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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Vývoj a zkoušení vysokohodnotných betonů pro subtilní konstrukce / Development and testing of high performance concrete for subtle structures

Myšičková, Lucie January 2014 (has links)
Thesis describes properties of HPC compared to concretes of normal and high strength. It further describes the input materials and the procedure for designing the composition of the mixture. It gives examples of already completed structures made of HPC. The experimental part describes the optimization of concrete mix and production of specimens. In the end results of testing the properties of the developed mixes from tests of dynamic and static modulus of elasticity, compressive strength and tensile strength by bending are described.
52

Možnosti hodnocení trvanlivosti povrchové vrstvy betonu stavebních konstrukcí / Possibilities of evaluation durability of the surface layer of concrete structures

Blažek, Michal January 2014 (has links)
The thesis is focused on possibilities of durability evaluation of surface layer of concrete structures. The durability of concrete surface layer usually determines the durability of the structure as a unit. It has to be determined in what environment the structure is situated and what influences it has to face, to set the durability of the structure. There is a several normative prescription to set the resistance of the structure. There is formulated a summary of the most widely used and known prescriptions in the theoretical part of the thesis. It is a lot of effort to estimate the durability of the concrete by estimation of permeability of the concrete surface layer recently. Thus these methods are also formulated in the summary and there are compared the individual outputs of the tests. The permeability and pore structures of the concrete surface layer are crucial parameters for the durability of concrete structure. These parameters influence the construction properties of the concrete as well, thus the thesis is focused on relationship of the pore structure and the strength in press of the concrete.
53

Čištění bioplynu pomocí metody PSA (adsorpce za měnícího se tlaku) / Cleaning of biogas by the PSA (pressure swing adsorption)

Navrátil, Petr January 2014 (has links)
The topic of this master thesis is upgrading of biogas. As a mixture of gases produced during anaerobic digestion, contains methane which is highly energy valuable gas. But also other substances that we want to remove. We will present the motivation for upgrading biogas and the possibility of separation, generally the pressure swing adsorption method. The key parameter of this technique is the choice of a suitable adsorbent. This is possible based on the knowledge of adsorption processes, therefore, is also described below. The objective of this thesis is to determine the parameters of the pressure swing adsorption metod. To do this it is necessary to determine the adsorption capacity of the adsorbent, measure breakthrough curves of carbon dioxide and methane, and determine the pressure drop of solid bed, etc. As a result we can finally make a balance and evaluate the applicability in practice.
54

Využití fuzzy clusteringu při modelování vlastností ztvrdlých betonů / Using fuzzy clustering in modelling of hardened concrete properties

Haluska, Lukáš January 2015 (has links)
Compressive strength is one of the most monitored parameter of hardened concrete and it is usually determinated by destructive testing. Non-destructive testing applied on existing constructions uses regression analysis to estimate compressive strength. High variability of outputs and eventually failure of necessary requirements for using regression analysis complicate these methods. The aim of this thesis is to show posibility of using fuzzy clustering in this topic and to compare outputs with classic methods.
55

Výzkum a vývoj moderních emisních senzorů typu MEMS / Research and Development of Modern Emission MEMS Sensors

Pekárek, Jan January 2014 (has links)
The dissertation thesis is focused on research and development of modern emission MEMS sensors. The emission sensor based on the field emission from nanostructured materials represents innovative approach to pressure sensing. The nanostructures serve as electron emitter in an electric field between the cathode and anode in the pressure sensor. This electric field is constant and the change in ambient pressure causes the change of distance between electrodes, thereby the electric field is increasing. This intensity is proportional to the emission from the cathode made of nanostructured material. Changing the distance between the electrodes is caused by the deflection of the deformation element - the membrane, which operates the measured pressure. In the current state of the art an extensive research is carried out to find new nanostructured materials with good emission properties. Four nanostructured materials have been chosen and then experimentally prepared and characterized inside the vacuum chamber. For the simulation of diaphragm bending, the chamber is equipped with linear nano-motion drive SmarAct that enables precise changes of the distance between two electrodes inside the vacuum chamber. The computer model to predict the deformation of diaphragm was prepared in the simulation program CoventorWare. The behavior of diaphragm in a wide range of dimensions of the membrane, its thickness and the applied pressure are possible to predict. The dependencies of the current density on the electric field are plotted from the measured emission characteristics of nanostructured materials and thus characterized nanostructured materials can be compared. The dependencies are further converted by Fowler-Nordheimovy theory on the curve (ln(J/E2) vs. 1/E), whose advantage is linear shape. Basic parameters describing the emission properties of characterized nanostructured materials are deducted. Two methods for vacuum packaging of the sensor electrodes are designed. Anodic bonding technology and encapsulating using glass frit bonding are tested. To evaluate the bonding strength, the bonded substrates are tested for tensile strength.
56

Akustické vlastnosti vodorovného dopravního značení / Acoustic properties of road markings

Drnovský, Ondřej January 2017 (has links)
The thesis deals with verifying the acoustic properties of road markings in real conditions the vehicle travels. It contains basic information about the acoustics of the sources of traffic noise and methods of measuring noise. Below are the main information about the horizontal signposts and its impact on safety. The practical part contains descriptions of results, estimation of measurement and subsequently implemented economic assessment.
57

Tekutiny s viskozitou závislou na tlaku proudící porézním prostředím / On fluids with pressure-dependent viscosity flowing through a porous medium

Žabenský, Josef January 2015 (has links)
Experimental data convincingly show that viscosity of a fluid may change significantly with pressure. This observation leads to various generalizations of well-known models, like Darcy's law, Stokes' law or the Navier-Stokes equations, among others. This thesis investigates three such models in a series of three published papers. Their unifying topic is development of existence theory and finding a weak solution to systems of partial differential equations stemming from the considered models.
58

Variabilita krevního tlaku a tepové frekvence při vertikalizaci u tetraplegiků / Blood pressure and heart rate variability when verticalizating tetraplegics

Čeloudová, Kateřina January 2019 (has links)
An autonomic dysfunction caused by spinal cord injury may have a significant impact on quality of life, especially in cases of lesions occuring above the sixth spinal segment. In these cases also cardiovascular system control is damaged in a different extent, which is subsequently presented by e.g. persisting bradycardia, heart frequency inadequate reaction to strain and stress or by huge variations of blood pressure values, which the situation complicate even more. The fact that cardiovascular diseases take now the frontmost place in causes of mortality of people with spinal cord injury is another evidence how important this topic is. The main aim of my thesis was to describe impacts of autonomic injury on cardiovascular functions and to try to objectify them using heart rate and blood pressure variability. Twenty-one patients of Motol University Hospitalv Spinal Unit with spinal cord lesion above Th6 segment and ten healthy people as a control group participated in the study. We created suitable conditions for highlighting disrupted cardiovascular functions of urgent spinal patients by modification of the standardized Head Up Tilt Test (HUTT). The heart rate and blood pressure values were continuously monitored by Finapres device before, during and also after verticalization on a tilt table....
59

Příprava a vlastnosti pěnových materiálů na bázi Bioskla / Preparation and properties of Bioglass based foam materials

Nedbalová, Radka January 2014 (has links)
The work deals with the preparation and mechanical properties of coated Bioglass® 45S5 based foam materials with open porosity. The samples have been fabricated applying the replication method with use of polyurethane foam. Furthermore, these samples were coated in order to increase the strength characteristics and crack resistance. Polyvinylalcohol and PVA with cellulose microfibrils have been used as coating. Besides microstructural parameters of investigated materials using the SEM images strength characteristics in compression and in tension were also quantified.
60

Akustika malých ventilátorů / Acoustics of small fans

Hájková, Lenka January 2017 (has links)
Dissertation thesis falls within area of indoor climate and deals with investigation of acoustic microclimate in sanitary rooms of residential buildings during a mechanical ventilation. Sources of a noise in these areas are small fans. The thesis contains the evaluation of the existing situation concerning the referred issue, physical laws of acoustics and theoretical basics of acoustics of air conditioning. The part of the thesis is experimental measurement which aims to evaluate the situation in real applications and the possibility of influencing the acoustic microclimate by affixing of small fans on the building structure. The work contains a model for the verification of certain anticipated dependencies and theoretical investigation of the distribution of sound pressure levels in the sanitary room, depending on the location of the noise source. The last part of the work offers possible measures to improve the acoustic microclimate and elimination of the noise in sanitary rooms and in protected areas of residential buildings.

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