Time Reversal Signal Processing in Communications - A Feasibility Study (open access)

Time Reversal Signal Processing in Communications - A Feasibility Study

A typical communications channel is subjected to a variety of signal distortions, including multipath, that corrupt the information being transmitted and reduce the effective channel capacity. The mitigation of the multipath interference component is an ongoing concern for communication systems operating in complex environments such as might be experienced inside buildings, urban environments, and hilly or heavily wooded areas. Communications between mobile units and distributed sensors, so important to national security, are dependent upon flawless conveyance of information in complex environments. The reduction of this multipath corruption necessitates better channel equalization, i.e., the removal of channel distortion to extract the transmitted information. But, the current state of the art in channel equalization either requires a priori knowledge of the channel or the use of a known training sequence and adaptive filtering. If the ''assumed'' model within the equalization processor does not at least capture the dominant characteristics of the channel, then the received information may still be highly distorted and possibly useless. Also, the processing required for classical equalization is demanding in computational resources. To remedy this situation, many techniques have been investigated to replace classical equalization. Such a technique, the subject of this feasibility study, is Time Reversal Signal …
Date: January 30, 2002
Creator: Meyer, A W; Candy, J V & Poggio, A J
Object Type: Report
System: The UNT Digital Library
Final ROI Report - Technology Transfer of Waste-Reducing Groundwater Sampling Systems (open access)

Final ROI Report - Technology Transfer of Waste-Reducing Groundwater Sampling Systems

This report presents the findings of a U.S. DOE Environmental Management technology transfer initiative of waste-reducing ground water sampling systems between Savannah River Site (SRS) and Lawrence Livermore National Laboratory (LLNL) which occurred during fiscal years 2001 and 2002. The report describes the collaboration between the two sites, the deployment of the Savannah River Site Purge Water Management System at LLNL, the changes made to that system for use at LLNL, and documents the return-on-investment derived from the system's use at LLNL as well as other benefits generated through this inter-laboratory collaboration. An evaluation of the deployment of the LLNL EasyPump sampling technology at SRS will be covered in a separate report from SRS.
Date: September 30, 2002
Creator: Noyes, Charles; Howard, Greg; Bishop, Dorothy; Tuckfield, Cary & Hiergesell, Robert
Object Type: Report
System: The UNT Digital Library
A 2-Liter, 2000 MPa Air Source for the Radiatively Driven Hypersonic Wind Tunnel (open access)

A 2-Liter, 2000 MPa Air Source for the Radiatively Driven Hypersonic Wind Tunnel

The A2 LITE is a 2 liter, 2000 MPa, 750 K ultra-high pressure (UHP) vessel used to demonstrate UHP technology and to provide an air flow for wind tunnel nozzle development. It is the largest volume UHP vessel in the world. The design is based on a 100:1 pressure intensification using a hydraulic ram as a low pressure driver and a three-layer compound cylinder UHP section. Active control of the 900 mm piston stroke in the 63.5 mm bore permits pressure-time profiles ranging from static to constant pressure during flow through a 1 mm throat diameter nozzle for 1 second.
Date: May 30, 2002
Creator: Costantino, M & Lofftus, D
Object Type: Article
System: The UNT Digital Library
Electrochemical Behavior of Alloy 22 in 5 M CaC12 (open access)

Electrochemical Behavior of Alloy 22 in 5 M CaC12

The corrosion resistance of Alloy 22 (UNS No.: N06022) was studied in 5 M CaCl{sub 2} electrolyte at various temperatures. Potentiodynamic polarization was used to examine the electrochemical behavior and measure the key potentials. Alloy 22 was found to be susceptible to localized corrosion in this high chloride [10M Cl{sup -}] environment at temperatures as low as 6O C.
Date: May 30, 2002
Creator: Ilevbare, G O
Object Type: Article
System: The UNT Digital Library
A Catalog of Vadose Zone Hydraulic Properties for the Hanford Site (open access)

A Catalog of Vadose Zone Hydraulic Properties for the Hanford Site

To predict contaminant release to the groundwater, it is necessary to understand the hydraulic properties of the material between the release point and the water table. Measurements of the hydraulic properties of the Hanford unsaturated sediments that buffer the water table are available from many areas of the site; however, the documentation is not well cataloged nor is it easily accessible. The purpose of this report is to identify what data is available for characterization of the unsaturated hydraulic properties at Hanford and Where these data can be found.
Date: September 30, 2002
Creator: Freeman, Eugene J.; Khaleel, Raziuddin & Heller, Paula R.
Object Type: Report
System: The UNT Digital Library
Shock Propagation and Instability Structures in Compressed Silica Aerogels (open access)

Shock Propagation and Instability Structures in Compressed Silica Aerogels

We have performed a series of experiments examining shock propagation in low density aerogels. High-pressure ({approx}100 kbar) shock waves are produced by detonating high explosives. Radiography is used to obtain a time sequence imaging of the shocks as they enter and traverse the aerogel. We compress the aerogel by impinging shocks waves on either one or both sides of an aerogel slab. The shock wave initially transmitted to the aerogel is very narrow and flat, but disperses and curves as it propagates. Optical images of the shock front reveal the initial formation of a hot dense region that cools and evolves into a well-defined microstructure. Structures observed in the shock front are examined in the framework of hydrodynamic instabilities generated as the shock traverses the low-density aerogel. The primary features of shock propagation are compared to simulations, which also include modeling the detonation of the high explosive, with a 2-D Arbitrary Lagrange Eulerian hydrodynamics code The code includes a detailed thermochemical equation of state and rate law kinetics. We will present an analysis of the data from the time resolved imaging diagnostics and form a consistent picture of the shock transmission, propagation and instability structure.
Date: May 30, 2002
Creator: Howard, W. M.; Molitoris, J. D.; DeHaven, M. R.; Gash, A. E. & Satcher, J. H.
Object Type: Article
System: The UNT Digital Library
An Overview of Raster Scanning for ICF-Class Laser Optics (open access)

An Overview of Raster Scanning for ICF-Class Laser Optics

Recent work has shown that the damage resistance of both ICF-class (1600 cm') DKDP tripler crystals and SiO{sub 2} components (lenses, gratings and debris shields) benefits from laser raster scanning using pulsed lasers in the 350 nm range. For laser raster scanning to be a viable optical improvement tool for these large optics, damage improvement must be optimized while maintaining scan times of less than 8 hours/optic. In this paper we examine raster scanning with small beams from tabletop laser systems. We show that 120 Watts of average power is required for a tabletop scanning system at one optic/day. Next, we develop equations for total scan time for square and round top hat beams and round and rectangular Gaussian beams. We also consider the effect of packing geometry (square vs. hexagonal), examine the deviations from uniform coverage with each scan geometry and show that hexagonal packing yields lower scan times but is less efficient in coverage than square geometry. We also show that multiple passes at low packing densities are temporally equivalent to a single pass with higher packing density, and discuss the advantages of each method. In addition, we show that the differences between hexagonal and square scan geometries …
Date: October 30, 2002
Creator: Runkel, M J & Nostrand, M
Object Type: Article
System: The UNT Digital Library
Nonlinear Schwarz-Fas Methods for Unstructured Finite Element Elliptic Problems (open access)

Nonlinear Schwarz-Fas Methods for Unstructured Finite Element Elliptic Problems

This paper provides extensions of an element agglomeration AMG method to nonlinear elliptic problems discretized by the finite element method on general unstructured meshes. The method constructs coarse discretization spaces and corresponding coarse nonlinear operators as well as their Jacobians. We introduce both standard (fairly quasi-uniformly coarsened) and non-standard (coarsened away) coarse meshes and respective finite element spaces. We use both kind of spaces in FAS type coarse subspace correction (or Schwarz) algorithms. Their performance is illustrated on a number of model problems. The coarsened away spaces seem to perform better than the standard spaces for problems with nonlinearities in the principal part of the elliptic operator.
Date: September 30, 2002
Creator: Jones, J E; Vassilevski, P S & Woodward, C S
Object Type: Article
System: The UNT Digital Library
Metal Oxides in the Environment (open access)

Metal Oxides in the Environment

Oxides are ubiquitous in much of environmental chemistry. Silica and related glasses are potential vehicles by which radioactive elements may be sequestered and stored. The migration of toxic waste in ground water is largely influenced by interactions at the liquid-solid interface, with several metal oxides making up the bulk of soil. In addition, metal oxides with Bronsted acid or Lewis base functionality are potential replacements for many traditional liquid catalysis that are hazardous to work with and difficult to dispose. In this proposal, we targeted two such areas of oxide chemistry. The long-term behavior of silicate materials slated for use in the entombment of high-level waste (HLW), and the use of solid acid metal oxides as replacements for toxic sulfuric and hydrofluoric acid used in industry (referred to as Green Chemistry). Thus, this project encompassed technology that can be used to both remediate and prevent pollution. These oxide systems were studied using density functional theory (DFT). The comparatively large size and complexity of the systems that will bweree studied made use of high-accuracy electronic structure studies intractable on conventional computers. The 512 node parallel processor housed in the Molecular Science Computing Facility (MSCF) provided the required capability.
Date: August 30, 2002
Creator: Jonsson, Hannes; Corrales, L. Rene; Gabriel, Peggy; Haw, James F.; Henkelman, Graeme A.; Neurock, Matthew et al.
Object Type: Report
System: The UNT Digital Library
Report on Radiation Damage Effects in a Titanium Target Under Photon Irradiation (open access)

Report on Radiation Damage Effects in a Titanium Target Under Photon Irradiation

Following the same approach as with the W-Re targets [l], we have calculated the damage induced by photon irradiation (22.1 MeV average energy) in titanium targets. Stefan Roesler calculated, using FLUKA [2] the spallation products, neutrons and fission products from the interaction of the photons with the titanium target. Using these initial values of energies and positions, we calculated the number of defects produced per incoming photon. It should be noted that the threshold displacement energy for defect production of Titanium as measured experimentally is between 21 and 30 eV [3]. We used a value of 25eV. This is a much lower value than for the case of W-alloys (90 eV) which implies a larger defect production for the same deposited energy in the case of Titanium. The number of defects for different neutron energies was calculated using SPECTER [4] Figure 1(a) shows the number of defects as a function of energy for the case of Ti as compared to W, in Figure 1(b). The number of defects is much larger in the Ti case due to the low threshold displacement energy as explained.
Date: August 30, 2002
Creator: Caturla, M J; Roesler, S; Bharadwaj, V K; Schultz, D C; Sheppard, J C; Marian, J et al.
Object Type: Report
System: The UNT Digital Library
Material Balance Assessment for Double-Shell Tank Waste Pipeline Transfer (open access)

Material Balance Assessment for Double-Shell Tank Waste Pipeline Transfer

PNNL developed a material balance assessment methodology based on conservation of mass for detecting leaks and mis-routings in pipeline transfer of double-shell tank waste at Hanford. The main factors causing uncertainty in these transfers are variable property and tank conditions of density, existence of crust, and surface disturbance due to mixer pump operation during the waste transfer. The methodology was applied to three waste transfers from Tanks AN-105 and AZ-102.
Date: October 30, 2002
Creator: Onishi, Yasuo; Wells, Beric E.; Hartley, Stacey A.; Enderlin, Carl W. & White, Mike
Object Type: Report
System: The UNT Digital Library
Mechanical Properties and Corrosion Characteristics of Thermally Aged Alloy 22 (open access)

Mechanical Properties and Corrosion Characteristics of Thermally Aged Alloy 22

Alloy 22 (UNS N06022) is a candidate material for the external wall of the high level nuclear waste containers for the potential repository site at Yucca Mountain. In the mill-annealed (MA) condition, Alloy 22 is a single face centered cubic phase. When exposed to temperatures on the order of 600 C and above for times higher than 1 h, this alloy may develop secondary phases that reduce its mechanical toughness and corrosion resistance. The objective of this work was to age Alloy 22 at temperatures between 482 C and 760 C for times between 0.25 h and 6,000 h and to study the mechanical and corrosion performance of the resulting material. Aging was carried out using wrought specimens as well as gas tungsten arc welded (GTAW) specimens. Mechanical and corrosion testing was carried out using ASTM standards. Results show-that the higher the aging temperature and the longer the aging time, the lower the impact toughness of the aged material and the lower its corrosion resistance. However, extrapolating both mechanical and corrosion laboratory data predicts that Alloy 22 will remain corrosion resistant and mechanically robust for the projected lifetime of the waste container.
Date: May 30, 2002
Creator: Rebak, R B & Crook, P
Object Type: Article
System: The UNT Digital Library
A study on D0 Run2b stave structural performance (open access)

A study on D0 Run2b stave structural performance

Two different structural solutions have been proposed and studied for the D0 Run2b stave. The way the stave structural stiffness is achieved in both designs is essentially the same: the structural material is displaced as far as possible from the neutral axis in order to increase the bending moment of the stave. The agreement of the measured data with what has been theoretically predicted is excellent. The C channel stave with dog-bones glued on top of the sensor (stave No.2) has outperformed the other mockups with a predicted sag of 51{micro}m for a distributed load of 2.28 N/m [0.013 lbf/in] and a consequent natural frequency of 89.2Hz. The other three C channel staves with the dog-bones not glued on the sensor have a bending stiffness that is -19.0%, -10.8%, +4.0% of that of stave No.2, being 11.0%, 7.8%, 15.1% lighter respectively. An optimized stave structural proposal with 130.5% of the design stiffness within the mass budget is presented at the end of this paper.
Date: April 30, 2002
Creator: Lanfranco, Giobatta
Object Type: Report
System: The UNT Digital Library
Susceptibility of Alloy 22 to Environmentally Assisted Cracking in Yucca Mountain Relevant Environments (open access)

Susceptibility of Alloy 22 to Environmentally Assisted Cracking in Yucca Mountain Relevant Environments

In its current design, the high level nuclear waste containers will include an external layer of Alloy 22 (Ni-22Cr-13Mo-3W-3Fe). Since over their life-time the containers may be exposed to multi-ionic aqueous environments, a potential degradation mode of the outer layer could be environmental assisted cracking (EAC). The objective of the current research work was to quantify the susceptibility of Alloy 22 to EAC in a several environmental conditions including solution composition, temperature and electrochemical potential. The susceptibility to EAC was evaluated using the constant deformation technique, the compact specimen--low cycle fatigue method and the slow strain rate test (SSRT). The alloy was tested in the wrought mill annealed (MA) and in the as-welded conditions. Results show that Alloy 22 was extremely resistant to EAC in a wide range of environmental conditions. Using SSRT, Alloy 22 was found susceptible to EAC in one electrolyte at one temperature and at one electrochemical potential.
Date: January 30, 2002
Creator: Estill, J. C.; King, K. J.; Fix, D. V.; Spurlock, D. G.; Hust, G. A.; Gordon, S. R. et al.
Object Type: Article
System: The UNT Digital Library
Optical Design Capabilities at Lawrence Livermore National Laboratory (open access)

Optical Design Capabilities at Lawrence Livermore National Laboratory

Optical design capabilities continue to play the same strong role at Lawrence Livermore National Laboratory (LLNL) that they have played in the past. From defense applications to the solid-state laser programs to the Atomic Vapor Laser Isotope Separation (AVLIS), members of the optical design group played critical roles in producing effective system designs and are actively continuing this tradition. This talk will explain the role optical design plays at LLNL, outline current capabilities and summarize a few activities in which the optical design team has been recently participating.
Date: December 30, 2002
Creator: Lawson, J K
Object Type: Article
System: The UNT Digital Library
Effects of Globally Waste-Disturbing Activities on Gas Generation, Retention, and Release in Hanford Waste Tanks (open access)

Effects of Globally Waste-Disturbing Activities on Gas Generation, Retention, and Release in Hanford Waste Tanks

Various operations are authorized in Hanford single-shell and double-shell tanks that disturb all or a large fraction of the waste. These globally waste-disturbing activities have the potential to release a significant volume of retained gas. Analyses are presented for expected gas release mechanisms and the potential release rates and volumes resulting from these activities. Recommendations for gas monitoring and assessment of the potential for changes in tank classification and steady-state flammability are also given.
Date: August 30, 2002
Creator: Stewart, Charles W. (BATTELLE (PACIFIC NW LAB)); Huckaby, James L. (BATTELLE (PACIFIC NW LAB)) & Meyer, Perry A. (BATTELLE (PACIFIC NW LAB))
Object Type: Report
System: The UNT Digital Library
Creation of a Reference Image with Monte Carlo Simulations for Online EPID Verification of Daily Patient Setup (open access)

Creation of a Reference Image with Monte Carlo Simulations for Online EPID Verification of Daily Patient Setup

Patient positioning accuracy remains an issue for external beam radiotherapy. Currently, kilovoltage verification images are used as reference by clinicians to compare the actual patient treatment position with the planned position. These images are qualitatively different from treatment-time megavoltage portal images. This study will investigate the feasibility of using PEREGRINE, a 3D Monte Carlo calculation engine, to create reference images for portal image comparisons. Portal images were acquired using an amorphous-silicon flat-panel EPID for (1) the head and pelvic sections of an anthropomorphic phantom with 7-8 mm displacements applied, and (2) a prostate patient on five treatment days. Planning CT scans were used to generate simulated reference images with PEREGRINE. A correlation algorithm quantified the setup deviations between simulated and portal images. Monte Carlo simulated images exhibit similar qualities to portal images, the phantom slabs appear clearly. Initial positioning differences and applied displacements were detected and quantified. We find that images simulated with Monte Carlo methods can be used as reference images to detect and quantify set-up errors during treatment.
Date: January 30, 2002
Creator: Descalle, M. A.; Chuang, C. & Pouliot, J.
Object Type: Article
System: The UNT Digital Library
Astrophysical and Astrochemical Insights into the Origin of Life (open access)

Astrophysical and Astrochemical Insights into the Origin of Life

Nucleosynthesis of heavy elements such as carbon in stars allowed the formation of organic molecules in space, which appear to be widespread in our Galaxy. The physical and chemical conditions - including density, temperature, ultraviolet radiation and energetic particles - determine reaction pathways and the complexity of organic molecules in different space environments. Dense interstellar clouds are the birth sites of stars of all masses and their planetary systems. During the protostellar collapse, gaseous and solid interstellar organic molecules are integrated into protostellar disks from which planets and smaller solar system bodies form. After the formation of the planets in our own solar system, 4.6 billion years ago, all of them, including the Earth, were subjected to frequent impacts for several hundred million years. First indications for life on Earth are dated 3.8-3.5 billion years ago. That life arose very shortly after this heavy bombardment phase raises many questions. A prebiotic non-reducing atmosphere predicts that building blocks of macromolecules--such as amino acids, sugars, purines and pyrimidines were not formed in abundance. A part of the prebiotic organic content of the early Earth could have been delivered by asteroids, comets and smaller fragments such as meteorites and interplanetary dust particles (IDPs). …
Date: April 30, 2002
Creator: Ehrenfreund, P; Becker, L; Blank, J; Brucato, J; Colangeli, L; Derenne, S et al.
Object Type: Report
System: The UNT Digital Library
A Catalog of Geologic Data for the Hanford Site (open access)

A Catalog of Geologic Data for the Hanford Site

This is the first update of the catalog that was published in 2001. This report catalogs the existing geologic data that can be found in various databases, published and unpublished reports, and in individuals' technical files. The scope of this catalog is primarily on the 100, 200, and 300 Areas, with a particular emphasis on the 200 Areas. Over 2,922 wells are included in the catalog. Nearly all of these wells (2,459) have some form of driller's or geologist's log. Archived samples are available for 1,742 wells. Particle size data are available from 1,078 wells and moisture data are available from 356 wells. Some form of chemical property data is available from 588 wells. However, this catalog is by no means complete. Numerous individuals have been involved in various geologic-related studies of the Hanford Site. The true extent of unpublished data retained in their technical files is unknown. However, this data catalog is believed to represent the majority (>90%) of the geologic data that is currently retrievable.
Date: September 30, 2002
Creator: Horton, Duane G.; Last, George V.; Gilmore, Tyler J. & Bjornstad, Bruce N.
Object Type: Report
System: The UNT Digital Library
Mechanistic Process Modeling for Subsurface Remediation (open access)

Mechanistic Process Modeling for Subsurface Remediation

The goal of this project was to develop the first generation of models that fully address the coupling of dominant processes controlling the behavior of fluid, chemical and biological components in the subsurface. The large memory and computational performance of multiprocessor computing architectures would be exploited to provide modeling capabilities with unprecedented process detail and resolution to assess new scientific hypotheses, assist with experimental design, and to evaluate environmental technologies and remediation design. Moreover, the proposed capability developments would advance the scientific agenda for the subsurface through the realized advances in complex multiple-phase reaction modeling.
Date: August 30, 2002
Creator: Yabusaki, Steven B.; Bryant, Steven L.; Chen, Shi-Yi; Fann, George I.; Flach, Gregory P.; Gray, William G. et al.
Object Type: Report
System: The UNT Digital Library
Geologic and Wireline Summaries from Fiscal Year 2002 ILAW Boreholes (open access)

Geologic and Wireline Summaries from Fiscal Year 2002 ILAW Boreholes

Four boreholes were drilled at the Immobilized Low-Activity Waste Disposal Site in April 2002. Three were completed as groundwater monitoring wells. This report documents the results of the drilling and data collected from the drilling.
Date: September 30, 2002
Creator: Reidel, Steve P. & Ho, Anita M.
Object Type: Report
System: The UNT Digital Library
Effect of Insolation Boundary Conditions on Type B Package Internal Temperatures (open access)

Effect of Insolation Boundary Conditions on Type B Package Internal Temperatures

The prescription of the initial conditions and the final conditions for a thermal accident for Type B packages are different for differing regulations. This paper presents an analytical method for estimating the effect of the boundary conditions on post-fire peak internal package temperatures. Results are given for several boundary conditions for a Type B drum-type package.
Date: May 30, 2002
Creator: Hovingh, J & Shah, VL
Object Type: Article
System: The UNT Digital Library
Characterization of the Resistance of Alloy 22 to Stress Corrosion Cracking (open access)

Characterization of the Resistance of Alloy 22 to Stress Corrosion Cracking

In its current design, the high-level nuclear waste containers include an external layer of Alloy 22 (Ni-22Cr-13Mo-3W-3Fe). Since over their lifetime, the containers may be exposed to multi-ionic aqueous environments, a potential degradation mode of the outer layer could be environmentally assisted cracking (EAC). The objective of the current research was to characterize the effect of applied potential and temperature on the susceptibility of Alloy 22 to EAC in simulated concentrated water (SCW) using the slow strain rate test (SSRT). Results show that Alloy 22 may suffer EAC at applied potentials approximately 400 mV more anodic than the corrosion potential (E{sub corr}).
Date: May 30, 2002
Creator: King, K. J.; Estill, J. C. & Rebak, R. B.
Object Type: Article
System: The UNT Digital Library
Ultrasonic Technology for Characterizing Laser Damage in Optics (open access)

Ultrasonic Technology for Characterizing Laser Damage in Optics

An ultrasonic technique was developed to detect and characterize laser damage in critical optics. During normal usage, sub critical flaws induced by high laser fluence can grow to critical size and potentially can cause unanticipated failure of the optics. This ultrasonic technique monitors the optic in situ and provides a quick, reliable way to quantify the location, number and, ultimately, the size of defects that may initiate and grow during firing of the laser. The feasibility of detecting and sizing laser-induced damage with an ultrasonic technology was theoretically and experimentally demonstrated. An experiment was conducted whereby ultrasonic data was acquired in situ on an optic as it was damaged by a laser. This monitoring of laser induced damage clearly demonstrated the potential for ultrasonic monitoring of critical optics for laser-induced damage.
Date: April 30, 2002
Creator: Thomas, G; Martin, L P & Chambers, D
Object Type: Article
System: The UNT Digital Library