Impedance spectroscopy measurement of metakaolin-based alkali-activated building materials

Cement-containing as well as cement-free building materials are regarded as dielectrics. Therefore, electrically conducting admixtures are to be added to them in order to increase their electrical conductivity. Steel or carbon fibres, metal powder, graphite, carbon soot or carbon nanotubes are commonly used for this purpose. The conductivity increase offers new application options, such as sensor property materials, self-heated materials, or electromagnetic smog shielding materials. The specimens of the mixes to be studied were subjected to an electrical analysis carried out within the frequency range from 100 MHz to 3 GHz by means of an ZNC vector analyser and an SPEAG-made DAK-12 coaxial probe and, furthermore, a dedicated automatically measuring device operating within the frequency range from 40 Hz to 1 MHz. The frequency spectra of interest were measured on various copolymer specimens differing from each other by the content of graphite and carbon nanotubes. Higher content of these admixtures increases the electrical conductivity and the building materials thus become easier to measure by means of electromagnetic measuring methods

Generating Realistic Tree Models

Tato páce se zabývá generováním realistických modelů stromů. Implementovaný algoritmus má mnoho nastavitelných parametrů, které mu umožňují generovat velké množství druhů listnatých stromů. Generované modely jsou také poměrně realistické.This thesis deals with generation of realistic tree models. Implemented algorithm has many variable parameters, which allow generating large amount of species of broad-leaved trees. Generated models are also quite realistic looking.

Graphics Intro 64kB Using Ray Tracing

This thesis is concerning the description of creation of graphic intro 64kB using ray tracing. The main focus is the problems and principles connected with the topic of the thesis. Further on, the thesis describes the actual realization of the application and the achieved results. The conclusion covers the evaluation of thesis and possible ways for further improvement of the project

Změny elektrické vodivosti geopolymerních vzorků s uhlíkovými nanotrubičkami

By incorporation of nanotubes to the current composite materials, their properties can be significantly improved. Carbon nanotubes can act as filler, which minimizes the air gaps content in the matrix. The denser structure positively affects the physical and mechanical properties of the whole composite.Začleněním nanotrubiček do současných kompozitních materiálů lze výrazně zlepšit jejich vlastnosti. Uhlíkové nanotrubice působit jako výplň, která minimalizuje obsah vzduchu mezery v matrici. Struktura příznivě ovlivňuje fyzikální a mechanické vlastnosti

Srovnání výsledků metod impedanční spektroskopie s výsledky impact echo metody při vyšetřování degradace betonu zatěžovaného vysokými teplotami

The growth in the transport industry results in more accidents, which often include fire in locations with the concrete structures, which also effects its lifetime and its functionality. After any case of fire loading it is required to verify structure’s condition. One way how to assess the risks connected with further usage of the structures after being exposed to the fire is the non-destructive testing. This paper is dealing with non-destructive measurement of changes of electric parameters of the cement based mortars subjected to the high temperatures.Způsob, jak posoudit rizika spojena s narušením struktury, poté, co byla vystavena ohni je nedestruktivní zkoušení. Příspěvek se zabývá nedestruktivním měřením změn elektrických parametrů cementové maltové směsi vystavené vysokým teplotám

Monitorování betonu při hydrataci elektrický zaměřenou metodou

Analysis of impedance spectra of inhomogeneous materials is a part of the impedance spectroscopy which is still waiting for its development. Materials having higher electric resistance values (over 500 kohm) can be considered – under certain simplifying assumptions – as dielectrics. A theory of dielectric polarization was formulated by Debye for homogeneous materials.Analýza spekter impedance nehomogenních materiálů je součástí impedanční spektroskopie, která čeká na svůj rozvoj. Materiály, které mají vyšší hodnoty elektrického odporu (přes 500 kohm) lze považovat – za určitých předpokladů – dielektrika. Teorie dielectric polarizací formuloval Debye u homogenních materiálů