21 Matching Results

Search Results

Results: 1 - 21
open access

Combustion in Homogeneous Charge Compression Ignition Engines: Experiments and Detailed Chemical Kinetic Simulations

Description: Homogeneous charge compression ignition (HCCI) engines are being considered as an alternative to diesel engines. The HCCI concept involves premixing fuel and air prior to induction into the cylinder (as is done in current spark-ignition engine) then igniting the fuel-air mixture through the compression process (as is done in current diesel engines). The combustion occurring in an HCCI engine is fundamentally different from a spark-ignition or Diesel engine in that the heat release occurs as a g… more
Date: June 7, 2002
Creator: Flowers, D L
Partner: UNT Libraries Government Documents Department
open access

Design of a rural water provision system to decrease arsenic exposure in Bangladesh

Description: Researchers at the Lawrence Berkeley National Laboratory have invented ARUBA (Arsenic Removal Using Bottom Ash) a material that effectively and affordably removes high concentrations of arsenic from contaminated groundwater. The technology is cost-effective because the substrate?bottom ash from coal fired power plants?is a waste material readily available in South Asia. During fieldwork in four sub-districts ofBangladesh, ARUBA reduced groundwater arsenic concentrations as high as 680 ppb to be… more
Date: January 7, 2009
Creator: Mathieu, Johanna
Partner: UNT Libraries Government Documents Department
open access

Effect of surface structure on catalytic reactions: A sum frequency generation surface vibrational spectroscopy study

Description: In the results discussed above, it is clear that Sum Frequency Generation (SFG) is a unique tool that allows the detection of vibrational spectra of adsorbed molecules present on single crystal surfaces under catalytic reaction conditions. Not only is it possible to detect active surface intermediates, it is also possible to detect spectator species which are not responsible for the measured turnover rates. By correlating high-pressure SFG spectra under reaction conditions and gas chromatograph… more
Date: September 7, 2001
Creator: McCrea, Keith R.
Partner: UNT Libraries Government Documents Department
open access

Fundamental studies of hydrogen interaction with supported meta and bimetallic catalysts

Description: The thesis is divided into 3 parts: interaction of H with silica supported Ru catalysts (high pressure in situ NMR), in situ NMR study of H interaction with supported Ru-group IB bimetallic catalysts, and in-situ NMR study of H effects on silica-supported Pt, Rh and Ru catalysts.
Date: December 7, 1993
Creator: Bhatia, S.
Partner: UNT Libraries Government Documents Department
open access

Gas phase thermochemistry of organogermanium compounds

Description: A variety of silyl- and alkyl-germylene precursors have been synthesized and subsequently pyrolyzed in the gas phase. Arrhenius parameters were obtained employing a pulsed-stirred flow reactor for these unimolecular decompositions. These precursors are divided into two major categories by mechanism of germylene extrusion: {alpha}-elimination precursors and germylacetylenes. The extrusion of germylenes from germylacetylene precursors is of primary interest. A mechanism is proposed employing a ge… more
Date: December 7, 1993
Creator: Engel, J. P.
Partner: UNT Libraries Government Documents Department
open access

Implementation of the Immersed Boundary Method in the Weather Research and Forecasting model

Description: Accurate simulations of atmospheric boundary layer flow are vital for predicting dispersion of contaminant releases, particularly in densely populated urban regions where first responders must react within minutes and the consequences of forecast errors are potentially disastrous. Current mesoscale models do not account for urban effects, and conversely urban scale models do not account for mesoscale weather features or atmospheric physics. The ultimate goal of this research is to develop and i… more
Date: December 7, 2006
Creator: Lundquist, K A
Partner: UNT Libraries Government Documents Department
open access

Inertial fusion energy target injection, tracking, and beam pointing

Description: Several cryogenic targets must be injected each second into a reaction chamber. Required target speed is about 100 m/s. Required accuracy of the driver beams on target is a few hundred micrometers. Fuel strength is calculated to allow acceleration in excess of 10,000 m/s{sup 2} if the fuel temperature is less than 17 K. A 0.1 {mu}m thick dual membrane will allow nearly 2,000 m/s{sup 2} acceleration. Acceleration is gradually increased and decreased over a few membrane oscillation periods (a few… more
Date: March 7, 1995
Creator: Petzoldt, R.W.
Partner: UNT Libraries Government Documents Department
open access

Inertial fusion technology spin-offs-history provides a glimpse of the future

Description: The development and demonstration of inertial fusion is incredibly challenging because it requires simultaneously controlling and precisely measuring parameters at extreme values in energy, space, and time. The challenges range from building megajoule (10{sup 6} J) drivers that perform with percent-level precision to fabricating targets with submicron specifications to measuring target performance at micron scale (10{sup -6} m) with picosecond (10{sup -12} s) time resolution. Over the past 30 y… more
Date: March 7, 2000
Creator: Powell, H
Partner: UNT Libraries Government Documents Department
open access

Matrix effects in inductively coupled plasma mass spectrometry

Description: The inductively coupled plasma is an electrodeless discharge in a gas (usually Ar) at atmospheric pressure. Radio frequency energy generated by a RF power source is inductively coupled to the plasma gas through a water cooled load coil. In ICP-MS the {open_quotes}Fassel{close_quotes} TAX quartz torch commonly used in emission is mounted horizontally. The sample aerosol is introduced into the central flow, where the gas kinetic temperature is about 5000 K. The aerosol is vaporized, atomized, exc… more
Date: July 7, 1995
Creator: Chen, Xiaoshan
Partner: UNT Libraries Government Documents Department
open access

Measurement and Modeling of Blocking Contacts for Cadmium Telluride Gamma Ray Detectors

Description: Gamma ray detectors are important in national security applications, medicine, and astronomy. Semiconductor materials with high density and atomic number, such as Cadmium Telluride (CdTe), offer a small device footprint, but their performance is limited by noise at room temperature; however, improved device design can decrease detector noise by reducing leakage current. This thesis characterizes and models two unique Schottky devices: one with an argon ion sputter etch before Schottky contact d… more
Date: January 7, 2010
Creator: Beck, P R
Partner: UNT Libraries Government Documents Department
open access

Measurement of branching fractions of B decays to K1(1270)pi and K1(1400)pi and determination of the CKM angle alpha from B0 --> a1(1260) - pi-

Description: In the Standard Model, CP violation in weak interactions involving quarks is parameterized by an irreducible complex phase in the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing-matrix. The precise determination of the CKM elements is a necessary ingredient for a stringent test of the Standard Model predictions, and is a crucial input for reducing the theoretical error in many New Physics searches with flavor, e.g., in the kaon sector. The unitarity of the CKM matrix is typically expressed as a tr… more
Date: February 7, 2011
Creator: Stracka, Simone & /SLAC, /Milan U.
Partner: UNT Libraries Government Documents Department
open access

Measurement of the Angular Distribution of the Electron From W {r_arrow} E = {Nu} decay, in P{Anti P} at {Radical}S = 1.8 Tev, as Function of P{Sub T}{Sup W}; Medida De La Distribucion Angular Del Electron De W en E + Neutrino en P{Anti P} a 1.8 Tev

Description: The goal of this work was to study the behavior of the angular distribution of the electron form the decay of the W boson in a specific rest-frame of the W, the Collins-Soper frame. This thesis consists of four major divisions, each dealing with closely related themes: (a) Physics Background, (b) Description of the Hardware and General Software Tools, (c) Description of the Analysis and Specific Tools, and (d) Results and Conclusions. Each division is comprised of one or more chapters and each … more
Date: October 7, 1996
Creator: Ramos, M. I. M.
Partner: UNT Libraries Government Documents Department
open access

Oxygen electrode reaction in molten carbonate fuel cells. Final report, September 15, 1987--September 14, 1990

Description: Molten carbonate fuel cell system is a leading candidate for the utility power generation because of its high efficiency for fuel to AC power conversion, capability for an internal reforming, and a very low environmental impact. However, the performance of the molten carbonate fuel cell is limited by the oxygen reduction reaction and the cell life time is limited by the stability of the cathode material. An elucidation of oxygen reduction reaction in molten alkali carbonate is essential because… more
Date: July 7, 1992
Creator: Appleby, A. J. & White, R. E.
Partner: UNT Libraries Government Documents Department
open access

Solid state NMR method development and studies of biological and biomimetic nanocomposites

Description: This thesis describes application and development of advanced solid-state nuclear magnetic resonance techniques for complex materials, in particular organic-inorganic nanocomposites and thermoelectric tellurides. The apatite-collagen interface, essential for understanding the biomineralization process in bone and engineering the interface for controlled bio-mimetic synthesis and optimized mechanical properties, is buried within the nanocomposite of bone. We used multinuclear solid-state NMR to … more
Date: February 7, 2011
Creator: Hu, Yanyan
Partner: UNT Libraries Government Documents Department
open access

Synthesis, characterization and application of electrode materials

Description: It has been known that significant advances in electrochemistry really depend on improvements in the sensitivity, selectivity, convenience, and/or economy of working electrodes, especially through the development of new working electrode materials. The advancement of solid state chemistry and materials science makes it possible to provide the materials which may be required as satisfactory electrode materials. The combination of solid state techniques with electrochemistry expands the applicati… more
Date: July 7, 1995
Creator: He, L.
Partner: UNT Libraries Government Documents Department
open access

Synthesis of heterocycles: Indolo (2,1-a) isoquinolines, renewables, and aptamer ligands for cellular imaging

Description: In this thesis, we explore both total syntheses and methodologies of several aromatic heterocyclic molecules. Extensions of the Kraus indole synthesis toward 2-substituted and 2,3-disubstituted indoles, as well as biologically attractive indolo[2,1-a]isoquinolines are described. Recent renewable efforts directed to commodity maleic acid and the first reported furan-based ionic liquids are described. Our total synthesis of mRNA aptamer ligand PDC-Gly, and its dye coupled forms, plus aminoglycosi… more
Date: May 7, 2013
Creator: Beasley, Jonathan
Partner: UNT Libraries Government Documents Department
open access

Templated synthesis of nickel nanoparticles: Toward heterostructured nanocomposites for efficient hydrogen storage

Description: The world is currently facing an energy and environmental crisis for which new technologies are needed. Development of cost-competitive materials for catalysis and hydrogen storage on-board motor vehicles is crucial to lead subsequent generations into a more sustainable and energy independent future. This thesis presents work toward the scalable synthesis of bimetallic heterostructures that can enable hydrogen to compete with carbonaceous fuels by meeting the necessary gravimetric and volumetri… more
Date: May 7, 2013
Creator: Nelson, Nicholas Cole
Partner: UNT Libraries Government Documents Department
open access

Terfenol: A study of the phase equilibrium diagram and the solidification process

Description: Terfenol is a rare earth-iron alloy that was first developed at the Naval Ordinance Laboratory because of its rare magnetostrictive properties. Terfenol is composed of terbium and dysprosium combined with iron in a composition Tb{sub x}Dy{sub 1{minus}x}Fe{sub 2}, where x{approximately}0.3. The objective of this work was to determine the growth characteristics of Terfenol and its dependence on solidification rate, temperature gradient, and stoichiometry. Specific goals of this work were to verif… more
Date: December 7, 1993
Creator: Anderson, M.
Partner: UNT Libraries Government Documents Department
open access

Thermodynamics of the Aqueous Ions of Americium

Description: Thesis discussing the heats of reduction, oxidation potentials, and measurements of autoreduction and disproportionation for aqueous ions of americium.
Date: April 7, 1954
Creator: Gunn, Stuart Richard
Partner: UNT Libraries Government Documents Department
open access

Topics in electroweak baryogenesis: The sphaleron and t-violation

Description: Assuming that beyond the standard model physics can be parametrized in terms of high dimensional operators, we examine their effects on the energy of the sphaleron and the classical solution of the gauge and Higgs fields. In the absence of fermions, all of the six dimension 6 operators which are SU(2) symmetric have a small effect when calculated perturbatively. However, calculated non-perturbatively, one of the operators alters the boundary conditions of the equations of motion of the Higgs an… more
Date: December 7, 1993
Creator: SeungKoog, L.
Partner: UNT Libraries Government Documents Department
Back to Top of Screen