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Variabilita šířky letokruhu a konvenční hustoty dřeva smrku ztepilého po výšce kmene na Drahanské vrchovině
Jelínek, Michal
An aim of this bachelor thesis was a setting of part earlywood and latewood, a width of tree-ring and a basic density of a norway spruce wood depending on a trunk height. For those purposes were on Drahany highlands singled out four-levels spruces, that grew in an altitude from 600 to 660 m. a. s.From these spruces was cut out ten wheels along the trunk height. Dendrochronological analyse was performed according to a standard dendrochronological methodology. Measurement of tree-rings width and earlywood and latewood was made in a programm Past 4 and WinDendro. A calculation of a maximum amount for the basic density calculation was made according to Olsen's methodology. It was found out that with increasing age of a tree comes slightly reduction of the tree-ring width. Furthermore it was found out that with increasing trunk height rises the tree-ring width and with increasing tree-ring width rises part of earlywood and latewood, while the earlywood width stays the same. Percentage latewood agency in the tree-ring was at about 7,4 to 96,2 %.
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Evaluation of the gamma-ray spectrum transmitted upon alteration in scintillator shading
Zbožínek, Tadeáš ; Jelínek, Michal ; Mikel, Břetislav
This paper deals with determining the properties of optical fibres required for transmitting energy spectra in ionising radiation measurements by scintillation. Specifically, optical fibres that provide the communication link between the scintillator and the photosensitive electronic devices. The primary objective is focused on the basic diameter and numerical aperture values required for efficient transmission of energy spectra. An iris mechanism gradually shaded the scintillator crystal, simulating the optical fibre diameter. The results can be used to calculate the numerical aperture to achieve this goal. This way, we can establish basic properties for further energy spectra measurements with optical fibres.
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Preparation of LiNbO3 nanostructures and their characterization
Pikna, Štěpán ; Jelínek, Michal (referee) ; Dvořák, Petr (advisor)
This master thesis is focused on the deposition of LiNbO3 on c-cut Al2O3 substrate. This material exhibits an electro-optic effect, which refers to the change in the refractive index upon the application of an external voltage, and it has extensive applications in electro-optic modulators. Currently, there is significant interest in miniaturizing these devices for use in the fields of meta-optics and photonics, where its transparency is also advantageous. The first part of this thesis is dedicated to a review of the electro-optic effect and its application in optical metasurfaces. Subsequently, the review addresses the pulsed laser deposition of LiNbO3. The practical part begins with the optimization of target fabrication from LiNbO3 wafers using a laser cutter. Following this, the measurement of the electro-optic effect from a monocrystalline LiNbO3 wafer is discussed. The final section is devoted to the deposition of this material onto a sapphire substrate and further analysis using SPM, XPS, XRD, and SEM. Monocrystalline growth of 30 nm grains was observed, and the physical dependencies of the growth was studied.
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Investment Plan Evaluation
Jelínek, Michal ; Nováčková, Eva (referee) ; Luňáček, Jiří (advisor)
The diploma thesis focuses on complex economic evaluation of the investment project regarding the purchase of machining centre. Based on the elaborated literature review are those findings applied to the real investment project. Economic efficiency is calculated using the identified cash flows, discount rate and static and dynamic methods. Subsequently are identified project risks and their significance. In conclusion, the results are summarized and is reported recommendation whether or not to implement the project.
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Design of the method to increasing of accuracy of the tunable optical filter optical spectra measurement
Jelínek, Michal ; Holík, Milan (referee) ; Mikel, Břetislav (advisor)
The thesis deals with the method for the improvement of the measurement accuracy in the optical frequency spectra measurements based on tunable optical filters. The thesis starts with the selection of the proper optical filter that is suitable for accurate light spectrum measurement. The selected filter was then used for the design and realization of the measurement system for the inspection of the fibre Bragg gratings. The system incorporates a reference block for the compensation of environmental influences, an interferometric verification subsystem and a PC - based control software implemented in LabView. The preliminary experimental verification of the measurement principle and the measurement system functionality were carried out on a testing rig with a specially prepared concrete console in the UJV Řež. Advanced tests were conducted on nuclear power plant’s containment shape deformation measurement in Temelin.
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Design of the optofiber sensor system to monitoring change of length
Jelínek, Michal ; Stehlík, Jiří (referee) ; Mikel, Břetislav (advisor)
The bachelor´s thesis deals with design and verification of optical fiber sensor system for measuring changes of length. This system is designed to shape monitoring of the nuclear power plant containment. The principle of measurement, design and realization of the first version is described in the work. Principle of measurement and functionality of the whole system was verified by measurement of specially prepared reinforced concrete console. The console was prepared in the way to simulate behaviour of containment of the nuclear power plant. Within development of system there were prepared of optical fiber sensors with Bragg´s grattings which are later used for measurement.
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Optical fibres for ionising radiation measurements
Zbožínek, Tadeáš ; Jelínek, Michal (referee) ; Mikel, Břetislav (advisor)
The work focuses on studying methods of measuring ionizing radiation using optical fibres. More attention is paid to their use, together with scintillation materials. The proposed method allows the connection of an electronic detector with a scintillation sensor by optical means. The interconnection provides the possibility of shielding the detector from the effects of high ionizing radiation activities. The shielded detector will thus not be subject to the adverse effects of this radiation and can be used even for long-term measurements of high activities. First experimental measurements of reference sources verify the principle of the proposed method and help to select the best choice for the type of optical fibre.
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Fibre optic tapering and shaping methods for special applications
Hruška, Andrej ; Jelínek, Michal (referee) ; Mikel, Břetislav (advisor)
The thesis deals with the tapering of optical fibres and the shaping of their ends. The thesis describes the fibre tapering and shaping methods and compares them in terms of advantages and disadvantages. It mainly focuses on methods using electric arc, flame and chemical etching. The practical part of the work describes the methodology of fibre tapering for 125 m, 400 m and 1000 m fibre diameters and the methodology of fibre end shaping for 400 m and 1000 m fibre diameters.
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