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High-temperature compressive deformation of Si{sub 3}N{sub 4}/BN fibrous monoliths.

Description: Fibrous monolithic Si{sub 3}N{sub 4}/BN ({approx}85 vol.% Si{sub 3}N{sub 4}/15 vol.% BN) and monolithic Si{sub 3}N{sub 4} ceramics were compressed at a nearly constant strain rate ({var_epsilon}) at 1200-1400 C in N{sub 2}. The {var_epsilon} range was {approx}1 x 10{sup {minus}6} to 5 x 10{sup {minus}6} s{sup {minus}1}; the stress ({sigma}) range was 37-202 MPa. The Si{sub 3}N{sub 4} and the unidirectional fibrous monoliths that were oriented with the long axis of the Si{sub 3}N{sub 4} cells parallel to the compression direction exhibited plasticity at 1300 and 1400 C, with {var_epsilon} {proportional_to} {sigma}. A 0/90{degree} cross-ply Si{sub 3}N{sub 4}/BN laminate also exhibited significant plasticity, but it was weaker than the above-mentioned ceramics. The unidirectional fibrous monoliths that were compressed perpendicular to the cell direction fractured at {approx}50 MPa in all tests. A {+-}45{degree} laminate tested at 1300 C fractured at a stress of {approx}40 MPa. Low fracture stress correlated with shear through BN layers.
Date: February 4, 1999
Creator: Routbort, J. L.
Partner: UNT Libraries Government Documents Department

Mechanical properties of Ce{sub 0.9}Gd{sub 0.1}O{sub 2-x} and Ce{sub 0.9}Gd{sub 0.1}O{sub 2-x} + Al{sub 2}O{sub 3} composites.

Description: The room-temperature elastic moduli, fracture strength, and fracture toughness of dense, fine-grained, pure Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} and composites containing 1.3 and 9.1 wt. % Al{sub 2}O{sub 3} were investigated. Addition of 9.1 wt.% Al{sub 2}O{sub 3} to Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} changed the fracture mode from intergranular to transgranular and increased room-temperature fracture strength from 65 to 125 MPa and fracture toughness from 1.3 to 1.6 MPam{sup 1/2}. In addition, steady-state compressive creep was measured for Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} and the Ce{sub 0.9}Gd{sub 0.1}O{sub 2{minus}x} + 9.1 wt.% Al{sub 2}O{sub 3} composite. The stress exponent {approx}1.3 and the activation energy {approx}480 kJ/mole for Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} suggested diffusional flow controlled by the cations. There was no difference in creep rate between Ce{sub 0.9}Gd{sub 0.1}O{sub 2{minus}x} and the composite.
Date: January 12, 1998
Creator: Routbort, J. L.
Partner: UNT Libraries Government Documents Department

Degradation of structural ceramics by erosion

Description: Materials wastage by solid-particle erosion can be severe and can limit lifetimes. This paper will review the theoretical description of solid-particle erosion in brittle materials, which is well-developed for monolithic ceramics. The models can usually account for effects from the principal projectile properties of size, impact velocity, and impact angle. Materials parameters such as fracture toughness and hardness can be included. Steady-state erosion measurements on a wide variety of ceramics, ranging from Si single crystals to SiC-whisker-reinforced Al{sub 2}O{sub 3}, are reviewed and compared with the models. It is believed that R-curve behavior and/or particle fragmentation is responsible for discrepancies between theory and experimental results for composite ceramics. In addition, the theories make no attempt to describe threshold or incubation effects.
Date: December 1, 1994
Creator: Routbort, J.L.
Partner: UNT Libraries Government Documents Department

Erosion of composite ceramics

Description: The theoretical basis to describe solid-particle erosion of monolithic ceramics is well developed. In many cases, the models can account for the impact velocity, impact angle and erodent-size dependencies of the steady-state erosion rate. In addition, the models account for effects of materials parameters such as fracture toughness and hardness. Steady-state erosion measurements on a wide variety of composite ceramics, including SiC whisker-reinforced Al[sub 2]O[sub 3], Si[sub 3]N[sub 4] containing Si[sub 3]N[sub 4] or SiC whiskers, Y[sub 2]O[sub 3]-stabilized ZrO[sub 2] reinforced with SiC whiskers, and duplex-microstructure Si[sub 3]N[sub 4] have been reported. The theories developed for monolithic ceramics are, however, less successful in describing the results for composites.
Date: August 1, 1992
Creator: Routbort, J.L.
Partner: UNT Libraries Government Documents Department

Erosion of Composite Ceramics

Description: The theoretical basis to describe solid-particle erosion of monolithic ceramics is well developed. In many cases, the models can account for the impact velocity, impact angle and erodent-size dependencies of the steady-state erosion rate. In addition, the models account for effects of materials parameters such as fracture toughness and hardness. Steady-state erosion measurements on a wide variety of composite ceramics, including SiC whisker-reinforced Al{sub 2}O{sub 3}, Si{sub 3}N{sub 4} containing Si{sub 3}N{sub 4} or SiC whiskers, Y{sub 2}O{sub 3}-stabilized ZrO{sub 2} reinforced with SiC whiskers, and duplex-microstructure Si{sub 3}N{sub 4} have been reported. The theories developed for monolithic ceramics are, however, less successful in describing the results for composites.
Date: August 1992
Creator: Routbort, J. L.
Partner: UNT Libraries Government Documents Department

High-temperature deformation and diffusion in oxides

Description: High-temperature, steady-state deformation is usually controlled by diffusion of the slowest moving ion along its fastest diffusion path. Therefore, measurements of steady-state deformation can, in principle, be used to obtain information concerning diffusion. This paper will briefly review the assumptions that relate creep, defect chemistry, and diffusion. Steady-state deformation of the NaCI-structured oxides, Co{sub 1-x}O and Mn{sub l-x}O, and the perovskite-structured high-temperature superconductors YBa{sub 2}Cu{sub 3}0{sub x} and Bi{sub 2}Sr{sub 2}CaCu{sub 2}0{sub x} will be discussed, emphasizing diffusion of the minority defects.
Date: June 1, 1992
Creator: Routbort, J. L.
Partner: UNT Libraries Government Documents Department

Effect of composition and radiation on the Hertzian indentation behavior of nuclear waste glasses. [77-MeV alpha particles]

Description: The Hertzian indentation technique has been used to determine the fracture toughness, K/sub Ic/ of two borosilicate glasses developed to contain high-level nuclear waste. For the product VG 98/12, adding selected groups of fission products leaves K/sub Ic/ unchanged, but addition of Pb lowers K/sub Ic/ by approx. 20%. Radiation with 77 MeV ..cap alpha..-particles to a dose of approx. 10/sup 15/ ..cap alpha../cm/sup 2/ increases K/sub Ic/ by approx. 75%. For the product SM 58 LW 11, the fracture toughness was measured on pieces taken from different parts of a large cylinder to investigate the effects of segregation phenomena and of partial crystallization and formation of small cristobalite inclusions which decrease K/sub Ic/ by approx. 25%.
Date: January 1, 1983
Creator: Matzke, H.; Kahl, L.; Routbort, J.L. & Saidl, J.
Partner: UNT Libraries Government Documents Department

Oxygen diffusion in cuprate superconductors

Description: Superconducting properties of the cuprate superconductors depend on the oxygen content of the material; the diffusion of oxygen is thus an important process in the fabrication and application of these materials. This article reviews studies of the diffusion of oxygen in La{sub 2}{sub {minus}}{sub {times}}Sr{sub {times}}CuO{sub 4}, YBa{sub 2}Cu{sub 3}O{sub 7}{sub {minus}}{delta}, YBa{sub 2}Cu{sub 4}O{sub 8}, and the Bi{sub 2}Sr{sub 2}Ca{sub n}{sub {minus}}{sub 1}Cu{sub n}O{sub 2}{sub +}{sub 4} (n = 1, and 2) superconductors, and attempt to elucidate the atomic mechanisms responsible.
Date: January 1, 1995
Creator: Routbort, J.L. & Rothman, S.J.
Partner: UNT Libraries Government Documents Department

Oxygen diffusion in high- Tc superconductors

Description: The cuprate superconductors are fascinating not only because of their technical promise, but also because of their structures, especially the anisotropy of the crystal lattice. There are some structural similarities among these compounds, but also significant differences. Measurements of the oxygen tracer diffusion coefficients have been carried out as a function of temperature, oxygen partial pressure, crystal orientation, and doping in the La-Sr-Cu-0, Y-Ba-Cu-0, and Bi-Sr-Ca-Cu-0 systems. These measurements have revealed a variety of defect mechanisms operating in these compounds; the exact nature of the mechanism depends on the details of the structure.
Date: July 1, 1992
Creator: Rothman, S.J. & Routbort, J.L.
Partner: UNT Libraries Government Documents Department

Atomic transport of oxygen

Description: Atomic transport of oxygen in nonstoichiometric oxides is an extremely important topic which overlaps science and technology. In many cases the diffusion of oxygen controls sintering, grain growth, and creep. High oxygen diffusivity is critical for efficient operation of many fuel cells. Additionally, oxygen diffusivities are an essential ingredient in any point defect model. Secondary Ion Mass Spectrometry (SIMS) is the most accurate modern technique to measure oxygen tracer diffusion. This paper briefly reviews the principles and applications of SIMS for the measurement of oxygen transport. Case studies are taken from recent work on ZnO and some high-temperature superconductors.
Date: June 15, 1994
Creator: Routbort, J. L. & Tomlins, G. W.
Partner: UNT Libraries Government Documents Department

Oxygen diffusion in high-{Tc} superconductors

Description: The cuprate superconductors are fascinating not only because of their technical promise, but also because of their structures, especially the anisotropy of the crystal lattice. There are some structural similarities among these compounds, but also significant differences. Measurements of the oxygen tracer diffusion coefficients have been carried out as a function of temperature, oxygen partial pressure, crystal orientation, and doping in the La-Sr-Cu-0, Y-Ba-Cu-0, and Bi-Sr-Ca-Cu-0 systems. These measurements have revealed a variety of defect mechanisms operating in these compounds; the exact nature of the mechanism depends on the details of the structure.
Date: July 1, 1992
Creator: Rothman, S. J. & Routbort, J. L.
Partner: UNT Libraries Government Documents Department

Creep in electronic ceramics

Description: High-temperature creep measurements combined with microstructural investigations can be used to elucidate deformation mechanisms that can be related to the diffusion kinetics and defect chemistry of the minority species. This paper will review the theoretical basis for this correlation and illustrate it with examples from some important electronic ceramics having a perovskite structure. Recent results on BaTiO{sub 3}, (La{sub 1{minus}x}Sr){sub 1{minus}y}MnO{sub 3+{delta}}, YBa{sub 2}Cu{sub 3}O{sub x}, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x}, (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} and Sr(Fe,Co){sub 1.5}O{sub x} will be presented.
Date: April 27, 2000
Creator: Routbort, J. L.; Goretta, K. C. & Arellano-Lopez, A. R.
Partner: UNT Libraries Government Documents Department

Steady-state deformation of some lithium ceramics

Description: The stress-strain behavior of Li/sub 2/O, LiAlO/sub 2/ and Li/sub 2/ZrO/sub 3/ polycrystals, with densities varying from 0.70 to 0.95 of the theoretical, has been measured in constant-crosshead-speed compression tests at temperatures of 700 to 1000/sup 0/C with strain rates ranging from about 10/sup -6/ to 10/sup -4/ s/sup -1/. A steady-state stress, sigma/sub s/, for which the work-hardening rate becomes zero, was achieved. These results, therefore, yield information equivalent to that obtained from creep experiments. Limited data on LiAlO/sub 2/ and Li/sub 2/ZrO/sub 3/ were obtained. Nevertheless, under comparable conditions the lithium aluminate and zirconate were considerably stronger than the Li/sub 2/O. This finding may be related to differences in crystal structure. It is, however, likely that in operation as a function breeder blanket material, the oxide will swell whereas the aluminate and the zirconate will crack. 5 refs., 6 figs., 1 tab.
Date: May 1, 1987
Creator: Poeppel, R.B.; Routbort, J.L.; Billone, M.C.; Applegate, D.S.; Buchmann, E. & Londschien, B.
Partner: UNT Libraries Government Documents Department

Search for small-angle neutron scattering in MnO at 1700K

Description: A preliminary small-angle scattering (SANS) experiment has been performed on MnO single crystal at the Intense Pulsed Neutron Source. The experiment was preformed at 1700/sup 0/K at oxygen partial pressures of 2.2 x 10/sup -4/, 1 x 10/sup 2/, and 2 x 10/sup 2/ Pa, which resulted in deviations from stoichiometry of about 0.0015, 0.082, and 0.127. No statistically significant change in SANS was observed at this temperature with the pressure changes. Neither was any significant change observed in the wavelength-dependent sample transmission, also measured in-situ as a function of pressure. Therefore, either clustering of cation vacancies is negligible in MnO for these conditions, or the clusters are smaller than about 5 A. Of proposed cluster configurations, only the existence of the smallest (4:1, 6:2, or possible 8:3) appears to be consistent with these results.
Date: 1986
Creator: Routbort, J. L.; Epperson, J. E.; Klippert, T. E. & Goretta, K. C.
Partner: UNT Libraries Government Documents Department

Deformation of nonstoichiometric CuO polycrystals

Description: The current interest in fabrication methods for high temperature superconductors has fostered heightened interest in the precursor materials. It has been shown that the reaction kinetics for formation of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x}, (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} and YBa{sub 2}Cu{sub 3}O{sub x} are related to the copper oxide precursor through both the size of the starting powder and the oxidation state, with finer CuO powders reacting faster. Many proposed fabrication methods include a high temperature mechanical working step during the reaction process. However, little is known about the diffusional and mechanical properties of CuO at the fabrication temperatures of interest. The literature indicates only that the electrical conductivity of CuO is independent of the oxygen partial pressure (PO{sub 2}). Therefore, only intrinsic ionization occurs for CuO. Thus, for a given temperature, the concentrations of electrons and holes are fixed. In this study, compression creep was employed to shed light upon the diffusion of rate-controlling defects in nonstoichiometric CuO. Tests were performed on polycrystalline samples over a range of temperature (T), PO{sub 2}, and strain rate ({epsilon}). Data were analyzed with standard equations for steady-state creep. Electron microscopy was used in conjunction with the data analysis to identify the operative creep mechanisms. These results for CuO will be contrasted with previous work performed on another copper oxide compound, Cu{sub 2}O.
Date: July 1, 1994
Creator: Boling-Risser, M. A.; Goretta, K. C. & Routbort, J. L.
Partner: UNT Libraries Government Documents Department

Pressure drop, heat transfer, critical heat flux, and flow stability of two-phase flow boiling of water and ethylene glycol/water mixtures - final report for project "Efficent cooling in engines with nucleate boiling."

Description: Because of its order-of-magnitude higher heat transfer rates, there is interest in using controllable two-phase nucleate boiling instead of conventional single-phase forced convection in vehicular cooling systems to remove ever increasing heat loads and to eliminate potential hot spots in engines. However, the fundamental understanding of flow boiling mechanisms of a 50/50 ethylene glycol/water mixture under engineering application conditions is still limited. In addition, it is impractical to precisely maintain the volume concentration ratio of the ethylene glycol/water mixture coolant at 50/50. Therefore, any investigation into engine coolant characteristics should include a range of volume concentration ratios around the nominal 50/50 mark. In this study, the forced convective boiling heat transfer of distilled water and ethylene glycol/water mixtures with volume concentration ratios of 40/60, 50/50, and 60/40 in a 2.98-mm-inner-diameter circular tube has been investigated in both the horizontal flow and the vertical flow. The two-phase pressure drop, the forced convective boiling heat transfer coefficient, and the critical heat flux of the test fluids were determined experimentally over a range of the mass flux, the vapor mass quality, and the inlet subcooling through a new boiling data reduction procedure that allowed the analytical calculation of the fluid boiling temperatures along the experimental test section by applying the ideal mixture assumption and the equilibrium assumption along with Raoult's law. Based on the experimental data, predictive methods for the two-phase pressure drop, the forced convective boiling heat transfer coefficient, and the critical heat flux under engine application conditions were developed. The results summarized in this final project report provide the necessary information for designing and implementing nucleate-boiling vehicular cooling systems.
Date: January 19, 2011
Creator: Yu, W.; France, D. M. & Routbort, J. L. (Energy Systems)
Partner: UNT Libraries Government Documents Department

Comparison of short and longer term loading on the creep behaviour of alumina-silicon carbide whisker composites

Description: The incorporation of SiC whiskers into alumina ceramics has resulted in several improved room temperature properties of the composite such as fracture toughness, strength, erosion resistance and fatigue. The creep resistance has also been generally observed to increase with the addition of whiskers. However, significant scatter in measured secondary creep rates still exist, depending on the material and the test conditions that were utilized. The objective of this investigation was to compare two separate creep tests performed in compression using a SiC{sub w}/Al{sub 2}O{sub 3} material obtained from the same process batch. The differences in creep behavior between the tests could thus be ascribed to the difference in creep conditions solely. In one case the creep behavior was studied under short term loading (<3 h) conditions in air, while longer term loading (<100 h) conditions in argon were applied in the other case. The creep results and the microstructure of the samples were compared and related to each other, and to previous results in the literature.
Date: November 1, 1992
Creator: Swan, H.; Arellano-Lopez, A.R. de; Dominguez-Rodriguez, A.; Routbort, J.L. & Swain, M.V.
Partner: UNT Libraries Government Documents Department

Superplasticity and joining of zirconia-based ceramics

Description: Steady-state creep and joining of alumina/zirconia composites containing alumina volume fractions of 20, 60, and 85% have been investigated between 1,250 and 1,350 C. Superplasticity of these compounds is controlled by grain-boundary sliding and the creep rate is a function of alumina volume fraction, not grain size. Using the principles of superplasticity, pieces of the composite have been joined by applying the stress required to achieve 5 to 10% strain to form a strong interface at temperatures as low as 1,200 C.
Date: December 10, 1999
Creator: Dominguez-Rodriguez, A.; Gutierrez-Mora, F.; Jimenez-Melendo, M.; Chaim, R. & Routbort, J. L.
Partner: UNT Libraries Government Documents Department

Transient and steady-state erosion of in-situ reinforced silicon nitride

Description: Relative to most other materials silicon nitride is very erosion resistant. However, the resulting surface flaws degrade strength - a serious concern for component designers. AlliedSignal Ceramic Components GS-44 in-situ reinforced silicon nitride was eroded in a slinger apparatus. Both transient (extremely low level) and steady-state erosion regimes were investigated. Alumina particles with effective average diameters of 140 Jim and 63 {mu}m were used at velocities of 50 m/s, 100 m/s, and 138 m/s. Biaxial tensile strength was measured. Strength decreased by about 15% after a very small erodent dosage and then remained virtually constant with further erosion. In-situ reinforcement produces R-curve behavior in which the fracture toughness increases with crack size. The effect of this is quite dramatic with strength loss being significantly less than expected for a normal silicon nitride with constant fracture toughness.
Date: October 1, 1994
Creator: Karasek, K.R.; Whalen, P.J.; Rateick, R.G. Jr.; Hamilton, A.C. & Routbort, J.L.
Partner: UNT Libraries Government Documents Department

Erosion of a geopolymer.

Description: Solid-particle erosion studies were conducted on a representative geopolymer. The test conditions were normal impact of 390-{micro}m angular Al{sub 2}O{sub 3} erodent particles moving at 50, 70, or 100 m/s. Steady-state erosion rates were obtained and the material-loss mechanism was studied by scanning electron microscopy. The geopolymer responded as a classic brittle material. Elastic-plastic indentation events led to formation of brittle cleavage cracks that resulted in spallation of material. The erosion rate was proportional to erodent velocity to the 2.3 power. The erosion rate and mechanism for the geopolymer were nearly identical to what has been observed for erosion of Si single crystals.
Date: July 2, 2002
Creator: Goretta, K. C.; Chen, N.; Routbort, J. L.; Lukey, G. C. & van Deventer, J. S. J.
Partner: UNT Libraries Government Documents Department

Mechanical properties and deformation of polycrystalline lithium orthosilicate

Description: Room-temperature strength, fracture toughness, Young's modulus, and thermal-shock resistance were determined for 68--98% dense lithium orthosilicate (Li/sub 4/SiO/sub 4/) specimens. In the low-density regime, both strength and fracture toughness were controlled by the density of the specimen. At high density, the strength depends on grain size. Young's modulus values ranged from 30--103 GPa at densities between 68 and 98% TD. A critical quenching temperature difference in the range of 150--170/degree/C was observed in thermal-shock tests of bar specimens. Steady-state creep tests indicated 90% dense Li/sub 4/SiO/sub 4/ fractures at T less than or equal to 800/degree/C before reaching steady state and deforms plastically at 900/degree/C. It is more creep-resistant at 900/degree/C than Li/sub 2/O, about equal to Li/sub 2/Zr)/sub 3/, and less than LiA10/sub 2/. 13 refs., 4 figs., 1 tab.
Date: February 1, 1988
Creator: Bar, K.; Chu, C.Y.; Singh, J.P.; Goretta, K.C.; Routbort, J.L.; Billone, M.C. et al.
Partner: UNT Libraries Government Documents Department

Deformation of an alumina-zirconia-silicon carbide-whisker reinforced composite

Description: Alumina-zirconia composites (MERC) with the addition of 0 and 28 vol % of silicon carbide whiskers have been deformed under compression at constant rate at 1450C, in air. Mechanical results are compared with the behavior of a commercial alumina (ARCO) with analogous proportions of silicon carbide-whiskers (0 and 30 vol %), under the same testing conditions. Flow stresses are typically higher for ARCO materials than for MERC materials. The addition of SiC whiskers increases flow stresses in ARCO composites, and decreases them for MERC samples. Microstructural observations confirm that the change in flow stress is the result of the presence of a glass phase in the MERC samples.
Date: April 1, 1993
Creator: Calderon-Moreno, J. M.; DeArellano-Lopez, A. R.; Dominguez-Rodriguez, A.; Routbort, J. L. & Leasky, T.
Partner: UNT Libraries Government Documents Department

Review and assessment of nanofluid technology for transportation and other applications.

Description: This report provides a literature review on the research and development work contributing to the current status of nanofluid technology for heat transfer applications in industrial processes. Nanofluid technology is a relatively new field, and as such, the supporting studies are not extensive. Specifically, the experimental results and theoretical predictions regarding the enhancement of the thermal conductivity and convective heat transfer of nanofluids relative to conventional heat transfer fluids were reviewed and assessments were made of the current status to derive future research and development directions for industrial applications. Pertinent parameters were considered individually as to the current state of knowledge. Experimental results from multiple research groups were cast into a consistent parameter, 'the enhancement ratio,' to facilitate comparisons of data among research groups and identification of thermal property and heat transfer trends. The current state of knowledge is presented as well as areas where the data are currently inconclusive or conflicting. Heat transfer enhancement for available nanoparticles is known to be in the 15-40% range, with a few situations resulting in orders of magnitude enhancement. The direction of future research should be to substantiate the lower range results and to continue investigations into the higher enhancements. The focus of this study is primarily transportation applications. However, some attention is given to other industrial applications of nanofluid heat transfer. Also discussed are barriers to be addressed prior to commercialization of nanofluids.
Date: May 31, 2007
Creator: Yu, W.; France, D. M.; Choi, S. U. S.; Routbort, J. L. & Systems, Energy
Partner: UNT Libraries Government Documents Department

Solid-particle erosion of an Al{sub 2}O{sub 3}-SiC-TiC composite

Description: An electrodischarge-machinable Al{sub 2}O{sub 3}-SiC-TiC composite developed by Industrial Ceramic Technology, Inc., has a high fracture toughness, 9.6{+-}0.6 MPm{sup 1/2}, as measured by indentation, and a Vickers hardness of 20.3{+-}0.6 GPa. The composite`s resistance to solid-particle erosion was measured for 143-{mu}m dia SiC particles impacting at 20-90{degree} angles and 50-100 m/s velocities. Erosion rate exhibited a maximum for normal incidence, and the erosion resistance was better than that of commercial Al{sub 2}O{sub 3}. SEM indicated that material wastage was by a combination of brittle fracture and microplasticity.
Date: November 1, 1996
Creator: Jiang, M.; Goretta, K.C.; Singh, D.; Routbort, J.L. & Schuldies, J.J.
Partner: UNT Libraries Government Documents Department