This master's thesis deals with the development and verification of the model of the piezoelectric generator, incl. determination of its parameters. This mathematical model should be used as a tool for development of new devices, especially for analysis of applicability of available energy source (vibration) and for design of device itself. At first the review of energy harvesting is described deeply. Subsequently piezoelectric generators and the ways how we can model them, are depicted in details. The methodology of parameters estimation and model development is presented in state space or in MATLAB/Simulink environment and applied on the commercial generator Midé V21BL. A device has been made within the scope of the thesis, which can be used as an universal tool in experiments with generator. Finally the model is applied on the analysis of energy yield from man's walk and there is also brief introduction to model modifications.

This work deals with design and implementation of simple demonstration aplication for simulation of a water flow on irregular terrain. The work examines essential building blocks of the simulation. It also suggests approaches that can be used to optimize and/or extend used method.

This thesis discusses of the intake tract four-stroke ignition internal combustion engine and the filling efficiency and opportunities to increase this efficiency and consequently to optimize the course of torque and power at the specified serial engine. 3D model is the last point of this thesis.

Study of electric field in radiation detectors by Pockels effect (Master Thesis) by Michael Hakl Abstract Cadmium Telluride (CdTe) is a convenient candidate for room tem- perature detection of X-ray and gama radiation due to 1.5 eV band- gap energy and high atomic mass. Since CdTe has the highest linear electro-optical coefficient among II-VI compounds, the detector rep- resents a Pockels cell. Transmittance of the crystal is modulated by the internal electric field. Processing of infrared camera photographs results in an electric field profile between biasing electrodes. The elec- tric field in semi-insulting CdTe is influenced with deep level traps causing charge polarization under the electrodes. Occupation of traps is dependent on metal-semiconductor interface. Relation of charge accumulation and band bending for gold and indium contacts was studied. Repolarization/depolarization induced by additional illumi- nation with sub/above bandgap excitation laser was observed and ex- ploited for determination of the deep level energy. Results obtained by the Pockels-effect method were supported with luminescence measure- ments. Correlation between the occurrence of deep levels and surface point defects was discovered. Keywords: Pockels electro-optical effect, Cadmium Telluride ra- diation detector, Electric field, Schottky...

Modification of interfaces in nanostructures can significantly influence their overall properties. Magneto-optical spectroscopy and spectroscopic ellipsometry are ideal for studying these phenomena thanks to their in-depth sensitivity and contactless measurements. Two methods of nonreversible modification of magnetic properties, especially the magnetic anisotropy, are investigated. The measured spectral dependence of magneto-optical Kerr effect is compared to a theoretical calculation in order to determine the profile of the samples for different levels and methods of modification. In addition to this, ellipsometric measurements are performed on a device whose optical properties change by voltage application.

Two important mechanisms in preparation of ultrathin films of magnetic oxides were systematically investigated in this work. First, influence of epitaxial strain on resulting magneto-optical properties of La2/3Sr1/3MnO3 (LSMO) ultrathin films was studied. The investigated films were grown by pulsed laser deposition on four different substrates, providing a broad range of induced epitaxial strains. Magnetic properties were found to deteriorate with increasing value of the epitaxial strain, as expected due to the unit cell distortion increasingly deviating from the bulk and effect of the magnetically inert layer. A combination of spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy was used to determine spectra of the diagonal and off-diagonal elements of permittivity tensor. The off-diagonal elements confirmed presence of two previously reported electronic transitions in spectra of all films. Moreover, they revealed another electronic transition around 4.3 eV only in spectra of films grown under compressive strain. We proposed classification of this transition as crystal field paramagnetic Mn t2g → eg transition, which was further supported by ab initio calculations. A key role of strain in controlling electronic structure of ultrathin perovskite films was demonstrated. Dynamic application of...

Title: Point defects in materials for detection of X-ray and gamma radiation Author: Martin Rejhon Department: Institute of Physics of Charles University Supervisor: prof. Ing. Jan Franc, DrSc., Institute of Physics of Charles Uni- versity Abstract: Cadmium telluride and its compounds are suitable materials for pro- duction of X-ray and gamma-ray detectors working at room temperature. How- ever, the detector quality is affected by material imperfections, such as crystal defects and impurities. It results into forming of deep levels which act as re- combination and trapping centers. Then, the accumulated space charge at these deep levels influences electric and spectroscopic properties of the detector. In the end it may result in the polarization effect, when the electric field is localized in vicinity of one contact and detection properties are decreased. This thesis reports a complex study of a detector band structure by various meth- ods with focus on differences between CdTe, CdZnTe, CdTeSe and CdZnTeSe. The electro-optic Pockels effect is used to investigate the influence of the illumi- nation in range 900 − 1800 nm on the inner electric field. The temperature and time evolutions of the electric field after application of bias or switching of the additional light at 940 nm were measured to determine deep levels...

Title: Martensite microstructures in thin films and monocrystals of Heusler alloys Ni-Mn-Ga Author: Kristýna Onderková Department: Department of Surface and Plasma Science Supervisor: Mgr. Ing. Oleg Heczko, Dr., Institute of Physics of the Czech Academy of Sciences Abstract: The submitted thesis examines mainly the first thin films from Ni-Mn-Ga Heusler alloy prepared by magnetron sputtering on the new equipment at Institute of Physics of Charles University. However, the work also analysed the thin films prepared in IFW Dresden and bulk material. The main focus of the work is primarily on the martensitic microstructures, because of the significant effect that their twin boundaries have on the magnetic shape memory phenomena. Microscopic techniques used for the research were mainly Scanning Electron Microscopy (SEM), but also Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). As the Ni-Mn-Ga properties are stronly dependent on chemical composition, the composition was evaluated by two different methods (Electron Dispersive X-ray Spectroscopy and X-ray Fluorescence) and observed differences discussed. Finally the results were compared with X-ray diffraction (XRD) measurements and the films were further characterised by magnetic measurements using Vibrating Sample Magnetometer (VSM)....

The aim of this master thesis is to prepare and systematically characterize two groups of ultra-thin films of iron garnets with different compositions and deposition conditions. The first set consists of approximately 10 nm thick samples of gallium-doped yttrium-iron garnet on gadolinium gallium garnet (Gd3Ga5O12) (GGG) substrates with different crys- tallographic orientations and different annealing temperatures. The second group con- tains gallium-bismuth-doped neodymium-iron garnet on GGG substrates. These samples have different thicknesses, the concentration of individual elements and different annealing temperatures. All samples were prepared by the metal-organic decomposition method. The analysis of their physical properties was done by magneto-optical Kerr effect (MOKE) and optical experiments. Specifically, MOKE spectroscopy, Faraday hystere- sis loops measurements and spectroscopic ellipsometry. Obtained experimental results were further used to deduce the spectral dependence of complete permittivity tensor. Its spectral dependence was than discussed with relation to the electronic structure of in- vestigated materials which helped to select the best deposition conditions and substrate orientation. 1

My master’s thesis deals with methods of measuring the ultrasonic blood flow blood vessel with a detailed focus on Doppler ultrasound systems, which find application in the diagnosis of superficial vascular and obstetrics. The thesis is described a proposal indicating polydirectional Doppler system with a continuous carrier wave frequency of 4 MHz, the intensity of ultrasound 100 mW/cm2 and diameter D-shaped transducers 8 mm. As a result, the indicator will be able to measure blood flow velocity in the range of 5-40 cm/s, which appears to 3.5 digit display. After describing important theoretical assumptions, the work pays block diagram indicator. Furthermore, it examines the various functional blocks on the requirements imposed on them. It looks at the options of each functional block, and finally describes the implementation of the selected option and including peripheral solutions. Great attention is paid to the power of the indicator, where the power supply will be used 9 V battery. Create a symmetric voltage for operate amplifier and other auxiliary voltage will procure DC/DC converters. In conclusion, the work is located around the perimeter solutions indicator. The following draft for the production of double-sided PCB, its installation and a list of elements. The outcome of the thesis is complete documentation for the implementation of an indicator of blood flow, which allows us to obtain information on throughput vessels, especially the lower and upper limbs.