| Isogeometric Divergence-conforming B-splines for the Unsteady Navier-Stokes Equations |
Apr 2012 |
49 pages |
| Authors:
John A Evans; Thomas J Hughes; TEXAS UNIV AT AUSTIN INST FOR COMPUTATIONAL ENGINEERING AND SCIENCES
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 | Divergence-conforming B-splines are developed for application to the incompressible Navier-Stokes equations on geometrically mapped domains. These enable smooth pointwise divergence-free solutions and thus satisfy mass conservation in the strongest possible sense. Semi-discrete methods based on divergence-conforming B-splines are shown to conserve linear and angular momentum and satisfy balance laws for energy vorticity, enstrophy, and helicity. These are geometric structure-preserving quantities and numerical simulations that are sensitive to them are shown ... |
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| Nearest Neighbor Classification Using a Density Sensitive Distance Measurement |
Sep-2009 |
120 pages |
| Authors:
Joshua J Burkholder; NAVAL POSTGRADUATE SCHOOL MONTEREY CA MODELING VIRTUAL ENVIRONMENTS AND SIMULATION (MOVES)
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| This work proposes a density sensitive distance measurement that takes into account the density of an underlying dataset to better represent the shape of the data when measuring distance. Kernel density estimation, using kernel bandwidths determined by k -nearest neighbor distances, is used to approximate the density of the underlying dataset. A scale is applied to the resulting kernel density estimate and a line integral is performed along its surface ... |
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| Approximation of Bit Error Rates in Digital Communications |
Jun-2007 |
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| Authors:
Graham V Weinberg; Sharon Lee; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION EDINBURGH (AUSTRALIA) ELECTRONIC WARFARE AND RADAR DIVISION
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 | This report examines the estimation of bit error rates (BERs) in digital communications. Specifically, the authors will investigate recent work on using bounds to construct approximations for differential quaternary phase shift keying (DQPSK) transmission with Gray coding over an additive white Gaussian noise channel (AWGNC). In previous research, an estimate of this BER was constructed by averaging a lower and upper bound. The authors show that more direct methods can ... |
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| Theory of Second Harmonic Generation in Presence of Diffraction, Beam Walk-Off and Pump Depletion (Preprint) |
MAR 2007 |
16 pages |
| Authors:
Shekhar Guha; Leonel P. Gonzalez; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
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| Integral expressions for the pump and generated fields are presented here for the case of second harmonic generation of a focused Gaussian pump beam incident on a nonlinear crystal. The birefringent walk-off of the generated beam and the effect of pump depletion are included in the theory. |
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| Radiation by a Linear Array of Half-Width Leaky-Wave Antennas (Preprint) |
MAY 2006 |
9 pages |
| Authors:
Killips Daniel; Joshua Radcliffe; Leo Kempel; Stephen Schneider; MICHIGAN STATE UNIV EAST LANSING DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| Leaky-wave antennas are interesting apertures for a variety of applications due to their low profile and wide bandwidth. They are inherently traveling wave antennas, and hence are best suited for end-fire applications. A new type of leaky-wave antenna, the half-width leaky-wave antenna (HWLW), has been recently investigated and found to have similar radiation properties as its full-width leaky-wave (FWLW) counterpart, but only requiring half the transverse dimension. In addition, the ... |
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| Qubit Complexity of Continuous Problems |
09 DEC 2005 |
7 pages |
| Authors:
A. Papageorgiou; J. F. Traub; COLUMBIA UNIV NEW YORK DEPT OF COMPUTER SCIENCE
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| The number of qubits used by a quantum algorithm will be a crucial computational resource for the foreseeable future. The authors show how to obtain the classical query complexity for continuous problems. They then establish a simple formula for a lower bound on the qubit complexity in terms of the classical query complexity. Sections discuss classical information complexity, fundamental concepts and notation for quantum computation, and lower bound on qubit ... |
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| Fundamentals of Combinatorial Optimization and Algorithm Design |
24 MAY 2005 |
8 pages |
| Authors:
Bruce Shepherd; Peter Winkler; Chandra Chekuri; LUCENT TECHNOLOGIES INC MURRAY HILL NJ
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| The main activities supported under this grant are research and support for C. Chekuri, B. Shepherd and P. Winkler. Funds also supported one summer intern, Andrew McGregory from U-Penn, who worked with Shepherd on recognizing Hilbert Bases and other theoretical topics in Math Programming. Visits from scientists include a 2-week visit from Gianpaolo Oriolo (Rome), which resulted in new joint work on robust network design, a week visit from Seffi ... |
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| Approximation of Integrals via Monte Carlo Methods, With an Applications to Calculating Radar Detection Probabilities |
MAR 2005 |
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| Authors:
Graham V. Weinberg; Ross Kyprianou; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION SALISBURY (AUSTRALIA) SYSTEMS SCIENCES LAB
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| The approximation of definite integrals using Monte Carlo simulations is the focus of the work presented here. The general methodology of estimation by sampling is introduced, and is applied to the approximation of two special functions of mathematics: the Gamma and Beta functions. A significant application, in the context of radar detection theory, is based upon the work of Shnidman 1998. The latter considers problems associated with the optimal choice ... |
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| Application of Differential Geometry to Acoustics: Development of a Generalized Paraxial Ray-Trace Procedure from Geodesic Deviation |
18 JAN 2005 |
66 pages |
| Authors:
David R. Bergman; NAVAL RESEARCH LAB WASHINGTON DC
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| In this report, the application of abstract differential geometry acoustics is explored. The results of this application are as follows: (1) a generalized paraxial ray-trace procedure valid for acoustic propagation in a random media with subsonic flow; (2) the demonstration of a continuum of equivalent paraxial systems related by a conformal transformation; and (3) a unified approach to treating problems in acoustics, which leads to generalized versions of Snell's law, ... |
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| Noether's Theorem for Smooth, Discrete and Finite Element Models |
03 JAN 2005 |
32 pages |
| Authors:
Elizabeth Mansfield; KENT UNIV CANTERBURY (UNITED KINGDOM)
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| Noether's Theorem links symmetries and conservation laws for Euler Lagrange Systems. What is a conservation law? Answer: a divergence expression which is zero on solutions of the system. CONCLUSIONS: * The underlying algebraic pattern of the exact variational complexes provide a framework for generalisations of Noether's Theorem and conservation laws in general. * Symmetry-adapted moments would appear to be necessary. |
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| Saddlepoint Approximations for the Combined Probability and Joint Probability Density Function of Selected Order Statistics and the Sum of the Remainder |
17 FEB 2004 |
72 pages |
| Authors:
Albert H. Nuttall; NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
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| A set of N independent random variables ?Xn! with arbitrary probability density functions (pn(X)! are ordered into a new set of dependent random variables, each with a different probability density function. From this new set, the M - I largest random variables are selected. Then, the sum of the remaining N + I - M random variables is computed, giving a total of M dependent random variables. Several statistics have ... |
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| Far Field Extrapolation Technique Using CHIEF Enclosing Sphere Deduced Pressures and Velocities |
DEC 2003 |
191 pages |
| Authors:
Robert M. Drake; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| A Combined Helmholtz Integral Equation Formulation (CHIEF)-defined enclosing sphere placed around an acoustic projector is used to calculate far field response data from near field measurements. Pressure response data at a specified frequency is obtained from a near field linear array. Helmholtz integral relations for the enclosing sphere and integrals of the free-space Green's function and its gradient for defined near field point locations are used along with physical assumptions ... |
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| Computing Normalizing Constants for Finite Mixture Models via Incremental Mixture Importance Sampling (IMIS) |
30 JUL 2003 |
33 pages |
| Authors:
Russell J. Steele; Adrian E. Raftery; Mary J. Emond; WASHINGTON UNIV SEATTLE DEPT OF STATISTICS
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| We propose a method for approximating integrated likelihoods in finite mixture models. We formulate the model in terms of the unobserved group memberships, z, and make them the variables of integration. The integral is then evaluated using importance sampling over the z. We propose an adaptive importance sampling function which is itself a mixture, with two types of component distributions, one concentrated and one diffuse. The more concentrated type of ... |
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| Implementation of a Discontinuous Galerkin Discretization of the Conversation of Mass Equation in QUODDY |
19 MAR 2003 |
19 pages |
| Authors:
M. J. Guillot; C. A. Blain; C. N. Dawson; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| Two variations of a discontinuous Galerkin method are investigated for the primitive form of the time-dependent, 2-D, depth-averaged conservation of mass equation for shallow water. Linear approximating functions are employed, which are defined locally on each element, providing three degrees of freedom per element. In the first method, the degrees of freedom are the nodal values for each element. Analytical integration rules are developed to evaluate the volume integrals, and ... |
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| Broadband, Range-Dependent Normal Mode Model Development |
09 JUL 2002 |
18 pages |
| Authors:
Evan K. Westwood; TEXAS UNIV AT AUSTIN APPLIED RESEARCH LABS
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| Practical approaches to modeling broadband acoustic propagation in range-dependent environments using normal mode theory were developed. A method for eliminating the branch line integral from the normal mode solution was developed, analyzed, and documented in a JASA article. The accuracy and characteristics of various adiabatic- and coupled-mode approaches for range- dependent benchmark problems were investigated. A method for extracting the acoustic modes of propagation and inverting for the acoustic parameters ... |
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| L = 1 Diocotron Instability of Single Charged Plasmas in a Cylindrical Penning Trap with Central Conductor |
24 JUN 2002 |
6 pages |
| Authors:
M. Rome; A. V. Arefiev; I. A. Kotelnikov; R. Pozzoli; TEXAS UNIV AT AUSTIN DEPT OF PHYSICS
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| The linear stability analysis of the l = 1 diocotron perturbations in a single charged plasma confined in a cylindrical Penning trap is critically revisited. Particular attention is devoted to the instability due to the presence of stationary points in the radial profile of the azimuthal rotation frequency. The asymptotic analysis of Smith and Rosenbluth 1 for the case of a single-bounded plasma column (algebraic instability proportional to t(exp 1/2) ... |
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| A Commodity Supercomputer for Turbulence-Control Simulations |
10 OCT 2001 |
59 pages |
| Authors:
Jonathan B. Freund; CALIFORNIA UNIV LOS ANGELES
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| Recent experiments have shown that properly designed high amplitude, low mass flux pulsed slot jets blowing normal to a jet's shear layer near the nozzle can significantly alter the jet's development (Parekh et al., AIAA Paper 96-0308). In contrasts to commonly used low amplitude forcing, this strong excitation appears to overwhelm the turbulence, having nearly the same effect at high and low Reynolds numbers. It can therefore be studied in ... |
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| Approximation with the Radial Basis Functions of Lewitt |
JUL 2001 |
8 pages |
| Authors:
J. J. Green; SHEFFIELD UNIV (UNITED KINGDOM) DEPT OF APPLIED MATHEMATICS
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| R. M. Lewitt has introduced a family of compactly supported radial basis functions which are particularly useful in discretising for inversion ill-posed problems involving line integrals. We consider some practical considerations in their use and implementation, compare square and triangular grids of the functions in two dimensions, and describe some particularly favourable choices of the defining parameters. |
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| Evaluation of Singular Electric Field Integral Equation (EFIE) Matrix Elements |
25 JUN 2001 |
33 pages |
| Authors:
Douglas J. Taylor; NAVAL RESEARCH LAB WASHINGTON DC
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| The electric field integral equation (EFIE) solution for scattering from an arbitrary three-dimensional geometry was published by Rao, Wilton, and Glisson (RWG) in 1982. For electrically large problems, with large systems of equations, the physical fidelity of the solution can be improved with increased numerical accuracy of the Galerkin inner products which populate the method of moments (MoM) impedance matrix. A new treatment of these inner products is presented here ... |
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| Propagation of Energy Pulses in Absorbing/Viscous Material Media |
OCT 2000 |
13 pages |
| Authors:
G. C. Gaunaurd; G. C. Everstine; NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD
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| A delta-pulse that emerges from the origin of coordinates in a lossy, viscous, homogenes medium is studied as it propagates through the medium experiencing absorption and dispersion. Elementary models for such propagation problems have appeared in classical textbooks (e.g., J.D. Jackson, Classical Electrodynamics, pp. 212-215, Wiley, 1962). Generally speaking, as the pulse propagates, its amplitude decreases, and its width broadens. A more detailed, exact analysis of this problem emerges from ... |
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| Numerical Evaluation of an Integral Found in the Theory of Scattering From Rough Interfaces (CD-ROM) |
19 APR 2000 |
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| Authors:
David M. Drumheller; Robert F. Gragg; NAVAL RESEARCH LAB WASHINGTON DC ACOUSTICS SYSTEMS BRANCH
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| ELECTRONIC FILE CHARACTERISTICS: 85 files; 1 PDF report, m-files (MATLAB functions), and Adobe Acrobat 4.0 software. PHYSICAL DESCRIPTION: 1 computer laser optical disc (CD-ROM); 4 3/4 in.; 11.9MB. SYSTEMS DETAIL NOTE: IBM-clone PC compatible; requires CD-ROM drive. ABSTRACT: In this report, an algorithm is presented for the numerical evaluation of an integral that occurs throughout the physical theory of wave-field scattering from random, rough surfaces. The algorithm is based on ... |
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| Valid Integer Polytope (VIP) Penalties for Branch-and-Bound Enumeration |
01-Jan-2000 |
11 pages |
| Authors:
Gerald G Brown; Robert F Dell; Michael P Olson; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF OPERATIONS RESEARCH
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| The authors introduce new penalties, called valid integer polytope (VIP) penalties, that tighten the bound of an integer-linear program during branch-and-bound enumeration. Early commercial codes for branch and bound commonly employed penalties developed from the dual simplicial lower bound on the cost of restricting fractional integer variables to proximate integral values. VIP penalties extend and tighten these for ubiquitous k-pack, k-partition, and k-cover constraints. In real-world problems, VIP penalties occasionally ... |
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| Adaptive Wavelet Galerkin Methods on Distorted Domains: Setup of the Algebraic System |
2000 |
10 pages |
| Authors:
Stefano Berrone; Karsten Urban; POLITECNICO DI TORINO (ITALY) DEPT DI INGEGNERIA AERONAUTICA E SPAZIALE
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| We use the algorithm of Bertoluzza, Canuto and Urban for computing integrals of products (of derivatives) of wavelets in order to solve elliptic PDEs on 2D distorted domains. We construct a variant of the original method which turns out to be more efficient. Several numerical results are presented. |
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| Efficient and Robust Numerical Modeling of Variably Saturated Flow in Layered Porous Media |
1998 |
10 pages |
| Authors:
C. T. Miller; G. A. Williams; NORTH CAROLINA UNIV AT CHAPEL HILL DEPT OF ENVIRONMENTAL SCIENCES AND ENGINEERING
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| We extend our recent work on higher-order time integration of Richards equation to layered heterogeneous porous media, using a differential-algebraic-equation-based method of lines (DAE/MOL) approach. We show that the DAE/MOL approach is robust and efficient compared to standard low-order time integration methods for heterogeneous media. We also show the advantage of using an integral representation of permeability compared to a standard arithmetic mean for the test problems considered herein. |
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| Monte Carlo Simulation of Mercury Cadmium Telluride |
16 SEP 97 |
5 pages |
| Authors:
M. Shur; B. Gelmont; VIRGINIA UNIV CHARLOTTESVILLE
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| We derived basic equations for basic electron scattering processes in narrow band gap semiconductors. However even in the case when the relaxation time approximation can be introduced a set of cumbersome integrals has to numerically calculated for intermediate degeneracy of an electron gas which is characteristic for narrow band gap semiconductors at liquid nitrogen temperature. As to the scattering by optical phonons the standard relaxation time approximation is, in general, ... |
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| Strategies for Effectively Visualizing a 3D Flow Using Volume Line Integral Convolution |
AUG 97 |
12 pages |
| Authors:
Victoria Interrante; Chester Grosch; INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING HAMPTON VA
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| This paper discusses strategies for effectively portraying 3D flow using volume line integral convolution. Issues include defining an appropriate input texture, clarifying the distinct identities and relative depths of the advected texture elements, and selectively highlighting regions of interest in both the input and output volumes. A part from offering insights into the greater potential of 3D LIC as a method for effectively representing flow in a volume, a principal ... |
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| Passage-Averaged Description of Wave Rotor Flow |
JUL 97 |
11 pages |
| Authors:
Gerald E. Welch; Louis M. Larosiliere; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER
|
| The unsteady flow within wave rotor passages is influenced by the rotor blade, hub, and tip shroud surface profiles. By averaging from hub to shroud and from blade to blade, a reduced set of the governing equations is obtained that is appropriate for design studies and parametric analyses. The application of these equations requires closure models for force integrals and for correlation terms that arise when the density averages of ... |
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| Box-Like Seating Structures; Interface Shape Dependence |
OCT 96 |
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| Authors:
Bjoern A. Petersson; TECHNISCH PHYSISCHE DIENST TNO-TH DELFT (NETHERLANDS)
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| The influence of the shape of the interface between a superstructure and a recipient on the vibrational energy transmission is analyzed. The real parts of the zero and first order interface mobilities are derived for a basic rectangular shape. Numerical results are presented for various aspect ratios but comparisons are also made with the corresponding results for an annular shape. It is concluded that the primary parameter is the perimeter ... |
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| A Computer Program for the Computation of Running Gear Temperatures Using Green's Function |
SEP 96 |
11 pages |
| Authors:
S. Koshigoe; J. W. Murdock; L. S. Akin; D. P. Townsend; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER
|
| A new technique has been developed to study two dimensional heat transfer problems in gears. This technique consists of transforming the heat equation into a line integral equation with the use of Green's theorem. The equation is then expressed in terms of eigenfunctions that satisfy the Helmholtz equation, and their corresponding eigenvalues for an arbitrarily shaped region of interest. The eigenfunction are obtalned by solving an intergral equation. Once the ... |
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| Full Wave Theory for Rough Surface Scattering Using the Kirchhoff Solution for Primary Field |
25 JUN 96 |
13 pages |
| Authors:
R. E. Collin; CASE WESTERN RESERVE UNIV CLEVELAND OH
|
| This final report summarizes work done under Grant DAAHO4-94- g-0035. The objective of the investigation was to develop a more rigorous full wave approach to rough surface scattering than that used by Bahar in his full wave method Instead of relying on the use of telegraphists equations a local spectral expansion method was found that is applicable to general rough surface scattering, not just surfaces with roughness in one dimension ... |
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| High Speed Numerical Integration of Fermi Dirac Integrals |
JUN 96 |
54 pages |
| Authors:
Jeremy S. Thompson; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| In this thesis we present an algorithm for the precise determination of Fermi-Dirac (FD) integral functions, for arbitrary values of the parameter and the argument. The FD integrals are a class of functions that are used extensively in the modeling of semiconductor devices, e.g., when the charge carriers are in a strongly quantum, degenerate regime, such as in heavily doped semiconductors. The determination of FD integrals has a long history. ... |
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| Quantum Mechanical Investigation of Polymeric Properties Using a Combination of First Principle Quantum Chemical and Solid State Physical Methods |
30 SEP 95 |
23 pages |
| Authors:
Janos Ladik; ERLANGEN-NUERNBERG UNIV (GERMANY) INST FOR THEORETICAL CHEMISTRY
|
| In the HF and correlation corrected energy band structure program packages in the last year we have introduced: (1) A better localization procedure for the Wannier functions (WF) used as intermediate step in the integral transformation. (2) By changing the order of loops the integrals belonging to a certain WF group are kept in the core memory during the transformation. In this way, the amount of I/O during the calculation ... |
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| ZETA II Code for Determining the Flow Around Multielement and Deformable Airfoils |
JUL 95 |
46 pages |
| Authors:
C. M. Wang; J. C. Wu; K. W. McAlister; C. Tung; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION MOFFETT FIELD CA AMES RESEARCH CENTER
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| The present NASA-University consortium involves research on the development of an efficient and accurate numerical procedure to treat general unsteady viscous flows. Of particular interest in the present work are flows relevant to helicopter rotors. Special efforts are centered on new concepts applied to the rotorblade configuration on the helicopter to improve the rotor aerodynamic characteristics. Among them airfoil dynamic stall and the aerodynamic noise of vortex-airfoil interactions were extensively ... |
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| Multifractal Analysis of Imprecise Data: Badii-Politi and Correlation Integral Approaches |
APR 95 |
23 pages |
| Authors:
L. V. Meisel; M. A. Johnson; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
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| Analytic and numerical implementations of the correlation integral and the Badii. Politi multifractal analysis algorithms are described and applied to machine precision and imprecise model multifractal data. The correlation integral technique yields good results for machine precision data and for data with 1 percent random errors. The standard numerical Badii-Politi algorithm did not yield satisfactory results for data with 0.05 percent or larger random errors. However, the present results suggest ... |
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| Convergence of Numerical Box-Counting and Correlation Integral Multifractal Analysis Techniques |
APR 95 |
19 pages |
| Authors:
L. V. Meisel; M. A. Johnson; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
|
| A systematic study of the rate of convergence for a numerical box- counting and a numerical correlation integral algorithm applied to Euclidean point sets, Koch constructions, and a symmetric chaotic mapping is described. The number of points N(5) required for 5 percent convergence of the box-counting (for 0 < or = q < or = 25) and correlation integral (for q between -25 and 25) ... |
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| Developing a Template for Logistics Test and Evaluation |
SEP 94 |
119 pages |
| Authors:
Timothy J. Fennell; Jason S. Mogle; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF LOGISTICS AND ACQUIS ITION MANAGEMENT
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| Logistics test and evaluation, performed during the developmental test and evaluation effort, is an integral part of the aircraft acquisition process. However, there has been no standard approach to conducting logistics test and evaluation. This study researched past and present approaches to aircraft logistics test and evaluation to determine the most effective method for future programs. We conducted this study using the Delphi method. We solicited the expert opinions of ... |
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| Structure-Function Aspects of Membrane Associated Prokaryotic DNA replication |
SEP 94 |
6 pages |
| Authors:
William Firshein; WESLEYAN UNIV MIDDLETOWN CT
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| Membrane associated DNA replication in prokaryotes has been studied intensively using two model systems, Bacillus subtilis and plasmid RK2 cultured in its Escherichia coli host. In the former a new membrane protein that had previously been found to act as an inhibitor of DNA replication was identified (by gene cloning procedures) to be an enzyme of the pyruvate dehydrogenase complex, the E2 subunit dihydrolipoamide acetyl transferase. The identification of this ... |
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| Vasopressin Receptor Signaling and Cycling of Water Channels in Renal Epithelia |
31 AUG 94 |
48 pages |
| Authors:
A. J. Mia; T. Yorio; JARVIS CHRISTIAN COLL HAWKINS TX
|
| Water reabsorption and urinary volume regulation are important processes in maintaining normal physiological function and vasopressin (ADH) regulates water reabsorption by the kidney in response to changes in plasma volume as may occur during dehydration. This process is particularly important to soldiers who are subject to excess heat and fluid deprivation in and environments. We have been examining the mechanisms whereby ADH enhances water permeability in renal epithelia so we ... |
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| Nonasymptotic Formulae for the Distribution of the Maximum of Smooth Gaussian Processes |
11 AUG 94 |
28 pages |
| Authors:
J. Diebolt; C. Posse; STANFORD UNIV CA DEPT OF STATISTICS
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| We derive an integral formula for the density of the maximum of smooth Gaussian processes. This expression induces explicit lower and upper bounds which are in general asymptotic to the density. Our constructive approach relies on a geometric representation of Gaussian processes involving a unit speed parameterized curve embedded in the unit sphere. Differential geometry, Gaussian processes, Extreme value, Nonasymptotic formulae, Density |
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| Study of Improved Critical Currents and Mechanical Properties in the Y- Ba-Cu-O Superconductor with Silver or Y2BaCuO3 or 211 Dispersions |
AUG 94 |
93 pages |
| Authors:
Siu-Wai Chan; TRUSTEES OF COLUMBIA UNIV NEW YORK
|
| The microstructure of the top-seeded, single grain, melted textured YBCO materials with different vol% 211 were investigated. The homogeneity of 211 distribution was greatly improved by using a solution precipitated 211 powder in preparation. Crack spacings and twin spacings were found to decrease with increasing vol% of the 211 particles. The 211 particles were found to be effective in holding crack propagation. Relationship between twin spacing and interparticle spacing was ... |
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| Experimental Application of Methodologies to Quantify the Effect of Constraint on Jc for a 3-D Flaw Geometry |
AUG 94 |
26 pages |
| Authors:
W. C. Porr Jr.; R. E. Link; J. P. Waskey; R. H. Dodds Jr; NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD
|
| In an effort to validate methodologies to quantify the effect of crack tip constraint on cleavage fracture toughness, a series of experiments were conducted to measure the cleavage fracture toughness, Jc, of an ASTM A515 Grade 70 steel utilizing large plate bend specimens containing semi-elliptical surface cracks, SC(B), (3-D flaw geometry). Jc was estimated with modified EPRI and Turner design curve schemes from load and remote strains measured at initiation. ... |
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| Perception of Auditory Events: Attentional Limitations |
26 JUL 94 |
5 pages |
| Authors:
Richard E. Pastore; STATE UNIV OF NEW YORK AT BINGHAMTON
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| There is strong evidence that objects presented simultaneously in a visual array have their component features initially processed in parallel, then subsequently combined to form the perceived objects. The evidence is in the form of the nature and frequency of perceptual errors and the pattern of reaction times for recognition of presented features and objects. Continuing project research is providing equivalent evidence which demonstrates, for the first time, similar analyses ... |
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| Finite Markov Chains and Random Discrete Structures |
26 JUL 94 |
5 pages |
| Authors:
Avner Friedman; Willard Miller Jr; MINNESOTA UNIV MINNEAPOLIS INST FOR MATHEMATICS AND ITS APPLICATIONS
|
| This grant from the Air Force Office of Scientific Research supported the research related to the two IMA Workshops Finite Markov Chain Renaissance held on October 18-22, 1993 and Random Discrete Structures held on November 15- 19, 1993. The first workshop was organized by Persi Diaconis and David Aldous, while the second one by David Aldous and Robin Pemantle. Both workshops were integral parts of the IMA 1993-1994 year-long program ... |
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| Experimental and Theoretical Evaluation of Elastic Waves in Curved Layered Media |
JUL 94 |
73 pages |
| Authors:
Dale E. Chimenti; Ali Safaeinilli; IOWA STATE UNIV AMES CENTER FOR NONDESTRUCTIVE EVALUATION
|
| This report describes the progress achieved during the third period of the study of elastic wave reflection from the curved and planar media subject to water loading. During the previous period, extensive experimental investigations were initiated to study parametrically the behavior of acoustic beams at curved and planar fluid-solid interfaces. Three types of materials, representative of Navy applications, in two geometries and two sizes, and many values of incident angle ... |
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| Fundamental Studies of Diamond Growth and Surface Reactions |
JUL 94 |
143 pages |
| Authors:
Alan B. Harker; ROCKWELL INTERNATIONAL THOUSAND OAKS CA SCIENCE CENTER
|
| This report summarizes the research carried out during the period March 1991 through May 1994 at Rockwell Science Center under ONR contract No. Nooo14-91-C-0048. This contract was part of the ONR directed effort on the development of polycrystalline diamond as an optical material. A primary focus of the research was investigating the relationships between the microstructure of polycrystalline diamond and its optical and mechanical properties. The program also involved a ... |
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| Understanding and Avoiding the Contract Negotiation Impasse |
07 JUN 94 |
152 pages |
| Authors:
Arno J. Sist; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Negotiation is an integral part of everyday life. It is a process whereby parties come together and attempt to reach an agreement that is of mutual benefit and that sets the framework for future dealings. While the goal of any contract negotiation is to reach an agreement, there are instances when, for various reasons, negotiations reach an impasse. The consequences can be serious for both DOD and industry. If a ... |
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| Controlled Environment Soil-Core Microcosm Unit (CESMU) for Investigating Fate, Transport, and Transformation of Chemicals in Site-Specific Soils |
JUN 94 |
19 pages |
| Authors:
Ronald T. Checkai; Randall S. Wentsel; Carlton T. Phillips; Roy L. Yon; EDGEWOOD RESEARCH DEVELOPMENT AND ENGINEERING CENTER ABERDEEN PROVING GROUND MD
|
| The controlled environment soil-core microcosm unit (CESMU) methods embody a collection of techniques that began with soil sampling in the field, and continued throughout laboratory investigations of chemical fate, migration, and transformation in site-specific soils. Intact soil cores were collected in the field using a hydraulically-controlled probe, delivering intact soil-cores with minimal disturbance directly into high density polyethylene pipe (HDPE; 10. 3-cm ID). The HDPE remained an integral part of ... |
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| A Uniaxial Nonlinear Thermoviscoelastic Constitutive Model with Damage for M30 Gun Propellant |
JUN 94 |
39 pages |
| Authors:
George A. Gazonas; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| The nonlinear thermoviscoelastic constitutive behavior of a conventional tank gun propellant, M30, is modeled using a modified superposition integral that incorporates the effects of microstructural fracture damage. This work represents a thermoviscoelastic extension of previous work (Gazonas 1992, 1993) that modeled the loading rate behavior of the propellant over nearly five decades in strain rate. In this work, uniaxial compression tests are conducted on the propellant at constant strain rates ... |
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| Quantum Simulation of Heterogeneous Electron Transfer Free Energies at the Water-Metal Interface |
06 MAY 94 |
38 pages |
| Authors:
Jay B. Straus; Gregory A. Voth; PENNSYLVANIA UNIV PHILADELPHIA DEPT OF CHEMISTRY
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| The free energy for electron transfer is studied for the Fe(2+)/ Fe(3+) charge transfer system at the water-Pt(111) interface. Classical adiabatic free energy curves are calculated along with an adiabatic curve based on the Anderson-Newns Hamiltonian. Reactive flux calculations are then performed on this curve to determine the effect of recrossings on the classical rate constant. These effects are not found to be large (Kappa approx. 0.6) The solvent model ... |
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| The Formulation of Quantum Statistical Mechanics Based on the Feynman Path Centroid Density IV. Algorithms for Centroid Molecular Dynamics |
06 MAY 94 |
56 pages |
| Authors:
Jianshu Cao; Gregory A. Voth; PENNSYLVANIA UNIV PHILADELPHIA DEPT OF CHEMISTRY
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| Numerical algorithms are developed for the centroid molecular dynamics (centroid MD) method to calculate dynamical time correlation functions for general many-body quantum systems. Approaches based on the normal mode path integral molecular dynamics and staging path integral Monte Carlo methods are described to carry out a direct calculation of the force on the centroid variables in the centroid MD algorithm. A more efficient, but approximate, scheme to compute the centroid ... |
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