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Ethics Gaming Survey Results

Description: Dataset generated for a National Science Foundation grant project, "EAGER: Prototyping a Virtue Ethics Game." These files contain the research results of the pre-test and post-test surveys.
Date: August 29, 2013
Creator: Oppong, Joseph R.
Partner: UNT College of Arts and Sciences

Computational modeling of material aging effects

Description: Progress is being made in our efforts to develop computational models for predicting material property changes in weapon components due to aging. The first version of a two-dimensional lattice code for modeling thermomechanical fatigue, such as has been observed in solder joints on electronic components removed from the stockpile, has been written and tested. The code does a good qualitative job of presenting intergranular and/or transgranular cracking in a polycrystalline material when under thermomechanical deformation. The current progress is an encouraging start for our long term effort to develop multi-level simulation capabilities, with the technology of high performance computing, for predicting age-related effects on the reliability of weapons.
Date: July 1, 1996
Creator: Fang, H.E.
Partner: UNT Libraries Government Documents Department

Electromagnetic waves in a strong Schwarzschild plasma

Description: The physics of high frequency electromagnetic waves in a general relativistic plasma with the Schwarzschild metric is studied. Based on the 3 + 1 formalism, we conformalize Maxwell`s equations. The derived dispersion relations for waves in the plasma contain the lapse function in the plasma parameters such as in the plasma frequency and cyclotron frequency, but otherwise look {open_quotes}flat.{close_quotes} Because of this property this formulation is ideal for nonlinear self-consistent particle (PIC) simulation. Some of the physical consequences arising from the general relativistic lapse function as well as from the effects specific to the plasma background distribution (such as density and magnetic field) give rise to nonuniform wave equations and their associated phenomena, such as wave resonance, cutoff, and mode-conversion. These phenomena are expected to characterize the spectroscopy of radiation emitted by the plasma around the black hole. PIC simulation results of electron-positron plasma are also presented.
Date: November 1, 1996
Creator: Daniel, J. & Tajima, T.
Partner: UNT Libraries Government Documents Department

Microbial ecology of terrestrial Antarctica: Are microbial systems at risk from human activities?

Description: Many of the ecological systems found in continental Antarctica are comprised entirely of microbial species. Concerns have arisen that these microbial systems might be at risk either directly through the actions of humans or indirectly through increased competition from introduced species. Although protection of native biota is covered by the Protocol on Environmental Protection to the Antarctic Treaty, strict measures for preventing the introduction on non-native species or for protecting microbial habitats may be impractical. This report summarizes the research conducted to date on microbial ecosystems in continental Antarctica and discusses the need for protecting these ecosystems. The focus is on communities inhabiting soil and rock surfaces in non-coastal areas of continental Antarctica. Although current polices regarding waste management and other operations in Antarctic research stations serve to reduce the introduction on non- native microbial species, importation cannot be eliminated entirely. Increased awareness of microbial habitats by field personnel and protection of certain unique habitats from physical destruction by humans may be necessary. At present, small-scale impacts from human activities are occurring in certain areas both in terms of introduced species and destruction of habitat. On a large scale, however, it is questionable whether the introduction of non-native microbial species to terrestrial Antarctica merits concern.
Date: August 1, 1996
Creator: White, G.J.
Partner: UNT Libraries Government Documents Department

NMR studies of DNA oligomers and their interactions with minor groove binding ligands

Description: The cationic peptide ligands distamycin and netropsin bind noncovalently to the minor groove of DNA. The binding site, orientation, stoichiometry, and qualitative affinity of distamycin binding to several short DNA oligomers were investigated by NMR spectroscopy. The oligomers studied contain A,T-rich or I,C-rich binding sites, where I = 2-desaminodeoxyguanosine. I{center_dot}C base pairs are functional analogs of A{center_dot}T base pairs in the minor groove. The different behaviors exhibited by distamycin and netropsin binding to various DNA sequences suggested that these ligands are sensitive probes of DNA structure. For sites of five or more base pairs, distamycin can form 1:1 or 2:1 ligand:DNA complexes. Cooperativity in distamycin binding is low in sites such as AAAAA which has narrow minor grooves, and is higher in sites with wider minor grooves such as ATATAT. The distamycin binding and base pair opening lifetimes of I,C-containing DNA oligomers suggest that the I,C minor groove is structurally different from the A,T minor groove. Molecules which direct chemistry to a specific DNA sequence could be used as antiviral compounds, diagnostic probes, or molecular biology tools. The author studied two ligands in which reactive groups were tethered to a distamycin to increase the sequence specificity of the reactive agent.
Date: May 1, 1996
Creator: Fagan, P.A.
Partner: UNT Libraries Government Documents Department

Mitigation of earthquake hazards using seismic isolation systems

Description: This paper describes mitigation of earthquake hazards using seismic base isolation systems. A numerical algorithm for analyzing system response of base-isolated structures with laminated elastomer bearings is briefly described. Seismic response analyses of both base- isolated and unisolated buildings under earthquakes {number_sign}42 and {number_sign}44 are performed and the results are compared to illustrate the mitigating effect of base-isolated systems.
Date: June 1, 1996
Creator: Wang, C.-Y.
Partner: UNT Libraries Government Documents Department

Nuclear/High Energy Physics (NuHEP) research center of excellence

Description: This report contains the manuscripts from the proceedings of the third annual Undergraduate Institute in Physics Program. The titles of these manuscripts are: flow measurements for the hall c cryogenic target loops; calibrations for the hall c drift chambers gas mixing system; the electromagnetic structure of the nucleon; investigation of drift chambers in hall c at CEBAF; seek and ye shall find; commissioning techniques; and instruments used in particle detection.
Date: December 31, 1994
Partner: UNT Libraries Government Documents Department

Copper Mountain conference on multigrid methods. Preliminary proceedings -- List of abstracts

Description: This report contains abstracts of the papers presented at the conference. Papers cover multigrid algorithms and applications of multigrid methods. Applications include the following: solution of elliptical problems; electric power grids; fluid mechanics; atmospheric data assimilation; thermocapillary effects on weld pool shape; boundary-value problems; prediction of hurricane tracks; modeling multi-dimensional combustion and detailed chemistry; black-oil reservoir simulation; image processing; and others.
Date: December 31, 1995
Partner: UNT Libraries Government Documents Department

The Promise and Perils of Transformative Research

Description: This report is on the workshop 'Transformative Research: Ethical and Societal Implications'. Workshop conversations cluster under the four headings of the history and definitions, promotion, evaluation, and integration of transformative research.
Date: March 2012
Creator: Frodeman, Robert & Holbrook, J. Britt
Partner: UNT College of Arts and Sciences

Demand Controlled Ventilation using CO2 Sensors in a Wireless Sensor Network [Poster]

Description: Poster presented as part of the 2013 Research Experiences for Teachers (RET) in Sensor Education, a National Science Foundation (NSF) funded grant project. This poster discusses research on demand controlled ventilation using CO₂ sensors in a wireless sensor network.
Date: 2013
Creator: Parsons, David; Jordan, Georgette; Li, Xinrong; Thompson, Ruthanne & Abraham, Sherin
Partner: UNT College of Engineering

Demand Controlled Ventilation using CO₂ Sensors in a Wireless Sensor Network

Description: This report discusses research on demand controlled ventilation using CO₂ sensors in a wireless sensor network. The focus of this research project was to investigate Indoor Air Quality (IAQ) monitoring technologies, government regulations and policies, and best practices to improve IAQ. This research is part of Research Experiences for Teachers (RET) in Sensor Education, a National Science Foundation (NSF) funded grant project.
Date: 2013
Creator: Parsons, David; Jordan, Georgette; Li, Xinrong; Thompson, Ruthanne & Abraham, Sherin
Partner: UNT College of Engineering

Shell model Monte Carlo methods

Description: We review quantum Monte Carlo methods for dealing with large shell model problems. These methods reduce the imaginary-time many-body evolution operator to a coherent superposition of one-body evolutions in fluctuating one-body fields; resultant path integral is evaluated stochastically. We first discuss the motivation, formalism, and implementation of such Shell Model Monte Carlo methods. There then follows a sampler of results and insights obtained from a number of applications. These include the ground state and thermal properties of pf-shell nuclei, thermal behavior of {gamma}-soft nuclei, and calculation of double beta-decay matrix elements. Finally, prospects for further progress in such calculations are discussed. 87 refs.
Date: October 1996
Creator: Koonin, S. E. & Dean, D. J.
Partner: UNT Libraries Government Documents Department

Microwave-assisted pyrolysis of SiC and its application to joining

Description: Microwave energy has been used to pyrolyze silicon carbide from commercially available polycarbosilane precursor. The pyrolysis was performed on SiC surfaces having various surface treatments, to identify conditions which improve the wetting and adherence. Grinding and etching of the surfaces in hydrofluoric (HF) acid promotes the bonding of precursor derived ceramic to the SiC ceramic. Finally, the polycarbosilane precursor mixed with fine silicon carbide powder was used as the interlayer material to join silicon carbide specimens.
Date: July 1995
Creator: Ahmad, I.; Silberglitt, R. & Shan, T. A.
Partner: UNT Libraries Government Documents Department

Modeling and characterization of molecular structures in self assembled and Langmuir-Blodgett films for controlled fabrication

Description: Self Assembled (SA) thin films and Langmuir-Blodgett (LB) thin films are emerging technologies for the development of chemical and bio-chemical sensors, electrooptic films, second harmonic generators (frequency doublers), templates for biomimetic growth etc. One of the goals of this project was to extend Sandia`s characterization techniques and molecular modeling capabilities for these complex two-dimensional geometries with the objective of improving the control of the fabrication of these structures for specific applications. Achieving this requires understanding both the structure throughout the thickness of the films and the in-plane lattice of the amphiphilic molecules. To meet these objectives they used atomic force microscopy (AFM), X-ray reflectivity, and molecular modeling. While developing these capabilities, three different materials systems were fabricated and characterized: (1) Self Assembled Monolayers (SAMs) of octadecyltrichlorosilane (OTS) and LB films of arachidic acid on silicon wafers; (2) SAMs on PZT substrates; and (3) electrochemical deposition of CdS on LB film templates.
Date: October 1997
Creator: Cesarano, J., III
Partner: UNT Libraries Government Documents Department

Paramagnetism and reentrant behavior in quasi-one-dimensional superconductors at high magnetic fields

Description: The thermodynamics of quasi-one-dimensional superconductors in the presence of large magnetic fields is studied. When the quantum effects of the magnetic field are taken into account, several reentrant superconducting phases persist at very high fields. In the last reentrant phase the free energy change, the specific heat jump and the excess magnetization are estimated near the critical temperature. In particular, the excess magnetization is found to be paramagnetic as opposed to diamagnetic in weak fields and its sign is controlled by the slope of H{sub c{sub 2}} (T). The authors further generalize this result to the entire phase diagram (including all quantum phases) and to different physical systems using general thermodynamic relations which show that the sign of the excess magnetization {Delta}M of the superconducting state near H{sub c{sub 2}}(T) follows dH{sub c{sub 2}}(T)/dT. These relations provide a scenario for the evolution of the sign of {Delta}M from weak fields to strong fields.
Date: February 1996
Creator: Sa de Melo, C. A. R.
Partner: UNT Libraries Government Documents Department

Light-cone quantization and QCD phenomenology

Description: In principle, quantum chromodynamics provides a fundamental description of hadronic and nuclear structure and dynamics in terms of their elementary quark and gluon degrees of freedom. In practice, the direct application of QCD to reactions involving the structure of hadrons is extremely complex because of the interplay of nonperturbative effects such as color confinement and multi-quark coherence. A crucial tool in analyzing such phenomena is the use of relativistic light-cone quantum mechanics and Fock state methods to provide tractable and consistent treatments of relativistic many-body systems. In this article we present an overview of this formalism applied to QCD, focusing in particular on applications to the final states in deep inelastic lepton scattering that will be relevant for the proposed European Laboratory for Electrons (ELFE), HERMES, HERA, SLAC, and CEBAF. We begin with a brief introduction to light-cone field theory, stressing how it many allow the derivation of a constituent picture, analogous to the constituent quark model, from QCD. We then discuss several applications of the light-cone Fock state formalism to QCD phenomenology. The Fock state representation includes all quantum fluctuations of the hadron wavefunction, including far off-shell configurations such as intrinsic charm and, in the case of nuclei, hidden color. In some applications, such as exclusive processes at large momentum transfer, one can make first-principle predictions using factorization theorems which separate the hard perturbative dynamics from the nonpertubative physics associated with hadron binding. The Fock state components of the hadron with small transverse size, which dominate hard exclusive reactions, have small color dipole moments and thus diminished hadronic interactions. Thus QCD predicts minimal absorptive corrections, i.e., color transparency for quasi-elastic exclusive reactions in nuclear targets at large momentum transfer.
Date: December 1995
Creator: Brodsky, S. J. & Robertson, D. G.
Partner: UNT Libraries Government Documents Department

Cell asymmetry correction for temperature modulated differential scanning calorimetry

Description: The quality of measurement of heat capacity by differential scanning calorimetry (DSC) is based on strict symmetry of the twin calorimeter, which is important for temperature-modulated DSC. Heat capacities for sapphire-filled and empty aluminium calorimeters (pans) under designed cell imbalance caused by different pan-masses were measured. In addition, positive and negative signs of asymmetry were explored by analyzing the phase-shift between temperature and heat flow for sapphire and empty runs. The phase shifts change by more than 18{degree} depending on asymmetry sign. Once the asymmetry sign is determined, the asymmetry correction for modulated DSC can be made.
Date: December 31, 1996
Creator: Ishikiriyama, K. & Wunderlich, B.
Partner: UNT Libraries Government Documents Department

The mechanics of manufacturing processes

Description: Economic pressures, particularly related to the quality of manufactured goods and `time-to-market` are forcing designers to think not only in terms of product design but also in terms of integrated product and process design, and finally in terms of deterministic manufacturing planning and control. As a result of these three high level needs, there is now an even greater need for comprehensive simulations that predict material behavior during a manufacturing process, the stresses and/or temperatures on associated tooling, and the final-product integrity. The phrase `manufacturing processes` of course covers a broad scope; it includes semiconductor manufacturing, injection molding of polymers, metal machining and precision lapping, wood and textile production, and the final assembly of piece-parts into a consumer product. It can be seen from this partial listing that the fields of fluid mechanics, solid mechanics, dynamics and tribology can all play a role. The introduction to the paper will contain a review of manufacturing processes and describe where simulations have been successfully applied, and where simulations are still lacking. The best of the simulations are those where the models accurately fit the physical phenomena, where accurate constitutive equations are available, and where boundary conditions are realistic. Thus, the body of the paper will focus on the results from one of these more successful simulations. It has been used to predict the deflections of tooling and the most appropriate operating conditions for the manufacturing process under study. A new method for manufacturing planning is described. In this method, closed form, somewhat simplified, analytical models are used to determine manufacturing planning parameters and then the results from these simpler models are refined by the fuller simulations. A case study in machining parameter selection for peripheral finish milling operations is developed.
Date: October 1, 1996
Creator: Wright, P.; Stori, J. & King, C.
Partner: UNT Libraries Government Documents Department

AGU Chapman Conference Hydrogeologic Processes: Building and Testing Atomistic- to Basin-Scale Models

Description: This report presents details of the Chapman Conference given on June 6--9, 1994 in Lincoln, New Hampshire. This conference covered the scale of processes involved in coupled hydrogeologic mass transport and a concept of modeling and testing from the atomistic- to the basin- scale. Other topics include; the testing of fundamental atomic level parameterizations in the laboratory and field studies of fluid flow and mass transport and the next generation of hydrogeologic models. Individual papers from this conference are processed separately for the database.
Date: December 1994
Creator: Weaver, B.
Partner: UNT Libraries Government Documents Department

Low temperature carrier transport properties in isotopically controlled germanium

Description: Investigations of electronic and optical properties of semiconductors often require specimens with extremely homogeneous dopant distributions and precisely controlled net-carrier concentrations and compensation ratios. The previous difficulties in fabricating such samples are overcome as reported in this thesis by growing high-purity Ge single crystals of controlled {sup 75}Ge and {sup 70}Ge isotopic compositions, and doping these crystals by the neutron transmutation doping (NTD) technique. The resulting net-impurity concentrations and the compensation ratios are precisely determined by the thermal neutron fluence and the [{sup 74}Ge]/[{sup 70}Ge] ratios of the starting Ge materials, respectively. This method also guarantees unprecedented doping uniformity. Using such samples the authors have conducted four types of electron (hole) transport studies probing the nature of (1) free carrier scattering by neutral impurities, (2) free carrier scattering by ionized impurities, (3) low temperature hopping conduction, and (4) free carrier transport in samples close to the metal-insulator transition.
Date: December 1994
Creator: Itoh, K.
Partner: UNT Libraries Government Documents Department

Ultrafast infrared studies of complex ligand rearrangements in solution

Description: The complete description of a chemical reaction in solution depends upon an understanding of the reactive molecule as well as its interactions with the surrounding solvent molecules. Using ultrafast infrared spectroscopy it is possible to observe both the solute-solvent interactions and the rearrangement steps which determine the overall course of a chemical reaction. The topics addressed in these studies focus on reaction mechanisms which require the rearrangement of complex ligands and the spectroscopic techniques necessary for the determination of these mechanisms. Ligand rearrangement is studied by considering two different reaction mechanisms for which the rearrangement of a complex ligand constitutes the most important step of the reaction. The first system concerns the rearrangement of a cyclopentadienyl ring as the response of an organometallic complex to a loss of electron density. This mechanism, commonly referred to as ''ring slip'', is frequently cited to explain reaction mechanisms. However, the ring slipped intermediate is too short-lived to be observed using conventional methods. Using a combination of ultrafast infrared spectroscopy and electronic structure calculations it has been shown that the intermediate exists, but does not form an eighteen-electron intermediate as suggested by traditional molecular orbital models. The second example examines the initial steps of alkyne polymerization. Group 6 (Cr, Mo, W) pentacarbonyl species are generated photolytically and used to catalyze the polymerization of unsaturated hydrocarbons through a series of coordination and rearrangement steps. Observing this reaction on the femto- to millisecond timescale indicates that the initial coordination of an alkyne solvent molecule to the metal center results in a stable intermediate that does not rearrange to form the polymer precursor. This suggests that polymerization requires the dissociation of additional carbonyl ligands before rearrangement can occur. Overall, this research demonstrates the importance of examining reaction dynamics on the ultrafast timescale. In the case of both ...
Date: Spring 2003
Creator: Payne, Christine K.
Partner: UNT Libraries Government Documents Department

Algorithms for biomagnetic source imaging with prior anatomical and physiological information

Description: This dissertation derives a new method for estimating current source amplitudes in the brain and heart from external magnetic field measurements and prior knowledge about the probable source positions and amplitudes. The minimum mean square error estimator for the linear inverse problem with statistical prior information was derived and is called the optimal constrained linear inverse method (OCLIM). OCLIM includes as special cases the Shim-Cho weighted pseudoinverse and Wiener estimators but allows more general priors and thus reduces the reconstruction error. Efficient algorithms were developed to compute the OCLIM estimate for instantaneous or time series data. The method was tested in a simulated neuromagnetic imaging problem with five simultaneously active sources on a grid of 387 possible source locations; all five sources were resolved, even though the true sources were not exactly at the modeled source positions and the true source statistics differed from the assumed statistics.
Date: December 1995
Creator: Hughett, P. W.
Partner: UNT Libraries Government Documents Department

Physics prospects: Why do we want a linear collider?

Description: The need to understand physics of electroweak symmetry breaking is reviewed. An electron positron linear collider will play crucial roles in that respect. It is discussed how the LHC and a linear collider need each other to understand symmetry breaking mechanism unambiguously. Two popular scenarios, supersymmetry and technicolor- like models, are used to demonstrate this point.
Date: December 1995
Creator: Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department