Anisoplanatic Performance of Horizontal-Path Speckle Imaging (open access)

Anisoplanatic Performance of Horizontal-Path Speckle Imaging

We have previously demonstrated and reported on the use of sub-field speckle processing for the enhancement of both near and far-range surveillance imagery of people and vehicles that have been degraded by atmospheric turbulence. We have obtained near diffraction-limited imagery in many cases and have shown dramatic image quality improvement in other cases. As it is possible to perform only a limited number of experiments in a limited number of conditions, we have developed a computer simulation capability to aid in the prediction of imaging performance in a wider variation of conditions. Our simulation capability includes the ability to model extended scenes in distributed turbulence. Of great interest is the effect of the isoplanatic angle on speckle imaging performance as well as on single deformable mirror and multiconjugate adaptive optics system performance. These angles are typically quite small over horizontal and slant paths. This paper will begin to explore these issues which are important for predicting the performance of both passive and active horizontal and slant-path imaging systems.
Date: July 1, 2003
Creator: Carrano, C J
System: The UNT Digital Library
Application of RAD-BCG calculator to Hanford's 300 area shoreline characterization dataset (open access)

Application of RAD-BCG calculator to Hanford's 300 area shoreline characterization dataset

Abstract. In 2001, a multi-agency study was conducted to characterize potential environmental effects from radiological and chemical contaminants on the near-shore environment of the Columbia River at the 300 Area of the U.S. Department of Energy’s Hanford Site. Historically, the 300 Area was the location of nuclear fuel fabrication and was the main location for research and development activities from the 1940s until the late 1980s. During past waste handling practices uranium, copper, and other heavy metals were routed to liquid waste streams and ponds near the Columbia River shoreline. The Washington State Department of Health and the Pacific Northwest National Laboratory’s Surface Environmental Surveillance Project sampled various environmental components including river water, riverbank spring water, sediment, fishes, crustaceans, bivalve mollusks, aquatic insects, riparian vegetation, small mammals, and terrestrial invertebrates for analyses of radiological and chemical constituents. The radiological analysis results for water and sediment were used as initial input into the RAD-BCG Calculator. The RAD-BCG Calculator, a computer program that uses an Excel® spreadsheet and Visual Basic® software, showed that maximum radionuclide concentrations measured in water and sediment were lower than the initial screening criteria for concentrations to produce dose rates at existing or proposed limits. Radionuclide concentrations measured …
Date: July 1, 2003
Creator: Antonio, Ernest J.; Poston, Ted M.; Tiller, Brett L. & Patton, Gene W.
System: The UNT Digital Library
Changes in Particle Pumping Due to Variation in Magnetic Balance Near Double-Null in DIII-D (open access)

Changes in Particle Pumping Due to Variation in Magnetic Balance Near Double-Null in DIII-D

OAK-B135 The authors report on a recent experiment examining how changes in the divertor magnetic balance affect the rate that particles can be pumped at the divertor targets. They find that both the edge density of the core plasma and divertor recycling play important roles in properly interpreting this pumping result. Previous studies on DIII-D have identified several important differences between double-null (DN) and single-null (SN) divertor operation. Small variations in the magnetic balance near-DN have large effects on both the power- and particle loadings at the divertor targets. These most likely result from an interplay between the plasma geometry and ion particle drifts, e.g., ''B x {del}B'' and ''E x B'' drifts. Other studies have shown that changes in magnetic balance affect the core plasma and where ELMs strike the vessel. In this paper, they examine how variations in the magnetic balance impact the rate at which particles are removed from the core plasma via pumping.
Date: July 1, 2003
Creator: Petrie, T. W.; Watkins, J. G.; Allen, S. L.; Brooks, N. H.; Fenstermacher, M. E.; Ferron, J. R. et al.
System: The UNT Digital Library
A Comparison of three high-precision quadrature schemes (open access)

A Comparison of three high-precision quadrature schemes

The authors have implemented three numerical quadrature schemes, using the new Arbitrary Precision (ARPREC) software package, with the objective of seeking a completely ''automatic'' arbitrary precision quadrature facility, namely one that does not rely on a priori information of the function to be integrated. Such a facility is required, for example, to permit the experimental identification of definite integrals based on their numerical values. The performance and accuracy of these three quadrature schemes are compared using a suite of 15 integrals, ranging from continuous, well-behaved functions on finite intervals to functions with vertical derivatives and integrable singularities at endpoints, as well as several integrals on an infinite interval.
Date: July 1, 2003
Creator: Bailey, David H. & Li, Xiaoye S.
System: The UNT Digital Library
Complete Suppression of the M/N = 2/1 Neoclassical Tearing Mode Using Radially Localized Electron Cyclotron Current Drive on Diii-D and the Requirements for Iter (open access)

Complete Suppression of the M/N = 2/1 Neoclassical Tearing Mode Using Radially Localized Electron Cyclotron Current Drive on Diii-D and the Requirements for Iter

A271 COMPLETE SUPPRESSION OF THE M/N = 2/1 NEOCLASSICAL TEARING MODE USING RADIALLY LOCALIZED ELECTRON CYCLOTRON CURRENT DRIVE ON DIII-D AND THE REQUIREMENTS FOR ITER. DIII-D experiments demonstrate the first real-time feedback control of the relative location of a narrow beam of microwaves to completely suppress and eliminate a growing tearing mode at the q = 2 surface. long wavelength tearing modes such as the m/n = 2/1 instability are particularly deleterious to tokamak operation. Confinement is seriously degraded by the island, plasma rotation can cease (mode-lock) and disruption can occur. The neoclassical tearing mode (NTM) becomes unstable due to the presence of a helically-perturbed bootstrap current and can be stabilized by replacing the missing bootstrap current in the island O-point by precisely located co-electron cyclotron current drive (ECCD). The optimum position is found when the DIII-D plasma control system (PCS) is put into a search and suppress mode that makes small radial shifts (in about 1 cm steps) in the ECCD location based on minimizing the Mirnov amplitude. Requirements for ITER are addressed.
Date: July 1, 2003
Creator: Lahaye, R. J.; Luce, T. C.; Petty, C. C.; Humphreys, D. A.; Hyatt, A. W.; Perkins, F. W. et al.
System: The UNT Digital Library
A Conceptual and Numerical Model for Thermal-Hydrological-Chemical Processes in the Yucca Mountain Drift Scale Test (open access)

A Conceptual and Numerical Model for Thermal-Hydrological-Chemical Processes in the Yucca Mountain Drift Scale Test

A numerical model was developed to predict the coupled thermal, hydrological, and chemical (THC) processes accompanying the Drift Scale Test (DST) at Yucca Mountain, NV. The DST has been closely monitored through the collection of gas, water, and mineral samples as well as thermal, hydrological, and mechanical measurements. A two-dimensional dual permeability model was developed to evaluate multiphase, multicomponent, reaction-transport processes in the fractured tuff. Comparisons between results using the TOUGHREACT code and measured water (e.g., pH, SiO2(aq), Na+, K+) and gas (CO2) compositions show that the model captures the chemical evolution in the DST. Non-reactive aqueous species (e.g., Cl) show strong dilution in fracture waters, indicating little fracture-matrix interaction. Silica concentrations are higher than in the initial pore water and show a trend of increasing reaction with fracture-lining silicates at higher temperatures. The narrow precipitation zone of predominantly amorphous silica observed above the heaters was also captured.
Date: July 1, 2003
Creator: Sonnenthal, Eric L.; Spycher, Nicolas F.; Conrad, Mark & Apps, John
System: The UNT Digital Library
Correlation between exchange bias and pinned interfacialspins (open access)

Correlation between exchange bias and pinned interfacialspins

Using x-ray magnetic circular dichroism, we have detectedthe very interfacial spins that are responsible for the horizontal loopshift in three different exchange bias sandwiches, chosen because oftheir potential for device applications. The "pinned" uncompensatedinterfacial spins constitute only a fraction of a monolayer and do notrotate in an external magnetic field since they are tightly locked to theantiferromagnetic lattice. A simple extension of the Meiklejohn and Beanmodel is proposed to account quantitatively for the exchange bias fieldsin the three studied systems from the experimentally determined number ofpinned moments and their sizes.
Date: July 1, 2003
Creator: Ohldag, H.; Scholl, A.; Nolting, F.; Arenholz, E.; Maat, S.; Young, A. T. et al.
System: The UNT Digital Library
Current Drive and Pressure Profile Modification with Electron Cyclotron Power in DIII-D Quiescent Double Barrier Experiments (open access)

Current Drive and Pressure Profile Modification with Electron Cyclotron Power in DIII-D Quiescent Double Barrier Experiments

OAK-B135 High confinement mode (H-mode) operation is a leading scenario for burning plasma devices due to its inherently high energy-confinement characteristics. The quiescent H-mode (QH-mode) offers these same advantages with the additional attraction of more steady edge conditions where the highly transient power loads due to edge localized mode (ELM) activity is replaced by the steadier power and particle losses associated with an edge harmonic oscillation (EHO). With the addition of an internal transport barrier (ITB), the capability is introduced for independent control of both the edge conditions and the core confinement region giving potential control of fusion power production for an advanced tokamak configuration. The quiescent double barrier (QDB) conditions explored in DIII-D experiments exhibit these characteristics and have resulted in steady plasma conditions for several confinement times ({approx} 26 {tau}{sub E}) with moderately high stored energy, {beta}{sub N}H{sub 89} {approx} 7 for 10 {tau}{sub E}.
Date: July 1, 2003
Creator: Casper, T. A.; Burrell, K. H.; Doyle, E. J.; Gohil, P.; Greenfield, C. M.; Groebner, R. J. et al.
System: The UNT Digital Library
Diagnostic studies of polyolefin separators in high-power lithium-ion cells (open access)

Diagnostic studies of polyolefin separators in high-power lithium-ion cells

None
Date: July 1, 2003
Creator: Kostecki, Robert; Norin, Laura; Song, Xiangyun & McLarnon, Frank
System: The UNT Digital Library
Dynamics of the flame flowfields in a low-swirl burner (open access)

Dynamics of the flame flowfields in a low-swirl burner

The concept of using low swirl to stabilize lean premixed turbulent flame was introduced in 1992. Since then, the low-swirl burner (LSB) has become a useful laboratory tool for the study of detailed flame structures as well as turbulent burning speeds. Its main attribute is that the flame is freely propagating and is locally normal to the turbulent approach flow (Figure 1). Therefore, the turbulent flame brush is not influence by physical boundaries. The capability of LSB to support very lean flames and very turbulent flames [1, 2] was further exploited in recent studies to test the validity of the flame regime concept. Using 2D imaging diagnostics (e.g. planar laser induced fluorescence, PLIF, and planar laser induced Rayleigh scattering) our analysis showed that the wrinkled flame regime to be valid at a turbulence intensity level much higher than previously thought [3-5]. This provided experimental verification of a new 'thin reaction zone' regime for the Kalovitz number range of 1 < Ka < 10 (Ka = (u{prime}/s{sub L}){sup 3/2} (l{sub x}/d{sub L}){sup 1/2}) proposed by Peters. Due to its freely propagating nature, modeling and simulations of LSB flames are non-trivial. The flame position cannot be specified a priori because it is …
Date: July 1, 2003
Creator: Cheng, Robert; Johnson, Matthew R. & Cheng, Robert K.
System: The UNT Digital Library
Dynamics of the flame flowfields in a low-swirl burner (open access)

Dynamics of the flame flowfields in a low-swirl burner

None
Date: July 1, 2003
Creator: Cheng, Robert; Johnson, Matthew R. & Cheng, Robert K.
System: The UNT Digital Library
Effect of ION B Drift Direction on Turbulence Flow and Flow Shear (open access)

Effect of ION B Drift Direction on Turbulence Flow and Flow Shear

The divertor magnetic geometry has a significant effect on the poloidal flow and resulting flow shear of turbulence in the outer region of L-mode tokamak plasmas, as determined via two-dimensional measurements of density fluctuations with Beam Emission Spectroscopy on DIII-D. Plasmas with similar parameters, except that in one case the ion {del}B drift points towards the divertor X-point (lower single-null, LSN), and in the other case, the ion {del}B drift points away from the divertor X-point (upper single-null, USN), are compared. Inside of r/a=0.9, the turbulence characteristics (amplitude, flow direction, correlation lengths) are similar in both cases, while near r/a=0.92, a dramatic reversal of the poloidal flow of turbulence relative to the core flow direction is observed in plasmas with the ion {del}B drift pointing towards the divertor X-point. No such flow reversal is observed in plasmas with the ion {del}B drift pointing away from the divertor X-point. This poloidal flow reversal results in a significantly larger local shear in the poloidal turbulence flow velocity in plasmas with the ion {del}B drift pointing towards the divertor X-point. Additionally, these plasmas locally exhibit significant dispersion, with two distinct and counter-propagating turbulence modes. Likewise, the radial correlation length of the turbulence is …
Date: July 1, 2003
Creator: Fenzi, C.; McKee, G. R.; Burrell, K. H.; Carlstrom, T. N.; Fonick, R. J. & Groebner, R. J.
System: The UNT Digital Library
Electron Cyclotron Current Drive in Diii-D: Experiment and Theory (open access)

Electron Cyclotron Current Drive in Diii-D: Experiment and Theory

A271 ELECTRON CYCLOTRON CURRENT DRIVE IN DIII-D: EXPERIMENT AND THEORY. Experiments on the DIII-D tokamak in which the measured off-axis electron cyclotron current drive has been compared systematically to theory over a broad range of parameters have shown that the Fokker-Planck code CQL3D provides an excellent model of the relevant current drive physics. This physics understanding has been critical in optimizing the application of ECCD to high performance discharges, supporting such applications as suppression of neoclassical tearing modes and control and sustainment of the current profile.
Date: July 1, 2003
Creator: Prater, R.; Petty, C. C.; Luce, T. C.; Harvey, R. W.; Choi, M.; Lahaye, R. J. et al.
System: The UNT Digital Library
Electron Temperature Fluctuations and Cross-Field Heat Transport in the Edge of Diii-D (open access)

Electron Temperature Fluctuations and Cross-Field Heat Transport in the Edge of Diii-D

OAK-B135 The fluctuating E x B velocity due to electrostatic turbulence is widely accepted as a major contributor to the anomalous cross-field transport of particles and heat in the tokamak edge and scrape-off layer (SOL) plasmas. This has been confirmed by direct measurements of the turbulent E x B transport in a number of experiments. Correlated fluctuations of the plasma radial velocity v{sub r}, density n, and temperature T{sub e} result in time-average fluxes of particles and heat given by (for electrons): Equation 1--{Lambda}{sub r}{sup ES} = <n{tilde v}{sub r}> = 1/B{sub {var_phi}}<{tilde n}{tilde E}{sub {theta}}; Equation 2--Q{sub r}{sup ES} = <n T{sub e} {tilde v}{sub r}> {approx} 3/2 kT{sub e}{Lambda}{sub r}{sup ES} + 3 n{sub e}/2 B{sub {var_phi}} <k{tilde T}{sub e}{tilde E}{sub {theta}}> = Q{sub conv} + Q{sub cond}. The first term in Equation 2 is referred to as convective and the second term as conductive heat flux. Experimental determination of fluxes given by Equations 1 and 2 requires simultaneous measurements of the density, temperature and poloidal electric field fluctuations with high spatial and temporal resolution. Langmuir probes provide most readily available (if not the only) tool for such measurements. However, fast measurements of electron temperature using probes are …
Date: July 1, 2003
Creator: Rudakov, D. L.; Boedo, J. A.; Moyer, R. A.; Kraseninnikov, S.; Mahdavi, M. A.; McKee, G. R. et al.
System: The UNT Digital Library
An energy standard for residential buildings in south China (open access)

An energy standard for residential buildings in south China

To curb the spiraling demand for building energy use, China's Ministry of Construction has worked at developing and implementing building energy standards, starting with a standard for heated residential buildings in the Cold regions in 1986, followed by a standard for residential buildings in the Hot Summer Cold Winter Region in central China in 2001. In July 2001, a similar effort was started to develop a standard for residential buildings in the Hot Summer Warm Winter Region, comprising of the entirety or large portions of Guangdong, Guangxi, Hainan and Fujian. The target for the standard is to improve the thermal efficiency of buildings by 50 percent compared to current construction, which are typically uninsulated and have single-pane windows. Because of the importance of controlling window solar gain, the standard developed tables specifying the required window thermal transmittance and shading coefficient for differing window-to-wall ratios. The intent of such trade-off table is to permit flexibility in the location and size of windows, as long as their thermal performances meet the requirements of the standard. For further flexibility, the standard provides three methods of compliance: (1) a simple set of prescriptive requirements, (2) a simplified performance calculation, and (3) a detailed computer-based …
Date: July 1, 2003
Creator: Huang, Yu Joe; Lang, Siwei; Hogan, John & Lin, Haiyan
System: The UNT Digital Library
Fine-grained authorization for job and resource management usingakenti and the globus toolkit(R) (open access)

Fine-grained authorization for job and resource management usingakenti and the globus toolkit(R)

As the Grid paradigm is adopted as a standard way of sharing remote resources across organizational domains, the need for fine-grained access control to these resources increases. This paper presents an authorization solution for job submission and control, developed as part of the National Fusion Collaboratory, that uses the Globus Toolkit 2 and the Akenti authorization service in order to perform fine-grained authorization of job and resource management requests in a Gridenvironment. At job startup, it allows the system to evaluate a user's Resource Specification Language request against authorization policies on resource usage determining how many CPUs or memory a user can use on a given resource or which executables the user can run based on authorization policies, it allows other virtual organization members to manage the user's job.
Date: July 1, 2003
Creator: Thompson, Mary R.; Essiari, Abdelilah; Keahey, Kate; Welch, Von; Lang, S. & Liu, Bo
System: The UNT Digital Library
Fullerene Coalescence in Nanopeapods: A Path to Novel Tubular Carbon (open access)

Fullerene Coalescence in Nanopeapods: A Path to Novel Tubular Carbon

Article on fullerene coalescence in nanopeapods, which is responsible for forming stable zeppelinlike carbon molecules.
Date: July 1, 2003
Creator: Hernández, E.; Meunier, Vincent; Smith, B. W.; Rurali, R.; Terrones, Humberto; Buongiorno Nardelli, Marco et al.
System: The UNT Digital Library
GRETA - Gamma ray energy tracking array (open access)

GRETA - Gamma ray energy tracking array

None
Date: July 1, 2003
Creator: Lee, I.Y.
System: The UNT Digital Library
HIFLUX: OBLATE FRCS, DOUBLE HELICES,SPHEROMAKS AND RFPS IN ONE SYSTEM (open access)

HIFLUX: OBLATE FRCS, DOUBLE HELICES,SPHEROMAKS AND RFPS IN ONE SYSTEM

OAK-B135 High magnetic flux is required for thermonuclear FRC reactors and, more immediately, to advance the FRC experimental program in general. Oblate FRCs are of special interest because they are predicted to have certain improved MHD stability over elongated FRCs, and oblate FRCs may yield the most compact, magnetically confined fusion reactors. Neither oblate nor high-flux FRCs have been investigated experimentally to date. Our presently proposed technique is to make two high-flux, oppositely-handed plasmas by a pair of large, external, reversed-field pinch (RFP) sources. The plasmas would propagate as two Taylor-relaxed double-helix plasmas, to an oblate main plasma chamber, where they would relax further to a counter-helicity pair of spheromaks, which would finally merge into a single high-flux FRC. A concept for a new experimental facility, HIFLUX, to make and study high-magnetic-flux oblate Field-Reversed Configuration (FRC) plasmas, is described. Similar principles might also enable high flux non-inductive startup of other plasma devices.
Date: July 1, 2003
Creator: SCHAFFER,MJ & BOEDO,JA
System: The UNT Digital Library
Indoor air quality, ventilation and health symptoms in schools: An analysis of existing information (open access)

Indoor air quality, ventilation and health symptoms in schools: An analysis of existing information

None
Date: July 1, 2003
Creator: Daisey, Joan M.; Angell, William J. & Apte, Michael G.
System: The UNT Digital Library
Indoor Pollutant Mixing Time in an Isothermal Closed Room: An Investigation Using CFD (open access)

Indoor Pollutant Mixing Time in an Isothermal Closed Room: An Investigation Using CFD

We report on computational fluid dynamics (CFD) predictions of mixing time of a pollutant in an unventilated, mechanically mixed, isothermal room. The study aims to determine: (1) the adequacy of the standard Reynolds Averaged Navier Stokes two-equation ({kappa}-{var_epsilon}) turbulence model for predicting the mixing time under these conditions and (2) the extent to which the mixing time depends on the room airflow, rather than the source location within the room. The CFD simulations modeled the 12 mixing time experiments performed by Drescher et al. (Indoor Air 5 (1995) 204) using a point pulse release in an isothermal, sealed room mechanically mixed with variable power blowers. Predictions of mixing time were found in good agreement with experimental measurements, over an order of magnitude variation in blower power. Additional CFD simulations were performed to investigate the relation between pollutant mixing time and source location. Seventeen source locations and five blower configurations were investigated. Results clearly show large dependence of the mixing time on the room airflow, with some dependence on source location. We further explore dependence of mixing time on the velocity and turbulence intensity at the source location. Implications for positioning air-toxic sensors in rooms are briefly discussed.
Date: July 1, 2003
Creator: Gadgil, A. J.; Lobscheid, C.; Abadie, M. O. & Finlayson, E. U.
System: The UNT Digital Library
The integration of cryogenic cooling systems with superconducting electronic systems (open access)

The integration of cryogenic cooling systems with superconducting electronic systems

The need for cryogenic cooling has been critical issue that has kept superconducting electronic devices from reaching the market place. Even though the performance of the superconducting circuit is superior to silicon electronics, the requirement for cryogenic cooling has put the superconducting devices at a disadvantage. This report will talk about the various methods for refrigerating superconducting devices. Cryocooler types will be compared for vibration, efficiency, and cost. Some solutions to specific problems of integrating cryocoolers to superconducting devices are presented.
Date: July 1, 2003
Creator: Green, Michael A.
System: The UNT Digital Library
Interactive protein manipulation (open access)

Interactive protein manipulation

We describe an interactive visualization and modeling program for the creation of protein structures ''from scratch''. The input to our program is an amino acid sequence -decoded from a gene- and a sequence of predicted secondary structure types for each amino acid-provided by external structure prediction programs. Our program can be used in the set-up phase of a protein structure prediction process; the structures created with it serve as input for a subsequent global internal energy minimization, or another method of protein structure prediction. Our program supports basic visualization methods for protein structures, interactive manipulation based on inverse kinematics, and visualization guides to aid a user in creating ''good'' initial structures.
Date: July 1, 2003
Creator: SNCrivelli@lbl.gov
System: The UNT Digital Library
Intermediates and the folding of proteins L and G (open access)

Intermediates and the folding of proteins L and G

We use a minimalist protein model, in combination with a sequence design strategy, to determine differences in primary structure for proteins L and G that are responsible for the two proteins folding through distinctly different folding mechanisms. We find that the folding of proteins L and G are consistent with a nucleation-condensation mechanism, each of which is described as helix-assisted {beta}-1 and {beta}-2 hairpin formation, respectively. We determine that the model for protein G exhibits an early intermediate that precedes the rate-limiting barrier of folding and which draws together misaligned secondary structure elements that are stabilized by hydrophobic core contacts involving the third {beta}-strand, and presages the later transition state in which the correct strand alignment of these same secondary structure elements is restored. Finally the validity of the targeted intermediate ensemble for protein G was analyzed by fitting the kinetic data to a two-step first order reversible reaction, proving that protein G folding involves an on-pathway early intermediate, and should be populated and therefore observable by experiment.
Date: July 1, 2003
Creator: Brown, Scott & Head-Gordon, Teresa
System: The UNT Digital Library