Forming and smoothing D{sub 2} and HD layers for ICF by infra-red heating (open access)

Forming and smoothing D{sub 2} and HD layers for ICF by infra-red heating

We describe a technique to form and smooth uniform solid D{sub 2}, HD or DT layers for inertial confinement fusion targets. Pumping the infrared (IR) collision induced vibration-rotation band generates a bulk heating of the solid. Shadowgraphs reveal that this bulk heat quickly redistributes the solid into a relatively uniform layer depending on the IR intensity profile. Measured redistribution time constants are used to determine the conversion efficiency of IR light into bulk heat. Phase shifting interferometry reveals that the surface roughness decreases with increasing IR heating.
Date: May 31, 1996
Creator: Collins, G.W.; Tiszauer, D.; Feit, M.; Mapoles, E.R.; Bernat, T.P.; Bittner, D.N. et al.
System: The UNT Digital Library
Design and reality for NIF ignition targets (open access)

Design and reality for NIF ignition targets

Advances in ICF experiments and modeling have led to improved understanding of the growth of instabilities during capsule implosion and the effects on capsule performance. This has led to more refined specifications on the characteristics of igniting capsules, all of which have solid D-T fuel layers. These specifications involve a trade-off between the interior ice surface structure, outer capsule surface structure, and time-dependent drive asymmetry.
Date: May 31, 1996
Creator: Bernat, T.P.
System: The UNT Digital Library
Developing shape analysis tools to assist complex spatial decision making (open access)

Developing shape analysis tools to assist complex spatial decision making

The objective of this research was to develop and implement a shape identification measure within a geographic information system, specifically one that incorporates analytical modeling for site location planning. The application that was developed incorporated a location model within a raster-based GIS, which helped address critical performance issues for the decision support system. Binary matrices, which approximate the object`s geometrical form, are passed over the grided data structure and allow identification of irregular and regularly shaped objects. Lastly, the issue of shape rotation is addressed and is resolved by constructing unique matrices corresponding to the object`s orientation
Date: May 31, 1996
Creator: Mackey, H. E.; Ehler, G. B. & Cowen, D.
System: The UNT Digital Library
Modular redundant number systems (open access)

Modular redundant number systems

With the increased use of public key cryptography, faster modular multiplication has become an important cryptographic issue. Almost all public key cryptography, including most elliptic curve systems, use modular multiplication. Modular multiplication, particularly for the large public key modulii, is very slow. Increasing the speed of modular multiplication is almost synonymous with increasing the speed of public key cryptography. There are two parts to modular multiplication: multiplication and modular reduction. Though there are fast methods for multiplying and fast methods for doing modular reduction, they do not mix well. Most fast techniques require integers to be in a special form. These special forms are not related and converting from one form to another is more costly than using the standard techniques. To this date it has been better to use the fast modular reduction technique coupled with standard multiplication. Standard modular reduction is much more costly than standard multiplication. Fast modular reduction (Montgomery`s method) reduces the reduction cost to approximately that of a standard multiply. Of the fast multiplication techniques, the redundant number system technique (RNS) is one of the most popular. It is simple, converting a large convolution (multiply) into many smaller independent ones. Not only do redundant number …
Date: May 31, 1998
Creator: unknown
System: The UNT Digital Library
Trends in emissions of acidifying species in Asia, 1985-1997. (open access)

Trends in emissions of acidifying species in Asia, 1985-1997.

Acid deposition is a serious problem throughout much of Asia. Emissions of sulfur dioxide (SO{sub 2}) and nitrogen oxides (NO{sub x}) have been increasing steadily, as nations strive to increase their levels of economic development. Coal and fuel oil have been the main choices for powering industrial development; and, until recently, only a few countries (notably Japan and Taiwan) had taken significant steps to avert the atmospheric emissions that accompany fuel combustion. This paper discusses trends in emissions of SO{sub 2} and NO{sub x} that have occurred in Asian countries in the period 1985--1997, using results from the RAINS-ASIA computer model and energy-use trends from the IEA Energy Statistics and Balances database. Emissions of SO{sub 2} in Asia grew from 26.6 Tg in 1985 to 33.7 Tg in 1990 and to 39.2 Tg in 1997. Though SO{sub 2} emissions used to grow as fast as fossil-fuel use, recent limitations on the sulfur content of coal and oil have slowed the growth. The annual-average emissions growth between 1990 and 1997 was only 1.1%, considerably less than the economic growth rate. Emissions of NO{sub x}, on the other hand, continue to grow rapidly, from 14.1 Tg in 1985 to 18.7 Tg in …
Date: May 31, 2000
Creator: Streets, D. G.; Tsai, N. Y.; Akimoto, H. & Oka, K.
System: The UNT Digital Library
Corrosion performance of structural alloys in coal-combustion environments. (open access)

Corrosion performance of structural alloys in coal-combustion environments.

None
Date: May 31, 2000
Creator: Natesan, K.; Mathur, M. & Freeman, M.
System: The UNT Digital Library
Thermal characterization of Li-ion cells using calorimetric techniques (open access)

Thermal characterization of Li-ion cells using calorimetric techniques

The thermal stability of Li-ion cells with intercalating carbon anodes and metal oxide cathodes was measured as a function of state of charge and temperature for two advanced cell chemistries. Cells of the 18650 design with Li{sub x}CoO{sub 2} cathodes (commercial Sony cells) and Li{sub x}Ni{sub 0.8}Co{sub 0.2}O{sub 2} cathodes were measured for thermal reactivity. Accelerating rate calorimetry (ARC) was used to measure cell thermal runaway as a function of state of charge (SOC), microcalorimetry was used to measure the time dependence of thermal output, and differential scanning calorimetry (DSC) was used to study the thermal reactivity of the individual components. Thermal decomposition of the anode solid electrolyte interphase (SEI) layer occurred at low temperatures and contributes to the initiation of thermal runaway. Low temperature reactions from 40 C--70 C were observed during the ARC runs that were SOC dependent. These reactions measured in the microcalorimeter decayed over time with power-law dependence and were highly sensitive to SOC and temperature. ARC runs of aged and cycled cells showed complete absence of these low-temperature reactions but showed abrupt exothermic spikes between 105--135 C. These results suggest that during aging the anode SEI layer is decomposing from a metastable state to a …
Date: May 31, 2000
Creator: ROTH,EMANUEL P.
System: The UNT Digital Library
Automating the search for answers to open questions (open access)

Automating the search for answers to open questions

This article provides evidence for the arrival of automated reasoning. Indeed, one of its primary goals of the early 1960s has been reached: The use of an automated reasoning program frequently leads to significant contributions to mathematics and to logic. In addition, although not clearly an original objective, the use of such a program now plays an important role for chip design and for program verification. That importance can be sharply increased; indeed, in this article the authors discuss the possible value of automated reasoning to finding better designs of chips, circuits, and computer code. They also provide insight into the mechanisms--in particular, strategy--that have led to numerous successes. To complement the evidence they present and to encourage further research, the offer challenges and open questions for consideration. They include a glimpse of the future and some commentary on the possibly unexpected benefits of automating the search for answers to open questions.
Date: May 31, 2000
Creator: Wos, L. & Fitelson, B.
System: The UNT Digital Library
Shielding analysis for the MDAS facility. (open access)

Shielding analysis for the MDAS facility.

None
Date: May 31, 2000
Creator: Klann, R. T. & Grimm, K. N.
System: The UNT Digital Library
Appendix: Conjectures concerning proof, design, and verification. (open access)

Appendix: Conjectures concerning proof, design, and verification.

This article focuses on an esoteric but practical use of automated reasoning that may indeed be new to many, especially those concerned primarily with verification of both hardware and software. Specifically, featured are a discussion and some methodology for taking an existing design -- of a circuit, a chip, a program, or the like--and refining and improving it in various ways. Although the methodology is general and does not require the use of a specific program, McCune's program OTTER does offer what is needed. OTTER has played and continues to play the key role in my research, and an interested person can gain access to this program in various ways, not the least of which is through the included CD-ROM in [3]. When success occurs, the result is a new design that may require fewer components, avoid the use of certain costly components, offer more reliability and ease of verification, and, perhaps most important, be more efficient in the contexts of speed and heat generation. Although the author has minimal experience in circuit design, circuit validation, program synthesis, program verification, and similar concerns, (at the encouragement of colleagues based on successes to be cited) he presents materials that might indeed …
Date: May 31, 2000
Creator: Wos, L.
System: The UNT Digital Library
Adaptive Position and Orientation Regulation for the Camera-in-hand Problem (open access)

Adaptive Position and Orientation Regulation for the Camera-in-hand Problem

None
Date: May 31, 2001
Creator: Setlur, P
System: The UNT Digital Library
The D-Zero Run II Detector and physics prospects (open access)

The D-Zero Run II Detector and physics prospects

The DO Detector at Fermilab is currently undergoing an extensive upgrade to participate in the Run II data taking which shall begin on March 1, 2001. The design of the detector meets the requirements of the high luminosity environment provided by the accelerator. This paper describes the upgraded detector subsystems and gives a brief outline of the physics prospects associated with the upgrade.
Date: May 31, 2001
Creator: Parashar, Neeti
System: The UNT Digital Library
Characteristic Features of the Exotic Superconductors: Evidence for a Common Pairing Mechanism (open access)

Characteristic Features of the Exotic Superconductors: Evidence for a Common Pairing Mechanism

We report on a comprehensive examination of the exotic superconductors (the materials so-labelled by Uemura and co-workers), to determine as far as possible the true systematics among their many anomalous features. In the crystal-chemistry aspects as well as in the electronic properties, we find features which appear to be universal for these materials, and also features which are clearly not universal but which are common enough to be considered typical for these materials. A number of implications are presented. It appears that all of these materials are sharing some ''new'' pairing mechanism, usually in addition to the conventional phonon mechanism.
Date: May 31, 1999
Creator: Brandow, B.
System: The UNT Digital Library
Influence of microstructure on electrical properties of diluted GaNxAs1-x formed by nitrogen implantation (open access)

Influence of microstructure on electrical properties of diluted GaNxAs1-x formed by nitrogen implantation

None
Date: May 31, 2001
Creator: Jasinski, J.; Yu, K. M.; Walukiewicz, W.; Washburn, J. & Liliental-Weber, Z.
System: The UNT Digital Library
The Integration of Engineering and Architecture: A Perspective on Natural Ventilation for the New San Francisco Federal Building (open access)

The Integration of Engineering and Architecture: A Perspective on Natural Ventilation for the New San Francisco Federal Building

A description of the in-progress design of a new Federal Office Building for San Francisco is used to illustrate a number of issues arising in the design of large, naturally ventilated office buildings. These issues include the need for an integrated approach to design involving the architects, mechanical and structural engineers, lighting designers and specialist simulation modelers. In particular, the use of natural ventilation, and the avoidance of air-conditioning, depends on the high degree of exposed thermal mass made possible by the structural scheme and by the minimization of solar heat gains while maintaining the good daylighting that results from optimization of the fagade. Another issue was the need for a radical change in interior space planning in order to enhance the natural ventilation; all the individual enclosed offices are located along the central spine of each floorplate rather than at the perimeter. The role of integration in deterring the undermining of the design through value engineering is discussed. The comfort criteria for the building were established based on the recent extension to the ASHRAE comfort standard based on the adaptive model for naturally ventilated buildings. The building energy simulation program EnergyPlus was used to compare the performance of different …
Date: May 31, 2002
Creator: McConahey, Erin; Haves, Philip & Christ, Tim
System: The UNT Digital Library
Laser-driven formation of a high-pressure phase in amorphous silica (open access)

Laser-driven formation of a high-pressure phase in amorphous silica

A combination of electron diffraction and infrared reflectance measurements shows that synthetic silica transforms partially into stishovite under high-intensity (GW/cm2) laser irradiation, probably by the formation of a dense ionized plasma above the silica surface. During the transformation the silicon coordination changes from four-fold to six-fold and the silicon-oxygen bond changes from mostly covalent to mostly ionic, such that optical properties of the transformed material differ significantly from those of the original glass. This phase transformation offers one suitable mechanism by which laser-induced damage grows catastrophically once initiated, thereby dramatically shortening the service lifetime of optics used for high-power photonics applications such as inertial confinement fusion.
Date: May 31, 2002
Creator: Salleo, Alberto; Taylor, Seth T.; Martin, Michael C.; Panero, Wendy R.; Jeanloz, Raymond; Genin, Francois Y. et al.
System: The UNT Digital Library
Accurate estimation of the RMS emittance from single current amplifier data (open access)

Accurate estimation of the RMS emittance from single current amplifier data

This paper presents the SCUBEEx rms emittance analysis, a self-consistent, unbiased elliptical exclusion method, which combines traditional data-reduction methods with statistical methods to obtain accurate estimates for the rms emittance. Rather than considering individual data, the method tracks the average current density outside a well-selected, variable boundary to separate the measured beam halo from the background. The average outside current density is assumed to be part of a uniform background and not part of the particle beam. Therefore the average outside current is subtracted from the data before evaluating the rms emittance within the boundary. As the boundary area is increased, the average outside current and the inside rms emittance form plateaus when all data containing part of the particle beam are inside the boundary. These plateaus mark the smallest acceptable exclusion boundary and provide unbiased estimates for the average background and the rms emittance. Small, trendless variations within the plateaus allow for determining the uncertainties of the estimates caused by variations of the measured background outside the smallest acceptable exclusion boundary. The robustness of the method is established with complementary variations of the exclusion boundary. This paper presents a detailed comparison between traditional data reduction methods and SCUBEEx by …
Date: May 31, 2002
Creator: Stockli, Martin P.; Welton, R. F.; Keller, R.; Letchford, A. P.; Thomae, R. W. & Thomason, J. W. G.
System: The UNT Digital Library
Responses of Conventional Ring Closures of Drum Type Packages to Regulatory Drop Tests with Application to the 9974/9975 Package (open access)

Responses of Conventional Ring Closures of Drum Type Packages to Regulatory Drop Tests with Application to the 9974/9975 Package

DOT, DOE and NRC Type A and Type B radioactive material (RAM) transport packages routinely use industrial or military specification drums with conventional clamp ring closures as an overpack. Considerable testing has been performed on these type packages over the past 30 years. Observations from test data have resulted in various design changes and recommendations to the standard drum specification and use, enhancing the reliability of the overpack. Recently, performance capability of the 9975 conventional clamp ring closure design was questioned by the Regulatory Authority. This paper highlights the observations of recent 9974 and 9975 package testing that led to redesign of the 9975, replacing the standard clamp ring closure with a bolted ring closure. In the course of this review and redesign effort, 18 package designs and approximately 100 Hypothetical Accident Condition (HAC) drops of various size and weight drum packages were evaluated. A trend was observed with respect to overpack lid failures for packages utilizing conventional ring closure. Based on this trend, a limit on the ratio of the content weight to total package weight was identified, beyond which clamp ring closure failure may be expected.
Date: May 31, 2002
Creator: Blanton, P.S.
System: The UNT Digital Library
Demonstration of electronic pattern switching and 10x pattern demagnification in a maskless micro-ion beam reduction lithography system (open access)

Demonstration of electronic pattern switching and 10x pattern demagnification in a maskless micro-ion beam reduction lithography system

A proof-of-principle ion projection lithography (IPL) system called Maskless Micro-ion beam Reduction Lithography (MMRL) has been developed and tested at the Lawrence Berkeley National Laboratory (LBNL) for future integrated circuits (ICs) manufacturing and thin film media patterning [1]. This MMRL system is aimed at completely eliminating the first stage of the conventional IPL system [2] that contains the complicated beam optics design in front of the stencil mask and the mask itself. It consists of a multicusp RF plasma generator, a multi-beamlet pattern generator, and an all-electrostatic ion optical column. Results from ion beam exposures on PMMA and Shipley UVII-HS resists using 75 keV H+ are presented in this paper. Proof-of-principle electronic pattern switching together with 10x reduction ion optics (using a pattern generator made of nine 50-{micro}m switchable apertures) has been performed and is reported in this paper. In addition, the fabrication of a micro-fabricated pattern generator [3] on an SOI membrane is also presented.
Date: May 31, 2002
Creator: Ngo, V. V.; Akker, B.; Leung, K. N.; Noh, I.; Scott, K. L. & Wilde, S.
System: The UNT Digital Library
Frequency domain multiplexing for large-scale bolometer arrays (open access)

Frequency domain multiplexing for large-scale bolometer arrays

The development of planar fabrication techniques for superconducting transition-edge sensors has brought large-scale arrays of 1000 pixels or more to the realm of practicality. This raises the problem of reading out a large number of sensors with a tractable number of connections. A possible solution is frequency-domain multiplexing. I summarize basic principles, present various circuit topologies, and discuss design trade-offs, noise performance, cross-talk and dynamic range. The design of a practical device and its readout system is described with a discussion of fabrication issues, practical limits and future prospects.
Date: May 31, 2002
Creator: Spieler, Helmuth
System: The UNT Digital Library
Highly-Resolved LES of the Stable Boundary Layer Over Terrain (open access)

Highly-Resolved LES of the Stable Boundary Layer Over Terrain

One of the most important scenarios for atmospheric modelers is the stable boundary layer (SBL). Airborne material released near the ground will likely be trapped near the ground in high concentrations due to the reduced dispersion in the SBL. Hence the SBL is often the worst case scenario for studies of health impacts from routine or accidental release of toxic materials to the atmosphere. Unfortunately the SBL is very challenging to understand and model correctly. There is also a limited number of field studies with which to verify models, although recent studies (such as CASES-99) are promising. It is difficult for traditional Reynolds-averaged models of turbulence to capture the weak, spatially- and temporally-varying fluctuations that contribute to dispersion the SBL. Large-eddy simulation (LES) has become a promising approach study the SBL because much of the dynamical structure is explicitly resolved and allowed to develop according to the full equations of motion. The presence of topography further complicates the simulation of SBL flows. The drainage flows that develop as the surface cools must be resolved, along with their interaction with other drainage flows of varying scales and the main forcing (synoptic scale) flow. In this study, we have used LES techniques …
Date: May 31, 2000
Creator: Calhoun, R.; Cederwall, R.T.; Stevens, D. & Street, R.
System: The UNT Digital Library
Overture: Object-Oriented Tools for Application with Complex Geometry (open access)

Overture: Object-Oriented Tools for Application with Complex Geometry

The Overture framework is an object-oriented environment for solving partial differential equations in two and three space dimensions. It is a collection of C++ libraries that enables the use of finite difference and finite volume methods at a level that hides the details of the associated data structures. Overture can be used to solve problems in complicated, moving geometries using the method of overlapping grids. It has support for grid generation, difference operators, boundary conditions, data-base access and graphics. Short sample code segments are presented to show the power of this approach.
Date: May 31, 1999
Creator: Brown, D.; Henshaw, B. & Quinlan, D.
System: The UNT Digital Library
Frequency domain multiplexing for large-scale bolometer arrays (open access)

Frequency domain multiplexing for large-scale bolometer arrays

The development of planar fabrication techniques for superconducting transition-edge sensors has brought large-scale arrays of 1000 pixels or more to the realm of practicality. This raises the problem of reading out a large number of sensors with a tractable number of connections. A possible solution is frequency-domain multiplexing. I summarize basic principles, present various circuit topologies, and discuss design trade-offs, noise performance, cross-talk and dynamic range. The design of a practical device and its readout system is described with a discussion of fabrication issues, practical limits and future prospects.
Date: May 31, 2002
Creator: Spieler, Helmuth
System: The UNT Digital Library
Development and calibration of the shielded measurement system for fissile contents measurements on irradiated nuclear fuel in dry storage. (open access)

Development and calibration of the shielded measurement system for fissile contents measurements on irradiated nuclear fuel in dry storage.

In recent years there has been a trend towards storage of Irradiated Nuclear Fuel (INF) in dry conditions rather than in underwater environments. At the same time, the Department of Energy (DOE) has begun encouraging custodians of INF to perform measurements on INF for which no recent fissile contents measurement data exists. INF, in the form of spent fuel from Experimental Breeder Reactor 2 (EBR-II), has been stored in close-fitting, dry underground storage locations at the Radioactive Scrap and Waste Facility (RSWF) at Argonne National Laboratory-West (ANL-W) for many years. In Fiscal Year 2000, funding was obtained from the DOE Office of Safeguards and Security Technology Development Program to develop and prepare for deployment a Shielded Measurement System (SMS) to perform fissile content measurements on INF stored in the RSWF. The SMS is equipped to lift an INF item out of its storage location, perform scanning neutron coincidence and high-resolution gamma-ray measurements, and restore the item to its storage location. The neutron and gamma-ray measurement results are compared to predictions based on isotope depletion and Monte Carlo neutral-particle transport models to provide confirmation of the accuracy of the models and hence of the fissile material contents of the item as …
Date: May 31, 2002
Creator: Mosby, W. R. & Jensen, B. A.
System: The UNT Digital Library