Title: Laboratory study of field ion emission from dust grains Author: Martin Jeřáb Department: Department of Surface and Plasma Science Supervisor: Prof. RNDr. Jana Šafránková, DrSc., KFPP Abstract: Dust particles are common objects in space environment. As a dust particles, we call objects with typical sizes of several atoms up to approximately 100 µm. However, a total mass of dust particles is only about 1% of total mass of our galaxy, the presence of dust particles significantly affects environment. The most interesting is dynamics of dust particles and attached dust charging processes. The presented thesis consists of two main parts. The first part deals with the experimental study of field ion emission. Our measurements have been performed using gold and carbon spherical dust grains. It has been found that during the charging of dust particle using ion gun are the primary ions implanted under the surface of the dust particle from where they are release in the form of neutral gas. This releasing of implanted ions affects field ion emission for several hours. The second part of the thesis describes a development of new experimental apparatus determined to the study of photoemission dust charging and con- sequently to the "true" field ion emission study. Keywords: dust, dusty plasmas, charging properties, field...

Title: Matter Models in General Relativity with a Decreasing Number of Sym- metries Author: Norman Gürlebeck Institute: Institute of theoretical physics Supervisor: Prof. RNDr. Jiří Bičák, DrSc., dr.h.c. Abstract: We investigate matter models with different symmetries in general relativity. Among these are thin (massive and massless) shells endowed with charge or dipole densities, dust distributions and rotating perfect fluid solutions. The electromagnetic sources we study are gravitating spherical symmetric condensers (including the implications of the energy conditions) and arbitrary gravitating shells endowed with a general test dipole distribution. For the latter the Israel formalism is extended to cover also general discontinuous tangential components of the electromagnetic test field, i.e., surface dipole densities. The formalism is applied to two examples and used to prove some general properties of dipole distributions. This is followed by a discussion of axially symmetric, stationary rigidly rotating dust with non-vanishing proper volume. The metric in the interior of such a configuration can be determined completely in terms of the mass density along the axis of rotation. The last matter models we consider are non-axially symmetric, stationary and rotating perfect fluid solutions. This is done with a...

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One important source of coarse particulate matter in urban atmosphere is the resuspended street dust. The aim of this study was to determine the emission potential of street dust samples, to conduct shape and mineralogical analysis of resuspendable fraction and on the bases of the findings carry out a comparison between the different sampling sites. The dust samples were collected in February 2014 in three cities: Ostrava, Prague and Pilsen. For the purpose of this study, nine samples from the selected sites were dispersed in a resuspension chamber. The samples were collected in the center of every city in the following locations: the main square, the tram railway and the curbside. Morphological and elemental analysis was performed using a Scanning Electron Microscope with EDS detector. The presence of mineral components such as quartz, chlorite, calcite, feldspar and kaolinite was observed. In samples from Ostrava were found spherical-shaped particles composed of iron oxides. The samples of Pilsen contained amphibole mineral fibers - actinolite. X-ray Powder Diffraction at high sensitivity showed the presence of amphibole asbestos in the samples from Ostrava and Prague. The mass of each size fraction of resuspended samples was determined. The mass size distribution was bimodal (2.5 µm and 8 µm),...

The workers are exposed to aerosol particles in a coal strip mine. These particles are usually generated by the Bucket-wheel excavators which break the mined rock. The goal of the thesis thesis was to compare the concentrations of atmospheric aerosol particles - PM on the Bucket-wheel excavator Schrs 1320, the Stacker ZPDH 6300 and the Bucket- wheel excavator K 800/N2 in the coal quarry Doly Nástup Tušimice, and then to answer the questions what is the main cause of increased concentration PMx and whether the mining machines are different from each other. The measurement was realized stepwise on every mining machine in the time period from 12. 8. to 2. 9. 2016. The concentrations of PM1, PM2,5 and PM10 were measured by two portable laser nephelometers in the cab drivers and the outdoor walkway of the mining machines with the integration time of 1 minute. The air temperature and the relative humidity were monitored in both types of settings in every five minutes. The PMx concentrations variability is usually determined by the type of work and by the type of smoking. Consequently, PM concentrations on the mining machines were compared at the morning exchanges and evening exchanges, during the outdoor cleaning by sweeping, the indoor cleaning by hoovering and during the smoking. The highest...

The thesis is focused on the application of brick powder in production of binary alkali-activated binders with metakaolin, slag and fly ash. The theoretical part summarizes recent fields of use of the ceramic waste in construction and binder industry and prerequisite properties of the brick powder for alkaline activation. Brick powder based geopolymers made in the experimental work were tested for their mechanical properties, porosity and microstructure, flow properties of the fresh geopolymers were evaluated by rheometric measurements. In accordance with the results it can be concluded that brick powder could be a suitable precursor for blended binders with metakaolin and slag, these samples exhibited good mechanical properties and microstructure characteristics. The combination with fly ash was less applicable due to a rapid setting, hardening retarder used in these binders caused significant deterioration of the mechanical properties of the material.

This thesis is focused on the determination of platinum in samples of road dust and soil by atomic absorption spectrometry. The theoretical part describes the basic physical and chemical properties of platinum, platinum function in automotive converters and its behavior in the environment. In the experimental section summarizes the methods used to decompositions samples, concentration of the analyte and the main results of the measurements.

Electroconductive silicate-based composites are advanced materials that allow building structures to perform several different functions simultaneously. Addressing the issues of their development and use is a suitable topic for research work. The aim of this work is to study the effect of structure on the resistivity of silicate composite. The structure of electrically conductive composites is studied on dry cement paste and mortar mixtures as well as on test bodies made of hardened cement paste and mortar after 28 days of curing. Based on the analysis of the raw materials, six suitable electroconductive fillers are selected based on particle size, resistivity, and water absorption. The parameters of dry cement paste and hardened cement paste with replacement of 4-19 wt. % cement by the selected fillers are determined. Two of the fillers are selected for use in dry and hardened mortar. Resistivity is determined for all dry mixes and hardened composites variants, and percolation thresholds are approximately determined. By studying the structure of the selected variants, it is shown that the most important parameters that have the greatest influence on the resistivity of the silicate composites are mainly the particle size and the intrinsic resistivity of the electrically conductive filler. For silicate composites in the hardened state, the volume of hydration products, especially portlandite and C-S-H gels, also has a significant influence. For both dry blends and hardened composites, it was found that the smaller the particle size of the electroconductive filler, the smaller the representation needed to reach the percolation threshold. Portlandite and C-S-H gels in the volume of the hardened composite cause its high resistivity. The resistivity of the hardened composite is always higher than that of the dry blends. Thus, the proportion of electroconductive filler needed to reach the percolation threshold is higher in hardened composites than in dry mixes. The resist

This thesis deals with the development of the hand-held firearms in the Middle East with an emphasis on the period from the 15th to the end of the 18th century. In some passages it also marginally mentions the early 19th century. The first part of the thesis concentrates on the development of firearms in a historical context. The focus is primarily on the Ottoman Empire and partially on Egypt. Among other topics it also analyses the practical use of firearms and the related military tactics including the presence of firearms in major battles, as shown on contemporary paintings and miniatures. In the second part the author deals with the technical development of hand-held firearms. This section focuses mostly on the components of firearms and their development. This section also in some degree deals with the artistic aspects of the preserved firearms. The supplements consist of numerous photographs of the preserved exhibits in Czech and foreign collections and also of other visual materials. Keywords firearms, gunpowder, Middle East, Ottoman Empire, Mamluks, Egypt, flintlock, matchlock, miquelet, stock, barrel, decoration, miniatures

My diploma work is focusing on the health problems of selected factors in the working enviroment of grinding the metal castings. There are high-risk factors, which are harmful to worker´s health, especially physical stress, noise, dust and vibrations, which are passed on hands. The employer is under the obligation to take precautions to carry on worker´s health, in consideration of exceed the health limits. The aim of this diploma work was setting the efficiency of precautions to health protection in work enviroment. The situation had been monitoring in a company in the South Bohemia over ten years. There were used results of factor´s precautions (noise, dust, vibrations) in work enviroment, where workers grind the metal castings by hand grinders. The monitoring ensemble was created by employess in a company, which makes the metal castings by hand grinders in its work enviroment. To data collecting were used the following methods: non-aligned observation, conversation with the chief of the company, studying of positive law and technical literature incl. test codes of the health institute (department Ceske Budejovice). The data of the test codes were processed by the secundary analysis and summarized to tables and graphs. Within qualitative analysis I determinated four research questions, which were answered gradually in my work: 1)Which precautions are carry out by employers to particular factors of employee´s health protection? 2)What is the factor´ s efficiency? 3)What impact do the precautions have on results of factor´s measuring? 4)Which precautions can I recommend on the grounds of the evalutation of the work enviroment? Both means of collective and individual protection belong to the precautions of worker´s health protection today. The technical, technologiacal and organisational precautions are included to collective protections. The individual precautions are focusing especially on employees and offer the substitute solutions. All precautions are specific to individual factors. I found out, that all precautions, which are used by the employers in work enviroment of metal casting, are effective. Especially we can talk about the precautions to protection of employee´s health against excessive dust (instalation of air ventilation with strong effect), which caused the exceed of dust concetration in work enviroment of grinding. Finally I can say, that this branch of metal casting has been connecting with certain high-risk factors all the time. Although all the protective precautions has been realized, the health limits given for noise, vibrations passed on hands and dust are still exceed. For this reason it´s very important to regularly inform the workers of high-risk factors, which they could meet in their work enviroment of cast grinding.