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in subjects: "Frequency Dependence"  
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Calibration of LSST Instrumental and Atmospheric Photometric Passbands

Description: The Large Synoptic Survey Telescope (LSST) will continuously image the entire sky visible from Cerro Pachon in northern Chile every 3-4 nights throughout the year. The LSST will provide data for a broad range of science investigations that require better than 1% photometric precision across the sky (repeatability and uniformity) and a similar accuracy of measured broadband color. The fast and persistent cadence of the LSST survey will significantly improve the temporal sampling rate with which … more
Date: July 6, 2011
Creator: Burke, David L.; Axelrod, T.; Barrau, Aurelien; Baumont, Sylvain; Blondin, Stephane; Claver, Chuck et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Direct Comparison of Brookhaven Reflectivity Measurements with Free-Electron Theory

Description: The reflectivity at normal incidence of copper and aluminum samples was recently measured over a large frequency range at Brookhaven by one of us (JT). Then using the Kramers-Kroning integrals, and assuming the free-electron model of conductivity, the dependence of conductivity on frequency was obtained. The results seemed to suggest, for example, that the dc conductivities of the copper and evaporated aluminum samples are a factor of 3 lower than expected. We propose in this report, instead, d… more
Date: December 13, 2010
Creator: Bane, Karl L.F.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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HIGHER MODE FREQUENCY EFFECTS ON RESONANCE IN MACHINERY, STRUCTURES, AND PIPE SYSTEMS

Description: The complexities of resonance in multi-degree of freedom systems (multi-DOF) may be clarified using graphic presentations. Multi-DOF systems represent actual systems, such as beams or springs, where multiple, higher order, natural frequencies occur. Resonance occurs when a cyclic load is applied to a structure, and the frequency of the applied load equals one of the natural frequencies. Both equations and graphic presentations are available in the literature for single degree of freedom (SDOF) … more
Date: May 2, 2010
Creator: Leishear, R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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An Extension of Implicit Monte Carlo Diffusion: Multigroup and The Difference Formulation

Description: Implicit Monte Carlo (IMC) and Implicit Monte Carlo Diffusion (IMD) are approaches to the numerical solution of the equations of radiative transfer. IMD was previously derived and numerically tested on grey, or frequency-integrated problems. In this research, we extend Implicit Monte Carlo Diffusion (IMD) to account for frequency dependence, and we implement the difference formulation as a source manipulation variance reduction technique. We derive the relevant probability distributions and pre… more
Date: April 19, 2010
Creator: Cleveland, M A; Gentile, N & Palmer, T S
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Contained Modes In Mirrors With Sheared Rotation

Description: In mirrors with E × B rotation, a fixed azimuthal perturbation in the lab frame can appear as a wave in the rotating frame. If the rotation frequency varies with radius, the plasma-frame wave frequency will also vary radially due to the Doppler shift. A wave that propagates in the high rotation plasma region might therefore be evanescent at the plasma edge. This can lead to radially localized Alfven eigenmodes with high azimuthal mode numbers. Contained Alfven modes are found both for peaked an… more
Date: October 8, 2010
Creator: Fetterman, Abraham J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Research on micro-sized acoustic bandgap structures.

Description: Phononic crystals (or acoustic crystals) are the acoustic wave analogue of photonic crystals. Here a periodic array of scattering inclusions located in a homogeneous host material forbids certain ranges of acoustic frequencies from existence within the crystal, thus creating what are known as acoustic (or phononic) bandgaps. The vast majority of phononic crystal devices reported prior to this LDRD were constructed by hand assembling scattering inclusions in a lossy viscoelastic medium, predomin… more
Date: January 1, 2010
Creator: Fleming, James Grant; McCormick, Frederick Bossert; Su, Mehmet F.; El-Kady, Ihab Fathy; Olsson, Roy H., III & Tuck, Melanie R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Three-Dimensional Analysis of Frequency-Chirped FELs

Description: Frequency-chirped free-electron lasers (FELs) are useful to generate a large photon bandwidth or a shorter x-ray pulse duration. In this paper, we present a three-dimensional analysis of a high-gain FEL driven by the energy-chirped electron beam. We show that the FEL eigenmode equation is the same for a frequency-chirped FEL as for an undulator-tapered FEL. We study the transverse effects of such FELs including mode properties and transverse coherence.
Date: September 14, 2010
Creator: Zhirong, Huang
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

A Two-Dimensional Fem Code for Impedance calculation in High Frequency Domain

Description: A new method, using the parabolic equation (PE), for the calculation of both high-frequency impedances of small-angle taper (or collimator) is developed in [1]. One of the most important advantages of the PE approach is that it eliminates the spatial scale of the small wavelength from the problem. As a result, only coarser spatial meshes are needed in calculating the numerical solution of the PE. We developed a new code based on Finite Element Method (FEM) which can handle arbitrary profile of … more
Date: August 25, 2010
Creator: Wang, Lanfa; Lee, Lie-Quan & Stupakov, Gennady
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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DOE-Imaging grant FG02-06ER15829, entitled "Developing Laser-Induced Re-Collision Electron Self-Diffraction" Brief summary of accomplishments

Description: Our principal goal was the experimental demonstration of Laser-Induced Electron Diffraction (LIED). Key steps along the development of this experimental technique have been accomplished and reported in the publications listed in this brief report. We started with measuring 3D electron momenta spectra in aligned nitrogen and oxygen molecules. Chakra Maharjan (Ph.D. student of Lew Cocke) was a lead researcher on this project. Although Chakra succeeded in obtaining those spectra, we were scooped b… more
Date: 2012-04~
Creator: Litvinyuk, Igor V. & Ben-Itzhak, Itzik
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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