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De-coupling of exchange and persistence times in atomistic modelsof glass formers

Description: With molecular dynamics simulations of a fluid mixture of classical particles interacting with pair-wise additive Weeks-Chandler-Andersen potentials, we consider the time series of particle displacements and thereby determine distributions for local persistence times and local exchange times. These basic characterizations of glassy dynamics are studied over a range of super-cooled conditions and shown to have behaviors, most notably de-coupling, similar to those found in kinetically constrained lattice models of structural glasses. Implications are noted.
Date: August 15, 2007
Creator: Hedges, Lester O.; Maibaum, Lutz; Chandler, David & Garrahan, Juan P.
Partner: UNT Libraries Government Documents Department

Phosphazene Based Additives for Improvement of Safety and Battery Lifetimes in Lithium-Ion Batteries

Description: There need to be significant improvements made in lithium-ion battery technology, principally in the areas of safety and useful lifetimes to truly enable widespread adoption of large format batteries for the electrification of the light transportation fleet. In order to effect the transition to lithium ion technology in a timely fashion, one promising next step is through improvements to the electrolyte in the form of novel additives that simultaneously improve safety and useful lifetimes without impairing performance characteristics over wide temperature and cycle duty ranges. Recent efforts in our laboratory have been focused on the development of such additives with all the requisite properties enumerated above. We present the results of the study of novel phosphazene based electrolytes additives.
Date: October 1, 2011
Creator: Harrup, Mason K; Gering, Kevin L; Rollins, Harry W; Sazhin, Sergiy V; Benson, Michael T; Jamison, David K et al.
Partner: UNT Libraries Government Documents Department

An infinite branching hierarchy of time-periodic solutions of the Benjamin-Ono equation

Description: We present a new representation of solutions of the Benjamin-Ono equation that are periodic in space and time. Up to an additive constant and a Galilean transformation, each of these solutions is a previously known, multi-periodic solution; however, the new representation unifies the subset of such solutions with a fixed spatial period and a continuously varying temporal period into a single network of smooth manifolds connected together by an infinite hierarchy of bifurcations. Our representation explicitly describes the evolution of the Fourier modes of the solution as well as the particle trajectories in a meromorphic representation of these solutions; therefore, we have also solved the problem of finding periodic solutions of the ordinary differential equation governing these particles, including a description of a bifurcation mechanism for adding or removing particles without destroying periodicity. We illustrate the types of bifurcation that occur with several examples, including degenerate bifurcations not predicted by linearization about traveling waves.
Date: July 1, 2008
Creator: Wilkening, Jon
Partner: UNT Libraries Government Documents Department


Description: This paper reports the results in the effort to destabilize lithium borohydride for reversible hydrogen storage. A number of metals, metal hydrides, metal chlorides and complex hydrides were selected and evaluated as the destabilization agents for reducing dehydriding temperature and generating dehydriding-rehydriding reversibility. It is found that some additives are effective. The Raman spectroscopic analysis shows the change of B-H binding nature.
Date: May 10, 2006
Creator: Au, Ming
Partner: UNT Libraries Government Documents Department

Test report - caustic addition system operability test procedure

Description: This Operability Test Report documents the test results of test procedure WHC-SD-WM-OTP-167 ``Caustic Addition System Operability Test Procedure``. The Objective of the test was to verify the operability of the 241-AN-107 Caustic Addition System. The objective of the test was met
Date: October 13, 1995
Creator: Parazin, R.E.
Partner: UNT Libraries Government Documents Department

A nonlocal, ordinary, state-based plasticity model for peridynamics.

Description: An implicit time integration algorithm for a non-local, state-based, peridynamics plasticity model is developed. The flow rule was proposed in [3] without an integration strategy or yield criterion. This report addresses both of these issues and thus establishes the first ordinary, state-based peridynamics plasticity model. Integration of the flow rule follows along the lines of the classical theories of rate independent J{sub 2} plasticity. It uses elastic force state relations, an additive decomposition of the deformation state, an elastic force state domain, a flow rule, loading/un-loading conditions, and a consistency condition. Just as in local theories of plasticity (LTP), state variables are required. It is shown that the resulting constitutive model does not violate the 2nd law of thermodynamics. The report also develops a useful non-local yield criterion that depends upon the yield stress and horizon for the material. The modulus state for both the ordinary elastic material and aforementioned plasticity model is also developed and presented.
Date: May 1, 2011
Creator: Mitchell, John Anthony
Partner: UNT Libraries Government Documents Department

Stack filter classifiers

Description: Just as linear models generalize the sample mean and weighted average, weighted order statistic models generalize the sample median and weighted median. This analogy can be continued informally to generalized additive modeels in the case of the mean, and Stack Filters in the case of the median. Both of these model classes have been extensively studied for signal and image processing but it is surprising to find that for pattern classification, their treatment has been significantly one sided. Generalized additive models are now a major tool in pattern classification and many different learning algorithms have been developed to fit model parameters to finite data. However Stack Filters remain largely confined to signal and image processing and learning algorithms for classification are yet to be seen. This paper is a step towards Stack Filter Classifiers and it shows that the approach is interesting from both a theoretical and a practical perspective.
Date: January 1, 2009
Creator: Porter, Reid B & Hush, Don
Partner: UNT Libraries Government Documents Department


Description: This first semiannual report covers efforts to select the materials that will be used in this project. Discussions of crude oils, rocks, smooth mineral surfaces, and drilling mud additives are included in this report.
Date: June 1, 2002
Creator: Buckley, Jill S. & Morrow, Norman r.
Partner: UNT Libraries Government Documents Department

Tailoring the intergranular phases in silicon nitride for improved toughness

Description: Intergranular glass phases can have a significant influence on fracture resistance (R-curve behavior) of Si nitride ceramics and appears to be related to debonding of the {beta}-Si{sub 3}N{sub 4}/oxynitride-glass interfaces. Applying the results from {beta}- Si{sub 3}N{sub 4}-whisker/oxynitride-glass model systems, self- reinforced Si nitrides with different sintering additive ratios were investigated. Si nitrides sintered with a lower Al{sub 2}O{sub 3}: Y{sub 2}O{sub 3} additive ratio exhibited higher stead-state fracture toughness together with a steeply rising R-curve. Analytical electron microscopy suggested that the different fracture behavior is related to the Al content in the SiAlON growth band on the elongated grains, which could result in differences in interfacial bonding structures between the grains and the intergranular glass.
Date: December 31, 1996
Creator: Sun, E. Y.; Becher, P. F.; Plucknett, K. P.; Waters, S. B.; Hirao, K. & Brito, M. E.
Partner: UNT Libraries Government Documents Department

Metallic fuels: The EBR-II legacy and recent advances

Description: Experimental Breeder Reactor – II (EBR-II) metallic fuel was qualified for high burnup to approximately 10 atomic per cent. Subsequently, the electrometallurgical treatment of this fuel was demonstrated. Advanced metallic fuels are now investigated for increased performance, including ultra-high burnup and actinide burning. Advances include additives to mitigate the fuel/cladding chemical interaction and uranium alloys that combine Mo, Ti and Zr to improve alloy performance. The impacts of the advances—on fabrication, waste streams, electrorefining, etc.—are found to be minimal and beneficial. Owing to extensive research literature and computational methods, only a modest effort is required to complete their development.
Date: September 1, 2012
Creator: Porter, Douglas L.; Hayes, Steven L. & Kennedy, J. Rory
Partner: UNT Libraries Government Documents Department

Detailed chemical kinetic modeling of diesel combustion with oxygenated fuels

Description: The influence of oxygenated hydrocarbons as additives to diesel fuels on ignition, NOx emissions and soot production has been examined using a detailed chemical kinetic reaction mechanism. N-heptane was used as a representative diesel fuel, and methanol, ethanol, dimethyl ether and dimethoxymethane were used as oxygenated fuel additives. It was found that addition of oxygenated hydrocarbons reduced NOx levels and reduced the production of soot precursors. When the overall oxygen content in the fuel reached approximately 25% by mass, production of soot precursors fell effectively to zero, in agreement with experimental studies. The kinetic factors responsible for these observations are discussed.
Date: October 28, 1999
Creator: Pitz, W J; Curran, H J; Fisher, E; Glaude, P A; Marinov, N M & Westbrook, C K
Partner: UNT Libraries Government Documents Department

Enzymology of acetone-butanol-isopropanol formation. Final technical report, June 1, 1985--July 31, 1997

Description: Several species of anaerobic bacteria within the genus Clostridium produce acetone, n-butanol, and isopropanol (solvents), which are important industrial chemicals and fuel additives. Commercial production of solvents by the clostridia is a classical example of largescale chemical production by bacterial fermentation. Although the fermentation has been in use for decades, it still faces problems that include strain degeneration, a relatively low final product concentration due to butanol toxicity, and a need to fine-tune the growth conditions to achieve a high yield. The long-term goal of this project was to understand the fundamental properties of bacterial solvent production for the purpose of achieving a positive control on the metabolic switch leading to solvent production and on the proportion of useful products formed as well as of developing strategies for preventing the degeneration of producing strains. The objectives for the project included those approved in 1985 for the initial project period and those approved in 1988, 1991, and 1994 when the project was renewed. The objectives for the entire project period may be summarized as (1) To purify and characterize the enzymes that are specifically required for the formation of acetone, butanol, and isopropanol by the clostridia, (2) To clone and characterize the genes that encode enzymes or regulatory proteins for the production of solvents, and the emphasis was to determine the control mechanism for the transcription of the solvent-production genes, (3) To characterize the onset of solvent production and the intra- and extra-cellular parameters surrounding the metabolic switch to solvent production, and (4) To determine the genetic identity of the strains of solvent-producing clostridia that are currently in use by investigators around the world.
Date: March 1, 1998
Creator: Chen, Jiann-Shin
Partner: UNT Libraries Government Documents Department

Clean, agile alternative binders, additives and plasticizers for propellant and explosive formulations

Description: As part of the Strategic Environmental Research and Development Program (SERDP) a clean, agile manufacturing of explosives, propellants and pyrotechniques (CANPEP) effort set about to identify new approaches to materials and processes for producing propellants, explosives and pyrotechniques (PEP). The RDX based explosive PBXN-109 and gun propellant M-43 were identified as candidates for which waste minimization and recycling modifications might be implemented in a short time frame. The binders, additives and plasticizers subgroup identified cast non-curable thermoplastic elastomer (TPE) formulations as possible replacement candidates for these formulations. Paste extrudable explosives were also suggested as viable alternatives to PBXN-109. Commercial inert and energetic TPEs are reviewed. Biodegradable and hydrolyzable binders are discussed. The applicability of various types of explosive formulations are reviewed and some issues associated with implementation of recyclable formulations are identified. It is clear that some processing and weaponization modifications will need to be made if any of these approaches are to be implemented. The major advantages of formulations suggested here over PBXN-109 and M-43 is their reuse/recyclability. Formulations using TPE or Paste could by recovered from a generic bomb or propellant and reused if they met specification or easily reprocessed and sold to the mining industry.
Date: December 1, 1994
Creator: Hoffman, D.M.; Hawkins, T.W. & Lindsay, G.A.
Partner: UNT Libraries Government Documents Department

Zone sintering of ceramic fuels

Description: Cold pressed UC{sup 2} fuel compacts are sintered at temperatures greater than about 1850 C while in contract with a sintering facilitator material, e.g., tantalum, niobium, tungsten or a metal carbide such as uranium carbide, thereby allowing for a reduction in the overall porosity and leaving the desired product, i.e., a highly dense, large-grained uranium dicarbide. The process of using the sintering facilitator materials can be applied in the preparation of other carbide materials.
Date: December 31, 1991
Creator: Matthews, R.B.; Chidester, K.M. & Moore, H.G.
Partner: UNT Libraries Government Documents Department

The physics of coal liquid slurry atomization. Quarterly technical report, January 1995--March 1995

Description: In this reporting period, the major objective of the research was to develop a technique for measuring the extensional viscosity of coal-water slurries. The Extensional properties of the suspending solutions (water + additives) and the slurries (coal + water + additives) are determined using the breakup of droplets in the drip mode. Photographic visualization of the breakup of viscoelastic materials in the drip mode has shown that these materials exhibit completely different breakup patterns when contrasted to viscoinelastic materials. The ligaments were seen to undergo a very large stretching motion before they breakup, resulting in long threads of liquid attached to droplets. The diameter of the ligaments at breakup, as measured by the Greenfield digital spray analyzer, was of the order of 30 {mu}m. The drip mode of breakup was used to extract useful information on the extensional properties of CWS.
Date: September 1, 1995
Partner: UNT Libraries Government Documents Department

Gas pressure sintering of silicon nitride to optimize fracture toughness

Description: Gas-pressure sintering (GPS) can be used to densify silicon nitride containing a wide variety of sintering additives. Parameters affecting the sintering behavior include densification temperature, densification time, grain growth temperature, grain growth time and heating rates. The Si{sub 3}N{sub 4}-6% Y{sub 2}O{sub 3}-2% A1{sub 2}O{sub 3} samples sintered to high densities at all conditions used in the present study, whereas the Si{sub 3}N{sub 4}-Sr{sub 2}La{sub 4}Yb{sub 4}(SiO{sub 4}){sub 6}O{sub 2} samples required the highest temperatures and longest times to achieve densities {ge}98 % T. D. The main effect on the fracture toughness for Si{sub 3}N{sub 4}-6% Y{sub 2}O{sub 3}-2% A1{sub 2}O{sub 3} samples was the use of a lower densification temperature, which was 1900C in the present study. For the Si{sub 3}N{sub 4}-Sr{sub 2}La{sub 4}Yb{sub 4}SiO4{sub 4}){sub 6}O{sub 2} composition, fracture toughness was sensitive to and improved by a slower heating rate (10c/min), a lower densification temperature (1900`), a higher grain growth temperature (2000C), and a longer grain growth time (2 h).
Date: June 1, 1995
Creator: Tiegs, T.N.; Nunn, S.D.; Beavers, T.M.; Menchhofer, P.A.; Barker, D.L. & Coffey, D.W.
Partner: UNT Libraries Government Documents Department

Surfactant loss control in chemical flooding: Spectroscopic and calorimetric study of adsorption and precipitation on reservoir minerals. Quarterly technical progress report, January 1, 1995--March 31, 1995

Description: Earlier reported results on the adsorption/desorption behaviors of single surfactant as well as mixtures of surfactant of tetradecyl trimethyl ammonium chloride (TTAC) and pentadecyl ethoxylated nonyl phenol (NP-15) indicated that the phenomena in mixed surfactant systems are more complex than those in single surfactant systems. To better understand the mechanisms involved in adsorption and desorption processes of mixed surfactant system, changes in the ratios of TTAC:NP-15 mixtures after adsorption both at the alumina-water interface and in the bulk are discussed in this report. It was found that the initial mixing ratios of TTAC:NP-15 changed significantly after adsorption over the concentration ranges studied. The adsorption behavior is directly related to these changes of mixing ratios. The possible structure of the adsorbed layer is also discussed for dfferent mixing ratios. In the low concentration range, electrostatic attraction between the cationic surfactant, TTAC, and the negatively charged alumina surface is dominant and the adsorption of TTAC,is higher than that of NP-15. With an increase in total surfactant concentration pre-adsorbed TTAC molecules function as anchors and induce the adsorption of NP-15. Strong synergism between the two surfactants is observed over this concentration range. Adsorbed pentadecylethoxylated nonyl phenol (NP-15) provides a steric barrier to further adsorption of tetradecyl trimethyl ammonium chloride (TTAC), and the adsorption of TTAC is suppressed. To develop a model that can predict adsorption of both components as a function of their activity in the mixed surfactant system, the monomer concentrations of TTAC and NP-15 in mixtures of different ratios were measured using ultrafiltration. Interestingly, the monomer concentrations measured by ultrafiltration method were different from the predictions of the regular solution theory.
Date: July 1, 1995
Creator: Somasundaran, P.
Partner: UNT Libraries Government Documents Department

Investigation of the rate-controlling mechanism(s) for high temperature creep and the relationship between creep and melting by using high pressure as a variable. Final report

Description: Silicon nitride (Si3N4) offers the advantages of high strength, high thermal shock resistance and a low coefficient of thermal expansion, which are attractive for high thermal efficiency heat engine parts such as in the automotive industry. A consolidation process is required in which the equiaxed {alpha} phase of the starting powders are retained along with a submicrongrain size; after forming, the strong {beta} phase is then formed by heat treatment. Conventional sintering and the mechanisms of consolidation therein are discussed. The plasma-activated (or assisted) sintering (PAS) process, a form of electrical resistance sintering, uses a cycled current to create an electric discharge that would break down the oxide layers at points of contact between the particles, while the plasma would attack the oxide layers on the noncontacting areas of the particles. PAS consolidation experiments were conducted with pure and doped Si3N4. The ability to consolidate Si3N4 with additives to 99% TD while retaining >88% {alpha} phase was demonstrated with the PAS equipment. The additive should be a mixture of oxides rather than a single oxide, and the amount should be minimum. Once the parts have been densified and deformed, it may be possible to lock in the shape by completing the {alpha} to {beta} transformation in a furnace.
Date: December 31, 1994
Creator: Mukherjee, A.K. & Green, H.
Partner: UNT Libraries Government Documents Department

Research on oil recovery mechanisms in heavy oil reservoirs. Progress report, July 1, 1995--September 30, 1995

Description: The goal of this research is to conduct studies towards the enhanced recovery of heavy petroleum. Five areas are being studied: flow properties; in-situ combustion; steam with additives; formation evaluation; and field support services. Progress is described.
Date: December 1, 1995
Creator: Brigham, W.E.
Partner: UNT Libraries Government Documents Department

Compositions, Functions, and Testing of Friction Brake Materials and Their Additives

Description: The purpose of this report is to present a survey of commercial brake materials and additives, and to indicate their typical properties and functions, especially as regards their use in heavy trucks. Most truck pad and shoe materials described here were designed to wear against cast iron. Brake material test methods are also briefly described. This report does not address issues associated with the fabrication and manufacturing of brake materials. Since there are literally thousands of brake material additives, and their combinations are nearly limitless, it is impractical to list them all here. Rather, an attempt has been made to capture the primary constituents and their functions. An Appendix contains thermo-physical properties of some current and potential brake materials.
Date: October 22, 2001
Creator: Blau, PJ
Partner: UNT Libraries Government Documents Department