Resource Type

States

365 Matching Results

Results open in a new window/tab.

3-D Simulations of Plasma Wakefield Acceleration with Non-Idealized Plasmas and Beams (open access)

3-D Simulations of Plasma Wakefield Acceleration with Non-Idealized Plasmas and Beams

3-D Particle-in-cell OSIRIS simulations of the current E-162 Plasma Wakefield Accelerator Experiment are presented in which a number of non-ideal conditions are modeled simultaneously. These include tilts on the beam in both planes, asymmetric beam emittance, beam energy spread and plasma inhomogeneities both longitudinally and transverse to the beam axis. The relative importance of the non-ideal conditions is discussed and a worst case estimate of the effect of these on energy gain is obtained. The simulation output is then propagated through the downstream optics, drift spaces and apertures leading to the experimental diagnostics to provide insight into the differences between actual beam conditions and what is measured. The work represents a milestone in the level of detail of simulation comparisons to plasma experiments.
Date: September 27, 2005
Creator: Deng, S.; Katsouleas, T.; Lee, S.; Muggli, P.; Mori, W. B.; Hemker, R. et al.
System: The UNT Digital Library
A 90-GHz Photoinjector (open access)

A 90-GHz Photoinjector

Photocathode rf guns depend on mode locked laser systems to produce an electron beam at a given phase of the rf. In general, the laser pulse is less than {sigma}{sub z} = 10{sup o} of rf phase in length and the required stability is on the order of {Delta}{phi} = 1{sup o}. At 90 GHz (W-band), these requirements correspond to {sigma}{sub z} = 333 fsec and {Delta}{phi} = 33 fsec. Laser system with pulse lengths in the fsec regime are commercially available, the timing stability is a major concern. We propose a multi-cell W-band photoinjector that does not require a mode locked laser system. Thereby eliminating the stability requirements at W-band. The laser pulse is allowed to be many rf periods long. In principle, the photoinjector can now be considered as a thermionic rf gun. Instead of using an alpha magnet to compress the electron bunch, which would have a detrimental effect on the transverse phase space quality due to longitudinal phase space mixing, we propose to use long pulse laser system and a pair of undulators to produce a low emittance, high current, ultra-short electron bunch for beam dynamics experiments in the 90 GHz regime.
Date: September 12, 2005
Creator: Palmer, D. T.; Hogan, M. J.; Ferrario, M. & Serafini, L.
System: The UNT Digital Library
The 100,000 amp dc power supply for a staged hadron collider super ferric magnet (open access)

The 100,000 amp dc power supply for a staged hadron collider super ferric magnet

A 1.5 volt 100,000 amp DC switcher power supply was developed for testing a superferric magnet string at FNAL. This supply was used during testing as both the ramping supply and holding supply powering a single magnet load with a total load resistance of 0.7{micro} Ohms. The supply consists of ten paralleled switcher cells, powered by a 400 volt/600 Amp DC power supply. Each cell consists of an IGBT H-bridge driving a step-down transformer at a switching frequency of 2 kHz. The transformer has an effective turns ratio of 224:1. The secondary consists of 32 parallel single-turn full wave rectifier windings. The rectification is done with 64 Shottky diodes. Each cell is rated at 1.5 volts/10,000 amps. During this test each cell was operated as a constant power source without load current or field feedback. This paper will describe the design of the switcher cell and control system used during testing. We will also describe the next level of improvements to the current feedback system to improve the ramp control.
Date: September 1, 2005
Creator: Hays, Steven L.; Claypool, Bradley & Foster, G. William
System: The UNT Digital Library
The 100 kA current leads for a superconducting transmission line magnet (open access)

The 100 kA current leads for a superconducting transmission line magnet

A pair of current leads to power a transmission line magnet cooled at liquid helium temperature has been designed and developed at Fermilab. The leads designed to carry 100 kA dc current. Each lead consists of a warm end, heat exchange section and a cold end. The warm end is a half moon plate and cylinder brazed together. The heat exchange section is made of 202 copper rods arranged in a staggered pattern. Each rod is 6.35 mm in diameter and 1650 mm in length. The rods were soft-soldered into 12.7 mm deep holes at both warm and cold ends. The helium gas flow, guided by anodized aluminum baffles along the lead length, allows for a relatively high heat transfer coefficient between the current carrying rods and cooling helium gas. As a result the current leads were successfully tested with a ramping current of up to 104 kA. The current lead design, assembly work and the test results are presented.
Date: September 1, 2005
Creator: Huang, Yuenian; Foster, William; Kim, Seog-Whan; Mazur, Peter; Oleck, Andrew; Piekarz, Henryk et al.
System: The UNT Digital Library
2004 Electron Donor Acceptor Interactions Gordon Conference - August 8-13, 2004 (open access)

2004 Electron Donor Acceptor Interactions Gordon Conference - August 8-13, 2004

The 2004 Gordon Conference on Donor/Acceptor Interactions will take place at Salve Regina University in Newport, Rhode Island on August 8-13, 2004. The conference will be devoted to the consequences of charge interaction and charge motion in molecular and materials systems.
Date: September 14, 2005
Creator: GUILFORD JONES BOSTON UNIVERSITY PHOTONICS CENTER 8 ST. MARY'S ST BOSTON, MA 02215
System: The UNT Digital Library
2004 Inorganic Chemistry Gordon Research Conference - July 18-23, 2004 (open access)

2004 Inorganic Chemistry Gordon Research Conference - July 18-23, 2004

The Gordon Research Conference (GRC) on 2004 Inorganic Chemistry Gordon Research Conference - July 18-23, 2004 was held at Salve Regina College, July 18-23, 2004. The Conference was well-attended with 110 participants (attendees list attached). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both U.S. and foreign scientists, senior researchers, young investigators, and students. In designing the formal speakers program, emphasis was placed on current unpublished research and discussion of the future target areas in this field. There was a conscious effort to stimulate lively discussion about the key issues in the field today. Time for formal presentations was limited in the interest of group discussions. In order that more scientists could communicate their most recent results, poster presentation time was scheduled. Attached is a copy of the formal schedule and speaker program and the poster program. In addition to these formal interactions, 'free time' was scheduled to allow informal discussions. Such discussions are fostering new collaborations and joint efforts in the field.
Date: September 16, 2005
Creator: Clark, David
System: The UNT Digital Library
2004 Molecular Basis of Microbial One-Carbon Metabolism Gordon Conference - August 1-6, 2004 (open access)

2004 Molecular Basis of Microbial One-Carbon Metabolism Gordon Conference - August 1-6, 2004

The Gordon Research Conference (GRC) on 2004 Molecular Basis of Microbial One-Carbon Metabolism Gordon Conference - August 1-6, 2004 was held at Mount Holyoke College, South Hadley, MA from August 1-6, 2004. The Conference was well-attended with 117 participants (attendees list attached). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both U.S. and foreign scientists, senior researchers, young investigators, and students. In designing the formal speakers program, emphasis was placed on current unpublished research and discussion of the future target areas in this field. There was a conscious effort to stimulate lively discussion about the key issues in the field today. Time for formal presentations was limited in the interest of group discussions. In order that more scientists could communicate their most recent results, poster presentation time was scheduled. Attached is a copy of the formal schedule and speaker program and the poster program. In addition to these formal interactions, 'free time' was scheduled to allow informal discussions. Such discussions are fostering new collaborations and joint efforts in the field.
Date: September 15, 2005
Creator: Krzycki, Joseph A.
System: The UNT Digital Library
2004 Mutagenesis Gordon Conference (open access)

2004 Mutagenesis Gordon Conference

Mutations are genetic alterations that drive biological evolution and cause many, if not all, human diseases. Mutation originates via two distinct mechanisms: ''vertical'' variation is de novo change of one or few bases, whereas ''horizontal'' variation occurs by genetic recombination, which creates new mosaics of pre-existing sequences. The Mutagenesis Conference has traditionally focused on the generation of mutagenic intermediates during normal DNA synthesis or in response to environmental insults, as well as the diverse repair mechanisms that prevent the fixation of such intermediates as permanent mutations. While the 2004 Conference will continue to focus on the molecular mechanisms of mutagenesis, there will be increased emphasis on the biological consequences of mutations, both in terms of evolutionary processes and in terms of human disease. The meeting will open with two historical accounts of mutation research that recapitulate the intellectual framework of this field and thereby place the current research paradigms into perspective. The two introductory keynote lectures will be followed by sessions on: (1) mutagenic systems, (2) hypermutable sequences, (3) mechanisms of mutation, (4) mutation avoidance systems, (5) mutation in human hereditary and infectious diseases, (6) mutation rates in evolution and genotype-phenotype relationships, (7) ecology, mutagenesis and the modeling of evolution …
Date: September 16, 2005
Creator: Jinks-Robertson, Dr. Sue
System: The UNT Digital Library
Activation Energy for Grain Growth in Bismuth Coatings (open access)

Activation Energy for Grain Growth in Bismuth Coatings

The knowledge of both activation energy and diffusion coefficient is needed for a predictive processing of grain size in coatings. However, for metals as Bismuth there is insufficient information available in the literature for these parameters. To determine these values, a method is adopted wherein an examination of the grain size is conducted for coatings deposited isothermally. The exponent for grain growth with time is determined, thereby enabling quantification of the activation energy and diffusion coefficient. Bismuth coatings that range from 10 {micro}m to 1 mm thick are deposited using electron-beam evaporation onto temperature-controlled substrate surfaces of glass and lithium fluoride. The grain size of each coating is measured upon examination of the microstructure in cross-section using the intercept method. Ideal grain growth is observed over the experimental range of deposition temperatures examined from 317 to 491 K. The activation energy (Q) for grain growth in bismuth is fit as 0.47 eV {center_dot} atom{sup -1} with a diffusion coefficient (D{sub 0}) of 3.3 x 10{sup -4} cm{sup 2} {center_dot} sec{sup -1}.
Date: September 9, 2005
Creator: Jankowski, Alan Frederic; Hayes, Jeffrey P.; Smith, R. F.; Reed, B. W.; Kumar, M. & Colvin, J. D.
System: The UNT Digital Library
Advanced Control Technologies and Strategies Linking DemandResponse and Energy Efficiency (open access)

Advanced Control Technologies and Strategies Linking DemandResponse and Energy Efficiency

This paper presents a preliminary framework to describe how advanced controls can support multiple modes of operations including both energy efficiency and demand response (DR). A general description of DR, its benefits, and nationwide status is outlined. The role of energy management and control systems for DR is described. Building systems such as HVAC and lighting that utilize control technologies and strategies for energy efficiency are mapped on to DR and demand shedding strategies are developed. Past research projects are presented to provide a context for the current projects. The economic case for implementing DR from a building owner perspective is also explored.
Date: September 2, 2005
Creator: Kiliccote, Sila & Piette, Mary Ann
System: The UNT Digital Library
Advanced Off-Gas Control System Design For Radioactive And Mixed Waste Treatment (open access)

Advanced Off-Gas Control System Design For Radioactive And Mixed Waste Treatment

Treatment of radioactive and mixed wastes is often required to destroy or immobilize hazardous constituents, reduce waste volume, and convert the waste to a form suitable for final disposal. These kinds of treatments usually evolve off-gas. Air emission regulations have become increasingly stringent in recent years. Mixed waste thermal treatment in the United States is now generally regulated under the Hazardous Waste Combustor (HWC) Maximum Achievable Control Technology (MACT) standards. These standards impose unprecedented requirements for operation, monitoring and control, and emissions control. Off-gas control technologies and system designs that were satisfactorily proven in mixed waste operation prior to the implementation of new regulatory standards are in some cases no longer suitable in new mixed waste treatment system designs. Some mixed waste treatment facilities have been shut down rather than have excessively restrictive feed rate limits or facility upgrades to comply with the new standards. New mixed waste treatment facilities in the U. S. are being designed to operate in compliance with the HWC MACT standards. Activities have been underway for the past 10 years at the INL and elsewhere to identify, develop, demonstrate, and design technologies for enabling HWC MACT compliance for mixed waste treatment facilities. Some specific off-gas …
Date: September 1, 2005
Creator: Soelberg, Nick
System: The UNT Digital Library
Advanced Test Reactor Capabilities and Future Operating Plans (open access)

Advanced Test Reactor Capabilities and Future Operating Plans

The Advanced Test Reactor (ATR), at the Idaho National Laboratory (INL), is one of the world’s premier test reactors for providing the capability for studying the effects of intense neutron and gamma radiation on reactor materials and fuels. The physical configuration of the ATR, a 4-leaf clover shape, allows the reactor to be operated at different power levels in the corner “lobes” to allow for different testing conditions for multiple simultaneous experiments. The combination of high flux (maximum thermal neutron fluxes of 1E15 neutrons per square centimeter per second and maximum fast [E>1.0 MeV] neutron fluxes of 5E14 neutrons per square centimeter per second) and large test volumes (up to 48" long and 5.0" diameter) provide unique testing opportunities. The current experiments in the ATR are for a variety of test sponsors - US government, foreign governments, private researchers, and commercial companies needing neutron irradiation services. There are three basic types of test configurations in the ATR. The simplest configuration is the sealed static capsule, wherein the target material is placed in a capsule, or plate form, and the capsule is in direct contact with the primary coolant. The next level of complexity of an experiment is an instrumented lead …
Date: September 1, 2005
Creator: Marshall, Frances M.
System: The UNT Digital Library
[After a Fashion, September 22, 2005] (open access)

[After a Fashion, September 22, 2005]

Article about the Ballet Austin Fete Gothic event, the One Country Concert, and La Cage: Vegas in Austin.
Date: September 22, 2005
Creator: Moser, Stephen MacMillan
System: The UNT Digital Library
Amish Teacher Dialogues with Teacher Educators: Research, Culture, and Voices of Critique (open access)

Amish Teacher Dialogues with Teacher Educators: Research, Culture, and Voices of Critique

Article discussing a collaborative project to examine literature and research on the Amish culture.
Date: September 2005
Creator: Zehr, Henry; Moss, Glenda & Nichols, Joe
System: The UNT Digital Library
Analysis of Hydrogen Production from Renewable Electricity Sources: Preprint (open access)

Analysis of Hydrogen Production from Renewable Electricity Sources: Preprint

To determine the potential for hydrogen production via renewable electricity sources, three aspects of the system are analyzed: a renewable hydrogen resource assessment, a cost analysis of hydrogen production via electrolysis, and the annual energy requirements of producing hydrogen for refueling. The results indicate that ample resources exist to produce transportation fuel from wind and solar power. However, hydrogen prices are highly dependent on electricity prices.
Date: September 1, 2005
Creator: Levene, J. I.; Mann, M. K.; Margolis, R. & Milbrandt, A.
System: The UNT Digital Library
Analysis of Longitudinal Space Charge Effects With Radial Dependence (open access)

Analysis of Longitudinal Space Charge Effects With Radial Dependence

Longitudinal space charge (LSC) force can be a main effect driving the microbunching instability in the linac for an x-ray free-electron laser (FEL). In this paper, the LSC-induced beam modulation is studied using an integral equation approach that takes into account the transverse (radial) variation of LSC field for both the coasting beam limit and bunched beam. Changes of beam energy and the transverse beam size can be also incorporated. We discuss the validity of this approach and compare it with other analyses as well as numerical simulations.
Date: September 30, 2005
Creator: Wu, Juhao; Huang, Z. & Emma, P.
System: The UNT Digital Library
Applications of AdS/CFT Duality to QCD (open access)

Applications of AdS/CFT Duality to QCD

Even though quantum chromodynamics is a broken conformal theory, the AdS/CFT correspondence has led to important insights into the properties of QCD. For example, as shown by Polchinski and Strassler, dimensional counting rules for the power-law falloff of hadron scattering amplitudes follow from dual holographic models with conformal behavior at short distances and confinement at large distances. We find that one also obtains a remarkable representation of the entire light-quark meson and baryon spectrum, including all orbital excitations, based on only one mass parameter. We also show how hadron light-front wavefunctions and hadron form factors in both the space-like and time-like regions can be predicted.
Date: September 28, 2005
Creator: Brodsky, Stanley J. & de Teramond, Guy F.
System: The UNT Digital Library
APPROXIMATION OF MULTIFLUID MIXTURE RESPONSE FOR SIMULATION OF SHARP AND DIFFUSE MATERIAL INTERFACES ON AN EULERIAN GRID (open access)

APPROXIMATION OF MULTIFLUID MIXTURE RESPONSE FOR SIMULATION OF SHARP AND DIFFUSE MATERIAL INTERFACES ON AN EULERIAN GRID

Multimaterial Eulerian and Arbitrary Lagragian-Eulerian (ALE) codes usually use volume fractions of materials to track individual components in mixed cells. Material advection usually is calculated either by interface capturing, where a high-order van Leer-like slope reconstruction technique is applied, or interface tracking, where a normal reconstruction technique is applied. The former approach is more appropriate for gas-like substances, and the latter is ideal for solids and liquids, since it does not smear out material interfaces. A wide range of problems involves both diffuse and sharp interfaces between substances and demands a combination of these techniques. It is possible to treat all substances that can diffuse into each other as a single material and only keep mass fractions of the individual components of the mixture. The material response can be determined based on the assumption of pressure and temperature equilibrium between components of the mixture. Unfortunately, it is extremely difficult to solve the corresponding system of equations. In order to avoid these problems one can introduce an effective gamma and employ the ideal gas approximation to calculate mixture response. This method provides reliable results, is able to compute strong shock waves, and deals with complex equations of state. Results from a …
Date: September 29, 2005
Creator: Lomov, I & Liu, B
System: The UNT Digital Library
An assumed partition algorithm for determining processor inter-communication (open access)

An assumed partition algorithm for determining processor inter-communication

The recent advent of parallel machines with tens of thousands of processors is presenting new challenges for obtaining scalability. A particular challenge for large-scale scientific software is determining the inter-processor communications required by the computation when a global description of the data is unavailable or too costly to store. We present a type of rendezvous algorithm that determines communication partners in a scalable manner by assuming the global distribution of the data. We demonstrate the scaling properties of the algorithm on up to 32,000 processors in the context of determining communication patterns for a matrix-vector multiply in the hypre software library. Our algorithm is very general and is applicable to a variety of situations in parallel computing.
Date: September 23, 2005
Creator: Baker, A H; Falgout, R D & Yang, U M
System: The UNT Digital Library
B physics at hadron colliders (open access)

B physics at hadron colliders

This paper discusses the physics opportunity and challenges for doing high precision B physics experiments at hadron colliders. It describes how these challenges have been addressed by the two currently operating experiments, CDF and D0, and how they are addressed by three experiments, ATLAS, CMS, and LHCb, at the LHC.
Date: September 1, 2005
Creator: Butler, J.N.
System: The UNT Digital Library
Bacterial Cyanide Oxygenase Is a Suite of Enzymes Catalyzing the Scavenging and Adventitious Utilization of Cyanide as a Nitrogenous Growth Substrate (open access)

Bacterial Cyanide Oxygenase Is a Suite of Enzymes Catalyzing the Scavenging and Adventitious Utilization of Cyanide as a Nitrogenous Growth Substrate

Article on bacterial cyanide oxygenase as a suite of enzymes catalyzing the scavenging and adventitious utilization of cyanide as a nitrogenous growth substrate.
Date: September 2005
Creator: Fernandez, Ruby F. & Kunz, Daniel A.
System: The UNT Digital Library
Balancing Cost and Risk: The Treatment of Renewable Energy inWestern Utility Resource Plans (open access)

Balancing Cost and Risk: The Treatment of Renewable Energy inWestern Utility Resource Plans

Markets for renewable electricity have grown significantly in recent years, motivated in part by federal tax incentives and in part by state renewables portfolio standards and renewable energy funds. State renewables portfolio standards, for example, motivated approximately 45% of the 4,300 MW of wind power installed in the U.S. from 2001 through 2004, while renewable energy funds supported an additional 15% of these installations. Despite the importance of these state policies, a less widely recognized driver for renewable energy market growth is poised to also play an important role in the coming years: utility integrated resource planning (IRP). Formal resource planning processes have re-emerged in recent years as an important tool for utilities and regulators, particularly in regions where retail competition has failed to take root. In the western United States, recent resource plans contemplate a significant amount of renewable energy additions. These planned additions - primarily coming from wind power - are motivated by the improved economics of wind power, a growing acceptance of wind by electric utilities, and an increasing recognition of the inherent risks (e.g., natural gas price risk, environmental compliance risk) in fossil-based generation portfolios. The treatment of renewable energy in utility resource plans is not …
Date: September 1, 2005
Creator: Wiser, Ryan & Bolinger, Mark
System: The UNT Digital Library
Baryon Number Violation Involving Higher Generations (open access)

Baryon Number Violation Involving Higher Generations

None
Date: September 2, 2005
Creator: Hou, Wei-Shu; /Taiwan, Natl. Taiwan U. /SLAC; Nagashima, Makiko; /Taiwan, Natl. Taiwan U.; Soddu, Andrea & /Taiwan, Natl. Taiwan U. /Weizmann Inst.
System: The UNT Digital Library
Bat response to carolina bays and wetland restoration in the southeastern U.S. Coastal Plain. (open access)

Bat response to carolina bays and wetland restoration in the southeastern U.S. Coastal Plain.

Abstract: Bat activity in the southeastern United States is concentrated over riparian areas and wetland habitats. The restoration and creation of wetlands for mitigation purposes is becoming common in the Southeast. Understanding the effects of these restoration efforts on wetland flora and fauna is thus becoming increasingly important. Because bats (Order: Chiroptera) consist of many species that are of conservation concern and are commonly associated with wetland and riparian habitats in the Southeast (making them a good general indicator for the condition of wetland habitats), we monitored bat activity over restored and reference Carolina bays surrounded by pine savanna (Pinus spp.) or mixed pine-hardwood habitat types at the Savannah River Site in South Carolina. In order to determine how wetland restoration efforts affected the bat community, we monitored bat activity above drained Carolina bays pre- and post-restoration. Our results indicate that bat activity was greater over reference (i.e., undrained) than drained bays prior to the restorative efforts. One year following combined hydrologic and vegetation treatment, however, bat activity was generally greater over restored than reference bays. Bat activity was also greater over both reference and restored bays than in random, forested interior locations. We found significantly more bat activity after …
Date: September 1, 2005
Creator: Menzel, Jennifer M.; Menzel, Michael A.; Kilgo, John C.; Ford, W. Mark & Edwards., John W.
System: The UNT Digital Library