13.2 nm Table-Top Inspection Microscope for Extreme Ultraviolet Lithography Mask Defect Characterization (open access)

13.2 nm Table-Top Inspection Microscope for Extreme Ultraviolet Lithography Mask Defect Characterization

We report on a reflection microscope that operates at 13.2-nm wavelength with a spatial resolution of 55{+-}3 nm. The microscope uses a table-top EUV laser to acquire images of photolithography masks in 20 seconds.
Date: April 7, 2009
Creator: Brizuela, F.; Wang, Y.; Brewer, C.; Pedaci, F.; Chao, W.; Anderson, E. et al.
System: The UNT Digital Library
Net Metering and Interconnection Procedures-- Incorporating Best Practices (open access)

Net Metering and Interconnection Procedures-- Incorporating Best Practices

State utility commissions and utilities themselves are actively developing and revising their procedures for the interconnection and net metering of distributed generation. However, the procedures most often used by regulators and utilities as models have not been updated in the past three years, in which time most of the distributed solar facilities in the United States have been installed. In that period, the Interstate Renewable Energy Council (IREC) has been a participant in more than thirty state utility commission rulemakings regarding interconnection and net metering of distributed generation. With the knowledge gained from this experience, IREC has updated its model procedures to incorporate current best practices. This paper presents the most significant changes made to IREC’s model interconnection and net metering procedures.
Date: April 1, 2009
Creator: Jason Keyes, Kevin Fox, Joseph Wiedman, Staff at North Carolina Solar Center
System: The UNT Digital Library
California Wintertime Precipitation in Regional and Global Climate Models (open access)

California Wintertime Precipitation in Regional and Global Climate Models

In this paper, wintertime precipitation from a variety of observational datasets, regional climate models (RCMs), and general circulation models (GCMs) is averaged over the state of California (CA) and compared. Several averaging methodologies are considered and all are found to give similar values when model grid spacing is less than 3{sup o}. This suggests that CA is a reasonable size for regional intercomparisons using modern GCMs. Results show that reanalysis-forced RCMs tend to significantly overpredict CA precipitation. This appears to be due mainly to overprediction of extreme events; RCM precipitation frequency is generally underpredicted. Overprediction is also reflected in wintertime precipitation variability, which tends to be too high for RCMs on both daily and interannual scales. Wintertime precipitation in most (but not all) GCMs is underestimated. This is in contrast to previous studies based on global blended gauge/satellite observations which are shown here to underestimate precipitation relative to higher-resolution gauge-only datasets. Several GCMs provide reasonable daily precipitation distributions, a trait which doesn't seem tied to model resolution. GCM daily and interannual variability is generally underpredicted.
Date: April 27, 2009
Creator: Caldwell, P M
System: The UNT Digital Library
Energy dependence of transverse momentum fluctuations in Pb+Pb collisions at the CERN Super Proton Synchrotron (SPS) at 20A to 158A GeV (open access)

Energy dependence of transverse momentum fluctuations in Pb+Pb collisions at the CERN Super Proton Synchrotron (SPS) at 20A to 158A GeV

Results are presented on event-by-event fluctuations of transverse momenta p{sub T} in central Pb+Pb interactions at 20A, 30A, 40A, 80A, and 158A GeV. The analysis was performed for charged particles at forward center-of-mass rapidity (1.1 < y*{sub {pi}} < 2.6). Three fluctuation measures were studied: the distribution of average transverse momentum M(p{sub T}) in the event, the {phi}{sub p{sub T}} fluctuation measure, and two-particle transverse momentum correlations. Fluctuations of p{sub T} are small and show no significant energy dependence in the energy range of the CERN Super Proton Synchrotron. Results are compared with QCD-inspired predictions for the critical point, and with the UrQMD model. Transverse momentum fluctuations, similar to multiplicity fluctuations, do not show the increase expected for freeze-out near the critical point of QCD.
Date: April 15, 2009
Creator: Collaboration, NA49 & Anticic, T.
System: The UNT Digital Library
Workforce Development: A Survey of Industry Needs and Training Approaches (open access)

Workforce Development: A Survey of Industry Needs and Training Approaches

This paper presents information and data collected during 2008 on PV workforce needs by the Interstate Renewable Energy Council for the U.S. Department of Energy. The data was collected from licensed contractors, PV practitioners, educators and expert instructors at training sessions, and at focus group and advisory committee meetings. Respondents were primarily from three states: Florida, New York and California. Other states were represented, but to a lesser extent. For data collection, a 12-item questionnaire was developed that addressed key workforce development issues from the perspectives of both the PV industry and training institutions. A total of 63 responses were collected, although not every respondent answered every question. Industry representatives slightly outnumbered the educators, although the difference in responses was not significant.
Date: April 1, 2009
Creator: Ventre, Jerry & Weissman, Jane
System: The UNT Digital Library
Airflow Simulations around OA Intake Louver with Electronic Velocity Sensors (open access)

Airflow Simulations around OA Intake Louver with Electronic Velocity Sensors

It is important to control outdoor airflow rates into HVAC systems in terms of energy conservation and healthy indoor environment. Technologies are being developed to measure outdoor air (OA) flow rates through OA intake louvers on a real time basis. The purpose of this paper is to investigate the airflow characteristics through an OA intake louver numerically in order to provide suggestions for sensor installations. Airflow patterns are simulated with and without electronic air velocity sensors within cylindrical probes installed between louver blades or at the downstream face of the louver. Numerical results show quite good agreements with experimental data, and provide insights regarding measurement system design. The simulations indicate that velocity profiles are more spatially uniform at the louver outlet relative to between louver blades, that pressure drops imposed by the sensor bars are smaller with sensor bars at the louver outlet, and that placement of the sensor bars between louver blades substantially increases air velocities inside the louver. These findings suggest there is an advantage to placing the sensor bars at the louver outlet face.
Date: April 1, 2009
Creator: Han, Hwataik; Sullivan, Douglas P. & Fisk, William J.
System: The UNT Digital Library
Task 2: Boiler Corrosion, (open access)

Task 2: Boiler Corrosion,

For continued use of coal for power generation, there are needs to: –Improve efficiency –Decrease emissions (esp. CO2) –Use alternate fuels or fuel mixes
Date: April 1, 2009
Creator: Holcomb, G. R.; Covino, B. S., Jr.; Shim, H.-S.; Davis, K.; Eden, D. A.; White, M. et al.
System: The UNT Digital Library
Opto-electrical characterization and X-ray mapping of large-volume cadmium zinc telluride radiation detectors (open access)

Opto-electrical characterization and X-ray mapping of large-volume cadmium zinc telluride radiation detectors

Large-volume cadmium zinc telluride (CZT) radiation detectors would greatly improve radiation detection capabilities and, therefore, attract extensive scientific and commercial interests. CZT crystals with volumes as large as hundreds of centimeters can be achieved today due to improvements in the crystal growth technology. However, the poor performance of large-volume CZT detectors is still a challenging problem affecting the commercialization of CZT detectors and imaging arrays. We have employed Pockels effect measurements and synchrotron X-ray mapping techniques to investigate the performance-limiting factors for large-volume CZT detectors. Experimental results with the above characterization methods reveal the non-uniform distribution of internal electric field of large-volume CZT detectors, which help us to better understand the responsible mechanism for the insufficient carrier collection in large-volume CZT detectors.
Date: April 13, 2009
Creator: Yang, G.; Bolotnikov, A.E.; Camarda, G.S.; Cui, Y.; Hossain, A.; Yao, H.W. et al.
System: The UNT Digital Library
UNCERTAINTY IN THE GLOBAL FORECAST SYSTEM (open access)

UNCERTAINTY IN THE GLOBAL FORECAST SYSTEM

We validated one year of Global Forecast System (GFS) predictions of surface meteorological variables (wind speed, air temperature, dewpoint temperature, air pressure) over the entire planet for forecasts extending from zero hours into the future (an analysis) to 36 hours. Approximately 12,000 surface stations world-wide were included in this analysis. Root-Mean-Square- Errors (RMSE) increased as the forecast period increased from zero to 36 hours, but the initial RMSE were almost as large as the 36 hour forecast RMSE for all variables. Typical RMSE were 3 C for air temperature, 2-3mb for sea-level pressure, 3.5 C for dewpoint temperature and 2.5 m/s for wind speed. Approximately 20-40% of the GFS errors can be attributed to a lack of resolution of local features. We attribute the large initial RMSE for the zero hour forecasts to the inability of the GFS to resolve local terrain features that often dominate local weather conditions, e.g., mountain- valley circulations and sea and land breezes. Since the horizontal resolution of the GFS (about 1{sup o} of latitude and longitude) prevents it from simulating these locally-driven circulations, its performance will not improve until model resolution increases by a factor of 10 or more (from about 100 km to …
Date: April 15, 2009
Creator: Werth, D. & Garrett, A.
System: The UNT Digital Library
Community Net Energy Metering: How Novel Policies Expand Benefits of Net Metering to Non-Generators (open access)

Community Net Energy Metering: How Novel Policies Expand Benefits of Net Metering to Non-Generators

As interest in community solutions to renewable energy grows, more states are beginning to develop policies that encourage properties with more than one meter to install shared renewable energy systems. State net metering policies are evolving to allow the aggregation of multiple meters on a customer’s property and to dissolve conventional geographical boundaries. This trend means net metering is expanding out of its traditional function as an enabling incentive to offset onsite customer load at a single facility. This paper analyzes community net energy metering (CNEM) as an emerging vehicle by which farmers, neighborhoods, and municipalities may more easily finance and reap the benefits of renewable energy. Specifically, it aims to compare and contrast the definition of geographical boundaries among different CNEM models and examine the benefits and limitations of each approach. As state policies begin to stretch the geographic boundaries of net metering, they allow inventive solutions to encourage renewable energy investment. This paper attempts to initiate the conversation on this emerging policy mechanism and offers recommendations for further development of these policies.
Date: April 1, 2009
Creator: Rose, James & Varnado, Laurel
System: The UNT Digital Library
Conference for Undergraduate Women in Physics (open access)

Conference for Undergraduate Women in Physics

The Yale Conference for Undergraduate Women in Physics was held on January 18th and 19th, 2008. The conference, targeted toward undergraduates in the Northeast, was a huge success. It was well attended by both a slate of impressive speakers including Janet Conrad, Mildred Dresselhaus, Elsa Garmire, Howard Georgi, Liz Rhodes, Meg Urry and Wendy Zhang, and many interested attendees. Talks were on current research, about issues for women in physics, and on the application process for graduate school. There was also a career panel, student talks, and a student poster session. The conference ran concurrently with the third annual conference at USC, as well as a first annual conference at the University of Michigan. Our purpose in creating this conference was to provide a supportive atmosphere for young physicists to connect with peers and with successful women in the field. We hope that from this conference, attendees have become confident and knowledgeable about applying to graduate school and be further inspired to pursue a career in physics. The following describes the conference program, participation and impact, logistics of running the conference and plans for the future.
Date: April 1, 2009
Creator: Fleming, Bonnie
System: The UNT Digital Library
Prospects for High Energy Resolution Gamma Ray Spectroscopy with Europium-Doped Strontium Iodide (open access)

Prospects for High Energy Resolution Gamma Ray Spectroscopy with Europium-Doped Strontium Iodide

Europium-doped strontium iodide scintillators offer a light yield exceeding 100,000 photons/MeV and excellent light yield proportionality, while at the same time, SrI{sub 2} is readily grown in single crystal form. Thus far, our collaboration has demonstrated an energy resolution with strontium iodide of 2.6% at 662 keV and 7.6% at 60 keV, and we have grown single crystals surpassing 30 cm{sup 3} in size (with lower resolution). Our analysis indicates that SrI{sub 2}(Eu) has the potential to offer 2% energy resolution at 662 keV with optimized material, optics, and read-out. In particular, improvements in feedstock purity may result in crystal structural and chemical homogeneity, leading to improved light yield uniformity throughout the crystal volume, and consequently, better energy resolution. Uniform, efficient light collection and detection, is also required to achieve the best energy resolution with a SrI{sub 2}(Eu) scintillator device.
Date: April 3, 2009
Creator: Cherepy, Nerine J.; Payne, Stephen A.; Hawrami, Rastgo; Burger, Arnold; Boatner, Lynn; Van Loef, Edgar et al.
System: The UNT Digital Library
Improving the Performance Scalability of the Community Atmosphere Model (open access)

Improving the Performance Scalability of the Community Atmosphere Model

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Date: April 12, 2009
Creator: Mirin, A. A. & Worley, P. H.
System: The UNT Digital Library
Eddy covariance observations of surface leakage during shallow subsurface CO2 releases (open access)

Eddy covariance observations of surface leakage during shallow subsurface CO2 releases

We tested the ability of eddy covariance (EC) to detect, locate, and quantify surface CO{sub 2} flux leakage signals within a background ecosystem. For 10 days starting on 07/09/2007, and for seven days starting on 08/03/2007, 0.1 (Release 1) and 0.3 (Release 2) t CO{sub 2}d{sup -1}, respectively, were released from a horizontal well {approx}100 m in length and {approx}2.5 m in depth located in an agricultural field in Bozeman, MT. An EC station measured net CO{sub 2} flux (F{sub c}) from 06/08/2006 to 09/04/2006 (mean and standard deviation = -12.4 and 28.1 g m{sup -2} d{sup -1}, respectively) and from 05/28/2007 to 09/04/2007 (mean and standard deviation = -12.0 and 28.1 g m{sup -2} d{sup -1}, respectively). The Release 2 leakage signal was visible in the F{sub c} time series, whereas the Release 1 signal was difficult to detect within variability of ecosystem fluxes. To improve detection ability, we calculated residual fluxes (F{sub cr}) by subtracting fluxes corresponding to a model for net ecosystem exchange from F{sub c}. F{sub cr} had reduced variability and lacked the negative bias seen in corresponding F{sub c} distributions. Plotting the upper 90th percentile F{sub cr} versus time enhanced the Release 2 leakage signal. …
Date: April 1, 2009
Creator: Lewicki, J. L.; Hilley, G. E.; Fischer, M. L.; Pan, L.; Oldenburg, C. M.; Dobeck, L. et al.
System: The UNT Digital Library
Diagnosis of Solar Water Heaters Using Solar Storage Tank Surface Temperature Data: Preprint (open access)

Diagnosis of Solar Water Heaters Using Solar Storage Tank Surface Temperature Data: Preprint

Study of solar water heaters by using surface temperature data of solar storage tanks to diagnose proper operations.
Date: April 1, 2009
Creator: Burch, J.; Magnuson, L.; Barker, G. & Bullwinkel, M.
System: The UNT Digital Library
Safeguards-by-Design: An Element of 3S Integration (open access)

Safeguards-by-Design: An Element of 3S Integration

In 2008, the “20/20 Vision for the Future” background report by the IAEA Director General identified the possibility of integrating certain activities related to safeguards, safety, and security. Later in the year, the independent Commission report prepared at the request of the IAEA Director General noted that the Agency’s roles in nuclear safeguards, safety, and security (3S) complement and can mutually reinforce each other. Safeguards-by-design (SBD) is a practical measure that strengthens 3S integration, especially for the stage of nuclear facility design and construction, but also with ramifications for other stages of the facility life-cycle. This paper describes the SBD concept, with examples for diverse regulatory environments, being developed in the U.S under the U.S. Department of Energy (DOE) Next Generation Safeguards Initiative and the Advanced Fuel Cycle Initiative. This is compared with related international SBD work performed in the recent IAEA workshop on “Facility Design and Plant Operation Features that Facilitate the Implementation of IAEA Safeguards”. Potential future directions for further development of SBD and its integration within 3S are identified.
Date: April 1, 2009
Creator: Bean, R. S.; Bjornard, T. A. & Hebdich, D. J.
System: The UNT Digital Library
GLOVEBOX WINDOWS, FIRE PROTECTION AND VOICES FROM THE PAST (open access)

GLOVEBOX WINDOWS, FIRE PROTECTION AND VOICES FROM THE PAST

'Study the past--what is past is prologue'. These words appear as the motto on a pair of statues at the National Archives Building in Washington DC. They are also the opening sentence in the preface of a document written in August of 1956 entitled 'A Summary of Accidents and Incidents Involving Radiation in Atomic Energy Activities--June 1945 thru December 1955'. This document, one of several written by D.F. Hayes of the Safety and Fire Protection Branch, Division of Organization and Personnel, U.S. Atomic Energy Commission in Washington DC, and many others are often forgotten even though they contain valuable glovebox fire protection lessons for us today.
Date: April 15, 2009
Creator: Till, W
System: The UNT Digital Library
CDF experimental results on diffraction (open access)

CDF experimental results on diffraction

Experimental results on diffraction from the Fermilab Tevatron collider obtained by the CDF experiment are reviewed and compared. We report on the diffractive structure function obtained from dijet production in the range 0 < Q{sup 2} < 10,000 GeV{sup 2}, and on the |t| distribution in the region 0 < |t| < 1 GeV{sup 2} for both soft and hard diffractive events up to Q{sup 2} {approx} 4,500 GeV{sup 2}. Results on single diffractive W/Z production, forward jets, and central exclusive production of both dijets and diphotons are also presented.
Date: April 1, 2009
Creator: Gallinaro, Michele
System: The UNT Digital Library
Linear pi-Acceptor-Templated Dynamic Clipping to Macrobicycles and[2]Rotaxanes (open access)

Linear pi-Acceptor-Templated Dynamic Clipping to Macrobicycles and[2]Rotaxanes

Functional rotaxanes are one of the representative nanoscale molecular machines that have found applications in many areas, including molecular electronics, nanoelectromechanical systems (NEMS), photo controllable smart surfaces, and nanovalves. With the advent of molecular recognition and self-assembly, such molecular compounds can now be obtained efficiently through template-directed synthesis. One of the common strategies of making [2]rotaxanes involves the clipping of a macrocycle around a preformed dumbbell-shaped template in a [1+1] or [2+2] manner. While early examples were based on irreversible kinetic pathway through covalent bond formation, recent advances on reversible dynamic covalent chemistry (DCC) has attracted great attention to this field. By virtue of thermodynamically controlled equilibria, DCC has provided highly efficient and versatile synthetic routes in the selection of specific products from a complex system. Among the several reversible reactions in the category of DCC reactions, the imine formation has proven to be very versatile in macrocyclization to give complex interlocked molecular compounds. Cryptands are three dimensional bicyclic hosts with preorganized cavities capable of inclusion of ions and small molecules. Replacing the nitrogen bridgeheads in common cryptands with aromatic ring systems gives cyclophane-based macrobicycles. The introduction of aromatic ring systems into a preorganized cage-like geometry facilitates ion-{pi} interactions and …
Date: April 30, 2009
Creator: Klivansky, Liana M.; Koshkakaryan, Gayane; Cao, Dennis & Liu, Yi
System: The UNT Digital Library
Analysis of the Current Use, Benefit, and Value of the Open Science Grid (open access)

Analysis of the Current Use, Benefit, and Value of the Open Science Grid

The Open Science Grid usage has ramped up more than 25% in the past twelve months due to both the increase in throughput of the core stakeholders - US LHC, LIGO and Run II - and increase in usage by nonphysics communities. It is important to understand the value collaborative projects, such as the OSG, contribute to the scientific community. This needs to be cognizant of the environment of commercial cloud offerings, the evolving and maturing middleware for grid based distributed computing, and the evolution in science and research dependence on computation. We present a first categorization of OSG value and analysis across several different aspects of the Consortium's goals and activities. And lastly, we presents some of the upcoming challenges of LHC data analysis ramp up and our ongoing contributions to the World Wide LHC Computing Grid.
Date: April 1, 2009
Creator: Pordes, R.
System: The UNT Digital Library
Characterizing the effects of silver alloying in chalcopyrite CIGS solar cells with junction capacitance methods (open access)

Characterizing the effects of silver alloying in chalcopyrite CIGS solar cells with junction capacitance methods

A variety of junction capacitance-based characterization methods were used to investigate alloys of Ag into Cu(In1-xGax)Se2 photovoltaic solar cells over a broad range of compositions. These alloys show encouraging trends of increasing VOC with increasing Ag content, opening the possibility of wide-gap cells for use in tandem device applications. Drive level capacitance profiling (DLCP) has shown very low free carrier concentrations for all Ag-alloyed devices, in some cases less than 1014 cm-3, which is roughly an order of magnitude lower than that of CIGS devices. Transient photocapacitance spectroscopy has revealed very steep Urbach edges, with energies between 10 meV and 20 meV, in the Ag-alloyed samples. This is in general lower than the Urbach edges measured for standard CIGS samples and suggests a significantly lower degree of structural disorder.
Date: April 1, 2009
Creator: Erslev, Peter T.; Hanket, Gregory M.; Shafarman, William N. & Cohen, J. David
System: The UNT Digital Library
Beam Test of a Time-of-Flight Detector Prototype (open access)

Beam Test of a Time-of-Flight Detector Prototype

We report on results of a Time-of-Flight, TOF, counter prototype in beam tests at SLAC and Fermilab. Using two identical 64-pixel Photonis Microchannel Plate Photomultipliers, MCP-PMTs, to provide start and stop signals, each having a 1 cm-long quartz Cherenkov radiator, we have achieved a timing resolution of {sigma}{sub Single{_}detector} {approx} 14 ps.
Date: April 1, 2009
Creator: Va'vra, J.; Leith, D. W. G. S.; Ratcliff, B.; Ramberg, E.; Albrow, M.; Ronzhin, A. et al.
System: The UNT Digital Library
Tevatron top physics (open access)

Tevatron top physics

A summary of the most recent results on top quark physics obtained at Fermilab's Tevatron proton-antiproton collider, operating at a centre of mass energy of 1.96 TeV, is presented. Measurements of the top pair and single top quark production cross sections, the investigation of top quark decay properties, the precision measurement of the top quark mass as well as searches for physics beyond the standard model are discussed.
Date: April 1, 2009
Creator: Wagner-Kuhr, Jeannine & U., /Karlsruhe
System: The UNT Digital Library
Moving toward multilateral mechanisms for the fuel cycle (open access)

Moving toward multilateral mechanisms for the fuel cycle

Multilateral mechanisms for the fuel cycle are seen as a potentially important way to create an industrial infrastructure that will support a renaissance and at the same time not contribute to the risk of nuclear proliferation. In this way, international nuclear fuel cycle centers for enrichment can help to provide an assurance of supply of nuclear fuel that will reduce the likelihood that individual states will pursue this sensitive technology, which can be used to produce nuclear material directly usable nuclear weapons. Multinational participation in such mechanisms can also potentially promote transparency, build confidence, and make the implementation of IAEA safeguards more effective or more efficient. At the same time, it is important to ensure that there is no dissemination of sensitive technology. The Russian Federation has taken a lead role in this area by establishing an International Uranium Enrichment Center (IUEC) for the provision of enrichment services at its uranium enrichment plant located at the Angarsk Electrolysis Chemical Complex (AECC). This paper describes how the IUEe is organized, who its members are, and the steps that it has taken both to provide an assured supply of nuclear fuel and to ensure protection of sensitive technology. It also describes the …
Date: April 17, 2009
Creator: Panasyuk,A.; Rosenthal,M. & Efremov, G. V.
System: The UNT Digital Library