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  • Author or Editor: P. Hart x
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Abstract  

Data were compiled and linearly correlated on the growth in the gross domestic product (GDP) with the academic chemical engineering literature over a recent 26-year period for five different English-speaking countries, namely, the United States, Canada, Great Britain, India and Australia. The publication figures were also scaled to the total number of chemical engineering schools in the country; furthermore, all of these data were normalized from zero to unity, using the figures for the most recent year (1996) as the denominators, and then correlated against each other in linear fashion. Resulting confidence levels were in excess of 99% for each of the individual five countries, as well as for the entire set of normalized data for all of the countries.

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A method, based on the measurement of the -photopeak at 332 keV arising from a124Sn(n, )125mSn reaction, has been developed for the rapid measurement of Sn at concentrations of 20 g g–1, present as the cross-linking agent, in explosive charges. The method is comparative, and has a limit of detection of 0.6 g g–1 and a precision of 5% RSD. The method requires no sample preparation and is economical in effort.

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Adsorption of supercritical fluids methane, nitrogen and argon by active carbons was studied up to a pressure of 500 bar. A three-parameter isothermal equation was used to represent the adsorption equilibrium. This isothermal equation is based on a physical model conception which had already been used for the modelling of adsorption processes with a pressure up to 150 bar. Beside the exact knowledge of the measurable parameters pressure, temperature and fluid composition, the density of the adsorbate are essential for the evaluation of the adsorption analysis. The fluid density can be determined either via equations of state, which is normally the most practicable and fastest way, or via lift measurements of a lowering body in the fluid based on the principle of Archimedes. This work represents and discusses the question of to what extent the fluid density determined under real conditions via equations of state, using, for example, equation of Bender, corresponds to the fluid density measured under high-pressure.

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In the present work the supercritical fluids argon, methane, nitrogen, carbon dioxide, ethane, ethylene and propane were picked out as examples, and the results of analysis concerning the adsorption of these fluids at activated carbon Norit R1 (Norit Company, Germany) and SCS-3 (ISPE, Kiev) at different temperatures up to a pressure of 50 MPa are presented and discussed in this paper. The principle of working of the measuring device is described in this context as well.A three-parameter isothermal equation is used to represent the adsorption equilibrium. The isothermal equation is based on a physical model concept which has already been used for the modelling of adsorption processes with a pressure up to 15 MPa.

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A method, based on epithermal neutron activation analysis using a boron filter is described for the determination of 60 trace elements in boron and its compounds. The method has an accuracy of 20%, a precision of 15% RSD and limits of detection for most elements are either at the sub-ppm or low ppm levels. The method requires no sample preparation and is economical in effort.

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Abstract  

Citation analysis is a useful method for studying a wide range of topics in bibliometrics and the sociology of science. However, many challenges have been made to the validity and reliability of the underlying assumptions, the data, and the methods used in citation studies. This article addresses these issues in three parts. First is a brief review of validity and reliability issues in citation research. Next we explore measurement error in a principal source of journal-to-journal citation data, the Institute for Scientific Information'sJournal Citation Reports. Possible sources of measurement error include discrepancies between citing and cited data, changed or deleted journal titles, aberrant abbreviations, and listing algorithms. The last section is a detailed description of ways to overcome some of the measurement errors. The data and examples are drawn from a journal-to-journal citation study in the fields of Communication, Information Science, and Library Science.

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Abstract

Thermal analysis techniques have been used in characterizing building materials from significant historic properties in the Charleston, South Carolina area. Determining the chemical and physical effects of deterioration resulting from long periods of exposure is a first step in formulating preservation strategies. In this regard, simultaneous thermal analysis coupled with evolved gas analysis has been used to study reactions between air, seawater, and masonry materials. Further, the traditional petrographic identification of mortar composition is greatly facilitated through use of thermal analysis. Simultaneous thermal analysis allows for an exact determination of the calcium carbonate content in mortars as an alternative to the use of an inferred value based on chemical analysis data. The partial dissolution of calcium carbonate in the presence of sea salt is a major deterioration process. Further, natural cements manufactured in the United States are identified, in part, based on their thermogravimetric (TG) traces and their evolved gases. The data indicates that natural cements form some carbonate phases in addition to the major hydrate phases. Clay bricks are found to exhibit interaction with sea water, with uptake of bicarbonate suggested. Additionally, there is evidence of re-hydroxylation in the 160 year old bricks. The bricks made in coastal zones contain a considerable free silica fraction that is composed of a small percentage of cristobalite. The silica content of the clay bricks is seen to result in very high thermal expansion coefficients in the area of 10 × 10−6 to 12 × 10−6 K−1. These studies provide guidance in restoration efforts where authenticity of cements is important. In the event that replacement bricks are required, matching the thermal expansion coefficient of the original bricks is a requirement for preservation of the masonry structure.

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Abstract  

An irradiation position in the 250 kW Triga reactor was characterized for instrumental neutron activation analysis of chlorine in an iron oxide matrix. Factors that affect the accuracy of the determination include variations in the reactor neutron spectrum and flux as a function of spatial position and the presence of chlorine impurities. Gold wire and foils were used to determine the neutron flux and cadmium ratio as a function of height in an air-filled irradiation tube.

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