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15,492 Matching Results
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Development of improved iron Fischer-Tropsch catalysts
The objective of proposed research is development of catalysts with enhanced slurry phase activity and better selectivity to fuel range products, through a more detailed understanding and systematic studies of the effects of pretreatment procedures and promoters/binders (silica) on catalyst performance.
Date:
January 15, 1990
Creator:
Bukur, D.B. & Patel, S.A.
Object Type:
Report
System:
The UNT Digital Library
Theoretical modeling and experimental characterization of planar defects in Y sub 2 Ba sub 4 Cu sub 6+x O sub 14+x
Crystallographic defects and phase transformations in the system Y{sub 2}Ba{sub 4}Cu{sub 6 + x}O{sub 14 + x}(0{le}{times}{le}4) are investigated by high resolution transmission electron microscopy (TEM) and static lattice, three dimensional Monte Carlo computer simulations. High resolution images of partially transformed (x = 2 to x = 1) material reveal a prevalence of CuO planar defects (stacking faults) associated with the transformation and an absence of disturbance to the perovskite Ba-Y-Ba blocks. An atomic mechanism involving the intercalculation and removal of extra CuO planes by partial dislocation climb, and requiring only a-b plane diffusion, is developed for the formation of such planar defects during changes in the layered YBaCuO crystal structure. Monte Carlo simulations based on the proposed transformation mechanism accurately reproduce the observed defects and known equilibrium structures. 24 refs., 4 figs.
Date:
November 1, 1990
Creator:
Burmester, C. P.; Fendorf, M.; Gronsky, R. & Wille, L. T.
Object Type:
Article
System:
The UNT Digital Library
Establishment and maintenance of a coal sample bank and data base
In this Project Status Report for 7/9/89--10/8/89, results of a comparative study of coal sample deterioration in several container types were presented. In April 1990, one year after the initial analyses, the set of analyses was repeated on the most important container types. The new results are included in Table 2. During the current reporting period a total of 42 data printouts were distributed. In addition, 7 special data requests were fulfilled by either search/sort and printout or creation of a data disk, resulting in distribution of limited information on 2083 samples. Several preliminary requests for Sample Bank and Data Base information and price quotations have also been handled.
Date:
July 11, 1990
Creator:
Davis, A.
Object Type:
Report
System:
The UNT Digital Library
Prototype photon position monitors for undulator beams at the Advanced Light Source
Design criteria are described, and test results are presented, for prototype ALS undulator beam position monitors. The design is based on monitors presently in use at NSLS, with modifications to account for the widely varying and large K values of the undulators to be installed at the ALS. In particular, we have modified the design to simplify the thermal engineering and we have explored techniques to suppress the response of the monitors to soft photons, so that the beam position can be determined by measuring the higher energy photons which are better collimated. 4 refs., 8 figs.
Date:
October 17, 1990
Creator:
Warwick, T.; Shu, D. (Lawrence Berkeley Lab., CA (United States)); Rodricks, B. (Argonne National Lab., IL (United States)) & Johnson, E.D. (Brookhaven National Lab., Upton, NY (United States))
Object Type:
Article
System:
The UNT Digital Library
Vertical bridgman and gradient freeze growth of III-V compound semiconductors
Major improvements in the structural and electrical perfection of single crystals of III-V compound semiconductors have been achieved by using new vertical Bridgman-type and vertical gradient freeze techniques. A general review of experimental set-ups used for growth of large diameter crystals of GaP, InP and GaAs is presented. Crystal properties and characteristic features are discussed to illustrate advantages and disadvantages of the vertical Bridgman-type growth techniques. 22 refs., 5 figs.
Date:
July 1, 1990
Creator:
Bourret, E.D.
Object Type:
Article
System:
The UNT Digital Library
Po-210 as long-term integrating radon indicator in the indoor environment
The general objective is to improve the knowledge about the transferring processes leading from airborne radon/radon daughters to embedded Po-210 in hard surfaces in the indoor environment. The specific goal of the research is to identify situations in which the surface activity of Po-210 can be used as a long-term indicator of lung cancer risk from past or future radon exposures.
Date:
July 1, 1990
Creator:
Samuelsson, C.
Object Type:
Report
System:
The UNT Digital Library
Thermally Induced Structural Changes in Coal Combustion
The effect of particle shape on char burnout is investigated in the limit of shrinking core combustion. As a first step, the particle temperature is assumed to proceed in the shrinking core regime and under conditions of negligible Stefan flow. The problem then reduces to calculating the oxygen concentration field around a non-spherical particle with the oxidation reaction taking place on the external surface. This problem has been addressed by an analytical technique and a numerical technique. An analytical technique known as domain perturbation'' was used to examine the change due to reaction in the shape of a slightly nonspherical, but axisymmetric, particle. It was found that the aspect ratio always increases with conversion, i.e., the particle becomes less spherical. A numerical technique, based on the boundary integral'' method was developed to handle the case of an axisymmetric particle with otherwise arbitrary shape. Numerical results are presented which again show the aspect ratio to increase with conversion. 8 refs.
Date:
January 17, 1990
Creator:
Gavalas, G. R. & Flagan, R. C.
Object Type:
Report
System:
The UNT Digital Library
Characterization of Nb-Ti superconductors with artificial pinning structures
A series of multifilamentary APC Nb-Ti superconductors have been made with Nb added as a normal second phase to provide flux pinning centers. Two compositions, 12.5% vol % and 25 vol % Nb in Nb-Ti, have fabricated into multifilamentary composites using two different fabrication methods. One method used hot isostatic compaction and hot extrusion thoughout the processing. The other method (bundle-and-draw process) discontinued all hot processing at an intermediate level. While the J{sub c} values of the bundle-and-draw wires are quite promising, the critical current of the extruded wires appears to be limited by poor uniformity of the filament cross-sectional area along the conductor length. The large values of the index of the resistive transition and small filament standard-deviation-to-average area ratios observed in the wires produced by the bundle-and-draw process suggest extrinsic factors have little effect on J{sub c}. The variation in J{sub c} as the wire diameter is reduced appears to be most strongly affected by intrinsic factors: Nb distribution and pinning strength. The final filament microstructure and Nb spacing are shown to be difficult to calculate, e.g., the mean Nb spacing near the final wire size may be {1/2} to 1/3 that of the calculated value. 5 refs., …
Date:
June 1, 1990
Creator:
Dietderich, D. R. & Scanlan, R. M.
Object Type:
Article
System:
The UNT Digital Library
Removal of trichloroethylene contamination from the subsurface: A comparative evaluation of different remediation strategies by means of numerical simulation
Volatile organic compounds such as petroleum hydrocarbons and halogenated hydrocarbon solvents are common contaminants of the subsurface environment. Although immiscible with water, many of these organics have large enough aqueous phase solubilities to significantly degrade the quality of groundwater with which they come in contact. In addition, many of these substances exhibit high vapor pressures, causing them to partition strongly into the gas phase in their surroundings. Because of these properties, a volatile organic compound (VOC), once introduced into the subsurface may be transported as a solute, a vapor, or as a constituent in a non- aqueous phase liquid (NAPL). This implies that at some sits, an adequate description of the migration of these contaminants in the subsurface would necessarily involve three phases, -- gas, aqueous and NAPL. For example, to design an effective aquifer remediation scheme for a site where NAPL is present, it would be wrong to focus solely on the aqueous phase while ignoring either the gas phase or the NAPL phase. In the present work, we use a simulator developed by Falta et al. (1990a), known as STMVOC,'' which models true three-phase flow in which NAPL, gas and aqueous phases can move in response to pressure, …
Date:
December 1, 1990
Creator:
Adenekan, A.E.; Pruess, K. & Falta, R.W.
Object Type:
Report
System:
The UNT Digital Library
Surface electrochemical control for fine coal and pyrite separation
Ongoing work includes the characterization of coal pyrites, the floatability evaluation typical US coal samples, the flotation behavior of coal pyrites, the electrochemical measurement of the surface properties of coal pyrites, and the characterization of species produced at pyrite surfaces.
Date:
January 1, 1990
Creator:
Hu, Weibai; Zhu, Ximeng; Bodily, D. M. & Wadsworth, M. E.
Object Type:
Report
System:
The UNT Digital Library
Biological Production of Ethanol From Coal
A batch kinetic study involving Clostridium lungdahlii in a mineral medium was carried out in order to provide baseline data for the effects of nutrients on product ratio and kinetics. The use of this minimal medium containing vitamins, minerals, select amino acids and salts showed both a lower maximum specific growth rate and a lower maximum specific uptake rate than found when using a complex medium supplemented with 0.01% yeast extract. At the same time, the product ratio was improved slightly in favor of ethanol over acetate. Future experiments will measure the effects of ammonia and phosphate limitation on product ratio and process kinetics.
Date:
January 1, 1990
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Automatic lighting controls demonstration
The purpose of this work was to demonstrate, in a real building situation, the energy and peak demand reduction capabilities of an electronically ballasted lighting control system that can utilize all types of control strategies to efficiently manage lighting. The project has demonstrated that a state-of-the-art electronically ballasted dimmable lighting system can reduce energy and lighting demand by as least 50% using various combinations of control strategies. By reducing light levels over circulation areas (tuning) and reducing after hours light levels to accommodate the less stringent lighting demands of the cleaning crew (scheduling), lighting energy consumption on weekdays was reduced an average of 54% relative to the initial condition. 10 refs., 14 figs., 3 tabs.
Date:
March 1, 1990
Creator:
Rubinstein, F. & Verderber, R.
Object Type:
Report
System:
The UNT Digital Library
Technological challenges of third generation synchrotron radiation sources
New third generation'' synchrotron radiation research facilities are now in construction in France, Italy, Japan, Taiwan and the USA. Designs for such facilities are being developed in several other countries. Third generation facilities are based on storage rings with low electron beam emittance and space for many undulator magnets to produce radiation with extremely high brightness and coherent power. Photon beam from these rings will greatly extend present research capabilities and open up new opportunities in imaging, spectroscopy, structural and dynamic studies and other applications. The technological problems of the third generation of synchrotron radiation facilities are reviewed. These machines are designed to emit radiation of very high intensity, extreme brightness, very short pulses, and partial coherence. These performance goals put severe requirements on the quality of the electron or positron beams. Phenomena affecting the injection process and the beam lifetime are discussed. Gas desorption by synchrotron radiation and collective effects play an important role. Low emittance lattices are more sensitive to quadrupole movements and at the same time, in order not to lose the benefits of high brilliance, require tighter tolerances on the allowed movement of the photon beam source. We discuss some of the ways that should be …
Date:
January 1, 1990
Creator:
Cornacchia, M. & Winick, H.
Object Type:
Article
System:
The UNT Digital Library
A novel process for methanol synthesis
A bench-salce reactor is being used to conduct studies of the conversion of synthesis gas to methanol by a novel process. During the last quarter, we investigated the nature of the reactions involved and the nature of the Cu-chromite catalyst being used. There is evidence that methanol is formed via a two step reaction with a methyl formate intermediate rather than by the direct hydrogenation of CO. The carbonylation reaction predominantly takes place in the liquid phase while the hydrogenolysis reaction is restricted to the surface of Cu-chromite. At steady state, the carbonylation reaction taking place in the region close to the Cu-chromite surface is probably the main source of MeF. This model also explains the increased tolerance of the process to CO. A mechanistic model is proposed to explain the interaction of different species in the reaction mixture. The topography of the Cu-chromite surface is also investigated by X-ray diffraction and scanning electron microscopy. 15 refs., 5 figs., 1 tab.
Date:
January 1, 1990
Creator:
Tierney, J. W. & Wender, I.
Object Type:
Report
System:
The UNT Digital Library
A Novel Coal Feeder for Production of Low Sulfur Fuel
A novel coal feeding system is currently undergoing testing and evaluation at the University of Cincinnati. The system consists primarily of an auger feed tube which is used to both convey and provide desulfurization of a high sulfur coal feedstock. The coal is conveyed at temperatures ranging from 350 to 550 {degrees}C and under normal atmospheric pressure. Under these mild processing conditions, the coal partially pyrolizes and emits sulfur in the form of hydrogen sulfide while maintaining a relatively high heating value in the char product. The evolved gases are evacuated from the reactor (the feed tube) to another absorbing bed where H{sub 2}S reacts with the sorbent, usually lime or limestone. The resultant sorbent utilization is substantially higher than the values found in current dry scrubbing system and the produced low-sulfur char may then be used in a conventional steam boiler.
Date:
January 1, 1990
Creator:
Keener, T. C.; Khang, S. J. & Yu, X. L.
Object Type:
Report
System:
The UNT Digital Library
Genes and gene expression: Localization, damage and control -- A multilevel and inter-disciplinary study
All projects are working toward a goal for describing the three dimensional nuclear topography in terms of relative spatial relationships among genes (specific DNA sequence). Methods are now being perfected to detect these genes, quantitatively and spatially, to perturb these genes specifically, and to measure the perturbation in order to assure specificity. We are developing methods to assay, after perturbation of the target DNA within living cells, whether or not only the target sequence are attacked while other sequences remain unharmed. We are now at the stage to do chemical gene modification or masking within living cells in a strictly sequence-specific manner. Soon, we will be able to study the function and the physical location of each gene in living cells with exquisite specificity. 25 refs., 15 figs.
Date:
September 1, 1990
Creator:
Ts'o, P.O.P.
Object Type:
Report
System:
The UNT Digital Library
Establishment and maintenance of a coal sample bank and data base. [Including sample preparation without oxidation]
Retrieval of 5-lb splits of -1/4 inch coal from designated 30-gallon drums was completed. Preparation and analysis of these samples for the second yearly quality evaluation is in progress. After consultation with the DOE Project Manager, two replacement samples were collected. These are the first of the series which will be stored in foil laminate bags. Both of these samples were placed in 30 gallon steel drums lined with polyethylene bags at the mine site. They were equipped with lid gaskets made from Tygon tubing, and 1/4 in. metal tubing fittings to purge and pressurize the drum with argon.
Date:
January 19, 1990
Creator:
Davis, A.
Object Type:
Report
System:
The UNT Digital Library
Research on thermophoretic and inertial aspects of ash particle deposition on heat exchanger surfaces in coal-fired equipment
The overall goal of this research in the area of ash transport was to advance the capability of making reliable engineering predictions of the dynamics and consequences of net deposit growth for surfaces exposed to the products of coal combustion. To accomplish this for a wide variety of combustor types, coal types, and operating conditions, this capability must be based on a quantitative understanding of each of the important mechanisms of mineral matter transport, as well as the nature of the interactions between these substances and the prevailing fireside'' surface of the deposit. This level of understanding and predictive capability could ultimately be translated into very significant cost reductions for coal-fired equipment design, development and operation.
Date:
May 1, 1990
Creator:
Rosner, D.E.
Object Type:
Report
System:
The UNT Digital Library
Seismic analysis of reactor exhaust air filter compartment
The Filter Compartment (FC) in this analysis is a generic reactor airborne activity confinement filter compartment which possesses all the essential physical and mechanical properties of the Savannah River Site (SRS) confinement filters of Reactor Buildings K, L, and P. The filters belong to the Airborne Activity Confinement System (AACS). These filters absorb a significant amount of radioactive effluents from the exhausting air. The seismic excitation is input indirectly from the output of the seismic analysis of the 105 exhaust stack building in the form of floor response spectra. However, the 105 exhaust stack building was analyzed for seismic motions defined by free-field ground response spectra with a ZPA (Zero Period Acceleration) of 0.2G for all three orthogonal components of ground motion and a shape consistent with USNRC Regulatory Guide 1.60. Based upon equivalent dynamic analysis of the FC, DuPont engineers suggested modifications on the existing FC with heavy I-section beams (1). The scope of this phase I'' analysis, as requested by Seismic Engineering (2), is to carry out a scoping analysis'' of Frequency Analysis and Response Spectrum Analysis of the FC with DuPont suggested conceptual modifications. Our suggestion was that the existing FC without conceptual modifications be analyzed first. …
Date:
September 24, 1990
Creator:
Gong, Chung; Funderburk, E.L. & Jerrell, J.W.
Object Type:
Report
System:
The UNT Digital Library
Particle correlations in JACEE (Japanese-American Cooperative Emulsion Experiment) nucleus-nucleus collisions
Correlations in the production of charged particles and photons can be examined in detail in the central and forward rapidity range using high multiplicity ({ge}100 charged tracks) events from JACEE emulsion chambers. Results are presented on several forms of correlations studies. 9 refs., 2 figs.
Date:
January 1, 1990
Creator:
unknown
Object Type:
Article
System:
The UNT Digital Library
Proof of concept testing of an integrated dry injection system for SO sub x /NO sub x control
The objective of the subscale test program were designed to provide sorbent and additive selection guidance, and, in so doing, supply answers to the questions posed in the preceding section. The objectives are: Identify the best commercial hydrate sorbent and the best enhanced hydrate sorbent from a list of nine types, based upon S0{sub 2} removal at Ca/S=2. Determine the relative effectiveness of sodium sesquicarbonate versus sodium bicarbonate for S0{sub 2} and NO{sub x} control over the temperature range of 200{degrees}F--400{degrees}F. Identify the best NO{sub 2} suppressing additive among the group of ammonia, urea, and activated carbon.
Date:
January 1, 1990
Creator:
Helfritch, D.J.; Bortz, S.J. (Research-Cottrell, Inc., Somerville, NJ (United States). Environmental Services and Technologies Div.) & Beittel, R. (Riley Stoker Corp., Worcester, MA (United States))
Object Type:
Report
System:
The UNT Digital Library
Molecular biological enhancement of coal biodesulfurization. [Rhodococcus]
The objective of this project is to produce one or more microorganisms capable of removing the organic and inorganic sulfur in coal. The original specific technical objectives of the project were to: Clone and characterize the genes encoding the enzymes of the 4S'' pathway (sulfoxide/sulfone/sulfonate/sulfate) for release of organic sulfur from coal; Return multiple copies of genes to the original host to enhance the biodesulfurization activity of that organism; Transfer this pathway into a fast-growing chemolithotrophic bacterium; Conduct a batch-mode optimization/analysis of scale-up variables.
Date:
March 15, 1990
Creator:
Litchfield, J. H.; Fry, I.; Wyza, R. E.; Palmer, D. T.; Zupancic, T. J. & Conkle, H. N.
Object Type:
Report
System:
The UNT Digital Library
Molecular biological enhancement of coal biodesulfurization. [Rhodococcus, thiobacillus]
The objective of this project is to produce one or more microorganisms capable of removing the organic and inorganic sulfur in coal. The original specific technical objectives of the project were to: clone and characterize the genes encoding the enzymes of the 4S'' pathway (sulfoxide/sulfone/sulfonate/sulfate) for release of organic sulfur from coal; return multiple copies of genes to the original host to enhance the biodesulfurization activity of that organism; transfer this pathway into a fast-growing chemolithotropic bacterium; conduct a batch-mode optimization/analysis of scale-up variables.
Date:
June 14, 1990
Creator:
Litchfield, J. H.; Fry, I.; Wyza, R. E.; Palmer, D. T.; Zupancic, T. J. & Conkle, H. N.
Object Type:
Report
System:
The UNT Digital Library
Biological Production of Ethanol From Coal
Previous results have shown that the yeast extract concentration and the medium pH significantly affect the ratio of ethanol to acetate in the product stream when fermenting CO, CO{sub 2} and H{sub 2} in synthesis gas to products by Clostridium ljungdahlii. Further experimentation has demonstrated the impact of eliminating yeast extract from the medium (except for the slight quantity transferred with the inoculm), especially when coupled with low pH. An ethanol to acetate product ratio of 4.0 was obtained at pH 4.5 without yeast extract present in the medium when using culture previously exposed to growth-limiting H{sub 2}S. The product ratio was 2.0 at pH 4.0 (nearly three times the value of pH 4.5 and nine times the value of pH 5.0) without yeast extract present in the media when using the standard (unexposed) culture.
Date:
January 1, 1990
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library