Collection
Office of Scientific & Technical Information Technical Reports
14,163
Texas State Publications
460
Texas Attorney General Opinions
203
Texas Register
112
USGS Topographic Map Collection
106
Congressional Research Service Reports
67
Technical Report Archive and Image Library
64
Office of Technology Assessment
63
Federal Communications Commission Record
27
Advisory Commission on Intergovernmental Relations
13
9 More
Serial/Series Title
Texas Register
112
7.5 Minute Series (Topographic)
59
Texas Motor Vehicle Traffic Accident Summaries
55
30 x 60 Minute Series (Topographic)
44
Texas Parks & Wildlife News
42
Argonne National Laboratory Reports
34
FCC Record
27
Texas Disease Prevention News
24
Fiscal Year 1993
23
73rd Legislature of Texas
18
220 More
Country
States
Year
Month
Language
15,322 Matching Results
Results open in a new window/tab.
Characterization of porosity via secondary reactions. Quarterly technical progress report, 1 October 1993--31 December 1993
The following was accomplished during the reporting period: TPD spectra were obtained from Wyodak coal char samples CO and CO{sub 2} prepared at varying burn-offs in 0.1 MPa oxygen at 410{degrees}C. Both the CO and CO{sub 2} spectra were fit to two Gaussian peaks. Nitrogen isotherms (77K) were obtained for all the samples in order to characterize their porosity. The conclusions were derived from these data include: (1) The TPD desorption data indicated the same general porosity development with burn-off as the nitrogen adsorption isotherms. (2) The two high temperature CO{sub 2} peaks are attributable to secondary interactions of desorbed CO with surface oxygen complexes as it percolates out through the pore structure. This reaction may be catalyzed by the mineral matter in the Wyodak char.
Date:
December 31, 1993
Creator:
Calo, J. M. & Zhang, L.
Object Type:
Report
System:
The UNT Digital Library
Characterization of structure and mechanical properties of MoSi{sub 2}-SiC nanolayer composites
A systematic study of structure-mechanical properties relation is reported for MoSi{sub 2}-SiC nanolayer composites. Alternating layers of MoSi{sub 2} and SiC were synthesized by DC magnetron and rf-diode sputtering, respectively. Cross-sectional transmission electron microscopy was used to examine three distinct reactions in the specimens when exposed to different annealing conditions: Crystallization and phase transformation of MoSi{sub 2}, crystallization of SiC, and spheroidization of the layer structures. Nanoindentation was employed to characterize the mechanical response as a function of structural changes. As-sputtered material exhibits amorphous structures in both types of layers and has a hardness of 11 GPa and a modulus of 217GPa. Subsequent heat treatment induces crystallization of MoSi{sub 2} to form the C40 structure at 500C and SiC to form the a structure at 700C. The crystallization process is directly responsible for hardness and modulus increase in multilayers. A hardness of 24GPa and a modulus of 340GPa can be achieved through crystallizing both MoSi{sub 2} and SiC layers. Annealing at 900C for 2h causes the transformation of MoSi{sub 2} into the C11{sub b} structure, as well as spheroidization of the layering to form a nanocrystaulline equiaxed microstructure. A slight degradation in hardness but not in modulus is observed accompanying …
Date:
December 31, 1993
Creator:
Kung, H.; Jervis, T. R.; Nastasi, M.; Mitchell, T. E. & Hirvonen, J. P.
Object Type:
Article
System:
The UNT Digital Library
Characterization of the glycolytic enzyme enolase which is abundant in the hyperthermophilic archaeon, Pyrococcus furiosus
High enolase activity, as measured by the conversion of 2-phosphoglycerate to phosphoenolphyruvate, was found in the cytoplasm of Pyrococcus (an anaerobic, hyperthermophilic archaeon that grows optimally at 100{degree}C). In this organism, the enzyme probably functions in a sugar fermentation pathway. The enzyme was purified to homogeneity. It had a temperature optimum of >90 {degree}C, and a pH optimum of 8.1. The enzyme was extremely thermostable with a half time for inactivation at 100{degree}C of 40 min. In contrast, an enolase from yeast was inactivated in 1 min at 88{degree}C. Both the P. furiosus and yeast enzymes required a metal ion for activity, but whereas the yeast enzyme has an absolute requirement for Mg{sup ++} the P. furiosus enolase was equally active in the presence of Mn{sup ++}. Both enzymes were competitively inhibited by citrate. P. furiosus enolase, as for mesophilic enolases, probably has a homodimeric structure with subunit M{sub r} greater than 45,000. A highly conserved sequence of eight amino acids in the N-terminal region was found in enolases from P. furiosus and a wide range of other organisms including bacteria, yeast, birds, and mammals.
Date:
December 31, 1993
Creator:
Peak, M. J.; Peak, J. G.; Stevens, F. J.; Blamey, J.; Mai, X.; Zhou, Z. H. et al.
Object Type:
Report
System:
The UNT Digital Library
Characterization of the internal surfaces of two emptied 30A UF{sub 6} storage cylinders
Before any cylinders used for storage of uranium hexafluoride (UF{sub 6}) can be decommissioned, all chemical and metallurgical changes in the cylinder walls during storage need to be known. This study was conducted to obtain initial data on changes that may have occurred in cylinders because of long-term contact with UF{sub 6}. Two 2.5-ton cylinders, emptied of UF{sub 6} and rinsed, were selected based on the extent of residual radioactivity, as judged from sweeps of a field survey meter over the outside surfaces of a batch of cylinders. A videoprobe was used to record the appearance of the internal surface of the selected cylinder. Sections of the cylinders representing various levels of residual radioactivity were cut out using a 6 in. diameter hole saw. These sections were further characterized by nuclear spectroscopy to identify the radionuclides present. Pieces were cut from the sections, mounted in taper section, and metallographically examined to characterize near-surface changes, including those resulting from surface corrosion from the moisture present in the washed cylinders. X-ray diffraction was used to further identify the various phases present, both in the corroded surface layers and in the immediate subsurface areas. Samples were examined using scanning electron microscopy and energy …
Date:
December 31, 1993
Creator:
Rao, M.; Ellis, A. & Freels, D.
Object Type:
Report
System:
The UNT Digital Library
Characterization of the organic-sulfur-degrading enzymes. Final report, August 23, 1991--August 22, 1993
None
Date:
December 31, 1993
Creator:
Ho, N. W. Y.
Object Type:
Report
System:
The UNT Digital Library
Characterization of the rare earth orthophosphates and Ce-doped LaPO{sub 4} by X-ray Absorption Spectroscopy
X-ray Absorption Spectroscopy (XAS) of the Rare Earth (RE) 3d levels yields sharp peaks near the edges as a result of strong, quasi-atomic 3d{sup 10}4f {yields} 3d{sup 9}4f{sup n+1} (M{sub 4,5}) transitions that contain a wealth of spectroscopic features. XAS is a useful technique for the characterization of 4f-occupancy, 4f-hybridization, and valence in RE-containing materials. The XAS measurements of the single crystal RE-orthophosphates, as well as a range of Cedoped ({approx}1--30%) LaPO{sub 4} hosts were performed at the 3d edge in the total electron yield mode at beamline 8-2 at the Stanford Synchrotron Radiation Laboratory (SSRL). The XAS spectra of the RE ions in the orthophosphate matrix generally resemble that of the corresponding RE metal and emphasize the major contribution of the trivalent state to the electronic transitions occurring at the 3d edge. There is no energy shift of the La and Ce absorption peaks with Ce doping and furthermore, no additional transitions are observed in either spectral region. However, accompanying the Ce doping there is a significant narrowing of the La absorption peak full width half maximum that contrasts to the Ce features that exhibit no contraction. The La and Ce spectra indicate that the Ce-doping of LaPO{sub 4} …
Date:
December 31, 1993
Creator:
Shuh, D. K.; Perry, D.; Terminello, L. J.; Boatner, L. A. & Abraham, M. M.
Object Type:
Article
System:
The UNT Digital Library
Characterization of thermally stable dye-doped polyimide based electrooptic materials
Polymeric electrooptic materials have the potential to replace electronic switches in applications which require minimization of heat dissipation while maintaining high switching speeds. Polyimide matrices incorporating electrooptic dyes are promising materials for such applications due to their low cost and compatibility with existing processing environments. Preparation and characterization of novel dye-doped polyimide films for electrooptics is described. Thermal stabilities of donor-acceptor 2,5-diaryl oxazoles were evaluated by differential scanning calorimetry. Absorptive losses in thin films of Ultradel 9000D{reg_sign} doped with donor-acceptor oxazoles were measured by photothermal deflection spectroscopy. Absorptive losses at high doping levels may be explainable by dye-dye aggregation or dye degradation during the curing process. Lower doping levels, however, show losses of {le} 3.0 dB/cm at 830 nm and {le} 2.4 dB/cm at 1,320 nm.
Date:
December 31, 1993
Creator:
Meinhardt, M. B.; Cahill, P. A.; Seager, C. H.; Beuhler, A. J. & Wargowski, D. A.
Object Type:
Report
System:
The UNT Digital Library
Characterization of transducer cavities to oscillatory inputs
The design and use of measurement systems must ensure that the data are not computed by the measurement system. A wide variety of sources can be responsible for compromising the integrity of test data. Among the sources of error are transducer calibration errors, signal conditioning problems, recording problems, and characteristics of the mechanical system which introduce errors. In this paper, the characteristics of an acoustic cavity are discussed as they apply to a pressure measurement problem.
Date:
December 31, 1993
Creator:
Rogers, J. D. & Hollingshead, J. R.
Object Type:
Article
System:
The UNT Digital Library
Characterizing fluidized bed behavior by decomposition of chaotic phase space trajectories
Recent applications of chaotic time series analysis to gas fluidized beds have demonstrated that substantial information about fluidization conditions within the. bed can be extracted from voidage and pressure drop data. In this paper, a technique is presented to characterize fluidized bed behavior based on the crossings of the phase space trajectory through the principal component planes. Starting with either pressure drop or void fraction versus time data, time series embedding and principal component analysis is used to construct a phase space trajectory for the data. This trajectory characterizes the dynamical state of the bed. The technique presented decomposes the trajectory by sorting the orbits into types characteristic of different modes of bed behavior, such as emulsion phase fluctuations, bubbling, slugging, bubble coalescence, and de-fluidization. The basis for the method and the analysis of data from experiments in several fluidized beds will be presented. The overall goal of these studies is to improve the diagnostic and control of fossil energy fluidized bed processes.
Date:
December 31, 1993
Creator:
Halow, J. S. & Daw, C. S.
Object Type:
Article
System:
The UNT Digital Library
Characterizing fractured rock for fluid-flow, geomechanical, and paleostress modeling: Methods and preliminary results from Yucca Mountain, Nevada
Fractures have been characterized for fluid-flow, geomechanical, and paleostress modeling at three localities in the vicinity of drill hole USW G-4 at Yucca Mountain in southwestern Nevada. A method for fracture characterization is introduced that integrates mapping fracture-trace networks and quantifying eight fracture parameters: trace length, orientation, connectivity, aperture, roughness, shear offset, trace-length density, and mineralization. A complex network of fractures was exposed on three 214- to 260-m 2 pavements cleared of debris in the upper lithophysal unit of the Tiva Canyon Member of the Miocene Paint-brush Tuff. The pavements are two-dimensional sections through the three-dimensional network of strata-bound fractures. All fractures with trace lengths greater than 0.2 m were mapped and studied.
Date:
December 31, 1993
Creator:
Barton, C.C.; Larsen, E.; Page, W.R. & Howard, T.M.
Object Type:
Report
System:
The UNT Digital Library
A charge distribution analysis instrument for catalysis and material science applications; First quarterly technical progress report, October 1, 1993--December 31, 1993
Charge Distribution Analysis (CDA) is a technique to measure mobile charge carriers in dielectric materials in general and more specifically in catalysts. The measurements are based on the dielectric polarization of a given material in an electric field They are contact-free and performed at O Hertz under minimum perturbation conditions. It allows one to determine the sign of the majority charge carriers and to obtain information on their diffusive mobility. Under certain conditions the density of surface charges can be measured quantitatively. The density of surface charges is expected to correlate to the catalytic activity. We have proposed to develop CDA modules which could be used in conjunction with commercial thermal analysis equipment, in particular thermobalances, and convert them into CDA instruments. The first three months of the Project have been used to carefully evaluate all options that relate to this development task. We have evaluated the basic concepts for a commercially viable CDA instrument and formulated its design specifications.
Date:
December 31, 1993
Creator:
Freund, F.
Object Type:
Report
System:
The UNT Digital Library
Charge distribution analysis of catalysts under simulated reaction conditions. Fifth quarterly technical progress report, October 1--December 31, 1993
CDA runs with iron oxide catalyst {number_sign}7 (with SO{sub 4}) were performed under nitrogen. Preparations are being made for H{sub 2}S atmosphere.
Date:
December 31, 1993
Creator:
Freund, F.
Object Type:
Report
System:
The UNT Digital Library
Charge distribution analysis of catalysts under simulated reaction conditions. Fourth quarterly technical progress report, July 1--September 30, 1993
Only moderate progress was made in collecting data using the Charge Distribution Analysis (CDA) apparatus. Initial runs performed with the furnace built on a boron nitride (BN) support showed unacceptable limitations. A new furnace design was immediately begun; the new microfurnace gave rapid heating and cooling rates almost 4 times faster than the BN furnace. Baseline data runs with fused silica were made.
Date:
December 31, 1993
Creator:
Freund, F.
Object Type:
Report
System:
The UNT Digital Library
Chemical vapor infiltration of non-oxide ceramic matrix composites
Continuous fiber ceramic composites are enabling new, high temperature structural applications. Chemical vapor infiltration methods for producing these composites are being investigated, with the complexity of filament weaves and deposition chemistry merged with standard heat and mass transport relationships. Silicon carbide- based materials are, by far, the most mature, and are already being used in aerospace applications. This paper addresses the state-of-the-art of the technology and outlines current issues.
Date:
December 31, 1993
Creator:
Besmann, T. M.; Stinton, D. P. & Lowden, R. A.
Object Type:
Article
System:
The UNT Digital Library
Chemically Assisted in Situ Recovery of Oil Shale
The purpose of the research project was to investigate the feasibility of the chemically assisted in situ retort method for recovering shale oil from Colorado oil shale. The chemically assisted in situ procedure uses hydrogen chloride (HCl), steam (H{sub 2}O), and carbon dioxide (CO{sub 2}) at moderate pressure to recovery shale oil from Colorado oil shale at temperatures substantially lower than those required for the thermal decomposition of kerogen. The process had been previously examined under static, reaction-equilibrium conditions, and had been shown to achieve significant shale oil recoveries from powdered oil shale. The purpose of this research project was to determine if these results were applicable to a dynamic experiment, and achieve penetration into and recovery of shale oil from solid oil shale. Much was learned about how to perform these experiments. Corrosion, chemical stability, and temperature stability problems were discovered and overcome. Engineering and design problems were discovered and overcome. High recovery (90% of estimated Fischer Assay) was observed in one experiment. Significant recovery (30% of estimated Fischer Assay) was also observed in another experiment. Minor amounts of freed organics were observed in two more experiments. Penetration and breakthrough of solid cores was observed in six experiments.
Date:
December 31, 1993
Creator:
Ramierz, W. F.
Object Type:
Report
System:
The UNT Digital Library
Chlorine in coal and its relationship with boiler corrosion. Technical report, September 1--November 30, 1993
Limited literature and use history data have suggested that some high-chlorine Illinois coals do not cause boiler corrosion while extensive data developed by the British correlate corrosion with chlorine content and other parameters of coal and boiler. Providing concrete scientific evidence to explain the variations in corrosivity of the high-chlorine coals and supporting the premise that high chlorine Illinois coals do not cause corrosion will help relieve market concerns and increase usage of these coals. The differences in corrosivity in coals may be due to the coal properties, to coal blends, or to the boiler parameters in which they were burned. The goals of this study focus on these coal properties. They are: (1) to determine the forms of chlorine and other chemical components (mineral, major, minor, and trace elements) in coals which have been reported to behave differently with respect to corrosion problems during combustion; (2) to determine the evolution profiles of chlorine-containing compounds in coals during pyrolysis and oxidation; and (3) to examine the behavior of Cl-, S-, N-, containing compounds in coal during pyrolysis.
Date:
December 31, 1993
Creator:
Lytle, J. M; Ruch, R. R. & Chou, C. L.
Object Type:
Report
System:
The UNT Digital Library
Clean, premium-quality chars: Demineralized and carbon enriched. Final technical report, 1 September, 1992--31 August, 1993
The overall objective of this two-year project was to evaluate methods of preparing demineralized and carbon enriched chars from Illinois Basin coals. The two processing steps, physical cleaning and devolatilization under different environments, led to the following results. Cleaning coal incompletely removes mineral matter which decreases catalytic activity and increases micropore structure. Water forms hydrogen bonds to oxygen functional groups in coal, and during drying, coals undergo structural changes which affect mild gasification. When methane reacts wit coal, devolatilization and carbon deposition occur, the rates of which depend on temperature and amount of ash. Thermal decomposition of IBC-101 coal starts at 300 C, which is much lower than previously believed, but maximum yields of liquids occur at 500 C for IBC-101 coal and at 550 C for IBC-102 coal. Aliphatic-to-aromatic ratios increase with increasing pyrolysis temperatures to 300 C and then decrease; therefore, liquids formed during gasification of 550 C or higher contain mainly aromatic compounds. Btu values of chars are higher after methane treatment than after helium treatment.
Date:
December 31, 1993
Creator:
Smith, G. V.; Malhotra, V. M. & Wiltowski, T.
Object Type:
Report
System:
The UNT Digital Library
CO{sub 2}/Sand Fracturing in Devonian Shales
A total of five carbon dioxide (CO{sub 2})/sand well stimulations were successfully executed with two Devonian shale operators in Perry and Pike Counties, Kentucky. This new stimulation method offers a minimum formation damage proppant stimulation approach for natural gas producers in the United States. Some operators have been concerned about the frac fluid formation damage associated with the water and chemicals used in conventional foam stimulations, whereas other operators have been concerned about the lack of proppant in straight nitrogen fracs used by service companies today. Two carefully screened geological areas of established Devonian shale production were selected based on active ongoing drilling and completion operations. One selected control area contained an existing set of wells with established production histories. More specifically, one operator furnished three offset wells which were stimulated with the carbon dioxide/sand frac method. The quantity of proppant and fluids pumped during each well stimulation ranged from 23,000 to 43,000 pounds of proppant and from 120 to 160 tons of liquid carbon dioxide. Another operator furnished two offset wells which were each stimulated with approximately 47,000 pounds of proppant and 120 tons of carbon dioxide. The logistics and field layout of a typical carbon dioxide/sand frac treatment …
Date:
December 31, 1993
Creator:
Yost, A. B., II; Mazza, R. L. & Gehr, J. B.
Object Type:
Report
System:
The UNT Digital Library
CO{sub 2}/sand fracturing in low permeability reservoirs
The objectives of this study are: to demonstrate the effectiveness of a non-damaging liquid, carbon dioxide (CO{sub 2}) in creating sand-propped hydraulic fractures in ``tight`` gas bearing formations within the Appalachian Basin; and to compare and rank the gas production responses from wells treated with liquid CO{sub 2} with other types of treatments (shooting, water based, nitrogen, etc.). The preliminary results are encouraging, and although only a few months of production is available, the rate of gas production from the CO{sub 2} treated candidate wells is greater than that from the control wells. The CO{sub 2}/sand fracs appear to be 56 percent better than the nitrogen fracs in Pike County. In addition, the CO{sub 2}/sand fracs are 4.8 times better than conventional shot wells in the Pike County study area. It should be recognized that these results are from a very limited data set and overall conclusions may change as more control wells are added to the analysis. From a stimulation process achievement viewpoint, the maximum amount of sand pumped is 46,000 pounds at an average concentration of 3.1 pound per gallon. It should be pointed out that additional foam and nitrogen stimulations have recently been performed by the operator …
Date:
December 31, 1993
Creator:
Mazza, R. L. & Gehr, J. B.
Object Type:
Report
System:
The UNT Digital Library
Coal combustion: Effect of process conditions on char reactivity. Ninth quarterly technical report, September 1, 1992--December 1, 1993
Our efforts during the past quarter focused on the development of an image processing technique for characterizing the macropore structure of chars produced from Illinois No. 6 coal. Pyrolysis experiments were carried out in a microscope-stage reactor in inert and reacting atmospheres and at various pyrolysis heating rates. Particles from several pyrolysis runs were embedded in an epoxy resin block and polished sections . were prepared. Digital images of char particle cross-sections were acquired and analyzed to measure the structural properties of the chars. The macropore analysis procedure is presented here in detail. Future reports will present the data showing the effects of pyrolysis conditions on the macropore structure of Illinois No. 6 chars.
Date:
December 31, 1993
Creator:
Zygourakis, K.
Object Type:
Report
System:
The UNT Digital Library
Coal combustion under conditions of blast furnace injection. Final technical report, September 1, 1992--August 31, 1993
A potentially new use for Illinois coal is as a fuel injected into a blast furnace to produce molten iron as the first step in steel production. Because of its increasing cost and decreasing availability, metallurgical coke is now being replaced by coal injected at the tuyere area of the furnace where the blast air enters. The purpose of this study is to evaluate the combustion of coal during the blast furnace injection process and to delineate the optimum properties of the feed coal. This investigation is significant to the use of Illinois coal in that the limited research to date suggests that coals of low fluidity and moderate to high sulfur and chlorine contents are suitable feedstocks for blast furnace injection. During the first phase of this project a number of the objectives were realized, specifically: (1) a blast furnace sampling system was developed and used successfully to collect samples inside an active furnace; (2) two sets of blast furnace samples were collected and petrographic analysis showed that char derived from injected coal is entering the reduction zone of the furnace; (3) a coal/char sampling probe was designed and fabricated; (4) the completion of a program of reactivity experiments …
Date:
December 31, 1993
Creator:
Crelling, J. C. & Case, E. R.
Object Type:
Report
System:
The UNT Digital Library
Coal combustion under conditions of blast furnace injection; [Quarterly] technical report, September 1--November 30, 1993
A potentially new use for Illinois coal is its use as a fuel injected into a blast furnace to produce molten iron as the first step in steel production. Because of its increasing cost and decreasing availability, metallurgical coke is now being replaced by coal injected at the tuyere area of the furnace where the blast air enters. The purpose of this study is to evaluate the combustion of coal during the blast furnace injection process and to delineate the optimum properties of the feed coal. This investigation is significant to the use of Illinois coal in that the limited research to date suggests that coals of low fluidity and moderate to high sulfur and chlorine contents are suitable feedstocks for blast furnace injection. This study is unique in that it will be the first North American effort to directly determine the nature of the combustion of coal injected into a blast furnace. This proposal is a follow-up to one funded for the 1992--1993 period. It is intended to complete the study already underway with the Armco Inc. steel company and to initiate a new cooperative study along somewhat similar lines with the Inland Steel Company. The results of this …
Date:
December 31, 1993
Creator:
Crelling, J.C.
Object Type:
Report
System:
The UNT Digital Library
Coal-fired high performance power generating system. Quarterly progress report, July 1, 1993--September 30, 1993
This report covers work carried out under Task 3, Preliminary Research and Development, and Task 4, Commercial Generating Plant Design, under contract DE-AC22-92PC91155, {open_quotes}Engineering Development of a Coal Fired High Performance Power Generation System{close_quotes} between DOE Pittsburgh Energy Technology Center and United Technologies Research Center. The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) by the year 2000 that is capable of >47% thermal efficiency; NO{sub x}, SO{sub x}, and particulates {le} 25% NSPS; cost {ge} 65% of heat input; and all solid wastes benign. The report discusses progress in cycle analysis, chemical reactor modeling, ash deposition rate calculations for HITAF (high temperature advanced furnace) convective air heater, air heater materials, and deposit initiation and growth on ceramic substrates.
Date:
December 31, 1993
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Coal liquefaction and gas conversion: Proceedings. Volume 1
Volume I contains papers presented at the following sessions: AR-Coal Liquefaction; Gas to Liquids; and Direct Liquefaction. Selected papers have been processed separately for inclusion in the Energy Science and Technology Database.
Date:
December 31, 1993
Creator:
unknown
Object Type:
Article
System:
The UNT Digital Library