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5,223 Matching Results
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Interprocessor communication with limited memory
Many parallel applications require periodic redistribution of workloads and associated data. In a distributed memory computer, this redistribution can be difficult if limited memory is available for receiving messages. We propose a model for optimizing the exchange of messages under such circumstances which we call the minimum phase remapping problem. We first show that the problem is NP-Complete, and then analyze several methodologies for addressing it. First, we show how the problem can be phrased as an instance of multi-commodity flow. Next, we study a continuous approximation to the problem. We show that this continuous approximation has a solution which requires at most two more phases than the optimal discrete solution, but the question of how to consistently obtain a good discrete solution from the continuous problem remains open. We also devise simple and practical approximation algorithm for the problem with a bound of 1.5 times the optimal number of phases. We also present an empirical study of variations of our algorithms which indicate that our approaches are quite practical.
Date:
May 7, 2003
Creator:
Pinar, Ali & Hendrickson, Bruce
Object Type:
Article
System:
The UNT Digital Library
Gyrocenter-gauge kinetic theory
Gyrocenter-gauge kinetic theory is developed as an extension of the existing gyrokinetic theories. In essence, the formalism introduced here is a kinetic description of magnetized plasmas in the gyrocenter coordinates which is fully equivalent to the Vlasov-Maxwell system in the particle coordinates. In particular, provided the gyroradius is smaller than the scale-length of the magnetic field, it can treat high frequency range as well as the usual low frequency range normally associated with gyrokinetic approaches. A significant advantage of this formalism is that it enables the direct particle-in-cell simulations of compressional Alfven waves for MHD applications and of RF waves relevant to plasma heating in space and laboratory plasmas. The gyrocenter-gauge kinetic susceptibility for arbitrary wavelength and arbitrary frequency electromagnetic perturbations in a homogeneous magnetized plasma is shown to recover exactly the classical result obtained by integrating the Vlasov-Maxwell system in the particle coordinates. This demonstrates that all the waves supported by the Vlasov-Maxwell system can be studied using the gyrocenter-gauge kinetic model in the gyrocenter coordinates. This theoretical approach is so named to distinguish it from the existing gyrokinetic theory, which has been successfully developed and applied to many important low-frequency and long parallel wavelength problems, where the conventional …
Date:
August 7, 2000
Creator:
Qin, H.; Tang, W. M. & Lee, W. W.
Object Type:
Report
System:
The UNT Digital Library
Geometrical theory of nonlinear phase distortion of intense laser beams
Phase distortion arising from whole beam self-focusing of intense laser pulses with arbitrary spatial profiles is treated in the limit of geometrical optics. The constant shape approximation is used to obtain the phase and angular distribution of the geometrical rays in the near field. Conditions for the validity of this approximation are discussed. Geometrical focusing of the aberrated beam is treated for the special case of a beam with axial symmetry. Equations are derived that show both the shift of the focus and the distortion of the intensity distribution that are caused by the nonlinear index of refraction of the optical medium. An illustrative example treats the case of beam distortion in a Nd:Glass amplifier.
Date:
May 7, 1975
Creator:
Glaze, J. A.; Hunt, J. T. & Speck, D. R.
Object Type:
Report
System:
The UNT Digital Library
On the Statistical Theory of Electromagnetic Waves in a Fluctuating Medium (II): Mathematical Basis of the Analogies to Quantum Field Theory
Report discussing the relationship between quantum field theory and the the statistical theory of waves. Basic equations exist in the latter theory which correspond closely to the fundamental equations of the former theory; i.e., to the commutation relations and the Heisenberg equation of motion. A probability density function of waves is introduced here which corresponds to the probability amplitude function in quantum mechanics. The theory of the statistical Green's functions and their relationships to the expectation values of the physical variables is also extensively developed. It is found that there exists a one-to-one correspondence between the formalism of Green's functions presented here and that used in field theory.
Date:
December 7, 1964
Creator:
Furutsu, K.
Object Type:
Report
System:
The UNT Digital Library
The perils of untested assumptions in theory testing: A reply to Patrick et al. (2020)
This article is a comment responding to a critique by Patrick et. al (2020) of the authors' recent study that raised questions regarding the three-factor model of the Triarchic Psychopathy Measure (TriPM). The reply demonstrates additional problems with the three-factor TriPM model and shows that the seven-factor model out-performs the three-factor model in predicting correlates of psychopathy.
Date:
September 7, 2020
Creator:
Roy, Sandeep; Vize, Colin; Uzieblo, Kasia; Van Dongen, Josanne D. M.; Miller, Joshua D.; Lynam, Donald R. et al.
Object Type:
Article
System:
The UNT Digital Library
Ultraviolet Behavior of N = 8 supergravity
In these lectures the author describes the remarkable ultraviolet behavior of N = 8 supergravity, which through four loops is no worse than that of N = 4 super-Yang-Mills theory (a finite theory). I also explain the computational tools that allow multi-loop amplitudes to be evaluated in this theory - the KLT relations and the unitarity method - and sketch how ultraviolet divergences are extracted from the amplitudes.
Date:
June 7, 2010
Creator:
Dixon, Lance J.
Object Type:
Article
System:
The UNT Digital Library
Inflation in AdS/CFT
We study the realization of inflation within the AdS/CFT correspondence. We assume the existence of a string landscape containing at least one stable AdS vacuum and a (nearby) metastable de Sitter state. Standard arguments imply that the bulk physics in the vicinity of the AdS minimum is described by a boundary CFT. We argue that large enough bubbles of the dS phase, including those able to inflate, are described by mixed states in the CFT. Inflating degrees of freedom are traced over and do not appear explicitly in the boundary description. They nevertheless leave a distinct imprint on the mixed state. Analytic continuation allows us, in principle, to recover a large amount of nonperturbatively defined information about the inflating regime. Our work also shows that no scattering process can create an inflating region, even by quantum tunneling, since a pure state can never evolve into a mixed state under unitary evolution.We study the realization of inflation within the AdS/CFT correspondence. We assume the existence of a string landscape containing at least one stable AdS vacuum and a (nearby) metastable de Sitter state. Standard arguments imply that the bulk physics in the vicinity of the AdS minimum is described by a …
Date:
October 7, 2005
Creator:
Freivogel, Ben; /Stanford U., Phys. Dept. /LBL, Berkeley; Hubeny, Veronika E.; /LBL, Berkeley /Durham U., Dept. of Math.; Maloney, Alexander; /Stanford U., Phys. Dept. /SLAC et al.
Object Type:
Report
System:
The UNT Digital Library
PubMed Central: Behind the HTML
Presentation for the 2018 University of North Texas Open Access Symposium. This presentation provides a behind-the-scnees tour of the architecture, workflows, and policies of PubMed Central.
Date:
June 7, 2018
Creator:
Beck, Jeffrey
Object Type:
Presentation
System:
The UNT Digital Library
Self-organizing Complex Networks: individual versus global rules
This article introduces a form of Self-organized Criticality (SOC) inspired by the new generation of evolutionary game theory, which ranges from physiology to sociology.
Date:
June 7, 2017
Creator:
Mahmoodi, Korosh; West, Bruce J. & Grigolini, Paolo
Object Type:
Article
System:
The UNT Digital Library
Gluons and the Quark Sea at High Energies: Distributions, Polarization, Tomography
This report on the science case for an Electron-Ion Collider (EIC) is the result of a ten-week program at the Institute for Nuclear Theory (INT) in Seattle (from September 13-November 19, 2010), motivated by the need to develop a strong case for the continued study of the QCD description of hadron structure in the coming decades. Hadron structure in the valence quark region will be studied extensively with the Jefferson Lab 12 GeV science program, the subject of an INT program the previous year. The focus of the INT program was on understanding the role of gluons and sea quarks, the important dynamical degrees of freedom describing hadron structure at high energies. Experimentally, the most direct and precise way to access the dynamical structure of hadrons and nuclei at high energies is with a high luminosity lepton probe in collider mode. An EIC with optimized detectors offers enormous potential as the next generation accelerator to address many of the most important, open questions about the fundamental structure of matter. The goal of the INT program, as captured in the writeups in this report, was to articulate these questions and to identify golden experiments that have the greatest potential to provide …
Date:
June 7, 2012
Creator:
Boer, Daniel; Diehl, Markus; Milner, Richard; Venugopalan, Raju; Vogelsang, Werner; Kaplan, David et al.
Object Type:
Article
System:
The UNT Digital Library
Pthreads vs MPI Parallel Performance of Angular-Domain Decomposed S
Two programming models for parallelizing the Angular Domain Decomposition (ADD) of the discrete ordinates (S{sub n}) approximation of the neutron transport equation are examined. These are the shared memory model based on the POSIX threads (Pthreads) standard, and the message passing model based on the Message Passing Interface (MPI) standard. These standard libraries are available on most multiprocessor platforms thus making the resulting parallel codes widely portable. The question is: on a fixed platform, and for a particular code solving a given test problem, which of the two programming models delivers better parallel performance? Such comparison is possible on Symmetric Multi-Processors (SMP) architectures in which several CPUs physically share a common memory, and in addition are capable of emulating message passing functionality. Implementation of the two-dimensional,(S{sub n}), Arbitrarily High Order Transport (AHOT) code for solving neutron transport problems using these two parallelization models is described. Measured parallel performance of each model on the COMPAQ AlphaServer 8400 and the SGI Origin 2000 platforms is described, and comparison of the observed speedup for the two programming models is reported. For the case presented in this paper it appears that the MPI implementation scales better than the Pthreads implementation on both platforms.
Date:
May 7, 2000
Creator:
Azmy, Y. Y. & Barnett, D. A.
Object Type:
Article
System:
The UNT Digital Library
Dynamic Range of Vertical Cavity Surface Emitting Lasers in Multimode Links
The authors report spurious free dynamic range measurements of 850nm vertical cavity surface emitting lasers in short multimode links for radio frequency communication. For a 27m fiber link, the dynamic range at optimal bias was greater than 95dB-Hz{sup 2/3} for modulation frequencies between 1 and 5.5 GHz, which exceeds the requirements for antenna remoting in microcellular networks. In a free space link, they have measured the highest dynamic range in an 850nm vertical cavity surface emitting laser of 113dB-Hz{sup 2/3} at 900MHz. We have also investigated the effects of modal noise and differential mode delay on the dynamic range for longer lengths of fiber.
Date:
July 7, 1999
Creator:
Lee, H. L. T.; Dalal, R. V.; Ram, R. J. & Choquette, K. D.
Object Type:
Article
System:
The UNT Digital Library
[Lone Star Sesquicentennial - audio presentations by Doughty and guest panelist]
Sound recording of panelists at the Lone Star Sesquicentennial conference hosted by the University of Texas at Austin. First panelist: unknown; Second panelist: Robin Doughty, PhD. Clip 1 begins in the middle of the first presentation. Clip 2 ends in the middle of Doughty's lecture.
Date:
November 7, 1985
Creator:
Hays, Margaret Parx
Object Type:
Sound
System:
The UNT Digital Library
Importance of level structure in nuclear reaction cross-section calculations. Revision 1
It is shown that level-density expressions cannot adequately represent or substitute for level structure information when making calculations of the Hauser-Feshbach type for cross sections or isomer-ratios for nuclei in the first few MeV above their ground state. It is stated that such discrete level information should include both experimentally confirmed and theoretically predicted levels. The utility of discrete level information to optimize level density calculations, to compute isomer ratios, in deriving dipole strength functions, and in the analysis of primary gamma ray spectra is emphasized, especially for nuclei far from the line of stability. 29 refs., 12 figs., 6 tabs. (DWL)
Date:
November 7, 1985
Creator:
Gardner, M. A. & Gardner, D. G.
Object Type:
Article
System:
The UNT Digital Library
Stars in Photographic Emulsions Initiated by Deuterons Part II. Theoretical
The theory of high energy nuclear stars depends on a theory of nuclear transparency and on a theory of nuclear evaporation. The transparency can be computed on the basis of a model proposed by R. Serber as soon as the interactions between the nucleons and the incident particle are known. The evaporation can be computed on the basis of the statistical model of the nucleus as soon as the nuclear entropy and binding energies of the evaporated particles are known. With approximate values for the above interactions, entropies, and binding energies, a probability distribution has been computed for the number of prongs per star. The results are in qualitative agreement with the observations on photographic emulsions described in Part 1.
Date:
September 7, 1948
Creator:
Horning, W. & Baumhoff, L.
Object Type:
Report
System:
The UNT Digital Library
SC'11 Poster: A Highly Efficient MGPT Implementation for LAMMPS; with Strong Scaling
The MGPT potential has been implemented as a drop in package to the general molecular dynamics code LAMMPS. We implement an improved communication scheme that shrinks the communication layer thickness, and increases the load balancing. This results in unprecedented strong scaling, and speedup continuing beyond 1/8 atom/core. In addition, we have optimized the small matrix linear algebra with generic blocking (for all processors) and specific SIMD intrinsics for vectorization on Intel, AMD, and BlueGene CPUs.
Date:
December 7, 2011
Creator:
Oppelstrup, T.; Stukowski, A. & Marian, J.
Object Type:
Article
System:
The UNT Digital Library
The Panola Watchman (Carthage, Tex.), Vol. 128, No. 90, Ed. 1 Wednesday, November 7, 2001
Semiweekly newspaper from Carthage, Texas that includes local, state, and national news along with advertising.
Date:
November 7, 2001
Creator:
unknown
Object Type:
Newspaper
System:
The Portal to Texas History
The Panola Watchman (Carthage, Tex.), Vol. 129, No. 62, Ed. 1 Wednesday, August 7, 2002
Semiweekly newspaper from Carthage, Texas that includes local, state, and national news along with advertising.
Date:
August 7, 2002
Creator:
unknown
Object Type:
Newspaper
System:
The Portal to Texas History
Pathway and kinetic analysis on the iso-propyl radical + O{sub 2} reaction system
We analyze the isopropyl + 02 reaction system using thermochemical Transition State Theory (TST), molecular thermodynamic properties, analysis (quantum RRK) for k(E) and modified strong collision analyze Cyclic transition states for both hydrogen transfer and concerted propylene from isopropylperoxy are calculated using semi-empirical theory in addition to transition states for H02 elimination from hydroperoxy-isopropyl. Computed rate constants are compared to constant measurements of for isopropyl + H02.
Date:
April 7, 1997
Creator:
Bozzelli, J. W. & Pitz, W. J.
Object Type:
Article
System:
The UNT Digital Library
SUBSURFACE REPOSITORY INTEGRATED CONTROL SYSTEM DESIGN
The primary purpose of this document is to develop a preliminary high-level functional and physical control system architecture for the potential repository at Yucca Mountain. This document outlines an overall control system concept that encompasses and integrates the many diverse process and communication systems being developed for the subsurface repository design. This document presents integrated design concepts for monitoring and controlling the diverse set of subsurface operations. The Subsurface Repository Integrated Control System design will be composed of a series of diverse process systems and communication networks. The subsurface repository design contains many systems related to instrumentation and control (I&C) for both repository development and waste emplacement operations. These systems include waste emplacement, waste retrieval, ventilation, radiological and air monitoring, rail transportation, construction development, utility systems (electrical, lighting, water, compressed air, etc.), fire protection, backfill emplacement, and performance confirmation. Each of these systems involves some level of I&C and will typically be integrated over a data communications network throughout the subsurface facility. The subsurface I&C systems will also interface with multiple surface-based systems such as site operations, rail transportation, security and safeguards, and electrical/piped utilities. In addition to the I&C systems, the subsurface repository design also contains systems related to …
Date:
January 7, 2000
Creator:
Randle, D.C.
Object Type:
Report
System:
The UNT Digital Library
Some highlights in few-body nuclear physics.
During the past five years, there have been tremendous advances in both experiments and theoretical calculations in few-body nuclear systems. Advances in technology have permitted experiments of unprecedented accuracy. Jefferson Laboratory has begun operation and the first round of experimental results have become available. New polarization techniques have been exploited at a number of laboratories, in particular, at Jefferson Lab, IUCF, RIKEN, NIKHEF, Mainz, MIT-Bates and HERMES. Some of these results will be shown here. In addition, there have been tremendous advances in few-body theory. Five modern two-nucleon potentials have which describe the nucleon-nucleon data extremely well have become available. A standard model of nuclear physics based on these two nucleon potentials as well as modern three-nucleon forces has emerged. This standard model has enjoyed tremendous success in the few body systems. Exact three-body calculations have been extended into the continuum in order to take full advantage of scattering data in advancing our understanding of the the few-nucleon system. In addition, the application of chiral symmetry has become an important constraint on nucleon-nucleon as well as three-nucleon forces. As a result of all these efforts, we have seen rapid developments in the three-body force. Despite these advances, there remain some …
Date:
December 7, 2000
Creator:
Holt, R. J.
Object Type:
Article
System:
The UNT Digital Library
The Equilibrium Length of High-Current Bunches in Electron Storage Rings
An equilibrium theory of the length of intense electron bunches circulating in a storage ring is presented. The consequence of electrical interaction with various resonant structures is expressed in terms of quadratures over the impedance of the structures, and impedance functions for a variety of elements are evaluated. It is shown that elements having resonances at high frequency can, above transition, cause bunches to increase in length with increasing current. The parametric dependence of the bunch lengthening is found to be in good agreement with observations, and numerical estimates, which are in substantial agreement with experiment, are presented.
Date:
August 7, 1970
Creator:
Pellegrini, C. & Sessler, A. M.
Object Type:
Article
System:
The UNT Digital Library
The Optimist (Abilene, Tex.), Vol. 100, No. 13, Ed. 1 Friday, October 7, 2011
Bi-weekly student newspaper from Abilene Christian University in Abilene, Texas that includes local, state and campus news along with advertising.
Date:
October 7, 2011
Creator:
unknown
Object Type:
Newspaper
System:
The Portal to Texas History
Computation of Three Dimensional Tokamak and Spherical Torus Equilibria
A nominally axisymmetric plasma con�guration, such as a tokamak or a spherical torus, is highly sensitive to non-axisymmetric magnetic perturbations due to currents outside of the plasma. The high sensitivity means that the primary interest is in the response of the plasma to very small perturbations, | →(over) β/→(over)Β | ≈ 10–2 to 10–4, which can be calculated using the theory of perturbed equilibria. The Ideal Perturbed Equilibrium Code (IPEC) is described and applied to the study of the plasma response in a spherical torus to such external perturbations.
Date:
May 7, 2007
Creator:
Jong-kyu Park, Allen H. Boozer, and Alan H. Glasser
Object Type:
Report
System:
The UNT Digital Library