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Measurement of gradient magnetic field decay in MR tomograph
Kubásek, Ondřej ; Kubásek, Radek (referee) ; Bartušek, Karel (advisor)
The objective of my thesis is to measure magnetic field gradient decay in an MR tomograph, process and evaluate the data measured and analyse the issue. The theoretical section focuses on the reasons for the gradient distortion which has a negative impact on NMR measuring techniques and it also describes options to eliminate the negative effects, focusing mainly on pre-emphasis filtration. It also lists methods of gradient magnetic field measuring. The practical section contains results of magnetic field decay measurements taken with the tomograph in the Institute of scientific instruments of the Academy of sciences in Brno using the method of instantaneous frequency with and without pre-emphasis compensation. The data are processed with MAREVISI and MATLAB programmes. MATLAB is used to develop a modern method of filtration to eliminate noise in useful signal leading to more accurate measurements of MR magnetic fields. This filtration uses a method of time-dependent variable thresholds and two-channel filter banks. MATLAB is also used to design a programme for approximation of the measured gradient magnetic field decay. The decay must be approximated in order to obtain time constants and the degree of exponential decay, which serve to set up the pre-emphasis compensation.
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FTTx networks
Hradílek, Pavel ; Reichert, Pavel (referee) ; Filka, Miloslav (advisor)
The aim of this thesis is to clarify the issue of optical access networks, and to acquaint the reader with problems of their design and implementation. The introductory chapter describes the technologies and topologies, which are the most experienced in dealing with optical access network. There are a comparison of their basic parameters and limiting factors. Another part of the work is dedicated to progressive methods of construction such as microtubes and solution using the hanging cables, which due to the efficiency of construction, rapidity, economic and facilitate implementation. In conclusion the theoretical part there is issues of measurement. It describes a Optical Loss Test Set, OTDR method and method of measuring dispersion. Increasing demands on the capacity of the transmission paths, and their quality are caused of monitoring optical access networks, which can evaluate the failure on a route, target problems and inform service. The practical part compares EPON and GPON. In program OptiSystem was created model which these technologies are evaluated in terms of performance parameters, noise, jitter and eye diagram quality. The common feature of technology is transmission TDM frames, where EPON uses Ethernet and GPON technologies ATM. The outcome of simulation don´t show which technology is better, but result shows the conditions of the proposal of these technologies. At the end of work there are created several models for solving the optical access network with pricing per user. The most developed technology is FTTB in urban areas, when transmission in last mile uses copper circuit. This solution causing a rapid return on investment. Other technologies such as point-to-point FTTH or PON are implemented as individual proposals. Each of these solutions has advantages and disadvantages, so each project is unique and the solution is dependent on the project site and the requirements of customers.
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THE UNCERTAINTIES DEFORMATION AND STRESS USING THE STRAIN GAUGES
Dokoupil, Pavel ; Vlk, Miloš (referee) ; Koška, Petr (referee) ; Habán, Vladimír (advisor)
The dissertation thesis deals with the determination of uncertainty of strain measurement and the stress using resistance strain gages. You can find two methods to define the uncertainty in the thesis, GUF and MMC, and both are applied for measurements carried out with resistance strain gages. Definition of the measurement uncertainty was set for the strain measured by uniaxial and biaxial strain gages. The uncertainty of the stress was defined for linear strain gages, T Rosettes and Rosettes. There were universal mathematic-technical models defined to measure strain and stress, these models can be used either for standard and special measurements i.e. high-temperature, or for measurements in radiation field. Each part of the strain uncertainty and stress is analyzed from the point of view of a size of uncertainty and a form of probability of the function that strain and stress can adopt. The maximum focus was dedicated to the mistakes influencing measured strain like strain gage properties, installation and operating influences, external influences, time effects and the influence of the measured object. There are two mistakes influencing the stress described and analyzed in the thesis, the mistake of the Young’s modulus of elasticity and the mistake of the Poisson’s ratio. The thesis is conceived as a complex of information related to the measurement uncertainties using the resistance strain gages and methods of defining the measurement uncertainty in a way that the experimenter can apply the gained info and methods in the required measurements. The final chapters give representative examples to define measurement uncertainties for uniaxial and biaxial stress applying GUF and MMC method. The thesis also includes the experiment that compares measured values of strain, stress and measurement uncertainties, using several different types of strain gages at different temperatures, with theoretical calculation of strain and with stress. The experiment was carried out using the displacement sensor that works on an elementary principle of bending load.
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Measurements of the stress in the turbine spiral casing using the strain gauges
Dokoupil, Pavel ; Pochylý, František (referee) ; Habán, Vladimír (advisor)
The Master‘s thesis is focused on measuring of the stress in the spiral case of water turbine using the strain gauges measurement. It contains the theoretical and the practical part. The theoretical part includes a description of theoretical background (basic mechanics, measurement and evaluation, strain gauges, pressure measurement, uncertainty of measurement). One of the chapters describes Water Power Plant Lipno nad Vltavou (history of power plant, issues and the history of measurement). The practical part contains a theoretical calculation of measurement uncertainty and measuring of stress on spiral case Francis turbine at Water Power Plant Lipno I (Unit TG2). Measurement was made before and after overhaul. There are described technical data of spiral cases, description of measurement, results of measuring of strain and stress including comparison with the pressure in spiral case and calculation of uncertainties of measurement.
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Nonlinear models of DC machines
Král, Michal ; Mišinger, Lukáš (referee) ; Mach, Martin (advisor)
This bachelor thesis deals with modeling and simulation of DC motors. Four models of DC motors were created, according to four types of excitation ( derivative, serial, compound and separated). These models were designed in simulation program MATLAB & Simulink. Models were adjusted in order to respect magnetic non-linearity. Parameters for simulations were measured on real DC machine and the simulations were executed. This theses focuses on examination of temporary effects and comparing with real measured developments.
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Dynamic parameters of sports and conventional vehicles
Tesař, Michal ; Janoušek, Michal (referee) ; Vémola, Aleš (advisor)
This master´s thesis is focused on chosen dynamic parameters of a sport vehicle represented by student formula Dragon 7 and comparison of these parameters with conventional vehicles represented by two exemplars of ŠKODA Superb III. Driving tests used for the comparison are simulating the real driving situations from the roads in order to possibly use those for the road accident analysis in the future. All the measurements were taken under lower adhesion conditions which might help solving of the road accidents under such conditions in the future. There is also a description of vehicle driving systems and components which have an influence on the vehicle´s driving dynamics incorporated in the thesis.
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Software for control and evaluation of climatic and temperature tests
Malinka, Rostislav ; Pikula, Stanislav (referee) ; Šedivá, Soňa (advisor)
This thesis deals with design of software for control and evaluation of climatic and temperature test in accredited testing laboratory CVVOZE. It includes literar research in field of climatic and temperature tests, definition of software requirements and making of application flowchart diagram. The thesis also includes implementation description of proposed control software in terms of the program and also a documentation of the application, which focuses on explanation of all application functions to the user.
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The issue of revision of electrical equipment
Mašin, Dominik ; Huzlík, Rostislav (referee) ; Veselka, František (advisor)
My bachelor’s thesis is focused on preparation and regulations for executing base technical revision and professional inspection. Next part is concentrated mainly on periodical revision, its contents and evaluation of archieved results during measurement. Each type of measurement, which is recomended to execute during technical revision and professional inspection, is described. Thesis also contains overwiev of special measurement devices and benefits of their usage. Summary of the most common flaws in execution of technical revision and professional inspection was worked out and divided into three parts: lack of preparation, flaws in measurement, testing and in revised device's measurement results evaluation. Final part of my bachelor's thesis contains practical preparation process, measurement and testing and evaluation of chosen revised electrical device.
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The Calculation Of The Amount Of Material Injury Caused By The Forests In The Areas Of Implementation Of Water Management Structures
Bureš, Petr ; Čermák, Jan (referee) ; Vala,, Vlastimil (referee) ; Alexandr, Pavel (advisor)
Problem situations in damage to forests as a result of construction activities is the total of its quantification, because of not only to damage to the forest and the land intended for the performance of the function of the forest, but also to damage to the water feature of the forest. The emergence of the crop damage and forest grounds occurs at the same time damage to the management. Broken water conditions on the forest grounds, inter alia, that the environmental damage (or one of its components), are also material injury for the owner of the forest, because it directly affect the amount of the additional costs linked to its management in the forest. The existing decree MZe ČR no. 55/1999 Coll. on the method of calculating the amount of loss or damage caused to forests assesses only the injury or damage to the forest and the land intended for the performance of the functions of the forest, but does the forest and its other non-production function as a forest ecosystem. The damage (the material injury) on the water feature of the forest is not the above mentioned decree dealt with. Initially formulated the problem lies in finding the right way of solving how to objectively quantify the financial damage to the forest, inc. damage to the water feature of the forest and thus closer to the actual damage to the exaktnosti forest, resulting in direct connection with the location and the realisation of the buildings.
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