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Exciton dynamicsstudied via internal THz transitions
We employ a novel, ultrafast terahertz probe to investigatethe dynamical interplay of optically-induced excitons and unboundelectron-hole pairs in GaAs quantum wells. Resonant creation ofheavy-hole excitons induces a new low-energy oscillator linked totransitions between the internal exciton degrees of freedom. The timeresolved terahertz optical conductivity is found to be a probe wellsuited for studies of fundamental processes such as formation, relaxationand ionization of excitons.
Date:
February 26, 2003
Creator:
Kaindl, R. A.; Hagele, D.; Carnahan, M. A.; Lovenich, R. & Chemla, D. S.
Object Type:
Article
System:
The UNT Digital Library
Compound-Nuclear Reaction Cross Sections from Surrogate Measurements: Status and Challenges
None
Date:
February 26, 2008
Creator:
Escher, J.
Object Type:
Article
System:
The UNT Digital Library
Identifying Oil Exploration Leads using Intergrated Remote Sensing and Seismic Data Analysis, Lake Sakakawea, Fort Berthold Indian Reservation, Willistion Basin
The Fort Berthold Indian Reservation, inhabited by the Arikara, Mandan and Hidatsa Tribes (now united to form the Three Affiliated Tribes) covers a total area of 1530 mi{sup 2} (980,000 acres). The Reservation is located approximately 15 miles east of the depocenter of the Williston basin, and to the southeast of a major structural feature and petroleum producing province, the Nesson anticline. Several published studies document the widespread existence of mature source rocks, favorable reservoir/caprock combinations, and production throughout the Reservation and surrounding areas indicating high potential for undiscovered oil and gas resources. This technical assessment was performed to better define the oil exploration opportunity, and stimulate exploration and development activities for the benefit of the Tribes. The need for this assessment is underscored by the fact that, despite its considerable potential, there is currently no meaningful production on the Reservation, and only 2% of it is currently leased. Of particular interest (and the focus of this study) is the area under the Lake Sakakawea (formed as result of the Garrison Dam). This 'reservoir taking' area, which has never been drilled, encompasses an area of 150,000 acres, and represents the largest contiguous acreage block under control of the Tribes. Furthermore, …
Date:
February 26, 2004
Creator:
Reeves, Scott R. & Billingsley, Randal L.
Object Type:
Report
System:
The UNT Digital Library
Spectroscopy of neutron-rich palladium and cadmium isotopes near A=120
New high-spin levels have been identified in the nucleus {sup 120}Pd from analysis of the coincidence gamma rays observed in the {sup 238}U({alpha}, f{gamma}{gamma}{gamma}) reaction. Recoiling fragments were detected with the Rochester heavy-ion detector array, CHICO, in coincidence with gamma-rays using Gammasphere. An A=110-130 mass-gated {gamma} - {gamma} - {gamma} cube from this experiment was constructed and analyzed for coincident gamma-rays in several nuclei near A=120. New results for neutron-rich {sup 118}Pd and {sup 120}Pd have been obtained. The {sup 120}Pd level scheme was extended to spin of 10{sup +} by building on the new low-energy gamma rays identified in decay studies of {sup 120}Rh. The details of the {sup 118}Pd level scheme derived from this work are compared to previous work. The systematics of the yrast levels in even-even Pd and Cd isotopes are presented and the symmetry of energy levels around N = 68 is discussed. A new 10{sup +} level in {sup 124}Cd has been observed. The population intensity of even-even neutron-rich Cd isotopes is deduced, indicating that nuclides near {sup 120}Cd are preferentially populated following alpha-induced fission of {sup 238}U.
Date:
February 26, 2008
Creator:
Stoyer, M A & Walters, W B
Object Type:
Article
System:
The UNT Digital Library
A review of ground-based heavy-ion radiobiology relevant to space radiation risk assessment: Part II. Cardiovascular and immunological effects
The future of manned space flight depends on an analysis of the numerous potential risks of travel into deep space. Currently no radiation dose limits have been established for these exploratory missions. To set these standards more information is needed about potential acute and late effects on human physiology from appropriate radiation exposure scenarios, including pertinent radiation types and dose rates. Cancer risks have long been considered the most serious late effect from chronic daily relatively low-dose exposures to the complex space radiation environment. However, other late effects from space radiation exposure scenarios are under study in ground-based accelerator facilities and have revealed some unique particle radiation effects not observed with conventional radiations. A comprehensive review of pertinent literature that considers tissue effects of radiation leading to functional detriments in specific organ systems has recently been published (NCRP National Council on Radiation Protection and Measurements, Information Needed to Make Radiation Protection Recommendations for Space Missions Beyond Low-Earth Orbit, Report 153, Bethesda, MD, 2006). This paper highlights the review of two non-cancer concerns from this report: cardiovascular and immunological effects.
Date:
February 26, 2007
Creator:
Blakely, Eleanor A. & Chang, Polly Y.
Object Type:
Article
System:
The UNT Digital Library
Reduction of pertechnetate by acetohydroxamic acid: Formation of [TcNO(AHA)2(H2O)]+ and implications for the UREX process.
Reductive nitrosylation and complexation of ammonium pertechnetate by acetohydroxamic acid has been achieved in aqueous nitric and perchloric acid solutions. The kinetics of the reaction depend on the relative concentrations of the reaction components and are accelerated at higher temperatures. The reaction does not occur unless conditions are acidic. Analysis of the x-ray absorption fine structure spectroscopic data is consistent with a pseudo-octahedral geometry with the linear Tc-N-O bond typical of technetium nitrosyl compounds, and electron spin resonance spectroscopy is consistent with a the d{sup 5} Tc(II) nitrosyl complex. The nitrosyl source is generally AHA, but may be augmented by products of reaction with nitric acid. The resulting low-valency trans-aquonitrosyl(diacetohydroxamic)-technetium(II) complex (1) is highly soluble in water, extremely hydrophilic, and is not extracted by tri-n-butylphosphate in a dodecane diluent. Its extraction properties are not pH-dependent; titration studies indicate a single species from pH 4.5 down to -0.6 (calculated). This molecule is resistant to oxidation by H{sub 2}O{sub 2}, even at high pH, and can undergo substitution to form other technetium nitrosyl complexes. The formation of 1 may strongly impact the fate of technetium in the nuclear fuel cycle.
Date:
February 26, 2008
Creator:
1Harry Reid Center for Environmental Studies, Nuclear Science and Technology Division, University of Nevada, Las Vegas, Las Vegas, NV, 89154-4006; Gong, Cynthia-May S; Poineau, Frederic; Lukens, Wayne W & Czerwinski, Kenneth R.
Object Type:
Article
System:
The UNT Digital Library
Stochastic Hard-Sphere Dynamics for Hydrodynamics of Non-Ideal Fluids
A novel stochastic fluid model is proposed with a nonideal structure factor consistent with compressibility, and adjustable transport coefficients. This stochastic hard-sphere dynamics (SHSD) algorithm is a modification of the direct simulation Monte Carlo algorithm and has several computational advantages over event-driven hard-sphere molecular dynamics. Surprisingly, SHSD results in an equation of state and a pair correlation function identical to that of a deterministic Hamiltonian system of penetrable spheres interacting with linear core pair potentials. The fluctuating hydrodynamic behavior of the SHSD fluid is verified for the Brownian motion of a nanoparticle suspended in a compressible solvent.
Date:
February 26, 2008
Creator:
Donev, A; Alder, B J & Garcia, A L
Object Type:
Article
System:
The UNT Digital Library
Automotive Underhood Thermal Management Analysis Using 3-D Coupled Thermal-Hydrodynamic Computer Models: Thermal Radiation Modeling
The goal of the radiation modeling effort was to develop and implement a radiation algorithm that is fast and accurate for the underhood environment. As part of this CRADA, a net-radiation model was chosen to simulate radiative heat transfer in an underhood of a car. The assumptions (diffuse-gray and uniform radiative properties in each element) reduce the problem tremendously and all the view factors for radiation thermal calculations can be calculated once and for all at the beginning of the simulation. The cost for online integration of heat exchanges due to radiation is found to be less than 15% of the baseline CHAD code and thus very manageable. The off-line view factor calculation is constructed to be very modular and has been completely integrated to read CHAD grid files and the output from this code can be read into the latest version of CHAD. Further integration has to be performed to accomplish the same with STAR-CD. The main outcome of this effort is to obtain a highly scalable and portable simulation capability to model view factors for underhood environment (for e.g. a view factor calculation which took 14 hours on a single processor only took 14 minutes on 64 processors). …
Date:
February 26, 2002
Creator:
Pannala, S.; D'Azevedo, E. & Zacharia, T.
Object Type:
Report
System:
The UNT Digital Library
2009 EVALUATION OF TRITIUM REMOVAL AND MITIGATION TECHNOLOGIES FOR WASTEWATER TREATMENT
Since 1995, a state-approved land disposal site (SALDS) has received tritium contaminated effluents from the Hanford Site Effluent Treatment Facility (ETF). Tritium in this effluent is mitigated by storage in slow moving groundwater to allow extended time for decay before the water reaches the site boundary. By this method, tritium in the SALDS is isolated from the general environment and human contact until it has decayed to acceptable levels. This report contains the 2009 update evaluation of alternative tritium mitigation techniques to control tritium in liquid effluents and groundwater at the Hanford site. A thorough literature review was completed and updated information is provided on state-of-the-art technologies for control of tritium in wastewaters. This report was prepared to satisfy the Hanford Federal Facility Agreement and Consent Order (Tri-Party Agreement) Milestone M-026-07B (Ecology, EPA, and DOE 2007). Tritium separation and isolation technologies are evaluated periodically to determine their feasibility for implementation to control Hanford site liquid effluents and groundwaters to meet the Us. Code of Federal Regulations (CFR), Title 40 CFR 141.16, drinking water maximum contaminant level (MCL) for tritium of 20,000 pOll and/or DOE Order 5400.5 as low as reasonably achievable (ALARA) policy. Since the 2004 evaluation, there have been …
Date:
February 26, 2009
Creator:
KJ, LUECK; DJ, GENESSE & GE, STEGEN
Object Type:
Report
System:
The UNT Digital Library
Calibration of Chemical Kinetic Models Using Simulations of Small-Scale Cookoff Experiments
Establishing safe handling limits for explosives in elevated temperature environments is a difficult problem that often requires extensive simulation. The largest influence on predicting thermal cookoff safety lies in the chemical kinetic model used in these simulations, and these kinetic model reaction sequences often contain multiple steps. Several small-scale cookoff experiments, notably Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), One-Dimensional Time-to-Explosion (ODTX), and the Scaled Thermal Explosion (STEX) have been performed on various explosives to aid in cookoff behavior determination. Past work has used a single test from this group to create a cookoff model, which does not guarantee agreement with the other experiments. In this study, we update the kinetic parameters of an existing model for the common explosive 2,4,6-Trinitrotoluene (TNT) using DSC and ODTX experimental data at the same time by minimizing a global Figure of Merit based on hydrodynamic simulated data. We then show that the new kinetic model maintains STEX agreement, reduces DSC agreement, and improves ODTX and TGA agreement when compared to the original model. In addition, we describe a means to use implicit hydrodynamic simulations of DSC experiments to develop a reaction model for TNT melting.
Date:
February 26, 2008
Creator:
Wemhoff, A P; Becker, R C & Burnham, A K
Object Type:
Article
System:
The UNT Digital Library
Quantitative film radiography
We have developed a system of quantitative radiography in order to produce quantitative images displaying homogeneity of parts. The materials that we characterize are synthetic composites and may contain important subtle density variations not discernible by examining a raw film x-radiograph. In order to quantitatively interpret film radiographs, it is necessary to digitize, interpret, and display the images. Our integrated system of quantitative radiography displays accurate, high-resolution pseudo-color images in units of density. We characterize approximately 10,000 parts per year in hundreds of different configurations and compositions with this system. This report discusses: the method; film processor monitoring and control; verifying film and processor performance; and correction of scatter effects.
Date:
February 26, 1991
Creator:
Devine, G.; Dobie, D.; Fugina, J.; Hernandez, J.; Logan, C.; Mohr, P. et al.
Object Type:
Report
System:
The UNT Digital Library
Summary of results from the Tandem Mirror Experiment (TMX)
This report summarizes results from the successful experimental operation of the Tandem Mirror Experiment (TMX) over the period October 1978 through September 1980. The experimental program, summarized by the DOE milestones given in Table 1-1, had three basic phases: (1) an 8-month checkout period, October 1978 through May 1979; (2) a 6-month initial period of operation, June through November 1979, during which the basic principles of the tandem configuration were demonstrated (i.e., plasma confinement was improved over that of a single-cell mirror); and (3) a 10-month period, December 1979 through September 1980, during which the initial TMX results were corroborated by additional diagnostic measurements and many detailed physics investigations were carried out. This report summarizes the early results, presents results of recent data analysis, and outlines areas of ongoing research and data analysis which will be reported in future journal publications.
Date:
February 26, 1981
Creator:
Simonen, T.C. (ed.)
Object Type:
Report
System:
The UNT Digital Library
Feasibility study for a low-head hydroelectric installation at Archusa Creek Dam. Final report to the Pat Harrison Waterway District
The rising cost, uncertain future supply, and environmental problems associated with energy sources have resulted in serious investigation of energy sources that have not previously been considered economically and technically feasible. One such source involves low-head hydroelectric generation. The Department of Energy has funded several feasibility studies for the installation of hydroelectric generators at existing low-head dams. Such a feasibility study for the Archusa Creek Dam near Quitman, Mississippi, is described. The study indicates that there are no apparent technical dificulties to prevent such a project and that a suitable turbine-generator could be obtained. The study further indicates that the project should be economically feasible for the Pat Harrison Waterway District (owners of the dam and lake) to construct if arrangements could be completed for interconnecting with the local utility and selling the energy to the utility. The utility (Mississippi Power Company) has expressed interest in such an arrangement.
Date:
February 26, 1979
Creator:
Carlson, K. W. & Herring, J. W. Jr.
Object Type:
Report
System:
The UNT Digital Library
Mixed Waste Management Facility (MWMF) closure, Savannah River Plant: Clay cap test section construction report
This report contains appendices 3 through 6 for the Clay Cap Test Section Construction Report for the Mixed Waste Management Facility (MWMF) closure at the Savannah River Plant. The Clay Cap Test Program was conducted to evaluate the source, lab. permeability, in-situ permeability, and compaction characteristics, representative of kaolin clays from the Aiken, South Carolina vicinity. (KJD)
Date:
February 26, 1988
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Mixed Waste Management Facility (MWMF) closure, Savannah River Plant: Clay cap test section construction report
This report contains appendix 2 for the Clay Cap Test Section Construction Report for the Mixed Waste Management Facility (MWMF) closure at the Savannah River Plant. The Clay Cap Test Program was conducted to evaluate the source, Laboratory permeability, and compaction characteristics representative of Kaolin clays from the aiken, South Carolina vicinity. Included in this report are daily field reports Nos. 1 to 54. (KJD)
Date:
February 26, 1988
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Burial Ground Expansion Hydrogeologic Characterization
Sirrine Environmental Consultants provided technical oversight of the installation of eighteen groundwater monitoring wells and six exploratory borings around the location of the Burial Ground Expansion.
Date:
February 26, 1999
Creator:
Gaughan , T. F.
Object Type:
Report
System:
The UNT Digital Library
Mixed Waste Management Facility (MWMF) closure, Savannah River Plant: Clay cap test section construction report
This report summarizes the information gathered in constructing the clay cap test section. The purpose of the test section was to determine compaction characteristics of four representative kaolin clays and demonstrate in-situ permeability for these clays of 1 {times} 10 {sup {minus}7} cm/sec or less. The final technical specifications with regard to maximum clod size, acceptable ranges of placement water content, lift thickness, and degree of compaction will be based on experience gained from the test section. The data derived from this study will also be used in the development of Quality Assurance (QA) and Quality Control (QC) methods to be used during actual cap construction of the Mixed Waste Management Facility (MWMF) Closure project. 7 tabs.
Date:
February 26, 1988
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Method of sputter etching a surface
A surface is textured by co-sputter etching with a target and a seed material with the surface at a pre-selected temperature. By pre-selecting the temperature of the surface while sputter etching, it is possible to predetermine the reflectance properties of the etched surface. The surface may be textured to absorb sunlight efficiently and have minimal emittance in the infrared region so as to be well-suited for use as a solar absorber for photothermal energy conversion.
Date:
February 26, 1982
Creator:
Henager, C.H. Jr.
Object Type:
Patent
System:
The UNT Digital Library
Oak Ridge K-25 Site Technology Logic Diagram
The Oak Ridge K-25 Technology Logic Diagram (TLD), a decision support tool for the K-25 Site, was developed to provide a planning document that relates environmental restoration and waste management problems at the Oak Ridge K-25 Site to potential technologies that can remediate these problems. The TLD technique identifies the research necessary to develop these technologies to a state that allows for technology transfer and application to waste management, remedial action, and decontamination and decommissioning activities. The TLD consists of four separate volumes-Vol. 1, Vol. 2, Vol. 3A, and Vol. 3B. This Volume, Volume 1 provides introductory and overview information about the TLD. Volume 2 contains logic diagrams. Volume 3 has been divided into two separate volumes to facilitate handling and use. This volume is divided into ten chapters. The first chapter is a brief introduction, and the second chapter details the technical approach of the TLD. These categories are the work activities necessary for successful decontamination and decommissioning, waste management, and remedial action of the K-25 Site. The categories are characterization, decontamination, dismantlement, robotics and automation, remedial action, and waste management. Materials disposition is addressed in Chap. 9. The final chapter contains regulatory compliance information concerning waste management, remedial …
Date:
February 26, 1993
Creator:
Fellows, R.L. (ed.)
Object Type:
Report
System:
The UNT Digital Library
Stabilizing windings for tilting and shifting modes
This invention provides simple, inexpensive, independent and passive, conducting loops for stabilizing a plasma ring having externally produced equilibrium fields on opposite sides of the plasma ring and internal plasma currents that interact to tilt and/or shift the plasma ring relative to the externally produced equilibrium field so as to produce unstable tilting and/or shifting modes in the plasma ring. More particularly this invention provides first and second passive conducting loops for containing first and second induced currents in first and second directions corresponding to the amplitude and directions of the unstable tilting and/or shifting modes in the plasma ring. To this end, the induced currents provide additional magnetic fields for producing restoring forces and/or restoring torques for counteracting the tilting and/or shifting modes when the conducting loops are held fixed in stationary positions relative to the externally produced equilibrium fields on opposite sides of the plasma ring.
Date:
February 26, 1982
Creator:
Jardin, S. C. & Christensen, U. R.
Object Type:
Patent
System:
The UNT Digital Library
Summary of TMX results: executive summary
This report summarizes results from the successful experimental operation of the Tandem Mirror Experiment (TMX) over the period October 1978 through September 1980. The experimental program, summarized by the DOE milestones given in Table 1, had three basic phases: (1) an 8-month checkout period, October 1978 through May 1979; (2) a 6-month initial period of operation, June through November 1979, during which the basic principles of the tandem configuration were demonstrated (i.e., plasma confinement was improved over that of a single-cell mirror); and (3) a 10-month period, December 1979 through September 1980, during which the initial TMX results were corroborated by additional diagnostic measurements and many detailed physics investigations were carried out. This report summarizes the early results, presents results of recent data analysis, and outlines areas of ongoing research.
Date:
February 26, 1981
Creator:
Simonen, T.C. (ed.)
Object Type:
Report
System:
The UNT Digital Library
Bag-out material handling system
A bagging device for transferring material from a first chamber through an opening in a wall to a second chamber includes an outer housing communicating with the opening and having proximal and distal ends relative to the wall. An inner housing having proximal and distal ends corresponding to those of the outer housing is mounted in a concentrically spaced, sealed manner with respect to the distal end of the outer housing. The inner and outer housings and mounting means therebetween define an annular chamber, closed at its distal end and open at its proximal end, in which a pliable tube is slidably positioned in sealed engagement with the housings. The pliable tube includes a sealed end positioned adjacent the proximal end of the inner housing so as to maintain isolation between the first and second chambers. Displacement of the material to be bagged from the first chamber along the inner housing so as to contact the sealed portion of the pliable bag allows the material to be positioned within the pliable bag in the second chamber. The bag is then sealed and severed between where the material is positioned therein and the wall in providing a sealed container for handling …
Date:
February 26, 1982
Creator:
Brak, S.B.
Object Type:
Patent
System:
The UNT Digital Library
Optimum utilization of site energy sources for all-season thermal comfort in new residential construction for single-family attached (rowhouse/townhouse) designs
A proposed design analysis is presented of a passive solar energy efficient system for a typical three-level, three bedroom, two story, garage-under townhouse. The design incorporates the best, most performance-proven and cost effective products, materials, processes, technologies, and sub-systems which are available today. Seven distinct categories recognized for analysis are identified as: the exterior environment; the interior environment; conservation of energy; natural energy utilization; auxiliary energy utilization; control and distribution systems; and occupant adaptation. Preliminary design features, fenestration sysems, the plenum-supply system, the thermal-storage party-fire walls, direct gain storage, the radiant comfort system, and direct passive cooling systems are briefly described. Features of the design under analysis and on which conclusions have not yet been formulated are: the energy reclamation system, auxiliary energy back-up systems, the distribution system and operating modes, the control systems, and non-comfort energy systems and inputs. (MCW)
Date:
February 26, 1981
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Results on neutrino-electron elastic scattering at AGS energies
In an experiment designed to study elastic scattering of nu/sub ..mu../ (and anti nu/sub ..mu../) from electrons and protons via the weak neutral current, we have recently completed several extensive data taking runs. Results for the cross section of nu/sub ..mu../ + e/sup -/ ..-->.. nu/sub ..mu../ + e/sup -/ are presented based upon the first third of the available sample. Preliminary analysis of anti nu/sub ..mu../ + e/sup -/ ..-->.. anti nu/sub ..mu../ + e/sup -/ is in progress and evidence for the signal is presented.
Date:
February 26, 1984
Creator:
Lanou, R. E.
Object Type:
Report
System:
The UNT Digital Library