Aberration correction for analytical in situ TEM - the NTEAM concept. (open access)

Aberration correction for analytical in situ TEM - the NTEAM concept.

Future aberration corrected transmission electron microscopes (TEM) will have a strong impact in materials science, since such microscopes yield information on chemical bonding and structure of interfaces, grain boundaries and lattice defects at an atomic level. Beyond this aberration correction offers new possibilities for in situ experiments performed under controlled temperature, magnetic field, strain etc. at atomic resolution. Such investigations are necessary for solving problems arising from electronic component miniaturization, for example. Significant progress can be expected by means of analytical aberration corrected TEM. These next generation microscopes will be equipped with an aberration corrected imaging system, a monochromator and aberration corrected energy filters. These novel elements have already been designed and partially realized [1,2,3].
Date: March 5, 2002
Creator: Kabius, B.; Allen, C. W. & Miller, D. J.
System: The UNT Digital Library
Accelerator physics and technology limitations to ultimate energy and luminosity in very large hadron colliders (open access)

Accelerator physics and technology limitations to ultimate energy and luminosity in very large hadron colliders

The following presents a study of the accelerator physics and technology limitations to ultimate energy and luminosity in very large hadron colliders (VLHCs). The main accelerator physics limitations to ultimate energy and luminosity in future energy frontier hadron colliders are synchrotron radiation (SR) power, proton-collision debris power in the interaction regions (IR), number of events-per-crossing, stored energy per beam and beam-stability [1]. Quantitative estimates of these limits were made and translated into scaling laws that could be inscribed into the particle energy versus machine size plane to delimit the boundaries for possible VLHCs. Eventually, accelerator simulations were performed to obtain the maximum achievable luminosities within these boundaries. Although this study aimed at investigating a general VLHC, it was unavoidable to refer in some instances to the recently studied, [2], 200 TeV center-of-mass energy VLHC stage-2 design (VLHC-2). A more thorough rendering of this work can be found in [3].
Date: December 5, 2002
Creator: al., P. Bauer et
System: The UNT Digital Library
Advanced Techniques for Fourier Transform Wavefront Reconstruction (open access)

Advanced Techniques for Fourier Transform Wavefront Reconstruction

The performance of Fourier transform (FT) reconstructors in large adaptive optics systems with Shack-Hartmann sensors and a deformable mirror is analyzed. FT methods, which are derived for point-based geometries, are adapted for use on the continuous systems. Analysis and simulation show how to compensate for effects such as misalignment of the deformable mirror and wavefront sensor gain. Further filtering methods to reduce noise and improve performance are presented. All these modifications can be implemented at the filtering stage, preserving the speed of FT reconstruction. Simulation of a large system shows how compensated FT methods can have equivalent or better performance to slower vector-matrix-multiply reconstructions.
Date: August 5, 2002
Creator: Poyneer, L A
System: The UNT Digital Library
Assessing mixtures risks for cleanup and stewardship. (open access)

Assessing mixtures risks for cleanup and stewardship.

The U.S. Department of Energy (DOE) is responsible for addressing contamination from past research, production, and disposal activities at over 100 sites and facilities across the country. Use of emerging science to assess risks for these facilities is the key to defining appropriate solutions. Safely managing contamination is a priority to protect workers in the near term, and sustained protection is a priority for local communities over the long term. The Department conducts its environmental management program with input from a number of groups who have expressed concern about the safety of DOE sites over time and the possible conversion of some lands to other uses. In general, past facility activities and disposal operations have contaminated about 10% of the total collective area of DOE sites while surrounding lands have served as buffer zones. Portions of several sites have been released for other uses, such as wildlife preserves. Soil, surface water, and groundwater have been contaminated in most instances, and on-site waste disposal is targeted for many sites. Wastes and contamination that will remain in the environment are at the heart of ongoing future use and long-term management deliberations. For this reason, oversight groups and local citizens are scrutinizing the …
Date: March 5, 2002
Creator: MacDonell, M. M. & Hertzberg, R.
System: The UNT Digital Library
Autophosphorylation of the DNA-Dependent Protein Kinase Catalyticsubunit is Required for Rejoining of DNA Double-Strand Breaks (open access)

Autophosphorylation of the DNA-Dependent Protein Kinase Catalyticsubunit is Required for Rejoining of DNA Double-Strand Breaks

This report is a descriptive journey of the Autophosphorylation of the DNA-Dependent Protein Kinase Catalyticsubunit is Required for Rejoining of DNA Double-Strand Breaks.
Date: June 5, 2002
Creator: Chan, Doug W.; Chen, Benjamin Ping-Chi; Yang, Shun-Jen; Singh,Sheela; Murphy, Michael B.; Kurimasa, Akihiro et al.
System: The UNT Digital Library
Carbon Resistor Pressure Gauge Calibration at Stresses Up to 1 GPa (open access)

Carbon Resistor Pressure Gauge Calibration at Stresses Up to 1 GPa

Calibration of the 470-Ohm carbon resistor gauge is desired in the low stress region up to 1 GPa. A split-Hopkinson pressure bar, drop tower apparatus, gas pressure chamber, and gas gun have been used to perform the calibration experiments. The gauge behavior at elevated temperature was also investigated by heating the resistors to 200 C at atmospheric pressure while observing the resistance change. The motivation for this calibration work arises from the desire to increase the number of data points in the low stress regime to better establish the accuracy and precision of the gauge. Details of the various calibration arrangements and the results are discussed and compared to calibration curves fit to previously published calibration data. It was found that in most cases, the data from this work fit the calibration curves fit to previously published data rather well.
Date: March 5, 2002
Creator: Vandersall, K S; Niles, A M; Greenwood, D W; Cunningham, B; Garcia, F & Forbes, J W
System: The UNT Digital Library
Chamber wall response to target implosion in inertial fusion reactors : new and critical assessments. (open access)

Chamber wall response to target implosion in inertial fusion reactors : new and critical assessments.

The chamber walls in inertial fusion energy (IFE) reactors are exposed to harsh conditions following each target implosion. Key issues of the cyclic IFE operation include intense photon and ion deposition, wall thermal and hydrodynamic evolution, wall erosion and fatigue lifetime, and chamber clearing and evacuation to ensure desirable conditions prior to target implosion. Several methods for wall protection have been proposed in the past, each having its own advantages and disadvantages. These methods include use of solid bare walls, gas-filled cavities, and liquid walls/jets. Detailed models have been developed for reflected laser light, emitted photons, and target debris deposition and interaction with chamber components and have been implemented in the comprehensive HEIGHTS software package. The hydrodynamic response of gas filled cavities and photon radiation transport of the deposited energy has been calculated by means of new and advanced numerical techniques. Fragmentation models of liquid jets as a result of the deposited energy have also been developed, and the impact on chamber clearing dynamics has been evaluated. The focus of this study is to critically assess the reliability and the dynamic response of chamber walls in various proposed protection methods for IFE systems. Of particular concern is the effect on …
Date: August 5, 2002
Creator: Hassanein, A. & Morozov, V.
System: The UNT Digital Library
Contributions of inelastically scattered electrons to defect images. (open access)

Contributions of inelastically scattered electrons to defect images.

We have made measurements of the contribution of inelastically scattered electrons to images of dislocations in Ni{sub 3}Ga and nanometer-sized defects in ion-irradiated Au under weak-beam dark-field diffraction conditions [1]. The purpose is to determine the conditions for data acquisition required to eventually make detailed and quantitative comparisons to simulations of images for various defect models, thus determining defect structure, composition, and local strain field. Such image simulations usually consider only elastically scattered electrons, and thus it is important to understand and possibly eliminate the contribution of inelastically scattered electrons to the experimental images for quantitative comparisons with image simulations. Experimental data have been acquired with either JEOL 2010F or 3000F microscopes, both equipped with Gatan Imaging Filter electron spectrometers. Samples examined in the 2010F were Au, ion-irradiated to low dose (10{sup 11}Kr ions at 1 MeV energy) to form individual defects (1-10nm sized Frank dislocation loops and partial stacking fault tetrahedra). Samples examined in the 3000F were Ni{sub 3}Ga with long dislocation defects. Imaging conditions included weak-beam dark-field with deviation parameter generally > 0.2 nm{sup -1}. Energy filter slit width was set to 10 eV and centered on the zero loss peak in both instruments to obtain images produced …
Date: March 5, 2002
Creator: Kirk, M. A.; Twesten, R.; Martin, S. P.; Hetherington, C. J. D. & Jenkins, M. L.
System: The UNT Digital Library
Controlling the morphology of nanocrystal-polymer composites for solar cells (open access)

Controlling the morphology of nanocrystal-polymer composites for solar cells

None
Date: June 5, 2002
Creator: Huynh, Wendy U.; Dittmer, Janke J.; Libby, William C.; Whiting, Gregory L. & Alivisatos, A. Paul
System: The UNT Digital Library
A cosmic perspective from Lapland in 2001 (open access)

A cosmic perspective from Lapland in 2001

A convergence of ideas, observations and technology have led to the greatest period of cosmological discovery yet. Over the past three years we have determined the basic features of our Universe. We are now challenged to make sense of what we have found. The outcome of planned experiments and observations as well as new ideas will be required. If we succeed, ours truly will be a Golden Age of Cosmology.
Date: December 5, 2002
Creator: Turner, Michael s.
System: The UNT Digital Library
A density functional theory study of the oxidation of methanol to formaldehyde over vanadia supported on silica, titania, and zirconia (open access)

A density functional theory study of the oxidation of methanol to formaldehyde over vanadia supported on silica, titania, and zirconia

Density functional theory was used to investigate the mechanism and kinetics of methanol oxidation to formaldehyde over vanadia supported on silica, titania, and zirconia. The catalytically active site was modeled as an isolated VO{sub 4} unit attached to the support. The calculated geometry and vibrational frequencies of the active site are in good agreement with experimental measurements both for model compounds and oxide-supported vanadia. Methanol adsorption is found to occur preferentially with the rupture of a V-O-M bond (M = Si, Ti, Zr) and with preferential attachment of a methoxy group to V. The vibrational frequencies of the methoxy group are in good agreement with those observed experimentally as are the calculated isobars. The formation of formaldehyde is assumed to occur via the transfer of an H atom of a methoxy group to the O atom of the V=O group. The activation energy for this process is found to be in the range of 199-214 kJ/mol and apparent activation energies for the overall oxidation of methanol to formaldehyde are predicted to lie in the range of 112-123 kJ/mol, which is significantly higher than that found experimentally. Moreover, the predicted turnover frequency (TOF) for methanol oxidation is found to be essentially …
Date: September 5, 2002
Creator: Khaliullin, Rustam Z. & Bell, Alexis T.
System: The UNT Digital Library
Design of High Explosive Pulsed Power Systems for 20 MB Isentropic Compression Experiments (open access)

Design of High Explosive Pulsed Power Systems for 20 MB Isentropic Compression Experiments

None
Date: July 5, 2002
Creator: Goforth, J. H.; Atchison, W. L.; Fowler, C. M.; Kienigs, R. K.; Oona, H.; Tasker, D. G. et al.
System: The UNT Digital Library
The Development and Application of SCDAP-3D (open access)

The Development and Application of SCDAP-3D

The SCDAP-3D computer code (Coryell 2001) has been developed at the Idaho National Engineering and Environmental Laboratory (INEEL) for the analysis of severe reactor accidents. A prominent feature of SCDAP-3D relative to other versions of the code is its linkage to the state-of-the-art thermal/hydraulic analysis capabilities of RELAP5-3D. Enhancements to the severe accident models include the ability to simulate high burnup and alternative fuel, as well as modifications to support advanced reactor analyses, such as those described by the Department of Energy's Generation IV (GenIV) initiative. Initial development of SCDAP-3D is complete and two widely varying but successful applications of the code are summarized. The first application is to large break loss of coolant accident analysis performed for a reactor with alternative fuel, and the second is a calculation of International Standard Problem 45 (ISP-45) or the QUENCH 6 experiment.
Date: March 5, 2002
Creator: Coryell, E. W.; Harvego, E. A. & Siefken, L. J.
System: The UNT Digital Library
The DFBX cryogenic distribution boxes for the LHC straightsections (open access)

The DFBX cryogenic distribution boxes for the LHC straightsections

None
Date: July 5, 2002
Creator: Zbasnik, Jon P.; Corradi, Carol A.; Green, Michael A.; Kajiyama,Y.; Knolls, Michael J.; LaMantia, Roberto F. et al.
System: The UNT Digital Library
Diffractive optical elements based on Fourier optical techniques: A new class of optics for extreme ultraviolet and soft x-ray wavelengths (open access)

Diffractive optical elements based on Fourier optical techniques: A new class of optics for extreme ultraviolet and soft x-ray wavelengths

None
Date: May 5, 2002
Creator: Chang, Chang; Naulleau, Patrick; Anderson, Erik; Rosfjord, Kristine & Attwood, David
System: The UNT Digital Library
The dynamic information architecture system : a simulation framework to provide interoperability for process models. (open access)

The dynamic information architecture system : a simulation framework to provide interoperability for process models.

As modeling and simulation becomes a more important part of the day-to-day activities in industry and government, organizations are being faced with the vexing problem of how to integrate a growing suite of heterogeneous models both within their own organizations and between organizations. The Argonne National Laboratory, which is operated by the University of Chicago for the United States Department of Energy, has developed the Dynamic Information Architecture System (DIAS) to address such problems. DIAS is an object-oriented, subject domain independent framework that is used to integrate legacy or custom-built models and applications. In this paper we will give an overview of the features of DIAS and give examples of how it has been used to integrate models in a number of applications. We shall also describe some of the key supporting DIAS tools that provide seamless interoperability between models and applications.
Date: February 5, 2002
Creator: Hummel, J. R. & Christiansen, J. H.
System: The UNT Digital Library
Effect of small-scale fractures on flow and transport processes at Yucca Mountain, Nevada (open access)

Effect of small-scale fractures on flow and transport processes at Yucca Mountain, Nevada

Although many conceptual models for fracture-matrix interaction have been evaluated for Yucca Mountain site-characterization studies, the most widely used model is currently based on the dual-permeability concept. It was chosen for use in site-characterization partially because it has proved to be capable of matching many types of field observed data. Another consideration is that net infiltration rates at the site are estimated to be very low (on the order of millimeters/year), or close to saturated matrix hydraulic conductivity. Recent field studies and tests, in particular, fracture mapping data, collected along the walls of the underground tunnels reveal that there exists a significantly large variety in fracture sizes from centimeters to tens of meters. There is a considerable amount of small-scale fractures that have not been considered in the previous modeling studies. Although the majority of these small fractures may not contribute much to global flow and transport through the fracture-matrix system, they may provide large amounts of storage pore space and allow for additional connection areas for well-connected, large-scale fractures and surrounding matrix blocks, which ultimately affect fracture-matrix interactions. However, the currently used dual-permeability model is unable to include the potentially important effect of small fractures. To overcome the limitations …
Date: December 5, 2002
Creator: Wu, Yu-Shu; Liu, H.H. & Bodvarsson, G.S.
System: The UNT Digital Library
Effect of uncertain hydraulic conductivity on the fate and transport of BTEX compounds at a field site (open access)

Effect of uncertain hydraulic conductivity on the fate and transport of BTEX compounds at a field site

A Monte Carlo analysis was conducted to investigate the effect of uncertain hydraulic conductivity on the fate and transport of BTEX compounds (benzene, toluene, ethyl benzene, and xylene) at a field site on Hill Air Force Base, Utah. Microbially mediated BTEX degradation has occurred at the site through multiple terminal electron-accepting processes, including aerobic respiration, denitrification, Fe(III) reduction, sulfate reduction, and methanogenesis degradation. Multiple realizations of the hydraulic conductivity field were generated and substituted into a multispecies reactive transport model developed and calibrated for the Hill AFB site in a previous study. Simulation results show that the calculated total BTEX masses (released from a constant-concentration source) that remain in the aquifer at the end of the simulation period statistically follow a lognormal distribution. In the first analysis (base case), the calculated total BTEX mass varies from a minimum of 12% less and a maximum of 60% more than that of the previously calibrated model. This suggests that the uncertainty in hydraulic conductivity can lead to significant uncertainties in modeling the fate and transport of BTEX. Geometric analyses of calculated plume configurations show that a higher BTEX mass is associated with wider lateral spreading, while a lower mass is associated with …
Date: January 5, 2002
Creator: Lu, Guoping; Zheng, Chunmiao & Wolfsberg, Andrew
System: The UNT Digital Library
Effects of momentum conservation on the analysis of anisotropic flow (open access)

Effects of momentum conservation on the analysis of anisotropic flow

We present a general method for taking into account correlations due to momentum conservation in the analysis of anisotropic flow. Momentum conservation mostly affects the first harmonic in azimuthal distributions, i.e., directed flow. It also modifies higher harmonics, for instance elliptic flow, when they are measured with respect to a first harmonic event plane such as one determined with the standard transverse momentum method. Our method is illustrated by application to NA49 data on pion directed flow.
Date: February 5, 2002
Creator: Borghini, N.; Dinh, P. M.; Ollitrault, J. -Y.; Poskanzer, A. M. & Voloshin, S. A.
System: The UNT Digital Library
The Enemy Below - The Global Diffusion of Submarines and Related Technology (open access)

The Enemy Below - The Global Diffusion of Submarines and Related Technology

The end of the Cold War seemed to create a more peaceful international environment. September 11 reminded us of the dangers of complacency. Indeed, even before September 11 US forces had intervened in a number of wars and crises, including Panama, the Persian Gulf War, Somalia, Rwanda, Bosnia, Kosovo, several Taiwan Straits crises, the North Korea nuclear weapons crisis, and most recently Afghanistan. US ability to intervene in remote areas of the world is often dependent on the Navy's ability to project power ashore. As a result, US ability to influence events in crisis situations, especially between or among nuclear powers, may become more difficult along with our ability to conduct littoral warfare. Although the numbers of potentially hostile submarines have declined with the end of the Cold War, US anti-submarine warfare capabilities have also declined. Moreover, foreign submarines and related technologies are likely to diffuse globally. New technologies like Air Independent Propulsion (AIP), improved weapons and sensors will make conventional submarines more dangerous, and the spread of nuclear submarines even to a few more countries raise political, military, environmental, and safety concerns. Submarines are one of the key weapon systems used alone or in combination with other weapon systems …
Date: September 5, 2002
Creator: Weiss, K G
System: The UNT Digital Library
Energetic Nanocomposites with Sol-gel Chemistry: Synthesis, Safety, and Characterization (open access)

Energetic Nanocomposites with Sol-gel Chemistry: Synthesis, Safety, and Characterization

The preparation and characterization of energetic composite materials containing nanometer-sized constituents is currently a very active and exciting area of research at laboratories around the world. Some of these efforts have produced materials that have shown very unique and important properties relative to traditional energetic materials. We have previously reported on the use of sol-gel chemical methods to prepare energetic nanocomposites. Primarily we reported on the sol-gel method to synthesize nanometer-sized ferric oxide that was combined with aluminum fuel to make pyrotechnic nanocomposites. Since then we have developed a synthetic approach that allows for the preparation of hybrid inorganic/organic energetic nanocomposites. This material has been characterized by thermal methods, energy-filtered transmission electron microscopy (EFTEM), N{sub 2} adsorption/description methods, and Fourier-Transform (FT-IR) spectroscopy, results of which will be discussed. According to these characterization methods the organic polymer phase fills the nanopores of the composite material, providing superb mixing of the component phases in the energetic nanocomposite. The EFTEM results provide a convenient and effective way to evaluate the intimacy of mixing between these component phases. The safe handling and preparation of energetic nanocomposites is of paramount importance to this research and we will report on studies performed to ensure such.
Date: June 5, 2002
Creator: Gash, A. E.; Simpson, R. L. & Satcher, J. H.
System: The UNT Digital Library
Flavor structure of the nucleon as revealed at HERMES. (open access)

Flavor structure of the nucleon as revealed at HERMES.

The flavor structure of the nucleon as revealed in parton distributions (PDF's) is central to understanding the partonic structure of the nucleon. Recent data on unpolarized PDF's and their implications for the flavor-dependent quark helicity distributions are discussed. Results are presented for spin asymmetries in inclusive and semi-inclusive cross sections for production of pions, and kaons measured by the HERMES experiment in deep-inelastic scattering of polarized positrons on proton and deuterium Targets. A full 5 component extraction of polarized quark distributions for u, d, {bar u}, {bar d}, and (s + {bar s}) is reported. Resulting valence quark distributions conform to results of earlier experiments. There is no evidence for a significant polarization of the light sea. In contrast to the conclusions inferred from studies of polarized inclusive scattering, a leading order analysis of the HERMES data suggests a zero or slightly positive polarization of the strange sea. There is no evidence for a measurable flavor asymmetry in the polarized distributions for the light sea.
Date: September 5, 2002
Creator: Jackson, H. E.
System: The UNT Digital Library
Growth of large patterned arrays of neurons using plasma methods (open access)

Growth of large patterned arrays of neurons using plasma methods

None
Date: July 5, 2002
Creator: Brown, I. G.; Bjornstad, K. A.; Blakely, E. A.; Galvin, J. E.; Monteiro, O. R. & Sangyuenyongpipat, S.
System: The UNT Digital Library
How Root Cause Analysis Can Improve the Value Methodology (open access)

How Root Cause Analysis Can Improve the Value Methodology

Root cause analysis (RCA) is an important methodology that can be integrated with the VE Job Plan to generate superior results from the VE Methodology. The point at which RCA is most appropriate is after the function analysis and FAST Model have been built and functions for improvement have been chosen. These functions are then subjected to a simple, but, rigorous RCA to get to the root cause of their deficiencies, whether it is high cost/poor value, poor quality, or poor reliability. Once the most probable causes for these problems have been arrived at, better solutions for improvement can be developed in the creativity phase because the team better understands the problems associated with these functions.
Date: February 5, 2002
Creator: Wixson, J. R.
System: The UNT Digital Library