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High-Temperature Superconductivity in Perspective

Description: This is the second of two OTA assessments on the subject of high-temperature superconductivity (HTS). As the title suggests, this study attempts to put HTS in perspective, both in terms of competing technologies (e.g., the more mature low-temperature superconductors), and in terms of the many technical and economic problems that must be overcome before HTS can be widely used.
Date: April 1990
Creator: United States. Congress. Office of Technology Assessment.
Partner: UNT Libraries Government Documents Department
open access

Commercializing high-temperature superconductivity

Description: Since the discovery of high-temperature superconductivity (HTS), research laboratories around the world have pushed the temperature limits steadily upward, opening the way to commercial applications with potentially revolutionary impacts. The scientific race is becoming a commercial race, one featuring U.S. and Japanese companies, and one that the United States could lose. Indeed, American firms may already be falling behind in commercializing the technology of superconductivity.
Date: June 1988
Creator: United States. Congress. Office of Technology Assessment.
Partner: UNT Libraries Government Documents Department
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Perspectives on Temperature in the Pacific Northwest's Fresh Waters

Description: This report provides a perspective on environmental water temperatures in the Pacific Northwest as they relate to the establishment of water temperature standards by the state and their review by the US Environmental Protection Agency. It is a companion to other detailed reviews of the literature on thermal effects on organisms important to the region. Many factors, both natural and anthropogenic, affect water temperatures in the region. Different environmental zones have characteristic temperatures and mechanisms that affect them. There are specific biotic adaptations to environmental temperatures. Life-cycle strategies of salmonids, in particular, are attuned to annual temperature patterns. Physiological and behavioral requirements on key species form the basis of present water temperature criteria, but may need to be augmented with more concern for environmental settings. There are many issues in the setting of standards, and these are discussed. There are also issues in compliance. Alternative temperature-regulating mechanisms are discussed, as are examples of actions to control water temperatures in the environment. Standards-setting is a social process for which this report should provide background and outline options, alternatives, limitations, and other points for discussion by those in the region.
Date: June 1, 1999
Creator: Coutant, C.C.
Partner: UNT Libraries Government Documents Department
open access

Thermal effects in intense laser-plasma interactions

Description: We present an overview of a new warm fluid model that incorporates leading-order kinetic corrections to the cold fluid model without making any near-equilibrium assumptions. In the quasi-static limit we obtain analytical expressions for the momentum spread and show excellent agreement with solutions of the full time-dependant equations. It is shown that over a large range of initial plasma temperatures, the fields are relatively insensitive to the pressure force. We discuss implications of this work for model validation.
Date: October 22, 2004
Creator: Shadwick, B.A.; Tarkenton, G.M. & Esarey, E.H.
Partner: UNT Libraries Government Documents Department
open access

A Search for Periodic and Quasi-Periodic Patterns in Select Proxy Data with a Goal to Understanding Temperature Variation

Description: In this work over 200 temperature proxy data sets have been analyzed to determine if periodic and or quasi-periodic patterns exist in the data sets. References to the journal articles where data are recorded are provided. Chapter 1 serves an introduction to the problem of temperature determination in providing information on how various proxy data sources are derived. Examples are given of the techniques followed in producing proxy data that predict temperature for each method used. In chapter 2 temperature proxy data spanning the last 4000 years, from 2,000 BCE to 2,000 CE, are analyzed to determine if overarching patterns exist in proxy data sets. An average of over 100 proxy data sets was used to produce Figure 4. An overview of the data shows that several “peaks” can be identified. The data were then subjected to analysis using a series of frequency modulated cosine waves. This analysis led to a function that can be expressed by equation 3. The literature was examined to determine what mathematical models had been published to fit the experimental proxy data for temperature. A number of attempts have been made to fit data from limited data sets with some degree of success. Some other papers have used a sinusoidal function to best fit the changes in the temperature. After consideration of many published papers and reviewing long time streams of proxy data that appeared to have sine wave patterns, a new model was proposed for trial. As the patterns observed showed “almost” repeating sine cycles, a frequency modulated sine wave was chosen to obtain a best fit function. Although other papers have used a sinusoidal function to best fit the changes in the temperature, the “best fit” was limited. Thus, it was decided that a frequency modulated sine wave may be a better model …
Date: May 2016
Creator: Otto, James (James Robert)
Partner: UNT Libraries
open access

Variable-temperature sample system for ion implantation at -192 to +500/sup 0/C

Description: A variable-temperature sample system based on exchange-gas coupling was developed for ion-implantation use. The sample temperature can be controlled from -192/sup 0/C to +500/sup 0/C with rapid cooling. The system also has provisions for focusing and alignment of the ion beam, electron suppression, temperature monitoring, sample current measuring, and cryo-shielding. Design considerations and operating characteristics are discussed. 5 figures.
Date: April 1, 1978
Creator: Fuller, C. T.
Partner: UNT Libraries Government Documents Department
open access

Temperature dependence of phonons in pyrolitic graphite

Description: Dispersion curves for longitudinal and transverse phonons propagating along and near the c-axis in pyrolitic graphite at temperatures between 4/sup 0/K and 1500/sup 0/C have been measured by neutron spectroscopy. The observed frequencies decrease markedly with increasing temperature (except for the transverse optical ''rippling'' modes in the hexagonal planes). The neutron groups show interesting asymmetrical broadening ascribed to interference between one phonon and many phonon processes.
Date: January 1, 1977
Creator: Brockhouse, B.N. & Shirane, G.
Partner: UNT Libraries Government Documents Department
open access

Real-Time Temperature Measurement in a Vacuum Degasser Using Optical Pyrometry

Description: The objective of the research was the development of a fiber-coupled, optical pyrometer for continuous temperature measurement in a vacuum degasser that reduces process time, enhances process control, and eliminates manual or robot-operated thermocouples. Through the live testing performed at US Steel's Edgar Thompson Works, the challenges associated with making optical temperature measurements in a vacuum chamber were identified. As a result of these challenges it was determined that continuous temperature monitoring in RH-type degassers was not a viable alternative to standard immersion thermocouples. The project was not successful.
Date: February 14, 2007
Creator: Metrix, Michel Bonin - Process; Metrix, Peter Hues - Process; Metals, William Federoff - US Steel Nichloas Rymarchyk - Berry & Metals, Todd Smith - Berry
Partner: UNT Libraries Government Documents Department
open access

Dislocations and mechanical properties of single crystal niobium disilicide

Description: The mechanical properties of single crystal NbSi{sub 2} have been investigated along [0001] and 45{degree} from [0001] toward [11{bar 2}0] using a Nikon QM-2 hot hardness tester from room temperature to 900 C in vacuum. The hardness along [0001] increases from room temperature to 300 C followed by a sharp decrease in hardness with temperature which is accompanied by a large uplift observed surrounding the indentations. Dislocations surrounding the indentations at room temperature and 300 C were analyzed using techniques in transmission electron microscopy to find slip by <10{bar 1}0> dislocations at room temperature with a change in the active slip systems at 300 C. The hardness along a direction 45{degree} from [0001] toward [11{bar 2}0] sharply decreases with increasing temperature above room temperature. Coarse slip lines surround the indentations referring to slip on the basal plane.
Date: September 1, 1996
Creator: Maloy, S. A.; Chu, F.; Petrovic, J. J. & Mitchell, T. E.
Partner: UNT Libraries Government Documents Department
open access

Infrared Imaging of Temperature Distribution in a High Temperature X-Ray Diffraction Furnace

Description: High Temperature X-ray Diffraction (HTXRD) is a very powerful tool for studies of reaction kinetics, phase transformations, and lattice thermal expansion of advanced materials. Accurate temperature measurement is a critical part of the technique. Traditionally, thermocouples, thermistors, and optical pyrometers have been used for temperature control and measurement and temperature could only be measured at a single point. Infrared imaging was utilized in this study to characterize the thermal gradients resulting from various sample and furnace configurations in a commercial strip heater furnace. Furnace configurations include a metallic strip heater, with and without a secondary surround heater, or a surround heater alone. Sample configurations include low and high thermal conductivity powders and solids. The IR imaging results have been used to calibrate sample temperatures in the HTXRD furnace.
Date: April 5, 1999
Creator: Payzant, E. A. & Wang, H.
Partner: UNT Libraries Government Documents Department
open access

Transport From Overlapping Electron and Ion Driftwave Instabilities

Description: The electron temperature gradient (ETG) mode is a likely contributor to electron thermal transport in tokamaks. The ETG modes are dominantly unstable for poloidal wavelengths shorter than the ion gyroradius (high-k) where the ion response is adiabatic. Thus, they do not directly produce ion thermal or momentum transport or particle transport. Two potential mechanisms whereby ETG modes could produce transport in these channels are explored in this paper: a nonlinear coupling between high-k ETG modes and ions at low-k and a direct coupling when ETG modes and ion temperature gradient (ITG) modes are unstable in overlapping wavenumber ranges. It will be shown that the particle and momentum transport required to match experiment is small compared to the ETG driven electron thermal transport. Even quasilinearly ETG modes can produce ion transport if the ITG and ETG modes are both unstable at low-k. The implications of this for transport will be explored at the quasilinear level. A new gyro-Landau-fluid (GLF) closure model has been constructed in order to build a transport model which can include the coupling between electron and ion modes including trapped particles. The first growth rate spectra from this model will be shown to give an accurate approximation to the kinetic linear growth rates of drift-ballooning modes in tokamaks.
Date: July 2, 2004
Creator: Staebler, G. M.; Kinsey, J. E. & Waltz, R. E.
Partner: UNT Libraries Government Documents Department
open access

Observations on Ocean Temperatures in the Vicinity of Icebergs and in Other Parts of the Ocean

Description: Report issued by the Bureau of Standards over studies on ocean temperatures. Temperatures in the vicinity of icebergs are measured and compared with temperatures taken from other areas of the ocean. This report includes photographs, and illustrations.
Date: 1914
Creator: Waidner, C. W.; Dickinson, H. C. & Crowe, J. J.
Partner: UNT Libraries Government Documents Department
open access

Thermographic properties of eight blue-emitting phosphors

Description: We examined the effect of temperature on the light absorption and emission properties of eight phosphorescent compounds. These phosphors are commercially produced powders that emit mainly in the blue region when illuminated with ultraviolet light in the range 220 to 400 mn. Excitation and emission spectra measured over the range 20 to 350{degrees}C are examined for these phosphors. Data from the emission spectra indicate that there is a significant temperature dependence in this temperature range. In all eight phosphors, the maximum relative intensity decreased as the temperature increased. In some samples, the emission bandwidth and position also changed with temperature. Of these phosphors, BaMg{sub 2}Al{sub 16}O{sub 27}:Eu and Ba{sub 3}(PO{sub 4}){sub 2}:Eu are candidates for studies at higher temperatures.
Date: May 1, 1993
Creator: Cunningham, D. M.; Allison, S. W. & Smith, D. B.
Partner: UNT Libraries Government Documents Department
open access

A study on the temperature dependence of the isotropic Debye-Waller factor and the absorption potential of silicon using energy-filtered CBED technique

Description: Debye-Waller (D-W) factors are conventional determined by neutron or X-ray diffraction methods. Because of the difficulties in conducting high temperature X-ray and neutron diffraction experiments, D-W factors are rarely measured at temperatures above room temperature. Electron diffraction experiments in Transmission Electron Microscope (TEM) with hot stage attachment offers the potential for determination of D-W factors at high temperatures. This reports our attempts to determine the temperature dependence of the isotropic D-W factor and absorption potential, V{prime}{sub 220}, of silicon using CBED experiments and dynamical theory calculations.
Date: May 1, 1994
Creator: Zaluzec, N. J.; Swaminathan, S.; Altynov, S.; Fraser, H. L.; Jones, I. P. & Maher, D. M.
Partner: UNT Libraries Government Documents Department
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