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Advanced Low-Temperature Fluid Bed Sorbents
This paper discusses the results obtained in an ongoing study geared towards developing advanced mixed-metal oxide sorbents for desulfurization of coal-derived fuel gases in the temperature range of 350 to 550{degrees}C. The paper focuses on the study related to the development of durable sorbents suitable for fluidized-bed application and addresses thermodynamic considerations, sulfidation kinetics, regenerability, and the physical and chemical characteristics of a number of novel sorbents.
Date:
December 31, 1996
Creator:
Abbasian, J.; Slimane, R. B. & Wangerow, J. R.
Object Type:
Article
System:
The UNT Digital Library
Surface modified coals for enhanced catalyst dispersion and liquefaction. Quarterly report, 1996
The aim of this work is to enhance catalyst loading and dispersion in coal for improved liquefaction by preadsorption of surfactants onto coal. The application of surfactants to coal beneficiation and coal-water slurry preparation is well known. However, the effects of surfactants on catalyst loading and dispersion prior to coal conversion processes have not been investigated. The current work is focused on the influence of the cationic surfactant dodecyl dimethyl ethyl ammonium bromide (DDAB) and sodium dodecyl sulfate (SDS, anionic) on the surface properties of a bituminous coal and its molybdenum and iron uptake from solution. In the previous report, it was shown that molybdenum loading onto the coal was enhanced by preadsorption of DDAB. The optimum concentration of this surfactant for effective adsorption of molybdenum at the natural pH of the coal slurry has been determined to be in the 0.1 to 0.25 M range. Preadsorption of SDS onto the coal was found to increase the uptake of iron by the coal; iron loading increased with increase in the concentration of the catalyst precursor. This observation is attributed to the increase in the negative surface charge properties of the coal with increase in the concentration of the surfactant. The …
Date:
December 31, 1996
Creator:
Abotsi, G.M.K.
Object Type:
Report
System:
The UNT Digital Library
The Nimrod computational workbench: a case study in desktop metacomputing
The coordinated use of geographically distributed computers, or metacomputing, can in principle provide more accessible and cost- effective supercomputing than conventional high-performance systems. However, we lack evidence that metacomputing systems can be made easily usable, or that there exist large numbers of applications able to exploit metacomputing resources. In this paper, we present work that addresses both these concerns. The basis for this work is a system called Nimrod that provides a desktop problem-solving environment for parametric experiments. We describe how Nimrod has been extended to support the scheduling of computational resources located in a wide-area environment, and report on an experiment in which Nimrod was used to schedule a large parametric study across the Australian Internet. The experiment provided both new scientific results and insights into Nimrod capabilities. We relate the results of this experiment to lessons learned from the I-WAY distributed computing experiment, and draw conclusions as to how Nimrod and I-WAY- like computing environments should be developed to support desktop metacomputing.
Date:
December 31, 1996
Creator:
Abramson, D.; Sosic, R.; Foster, I.; Giddy, J.; Lewis, A. & White, N.
Object Type:
Article
System:
The UNT Digital Library
Composition and function in AB{sub 5} hydride electrodes
Multicomponent AB, hydrides are attractive replacements for the cadmium electrode in nickel - cadmium batteries. This paper is concerned with the differential effects of Ni substitution by cobalt, Mn and Al upon electrode corrosion and capacity, using alloys having the generic composition of Al(NiCoMnAl){sub 5} and similar to those used for the preparation of commercial battery electrodes. The corrosion of metal hydride electrodes is determined by two factors, surface passivation due to the presence of surface oxides or hydroxides and crystal lattice expansion - contraction the charge - discharge process. Thus, in addition to determining the effects of Ni substitution we will also address the question of whether an observed change is due to a change lattice expansion or to a change in surface passivation, e.g. the formation a corrosion resistant oxide layer.
Date:
December 31, 1996
Creator:
Adzic, G. D.; Johnson, J. R.; Mukerjee, S.; McBreen, J. & Reilly, J. J.
Object Type:
Report
System:
The UNT Digital Library
Growth and mechanical and tribological characterization of multi-layer hard carbon films
Vacuum-arc deposition is used to deposit multilayer C films by modulating the sample bias during deposition. Effect of varying the sublayer thickness in multilayer films consisting of alternating layers of ``hard`` (68.4 GPa, -100 V bias) and ``soft`` (27.5 GPa, - 200 V bias) was investigated. Films consisting of equal thickness layers of hard and soft material and an individual layer thickness varying from 10 to 35 nm were deposited. Mechanical property measurements were obtained by finite element modeling of nanoindentation load-displacement curves. The film hardness values were about 20% below the average of the component layers and relatively independent of the layer thickness. TEM revealed deterioration of the multilayer structure when the sublayer thickness was below 15 nm due to implantation damage of the hard layers caused by the energetic C{sup +} ions of the soft layers (-2000 V bias) deposited over them. Pin-on-disk wear tests show that the wear rate drops when sublayer thickness is decreased below 20 nm and remains constant with further decreases in the layer thickness.
Date:
December 31, 1996
Creator:
Ager, J.; Brown, I.; Monteiro, O.; Knapp, J.A.; Follstaedt, D.M.; Nastasi, M. et al.
Object Type:
Article
System:
The UNT Digital Library
Ash and pulverized coal deposition in combustors and gasifiers. Quarterly technical progress report, July 1, 1996--September 30, 1996
The computational model for simulating particle motions in turbulent flows was further developed and used to analyze the transport and dispersion of particles in a recirculating flow region. The model for resuspension of particles from surfaces in a gas flow is also further developed; it accounts for the surface adhesion as well as hydrodynamic forces and torques. It includes effects of the structure of near wall turbulent flows as well as surface roughness. In addition, a direct numerical simulation procedure for analyzing the particle removal process in turbulent gas flows is also developed. The sublayer model for evaluating the particle deposition in turbulent flows is being extended to include the effect of particle rebound. Further progress was also made in the experimental study of glass fiber transport and deposition in the aerosol wind tunnel.
Date:
December 31, 1996
Creator:
Ahmadi, G.
Object Type:
Report
System:
The UNT Digital Library
A micromachined surface acoustic wave sensor for detecting inert gases
Surface acoustic wave (SAW) sensors must be specifically designed for each application because many variables directly affect the acoustic wave velocity. In the present work, the authors have designed, fabricated, and tested an SAW sensor for detection of metastable states of He. The sensor consists of two sets of micromachined interdigitated transducers (IDTs) and delay lines fabricated by photolithography on a single Y-cut LiNbO{sub 3} substrate oriented for Z-propagation of the SAWs. One set is used as a reference and the other set employs a delay line coated with a titanium-based thin film sensitive to electrical conductivity changes when exposed to metastable states of He. The reference sensor is used to obtain a true frequency translation in relation to a voltage controlled oscillator. An operating frequency of 109 MHz has been used, and the IDT finger width is 8 {micro}m. Variation in electrical conductivity of the thin film at the delay line due to exposure to He is detected as a frequency shift in the assembly, which is then used as a measure of the amount of metastable He exposed to the sensing film on the SAW delay line. A variation in the He pressure versus frequency shifts indicates the …
Date:
December 31, 1996
Creator:
Ahuja, S.; Hersam, M.; Ross, C.; Chien, H. T. & Raptis, A. C.
Object Type:
Article
System:
The UNT Digital Library
Parameter optimization of a microfabricated surface acoustic wave sensor for inert gas detection
This work is related to designing, fabricating, and testing a surface acoustic wave sensor to be used for detecting metastable inert gases, particularly helium. The assembly consists of two microsensor configurations: (a) a reference device with no deposition at the delay line and (b) a sensing device with an Au-activated TiO{sub 2} e-beam-deposited thin film on the delay line. The interdigitated transducers and delay lines are fabricated by photolithography techniques on a single Y-cut LiNbO{sub 3} substrate oriented for Z-propagation of the acoustic waves. Variation in electrical conductivity of the Au-activated TiO{sub 2} film due to exposure to metastable He is translated as a frequency change in the assembly. Various characteristics of the surface acoustic microsensor have been studied to better understand and optimize the variation of acoustic wave velocity and the operating frequency of the microdevice. Methods for the TiO{sub 2} thin-film deposition are discussed.
Date:
December 31, 1996
Creator:
Ahuja, S.; Ross, C.; Chien, H. T. & Raptis, A. C.
Object Type:
Article
System:
The UNT Digital Library
Fischer-Tropsch synthesis in supercritical fluids. Quarterly technical progress report, April 1, 1996--June 30, 1996
For the task on diffusion coefficients of F-T products in supercritical fluids, we attempted to find a model for the {beta} parameter to predict the molecular diffusion coefficients to a high degree of accuracy so we may be able to predict both the molecular diffusion coefficient and thus the effective diffusivity a priori. The dependency of solvent/solute interactions on the {beta} parameter was analyzed and a correlation developed to predict the functionality. This allowed us to develop an empirical formula to correlate the molecular diffusion coefficient to ratios of mass, size, and density. Thus finally allowing for supercritical fluid diffusion predictions a priori. Figure 6 shows our predictions of the data available on the self diffusion coefficient of carbon dioxide (Chen, 1983; Takahashi and Iwasaki, 1966) ethylene (Arends et al., 1981; Baker et al., 1984), toluene (Baker et al., 1985) and chlorotrifuoromethane (Harris, 1978). The predictions, with no parameters adjusted from the data, are excellent with an average absolute error of 3.64%.
Date:
December 31, 1996
Creator:
Akgerman, A. & Bukur, D.B.
Object Type:
Report
System:
The UNT Digital Library
{sup 17}O NMR investigations of oxidative degradation in polymers
We have initiated studies using both solution and solid state magic angle spinning {sup 17}O NMR for a series of oxidatively aged polymers. This short note reports the solution {sup 17}O NMR for oxidatively degraded polypropylene, ethylene-propylene-diene, polyisoprene, and nitrile rubber. Enriched O{sub 2} is used during the accelerated aging. 3 figs, 7 refs.
Date:
December 31, 1996
Creator:
Alam, T. M.; Celina, M.; Assink, R. A.; Gillen, K. T. & Clough, R. L.
Object Type:
Article
System:
The UNT Digital Library
DANTSYS: a system for deterministic, neutral particle transport calculations
The THREEDANT code is the latest addition to our system of codes, DANTSYS, which perform neutral particle transport computations on a given system of interest. The system of codes is distinguished by geometrical or symmetry considerations. For example, ONEDANT and TWODANT are designed for one and two dimensional geometries respectively. We have TWOHEX for hexagonal geometries, TWODANT/GQ for arbitrary quadrilaterals in XY and RZ geometry, and THREEDANT for three-dimensional geometries. The design of this system of codes is such that they share the same input and edit module and hence the input and output is uniform for all the codes (with the obvious additions needed to specify each type of geometry). The codes in this system are also designed to be general purpose solving both eigenvalue and source driven problems. In this paper we concentrate on the THREEDANT module since there are special considerations that need to be taken into account when designing such a module. The main issues that need to be addressed in a three-dimensional transport solver are those of the computational time needed to solve a problem and the amount of storage needed to accomplish that solution. Of course both these issues are directly related to the …
Date:
December 31, 1996
Creator:
Alcouffe, R.E. & Baker, R.S.
Object Type:
Article
System:
The UNT Digital Library
The Boerne Star (Boerne, Tex.), Vol. 92, No. 35, Ed. 1 Friday, May 31, 1996
Semiweekly newspaper from Boerne, Texas that includes local, state, and national news along with advertising.
Date:
May 31, 1996
Creator:
Aldridge, Leon & D'Amico, Rob
Object Type:
Newspaper
System:
The Portal to Texas History
The Boerne Star (Boerne, Tex.), Vol. 92, No. 96, Ed. 1 Tuesday, December 31, 1996
Semiweekly newspaper from Boerne, Texas that includes local, state, and national news along with advertising.
Date:
December 31, 1996
Creator:
Aldridge, Leon & D'Amico, Rob
Object Type:
Newspaper
System:
The Portal to Texas History
The Boerne Star (Boerne, Tex.), Vol. 92, No. 5, Ed. 1 Wednesday, January 31, 1996
Weekly newspaper from Boerne, Texas that includes local, state, and national news along with advertising.
Date:
January 31, 1996
Creator:
Aldridge, Leon & Priddy, Travis
Object Type:
Newspaper
System:
The Portal to Texas History
Robotic control of whole blood processing in functional brain imaging research
This paper describes progress in automation of routine clinical laboratory tasks which support PET. The system examined is based on standard components of Zymark Corporation`s PyTechnology system. The system proved a reliable and robust source of laboratory automation modules suitable for automating a major task associated withe the clinical chemistry portions of PET.
Date:
December 31, 1996
Creator:
Alexoff, D.L.; King, P. & Gatley, S.J.
Object Type:
Article
System:
The UNT Digital Library
Preparation of AlAsSb and Mid-Infrared (3-5 {mu}m) Lasers by Metal-Organic Chemical Vapor Deposition
Mid-infrared (3-5 {mu}m) infrared lasers and LEDs are being developed for use in chemical sensor systems. As-rich, InAsSb heterostructures display unique electronic properties that are beneficial to the performance of these midwave infrared emitters. The authors have grown AlAs{sub 1{minus}x}Sb{sub x} epitaxial layers by metal-organic chemical vapor deposition using trimethylamine (TMAA) or ethyldimethylamine alane (EDMAA), triethylantimony (TESb) and arsine. They examined the growth of AlAs{sub 1{minus}x}Sb{sub x} using temperatures of 500 to 600 {degrees}C, pressures of 70 to 630 torr, V/III ratios of 1-27, and growth rates of 0.3 to 2.7 {mu}m/hour in a horizontal quartz reactor. The semi-metal properties of a p-GaAsSb/n-InAs heterojunction are utilized as a source for injection of electrons into the active region of lasers. A regrowth technique has been used to fabricate gain-guided lasers using AlAs{sub 1{minus}x}Sb{sub x} for optical confinement with either a strained InAsSb/InAs multi-quantum well (MQW) or an InAsSb/InAsP strained layer superlattice (SLS) as the active region. Under pulsed injection, the InAsSb/InAs MQW laser operated up to 210K with an emission wavelength of 3.8-3.9 {mu}m. Under pulsed optical pumping, the InAsSb/InAsP SLS operated to 240K with an emission wavelength of 3.5-3.7 {mu}m. LED emission has been observed with both active regions in …
Date:
December 31, 1996
Creator:
Allerman, A. A.; Biefeld, R. M. & Kurtz, S. R.
Object Type:
Article
System:
The UNT Digital Library
How significant is perceived environmental risk to business location decisions?
It has been argued that adverse perceptions of risk associated with high-level nuclear waste (HLNW) facilities will have significant impacts on the attraction of new, and the maintenance of existing business activities in areas in which adverse perceptions develop. We examine this proposition by the considering the importance of environmental amenities and a range of other factors to business location decisions using evidence from surveys of more than 400 manufacturing and business service establishments in Colorado and Utah. We show that the importance of environmental amenities varies according to a number of factors, in particular the type of product (manufactured product or business service), type of establishment (single-establishment firm or establishment of a multilocational firm) and establishment employment size. Policies designed to offset the loss of business activity that might result from adverse risk perceptions associated with HLNW facilities must therefore take into account how sensitive various forms of business activity present or likely to locate in any particular area might be to environmental factors.
Date:
December 31, 1996
Creator:
Allison, T. & Calzonetti, F.
Object Type:
Report
System:
The UNT Digital Library
The Sputter Generation of Negative Ion Beams
A brief review is given of recent progress toward a quantitative understanding of negative ion formation by sputtering from surfaces covered with fractional layers of highly electropositive adsorbates. Practical models developed for estimating changes in work functions {Delta}{phi} by electropositive adsorbates are described. The secondary negative ion generation process is examined through the use of composite energy/velocity dependent analytical models. These models are used to illustrate the effect of work function on the energy distributions of negative ions sputter ejected from a polycrystalline molybdenum surface covered with fractional layers of cesium. Predictions are also made of the functional dependence of the probability for negative ion formation on cesium coverage. The models predict energy distributions which are in basic disagreement with experimental observations, implying their inappropriateness for describing the sputter negative ion generation process. We have also developed a model for calculating sputter ratios based on the use of simple scaling procedures to bring Sigmund theory into close agreement with experimental observation accounting for the threshold effect. Scaling factors for projectile energies E > 1000 eV are found to be independent of energy while those for projectile energies E{sub th} < E < 1000 eV were found to be energy dependent. …
Date:
December 31, 1996
Creator:
Alton, G. D.
Object Type:
Article
System:
The UNT Digital Library
A Combination Thermal Dissociation/Electron Impact Ionization Source for RIB Generation
The flourishing interest in radioactive ion beams (RIBs) with intensities adequate for astrophysics and nuclear physics research place a premium on targets that will swiftly release trace amounts of short lived radio-nuclei in the presence of bulk quantities of target material and ion sources that have the capability of efficiently ionizing the release products. Because of the low probability of simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecules containing the element of interest with conventional, hot-cathode, electron-impact ion sources, the species of interest is often distributed in several mass channels in the form of molecular sideband beams and, consequently, the intensity is diluted. The authors have conceived an ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high efficiency characteristics of an electron impact ionization source to address these problems. If the concept proves to be a viable option, the source will be used as a complement to the electron beam plasma ion sources already in use at the HRIBF. The design features and principles of operation of the source are described in this article.
Date:
December 31, 1996
Creator:
Alton, G. D.; Cui, B. & Welton, R. F.
Object Type:
Article
System:
The UNT Digital Library
A New Concept Positive (Negative) Surface Ionization Source for RIB Applications
A versatile, new concept, spherical-geometry, positive (negative) surface-ionization source has been designed. fabricated, and tests completed which can operate in either positive- or negative-ion beam generation modes without mechanical changes to the source. The highly permeable, composite Ir/C has an intrinsic work function of 0 = 5.29 eV and can be used directly for the generation of positive-ion beams of highly electropositive elements. For negative-surface ionization, the work function is lowered by dynamic flow of a highly electropositive adsorbate such as Cs through the ionizer matrix. The results of initial testing indicate that the source is reliable, stable and easy to operate, with efficiencies for Cs{sup +} estimated to exceed 60% and as high as {approximately}50% for F{sup -} generation. The design features, operational principles, and initial performance of the source for generating Cs{sup +} and F{sup -}, when operated with Cs, are discussed in this article.
Date:
December 31, 1996
Creator:
Alton, G. D.; Welton, R. F. & Cui, B.
Object Type:
Article
System:
The UNT Digital Library
Finite element model update via Bayesian estimation and minimization of dynamic residuals
An algorithm is presented for updating finite element models based upon a minimization of dynamic residuals. The dynamic residual of interest is the force unbalance in the homogeneous form of the equations of motion arising from errors in the model`s mass and stiffness when evaluated with the identified modal parameters. The present algorithm is a modification and extension of a previously-developed Sensitivity-Based Element-By-Element (SB-EBE) method for damage detection and finite element model up- dating. In the present algorithm, SB-EBE has been generalized to minimize a dynamic displacement residual quantity, which is shown to improve test- analysis mode correspondence. Furthermore, the algorithm has been modified to include Bayesian estimation concepts, and the underlying nonlinear optimization problem has been consistently linearized to improve the convergence properties. The resulting algorithm is demonstrated via numerical and experimental examples to be an efficient and robust method for both localizing model errors and estimating physical parameters.
Date:
December 31, 1996
Creator:
Alvin, Kenneth F.
Object Type:
Article
System:
The UNT Digital Library
Filter Component Assessment
Advanced particulate filtration systems are currently being developed at Westinghouse for use in both coal-fired Integrated Gasification Combined Cycle (IGCC) and Pressurized Fluidized Bed Combustion (PFBC) systems. To date, Westinghouse has demonstrated 5855 hours of successful operation of first generation monolithic filter elements in PFBC applications when ash bridging or process thermal transient excursions are avoided. Alternate advanced monolithic and second generation fiber reinforced, filament wound and vacuum infiltrated filters are also being developed which are considered to have enhanced high temperature creep resistance, improved fracture toughness, or enhanced thermal shock characteristics, respectively. Mechanical and component fabrication improvements, as well as degradation mechanisms for each filter element have been identified by Westinghouse during exposure to simulated PFBC operating conditions and alkali-containing steam/air environments. Additional effort is currently being focused on determining the stability of the advanced monolithic high temperature creep resistant clay bonded silicon carbide (SiC) materials, alumina/mullite, and chemically vapor infiltrated (CVI) SiC materials during operation in the Westinghouse Advanced Particulate Filtration (W-APF) system at Foster Wheeler`s pressurized circulating fluidized-bed combustion (PCFBC) test facility in Karhula, Finland. Select advanced filter materials are being defined for additional long-term exposure in integrated gasification combined cycle (IGCC) gas streams. The results of …
Date:
December 31, 1996
Creator:
Alvin, M. A.; Lippert, T. E.; Diaz, E. S. & Smeltzer, E. E.
Object Type:
Report
System:
The UNT Digital Library
Steerable/distance enhanced penetrometer delivery system
Characterization, monitoring, and remediation of many of the nation`s highly contaminated sites are high priority at DOE. Penetrometers are often used for rapid characterization of underground contamination (plumes). Because of their heavy weight, use of penetrometer trucks over shallow buried storage tanks is restricted and risky. To close this gap, UTD developed a new position location device for penetrometers, called POLO (POsition LOcator), which provides real- time position location without blocking downhole access for environmental sensors. UTD also developed a system to make penetrometers steerable and capable of deeper penetration. Products of this work is a Steerable Vibratory System, which a relatively lightweight rig capable of greater penetration than traditional penetrometers of the same weight.
Date:
December 31, 1996
Creator:
Amini, A. & Boyd, G.M.
Object Type:
Article
System:
The UNT Digital Library
A polygonal method for haptic force generation
Algorithms for computing forces and associated surface deformations (graphical and physical) are given, which, together with a force feedback device can be used to haptically display virtual objects. The Bendable Polygon algorithm, created at Sandia National Labs and the University of New Mexico, for visual rendering of computer generated surfaces is also presented. An implementation using the EIGEN virtual reality environment, and the PHANToM (Trademark) haptic interface, is reported together with suggestions for future research.
Date:
December 31, 1996
Creator:
Anderson, T.
Object Type:
Article
System:
The UNT Digital Library