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4,176 Matching Results
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Femtosecond Laser Manufacturing Experiments
The femtosecond laser utilizes an unusually short laser pulse that results in little, if any, metallurgical damage in stainless steel and other materials. Studies of the process demonstrated high quality wall contours (metallurgically clean) when the laser was used to cut grooves in stainless steel discs. This study did prove the feasibility of the process as an alternate potential for the existing process for making burst discs. Significant additional work is required to increase groove reproducibility and produce three-dimensional cuts, requiring development of appropriate tooling and controllers.
Date:
January 19, 2000
Creator:
Gillespie, L. K.
Object Type:
Report
System:
The UNT Digital Library
Final Report: Support for Polytechnic PhD Student, September 24, 1996 - June 30, 1999
Polytechnic University PhD student working on research projects in the area of fossil energy and renewable energy were supported in this program and did their research work at Brookhaven National Laboratory in the Department of Applied Sciences. One of these students had completed an MS degree in Chemical Engineering at Howard University while doing his research at Brookhaven. This student continued his studies by becoming a Polytechnic PhD student while doing his research work at Brookhaven.
Date:
January 19, 2000
Creator:
Myerson, Allan S.
Object Type:
Report
System:
The UNT Digital Library
Full color laser television
Television image display using red, green, and blue solid state lasers is discussed.
Date:
January 19, 2000
Creator:
Fox, Brian E.
Object Type:
Report
System:
The UNT Digital Library
Hydrogen atoms in radiolysis of liquids, solids and ordered systems: Zeolites and mesoporous solids
Hydrogen atoms are ubiquitous species in radiolysis of many liquid and solid systems. They serve a very important role in passivation of solid-state defects in silica-based devices and there is concern about the role of radiolytic generation of molecular hydrogen in radioactive waste storage. The authors have made extensive studies of H atoms in water, ice and amorphous silica using conventional and time-resolved magnetic resonance. H atoms are exquisite probes of reaction dynamics and phase structure in these systems. Furthermore, via the study of Chemically Induced Dynamic Electron Polarization (CIDEP), additional insights into the mechanisms of radiolytic generation of H atoms and their fate can be obtained. With this considerable experience they embarked on the study of H atoms in zeolites and mesoporous solids to address the following questions: (1) What is the source of H atoms--bound hydroxyls or confined water? (2) Do the H atom dynamics in the water-saturated powders exhibit kinetics and spin relaxation that is similar to that in bulk silica, liquid water or ice? (3) What are the formation and destruction pathways of H atoms? This could be important for understanding radiolysis in silica-water systems, e.g., nuclear waste.
Date:
January 19, 2000
Creator:
Chemerisov, S. D.; Shkrob, I. A.; Trifunac, A. D. & Werst, D. W.
Object Type:
Article
System:
The UNT Digital Library
In-beam studies of proton emitters using the Recoil-Decay Tagging method
The last five years have witnessed a rapid increase in the volume of data on proton decaying nuclei. The path was led by decay studies with recoil mass separators equipped with double-sided Si strip detectors. The properties of many proton-decaying states were deduced, which triggered renewed theoretical interest in the process of proton decay. The decay experiments were closely followed by in-beam {gamma}-ray studies which extended one's knowledge of high-spin states of proton emitters. The unparalleled selectivity of the Recoil-Decay Tagging method combined with the high efficiency of large arrays of Ge detectors allowed, despite small cross sections and overwhelming background from strong reaction channels, the observation of excited states in several proton emitters. Recently, in-beam studies of the deformed proton emitters {sup 141}Ho and {sup 131}Eu have been performed with the GAMMASPHERE array of Ge detectors and the Fragment Mass Analyzer at ATLAS. Evidence was found for rotational bands in {sup 141}Ho and {sup 131}Eu. The deformations and the single-particle configurations proposed for the proton emitting states from the earlier proton-decay studies were confronted with the assignments deduced based on the in-beam data. It should be noted that the cross section for populating {sup 131}Eu is only about 50 …
Date:
January 19, 2000
Creator:
Seweryniak, D.; Woods, P. J.; Ressler, J.; Davids, C. N.; Heinz, A.; Sonzogni, A. et al.
Object Type:
Article
System:
The UNT Digital Library
Investigation of Multiscale and Multiphase Flow, Transport and Reaction in Heavy Oil Recovery Process
The emphasis of this work was on investigating the mechanisms and factors that control the recovery of heavy oil, with the objective to improve recovery efficiencies. For this purpose, the interaction of flow, transport and reaction at various scales (from the pore-network to the field scales) were studied. Particular mechanisms investigated included the onset of gas flow in foamy oil production and in in-situ steam drive, gravity drainage in steam process, the development of sustained combustion fronts and the propagation of foams in porous media. Analytical, computational and experimental methods were utilized to advance the state of the art in heavy oil recovery. Successful completion of this research was expected to lead to improvements in the recovery efficiency of various heavy oil processes.
Date:
January 19, 2000
Creator:
Yortsos, Yanis C.; Akkutlu, Yucel; Amilik, Pouya; Kechagia, Persefoni; Lu, Chuan; Shariati, Maryam et al.
Object Type:
Report
System:
The UNT Digital Library
Josephson coupling and plasma resonance in vortex crystal
The authors consider the magnetic field dependence of the plasma resonance frequency in vortex crystal state. The authors found that low magnetic field induces a small correction to the plasma frequency proportional to the field. The slope of this linear field dependence is directly related to the average distance between the pancake vortices in the neighboring layers, wandering length. This length is determined by both Josephson and magnetic couplings between layers. At higher fields the Josephson coupling is suppressed collectively and is determined by elastic energy of the vortex lattice. Analyzing experimental data, they found that (1) the wandering length becomes comparable with the London penetration depth near {Tc}, (2) at small melting fields (< 20 G) the wandering length does not change much at the melting transition demonstrating existence of the line liquid phase in this field range, and (3) the self consistent theory of pancake fluctuations describes very well the field dependence of the Josephson plasma resonance frequency up to the melting point.
Date:
January 19, 2000
Creator:
Bulaevskii, L. N. & Koshelev, A. E.
Object Type:
Article
System:
The UNT Digital Library
MEMS Packaging - Current Issues and Approaches
The assembly and packaging of MEMS (Microelectromechanical Systems) devices raise a number of issues over and above those normally associated with the assembly of standard microelectronic circuits. MEMS components include a variety of sensors, microengines, optical components, and other devices. They often have exposed mechanical structures which during assembly require particulate control, space in the package, non-contact handling procedures, low-stress die attach, precision die placement, unique process schedules, hermetic sealing in controlled environments (including vacuum), and other special constraints. These constraints force changes in the techniques used to separate die on a wafer, in the types of packages which can be used in the assembly processes and materials, and in the sealing environment and process. This paper discusses a number of these issues and provides information on approaches being taken or proposed to address them.
Date:
January 19, 2000
Creator:
DRESSENDORFER,PAUL V.; PETERSON,DAVID W. & REBER,CATHLEEN ANN
Object Type:
Article
System:
The UNT Digital Library
Modification of chemical and physical factors in steamflood to increase heavy oil recovery
This report covers the work performed in the various physicochemical factors for the improvement of oil recovery efficiency. In this context the following general areas were studied: (1) The understanding of vapor-liquid flows in porous media, including processes in steam injection; (2) The effect of reservoir heterogeneity in a variety of foams, from pore scale to macroscopic scale; (3) The flow properties of additives for improvement of recovery efficiency, particularly foams and other non-Newtonian fluids; and (4) The development of optimization methods to maximize various measures of oil recovery.
Date:
January 19, 2000
Creator:
Yortsos, Yanis C.
Object Type:
Report
System:
The UNT Digital Library
Near-frictionless carbon coatings for use in fuel injectors and pump systems operating with low-sulfur diesel fuels
While sulfur in diesel fuels helps reduce friction and prevents wear and galling in fuel pump and injector systems, it also creates environmental pollution in the form of hazardous particulates and SO{sub 2} emissions. The environmental concern is the driving force behind industry's efforts to come up with new alternative approaches to this problem. One such approach is to replace sulfur in diesel fuels with other chemicals that would maintain the antifriction and antiwear properties provided by sulfur in diesel fuels while at the same time reducing particulate emissions. A second alternative might be to surface-treat fuel injection parts (i.e., nitriding, carburizing, or coating the surfaces) to reduce or eliminate failures associated with the use of low-sulfur diesel fuels. This research explores the potential usefulness of a near-frictionless carbon (NFC) film developed at Argonne National Laboratory in alleviating the aforementioned problems. The lubricity of various diesel fuels (i.e., high-sulfur, 500 ppm; low sulfur, 140 ppm; ultra-clean, 3 ppm; and synthetic diesel or Fischer-Tropsch, zero sulfur) were tested by using both uncoated and NFC-coated 52100 steel specimens in a ball-on-three-disks and a high-frequency reciprocating wear-test rig. The test program was expanded to include some gasoline fuels as well (i.e., regular gasoline …
Date:
January 19, 2000
Creator:
Erdemir, A.; Ozturk, O.; Alzoubi, M.; Woodford, J.; Ajayi, L. & Fenske, G.
Object Type:
Article
System:
The UNT Digital Library
Nuclear Regulation: NRC Staff Have Not Fully Accepted Planned Changes
A letter report issued by the General Accounting Office with an abstract that begins "Pursuant to a congressional request, GAO provided information on the Nuclear Regulatory Commission's (NRC) shift to a risk-informed regulation, focusing on the: (1) views of NRC's staff on the quality of the work that NRC performs, the management of and staff's involvement in changes occurring in the agency, and the move to a risk-informed regulatory approach; and (2) status of NRC's efforts to develop a strategy to implement a risk-informed regulatory approach."
Date:
January 19, 2000
Creator:
United States. General Accounting Office.
Object Type:
Report
System:
The UNT Digital Library
NWTC AWT-26 research and retrofit project-summary of AWT-26/27 turbine research and development
This report summarizes the AWT design, the testing and modeling completed on the design, the operating history of AWT turbines, and the additional work required to commercialize the design.
Date:
January 19, 2000
Creator:
Poore, R.
Object Type:
Report
System:
The UNT Digital Library
Plasma simulation studies using multilevel physics models
The question of how to proceed toward ever more realistic plasma simulation studies using ever increasing computing power is addressed. The answer presented here is the M3D (Multilevel 3D) project, which has developed a code package with a hierarchy of physics levels that resolve increasingly complete subsets of phase-spaces and are thus increasingly more realistic. The rationale for the multilevel physics models is given. Each physics level is described and examples of its application are given. The existing physics levels are fluid models (3D configuration space), namely magnetohydrodynamic (MHD) and two-fluids; and hybrid models, namely gyrokinetic-energetic-particle/MHD (5D energetic particle phase-space), gyrokinetic-particle-ion/fluid-electron (5D ion phase-space), and full-kinetic-particle-ion/fluid-electron level (6D ion phase-space). Resolving electron phase-space (5D or 6D) remains a future project. Phase-space-fluid models are not used in favor of delta f particle models. A practical and accurate nonlinear fluid closure for noncollisional plasmas seems not likely in the near future.
Date:
January 19, 2000
Creator:
Park, W.; Belova, E. V. & Fu, G. Y.
Object Type:
Report
System:
The UNT Digital Library
Radiolytic and electron-transfer reactions in supercritical CO{sub 2}
Using supercritical fluids as solvents is useful for both practical and theoretical reasons. It has been proposed to use supercritical CO{sub 2} as a solvent for synthesis because it eliminates the air pollution arising from other solvents. The properties of supercritical fluids can be easily varied with only modest changes in temperature and density, so they provide a way of testing theories of chemical reactions. It has also been proposed to use supercritical fluids for the treatment of hazardous mixed waste. For these reasons the authors have studied the production of radiolytic species in supercritical CO{sub 2} and have measured their reactivity as a function of density. They have shown that the C{sub 2}O{sub 4}{sup +} is formed. They also have shown that the electron transfer reactions of dimethylaniline to C{sub 2}O{sub 4}{sup +} and CO{sub 2}(e{sup {minus}}) to benzoquinone are diffusion controlled over a considerable density range.
Date:
January 19, 2000
Creator:
Bartels, D. M.; Dimitrijevic, N. M.; Jonah, C. D. & Takahashi, K.
Object Type:
Article
System:
The UNT Digital Library
Renormalized dissipation in the nonconservatively forced Burgers equation
A previous calculation of the renormalized dissipation in the nonconservatively forced one-dimensional Burgers equation, which encountered a catastrophic long-wavelength divergence approximately [k min]-3, is reconsidered. In the absence of velocity shear, analysis of the eddy-damped quasi-normal Markovian closure predicts only a benign logarithmic dependence on kmin. The original divergence is traced to an inconsistent resonance-broadening type of diffusive approximation, which fails in the present problem. Ballistic scaling of renormalized pulses is retained, but such scaling does not, by itself, imply a paradigm of self-organized criticality. An improved scaling formula for a model with velocity shear is also given.
Date:
January 19, 2000
Creator:
Krommes, John A.
Object Type:
Report
System:
The UNT Digital Library
Resistor Printing on Dielectric
None
Date:
January 19, 2000
Creator:
Barner, G. E.
Object Type:
Report
System:
The UNT Digital Library
Review of Astrophysics Experiments on Intense Lasers
Astrophysics has traditionally been pursued at astronomical observatories and on theorists' computers. Observations record images from space, and theoretical models are developed to explain the observations. A component often missing has been the ability to test theories and models in an experimental setting where the initial and final states are well characterized. Intense lasers are now being used to recreate aspects of astrophysical phenomena in the laboratory, allowing the creation of experimental testbeds where theory and modeling can be quantitatively tested against data. We describe here several areas of astrophysics--supernovae, supernova remnants, gamma-ray bursts, and giant planets--where laser experiments are under development to test our understanding of these phenomena.
Date:
January 19, 2000
Creator:
Remington, B. A.; Drake, R. P.; Takabe, H. & Arnett, D.
Object Type:
Article
System:
The UNT Digital Library
Selection Intensity in Genetic Algorithms with Generation Gaps
This paper presents calculations of the selection intensity of common selection and replacement methods used in genetic algorithms (GAs) with generation gaps. The selection intensity measures the increase of the average fitness of the population after selection, and it can be used to predict the average fitness of the population at each iteration as well as the number of steps until the population converges to a unique solution. In addition, the theory explains the fast convergence of some algorithms with small generation gaps. The accuracy of the calculations was verified experimentally with a simple test function. The results of this study facilitate comparisons between different algorithms, and provide a tool to adjust the selection pressure, which is indispensable to obtain robust algorithms.
Date:
January 19, 2000
Creator:
Cantu-Paz, E.
Object Type:
Article
System:
The UNT Digital Library
Single-mode operation of a coiled multimode fiber amplifier
The authors report a new approach to obtain single-transverse-mode operation of a multimode fiber amplifier, in which the gain fiber is coiled to induce significant bend loss for all but the lowest-order mode. They have demonstrated this method by constructing a coiled amplifier using Yb-doped, double-clad fiber with a core diameter of 25 {micro}m and NA of {minus}0.1 (V {approx} 7.4). When operated as an ASE source, the output beam had an M{sup 2} value of 1.09 {+-} 0.09; when seeded at 1,064 nm, the slope efficiency was similar to that of an uncoiled amplifier. This technique does not require exotic fiber designs or increase system complexity and is inexpensive to implement. It will allow scaling of pulsed fiber lasers and amplifiers to significantly higher pulse energies and peak powers and cw fiber sources to higher average powers while maintaining excellent beam quality.
Date:
January 19, 2000
Creator:
Koplow, Jeffrey P.; Kliner, Dahv A. V. & Goldberg, Lew
Object Type:
Article
System:
The UNT Digital Library
Social Security Reform: Information on the Archer-Shaw Proposal
A letter report issued by the General Accounting Office with an abstract that begins "Pursuant to a congressional request, GAO provided information on the Archer-Shaw Social Security reform proposal, focusing on: (1) the extent to which the proposal achieves sustainable solvency and how it would affect the U.S. economy and the federal budget; (2) the balance struck between the twin goals of income adequacy (level and certainty of benefits) and individual equity (rates of return on individual contributions); and (3) how readily such changes could be implemented, administered, and explained to the public."
Date:
January 19, 2000
Creator:
United States. General Accounting Office.
Object Type:
Report
System:
The UNT Digital Library
Suspended Solids Profiler Shop Test Report
The Suspended Solids Profiler (SSP) Instrument is planned to be installed in the AZ-101 tank to measure suspended solids concentrations during mixer pump testing. The SSP sensor uses a reflectance measurement principle to determine the suspended solids concentrations. The purpose of this test is to provide a documented means of verifying that the functional components of the SSP operate properly.
Date:
January 19, 2000
Creator:
STAEHR, T.W.
Object Type:
Report
System:
The UNT Digital Library
Synthesis of diamondlike carbon films with superlow friction and wear properties
In this study, the authors introduce a new diamondlike carbon (DLC) film providing a friction coefficient of 0.001 and wear rates of 10{sup {minus}9} to 10{sup {minus}10} mm{sup 3}/N.m in inert-gas environments (e.g., dry nitrogen and argon). The film was grown on steel and sapphire substrates in a plasma enhanced chemical vapor deposition system that uses using a hydrogen-rich plasma. Employing a combination of surface and structure analytical techniques, they explored the structural chemistry of the resultant DLC films and correlated these findings with the friction and wear mechanisms of the films. The results of tribological tests under a 10-N load (creating initial peak Hertz pressures of 1 and 2.2 GPa on steel and sapphire test pairs, respectively) and at 0.2 to 0.5 m/s sliding velocities indicated that a close correlation exists between the friction and wear coefficients of DLC films and the source gas chemistry. Specifically, films grown in source gases with higher hydrogen-to-carbon ratios had the lowest fiction coefficients and the highest wear resistance. The lowest friction coefficient (0.001) was achieved with a film on sapphire substrates produced in a gas discharge plasma consisting of 25% methane and 75% hydrogen.
Date:
January 19, 2000
Creator:
Erdemir, A.; Eryilmaz, O. L. & Fenske, G.
Object Type:
Article
System:
The UNT Digital Library
Tribological behavior of near-frictionless carbon coatings in high- and low-sulfur diesel fuels.
The sulfur content in diesel fuel has a significant effect on diesel engine emissions, which are currently subject to environmental regulations. It has been observed that engine particulate and gaseous emissions are directly proportional to fuel sulfur content. With the introduction of low-sulfur fuels, significant reductions in emissions are expected. The process of sulfur reduction in petroleum-based diesel fuels also reduces the lubricity of the fuel, resulting in premature failure of fuel injectors. Thus, another means of preventing injector failures is needed for engines operating with low-sulfur diesel fuels. In this study, the authors evaluated a near-frictionless carbon (NFC) coating (developed at Argonne National Laboratory) as a possible solution to the problems associated with fuel injector failures in low-lubricity fuels. Tribological tests were conducted with NFC-coated and uncoated H13 and 52100 steels lubricated with high- and low- sulfur diesel fuels in a high-frequency reciprocating test machine. The test results showed that the NFC coatings reduced wear rates by a factor of 10 over those of uncoated steel surfaces. In low-sulfur diesel fuel, the reduction in wear rate was even greater (i.e., by a factor of 12 compared to that of uncoated test pairs), indicating that the NFC coating holds promise …
Date:
January 19, 2000
Creator:
Alzoubi, M. F.; Ajayi, O. O.; Eryilmaz, O. L.; Ozturk, O.; Erdemir, A. & Fenske, G.
Object Type:
Article
System:
The UNT Digital Library
User Fees: Applicable Budget Enforcement Procedures
None
Date:
January 19, 2000
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library