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Analysis of laser usage in machining technology.
Kavan, Petr ; Osička, Karel (referee) ; Zemčík, Oskar (advisor)
The main object of this bachelor’s thesis is analyzing the laser and its application in mechanical engineering especially in material machining. The work introduces basic laser´s types and laser´s systems analysis used in current industrial profession. The problems of laser ray interaction with machined material are analysed and the most occurred technological processes in machining of material by laser in engineering in current time are analysed. The author is focused on general and complex summary of relevant problem firstly.
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Advanced techniques of micromachining
Šalomoun, Vojtěch ; Prášek, Jan (referee) ; Pekárek, Jan (advisor)
Fabrication of micro-electro-mechanical systems (MEMS) requires advanced level of miniaturization, which is not achievable by technology used in microeletronics. Socalled micromachining covers many unique techniques of material processing to get microstructures with possible dimensions below 1 m. This bachelor’s thesis gives a general introduce to micromachining of MEMS. Its focus is on bulk and surface micromachining by wet and dry etching. The practical part contains design of microstructures, their manufacturing process and creation of computer models in CoventorWare suite.
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Piezoelectric MEMS resonators for sensing applications
Klempa, Jaroslav ; Svatoš, Vojtěch (referee) ; Gablech, Imrich (advisor)
Basic principles and processes used during fabrication of microelectromechanical systems are presented in this work. This thesis is focused on material properties, deposition, lithographic and micromachining processes. Fundamental principles and applications of piezoelectric resonant structures are described as well. Final part of this work is devoted to simulation of resonant beams using FEM method in ANSYS® Workbench, practical fabrication and characterization of piezoelectric MEMS resonators.
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Research and Development of Modern Emission MEMS Sensors
Pekárek, Jan ; Husák, Miroslav (referee) ; Vlach, Radek (referee) ; Vrba, Radimír (advisor)
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.
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Use of unconventional technologies in the production of a selected component
Havlínová, Denisa ; Kalivoda, Milan (referee) ; Dvořáková, Jana (advisor)
The biggest challenge during manufacturing copper part with microslit for optical spectrometer by the means of unconventional technologies was to meet specified narrow range of tolerances and reach right angles at the microslit corners. Electrical discharge machining and laser beam machining were two practically performed methos and both successfully met these tolerances. After consultation is focused ion beam also considered as suitable method for this task, while for photochemical machining is impossible to meet those narrow tolerances. Right angles were not achieved by any of tested methods. At laser cutting edges were proven defects (burrs, molten material), while we saw no negative defects on electrical discharge workpiece surface. Even after optimalization of EDM was machining time longer and there is assumed higher other production cost (tool manufacturing for every single workpiece), but still EDM seems to be more advantageous from financial and surface quality aspect. Based on theoretical research and practical manufacturing is recommend to manufacture specified component with microslit by EDM.
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Terahertz Antenna Arrays for Communications
Warmowska, Dominika ; Joler, Miroslav (referee) ; Pokorný, Michal (referee) ; Raida, Zbyněk (advisor)
The thesis is focused on the research of THz antenna arrays to be used for communications. Attention is turned to modeling metallic surfaces at THz frequencies, a proper characterization of gold conductivity, its relation to Drude model and corresponding measurements. Moreover, the best methods for modeling thin metallic layers (depending on the skin depth related to the metal thickness) are presented. An optimized element of a THz 2×2 antenna array designed for the application of communications is developed in a way that enables an expansion to a larger array. The expansion ability is demonstrated on a 4×4 antenna array which is presented in the thesis too. The designed antennas achieve parameters better than the state-of-art antennas. The presented antennas radiate circularly polarized wave at THz frequencies, operate in a wide bandwidth, have a high gain and are of a compact size. In the thesis, an 8×8 antenna array with a beam steering capability is presented. The main beam of the antenna array can be controlled in two dimensions. A high gain of the radiated circularly-polarized wave can be achieved that way. Different approaches to modeling antennas with thin metallic layers are compared and the best methods are recommended from the viewpoint of different requirements. The designed 2×2 and 4×4 antenna arrays are manufactured using a microfabrication technology. Each step of the fabrication is described in detail and discussed. The reflection coefficient at the input of antennas is measured and compared with simulations. Discrepancies in results are associated with surface roughness which is analyzed by a scanning probe microscope and a scanning electron microscope. By down-scaling the developed THz antenna, a low-profile high-gain antenna for Ka-band space applications is designed. The presented antenna achieves better results than state-of-art CubeSat antennas. The antenna performance is verified by a prototype to be operated at 9 GHz, and the radiation characteristics are experimentally confirmed.
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Aplication of picosecond laser micromachinning for manufacturing of reflective DOE for CW power lasers
Mrňa, Libor ; Novotný, Jan ; Kolařík, Vladimír
Reflective optical elements are advantageous in terms of ease of cooling, where even a less efficient element can be easily operated without damage by a simple cooling system. When material interacts with the ultrashort pulses, the interaction is largely non-thermal and the material can be removed in a very defined manner without affecting the surrounding area. Direct ablation with ultrashort laser pulses enables fast and flexible fabrication of diffractive optical elements (DOEs). Ultrashort pulses can also be used to machine difficult-to-machine materials with conventional lasers and easily create spatial structures on the order of tens of micrometers.
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Use of unconventional technologies in the production of a selected component
Havlínová, Denisa ; Kalivoda, Milan (referee) ; Dvořáková, Jana (advisor)
The biggest challenge during manufacturing copper part with microslit for optical spectrometer by the means of unconventional technologies was to meet specified narrow range of tolerances and reach right angles at the microslit corners. Electrical discharge machining and laser beam machining were two practically performed methos and both successfully met these tolerances. After consultation is focused ion beam also considered as suitable method for this task, while for photochemical machining is impossible to meet those narrow tolerances. Right angles were not achieved by any of tested methods. At laser cutting edges were proven defects (burrs, molten material), while we saw no negative defects on electrical discharge workpiece surface. Even after optimalization of EDM was machining time longer and there is assumed higher other production cost (tool manufacturing for every single workpiece), but still EDM seems to be more advantageous from financial and surface quality aspect. Based on theoretical research and practical manufacturing is recommend to manufacture specified component with microslit by EDM.
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