Resource Type

Country

Language

Ab initio Guided Optimization of GaTe for Radiation Detection Applications (open access)

Ab initio Guided Optimization of GaTe for Radiation Detection Applications

None
Date: April 5, 2011
Creator: Leao, C R & Lordi, V
System: The UNT Digital Library
Ab Initio No-Core Shell Model (open access)

Ab Initio No-Core Shell Model

A long-standing goal of nuclear theory is to determine the properties of atomic nuclei based on the fundamental interactions among the protons and neutrons (i.e., nucleons). By adopting nucleon-nucleon (NN), three-nucleon (NNN) and higher-nucleon interactions determined from either meson-exchange theory or QCD, with couplings fixed by few-body systems, we preserve the predictive power of nuclear theory. This foundation enables tests of nature's fundamental symmetries and offers new vistas for the full range of complex nuclear phenomena. Basic questions that drive our quest for a microscopic predictive theory of nuclear phenomena include: (1) What controls nuclear saturation; (2) How the nuclear shell model emerges from the underlying theory; (3) What are the properties of nuclei with extreme neutron/proton ratios; (4) Can we predict useful cross sections that cannot be measured; (5) Can nuclei provide precision tests of the fundamental laws of nature; and (6) Under what conditions do we need QCD to describe nuclear structure, among others. Along with other ab initio nuclear theory groups, we have pursued these questions with meson-theoretical NN interactions, such as CD-Bonn and Argonne V18, that were tuned to provide high-quality descriptions of the NN scattering phase shifts and deuteron properties. We then add meson-theoretic NNN …
Date: April 11, 2011
Creator: Barrett, B R; Navratil, P & Vary, J P
System: The UNT Digital Library
Absolute beam flux measurement at NDCX-I using gold-melting calorimetry technique (open access)

Absolute beam flux measurement at NDCX-I using gold-melting calorimetry technique

We report on an alternative way to measure the absolute beam flux at the NDCX-I, LBNL linear accelerator. Up to date, the beam flux is determined from the analysis of the beam-induced optical emission from a ceramic scintilator (Al-Si). The new approach is based on calorimetric technique, where energy flux is deduced from the melting dynamics of a gold foil. We estimate an average 260 kW/cm2 beam flux over 5 {micro}s, which is consistent with values provided by the other methods. Described technique can be applied to various ion species and energies.
Date: April 1, 2011
Creator: Ni, P. A.; Bieniosek, F. M.; Lidia, S. M. & Welch, J.
System: The UNT Digital Library
An Accumulator/Pre-Booster for the Medium-Energy Electron Ion Collider at Jlab (open access)

An Accumulator/Pre-Booster for the Medium-Energy Electron Ion Collider at Jlab

Future nuclear physics facilities such as the proposed electron ion collider (MEIC) will need to achieve record high luminosities in order to maximize discovery potential. Among the necessary ingredients is the ability to generate, accumulate , accelerate, and store high current ion beams from protons to lead ions. One of the main components of this ion accelerator complex for MEIC chain is the accumulator that also doubles as a pre-booster, which takes 200 MeV protons from a superconducting linear accelerator, accumulates on the order of 1A beam, and boosts its energy to 3GeV, before extraction to the next accelerator in the chain, the large booster. This paper describes its design concepts, and summarizes some preliminary results, including linear optics, space charge dynamics, and spin polarization resonance analysis.
Date: April 1, 2011
Creator: Erdelyi, B.; Manikonda, S. L.; Ostroumov, P. N.; Abeyratne, S.; Derbenev, Y. S.; Krafft, G. A. et al.
System: The UNT Digital Library
Advancements in Ti Alloy Powder Production by Close-Coupled Gas Atomization (open access)

Advancements in Ti Alloy Powder Production by Close-Coupled Gas Atomization

As the technology for titanium metal injection molding (Ti-MIM) becomes more readily available, efficient Ti alloy fine powder production methods are required. An update on a novel close-coupled gas atomization system has been given. Unique features of the melting apparatus are shown to have measurable effects on the efficiency and ability to fully melt within the induction skull melting system (ISM). The means to initiate the melt flow were also found to be dependent on melt apparatus. Starting oxygen contents of atomization feedstock are suggested based on oxygen pick up during the atomization and MIM processes and compared to a new ASTM specification. Forming of titanium by metal injection molding (Ti-MIM) has been extensively studied with regards to binders, particle shape, and size distribution and suitable de-binding methods have been discovered. As a result, the visibility of Ti-MIM has steadily increased as reviews of technology, acceptability, and availability have been released. In addition, new ASTM specification ASTM F2885-11 for Ti-MIM for biomedical implants was released in early 2011. As the general acceptance of Ti-MIM as a viable fabrication route increases, demand for economical production of high quality Ti alloy powder for the preparation of Ti-MIM feedstock correspondingly increases. The production …
Date: April 1, 2011
Creator: Heidloff, Andy; Rieken, Joel; Anderson, Iver & Byrd, David
System: The UNT Digital Library
ALLOYING-DRIVEN PHASE STABILITY IN GROUP-VB TRANSITION METALS UNDER COMPRESSION (open access)

ALLOYING-DRIVEN PHASE STABILITY IN GROUP-VB TRANSITION METALS UNDER COMPRESSION

The change in phase stability of Group-VB (V, Nb, and Ta) transition metals due to pressure and alloying is explored by means of first-principles electronic-structure calculations. It is shown that under compression stabilization or destabilization of the ground-state body-centered cubic (bcc) phase of the metal is mainly dictated by the band-structure energy that correlates well with the position of the Kohn anomaly in the transverse acoustic phonon mode. The predicted position of the Kohn anomaly in V, Nb, and Ta is found to be in a good agreement with data from the inelastic x-ray or neutron scattering measurements. In the case of alloying the change in phase stability is defined by the interplay between the band-structure and Madelung energies. We show that band-structure effects determine phase stability when a particular Group-VB metal is alloyed with its nearest neighbors within the same d-transition series: the neighbor with less and more d electrons destabilize and stabilize the bcc phase, respectively. When V is alloyed with neighbors of a higher (4d- or 5d-) transition series, both electrostatic Madelung and band-structure energies stabilize the body-centered-cubic phase. The opposite effect (destabilization) happens when Nb or Ta is alloyed with neighbors of the 3d-transition series.
Date: April 11, 2011
Creator: Landa, A & Soderlind, P
System: The UNT Digital Library
Analysis of 1w Bulk Laser Damage in KDP (open access)

Analysis of 1w Bulk Laser Damage in KDP

The influence of laser parameters on laser-induced damage in the bulk of KDP is difficult to determine because the damage manifests as discrete sites a few microns in diameter distributed throughout a relatively large volume of material. Here, they present a method to directly measure the size and location of many thousands of such sites and correlate them to the laser conditions which produced them. This technique is used to characterize the effects of pulse duration on damage initiated by 1053 nm light in the bulk of KDP crystals. They find that the density of damage sites produced by 1053 nm light is less sensitive to pulse duration than was previously reported for 526 nm and 351 nm light. In addition, the effect of pulse duration on the size of the damage sites produced appears insensitive to wavelength.
Date: April 11, 2011
Creator: Cross, D A & Carr, C W
System: The UNT Digital Library
Analysis of a Small Loop Antenna with Inductive Coupling to Nearby Loops (open access)

Analysis of a Small Loop Antenna with Inductive Coupling to Nearby Loops

None
Date: April 1, 2011
Creator: Perkins, M. P.; Ong, M. M.; Speer, R. D. & Brown, C. G.
System: The UNT Digital Library
Analysis of electric vehicle interconnection with commercial building microgrids (open access)

Analysis of electric vehicle interconnection with commercial building microgrids

The outline of this presentation is: (1) global concept of microgrid and electric vehicle (EV) modeling; (2) Lawrence Berkeley National Laboratory's Distributed Energy Resources Customer Adoption Model (DER-CAM); (3) presentation summary - how does the number of EVs connected to the building change with different optimization goals (cost versus CO{sub 2}); (3) ongoing EV modeling for California: the California commercial end-use survey (CEUS) database, objective: 138 different typical building - EV connections and benefits; (4) detailed analysis for healthcare facility: optimal EV connection at a healthcare facility in southern California; and (5) conclusions. Conclusions are: (1) EV Charging/discharging pattern mainly depends on the objective of the building (cost versus CO{sub 2}); (2) performed optimization runs show that stationary batteries are more attractive than mobile storage when putting more focus on CO{sub 2} emissions. Why? Stationary storage is available 24 hours a day for energy management - more effective; (3) stationary storage will be charged by PV, mobile only marginally; (4) results will depend on the considered region and tariff - final work will show the results for 138 different buildings in nine different climate zones and three major utility service territories.
Date: April 1, 2011
Creator: Stadler, Michael; Mendes, Goncalo; Marnay, Chris; Mé gel, Olivier & Lai, Judy
System: The UNT Digital Library
An Analysis of the Effects of Photovoltaic Energy Systems on Residential Selling Prices in California. (open access)

An Analysis of the Effects of Photovoltaic Energy Systems on Residential Selling Prices in California.

An increasing number of homes with existing photovoltaic (PV) energy systems have sold in the U.S., yet relatively little research exists that estimates the marginal impacts of those PV systems on the sales price. A clearer understanding of these effects might influence the decisions of homeowners, home buyers and PV home builders. This research analyzes a large dataset of California homes that sold from 2000 through mid-2009 with PV installed. Across a large number of hedonic and repeat sales model specifications and robustness tests, the analysis finds strong evidence that homes with PV systems sold for a premium over comparable homes without. The effects range, on average, from approximately $3.9 to $6.4 per installed watt (DC), with most models coalescing near $5.5/watt, which corresponds to a premium of approximately $17,000 for a 3,100 watt system. The research also shows that, as PV systems age, the premium enjoyed at the time of home sale decreases. Additionally, existing homes with PV systems are found to have commanded a larger sales price premium than new homes with similarly sized PV systems. Reasons for this discrepancy are suggested, yet further research is warranted in this area as well as a number of other areas …
Date: April 12, 2011
Creator: Cappers, Peter; Wiser, Ryan; Thayer, Mark & Hoen, Ben
System: The UNT Digital Library
Applications of Optimal Building Energy System Selection and Operation (open access)

Applications of Optimal Building Energy System Selection and Operation

Berkeley Lab has been developing the Distributed Energy Resources Customer Adoption Model (DER-CAM) for several years. Given load curves for energy services requirements in a building microgrid (u grid), fuel costs and other economic inputs, and a menu of available technologies, DER-CAM finds the optimum equipment fleet and its optimum operating schedule using a mixed integer linear programming approach. This capability is being applied using a software as a service (SaaS) model. Optimisation problems are set up on a Berkeley Lab server and clients can execute their jobs as needed, typically daily. The evolution of this approach is demonstrated by description of three ongoing projects. The first is a public access web site focused on solar photovoltaic generation and battery viability at large commercial and industrial customer sites. The second is a building CO2 emissions reduction operations problem for a University of California, Davis student dining hall for which potential investments are also considered. And the third, is both a battery selection problem and a rolling operating schedule problem for a large County Jail. Together these examples show that optimization of building u grid design and operation can be effectively achieved using SaaS.
Date: April 1, 2011
Creator: Marnay, Chris; Stadler, Michael; Siddiqui, Afzal; DeForest, Nicholas; Donadee, Jon; Bhattacharya, Prajesh et al.
System: The UNT Digital Library
The Arabidopsis lyrata genome sequence and the basis of rapid genome size change (open access)

The Arabidopsis lyrata genome sequence and the basis of rapid genome size change

In our manuscript, we present a high-quality genome sequence of the Arabidopsis thaliana relative, Arabidopsis lyrata, produced by dideoxy sequencing. We have performed the usual types of genome analysis (gene annotation, dN/dS studies etc. etc.), but this is relegated to the Supporting Information. Instead, we focus on what was a major motivation for sequencing this genome, namely to understand how A. thaliana lost half its genome in a few million years and lived to tell the tale. The rather surprising conclusion is that there is not a single genomic feature that accounts for the reduced genome, but that every aspect centromeres, intergenic regions, transposable elements, gene family number is affected through hundreds of thousands of cuts. This strongly suggests that overall genome size in itself is what has been under selection, a suggestion that is strongly supported by our demonstration (using population genetics data from A. thaliana) that new deletions seem to be driven to fixation.
Date: April 29, 2011
Creator: Hu, Tina T.; Pattyn, Pedro; Bakker, Erica G.; Cao, Jun; Cheng, Jan-Fang; Clark, Richard M. et al.
System: The UNT Digital Library
Assessing the cleanliness of surfaces: Innovative molecular approaches vs. standard spore assays (open access)

Assessing the cleanliness of surfaces: Innovative molecular approaches vs. standard spore assays

A bacterial spore assay and a molecular DNA microarray method were compared for their ability to assess relative cleanliness in the context of bacterial abundance and diversity on spacecraft surfaces. Colony counts derived from the NASA standard spore assay were extremely low for spacecraft surfaces. However, the PhyloChip generation 3 (G3) DNA microarray resolved the genetic signatures of a highly diverse suite of microorganisms in the very same sample set. Samples completely devoid of cultivable spores were shown to harbor the DNA of more than 100 distinct microbial phylotypes. Furthermore, samples with higher numbers of cultivable spores did not necessarily give rise to a greater microbial diversity upon analysis with the DNA microarray. The findings of this study clearly demonstrated that there is not a statistically significant correlation between the cultivable spore counts obtained from a sample and the degree of bacterial diversity present. Based on these results, it can be stated that validated state-of-the-art molecular techniques, such as DNA microarrays, can be utilized in parallel with classical culture-based methods to further describe the cleanliness of spacecraft surfaces.
Date: April 1, 2011
Creator: Cooper, Moogega; La Duc, Myron T.; Probst, Alexander; Vaishampayan, Parag; Stam, Christina; Benardini, James N. et al.
System: The UNT Digital Library
Atmospheric Stability Affects Wind Turbine Power Collection (open access)

Atmospheric Stability Affects Wind Turbine Power Collection

None
Date: April 21, 2011
Creator: Wharton, S & Lundquist, J K
System: The UNT Digital Library
Atomic Physics Measurements in Support of X-Ray Astronomy (open access)

Atomic Physics Measurements in Support of X-Ray Astronomy

None
Date: April 29, 2011
Creator: Beiersdorfer, P
System: The UNT Digital Library
Autonomous Rule Creation for Intrusion Detection (open access)

Autonomous Rule Creation for Intrusion Detection

Many computational intelligence techniques for anomaly based network intrusion detection can be found in literature. Translating a newly discovered intrusion recognition criteria into a distributable rule can be a human intensive effort. This paper explores a multi-modal genetic algorithm solution for autonomous rule creation. This algorithm focuses on the process of creating rules once an intrusion has been identified, rather than the evolution of rules to provide a solution for intrusion detection. The algorithm was demonstrated on anomalous ICMP network packets (input) and Snort rules (output of the algorithm). Output rules were sorted according to a fitness value and any duplicates were removed. The experimental results on ten test cases demonstrated a 100 percent rule alert rate. Out of 33,804 test packets 3 produced false positives. Each test case produced a minimum of three rule variations that could be used as candidates for a production system.
Date: April 1, 2011
Creator: Vollmer, Todd; Alves-Foss, Jim & Manic, Milos
System: The UNT Digital Library
Award Nomination Information for Lawrence Livermore National Laboratory SkillSoft Perspectives Conference 2011 (open access)

Award Nomination Information for Lawrence Livermore National Laboratory SkillSoft Perspectives Conference 2011

None
Date: April 6, 2011
Creator: Positeri, L A; Molyneaux, B R & Morley, M B
System: The UNT Digital Library
BETR Global - A geographically explicit global-scale multimedia contaminant fate model (open access)

BETR Global - A geographically explicit global-scale multimedia contaminant fate model

We present two new software implementations of the BETR Global multimedia contaminant fate model. The model uses steady-state or non-steady-state mass-balance calculations to describe the fate and transport of persistent organic pollutants using a desktop computer. The global environment is described using a database of long-term average monthly conditions on a 15{sup o} x 15{sup o} grid. We demonstrate BETR Global by modeling the global sources, transport, and removal of decamethylcyclopentasiloxane (D5).
Date: April 1, 2011
Creator: Macleod, M.; Waldow, H. von; Tay, P.; Armitage, J. M.; Wohrnschimmel, H.; Riley, W. et al.
System: The UNT Digital Library
Biospecimen Reporting for Improved Study Quality (BRISQ) (open access)

Biospecimen Reporting for Improved Study Quality (BRISQ)

Human biospecimens are subject to a number of different collection, processing, and storage factors that can significantly alter their molecular composition and consistency. These biospecimen preanalytical factors, in turn, influence experimental outcomes and the ability to reproduce scientific results. Currently, the extent and type of information specific to the biospecimen preanalytical conditions reported in scientific publications and regulatory submissions varies widely. To improve the quality of research utilizing human tissues it is critical that information regarding the handling of biospecimens be reported in a thorough, accurate, and standardized manner. The Biospecimen Reporting for Improved Study Quality (BRISQ) recommendations outlined herein are intended to apply to any study in which human biospecimens are used. The purpose of reporting these details is to supply others, from researchers to regulators, with more consistent and standardized information to better evaluate, interpret, compare, and reproduce the experimental results. The BRISQ guidelines are proposed as an important and timely resource tool to strengthen communication and publications around biospecimen-related research and help reassure patient contributors and the advocacy community that the contributions are valued and respected.
Date: April 26, 2011
Creator: Moore, Ph.D., Helen M.; Kelly Ph.D., Andrea; Jewell Ph.D., Scott D.; McShane Ph.D., Lisa M.; Clark M.D., Douglas P.; Greenspan M.D., Renata et al.
System: The UNT Digital Library
Bismuth-Loaded Polymer Scintillators for Gamma Ray Spectroscopy (open access)

Bismuth-Loaded Polymer Scintillators for Gamma Ray Spectroscopy

We synthesize a series of polyvinylcarbazole monoliths containing varying loadings of triphenyl bismuth as a high-Z dopant and varying fluors, either organic or organometallic, in order to study their use as scintillators capable of gamma ray spectroscopy. A trend of increasing bismuth loading resulting in a better-resolved photopeak is observed. For PVK parts with no fluor or a standard organic fluor, diphenylanthracene, increasing bismuth loading results in decreasing light yield while with samples 1 or 3 % by weight of the spin-orbit coupling organometallic fluor FIrpic, which emits light from both singlet and triple excitons, show increasing light yield with increasing bismuth loading. Our best performing PVK/ BiPh{sub 3}/FIrpic scintillator with 40 wt % BiPh3 and 3 wt % FIrpic has an emission maximum of 500 nm, a light yield of {approx}30,000 photons/MeV, and energy resolution better than 7% FWHM at 662 keV. Replacing the Ir complex with an equal weight of diphenylanthracene produces a sample with a light yield of {approx}6,000 photons/MeV, with an emission maximum at 420 nm and energy resolution of 9% at 662 keV. Transmission electron microscopy studies show that the BiPh{sub 3} forms small clusters of approximately 5 nm diameter.
Date: April 11, 2011
Creator: Rupert, B L; Cherepy, N J; Sturm, B W; Sanner, R D; Dai, Z & Payne, S A
System: The UNT Digital Library
Calculating the probability of injected carbon dioxide plumes encountering faults (open access)

Calculating the probability of injected carbon dioxide plumes encountering faults

One of the main concerns of storage in saline aquifers is leakage via faults. In the early stages of site selection, site-specific fault coverages are often not available for these aquifers. This necessitates a method using available fault data to estimate the probability of injected carbon dioxide encountering and migrating up a fault. The probability of encounter can be calculated from areal fault density statistics from available data, and carbon dioxide plume dimensions from numerical simulation. Given a number of assumptions, the dimension of the plume perpendicular to a fault times the areal density of faults with offsets greater than some threshold of interest provides probability of the plume encountering such a fault. Application of this result to a previously planned large-scale pilot injection in the southern portion of the San Joaquin Basin yielded a 3% and 7% chance of the plume encountering a fully and half seal offsetting fault, respectively. Subsequently available data indicated a half seal-offsetting fault at a distance from the injection well that implied a 20% probability of encounter for a plume sufficiently large to reach it.
Date: April 1, 2011
Creator: Jordan, P.D.
System: The UNT Digital Library
Causal Latent Semantic Analysis (cLSA): An Illustration (open access)

Causal Latent Semantic Analysis (cLSA): An Illustration

Article discussing an illustration of causal latent semantic analysis (cLSA).
Date: April 2011
Creator: Hossain, Muhammad Muazzem; Prybutok, Victor R. & Evangelopoulos, Nicholas
System: The UNT Digital Library
Charge and fluence lifetime measurements of a dc high voltage GaAs photogun at high average current (open access)

Charge and fluence lifetime measurements of a dc high voltage GaAs photogun at high average current

GaAs-based dc high voltage photoguns used at accelerators with extensive user programs must exhibit long photocathode operating lifetime. Achieving this goal represents a significant challenge for proposed high average current facilities that must operate at tens of milliamperes or more. This paper describes techniques to maintain good vacuum while delivering beam, and techniques that minimize the ill effects of ion bombardment, the dominant mechanism that reduces photocathode yield of a GaAs-based dc high voltage photogun. Experimental results presented here demonstrate enhanced lifetime at high beam currents by: (a) operating with the drive laser beam positioned away from the electrostatic center of the photocathode, (b) limiting the photocathode active area to eliminate photoemission from regions of the photocathode that do not support efficient beam delivery, (c) using a large drive laser beam to distribute ion damage over a larger area, and (d) by applying a relatively low bias voltage to the anode to repel ions created within the downstream beam line. A combination of these techniques provided the best total charge extracted lifetimes in excess of 1000 C at dc beam currents up to 9.5 mA, using green light illumination of bulk GaAs inside a 100 kV photogun.
Date: April 1, 2011
Creator: J. Grames, R. Suleiman, P.A. Adderley, J. Clark, J. Hansknecht, D. Machie, M. Poelker, M.L. Stutzman
System: The UNT Digital Library
CLARREO shortwave observing system simulation experiments of the twenty-first century: Simulator design and implementation (open access)

CLARREO shortwave observing system simulation experiments of the twenty-first century: Simulator design and implementation

Projected changes in the Earth system will likely be manifested in changes in reflected solar radiation. This paper introduces an operational Observational System Simulation Experiment (OSSE) to calculate the signals of future climate forcings and feedbacks in top-of-atmosphere reflectance spectra. The OSSE combines simulations from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report for the NCAR Community Climate System Model (CCSM) with the MODTRAN radiative transfer code to calculate reflectance spectra for simulations of current and future climatic conditions over the 21st century. The OSSE produces narrowband reflectances and broadband fluxes, the latter of which have been extensively validated against archived CCSM results. The shortwave reflectance spectra contain atmospheric features including signals from water vapor, liquid and ice clouds, and aerosols. The spectra are also strongly influenced by the surface bidirectional reflectance properties of predicted snow and sea ice and the climatological seasonal cycles of vegetation. By comparing and contrasting simulated reflectance spectra based on emissions scenarios with increasing projected and fixed present-day greenhouse gas and aerosol concentrations, we find that prescribed forcings from increases in anthropogenic sulfate and carbonaceous aerosols are detectable and are spatially confined to lower latitudes. Also, changes in the intertropical convergence zone and …
Date: April 1, 2011
Creator: Feldman, Daniel R.; Algieri, Chris A.; Ong, Jonathan R. & Collins, William D.
System: The UNT Digital Library