Full multiple scattering analysis of XANES at the Cd L3 and O K edges in CdO films combined with a soft-x-ray emission investigation (open access)

Full multiple scattering analysis of XANES at the Cd L3 and O K edges in CdO films combined with a soft-x-ray emission investigation

X-ray absorption near edge structure (XANES) at the cadmium L3 and oxygen K edges for CdO thin films grown by pulsed laser deposition method, is interpreted within the real-space multiple scattering formalism, FEFF code. The features in the experimental spectra are well reproduced by calculations for a cluster of about six and ten coordination shells around the absorber for L3 edge of Cd and K edge of O, respectively. The calculated projected electronic density of states is found to be in good agreement with unoccupied electronic states in experimental data and allows to conclude that the orbital character of the lowest energy of the conductive band is Cd-5s-O-2p. The charge transfer has been quantified and not purely ionic bonding has been found. Combined XANES and resonant inelastic x-ray scattering measurements allow us to determine the direct and indirect band gap of investigated CdO films to be {approx}2.4-eV and {approx}0.9-eV, respectively.
Date: July 5, 2010
Creator: Demchenko, I. N.; Denlinger, J. D.; Chernyshova, M.; Yu, K. M.; Speaks, D. T.; Olalde-Velasco, P. et al.
Object Type: Article
System: The UNT Digital Library
Preliminary Evaluation of the Section 1603 Treasury Grant Program for Renewable Power Projects in the United States (open access)

Preliminary Evaluation of the Section 1603 Treasury Grant Program for Renewable Power Projects in the United States

This article evaluates the first year of the Section 1603 Treasury cash grant program, which enables renewable power projects in the U.S. to elect cash grants in lieu of the federal tax credits that are otherwise available. To date, the program has been heavily subscribed, particularly by wind power projects, which had received 86% of the nearly $2.6 billion in grants that had been disbursed as of March 1, 2010. As of that date, 6.2 GW of the 10 GW of new wind capacity installed in the U.S. in 2009 had applied for grants in lieu of production tax credits. Roughly 2.4 GW of this wind capacity may not have otherwise been built in 2009 absent the grant program; this 2.4 GW may have supported approximately 51,600 short-term full-time-equivalent (FTE) gross job-years in the U.S. during the construction phase of these wind projects, and 3,860 longterm FTE gross jobs during the operational phase. The program’s popularity stems from the significant economic value that it provides to renewable power projects, relative to the otherwise available tax credits. Although grants reward investment rather than efficient performance, this evaluation finds no evidence at this time of either widespread “gold-plating” or performance problems.
Date: May 5, 2010
Creator: Bolinger, Mark; Wiser, Ryan & Darghouth, Naim
Object Type: Article
System: The UNT Digital Library
2009 International Conference on Neutron Scattering (ICNS 2009) (open access)

2009 International Conference on Neutron Scattering (ICNS 2009)

The ICNS provides a focal point for the worldwide neutron user community to strengthen ties within this diverse group, while at the same time promoting neutron research among colleagues in related disciplines identified as “would-be” neutron users. The International Conference on Neutron Scattering thus serves a dual role as an international user meeting and a scientific meeting. As a venue for scientific exchange, the ICNS showcases recent results and provides forums for scientific discussion of neutron research in diverse fields such as hard and soft condensed matter, liquids, biology, magnetism, engineering materials, chemical spectroscopy, crystal structure, and elementary excitations, fundamental physics and development of neutron instrumentation through a combination of invited talks, contributed talks and poster sessions. Each of the major national neutron facilities (NIST, LANSCE, ANL, HFIR and SNS), along with their international counterparts, has an opportunity to exchange information with each other and to update users, and potential users, of their facility. This is also an appropriate forum for users to raise issues that relate to the facilities.
Date: August 5, 2010
Creator: Rao, Gopal & Gillespie, Donna
Object Type: Report
System: The UNT Digital Library
A Multi-Dimensional Classification Model for Scientific Workflow Characteristics (open access)

A Multi-Dimensional Classification Model for Scientific Workflow Characteristics

Workflows have been used to model repeatable tasks or operations in manufacturing, business process, and software. In recent years, workflows are increasingly used for orchestration of science discovery tasks that use distributed resources and web services environments through resource models such as grid and cloud computing. Workflows have disparate re uirements and constraints that affects how they might be managed in distributed environments. In this paper, we present a multi-dimensional classification model illustrated by workflow examples obtained through a survey of scientists from different domains including bioinformatics and biomedical, weather and ocean modeling, astronomy detailing their data and computational requirements. The survey results and classification model contribute to the high level understandingof scientific workflows.
Date: April 5, 2010
Creator: Ramakrishnan, Lavanya & Plale, Beth
Object Type: Article
System: The UNT Digital Library
Infrared birefringence imaging of residual stress and bulk defects in multicrystalline silicon (open access)

Infrared birefringence imaging of residual stress and bulk defects in multicrystalline silicon

This manuscript concerns the application of infrared birefringence imaging (IBI) to quantify macroscopic and microscopic internal stresses in multicrystalline silicon (mc-Si) solar cell materials. We review progress to date, and advance four closely related topics. (1) We present a method to decouple macroscopic thermally-induced residual stresses and microscopic bulk defect related stresses. In contrast to previous reports, thermally-induced residual stresses in wafer-sized samples are generally found to be less than 5 MPa, while defect-related stresses can be several times larger. (2) We describe the unique IR birefringence signatures, including stress magnitudes and directions, of common microdefects in mc-Si solar cell materials including: {beta}-SiC and {beta}-Si{sub 3}N{sub 4} microdefects, twin bands, nontwin grain boundaries, and dislocation bands. In certain defects, local stresses up to 40 MPa can be present. (3) We relate observed stresses to other topics of interest in solar cell manufacturing, including transition metal precipitation, wafer mechanical strength, and minority carrier lifetime. (4) We discuss the potential of IBI as a quality-control technique in industrial solar cell manufacturing.
Date: May 5, 2010
Creator: Ganapati, Vidya; Schoenfelder, Stephan; Castellanos, Sergio; Oener, Sebastian; Koepge, Ringo; Sampson, Aaron et al.
Object Type: Article
System: The UNT Digital Library
Multiple Syntrophic Interactions in a Terephthalate-Degrading Methanogenic Consortium (open access)

Multiple Syntrophic Interactions in a Terephthalate-Degrading Methanogenic Consortium

Terephthalate (TA) is one of the top 50 chemicals produced worldwide. Its production results in a TA-containing wastewater that is treated by anaerobic processes through a poorly understood methanogenic syntrophy. Using metagenomics, we characterized the methanogenic consortium tinside a hyper-mesophilic (i.e., between mesophilic and thermophilic), TA-degrading bioreactor. We identified genes belonging to dominant Pelotomaculum species presumably involved in TA degradation through decarboxylation, dearomatization, and modified ?-oxidation to H{sub 2}/CO{sub 2} and acetate. These intermediates are converted to CH{sub 4}/CO{sub 2} by three novel hyper-mesophilic methanogens. Additional secondary syntrophic interactions were predicted in Thermotogae, Syntrophus and candidate phyla OP5 and WWE1 populations. The OP5 encodes genes capable of anaerobic autotrophic butyrate production and Thermotogae, Syntrophus and WWE1 have the genetic potential to oxidize butyrate to COsub 2}/H{sub 2} and acetate. These observations suggest that the TA-degrading consortium consists of additional syntrophic interactions beyond the standard H{sub 2}-producing syntroph ? methanogen partnership that may serve to improve community stability.
Date: August 5, 2010
Creator: Lykidis, Athanasios; Chen, Chia-Lung; Tringe, Susannah G.; McHardy, Alice C.; Copeland, Alex 5; Kyrpides, Nikos C. et al.
Object Type: Article
System: The UNT Digital Library
LANL Virtual Center for Chemical Hydrogen Storage: Chemical Hydrogen Storage Using Ultra-high Surface Area Main Group Materials (open access)

LANL Virtual Center for Chemical Hydrogen Storage: Chemical Hydrogen Storage Using Ultra-high Surface Area Main Group Materials

The focus of the project was to design and synthesize light element compounds and nanomaterials that will reversibly store molecular hydrogen for hydrogen storage materials. The primary targets investigated during the last year were amine and hydrogen terminated silicon (Si) nanoparticles, Si alloyed with lighter elements (carbon (C) and boron (B)) and boron nanoparticles. The large surface area of nanoparticles should facilitate a favorable weight to volume ratio, while the low molecular weight elements such as B, nitrogen (N), and Si exist in a variety of inexpensive and readily available precursors. Furthermore, small NPs of Si are nontoxic and non-corrosive. Insights gained from these studies will be applied toward the design and synthesis of hydrogen storage materials that meet the DOE 2010 hydrogen storage targets: cost, hydrogen capacity and reversibility. Two primary routes were explored for the production of nanoparticles smaller than 10 nm in diameter. The first was the reduction of the elemental halides to achieve nanomaterials with chloride surface termination that could subsequently be replaced with amine or hydrogen. The second was the reaction of alkali metal Si or Si alloys with ammonium halides to produce hydrogen capped nanomaterials. These materials were characterized via X-ray powder diffraction, TEM, …
Date: September 5, 2010
Creator: Kauzlarich, Susan M.; Power, Phillip P.; Neiner, Doinita; Pickering, Alex; Rivard, Eric; Bobby Ellis, T. M. et al.
Object Type: Report
System: The UNT Digital Library
Aquifer Testing and Rebound Study in Support of the 100-H Deep Chromium Investigation (open access)

Aquifer Testing and Rebound Study in Support of the 100-H Deep Chromium Investigation

The 100-HR-3 Groundwater Operable Unit (OU) second Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) 5-year review (DOEIRL-2006-20, The Second CERCLA Five-Year Review Report for the Hanford Site) set a milestone to conduct an investigation of deep hexavalent chromium contamination in the sediments of the Ringold upper mud (RUM) unit, which underlies the unconfined aquifer in the 100-H Area. The 5-year review noted that groundwater samples from one deep well extending below the aquitard (i.e., RUM) exceeded both the groundwater standard of 48 parts per billion (ppb) (Ecology Publication 94-06, Model Toxics Control Act Cleanup Statute and Regulation) and the federal drinking water standard of 100 {mu}g/L for hexavalent chromium. The extent of hexavalent chromium contamination in this zone is not well understood. Action 12-1 from the 5-year review is to perform additional characterization of the aquifer below the initial aquitard. Field characterization and aquifer testing were performed in the Hanford Site's 100-H Area to address this milestone. The aquifer tests were conducted to gather data to answer several fundamental questions regarding the presence of the hexavalent chromium in the deep sediments of the RUM and to determine the extent and magnitude of deeper contamination. The pumping tests …
Date: November 5, 2010
Creator: Smoot, J. L.
Object Type: Report
System: The UNT Digital Library

Module Technology: Current Practice and Issues

PV modules must provide mechanical support for the cells, protect the world from the voltages inside, protect the cells, diodes and interconnects from the weather outside, couple as much light as possible into the PV cells and minimize the temperature increase of the cells. The package must continue to serve these functions for at least 25 years as that is the typical module warranty period today. Furthermore the package must do all this for as low a cost as possible since the key to large scale PV growth is a reduction in cost while retaining excellent module reliability and durability. This paper will review current module construction practices for both crystalline silicon and thin film PV with emphasis on explaining why the present designs and materials have been selected. Possible long term issues with today's designs and materials will be discussed. Several proposed solutions to these issues will be presented, highlighting the research efforts that will be necessary in order to verify that they can cost effectively solve the identified issues.
Date: October 5, 2010
Creator: Wohlgemuth, J.
Object Type: Presentation
System: The UNT Digital Library
Electron-cloud Build-up Simulations in the Proposed PS2: Status Report (open access)

Electron-cloud Build-up Simulations in the Proposed PS2: Status Report

A replacement for the PS storage ring is being considered, in the context of the future LHC accelerator complex upgrade, that would likely place the new machine (the PS2) in a regime where the electron-cloud (EC) effect might be significant. We report here our current estimate of the EC density ne in the bending magnets and the field-free regions at injection and extraction beam energy, for both proposed bunch spacings, tb = 25 and 50 ns. The primary model parameters exercised are the peak secondary emission yield (SEY) delta max, the electron-wall impact energy at which the SEY peaks, Emax, and the chamber radius a in the fieldfree regions. We present many of our results as a function of the bunch intensity Nb, and we provide a tentative explanation for the non-monotonic behavior of ne as a function of Nb.
Date: May 5, 2010
Creator: Furman, M. A.; De Maria, R.; Papaphilippou, Y. & Rumolo, G.
Object Type: Article
System: The UNT Digital Library
Terrestrial biogeochemical feedbacks in the climate system: from past to future (open access)

Terrestrial biogeochemical feedbacks in the climate system: from past to future

The terrestrial biosphere plays a major role in the regulation of atmospheric composition, and hence climate, through multiple interlinked biogeochemical cycles (BGC). Ice-core and other palaeoenvironmental records show a fast response of vegetation cover and exchanges with the atmosphere to past climate change, although the phasing of these responses reflects spatial patterning and complex interactions between individual biospheric feedbacks. Modern observations show a similar responsiveness of terrestrial biogeochemical cycles to anthropogenically-forced climate changes and air pollution, with equally complex feedbacks. For future conditions, although carbon cycle-climate interactions have been a major focus, other BGC feedbacks could be as important in modulating climate changes. The additional radiative forcing from terrestrial BGC feedbacks other than those conventionally attributed to the carbon cycle is in the range of 0.6 to 1.6 Wm{sup -2}; all taken together we estimate a possible maximum of around 3 Wm{sup -2} towards the end of the 21st century. There are large uncertainties associated with these estimates but, given that the majority of BGC feedbacks result in a positive forcing because of the fundamental link between metabolic stimulation and increasing temperature, improved quantification of these feedbacks and their incorporation in earth system models is necessary in order to develop …
Date: January 5, 2010
Creator: Arneth, A.; Harrison, S. P.; Zaehle, S.; Tsigaridis, K.; Menon, S.; Bartlein, P. J. et al.
Object Type: Article
System: The UNT Digital Library
Gene by Disease Interaction on Orbitofrontal Gray Matter in Cocaine Addiction (open access)

Gene by Disease Interaction on Orbitofrontal Gray Matter in Cocaine Addiction

Chronic cocaine use has been associated with structural deficits in brain regions having dopamine receptive neurons. However, the concomitant use of other drugs and common genetic variability in monoamine regulation present additional structural variability. We therefore examined variations in gray matter volume (GMV) as a function of lifetime drug use and the monoamine oxidase A (MAOA) genotype in cocaine use disorders (CUD) and healthy controls.
Date: December 5, 2010
Creator: Alia-Klein, N.; Alia-Klein, N.; Parvaz, M. A.; Woicik, P. A.; Konova, A.; Maloney, T. et al.
Object Type: Article
System: The UNT Digital Library
Identification of 300 Area Contaminants of Potential Concern for Soil (open access)

Identification of 300 Area Contaminants of Potential Concern for Soil

This report documents the process used to identify source area contaminants of potential concern (COPCs) in support of the 300 Area remedial investigation/feasibility study (RI/FS) work plan. This report also establishes the exclusion criteria applicable for 300 Area use and the analytical methods needed to analyze the COPCs.
Date: April 5, 2010
Creator: Ovink, R.W.
Object Type: Report
System: The UNT Digital Library
Calibration of the ERL cavity FPC and PU couplers (open access)

Calibration of the ERL cavity FPC and PU couplers

The performance parameters of a superconducting cavity, notably accelerating field and quality factor, are first obtained in a cryogenic vertical test Dewar, and again after the final assembly in its cryostat. The tests involve Network Analyzer (NA) measurements in which the cavity is excited through an input coupler and the properties are obtained from the reflected signal at the input and the transmitted signal from the output coupler. The interpretation of the scattering coefficients in terms of field strength requires the knowledge of the Fundamental Power Coupler (FPC) and Pick-Up (PU) coupler strength, as expressed by their 'external' and Q{sub FPC} Q{sub PU}. The coupler strength is independent of the field level or cavity losses and thus can be determined at low levels with the scattering coefficients S{sub 11} and S{sub 21}, assuming standard 50 {Omega} terminations in the network analyzer. Also needed is the intrinsic cavity parameter, R{sub a} /Q{sub 0} {triple_bond} {l_brace}R/Q{r_brace}, a quantity independent of field or losses which must be obtained from simulation programs, such as the Microwave Studio.
Date: April 5, 2010
Creator: Hahn, H.; Johnson, E. & Kayran, D.
Object Type: Report
System: The UNT Digital Library
Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol (open access)

Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol

A detailed understanding of the sources, transformations, and fates of organic species in the environment is crucial because of the central roles that organics play in human health, biogeochemical cycles, and Earth's climate. However, such an understanding is hindered by the immense chemical complexity of environmental mixtures of organics; for example, atmospheric organic aerosol consists of at least thousands of individual compounds, all of which likely evolve chemically over their atmospheric lifetimes. Here we demonstrate the utility of describing organic aerosol (and other complex organic mixtures) in terms of average carbon oxidation state (OSC), a quantity that always increases with oxidation, and is readily measured using state-of-the-art analytical techniques. Field and laboratory measurements of OSC , using several such techniques, constrain the chemical properties of the organics and demonstrate that the formation and evolution of organic aerosol involves simultaneous changes to both carbon oxidation state and carbon number (nC).
Date: November 5, 2010
Creator: Technology, Massachusetts Institute of; Kroll, Jesse H.; Donahue, Neil M.; Jimenez, Jose L.; Kessler, Sean H.; Canagaratna, Manjula R. et al.
Object Type: Article
System: The UNT Digital Library
Derivation and Solution of Multifrequency Radiation Diffusion Equations for Homogeneous Refractive Lossy Media (open access)

Derivation and Solution of Multifrequency Radiation Diffusion Equations for Homogeneous Refractive Lossy Media

Starting from the radiation transport equation for homogeneous, refractive lossy media, we derive the corresponding time-dependent multifrequency diffusion equations. Zeroth and first moments of the transport equation couple the energy density, flux and pressure tensor. The system is closed by neglecting the temporal derivative of the flux and replacing the pressure tensor by its diagonal analogue. The system is coupled to a diffusion equation for the matter temperature. We are interested in modeling annealing of silica (SiO{sub 2}). We derive boundary conditions at a planar air-silica interface taking account of reflectivities. The spectral dimension is discretized into a finite number of intervals leading to a system of multigroup diffusion equations. Three simulations are presented. One models cooling of a silica slab, initially at 2500 K, for 10 s. The other two are 1D and 2D simulations of irradiating silica with a CO{sub 2} laser, {lambda} = 10.59 {micro}m. In 2D, we anneal a disk (radius = 0.4, thickness = 0.4 cm) with a laser, Gaussian profile (r{sub 0} = 0.5 mm for 1/e decay).
Date: January 5, 2010
Creator: Shestakov, A I; Vignes, R M & Stolken, J S
Object Type: Article
System: The UNT Digital Library
Visualization and Analysis-Oriented Reconstruction of Material Interfaces (open access)

Visualization and Analysis-Oriented Reconstruction of Material Interfaces

Reconstructing boundaries along material interfaces from volume fractions is a difficult problem, especially because the under-resolved nature of the input data allows for many correct interpretations. Worse, algorithms widely accepted as appropriate for simulation are inappropriate for visualization. In this paper, we describe a new algorithm that is specifically intended for reconstructing material interfaces for visualization and analysis requirements. The algorithm performs well with respect to memory footprint and execution time, has desirable properties in various accuracy metrics, and also produces smooth surfaces with few artifacts, even when faced with more than two materials per cell.
Date: March 5, 2010
Creator: Childs, Henry R.
Object Type: Article
System: The UNT Digital Library
REGULATORY STRATEGIES TO MINIMIZE GENERATION OF REGULATED WASTES FROM CLEANUP, CONTINUED USE OR DECOMMISSIONING OF NUCLEAR FACILITIES CONTAMINATED WITH POLYCHLORINATED BIPHENYLS (PCBS) - 11198 (open access)

REGULATORY STRATEGIES TO MINIMIZE GENERATION OF REGULATED WASTES FROM CLEANUP, CONTINUED USE OR DECOMMISSIONING OF NUCLEAR FACILITIES CONTAMINATED WITH POLYCHLORINATED BIPHENYLS (PCBS) - 11198

Disposal costs for liquid PCB radioactive waste are among the highest of any category of regulated waste. The high cost is driven by the fact that disposal options are extremely limited. Toxic Substances Control Act (TSCA) regulations require most liquids with PCBs at concentration of {ge} 50 parts-per-million to be disposed by incineration or equivalent destructive treatment. Disposal fees can be as high as $200 per gallon. This figure does not include packaging and the cost to transport the waste to the disposal facility, or the waste generator's labor costs for managing the waste prior to shipment. Minimizing the generation of liquid radioactive PCB waste is therefore a significant waste management challenge. PCB spill cleanups often generate large volumes of waste. That is because the removal of PCBs typically requires the liberal use of industrial solvents followed by a thorough rinsing process. In a nuclear facility, the cleanup process may be complicated by the presence of radiation and other occupational hazards. Building design and construction features, e.g., the presence of open grating or trenches, may also complicate cleanup. In addition to the technical challenges associated with spill cleanup, selection of the appropriate regulatory requirements and approach may be challenging. The …
Date: November 5, 2010
Creator: Lowry, N.
Object Type: Article
System: The UNT Digital Library
Modeling Studies on the Transport of Benzene and H2S in CO2-Water Systems (open access)

Modeling Studies on the Transport of Benzene and H2S in CO2-Water Systems

In this study, reactive transport simulations were used to assess the mobilization and transport of organics with supercritical CO{sub 2} (SCC), and the co-injection and transport of H{sub 2}S with SCC. These processes were evaluated at conditions of typical storage reservoirs, and for cases of hypothetical leakage from a reservoir to an overlying shallower fresh water aquifer. Modeling capabilities were developed to allow the simulation of multiphase flow and transport of H{sub 2}O, CO{sub 2}, H{sub 2}S, as well as specific organic compounds (benzene), coupled with multicomponent geochemical reaction and transport. This included the development of a new simulator, TMVOC-REACT, starting from existing modules of the TOUGH2 family of codes. This work also included an extensive literature review, calculation, and testing of phase-partitioning properties for mixtures of the phases considered. The reactive transport simulations presented in this report are primarily intended to illustrate the capabilities of the new simulator. They are also intended to help evaluate and understand various processes at play, in a more qualitative than quantitative manner, and only for hypothetical scenarios. Therefore, model results are not intended as realistic assessments of groundwater quality changes for specific locations, and they certainly do not provide an exhaustive evaluation of …
Date: November 5, 2010
Creator: Zheng, L.; Spycher, N.; Xu, T.; Apps, J.; Kharaka, Y. & Birkholzer, J.T.
Object Type: Report
System: The UNT Digital Library
Attrition Resistant Fischer-Tropsch Catalysts Based on FCC Supports (open access)

Attrition Resistant Fischer-Tropsch Catalysts Based on FCC Supports

Commercial spent fluid catalytic cracking (FCC) catalysts provided by Engelhard and Albemarle were used as supports for Fe-based catalysts with the goal of improving the attrition resistance of typical F-T catalysts. Catalysts with the Ruhrchemie composition (100 Fe/5 Cu/4.2 K/25 spent FCC on mass basis) were prepared by wet impregnation. XRD and XANES analysis showed the presence of Fe{sub 2}O{sub 3} in calcined catalysts. FeC{sub x} and Fe{sub 3}O{sub 4} were present in the activated catalysts. The metal composition of the catalysts was analyzed by ICP-MS. F-T activity of the catalysts activated in situ in CO at the same conditions as used prior to the attrition tests was measured using a fixed bed reactor at T = 573 K, P = 1.38 MPa and H{sub 2}:CO ratio of 0.67. Cu and K promoted Fe supported over Engelhard provided spent FCC catalyst shows relatively good attrition resistance (8.2 wt% fines lost), high CO conversion (81%) and C{sub 5}+ hydrocarbons selectivity (18.3%).
Date: February 5, 2010
Creator: Adeyiga, Adeyinka
Object Type: Report
System: The UNT Digital Library
Image analysis of ocular fundus for retinopathy characterization (open access)

Image analysis of ocular fundus for retinopathy characterization

Automated analysis of ocular fundus images is a common procedure in countries as England, including both nonemergency examination and retinal screening of patients with diabetes mellitus. This involves digital image capture and transmission of the images to a digital reading center for evaluation and treatment referral. In collaboration with the Optometry Department, University of California, Berkeley, we have tested computer vision algorithms to segment vessels and lesions in ground-truth data (DRIVE database) and hundreds of images of non-macular centric and nonuniform illumination views of the eye fundus from EyePACS program. Methods under investigation involve mathematical morphology (Figure 1) for image enhancement and pattern matching. Recently, we have focused in more efficient techniques to model the ocular fundus vasculature (Figure 2), using deformable contours. Preliminary results show accurate segmentation of vessels and high level of true-positive microaneurysms.
Date: February 5, 2010
Creator: Ushizima, Daniela & Cuadros, Jorge
Object Type: Report
System: The UNT Digital Library
Progress Towards Deployable Antineutrino Detectors for Reactor Safeguards (open access)

Progress Towards Deployable Antineutrino Detectors for Reactor Safeguards

Fission reactors emit large numbers of antineutrinos and this flux may be useful for the measurement of two quantities of interest for reactor safeguards: the reactor's power and plutonium inventory throughout its cycle. The high antineutrino flux and relatively low background rates means that simple cubic meter scale detectors at tens of meters standoff can record hundreds or thousands of antineutrino events per day. Such antineutrino detectors would add online, quasi-real-time bulk material accountancy to the set of reactor monitoring tools available to the IAEA and other safeguards agencies with minimal impact on reactor operations. Between 2003 and 2008, our LLNL/SNL collaboration successfully deployed several prototype safeguards detectors at a commercial reactor in order to test both the method and the practicality of its implementation in the field. Partially on the strength of the results obtained from these deployments, an Experts Meeting was convened by the IAEA Novel Technologies Group in 2008 to assess current antineutrino detection technology and examine how it might be incorporated into the safeguards regime. Here we present a summary of our previous deployments and discuss current work that seeks to provide expanded capabilities suggested by the Experts Panel, in particular aboveground detector operation.
Date: April 5, 2010
Creator: Bowden, N; Bernstein, A; Dazeley, S; Keefer, G; Reyna, D; Cabrera-Palmer, B et al.
Object Type: Article
System: The UNT Digital Library
Imaging the early material response associated with exit surface damage in fused silica (open access)

Imaging the early material response associated with exit surface damage in fused silica

The processes involved at the onset of damage initiation on the surface of fused silica have been a topic of extensive discussion and thought for more than four decades. Limited experimental results have helped develop models covering specific aspects of the process. In this work we present the results of an experimental study aiming at imaging the material response from the onset of the observation of material modification during exposure to the laser pulse through the time point at which material ejection begins. The system involves damage initiation using a 355 nm pulse, 7.8 ns FWHM in duration and imaging of the affected material volume with spatial resolution on the order of 1 {micro}m using as strobe light a 150 ps laser pulse that is appropriately timed with respect to the pump pulse. The observations reveal that the onset of material modification is associated with regions of increased absorption, i.e., formation of an electronic excitation, leading to a reduction in the probe transmission to only a few percent within a time interval of about 1 ns. This area is subsequently rapidly expanding with a speed of about 1.2 {micro}m/ns and is accompanied by the formation and propagation of radial cracks. …
Date: November 5, 2010
Creator: Demos, S G; Raman, R N & Negres, R A
Object Type: Article
System: The UNT Digital Library
Concentrating Solar Panels: Bringing the Highest Power and Lowest Cost to the Rooftop (open access)

Concentrating Solar Panels: Bringing the Highest Power and Lowest Cost to the Rooftop

Soliant Energy is a venture-capital-backed startup focused on bringing advanced concentrating solar panels to market. Our fundamental innovation is that we are the first company to develop a racking solar concentrator specifically for commercial rooftop applications, resulting in the lowest LCOE for rooftop electricity generation. Today, the commercial rooftop segment is the largest and fastest-growing market in the solar industry. Our concentrating panels can make a major contribution to the SAI's objectives: reducing the cost of solar electricity and rapidly deploying capacity. Our commercialization focus was re-shaped in 2009, shifting from an emphasis solely on panel efficiency to LCOE. Since the inception of the SAI program, LCOE has become the de facto standard for comparing commercial photovoltaic systems. While estimation and prediction models still differ, the emergence of performance-based incentive (PBI) and feed-in tariff (FIT) systems, as well as power purchase agreement (PPA) financing structures make LCOE the natural metric for photovoltaic systems. Soliant Energy has designed and demonstrated lower-cost, higher-power solar panels that consists of 6 (500X) PV module assemblies utilizing multi-junction cells and an integrated two-axis tracker. In addition, we have designed and demonstrated a prototype 1000X panel assembly with 8. Cost reductions relative to conventional flat panel …
Date: January 5, 2010
Creator: Deck, Michael & Russell, Rick
Object Type: Report
System: The UNT Digital Library