72,258 research outputs found
Final-state interactions and superscaling in the semi-relativistic approach to quasielastic electron and neutrino scattering
The semi-relativistic approach to electron and neutrino quasielastic
scattering from nuclei is extended to include final-state interactions.
Starting with the usual non-relativistic continuum shell model, the problem is
relativized by using the semi-relativistic expansion of the current in powers
of the initial nucleon momentum and relativistic kinematics. Two different
approaches are considered for the final-state interactions: the Smith-Wambach
2p-2h damping model and the Dirac-equation-based potential extracted from a
relativistic mean-field plus the Darwin factor. Using the latter the scaling
properties of and cross sections for intermediate
momentum transfers are investigated.Comment: 36 pages, 17 figure
The RHMC algorithm for theories with unknown spectral bounds
The Rational Hybrid Monte Carlo (RHMC) algorithm extends the Hybrid Monte
Carlo algorithm for lattice QCD simulations to situations involving fractional
powers of the determinant of the quadratic Dirac operator. This avoids the
updating increment () dependence of observables which plagues the Hybrid
Molecular-dynamics (HMD) method. The RHMC algorithm uses rational
approximations to fractional powers of the quadratic Dirac operator. Such
approximations are only available when positive upper and lower bounds to the
operator's spectrum are known. We apply the RHMC algorithm to simulations of 2
theories for which a positive lower spectral bound is unknown: lattice QCD with
staggered quarks at finite isospin chemical potential and lattice QCD with
massless staggered quarks and chiral 4-fermion interactions (QCD). A
choice of lower bound is made in each case, and the properties of the RHMC
simulations these define are studied. Justification of our choices of lower
bounds is made by comparing measurements with those from HMD simulations, and
by comparing different choices of lower bounds.Comment: Latex(Revtex 4) 25 pages, 8 postscript figure
Analyzing the Data from X-ray Polarimeters with Stokes Parameters
X-ray polarimetry promises to deliver unique information about the geometry
of the inner accretion flow of astrophysical black holes and the nature of
matter and electromagnetism in and around neutron stars. In this paper, we
discuss the possibility to use Stokes parameters - a commonly used tool in
radio, infrared, and optical polarimetry - to analyze the data from X-ray
polarimeters such as scattering polarimeters and photoelectric effect
polarimeters, which measure the linear polarization of the detected X-rays.
Based on the azimuthal scattering angle (in the case of a scattering
polarimeter) or the azimuthal component of the angle of the electron ejection
(in the case of a photoelectric effect polarimeter), the Stokes parameters can
be calculated for each event recorded in the detector. Owing to the additive
nature of Stokes parameters, the analysis reduces to adding the Stokes
parameters of the individual events and subtracting the Stokes parameters
characterizing the background (if present). The main strength of this kind of
analysis is that the errors on the Stokes parameters can be computed easily and
are well behaved - in stark contrast of the errors on the polarization fraction
and polarization direction. We demonstrate the power of the Stokes analysis by
deriving several useful formulae, e.g. the expected error on the polarization
fraction and polarization direction for a detection of signal and
background events, the optimal observation times of the signal and
background regions in the presence of non-negligible background contamination
of the signal, and the minimum detectable polarization (MDP) that can be
achieved when following this prescription.Comment: 9 pages, 2 figures, accepted for publication in Astropart. Phy
Flight-Effects on Predicted Fan Fly-By Noise
The impact on PNLT (Perceived Noise Level, Tone corrected) and Fly-by EPNL (Effective Perceived Noise Level) when forward motion reduces the noise generated by the bypass fan of an aircraft engine was studied. Calculated noise spectra for a typical subsonic tip speed fan designed for blade passage frequency (BPF) tone cutoff were translated in frequency by systematically varying the BPF from 0.5 to 8 kHz. Two cases of predicted flight-effects on fan source noises were considered: reduced BPF tone level of 8 db and reduced broadband noise level of about 2 db in addition to reduced tone level. The maximum reduction in PNLT of the noise as emitted from the fan occurred when the BPF was at 4 kHz where the reductions were 7.4 and 10.0 db. The maximum reduction in EPNL of the noise as received during a 500-foot altitude fly-by occurred when the BPF was at 2.5 kHz where the reductions were 5.0 and 7.8 db
Development of fuel cell electrodes Semiannual report, 30 Jun. 1966 - 30 Dec. 1966
Fuel cell using circulating liquid electrolyte and water removal by transpiration through porous electrode
Advanced dosimetry systems for the space transport and space station
Advanced dosimetry system concepts are described that will provide automated and instantaneous measurement of dose and particle spectra. Systems are proposed for measuring dose rate from cosmic radiation background to greater than 3600 rads/hr. Charged particle spectrometers, both internal and external to the spacecraft, are described for determining mixed field energy spectra and particle fluxes for both real time onboard and ground-based computer evaluation of the radiation hazard. Automated passive dosimetry systems consisting of thermoluminescent dosimeters and activation techniques are proposed for recording the dose levels for twelve or more crew members. This system will allow automatic onboard readout and data storage of the accumulated dose and can be transmitted to ground after readout or data records recovered with each crew rotation
Radio detection of H2O in comet Bradfield (1974b)
Results of observations of comet Bradfield using the Haystack telescope are summarized with emphasis on the detection of the 1.35 cm emission line of water in the comet. The excitation of water and methyl cyanide in comets is briefly considered
Workplace Accommodations for Individuals with Arthritis
This brochure on individuals with arthritis and the Americans with Disabilities Act (ADA) is one of a series on human resources practices and workplace accommodations for persons with disabilities edited by Susanne M. Bruyère, Ph.D., CRC, SPHR, Director, Program on Employment and Disability, School of Industrial and Labor Relations – Extension Division, Cornell University.
Cornell University was funded in the early 1990’s by the U.S. Department of Education National Institute on Disability and Rehabilitation Research as a National Materials Development Project on the employment provisions (Title I) of the ADA (Grant #H133D10155). These updates, and the development of new brochures, have been funded by Cornell’s Program on Employment and Disability, the Pacific Disability and Business Technical Assistance Center, and other supporters
Design and performance of an adaptive MFSK HF terminal.
The paper describes the implementation of a real-time integrated modem/codec system for long-range radio communications, e.g. HF. The system has been developed by the Hull-Lancaster Communication Research Group. The system has been implemented using a proprietary DSP-based architecture which uses the AT&T DSP32C digital signal processor and the transmission format comprises MFSK modulation combined with RS coding. The main features of the system are described and results from on-air HF trials over both static and aeromobile channels are presente
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