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2,355 Matching Results
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Measures of microstructure to improve estimates and bounds on elastic constants and transport coefficients in heterogeneous media
The most commonly discussed measures of microstructure in composite materials are the spatial correlation functions, which in a porous medium measure either the grain-to-grain correlations, or the pore-to-pore correlations in space. Improved bounds based on this information such as the Beran-Molyneux bounds for bulk modulus and the Beran bounds for conductivity are well-known. It is first shown here how to make direct use of this information to provide estimates that always lie between these upper and lower bounds for any microstructure whenever the microgeometry parameters are known. Then comparisons are made between these estimates, the bounds, and two new types of estimates. One new estimate for elastic constants makes use of the Peselnick-Meister bounds (based on Hashin-Shtrikman methods) for random polycrystals of laminates to generate self-consistent values that always lie between the bounds. A second new type of estimate for conductivity assumes that measurements of formation factors (of which there are at least two distinct types in porous media, associated respectively with pores and grains) are available, and computes new bounds based on this information. The paper compares and contrasts these various methods in order to clarify just what microstructural information and how precisely that information needs to be known …
Date:
October 7, 2004
Creator:
Berger, E. L.
Object Type:
Article
System:
The UNT Digital Library
Analysis of multichannel internet communication.
A novel method employing machine-based learning to identify messages related to other messages is described and evaluated. This technique may enable an analyst to identify and correlate a small number of related messages from a large sample of individual messages. The classic machine learning techniques of decision trees and naive Bayes classification are seeded with few (or no) messages of interest and 'learn' to identify other related messages. The performance of this approach and these specific learning techniques are evaluated and generalized.
Date:
October 1, 2004
Creator:
Nove, Charles E.; Maclin, Richard Frank; Theuninck, Andrew K. (University of Minnesota-Duluth, Duluth, MN); Newland, Jeremy L. (University of Minnesota-Duluth, Duluth, MN); Torrey, Lisa A. (University of Wisconsin-Madison, Madison, WI) & Robinson, Eric R. (University of Wisconsin-Madison, Madison, WI)
Object Type:
Report
System:
The UNT Digital Library
A Framework for viewing theoretical, technological, economic and market potential of carbon dioxide capture and storage
Paper presents an intelectual framework for viewing how the theoretical, technological, economic and market potentials of carbon dioxide capture and storage are related to each other.
Date:
October 4, 2004
Creator:
Dooley, James J.
Object Type:
Report
System:
The UNT Digital Library
Environmental Barrier Coatings for the Energy Efficient Heat Engines Program
This program aimed to develop a fundamental understanding of the microstructural, mechanical, and chemical properties of Ta{sub 2}O{sub 5}-based coatings for Si{sub 3}N{sub 4} (AS800) substrates and optimize such coatings for environmental barriers. The program consisted of three tasks: processing of Ta{sub 2}O{sub 5} coatings, phase and microstructural development, and life-limiting phenomena. Northwestern University formed a cross-functional team with Lehigh University, Honeywell Inc., and Oak Ridge National Laboratory. The major accomplishments are: (1) Conditions for the plasma spray of Ta{sub 2}O{sub 5} and its alloys were optimized to provide maximum density and thickness. (2) Adherent small particle plasma spray coatings of Ta{sub 2}O{sub 5} can be routinely prepared. (3) Ta{sub 2}O{sub 5} can be stabilized against its disruptive phase transformation to 1400 C by the addition of one or more oxides of Al, La, and/or Nb. (4) Residual stresses in the Ta{sub 2}O{sub 5} coatings were measured using X-rays and changed with thermal exposure. (5) Properly doped coatings are more resistant against thermal cycling than undoped coatings, and can be cycled many thousand times without spallation. (6) Water vapor testing in the ORNL Keiser Rig of adherent coatings showed that undoped Ta{sub 2}O{sub 5} is not an effective barrier at …
Date:
October 31, 2004
Creator:
Faber, Katherine
Object Type:
Report
System:
The UNT Digital Library
Dose Rate Calibration of a Commercial Beta-Particle Irradiator Used in Archeological and Geological Dating
None
Date:
October 31, 2004
Creator:
Bernal, S. M.
Object Type:
Report
System:
The UNT Digital Library
Laser hazard analysis for various candidate diode lasers associated with the high resolution pulsed scanner.
A laser hazard analysis and safety assessment was performed for each various laser diode candidates associated with the High Resolution Pulse Scanner based on the ANSI Standard Z136.1-2000, American National Standard for the Safe Use of Lasers. A theoretical laser hazard analysis model for this system was derived and an Excel{reg_sign} spreadsheet model was developed to answer the 'what if questions' associated with the various modes of operations for the various candidate diode lasers.
Date:
October 1, 2004
Creator:
Augustoni, Arnold L.
Object Type:
Report
System:
The UNT Digital Library
A Unified Model of Secondary Electron Cascades in Diamond
In this paper we present a detailed and unified theoretical treatment of secondary electron cascades that follow the absorption of an X-ray photon. A Monte Carlo model has been constructed that treats in detail the evolution of electron cascades induced by photoelectrons and by Auger electrons following inner shell ionizations. Detailed calculations are presented for cascades initiated by electron energies between 0.1-10 keV. The present paper expands our earlier work by extending the primary energy range, by improving the treatment of secondary electrons, especially at low electron energies, by including ionization by holes, and by taking into account their coupling to the crystal lattice. The calculations describe the three-dimensional evolution of the electron cloud, and monitor the equivalent instantaneous temperature of the free-electron gas as the system cools. The dissipation of the impact energy proceeds predominantly through the production of secondary electrons whose energies are comparable to the binding energies of the valence (40-50 eV) and of the core electrons (300 eV). The electron cloud generated by a 10 keV electron is strongly anisotropic in the early phases of the cascade (t {le} 1 fs). At later times, the sample is dominated by low energy electrons, and these are scattered …
Date:
October 13, 2004
Creator:
Ziaja, B; London, R A & Hajdu, J
Object Type:
Article
System:
The UNT Digital Library
The evaluation of several corrosion mitigation strategies for oil coolers used by the strategic petroleum reserve.
The goal of this study was to first establish the fitness for service of the carbon steel based oil coolers presently located at the Bryan Mound and West Hackberry sites, and second, to compare quantitatively the performance of two proposed corrosion mitigation strategies. To address these goals, a series of flow loops were constructed to simulate the conditions present within the oil coolers allowing the performance of each corrosion mitigation strategy, as well as the baseline performance of the existing systems, to be assessed. As prior experimentation had indicated that the corrosion and fouling was relatively uniform within the oil coolers, the hot and cold side of the system were simulated, representing the extremes of temperature observed within a typical oil cooler. Upon completion of the experiment, the depth of localized attack observed on carbon steel was such that perforation of the tube walls would likely result within a 180 day drawdown procedure at West Hackberry. Furthermore, considering the average rate of wall recession (from LPR measurements), combined with the extensive localized attack (pitting) which occurred in both environments, the tubing wall thickness remaining after 180 days would be less than that required to contain the operating pressures of the …
Date:
October 1, 2004
Creator:
Hinkebein, Thomas E.; Levin, Bruce L. & Enos, David George
Object Type:
Report
System:
The UNT Digital Library
Phase transformation of poled "chem-prep" PZT 95/5-2Nb ceramic under quasi-static loading conditions.
Specimens of poled 'chem-prep' PNZT ceramic from batch HF803 were tested under hydrostatic, uniaxial, and constant stress difference loading conditions at three temperatures of -55, 25, and 75 C and pressures up to 500 MPa. The objective of this experimental study was to obtain the electro-mechanical properties of the ceramic and the criteria of FE (Ferroelectric) to AFE (Antiferroelectric) phase transformations so that grain-scale modeling efforts can develop and test models and codes using realistic parameters. The poled ceramic undergoes anisotropic deformation during the transition from a FE to an AFE structure. The lateral strain measured parallel to the poling direction was typically 35 % greater than the strain measured perpendicular to the poling direction. The rates of increase in the phase transformation pressures per temperature changes were practically identical for both unpoled and poled PNZT HF803 specimens. We observed that the retarding effect of temperature on the kinetics of phase transformation appears to be analogous to the effect of shear stress. We also observed that the FE-to-AFE phase transformation occurs in poled ceramic when the normal compressive stress, acting perpendicular to a crystallographic plane about the polar axis, equals the hydrostatic pressure at which the transformation otherwise takes place.
Date:
October 1, 2004
Creator:
Lee, Moo Yul; Montgomery, Stephen Tedford & Hofer, John H.
Object Type:
Report
System:
The UNT Digital Library
Laboratory evaluation of frozen soil target materials with a fused interface.
To investigate the performance of artificial frozen soil materials with a fused interface, split tension (or 'Brazilian') tests and unconfined uniaxial compression tests were carried out in a low temperature environmental chamber. Intact and fused specimens were fabricated from four different soil mixtures (962: clay-rich soil with bentonite; DNA1: clay-poor soil; DNA2: clay-poor soil with vermiculite; and DNA3: clay-poor soil with perlite). Based on the 'Brazilian' test results and density measurements, the DNA3 mixture was selected to closely represent the mechanical properties of the Alaskan frozen soil. The healed-interface by the same soil layer sandwiched between two blocks of the same material yielded the highest 'Brazilian' tensile strength of the interface. Based on unconfined uniaxial compression tests, the frictional strength of the fused DNA3 specimens with the same soil appears to exceed the shear strength of the intact specimen.
Date:
October 1, 2004
Creator:
Bronowski, David R. & Lee, Moo Yul
Object Type:
Report
System:
The UNT Digital Library
Natural gas production problems : solutions, methodologies, and modeling.
Natural gas is a clean fuel that will be the most important domestic energy resource for the first half the 21st centtuy. Ensuring a stable supply is essential for our national energy security. The research we have undertaken will maximize the extractable volume of gas while minimizing the environmental impact of surface disturbances associated with drilling and production. This report describes a methodology for comprehensive evaluation and modeling of the total gas system within a basin focusing on problematic horizontal fluid flow variability. This has been accomplished through extensive use of geophysical, core (rock sample) and outcrop data to interpret and predict directional flow and production trends. Side benefits include reduced environmental impact of drilling due to reduced number of required wells for resource extraction. These results have been accomplished through a cooperative and integrated systems approach involving industry, government, academia and a multi-organizational team within Sandia National Laboratories. Industry has provided essential in-kind support to this project in the forms of extensive core data, production data, maps, seismic data, production analyses, engineering studies, plus equipment and staff for obtaining geophysical data. This approach provides innovative ideas and technologies to bring new resources to market and to reduce the overall …
Date:
October 1, 2004
Creator:
Rautman, Christopher Arthur; Herrin, James M.; Cooper, Scott Patrick; Basinski, Paul M. (El Paso Production Company, Houston, TX); Olsson, William Arthur; Arnold, Bill Walter et al.
Object Type:
Report
System:
The UNT Digital Library
Passive microwave tags : LDRD 52709, FY04 final report.
This report describes both a general methodology and specific examples of completely passive microwave tags. Surface acoustic wave (SAW) devices were used to make tags for both identification and sensing applications at different frequencies. SAW correlators were optimized for wireless identification, and SAW filters were developed to enable wireless remote sensing of physical properties. Identification tag applications and wireless remote measurement applications are discussed. Significant effort went into optimizing the SAW devices used for this work, and the lessons learned from that effort are reviewed.
Date:
October 1, 2004
Creator:
Brocato, Robert Wesley
Object Type:
Report
System:
The UNT Digital Library
Shroud boundary condition characterization experiments at the Radiant Heat Facility.
A series of experiments was performed to better characterize the boundary conditions from an inconel heat source ('shroud') painted with Pyromark black paint. Quantifying uncertainties in this type of experimental setup is crucial to providing information for comparisons with code predictions. The characterization of this boundary condition has applications in many scenarios related to fire simulation experiments performed at Sandia National Laboratories Radiant Heat Facility (RHF). Four phases of experiments were performed. Phase 1 results showed that a nominal 1000 C shroud temperature is repeatable to about 2 C. Repeatability of temperatures at individual points on the shroud show that temperatures do not vary more than 10 C from experiment to experiment. This variation results in a 6% difference in heat flux to a target 4 inches away. IR camera images showed the shroud was not at a uniform temperature, although the control temperature was constant to about {+-}2 C during a test. These images showed that a circular shaped, flat shroud with its edges supported by an insulated plate has a temperature distribution with higher temperatures at the edges and lower temperatures in the center. Differences between the center and edge temperatures were up to 75 C. Phase 3 …
Date:
October 1, 2004
Creator:
Suo-Anttila, Jill Marie; Nakos, James Thomas & Gill, Walter
Object Type:
Report
System:
The UNT Digital Library
High fidelity frictional models for MEMS.
The primary goals of the present study are to: (1) determine how and why MEMS-scale friction differs from friction on the macro-scale, and (2) to begin to develop a capability to perform finite element simulations of MEMS materials and components that accurately predicts response in the presence of adhesion and friction. Regarding the first goal, a newly developed nanotractor actuator was used to measure friction between molecular monolayer-coated, polysilicon surfaces. Amontons law does indeed apply over a wide range of forces. However, at low loads, which are of relevance to MEMS, there is an important adhesive contribution to the normal load that cannot be neglected. More importantly, we found that at short sliding distances, the concept of a coefficient of friction is not relevant; rather, one must invoke the notion of 'pre-sliding tangential deflections' (PSTD). Results of a simple 2-D model suggests that PSTD is a cascade of small-scale slips with a roughly constant number of contacts equilibrating the applied normal load. Regarding the second goal, an Adhesion Model and a Junction Model have been implemented in PRESTO, Sandia's transient dynamics, finite element code to enable asperity-level simulations. The Junction Model includes a tangential shear traction that opposes the relative …
Date:
October 1, 2004
Creator:
Carpick, Robert W.; Reedy, Earl David, Jr.; Bitsie, Fernando; de Boer, Maarten Pieter; Corwin, Alex David; Ashurst, William Robert et al.
Object Type:
Report
System:
The UNT Digital Library
Damage displacement phenomena in Si junction devices : mapping and interpreting a science and technology knowledge domain.
As technical knowledge grows deeper, broader, and more interconnected, knowledge domains increasingly combine a number of sub-domains. More often than not, each of these sub-domains has its own community of specialists and forums for interaction. Hence, from a generalist's viewpoint, it is sometimes difficult to understand the relationships between the sub-domains within the larger domain; and, from a specialist's viewpoint, it may be difficult for those working in one sub-domain to keep abreast of knowledge gained in another sub-domain. These difficulties can be especially important in the initial stages of creating new projects aimed at adding knowledge either at the domain or sub-domain level. To circumvent these difficulties, one would ideally like to create a map of the knowledge domain--a map which would help clarify relationships between the various sub-domains, and a map which would help inform choices regarding investing in the production of knowledge either at the domain or sub-domain levels. In practice, creating such a map is non-trivial. First, relationships between knowledge subdomains are complex, and not likely to be easily simplified into a visualizable 2-or-few-dimensional map. Second, even if some of the relationships can be simplified, capturing them would require some degree of expert understanding of the …
Date:
October 1, 2004
Creator:
Tsao, Jeffrey Yeenien
Object Type:
Report
System:
The UNT Digital Library
A Classification Compliance Audit Report on the State's Library and Records Positions
Report of the Texas State Auditor's Office related to determining whether state agencies conform to the Position Classification Plan by ensuring proper classification of library and records positions.
Date:
October 2004
Creator:
Texas. Office of the State Auditor.
Object Type:
Report
System:
The Portal to Texas History
A Review of Implementation of Sunset Advisory Commission Management Actions at 15 State Agencies
Report of the Texas State Auditor's Office related to determining the implementation status of non-statutory recommendations (management actions) included in the Sunset Advisory Commission's (Sunset) report to the 78th Legislature.
Date:
October 2004
Creator:
Texas. Office of the State Auditor.
Object Type:
Report
System:
The Portal to Texas History
An Audit Report on Cash Controls at the University of Texas Health Science Center at Houston
Report of the Texas State Auditor's Office related to the University of Texas Health Science Center at Houston's (Health Science Center) controls for receiving, safeguarding, and disbursing cash, the accuracy of its accounting and record-keeping of collections and of state revenues, receipts, and disbursements, and its compliance with state laws and regulations related to cash management.
Date:
October 2004
Creator:
Texas. Office of the State Auditor.
Object Type:
Report
System:
The Portal to Texas History
An Audit Report on the Department of Transportation's Administration of Construction Contracts
Report of the Texas State Auditor's Office related to assessing controls over the Department of Transportation's payments on construction contracts, specifically regarding whether the Department effectively monitors and controls payments on construction projects, and whether Department management has the information necessary to support decision-making related to construction projects.
Date:
October 2004
Creator:
Texas. Office of the State Auditor.
Object Type:
Report
System:
The Portal to Texas History
[Victoria County Courthouse Photograph #2]
Photograph of the Victoria County Courthouse in Victoria, Texas.
Date:
October 20, 2004
Creator:
unknown
Object Type:
Photograph
System:
The Portal to Texas History
[Ott Hotel Photograph #13]
Photograph of the Ott Hotel in Liberty, Texas.
Date:
October 2004
Creator:
unknown
Object Type:
Photograph
System:
The Portal to Texas History
[Victoria County Courthouse Photograph #4]
Photograph of the Victoria County Courthouse in Victoria, Texas.
Date:
October 20, 2004
Creator:
unknown
Object Type:
Photograph
System:
The Portal to Texas History
[Ott Hotel Photograph #7]
Photograph of the Ott Hotel in Liberty, Texas.
Date:
October 2004
Creator:
unknown
Object Type:
Photograph
System:
The Portal to Texas History
[Ott Hotel Photograph #10]
Photograph of the Ott Hotel in Liberty, Texas.
Date:
October 2004
Creator:
unknown
Object Type:
Photograph
System:
The Portal to Texas History