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in subjects: "Distribution Functions"

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Is Climate Change Predictable? Really?

This project is the first application of a completely different approach to climate modeling, in which new prognostic equations are used to directly compute the evolution of two-point correlations. This project addresses three questions that are critical for the credibility of the science base for climate prediction: (1) What is the variability spectrum at equilibrium? (2) What is the rate of relaxation when subjected to external perturbations? (3) Can variations due to natural processes be dis… more

Date: November 14, 2005

Creator: Dannevik, W P & Rotman, D A

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Local Structure of La1-xSrxCoO3 determined from EXAFS and neutron PDF studies

The combined local structure techniques, extended x-ray absorption fine structure (EXAFS) and neutron pair distribution function analysis, have been used for temperatures 4<= T<= 330 K to rule out a large Jahn-Teller (JT) distortion of the Co-O bond in La1?xSrxCoO3 for a significant fraction of Co sites (x<= 0.35), indicating few, if any, JT-active, singly occupied eg Co sites exist.

Date: January 26, 2009

Creator: Sundaram, N.; Jiang, Y.; Anderson, I. E.; Belanger, D. P.; Booth, C. H.; Bridges, F. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Demonstrating fractal scaling of residence time distributions on the catchment scale using a fully-coupled, variably-saturated groundwater and land surface model and a Lagrangian particle tracking approach

The influence of the vadose zone, land surface processes, and macrodispersion on scaling behavior of residence time distributions (RTDs) is studied using a fully coupled watershed model in conjunction with a Lagrangian, particle-tracking approach. Numerical experiments are used to simulate groundwater flow paths from recharge locations along the hillslope to the streambed. These experiments are designed to isolate the influences of topography, vadose zone/land surface processes, and macrodisper… more

Date: November 7, 2007

Creator: Kollet, S J & Maxwell, R M

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

AFM Morphology Study of Si1-Y GeY:H Films Deposited by LF PE CVD from Silane-Germane with Different

The morphology of Si{sub 1-Y} Ge{sub Y}:H films in the range of Y=0.23 to 0.9 has been studied by AFM. The films were deposited by Low Frequency (LF) PE CVD at substrate temperature T{sub s}=300 C and discharge frequency f=110 kHz from silane+germane mixture with and without, Ar and H{sub 2} dilution. The films were deposited on silicon and glass substrates. AFM images were taken and analyzed for 2 x 2 mm{sup 2} area. All the images demonstrated ''grain'' like structure, which was characterized… more

Date: March 28, 2005

Creator: Sanchez, L & Kosarev, A

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A Hybrid Method for Accelerated Simulation of Coulomb Collisions in a Plasma

If the collisional time scale for Coulomb collisions is comparable to the characteristic time scales for a plasma, then simulation of Coulomb collisions may be important for computation of kinetic plasma dynamics. This can be a computational bottleneck because of the large number of simulated particles and collisions (or phase-space resolution requirements in continuum algorithms), as well as the wide range of collision rates over the velocity distribution function. This paper considers Monte C… more

Date: October 9, 2007

Creator: Caflisch, R.; Wang, C.; Dimarco, G.; Cohen, B. & Dimits, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Representation of analysis results involving aleatory and epistemic uncertainty.

Procedures are described for the representation of results in analyses that involve both aleatory uncertainty and epistemic uncertainty, with aleatory uncertainty deriving from an inherent randomness in the behavior of the system under study and epistemic uncertainty deriving from a lack of knowledge about the appropriate values to use for quantities that are assumed to have fixed but poorly known values in the context of a specific study. Aleatory uncertainty is usually represented with probab… more

Date: August 1, 2008

Creator: Johnson, Jay Dean (ProStat, Mesa, AZ); Helton, Jon Craig (Arizona State University, Tempe, AZ); Oberkampf, William Louis & Sallaberry, Cedric J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

In-Flight Measurements of Capsule Adiabats in Laser Driven Spherical Implosions

We present the first x-ray Thomson scattering measurements of temperature and density from spherically imploding matter. The shape of the Compton downscattered spectrum provides a first-principles measurement of the electron velocity distribution function, dependent on T{sub e} and the Fermi temperature T{sub F} {approx} n{sub e}{sup 2/3}. In flight compressions of Be and CH targets reach 6-13 times solid density, with T{sub e}/T{sub F} {approx} 0.4-0.7, resulting in minimum adiabats of {approx… more

Date: March 7, 2011

Creator: Kritcher, A L; Doppner, T; Fortman, C; Ma, T; Landen, O L; Wallace, R et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Local structure of La1-xSrxCoO3 determined from EXAFS and neutron PDF studies

The combined local structure techniques, extended X-ray absorption fine struture (EXAFS) and neutron pair distribution function (PDF) analysis, have been used for temperatures 4 {<=} T {<=} 330 K to rule out a large Jahn-Teller (J-T) distortion of the Co-O bond in La{sub 1-x}Sr{sub x}CoO{sub 3} for a significant fraction of Co sites (x {<=} 0.35), indicating few, if any, J-T active, single-occupied e{sub g} Co sites exist.

Date: January 1, 2008

Creator: Proffen, Thomas; Sundaram, Nalini; Jiang, Y; Anderson, Ingrid; Belanger, D P; Booth, C H et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Design and Implementation of Ceph: A Scalable Distributed File System

File system designers continue to look to new architectures to improve scalability. Object-based storage diverges from server-based (e.g. NFS) and SAN-based storage systems by coupling processors and memory with disk drives, delegating low-level allocation to object storage devices (OSDs) and decoupling I/O (read/write) from metadata (file open/close) operations. Even recent object-based systems inherit decades-old architectural choices going back to early UNIX file systems, however, limiting t… more

Date: April 19, 2006

Creator: Weil, S A; Brandt, S A; Miller, E L; Long, D E & Maltzahn, C

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Measurement of the muon charge asymmetry from W boson decays

We present a measurement of the muon charge asymmetry from W boson decays using 0.3 fb{sup -1} of data collected at {radical}s = 1.96 GeV between 2002 and 2004 with the D0 detector at the Fermilab Tevatron p{bar p} Collider. We compare our findings with expectations from next-to-leading-order calculations performed using the CTEQ6.1M and MRST04 NLO parton distribution functions. Our findings can be used to constrain future parton distribution function fits.

Date: September 1, 2007

Creator: Abazov, V. M.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adams, M.; Adams, T. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Ion energy distribution functions of vacuum arc plasmas

The velocity distribution function of vacuum arc ions can be measured by a time-of-flight technique similar to a method originally proposed by Yushkov. The measuring principle makes use of the well-justified assumption that the ion drift velocity from the cathode spot region to a collector is approximately constant. It is shown that the negative time derivative of the collector current is directly proportional to the ion distribution function provided that the time-averaged source intensity (i.… more

Date: September 16, 2002

Creator: Byon, Eungsun & Anders, Andre

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Surface chemistry controls crystallinity of ZnSnanoparticles

Combined small-angle and high energy wide-angle x-ray scattering measurements of nanoparticle size and structure permit interior strain and disorder to be directly observed in the real-space pair distribution function (PDF). PDF analysis showed that samples of ZnS nanoparticle with similar mean diameters (3.2-3.6 nm) but synthesized and treated differently possess a dramatic range of interior disorder. We used Fourier transform infra-red spectroscopy to detect the surface species and the nature… more

Date: December 20, 2005

Creator: Gilbert, Benjamin; Huang, Feng; Lin, Zhang; Goodell, Carmen; Zhang, Hengzhong & F., Banfield Jillian

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Applications of Sunphotometry to Aerosol Extinction and Surface Anisotropy

Support cost-sharing of a newly developed sunphotometer in field deployment for aerosol studies. This is a cost-sharing research to deploy a newly developed sun-sky-surface photometer for studying aerosol extinction and surface anisotropy at the ARM SGP, TWP, and NSA-AAO CART sites and in many field campaigns. Atmospheric aerosols affect the radiative energy balance of the Earth, both directly by perturbing the incoming/outgoing radiation fields and indirectly by influencing the properties/proc… more

Date: September 30, 2002

Creator: Tsay, S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Jet Physics at CDF

Jets have been studied by the CDF Collaboration [1] as a means of searching for new particles and interactions, testing a variety of perturbative QCD predictions, and providing input for the global parton distribution function (PDF) fits. Unless otherwise indicated below, the jets were reconstructed using a cone algorithm [2] with cone radius R = 0.7 from data taken at the Fermilab Tevatron collider in Run 2, 2001-2003, with {radical}s = 1.96 TeV. Central jets, in the pseudorapidity range relat… more

Date: June 28, 2004

Creator: Seidel, Sally

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Collective Space-Charge Phenomena in the Source Region

For many devices space-charge-dominated behavior, including the excitation of space-charge collective modes, can occur in the source region, even when the downstream characteristics are not space-charge-dominated. Furthermore, these modes can remain undamped for many focusing periods. Traditional studies of the source region in particle beam systems have emphasized the behavior of averaged beam characteristics, such as total current, rms beam size, or emittance, rather than the details of the f… more

Date: September 18, 2004

Creator: Haber, I.; Bernal, S.; Celata, C. M.; Friedman, A.; Grote, D. P.; Kishek, R. A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Loss of Landau Damping for Bunch Oscillations

Conditions for the existence, uniqueness and stability of self-consistent bunch steady states are considered. For the existence and uniqueness problems, simple algebraic criteria are derived for both the action and Hamiltonian domain distributions. For the stability problem, van Kampen theory is used. The onset of a discrete van Kampen mode means the emergence of a coherent mode without any Landau damping; thus, even a tiny couple-bunch or multi-turn wake is sufficient to drive the instability.… more

Date: April 11, 2011

Creator: Burov, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

SPS data on tunnel displacements and the ATL law

In this article we analyze data from long-term measurements of quadrupole displacements in the Super Proton Synchrotron ring at CERN. The variance of displacement can be approximated by ATL law with coefficient A = (0.1--0.4) * 10{sup {minus}4} {mu}m{sup 2}/s/m, with T the time interval between measurements and L the distance between two points of the tunnel. The shape of the distribution function is found to be close to Gaussian. The results of the analysis are compared with other data on slow… more

Date: September 1, 1993

Creator: Shiltsev, V. & Stiening, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Overdispersion: Notes on discrete distributions

We introduce mixtures of binomial distributions derived by assuming that the probability parameter p varies according to some law. We use the transformation p = exp({minus}t) and consider various appropriate densities for the transformed variables. In the process, the Laplace transform becomes the fundamental entity. Large numbers of new binomial mixtures are generated in this way. Some transformations may involve several variates that lead to ``multivariate`` binomial mixtures. An extension of… more

Date: September 1, 1992

Creator: Bowman, K. O.; Shenton, L. R.; Kastenbaum, M. A. & Broman, K.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Using cloud resolving model simulations of deep convection to inform cloud parameterizations in large-scale models

Cloud parameterizations in large-scale models struggle to address the significant non-linear effects of radiation and precipitation that arise from horizontal inhomogeneity in cloud properties at scales smaller than the grid box size of the large-scale models. Statistical cloud schemes provide an attractive framework to self-consistently predict the horizontal inhomogeneity in radiation and microphysics because the probability distribution function (PDF) of total water contained in the scheme c… more

Date: June 23, 2003

Creator: Klein, Stephen A.; Pincus, Robert & Xu, Kuan-man

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Stochastic Characterization of Cast Metal Microstructure

The major goal of this work is to provide a means to characterize the final structure of a metal that has solidified from a melt. The thermally controlled solidification of a binary alloy, nucleated at isolated sites, is described by the evolution of a probability distribution function (PDF). The relevant equation required for propagating the PDF is developed with variables for grain size and distance to nearest neighbor. The phenomena of nucleation, growth, and impingement of the grains are di… more

Date: June 1, 1999

Creator: Steinzig, M.

Item Type: Thesis or Dissertation

Partner: UNT Libraries Government Documents Department

open access

Inclusive jet production at CDF

The CDF results on the inclusive jet cross section at {radical}{ital s} = 1800 GeV are presented. The corrected cross section is compared with NLO QCD calculations.

Date: October 1, 1996

Creator: Bhatti, A. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

QCD: Challenges for the future

Despite many experimental verifications of the correctness of our basic understanding of QCD, there remain numerous open questions in strong interaction physics and we focus on the role of future colliders in addressing these questions. We discuss possible advances in the measurement of {alpha}{sub s}, in the study of parton distribution functions, and in the understanding of low x physics at present colliders and potential new facilities. We also touch briefly on the role of spin physics in ad… more

Date: January 13, 1997

Creator: Burrows, P.; Dawson, S.; Orr, L. & Smith, W.H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Structure and Dynamics of Quasi-Ordered Systems

The functionality of many materials of both fundamental and technological interest is often critically dependent on the nature and extent of any disorder that may be present. In addition, it is often difficult to understand the nature of disorder in quite well ordered systems. There is therefore an urgent need to develop better tools, both experimental and computational, for the study of such quasi-ordered systems. To this end, the authors have used neutron diffraction studies in an attempt to … more

Date: July 9, 1999

Creator: Eckert, Juergen; Redondo, Antonio; Henson, Neil J.; Wang, Wanshu & Hay, P. Jeffrey

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Nonlinear Gyroviscous Force in a Collisionless Plasma

Nonlinear gyroviscous forces in a collisionless plasma with temperature variations are calculated from the gyrofluid moments of the gyrokinetic Vlasov equation. The low-frequency gyrokinetic ordering and electrostatic perturbations are assumed, and an additional finite Larmor radius (FLR) expansion is performed. This approach leads naturally to an expression for the gyroviscous force in terms of the gyrocenter distribution function, thus including all resonant effects, and represents a systemat… more

Date: May 23, 2001

Creator: Belova, E. V.

Item Type: Report

Partner: UNT Libraries Government Documents Department