9 Matching Results

Search Results

Advanced search parameters have been applied.

Coupled modeling of groundwater flow solute transport, chemical reactions and microbial processes in the 'SP' island

Description: The Redox Zone Experiment was carried out at the Aespoe HRL in order to study the redox behavior and the hydrochemistry of an isolated vertical fracture zone disturbed by the excavation of an access tunnel. Overall results and interpretation of the Redox Zone Project were reported by /Banwart et al, 1995/. Later, /Banwart et al, 1999/ presented a summary of the hydrochemistry of the Redox Zone Experiment. Coupled groundwater flow and reactive transport models of this experiment were carried out by /Molinero, 2000/ who proposed a revised conceptual model for the hydrogeology of the Redox Zone Experiment which could explain simultaneously measured drawdown and salinity data. The numerical model was found useful to understand the natural system. Several conclusions were drawn about the redox conditions of recharge waters, cation exchange capacity of the fracture zone and the role of mineral phases such as pyrite, calcite, hematite and goethite. This model could reproduce the measured trends of dissolved species, except for bicarbonate and sulfate which are affected by microbially-mediated processes. In order to explore the role of microbial processes, a coupled numerical model has been constructed which accounts for water flow, reactive transport and microbial processes. The results of this model is presented in this report. This model accounts for groundwater flow and reactive transport in a manner similar to that of /Molinero, 2000/ and extends the preliminary microbial model of /Zhang, 2001/ by accounting for microbially-driven organic matter fermentation and organic matter oxidation. This updated microbial model considers simultaneously the fermentation of particulate organic matter by yeast and the oxidation of dissolved organic matter, a product of fermentation. Dissolved organic matter is produced by yeast and serves also as a substrate for iron-reducing bacteria. Model results reproduce the observed increase in bicarbonate and sulfate concentration, thus adding additional evidence for ...
Date: December 1, 2003
Creator: Samper, Javier; Molinero, Jorg; Changbing, Yang & Zhang, Guoxiang
Partner: UNT Libraries Government Documents Department

Large deformation solid-fluid interaction via a level set approach.

Description: Solidification and blood flow seemingly have little in common, but each involves a fluid in contact with a deformable solid. In these systems, the solid-fluid interface moves as the solid advects and deforms, often traversing the entire domain of interest. Currently, these problems cannot be simulated without innumerable expensive remeshing steps, mesh manipulations or decoupling the solid and fluid motion. Despite the wealth of progress recently made in mechanics modeling, this glaring inadequacy persists. We propose a new technique that tracks the interface implicitly and circumvents the need for remeshing and remapping the solution onto the new mesh. The solid-fluid boundary is tracked with a level set algorithm that changes the equation type dynamically depending on the phases present. This novel approach to coupled mechanics problems promises to give accurate stresses, displacements and velocities in both phases, simultaneously.
Date: December 1, 2003
Creator: Schunk, Peter Randall; Noble, David R.; Baer, Thomas A.; Rao, Rekha Ranjana; Notz, Patrick K. & Wilkes, Edward Dean
Partner: UNT Libraries Government Documents Department

Photonic encryption using all optical logic.

Description: With the build-out of large transport networks utilizing optical technologies, more and more capacity is being made available. Innovations in Dense Wave Division Multiplexing (DWDM) and the elimination of optical-electrical-optical conversions have brought on advances in communication speeds as we move into 10 Gigabit Ethernet and above. Of course, there is a need to encrypt data on these optical links as the data traverses public and private network backbones. Unfortunately, as the communications infrastructure becomes increasingly optical, advances in encryption (done electronically) have failed to keep up. This project examines the use of optical logic for implementing encryption in the photonic domain to achieve the requisite encryption rates. In order to realize photonic encryption designs, technology developed for electrical logic circuits must be translated to the photonic regime. This paper examines two classes of all optical logic (SEED, gain competition) and how each discrete logic element can be interconnected and cascaded to form an optical circuit. Because there is no known software that can model these devices at a circuit level, the functionality of the SEED and gain competition devices in an optical circuit were modeled in PSpice. PSpice allows modeling of the macro characteristics of the devices in context of a logic element as opposed to device level computational modeling. By representing light intensity as voltage, 'black box' models are generated that accurately represent the intensity response and logic levels in both technologies. By modeling the behavior at the systems level, one can incorporate systems design tools and a simulation environment to aid in the overall functional design. Each black box model of the SEED or gain competition device takes certain parameters (reflectance, intensity, input response), and models the optical ripple and time delay characteristics. These 'black box' models are interconnected and cascaded in an encrypting/scrambling algorithm based on ...
Date: December 1, 2003
Creator: Blansett, Ethan L.; Schroeppel, Richard Crabtree; Tang, Jason D.; Robertson, Perry J.; Vawter, Gregory Allen; Tarman, Thomas David et al.
Partner: UNT Libraries Government Documents Department

Summary of Vadose -- Zone Conceptual Models for Flow and Contaminant Transport and 1999 - 2003 Progress on Resolving Deficiencies in Understanding the Vadose Zone at the INEEL

Description: The thick vadose zone that underlies the Idaho National Engineering and Environmental Laboratory has been recognized both as an avenue through which contaminants disposed at or near the ground surface can migrate to groundwater in the underlying Eastern Snake River Plain aquifer, and as a barrier to the movement of contaminants into the aquifer. Flow and contaminant transport in the vadose zone at the INEEL is complicated by the highly heterogeneous nature of the geologic framework and by the variations in the behavior of different contaminants in the subsurface. The state of knowledge concerning flow and contaminant transport in the vadose zone at and near the INEEL IN 1999 was summarized in Deficiencies in Vadose Zone Understanding at the Idaho National Engineering and Environmental Laboratory (Wood et al., 2000). These authors identified deficiencies in knowledge of flow and contaminant transport processes in the vadose zone, and provided recommendations for additional work that should be conducted to address these deficiencies. In the period since (Wood et al., 2000) was prepared, research has been published that, to some degree, address these deficiencies. This document provides a bibliography of reports, journal articles, and conference proceedings published 1999 through mid-2003 that are relevant to the vadose zone at or near the INEEL and provides a brief description of each work. Publications that address specific deficiencies or recommendations are identified, and pertinent information from selected publications is presented.
Date: December 1, 2003
Creator: Starr, Robert C.; Dettmers, Dana L.; Orr, Brennon R. & Wood, Thomas R.
Partner: UNT Libraries Government Documents Department

TRUPACT-II 157 Examination Report

Description: This report presents the results of examination and recovery activities performed on the TRUPACT-II 157 shipping container. The container was part of a contact-handled transuranic waste shipment being transported on a truck to the Waste Isolation Pilot Plant in New Mexico when an accident occurred. Although the transport vehicle sustained only minor damage, airborne transuranic contamination was detected in air samples extracted from inside TRUPACT-II 157 at the Waste Isolation Pilot Plant. Consequently, the shipping container was rejected, resealed, and returned to the Idaho National Engineering and Environmental Laboratory where the payload was disassembled, examined, and recovered for subsequent reshipment to the Waste Isolation Pilot Plant. This report documents the results of those activities.
Date: December 1, 2003
Creator: O'Brien, Barry H.; Lacy, Jeffrey M. & Archibald, Kip E.
Partner: UNT Libraries Government Documents Department

III-antimonide/nitride based semiconductors for optoelectronic materials and device studies : LDRD 26518 final report.

Description: The goal of this LDRD was to investigate III-antimonide/nitride based materials for unique semiconductor properties and applications. Previous to this study, lack of basic information concerning these alloys restricted their use in semiconductor devices. Long wavelength emission on GaAs substrates is of critical importance to telecommunication applications for cost reduction and integration into microsystems. Currently InGaAsN, on a GaAs substrate, is being commercially pursued for the important 1.3 micrometer dispersion minima of silica-glass optical fiber; due, in large part, to previous research at Sandia National Laboratories. However, InGaAsN has not shown great promise for 1.55 micrometer emission which is the low-loss window of single mode optical fiber used in transatlantic fiber. Other important applications for the antimonide/nitride based materials include the base junction of an HBT to reduce the operating voltage which is important for wireless communication links, and for improving the efficiency of a multijunction solar cell. We have undertaken the first comprehensive theoretical, experimental and device study of this material with promising results. Theoretical modeling has identified GaAsSbN to be a similar or potentially superior candidate to InGaAsN for long wavelength emission on GaAs. We have confirmed these predictions by producing emission out to 1.66 micrometers and have achieved edge emitting and VCSEL electroluminescence at 1.3 micrometers. We have also done the first study of the transport properties of this material including mobility, electron/hole mass, and exciton reduced mass. This study has increased the understanding of the III-antimonide/nitride materials enough to warrant consideration for all of the target device applications.
Date: December 1, 2003
Creator: Kurtz, Steven Ross; Hargett, Terry W.; Serkland, Darwin Keith; Waldrip, Karen Elizabeth; Modine, Normand Arthur; Klem, John Frederick et al.
Partner: UNT Libraries Government Documents Department

PROTON-CONDUCTING DENSE CERAMIC MEMBRANES FOR HYDROGEN SEPARATION

Description: Dense perovskite-type structured ceramic membranes, SrCe{sub 0.95}Tm{sub 0.05}O{sub 3} (SCTm), of different thickness, were prepared by the dry-press method. Membrane thickness was varied from 3 mm to 150 {micro}m. The hydrogen permeation flux was found to be inversely proportional to the thickness of the dense films, indicating that the bulk diffusion rather than the surface reaction played a dominant role in the H{sub 2} transport through these dense membranes within the studied thickness range. Hydrogen permeation flux increases with increasing upstream hydrogen partial pressure and decreasing downstream hydrogen partial pressure. The activation energy for hydrogen permeation through the SCTm membrane is about 116 kJ/mol in 600-700 C and 16 kJ/mol in 750-950 C. This indicates a change in the electrical and protonic conduction mechanism at around 700 C. Pd-Cu thin films were synthesized with elemental palladium and copper targets by the sequential R.F. sputter deposition on porous substrates. Pd-Cu alloy films could be formed after proper annealing. The deposited Pd-Cu films were gas-tight. This result demonstrated the feasibility of obtaining an ultrathin SCTm film by the sequential sputter deposition of Sr, Ce and Tm metals followed by proper annealing and oxidation. Such ultrathin SCTm membranes will offer sufficiently high hydrogen permeance for practical applications.
Date: December 1, 2003
Creator: Lin, Jerry Y. S.; Cheng, Scott & Gupta, Vineet
Partner: UNT Libraries Government Documents Department

MODELING THE TRANSPORT AND CHEMICAL EVOLUTION OF ONSHORE AND OFFSHORE EMISSIONS AND THEIR IMPACT ON LOCAL AND REGIONAL AIR QUALITY USING A VARIABLE-GRID-RESOLUTION AIR QUALITY MODEL

Description: This document, the project's first semiannual report, summarizes the research performed from 04/17/2003 through 10/16/2003. Portions of the research in several of the project's eight tasks were completed, and results obtained are briefly presented. We have tested the applicability of two different atmospheric boundary layer schemes for use in air quality model simulations. Preliminary analysis indicates that a scheme that uses sophisticated atmospheric boundary physics resulted in better simulation of atmospheric circulations. We have further developed and tested a new surface data assimilation technique to improve meteorological simulations, which will also result in improved air quality model simulations. Preliminary analysis of results indicates that using the new data assimilation technique results in reduced modeling errors in temperature and moisture. Ingestion of satellite-derived sea surface temperatures into the mesoscale meteorological model led to significant improvements in simulated clouds and precipitation compared to that obtained using traditional analyzed sea surface temperatures. To enhance the capabilities of an emissions processing system so that it can be used with our variable-grid-resolution air quality model, we have identified potential areas for improvements. Also for use in the variable-grid-resolution air quality model, we have tested a cloud module offline for its functionality, and have implemented and tested an efficient horizontal diffusion algorithm within the model.
Date: December 1, 2003
Creator: Alapaty, Kiran
Partner: UNT Libraries Government Documents Department

A Review of Carbon Dioxide Selective Membranes: A Topical Report

Description: Carbon dioxide selective membranes provide a viable energy-saving alternative for CO2 separation, since membranes do not require any phase transformation. This review examines various CO2 selective membranes for the separation of CO2 and N2, CO2 and CH4, and CO2 and H2 from flue or fuel gas. This review attempts to summarize recent significant advances reported in the literature about various CO2 selective membranes, their stability, the effect of different parameters on the performance of the membrane, the structure and permeation properties relationships, and the transport mechanism applied in different CO2 selective membranes.
Date: December 1, 2003
Creator: Shekhawat, Dushyant; Luebke, David R. & Pennline, Henry W.
Partner: UNT Libraries Government Documents Department