic beam-splitter; interchangeable VPH gratings; and articulating red and
blue f/1.3 Schmidt cameras. Pupil size is 190mm, determined by the competing
demands of cost, obstruction losses, and maximum resolution. A full suite of
VPH gratings has been provided to cover resolutions 1,000 to 7,500, and up to
10,000 at particular wavelengths.Comment: 13 pages, 4 figures; presented at SPIE, Astronomical Telescopes and
Instrumentation, 24 - 31 May 2006, Orlando, Florida US
ROGUE:an R Shiny app for RNA sequencing analysis and biomarker discovery
Background: The growing power and ever decreasing cost of RNA sequencing (RNA-Seq) technologies have resulted in an explosion of RNA-Seq data production. Comparing gene expression values within RNA-Seq datasets is relatively easy for many interdisciplinary biomedical researchers; however, user-friendly software applications increase the ability of biologists to efficiently explore available datasets. Results: Here, we describe ROGUE (RNA-Seq Ontology Graphic User Environment, https://marisshiny.research.chop.edu/ROGUE/), a user-friendly R Shiny application that allows a biologist to perform differentially expressed gene analysis, gene ontology and pathway enrichment analysis, potential biomarker identification, and advanced statistical analyses. We use ROGUE to identify potential biomarkers and show unique enriched pathways between various immune cells. Conclusions: User-friendly tools for the analysis of next generation sequencing data, such as ROGUE, will allow biologists to efficiently explore their datasets, discover expression patterns, and advance their research by allowing them to develop and test hypotheses.</p
Model for nucleation in GaAs homoepitaxy derived from first principles
The initial steps of MBE growth of GaAs on beta 2-reconstructed GaAs(001) are
investigated by performing total energy and electronic structure calculations
using density functional theory and a repeated slab model of the surface. We
study the interaction and clustering of adsorbed Ga atoms and the adsorption of
As_2 molecules onto Ga atom clusters adsorbed on the surface. The stable nuclei
consist of bound pairs of Ga adatoms, which originate either from dimerization
or from an indirect interaction mediated through the substrate reconstruction.
As_2 adsorption is found to be strongly exothermic on sites with a square array
of four Ga dangling bonds. Comparing two scenarios where the first As_2 gets
incorporated in the incomplete surface layer, or alternatively in a new added
layer, we find the first scenario to be preferable. In summary, the
calculations suggest that nucleation of a new atomic layer is most likely on
top of those surface regions where a partial filling of trenches in the surface
has occurred before.Comment: 8 pages, 14 figures, Submitted to Phys. Rev. B (December 15, 1998).
Other related publications can be found at
http://www.fhi-berlin.mpg.de/th/paper.htm
Eigenvector statistics in non-Hermitian random matrix ensembles
We study statistical properties of the eigenvectors of non-Hermitian random
matrices, concentrating on Ginibre's complex Gaussian ensemble, in which the
real and imaginary parts of each element of an N x N matrix, J, are independent
random variables. Calculating ensemble averages based on the quantity , where and are left and right eigenvectors of J, we show for large N that
eigenvectors associated with a pair of eigenvalues are highly correlated if the
two eigenvalues lie close in the complex plane. We examine consequences of
these correlations that are likely to be important in physical applications.Comment: 4 pages, no figure
Performance of epoxy-coated steel in continuously reinforced concrete pavement (FHWA-OK-91-11) 2168
Sections of Interstate 35 in Noble and Logan Counties of Oklahoma were recently reconstructed. The reconstruction involved replacing the existing pavement with continuously reinforced concrete pavement. On both projects, northbound lanes were reinforced with epoxy-coated steel and southbound lanes were reinforced with uncoated steel. This side-by-side construction provides an excellent opportunity tor comparing the performance of pavement constructed with epoxy-coated reinforcement to pavement constructed with uncoated reinforcement. The investigation described herein included a complete crack survey on both projects, installation of half-cell sites and gauge points, construction of laboratory specimens. and comparison of measured crack spacings and widths to calculated values. Results of the crack survey indicate that average crack spacing is stabilizing between 4 and 6 ft. Average crack spacing on pavements constructed with coated steel is less than on pavements constructed with uncoated steel, but the difference is small. Initial half-cell readings indicate little or no corrosion activity on either the coated or uncoated steel. Comparison of laboratory specimens constructed with coated and uncoated steel reveals no significant difference in terms of stiffness, force required to cause cracking, or average crack width. On the basis of the results of this investigation, it is concluded that performance early in the life of a continuously reinforced concrete pavement is not significantly affected by the use of epoxycoated reinforcing steel. However, if the reinforcement begins to corrode, the coated steel should have a significant advantage. It is recommended that crack surveys and half-cell measurements be performed on a regular basis to assess long-term effects.Final Report March 1989-August 1991N
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