Pybus -- A Python Software Bus (open access)

Pybus -- A Python Software Bus

A software bus, just like its hardware equivalent, allows for the discovery, installation, configuration, loading, unloading, and run-time replacement of software components, as well as channeling of inter-component communication. Python, a popular open-source programming language, encourages a modular design on software written in it, but it offers little or no component functionality. However, the language and its interpreter provide sufficient hooks to implement a thin, integral layer of component support. This functionality can be presented to the developer in the form of a module, making it very easy to use. This paper describes a Pythonmodule, PyBus, with which the concept of a ''software bus'' can be realized in Python. It demonstrates, within the context of the ATLAS software framework Athena, how PyBus can be used for the installation and (run-time) configuration of software, not necessarily Python modules, from a Python application in a way that is transparent to the end-user.
Date: October 14, 2004
Creator: Lavrijsen, Wim T.L.P.
Object Type: Article
System: The UNT Digital Library
Classroom HVAC: Improving ventilation and saving energy -- field study plan (open access)

Classroom HVAC: Improving ventilation and saving energy -- field study plan

The primary goals of this research effort are to develop, evaluate, and demonstrate a very practical HVAC system for classrooms that consistently provides classrooms (CRs) with the quantity of ventilation in current minimum standards, while saving energy, and reducing HVAC-related noise levels. This research is motivated by the public benefits of energy efficiency, evidence that many CRs are under-ventilated, and public concerns about indoor environmental quality in CRs. This document provides a summary of the detailed plans developed for the field study that will take place in 2005 to evaluate the energy and IAQ performance of a new classroom HVAC technology. The field study will include measurements of HVAC energy use, ventilation rates, and IEQ conditions in 10 classrooms with the new HVAC technology and in six control classrooms with a standard HVAC system. Energy use and many IEQ parameters will be monitored continuously, while other IEQ measurements will be will be performed seasonally. Continuously monitored data will be remotely accessed via a LonWorks network. Instrument calibration plans that vary with the type of instrumentation used are established. Statistical tests will be employed to compare energy use and IEQ conditions with the new and standard HVAC systems. Strengths of this …
Date: October 14, 2004
Creator: Apte, Michael G.; Faulkner, David; Hodgson, Alfred T. & Sullivan, Douglas P.
Object Type: Report
System: The UNT Digital Library
Involvement of Linear Plasmids in Aerobic Biodegradation of Vinyl Chloride (open access)

Involvement of Linear Plasmids in Aerobic Biodegradation of Vinyl Chloride

Pseudomonas putida strain AJ and Ochrobactrum strain TD were isolated from hazardous waste sites based on their ability to use vinyl chloride (VC) as a sole source of carbon and energy under aerobic conditions. Strains AJ and TD also use ethene and ethylene oxide as growth substrates. Strain AJ contained a linear megaplasmid (approximately 260 kb) when grown on VC or ethene, but no circular plasmids. While growing on ethylene oxide, the size of the linear plasmid in strain AJ decreased to approximately 100 kb, although its ability to use VC as a substrate was retained. The linear plasmids in strain AJ were cured and its ability to consume VC, ethene, and ethylene oxide was lost following growth on a rich substrate (Luria-Bertani broth) through at least three transfers. Strain TD contained three linear plasmids, ranging in size from approximately 100 kb to 320 kb, when growing on VC or ethene. As with strain AJ, the linear plasmids in strain TD were cured following growth on Luria -Bertani broth and its ability to consume VC and ethene was lost. Further analysis of these linear plasmids may help reveal the pathway for VC biodegradation in strains AJ and TD and explain …
Date: June 14, 2004
Creator: BRIGMON, ROBINL.
Object Type: Article
System: The UNT Digital Library
Incorporation of Integral Fuel Burnable Absorbers Boron and Gadolinium into Zirconium-Alloy Fuel Clad Material (open access)

Incorporation of Integral Fuel Burnable Absorbers Boron and Gadolinium into Zirconium-Alloy Fuel Clad Material

Long-lived fuels require the use of higher enrichments of 235U or other fissile materials. Such high levels of fissile material lead to excessive fuel activity at the beginning of life. To counteract this excessive activity, integral fuel burnable absorbers (IFBA) are added to some rods in the fuel assembly. The two commonly used IFBA elements are gadolinium, which is added as gadolinium-oxide to the UO2 powder, and boron, which is applied as a zirconium-diboride coating on the UO2 pellets using plasma spraying or chemical vapor deposition techniques. The incorporation of IFBA into the fuel has to be performed in a nuclear-regulated facility that is physically separated from the main plant. These operations tend to be very costly because of their small volume and can add from 20 to 30% to the manufacturing cost of the fuel. Other manufacturing issues that impact cost and performance are maintaining the correct levels of dosing, the reduction in fuel melting point due to gadolinium-oxide additions, and parasitic neutron absorption at fuel's end-of-life. The goal of the proposed research is to develop an alternative approach that involves incorporation of boron or gadolinium into the outer surface of the fuel cladding material rather than as an …
Date: December 14, 2004
Creator: Sridharan, K.; Renk, T.J.; Lahoda, E.J. & Corradini, M.L
Object Type: Report
System: The UNT Digital Library
Hyperspectral Geobotanical Remote Sensing for CO2 Storage Monitoring (open access)

Hyperspectral Geobotanical Remote Sensing for CO2 Storage Monitoring

This project's goal is to develop remote sensing methods for early detection and spatial mapping, over whole regions simultaneously, of any surface areas under which there are significant CO2 leaks from deep underground storage formations. If large amounts of CO2 gas percolated up from a storage formation below to within plant root depth of the surface, the CO2 soil concentrations near the surface would become elevated and would affect individual plants and their local plant ecologies. Excessive soil CO2 concentrations are observed to significantly affect local plant and animal ecologies in our geothermal exploration, remote sensing research program at Mammoth Mountain CA USA. We also know from our geothermal exploration remote sensing programs, that we can map subtle hidden faults by spatial signatures of altered minerals and of plant species and health distributions. Mapping hidden faults is important because in our experience these highly localized (one to several centimeters) spatial pathways are good candidates for potentially significant CO2 leaks from deep underground formations. The detection and discrimination method we are developing uses primarily airborne hyperspectral, high spatial (3 meter) with 128 band wavelength resolution, visible and near infrared reflected light imagery. We also are using the newly available ''Quickbird'' satellite …
Date: May 14, 2004
Creator: Pickles, W & Cover, W
Object Type: Book
System: The UNT Digital Library
Material Property Estimation for Direct Detections of DNAPL using Integrated Ground-Penetrating Radar Velocity, Imaging and Attribute Analysis (open access)

Material Property Estimation for Direct Detections of DNAPL using Integrated Ground-Penetrating Radar Velocity, Imaging and Attribute Analysis

The focus of our work is direct detection of DNAPLs, specifically chlorinated solvents, via material property estimation from surface ground-penetrating radar (GPR) data. We combine sophisticated GPR processing methodology with quantitative attribute analysis and material property estimation to determine the location and extent of residual and/or pooled DNAPL in both the vadose and saturated zones. An important byproduct of our research is state-of-the-art imaging which allows us to pinpoint attribute anomalies, characterize stratigraphy, identify fracture zones, and locate buried objects. Implementation and verification of these methodologies will be a significant advance in GPR research and in meeting DOE's need for reliable in-situ characterization of DNAPL contamination. Chlorinated solvents have much lower electric permittivity and conductivity than water. An electrical property contrast is induced when solvents displace water in the sediment column resulting in an anomalous GPR signature. To directly identify zones of DNAPL contamination, we focus on three aspects of reflected wave behavior--propagation velocity, frequency dependent attenuation, and amplitude variation with offset (AVO). Velocity analysis provides a direct estimate of electric permittivity, attenuation analysis provides a measure of conductivity, and AVO behavior is used to estimate the permittivity ratio at a reflecting boundary. Areas of anomalously low electric permittivity and …
Date: June 14, 2004
Creator: Bradford, John; Smithson, Scott B. & Holbrook, W. Stephen
Object Type: Report
System: The UNT Digital Library
Field power measurements of imaging equipment (open access)

Field power measurements of imaging equipment

According to the U.S. Department of Energy, electricity use by non-PC commercial office equipment is growing at an annual rate of nearly 5 percent (AEO 2003). To help address this growth in consumption, U.S. EPA periodically updates its ENERGY STAR specifications as products and markets change. This report presents background research conducted to help EPA update the ENERGY STAR specification for imaging equipment, which covers printers, fax machines, copiers, scanners, and multifunction devices (MFDs). We first estimated the market impact of the current ENERGY STAR imaging specification, finding over 90 percent of the current market complies with the specification. We then analyzed a sample of typical new imaging products, including 11 faxes, 57 printers and 19 copiers/MFD. For these devices we metered power levels in the most common modes: active/ready/sleep/off, and recorded features that would most likely affect energy consumption. Our metering indicates that for many products and speed bins, current models consume substantially less power than the current specification. We also found that for all product categories, power consumption varied most considerably across technology (i.e. inkjet vs. laser). Although inkjet printers consumed less energy than laser printers in active, ready and sleep-mode, they consumed more power on average while …
Date: May 14, 2004
Creator: McWhinney, Marla; Homan, Gregory; Brown, Richard; Roberson, Judy; Nordman, Bruce & Busch, John
Object Type: Report
System: The UNT Digital Library
Modeling Laser Effects on the Final Optics in Simulated IFE Environments (open access)

Modeling Laser Effects on the Final Optics in Simulated IFE Environments

When laser light interacts with a material's surface, photons rapidly heat the electronic system, resulting in very fast energy transfer to the underlying atomic crystal structure. The intense rate of energy deposition in the shallow sub-surface layer creates atomic defects, which alter the optical characteristics of the surface itself. In addition, the small fraction of energy absorbed in the mirror leads to its global deformation by thermal and gravity loads (especially for large surface area mirrors). The aim of this research was to model the deformation of mirror surfaces at multiple length and time scales for applications in advanced Inertial Fusion Energy (IFE) systems. The goal is to control micro- and macro-deformations by material system and structural design. A parallel experimental program at UCSD has been set up to validate the modeling efforts. The main objective of the research program was to develop computer models and simulations for Laser-Induced Damage (LID) in reflective and transmissive final optical elements in IFE laser-based systems. A range of materials and material concepts were investigated and verified by experiments at UCSD. Four different classes of materials were considered: (1) High-reflectivity FCC metals (e.g. Cu, Au, Ag, and Al), (2) BCC metals (e.g. Mo, Ta …
Date: August 14, 2004
Creator: Ghoniem, Nasr
Object Type: Report
System: The UNT Digital Library
Fluorescent CdSe/ZnS nanocrystal-peptide conjugates for long-term, nontoxic imaging and nuclear targeting in living cells (open access)

Fluorescent CdSe/ZnS nanocrystal-peptide conjugates for long-term, nontoxic imaging and nuclear targeting in living cells

One of the biggest challenges in cell biology is the imaging of living cells. For this purpose, the most commonly used visualization tool is fluorescent markers. However, conventional labels, such as organic fluorescent dyes or green fluorescent proteins (GFP), lack the photostability to allow the tracking of cellular events that happen over minutes to days. In addition, they are either toxic to cells (dyes), or difficult to construct and manipulate (GFP). We report here the use of a new class of fluorescent labels, silanized CdSe/ZnS nanocrystal-peptide conjugates, for imaging the nuclei of living cells. CdSe/ZnS nanocrystals, or so called quantum dots (qdots), are extremely photostable, and have been used extensively in cellular imaging of fixed cells. However, most of the studies about living cells so far have been concerned only with particle entry into the cytoplasm or the localization of receptors on the cell membrane. Specific targeting of qdots to the nucleus of living cells ha s not been reported in previous studies, due to the lack of a targeting mechanism and proper particle size. Here we demonstrate for the first time the construction of a CdSe/ZnS nanocrystal-peptide conjugate that carries the SV40 large T antigen nuclear localization signal (NLS), …
Date: June 14, 2004
Creator: Chen, Fanqing & Gerion, Daniele
Object Type: Article
System: The UNT Digital Library
Design and characterization of a neutralized-transport experiment for heavy-ion fusion (open access)

Design and characterization of a neutralized-transport experiment for heavy-ion fusion

In heavy-ion inertial-confinement fusion systems, intense beams of ions must be transported from the exit of the final focus magnet system through the fusion chamber to hit millimeter-sized spots on the target. Effective plasma neutralization of intense ion beams in this final transport is essential for a heavy-ion fusion power plant to be economically competitive. The physics of neutralized drift has been studied extensively with particle-in-cell simulations. To provide quantitative comparisons of theoretical predictions with experiment, the Virtual National Laboratory for Heavy Ion Fusion has completed the construction and has begun experimentation with the Neutralized Transport Experiment (NTX). The experiment consists of three main sections, each with its own physics issues. The injector is designed to generate a very high-brightness, space-charge-dominated potassium beam while still allowing variable perveance by a beam aperturing technique. The magnetic-focusing section, consisting of four pulsed magnetic quadrupoles, permits the study of beam tuning, as well as the effects of phase space dilution due to higher-order nonlinear fields. In the final section, the converging ion beam exiting the magnetic section is transported through a drift region with plasma sources for beam neutralization, and the final spot size is measured under various conditions of neutralization. In this …
Date: March 14, 2004
Creator: Henestroza, E.; Eylon, S.; Roy, P. K.; Yu, S. S.; Anders, A.; Bieniosek, F. M. et al.
Object Type: Article
System: The UNT Digital Library
ADVANCED TECHNOLOGIES FOR STRIPPER GAS WELL ENHANCEMENT (open access)

ADVANCED TECHNOLOGIES FOR STRIPPER GAS WELL ENHANCEMENT

As part of Task 1 in Advanced Technologies for Stripper Gas Well Enhancement, Schlumberger Data & Consulting Services (DCS) joined with two Appalachian Basin producers, Great Lakes Energy Partners, LLC, and Belden & Blake Corporation to develop methodologies for identification and enhancement of stripper wells with economic upside potential. These industry partners previously provided us with data for more than 700 wells in northwestern Pennsylvania. Phase 1 goals of this project are to develop and validate methodologies that can quickly and cost-effectively identify underperforming wells with remediation potential. We have enhanced and streamlined our software and are using it with the latest versions of Microsoft's{trademark} Access and Excel programs. During the last quarter of 2002, Great Lakes provided us with additional data for approximately 2,200 wells located in their Cooperstown field situated in northwestern Pennsylvania. We identified approximately 130 potential remediation candidates, and Great Lakes personnel are currently reviewing this list for viable remediation. Within the last few weeks, a list of five candidates have been chosen for refract, in addition to two alternate wells. This field has provided a rigorous test of our software and analytical methods. We have processed all the information provided to us including the Cooperstown …
Date: July 14, 2004
Creator: MacDonald, Ronald J.
Object Type: Report
System: The UNT Digital Library
The Near Elimination of Hysteresis in Pd/Cr2O3 Composites (open access)

The Near Elimination of Hysteresis in Pd/Cr2O3 Composites

Although its value varies with the microstructure, hysteresis always accompanies hydride formation and decomposition in Pd(pure)-H, e.g., it is present even in nano-crystalline and thin films. Internal oxidation of Pd0.93Cr0.07 alloys leads to a pure Pd matrix containing nano-crystalline chromia precipitates. The characteristic hysteresis of Pd-H almost disappears in this form of Pd. The reasons for this are discussed. Hysteresis is an almost universal feature of first order solid state transitions. Its presence means that when such a transition is reversed, it follows a different path than that taken in the forward direction leading to a loss of useful work. Hysteresis is, of course, a reflection of the irreversibility of the transition.
Date: July 14, 2004
Creator: SHANAHAN, KIRKL
Object Type: Article
System: The UNT Digital Library
Diffusion in silicon isotope heterostructures (open access)

Diffusion in silicon isotope heterostructures

The simultaneous diffusion of Si and the dopants B, P, and As has been studied by the use of a multilayer structure of isotopically enriched Si. This structure, consisting of 5 pairs of 120 nm thick natural Si and {sup 28}Si enriched layers, enables the observation of {sup 30}Si self-diffusion from the natural layers into the {sup 28}Si enriched layers, as well as dopant diffusion from an implanted source in an amorphous Si cap layer, via Secondary Ion Mass Spectrometry (SIMS). The dopant diffusion created regions of the multilayer structure that were extrinsic at the diffusion temperatures. In these regions, the Fermi level shift due to the extrinsic condition altered the concentration and charge state of the native defects involved in the diffusion process, which affected the dopant and self-diffusion. The simultaneously recorded diffusion profiles enabled the modeling of the coupled dopant and self-diffusion. From the modeling of the simultaneous diffusion, the dopant diffusion mechanisms, the native defect charge states, and the self- and dopant diffusion coefficients can be determined. This information is necessary to enhance the physical modeling of dopant diffusion in Si. It is of particular interest to the modeling of future electronic Si devices, where the nanometer-scale …
Date: May 14, 2004
Creator: Silvestri, Hughes Howland
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Retention/Diffusivity Studies in Free-Surface Flowing Liquid Lithium (open access)

Retention/Diffusivity Studies in Free-Surface Flowing Liquid Lithium

FLIRE was designed to measure the hydrogen and helium retention and diffusivity in a flowing stream of liquid lithium, and it has accomplished these goals. Retention coefficients for helium in the flowing liquid stream were 0.1-2% for flow speeds of 44 cm/s and implantation energies between 500 and 2000 eV. The energy dependence of retention is linear for the energy range considered, as expected, and the dependence of retention on flow velocity fits the expected square-root of flow speed dependence. Estimates of the helium diffusion coefficient in the flowing lithium stream were {approx} 4 x 10{sup -7} cm{sup 2}/s, and are independent of implantation energy. This value is much lower than expected, which could be due to several factors, such as mixing, bubble formation or surface film formation. In the case of hydrogen, long term retention and release mechanisms are of greatest importance, since this relates to tritium inventory in flowing lithium PFCs for fusion applications. The amount of hydride formation was measured for flowing lithium exposed to neutral deuterium gas. Thermal desorption spectroscopy (TDS) measurements indicate that the hydride concentration was between 0.1 and 0.2% over a wide range of pressures (6.5 x 10{sup -5} to 1 Torr). This …
Date: December 14, 2004
Creator: Stubbers, R. A.; Miley, G. H.; Nieto, M.; Olczak, W.; Ruzic, D. N. & Hassanein, A.
Object Type: Report
System: The UNT Digital Library
Can fuzzy logic bring complex problems into focus? Modeling imprecise factors in environmental policy (open access)

Can fuzzy logic bring complex problems into focus? Modeling imprecise factors in environmental policy

In modeling complex environmental problems, we often fail to make precise statements about inputs and outcome. In this case the fuzzy logic method native to the human mind provides a useful way to get at these problems. Fuzzy logic represents a significant change in both the approach to and outcome of environmental evaluations. Risk assessment is currently based on the implicit premise that probability theory provides the necessary and sufficient tools for dealing with uncertainty and variability. The key advantage of fuzzy methods is the way they reflect the human mind in its remarkable ability to store and process information which is consistently imprecise, uncertain, and resistant to classification. Our case study illustrates the ability of fuzzy logic to integrate statistical measurements with imprecise health goals. But we submit that fuzzy logic and probability theory are complementary and not competitive. In the world of soft computing, fuzzy logic has been widely used and has often been the ''smart'' behind smart machines. But it will require more effort and case studies to establish its niche in risk assessment or other types of impact assessment. Although we often hear complaints about ''bright lines,'' could we adapt to a system that relaxes these …
Date: June 14, 2004
Creator: McKone, Thomas E. & Deshpande, Ashok W.
Object Type: Report
System: The UNT Digital Library
Inhalation of primary motor vehicle emissions: Effects of urbanpopulation and land area (open access)

Inhalation of primary motor vehicle emissions: Effects of urbanpopulation and land area

Urban population density can influence transportation demand, as expressed through average daily vehicle-kilometers traveled per capita (VKT). In turn, changes in transportation demand influence total passenger vehicle emissions. Population density can also influence the fraction of total emissions that are inhaled by the exposed urban population. Equations are presented that describe these relationships for an idealized representation of an urban area. Using analytic solutions to these equations, we investigate the effect of three changes in urban population and urban land area (infill, sprawl, and constant-density growth) on per capita inhalation intake of primary pollutants from passenger vehicles. The magnitude of these effects depends on density-emissions elasticity ({var_epsilon}{sub e}), a normalized derivative relating change in population density to change in vehicle emissions. For example, if urban population increases, per capita intake is less with infill development than with constant-density growth if {var_epsilon}{sub e} is less than -0.5, while for {var_epsilon}{sub e} greater than -0.5 the reverse is true.
Date: June 14, 2004
Creator: Marshall, Julian D.; McKone, Thomas E. & Nazaroff, William W.
Object Type: Article
System: The UNT Digital Library
Magnetic field measurements of the LHC inner triplet quadrupoles produced at Fermilab (open access)

Magnetic field measurements of the LHC inner triplet quadrupoles produced at Fermilab

Production of 18 superconducting low-beta quadrupoles (MQXB) for the LHC is well advanced. These 5.5 m long magnets are designed to operate at 1.9 K with a peak field gradient of 215 T/m in 70 mm aperture. Two MQXB cold masses with a dipole orbit corrector between them form a single cryogenic unit (LQXB) which is the Q2 optical element of the final focus triplets in the LHC interaction regions. A program of magnetic field quality and alignment measurements of the cold masses is performed at room temperature during magnet fabrication and of the LQXB assembly as well as at superfluid helium temperature. Results of these measurements are summarized in this paper.
Date: July 14, 2004
Creator: al., G. V. Velev et
Object Type: Article
System: The UNT Digital Library
Determining the surface and interface structure of nanomaterials (open access)

Determining the surface and interface structure of nanomaterials

This paper informally speculates on the challenges of determining the atomic-scale surface and interface structure of nanomaterials. The relative capabilities of different techniques are compared. This includes discussion of theoretical methods needed to interpret experimental techniques.
Date: June 14, 2004
Creator: Van Hove, Michel A.
Object Type: Article
System: The UNT Digital Library
Closure Plan for the E-Area Low-Level Waste Facility (open access)

Closure Plan for the E-Area Low-Level Waste Facility

To comply with the applicable requirements of the U.S. Department of Energy (US DOE), this closure plan has been developed for the E-Area Low-Level Waste Facility(LLWF). The plan is organized according to the specifications of the Format and Content Guide for U.S. Department of Energy Low-Level Waste Disposal Facility Closure Plans. Section 2 provides a brief overview of the general facility description, closure approach, closure schedule, related activities, and key assumptions. Sections 3 and 4 provide specific details of facility characteristics and the technical approach to closure, respectively, as well as supporting information. Additional schedule details are provided in Section 5. Section 6 provides a list of recommended items for consideration in association with future revisions to the E-Area LLWF Closure Plan and Performance Assessment (PA). Operation of the E-Area LLWF began with placement of the first low-level waste box within the Low Activity Waste (LAW) Vault. It is anticipated that operations will continue for at least 25 years, and that a 100-year institutional control period will follow cessation of operations. It is further anticipated that closure will be conducted in the following three phases: operational closure, interim closure, and final closure. Operational closure will be conducted during the 25 …
Date: July 14, 2004
Creator: PHIFER, MARKA.l
Object Type: Report
System: The UNT Digital Library
Techniques for assessing the performance of in situ bioreduction and immobilization of metals and radionuclides in contaminated subsurface environments (open access)

Techniques for assessing the performance of in situ bioreduction and immobilization of metals and radionuclides in contaminated subsurface environments

Department of Energy (DOE) facilities within the weapons complex face a daunting challenge of remediating huge below inventories of legacy radioactive and toxic metal waste. More often than not, the scope of the problem is massive, particularly in the high recharge, humid regions east of the Mississippi river, where the off-site migration of contaminants continues to plague soil water, groundwater, and surface water sources. As of 2002, contaminated sites are closing rapidly and many remediation strategies have chosen to leave contaminants in-place. In situ barriers, surface caps, and bioremediation are often the remedial strategies of chose. By choosing to leave contaminants in-place, we must accept the fact that the contaminants will continue to interact with subsurface and surface media. Contaminant interactions with the geosphere are complex and investigating long term changes and interactive processes is imperative to verifying risks. We must be able to understand the consequences of our action or inaction. The focus of this manuscript is to describe recent technical developments for assessing the performance of in situ bioremediation and immobilization of subsurface metals and radionuclides. Research within DOE's NABIR and EMSP programs has been investigating the possibility of using subsurface microorganisms to convert redox sensitive toxic metals …
Date: November 14, 2004
Creator: Jardine, P. M.; Watson, D. B.; Blake, D. A.; Beard, L. P.; Brooks, S. C.; Carley, J. M. et al.
Object Type: Article
System: The UNT Digital Library
An nth-order, Gaussian Energy Distribution Model for Sintering (open access)

An nth-order, Gaussian Energy Distribution Model for Sintering

Although it is well known that the rate of sintering is governed by deceleratory kinetics, it is often difficult to fit power-law and nth-order reaction models over broad time-temperature ranges. This work shows that a phenomenological model combining a reaction order with an activation energy distribution can correlate surface area as a function of sintering time and temperature over a greater range of those variables. Qualitatively, the activation energy distribution accounts the dependence of free energy on particle size and material defects, while the reaction order accounts for geometric factors such as a distribution of diffusion lengths. The model is demonstrated for sintering of hydroxyapatite using data of Bailliez and Nzihou (Chem. Eng. J. 98 (2004), 141-152).
Date: December 14, 2004
Creator: Burnham, A K
Object Type: Article
System: The UNT Digital Library
Mechanistic Studies of Improved Foam EOR Processes (open access)

Mechanistic Studies of Improved Foam EOR Processes

The objective of this research is to widen the application of foam to enhanced oil recovery (EOR) by investigating fundamental mechanisms of foams in porous media. This research will lay the groundwork for more applied research on foams for improved sweep efficiency in miscible gas, steam and surfactant-based EOR. Task 1 investigates the pore-scale interactions between foam bubbles and polymer molecules. Task 2 examines the mechanisms of gas trapping, and interaction between gas trapping and foam effectiveness. Task 3 investigates mechanisms of foam generation in porous media. Significant progress was made during this period on all three Tasks. Regarding Task 1, we continued comparisons of foam behavior in sandpacks with and without polymer and oil. As in our previous results, decane was moderately destabilizing to foam. Xanthan polymer did not stabilize foam in the presence of decane in this case. Rather, it appears to have destabilized foam, so that pressure gradient decreased in spite of the increase in aqueous-phase viscosity. Research on Task 2 included the first shake-down experiments with our new apparatus for gas-phase tracer tests for direct measurement of trapped-gas saturation with foam. In addition, we began to analyze CT images of gas-phase tracer in foam displacements, which …
Date: June 14, 2004
Creator: Rossen, William R.
Object Type: Report
System: The UNT Digital Library
Structural properties of the geometrically frustrated pyrochlore Tb2Ti2O7 (open access)

Structural properties of the geometrically frustrated pyrochlore Tb2Ti2O7

Although materials that exhibit nearest-neighbor-only antiferromagnetic interactions and geometrical frustration theoretically should not magnetically order in the absence of disorder, few such systems have been observed experimentally. One such system appears to be the pyrochlore Tb{sub 2}Ti{sub 2}O{sub 7}. However, previous structural studies indicated that Tb{sub 2}Ti{sub 2}O{sub 7} is an imperfect pyrochlore. To clarify the situation, we performed neutron powder diffraction (NPD) and x-ray absorption fine structure (XAFS) measurements on samples that were prepared identically to those that show no magnetic order. The NPD measurements show that the long-range structure of Tb{sub 2}Ti{sub 2}O{sub 7} is well ordered with no structural transitions between 4.5 and 600 K. In particular, mean-squared displacements (u{sup 2}'s) for each site follow a Debye model with no offsets. No evidence for Tb/Ti site interchange was observed within an upper limit of 2%. Likewise, no excess or deficiency in the oxygen stoichiometry was observed, within an upper limit of 2% of the nominal pyrochlore value. Tb L{sub III} and Ti K-edge XAFS measurements from 20-300 K similarly indicate a well-ordered local structure. Other aspects of the structure are considered. We conclude that Tb{sub 2}Ti{sub 2}O{sub 7} has, within experimental error, an ideal, disorder-free pyrochlore lattice, …
Date: June 14, 2004
Creator: Han, Sang-Wook; Gardner, Jason S. & Booth, Corwin H.
Object Type: Article
System: The UNT Digital Library
National Alliance of Clean Energy Incubator Activities - Final Technical Report (open access)

National Alliance of Clean Energy Incubator Activities - Final Technical Report

Summary of activity related to development of the Alliance of Clean Energy Business Incubators and incubation services provided to the clean energy sector by the Advanced Technology Development Center at the Georgia Institute of Technology.
Date: December 14, 2004
Creator: Chris Downing, P.E.
Object Type: Report
System: The UNT Digital Library