National Repository of Grey Literature 25 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Controller of three-axis nano-metric manipulator
Pernica, Lukáš ; Jedlička, Petr (referee) ; Drexler, Petr (advisor)
This semestral thesis describes the piezoelectric phenomenon and its use for positioning with nanometric precision in laboratory use. In the thesis is description of direct and indirect piezoelectric phenomenon, various types of piezoelectric actuators and ways of their control with the aim of eliminating their hysteresis. The goal is to design a controller for piezo actuator built in the three-axis nanometric manipulator Thorlabs MAX341/M.
Electrospinning of composite fiberous structures for piezoapplications
Schifferová, Zuzana ; Kaštyl, Jaroslav (referee) ; Částková, Klára (advisor)
Polymer and composite polymer-ceramic nanofibers were prepared by electrospinning process. Solution of 20 wt.% polyvinylidene fluoride (PVDF) in a mixture of dimethyl sulfoxide (DMSO) and acetone in the ratio of 7:3 was chosen as the most suitable precursor. When preparing composite nanofibers, 20 wt.% of barium calcium zirconate titanate (BCZT) or barium titanate (BT) nanoparticles was added to this PVDF solution. Given parameters were defined as the most suitable for the process of electrospinning: voltage of 50 kV, feeding rate of 30 l/min, distance between emitter and collector of 20 cm and needle diameter of 17 G. The effect of polymer molecular weight and the rotation speed of collector was also studied. Various properties of prepared samples were studied: morphology and fiber diameter, phase composition with the use of x-ray diffraction and Fourier transform infrared spectroscopy and also chosen electrical properties. Lower fiber diameters appeared with lower polymer molecular weight and higher rotation speed of the collector. These parameters resulted in higher percentage of the piezoelectric phase as well. The smallest achieved fiber diameter was around 300 nm, the highest percentage of phase was 92 % and the highest piezoelectric constant had a value of 16 pC/N. Composite fibers filled with BT particles showed better properties that the ones filled with BCZT particles.
Nano-ammeter with galvanic isolation
Šimka, Marek ; Kubíček, Michal (referee) ; Kolka, Zdeněk (advisor)
This bachelor thesis deals with all the aspects, that are important in the designing of the nano-ammeter. In theoretical part, there are described possible ways to measure electrical current of very low values. Other parts of the thesis describe all parameters, which are influencing measurement accuracy. These are, for example, unwanted and leakage currents, but also other parasitic phenomena that may occur. Thesis explains how to minimize unwanted currents and other influences. Practical section provides more detailed description of the proposed main scheme. There are also described components, that have been selected as the main parts of the nano-ammeter circuit. Subsequent part contains analysis of printed circuit board including all layers. Furthermore, the thesis deals with the realization of equipment and possible errors. The results of the bachelor are summarized in the last chapter.
Analytical model of composite cantilever with SMART layer
Dostal, Vojtěch ; Ševeček, Oldřich (referee) ; Majer, Zdeněk (advisor)
This bachelor's thesis deals with analytical modelling of composite cantilever with smart layer. The structure is based on the real piezoelectric generator, which is a solid cantilever beam with a layer of piezoelectric material attached to its bottom and top. The first part of this bachelor's thesis summarizes the knowledge of the energy harvesting, the process under which harvesting of electric energy from the piezoelectric generator belongs. Some piezoelectric materials are mentioned and described afterwards. At first, analytical modelling is implemented on the homogeneous cantilever beam. Then, the relations for required characteristics are derived for laminate structure, which is structurally similar to the piezoelectric generator. One chosen parameter will be changeable. Due to the ties of relations, the required characteristics will change as well, which are for the piezoelectric generator strain and deflection.
Piezoelectric vibration energy harvester
Klásek, Matyáš ; Rubeš, Ondřej (referee) ; Hadaš, Zdeněk (advisor)
The first goal of this bachelor’s thesis is to give an overview of piezoelectric materials and their utilization in energy harvesting applications. The second goal is to examine the effect of altering model parameters on generated power and natural frequency of the system using analytical model of a bimorph piezoelectric cantilever beam in MATLAB/Simulink.
Piezoelectricity in technical practice
Škarabelová, Lenka ; Frk, Martin (referee) ; Kazelle, Jiří (advisor)
Bachelor's thesis is dedicated to the study of the principle and possibilities of use of the piezoelectric effect. Since the use of piezoelectric effect in electrical engineering is very extensive, the main focus is placed on the ability to exploit this effect in the field of ultrasonic and piezoelectric resonators. Next aim of this work is practically and theoretically to get acquainted with the measurement of small changes in weight, using electrochemical quartz crystal microbalance (EQCM), also with an ultrasonic equipment from company Olympus and ultrasonic defectoscopy for detection of possible imperfections in the material and their evaluation.
Impact hammer calibration
Šafář, Jakub ; Havránek, Zdeněk (referee) ; Beneš, Petr (advisor)
The aim of this thesis is verification of sensitivity of an impact hammer ENDEVCO 2302-5. The tesis also discusses the possible negative influences of the experiment. Calibration of an impact hammer was performed using known mass.
Penile plethysmography
Koudelková, Zuzana ; Harabiš, Vratislav (referee) ; Hrozek, Jan (advisor)
This bachelor´s thesis focuses on methods that examine volumetric changes of genital organs (especially for volume changes in male sexual limb). These changes are used in the sex diagnosis. The most common type of examination is to determine sexual preference of the patient. The aim of this work is to describe how have been the changes investigated previously and how they are investigating in the routine practice now. Find out which are their limits. Try to build a new type of sensor which could help to better evaluate the volume changes. And try to create a program in LabVIEW environment in which the measured data is displayed and stored.
Electrical properties of ferroelectric materials
Hudeček, Ondřej ; Rozsívalová, Zdenka (referee) ; Frk, Martin (advisor)
This presented work deals with properties and application of ferroelectric materials in electrical engineering. Experiment was pointed on measuring and evaluation temperature and frequency dependence complex permittivity for various ferroelectric ceramic materials.
Measurement of Parameters of Piezoelectric Active Elements for Acoustic Emission Sensors
Fialka, Jiří ; Erhart,, Jiří (referee) ; Sedlák, Petr (referee) ; Beneš, Petr (advisor)
The doctoral thesis discusses the measurement of parameters of piezoelectric (PZT) materials and the influence of temperature on their stability. In the introductory sections, the author briefly explains the piezoelectric effect and its use; simultaneously, methods for the preparation of piezoelectric materials and the measurement of their properties are presented to illustrate the analyzed problem. The experimental part of the thesis describes the procedure of measuring and calculating the complete matrix of material coefficients from samples of PZT ceramics. The applied set of piezoelectric samples complying with relevant European and world standards was made in the form of thin plates, thin discs and cylinders, via gradual modification of the large disc. The NCE51 and/or the older PCM51 ceramics obtained from the company Noliac Ceramics were used in determining the complete matrix and describing the measurement method. Both these types are soft piezoceramics composed from a solid solution of lead zirconate and lead titanate with the general chemical formula of Pb(Zr1-x,Tix)O3. The real crystallographic structure and chemical composition of the samples were confirmed by X-ray diffraction spectroscopy and energy dispersive spectroscopy (EDS), respectively. The frequency method was used for the measurement and calculation of all material coefficients. An Agilent 4294A impedance analyzer and a set of measuring tweezers marketed as “Tweezers Contact Test Fixture 16334A” were used in the process. Fast determination of the entire matrix of coefficients without any special requirement for the preparation of the samples to be measured was tested and verified. The charge coefficients of the piezoelectric material were confirmed by direct methods including the laser interferometer technique, the vibrometric method, and the procedure utilizing changes of the force applied to the sample. The advantages and disadvantages of the methods were compared and defined based on measurements and their results. The main part of thesis was focused on the behavior of piezoelectric material at high temperatures near the Curie point. Depolarization performed by means of a high temperature approaching the Curie point constitutes a significant yet hardly measurable material property of PZT ceramics. Commonly available vibrometric methods (d33-meters) do not appear to be suitable for the measurement of temperature dependencies, and for that reason the frequency technique was used. The piezoelectric charge coefficient, whose value can be effectively measured via the above-discussed frequency method, was selected as the indicator showing the depolarization state in the applied piezoelectric ceramics. The accuracy of the procedure was verified via comparison of the vibrometric method in cylinders of the NCE51 ceramics with different sizes, which are designed for the longitudinal length mode. The result is an optimized measurement methodology which facilitates accurate determination of the Curie temperature, namely phase transition to the cubic crystallographic structure. The experiment also proved the applicability of progressive, controlled depolarization of PZT ceramics via high temperature, and it also enabled us to define the temperature limits at which there occur irreversible changes of the piezoelectric properties of piezoceramics. In the measured NCE51 and PCM51 materials, the limit for the irreversible changes was equal to 95% of the Curie temperature.

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