|
| |
|
|
Speciation analysis of chromium in particulate matter of urban dust
Rybínová, Marcela ; Hraníček, Jakub (referee) ; Rychlovský, Petr (advisor)
Anion-exchange chromatography with inductively coupled plasma - atomic emission spectrometry (ICP-AES) has been used for the speciation of chromium (Cr). Chromium speciation has attracted attention because of the different toxicity, Cr(III) is relatively non-toxic and Cr(VI) has been classified as a human carcinogen. The aim of the present study was to develop simple method for the speciation analysis of Cr (Cr(III) and Cr(VI)) in particulate matter of urban dust. A combination of 2% KOH + 3% Na2CO3 has been chosen as the optimal reagent for the extraction of chromium from particular matter. It was found that there was no conversion of Cr(VI) into Cr(III). The effect of separation parameters such as acidity of mobile phase was also studied. The detection limit for Cr(VI) was about 12 ng.ml-1 . Results for the determination of Cr(VI) were confirmed by the analysis of standard reference material (BCR CRM 545, Cr(VI) in welding dust loaded on a filter) with good agreement between certified (40,16 ± 0,60 μg.g-1 ) and found (37,83 ± 1,14 μg.g-1 ) values.
|
|
|
OS Chrome and the Chromium project
Pelcová, Lenka ; Vaněk, Jiří (advisor) ; Masner, Jan (referee)
The topic of this bachelor thesis is Google Chrome web-based operating system and open source Chromium project. In theoretical part of the thesis, general problematics of operating systems is shortly described, followed by the development of OS Chrome, description of the system architecture, and introduction of special hardware for usage of Chrome OS
The practical part is focused on the market analysis both in the Czech Republic and globally, including future prognoses, and comparison to Windows operating systems. Through a survey, knowledge of OS Chrome among people and most frequent usage in computers and laptops is found out. A comparison between OS Chrome and Windows 8.1 is made in these tasks.
|
|
|
Google Chrome OS - theory and practice
Pavelka, Martin ; Halbich, Čestmír (advisor) ; Radomír, Radomír (referee)
In my thesis, I focus on the operating system Google Chrome OS, determination of its characteristics, definition of target group of the operating system's users and comparison of available applications with those available for other operating systems. In the theoretical part, historical development of Google is analysed first, followed by the issue of Google Chrome web browser and analyse of the operating system Google Chrome OS. The practical part starts with evaluation of survey on the operating system Google Chrome OS and is followed by multi-criteria analysis of variants comparing various categories of applications available for the operating system Google Chrome OS and other operating systems, in this case represented by the operating system Microsoft Windows 8.1 and distribution of Linux operating system Ubuntu 14.04 LTS.
|
|
|
OS Google Chrome - theory and practice
Dorn, Michal ; Halbich, Čestmír (advisor) ; Radomír, Radomír (referee)
Thesis deals with the operating system Google Chrome. First, the system is described (how it works, its user interface). Next there is a characteristic of applications that can be downloaded to the system and how they work. Another part is devoted to security, which consists of several elements. The end of the theoretical part is focused on Chromebooks - devices in which the operating system is sold on the market.
The practical part is firstly characterized Dart programming language, which is then used for an application. This application shows not only work with the language, but also the benefits of Google Apps. It also shows compatibility with Windows and compares these two systems.
In conclusion are described advantages and disadvantages of Chrome system and summarizes all knowledge arising from this work.
|
|
|
Spectrophotometric determination of Chromium(III) with organic reagents
Nevrlá, Jana ; Komendová, Renata (referee) ; Sommer, Lumír (advisor)
The theoretical part of this master’s thesis is mainly focused on the physical and chemical properties of chromium, its toxicity and possibility of entering of various forms of chromium into the environment. There are also described the most common analytical methods for determination of chromium in water, including ways of modification and preconcentration water samples. The aim of experimental part is the optimalization and assessing the conditions spectrophotometric determination of Cr(III) by selected organic reagents (chromazurol S, eriochromcyanine R, 4-(2-thiazolylazo)resorcinol) and their comparison with the determination of total chromium, as Cr(III), using atomic absorption spectrometry with electrothermic atomization. The analytical procedure for spectrophotometric determination of chromium with chromazurol S, which was found to be most suitable and ET-AAS, were applied to real water samples.
|
|
| |
|
|
Chromium and chromium species cycle in environment
Nevrlá, Jana ; Sommer, Lumír (referee) ; Dočekalová, Hana (advisor)
This work focuses in the first theoretical part mainly on the possibility of entering various forms of chromium into the environment, their accumulation and transformation in environmental compartments. There are also described methods of sampling for analytical determination of chromium, the type of treatment of these samples and the most analytical methodologies for the determination of chromium in the oxidation stage III and VI. The experimental part is focused on the quantitative determination of Cr(III) and Cr(VI) in waste water, taken from the neutralizatoin station of the Chemical faculty of Brno University of Technology, by using selected spectrophotometric methods and the obtained results are compared with the results of analytical determination of total chromium by atomic absorption spectrometry.
|
|
|
Termodynamické možnosti a omezení pro výrobu čistého vodíku pomocí chromu, manganu a niklu s využitím cyklického chemického procesu za nižších teplot
Siewiorek, A. ; Svoboda, Karel ; Rogut, J.
Thermodynamics and chemical equilibrium for reduction of Cr2O3 , Mn3O4 and NiO by hydrogen, carbon monoxide, model syngas and methane and for oxidation of the relevant Cr, MnO and Ni by steam has been studied in a temperature range 400 – 1000 K. Attention was concentrated also on possible formation of undesired soot, carbides and carbonates during reduction step leading to CO and CO2 formation in the steam oxidation step. Reduction of Cr2O3 and MnO to metallic Cr and Mn by hydrogen, CO or CH4 at temperatures 400 – 1000 K is thermodynamically excluded. Reduction of Mn3O4 and NiO by hydrogen, CO and CH4 at such lower temperatures is thermodynamically favourable.
|
|
|
Analýza elektronové struktury Lavesových fází obsahujících chrom
Houserová, Jana ; Šob, Mojmír
Binary systems containing chromium can be found in many kinds of steels where the Laves-phase can be considered as a potential candidate for strengthening provided size and distribution of the particles are within certain limits. We performed electronic structure calculations to study the thermodynamic and structural properties of the C14 Laves phase with various compositions. In the frame of the thermodynamic study, we have evaluated the total energies of formation of Laves phase structure with different occupations of sublattices (Cr2Cr, Cr2X, X2Cr, X2X, where X stands for Fe, Mo, Si, Ta and W) with respect to the Standard Element Reference (SER) states. These energies of formation are of great importance for prediction of stability of studied configurations.
|
guest ::
