Microstructure, magnetic and mechanical properties of Ni-Zn ferrites prepared by Powder Injection Moulding

Nowadays, the electronic industry demands small and complex parts as a consequence of the miniaturization of electronic devices. Powder injection moulding (PIM) is an emerging technique for the manufacturing of magnetic ceramics. In this paper, we analyze the sintering process, between 900 °C and 1300 °C, of Ni–Zn ferrites prepared by PIM. In particular, the densification behaviour, microstructure and mechanical properties of samples with toroidal and bar geometry were analyzed at different temperatures. Additionally, the magnetic behaviour (complex permeability and magnetic losses factor) of these compacts was compared with that of samples prepared by conventional powder compaction. Finally, the mechanical behaviour (elastic modulus, flexure strength and fracture toughness) was analyzed as a function of the powder loading of feedstock. The final microstructure of prepared samples was correlated with the macroscopic behaviour. A good agreement was established between the densities and population of defects found in the materials depending on the sintering conditions. In general, the final mechanical and magnetic properties of PIM samples were enhanced relative those obtained by uniaxial compaction

Study of Nitrogen Atom Recombination by Optical Emission Spectroscopy

The reaction kinetics in nitrogen flowing afterglow was studied by optical emission spectroscopy. The DC flowing post-discharge in pure nitrogen was created in a quartz tube at the total gas pressure of 1000 Pa. The optical emission spectra were measured along the flow tube. It was found that N atoms are the most important particles in the late nitrogen afterglow. In order to explain the decrease of N atom concentration, it was also necessary to include the surface recombination of N atoms to the model

Study of ozone destruction reaction on surfaces

The ozone destruction was studied in a quartz cuvette. The time dependence of ozone concentration was measured by absorption spectroscopy. From this time dependence the pseudo first-order rate constant was derived. This rate constant depends on surface condition - the surface concentration of adsorbed oxygen atoms. This surface concentration was changed by reactions of adsorbed oxygen atoms with gaseous molecular oxygen just before the cuvette was filled by ozone. The decrease of atomic oxygen surface concentration leads to the decrease of rate constant for ozone destruction. The measured rate constants were in range 9.0 × 10−5 s−1 to 9.8 × 10−5 s−1

Virtual reality: History of immersive practices and future vision

Práce zachycuje historii virtuální reality a imerzivních praktik od poloviny 20. století, kdy došlo díky novým vizuálním technologiím a obrovskému rozšíření výpočetní techniky k jejímu rychlému vývoji. Součástí práce je zároveň analýza povědomí a využívanosti virtuální reality u veřejnosti, při které hledám zásadní důvody pro její úspěšný budoucí vývoj. K tomuto zkoumání je využito kvantitativního dotazníkového šetření u dvou věkových skupin, ze kterého je analyzován zájem veřejnosti o využívání virtuální reality, návrhy na její vylepšení či zájmu o úplné zastavení vývoje z důvodu problematických skutečností při jejím počátečním vývoji.This work provides a history overview of virtual reality and immersive practices since the mid- 20th century, when the development of virtual reality sped up, due to new visual technologies and massive expansion of information technology. Second part of this work aims at awareness and usage analysis of virtual reality in public and examining the solutions for its successful future development. I've used a quantitative survey in two age groups, from which I analysed the public interest about using virtual reality, suggestions for its improvements or interest in completely stopping the development due to its problematic circumstances in early development.Ústav informačních studií a knihovnictvíInstitute of Information Studies and LibrarianshipFaculty of ArtsFilozofická fakult

Study of Argon Afterglow with the Air Addition

The reaction kinetics in argon flowing afterglow (post-discharge) with the air addition was studied by optical emission spectroscopy. The optical emission spectra were measured along the~post-discharge flow tube. A zero-dimensional kinetic model for the reactions in the afterglow was developed. This model allows to calculate the time dependencies of particle concentrations

Influence of Gas Temperature on Gaseous Products Generated by Coplanar Barrier Discharge in Air and N2/O2 Mixtures

Absolute densities of gaseous products generated by coplanar dielectric barrier discharge in N2/O2 mixtures and in ambient air were determined by UV optical absorption spectroscopy (OAS). Ozone (O3) and nitrogen oxides (N2O, NO2 and N2O5) were identified as the stable products of the discharge. It was found that the actual product composition strongly depends on the gas temperature. At low input power with the low gas temperature, O3 density was high and the NO2 density was very low. When the input power increased and the gas temperature also increased, then O3 disappeared, while NO2 density started to increase steeply

GC-MS and GC-FID Analysis of Products from Glow Discharge in N2 + CH4 Mixture

This work extends our previous investigation of nitrogen-methane atmospheric glow discharge for the simulation of chemical processes in prebiotic atmospheres. Also reactions on surfaces of solid state bodies can be important. So in presented experiments the electrodes with different shapes and different surface areas were used. Exhaust products of discharge in this gas mixture were analyzed by Gas Chromatography - Mass Spectrometry (GC-MS) and Gas Chromatography - Flame Ionization Detector (GC-FID). The major products identified in chromatograms were hydrogen cyanide and acetylene