A coupled atmosphere-river flow simulation in California during the 1994-1995 winter (open access)

A coupled atmosphere-river flow simulation in California during the 1994-1995 winter

Calculation of river flow is important for managing reservoirs and flood forecasting. In the western United States, a complex terrain which is characterized by steep slopes and narrow valleys often cause a substantial rise of river levels in a short period during heavy precipitation events. Since flood control is one of the major tasks of reservoir operation, inaccurate predictions of precipitation and river flow may cause flooding or waste of water resources. Accurate calculations of river flow need accurate liquid water input to the river system at scales of individual watersheds. Precipitation and snowmelt are the most important natural source of water for a river. Reservoir operations significantly affect river flow in the western United States. Factors such as instantaneous soil water content, vegetation cover, terrain slope and ground water table structure are also crucial for river flow calculation. There are two types of precipitation: rain and snowfall. River flow quickly responds to rainfall while snowfall does not directly affect river flow until it melts afterwards. Therefore, these two types of precipitation must be separately provided to the river flow model for correct calculation of river flows. A large portion of snowfall is accumulated at high terrain during winter months …
Date: September 28, 1995
Creator: Kim, J. & Miller, N. L.
System: The UNT Digital Library
Properties of High Beta, Quasi-Axisymmetric NCSX Stellarator Configurations (open access)

Properties of High Beta, Quasi-Axisymmetric NCSX Stellarator Configurations

Quasi-axisymmetry, external kinks and ballooning stability are studied with respect to the plasma shaping and variation in the pressure and current profiles for NCSX. We show that while the kink stability may require a delicate boundary shaping, most quasi-axisymmetry may be achieved using a few low order modes that eliminate the large mirror fields arising partly from boundary shaping for the kink stability. In addition, we demonstrate that the kink and ballooning instability may be improved in the NCSX configurations by a more peaked pressure profile or a broader current profile. Finally, we show numerically that it is possible to construct a quasi-axisymmetric configuration that is stable to the external kink at all current levels for which the edge rotational transform is less than 0.5.
Date: September 28, 1999
Creator: Boozer, A.; Fu, G. Y.; Ku, L. P.; Monticello, D. & Reiman, A.
System: The UNT Digital Library
Application of microwave solidification technology to radioactive waste (open access)

Application of microwave solidification technology to radioactive waste

The EPA has declared vitrification to be the Best Available Demonstrated Technology (BDAT) for High Level Radioactive Waste (40 CFR 268.42). Vitrification has been chosen as the method of choice for treating a number of radioactive residues and wastes in the DOE complex. Vitrification offers advantages of waste volume reduction, the ability to handle changing waste forms, and a stable, nonleachable final waste form. Microwave heating is a superior method for vitrification of radioactive wastes. Advantages of microwave heating include: (1) direct waste heating, eliminates need for electrodes, refractories and other consumables; (2) ``in-can`` processing allows for treatment of the material in its final container, (3) a mechanically simple system where the microwaves are generated away from the treatment area and transmitted to the treatment applicator by a wave guide, thus minimizing worker exposure to radiation; (4) easier equipment maintenance; and (5) a high degree of public acceptance.
Date: September 28, 1995
Creator: Harris, M.; Sprenger, G.; Roushey, B.; Fenner, G. & Nieweg, R.
System: The UNT Digital Library
Mask substrate requirements and development for extreme ultraviolet lithography (EUVL) (open access)

Mask substrate requirements and development for extreme ultraviolet lithography (EUVL)

The mask is deemed one of the areas that require significant research and development in EUVL. Silicon wafers will be used for mask substrates for an alpha-class EUVL exposure tool due to their low-defect levels and high quality surface finish. However, silicon has a large coefficient of thermal expansion that leads to unacceptable image distortion due to absorption of EUV light. A low thermal expansion glass or glass-ceramic is likely to be required in order to meet error budgets for the 70nm node and beyond. Since EUVL masks are used in reflection, they are coated with multilayers prior to patterning. Surface imperfections, such as polishing marks, particles, scratches, or digs, are potential nucleation sites for defects in the multilayer coating, which could result in the printed defects. Therefore we are accelerating developments in the defect reduction and surface finishing of low thermal expansion mask substrates in order to understand long-term issues in controlling printable defects, and to establish the infrastructure for supplying masks. In this paper, we explain the technical requirements for EUVL mask substrates and describe our efforts in establishing a SEMI standard for EUVL masks. We will also report on the early progress of our suppliers in producing …
Date: September 28, 1999
Creator: Hector, S D; Shell, M; Taylor, J S & Tong, W M
System: The UNT Digital Library
JET Radiative Mantle Experiments in ELMy H-Mode (open access)

JET Radiative Mantle Experiments in ELMy H-Mode

Radiative mantle experiments were performed on JET ELMy H-mode plasmas. The Septum configuration was used where the X-point is embedded into the top of the Septum. Argon radiated 50% of the input power from the bulk plasma while Z{sub eff} rose from an intrinsic level of 1.5 to about 1.7 due to the injected Argon. The total energy content and global energy confinement time decreased 15% when the impurities were introduced. In contrast, the effective thermal diffusivity in the core confinement region (r/a = .4--.8) decreased by 30%. Usually, JET ELMy H-mode plasmas have confinement that is correlated to the edge pedestal pressure. The radiation lowered the edge pedestal and consequently lowered the global confinement. Thus the confinement was changed by a competition between the edge pedestal reduction lowering the confinement and the weaker RI effect upon the core transport coefficients raising the confinement. The ELM frequency increased from 10 Hz Type I ELMs, to 200 Hz type III ELMs. The energy lost by each ELM reduced to 0.5% of the plasma energy content.
Date: September 28, 1999
Creator: Budny, R.; Coffey, I.; Dumortier, P.; Grisolia, C.; Strachan, J.D. & al, et
System: The UNT Digital Library
Numerical simulation of precipitation over the Southwestern United States during the 1994-1995 winter season (open access)

Numerical simulation of precipitation over the Southwestern United States during the 1994-1995 winter season

Accurate assessments of precipitation and surface snow budget during winter seasons are crucial for managing water resources in the western United States. This region receives most of its annual precipitation during winter months and relies on water stored in snowpack and reservoirs for water supply during dry summer seasons. Rainfall directly affects water inflow into reservoirs while snowmelt determines it during spring and summer. Precipitation and snow budget result from interactions among large-scale forcing, mesoscale processes, and surface energy balance. Interaction among these elements is highly nonlinear and includes various processes such as large-scale water vapor and temperature advection, precipitation physics, orographic forcing, turbulence, solar and terrestrial radiative transfer, and snow-albedo feedback. Hence, one need to take these processes into consideration in order to obtain accurate assessments of regional water resources over time scales longer than a season. A regional model that interactively couples atmospheric and land surface processes is a cost-effective tool for an assessment of precipitation and surface hydrology over large areas at a relatively fine resolution. Such models can include complex physical and dynamical processes involved in the interaction between the atmosphere and land surfaces. Another advantage of coupled atmosphere-land surface modeling is that simulations, when verified …
Date: September 28, 1995
Creator: Kim, J.
System: The UNT Digital Library
Screening enhancement of thermonuclear reactions in high density stars (open access)

Screening enhancement of thermonuclear reactions in high density stars

The screening function for zero separation for two is reacting nuclei in a strongly coupled OCP plasma is obtained using new very accurate Monte Carlo OCP fluid simulation data by two methods. The first method obtains, H(0), the screening function at x =0, from the difference of free energies before and after the reaction. The second method is a direct fitting of the Widom expansion in powers of x{sup 2 }to the MC data for the pair distribution function, g(x). The two methods agree to 2%
Date: September 28, 1998
Creator: DeWitt, H. & Slattery, W.
System: The UNT Digital Library
Nuclear microscopy of sperm cell elemental structure (open access)

Nuclear microscopy of sperm cell elemental structure

Theories suggest there is a link between protamine concentrations in individual sperm and male fertility. Previously, biochemical analyses have used pooled samples containing millions of sperm to determine protamine concentrations. These methods have not been able to determine what percentage of morphologically normal sperm are biochemically defective and potentially infertile. Nuclear microscopy has been utilized to measure elemental profiles at the single sperm level. By measuring the amount of phosphorus and sulfur, the total DNA and protamine content in individual sperm from fertile bull and mouse semen have been determined. These values agree with results obtained from other biochemical analyses. Nuclear microscopy shows promise for measuring elemental profiles in the chromatin of individual sperm. The technique may be able to resolve theories regarding the importance of protamines to male fertility and identify biochemical defects responsible for certain types of male infertility.
Date: September 28, 1994
Creator: Bench, Graham S.; Balhorn, Rodney; Friz, Alexander M. & Freeman, Stewart P. H. T.
System: The UNT Digital Library
Behavior of Zircaloy Cladding in the Presence of Gallium (open access)

Behavior of Zircaloy Cladding in the Presence of Gallium

The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional MOX fuel, on cladding material performance. An experimental program was designed to evaluate the performance of prototypic Zircaloy cladding materials against (1) liquid gallium, and (2) various concentrations of G~03. Three types of tests were performed: (1) corrosion, (2) liquid metal embrittlement, and (3) corrosion-mechanical. These tests were to determine corrosion mechanisms, thresholds for temperature and concentration of gallium that delineate behavioral regimes, and changes in the mechanical properties of Zircaloy. Results have generally been favorable for the use of weapons-grade (WG) MOX fhel. The Zircaloy cladding does react with gallium to form intermetallic compounds at >3000 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (parts per million) of gallium in the MOX fuel. Furthermore, no evidence for grain boundary penetration by gallium or liquid …
Date: September 28, 1998
Creator: DiStefano, J. R.; King, J. F.; Manneschmidt, E. T.; Strizak, J. P. & Wilson, D. F.
System: The UNT Digital Library
Collection and Segregation of Radioactive Waste. Principals for Characterization and Classification of Radioactive Waste (open access)

Collection and Segregation of Radioactive Waste. Principals for Characterization and Classification of Radioactive Waste

Radioactive wastes are generated by all activities which utilize radioactive materials as part of their processes. Generally such activities include all steps in the nuclear fuel cycle (for power generation) and non-fuel cycle activities. The increasing production of radioisotopes in a Member State without nuclear power must be accompanied by a corresponding development of a waste management system. An overall waste management scheme consists of the following steps: segregation, minimization, treatment, conditioning, storage, transport, and disposal. To achieve a satisfactory overall management strategy, all steps have to be complementary and compatible. Waste segregation and minimization are of great importance mainly because they lead to cost reduction and reduction of dose commitments to the personnel that handle the waste. Waste characterization plays a significant part in the waste segregation and waste classification processes, it implicates required waste treatment process including the need for the safety assessment of treatment conditioning and storage facilities.
Date: September 28, 1998
Creator: Dziewinska, K.M.
System: The UNT Digital Library
Optical Investigation of GaNAs (open access)

Optical Investigation of GaNAs

A systematic study of the energy and time-resolved photoluminescence of GaInP/GaNxAs1-x double heterostructures has been performed for 0=x=1.3%. A large temperature-dependent optical-bowing coefficient (about 20-25 eV) is observed and the bandgap variation with temperature is found to depend on the nitrogen content. Finally, the minority-carrier lifetime is not simply related to the nitrogen content. Instead, the recombination rate is proportional to the majority-carrier concentration for x=0.3% and the carbon concentration for x=0.3%.
Date: September 28, 1998
Creator: Keyes, B. M.; Geisz, J. F.; Dippo, P. C.; Reedy, R.; Kramer, C.; Friedman, D. J. et al.
System: The UNT Digital Library
Treatment Options for Liquid Radioactive Waste. Factors Important for Selecting of Treatment Methods (open access)

Treatment Options for Liquid Radioactive Waste. Factors Important for Selecting of Treatment Methods

The cleanup of liquid streams contaminated with radionuclides is obtained by the selection or a combination of a number of physical and chemical separations, processes or unit operations. Among those are: Chemical treatment; Evaporation; Ion exchange and sorption; Physical separation; Electrodialysis; Osmosis; Electrocoagulation/electroflotation; Biotechnological processes; and Solvent extraction.
Date: September 28, 1998
Creator: Dziewinski, J.J.
System: The UNT Digital Library
Measurements of cross sections and resonance structures following electron-impact excitation/ionization of Na-like Kr and Xe (open access)

Measurements of cross sections and resonance structures following electron-impact excitation/ionization of Na-like Kr and Xe

We report high-resolution measurements of electron impact excitation and ionization cross sections for the Na-like ions Kr{sup 25+} and Xe{sup 43+}. Ions with ionization states centered on the Na-like configurations were produced in an electron beam ion trap (EBIT) using electrons with energies below the L shell ionization thresholds. The Na-like ions were exposed to an electron beam with an energy between 3 and 7 keV. The Na- and Ne-like ions were then extracted and their intensities measured as a function of the electron beam energy. Theoretical ionization cross sections were calculated using relativistic distorted wave methods. Complex resonance structures that appear in the computed cross sections are observed in the experimental results. These results are the first experimental observation of resonant-excitation-double-autoionization (REDA) in highly charged high-Z ions.
Date: September 28, 1994
Creator: Schneider, D.; DeWitt, D.; Knapp, D. A.; Reed, K. J. & Chen, M. H.
System: The UNT Digital Library
Statistical on-chip interconnect modeling : an application of automatic differentiation. (open access)

Statistical on-chip interconnect modeling : an application of automatic differentiation.

Automatic differentiation is a technique for computing derivatives accurately and efficiently with minimal human effort. We employed this technique to generate derivative information of FCAP2 (2-D) and FCAP3 (3-D) programs that simulate the parasitic effects of interconnects and devices. This derivative information is used in the statistical modeling of worst-case interconnect delays and on-chip crosstalks. The ADIC (Automatic Differentiation in C) tool generated new versions of FCAP2 and FCAP3 programs that compute both the original results and the derivative information. Given the ANSI C source code for the function, ADIC generates new code that computes derivatives of the model output with respect to the input parameters. We report on the use of automatic differentiation and divided difference approaches for computing derivatives for FCAP3 programs. The results show that ADIC-generated code computes derivatives more accurately, more robustly, and faster than the divided difference approach.
Date: September 28, 1998
Creator: Bischof, C.; Roh, L.; Chang, N.; Lee, K.; Kanevsky, V.; Nakagawa, O. S. et al.
System: The UNT Digital Library
An Enterprise Information Architecture: A Case Study for Decentralized Organizations (open access)

An Enterprise Information Architecture: A Case Study for Decentralized Organizations

As enterprises become increasingly information based, making improvements in their information activities is a top priority to assure their continuing competitiveness. A key to achieving these improvements is developing an Enterprise Information Architecture (EIA). An EIA can be viewed as a structured set of multidimensional interrelated elements that support all information processes. The current ad hoc EIAs in place within many enterprises can not meet their future needs because of a lack of a coherent framework, incompatibilities, missing elements, few and poorly understood standards, uneven quality and unnecessary duplications. This paper discusses the EIA developed at Lawrence Livermore National Laboratory as a case study, for other information based enterprises, particularly those with decentralized and autonomous organization structures and cultures. While the architecture is important, the process by which it is developed and sustained over time is equally important. This paper outlines the motivation for an EIA and discusses each of the interacting elements identified. It also presents an organizational structure and processes for building a sustainable EIA activity.
Date: September 28, 1999
Creator: Watson, R.W.
System: The UNT Digital Library
Schlieren observations of density channels in MPPE (open access)

Schlieren observations of density channels in MPPE

Schlieren imaging techniques were used to study the density depressions created by the ATA electron beam 37 cm after the entrance foil. Typical channel depressions were 5--10% of ambient density per pulse. Under IFR guiding channel depths as deep as 30% were seen on single pulse operation. Pulse 5 of the 5 pulse burst has passed through a channel reduced to 30% of ambient density. To lowest order, one would expect channel density depressions to scale as ({Delta}n/n) {proportional to} ({number sign} of pulses * I{sub beam}/channel area). Channel depth observations scaled roughly with beam current, {number sign} of pulses, and inversely with channel area. Pressure scaling was anomalous in that {Delta}n appeared to be less sensitive to pressure than the linear dependence expected. This would require that the energy deposition (stopping power) is independent of pressure and is a surprising result which can only be explained with collective effects. Scaling of channel expansion rates with pressure suggest classical diffusion (D {proportional to} 1/n) for times up to 200 mS. During these early times, the diffusion constant was, however, 3--5 times larger than the classical value. At later times, large scale turbulence was observed and the effective diffusion constant increased …
Date: September 28, 1990
Creator: Guethlein, G. (Lawrence Livermore National Lab., CA (USA)) & Pechacek, B. (Naval Research Lab., Washington, DC (USA))
System: The UNT Digital Library
The cascade ICF reactor with an x-ray and debris shield and a heavy-ion driver (open access)

The cascade ICF reactor with an x-ray and debris shield and a heavy-ion driver

The use of a 1-kg solid-lithium x-ray and debris shield around each fusion fuel pellet prevents vaporization of, and destructive shock waves in, the Cascade blanket granules thereby increasing their lifetime. The shield vaporizes as it absorbs energy and the vapor flows into the blanket several centimeters. The shield also increases tritium breeding and enhances vacuum pumping of high Z materials that are vaporized in the fuel pellet. Using heavy ion beams allows illumination of the fuel pellets with the restricted geometry present in Cascade. We used a 5 MJ driver with 18 beams (one 3 {times} 3 array from each end).
Date: September 28, 1990
Creator: Pitts, John H. & Tabak, Max
System: The UNT Digital Library
Liouville`s theorem and phase-space cooling (open access)

Liouville`s theorem and phase-space cooling

A discussion is presented of Liouville`s theorem and its consequences for conservative dynamical systems. A formal proof of Liouville`s theorem is given. The Boltzmann equation is derived, and the collisionless Boltzmann equation is shown to be rigorously true for a continuous medium. The Fokker-Planck equation is derived. Discussion is given as to when the various equations are applicable and, in particular, under what circumstances phase space cooling may occur.
Date: September 28, 1993
Creator: Mills, R. L. & Sessler, A. M.
System: The UNT Digital Library
Symposium report on frontier applications of accelerators (open access)

Symposium report on frontier applications of accelerators

This report contains viewgraph material on the following topics: Electron-Positron Linear Colliders; Unconventional Colliders; Prospects for UVFEL; Accelerator Based Intense Spallation; Neutron Sources; and B Physics at Hadron Accelerators with RHIC as an Example.
Date: September 28, 1993
Creator: Parsa, Z.
System: The UNT Digital Library
Excitation of a quantal and a classical gas in a time-dependent potential (open access)

Excitation of a quantal and a classical gas in a time-dependent potential

We report on computer simulations of oscillating Woods-Saxon or cavity potentials filled with either a classical or a quantal gas of independent particles. We have now available of the order of 600 excitation histories of such gases undergoing usually one period of oscillation (but sometimes several), classified according to frequency and multipolarity of the oscillation and of the degree of diffuseness of the potential. We are still in the process of displaying and interpreting some of the results, but certain important features are already apparent. A notable finding is that, contrary to concerns sometimes voiced in the literature, the classical wall formula does not fail catastrophically when confronted with quantal calculations. This is true even for relatively small systems -- in our case 112 neutrons in doubly degenerate eigenstates. On the contrary, the wall formula, in addition to reproducing accurately the classical computer simulations, gives also an approximate account of the quantal results in the regime where it is expected to be valid, namely for not too small oscillation frequencies and not too large surface diffuseness. In those cases it is gratifying to observe that the deviations from the wall formula actually correlate (semi-quantitatively) with the wave-mechanical corrections derived by …
Date: September 28, 1994
Creator: Blocki, J.; Brut, F.; Skalski, J. & Swiatecki, W. J.
System: The UNT Digital Library