120 research outputs found

    Development of new packing materials for high performance liquid chromatography

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    Characterization of porosity via secondary reactions. Final technical report, 1 September 1991--30 November 1995

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    Enhancement of process control using real-time simulation

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    Towards more effective simulation of minerals processing systems

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    Two aspects of the computer simulation of minerals processing systems were investigated in order to facilitate more effective use of simulation technology. A user-interface was designed and combined with an existing simulator executive, resulting in the implementation of a user-friendly microcomputer based minerals processing simulator, MicroSim. Ease of use was achieved by consideration of the needs of the user of such a program. This resulted in the use of graphical methods for information input and output. Efficient form-filling techniques were developed for numerical data entry and editing. Models for the carbon-in-pulp adsorption process and for continuous gold leaching were derived. The CIP models were derived using a population balance approach. The method of characteristics and the method of moments were found to be particularly useful in solving the resulting equations. Besides being important processes in themselves, the integration of these models into MicroSim provided valuable experience regarding the use of such models in a simulator.AC 201

    Analytical Ultrasonics in Materials Research and Testing

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    Research results in analytical ultrasonics for characterizing structural materials from metals and ceramics to composites are presented. General topics covered by the conference included: status and advances in analytical ultrasonics for characterizing material microstructures and mechanical properties; status and prospects for ultrasonic measurements of microdamage, degradation, and underlying morphological factors; status and problems in precision measurements of frequency-dependent velocity and attenuation for materials analysis; procedures and requirements for automated, digital signal acquisition, processing, analysis, and interpretation; incentives for analytical ultrasonics in materials research and materials processing, testing, and inspection; and examples of progress in ultrasonics for interrelating microstructure, mechanical properites, and dynamic response

    A Fundamental Study of Char Oxidation Kinetics Using Model Materials

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    A fundamental study concerning the reactivity of carbon to oxygen, under conditions pertinent to the combustion of pulverized fuel particles, was conducted. Model, man-made materials have been synthesized and produced to aid in understanding the events that occur during pyrolysis and oxidation of chars. The benefit of employing synthetic materials, along with natural fuels, was that they allowed control of the purity and composition of the chars, as well as enabled production of particles of specific physical properties relevant to modeling combustion processes. Monodisperse, spherical, glassy carbon particles, of various sizes, were manufactured from spraying and thermally treating a carbon-yielding, highly crosslinked polymer. Various pore-forming agents were introduced and copolymerized, aiming to alter the pore structure, density and pore size distribution of the materials. Characterization of the chars, at various stages of pyrolysis and partial oxidation, employed widely varying techniques such as mercury intrusion, gas sorption, helium pycnometry, wide and small-angle scattering and nuclear magnetic resonance. Upon characterization, the influence of the physical factors on the combustion behavior was accounted for and the intrinsic reaction rates of the chars were correlated with their chemical nature. The mechanisms of pore coarsening, opening of pore restrictions and development of a large accessible pore surface area in the interior of the particles, in conjunction to the kinetics of structural ordering and graphitization, have been shown to influence critically the reactivity of chars. furthermore, experiments with calcium treated chars revealed that the catalytic effect of mineral matter on enhancing the combustion rate is very important.</p

    Hillslope experiments in the north east Cape region to measure and model subsurface flow processes.

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    Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1997.Several hydrological studies claim that available water resources in a catchment are affected by large scale afforestation, especially where the regional rainfall is considered marginal for the support of silviculture. Nevertheless, the mechanisms and magnitude of the perturbations to the receiving water resources due to afforestation are still not clearly understood. To improve this understanding an intensive hydrological experiment has been initiated in the small grassed Weatherly catchment of the Mondi, North East Cape Forests. Details of the soil water dynamics on the Molteno formations in the catchment have been be studied. This research presents a description and first results of the establishment of an experiment which comprises monitoring the water budget of the grassed catchment prior to the afforestation of the catchment to plantations of exotic trees. The studies currently include, monitoring the infiltration and redistribution of soil water on a hillslope as well as monitoring of interflow mechanisms and localised mechanisms of soil water accumulation influenced by the topography and geology of the catchment. In addition to the intensive soil water monitoring, specific experimentation has been conducted at various locations on the hillslope. These comprise macropore flow process studies and 2-dimensional tracer experiments. Details of these experiments as well as the automated soil water and groundwater monitoring instrumentation are presented. An intensive soil survey on a 30 m x 30 m grid as well as a comprehensive measurement strategy of soil physical and hydraulic properties are highlighted. A review of 2-dimensional numerical hillslope soil water process models is also presented. Results from this research show that on hillslopes underlain by Molteno sandstones localised perched water tables form. These water bodies, upon reaching a critical height above the bedrock cascade downslope as interflow recharging the water bodies downslope. The response to infiltration increases downslope and in the toe region interflow occurs readily in response to rainfall compared to the midslope where substantial rain needs to infiltrate

    Inheritance of cold stress tolerance in grapes

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    1989 Fall.Covers not scanned.Includes bibliographical references.Cold hardy 'Valiant' was crossed to the lesser hardy cultivars 'Zinfandel' and 'French Colombard' to produce progeny that were later planted in the field for evaluation. In January and February, 1989, buds with subjacent stem tissue were evaluated by differential thermal analysis (DTA). The results were compared with those obtained from tests of browning that were performed following controlled freezing of buds in a methanol bath. DTA was found to be an accurate means to determine the mean midwinter killing temperature of grape buds. The apparatus used cooled the experimental tissues at a smooth linear rate (-15.8 C/hr) and produced low variances within replicates. An analysis of variance indicated that there were true differences between progeny means. Field evaluations in June, 1989, also verified the midwinter DTA data. These tests substantiate recommending DTA as a breeding tool for evaluating midwinter grape cold hardiness. Broad sense heritability was calculated using grape bud DTA data for both 'Valiant'x'Zinfandel' and 'Valiant'x'French Colombard' crosses. All calculations produced heritabilities near unity, indicating that of the progeny tested, the phenotypes were due primarily to expression of the genotypes. It was also found that poor seed germination commonly found in grapes can be ameliorated through the use of embryo rescue techniques. Data showed that low germination of grape seeds is not necessarily due to inviability, since rescued embryos grew and developed when placed on Nitsch's medium

    NASA Tech Briefs Index 1980

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    Tech Briefs are short announcements of new technology derived from the research and development activities of the National Aeronautics and Space Administration. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This Index to NASA Tech Briefs contains abstracts and four indexes -- subject,. personal author, originating Center, and Tech Brief number -- for 1980 Tech Briefs
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