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2,154 Matching Results
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1-MeV-Electron Irradiation of GaInAsN Cells: Preprint
This conference paper describes the GaInAsN cells that are measured to retain 933% and 894% of their original efficiency after exposure to 5 X 1014 and 1 X 1015 cm-2 1-MeV electrons, respectively. The rate of degradation is not correlated with the performance at beginning of life (BOL). The depletion width remains essentially unchanged, increasing by< 1%. Temperature-coefficient data for GaInAsN cells are also presented. These numbers are used to project the efficiency of GaInAsN-containing multijunction cells. The GaInAsN junction is not currently predicted to increase the efficiencies of the multijunction cells. Nevertheless, GaInAsN-containing multijunction cell efficiencies are predicted to be comparable to those of the conventional structures, and even small improvements in the GaInAsN cell may lead to higher multijunction cell efficiencies, especially for high-radiation applications and when cell operating temperature is low.
Date:
May 1, 2002
Creator:
Kurtz, Sarah; King, R. R.; Edmondson, K. M.; Friedman, D. J. & Karam, N. H.
Object Type:
Article
System:
The UNT Digital Library
2001 NSLS Activity Report (National Synchrotron Light Source).
This describes the advertising of cover page of 2001 NSLS Activity Report (National Synchrotron Light Source).
Date:
May 1, 2002
Creator:
Corwin, M. A.
Object Type:
Report
System:
The UNT Digital Library
2001 NSLS Activity Report (National Synchrotron Light Source)
The year 2001 has been another highly productive year at the NSLS, with over 2500 users, including 720 first time users, conducting nearly 1200 experiments in fields ranging from the life, materials, chemical, and environmental sciences to applied science and technology. An impressive array of highlights from this scientific activity is included in this Activity Report. They include the first demonstration of a direct structural probe of the superconducting ground state in the cuprates by utilizing anomalous soft x-ray resonance effects to selectively enhance the scattering from doped holes. Another highly significant result was the determination of the structure of the potassium channel membrane protein. This is especially significant as it provides insight into how the channel functions and how it selects a particular kind of ion. In the nanoscience area, small angle x-ray scattering measurements played an essential role in determining that preferential sequestering of tailored metal nanocrystals into a self-assembled lamellar diblock copolymer can produce high quality metallodielectric photonic bandgap structures, demonstrating the potential of these nanocomposites for photonic crystal engineering. The infrared microscopy program continued to yield noteworthy results, including an important study that characterized the types and abundances of organic materials in contaminated and uncontaminated sediments …
Date:
May 1, 2002
Creator:
Corwin, M. A.
Object Type:
Report
System:
The UNT Digital Library
Ability Estimation Under Different Item Parameterization and Scoring Models
A Monte Carlo simulation study investigated the effect of scoring format, item parameterization, threshold configuration, and prior ability distribution on the accuracy of ability estimation given various IRT models. Item response data on 30 items from 1,000 examinees was simulated using known item parameters and ability estimates. The item response data sets were submitted to seven dichotomous or polytomous IRT models with different item parameterization to estimate examinee ability. The accuracy of the ability estimation for a given IRT model was assessed by the recovery rate and the root mean square errors. The results indicated that polytomous models produced more accurate ability estimates than the dichotomous models, under all combinations of research conditions, as indicated by higher recovery rates and lower root mean square errors. For the item parameterization models, the one-parameter model out-performed the two-parameter and three-parameter models under all research conditions. Among the polytomous models, the partial credit model had more accurate ability estimation than the other three polytomous models. The nominal categories model performed better than the general partial credit model and the multiple-choice model with the multiple-choice model the least accurate. The results further indicated that certain prior ability distributions had an effect on the accuracy …
Date:
May 2002
Creator:
Si, Ching-Fung B.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Acceleration schedules for a recirculating heavy-ion accelerator
Recent advances in solid-state switches have made it feasible to design programmable, high-repetition-rate pulsers for induction accelerators. These switches could lower the cost of recirculating induction accelerators, such as the ''small recirculator'' at Lawrence Livermore National Laboratory (LLNL), by substantially reducing the number of induction modules. Numerical work is reported here to determine what effects the use of fewer pulsers at higher voltage would have on the beam quality of the LLNL small recirculator. Lattices with different numbers of pulsers are examined using the fluid/envelope code CIRCE, and several schedules for acceleration and compression are compared for each configuration. For selected schedules, the phase-space dynamics is also studied using the particle-in-cell code WARP3d.
Date:
May 1, 2002
Creator:
Sharp, W. M. & Grote, D. P.
Object Type:
Article
System:
The UNT Digital Library
Accuracy of flow hoods in residential applications
To assess whether houses can meet performance expectations, the new practice of residential commissioning will likely use flow hoods to measure supply and return grille airflows in HVAC systems. Depending on hood accuracy, these measurements can be used to determine if individual rooms receive adequate airflow for heating and cooling, to determine flow imbalances between different building spaces, to estimate total air handler flow and supply/return imbalances, and to assess duct air leakage. This paper discusses these flow hood applications and the accuracy requirements in each case. Laboratory tests of several residential flow hoods showed that these hoods can be inadequate to measure flows in residential systems. Potential errors are about 20% to 30% of measured flow, due to poor calibrations, sensitivity to grille flow non-uniformities, and flow changes from added flow resistance. Active flow hoods equipped with measurement devices that are insensitive to grille airflow patterns have an order of magnitude less error, and are more reliable and consistent in most cases. Our tests also show that current calibration procedures for flow hoods do not account for field application problems. As a result, a new standard for flow hood calibration needs to be developed, along with a new measurement …
Date:
May 1, 2002
Creator:
Wray, Craig P.; Walker, Iain S. & Sherman, Max H.
Object Type:
Article
System:
The UNT Digital Library
Adaptive Management Platform for Natural Resources in the Columbia River Basin
Adaptive management is a systematic and rigorous scientifically defensible program of learning from the outcomes of management actions, accommodating change, and improving management. The critical requirements and toolboxes of an information management framework, referred to as the Adaptive Management Platform (AMP), to realize the goal of adaptive management are described. The AMP design that connects various modules to ensure that the decision-making needs are met. The modules are data management, visualization tools, optimization algorithms, and models of Columbia Basin physical and biological processes. When fully developed, AMP will enable subbasin planners and responsible entities throughout the Basin to collectively and continuously integrate data and decisions, assess cumulative trends and outcomes over time, and demonstrate discipline and accountability. AMP would function at the basin, ecoprovince, as well as the subbasin scale. AMP would assist in ensuring that uncertainties from individual modules and analytical integration are properly presented to decision makers.
Date:
May 1, 2002
Creator:
Vail, Lance W. & Skaggs, Richard
Object Type:
Report
System:
The UNT Digital Library
ADVANCED FLUE GAS CONDITIONING AS A RETROFIT UPGRADE TO ENHANCE PM COLLECTION FROM COAL-FIRED ELECTRIC UTILITY BOILERS
The U.S. Department of Energy and ADA Environmental Solutions are engaged in a project to develop commercial flue gas conditioning additives. The objective is to develop conditioning agents that can help improve particulate control performance of smaller or under-sized electrostatic precipitators on utility coal-fired boilers. The new chemicals will be used to control both the electrical resistivity and the adhesion or cohesivity of the fly ash. There is a need to provide cost-effective and safer alternatives to traditional flue gas conditioning with SO{sub 3} and ammonia. During this reporting quarter, performance testing of flue gas conditioning was underway at the PacifiCorp Jim Bridger Power Plant. The product tested, ADA-43, was a combination resistivity modifier with cohesivity polymers. This represents the first long-term full-scale testing of this class of products. Modifications to the flue gas conditioning system at Jim Bridger, including development of alternate injection lances, was also undertaken to improve chemical spray distribution and to avoid spray deposition to duct interior surfaces. Also in this quarter, a firm commitment was received for another long-term test of the cohesivity additives. This plant fires a bituminous coal and has opacity and particulate emissions performance issues related to fly ash re-entrainment. Ammonia conditioning …
Date:
May 1, 2002
Creator:
Baldrey, Kenneth E.
Object Type:
Report
System:
The UNT Digital Library
Aerosol Property Comparison Within and Above the ABL at the ARM Program SGP Site
This thesis determines what, if any, measurements of aerosol properties made at the Earth surface are representative of those within the entire air column. Data from the Atmospheric Radiation Measurement site at the Southern Great Plains, the only location in the world where ground-based and in situ airborne measurements are routinely made. Flight legs during the one-year period from March 2000 were categorized as either within or above the atmospheric boundary layer (ABL) by use of an objective mixing height determination technique. Correlations between aerosol properties measured at the surface and those within and above the ABL were computed. Aerosol extensive and intensive properties measured at the surface were found representative of values within the ABL, but not of within the free atmosphere.
Date:
May 1, 2002
Creator:
Delle Monache, L
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
The Age, Volume 25, Number 5, May 2002
Monthly publication containing information related to Chambers County, Texas, including current events of the Chambers County Historical Commission, the Wallisville Heritage Park, and the Chambers County historical and genealogical societies; reprinted newspaper articles about county events and citizens; and historical news and records.
Date:
May 2002
Creator:
Wallisville Heritage Park (Organization)
Object Type:
Journal/Magazine/Newsletter
System:
The Portal to Texas History
Allied Partners: Your Connection to Energy Efficiency, Productivity, and Profits
Brochure to promote interest in Allied Partnerships with DOE's Office of Energy Efficiency and Renewable Energy among industrial manufacturers, suppliers, trade associations, and other organizations.
Date:
May 1, 2002
Creator:
unknown
Object Type:
Text
System:
The UNT Digital Library
Altus Times (Altus, Okla.), Vol. 104, No. 39, Ed. 1 Wednesday, May 1, 2002
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
May 1, 2002
Creator:
Bush, Michael
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
The Alvin Advertiser (Alvin, Tex.), Ed. 1 Wednesday, May 1, 2002
Weekly newspaper from Alvin, Texas that includes local, state, and national news along with advertising.
Date:
May 1, 2002
Creator:
Schwind, Jim & Holton, Kathleen
Object Type:
Newspaper
System:
The Portal to Texas History
Analysis of Potential Benefits and Costs of Adopting ASHRAE Standard 90.1-1999 as a Commercial Building Energy Code in Illinois Jurisdictions
ASHRAE Standard 90.1-1999 was developed in an effort to set minimum requirements for energy efficienty design and construction of new commercial buildings. This report assesses the benefits and costs of adopting this standard as the building energy code in Illinois. Energy and economic impacts are estimated using BLAST combined with a Life-Cycle Cost approach to assess corresponding economic costs and benefits.
Date:
May 1, 2002
Creator:
Belzer, David B.; Cort, Katherine A.; Winiarski, David W.; Richman, Eric E. & Friedrich, Michele
Object Type:
Report
System:
The UNT Digital Library
Analysis of potential for jet-impingement erosion from leaking steam generator tubes during severe accidents.
This report summarizes analytical evaluation of crack-opening areas and leak rates of superheated steam through flaws in steam generator tubes and erosion of neighboring tubes due to jet impingement of superheated steam with entrained particles from core debris created during severe accidents. An analytical model for calculating crack-opening area as a function of time and temperature was validated with tests on tubes with machined flaws. A three-dimensional computational fluid dynamics code was used to calculate the jet velocity impinging on neighboring tubes as a function of tube spacing and crack-opening area. Erosion tests were conducted in a high-temperature, high-velocity erosion rig at the University of Cincinnati, using micrometer-sized nickel particles mixed in with high-temperature gas from a burner. The erosion results, together with analytical models, were used to estimate the erosive effects of superheated steam with entrained aerosols from the core during severe accidents.
Date:
May 1, 2002
Creator:
Majumdar, S.; Diercks, D. R.; Shack, W. J. & Technology, Energy
Object Type:
Report
System:
The UNT Digital Library
Analysis of Staining Observed on Structures in the Georgetown, South Carolina Area
Beginning around 1970, the Georgetown, SC, community complained about black dust and red stains collecting on houses, cars, boats, and other structures. The community, through the South Carolina Department of Health and Environmental Control (SCDHEC), seeks to identify the source or cause of the staining and ways to reduce or eliminate it in the future.
Date:
May 2002
Creator:
Cramer, Stephen D.; Covino, Bernard S., Jr. & Govier, R. Dale
Object Type:
Report
System:
The UNT Digital Library
An Analysis of the Effectiveness of Computer Assisted Instruction in General Chemistry at an Urban University.
The science-major General Chemistry sequence offered at the University of Houston has been investigated with respect to the effectiveness of recent incorporation of various levels of computer technology. As part of this investigation, questionnaire responses, student evaluations and grade averages and distributions from up to the last ten years have been analyzed and compared. Increased use of web-based material is both popular and effective, particularly with respect to providing extra information and supplemental questions. Instructor contact via e-mail is also well-received. Both uses of technology should be encouraged. In contrast, electronic classroom presentation is less popular. While initial use may lead to improved grades and retention, these levels decrease quickly, possibly due to a reduction in instructor spontaneity.
Date:
May 2002
Creator:
McGuffey, Angela
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Analysis of the GaInP/GaAs/1-eV/Ge Cell and Related Structures for Terrestrial Concentrator Application: Preprint
This conference paper describes the analysis of the potential of GaInP/GaAs/1-eV/Ge four-junction solar cell to improve on the efficiency of the state-of-the-art GaInP/GaAs/Ge benchmark. We emphasize three factors: (1) The newly proposed terrestrial concentrator spectrum has a lower ratio of red to blue light than does the old AM1.5 direct standard spectrum. (2) Standard two-layer antireflection coatings do not provide near-zero reflectance over the full spectral range of interest for these devices. (3) GaInNAs junctions used to date for the 1-eV junction have quantum efficiencies less than {approx}75%. These factors all limit the device current, adversely affecting the four-junction efficiency. We discuss strategies for ameliorating this problem, including going to alternate structures such as a GaInP/GaAs/0.9-eV three-junction device.
Date:
May 1, 2002
Creator:
Friedman, D. J.; Kurtz, S. R. & Geisz, J. F.
Object Type:
Article
System:
The UNT Digital Library
And Drops of Rain Fall Like Tears: A Composition for Electroacoustic Music and Video
And Drops of Rain Fall Like Tears is a composition for electroacoustic music with an optional ambient video component. The composition consists of a single movement electroacoustic work twenty-two minutes in duration. The piece creates an immersive sonic environment within the confines of a typical concert space, thereby recreating the powerful temper and subtle beauty of nature from different sonic perspectives. The paper is divided into four chapters, each discussing an element of the piece in detail. The introduction presents background information and compositional approach for the composition. Chapters 1 through 4 present detailed information related to the creation of both the electroacoustic music and video elements of the piece. Chapter 4 contains relevant information to the performance of the piece.
Date:
May 2002
Creator:
Thompson, Michael Allen
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
APIVT-Grown Silicon Thin Layers and PV Devices: Preprint
Large-grained (5-20 ..mu..m) polycrystalline silicon layers have been grown at intermediate temperatures of 750-950C directly on foreign substrates without a seeding layer by iodine vapor transport at atmospheric pressure with rates as high as 3 mm/min. A model is constructed to explain the atypical temperature dependence of growth rate. We have also used this technique to grow high-quality epitaxial layers on heavily doped CZ-Si and on upgraded MG-Si substrates. Possible solar cell structures of thin-layer polycrystalline silicon on foreign substrates with light trapping have been examined, compared, and optimized by two-dimensional device simulations. The effects of grain boundary re-combination on device performance are presented for two grain sizes of 2 and 20 mm. We found that 104 cm/s recombination velocity is adequate for 20-m m grain-sized thin silicon, whereas a very low recombination velocity of 103 cm/s must be accomplished in order to achieve reasonable performance for a 2- mm grain-sized polycrystalline silicon device.
Date:
May 1, 2002
Creator:
Wang, T. H.; Ciszek, T. F.; Page, M. R.; Bauer, R. E.; Wang, Q. & Landry, M. D.
Object Type:
Article
System:
The UNT Digital Library
Applicability of Nacelle Anemometer Measurements for Use in Turbine Power Performance Tests: Preprint
Collection of accurate wind speed data is one of the more problematic elements in conducting wind turbine power performance tests. IEC 61400-12 specifies meteorological tower placement between two and four rotor diameters upwind of the test turbine. However, use of an upwind meteorological tower can be difficult at some sites. In some cases, complex terrain near the turbine may make placement of an upwind tower impossible. In addition, purchase and erection of a meteorological tower can be expensive, particularly as the hub height of large turbines increases. Because of these concerns, wind farm owners and turbine manufacturers have expressed interest in the use of turbine nacelle-mounted anemometers for collection of wind speed data. The U.S. Department of Energy (DOE)-Electric Power Research Institute (EPRI) Wind Turbine Verification Program (TVP) has performed data collection and power performance tests at wind energy facilities located in the United States. The purpose of this paper is to evaluate the data gathered from the Big Spring, Texas; Algona, Iowa; and Springview, Nebraska, facilities to determine whether a meaningful relationship can be derived between meteorological-tower and nacelle-anemometer wind speed measurements for Vestas V47 and V66 turbines (Big Spring) and Enron Z-50 turbines (Algona and Springview).
Date:
May 1, 2002
Creator:
Smith, B.; Link, H.; Randall, G. & McCoy, T.
Object Type:
Article
System:
The UNT Digital Library
Application of the Finite Element Method to Some Simple Systems in One and Two Dimensions.
The finite element method (FEM) is reviewed and applied to the one-dimensional eigensystems of the isotropic harmonic oscillator, finite well, infinite well and radial hydrogen atom, and the two-dimensional eigensystems of the isotropic harmonic oscillator and the propagational modes of sound in a rectangular cavity. Computer codes that I developed were introduced and utilized to find accurate results for the FEM eigensolutions. One of the computer codes was modified and applied to the one-dimensional unbound quantum mechanical system of a square barrier potential and also provided accurate results.
Date:
May 2002
Creator:
Hunnell, Jason C.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Applications of ICP magnetic sector multicollector mass spectrometry to basic energy research. Final report for period December 1st, 1993 - May 31st, 2000
The primary aims of this research were threefold: to develop and utilize the new technique of multiple collector inductively coupled plasma mass spectrometry and apply it to problems in the earth, ocean, and environmental sciences; to develop new chronometers and improve existing chronometers to allow the accurate determination of the ages of geological features and processes; and to study natural fluid-mediated mass transfer processes and source of components in the crust and the oceans. This technique has now become the preferred method for the determination of the isotopic compositions of a variety of elements in the periodic table. The prototype instrument was used to explore a vast array of isotopic systems and demonstrate applicability to problems as different as the origin of the solar system and smelting methods in the Bronze Age. Highlights of the program are briefly summarized under the following topics: tungsten isotopes and the early solar system; trace siderophile and chalcophile element geochemistry; hafnium isotopes and the early development of the continents; evolution of lead isotopic compositions of the oceans; the isotopic composition and residence time of Hf in seawater; the isotopic compositions of Sr, Hf, Pb, and Nd in dust; U-Th disequilibrium dating of carbonates and …
Date:
May 1, 2002
Creator:
Halliday, A.N.
Object Type:
Report
System:
The UNT Digital Library
Approach to Quantum Information starting from Bell's Inequality (Part I) and Statistical Analysis of Time Series Corresponding to Complex Processes (Part II)
Access:
Use of this item is restricted to the UNT Community
I: Quantum information obeys laws that subtly extend those governing classical information, making possible novel effect such as cryptography and quantum computation. Quantum computations are extremely sensitive to disruption by interaction of the computer with its environment, but this problem can be overcome by recently developed quantum versions of classical error-correcting codes and fault-tolerant circuits. Based on these ideas, the purpose of this paper is to provide an approach to quantum information by analyzing and demonstrating Bell's inequality and by discussing the problems related to decoherence and error-correcting. II: The growing need for a better understanding of complex processes has stimulated the development of new and more advanced data analysis techniques. The purpose of this research was to investigate some of the already existing techniques (Hurst's rescaled range and relative dispersion analysis), to develop a software able to process time series with these techniques, and to get familiar with the theory of diffusion processes.
Date:
May 2002
Creator:
Failla, Roberto
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library