The 1997/98 El Nino: A Test for Climate Models (open access)

The 1997/98 El Nino: A Test for Climate Models

Version 3 of the Hadley Centre Atmospheric Model (HadAM3) has been used to demonstrate one means of comparing a general circulation model with observations for a specific climate perturbation, namely the strong 1997/98 El Nino. This event was characterized by the collapse of the tropical Pacific's Walker circulation, caused by the lack of a zonal sea surface temperature gradient during the El Nino. Relative to normal years, cloud altitudes were lower in the western portion of the Pacific and higher in the eastern portion. HadAM3 likewise produced the observed collapse of the Walker circulation, and it did a reasonable job of reproducing the west/east cloud structure changes. This illustrates that the 1997/98 El Nino serves as a useful means of testing cloud-climate interactions in climate models.
Date: March 5, 2004
Creator: Lu, R; Dong, B; Cess, R D & Potter, G L
Object Type: Article
System: The UNT Digital Library
Relative x-ray backlighter intensity comparison of ti and ti/sc combination foils driven in double-sided and single-sided laser configuration (open access)

Relative x-ray backlighter intensity comparison of ti and ti/sc combination foils driven in double-sided and single-sided laser configuration

Use of multiple backlighter foils and/or double-sided laser interaction geometry with backlit imaging can result in improved backlighter efficiency. An experimental comparison of backlighter intensity for Ti foils and Ti/Sc combination foils in both the one-sided and double-sided laser-interaction configuration is presented. Spectrally-integrated framing camera images show intensity contributions of front and rear backlighter surfaces for both foil types. Analysis of time-resolved x-ray spectra collected from foil targets show the relative contribution of Ti and Sc 2-1 He-like resonance lines to the total backlighter intensity.
Date: June 5, 2000
Creator: Bullock, A. B.; Landen, O. L. & Bradley, D. K.
Object Type: Article
System: The UNT Digital Library
Feasibility Study of Passive Aerosol Sampler for Bio-Agent Detection (open access)

Feasibility Study of Passive Aerosol Sampler for Bio-Agent Detection

We propose to establish the feasibility of a passive aerosol sampler for bio-agent collection through laboratory experiments and theoretical analysis. The passive sampler, unlike the typical active sampler, does not require pumps and complex fixtures, and thereby allows for large-scale field monitoring not possible with current active samplers. We plan to conduct experiments using model (both biological and non-biological) aerosols generated in an instrumented test chamber and compare the particles collected on various passive samplers to conventional filter samplers, commercial aerosol measuring instruments and to conventional surface swipes. Theoretical analysis will be used to design prototype passive samplers and to compare experimental results with theory. A successful feasibility study will be used to seek outside funding for applications that will greatly enhance current LLNL programs such as NARAC's atmospheric dispersal modeling, NAI's programs in bioagent monitoring in public locations and fixed sampling stations, and EPD's environmental monitoring and decontamination research. In addition, the feasibility study will position us favorably for responding to new calls for proposals by NIH and EPA for large scale environmental studies.
Date: March 5, 2003
Creator: Keating, G. & Bergman, W.
Object Type: Report
System: The UNT Digital Library
A SPICE Model and Electrostatic Field Analysis of the MOS Turn-Off Thyristor (open access)

A SPICE Model and Electrostatic Field Analysis of the MOS Turn-Off Thyristor

This paper presents a circuit model and an electrostatic field analysis with an approximate model of the SDM170HK MOS turn-off thyristor (MTO) fabricated by Silicon Power Corporation. The circuit model consists of five cells, each containing two bipolar junction transistors and three resistors. The turn-off feature of the MTO was simulated by inserting an array of 21 Fairchild FDS6670A MOSFET importable sub-circuit components between the cathode and the turn-on gate. The model was then used to create a four-terminal sub-circuit component representing the MTO that can be readily imported into computer-aided circuit design programs such as PSPICE and Micro-Cap. The generated static I-V characteristics and simulated switching waveforms are shown. The electrostatic field analysis was done for the maximum operating voltage of 4.5 kV using the Ansoft Maxwell 3D field simulator. Electrostatic field magnitudes that exceed the nominal air breakdown threshold of 30 kV/cm were observed surrounding the simulated turn-off gate wire, the turn-off gate ring contact, and the cathode ring contact. The resulting areas of high fields are a concern, as arc track marks have been found on the inner surface of the ceramic insulator near the internal gate connections of a failed device.
Date: August 5, 2002
Creator: Kelly, D. Q.; Mayhall, D. J.; Wilson, M. J. & Lahowe, D. A.
Object Type: Report
System: The UNT Digital Library
SECONDARY ELECTRON EMISSION MEASUREMENTS FOR TIN COATING ON THE STAINLESS STEEL OF SNS ACCUMULATOR RING VACUUM CHAMBER. (open access)

SECONDARY ELECTRON EMISSION MEASUREMENTS FOR TIN COATING ON THE STAINLESS STEEL OF SNS ACCUMULATOR RING VACUUM CHAMBER.

BNL is responsible for the design and construction of the US Spallation Neutron Source (SNS) accumulator ring. Titanium Nitride (TiN) coating on the stainless steel vacuum chamber of the SNS accumulator ring is needed to reduce the secondary electron yield (SEY) and the undesirable resonant multiplication of electrons. The total SEY of TiN coated stainless steel material has been measured after coating samples were exposed to air and after electron and ion bombardment. We report here about TiN coating system setup at BNL and SEY measurements results at CERN, SLAC and KEK. We also present some simulation results of SNS accumulator ring electron-cloud effects using different SEY values.
Date: July 5, 2004
Creator: HE,P. HSEUH,H. C. TODD,R. J. ET AL.
Object Type: Article
System: The UNT Digital Library
Adapting high-resolution speckle imaging to moving targets and platforms (open access)

Adapting high-resolution speckle imaging to moving targets and platforms

High-resolution surveillance imaging with apertures greater than a few inches over horizontal or slant paths at optical or infrared wavelengths will typically be limited by atmospheric aberrations. With static targets and static platforms, we have previously demonstrated near-diffraction limited imaging of various targets including personnel and vehicles over horizontal and slant paths ranging from less than a kilometer to many tens of kilometers using adaptations to bispectral speckle imaging techniques. Nominally, these image processing methods require the target to be static with respect to its background during the data acquisition since multiple frames are required. To obtain a sufficient number of frames and also to allow the atmosphere to decorrelate between frames, data acquisition times on the order of one second are needed. Modifications to the original imaging algorithm will be needed to deal with situations where there is relative target to background motion. In this paper, we present an extension of these imaging techniques to accommodate mobile platforms and moving targets.
Date: February 5, 2004
Creator: Carrano, C J & Brase, J M
Object Type: Article
System: The UNT Digital Library
RF TECHNIQUES FOR IMPROVED LUMINOSITY IN RHIC. (open access)

RF TECHNIQUES FOR IMPROVED LUMINOSITY IN RHIC.

The luminosity of the Relativistic Heavy Ion Collider has improved significantly [1] over the first three physics runs. A number of special rf techniques have been developed to facilitate higher luminosity. The techniques described herein include: an ultra low-noise rf source for the 197 MHz storage rf system, a frequency shift switch-on technique for transferring bunches from the acceleration to the storage system, synchronizing the rings during the energy ramp (including crossing the transition energy) to avoid incidental collisions, installation of dedicated 200 MHZ cavities to provide longitudinal Landau damping on the ramp, and the development of a bunch merging scheme in the Booster to increase the available bunch intensity from the injectors.
Date: July 5, 2004
Creator: BRENNAN,J. M. BLASKIEWICZ,J. BUTLER,J. DELONG,J. FISCHER,W. HAYES,T.
Object Type: Article
System: The UNT Digital Library
Addressing Problems with Scene-Based Wave Front Sensing (open access)

Addressing Problems with Scene-Based Wave Front Sensing

Scene-Based Wave Front Sensing uses the correlation between successive subimages to determine phase aberrations which blur digital images. Adaptive Optics technology uses deformable mirrors to correct for these phase aberrations and make the images clearer. The correlation between temporal subimages gives tip-tilt information. If these images do not have identical image content, tip-tilt estimations may be incorrect. Motion detection is necessary to help avoid errors initiated by dynamic subimage content. In this document, I will discuss why edge detection fails as a motion detection method on low resolution images and how thresholding the normalized variance of individual pixels is successful for motion detection.
Date: August 5, 2003
Creator: Chan, C
Object Type: Report
System: The UNT Digital Library
Statistical Stability and Time-Reversal Imgaing in Random Media (open access)

Statistical Stability and Time-Reversal Imgaing in Random Media

Localization of targets imbedded in a heterogeneous background medium is a common problem in seismic, ultrasonic, and electromagnetic imaging problems. The best imaging techniques make direct use of the eigenfunctions and eigenvalues of the array response matrix, as recent work on time-reversal acoustics has shown. Of the various imaging functionals studied, one that is representative of a preferred class is a time-domain generalization of MUSIC (MUltiple Signal Classification), which is a well-known linear subspace method normally applied only in the frequency domain. Since statistical stability is not characteristic of the frequency domain, a transform back to the time domain after first diagonalizing the array data in the frequency domain takes optimum advantage of both the time-domain stability and the frequency-domain orthogonality of the relevant eigenfunctions.
Date: February 5, 2002
Creator: Berryman, J; Borcea, L; Papanicolaou, G & Tsogka, C
Object Type: Article
System: The UNT Digital Library
A Low Noise RF Source for RHIC (open access)

A Low Noise RF Source for RHIC

The Relativistic Heavy Ion Collider (RHIC) requires a low noise rf source to ensure that beam lifetime during a store is not limited by the rf system. The beam is particularly sensitive to noise from power line harmonics. Additionally, the rf source must be flexible enough to handle the frequency jump required for rebucketing (transferring bunches from the acceleration to the storage rf systems). This paper will describe the design of a Direct Digital Synthesizer (DDS) based system that provides both the noise performance and the flexibility required.
Date: July 5, 2004
Creator: Hayes, T.
Object Type: Article
System: The UNT Digital Library
Impaired fertility in T-stock female mice after superovulation (open access)

Impaired fertility in T-stock female mice after superovulation

Superovulation of female mice with exogenous gonadotrophins is routinely used for increasing the number of eggs ovulated by each female in reproductive and developmental studies. We report an unusual effect of superovulation on fertilization in mice. In vivo matings of superovulated T-stock females with B6C3F1 males resulted in a 2-fold reduction (P<0.001) in the frequencies of fertilized eggs compared to control B6C3F1 matings. In addition, {approx}22 hr after mating only 15% of fertilized eggs recovered in T-stock females had reached the metaphase stage of the first cleavage division versus 87% in B6C3F1 females (P < 0.0001). Matings with T-stock males did not improve the reproductive performance of T-stock females. To investigate the possible cause(s) for the impaired fertilization and zygotic development, the experiments were repeated using in vitro fertilization. Under these conditions, the frequencies of fertilized eggs were not different in superovulated T-stock and B6C3F1 females (51.7% {+-} 6.0 and 64.5% {+-}3.8, P=0.10). There was a 7-fold increase in the frequencies of fertilized T-stock eggs that completed the first cell cycle of development after in vitro versus in vivo fertilization. These results rule out an intrinsic deficiency of the T-stock oocyte as the main reason for the impaired fertility after …
Date: December 5, 2003
Creator: Wyrobek, A J; Bishop, J B; Marchetti, F & Zudova, D
Object Type: Article
System: The UNT Digital Library
Improved Energy Coupling into the Gain Region of the Ni-Like Pd Transient Collisional X-Ray Laser (open access)

Improved Energy Coupling into the Gain Region of the Ni-Like Pd Transient Collisional X-Ray Laser

We present within this paper a series of experiments, which yield new observations to further our understanding of the transient collisional x-ray laser medium. We use the recently developed technique of picosecond x-ray laser interferometry to probe the plasma conditions in which the x-ray laser is generated and propagates. This yields two dimensional electron density maps of the plasma taken at different times relative to the peak of the 600ps plasma-forming beam. In another experimental campaign, the output of the x-ray laser plasma column is imaged with a spherical multilayer mirror onto a CCD camera to give a two-dimensional intensity map of the x-ray laser output. Near-field imaging gives insights into refraction, output intensity and spatial mode structure. Combining these images with the density maps gives an indication of the electron density at which the x-ray laser is being emitted at (yielding insights into the effect of density gradients on beam propagation). Experimental observations coupled with simulations predict that most effective coupling of laser pump energy occurs when the duration of the main heating pulse is comparable to the gain lifetime ({approx}10ps for Ni-like schemes). This can increase the output intensity by more than an order of magnitude relative to …
Date: October 5, 2004
Creator: Smith, R.; Dunn, J.; Filevich, J.; Moon, S.; Nilsen, J.; Keenan, R. et al.
Object Type: Article
System: The UNT Digital Library
STK Bladestore Tests (open access)

STK Bladestore Tests

The STK Bladestore is a disk subsystem consisting of ATA disks, fiber channel connectivity, and a RAID controller (LSI manufactured). There are essentially four host connections and four backend fiber connections. The host side ports are 2Gb/sec and with their advertised 400MB/sec bandwidth, the disk side ports are 1GB/sec. Our goal is to test this flavor of disk to see what the real world performance might be.
Date: November 5, 2003
Creator: Heer, T.
Object Type: Report
System: The UNT Digital Library
Effect of the environment and alloy composition on the electrochemical behavior of Ni-Cr-Mo Alloys (open access)

Effect of the environment and alloy composition on the electrochemical behavior of Ni-Cr-Mo Alloys

Alloy 22 (UNS N06022) is the candidate material for the corrosion resistant, outer barrier of the Yucca Mountain nuclear waste containers. One of the potential corrosion degradation modes of the container is uniform or passive corrosion. Therefore it is of importance to understand the stability of the oxide film, which will control the passive corrosion rate of Alloy 22. Many variables such as temperature, composition and pH of the electrolyte, applied potential, and microstructure and composition of the base metal would determine the thickness and composition of the oxide film. The purpose of this research work was to use electrochemical and surface analysis techniques to explore the influence of solution pH and applied potential on the characteristics of the oxide film formed on Alloy 22 and two experimental alloys containing differing amounts of chromium (Cr) and molybdenum (Mo). Results confirm that bulk metal composition is fundamental to the passive behavior and potential breakdown of the studied alloys. In these preliminary results, welded and non-welded Alloy 22 did not show differences in their anodic behavior.
Date: January 5, 2004
Creator: Hayes, J R; Szmodis, A W; Anderson, K L & Orme, C A
Object Type: Article
System: The UNT Digital Library
Hyperspectral Imaging of Functional Patterns for Disease Assessment and Treatment Monitoring (open access)

Hyperspectral Imaging of Functional Patterns for Disease Assessment and Treatment Monitoring

We have designed and built a six-band multi-spectral NIR imaging system used in clinical testing on cancer patients. From our layered tissue model, we create blood volume and blood oxygenation images for patient treatment monitoring.
Date: December 5, 2003
Creator: Hassan, Moinuddin; Hattery, David; Vogel, Abby; Chernomorkik, Victor; Demos, Stavros; Aleman, Karen et al.
Object Type: Article
System: The UNT Digital Library
Simulation of Detonation Problems with MLS Grid Free Methodology (open access)

Simulation of Detonation Problems with MLS Grid Free Methodology

The MLS grid free rezone method, a simple, flexible finite difference method to solve general mechanics problems, especially detonation problems, is proposed in this paper. The spatial points that carry time dependent data are distributed in space in such a way that provides nearly uniform spacing of points, accurate presentation of boundaries, easy variation of resolutions and arbitrary deletion of irrelevant regions. Local finite difference operators are obtained with simple MLS differentiation. There is no specific topological or geometrical restriction with the distribution of data points. Therefore this method avoids many drawbacks of the traditional CFD methods. Because of its flexibility, it can be used to simulate a wide range of mechanics problems. Because of its simplicity, it has the potential to become a preferred method. Most traditional CFD methods, from a SPH view, can be considered as special cases of grid free methods of specific kernel functions. Such a generalization allows the development of a unified grid free CFD code that can be switched to various CFD methods by switching the kernel functions. Because of the flexibility in management and simplicity of coding, such a unified code is desired.
Date: June 5, 2002
Creator: Yao, J; Gunger, M E & Matuska, D A
Object Type: Article
System: The UNT Digital Library
NIF PEPC LRU Test Stand Safety Note Addendum (open access)

NIF PEPC LRU Test Stand Safety Note Addendum

It is necessary that the NIF PEPC LRU Test Stand be modified to accommodate a new experiment. This modification will involve boring two 1/2 inch holes in the Center Loaded Upper Beam of the stand. These holes will allow a small wire to pass through half of the length of one of the long sections of 80/20 part 3030. The holes could adversely effect the load-bearing capabilities of an important structural member of the stand so calculations must be done to assure a minimal risk of part failure.
Date: September 5, 2001
Creator: Mason, D
Object Type: Report
System: The UNT Digital Library
Final Focus Shielding Designs for Modern Heavy-Ion Fusion Power Plant Designs (open access)

Final Focus Shielding Designs for Modern Heavy-Ion Fusion Power Plant Designs

Recent work in heavy-ion fusion accelerators and final focusing systems shows a trend towards less current per beam, and thus, a greater number of beams. Final focusing magnets are susceptible to nuclear heating, radiation damage, and neutron activation. The trend towards more beams, however, means that there can be less shielding for each magnet, Excessive levels of nuclear heating may lead to magnet quench or an intolerable recirculating power for magnet cooling. High levels of radiation damage may result in short magnet lifetimes and low reliability. Finally, neutron activation of the magnet components may lead to difficulties in maintenance, recycling, and waste disposal. The present work expands upon previous, three-dimensional magnet shielding calculations for a modified version of the HYLIFE-I1 IFE power plant design. We present key magnet results as a function of the number of beams.
Date: July 5, 2000
Creator: Latkowski, J. F. & Meier, W. R.
Object Type: Article
System: The UNT Digital Library
High-Latitude Molecular Clouds as (Gamma)-ray Sources for GLAST (open access)

High-Latitude Molecular Clouds as (Gamma)-ray Sources for GLAST

For about two decades, a population of relative small and nearby molecular clouds has been known to exist at high Galactic latitudes. Lying more than 10{sup o} from the Galactic plane, these clouds have typical distances of {approx}150 pc, angular sizes of {approx}1{sup o}, and masses of order tens of solar masses. These objects are passive sources of high-energy {gamma}-rays through cosmic ray-gas interactions. Using a new wide-angle CO survey of the northern sky, we show that typical high-latitude clouds are not bright enough in {gamma}-rays to have been detected by EGRET, but that of order 100 of them will be detectable by the Large Area Telescope (LAT) on GLAST. Thus, we predict a new steady population of {gamma}-ray sources at high Galactic latitudes, perhaps the most numerous after active galactic nuclei.
Date: January 5, 2005
Creator: Torres, D F; Dame, T M & Digel, S W
Object Type: Article
System: The UNT Digital Library
Through Weld Inspection of Wrought Stainless Steel Piping Using Phased-Array Ultrasonic Probes. (open access)

Through Weld Inspection of Wrought Stainless Steel Piping Using Phased-Array Ultrasonic Probes.

A study was conducted to assess the ability of phased-array ultrasonic techniques to detect and accurately determine the size of flaws from the far-side of wrought austenitic piping welds. Far-side inspections of these welds are currently performed on a “best effort” basis and do not conform to ASME Code Section XI Appendix VIII performance demonstration requirements. For this study, four circumferential welds in 610mm diameter, 36mm thick ASTM A-358, Grade 304 vintage austenitic stainless steel pipe were examined. The welds were fabricated with varied welding parameters; both horizontal and vertical pipe orientations were used, with air and water backing, to simulate field welding conditions. A series of saw cuts, electro-discharge machined (EDM) notches, and implanted fatigue cracks were placed into the heat affected zones of the welds. The saw cuts and notches range in depth from 7.5% to 28.4% through-wall. The implanted cracks ranged in depth from 5% through wall to 64% through wall. The welds were examined with two phased-array probes, a 2.0 MHz transmit-receive longitudinal wave array and a 2.0 MHz transmit-receive shear wave array. These examinations showed that both phased-array transducers were able to detect and accurately length-size, but not depth size, all of the notches and …
Date: August 5, 2004
Creator: Anderson, Michael T.; Cumblidge, Stephen E. & Doctor, Steven R.
Object Type: Article
System: The UNT Digital Library
Search for New Physics at a Super-B Factory (open access)

Search for New Physics at a Super-B Factory

The importance of a Super-B Factory in the search for New Physics, in particular, due to CP-od phase(s) from physics beyond the Standard Model is surveyed. The first point to emphasize is that we know now how to directly measure all three angles of the unitarity triangle very cleanly, i. e. without theoretical assumptions with irreducible theory error {le} 1%; however this requires much more luminosity than is currently available at B-factories. Direct searches via penguin-dominated hadronic modes as well as radiative, pair-leptonic and semi-leptonic decays are also discussed. Null tests of the SM are stressed as these will play a crucial role especially if the effects of BSM phase(s) on B-physics are small.
Date: January 5, 2004
Creator: Browder, T. E. & Soni, A.
Object Type: Article
System: The UNT Digital Library
Signal and imaging sciences workshop 1999 proceedings (open access)

Signal and imaging sciences workshop 1999 proceedings

None
Date: January 5, 2001
Creator: Candy, J V
Object Type: Report
System: The UNT Digital Library
ICF Program: LDRD-ER Final Report (open access)

ICF Program: LDRD-ER Final Report

In the 01-ERD-107 LDRD-ER project, we have performed novel Thomson scattering experiments at the Trident and Omega laser facilities and provided high quality spectral data. These results have led to the development of the first quantitative understanding of laser-plasma interactions for NIF plasmas. For this purpose an green/ultraviolet probe laser, built for Nova in 1998 [1] and successfully used to measure both temperature and plasma wave amplitudes [2], has been deployed on Omega. The Thomson scattering diagnostics has been used twofold: (1) it provided independent measurements of the plasma electron and ion temperature, the plasma flow velocity, or the electron distribution function; (2) it provided measurements of the primary plasma wave and their secondary non-linear decay wave products. These experiments at Omega provide definitive quantitative results on the nonlinear saturation of stimulated Raman scattering for green (2{omega}) beams. In addition, the experiments on the Trident laser have led to a quantitative understanding of the stimulated Brillouin scattering in low-Z plasmas. A nonlinear frequency detuning model has successfully explained all the experimental observable including the SBS reflectivity. This model has been implemented into the laser-plasma interaction code pF3D as a tool to design and optimize NIF target experiments with SBS and …
Date: February 5, 2004
Creator: Glenzer, S H
Object Type: Report
System: The UNT Digital Library
STOCHASTIC COOLING POWER REQUIREMENTS. (open access)

STOCHASTIC COOLING POWER REQUIREMENTS.

A practical obstacle for stochastic cooling in high-energy colliders like RHIC is the large amount of power needed for the cooling system. Based on the coasting-beam Fokker-Planck (F-P) equation, we analytically derived the optimum cooling rate and cooling power for a beam of uniform distribution and a cooling system of linear gain function. The results indicate that the usual back-of-envelope formula over-estimated the cooling power by a factor of the mixing factor M. On the other hand, the scaling laws derived from the coasting-beam Fokker-Planck approach agree with those derived from the bunched-beam Fokker-Planck approach if the peak beam intensity is used as the effective coasting-beam intensity. A longitudinal stochastic cooling system of 4-8 GHz bandwidth in RHIC can effectively counteract intrabeam scattering, preventing the beam from escaping the RF bucket becoming debunched around the ring.
Date: July 5, 2004
Creator: Wei, J.; Blaskiewicz, M. & Brennan, M.
Object Type: Article
System: The UNT Digital Library