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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Využití a interpretace seismických povrchových vln v širokém oboru frekvencí / Application and interpretation of seismic surface waves in broad frequency range

Gaždová, Renata January 2012 (has links)
Submitted Ph.D. thesis is concerning the application and interpretation of seismic surface waves in a broad range of frequencies and scales. Using surface waves as a supplement to the methods dealing with body waves seems to be worth the effort. Surface wave interpretation can be used to obtain new information about the studied medium and simultaneously it can overcome, in some cases, the limitations of other seismic techniques. Moreover, surface waves are usually present on measured records and hence for its usage it is not necessary to modify the standard measuring procedures. One of the results of this thesis is an original algorithm for dispersive waveform calculation. The program works in an arbitrary range of frequencies and scales. The input parameter for the calculation is the dispersion curve. In this point the algorithm differs from all other approaches used so far. Algorithm is based on a summation of frequency components with shifts corresponding to the velocity dispersion and distance. The resulting waveform only contains an individual dispersive wave of the selected mode, thus being particularly suitable for testing of methodologies for dispersive wave analysis. The algorithm was implemented into the program DISECA. Furthermore, a new procedure was designed to calculate the dispersion...
22

Monitorování dynamických soustav s využitím piezoelektrických senzorů vibrací / Monitoring of dynamic systems with piezoelectric sensors

Svoboda, Lukáš January 2020 (has links)
The aim of this diploma thesis is to describe localization and calculation load identification of dynamic systems using piezoelectric sensors. Finding methods, which would allow us to evaluate loads on simple systems is the key to their application in the structural health monitoring of more complex systems. A theory necessary for understanding and application in aerospace, civil engineering, automobile industry, and train traffic of presented methods is given in the first part of the thesis. In these applications, the methods of wave propagation and different types of neural network methods are used to evaluate load identification. It is possible to evaluate loads by using a time reverse method, a method based on signal deconvolution, and a method based on a voltage amplitude ratio of the piezoelectric sensor. In the next part, the methods are described, the suitable place for gluing of a sensor, and the number of sensors for using method is given. These methods were verified and compared to a simple experimental system. In the following part, the model of the piezoelectric sensor is presented. It is possible to use the model for calculating voltage output from the strain. For methods verification, the problem of train passage in a specific place of the railway is chosen. The speed of the train and its load on the railway was calculated by using these methods.
23

Flíčková anténa s budicí štěrbinou / Centre-fed microstrip patch antenna

Jireček, Martin January 2011 (has links)
Systems with extreme bandwidth are part of advanced modern systems at radio high capacitive communication. Originally this technology was intended for radar scan. Thanks to wide frequency band had radar possibility „ see" a behind crimp, e.g. behind woody partitions etc . To his noise immunity, fail safe tapping plus small wattage heftiness began use for datal systŽm function. If is elementary antenna compound from coaxial probe and shorting outlet, it is possible use to actuating separate narrow slot placed in the middle of incandescent dabs. Impedance and radiating characteristics conventionally plumbed phlobaphene antennae excited tape lead and suggested microstrip phlobaphene antennae are experimentally explored plus collated. Explored is so and effect changes slotted longitude slot on characteristics elementary antenna.
24

Vysokofrekvenční měřič výkonu / RF power meter

Hlaváč, Štěpán January 2013 (has links)
This master’s thesis describes various principles of measurement of electromagnetic waves in a free space and on a line. Used sensors and their real parameters are given for every method. The analysis of protections of high-frequency inputs of measuring instruments is done here and the most suitable method and protections of input for realization are chosen. The analysis of design of secondary protection of high-frequency input is done in this project. The protection of input is realized and measured. The suitable method of measurement is chosen as well as the sensor for measurement of power. The block diagram and circuit diagram of the meter of power are designed. According to designed conception the measuring instrument for measurement of power is realized and its single qualities are measured during the realization. In the final part its precision is measured and the evaluation of results is done.

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