112 Matching Results

Results open in a new window/tab.

How an antenna launches its input power into radiation: thepattern of the Poynting vector at and near an antenna (open access)

How an antenna launches its input power into radiation: thepattern of the Poynting vector at and near an antenna

In this paper I first address the question of whether theseat of the power radiated by an antenna made of conducting members isdistributed over the "arms" of the antenna according to $ - \bf J \cdotE$, where $\bf J$ is the specified current density and $\bf E$ is theelectric field produced by that source. Poynting's theorem permits only aglobal identification of the total input power, usually from a localizedgenerator, with the total power radiated to infinity, not a localcorrespondence of $- \bf J \cdot E\ d^3x $ with some specific radiatedpower, $r^2 \bf S \cdot \hat r\ d\Omega $. I then describe a modelantenna consisting of two perfectly conducting hemispheres of radius\emph a separated by a small equatorial gap across which occurs thedriving oscillatory electric field. The fields and surface current aredetermined by solution of the boundary value problem. In contrast to thefirst approach (not a boundary value problem), the tangential electricfield vanishes on the metallic surface. There is no radial Poyntingvector at the surface. Numerical examples are shown to illustrate how theenergy flows from the input region of the gap and is guided near theantenna by its "arms" until it is launched at larger \emph r/a into theradiation pattern …
Date: May 18, 2005
Creator: Jackson, J.D.
System: The UNT Digital Library
Progress and Lessons Learned in Transuranic Waste Disposition at The Department of Energy's Advanced Mixed Waste Treatment Project (open access)

Progress and Lessons Learned in Transuranic Waste Disposition at The Department of Energy's Advanced Mixed Waste Treatment Project

This paper provides an overview of the Department of Energy's (DOE) Advanced Mixed Waste Treatment Project (AMWTP) located at the Idaho National Laboratory (INL) and operated by Bechtel BWXT Idaho, LLC(BBWI) It describes the results to date in meeting the 6,000-cubic-meter Idaho Settlement Agreement milestone that was due December 31, 2005. The paper further describes lessons that have been learned from the project in the area of transuranic (TRU) waste processing and waste certification. Information contained within this paper would be beneficial to others who manage TRU waste for disposal at the Waste Isolation Pilot Plant (WIPP).
Date: May 18, 2006
Creator: Mousseau, J. D.; Raish, S. C. & Russo, F. M.
System: The UNT Digital Library
Compatibility of the Radiating Divertor with High Performance Plasmas in DIII-D (open access)

Compatibility of the Radiating Divertor with High Performance Plasmas in DIII-D

A radiating divertor approach was successfully applied to high performance 'hybrid' plasmas [M.R. Wade, et al., Proc. 20th IAEA Fusion Energy Conf., Vilamoura, (2004)]. Our technique included: (1) injecting argon near the outer divertor target, (2) enhancing the plasma flow into the inner and outer divertors by a combination of particle pumping and deuterium gas puffing upstream of the divertor targets, and (3) isolating the inner divertor from the outer by a structure in the private flux region. Good hybrid conditions were maintained, as the peak heat flux at the outer divertor target was reduced by a factor of 2.5; the peak heat flux at the inner target decreased by 20%. This difference was caused by a higher concentration of argon at the outer target than at the inner target. Argon accumulation in the main plasma was modest (n{sub AR}/n{sub e} {le}0.004 on axis), although the argon profile was more peaked than the electron profile.
Date: May 18, 2006
Creator: Petrie, T. W.; Wade, M. R.; Brooks, N. H.; Fenstermacher, M. E.; Groth, M.; Hyatt, A. W. et al.
System: The UNT Digital Library
Blanket maintenance by remote means using the cassette blanket approach (open access)

Blanket maintenance by remote means using the cassette blanket approach

Induced radioactivity in the blanket and other parts of a fusion reactor close to the plasma zone will dictate remote assembly, disassembly, and maintenance procedures. Time will be of the essence in these procedures. They must be practicable and certain. This paper discusses the reduction of a complicated Tokamak reactor to a simpler assembly via the use of a vacuum building in which to house the reactor and the introduction in this new model of cassette blanket modules. The cassettes significantly simplify remote handling.
Date: May 18, 1978
Creator: Werner, R.W.
System: The UNT Digital Library
Shock wave effects and metallurgical parameters (open access)

Shock wave effects and metallurgical parameters

This review summarizes results from some principal investigations of shock-strain effects in metals. The strain contribution indeed plays a role in residual microstructures, particularly, if the strain becomes dominant as in ''under trapped'' experiments of low or moderate pressure or for that matter, of ''well trapped'' high pressure experiments. Not only does this strain contribution affect the microstructure by increasing deformation, a concommitant strain heat is generated and absorbed by the shocked material. This strain heat, if large enough (relative to the homologous temperature of the material), can and does have an annealing effect on the residual microstructure. This strain heat is over and above the values typically calculated for materials implying little or no strain. Although the accumulative effects of associated strain are not completely definite, the collective picture presented is one in which shock-induced strains, when large enough, have a significant effect on the residual microstructure. 43 refs., 20 figs.
Date: May 18, 1987
Creator: Staudhammer, K.P.
System: The UNT Digital Library
Molecular potentials and relaxation dynamics (open access)

Molecular potentials and relaxation dynamics

The use of empirical pseudopotentials, in evaluating interatomic potentials, provides an inexpensive and convenient method for obtaining highly accurate potential curves and permits the modeling of core-valence correlation, and the inclusion of relativistic effects when these are significant. Recent calculations of the X/sup 1/..sigma../sup +/ and a/sup 3/..sigma../sup +/ states of LiH, NaH, KH, RbH, and CsH and the X/sup 2/..sigma../sup +/ states of their anions are discussed. Pseudopotentials, including core polarization terms, have been used to replace the core electrons, and this has been coupled with the development of compact, higly-optimized basis sets for the corresponding one- and two-electron atoms. Comparisons of the neutral potential curves with experiment and other ab initio calculations show good agreement (within 1000 cm/sup -1/ over most of the potential curves) with the difference curves being considerably more accurate. In the method of computer molecular dynamics, the force acting on each particle is the resultant of all interactions with other atoms in the neighborhood and is obtained as the derivative of an effective many-body potential. Exploiting the pseudopotential approach, in obtaining the appropriate potentials may be very fruitful in the future. In the molecular dynamics example considered here, the conventional sum-of-pairwise-interatomic-potentials (SPP) approximation is …
Date: May 18, 1981
Creator: Karo, A.M.
System: The UNT Digital Library
Plasma crowbars in cylindrical flux compression experiments (open access)

Plasma crowbars in cylindrical flux compression experiments

We have done a series of one- and two-dimensional calculations of hard-core Z-pinch flux compression experiments in order to study the effect of a plasma on these systems. These calculations show that including a plasma can reduce the amount of flux lost during the compression. Flux losses to the outer wall of such experiments can be greatly reduced by a plasma conducting sheath which forms along the wall. This conducting sheath consists of a cold, dense high ..beta.., unmagnetized plasma which has enough pressure to balance a large field gradient. Flux which is lost into the center conductor is not effectively stopped by this plasma sheath until late in the implosion, at which time a layer similar to the one formed at the outer wall is created. Two-dimensionl simulations show that flux losses due to arching along the sliding contact of the experiment can be effectively stopped by the formation of a plasma conducting sheath.
Date: May 18, 1979
Creator: Suter, L.J.
System: The UNT Digital Library
Technology development for recirculating heavy-ion accelerators (open access)

Technology development for recirculating heavy-ion accelerators

The {open_quotes}recirculator,{close_quotes} a recirculating heavy-ion accelerator has been identified as a promising approach for an inertial fusion driver. System studies have been conducted to evaluate the recirculator on the basis of feasibility and cost. The recirculator has been shown to have significant cost advantages over other potential driver schemes, but some of the performance requirements exceed the capabilities of present technology. The system studies identified the high leverage areas where advances in technology will significantly impact the cost and performance of a recirculator. One of the high leverage areas is the modulator system which generates the acceleration potentials in the induction cells. The modulator system must be capable of generating the acceleration potentials at peak repetition rates in excess of 100 kHz with variable pulse widths. LLNL is developing a modulator technology capable of driving induction cells using the latest in solid state MOSFET technology. A small scale modulator has been built and tested to prove the concept and the next version is presently being designed. The objective is to demonstrate a modulator operating at 5 kV, 1 kA, with 0.2--1 {mu}s pulse widths while driving an induction cell at >100 kHz within the next year. This paper describes the …
Date: May 18, 1993
Creator: Newton, M. A. & Kirbie, H. C.
System: The UNT Digital Library
High Volume, Low Pressure Drop, Bioaerosol Collector Using a Multi-slit Virtual Impactor (open access)

High Volume, Low Pressure Drop, Bioaerosol Collector Using a Multi-slit Virtual Impactor

None
Date: May 18, 2004
Creator: Bergman, W; Shinn, J; Lochner, R; Sawyer, S; Milanovich, F & Jr, R M
System: The UNT Digital Library
Army Solid State Laser Program: Design, Operation, and Mission Analysis for a Heat-Capacity Laser (open access)

Army Solid State Laser Program: Design, Operation, and Mission Analysis for a Heat-Capacity Laser

Solid-state lasers have held great promise for the generation of high-average-power, high-quality output beams for a number of decades. However, the inherent difficulty of scaling the active solid-state gain media while continuing to provide efficient cooling has limited demonstrated powers to <5kW. Even at the maximum demonstrated average powers, the output is most often delivered as continuous wave (CW) or as small energy pulses at high pulse repetition frequency (PRF) and the beam divergence is typically >10X the diffraction limit. Challenges posed by optical distortions and depolarization arising from internal temperature gradients in the gain medium of a continuously cooled system are only increased for laser designs that would attempt to deliver the high average power in the form of high energy pulses (>25J) from a single coherent optical aperture. Although demonstrated phase-locking of multiple laser apertures may hold significant promise for the future scaling of solid-state laser systems,1 the continuing need for additional technical development and innovation coupled with the anticipated complexity of these systems effectively limits this approach for near-term multi-kW laser operation outside of a laboratory setting. We have developed and demonstrated a new operational mode for solid-state laser systems in which the cooling of the gain …
Date: May 18, 2001
Creator: Dane, C. B.; Flath, L.; Rotter, M.; Fochs, S.; Brase, J. & Bretney, K.
System: The UNT Digital Library
A study of extraterrestrial antineutrino sources with the KamLAND detector (open access)

A study of extraterrestrial antineutrino sources with the KamLAND detector

We present the results of a search for extraterrestrial electron antineutrinos ({bar {nu}}{sub e}'s) in the energy range 8.3 MeV < E{sub {bar {nu}}}{sub e} < 30.8 MeV using the KamLAND detector. In an exposure of 4.53 kton-year, we identify 25 candidate events. All of the candidate events can be attributed to background, most importantly neutral current atmospheric neutrino interactions, setting an upper limit on the probability of {sup 8}B solar {nu}{sub e}'s converting into {bar {nu}}{sub e}'s at 5.3 x 10{sup -5} (90% C.L.). The present data also allows us to set more stringent limits on the diffuse supernova neutrino flux and on the annihilation rates for light dark matter particles.
Date: May 18, 2011
Creator: Collaboration, The KamLAND; Gando, A.; Gando, Y.; Ichimura, K.; Ikeda, H.; Inoue, K. et al.
System: The UNT Digital Library
Focusing lenses for the 20-beam fusion laser, SHIVA (open access)

Focusing lenses for the 20-beam fusion laser, SHIVA

The focus lens design for the 20-beam SHIVA laser fusion facility involves considerations of uniform and normal pellet illumination. The resulting requirements dictate tailored beam intensity profiles and vacuum-loaded thin lenses.
Date: May 18, 1976
Creator: O'Neal, W. C.
System: The UNT Digital Library
Rydberg series in the lanthanides and actinides observed by stepwise laser excitation (open access)

Rydberg series in the lanthanides and actinides observed by stepwise laser excitation

The techniques of stepwise laser excitation were applied to obtain Ryberg series in the lanthanides and in uranium. The methods employed circumvent many of the experimental difficulties inherent in conventional absorption spectrosopy of these heavy atoms with very complex spectra. The Rydberg series observed have allowed the determination of accurate ionization limits. The values in eV are: Ce, 5.5387(4);Nd, 5.5250(6); Sm, 5.6437(10); Eu, 5.6704(3); Gd, 6.1502(6); Tb, 5.8639(6); Dy, 5.9390(6); Ho, 6.0216(6); Er 6.1077(6); U, 6.1941(5). A comparison of the f/sup n/s/sup 2/-f/sup n/s ionization limits as a function of n with theoretical calculations is made.
Date: May 18, 1977
Creator: Worden, E. F.; Solarz, R. W.; Paisner, J. A.; Rajnak, K.; Shore, B. W. & Conway, J. G.
System: The UNT Digital Library
Advances in full field microscopy with table-top soft x-ray lasers (open access)

Advances in full field microscopy with table-top soft x-ray lasers

We describe recent advances in the demonstration of table-top full field microscopes that use soft x-ray lasers for illumination. We have achieved wavelength resolution and single shot exposure operation with a very compact 46.9 nm microscope based on a desk-top size capillary discharge laser. This {lambda}-46.9 nm microscope has been used to capture full field images of a variety of nanostructure systems and surfaces. In a separate development we have demonstrated a zone plate microscope that uses {lambda}=13.2 nm laser illumination to image absorption defects in an extreme ultraviolet lithography (EUVL) mask in the same geometry used in a 4x demagnification EUVL stepper. Characterization of the microscope’s transfer function shows it can resolve 55 nm half period patterns. With these capabilities, the {lambda}-13.2 nm microscope is well suited for evaluation of pattern and defect printability of EUVL masks for the 22 nm node.
Date: May 18, 2009
Creator: Menoni, C. S.; Brizuela, F.; Wang, Y.; Brewer, C. A.; Luther, B. M.; Pedaci, F. et al.
System: The UNT Digital Library
An Experiment to Locate the Site of TeV Flaring in M87 (open access)

An Experiment to Locate the Site of TeV Flaring in M87

We describe a Chandra X-ray target-of-opportunity project designed to isolate the site of TeV flaring in the radio galaxy M87. To date, we have triggered the Chandra observations only once (2010 April) and by the time of the first of our nine observations, the TeV flare had ended. However, we found that the X-ray intensity of the unresolved nucleus was at an elevated level for our first observation. Of the more than 60 Chandra observations we have made of the M87 jet covering nine years, the nucleus was measured at a comparably high level only three times. Two of these occasions can be associated with TeV flaring, and at the time of the third event, there were no TeV monitoring activities. From the rapidity of the intensity drop of the nucleus, we infer that the size of the emitting region is of order a few light days x the unknown beaming factor; comparable to the same sort of estimate for the TeV emitting region. We also find evidence of spectral evolution in the X-ray band which seems consistent with radiative losses affecting the non-thermal population of the emitting electrons within the unresolved nucleus.
Date: May 18, 2012
Creator: Harris, D. E.; Massaro, F.; Cheung, C. C.; Horns, D.; Raue, M.; Stawarz, L. et al.
System: The UNT Digital Library
Residential Electricity Demand in China -- Can Efficiency Reverse the Growth? (open access)

Residential Electricity Demand in China -- Can Efficiency Reverse the Growth?

The time when energy-related carbon emissions come overwhelmingly from developed countries is coming to a close. China has already overtaken the United States as the world's leading emitter of greenhouse gas emissions. The economic growth that China has experienced is not expected to slow down significantly in the long term, which implies continued massive growth in energy demand. This paper draws on the extensive expertise from the China Energy Group at LBNL on forecasting energy consumption in China, but adds to it by exploring the dynamics of demand growth for electricity in the residential sector -- and the realistic potential for coping with it through efficiency. This paper forecasts ownership growth of each product using econometric modeling, in combination with historical trends in China. The products considered (refrigerators, air conditioners, fans, washing machines, lighting, standby power, space heaters, and water heating) account for 90percent of household electricity consumption in China. Using this method, we determine the trend and dynamics of demandgrowth and its dependence on macroeconomic drivers at a level of detail not accessible by models of a more aggregate nature. In addition, we present scenarios for reducing residential consumption through efficiency measures defined at the product level. The research …
Date: May 18, 2009
Creator: Letschert, Virginie; McNeil, Michael A. & Zhou, Nan
System: The UNT Digital Library
Waste Tank Heels and Heel Simulants (open access)

Waste Tank Heels and Heel Simulants

None
Date: May 18, 2009
Creator: Barton, W. B.
System: The UNT Digital Library
Status of the Super-B factory Design (open access)

Status of the Super-B factory Design

The SuperB international team continues to optimize the design of an electron-positron collider, which will allow the enhanced study of the origins of flavor physics. The project combines the best features of a linear collider (high single-collision luminosity) and a storage-ring collider (high repetition rate), bringing together all accelerator physics aspects to make a very high luminosity of 10{sup 36} cm{sup -2} sec{sup -1}. This asymmetric-energy collider with a polarized electron beam will produce hundreds of millions of B-mesons at the Y(4S) resonance. The present design is based on extremely low emittance beams colliding at a large Piwinski angle to allow very low {beta}{sub y} without the need for ultra short bunches. Use of crab-waist sextupoles will enhance the luminosity, suppressing dangerous resonances and allowing for a higher beam-beam parameter. The project has flexible beam parameters, improved dynamic aperture, and spin-rotators in the Low Energy Ring for longitudinal polarization of the electron beam at the Interaction Point. Optimized for best colliding-beam performance, the facility may also provide high-brightness photon beams for synchrotron radiation applications.
Date: May 18, 2012
Creator: Wittmer, W.; U., /Michigan State; Bertsche, K.; Chao, A.; Novokhatski, A.; Nosochkov, Y. et al.
System: The UNT Digital Library
DimaSense™: A Novel Nucleic Acid Detection System (open access)

DimaSense™: A Novel Nucleic Acid Detection System

Recently, we developed a suite of methods for the rational design and fabrication of well-defined nanoparticle architectures, including clusters using bio-encoded nanoscale building blocks and layer-by-layer stepwise assembly on a solid support. In particular, the Nano-Assembly platform using Encoded Solid Supports (NAESS) allows for controlled interactions, purification of side products, modularity of design, and the construction of complex nanoparticle architectures. This approach offers several advantages over the current art of designing nanoparticle clusters, which include the high-yield synthesis of desired architectures, a 'plug-and-play' design allowing for the introduction of a variety of sensing modalities, and ease of scalability in high-throughput and synthesis yield. As a utility proof of concept, we implemented our unique cluster fabrication platform to design gold nanoparticle dimers which are linked via a single-stranded DNA oligonucleotide recognition motif. The design of this motif is such that binding of complementary nucleic acids results in specific, selective and rapid dimer dissociation, which can be monitored by dynamic light scattering (DLS). We demonstrated single level mismatch selectivity using this approach. The limit of detection was determined to be 1011 molecules of synthetic target RNA or DNA within 30 minutes of incubation at 33 C. This detection limit is determined by …
Date: May 18, 2011
Creator: Stadler, A.
System: The UNT Digital Library
STREAM II-V5: REVISION OF STREAM II-V4 AQUEOUS TRANSPORT CODE TO ACCOUNT FOR THE EFFECTS OF RAINFALL EVENTS (open access)

STREAM II-V5: REVISION OF STREAM II-V4 AQUEOUS TRANSPORT CODE TO ACCOUNT FOR THE EFFECTS OF RAINFALL EVENTS

STREAM II is an aqueous transport model developed by the Savannah River National Laboratory (SRNL) for use in the Savannah River Site (SRS) emergency response program. The transport model of the Water Quality Analysis Simulation Program (WASP) is used by STREAM II to perform contaminant transport calculations. WASP5 is a US Environmental Protection Agency (EPA) water quality analysis program that simulates contaminant transport and fate through surface water. A recent version of the code (STREAM II-V4) predicts peak concentration and peak concentration arrival time at downstream locations for releases from the SRS facilities to the Savannah River. The input flows for STREAM II-V4 are derived from the historical flow records measured by the United States Geological Survey (USGS). The stream flow for STREAM II-V4 is fixed and the flow only varies with the month in which the releases are taking place. Therefore, the effects of flow surge due to a severe storm are not accounted for by STREAM IIV4. STREAM II-V5 is an upgraded version which accounts for the effects of a storm event. The revised model finds the proper stream inlet flow based on the total rainfall and rainfall duration as input by the user. STREAM II-V5 then adjusts …
Date: May 18, 2011
Creator: Chen, K.
System: The UNT Digital Library
Synchrotron Light Options at Super-B (open access)

Synchrotron Light Options at Super-B

None
Date: May 18, 2012
Creator: Wittmer, Walter; Nosochkov, Yuri; Novokhatski, Alexander; Seeman, John; Sullivan, Michael; Biagini, Maria Enrica et al.
System: The UNT Digital Library
Charm and Charmonium Spectroscopy at B-factories (open access)

Charm and Charmonium Spectroscopy at B-factories

Since a few years, charm and charmonium spectroscopy has revived, both from experimental and theoretical point of views. Many new states have been discovered triggering numerous theoretical publications. The B-factories with their large enriched charm sample have played a leading role on the experimental side with the observation and study of most of the new states. Other experiments such as CLEO and CDF have also contributed. Classical hadron spectroscopy predicted some of these new states, but not all of them. Therefore a lot of effort have been spent in order to understand the nature of the later. We are summarizing here the most recent and important results in hadron spectroscopy, including strange-charm mesons, charm baryons and charmonium and charmonium-like states.
Date: May 18, 2007
Creator: Grenier, Philippe & /SLAC /Ecole Normale Superieure, CNRS
System: The UNT Digital Library
Status of the National Ignition Facility Integrated Computer Control System (ICCS) on the Path to Ignition (open access)

Status of the National Ignition Facility Integrated Computer Control System (ICCS) on the Path to Ignition

None
Date: May 18, 2007
Creator: Lagin, L. J.; Bettenhausen, R. C.; Bowers, G. A.; Carey, R. W.; Edwards, O. D.; Estes, C. M. et al.
System: The UNT Digital Library