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15,742 Matching Results
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Advanced system analysis for indirect methanol fuel cell power plants for transportation applications
The indirect methanol cell fuel concept actively pursued by the USDOE and General Motors Corporation proposes the development of an electrochemical engine'' (e.c.e.), an electrical generator capable for usually efficient and clean power production from methanol fuel for the transportation sector. This on-board generator works in consort with batteries to provide electrical power to drive propulsion motors for a range of electric vehicles. Success in this technology could do much to improve impacted environmental areas and to convert part of the transportation fleet to natural gas- and coal-derived methanol as the fuel source. These developments parallel work in Europe and Japan where various fuel cell powered vehicles, often fueled with tanked or hydride hydrogen, are under active development. Transportation applications present design challenges that are distinctly different from utility requirements, the thrust of most of previous fuel cell programs. In both cases, high conversion efficiency (fuel to electricity) is essential. However, transportation requirements dictate as well designs for high power densities, rapid transients including short times for system start up, and consumer safety. The e.c.e. system is formed from four interacting components: (1) the fuel processor; (2) the fuel cell stack; (3) the air compression and decompression device; and (4) …
Date:
January 1, 1990
Creator:
Vanderborgh, N.E.; McFarland, R.D. & Huff, J.R.
Object Type:
Article
System:
The UNT Digital Library
Advanced, time-resolved imaging techniques for electron-beam characterizations
Several unique time-resolved imaging techniques have been developed to address radio frequency (RF)-linac generated electron beams and the free-electron lasers (FEL) driven by such systems. The time structures of these beams involve a series of micropulses with 10 to 15-ps duration, separated by tens of nanoseconds. Mechanisms to convert the e-beam information to optical radiation include optical transition radiation (OTR), Cherenkov radiation, spontaneous emission radiation (SER), and the FEL mechanism itself. The use of gated, intensified television cameras and synchroscan and dual-sweep streak cameras to time-resolve these signals has greatly enhanced the power of these techniques. A brief review of the less familiar conversion mechanisms and electro-optic techniques is followed by a series of specific experimental examples from the RF linac FEL facilities at Los Alamos and Boeing (Seattle, WA). 23 refs., 35 figs., 3 tabs.
Date:
January 1, 1990
Creator:
Lumpkin, A. H.
Object Type:
Article
System:
The UNT Digital Library
Advanced water-cooled phosphoric acid fuel cell development
Fabrication of repeat parts for the small area short stack is nearing completion and assembly activities are being initiated. Electrolyte reservoir plates (ERPs) were completed and processed into integral separator plates, and acid fill of parts was initiated. Fabrication of electrodes was also completed, including catalyzation and applications of seals and matrices.
Date:
January 1, 1990
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Advances in spheromak understanding and parameters
A spheromak is a toroidally-shaped magnetized plasma configuration in which no material links the torus so that the topology of the spheromak boundary is spherical. The magnetic fields in the plasma are generated by the internal plasma currents. In the period of ten years since the properties of a nearly force-free spheromak configuration were described using single-fluid MHD theory, remarkable theoretical and experimental advances have been made. This paper highlights some of that work. Spheromak not only have been successfully produced in the laboratory using a variety of methods, but also translated, compressed and stably sustained for many resistive-decay times. Spheromak formation, equilibrium and stability to current-driven modes have been successfully modeled by single-fluid MHD coupled with the concepts of magnetic helicity and relaxation toward the minimum-energy force-free state. There is evidence, however, that the relaxation mechanism which drives parallel plasma currents is due to effects beyond the scope of single-fluid resistive MHD. The confinement properties of clean spheromaks have been measured, and shown to be excellent, provided the fraction of open magnetic flux at the edge is decreased sufficiently. It has been shown theoretically how plasma {l angle}{beta}{r angle}{sub vol} limits of {approx}10% can be obtained by properly shaping …
Date:
January 1, 1990
Creator:
Fernandez, J. C.
Object Type:
Article
System:
The UNT Digital Library
Advantages of polarization experiments at RHIC
We point out various spin experiments that could be done if the polarized beam option is pursued at RHIC. The advantages of RHIC for investigating several current and future physics problems are discussed. In particular, the gluon spin dependent structure function of the nucleon could be measured cleanly and systematically. Relevant experience developed in conjunction with the Fermilab Polarized Beam program is also presented. 8 refs., 2 tabs.
Date:
January 1, 1990
Creator:
Underwood, D.G.
Object Type:
Article
System:
The UNT Digital Library
Aerodynamic testing of a rotating wind turbine blade
Aerodynamic, load, flow-visualization, and inflow measurements were taken on a downwind horizontal-axis wind turbine (HAWT). A video camera mounted on the rotor recorded video images of tufts attached to the low-pressure side of the blade. Strain gages, mounted every 10% of the blade's span, provided load and pressure measurements. Pressure taps at 32 chordwise positions recorded pressure distributions. Wind inflow was measured via a vertical-plane array of anemometers located 10 m upwind. The objectives of the test were to address whether airfoil pressure distributions measured on a rotating blade differed from those measured in the wind tunnel, if radial flow near or in the boundary layer of the airfoil affected pressure distributions, if dynamic stall could result in increased dynamic loads, and if the location of the separation boundary measured on the rotating blade agreed with that measured in two-dimensional flow in the wind tunnel. 6 refs., 9 figs., 1 tab.
Date:
January 1, 1990
Creator:
Butterfield, C.P. & Nelsen, E.N.
Object Type:
Article
System:
The UNT Digital Library
The AFDM (advanced fluid dynamics model) program: Scope and significance
The origins and goals of the advanced fluid dynamics model (AFDM) program are described, and the models, algorithm, and coding used in the resulting AFDM computer program are summarized. A sample fuel-steel boiling pool calculation is presented and compared with a similar SIMMER-II calculation. A subjective assessment of the AFDM developments is given, and areas where future work is possible are detailed. 10 refs.
Date:
January 1, 1990
Creator:
Bohl, W.R.; Parker, F.R. (Los Alamos National Lab., NM (USA)); Wilhelm, D. (Kernforschungszentrum Karlsruhe GmbH (Germany, F.R.). Inst. fuer Neutronenphysik und Reaktortechnik) & Berthier, J. (CEA Centre d'Etudes Nucleaires de Grenoble, 38 (France))
Object Type:
Article
System:
The UNT Digital Library
Affordable Spacecraft: Design and Launch Alternatives
This background paper examines several proposals for reducing the costs of spacecraft and other payloads and describes launch systems for implementing them. It is one of a series of products of a broad assessment of space transportation technologies undertaken by OTA at the request of the Senate Committee on Commerce, Science, and Transportation, and the House Committee on Science, Space, and Technology.
Date:
January 1990
Creator:
United States. Congress. Office of Technology Assessment.
Object Type:
Report
System:
The UNT Digital Library
Aging management of safety-related concrete structures in nuclear power plants
The Structural Aging Program has the overall objective of providing the US Nuclear Regulatory Commission with an improved basis for evaluating nuclear power plants for continued service. In meeting this objective, a materials property data base is being developed as well as an aging assessment methodology for concrete structures in nuclear power plants. Furthermore, studies are well under way to review and assess inservice inspection techniques for concrete structures and to develop a methodology which can be used for performing current as well as reliability-based future conditions assessments of these structures. 16 refs., 2 tabs.
Date:
January 1, 1990
Creator:
Naus, D.J.; Oland, C.B. (Oak Ridge National Lab., TN (USA)) & Arndt, E.G. (Nuclear Regulatory Commission, Washington, DC (USA))
Object Type:
Article
System:
The UNT Digital Library
Air ingestion into the external loops of a Savannah River Site reactor during a postulated LOCA
The outlets to the external loops of a Savannah River Site reactor become exposed to air as the moderator tank drains during a postulated LOCA. When this happens the behavior of the pumps is adversely affected as is the flow through the core. The problems encountered in the simulation are those of the non-condensable gas being pulled through a free surface into the loops and the behavior of the pumps with the two-phase mixture. This paper presents the results of a LOCA simulation, the attempts made to model the air flow into the loops, and the modeling of the pump under two-phase conditions. 3 refs., 6 figs., 1 tab.
Date:
January 1, 1990
Creator:
Taylor, G.A. & Bollinger, J.S.
Object Type:
Article
System:
The UNT Digital Library
ALARA at Nuclear Power Plants
Implementation of the As Low As Reasonably Achievable (ALARA) principle at nuclear power plants presents a continuing challenge for health physicists at utility corporate and plant levels, for plant designers, and for regulatory agencies. The relatively large collective doses at some plants are being addressed though a variety of dose reduction techniques. It is planned that this report will include material on historical aspects, management, valuation of dose reduction, quantitative and qualitative aspects of optimization, design, operational considerations, and training. The status of this work is summarized in this report. 30 refs., 1 fig., 6 tabs.
Date:
January 1, 1990
Creator:
Baum, J. W.
Object Type:
Article
System:
The UNT Digital Library
ALARA practices to minimize occupational radiation exposure from contamination at commercial nuclear power plants
None
Date:
January 1, 1990
Creator:
Reyes-Jimenez, J. & Tsoukalas, L. (Tennessee Univ., Knoxville, TN (United States). Dept. of Nuclear Engineering Oak Ridge National Lab., TN (United States))
Object Type:
Article
System:
The UNT Digital Library
Alaskan Water for California?: The Subsea Pipeline Option
This background paper focuses on one technological option for increasing the supply of fresh water to the Southwest-that of building a freshwater subsea pipeline to transport water from Alaska to California. Originally a suggestion by Governor Walter Hickel of Alaska, the proposal has recently attracted attention in southern California.
Date:
January 1990
Creator:
United States. Congress. Office of Technology Assessment.
Object Type:
Report
System:
The UNT Digital Library
Alcohol Transportation Fuels Demonstration Program
Hawaii has abundant natural energy resources, especially biomass, that could be used to produce alternative fuels for ground transportation and electricity. This report summarizes activities performed during 1988 to June 1991 in the first phase of the Alcohol Transportation Fuels Demonstration Program. The Alcohol Transportation Fuels Demonstration Program was funded initially by the Energy Division of the State of Hawaii's Department of Business, Economic Development and Tourism, and then by the US Department of Energy. This program was intended to support the transition to an altemative transportation fuel, methanol, by demonstrating the use of methanol fuel and methanol-fueled vehicles, and solving the problems associated with that fuel. Specific objectives include surveying renewable energy resources and ground transportation in Hawaii; installing a model methanol fueling station; demonstrating a methanol-fueled fleet of (spark-ignition engine) vehicles; evaluating modification strategies for methanol-fueled diesel engines and fuel additives; and investigating the transition to methanol fueling. All major objectives of Phase I were met (survey of local renewable resources and ground transportation, installation of methanol refueling station, fleet demonstration, diesel engine modification and additive evaluation, and dissemination of information on alternative fueling), and some specific problems (e.g., relating to methanol fuel contamination during handling and refueling) …
Date:
January 1, 1990
Creator:
Kinoshita, C. M.
Object Type:
Report
System:
The UNT Digital Library
Algorithmic chemistry: A model for functional self-organization
We conjecture that adaptive systems are characterized by a self- referential loop in which combinatorial objects encode functions that act back on these objects. A model for this loop is presented. It uses a simple and powerful recursive language to map character strings into algorithms that symbolically manipulate strings. The interaction between algorithms, i.e. functions, can be defined in a natural way within the language. The behavior of a fixed size ensemble of functions acting on each other is studied under various conditions. The function gas,'' or Turing gas,'' evolves cooperative interaction patterns of considerable intricacy. Such patterns are observed to adapt under the influence of perturbations consisting in the addition of new random functions to the system. Completely different organizational architectures emerge depending on the availability of self-replicators.
Date:
January 1, 1990
Creator:
Fontana, W.
Object Type:
Article
System:
The UNT Digital Library
Algorithmic information content, Church-Turing thesis, physical entropy, and Maxwell's demon
Measurements convert alternative possibilities of its potential outcomes into the definiteness of the record'' -- data describing the actual outcome. The resulting decrease of statistical entropy has been, since the inception of the Maxwell's demon, regarded as a threat to the second law of thermodynamics. For, when the statistical entropy is employed as the measure of the useful work which can be extracted from the system, its decrease by the information gathering actions of the observer would lead one to believe that, at least from the observer's viewpoint, the second law can be violated. I show that the decrease of ignorance does not necessarily lead to the lowering of disorder of the measured physical system. Measurements can only convert uncertainty (quantified by the statistical entropy) into randomness of the outcome (given by the algorithmic information content of the data). The ability to extract useful work is measured by physical entropy, which is equal to the sum of these two measures of disorder. So defined physical entropy is, on the average, constant in course of the measurements carried out by the observer on an equilibrium system. 27 refs., 6 figs.
Date:
January 1, 1990
Creator:
Zurek, W.H.
Object Type:
Article
System:
The UNT Digital Library
Alkali/TX[sub 2] catalysts for CO/H[sub 2] conversion to C[sub 1]-C[sub 4] alcohols
The objective of this research is to investigate and develop novel catalysts for the conversion of coal-derived synthesis gas into C[sub 1]-C[sub 4] alcohols by a highly selective process. Therefore, the variations of catalyst activity and selectivity for the synthesis of alcohols from H[sub 2]/CO [le]1 synthesis gas for a series of A/TX[sub 2] compounds, where A is a surface alkali dopant, T is a transition metal, and X is a S, Se, or Te, will be determined. The alkali component A, which is essential for C-O and C-C bond forming reactions leading to alcohols, will be highly dispersed on the TX[sub 2] surfaces by using chemical vapor deposition (CVD) and chemical complexation/anchoring (CCA) methods. The target alcohol space time yields are of the order of 1 kg of alcohol product per kg of catalyst per hour and the target selectivity is > 90% to alcohols. Among the A/TX[sub 2] compounds initially investigated, preference will be given to A = Cs, T = Group VB element (V, Nb, Ta), and X = S or Se. So delimited A/TX[sub 2] catalysts possess the strongest base (Cs), and the CCA preparation method using crown ethers is expected not only to disperse the …
Date:
January 1, 1990
Creator:
Klier, Kamil; Herman, Richard G.; Richards, Michelle & Bastian, Roy D.
Object Type:
Report
System:
The UNT Digital Library
Alkane Photoreactions With Mercury Vapor
None
Date:
January 1, 1990
Creator:
Crabtree, R. H.
Object Type:
Report
System:
The UNT Digital Library
All hot spots'' are not equal
Introduction of discontinuities increases the sensitivity of energetic material to initiation by shock waves. We have experimental evidence that the particular nature of these discontinuities significantly changes this sensitivity. The observations are preliminary, but they are significant in our understanding of heterogeneous initiation. Data from these studies, combined with literature data on the shock sensitivity of pressed explosives, show quantitatively different responses for materials with the three types of voids. In materials with the same porosity, damage creates the most sensitive material, but pressed explosives are affected less, and the addition of microballoons creates the smallest change in sensitivity. The analysis of these data employs an interesting, and as yet unexplored, representation of shock sensitivity as a function of density. 7 refs., 5 figs.
Date:
January 1, 1990
Creator:
Ramsay, J.B. (Los Alamos National Lab., NM (USA)) & Richter, H.P. (Naval Weapons Center, China Lake, CA (USA))
Object Type:
Article
System:
The UNT Digital Library
An alpha/beta/gamma health physics instrument with pulse-shape discrimination
A recent breakthrough in alpha scintillation detector design supports the feasibility of extending this new technology to the development of a monolithic alpha/beta/gamma ({alpha}/{beta}/{gamma}) scintillation detector. The new scintillator is physically robust and chemically resistant to environmental conditions encountered in radiation monitoring, and yet inexpensive to manufacture. The use of pulse-shape discrimination electronics allows pulses from each scintillator to be separated for particle identification. An {alpha}/{beta}/{gamma} detector has a wide variety of possible applications including laundry monitoring, wastewater monitoring, air sampling, and health physics instrumentation. 2 refs., 1 fig.
Date:
January 1, 1990
Creator:
McElhaney, S. A.; Chiles, M. M. & Ramsey, J. A.
Object Type:
Article
System:
The UNT Digital Library
Alpha-Particle Emission as a Probe of Nuclear Shapes and Structure Effects in Proton Evaporation Spectra
Emission barriers and subbarrier anisotropies from {alpha} decay of Sn* and Yb* compound nuclei are examined in the light of calculations incorporating deformation effects in the decay process. For the Yb* systems deformation which increases with spin is necessary to explain the data. For the Sn* systems the spectral shapes and anisotropies can be explained without deformation. For systems lighter than Sn this probe is not sensitive to the deformation. Energy spectra and angular correlations of evaporated protons from the {sup 52}Cr({sup 34}S, 2n2p){sup 82}Sr reaction were measured in coincidence with discrete transitions. Large shifts in proton spectra were observed when high spin states in different rotational bands are populated. They are interpreted as due to near-yrast stretched proton emission preferentially populating the yrast band by subbarrier protons. Simulations show that channel selected proton spectra cannot be used as probes of deformation.
Date:
January 1, 1990
Creator:
Nicolis, N. G.; Sarantites, D. G.; Abenante, V.; Adler, L. A.; Dilmanian, F .A.; Majka, Z. et al.
Object Type:
Article
System:
The UNT Digital Library
Alpha-Particles as Probes of Nuclear Shape and Structure Effects in Proton Evaporation Spectra
The emission barriers and subbarrier anisotropies in the alpha-particle decay with respect to the spin direction on Sn and rare earth compound nuclei are examined in the light of recent calculations incorporating deformation effects in the decay process. For the Sn systems the spectral shapes and anisotropies can be examined without involving deformation. For the rare earth systems deformation which increases with spin is necessary to explain the data. Energy spectra and angular correlations of evaporated protons from the {sup 52}Cr ({sup 34}S, 2p2n){sup 82}Sr reaction were measured in coincidence with discrete transitions. Large shifts in proton spectra were observed when high spin states in different rotational bands are populated. These effects cannot be explained by statistical model calculations that do not include explicitly nuclear structure effects in the deexcitation process. They are interpreted as due to near-yrast stretched proton emission, which preferentially populates the yrast band by subbarrier protons.
Date:
January 1, 1990
Creator:
Sarantites, D. G.; Nicolis, N. G.; Abenante, V.; Majka, Z.; Semkow, T. M.; Baktash, C. et al.
Object Type:
Article
System:
The UNT Digital Library
Altered phenotypes in plants transformed with chimeric tobacco peroxidase genes
Peroxidases have been implicated in a variety of secondary metabolic reactions including lignification, cross-linking of cell wall polysaccharides, oxidation of indole-3-acetic acid, regulation of cell elongation, wound-healing, phenol oxidation, and pathogen defense. However, due to the many different isoenzymes and even more potential substrates, it has proven difficult to verify actual physiological roles for peroxidase. We are studying the molecular biology of the tobacco peroxidase genes, and have utilized genetic engineering techniques to produce transgenic plants which differ only in their expression of an individual peroxidase isoenzyme. Many of the in planta functions for any individual isoenzyme may be predicted through the morphological and physiological analysis of transformed plants.
Date:
January 1, 1990
Creator:
Lagrimini, L.M.
Object Type:
Article
System:
The UNT Digital Library
An alternative approach to disturbances in boundary layers
By modelling the boundary layer on a flat plate as a piece-wise linear velocity profile it is possible to analyze disturbances in the flow in a systematic manner. The approach is that of an initial-value, boundary-value problem but, unlike classical normal modes employed in stability theory, the solutions here can be obtained in closed form and they are non separable. A specific example is treated where the vertical component of the perturbation velocity is prescribed as a localized pulse initially. The amplitude is then depicted as a function of time and the coordinates of the plane of the flat plate at a fixed vertical location. The role of three-dimensionality and the initial transient period of development -- heretofore unknown -- are both shown to be of significant importance in the dynamics. An argument is given to strongly suggest that the origin of large-scale oscillations known to be prevalent in turbulent shear flows may well be explained using these bases. 15 refs., 8 figs.
Date:
January 1, 1990
Creator:
Easthope, P.F. & Criminale, W.O.
Object Type:
Report
System:
The UNT Digital Library