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Novel ways of depositing ZnTe films by a solution growth technique

Description: Cu-doped ZnTe films, <1000{Angstrom}, were reproducibly deposited for the first time by an electrochemical method. A CdTe/CdS/ITO/glass substrate is externally short circuited to a zinc counter electrode in an aqueous bath consisting of ZnCl{sub 2} and TeO{sub 2} to complete an electrochemical cell. Control of both pH and TeO{sub 2} concentration was necessary to deposit single phase ZnTe films. A copper complex was added to the bath to control the ZnTe conductivity and dope the films p-type. CdTe/CdS solar cells using the ZnTe:Cu as the primary contact to the CdTe have achieved efficiencies of {approximately}9%. 15 refs., 7 figs., 2 tabs.
Date: June 1, 1991
Creator: Birkmire, R.W. (Delaware Univ., Newark, DE (USA). Inst. of Energy Conversion)
Partner: UNT Libraries Government Documents Department

Status and future opportunities for conversion of synthesis gas to liquid energy fuels: Final report

Description: The manufacture of liquid energy fuels from syngas (a mixture of H[sub 2] and CO, usually containing CO[sub 2]) is of growing importance and enormous potential because: (1) Abundant US supplies of coal, gas, and biomass can be used to provide the needed syngas. (2) The liquid fuels produced, oxygenates or hydrocarbons, can help lessen environmental pollution. Indeed, oxygenates are required to a significant extent by the Clean Air Act Amendments (CAAA) of 1990. (3) Such liquid synfuels make possible high engine efficiencies because they have high octane or cetane ratings. (4) There is new, significantly improved technology for converting syngas to liquid fuels and promising opportunities for further improvements. This is the subject of this report. The purpose of this report is to provide an account and evaluative assessment of advances in the technology for producing liquid energy fuels from syngas and to suggest opportunities for future research deemed promising for practical processes. Much of the improved technology for selective synthesis of desired fuels from syngas has resulted from advances in catalytic chemistry. However, novel process engineering has been particularly important recently, utilizing known catalysts in new configurations to create new catalytic processes. This report is an update of the 1988 study Catalysts for Fuels from Syngas: New Directions for Research (Mills 1988), which is included as Appendix A. Technology for manufacture of syngas is not part of this study. The manufacture of liquid synfuels is capital intensive. Thus, in evaluating advances in fuels technology, focus is on the potential for improved economics, particularly on lowering plant investment costs. A second important criteria is the potential for environmental benefits. The discussion is concerned with two types of hydrocarbon fuels and three types of oxygenate fuels that can be synthesized from syngas. Seven alternative reaction pathways are involved.
Date: May 1, 1993
Creator: Mills, G. (Delaware Univ., Newark, DE (United States). Center for Catalytic Science and Technology)
Partner: UNT Libraries Government Documents Department

A novel smoothing routine for the data processing in thermogravimetric analysis

Description: For a certain short interval of a TG scan, the correlation between mass and time is linear. A smoothing and filtering routine based on use of linear regression and error analysis was developed and successfully applied in the TG data processing. This method provides a filter to smooth the noise fluctuations and, at the same time, to introduce no distortions into the TGA experimental data. The computer program required is quite simple and effective. The method used in the program promises auto-convergence.
Date: December 31, 1996
Creator: Wang, Keyu; Wang, Shaojie; Huang, He; Klein, M.T. & Calkins, W.H.
Partner: UNT Libraries Government Documents Department

Fundamentals of polycrystalline thin film materials and devices

Description: This report presents the results of a one-year research program on polycrystalline thin-film solar cells. The research was conducted to better understand the limitations and potential of solar cells using CuInSe{sub 2} and CdTe by systematically investigating the fundamental relationships linking material processing, material properties, and device behavior. By selenizing Cu and In layers, we fabricated device-quality CuInSe{sub 2} thin films and demonstrated a CuInSe{sub 2} solar cell with 7% efficiency. We added Ga, to increase the band gap of CuInSe{sub 2} devices to increase the open-circuit voltage to 0.55 V. We fabricated and analyzed Cu(InGa)Se{sub 2}/CuInSe{sub 2} devices to demonstrate the potential for combining the benefits of higher V{sub oc} while retaining the current-generating capacity of CuInSe{sub 2}. We fabricated an innovative superstrate device design with more than 5% efficiency, as well as a bifacial spectral-response technique for determining the electron diffusion length and optical absorption coefficient of CuInSe{sub 2} in an operational cell. The diffusion length was found to be greater than 1 {mu}m. We qualitatively modeled the effect of reducing heat treatments in hydrogen and oxidizing treatments in air on the I-V behavior of CuInSe{sub 2} devices. We also investigated post-deposition heat treatments and chemical processing and used them to fabricate a 9.6%-efficient CdTe/CdS solar cell using physical vapor deposition.
Date: January 1, 1991
Creator: Baron, B.N.; Birkmire, R.W.; Phillips, J.E.; Shafarman, W.N.; Hegedus, S.S. & McCandless, B.E. (Delaware Univ., Newark, DE (USA). Inst. of Energy Conversion)
Partner: UNT Libraries Government Documents Department

Molecular biology in studies of oceanic primary production

Description: Remote sensing and the use of moored in situ instrumentation has greatly improved our ability to measure phytoplankton chlorophyll and photosynthesis on global scales with high temporal resolution. However, the interpretation of these measurements and their significance with respect to the biogeochemical cycling of carbon relies on their relationship with physiological and biochemical processes in phytoplankton. For example, the use of satellite images of surface chlorophyll to estimate primary production is often based on the functional relationship between photosynthesis and irradiance. A variety of environmental factors such as light, temperature, nutrient availability affect the photosynthesis/irradiance (P vs I) relationship in phytoplankton. We present three examples showing how molecular biology can be used to provide basic insight into the factors controlling primary productivity at three different levels of complexity: 1. Studies of light intensity regulation in unicellular alga show how molecular biology can help understand the processing of environmental cues leading to the regulation of photosynthetic gene expression. 2. Probing of the photosynthetic apparatus using molecular techniques can be used to test existing mechanistic models derived from the interpretation of physiological and biophysical measurements. 3. Exploratory work on the expression of specific proteins during nutrient-limited growth of phytoplankton may lead to the identification and production of molecular probes for field studies.
Date: January 1, 1992
Creator: LaRoche, J.; Falkowski, P.G. (Brookhaven National Lab., Upton, NY (United States)) & Geider, R. (Delaware Univ., Lewes, DE (United States). Coll. of Marine Studies)
Partner: UNT Libraries Government Documents Department

Structured hints : extracting and abstracting domain expertise.

Description: We propose a new framework for providing information to help optimize domain-specific application codes. Its design addresses problems that derive from the widening gap between the domain problem statement by domain experts and the architectural details of new and future high-end computing systems. The design is particularly well suited to program execution models that incorporate dynamic adaptive methodologies for live tuning of program performance and resource utilization. This new framework, which we call 'structured hints', couples a vocabulary of annotations to a suite of performance metrics. The immediate target is development of a process by which a domain expert describes characteristics of objects and methods in the application code that would not be readily apparent to the compiler; the domain expert provides further information about what quantities might provide the best indications of desirable effect; and the interactive preprocessor identifies potential opportunities for the domain expert to evaluate. Our development of these ideas is progressing in stages from case study, through manual implementation, to automatic or semi-automatic implementation. In this paper we discuss results from our case study, an examination of a large simulation of a neural network modeled after the neocortex.
Date: March 16, 2009
Creator: Hereld, M.; Stevens, R.; Sterling, T.; Gao, G. R.; Science, Mathematics and Computer; Tech., California Inst. of et al.
Partner: UNT Libraries Government Documents Department

Development of an experimental data base and theories for prediction of thermodynamic properties of aqueous electrolytes and nonelectrolytes of geochemical significance at supercritical temperatures and pressures

Description: This project is divided into method experimental measurements, theoretical development, and geochemical applications. We have completed experimental volumetric measurements on aqueous solutions of CO{sub 2} H{sub 2}S, CH{sub 4}, NH{sub 3} and B(OH){sub 3} at 25 to 432{degree}C and 280 and 350 bar. A vibrating tube densitometer that allows density measurements near bubble point and also measures the bubble pressure was developed and used to measure densities and bubble pressures of aqueous Co{sub 2}. Heat capacity measurements should be completed by the end of the grant period. Simulations of models for methane in water at temperatures to 1000{degrees}C are in progress. In order to facilitate these free energy calculations the possible errors associated with the calculations have been explored in two papers (Wood, 1991; Wood et al., 1991) and methods of controlling and estimating these errors have been developed. Applications of the new data to geochemical processes is now possible. Efforts have focussed on extracting equilibrium constants for carbonic acid dissociation at supercritical condition from published experiments on mineral equilibria in H{sub 2}0-CO{sub 2} fluids (Boehlke and Shock, 1990; and in prep.). As a result, estimates of pKa for carbonic acid are now available at temperatures from 300 to 750{degrees}C and pressures from 1 to 7 kilobars. They will be combined with {bar V}{sup {degree}} and {bar C}p{sup {degree}} data for CO{sup 2}(aq) to improve geochemical calculations.
Date: February 24, 1992
Creator: Wood, R.H.; Hnedkovsky, L.; Lin, Ching Lung (Delaware Univ., Newark, DE (United States). Dept. of Chemistry and Biochemistry) & Shock, E.L. (Washington Univ., St. Louis, MO (United States). Dept. of Earth and Planetary Sciences)
Partner: UNT Libraries Government Documents Department

The physical properties of microcellular composite foams

Description: Recently we reported on a method of preparing microcellular composite foams. In this procedure an open-celled polystyrene foam is prepared by the polymerization of a high-internal-phase water-in-oil emulsion containing styrene, divinylbenzene, surfactant, free-radial initiator and water. After drying, the cells of the polystyrene foam are then filled with other materials such as aerogel or resoles. The physical properties of these materials, e.g., surface area, density, thermal conductivity, and compressive strength will be presented. 10 refs., 1 fig., 3 tabs.
Date: January 1, 1989
Creator: Nyitray, A.M.; Williams, J.M.; Onn, D.; Witek, A. (Los Alamos National Lab., NM (USA) & Delaware Univ., Newark, DE (USA). Applied Thermal Physics Lab.)
Partner: UNT Libraries Government Documents Department

Polycrystalline thin film materials and devices

Description: Results of Phase II of a research program on polycrystalline thin film heterojunction solar cells are presented. Relations between processing, materials properties and device performance were studied. The analysis of these solar cells explains how minority carrier recombination at the interface and at grain boundaries can be reduced by doping of windows and absorber layers, such as in high efficiency CdTe and CuInSe{sub 2} based solar cells. The additional geometric dimension introduced by the polycrystallinity must be taken into consideration. The solar cells are limited by the diode current, caused by recombination in the space charge region. J-V characteristics of CuInSe{sub 2}/(CdZn)S cells were analyzed. Current-voltage and spectral response measurements were also made on high efficiency CdTe/CdS thin film solar cells prepared by vacuum evaporation. Cu-In bilayers were reacted with Se and H{sub 2}Se gas to form CuInSe{sub 2} films; the reaction pathways and the precursor were studied. Several approaches to fabrication of these thin film solar cells in a superstrate configuration were explored. A self-consistent picture of the effects of processing on the evolution of CdTe cells was developed.
Date: October 1, 1992
Creator: Baron, B.N.; Birkmire, R.W.; Phillips, J.E.; Shafarman, W.N.; Hegedus, S.S. & McCandless, B.E. (Delaware Univ., Newark, DE (United States). Inst. of Energy Conversion)
Partner: UNT Libraries Government Documents Department

Soft x-ray emission from classical novae in outburst

Description: Theoretical modeling of novae in outburst predicts that they should be active emitters of radiation at soft x-ray wavelengths twice during their outburst. The first time occurs very early in the outburst when only a very sensitive all sky survey will be able to detect them. This period lasts only a few hours for the very fastest novae. They again become bright in x-rays late in the outburst when the remnant object becomes very hot and is still luminous. Both simulations and observations show that novae can remain very hot for months to years. It is important to observe them at these late times because a measurement both of the flux and temperature can provide information about the mass of the white dwarf, the turn-off time scale, and the energy budget of the outburst. 8 refs., 2 figs.
Date: January 1, 1989
Creator: Starrfield, S. (Los Alamos National Lab., NM (USA) Arizona State Univ., Tempe, AZ (USA). Dept. of Physics and Astronomy); Truran, J.W. (Illinois Univ., Urbana, IL (USA). Dept. of Astronomy); Sparks, W.M. (Los Alamos National Lab., NM (USA)); Krautter, J. (Landessternwarte auf dem Koenigstuhl bei Heidelberg (Germany, F.R.)) & MacDonald, J. (Delaware Univ., Newark, DE (USA). Dept. of Physics and Ast
Partner: UNT Libraries Government Documents Department