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The development of high performance insulating materials incorporating nanotechnologies has enabled considerable decrease in the effective thermal conductivity. Besides the use of conventional insulating materials, such as mineral fibers, the adoption of new nano-technological materials such as aerogel, vacuum insulation panels, graphite expanded polystyrene, is growing. In order to reduce the thermal conductivity of polystyrene insulation materials, during the manufacturing, nano/micro-sized graphite particles are added to the melt of the polystyrene grains. The mixing of graphite flakes into the polystyrene mould further reduces the lambda value, since graphite parts significantly reflect the radiant part of the thermal energy. In this study, laboratory tests carried out on graphite insulation materials are presented. Firstly, thermal conductivity results are described, and then sorption kinetic curves at high moisture content levels are shown. The moisture up-taking behaviour of the materials was investigated with a climatic chamber where the relative humidity was 90% at 293 K temperature. Finally, calorific values of the samples are presented after combusting in a bomb calorimeter.

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Abstract  

The aim of this paper is to define the characteristics of crystalline phase ETS-10 obtained from gel with dodecyltrimethylammonium bromide, as an organic template. ETS-10 zeolites has been synthesised under hydrothermal conditions from gels of composition 5Na2O–3KF–TiO2–6.4HCl– xC12TMAB –7.45SiO2–197.5H2O (where x=0.0, 0.25, 0.55, 1.0 and 1.5) with dodecyltrimethylammonium bromide. The crystalline phases synthesised with organic salt have an exothermal peak at ca. 360°C, due to the degradation of organic entrapped in the porous structure. Physical-chemical properties of C12TMAB -ETS-10 are studied by XRD, SEM and thermal analyses.

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Jntti et al. published a method to reduce the time necessary for adsorption measurements. They proposed to extrapolate the equilibrium in the stepwise isobaric measurement of adsorption isotherms by measuring at each step three points of the kinetic curve. For that purpose they approximated the kinetic curve by an exponential function which they derived empirically from there measurements. In the present paper we discuss the applicability of the method for adsorption measurements under continuously varying gas pressure.

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Summary  

The adsorption kinetics of strontium ion was studied on seven natural clay samples with radioactive tracer method. The kinetic curves were determined and the kinetic data were evaluated by forms of first-rate kinetic equations with different terms, generally used for adsorption of ions of low concentration. The adsorption process was reduced to two steps. Film diffusion and participle diffusion were found in the case of five samples. Gel diffusion, film diffusion and participle diffusion were found in the case of the other two samples. The presence of significant amount of cristobalite can explain the gel phase in these two samples. The rate coefficients of steps were calculated from the kinetic curves.

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The porous particle is represented as a system of slabs of different thickness in order to evaluate the kinetic curve of isotope exchange. The physical reasons of such a representation are discussed. The model curves are compared for different distributions of slab thickness.

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INAA results for metal traces in human whole blood

Frequency and age characteristics of the distribution

Journal of Radioanalytical and Nuclear Chemistry
Authors: L. Mosulishvili, N. Shonia, E. Ginturi, E. Efremova, and N. Kharabadze

Abstract  

A special method of simultaneous serial INAA of about 18 elements in human whole blood samples has been developed. The frequency distribution of tracer contents in the blood of healthy people living in Georgia has been studied. The kinetic curves of age-dependent changes of various microelement contents in human blood over an interval from 15 to 110 years has been plotted.

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A direct curve simulation treatment has been worked out for the evaluation of the kinetic curves of heterogeneous isotope exchange. Based on the data obtained by a personal computer some considerations have been made on the transport processes in the fully and half exchanged sodium forms of crystalline zirconium phosphate.

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Abstract  

Relationships have been established between the average conversion degree and the dissociation time for polydisperse granular material, taking its grain size distribution into account. It has been checked in which cases the kinetic curves obtained by a numerical solution can be described in terms of KEKAM equation.

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Abstract  

The time for adsorption measurements can be substantially reduced by measuring several values at short time intervals at the beginning of the kinetic curve and extrapolation of the equilibrium value. The method used by Jntti for simple adsorption processes has been extended for complicated processes using a second order differential equation. A simulated example is calculated.

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Abstract  

Relationships have been established between the average conversion degree and the dissociation time for polydisperse granular material, taking into account its grain size distribution. It has been checked in which cases the kinetic curves, obtained by a numerical solution, can be described in terms of equations R2 and F0.

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