National Repository of Grey Literature 241 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Growth of organic semiconductor on heteromolecular layer
Mrhačová, Petra ; Redondo, Jesús (referee) ; Procházka, Pavel (advisor)
Tato diplomová práce se zabývá přípravou a analýzou heteromolekulárních vrstev obsahujících molekuly kyseliny 1,3,5-benzentribenzoové (BTB) nebo kyseliny 4,4'-bifenyl-dikarboxylové (BDA) spolu s pentacenovými molekulami na substrátu Ag(111). Uspořádání molekul v takových vrstvách závisí na několika faktorech, jako je množství deponovaných molekul na povrchu, pořadí, v jakém jsou molekuly deponovány, a míra deprotonace jejich karboxylových skupin. Následně byl studován růst organického polovodiče pentacenu na heterovrstvě obsahující BTB a pentacenové molekuly. Bylo zjištěno, že růst probíhá ve formě velkých ostrůvků, které se rozrůstají dendriticky. Tyto ostrůvky však nejsou kompaktní, ale skládají se z malých molekulových klastrů. Všechny vytvořené vrstvy byly zkoumány v podmínkách ultravysokého vakua (UHV) pomocí nízkoenergetického elektronového mikroskopu (LEEM) a rastrovacího tunelového mikroskopu (STM).
Growth of organic semiconductors on polycrystalline foils
Weisz, Hugo ; Průša, Stanislav (referee) ; Procházka, Pavel (advisor)
This bachelor thesis is focused on the utilization of silver and copper polycrystalline foils as substrates for the deposition of 4,4’-biphenyl-dicarboxylic acid (BDA). The first part of the experimental work focuses on the cleaning of polycrystalline foils, especially under ultra-high vacuum conditions. Silver and copper polycrystalline films were characterized using photoemission electron microscopy (PEEM) and low-energy electron microscopy (LEEM) before and after molecular deposition.
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.
Computational and experimental assessment of natural frequencies in a bladed disk system
Mekhalfia, Mohammed Lamine ; Procházka, Pavel ; Maturkanič, Dušan ; Voronova, Evgeniya ; Hodboď, Robert
This paper examines the modal characteristics of a bladed disk in rotating machinery systems using a combination of analytical and experimental modal analysis methods. The analysis involves measuring natural frequencies and mode shapes under different operational conditions. A comparative analysis is conducted to assess modal properties obtained from both analytical and experimental approaches, while also considering the influence of rotation speed. Additionally, Finite Element Method (FEM) outputs are used to accurately position the strain gauge. Integrating these techniques provides a comprehensive understanding of the bladed disk's behaviour under varying rotational speeds, enhancing result accuracy and facilitating thorough investigation within rotating machinery systems.
Modification of cooling system for laboratory measurement of rotor blade vibration
Maturkanič, Dušan ; Procházka, Pavel ; Hodboď, Robert ; Voronova, Evgeniya ; Mekhalfia, Mohammed Lamine
Last year, the replacement of the turbine wheel model was completed in the Laboratory of Rotational Laser Vibrometry of the Institute of Thermomechanics AS CR, v.v.i. Based on previous experience and the expected higher operating load planned for the new wheel, the cooling system was modified at the same time. The paper describes the main effort in this direction and the results that clarify the previous damage of the measuring device.
Verification of the dynamic properties of a new model turbine wheel with free blades
Voronova, Evgeniya ; Procházka, Pavel ; Maturkanič, Dušan ; Mekhalfia, Mohammed Lamine ; Hodboď, Robert
The paper describes a new experimental model of turbine wheel with free blades. Verification tests were carried out using a Doppler laser vibrometer, with a focus on the equipment parameters under various conditions. The measurements were performed in the Laboratory of Rotational Laser Vibrometry originated at the Institute of Thermomechanics AS CR, v.v.i.
Numerical and Experimental Investigation of the Flow Field in Five Blade Linear Cascade in Subsonic Flow
Šnábl, Pavel ; Chindada, Sony ; Bublík, O. ; Procházka, Pavel P. ; Prasad, Chandra Shekhar
In large steam turbines, last stage blades are very long and must be designed very thin and with no shroud to minimize the centrifugal force which leads to low eigenfrequencies and low structural damping. In this case, aero-elastic damping plays important role on last stage bladed disc’s dynamics. Three major aero-elastic issues found in turbomachinery are forced response, non-synchronous vibrations, and flutter. Flutter is an unstable, self-excited vibration resulting from coupling between the structural vibrations and unsteady aerodynamic forces. It is clear that this unstable behaviour must be avoided and predictions of flutter behaviour need to be performed during design stage of the turbine.\n
Statistical Approach for BTT probes distribution
Mekhalfia, Mohammed Lamine ; Procházka, Pavel ; Šmíd, R. ; Tchawou Tchuisseu, Eder Batista
Blade tip timing (BTT) system is a non-invasive method used for measuring the blade tip timing of rotating machinery. The BTT system typically consists of sensor probes, signal conditioning system, and data acquisition unit. The sensor probes are placed in proximity to the rotating blade tips, Sensors measure the time at which each blade passes by the probe. By measuring the blade tip timing, the BTT system can detect changes in the blade tip vibration, which is an important for the health monitoring and performance optimization of rotating machinery [1]. To ensure accurate measurement of blade tip timing, the probe arrangement is crucial. The placement of the probe relative to the blade tips can affect the measurement accuracy, and thus, several arrangement algorithms have been developed to optimize the placement of the probes. Instead of considering the condition number, a statistical algorithms is followed to optimize the placement of probes for accurate measurement of blade tip timing in turbo-machinery. The statistical approach will be employed to determine the optimal locations for probes, with the aim of reducing errors in the measurement of blade tip timing. \n
Manufacturing of pin with flange
Procházka, Pavel ; Řiháček, Jan (referee) ; Podaný, Kamil (advisor)
The bachelor thesis is focused on the design of the towing hitch, which is used in the tractor. The component will be the production of a die forging technology made of low-alloy steel 13 242. The material is supplied as hot-rolled bars with a diameter of 60 mm and a length of 6 000 mm. The size of the production series has been set at 25,000 pieces per year. Due to the issue and the size of the forging, the component will be made on a power hammer. The machine Šmeral KHZ 8A, appears to be a suitable machine as the forging work was calculated at 89 kJ. The technical - economic evaluation takes into account material costs, which amount to 1,364,271 CZK. The die is made of tool steel 19 663, its purchase price is 73 000 CZK.
Preparation of contacts to one-dimensional nanostructures
Citterberg, Daniel ; Procházka, Pavel (referee) ; Kolíbal, Miroslav (advisor)
This bachelor thesis deals with methodology of contacting one-dimensional nanostructures. Theoretical part of the thesis defines the concept of one-dimensional nanostructures, then it deals with the potential of their usage, especially in field effect transistors. This part also deals with the possibility of measuring the electrical properties of one-dimensional nanostructures and the possibility of fabricating contacts with sufficiently small sizes using litographic approach. Experimental part gives a brief overview of the tasks that need to be done during the contact fabrication. Subsequently, the individual steps are described in more detail and, finally, initial results of electrical characterization are shown.

National Repository of Grey Literature : 241 records found   1 - 10nextend  jump to record:
See also: similar author names
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19 Procházka, Pavel P.
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