505 Matching Results

Search Results

Advanced search parameters have been applied.

in subjects: "Topography"

open access

Topographic power spectral density study of the effect of surface treatment processes on niobium for superconducting radio frequency accelerator cavities

Microroughness is viewed as a critical issue for attaining optimum performance of superconducting radio frequency accelerator cavities. The principal surface smoothing methods are buffered chemical polish (BCP) and electropolish (EP). The resulting topography is characterized by atomic force microscopy (AFM). The power spectral density (PSD) of AFM data provides a more thorough description of the topography than a single-value roughness measurement. In this work, one dimensional average PSD fun… more

Date: April 1, 2012

Creator: Charles Reece, Hui Tian, Michael Kelley, Chen Xu

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Localization of Volcanic Activity: Topographic Effects on Dike Propagation, Eruption and COnduit Formation

Magma flow in a dike rising in a crack whose strike runs from a highland or a ridge to an adjacent lowland has been modeled to determine the effect of topography on the flow. It is found that there is a distinct tendency for the flow to be diverted away from the highland end of the strike toward the lowland. Separation of the geometric effect of the topography from its effect on lateral confining stresses on the crack indicates that both contribute to the effect but that the effect of stress is… more

Date: May 12, 2006

Creator: Gaffney, E.S. & Damjanac, B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Modeling the Effects of Crevice Former, Partculates, and the Evolving Surface Profile in Crevice Corrsion

Crevice corrosion is an important mode of localized corrosion to be evaluated for the long-term performance of corrosion resistant alloys in high temperature, aqueous environments. This work focuses on the evolution of corrosion damage of Ni-Cr-Mo alloys in hot brines. For the initiation of crevice corrosion, a critical crevice chemistry must develop within the crevice to break down the passive film. The geometry of the crevice and particularly the height of the crevice gap is an important para… more

Date: June 9, 2006

Creator: Landau, U.; Agarwal, A. S.; Shan, X. & Payer, J. H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Dilute Surfactant Methods for Carbonate Formations: Final Report

There are many fractured carbonate reservoirs in US (and the world) with light oil. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). The process of using dilute anionic surfactants in alkaline solutions has been investigated in this work for oil recovery from fractured oil-wet carbonate reservoirs both experimentally and numerically. Thi… more

Date: February 1, 2006

Creator: Mohanty, Kishore K.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

A Wildfire Behavior Modeling System at Los Alamos National Laboratory for Operational Applications

To support efforts to protect facilities and property at Los Alamos National Laboratory from damages caused by wildfire, we completed a multiyear project to develop a system for modeling the behavior of wildfires in the Los Alamos region. This was accomplished by parameterizing the FARSITE wildfire behavior model with locally gathered data representing topography, fuels, and weather conditions from throughout the Los Alamos region. Detailed parameterization was made possible by an extensive mon… more

Date: November 1, 2004

Creator: Koch, S.W. & R.G.Balice

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Incorporation of Chemical Reactions into Building-scale Flow

Many hazardous atmospheric releases involve chemical reactions that occur within a few kilometers of the source. Reactions with commonly occurring atmospheric compounds such as the OH radical, can transform and potentially neutralize original release compounds. Especially in these cases, accurately resolving flow around nearby structures and over surrounding topography can be critical to correctly predicting material dispersion, and thus, the extent of any hazard. Accurate prediction of materia… more

Date: October 30, 2003

Creator: Humphreys, T D; Jayaweera, T M & Lee, R L

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A Combined Experimental and Computational Approach for the Design of Mold Topography that Leads to Desired Ingot Surface and Microstructure in Aluminum Casting.

A coupled thermomechanical, thermal transport and segregation analysis of aluminum alloys solidifying on uneven surfaces is presented here. Uneven surfaces are modelled as sinusoids with different wavelengths and amplitudes. Effects of various coupling mechanisms between the solid-shell deformation, air-gap formation, heat transfer, fluid flow and segregation, near the mold-metal interface, are observed for different mold topographies during the early stages of solidification of an aluminum all… more

Date: September 28, 2005

Creator: Dr. Zabaras, N. & Samanta, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Good terrain geometry, cheap!

Real-time terrain rendering for interactive visualization remains a demanding task. We present a novel algorithm with several advantages over previous methods: our method is unusually stingy with polygons yet achieves real-time performance and is scalable to arbitrary regions and resolutions. The method provides a continuous terrain mesh of specified triangle count having provably minimum error in restricted but reasonably general classes of permissible meshes and error metrics. Our method prov… more

Date: April 1, 1997

Creator: Duchaineau, M.; Wolinsky, M. & Sigeti, D.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Determination of absolute interferometric phase using the beam-amplitude ratio technique

Determination of the absolute phase difference (i.e., not modulo 2{pi}) is a key problem in interferometric synthetic aperture radar (IFSAR) for topographic mapping. One way of solving this problem requires use of a technique different from the basic interferometry to resolve a `coarse` angle measurement that lies within the IFSAR ambiguity angle. The method investigated in this paper involves taking advantage of the difference in the amplitude ratio versus elevation angle that occurs when the … more

Date: March 1, 1996

Creator: Bickel, D.L. & Hensley, W.H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Water vapor retrieval over many surface types

In this paper we present a study of of the water vapor retrieval for many natural surface types which would be valuable for multi-spectral instruments using the existing Continuum Interpolated Band Ratio (CIBR) for the 940 nm water vapor absorption feature. An atmospheric code (6S) and 562 spectra were used to compute the top of the atmosphere radiance near the 940 nm water vapor absorption feature in steps of 2.5 nm as a function of precipitable water (PW). We derive a novel technique called `… more

Date: April 1, 1996

Creator: Borel, C.C.; Clodius, W.C. & Johnson, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

System administrator`s guide to CDPS. Version 1.0

The System Administrator`s Guide to CDPS is intended for those responsible for setting up and maintaining the hardware and software of a Common Mapping Standard (CMS) Date Production System (CDPS) installation. This guide assists the system administrator in performing typical administrative functions. It is not intended to replace the Ultrix Documentation Set that should be available for a DCPS installation. The Ultrix Documentation Set will be required to provide details on referenced Ultrix c… more

Date: May 1, 1994

Creator: Didier, B. T. & Portwood, M. H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Seismic Analysis of Morrow Point Dam

The main objective of this study is to perform nonlinear dynamic earthquake time history analyses on Morrow Point Dam, which is located 263 km southwest of Denver, Colorado. This project poses many significant technical challenges, one of which is to model the entire Morrow Point Dam/Foundation Rock/Reservoir system which includes accurate geology topography. In addition, the computational model must be initialized to represent the existing dead loads on the structure and the stress field cause… more

Date: April 1, 2002

Creator: Noble, C R

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Analysis of ''echo sounding'' data North-Central Pacific. Progress report, February 1, 1974--October 15, 1974

No Description Available.

Date: January 1, 1974

Creator: Hayes, D.E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Pre-shot simulations of far-field ground motion for the Source Physics Experiment (SPE) Explosions at the Climax Stock, Nevada National Security Site: SPE2

The Source Physics Experiment (SPE) is planning a 1000 kg (TNT equivalent) shot (SPE2) at the Nevada National Security Site (NNSS) in a granite borehole at a depth (canister centroid) of 45 meters. This shot follows an earlier shot of 100 kg in the same borehole at a depth 60 m. Surrounding the shotpoint is an extensive array of seismic sensors arrayed in 5 radial lines extending out 2 km to the north and east and approximately 10-15 to the south and west. Prior to SPE1, simulations using a fin… more

Date: October 18, 2011

Creator: Mellors, R J; Rodgers, A; Walter, W; Ford, S; Xu, H; Matzel, E et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Photothermal Multi-Pixel Imaging Microscope

Photothermal microscopy is a useful nondestructive tool for the identification of fluence-limiting defects in optical coatings. Traditional photothermal microscopes are single-pixel detection devices. Samples are scanned under the microscope to generate a defect map. For high-resolution images, scan times can be quite long (1 mm{sup 2} per hour). Single-pixel detection has been used traditionally because of the ease in separating the laser-induced topographical change due to defect absorption f… more

Date: December 1, 2003

Creator: Stolz, C J; Chinn, D J; Huber, R D; Weinzapfel, C L & Wu, Z

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Field investigation of a wake structure downwind of a VAWT in a windfarm array

The effects of upwind turbine wakes on the performance of a FloWind 17-m VAWT were investigated through a series of field experiments conducted at the FloWind windfarm on Cameron Ridge, Tehachapi, California. The field experiment was conducted within a VAWT array consisting of more than nine VAWTs with separations 3D crosswised by 8D downwind (where D is the turbine diameter) in a staggered configuration. The array is the upwind three rows of VAWTS in a total of six rows that are on top of the … more

Date: October 1, 1987

Creator: Liu, H. T.; Buck, J. W.; Germain, A. C.; Hinchee, M. E.; Solt, T. S.; LeRoy, G. M. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Performance of Bare and Sol-Gel Coated DKDP Crystal Surfaces Exposed to Multiple 351-nm Laser Pulses in Vacuum and Air

We have investigated the surface degradation of bare and sol-gel coated deuterated potassium dihydrogen phosphate (DKDP) crystals when exposed to 351-nm laser pulses in atmospheric air and nitrogen and at pressures ranging from atmospheric down to 10{sup -5} Torr vacuum. Optical microscopy, surface topography, surface chemical analyses, 351-nm pumped photoemission maps, and photometry results have been used to characterize these samples. We report the occurrence of two potentially linked surfac… more

Date: December 19, 2001

Creator: Whitman, P. K.; Norton, M.; Nostrand, M.; Molander, W.; Nelson, A.; Engelhard, M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Spatial and Temporal Patterns of Carbon Storage and Species Richness in Three South Carolina Coastal Plain Riparian Forests

Micro-topographic variations in carbon storage and their spatial distribution with respect to vegetation were studied in the Pen Branch system as well as intermediate and late successional forests. Overall measurements of above-ground biomass, soil carbon, and stand structure indicate rapid convergence with the patterns in late successional forests. Micro-site differences were small.

Date: March 19, 1999

Creator: Giese, Laura A.; Aust, W. Michael; Trettin, Carl C. & Kolka, Randall K.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Surface Analytical Study of CuInSe2 Treated in Cd-Containing Partial Electrolyte Solution

Junction formation in CuInSe2 (CIS) has been studied by exposing thin films and single-crystal samples to solutions containing NH4OH and CdSO4. The treated samples were analyzed by secondary ion mass spectrometry to determine the amount and distribution of Cd deposited on the surface of the films. Cadmium is found to react with the surface for all the solution exposure times and temperatures studied. The reaction rapidly approaches the endpoint and remains relatively unchanged for subsequent so… more

Date: November 19, 1998

Creator: Asher, S. E.; Ramanathan, K.; H., Wiesner; Moutinho, H. (National Renewable Energy Laboratory) & Niles, D. W. (Hewlett-Packard Corporation)

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Model for the formation of longshore sand ridges on the continental shelf

A model is proposed for the formation and evolution of three- dimensional sedimentary structures such as longshore sand ridges on the continental shelf in water deeper than that of the shoaling region. Owing to the striking similarity between the bar spacing and the length scales in which interactions among the most energetic modes of shallow water waves take place, we argue that these bars are formed slowly by flows in the turbulent boundary layer generated by weakly nonlinear, dispersive wave… more

Date: January 5, 1994

Creator: Restrepo, J. M. & Bona, J. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Siting technologies for large wind turbine clusters

Site selection for large wind turbine clusters requires thorough documentation of the wind characteristics at the site, because of the influence these characteristics will have on the economics, operations, and service life of the wind turbines. The wind prospecting strategy can be used by a utility to determine specific locations for each wind turbine in a cluster of 10 to 50 or more machines. The key to site selection is knowing what and where to measure. Siting techniques to be used at the v… more

Date: November 1, 1979

Creator: Hiester, T. R. & Pennell, W. T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Measuring sphericity on a roundness gage

The three-dimensional geometry of a spherical object may be determined by evaluation of a number of two-dimensional roundness measurements which have a known orientation with respect to one another. A suitable set of orientations appears to be one in which the plane of each roundness measurement coincides with every other such plane along a single diameter of the sphere. A device for producing the required set of orientations, adaptable to spheres of varying diameters and designed to avoid dama… more

Date: January 1, 1980

Creator: Gauler, A. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Areally averaged estimates of surface heat flux from ARM field studies

The determination of areally averaged surface fluxes is a problem of fundamental interest to the Atmospheric Radiation Measurement (ARM) program. The Cloud And Radiation Testbed (CART) sites central to the ARM program will provide high-quality data for input to and verification of General Circulation Models (GCMs). The extension of several point measurements of surface fluxes within the heterogeneous CART sites to an accurate representation of the areally averaged surface fluxes is not straight… more

Date: August 1, 1993

Creator: Coulter, R. L.; Martin, T. J. & Cook, D. R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Effect of Surface Flow on Topography in Niobium Electropolishing

Electropolishing (EP) is reliably delivering improved performance of multi-celled niobium SRF accelerator cavities, attributed to the smoother surface obtained. This superior leveling is a consequence of an etchant concentration gradient layer that arises in the HF-H2SO4 electrolyte adjacent to the niobium surface during polishing. Electrolyte circulation raises the prospect that fluid flow adjacent to the surface might affect the diffusion layer and impair EP performance. In this study, prelim… more

Date: March 1, 2011

Creator: Kelley, M. J.; Reece, C. E. & Zhao, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department