A comprehensive new detector for detailed study of the QGP, initial condition and spin physics at RHIC II. (open access)

A comprehensive new detector for detailed study of the QGP, initial condition and spin physics at RHIC II.

A case is presented for compelling physics at a high luminosity RHIC II collider. A comprehensive new detector system is introduced to address this physics. The experimental focus is on detailed jet tomography of the quark gluon plasma (QGP); measuring gluon saturation in the nucleus, investigating the color glass condensate, measuring effects of the QCD vacuum on particle masses, determining the structure and dynamics within the proton and possible new phenomena. The physics and detector capabilities are introduced.
Date: March 15, 2004
Creator: Harris, J. W.; Bellwied, R.; Smirnov, N.; Steinberg, P.; Surrow, B. & Ullrich, T.
System: The UNT Digital Library
Scanning Cloud Radar Observations at Azores: Preliminary 3D Cloud Products (open access)

Scanning Cloud Radar Observations at Azores: Preliminary 3D Cloud Products

The deployment of the Scanning W-Band ARM Cloud Radar (SWACR) during the AMF campaign at Azores signals the first deployment of an ARM Facility-owned scanning cloud radar and offers a prelude for the type of 3D cloud observations that ARM will have the capability to provide at all the ARM Climate Research Facility sites by the end of 2010. The primary objective of the deployment of Scanning ARM Cloud Radars (SACRs) at the ARM Facility sites is to map continuously (operationally) the 3D structure of clouds and shallow precipitation and to provide 3D microphysical and dynamical retrievals for cloud life cycle and cloud-scale process studies. This is a challenging task, never attempted before, and requires significant research and development efforts in order to understand the radar's capabilities and limitations. At the same time, we need to look beyond the radar meteorology aspects of the challenge and ensure that the hardware and software capabilities of the new systems are utilized for the development of 3D data products that address the scientific needs of the new Atmospheric System Research (ASR) program. The SWACR observations at Azores provide a first look at such observations and the challenges associated with their analysis and interpretation. …
Date: March 15, 2010
Creator: Kollias, P.; Johnson, K.; Jo, I.; Tatarevic, A.; Giangrande, S.; Widener, K. et al.
System: The UNT Digital Library
Merged Sounding VAP Version 2.0 (open access)

Merged Sounding VAP Version 2.0

The Merged Sounding Value-Added Product (VAP) has been in the ARM and ASR pipeline since 2001. Output data streams have been added to the Evaluation Products section of the ARM website for the past five years. Currently, there are data for all of the ACRF fixed sites and all deployments of the Mobile Facility. Fifty-three years of Merged Sounding data is available as an evaluation product. The process of moving all to the ARM Data Archive has been started and will be completed shortly. A second version of the Merged Sounding VAP was developed to address several concerns: (1) Vaisala radiosondes have inherent problems obtaining an accurate measurement of relative humidity, (2) the profile can be extended from 20 km to 60 km above ground level based upon the height achieved by ECMWF profiles, and (3) ECMWF temperatures require adjustments at high altitude (between 1mb and 100 mb). Solutions to these issues have been incorporated in the new version of this VAP. Along with producing that second version of Merged Sounding, a secondary data stream - Sonde Adjust - was created. This VAP incorporates any humidity corrections to the Vaisala RS-80, RS-90, and RS-92 radiosondes. The algorithms used to perform …
Date: March 15, 2010
Creator: Troyan, D.; Jensen, M.; Turner, D. & Miloshevich, L.
System: The UNT Digital Library
Non-isothermal flow in low permeable porous media: A comparison of Richards' and two-phase flow approaches (open access)

Non-isothermal flow in low permeable porous media: A comparison of Richards' and two-phase flow approaches

The present work compares the performance of two alternative flow models for the simulation of thermal-hydraulic coupled processes in low permeable porous media: non-isothermal Richards and two-phase flow concepts. Both models take vaporization processes into account: however, the Richards model neglects dynamic pressure variations and bulk flow of the gaseous phase. For the comparison of the two approaches first published data from a laboratory experiment is studied involving thermally driven moisture flow in a partially saturated bentonite sample. Then a benchmark test of longer-term thermal-hydraulic behavior in the engineered barrier system of a geological nuclear waste repository is analyzed (DECOVALEX project). It was found that both models can be used to reproduce the vaporization process if the intrinsic permeability is relative high. However, when a thermal-hydraulic coupled problem has the same low intrinsic permeability for both the liquid and the gas phase, only the two-phase flow approach provides reasonable results.
Date: March 15, 2010
Creator: Wang, W.; Rutqvist, J.; Gorke, U.-J.; Birkholzer, J.T. & Kolditz, O.
System: The UNT Digital Library
Geochemistry of clathrate-derived methane in Arctic Ocean waters (open access)

Geochemistry of clathrate-derived methane in Arctic Ocean waters

Alterations to the composition of seawater are estimated for microbial oxidation of methane from large polar clathrate destabilizations, which may arise in the coming century. Gas fluxes are taken from porous flow models of warming Arctic sediment. Plume spread parameters are then used to bracket the volume of dilution. Consumption stoichiometries for the marine methanotrophs are based on growth efficiency and elemental/enzyme composition data. The nutritional demand implied by extra CH{sub 4} removal is compared with supply in various high latitude water masses. For emissions sized to fit the shelf break, reaction potential begins at one hundred micromolar and falls to order ten a thousand kilometers downstream. Oxygen loss and carbon dioxide production are sufficient respectively to hypoxify and acidify poorly ventilated basins. Nitrogen and the monooxygenase transition metals may be depleted in some locations as well. Deprivation is implied relative to existing ecosystems, along with dispersal of the excess dissolved gas. Physical uncertainties are inherent in the clathrate abundance, patch size, outflow buoyancy and mixing rate. Microbial ecology is even less defined but may involve nutrient recycling and anaerobic oxidizers.
Date: March 15, 2010
Creator: Elliott, S.M.; Reagan, M.T.; Moridis, G.J. & Cameron-Smith, P.J.
System: The UNT Digital Library
Modeling preferential water flow and solute transport in unsaturated soil using the active region model (open access)

Modeling preferential water flow and solute transport in unsaturated soil using the active region model

Preferential flow and solute transport are common processes in the unsaturated soil, in which distributions of soil water content and solute concentrations are often characterized as fractal patterns. An active region model (ARM) was recently proposed to describe the preferential flow and transport patterns. In this study, ARM governing equations were derived to model the preferential soil water flow and solute transport processes. To evaluate the ARM equations, dye infiltration experiments were conducted, in which distributions of soil water content and Cl{sup -} concentration were measured. Predicted results using the ARM and the mobile-immobile region model (MIM) were compared with the measured distributions of soil water content and Cl{sup -} concentration. Although both the ARM and the MIM are two-region models, they are fundamental different in terms of treatments of the flow region. The models were evaluated based on the modeling efficiency (ME). The MIM provided relatively poor prediction results of the preferential flow and transport with negative ME values or positive ME values less than 0.4. On the contrary, predicted distributions of soil water content and Cl- concentration using the ARM agreed reasonably well with the experimental data with ME values higher than 0.8. The results indicated that the …
Date: March 15, 2009
Creator: Sheng, F.; Wang, K.; Zhang, R. & Liu, H.H.
System: The UNT Digital Library
Influence of uranyl speciation and iron oxides on uranium biogeochemical redox reactions (open access)

Influence of uranyl speciation and iron oxides on uranium biogeochemical redox reactions

Uranium is a pollutant of concern to both human and ecosystem health. Uranium's redox state often dictates its partitioning between the aqueous- and solid-phases, and thus controls its dissolved concentration and, coupled with groundwater flow, its migration within the environment. In anaerobic environments, the more oxidized and mobile form of uranium (UO{sub 2}{sup 2+} and associated species) may be reduced, directly or indirectly, by microorganisms to U(IV) with subsequent precipitation of UO{sub 2}. However, various factors within soils and sediments may limit biological reduction of U(VI), inclusive of alterations in U(VI) speciation and competitive electron acceptors. Here we elucidate the impact of U(VI) speciation on the extent and rate of reduction with specific emphasis on speciation changes induced by dissolved Ca, and we examine the impact of Fe(III) (hydr)oxides (ferrihydrite, goethite and hematite) varying in free energies of formation on U reduction. The amount of uranium removed from solution during 100 h of incubation with S. putrefaciens was 77% with no Ca or ferrihydrite present but only 24% (with ferrihydrite) and 14% (no ferrihydrite) were removed for systems with 0.8 mM Ca. Imparting an important criterion on uranium reduction, goethite and hematite decrease the dissolved concentration of calcium through adsorption …
Date: March 15, 2010
Creator: Stewart, B.D.; Amos, R.T.; Nico, P.S. & Fendorf, S.
System: The UNT Digital Library
Efficient algorithms for multi-file caching (open access)

Efficient algorithms for multi-file caching

Multi-File Caching issues arise in applications where a set of jobs are processed and each job requests one or more input files. A given job can only be started if all its input files are preloaded into a disk cache. Examples of applications where Multi-File caching may be required are scientific data mining, bit-sliced indexes, and analysis of sets of vertically partitioned files. The difference between this type of caching and traditional file caching systems is that in this environment, caching and replacement decisions are made based on ''combinations of files (file bundles),'' rather than single files. In this work we propose new algorithms for Multi-File caching and analyze their performance. Extensive simulations are presented to establish the effectiveness of the Multi-File caching algorithm in terms of job response time and job queue length.
Date: March 15, 2004
Creator: Otoo, Ekow J.; Rotem, Doron & Seshadri, Sridhar
System: The UNT Digital Library
An Acoustic Wave Equation for Tilted Transversely Isotropic Media (open access)

An Acoustic Wave Equation for Tilted Transversely Isotropic Media

A finite-difference method for computing the first arrival traveltimes by solving the Eikonal equation in the celerity domain has been developed. This algorithm incorporates the head and diffraction wave. We also adapt a fast sweeping method, which is extremely simple to implement in any number of dimensions, to obtain accurate first arrival times in complex velocity models. The method, which is stable and computationally efficient, can handle instabilities due to caustics and provide head waves traveltimes. Numerical examples demonstrate that the celerity-domain Eikonal solver provides accurate first arrival traveltimes. This new method is three times accurate more than the 2nd-order fast marching method in a linear velocity model with the same spacing.
Date: March 15, 2005
Creator: Zhang, Linbin; Rector, James W., III & Hoversten, G. Michael
System: The UNT Digital Library
Analytic electrostatic solution of an axisymmetric accelerator gap (open access)

Analytic electrostatic solution of an axisymmetric accelerator gap

Numerous computer codes calculate beam dynamics of particles traversing an accelerating gap. In order to carry out these calculations the electric field of a gap must be determined. The electric field is obtained from derivatives of the scalar potential which solves Laplace`s equation and satisfies the appropriate boundary conditions. An integral approach for the solution of Laplace`s equation is used in this work since the objective is to determine the potential and fields without solving on a traditional spatial grid. The motivation is to quickly obtain forces for particle transport, and eliminate the need to keep track of a large number of grid point fields. The problem then becomes one of how to evaluate the appropriate integral. In this work the integral solution has been converted to a finite sum of easily computed functions. Representing the integral solution in this manner provides a readily calculable formulation and avoids a number of difficulties inherent in dealing with an integral that can be weakly convergent in some regimes, and is, in general, highly oscillatory.
Date: March 15, 1995
Creator: Boyd, J. K.
System: The UNT Digital Library
Microtesla magnetic resonance imaging with a superconducting quantum interference device (open access)

Microtesla magnetic resonance imaging with a superconducting quantum interference device

We have constructed a magnetic resonance imaging (MRI) scanner based on a dc Superconducting QUantum Interference Device (SQUID) configured as a second-derivative gradiometer. The magnetic field sensitivity of the detector is independent of frequency; it is therefore possible to obtain high-resolution images by prepolarizing the nuclear spins in a field of 300 mT and detecting the signal at 132 fYT, corresponding to a proton Larmor frequency of 5.6 kHz. The reduction in the measurement field by a factor of 10,000 compared with conventional scanners eliminates inhomogeneous broadening of the nuclear magnetic resonance lines, even in fields with relatively poor homogeneity. The narrow linewidths result in enhanced signal-to-noise ratio and spatial resolution for a fixed strength of the magnetic field gradients used to encode the image. We present two-dimensional images of phantoms and pepper slices, obtained in typical magnetic field gradients of 100 fYT/m, with a spatial resolution of about 1mm. We further demonstrate a slice-selected image of an intact pepper. By varying the time delay between removal of the polarizing field and initiation of the spin echo sequence we acquire T1-weighted contrast images of water phantoms, some of which are doped with a paramagnetic salt; here, T1 is the nuclear …
Date: March 15, 2004
Creator: McDermott, Robert; Lee, SeungKyun; ten Haken, Bennie; Trabesinger, Andreas H.; Pines, Alexander & Clarke, John
System: The UNT Digital Library
A Physically Based Approach for Modeling Multiphase Fracture-Matrix Interaction in Fractured Porous Media (open access)

A Physically Based Approach for Modeling Multiphase Fracture-Matrix Interaction in Fractured Porous Media

Modeling fracture-matrix interaction within a complex multiple phase flow system is a key issue for fractured reservoir simulation. Commonly used mathematical models for dealing with such interactions employ a dual- or multiple-continuum concept, in which fractures and matrix are represented as overlapping, different, but interconnected continua, described by parallel sets of conservation equations. The conventional single-point upstream weighting scheme, in which the fracture relative permeability is used to represent the counterpart at the fracture-matrix interface, is the most common scheme by which to estimate flow mobility for fracture-matrix flow terms. However, such a scheme has a serious flaw, which may lead to unphysical solutions or significant numerical errors. To overcome the limitation of the conventional upstream weighting scheme, this paper presents a physically based modeling approach for estimating physically correct relative permeability in calculating multiphase flow between fractures and the matrix, using continuity of capillary pressure at the fracture-matrix interface. The proposed approach has been implemented into two multiphase reservoir simulators and verified using analytical solutions and laboratory experimental data. The new method is demonstrated to be accurate, numerically efficient, and easy to implement in dual- or multiple-continuum models.
Date: March 15, 2004
Creator: Wu, Yu-Shu; Pan, Lehua & Pruess, Karsten
System: The UNT Digital Library
Anomalous creep in Sn-rich solder joints (open access)

Anomalous creep in Sn-rich solder joints

This paper discusses the creep behavior of example Sn-rich solders that have become candidates for use in Pb-free solder joints. The specific solders discussed are Sn-3.5Ag, Sn-3Ag-0.5Cu, Sn-0.7Cu and Sn-10In-3.1Ag, used in thin joints between Cu and Ni-Au metallized pads.
Date: March 15, 2002
Creator: Song, Ho Geon; Morris, John W., Jr. & Hua, Fay
System: The UNT Digital Library
Geothermal Reservoir Dynamics - TOUGHREACT (open access)

Geothermal Reservoir Dynamics - TOUGHREACT

This project has been active for several years and has focused on developing, enhancing and applying mathematical modeling capabilities for fractured geothermal systems. The emphasis of our work has recently shifted towards enhanced geothermal systems (EGS) and hot dry rock (HDR), and FY05 is the first year that the DOE-AOP actually lists this project under Enhanced Geothermal Systems. Our overall purpose is to develop new engineering tools and a better understanding of the coupling between fluid flow, heat transfer, chemical reactions, and rock-mechanical deformation, to demonstrate new EGS technology through field applications, and to make technical information and computer programs available for field applications. The objectives of this project are to: (1) Improve fundamental understanding and engineering methods for geothermal systems, primarily focusing on EGS and HDR systems and on critical issues in geothermal systems that are difficult to produce. (2) Improve techniques for characterizing reservoir conditions and processes through new modeling and monitoring techniques based on ''active'' tracers and coupled processes. (3) Improve techniques for targeting injection towards specific engineering objectives, including maintaining and controlling injectivity, controlling non-condensable and corrosive gases, avoiding scale formation, and optimizing energy recovery. Seek opportunities for field testing and applying new technologies, and work …
Date: March 15, 2005
Creator: Pruess, Karsten; Xu, Tianfu; Shan, Chao; Zhang, Yingqi; Wu, Yu-Shu; Sonnenthal, Eric et al.
System: The UNT Digital Library
Non-universal SUSY breaking, hierarchy and squark degeneracty (open access)

Non-universal SUSY breaking, hierarchy and squark degeneracty

I discuss non-trivial effects in the soft SUSY breaking terms which appear when one integrates out heavy fields. The effects exist only when the SUSY breaking terms are non-universal. They may spoil (1) the hierarchy between the weak and high-energy scales, or (2) degeneracy among the squark masses even in the presense of a horizontal symmetry. I argue, in the end, that such new effects may be useful in probing physics at high-energy scales from TeV-scale experiments.
Date: March 15, 1995
Creator: Murayama, Hitoshi
System: The UNT Digital Library
A numerical study of the impacts of volatile component blending on diesel spray evaporation and combustion. (open access)

A numerical study of the impacts of volatile component blending on diesel spray evaporation and combustion.

A multiphase computational fluid dynamics (CFD) code is used to simulate the evaporation and combustion processes of a diesel spray blended with a highly volatile component. The CFD code uses an Eulerian approach to model the liquid phase of diesel fuel with components of different boiling temperatures. The approach divides the droplets into size groups and assigns different boiling temperatures for each group. The CFD code accounts for liquid droplet flow, turbulent mixing, interfacial drag and heat transfer, droplet evaporation and combustion, radiation heat transfer, and pollutant kinetics. Using the code, a parametric study was conducted to investigate the impacts of a volatile component on the spray evaporation and combustion characteristics. The results indicate that the blending of a highly volatile component can have an impact on droplet evaporation rate and that thermal radiation is significant in spray combustion due to the formation of soot.
Date: March 15, 2002
Creator: Lee, H.L.; Chang, S.L. & Petrick, M.
System: The UNT Digital Library
Overview of the NARSTO-NE-OPS Program. (open access)

Overview of the NARSTO-NE-OPS Program.

The NARSTO-NE-OPS (NorthEast Oxidant and Particle Study) is an investigation of the coupling of the meteorological and chemical processes that control the evolution of air pollution events. The project includes three major field programs carried out at a field site in northeast Philadelphia during the summers of 1998, 1999 and 2001. The activity brings together the research groups from 13 universities, 5 government laboratories and representatives of the electric power industry to apply the most advanced measurement techniques to understanding the physical and chemical processes contributing to air quality issues. Results have been obtained from three ground sites, two instrumented aircraft, many different instrumented balloon platforms, and several remote sensing techniques including satellites. In addition, the database used includes the ground-based measurements conducted at several surrounding state and city operated sites in Pennsylvania, New Jersey, Delaware, New York and Maryland. The results have shown the importance of developing the 3-dimensional regional scale picture of the atmosphere to understand and properly model air pollution events. It has been shown that only from such a perspective, which includes the vertical distribution and a regional context, can one hope to properly model and predict ozone and particulate pollution. A combination of photochemical and …
Date: March 15, 2002
Creator: Philbrick, C. R.; Ryan, W. F.; Clark, R. D.; Doddridge, B. G; Dickerson, R. R.; Gaffney, J. et al.
System: The UNT Digital Library
Bottom production (open access)

Bottom production

In the context of the LHC experiments, the physics of bottom flavoured hadrons enters in different contexts. It can be used for QCD tests, it affects the possibilities of B decays studies, and it is an important source of background for several processes of interest. The physics of b production at hadron colliders has a rather long story, dating back to its first observation in the UA1 experiment. Subsequently, b production has been studied at the Tevatron. Besides the transverse momentum spectrum of a single b, it has also become possible, in recent time, to study correlations in the production characteristics of the b and the b. At the LHC new opportunities will be offered by the high statistics and the high energy reach. One expects to be able to study the transverse momentum spectrum at higher transverse momenta, and also to exploit the large statistics to perform more accurate studies of correlations.
Date: March 15, 2000
Creator: Baines, J.; Baranov, S. P.; Bartalini, P.; Bay, A.; Bouhova, E.; Cacciari, M. et al.
System: The UNT Digital Library
Chemical and morphological changes at Al{sub 2}O{sub 3}/NiAl interfaces and their relationship to scale adhesion (open access)

Chemical and morphological changes at Al{sub 2}O{sub 3}/NiAl interfaces and their relationship to scale adhesion

Ni-(40,50)at%Al alloys with different C and S contents were oxidized at 1000-1150 C for various times in oxygen. Auger electron microscopy was used to study the interface chemistry after scale spallation in ultra high vacuum. The interfacial failure stresses were determined with a tensile pull tester and they were related to the interfacial pore density. Results show that sulfur did not segregate to the Al{sub 2}O{sub 3}/Ni50Al interface even after extended oxidation times. Small amounts, however, segregated to the Al{sub 2}O{sub 3}/Ni40Al interface. The difference in behavior may be related to the surface energy difference between Ni50Al and Ni40Al. On the interfacial void faces of Ni50Al, C first segregated, then it was replaced by S after longer oxidation times; the amount of segregants varied with different crystallographic orientation of the void face. On Ni40Al, S segregated much earlier on the void faces due to a faster diffusion rate in the Ni-rich NiAl. The apparent S diffusivity in Ni50Al and Ni40Al at 1000 C was determined to be 10{sup -9} and 6 x 10{sup -9} cm{sup 2}/s respectively. Excess sulfur in Ni40Al greatly increased the interfacial pore density. Preliminary results on interfacial failure stress showed that it decreased with increasing pore …
Date: March 15, 2003
Creator: Hou, Peggy Y.
System: The UNT Digital Library
Searches for new physics at Tevatron (open access)

Searches for new physics at Tevatron

This paper reviews the most recent results on searches for physics beyond the Standard Model at Tevatron. Both the collider experiments: CDF and D0 are performing a large variety of searches such as searches for scalar top and scalar bottom particles, search for new gauge bosons, search for long-lived massive particles and general searches for new particles decaying into dijets. The results, summarized here, are a selection of what obtained recently by both the collaborations using the Run II data, collected so far.
Date: March 15, 2004
Creator: Pagliarone, C.
System: The UNT Digital Library
An Accelerator Control Middle Layer Using MATLAB (open access)

An Accelerator Control Middle Layer Using MATLAB

Matlab is a matrix manipulation language originally developed to be a convenient language for using the LINPACK and EISPACK libraries. What makes Matlab so appealing for accelerator physics is the combination of a matrix oriented programming language, an active workspace for system variables, powerful graphics capability, built-in math libraries, and platform independence. A number of software toolboxes for accelerators have been written in Matlab--the Accelerator Toolbox (AT) for machine simulations, LOCO for accelerator calibration, Matlab Channel Access Toolbox (MCA) for EPICS connections, and the Middle Layer. This paper will describe the ''middle layer'' software toolbox that resides between the high-level control applications and the low-level accelerator control system. This software was a collaborative effort between ALS (LBNL) and SPEAR3 (SSRL) but easily ports to other machines. Five accelerators presently use this software. The high-level Middle Layer functionality includes energy ramp, configuration control (save/restore), global orbit correction, local photon beam steering, insertion device compensation, beam-based alignment, tune correction, response matrix measurement, and script-based programs for machine physics studies.
Date: March 15, 2005
Creator: Portmann, Gregory J.; Corbett, Jeff & Terebilo, Andrei
System: The UNT Digital Library
Report on generation IV technical working group 3 : liquid metal reactors. (open access)

Report on generation IV technical working group 3 : liquid metal reactors.

This paper reports on the first round of R&D roadmap activities of the Generation IV (Gen IV) Technical Working Group (TWG) 3, on liquid metal-cooled reactors. Liquid metal coolants give rise to fast spectrum systems, and thus the reactor systems considered in this TWG are all fast reactors. Gas-cooled fast reactors are considered in the context of TWG 2. As is noted in other Gen IV papers, this first round activity is termed ''screening for potential'', and includes collecting the most complete set of liquid metal reactor/fuel cycle system concepts possible and evaluating the concepts against the Gen IV principles and goals. Those concepts or concept groups that meet the Gen IV principles and which are deemed to have reasonable potential to meet the Gen IV goals will pass to the next round of evaluation. Although we sometimes use the terms ''reactor'' or ''reactor system'' by themselves, the scope of the investigation by TWG 3 includes not only the reactor systems, but very importantly the closed fuel recycle system inevitably required by fast reactors. The response to the DOE Request for Information (RFI) on liquid metal reactor/fuel cycle systems from principal investigators, laboratories, corporations, and other institutions, was robust and …
Date: March 15, 2002
Creator: Lineberry, M. J.; Rosen, S. L. & Sagayama, Y.
System: The UNT Digital Library
Laser impingement on bare and encased high explosives: safety limits (open access)

Laser impingement on bare and encased high explosives: safety limits

During the course of experiments involving high explosives, (HE), alignment lasers are often employed where the laser beam impinges upon a metal encased HE sample or on the bare HE itself during manned operations. While most alignment lasers are of low enough power so as not to be of concern, safety questions arise when considering the maximum credible power output of the laser in a failure mode, or when multiple laser spots are focused onto the experiment simultaneously. Safety questions also arise when the focused laser spot size becomes very small, on the order of 100 {micro}m or less. This paper addresses these concerns by describing a methodology for determining safety margins for laser impingement on metal encased HE as well as one for bare HE. A variety of explosives encased in Al, Cu, Ta and stainless steel were tested using the first of these techniques. Additional experiments were performed using the second method where the laser beam was focused directly on eight different samples of pressed-powder HE.
Date: March 15, 1999
Creator: Roeske, F.
System: The UNT Digital Library
Integration Window Position Estimation in TR Receivers (open access)

Integration Window Position Estimation in TR Receivers

Transmitted-reference (TR) receivers avoid the stringent synchronization requirements that exist in conventional pulse detection schemes. However, the performance of such receivers is highly sensitive to precise timing acquisition and tracking as well as the length of their integration window. This window in TR receivers defines the limits of the finite integrator prior to the final decision making block. In this paper, we propose a novel technique that allows us to extract the timing information of the integration window very accurately in UWB-TR receivers in the presence of channel noise. The principles of the method are presented and the BER performance of a modified UWB-TR receiver is investigated by computer simulation. Our studies show that the proposed estimation technique adds value to the conventional TR receiver structure with modest increase in complexity.
Date: March 15, 2005
Creator: Nekoogar, F.; Dowla, F. & Spiridon, A.
System: The UNT Digital Library