Solving the linear Boltzmann equation in neutron scattering phenomena presents many challenges to standard numerical schemes in computational physics. For an SN discretization, the so-called ray effects pollute the numerical solution. This pollution can be viewed mathematically as ''contamination'' from a poorly chosen approximating basis set for the angle component of the discretization-i.e., collocation in angle is equivalent to discretization with delta basis functions, which form a poor approximating basis set. Fortunately, a PN discretization, which uses a better approximating basis set (i.e., spherical harmonics), eliminates these ray effects. Unfortunately, solving for the moments or PN equations is difficult. Moments couple strongly with each other, creating a strongly coupled system of partial differential equations (pde's) ; numerical algorithms for solving such strongly coupled systems are difficult to develop. In this paper, novel algorithms for solving this coupled system are presented. In particular, algorithms for solving the PN discretization of the linear Boltzmann equation using a first-order system least-squares (FOSLS) methodology (c.f. [1]) are presented.

This report is intended to give a summary analysis of the candidate model configurations under consideration by NCAR for the atmospheric component of next version of the Community Climate System Model (CCSM). Intercomparison results are presented for each of the models available prior to the Atmospheric Model Working Group (AMWG) meeting, December 12-14, 2000. We present four types of figures in this report. The traditional methods of viewing zonal mean surface fields, latitude-longitude maps and zonal mean latitude-height cross sections are straightforward. In each of these cases, we present DJF and JJA climatological averages and a difference from an observational or reanalysis data set. The fourth method of analyzing the candidates' model performance involves the use of ''performance portraits'' and is explained in detail on following pages. As stated by NCAR and the AMWG, the information included in this report should be considered proprietary to NCAR and is not to be cited, consistent with the disclaimer on the AMWG password protected web pages. We deliberately have deferred our conclusions in this printed report to our presentation. Rather, we encourage you to draw your own conclusions based on these figures and other information made available at the AMWG meeting.

Using a combination of electronic-structure theory, variational transition-state theory, and solutions to the time-dependent master equation, the authors have studied the kinetics of the title reaction theoretically over wide ranges of temperature and pressure. The agreement between theory and experiment is quite good. By comparing the theoretical and experimental results describing the kinetic behavior, they have been able to deduce a value for the C{sub 2}H{sub 5}-O{sub 2} bond energy of {approximately}34 kcal/mole and a value for the exit-channel transition-state energy of {minus}4.3 kcal/mole (measured from reactants). These numbers compare favorably with the electronic-structure theory predictions of 33.9 kcal/mole and {minus}3.0 kcal/mole, respectively. The master-equation solutions show three distinct temperature regimes for the reaction, discussed extensively in the paper. Above T {approx} 700 K, the reaction can be written as an elementary step, C{sub 2}H{sub 5} + O{sub 2} {leftrightarrow} C{sub 2}H{sub 4} + HO{sub 2}, with the rate coefficient, k(T) = 3.19 x 10{sup {minus}17} T{sup 1.02} exp(2035/RT) cm{sup 3}/molec.-sec., independent of pressure even though the intermediate collision complex may suffer a large number of collisions.

This paper presents models and measurements of antenna input impedance in resonant cavities at high frequencies.The behavior of input impedance is useful in determining the transmission and reception characteristics of an antenna (as well as the transmission characteristics of certain apertures). Results are presented for both the case where the cavity is undermoded (modes with separate and discrete spectra) as well as the over moded case (modes with overlapping spectra). A modal series is constructed and analyzed to determine the impedance statistical distribution. Both electrically small as well as electrically longer resonant and wall mounted antennas are analyzed. Measurements in a large mode stirred chamber cavity are compared with calculations. Finally a method based on power arguments is given, yielding simple formulas for the impedance distribution.

We investigate a well-motivated mesh untangling objective function whose optimization automatically produces non-inverted elements when possible. Examples show the procedure is highly effective on simplicial meshes and on non-simplicial (e.g., hexahedral) meshes constructed via mapping or sweeping algorithms. The current whisker-weaving (WW) algorithm in CUBIT usually produces hexahedral meshes that are unsuitable for analyses due to inverted elements. The majority of these meshes cannot be untangled using the new objective function. The most likely source of the difficulty is poor mesh topology.

In this paper, an acetone planar laser-induced fluorescence (PLIF) technique for nonintrusive, temperature imaging is demonstrated in gas-phase (Pr = 0.72) turbulent Rayleigh-Benard convection at Rayleigh number, Ra = 1.3 x 10{sup 5}. The PLIF technique provides quantitative, spatially correlated temperature data without the flow intrusion or time lag associated with physical probes and without the significant path averaging that plagues most optical heat-transfer diagnostic tools, such as the Mach-Zehnder interferometer, thus making PLIF an attractive choice for quantitative thermal imaging in easily perturbed, complex three-dimensional flow fields. The instantaneous (20-ns integration time) thermal images presented have a spatial resolution of 176 x 176 x 500 {micro}m and a single-pulse temperature measurement precision of {+-}5.5 K, or 5.4 % of the total temperature difference. These images represent a 2-D slice through a complex, 3-D flow allowing for the thermal structure of the turbulence to be quantified. Statistics such as the horizontally averaged temperature profile, rms temperature fluctuation, two-point spatial correlations, and conditionally averaged plume structures are computed from an ensemble of 100 temperature images. The profiles of the mean temperature and rms temperature fluctuation are in good agreement with previously published data, and the results obtained from the two-point spatial …

Critical infrastructures are central to our national defense and our economic well-being, but many are taken for granted. Presidential Decision Directive (PDD) 63 highlights the importance of eight of our critical infrastructures and outlines a plan for action. Greatly enhanced physical security systems will be required to protect these national assets from new and emerging threats. Sandia National Laboratories has been the lead laboratory for the Department of Energy (DOE) in developing and deploying physical security systems for the past twenty-five years. Many of the tools, processes, and systems employed in the protection of high consequence facilities can be adapted to the civilian infrastructure.

A modeling study of benzene and phenyl radical formation is performed for three low-pressure premixed laminar flat flames having an unsaturated C{sub 2} or C{sub 3} hydrocarbon fuel (acetylene, ethylene, and propene). Predictions using three published detailed elementary-step chemical kinetics mechanisms are tested against MBMS species profile data for all three flames. The differences between the three mechanisms predictive capabilities are explored, with an emphasis on benzene formation pathways. A new chemical kinetics mechanism is created combining features of all three published mechanisms. Included in the mechanism are several novel benzene formation reactions involving combinations of radicals such as C{sub 2}H+C{sub 4}H{sub 5}, and C{sub 5}H{sub 3}+CH{sub 3}. Reactions forming fulvene (a benzene isomer) are included, such as C{sub 3}H{sub 3}+C{sub 3}H{sub 5},as well as fulvene-to-benzene reactions. Predictions using the new mechanism show virtually all of the benzene and phenyl radical to be formed by reactions of either C{sub 3}H{sub 3}+C{sub 3}H{sub 3} or C{sub 3}H{sub 3}+C{sub 3}H{sub 5}, with the relative importance being strongly dependent upon the fuel. C{sub 5}H{sub 3}+CH{sub 3} plays a minor role in fulvene formation in the acetylene flame. The C{sub 2}H{sub x}+C{sub 4}H{sub 4} reactions do not contribute noticeably to benzene or phenyl radical …

This paper summarizes the results of a wind mapping project and a validation study for the state of Vermont. The computerized wind resource mapping technique used for this project was developed at the National Renewable Energy Laboratory (NREL). The technique uses Geographic Information System (GIS) software and produces high resolution (1km{sup 2}) wind resource maps.