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Spectral Indices as a Tool for Hop Growth Evaluation
Seidlová, Jana ; Procházka, Pavel ; Kumhálová, Jitka
The use of unmanned aerial vehicles (UAV) to monitor crop growth is nowadays a common non-invasive way how to obtain information on the current state of crops. Spectral indices derived from multispectral images obtained in the right growth stage can then serve as a good data source for agro-technical interventions and yield estimation. Hop belongs among the crops where it is possible to scan the individual growth parameters very exactly. In the year 2021, significant precipitation amounts were recorded during the growing season, when it turned out that UAVs are a very powerful tool for determining the quality of production or quantification of vegetation damage compared to the previous year (2020). It was found that the common spectral indices were possible to use for calculation leaf area, structure, vigor and chlorophyll content of hop gardens.
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Growth of organic heterostructures on metal surfaces
Kugler, David ; Novák,, Jiří (referee) ; Procházka, Pavel (advisor)
Během depozice organických molekul na kovové substráty často dochází k spontánnímu uspořádání molekul vlivem mezimolekulárních a molekulárně-substrátových interakcí. Tento jev se nazývá samouspořádání a může být využit k vytváření atomárně přesných funkčních struktur. Vzrůstající zájem vzbuzují zejména tenké vrstvy organických polovodičů pro jejich potenciální využití v polovodičovém průmyslu. Efektivita takovýchto zařízení je však nevyhnutelně spojena s přechodovým odporem na rozhraní polovodiče a kovové elektrody. Studium typu růstu organických polovodičů na kovových substrátech je tak zcela zásadní pro jejich budoucí využití. Tato diplomová práce se nejprve zabývá vytvořením krycí monovrstvy substrátu Ag(111) z dobře uspořádaných molekul kyseliny 1,3,5-benzen-trikarboxylové (BTB). Hlavním cílem práce je pak použití této vrstvy jako substrátu pro růst dalších vrstvev tvořených molekulami pentacenu, což je jeden z intenzivně zkoumaných organických polovodičů. Bylo dosaženo pokrytí povrchu uspořádanou vrstvou pentacenu o rozloze vhodné pro praktické využití. Pro studium růstu molekulárních vrstev a jejich vlastností byla použita nízkoenergiová elektronová mikroskopie, skenovací tunelovací mikroskopie, rentgenová fotoelektronová spektroskopie a ultrafialová fotoelektronová spektroskopie.
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Organic semiconductors on topological insulators
Hrubá, Daniela ; Průša, Stanislav (referee) ; Procházka, Pavel (advisor)
This bachelor thesis is focused on the utilization of the topological insulator Bi2Se3 as a substrate for the deposition of different types of organic molecules. The substrate was prepared by exfoliation method under ultrahigh vacuum (UHV) conditions. The pentacene, 4,4'-biphenylcarboxylic acid (BDA), and tetracyanoquinodimethane (TCNQ) molecules were subsequently deposited using effusion cells. The quality and arrangement of the fabricated layers were characterized by low-energy electron microscopy (LEEM). The measured results and the behavior of the molecules on the crystal surface after their deposition are discussed. Diffraction patterns were used for design of real-space molecular arrangement model.
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Microscopic and spectroscopic analysis of elementary 2D materials
Jeřábek, František ; Procházka, Pavel (referee) ; Kolíbal, Miroslav (advisor)
Tato práce se zabývá analýzou struktur tvořených při depozici fosforu na monokrystal mědi Cu(111) za podmínek ultravysokého vakua. Součástí práce je komplexní shrnutí aktuálního pokroku v oblasti syntézy černého a modrého fosforenu. Kromě samotných metod přípravy je diskutována také předpovězená stabilita těchto struktur. V práci jsou prezentovány výsledky analýzy tří struktur pomocí skenovací tunelové mikroskopie a spektroskopie, prokazující možnost přípravy jednovrstvého modrého fosforenu na měděném substrátu. In-situ analýza stability připravených struktur pomocí skenovací tunelovací mikroskopie prokazuje velmi rychlou degradaci modrého fosforenu i za podmínek ultravysokého vakua.
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Aeroacoustic Noise Source Investigation in the Case of the Blade Cascade
Procházka, Pavel P. ; Antoš, Pavel ; Šnábl, Pavel
The blade cascade consisted of five NACA 0010 profiles is examined in the framework of project dealing with nonlinear dynamic phenomenon related to stall flutter of flexible profiles with pitch degree of freedom in subsonic flow. Various angles of attack (AoA) of the cascade generates different (broadband) aeroacoustic noise. The goal of this article is to describe the existence of possible noise sources using two experimental methods – Particle Image velocimetry (PIV) and hot-wire (HW) anemometry.
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On Harmonic Content of the Wake Behind a Circular Cylinder
Uruba, Václav ; Procházka, Pavel P.
The wake behind cylinder of circular cross-section is subjected to detailed analysis from the point of view harmonic content. The basic, fundamental frequency could be linked to well-known Bénard-von Kámán vortex street, it is called Strouhal frequency very often. However higher harmonics of 2nd and 3rd order have been detected, as well as important inharmonic partials. The topologies of the velocity flow-field corresponding to the harmonic is to be shown.
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Effect of oscillating blade on tonal noise of blade cascade with five NACA 0010 profiles
Šnábl, Pavel ; Pešek, Luděk ; Radolf, Vojtěch ; Antoš, Pavel ; Procházka, Pavel P. ; Prasad, Chandra Shekhar
The airfoil tonal noise is a well known phenomenon which appears on single airfoils in moderate Reynolds numbers at low angles of attack. It can appear on small aircrafts, fans, wind turbines etc. In thispaper, it was observed on a blade cascade consisting of five NACA 0010 profiles placed in a closed rectangular channel with hard walls when for given conditions, i.e. flow velocity and angle of attack, the cascade tunes to one single frequency. During the middle blade oscillation, the single tone splits up to several tones with lower intensity modulated by the excitation frequency. Thus, the oscillation of one blade suppresses the tonal noise generation in the cascade.
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Analytical procedures for solving blade vibration using the Blade Tip Timing - theoretical description of the method
Maturkanič, Dušan ; Procházka, Pavel ; Mekhalfia, Mohammed Lamine
The report focuses on an analytical approach to solving the problem of turbine and compressor blade vibration using the Blade Tip Timing method. The report contains a description of the new method with defined solution requirements. Verification of the method was performed by simulation, where the correct input data was used in the analysis of the reliability of the method when the calculation was repeated at a sufficiently large number of revolutions, while in the accuracy analysis, intentionally distorted input data was used. The report also includes connection to the results of frequency and amplitude calculation for fluctuating speeds obtained by the deterministic method, which was described in previous works aimed at achieving a precise calculation of the frequency and amplitude of blade vibration in real conditions.
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