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open access

LOWER BOUNDS ON SELF-FOCUSING SO AS TO MAINTAIN RING INTEGRITY NEAR THE INITIATION OF ACCELERATION IN AN ELECTRON RING ACCELERATOR

Relationships necessary for ring stability are derived between the self-focusing forces of an electron ring and the magnetic field gradient defocusing forces present near and just subsequent to the start of ring acceleration.

Date: April 16, 1970

Creator: Pellegrini, Claudio & Sessler, Andrew.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

NERSC News

This month's issue has the following 3 articles: (1) Kathy Yelick is the new director for the National Energy Research Scientific Computing Center (NERSC); (2) Head of the Class--A cray XT4 named Franklin passes a rigorous test and becomes an official member of the NERSC supercomputing family; and (3) Model Comparisons--Fusion research group published several recent papers examining the results of two types of turbulence simulations and their impact on tokamak designs.

Date: November 25, 2007

Creator: Wang, Ucilia

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

CARBON-13 NMR STUDIES OF LIQUID CRYSTALS

High resolution, proton decoupled {sup 13}C nmr are observed for a series of neat nematic liquid crystals, the p-alkoxyazoxybenzenes, and a smectic-A liquid crystal, diethylazoxydibenzoate in a magnetic field of 23 kG. The (uniaxial) order parameters S = <P{sub 2}(cos{theta})> are found to be about 0.4 and 0.9 for the nematic and smectic-A phase respectively at the clearing points. The order parameter increases with decreasing temperature in the nematic phase but is constant, or nearly so… more

Date: June 1, 1975

Creator: Allison, Stuart

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

Breaking the Curse of Cardinality on Bitmap Indexes

Bitmap indexes are known to be efficient for ad-hoc range queries that are common in data warehousing and scientific applications. However, they suffer from the curse of cardinality, that is, their efficiency deteriorates as attribute cardinalities increase. A number of strategies have been proposed, but none of them addresses the problem adequately. In this paper, we propose a novel binned bitmap index that greatly reduces the cost to answer queries, and therefore breaks the curse of cardinali… more

Date: April 4, 2008

Creator: Wu, Kesheng; Wu, Kesheng; Stockinger, Kurt & Shoshani, Arie

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A Cell-Centered Adaptive Projection Method for the IncompressibleNavier-Stokes Equations in Three Dimensions

We present a method for computing incompressible viscousflows in three dimensions using block-structured local refinement in bothspace and time. This method uses a projection formulation based on acell-centered approximate projection, combined with the systematic use ofmultilevel elliptic solvers to compute increments in the solutiongenerated at boundaries between refinement levels due to refinement intime. We use an L_0-stable second-order semi-implicit scheme to evaluatethe viscous terms. Res… more

Date: September 25, 2007

Creator: Martin, D.F.; Colella, P. & Graves, D.T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A fast contour descriptor algorithm for supernova imageclassification

We describe a fast contour descriptor algorithm and its application to a distributed supernova detection system (the Nearby Supernova Factory) that processes 600,000 candidate objects in 80 GB of image data per night. Our shape-detection algorithm reduced the number of false positives generated by the supernova search pipeline by 41% while producing no measurable impact on running time. Fourier descriptors are an established method of numerically describing the shapes of object contours, but tr… more

Date: July 16, 2006

Creator: Aragon, Cecilia R. & Aragon, David Bradburn

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

PROPERTIES OP LIQUID HELIUM-THREE IN THE TWO-BODY CORRELATION APPROXIMATION. I

This is the first of two papers in which the low-temperature properties of liquid He{sup 3} are to be calculated in the thermodynamically consistent 'T-matrix' approximation. The set of coupled integral equations which are to be solved is exhibited in Part A of this paper. Part B of this paper is devoted to a preliminary, zero-temperature calculation which employs the additional approximations of using separable potentials and a noninteracting spectral function to define the interaction of two … more

Date: November 17, 1965

Creator: Beck, Donald E. & Sessler, Andrew M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Flow Properties of Superfluid Systems of Fermions

The nonspherically symmetric solutions to the Bardeen-Cooper-Schrieffer theory are given a physical interpretation in terms of an anisotropic fluid model. These solutions have been used previously to predict a phase transition in liquid by He{sup 3} by Emery and Sessler and Anderson, Morel, Brueckner, and Soda. An investigation of the flow properties of such systems is made that involves the calculation of the effective mass for flow in a straight channel and the moment of inertia of a cylindri… more

Date: May 16, 1960

Creator: Glassgold, A. E. & Sessler, A. M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Experimental Determination of ETS Particle Deposition in a Low Ventilation Room

Deposition on indoor surfaces is an important removal mechanism for tobacco smoke particles. We report measurements of deposition rates of environmental tobacco smoke particles in a room-size chamber. The deposition rates were determined from the changes in measured concentrations by correcting for the effects of coagulation and ventilation. The air flow turbulent intensity parameter was determined independently by measuring the air velocities in the chamber. Particles with diameters smaller th… more

Date: May 1, 1993

Creator: Xu, M.; Nematollahi, M.; Sextro, R. G.; Gadgil, A. J. & Nazaroff, W. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Adiabatic Focuser

Theoretical analysis is made of an intense relativistic electron beam. such as would be available from a linear collider, moving through a plasma of increasing density, but density always less than that of the beam (underdense). In this situation. the plasma electrons are expelled from the beam channel and the electrons are subject to an ever-increasing focusing force provided by the channel ions. Analysis is made on the beam radiation energy loss in the classical, the transition, and the quant… more

Date: August 1, 1989

Creator: Chen, P.; Oide, K.; Sessler, Andrew M. & Yu, S. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Coherent Electromagnetic Effects in High-Current Particle Accelerators: [Part] 3. Electromagnetic-Coupling Instabilities in a Coasting Beam

The electromagnetic interaction of an intense relativistic coasting beam with itself, including the effect of a confining nonperfect vacuum tank, or a quiescent rf cavity, is investigated theoretically. It is shown that the resonances that may occur between harmonics of the particle circulation frequencies and the electromagnetic modes of the cavities can lead to a longitudinal instability of the beam. A criterion for stability of the beam against such longitudinal bunching is obtained as a res… more

Date: August 4, 1960

Creator: Laslett, L. J.; Neil, V. Kelvin & Sessler, A. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Reliability Results of NERSC Systems

In order to address the needs of future scientific applications for storing and accessing large amounts of data in an efficient way, one needs to understand the limitations of current technologies and how they may cause systeminstability or unavailability. A number of factors can impact system availability ranging from facility-wide power outage to a single point of failure such as network switches or global file systems. In addition, individual component failure in a system can degrade the per… more

Date: May 27, 2008

Creator: Petascale Data Storage Institute

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Estimation of the parameter covariance matrix for aone-compartment cardiac perfusion model estimated from a dynamic sequencereconstructed using map iterative reconstruction algorithms

In dynamic cardiac SPECT estimates of kinetic parameters ofa one-compartment perfusion model are usually obtained in a two stepprocess: 1) first a MAP iterative algorithm, which properly models thePoisson statistics and the physics of the data acquisition, reconstructsa sequence of dynamic reconstructions, 2) then kinetic parameters areestimated from time activity curves generated from the dynamicreconstructions. This paper provides a method for calculating thecovariance matrix of the kinetic p… more

Date: January 1, 2004

Creator: Gullberg, Grant T.; Huesman, Ronald H.; Reutter, Bryan W.; Qi,Jinyi & Ghosh Roy, Dilip N.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

NERSC Cyber Security Challenges That Require DOE Development andSupport

Traditional security approaches do not adequately addressall the requirements of open, scientific computing facilities. Many ofthe methods used for more restricted environments, including almost allcorporate/commercial systems, do not meet the needs of today's science.Use of only the available "state of the practice" commercial methods willhave adverse impact on the ability of DOE to accomplish its sciencegoals, and impacts the productivity of the DOE Science community. Inparticular, NERSC and … more

Date: January 16, 2007

Creator: Draney, Brent; Campbell, Scott & Walter, Howard

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Localized or Systemic {italic In Vivo} Heat-Inactivation of Human Immunodeficiency Virus (HIV): A Mathematical Analysis

Temperatures as low as 42 C, maintained for a little as 25 minutes, inactivate {approx}25% of HIV. Furthermore, human immunodeficiency virus (HIV)-infected T-cells are more sensitive to heat than healthy lymphocytes and susceptibility increases when the cells are pre-sensitized by exposure to tumor necrosis factor. Thus, induction of a whole-body hyperthermia, or hyperthermia specifically limited to tissues having a high viral load, are potential antiviral therapies for acquired immunodeficienc… more

Date: December 15, 1993

Creator: Pennypacker, Carl R.; Perelson, A.S.; Nys, N.; Nelson, G. & Sessler, D.I.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Diffraction Radiation Defocusing of an Electron Ring

The influence upon axial stability in an electron ring of the diffraction radiation reaction force, generated by a ring moving in an acceleration column, is calculated theoretically. A stability criterion is obtained, and numerical examples show that the criterion is not an important constraint upon the choice of parameters or the operation of an electron ring accelerator.

Date: December 1, 1970

Creator: Keil, E.; Pellegrini, C & Sessler, A. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

BETA-RAY SPECTROMETER WITH REDUCED SPHERICAL ABERRATION

Modern {beta}-ray spectrometers are based upon the concept, first introduced by Svartholm and Siegbahn in 1946, of focusing in both the radial and vertical directions. The theory of axially symmetric devices has been carefully studied by a large number of workers, culminating in the analysis, in 1956, of Lee-Whiting and Taylor. These last authors calculate aberrations through the sixth order and show that by appropriate choice of the magnetic field a spectrometer can be designed with a relative… more

Date: February 4, 1963

Creator: Sessler, Andrew M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The Performance Effect of Multi-core on ScientificApplications

The historical trend of increasing single CPU performancehas given way to roadmap of increasing core count. The challenge ofeffectively utilizing these multi-core chips is just starting to beexplored by vendors and application developers alike. In this study, wepresent some performance measurements of several complete scientificapplications on single and dual core Cray XT3 and XT4 systems with a viewto characterizing the effects of switching to multi-core chips. Weconsider effects within a node… more

Date: May 14, 2007

Creator: Carter, Jonathan; He, Yun; Shalf, John; Shan, Hongzhang; Strohmaier, Erich & Wasserman, Harvey

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Variable Interactions in Query-Driven Visualization

One fundamental element of scientific inquiry is discoveringrelationships, particularly the interactions between different variablesin observed or simulated phenomena. Building upon our prior work in thefield of Query-Driven Visualization, where visual data analysisprocessing is focused on subsets of large data deemed to be"scientifically interesting," this new work focuses on a novel knowledgediscovery capability suitable for use with petascale class datasets. Itenables visual presentation of … more

Date: October 25, 2007

Creator: Bethel, E. Wes; Gosink, Luke J.; Anderson, John C. & Joy, Kenneth I.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

On the Density Oscillations of a Warm Particle Bunch

The density oscillations of warm particle bunches is investigated theoretically. Two different mathematical approaches are employed to derive the basic equation describing density oscillations; one is a fluid approach and the second is a more general Green1s function formulation. The motion is analyzed in first order perturbation theory where it is shown, under the assumption of no degeneracy, that there are only stable oscillations. Second order perturbation theory gives damping of the motion.… more

Date: November 1, 1982

Creator: Channell, P. J.; Sessler, A. M. & Wurtele, J. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

LUsim: A Framework for Simulation-Based Performance Modelingand Prediction of Parallel Sparse LU Factorization

Sparse parallel factorization is among the most complicated and irregular algorithms to analyze and optimize. Performance depends both on system characteristics such as the floating point rate, the memory hierarchy, and the interconnect performance, as well as input matrix characteristics such as such as the number and location of nonzeros. We present LUsim, a simulation framework for modeling the performance of sparse LU factorization. Our framework uses micro-benchmarks to calibrate the param… more

Date: April 15, 2008

Creator: Univ. of California, San Diego

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Phase and Amplitude Control of the Radio Frequency Wave in the Two-Beam Accelerator

The sensitivity of the radio frequency (rf) wave generated by the free electron laser portion of a Two-Beam Accelerator (TBA) is analyzed, both analytically and numerically in a 'resonant particle' approximation. It is shown that the phase of the rf wave is strongly dependent upon errors in the wiggler strength and wavelength and upon the electron beam characteristics of energy and current. The resulting phase error is shown to be unacceptable for a TBA, given reasonable errors in various compo… more

Date: July 1, 1985

Creator: Kuenning, R. W. & Sessler, A. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Towards an Accurate Performance Modeling of Parallel SparseFactorization

We present a performance model to analyze a parallel sparseLU factorization algorithm on modern cached-based, high-end parallelarchitectures. Our model characterizes the algorithmic behavior bytakingaccount the underlying processor speed, memory system performance, aswell as the interconnect speed. The model is validated using theSuperLU_DIST linear system solver, the sparse matrices from realapplications, and an IBM POWER3 parallel machine. Our modelingmethodology can be easily adapted to stud… more

Date: May 26, 2006

Creator: Grigori, Laura & Li, Xiaoye S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

HIGH-INTENSITY EFFECTS IN THE LONGITUDINAL MOTION OF STORED PARTICLE BEAMS

A brief review is given of the various self-field phenomena associated with the longitudinal motion of particles in storage rings. Although there are some high-intensity phenomena for which the coupling of longitudinal and transverse motion is essential, such as, for example, the headtail effect; the great majority of high-intensity phenomena primarily involve either longitudinal or transverse degrees of freedom. In this review, we restrict our attention to phenomena which are essentially longi… more

Date: February 1, 1973

Creator: Sessler, Andrew M.

Item Type: Report

Partner: UNT Libraries Government Documents Department