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Speckle Imaging Over Horizontal Paths (open access)

Speckle Imaging Over Horizontal Paths

Atmospheric aberrations reduce the resolution and contrast in surveillance images recorded over horizontal or slant paths. This paper describes our recent horizontal and slant path imaging experiments of extended scenes as well as the results obtained using speckle imaging. The experiments were performed with an 8-inch diameter telescope placed on either a rooftop or hillside and cover ranges of interest from 0.5 km up to 10 km. The scenery includes resolution targets, people, vehicles, and other structures. The improvement in image quality using speckle imaging is dramatic in many cases, and depends significantly upon the atmospheric conditions. We quantify resolution improvement through modulation transfer function measurement comparisons.
Date: May 21, 2002
Creator: Carrano, C J
System: The UNT Digital Library
Ti-Cr-Al-O Thin Film Resistors (open access)

Ti-Cr-Al-O Thin Film Resistors

Thin films of Ti-Cr-Al-O are produced for use as an electrical resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O{sub 2}. Vertical resistivity values from 10{sup 4} to 10{sup 10} Ohm-cm are measured for Ti-Cr-Al-O films. The film resistivity can be design selected through control of the target composition and the deposition parameters. The Ti-Cr-Al-O thin film resistor is found to be thermally stable unlike other metal-oxide films.
Date: March 21, 2002
Creator: Jankowski, Alan Frederic & Hayes, J. P.
System: The UNT Digital Library
Micro-Fabricated Thin-Film Fuel Cells for Portable Power Requirements (open access)

Micro-Fabricated Thin-Film Fuel Cells for Portable Power Requirements

None
Date: March 21, 2002
Creator: Jankowski, Alan Frederic; Hayes, Jeffrey P.; Graff, R. T. & Morse, J. D.
System: The UNT Digital Library
Parallelization of an Adaptive Multigrid Algorithm for Fast Solution of Finite Element Structural Problems (open access)

Parallelization of an Adaptive Multigrid Algorithm for Fast Solution of Finite Element Structural Problems

Adaptive mesh refinement selectively subdivides the elements of a coarse user supplied mesh to produce a fine mesh with reduced discretization error. Effective use of adaptive mesh refinement coupled with an a posteriori error estimator can produce a mesh that solves a problem to a given discretization error using far fewer elements than uniform refinement. A geometric multigrid solver uses increasingly finer discretizations of the same geometry to produce a very fast and numerically scalable solution to a set of linear equations. Adaptive mesh refinement is a natural method for creating the different meshes required by the multigrid solver. This paper describes the implementation of a scalable adaptive multigrid method on a distributed memory parallel computer. Results are presented that demonstrate the parallel performance of the methodology by solving a linear elastic rocket fuel deformation problem on an SGI Origin 3000. Two challenges must be met when implementing adaptive multigrid algorithms on massively parallel computing platforms. First, although the fine mesh for which the solution is desired may be large and scaled to the number of processors, the multigrid algorithm must also operate on much smaller fixed-size data sets on the coarse levels. Second, the mesh must be repartitioned as …
Date: March 21, 2002
Creator: Crane, N K; Parsons, I D & Hjelmstad, K D
System: The UNT Digital Library
Evaluating the Carbon Cycle of a Coupled Atmosphere-Biosphere Model (open access)

Evaluating the Carbon Cycle of a Coupled Atmosphere-Biosphere Model

We investigate how well a coupled biosphere-atmosphere model, CCM3-IBIS, can simulate the functioning of the terrestrial biosphere and the carbon cycling through it. The simulated climate is compared to observations, while the vegetation cover and the carbon cycle are compared to an offline version of the biosphere model IBIS forced with observed climatic variables. The simulated climate presents some local biases that strongly affect the vegetation (e.g., a misrepresentation of the African monsoon). Compared to the offline model, the coupled model simulates well the globally averaged carbon fluxes and vegetation pools. The zonal mean carbon fluxes and the zonal mean seasonal cycle are also well represented except between 0{sup o} and 20{sup o}N due to the misrepresentation of the African monsoon. These results suggest that, despite regional biases in climate and ecosystem simulations, this coupled atmosphere-biosphere model can be used to explore geographic and temporal variations in the global carbon cycle.
Date: August 21, 2002
Creator: Delire, Christine; Foley, Jonathan A. & Thompson, Starley
System: The UNT Digital Library
A Hybrid Nodal Method for Time-Dependent Incompressible Flow in Two-Dimensional Arbitrary Geometries (open access)

A Hybrid Nodal Method for Time-Dependent Incompressible Flow in Two-Dimensional Arbitrary Geometries

A hybrid nodal-integral/finite-analytic method (NI-FAM) is developed for time-dependent, incompressible flow in two-dimensional arbitrary geometries. In this hybrid approach, the computational domain is divided into parallelepiped and wedge-shaped space-time nodes (cells). The conventional nodal integral method (NIM) is applied to the interfaces between adjacent parallelepiped nodes (cells), while a finite analytic approach is applied to the interfaces between parallelepiped and wedge-shaped nodes (cells). In this paper, the hybrid method is formally developed and an application of the NI-FAM to fluid flow in an enclosed cavity is presented. Results are compared with those obtained using a commercial computational fluid dynamics code.
Date: October 21, 2002
Creator: Toreja, Allen J. & Uddin, Rizwan
System: The UNT Digital Library
Charge transport in hybrid nanorod-polymer composite photovoltaiccells (open access)

Charge transport in hybrid nanorod-polymer composite photovoltaiccells

Charge transport in composites of inorganic nanorods and aconjugated polymer is investigated using a photovoltaic device structure.We show that the current-voltage (I-V) curves in the dark can be modelledusing the Shockley equation modified to include series and shuntresistance at low current levels, and using an improved model thatincorporates both the Shockley equation and the presence of a spacecharge limited region at high currents. Under illumination, theefficiency of photocurrent generation is found to be dependent on appliedbias. Furthermore, the photocurrent-light intensity dependence was foundto be sublinear. An analysis of the shunt resistance as a function oflight intensity suggests that the photocurrent as well as the fill factoris diminished as a result of increased photoconductivity of the activelayer at high light intensity. By studying the intensity dependence ofthe open circuit voltage for nanocrystals with different diameters andthus ! band gaps, it was inferred that Fermi-level pinning occurs at theinterface between the aluminum electrode and the nanocrystal.
Date: June 21, 2002
Creator: Huynh, Wendy U.; Dittmer, Janke J.; Teclemariam, Nerayo; Milliron, Delia; Alivisatos, A. Paul & Barnham, Keith W.J.
System: The UNT Digital Library
An integrated mechanical design concept for the final focusingregion for the HIF point design (open access)

An integrated mechanical design concept for the final focusingregion for the HIF point design

A design study was undertaken to develop a ''first cut'' integrated mechanical design concept of the final focusing region for a conceptual IFE power plant that considers the major issues which must be addressed in an integrated driver and chamber system. The conceptual design in this study requires a total of 120 beamlines located in two conical arrays attached on the sides of the target chamber 180 degrees apart. Each beamline consists of four large-aperture superconducting quadrupole magnets and a dipole magnet. The major interface issues include radiation shielding and thermal insulation of the superconducting magnets; reaction of electromagnetic loads between the quadrupoles; alignment of the magnets; isolation of the vacuum regions in the target chamber from the beamline, and assembly and maintenance.
Date: November 21, 2002
Creator: Brown, T.; Sabbi, G. L.; Barnard, J. J.; Heitzenroeder, P.; Chun, J.; Schmidt, J. et al.
System: The UNT Digital Library
Rates and technologies for mass-market demand response (open access)

Rates and technologies for mass-market demand response

Demand response programs are often quickly and poorlycrafted in reaction to an energy crisis and disappear once the crisissubsides, ensuring that the electricity system will be unprepared whenthe next crisis hits. In this paper, we propose to eliminate theevent-driven nature of demand response programs by considering demandresponsiveness a component of the utility obligation to serve. As such,demand response can be required as a condition of service, and theoffering of demand response rates becomes a requirement of utilities asan element of customer service. Using this foundation, we explore thecosts and benefits of a smart thermostat-based demand response systemcapable of two types of programs: (1) a mandatory, system-operatorcontrolled, contingency program, and (2) a voluntary, customercontrolled, bill management program with rate-based incentives. Anydemand response program based on this system could consist of either orboth of these components. Ideally, these programs would be bundled,providing automatic load management through customer-programmed priceresponse, plus up to 10 GW of emergency load shedding capability inCalifornia. Finally, we discuss options for and barriers toimplementation of such a program in California.
Date: July 21, 2002
Creator: Herter, Karen; Levy, Roger; Wilson, John & Rosenfeld, Arthur
System: The UNT Digital Library
Rates and technologies for mass-market demand response (open access)

Rates and technologies for mass-market demand response

Demand response programs are often quickly and poorly crafted in reaction to an energy crisis and disappear once the crisis subsides, ensuring that the electricity system will be unprepared when the next crisis hits. In this paper, we propose to eliminate the event-driven nature of demand response programs by considering demand responsiveness a component of the utility obligation to serve. As such, demand response can be required as a condition of service, and the offering of demand response rates becomes a requirement of utilities as an element of customer service. Using this foundation, we explore the costs and benefits of a smart thermostat-based demand response system capable of two types of programs: (1) a mandatory, system-operator controlled, contingency program, and (2) a voluntary, customer controlled, bill management program with rate-based incentives. Any demand response program based on this system could consist of either or both of these components. Ideally, these programs would be bundled, providing automatic load management through customer-programmed price response, plus up to 10 GW of emergency load shedding capability in California. Finally, we discuss options for and barriers to implementation of such a program in California.
Date: July 21, 2002
Creator: Herter, Karen; Levy, Roger; Wilson, John & Rosenfeld, Arthur
System: The UNT Digital Library
Detailed spectroscopic analysis of SN 1987A: The distance to the LMC using the SEAM method (open access)

Detailed spectroscopic analysis of SN 1987A: The distance to the LMC using the SEAM method

Supernova 1987A remains the most well-studied supernova to date. Observations produced excellent broad-band photometric and spectroscopic coverage over a wide wavelength range at all epochs. We model the observed spectra from Day 1 to Day 81 using a hydrodynamical model. We show that good agreement can be obtained at times up to about 60 days, if we allow for extended nickel mixing. Later than about 60 days the observed Balmer lines become stronger than our models can reproduce. We show that this is likely due to a more complicated distribution of gamma-rays than we allow for in our spherically symmetric calculations. We present synthetic light curves in UBVRIJHK and a synthetic bolometric light curve. Using this broad baseline of detailed spectroscopic models we find a distance modulus mu = 18.5 +/- 0.2 using the SEAM method of determining distances to supernovae. We find that the explosion time agrees with that of the neutrino burst and is constrained at 68 percent confidence to within +/- 0.9 days. We argue that the weak Balmer lines of our detailed model calculations casts doubt on the accuracy of the purely photometric EPM method. We also suggest that Type IIP supernovae will be most useful …
Date: May 21, 2002
Creator: Mitchell, Robert C.; Baron, E.; Branch, David; Hauschildt, Peter H.; Nugent, Peter E.; Lundqvist, Peter et al.
System: The UNT Digital Library
Characterization of Spatial Variability of Hydrogeologic Properties for Unsaturated Flow in the Fractured Rocks at Yucca Mountain, Nevada (open access)

Characterization of Spatial Variability of Hydrogeologic Properties for Unsaturated Flow in the Fractured Rocks at Yucca Mountain, Nevada

The spatial variability of layer-scale hydrogeologic properties of the unsaturated zone (UZ) at Yucca Mountain, Nevada, is investigated using inverse modeling. The thick UZ is grouped into five hydrostratigraphic units and further into 35 hydrogeologic layers. For each layer, lateral variability is represented by the variations in calibrated values of layer-scale properties at different individual deep boreholes. In the calibration model, matrix and fracture properties are calibrated for the one-dimensional vertical column at each individual borehole using the ITOUGH2 code. The objective function is the summation of the weighted misfits between the ambient unsaturated flow (represented by measured state variables: water saturation, water potential, and pneumatic pressure) and the simulated one in the one-dimensional flow system. The objective function also includes the weighted misfits between the calibrated properties and their prior information. Layer-scale state variables and prior rock properties are obtained from their core-scale measurements. Because of limited data, the lateral variability of three most sensitive properties (matrix permeability, matrix of the van Genuchten characterization, and fracture permeability) is calibrated, while all other properties are fixed at their calibrated layer-averaged values. Considerable lateral variability of hydrogeologic properties is obtained. For example, the lateral variability of is two to three orders …
Date: May 21, 2002
Creator: Zhou, Quanlin; Bodvarsson, Gudmundur S.; Liu, Hui-Hai & Oldenburg, Curtis M.
System: The UNT Digital Library
Estimating subsurface topography from surface-to-borehole seismic studies at the Rye Patch Geothermal Reservoir (open access)

Estimating subsurface topography from surface-to-borehole seismic studies at the Rye Patch Geothermal Reservoir

None
Date: May 21, 2002
Creator: Gritto, Roland; Daley, Thomas M. & Majer, Ernest L.
System: The UNT Digital Library
TEM characterization of GaN nanowires (open access)

TEM characterization of GaN nanowires

Transmission electron microscopy was applied to study GaN nanowires grown on carbon nanotube surfaces by chemical reaction between Ga{sub 2}O and NH{sub 3} gas in a conventional furnace. These wires grew in two crystallographic directions, <2{und 11}0> and <01{und 1}0> (fast growth directions of GaN), in the form of whiskers covered by small elongated GaN platelets. The morphology of these platelets is similar to that observed during the growth of single crystals from a Ga melt at high temperatures under high nitrogen pressure. It is thought that growth of nanowires in two different crystallographic directions and the arrangement of the platelets to the central whisker may be influenced by the presence of Ga{sub 2}O{sub 3} (based on the observation of the energy dispersive x-ray spectra), the interplanar spacings in the wire, and the presence of defects on the interface between the central part of the nanowire and the platelets surrounding it.
Date: February 21, 2002
Creator: Liliental-Weber, Zuzanna; Gao, Y.H. & Bando, Y.
System: The UNT Digital Library
Relationship of adiposity to the population distribution of plasma triglyceride concentrations in vigorously active men and women (open access)

Relationship of adiposity to the population distribution of plasma triglyceride concentrations in vigorously active men and women

Context and Objective: Vigorous exercise, alcohol and weight loss are all known to increase HDL-cholesterol, however, it is not known whether these interventions raise low HDL as effectively as has been demonstrated for normal HDL. Design: Physician-supplied medical data from 7,288 male and 2,359 female runners were divided into five strata according to their self-reported usual running distance, reported alcohol intake, body mass index (BMI) or waist circumference. Within each stratum, the 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles for HDL-cholesterol were then determined. Bootstrap resampling of least-squares regression was applied to determine the cross-sectional relationships between these factors and each percentile of the HDL-cholesterol distribution. Results: In both sexes, the rise in HDL-cholesterol per unit of vigorous exercise or alcohol intake was at least twice as great at the 95th percentile as at the 5th percentile of the HDL-distribution. There was also a significant graded increase in the slopes relating exercise (km run) and alcohol intake to HDL between the 5th and the 95th percentile. Men's HDL-cholesterol decreased in association with fatness (BMI and waist circumference) more sharply at the 95th than at the 5th percentile of the HDL-distribution. Conclusions: Although exercise, alcohol and adiposity were all …
Date: December 21, 2002
Creator: Williams, Paul T.
System: The UNT Digital Library
Electrochemical and physical analysis of a Li-ion cell cycled at elevated temperature (open access)

Electrochemical and physical analysis of a Li-ion cell cycled at elevated temperature

Laboratory-size LiNi0.8Co0.15Al0.05O2/graphite lithium-ion pouch cells were cycled over 100 percent DOD at room temperature and 60 degrees C in order to investigate high-temperature degradation mechanisms of this important technology. Capacity fade for the cell was correlated with that for the individual components, using electrochemical analysis of the electrodes and other diagnostic techniques. The high-temperature cell lost 65 percent of its initial capacity after 140 cycles at 60 degrees C compared to only 4 percent loss for the cell cycled at room temperature. Cell ohmic impedance increased significantly with the elevated temperature cycling, resulting in some of loss of capacity at the C/2 rate. However, as determined with slow rate testing of the individual electrodes, the anode retained most of its original capacity, while the cathode lost 65 percent, even when cycled with a fresh source of lithium. Diagnostic evaluation of cell components including XRD, Raman, CSAFM and suggest capacity loss occurs primarily due to a rise in the impedance of the cathode, especially at the end-of-charge. The impedance rise may be caused in part by a loss of the conductive carbon at the surface of the cathode and/or by an organic film on the surface of the cathode that becomes …
Date: June 21, 2002
Creator: Shim, Joongpyo; Kostecki, Robert; Richardson, Thomas; Song, Xiangyun & Striebel, Kathryn A.
System: The UNT Digital Library
PHOTOSYNTHESIS (open access)

PHOTOSYNTHESIS

The Gordon Research Conference (GRC)on PHOTOSYNTHESIS was held at Roger Williams University, Bristol, RI. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.
Date: June 21, 2002
Creator: unknown
System: The UNT Digital Library
K-corrections and extinction corrections for Type Ia supernovae (open access)

K-corrections and extinction corrections for Type Ia supernovae

The measurement of the cosmological parameters from Type Ia supernovae hinges on our ability to compare nearby and distant supernovae accurately. Here we present an advance on a method for performing generalized K-corrections for Type Ia supernovae which allows us to compare these objects from the UV to near-IR over the redshift range 0 < z < 2. We discuss the errors currently associated with this method and how future data can improve upon it significantly. We also examine the effects of reddening on the K-corrections and the light curves of Type Ia supernovae. Finally, we provide a few examples of how these techniques affect our current understanding of a sample of both nearby and distant supernovae.
Date: May 21, 2002
Creator: Nugent, Peter; Kim, Alex & Perlmutter, Saul
System: The UNT Digital Library
The future of fixed target physics : Snowmass E5 working group summary. (open access)

The future of fixed target physics : Snowmass E5 working group summary.

None
Date: January 21, 2002
Creator: Kumar, K.; Ray, R.; Reimer, R. & Strovink, M.
System: The UNT Digital Library
Electroweak Prospects for Tevatron RunII (open access)

Electroweak Prospects for Tevatron RunII

In RunI each experiment collected about 100 pb{sup -1} of data. During RunIIa, each experiment is expected to collect about 2 fb{sup -1} of data. The center-of-mass energy for RunII, {radical}s = 2.0 TeV, is a bit larger than the 1.8 TeV of RunI and results in an increase of about 10% (35%) in the production cross-sections for W and Z (t{bar t}) events. Additional gains in the event yield are expected due to improvements in the detector acceptance and performance. Taken together, the RunIIa upgrades are expected to yield 2300k (800) W (t{bar t}) events per experiment, including the effects of event selection and triggering, which can be compared to the RunI yields of 77k (20) events. With the RunI data-set, CDF and D0 produced a breadth of electroweak results and obtained the world's only sample of top quarks. While the RunII electroweak physics program is very similar, the RunII upgrade improvements should yield many precision results. The Tevatron began delivering steady data in about June, 2001. The first six months of data taking was ''commissioning dominated'' for CDF and D0. Starting around January, 2002, the experiments were largely commissioned and began taking ''analysis quality'' data. The physics results …
Date: October 21, 2002
Creator: Glenzinski, D.
System: The UNT Digital Library
U.S. Department of Energy sponsored in-depth safety assessments of VVER and RBMK reactors. (open access)

U.S. Department of Energy sponsored in-depth safety assessments of VVER and RBMK reactors.

None
Date: February 21, 2002
Creator: Petri, M. C. & Pasedag, W. F.
System: The UNT Digital Library
Towards a coherent theory of physics and mathematics. (open access)

Towards a coherent theory of physics and mathematics.

None
Date: January 21, 2002
Creator: Benioff, P.
System: The UNT Digital Library
Plasma considerations in the IPNS RCS. (open access)

Plasma considerations in the IPNS RCS.

Significant ionization appears to occur in the Rapid Cycling Synchrotron (RCS) during its 14 ms acceleration period leading to plasma formation and neutralization. The beam may in fact be over-neutralized, causing the tune to increase during the acceleration cycle. The overall tune shift in the RCS appears to be close to +0.5. The presence of plasma may help explain why longitudinal phase modulation can so quickly couple to transverse motion. In addition, plasmas tend to be inductive and the RCS appears to exhibit a relatively high inductance. Measurements of the electron cloud and plasma densities adjacent to the beam should be made. In addition to the RFA and Swept Analyzer diagnostics mentioned at the Workshop, other techniques might be attempted. If plasma is present, then a small, biased-probe might be useful (e.g., a Langmuir probe), or with the proper choice of geometry, an optics-based measurement for line density (e.g., an interferometer) might be employed, perhaps using microwaves for increased sensitivity.
Date: February 21, 2002
Creator: Dooling, J. C.; McMichael, G. E. & Brumwell, F. R.
System: The UNT Digital Library
The Physics of transmutation systems : system capabilities and performances. (open access)

The Physics of transmutation systems : system capabilities and performances.

This document is complementary to a document produced by Prof. Salvatores on ''The Physics of Transmutation in Critical or Subcritical Reactors and the Impact on the Fuel Cycle''. In that document, Salvatores describes the fundamental of transmutation, through basic physics properties and general parametric studies. In the present document we try to go one step further towards practical implementation (while recognizing that the practical issues such as technology development and demonstration, and economics, can only be mentioned in a very superficial manner). Section 1 briefly overviews the possible objectives of transmutation systems, and links these different objectives to possible technological paths. It also describes the overall constraints which have to be considered when developing and implementing transmutation systems. In section 2 we briefly overview the technological constraints which need to be accounted for when designing transmutation systems. In section 3 we attempt to provide a simplified classification of transmutation systems in order to clarify later comparisons. It compares heterogeneous and homogeneous recycle strategies, and single and multi-tier systems. Section 4 presents case analyses for assessing the transmutation performance of various individual systems, starting with LWR's (1. generic results; 2. multirecycle of plutonium; 3. an alternative: transmutation based on a Thorium …
Date: August 21, 2002
Creator: Finck, P. J.
System: The UNT Digital Library