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Lg excitation, attenuation, and source spectral scaling in central and eastern North America

Description: Seismic moments and corner frequencies were obtained for many earthquakes in the central and eastern United States, and for a few events in the western United States, using the Lg phase and a recently developed inversion algorithm. Additionally, Q values for the Lg phase along paths to individual stations were obtained simultaneously with the source parameters. Both corner frequencies and magnitudes were found to vary systematically with moment. For moments between 0.15 and 400 x 10{sup 15} N-m corner frequencies vary between about 4 and 0.2 Hz while body-wave magnitude varies between about 3.5 and 5.8. A map of Lg Q values displays a systematic decrease from east and west. Maximum and minimum values are 989 and 160, respectively. Lg coda Q values were obtained for the entire United States with excellent coverage in the eastern and western portions of the country and somewhat poorer coverage in the central portion. Lg coda Q is highest (700-750) in a region of the northeastern United States that includes portions of New York and Pennsylvania and lowest (>200) in California. Lg coda Q is lower (250-450) everywhere west of Rocky Mountains than in the rest of the country (450-750). Q determinations for both the direct Lg phase and Lg coda indicate that, for an earthquake of a given magnitude, Lg and its coda will propagate much more efficiently, and cause damage over a wider area, in the eastern and central United States than it will in the United States.
Date: October 1, 1997
Creator: Mitchell, B.J.; Xie, J. & Baqer, S.
Partner: UNT Libraries Government Documents Department

Moment-Based Probability Modeling and Extreme Response Estimation, The FITS Routine Version 1.2

Description: This report documents the use of the FITS routine, which provides automated fits of various analytical, commonly used probability models from input data. It is intended to complement the previously distributed FITTING routine documented in RMS Report 14 (Winterstein et al., 1994), which implements relatively complex four-moment distribution models whose parameters are fit with numerical optimization routines. Although these four-moment fits can be quite useful and faithful to the observed data, their complexity can make them difficult to automate within standard fitting algorithms. In contrast, FITS provides more robust (lower moment) fits of simpler, more conventional distribution forms. For each database of interest, the routine estimates the distribution of annual maximum response based on the data values and the duration, T, over which they were recorded. To focus on the upper tails of interest, the user can also supply an arbitrary lower-bound threshold, {chi}{sub low}, above which a shifted distribution model--exponential or Weibull--is fit.
Date: November 1, 1999
Creator: MANUEL,LANCE; KASHEF,TINA & WINTERSTEIN,STEVEN R.
Partner: UNT Libraries Government Documents Department

Evaluation of the discrete complex-image method for a NEC-like moment-method solution

Description: The discrete image approximation for the field of a half-space is tested in the NEC antenna modeling program as an alternative to the interpolation method presently used. The accuracy and speed of the discrete image approximation are examined for varying number of images and approximation contour, and the solution for current is obtained on a horizontal wire approaching the interface.
Date: January 5, 1996
Creator: Burke, G.J.
Partner: UNT Libraries Government Documents Department

Ionization cooling and muon dynamics

Description: Muon colliders potential to provide a probe for fundamental particle physics is very interesting. To obtain the needed collider luminosity, the phase space volume must be greatly reduced within the muon life time. The Ionization cooling is the preferred method used to compress the phase space and reduce the emittance to obtain high luminosity muon beams. The authors note that, the ionization losses results not only in damping, but also heating. They discuss methods used including moments methods, Focker Plank Equation, and Multi Particle Codes. In addition they show how a simple analysis permits us to estimate the most part of the optimal system parameters, such as optimal damping rates, length of the system and energy.
Date: January 1, 1998
Creator: Parsa, Z.
Partner: UNT Libraries Government Documents Department

Energy dependent bias in plutonium verification measurements using thermal neutron multiplicity counters

Description: Multiplicity analysis algorithms are extended to include the effect of ({alpha}, n) neutron energies on the detector efficiencies, induced fission probabilities, and induced fission factorial moments. The analysis is restricted to plutonium oxide. Bias is calculated as a function of ({alpha}, n) neutron energy for six thermal neutron coincidence counters: HLNC, AWCC, 3RMC, PSMC, PYRO, and 5RMC. Ring ratio data for the 3RMC are used to reduce energy dependent bias in the verification of impure plutonium oxide. The utility of the AWCC as a multiplicity counter is considered.
Date: October 1, 1997
Creator: Krick, M.S.; Langner, D.G. & Stewart, J.E.
Partner: UNT Libraries Government Documents Department

Flux limiting nature`s own way -- A new method for numerical solution of the transport equation

Description: The transport equation may be solved by expanding it in spherical harmonics, Y{sub lm}, and truncating the resultant infinite set of equations at some finite order L. This procedure leaves the (L + 1)th order moments which appear in the Lth order equation undetermined, and the standard procedure for obtaining a closed set of equations has been to set all the (L + 1)th order moments to zero. It has been shown here that this procedure actually violates the apriori knowledge that one is solving for the moments of a probability measure on the unit sphere. Using the theory of moments of a probability measure on the unit sphere. Using the theory of moments as discussed above, the (L + 1)th order moments can be chosen in accordance with apriori knowledge. The resultant truncated set of equations has properties much truer to the original transport equation than the usual set obtained by setting the (L + 1)th order moments to zero. In particular the truncated set of equations gets the solution of the transport equation exactly right in both the diffusion limit and the free streaming limit. Furthermore, this has been achieved by merely truncating the set of equations properly and not by any ad hoc changes in the basic equations as is the case in the approaches that use flux limiters.
Date: July 29, 1976
Creator: Kershaw, D.S.
Partner: UNT Libraries Government Documents Department

Nuclear Level Densities for Modeling Nuclear Reactions: An Efficient Approach Using Statistical Spectroscopy

Description: The general goal of the project is to develop and implement computer codes and input files to compute nuclear densities of state. Such densities are important input into calculations of statistical neutron capture, and are difficult to access experimentally. In particular, we will focus on calculating densities for nuclides in the mass range A {approx} 50-100. We use statistical spectroscopy, a moments method based upon a microscopic framework, the interacting shell model. Second year goals and milestones: Develop two or three competing interactions (based upon surface-delta, Gogny, and NN-scattering) suitable for application to nuclei up to A = 100. Begin calculations for nuclides with A = 50-70.
Date: August 10, 2005
Creator: Johnson, Calvin W.
Partner: UNT Libraries Government Documents Department

Discrete Ordinates Approximations to the First- and Second-Order Radiation Transport Equations

Description: The conventional discrete ordinates approximation to the Boltzmann transport equation can be described in a matrix form. Specifically, the within-group scattering integral can be represented by three components: a moment-to-discrete matrix, a scattering cross-section matrix and a discrete-to-moment matrix. Using and extending these entities, we derive and summarize the matrix representations of the second-order transport equations.
Date: June 1, 2002
Creator: FAN, WESLEY C.; DRUMM, CLIFTON R. & POWELL, JENNIFER L.
Partner: UNT Libraries Government Documents Department

Inverse scattering code

Description: A methodology for the evaluation of complex electromagnetics problems is presented. The methodology reduces the computational requirements for the analysis of large scale computational electromagnetics problems by hybridizing the method of moments and physical optics techniques. The target model is based on triangular facets and the incident field source by its system response function. Data which can be obtained from the analysis are radar cross section, power spectral density, and range profiles.
Date: September 1, 1997
Creator: Hale, A. & King, A.
Partner: UNT Libraries Government Documents Department

TABULATED VALUES OF SCATTERED GAMMA-RAY FLUXES IN WATER INTERPOLATED FROM MOMENTS METHOD CALCULATIONS

Description: Tables of scattered gamma-ray fluxes in water that are suitable for integration over source spectra were generated on the IBM-7090 computer by Lagrangian interpolation of moments method results for point isotropic gamma-ray sources. Values of the fluxes were obtained for a consistent set of scattered gamma-ray energies taken in steps of 0.1 Mev from 0.1 to 1.0 Mev and in steps of 0.25 Mev from 0.25 to 10 Mev. One table was obtained for each scattered energy for various values of the source energy and of the distance from the source in mean free paths. Tables were then generated in which the distance from the source was converted from mean free paths to centimeters. The latter set may be integrated over any source spectrum to obtain the flux of scattered gamma rays in water, and, with small error, in any material in which the cross section is dominated by the Compton scattering cross section. This includes the low-Z materials such as aluminum and air. (auth)
Date: July 29, 1963
Creator: Trubey, D.K.
Partner: UNT Libraries Government Documents Department

RCS and antenna modeling with MOM using hybrid meshes

Description: In this presentation, the authors will investigate the use of hybrid meshes for modeling RCS and antenna problems in three dimensions. They will consider two classes of hybrid basis functions. These include combinations of quadrilateral and triangular meshes for arbitrary 3D geometries, and combinations of axisymmetric body-of-revolution (BOR) basis functions and triangular facets. In particular, they will focus on the problem of enforcing current continuity between two surfaces which are represented by different types of surface discretizations and unknown basis function representations. They will illustrate the use of an operator-based code architecture for the implementation of these formulations, and how it facilitates the incorporation of the various types of boundary conditions in the code. Both serial and parallel code implementation issues for the formulations will be discussed. Results will be presented for both scattering and antenna problems. The emphasis will be on accuracy, and robustness of the techniques. Comparisons of accuracy between triangular meshed and quadrilateral meshed geometries will be shown. The use of hybrid meshes for modeling BORs with attached appendages will also be presented.
Date: February 1, 1997
Creator: Putnam, J.M. & Kotulski, J.D.
Partner: UNT Libraries Government Documents Department

Nuclear Level Densities for Modeling Nuclear Reactions: An Efficient Approach Using Statistical Spectroscopy: Annual Report 2003-2004

Description: The general goal of the project is to develop and implement computer codes and input files to compute nuclear densities of state. Such densities are important input into calculations of statistical neutron capture, and are difficult to access experimentally. In particular, we will focus on calculating densities for nuclides in the mass range A ?????? 50 - 100. We use statistical spectroscopy, a moments method based upon a microscopic framework, the interacting shell model. In this report we present our progress for the past year.
Date: July 30, 2004
Creator: Johnson, Calvin W.
Partner: UNT Libraries Government Documents Department

Final Report, DOE Award Number DE-FG02-02ER45964, Electromagnetic Properties of Matter at X-ray Wavelengths

Description: We report results of a collaborative study of photon and charged-particle interactions with matter between the University of Vermont and Argonne and Brookhaven National Laboratories. A major goal was to extend the study of electromagnetic properties of selected materials to as wide a spectral range as possible. This broad approach discloses systematic trends not apparent in isolated measurements and exploits the power of dispersion analysis and sum-rule constraints. Emphasis was largely on UV and X-ray processes and capitalized on the wide range of photon energies available at NSLS. A key finding is that, under favorable circumstances, dispersion theory relates dispersive processes (e.g. refractive index, dielectric constant) to spectral moments of absorptive processes. This appears to be a new method in optics; it yields significant simplifications and provides a precise, model-independent characterization of optical materials. Problems addressed included a) x-ray magnetooptics; b) UV/soft-x-ray processes in insulators and their contribution to visible dispersion; c) demonstration of moments/dispersion analysis in glasses and applications to fiber-optic systems; d) the optical constants of silicon and their application to the stopping power of silicon for charged-particles. Results include: ● Resolution of a long-standing conflict over the relation between x-ray Faraday rotation and x-ray magnetic circular dichroism. Specifically, the Kramers-Kronig relations must be generalized to account for the breaking of time-reversal symmetry by magnetic fields. Experimental reports to the contrary were shown to be inconclusive. Reanalysis of x-ray Faraday rotation data supports the generalization. ● Demonstration that the optical properties of dielectrics in their region of transparency are determined by a series expansion in spectral moments of the dielectric’s infrared and ultraviolet absorption spectra. Application of this to silicate glasses clarifies the role of glass modifiers in introducing charge-transfer, intra-ionic and perturbed-exciton transitions that combine to determine visible optical properties. Roughly, the refractive index is determined by ...
Date: February 28, 2007
Creator: Smith, David Y.
Partner: UNT Libraries Government Documents Department