The dihadron fragmentation function and its evolution (open access)

The dihadron fragmentation function and its evolution

Dihadron fragmentation functions and their evolution arestudied in the process of e+e- annihilation. Under the collinearfactorization approximation and facilitated by the cut-vertex technique,the two hadron inclusive cross section at leading order (LO) is shown tofactorize into a short distance parton cross section and a long distancedihadron fragmentation function. We provide the definition of such adihadron fragmentation function in terms of parton matrix elements andderive its DGLAP evolution equation at leading log. The evolutionequation for the non-singlet quark fragmentation function is solvednumerically with a simple ansatz for the initial condition and resultsare presented for cases of physical interest.
Date: February 24, 2004
Creator: Majumder, Abhijit & Wang, Xin-Nian
Object Type: Article
System: The UNT Digital Library
NAFEMS Finite Element Benchmarks for MDG Code Verification (open access)

NAFEMS Finite Element Benchmarks for MDG Code Verification

NAFEMS was originally founded at the United Kingdom's National Engineering Laboratory as the National Agency for Finite Element Methods and Standards. It was subsequently privatized as the not-for-profit organization NAFEMS, Ltd., but retains its mission ''To promote the safe and reliable use of finite element and related technology''. That mission has been pursued in part by sponsoring a series of studies that published benchmarked deemed suitable to assess the basic accuracy of engineering simulation tools. The early studies focused on FEA for linear solid and structural mechanics and then extended to nonlinear solid mechanics, eventually including contact. These benchmarks are complemented by educational materials concerning analysis technologies and approaches. More recently NAFEMS is expanding to consider thermal-fluid problems. Further information is available at www.nafems.org. Essentially all major commercial firms selling FEA for solid mechanics are members of NAFEMS and it seemed clear that Methods Development Group should leverage from this information resource, too. In 2002, W Program ASCI funding purchased a three-year membership in NAFEMS. In the summer of 2003 the first author hosted a summer graduate student to begin modeling some of the benchmark problems. We concentrated on NIKE3D, as the benchmarks are most typically problems most naturally run …
Date: February 24, 2004
Creator: Greer, R & Ferencz, R M
Object Type: Report
System: The UNT Digital Library
University Reactor Sharing Program (open access)

University Reactor Sharing Program

Research projects supported by the program include items such as dating geological material and producing high current super conducting magnets. The funding continues to give small colleges and universities the valuable opportunity to use the NSC for teaching courses in nuclear processes; specifically neutron activation analysis and gamma spectroscopy. The Reactor Sharing Program has supported the construction of a Fast Neutron Flux Irradiator for users at New Mexico Institute of Mining and Technology and the University of Houston. This device has been characterized and has been found to have near optimum neutron fluxes for A39/Ar 40 dating. Institution final reports and publications resulting from the use of these funds are on file at the Nuclear Science Center.
Date: February 24, 2004
Creator: Reese, W. D.
Object Type: Report
System: The UNT Digital Library
[Perovskite and Fluorite Grain Boundary Properties]. Final Project Report (open access)

[Perovskite and Fluorite Grain Boundary Properties]. Final Project Report

One of the main areas of research in the last two years in this program has been the properties of grain boundaries in perovskite and fluorite structure materials.
Date: February 24, 2004
Creator: Browning, N. D.
Object Type: Report
System: The UNT Digital Library
LCLS prototype undulator report. (open access)

LCLS prototype undulator report.

The Linac Coherent Light Source (LCLS) undulator line will consist of 33 undulator segments separated by breaks of two different lengths. The undulator segments are 3.4-m-long permanent-magnet planar hybrid devices with a period length of 30 mm and a magnetic gap of approximately 6 mm. Focusing quadrupoles, in a FODO lattice, and electron-beam diagnostics will be located in the breaks between undulator segments. Every third break will be longer in order to also accommodate x-ray diagnostics. Thus, taking the alternating focusing and defocusing quadrupoles into account, the ''super-period'' length before the undulator line repeats itself is six undulator segments. For additional details on the LCLS project and the undulator line, please refer to the conceptual design report (CDR). A full-length prototype undulator segment has been designed, manufactured and tested, and this document provides a comprehensive report of our experience with the prototype. It contains sections on the overall design philosophy and presents many important measurements including magnetic measurements of the magnet blocks, as well as of the assembled device, and mechanical and thermal measurements. It also contains a summary section (section 5) and one section that summarizes some remaining issues being investigated (section 6).
Date: February 24, 2004
Creator: Dejus, R.
Object Type: Report
System: The UNT Digital Library
Searches for physics beyond the standard model in ttbar events (open access)

Searches for physics beyond the standard model in ttbar events

The top quark is currently only observed at the Tevatron, where it is mainly produced in t{bar t} pairs. Due to the very high mass of the top quark compared to the other quarks and the gauge bosons, it is expected to play a special role in electroweak symmetry breaking. Therefore it might be especially sensitive to new physics. Measurements of various production and decay quantities of the top quark could lead to discoveries of physics beyond the standard model. Several such measurements were performed by the CDF collaboration during Run1 of the Tevatron. These measurements and first results from CDF in Run2 are presented.
Date: February 24, 2004
Creator: Merkel, P.
Object Type: Article
System: The UNT Digital Library
Deformation of Single Crystal Molybdenum at High Pressure (open access)

Deformation of Single Crystal Molybdenum at High Pressure

Single crystal samples of micron dimensions oriented in the [001] direction were shortened 10 to 40% in uniaxial compression with superposed hydrostatic pressure to begin investigation of how the onset of yielding evolves with pressure. A testing machine based on opposed anvil geometry with precision pneumatic control of the applied force and capability to measure sub micron displacements was developed to produce shape changing deformation at pressure. The experiments extend observations of pressure dependent deformation to {approx}5Gpa at shortening rates of {approx}2*10{sup -4}. Samples have been recovered for post run characterization and analysis to determine if deformation mechanisms are altered by pressure. Experiments under hydrostatic pressure provide insight into the nature of materials under extreme conditions, and also provide a means for altering deformation behavior in a controlled fashion. The approach has a long history demonstrating that pressure enhances ductility in general, and produces enhanced hardening relative to that expected from normal cold work in the BCC metals Mo, Ta and Nb{sup 2}. The pressure hardening is in excess of that predicted from the measured increase in shear modulus at pressure, and therefore is likely due to a dislocation mechanism, such as suppression of kink pair formation or the interaction …
Date: February 24, 2004
Creator: Bonner, B P; Aracne, C; Farber, D L; Boro, C O & Lassila, D H
Object Type: Report
System: The UNT Digital Library
LATTICE QCD AT FINITE TEMPERATURE AND DENSITY. (open access)

LATTICE QCD AT FINITE TEMPERATURE AND DENSITY.

With the operation of the RHIC heavy ion program, the theoretical understanding of QCD at finite temperature and density has become increasingly important. Though QCD at finite temperature has been extensively studied using lattice Monte-Carlo simulations over the past twenty years, most physical questions relevant for RHIC (and future) heavy ion experiments remain open. In lattice QCD at finite temperature and density there have been at least two major advances in recent years. First, for the first time calculations of real time quantities, like meson spectral functions have become available. Second, the lattice study of the QCD phase diagram and equation of state have been extended to finite baryon density by several groups. Both issues were extensively discussed in the course of the workshop. A real highlight was the study of the QCD phase diagram in (T, {mu})-plane by Z. Fodor and S. Katz and the determination of the critical end-point for the physical value of the pion mass. This was the first time such lattice calculations at, the physical pion mass have been performed. Results by Z Fodor and S. Katz were obtained using a multi-parameter re-weighting method. Other determinations of the critical end point were also presented, in …
Date: February 24, 2004
Creator: Blum, T.; Creutz, M. & Petreczky, P.
Object Type: Report
System: The UNT Digital Library
Science and Technology Review April 2004 (open access)

Science and Technology Review April 2004

This months issue has the following articles: (1)''Computing Science: One Arrow in the Quiver for Homeland Security''--Commentary by Wayne Shotts; (2) ''On the Front Lines of Biodefense''--The Laboratory's pathogen bioinformatics group is developing ways to rapidly identify microbes that could pose a threat to the nation's citizens, livestock, and crops. (3) ''Defending against Corrosion''--Livermore researchers are designing a rugged system to prevent nuclear wastes from seeping into the environment at the proposed underground repository at Yucca Mountain, Nevada. (4) ''Engine Shows Diesel Efficiency without the Emissions''--Computer models are helping Laboratory engineers better understand the homogeneous compression charge ignition engine, a fuel-efficient engine with reduced emissions.
Date: February 24, 2004
Creator: McMahon, D H
Object Type: Report
System: The UNT Digital Library
Note Hyperviscosity for Shock-Turbulence Interactions (open access)

Note Hyperviscosity for Shock-Turbulence Interactions

Over half a century ago, von Neumann and Richtmyer [1] introduced the idea of adding artificial viscosity to the Euler equations in order to help stabilize shock calculations. Their ideas regarding artificial viscosity influenced Smagorinsky [2, 3] in his development of a subgrid-scale model designed to match the Kolmogorov spectrum for atmospheric turbulence (C. E. Leith, private communication). Since that time, numerous artificial viscosity formulations have been proposed for simulating both shocks and turbulence [4, 5, 6, 7, 8, 9, 10]. Over the years however, a rift has developed between shock-capturing (monotonicity-preserving) and turbulence-capturing (large-eddy simulation) methods. Artificial viscosities for shock-capturing typically depend on sound speed, which makes them unsuitable for low Mach number flows. On the other hand, subgrid-scale models, customized for incompressible turbulence, usually fail to capture shocks in a monotonic fashion. The purpose of this paper is to introduce an artificial viscosity suitable for computing shock-turbulence interactions. This is accomplished by extending the model of Cook and Cabot [10] to multi-dimensions.
Date: February 24, 2004
Creator: Cook, A W & Cabot, W H
Object Type: Article
System: The UNT Digital Library
An Appraisal of Coupled Climate Model Simulations (open access)

An Appraisal of Coupled Climate Model Simulations

In 2002, the Program for Climate Model Diagnosis and Intercomparison (PCMDI) proposed the concept for a state-of-the-science appraisal of climate models to be performed approximately every two years. Motivation for this idea arose from the perceived needs of the international modeling groups and the broader climate research community to document progress more frequently than provided by the Intergovernmental Panel on Climate Change (IPCC) Assessment Reports. A committee of external reviewers, which included senior researchers from four leading international modeling centers, supported the concept by stating in its review: ''The panel enthusiastically endorses the suggestion that PCMDI develop an independent appraisal of coupled model performance every 2-3 years. This would provide a useful 'mid-course' evaluation of modeling progress in the context of larger IPCC and national assessment activities, and should include both coupled and single-component model evaluations.''
Date: February 24, 2004
Creator: Sperber, K.; Gleckler, P.; Covey, C.; Taylor, K.; Bader, D.; Phillips, T. et al.
Object Type: Report
System: The UNT Digital Library
Asian Summer Monsoon Intraseasonal Variability in General Circulation Models (open access)

Asian Summer Monsoon Intraseasonal Variability in General Circulation Models

The goals of this report are: (1) Analyze boreal summer Asian monsoon intraseasonal variability general circulation models--How well do the models represent the eastward and northward propagating components of the convection and how well do the models represent the interactive control that the western tropical Pacific rainfall exerts on the rainfall over India and vice-versa? (2) Role of air-sea interactions--prescribed vs. interactive ocean; and (3) Mean monsoon vs. variability.
Date: February 24, 2004
Creator: Sperber, K R & Annamalai, H
Object Type: Report
System: The UNT Digital Library
Seismic Waves in Finely Layered VTI Media: Poroelasticity, Thomsen Parameters, and Fluid Effects on Shear Waves (open access)

Seismic Waves in Finely Layered VTI Media: Poroelasticity, Thomsen Parameters, and Fluid Effects on Shear Waves

Layered earth models are well justified by experience, and provide a simple means of studying fairly general behavior of the elastic and poroelastic characteristics of seismic waves in the earth. Thomsen's anisotropy parameters for weak elastic and poroelastic anisotropy are now commonly used in exploration, and can be conveniently expressed in terms of the layer averages of Backus. Since our main interest is usually in the fluids underground, it would be helpful to have a set of general equations relating the Thomsen parameters as directly as possible to the fluid properties. This end can be achieved in a rather straightforward fashion for these layered earth models, and the present paper develops and then discusses these relations. Furthermore, it is found that, although there are five effective shear moduli for any layered VTI medium, one and only one effective shear modulus for the layered system contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves in VTI media. The effects of the pore fluids on this effective shear modulus can be substantial - an increase of shear wave speed on the order of 10% is shown to be possible …
Date: February 24, 2004
Creator: Berger, E. L.
Object Type: Article
System: The UNT Digital Library
NA22 Model Cities Project - LL244T An Intelligent Transportation System-Based Radiation Alert and Detection System (open access)

NA22 Model Cities Project - LL244T An Intelligent Transportation System-Based Radiation Alert and Detection System

The purpose of this project was twofold: first, provide an understanding of the technical foundation and planning required for deployment of Intelligent Transportation System (ITS)-based system architectures for the protection of New York City from a terrorist attack using a vehicle-deployed nuclear device; second, work with stakeholders to develop mutual understanding of the technologies and tactics required for threat detection/identification and establish guidelines for designing operational systems and procedures. During the course of this project we interviewed and coordinated analysis with people from the New Jersey State Attorney General's office, the New Jersey State Police, the Port Authority of New York/New Jersey, the Counterterrorism Division of the New York City Police Department, the New Jersey Transit Authority, the State of New Jersey Department of Transportation, TRANSCOM and a number of contractors involved with state and federal intelligent transportation development and implementation. The basic system architecture is shown in the figure below. In an actual system deployment, radiation sensors would be co-located with existing ITS elements and the data will be sent to the Traffic Operations Center. A key element of successful system operation is the integration of vehicle data, such as license plate, EZ pass ID, vehicle type/color and radiation …
Date: February 24, 2004
Creator: Peglow, S
Object Type: Report
System: The UNT Digital Library
Factors Affecting Zebra Mussel Kill by the Bacterium Pseudomonas fluorescens (open access)

Factors Affecting Zebra Mussel Kill by the Bacterium Pseudomonas fluorescens

The specific purpose of this research project was to identify factors that affect zebra mussel kill by the bacterium Pseudomonas fluorescens. Test results obtained during this three-year project identified the following key variables as affecting mussel kill: treatment concentration, treatment duration, mussel siphoning activity, dissolved oxygen concentration, water temperature, and naturally suspended particle load. Using this latter information, the project culminated in a series of pipe tests which achieved high mussel kill inside power plants under once-through conditions using service water in artificial pipes.
Date: February 24, 2004
Creator: Molloy, Daniel P.
Object Type: Report
System: The UNT Digital Library
PHOTOREDUCTIVE SEQUESTRATION OF CO2 TO FORM C1 PRODUCTS AND FUEL (open access)

PHOTOREDUCTIVE SEQUESTRATION OF CO2 TO FORM C1 PRODUCTS AND FUEL

We have investigated the photochemical reduction of CO{sub 2} in aqueous solution to form C{sub 1} products using a variety of oxide semiconductors and near UV light. Conventional oxide photosemiconductors including TiO{sub 2} and SrTiO{sub 3}, as well as modified oxide semiconductors including Pt/TiO{sub 2} and SrTiO{sub 3}/Cr-Sb, TiO{sub 2}/Fe{sub 3}O{sub 4} or TiO{sub 2}/Fe(CN){sub 6}{sup 3-} were used. Analysis for formate, acetate, formaldehyde, methanol and methane were conducted by a variety of analytical methods. Despite extensive published data on the facile reduction of CO{sub 2} by these semiconductors, we found only trace quantities of formate and acetate (typically less than 1 ppm) and no unequivocal evidence for formation of the other products. The quantum efficiencies of TiO{sub 2} and SrTiO{sub 3} for forming formate and acetate from CO{sub 2} are estimated to be 0.1-0.2% or less. The spectral properties of the unmodified oxides (TiO{sub 2}, SrTiO{sub 3}) restricts their use of solar irradiation to about 10% of the available near UV and visible spectrum, thereby giving an overall quantum and spectral efficiency of less than 0.01%. Semiconductor oxides modified with, Cr and Sb, Fe{sub 3}O{sub 4} or Fe(CN){sub 6}{sup 3-} exhibited no enhanced efficiency. However, Pt/TiO{sub 2} does produce …
Date: February 24, 2004
Creator: Mill, Theodore & Tungudomwongsa, Haruthai
Object Type: Report
System: The UNT Digital Library
A Comprehensive Study of Fracture Patterns and Densities in The Geysers Geothermal Reservoir Using Microearthquake Shear-Wave Splitting Tomography (open access)

A Comprehensive Study of Fracture Patterns and Densities in The Geysers Geothermal Reservoir Using Microearthquake Shear-Wave Splitting Tomography

In this project we developed a method for using seismic S-wave data to map the patterns and densities of sub-surface fractures in the NW Geysers Geothermal Field/ (1) This project adds to both the general methods needed to characterize the geothermal production fractures that supply steam for power generation and to the specific knowledge of these in the Geysers area. (2)By locating zones of high fracture density it will be possible to reduce the cost of geothermal power development with the targeting of high production geothermal wells. (3) The results of the project having been transferred to both US based and international geothermal research and exploration agencies and concerns by several published papers and meeting presentations, and through the distribution of the data handling and other software codes we developed.
Date: February 24, 2004
Creator: Malin, Peter E.; Shalev, Eylon; Lou, Min; Simiyu, Silas M.; Stroujkova, Anastasia & McCausland, Windy
Object Type: Report
System: The UNT Digital Library
Improved Miscible Nitrogen Flood Performance Utilizing Advanced Reservoir Characterization and Horizontal Laterals in a Class I Reservoir - East Binger (Marchand) Unit Quarterly Report (open access)

Improved Miscible Nitrogen Flood Performance Utilizing Advanced Reservoir Characterization and Horizontal Laterals in a Class I Reservoir - East Binger (Marchand) Unit Quarterly Report

Implementation of the work program of Budget Period 2 of the East Binger Unit (''EBU'') DOE Project is progressing and nearing completion. Two of three planned horizontal wells have been drilled and completed. The third horizontal well will be replaced by two vertical wells, both of which will be drilled in early 2004. Based on costs and performances of all new wells, it is believed that, in the setting of the East Binger Unit, the benefits of horizontal wells do not justify the additional cost. In addition to the drilling of new wells, the project also includes conversions of producing wells to injection service. Four wells have now been converted, and injection in the pilot area has doubled. A fifth planned conversion has been removed from the project. Overall response to the various projects continues to be very favorable. Gas injection into the pilot area has increased from 4.0 MMscf/d prior to development to 8.0 MMscf/d in November, while gas production has decreased from 4.1 MMscf/d to 3.0 MMscf/d. The nitrogen content of produced gas has dropped from 58% to 45%. This has reduced the nitrogen recycle within the pilot area from 60% to under 20%. Meanwhile, pilot area oil …
Date: February 24, 2004
Creator: Sinner, Joe
Object Type: Report
System: The UNT Digital Library