9,296 research outputs found
A study of longitudinal oscillations of propellant tanks and wave propagations in feed lines. Part II - Wave propagation in elastic pipe filled with incompressible viscous fluid
Fluid wave propagation in liquid propellant feed syste
A practical Hadamard transform spectrometer for astronomical application
The mathematical properties of Hadamard matrices and their application to spectroscopy are discussed. A comparison is made between Fourier and Hadamard transform encoding in spectrometry. The spectrometer is described and its laboratory performance evaluated. The algorithm and programming of inverse transform are given. A minicomputer is used to recover the spectrum
High-energy asymptotic behavior of the Bourrely-Soffer-Wu model for elastic scattering
Some time ago, an accurate phenomenological approach, the BSW model, was
developed for proton-proton and antiproton-proton elastic scattering cross
sections at center-of-mass energies above 10 GeV. This model has been used to
give successful theoretical predictions for these processes, at successive
collider energies. The BSW model involves a combination of integrals that,
while computable numerically at fairly high energies, require some mathematical
analysis to reveal the high-energy asymptotic behavior. In this paper we
present a high-energy asymptotic representation of the scattering amplitude at
moderate momentum transfer, for the leading order in an expansion parameter
closely related to the logarithm of the center-of-mass energy. The fact that
the expansion parameter goes as the logarithm of the energy means that the
asymptotic behavior is accurate only for energies greatly beyond any
foreseeable experiment. However, we compare the asymptotic representation
against the numerically calculated model for energies in a less extreme region
of energy. The asymptotic representation is given by a simple formula which, in
particular, exhibits the oscillations of the differential cross section with
momentum transfer. We also compare the BSW asymptotic behavior with the
Singh-Roy unitarity upper bound for the diffraction peak.Comment: 27 pages, 11 figures,revised version to appear in Physical Review
Flexible parylene actuator for micro adaptive flow control
This paper describes the first flexible parylene electrostatic actuator valves intended for micro adaptive flow control for the future use on the wings of micro-air-vehicle (MAV). The actuator diaphragm is made of two layers of parylene membranes with offset vent holes. Without electrostatic actuation, air can move freely from one side of the skin to the other side through the vent holes. With actuation, these vent holes are sealed and the airflow is controlled. The membrane behaves as a complete diaphragm.
We have successfully demonstrated this function using a 2-mm x 2-mm parylene diaphragm electrostatic actuator valves. This work also includes the novel anti-stiction technology that is crucial to make such large-area parylene actuator diaphragm with the combined use of anti-stiction posts, self-assembled monolayers (SAM), surface roughening, and bromine trifluoride (BrFe) dry etching. With the help of SAM treatment, the operating voltage is lowered from 30 volts to 13 volts. The load deflection method is then used to measure the effective thickness of the composite
diaphragm. The flexible parylene diaphragm can be deflected up to 100 ÎĽm when 150 Torr of pressure is applied. The result is fitted into a theoretical model and yields an effective thickness of 5.9 ÎĽm, which is agreeable with the actual thickness of 5.6 ÎĽm, thus proves the functionality of the device
A practical multi-spectrum Hadamard Transform Spectrometer
A Hadamard Transform Spectrometer (HTS) which simultaneously obtains fifteen infrared spectra, each having 255 spectral elements was constructed. Spectra are obtained essentially in real time through use of a minicomputer with 8K words of memory and a CRT display. This permits operation of the instrument in the field
Electromagnetic modes of Maxwell fisheye lens
We provide an analysis of the radial structure of TE and TM modes of the
Maxwell fisheye lens, by means of Maxwell equations as applied to the fisheye
case. Choosing a lens of size R = 1 cm, we plot some of the modes in the
infrared range.Comment: 2+6 pages in Latex, 3 figures to be found in the published referenc
Dijet Cross Section and Longitudinal Double Spin Asymmetry Measurements in Polarized Proton-proton Collisions at \sqrt{s}=200 GeV at STAR
These proceedings show the preliminary results of the dijet cross sections
and the dijet longitudinal double spin asymmetries A_LL in polarized
proton-proton collisions at \sqrt{s} = 200 GeV at the mid-rapidity |eta| < 0.8.
The integrated luminosity of 5.39 pb^{-1} collected during RHIC Run-6 was used
in the measurements. The preliminary results are presented as functions of the
dijet invariant mass M_jj. The dijet cross sections are in agreement with
next-to-leading-order pQCD predictions. The A_LL is compared with theoretical
predictions based on various parameterizations of polarized parton
distributions of the proton. Projected precision of data analyzed to date from
Run-9 are shown.Comment: 8 pages, 5 figures, Proceedings of the SPIN2010 conference (Juelich,
Germany, 2010
Casimir Forces and Graphene Sheets
The Casimir force between two infinitely thin parallel sheets in a setting of
such sheets is found. The finite two-dimensional conductivities, which
describe the dispersive and absorptive properties of each sheet, are taken into
account, whereupon the theory is applied to interacting graphenes. By exploring
similarities with in-plane optical spectra for graphite, the conductivity of
graphene is modeled as a combination of Lorentz type oscillators. We find that
the graphene transparency and the existence of a universal constant
conductivity result in graphene/graphene Casimir interaction at
large separations to have the same distance dependence as the one for perfect
conductors but with much smaller magnitude
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