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A Temperature-Profile Method for Estimating Flow Processes inGeologic Heat Pipes (open access)

A Temperature-Profile Method for Estimating Flow Processes inGeologic Heat Pipes

Above-boiling temperature conditions, as encountered, forexample, in geothermal reservoirs and in geologic repositories for thestorage of heat-producing nuclear wastes, may give rise to stronglyaltered liquid and gas flow processes in porous subsurface environments.The magnitude of such flow perturbation is extremely hard to measure inthe field. We therefore propose a simple temperature-profile method thatuses high-resolution temperature data for deriving such information. Theenergy that is transmitted with the vapor and water flow creates a nearlyisothermal zone maintained at about the boiling temperature, referred toas a heat pipe. Characteristic features of measured temperature profiles,such as the differences in the gradients inside and outside of the heatpipe regions, are used to derive the approximate magnitude of the liquidand gas fluxes in the subsurface, for both steady-state and transientconditions.
Date: December 6, 2004
Creator: Birkholzer, Jens T.
System: The UNT Digital Library
Edge Localized Mode Dynamics and Transport in the Scrape-Off Layer of the DIII-D Tokamak (open access)

Edge Localized Mode Dynamics and Transport in the Scrape-Off Layer of the DIII-D Tokamak

High temporal and spatial resolution measurements in the boundary of the DIII-D tokamak show that edge localized modes (ELMs) are produced in the low field side, are poloidally localized and are composed of fast bursts ({approx}20 to 40 {micro}s long) of hot, dense plasma on a background of less dense, colder plasma ({approx}5 x 10{sup 18} m{sup {+-}3}, 50 eV) possibly created by the bursts themselves. The ELMs travel radially in the scrapeoff layer (SOL), starting at the separatrix at {approx}450 m/s, and slow down to {approx}150 m/s near the wall, convecting particles and energy to the SOL and walls. The temperature and density in the ELM plasma initially correspond to those at the top of the density pedestal but quickly decay with radius in the SOL. The temperature decay length ({approx}1.2 to 1.5 cm) is much shorter than the density decay length ({approx}3 to 8 cm), and the latter decreases with increasing pedestal (and SOL) density. The local particle and energy flux at the midplane wall during the bursts are 10% to 50% ({approx}1 to 2 x 10{sup 21} m{sup {+-}2} s{sup {+-}1}) and 1% to 2 % ({approx}20 to 30 kW/m{sup 2}) respectively of the LCFS average fluxes, …
Date: December 3, 2004
Creator: Boedo, J. A.; Rudakov, D. L.; Hollmann, E.; Gray, D. S.; Burrell, K. H.; Moyer, R. A. et al.
System: The UNT Digital Library
Experimental astrophysics with high power lasers and Z pinches (open access)

Experimental astrophysics with high power lasers and Z pinches

With the advent of high energy density (HED) experimental facilities, such as high-energy lasers and fast Z-pinch, pulsed-power facilities, mm-scale quantities of matter can be placed in extreme states of density, temperature, and/or velocity. This has enabled the emergence of a new class of experimental science, HED laboratory astrophysics, wherein the properties of matter and the processes that occur under extreme astrophysical conditions can be examined in the laboratory. Areas particularly suitable to this class of experimental astrophysics include the study of opacities relevant to stellar interiors; equations of state relevant to planetary interiors; strong shock driven nonlinear hydrodynamics and radiative dynamics, relevant to supernova explosions and subsequent evolution; protostellar jets and high Mach-number flows; radiatively driven molecular clouds and nonlinear photoevaporation front dynamics; and photoionized plasmas relevant to accretion disks around compact objects, such as black holes and neutron stars.
Date: December 10, 2004
Creator: Remington, B. A.; Drake, R. P. & Ryutov, D. D.
System: The UNT Digital Library
Dynamic response of materials on sub-nanosecond time scales, and beryllium properties for inertial confinement fusion (open access)

Dynamic response of materials on sub-nanosecond time scales, and beryllium properties for inertial confinement fusion

During the past few years, substantial progress has been made in developing experimental techniques capable of investigating the response of materials to dynamic loading on nanosecond time scales and shorter, with multiple diagnostics probing different aspects of the behavior. these relatively short time scales are scientifically interesting because plastic flow and phase changes in common materials with simple crystal structures--such as iron--may be suppressed, allowing unusual states to be induced and the dynamics of plasticity and polymorphism to be explored. Loading by laser ablation can be particularly convenient. The TRIDENT laser has been used to impart shocks and isentropic compression waves from {approx}1 to 200GPa in a range of elements and alloys, with diagnostics including surface velocimetry (line-imaging VISAR), surface displacement (framed area imaging), x-ray diffraction (single crystal and polycrystal), ellipsometry, and Raman spectroscopy. A major motivation has been the study of the properties of beryllium under conditions relevant to the fuel capsule in inertial confinement fusion: magnetically-driven shock and isentropic compression shots at Z were used to investigate the equation of state and shock melting characteristics, complemented by laser ablation experiments to investigate plasticity and heterogeneous response. These results will help to constrain acceptable tolerances on manufacturing, and possible …
Date: December 9, 2004
Creator: Swift, D. C.; Tierney, T. E.; Luo, S. N.; Paisley, D. L.; Kyrala, G. A.; Hauer, A. et al.
System: The UNT Digital Library
Smart Libraries: Best SQE Practices for Libraries with an Emphasis on Scientific Computing (open access)

Smart Libraries: Best SQE Practices for Libraries with an Emphasis on Scientific Computing

As scientific computing applications grow in complexity, more and more functionality is being packaged in independently developed libraries. Worse, as the computing environments in which these applications run grow in complexity, it gets easier to make mistakes in building, installing and using libraries as well as the applications that depend on them. Unfortunately, SQA standards so far developed focus primarily on applications, not libraries. We show that SQA standards for libraries differ from applications in many respects. We introduce and describe a variety of practices aimed at minimizing the likelihood of making mistakes in using libraries and at maximizing users' ability to diagnose and correct them when they occur. We introduce the term Smart Library to refer to a library that is developed with these basic principles in mind. We draw upon specific examples from existing products we believe incorporate smart features: MPI, a parallel message passing library, and HDF5 and SAF, both of which are parallel I/O libraries supporting scientific computing applications. We conclude with a narrative of some real-world experiences in using smart libraries with Ale3d, VisIt and SAF.
Date: December 15, 2004
Creator: Miller, M C; Reus, J F; Matzke, R P; Koziol, Q A & Cheng, A P
System: The UNT Digital Library
Spin Polarized Electron Energy Loss Spectroscopy on Fe(100) Thin Films Grown on Ag(100) (open access)

Spin Polarized Electron Energy Loss Spectroscopy on Fe(100) Thin Films Grown on Ag(100)

We report sharp spin-dependent energy loss features in electron scattering from bcc Fe(100) thin films grown on Ag(100). Majority spin features are observed at {approx}1.8 and 2.5 eV energy loss, and a minority spin feature is observed at {approx}2.0 eV energy loss. The majority spin peaks are attributed to spin-flip exchange scattering from the Fe films, with the lowest energy feature corresponding to the exchange splitting for the Fe. The minority spin peak is attributed to non-flip exchange scattering with an energy corresponding to the separation between occupied and unoccupied minority spin bands.
Date: December 1, 2004
Creator: Komesu, T; Waddill, G D & Tobin, J G
System: The UNT Digital Library
Severe plastic deformation through adiabatic shear banding in Fe-C steels (open access)

Severe plastic deformation through adiabatic shear banding in Fe-C steels

Severe plastic deformation is observed within adiabatic shear bands in iron-carbon steels. These shear bands form under high strain rate conditions, in excess of 1000 s{sup -1}, and strains in the order 5 or greater are commonly observed. Studies on shear band formation in a ultrahigh carbon steel (1.3%C) are described in the pearlitic condition. A hardness of 11.5 GPa (4600 MPa) is obtained within the band. A mechanism is described to explain the high strength based on phase transformation to austenite from adiabatic heating resulting from severe deformation. Rapid re-transformation leads to an ultra-fine ferrite grain size containing carbon principally in the form of nanosize carbides. It is proposed that the same mechanism explains the ultrahigh strength of iron-carbon steels observed in ball-milling, ball drop tests and in severely deformed wires.
Date: December 1, 2004
Creator: Lesuer, D; Syn, C & Sherby, O
System: The UNT Digital Library
Comparison of Varve and 14C Chronologies from Steel Lake, Minnesota, USA (open access)

Comparison of Varve and 14C Chronologies from Steel Lake, Minnesota, USA

Annually laminated sediments (varves) offer an effective means of acquiring high-quality paleoenvironmental records. However, the strength of a varve chronology can be compromised by a number of factors, such as missing varves, ambiguous laminations, and human counting error. We assess the quality of a varve chronology for the last three millennia from Steel Lake, Minnesota, through comparisons with nine AMS {sup 14}C dates on terrestrial plant macrofossils from the same core. These comparisons revealed an overall 8.4% discrepancy, primarily because of missing/uncountable varves within two stratigraphic intervals characterized by low carbonate concentrations and obscure laminations. Application of appropriate correction factors to these two intervals results in excellent agreement between the varve and {sup 14}C chronologies. These results, together with other varve studies, demonstrate that an independent age-determination method, such as {sup 14}C dating, is usually necessary to verify, and potentially correct, varve chronologies.
Date: December 29, 2004
Creator: Tian, J; Brown, T A & Hu, F S
System: The UNT Digital Library
Diagnostic potential of cosmic-neutrino absorption spectroscopy (open access)

Diagnostic potential of cosmic-neutrino absorption spectroscopy

Annihilation of extremely energetic cosmic neutrinos on the relic-neutrino background can give rise to absorption lines at energies corresponding to formation of the electroweak gauge boson Z{sup 0}. The positions of the absorption dips are set by the masses of the relic neutrinos. Suitably intense sources of extremely energetic (10{sup 21} - 10{sup 25}-eV) cosmic neutrinos might therefore enable the determination of the absolute neutrino masses and the flavor composition of the mass eigenstates. Several factors--other than neutrino mass and composition--distort the absorption lines, however. We analyze the influence of the time-evolution of the relic-neutrino density and the consequences of neutrino decay. We consider the sensitivity of the lineshape to the age and character of extremely energetic neutrino sources, and to the thermal history of the Universe, reflected in the expansion rate. We take into account Fermi motion arising from the thermal distribution of the relic-neutrino gas. We also note the implications of Dirac vs. Majorana relics, and briefly consider unconventional neutrino histories. We ask what kinds of external information would enhance the potential of cosmic-neutrino absorption spectroscopy, and estimate the sensitivity required to make the technique a reality.
Date: December 1, 2004
Creator: Barenboim, Gabriela; U., /Valencia; Mena Requejo, Olga; Quigg, Chris & /Fermilab
System: The UNT Digital Library
The SAMGrid monitoring service and its integration with MonALISA (open access)

The SAMGrid monitoring service and its integration with MonALISA

The SAMGrid team is in the process of implementing a monitoring and information service, which fulfills several important roles in the operation of the SAMGrid system, and will replace the first generation of monitoring tools in the current deployments. The first generation tools are in general based on text log-files and represent solutions which are not scalable or maintainable. The roles of the monitoring and information service are: (1) providing diagnostics for troubleshooting the operation of SAMGrid services; (2) providing support for monitoring at the level of user jobs; (3) providing runtime support for local configuration and other information which currently must be stored centrally (thus moving the system toward greater autonomy for the SAMGrid station services, which include cache management and job management services); (4) providing intelligent collection of statistics in order to enable performance monitoring and tuning. The architecture of this service is quite flexible, permitting input from any instrumented SAMGrid application or service. It will allow multiple backend storage for archiving of (possibly) filtered monitoring events, as well as real time information displays and active notification service for alarm conditions. This service will be able to export, in a configurable manner, information to higher level Grid monitoring …
Date: December 1, 2004
Creator: Lyon, A.; Vokac, P.; Zimmler, M.; Baranovski, G.; Garzoglio, G.; Loebel-Carpenter, L. et al.
System: The UNT Digital Library
Measurement of orbitally excited D-mesons at CDF II (open access)

Measurement of orbitally excited D-mesons at CDF II

Results of the first measurement of {sup 3}P orbitally excited neutral D-meson states, D*{sub 2}{sup 0} and D{sub 1}{sup 0}, produced in hadron collisions at the Tevatron are presented. Using data from the displaced track trigger, CDF II collects a large sample of these states in decay modes D*{sup +} {pi}{sup -}, D{sup +} {pi}{sup -}. Masses and widths of both states have been measured with precision better than or comparable to that of the world average.
Date: December 1, 2004
Creator: Gorelov, Igor V.
System: The UNT Digital Library
Integrated Cabin and Fuel Cell System Thermal Management with a Metal Hydride Heat Pump (open access)

Integrated Cabin and Fuel Cell System Thermal Management with a Metal Hydride Heat Pump

Integrated approaches for the heating and cooling requirements of both the fuel cell (FC) stack and cabin environment are critical to fuel cell vehicle performance in terms of stack efficiency, fuel economy, and cost. An integrated FC system and cabin thermal management system would address the cabin cooling and heating requirements, control the temperature of the stack by mitigating the waste heat, and ideally capture the waste heat and use it for useful purposes. Current work at the National Renewable Energy Laboratory (NREL) details a conceptual design of a metal hydride heat pump (MHHP) for the fuel cell system and cabin thermal management.
Date: December 1, 2004
Creator: Hovland, V.
System: The UNT Digital Library
Future hadron physics facilities at Fermilab (open access)

Future hadron physics facilities at Fermilab

Fermilab's hadron physics research continues in all its accelerator-based programs. These efforts will be identified, and the optimization of the Fermilab schedules for physics will be described. In addition to the immediate plans, the Fermilab Long Range Plan will be cited, and the status and potential role of a new proton source, the Proton Driver, is described.
Date: December 1, 2004
Creator: Appel, Jeffrey A.
System: The UNT Digital Library
Effects of polar solvents on the fracture resistance of dentin: Role of water hydration (open access)

Effects of polar solvents on the fracture resistance of dentin: Role of water hydration

Although healthy dentin is invariably hydrated in vivo, from a perspective of examining the mechanisms of fracture in dentin, it is interesting to consider the role of water hydration. Furthermore, it is feasible that exposure to certain polar solvents, e.g., those found in clinical adhesives, can induce dehydration. In the present study, in vitro deformation and fracture experiments, the latter involving a resistance-curve (R-curve) approach (i.e., toughness evolution with crack extension), were conducted in order to assess changes in the constitutive and fracture behavior induced by three common solvents - acetone, ethanol and methanol. In addition, nanoindentation-based experiments to evaluate the deformation behavior at the level of individual collagen fibers and ultraviolet Raman spectroscopy to evaluate changes in bonding were performed. The results indicate a reversible effect of chemical dehydration, with increased fracture resistance, strength, and stiffness associated with lower hydrogen bonding ability of the solvent. These results are analyzed both in terms of intrinsic and extrinsic toughening phenomena to further understand the micromechanisms of fracture in dentin and the specific role of water hydration.
Date: December 10, 2004
Creator: Ritchie, R. O.; Nalla, R. K.; Balooch, M.; Ager, J. W., III; Kruzic, J. J. & Kinney, J. H.
System: The UNT Digital Library
Morphology of Methane Hydrate Host Sediments. (open access)

Morphology of Methane Hydrate Host Sediments.

Results from simulated experiments in several laboratories show that host sediments influence hydrate formation in accord with known heterogeneity of host sediments at sites of gas hydrate occurrence (1). For example, in Mackenzie Delta, NWT Canada (Mallik 2L-38 well), coarser-grained units (pore-filling model) are found whereas in the Gulf of Mexico, the found hydrate samples do not appear to be lithologically controlled. We have initiated a systematic study of sediments, initially focusing on samples from various depths at a specific site, to establish a correlation with hydrate occurrence (or variations thereof) to establish differences in their microstructure, porosity, and other associated properties. The synchrotron computed microtomography (CMT) set-up at the X-27A tomography beam line at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory was used as a tool to study sediments from Blake Ridge at three sub bottom depths of 0.2, 50, and 667 meters. Results from the tomographic analysis of the deepest sample (667 m) are presented here to illustrate how tomography can be used to obtain new insights into the structures of methane hydrate host sediments. The investigation shows the internal grain/pore space resolution in the microstructure and a 3-D visualization of the connecting pathways obtained following …
Date: December 1, 2004
Creator: Jones, K. W.; Feng, H.; Tomov, S.; Winter, W. J.; Eaton, M. & Mahajan, D.
System: The UNT Digital Library
OEDGE Modeling of {sup 13}C Deposition in the Inner Divertor of DIII-D (open access)

OEDGE Modeling of {sup 13}C Deposition in the Inner Divertor of DIII-D

Use of carbon in tokamaks leads to a major tritium retention issue due to co-deposition. To investigate this process a low power (no beams) L-mode experiment was performed on DIII-D in which {sup 13}CH{sub 4} was puffed into the main vessel through the toroidally-symmetric pumping plenum at the top of lower single-null discharges. Subsequently, the {sup 13}C content of tiles taken from the vessel wall was measured. The interpretive OEDGE code was used to model the results. It was found that the {sup 13}C deposition pattern is controlled by: (a) source strength of {sup 13}C{sup +}, (b) radial location of the {sup 13}C{sup +} source, (c) D{sub {perpendicular}}, (d) M{sub {parallel}}, the scrape-off layer parallel Mach number. Best agreement was found for (a) {approx}50% conversion efficiency {sup 13}CH{sub 4} {yields} {sup 13}C{sup +}, (b) {sup 13}C{sup +} source {approx}3.5 cm outboard of separatrix near {sup 13}CH{sub 4} injection location, (c)D{sub {perpendicular}} {approx} 0.3 m{sup 2}s{sup -1}, (d) M{sub {parallel}} {approx} 0.4 toward inside.
Date: December 1, 2004
Creator: Elder, J.; Stangeby, P.; Whyte, D.; Allen, S.; McLean, A.; Boedo, J. et al.
System: The UNT Digital Library
Lambdastation: a forwarding and admission control service to interface production network facilities with advanced research network paths (open access)

Lambdastation: a forwarding and admission control service to interface production network facilities with advanced research network paths

Over the past several years, there has been a great deal of research effort and funding put into the deployment of optical-based, advanced technology wide-area networks. Fermilab and CalTech have initiated a project to enable our production network facilities to exploit these advanced research network facilities. Our objective is to forward designated data transfers across these advanced wide area networks on a per-flow basis, making use our capacious production-use storage systems connected to the local campus network. To accomplish this, we intend to develop a dynamically provisioned forwarding service that would provide alternate path forwarding onto available wide area advanced research networks. The service would dynamically reconfigure forwarding of specific flows within our local production-use network facilities, as well as provide an interface to enable applications to utilize the service. We call this service LambdaStation. If one envisions wide area optical network paths as high bandwidth data railways, then LambdaStation would functionally be the railroad terminal that regulates which flows at the local site get directed onto the high bandwidth data railways. LambdaStation is a DOE-funded SciDac research project in its very early stage of development.
Date: December 1, 2004
Creator: DeMar, Philip & Petravick, Don
System: The UNT Digital Library
The Effect of Small-Size Habitat Disturbances on Population Density and Time to Extinction of the Prairie Vole (open access)

The Effect of Small-Size Habitat Disturbances on Population Density and Time to Extinction of the Prairie Vole

We present a study, based on simulations with SERDYCA, a spatially-explicit individual-based model of rodent dynamics, on the relation between population persistence and the presence of numerous isolated disturbances in the habitat. We are specifically interested in the effect of disturbances that do not fragment the environment on population persistence. Our results suggest that the presence of disturbances in the absence of fragmentation can actually increase the average time to extinction of the modeled population. The presence of disturbances decreases population density but can increase the chance for mating in monogamous species and consequently, the ratio of juveniles in the population. It thus provides a better chance for the population to restore itself after a severe period with critically low population density. We call this the ''disturbance-forced localization effect''.
Date: December 13, 2004
Creator: Kostova, T & Carlsen, T
System: The UNT Digital Library
New charm results from FOCUS (open access)

New charm results from FOCUS

New results from the photoproduction experiment FOCUS are reported: Dalitz plot analysis, semileptonic form factor ratios and excited meson spectroscopy. The author reports on three new results from the photoproduction experiment FOCUS: the first Dalitz plot analysis of charm meson decays using the K-matrix approach[ 1], new measurements of the D{sub s}{sup +} {yields} {delta}(1020) {mu}{sup +}{nu} form factor ratios [2], and new measurements on L=1 excited meson spectroscopy [3], i.e., precise measurements of the masses and widths of the D*{sub 2}{sup +} and D*{sub 2}{sup 0} mesons, and evidence for broad states decaying to D{sup +}{pi}{sup -}, D{sup 0}{pi}{sup +} (the first such evidence in D{sup 0}{pi}{sup +}). The data for this paper were collected in the Wideband photoproduction experiment FOCUS during the Fermilab 1996-1997 fixed-target run.
Date: December 1, 2004
Creator: Bianco, Stefano
System: The UNT Digital Library
Dynamic Load Balancing of Parallel Monte Carlo Transport Calculations (open access)

Dynamic Load Balancing of Parallel Monte Carlo Transport Calculations

The performance of parallel Monte Carlo transport calculations which use both spatial and particle parallelism is increased by dynamically assigning processors to the most worked domains. Since the particle work load varies over the course of the simulation, this algorithm determines each cycle if dynamic load balancing would speed up the calculation. If load balancing is required, a small number of particle communications are initiated in order to achieve load balance. This method has decreased the parallel run time by more than a factor of three for certain criticality calculations.
Date: December 22, 2004
Creator: O'Brien, M; Taylor, J & Procassini, R
System: The UNT Digital Library
Surface Based Differential Forms (open access)

Surface Based Differential Forms

Higher-order basis functions have been constructed for surface-based differential forms that are used in engineering simulations. These surface-based forms have been designed to complement the volume-based forms present in EMSolve[1], a finite element code. The basis functions are constructed on a reference element and transformed, as necessary, for each element in space. Lagrange polynomials are used to create the basis functions. This approach is a necessary step in creating a hybrid finite-element/integral-equation time-domain code for electromagnetic analysis.
Date: December 14, 2004
Creator: Pingenot, J.; Yang, C.; Jandhyala, V.; Champagne, N.; White, D.; Stowell, M. et al.
System: The UNT Digital Library
Femtosecond laser writing of waveguide structures in sodium calcium silicate glasses (open access)

Femtosecond laser writing of waveguide structures in sodium calcium silicate glasses

Waveguides were written in soda lime silicate glasses with a composition of xNa{sub 2}O xCaO (1-2x)SiO{sub 2}, where x = 15 and 20, using an amplified femtosecond laser. The waveguides formed around, not inside the exposed regions. This is similar to the waveguide behavior our group first observed in a phosphate glass, Schott IOG-1, and is distinctly different from fused silica in which the waveguides are inside the exposed regions. This data supports the rapid quenching theory, i.e. that the exposed regions cool rapidly, locking in a glass structure with a high fictive temperature, with the dependence of the refractive index on the glass cooling rate determining the qualitative behavior of the waveguides.
Date: December 13, 2004
Creator: Reichman, W J; Click, C A & Krol, D M
System: The UNT Digital Library
Ghost signals in Allison emittance scanners (open access)

Ghost signals in Allison emittance scanners

For over 20 years, Allison scanners have been used to measure emittances of low-energy ion beams. We show that scanning large trajectory angles produces ghost signals caused by the sampled beamlet impacting on an electric deflection plate. The ghost signal strength is proportional to the amount of beam entering the scanner. Depending on the ions, and their velocity, the ghost signals can have the opposite or the same polarity as the main beam signals. The ghost signals cause significant errors in the emittance estimates because they appear at large trajectory angles. These ghost signals often go undetected because they partly overlap with the real signals, are mostly below the 1% level, and often hide in the noise. A simple deflection plate modification is shown to reduce the ghost signal strength by over 99%.
Date: December 1, 2004
Creator: Stockli, Martin P.; Leitner, M.; Moehs, D. P.; Keller, R. & Welton, R. F.
System: The UNT Digital Library
The 'Road Warrior' for the CDF Online Silicon Vertix Tracker (open access)

The 'Road Warrior' for the CDF Online Silicon Vertix Tracker

None
Date: December 1, 2004
Creator: Adelman, J.; Annovi, A.; Bardi, A.; Belforte, S.; Carosi, R.; Catastini, P. et al.
System: The UNT Digital Library