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Lateral Torsional Buckling of Thin-Walled Steel Beams with Web Holes
Horáček, Martin ; Škaloud, Miroslav (referee) ; Juhás,, Pavol (referee) ; Melcher, Jindřich (advisor)
The current trend in the design of steel structures leads, due to the saving of the material, to the frequent use of thin-walled cold formed steel sections. Thin cold-formed steel profiles are often manufactured with web holes. A specific example of thin-walled steel profiles are Sigma beams used in additionally installed built-in floors systems in warehouses. The aim of doctoral thesis is the analysis, assessment and experimental verification of the technical solution of thin-walled steel beams with web openings loaded in bending with respect to lateral torsional buckling. The objective is to develop knowledge about the real properties of steel members of considered structural arrangement in order to specify the methods of analysis and design in industrial practice. The theoretical analysis describes the behavior of the beams by means of solving the differential equations of the equilibrium on deformed element of thin walled member under bending. In case of beams with web holes is used the solution in the form of introduction of substitute cross-section properties, which are defined as the weighted average of the properties of full and weakened section. The numerical analysis is focused on the use of commonly available software in order to predict the bending resistance of beams with web opening with respect to lateral torsional buckling. Since the software used in practice solves only the prismatic beams without option to model the web openings, it is in frame of numerical analysis verified the model of beam with reduced thickness of web constantly over the whole beam length in the zone of perforation. The experimental analysis is firstly focusing on the verification of real bending and torsion stiffness of the beams, based on which are being derived the values of basic cross-sectional properties. Subsequently the experimental verification of real bending resistance with respect to the lateral torsional buckling is being performed.
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Artificial heart on the principle of gas accumulators
Kunický, Ondřej ; Fialová, Simona (referee) ; Pochylý, František (advisor)
The diploma thesis deals with the design of an artificial heart based on the principle of gas accumulators. The introductory part describes the anatomy and physiology of the human cardiovascular system, mechanical heart replacement and the basic properties of pneumatic mechanisms. Furthermore, there is shown the procedure of pneumatic circuit design and its simulation in the program Simulink. The experimental part contains verification of the functionality of the pneumatic circuit, designed the positive displacement pump, and the measured characteristics of both ventricles. The last part of the work deals with the reduction possibilities of dimensions and weight of the whole mechanism. There is also included computational modelling of the pneumatic circuit using helium as a working medium.
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Modeling of cavitating flow
Frölich, Kamil ; Klas, Roman (referee) ; Rudolf, Pavel (advisor)
his thesis deals with the problems of cavitation flow in a Venturi tube. It is made for a multi-phase (water-vapour) flow calculation of two geometry tubes. Results of numerical calculations for the flow geometry (dimensions) are compared with performed experiment. Numerical flow calculation was performed in the Fluent 2.3.26.
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Experimental Verification of Optimal Shape of Beam
Uríček, Matúš ; Keršner, Zbyněk (referee) ; Frantík, Petr (advisor)
The thesis deals with design of beams of optimized shapes, which are than manufactured by 3D printer and their features are experimentally verified. When the limit strength of a given component is reached, ways of fracture development are observed. Information obtained from the experiments are then compared with assumptions generated by numerical methods.
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Study of Electronic Control and Real Behavior in Variable Filtering and Oscillating Applications of Modern Active Elements
Šotner, Roman ; Ondráček, Oldřich (referee) ; Martínek,, Pravoslav (referee) ; Petržela, Jiří (advisor)
The thesis deals with electronically adjustable and configurable applications of the modern active elements. In the field there were presented various active elements in applications of the analog filters and oscillators which stem from basic and more or less similar principles of circuit synthesis and design. However, there is not provided study of real behavior in detail and in most cases electronic control of the various parameters in application is not verified. In the precise design of application is very important to identify problematic features and determine how much it influences functionality of the device. In this work several filtering structures based on common and modified synthesis principles (integrator loops) are compared in the view of multifunctionality, configurability, variability, kind of used electronic control and impact of influences of real elements on behavior. There are used standard methods like adjusting of variable transconductance, intrinsic value of current input resistance and not so common method based on variable current gain in design of modified and improved multifunctional filtering circuits. The last method of mentioned control enabled to find quite unique filter which allows continuous electronic change of transfer from band-reject to all-pass filter of the 2nd order without reconnection. It is much simpler than previous and more common integrator loops. Larger part of this work is focused on electronically controllable oscillators mainly on quadrature types. There is presented several very simply and elementary realizations which require minimal number of active and passive elements. There are also slightly or more complicated solutions which remove some drawbacks of mentioned simpler variants. First of all there is given attention on study of real behavior which make obvious different problems with mutual dependence of oscillation condition and oscillation frequency, dependence of produced amplitudes (quadrature types) on parameter which is controlling oscillation frequency, influence of this parameter on oscillation condition, etc. In the framework of this part of the thesis there was introduced a novel modification of current conveyor transconductance amplifier (CCTA) so called current-gain-controlled current conveyor transconductance amplifier (CGCCCTA). Requirements for novel applications in the field of oscillators for newly developed controllable current amplifier and digitally controllable current amplifier (DACA) at the Department of Telecommunication FEEC BUT lead to creation of several chapters of this work where mentioned active elements can be used. The important contribution of this work (for practical approach) is also experimental testing of most of designed circuits and determination of exact design equations and rules which take into account real behavior of circuits and confirm results obtained from experiments.
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Optimization of hydrostatic bearing pad geometry using CFD simulation
Dryml, Tomáš ; Vimmr, Jan (referee) ; Michalec, Michal (advisor)
The master's thesis deals with the optimization of hydrostatic bearing pad geometry using CFD simulation and experimental measurements. By combining experimental and numerical approaches, the effect of variation of hydrostatic bearing recess shape and depth on individual operating parameters is investigated. The effect of geometry variations is determined by numerical simulations which have been validated with experimentally obtained data. The results show that the ideal recess depth should correspond to 20-50 times the lubrication layer height The simulations also show that depth variation has a significant effect on the operating parameters. In contrast, the variation of the recess shape does not significantly affect the operating parameters of the bearing. The design of the optimum geometry of the hydrostatic bearing is particularly important because it can bring significant financial and energy savings associated with the operation of (especially large-sized) hydrostatic bearings.
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Experimental Verification of Semi-Rigid Timber Connections Using Alumidi Connectors
Neusch, Matúš
This paper deals with experimental verification of semi-rigid timer connections using modern timber connectors Rothoblaas Alumidi. The experiment consists of the loading of timber bracket of structural wood. There are 4 alternatives of connection prepared. Each alternative has 4 specimens. So far, 4 specimens out of a total of 16 specimens have been verified. The paper describes the preparation of the experimental set-up, the loading procedure, the preliminary findings and the results of the performed experiments. These results are confronted with numerical calculations and assumptions of previous theoretical research. Experiment research continues with the testing of additional specimens.
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Artificial heart on the principle of gas accumulators
Kunický, Ondřej ; Fialová, Simona (referee) ; Pochylý, František (advisor)
The diploma thesis deals with the design of an artificial heart based on the principle of gas accumulators. The introductory part describes the anatomy and physiology of the human cardiovascular system, mechanical heart replacement and the basic properties of pneumatic mechanisms. Furthermore, there is shown the procedure of pneumatic circuit design and its simulation in the program Simulink. The experimental part contains verification of the functionality of the pneumatic circuit, designed the positive displacement pump, and the measured characteristics of both ventricles. The last part of the work deals with the reduction possibilities of dimensions and weight of the whole mechanism. There is also included computational modelling of the pneumatic circuit using helium as a working medium.
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Experimental Verification of Optimal Shape of Beam
Uríček, Matúš ; Keršner, Zbyněk (referee) ; Frantík, Petr (advisor)
The thesis deals with design of beams of optimized shapes, which are than manufactured by 3D printer and their features are experimentally verified. When the limit strength of a given component is reached, ways of fracture development are observed. Information obtained from the experiments are then compared with assumptions generated by numerical methods.
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