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  • 1
    Publication Date: 2021-03-29
    Description: In the mining industry, the separation of economically valuable metals from gangue materials is a well established process. As part of this field, hydrometallurgy uses chemical fluids (leachates) of acidic or basic pH to dissolve the target metal(s) for subsequent concentration, purification and recovery. The type and concentration of the leach solution is typically controlled to allow selective dissolution of the target metal(s), and other parameters such as oxidation potential, temperature and the presence of complexing/chelating agents. In the remediation industry the use of elemental metals (M0) for the removal of aqueous contaminant species is also a well established process. Removal is achieved by the oxidative corrosion of the M0 and associated pH and/or redox potential change. Whilst the two processes are directly opposed and mutually exclusive they both stem from the same theoretical background: metal dissolution/precipitation reactions. In the mining industry, with each prospective ore deposit physically and chemically unique, a robust series of tests are performed at each mine site to determine optimal hydrometallurgical fluid composition and treatment conditions (e.g. fluid temperature, flow rate) for target metal dissolution/yield. In comparison, within the remediation industry not all such variables are typically considered. In the present communication a comparison of the processes adopted in both industries are presented. The consequent need for a more robust empirical framework within the remediation industry is outlined.
    Keywords: Environmental remediation; Extractive metallurgy; Intrinsic reactivity; Metal dissolution; Zerovalent Metal ; 551
    Language: English
    Type: article , submittedVersion
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  • 2
    Publication Date: 2004-12-03
    Description: Attenuation by rain at frequencies above 10 GHz is a random process. The observed cumulative distribution of the time in a month or year an attenuation value is exceeded is a realization of the results of this random process. The distribution observed in one year may be a poor predictor of the distribution to be observed in the next year. Existing models are based on the extremely limited set of attenuation data that is available from more than a few years of observation on single, fixed propagation paths. The goal of the NASA Advanced Communication Technology Satellite (ACTS) propagation experiment is to expand the data base on which new attenuation prediction models can be developed or old models can be validated.
    Keywords: Communications and Radar
    Type: Proceedings of the Twentieth NASA Propagation Experimenters Meeting (NAPEX 20) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop; 191-197; JPL-Publ-96-20
    Format: text
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  • 3
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    In:  CASI
    Publication Date: 2005-11-27
    Description: Figure sensing interferometry for control of astronomical mirror optics
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA, WASHINGTON OPT. TELESCOPE TECHNOL. 1970; P 297-301
    Format: text
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  • 4
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    In:  Other Sources
    Publication Date: 2011-08-16
    Description: An experimental investigation of bistatic scatter from rain was conducted, using a 143-km scatter path at frequencies of 4.5 and 7.7 GHz. The ratio of transmitted to received power (transmission loss) was measured for scattering angles ranging from 6 to 130 deg. Simultaneous weather radar observations were made at a frequency of 1.3 GHz. Transmission loss estimates for the bistatic scatter path were computed, using the weather radar data, the bistatic radar equation, and a model for the scattering cross section per unit volume of rain based upon Rayleigh scattering by an ensemble of water spheres. The measured and estimated transmission loss values were compared to test the use of the scattering model for the estimation of interference. The averaged ratio of measured-to-calculated transmission loss for the 4.5 GHz data is 1.2 plus or minus 0.4 dB. The averaged ratio for the 7.7 GHz data is -1.6 plus or minus 0.5 dB.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; Mar. 197
    Format: text
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  • 5
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    In:  Other Sources
    Publication Date: 2011-08-12
    Description: Biosatellite experiments designed to investigate space environment effect on living organisms
    Keywords: SPACE SCIENCES
    Format: text
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  • 6
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    In:  Other Sources
    Publication Date: 2011-08-12
    Description: Segmented active mirror optics design concept for lightweight optically stable primary reflector used in large orbiting astronomical telescopes
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ; RO(
    Format: text
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  • 7
    Publication Date: 2013-08-31
    Description: Viewgraphs from a presentation on the estimation of risk associated with an attenuation prediction is presented. Topics covered include: link failure - attenuation exceeding a specified threshold for a specified time interval or intervals; risk - the probability of one or more failures during the lifetime of the link or during a specified accounting interval; the problem - modeling the probability of attenuation by rainfall to provide a prediction of the attenuation threshold for a specified risk; and an accounting for the inadequacy of a model or models.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL, Proceedings of the 16th NASA Propagation Experimenters Meeting (NAPEX 16) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop p 45-63 (SEE N93-26463 09-32; JPL, Proceedings of
    Format: application/pdf
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  • 8
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    In:  Other Sources
    Publication Date: 2011-08-18
    Description: The quantitative measurement of precipitation characteristics for any area on the surface of the Earth is not an easy task. Precipitation is rather variable in both space and time, and the distribution of surface rainfall data given location typically is substantially skewed. There are a number of precipitation process at work in the atmosphere, and few of them are well understood. The formal theory on sampling and estimating precipitation appears considerably deficient. Little systematic attention is given to nonsampling errors that always arise in utilizing any measurement system. Although the precipitation measurement problem is an old one, it continues to be one that is in need of systematic and careful attention. A brief history of the presently competing measurement technologies should aid us in understanding the problem inherent in this measurement task.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: NASA. Goddard Space Flight Center Precipitation Meas. from Space:; 9 p
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  • 9
    Publication Date: 2011-08-18
    Description: Precipitation estimates from satellites are subject to a number of uncertainties involving design characteristics, satellite positioning, natural variability of precipitation, and the noncontinuous acquisition of data. The sources and sizes of these uncertainties are in need of proper evaluation and estimation. The present sampling and estima-theory seems to be adequate for some measurement problems (e.g., determining precipitation at a point), while others require further theoretical work (e.g., determining the time history of precipitation over large areas).
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Precipitation Meas. from Space:; 5 p
    Format: text
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  • 10
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    In:  Other Sources
    Publication Date: 2011-08-18
    Description: Propagation phenomena affect the design of radio frequency (RF) transmission systems. Propagation phenomena limit the suitability of portions of the frequency band for some applications, limit the reliability of RF transmission systems, and provide a means of coupling unwanted signals from one system to another with the potential of producing interference. The possibility of interference is the fundamental limitation to the unrestricted use of the frequency band. Phenomena affecting suitability, reliability, and the potential for interference are considered for frequencies in the 1- to 300-GHz range.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE; vol. 69
    Format: text
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