Academic literature on the topic 'Distribuce velikostí'

Existuje mnoho různých způsobů jak analyzovat disperzní systémy a fyzikálně chemické processy ke kterým v takových systémech dochází. Tato práce byla zaměřena na charakterizaci těchto procesů pomocí metod harmonické fraktální analýzy. Obrazová data sledovaných systémů byly analyzovány pomocí waveletové analýzy. V průběhu práce byly navrženy různé optimalizace samotné analýzy, převážně zaměřené na odstranění manuálních operací během analýzy a tyto optimalizace byly také inkorporovány do softérového vybavení pro Harmonickou Fraktální Analýzu HarFA, který je vyvíjen na Fakultě chemické, VUT Brno.

Thermoporosimetry is a technique to determine small pore sizes based on melting and crystallization point depression. The temperature shift was measured by Differential Scanning Calorimetry (DSC). Development of thermoporosimetry was carried out on silica with a well-characterized narrow pore size distribution. Several parameters were studied, which a have a direct influence on melting and crystallization point depression (for example: a quality of the solvent, filling the pores with the solvent, time and frequency of centrifuging, superfluous solvent removal conditions, etc.). The optimum conditions for the thermoporosimetry method were developed using high porosity silica. The optimized experimental conditions found for silica were applied to polypropylene powder with much lower porosity. Several polypropylene powders were synthesized using different polymerization catalysts and their porosity determined. Polymer powder morphology and structure was characterized by standard methods. Powder porosity obtained by thermoporometry, gas sorption, and BET methods was compared.

The topic of the Ph.D. thesis was focused on the process of sintering alumina and zirconia ceramic materials with the aim to compare kinetics of sintering sub-micro and nanoparticle systems. Zirconia ceramic powders stabilized by different amount of yttria addition in the concentration range of 0 – 8 mol% were used. The different crystal structure (secured by yttria stabilization) of zirconia, as found, did not play statistically proven role in the process of zirconia sintering. The possible influence was covered by other major factors as particle size and green body structure, which does affect sintering in general. According to the Herrings law, the formula predicting sintering temperature of materials with different particle size was defined. The predicted sintering temperatures were in good correlation with the experimental data for zirconia ceramic materials prepared from both, coarser submicrometer, and also nanometer powders. In case of alumina ceramics the predicted and experimentally observed sintering temperature values did not match very well. Mainly the nanoparticle alumina materials real sintering temperature values were markedly higher than predicted. The reason was, as shown in the work, strong agglomeration of the powders and strong irregularities of particle shape. The major role of green body microstructure in the sintering process was confirmed. The final density of ceramic materials was growing in spite of sintering temperature, which was decreasing together with pore - particle size ratio (materials with similar particle size were compared). Sintering temperature was increasing together with growing size of pores trapped in the green body structure. Clear message received from the above mentioned results was the importance of elimination of stable pores with high coordination number out off the green body microstructure during shaping ceramic green parts. Same sintering kinetics model was successfully applied on the sintering process of submicro- and also nanometer zirconia ceramics. Activation energy of nanometer zirconia was notably lower in comparison to submicrometer material. For the sintering of nanoparticle zirconia was typical so called “zero stage” of sintering, clearly visible on kinetic curves. It was found out, that processes running in zirconia “green” material during zero stage of sintering are heat activated and their activation energy was determined. Pores of submicrometer zirconia were growing in an open porosity stage of sintering just a slightly (1.3 times) compared to the nanoparticle zirconia, where the growth was much higher (5.5 times of the initial pore diameter). This difference was most probably caused by preferential sintering of agglomerates within the green bodies and by particle rearrangement processes which appears in the zero stage of sintering of nanoparticular ceramics. The technology of preparation of bulk dense ytria stabilized zirconia nanomaterial with high relative density of 99.6 % t.d. and average grain size 65nm was developed within the thesis research.

Active pharmaceutical ingredients (APIs) are frequently delivered to the patient in the solid-state as part of an approved dosage form (tablets, capsules, etc.). Understanding and controlling the solid-state chemistry of APIs is therefore an important aspect of the drug development process. APIs can exist in a variety of distinct solid forms, including polymorphs, solvates, hydrates, co-crystals and amorphous solids. Each form displays unique physicochemical properties that can profoundly influence the bioavailability, manufacturability, stability and other performance characteristics of the drug. Most APIs are purified and isolated by crystallisation from an appropriate solvent during the final step in synthetic process. The main objective of a crystallisation process is to produce crystals with desired properties such as particle size distribution (PSD), shape and purity. All pharmaceutical dosage forms must be produced in uniform units, and good content of uniformity is only possible when the size of the active component is carefully controlled. For on-line control of crystallisations of Quetiapine Fumarate to achieve desired PSD and no changed physicochemical purity was used the Lasentec Focus Beam Reflectance Measurement (FBRM) system.

Telemetry system, Optimisation, Sensoric networks, Smart Grid, Internet of Things, Sensors, Information security, Cryptography, Cryptography algorithms, Cryptosystem, Confidentiality, Integrity, Authentication, Data freshness, Non-Repudiation.

Texture of igneous rocks, which includes size, shape and spatial distribution of grains, represents the final record of kinetic and mechanical processes operating during ascent and final emplacement of a magma. However, traditional geochemical approaches cannot assess and verify the physical processes of magma solidification, in particular, crystal nucleation and growth, textural coarsening, or mechanical crystal-melt interactions. In this work, I apply stereological methods to quantitatively characterize the textures and to interpret the crystallization history of granitic rocks in the Western Krušné hory/Erzgebirge and Vogtland. The Western Krušné hory/Erzgebirge granites consist of three suites: biotite granites (Kirchberg), muscovite-biotite microgranites (Walfischkopf), and topaz-zinnwaldite alkali- feldspar granites (Eibenstock), which consist of eight intrusive units and two aplite dyke sets. The entire granite sequence exhibits an extreme and nearly continuous differentiation range, but in detail the evolutionary trends of each suite are independent, and individual intrusive units are also clearly compositionally separated. The granites consist of 29-43 vol.% quartz, 20-30 vol. % plagioclase, 22-31 vol. % K-feldspar, 2-9 vol. % biotite, <2 vol. % muscovite, and minor topaz and apatite. All...

Magmatic processes are major agents responsible for the formation and differentiation of the Earth's crust. In contrast to extensive efforts to improve understanding and utility of igneous geochemistry, physical processes of magma differentiation and solidification remain largely unclear. Large variability of igneous textures provides record of these processes and intensive parameters governing the crystallization. In this thesis, we develop quantitative methods, which allow us to better interpret igneous textures in the framework of physics of solidification. We have developed a new three-dimensional model of crystallization from one- component melt driven by homogeneous and heterogeneous nucleation and crystal growth. The predicted textures are quantitatively characterized by crystal size distributions, spatial distribution functions and parameters representing grain contact relationships. The model employs high resolution in a large volume simulation domain in order to produce statistically stable results. Our simulations, performed for various functional forms of nucleation and growth rates with respect to time, imply that (i) crystals are ordered (anti-clustered) on short length scales. This reflects that other crystals already have a finite size at the time of nucleation of younger crystal,...

Phenomenon of industrial grounds placed near residential areas can be frequently detected in European cities, which may cause decrease of air quality in these areas. The aim of this diploma thesis is to determine level of concentration and size distribution of aerosol in the planetary boundary layer above the residential area and industrial complex of Škoda auto a.s. in Mladá Boleslav city by using remotely controlled airship. Thereby, the thesis extends terrestrial experiment realized in February and March 2013 which revealed no significant impact of industry and traffic on air quality. Size distribution and concentration of aerosol particles in range from 11.5nm to 10µm with integration time one second or one minute (depending on measure mode - SINGLE or SCAN) was measured by two aerosol spectrometers placed in dirigible gondola during 13 flights on February 11, 2015. SINGLE mode lead the airship in one stable flight level during one flight above residential area and industrial complex of Škoda auto a.s. Whereas SCAN mode changed flight level every two minutes during the flight of airship above sports fields in residential zone only. Exhausts of car painting halls and place of automobile loading were identified as the sources of nanoparticles, PM1 a PM2.5 and coarse aerosol in the industrial area...

The aim of the study was to determine the 13 health risk PAHs (phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perylene, ideno(1,2,3-cd)perylene and coronene; c-PAU highlighted) in the fractions of size-segregated aerosol of the urban air in Ostrava (2012, 2014) and Mlada Boleslav (2013) at low temperatures in winter, and to verify experimentally a sampling artifact, i.e., to quantify PAHs in the gas phase. For the particle size separation high-volume cascade impactor Hi-Vol BGI 900 was used. PAHs were determined by HPLC-FLD/PDA. In Ostrava in 2012 during the winter inversion (up to -25 řC), mean concentration of 13 PAHs in aerosol was 432 ng.m-3 ; in fraction 10 - 1 µm 119 ng.m-3 , 1 - 0,5 µm 185 ng.m-3 , 0,5 - 0,17 µm 91 ng.m-3 , in fraction < 0,17 µm 37 ng.m-3 and in the gaseous phase of min. 40 ng.m-3 . In the most unfavorable day 2. 2. 2012 (-18.6 ř C) reached the 24-hour average of 13 PAHs 890 ng.m-3 , the sum of carcinogenic PAHs 237 ng.m-3 and benzo(a)pyrene 32.3 ng.m-3 . An irregular and different decline of PAHs concentrations after inversion was measured: in fraction 1 - 10 µm 2.8 times, 0.5 - 1 µm 4.2 times, 0.5 - 0.17 µm 4 times and for <0.17 µm up to 7.6 times....