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A state-space Bayesian framework for estimating biogeochemical transformations using time-lapse geophysical data

Description: We develop a state-space Bayesian framework to combine time-lapse geophysical data with other types of information for quantitative estimation of biogeochemical parameters during bioremediation. We consider characteristics of end-products of biogeochemical transformations as state vectors, which evolve under constraints of local environments through evolution equations, and consider time-lapse geophysical data as available observations, which could be linked to the state vectors through petroph… more
Date: April 15, 2009
Creator: Chen, J.; Hubbard, S.; Williams, K.; Pride, S.; Li, L.; Steefel, C. et al.
Partner: UNT Libraries Government Documents Department
open access

Kinetics of the water adsorption driven structural transformationof ZnS nanoparticles

Description: Nanoparticles of certain materials can respond structurally to changes in their surface environments. We have previously shown that methanol, water adsorption, and aggregation-disaggregation can change the structure of 3 nm diameter zinc sulfide (ZnS). However, in prior observations of water-driven structure change, aggregation may also have taken place. Therefore, we investigated the structural consequences of water adsorption alone on anhydrous nanoparticles that were dried to minimize change… more
Date: August 1, 2007
Creator: Goodell, C. M.; Gilbert, B.; Weigand, S. J. & Banfield, J. F.
Partner: UNT Libraries Government Documents Department
open access

Optical multilayers with an amorphous fluoropolymer

Description: Multilayered coatings were made by physical vapor deposition (PVD) of a perfluorinated amorphous polymer, Teflon AF2400, together with other optical materials. A high reflector at 1064 run was made with ZnS and AF2400. An all-organic 1064-nm reflector was made from AF2400 and polyethylene. Oxide (HfO{sub 2}, SiO{sub 2}) compatibility was also tested. Each multilayer system adhered to itself. The multilayers were influenced by coating stress and unintentional temperature rises during PVD deposit… more
Date: July 1, 1994
Creator: Chow, R.; Loomis, G. E. & Lindsey, E. F.
Partner: UNT Libraries Government Documents Department
open access

HYDROGEN SEPARATION MEMBRANES

Description: A likely membrane for future testing of high-temperature hydrogen separation from a gasification product stream was targeted as an inorganic analog of a dense-metal membrane, where the hydrogen would dissolve into and diffuse through the membrane structure. An amorphous membrane such as zinc sulfide appeared to be promising. Previously, ZnS film coating tests had been performed using an electron-beam vacuum coating instrument, with zinc films successfully applied to glass substrates. The coatin… more
Date: August 1, 1999
Creator: McCollor, Donald P. & Kay, John P.
Partner: UNT Libraries Government Documents Department
open access

Characterization of Zns-GaP Naon-composites

Description: It proved possible to produce consistent, high-quality nanocrystalline ZnS powders with grain sizes as small as 8 nm. These powders are nano-porous and are readily impregnated with GaP precursor, although inconsistently. Both crystal structure and small grain size of the ZnS can be maintained through the use of GaP. Heat treatment of the impregnated powders results in a ZnS-GaP composite structure where the grain sizes of the phases are on the order of 10--20 nm. Conventional powder processing … more
Date: December 9, 1993
Creator: Todd, V.
Partner: UNT Libraries Government Documents Department
open access

Quasi-periodic quantum dot arrays produced by electrochemical synthesis

Description: We discuss a ``gentle`` electrochemical technique for fabricating quasi-periodic quantum dot arrays. The technique exploits a self-organizing phenomenon to produce quasi-periodic arrangement of dots and provides excellent control over dot size and interdot spacing. Unlike conventional nanolithography, it does not cause radiation damage to the structures during exposure to pattern delineating beams (e-beam, ion-beam or x-ray). Moreover, it does not require harsh processing steps like reactive io… more
Date: June 1, 1994
Creator: Bandyopadhyay, S.; Miller, A. E.; Yue, D. F.; Banerjee, G.; Ricker, R. E.; Jones, S. et al.
Partner: UNT Libraries Government Documents Department
open access

Alpha detection in pipes using an inverting membrane scintillator

Description: Characterization of surface alpha emitting contamination inside enclosed spaces such as piping systems presents an interesting radiological measurement challenge. Detection of these alpha particles from the exterior of the pipe is impossible since the alpha particles are completely absorbed by the pipe wall. Traditional survey techniques, using hand-held instruments, simply can not be used effectively inside pipes. Science and Engineering Associates, Inc. is currently developing an enhancement … more
Date: December 31, 1995
Creator: Kendrick, D. T.; Cremer, C. D.; Lowry, W. & Cramer, E.
Partner: UNT Libraries Government Documents Department
open access

Induced polarization response of microbial induced sulfideprecipitation

Description: A laboratory scale experiment was conducted to examine the use of induced polarization and electrical conductivity to monitor microbial induced sulfide precipitation under anaerobic conditions in sand filled columns. Three columns were fabricated; one for electrical measurements, one for geochemical sampling and a third non-inoculated column was used as a control. A continual upward flow of nutrients and metals in solution was established in each column. Desulfovibrio vulgaris microbes were inj… more
Date: June 4, 2004
Creator: Ntarlagiannis, Dimitrios; Williams, Kenneth Hurst; Slater, Lee & Hubbard, Susan
Partner: UNT Libraries Government Documents Department
open access

Pump-probe method for investigating laser ablation and optical damage threshold mechanisms in optical materials

Description: The method developed for investigating laser-surface interactions by measuring the ratio of ablation threshold fluence for a pair of picosecond or subpicosecond laser pulses to the single-pulse ablation threshold, was applied to ZnS (wurtzite)and to the borosilicate glass BK-7. Each sample was exposed to 1000 pulse pairs of 580-nm dye laser radiation. For ZnS, linear absorption was found to be the cause of the cumulative optical damage mechanism; the linear absorption is probably caused by defe… more
Date: September 1, 1993
Creator: Chase, L.L.
Partner: UNT Libraries Government Documents Department
open access

Ion beam synthesis of CdS, ZnS, and PbS compound semiconductor nanocrystals

Description: Sequential ion implantation followed by thermal annealing has been used to form encapsulated CdS, ZnS, and PbS nanocrystals in SiO{sub 2} and Al{sub 2}O{sub 3} matrices. In SiO{sub 2}, nanoparticles are nearly spherical and randomly oriented, and ZnS and PbS nanocrystals exhibit a bimodal size distribution. In Al{sub 2}O{sub 3}, nanoparticles are faceted and coherent with the matrix. Initial photoluminescence (PL) results are presented.
Date: December 1, 1997
Creator: White, C. W.; Budai, J. D. & Meldrum, A. L.
Partner: UNT Libraries Government Documents Department
open access

Growth of epitaxial semiconductor alloys and superlattices with continuously variable composition by pulsed-laser ablation

Description: We describe a new method to grow epitaxial semiconductor alloys with continuously variable composition, while using a single pulsed laser ablation target of fixed composition. Epitaxial ZnSe{sub 1{minus}x}S{sub x} films with continuously variable sulfur content ``x`` were grown by ablating a ZnSe target through low-pressure ambient H{sub 2}S gas. The sulfur content was easily controlled by varying the H{sub 2}S partial pressure. The composition of ZnSe{sub 1{minus}x}S{sub x} films differs by as… more
Date: August 1, 1993
Creator: McCamy, J. W. & Lowndes, D. H.
Partner: UNT Libraries Government Documents Department
open access

Low-flux neutron imaging

Description: Judicious use of scintillation screens greatly improves the capabilities for low-flux neutron imaging. Room temperature, cooled /sup 6/LiF-- ZnS(Ag) and gadolinium oxysulfide (Gd/sub 2/O/sub 2/S: Tb) were evaluated for direct exposures, and x-ray intensifying screens were evaluated with dysprosium and europium transfer screens. Although gadolinium oxysulfide provides improved resolution, it requires seven times the imaging time of /sup 6/LiF-- ZnS(Ag). Studies indicate that use of intensifying … more
Date: September 1, 1973
Creator: Swinth, K. L. & Nichols, L. L.
Partner: UNT Libraries Government Documents Department
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Development of Dewatering Aids for Minerals and Coal Fines

Description: MCT has developed a suite of novel dewatering chemicals (or aids) that are designed to cause a decrease in the capillary pressures of the water trapped in a filter cake by (1) decreasing the surface tension of water, (2) increasing the contact angles of the particles to be dewatered, and (3) causing the particles to coagulate, all at the same time. The decrease in capillary pressure in turn causes an increase in the rate filtration, an increase in throughput, and a decrease in pressure drop req… more
Date: July 1, 2004
Creator: Yoon, Roe-Hoam; Asmatulu, Ramazan; Yildirim, Ismail; Jansen, William; Zhang, Jinmig; Atkinson, Brad et al.
Partner: UNT Libraries Government Documents Department
open access

Calibration of scintillation detectors for MeV charged fusion products

Description: The light output of ZnS scintillators used to detect escaping fusion products in the TFTR Tokamak is studied with 3.5 MeV alpha and 3 MeV proton beams. The emitted light first increases linearly with beam current and then saturates. In all cases investigated, the onset of the saturation corresponds to a power of about 1 mW absorbed within the ZnS powder. The scintillators have adequate time response up to 50--100 kHz.
Date: December 31, 1991
Creator: Tuszewski, M. & Zweben, S. J.
Partner: UNT Libraries Government Documents Department
open access

A regenerable sorbent injection/filtration process for H{sub 2}S removal from hot gas

Description: The operational characteristics of a hot gas desulfurization process involving regenerable sorbent injection and its subsequent collection with a ceramic filtration device were studied utilizing a bench-scale transport reactor. Hydrogen sulfide removal from simulated hot gas was evaluated as a function of both zinc oxide-based sorbent physical and chemical characteristics and various process parameters. In addition, the sorbent capture efficiency and regenerability of the ceramic filtration dev… more
Date: December 31, 1996
Creator: Higgins, R. J.; Ji, W.; Connors, M. J.; Jones, J. F. & Goldsmith, R. L.
Partner: UNT Libraries Government Documents Department
open access

New infrared solid state laser materials for CALIOPE

Description: Tunable infrared laser light may serve as a useful means by which to detect the presence of the targeted effluents. Since optical parametric oscillators (OPOs) have proven to be a versatile method of generating coherent light from the ultraviolet to the mid-infrared, this technology is a promising choice by which to service the CALIOPE applications. In addition, since some uncertainty remains regarding the precise wavelengths and molecules that will be targeted, the deployment of OPOs retains t… more
Date: August 1, 1994
Creator: DeLoach, L.D.; Page, R.H. & Wilke, G.D.
Partner: UNT Libraries Government Documents Department
open access

Formation mechanism and yield of molecules ejected from ZnS, CdS, and FeS{sub 2} during ion bombardment

Description: Neutral species ejected from single crystals of ZnS, CdS, and FeS{sub 2} during ion bombardment by 3 keV Ar{sup +} were detected by laser post-ionization followed by time-of-flight mass spectrometry. While metal atoms (Fe, Zn, Cd) and S{sub 2} were the dominant species observed, substantial amounts of S, FeS, Zn{sub 2}, ZnS, Cd{sub 2}, and CdS were also detected. The experimental results demonstrate that molecules represent a larger fraction of the sputtered yield than was previously believed f… more
Date: March 1, 1994
Creator: Nikzad, S.; Calaway, W. F.; Pellin, M. J.; Young, C. E.; Gruen, D. M. & Tombrello, T. A.
Partner: UNT Libraries Government Documents Department
open access

Lithium and Zinc Sulfide Coated Plastic Neutron Detector Test

Description: Radiation portal monitors used for interdiction of illicit materials at borders include highly sensitive neutron detection systems. There is a declining supply of 3He in the world, and thus, methods to reduce the use of this gas in RPMs with minimal changes to the current system designs and sensitivity to cargo-borne neutrons are being investigated. Four technologies have been identified as being currently commercially available, potential alternative neutron detectors to replace the use of 3He… more
Date: July 16, 2010
Creator: Kouzes, Richard T. & Ely, James H.
Partner: UNT Libraries Government Documents Department
open access

Properties of transition metal-doped zinc chalcogenide crystals for tunable IR laser radiation

Description: The spectroscopic properties of Cr{sup 2+}, Co{sup 2+}, and Ni{sup 2+}-doped single crystals of ZnS, ZnSe, and ZnTe have been investigated to understand their potential application as mid-IR tunable solid-state laser media. The spectroscopy indicated divalent Cr was the most favorable candidate for efficient room temperature lasing, and accordingly, a laser-pumped laser demonstration of Cr:ZnS and Cr:ZnSe has been performed. The lasers` output were peaked at {approximately} 2.35 {mu}m and the h… more
Date: March 17, 1995
Creator: DeLoach, L.D.; Page, R.H. & Wilke, G.D.
Partner: UNT Libraries Government Documents Department
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