2020-01-23
14:06 |
Electron microscopy and spectroscopy in plasmonics
Horák, Michal ; Krenn, Joachim (oponent) ; Shegai, Timur (oponent) ; Šikola, Tomáš (vedoucí práce)
This thesis deals with electron and ion beam techniques for fabrication and characterization of plasmonic nanostructures. Analytical electron microscopy focusing on applications in the field of plasmonics is discussed. The emphasis is given to electron energy loss spectroscopy (EELS) and cathodoluminescence. Further, fabrication of plasmonic samples for transmission electron microscopy is introduced while the aim is put at focused ion beam lithography and at sample preparation using chemically synthesized particles in water solution. The main research results are divided into four parts. The first part covers a comparative study of plasmonic antennas fabricated by electron beam and focused ion beam lithography. While both techniques are suitable for the fabrication of plasmonic antennas, electron beam lithography shall be prioritized over focused ion beam lithography due to better quality of the resulting antennas and considerably stronger plasmonic response in EELS. Antennas fabricated by focused ion beam lithography have slightly dull edges, exhibit pronounced thickness fluctuation, and they are also strongly contaminated not only by organic contaminants, but also by residues of FIB milling including implanted milling ions and atoms of a titanium adhesion layer. In the second part, Babinet's principle of complementarity for plasmonic nanostructures is investigated on a set of gold disc-shaped antennas and complementary apertures in a gold layer with various diameters. The complementarity is confirmed for fundamental plasmon properties such as resonance energies, but differences rising from the limited validity of Babinet's principle are found, for example, for the spatial distribution of the near-field of plasmon polaritons. The third part summarizes a study of nanostructures with functional properties related to the local enhancement of electric and magnetic field. Bow-tie and diabolo plasmonic antennas, both in the form of particles and in the form of apertures, exhibit particularly strong local field enhancement. Our study identifies several modes of localized surface plasmons in these antennas and characterizes their properties including mode energy, near field electric and magnetic field distribution, and the qualitative distribution of charge nodes and current associated with electron gas oscillations. Next, we have studied mode energy tunability in near infrared and visible spectral regions and focused on Babinet's complementarity between direct and inverted antennas. The last part is focused on silver amalgam, which is a novel and very prospective plasmonic material. By changing the size of silver amalgam nanostructures their plasmon resonance can be tuned from ultraviolet through the whole visible to infrared region. As silver amalgam is well investigated in the field of electrochemistry, silver amalgam nanoparticles opens a possibility to combine plasmonics and electrochemistry together.
Úplný záznam
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2020-01-23
14:06 |
Diferenciály s řízeným dělením momentu pro těžká užitková vozidla
Fojtášek, Jan ; Magdolen,, Ľuboš (oponent) ; Tůma, Jiří (oponent) ; Porteš, Petr (vedoucí práce)
Tato práce se zabývá posouzením vlivu regulace stáčivého momentu prostřednictvím aktivního diferenciálu na dynamiku jízdy nákladního vozidla. Jsou zde shrnuty poznatky ohledně možností konstrukčního uspořádání aktivního diferenciálu, regulačních algoritmů i teoretické předpoklady týkající se výsledného vlivu na dynamiku jízdy. Na základě rešeršní části je vypracován vlastní návrh aktivního diferenciálu pro experimentální nákladní vozidlo. Hlavní část práce je věnována analýze vlivu aktivního diferenciálu na ovladatelnost vozu při manévrování a jeho stabilitu včetně limitních jízdních stavů. Za tímto účelem je sestaven kompletní multibody model vozidla s klasickým diferenciálem a výsledky simulací jízdy tohoto vozu experimentálně ověřeny pomocí měření vybraných parametrů dynamiky jízdy při jízdních manévrech reálného nákladního automobilu. Validovaný model je dále rozšířen o aktivní diferenciál včetně regulačního algoritmu. Ověření teoretických předpokladů a vyhodnocení vlivu aktivního diferenciálu na dynamiku jízdy nákladního vozidla je pak provedeno pomocí simulací vybraných manévrů zahrnujících ustálené i přechodové jízdní stavy. Na základě popsaných poznatků je pak vyhodnocen celkový přínos této technologie, jeho realizovatelnost a hlavní výhody a nevýhody.
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2020-01-23
14:06 |
Úplný záznam
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2020-01-13
08:30 |
Využití a potlačování dvojlomných jevů v optovláknových senzorických aplikacích
Motúz, Rastislav ; Hudcová, Lucie (oponent) ; Vlček, Čestmír (oponent) ; Drexler, Petr (vedoucí práce)
Práce se zabývá problematikou integrálních a distribuovaných optovláknových senzorů elektrického proudu. V oblasti integrálních senzorů je provedena analýza pomocí Jonesova maticového počtu a je zkoumán simultánní vliv indukovaného kruhového a nežádoucího lineárního dvojlomu při použití orto-konjugačního retroreflektoru. Dále je analyzována navržena varianta s konjugační smyčkou, která využívá půlvlnné fázové retardéry. Teoretické závěry jsou potvrzené simulací a experimentálním měřením. Na poli distribuovaných optovláknových senzorů je provedena analýza a simulace pro detekci plazmových proudů v termonukleárních fúzních reaktorech, na bázi techniky POTDR. Pro reaktory kruhového průřezu výbojové vakuové komory je navržen postup pro zlepšení detekce plazmových proudů a pro reaktory divertorového typu je nově navržena a provedena simulace zkoumající vliv šumu detektoru OTDR na přesnost detekce plazmových proudů.
Úplný záznam
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2020-01-13
08:30 |
Stochastic Calculus and Its Applications in Biomedical Practice
Klimešová, Marie ; Růžičková, Miroslava (oponent) ; Dzhalladova, Irada (oponent) ; Baštinec, Jaromír (vedoucí práce)
In the presented dissertation is defined the stochastic differential equation and its basic properties are listed. Stochastic differential equations are used to describe physical phenomena, which are also influenced by random effects. Solution of the stochastic model is a random process. Objective of the analysis of random processes is the construction of an appropriate model, which allows understanding the mechanisms. On their basis observed data are generated. Knowledge of the model also allows forecasting the future and it is possible to control and optimize the activity of the applicable system. In this dissertation is at first defined probability space and Wiener process. On this basis is defined the stochastic differential equation and the basic properties are indicated. The final part contains biology model illustrating the use of the stochastic differential equations in practice.
Úplný záznam
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2020-01-13
08:30 |
NÁVRH OPTOVLÁKNOVÉHO BIOSENZORU SE SPEKTRÁLNÍ ANALÝZOU V BLÍZKÉ INFRAČERVENÉ OBLASTI
Křepelka, Pavel ; Jakubec,, Martin (oponent) ; Skládal, Petr (oponent) ; Mikulka, Jan (vedoucí práce)
Práce se zabývá měřením a interpretací NIR spekter bakteriálních buněk a výzkumem biosenzorických technik, využívající tuto analytickou techniku. Je zde rozebrán současný stav vědění v oblasti NIR spektroskopie v mikrobiologii a technologie optovláknových biosenzorů. Z rozboru vyplývá, že NIR je vhodnou technikou pro přímou molekulární analýzu bakterií, která však trpí nízkou citlivostí a nedostatečnou interpretací bakteriálních spekter. V další části práce je uveden teoretický rozbor technik spektrální analýzy a technologie optovláknových senzorů. V praktické části práce jsou představeny experimenty a výzkum vedoucí k odstranění těchto nevýhod NIR spektroskopie v mikrobiologii. Je zde shrnuta řada experimentů sloužící k interpretaci NIR spekter bakterií a návrh optovláknového senzoru pro zvýšení citlivosti této techniky. V této práci byly určeny a částečně interpretovány spektrální regiony důležité pro identifikaci bakteriálních kmenů a navržen senzor pro analýzu bakterií, který je schopný klasifikovat kmeny na základě 105 zachycených buněk. Tím byly splněny cíle této práce.
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2020-01-13
08:29 |
X-ray nano computed tomography of structured polymeric biomaterials
Kalasová, Dominika ; Oberta,, Peter (oponent) ; Kataja, Markku (oponent) ; Kaiser, Jozef (vedoucí práce)
This thesis is focused on an advanced imaging method X-ray computed nanotomography (CT). This non-destructive technique is used for the research of various biomaterials in tissue engineering and material science in general (scaffolds, polymers, ceramics, composites, etc.). Visualisation and quantification in 3D are advantageous in multidisciplinary approach usually applied in these fields. The objective of the thesis is divided into two topics. The first topic is about optimisation of the measurement procedure for various soft materials by CT with the laboratory X-ray sources. Mostly, the phase contrast propagation-based CT imaging (PBI) is involved here. This work theoretically describes the PBI and demonstrates this phenomenon via several sets of measurements. The necessary post-processing of PBI data is implemented and evaluated based on data quality enhancement. The second topic shows specific applications of CT in material engineering. Several studies with different CT devices show a few examples of possible applications and image processing options. Examples of correlation of CT with other complementary techniques show how CT can be applied in a multidisciplinary approach to solving complex scientific problems.
Úplný záznam
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2020-01-13
08:29 |
Study of Electric and Dielectric Properties of Ionic Liquids
Altšmíd, Jakub ; Boušek, Jaroslav (oponent) ; Mikula, Milan (oponent) ; Nešpůrek, Stanislav (vedoucí práce)
Presented thesis is focused on study of electric and dielectric properties of ionic liquids (ILs). ILs may find its use in wide spectre of applications, namely in electrotechnics. Thesis is divided into theoretical and experimental part. The theoretical part is dedicated to description of basic properties of ILs and possibility of use in capacitors and electrochemical gas sensors. The experimental part describes used methods of characterisation of physical properties and evaluation of measured data. The results are divided into two main parts. The first part deals with the study of properties of ILs for their use as capacitors. The second part is dedicated to the study of prepared experimental NO2 sensor, namely to influence of ILs properties to commonly studied properties.
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2020-01-13
08:29 |
DEVELOPMENT OF ALGORITHMS FOR GUNSHOT DETECTION
Hrabina, Martin ; Tučková, Jana (oponent) ; Počta, Peter (oponent) ; Sigmund, Milan (vedoucí práce)
This work deals with gunshot recognition and problems connected to it. Firstly, the problem is briefly introduced and broken down to smaller steps. Next, overview of datasets is provided, relevant information sources and publications in this field, and state-of-the-art along with possible applications of gunshot recognition. The second part consists of feature selection and performance comparison. Next, sound recognition algorithms are introduced and compared, along with novel features suitable for gunshot detection. The work culminates in creating two stage gunshot detection system, with real time audio event detection. The conclusion sums up achieved results and sketches possible steps to consider for hardware realization.
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2020-01-13
08:29 |
Morphogenesis and Viscoelastic Properties of Dimethacrylate Networks
Bystřický, Zdeněk ; Lehocký, Marián (oponent) ; Bradna, Pavel (oponent) ; Jančář, Josef (vedoucí práce)
The thesis deals with the investigation of dimethacrylate networks morphogenesis. Simple model resin mixtures used in this work were based on the monomers, which are typically employed as the components of matrix systems of dental resin composites. Kinetics and mechanisms of polymer networks formation were studied with respect to a structure of monomers, molar ratio of comonomers, and a concentration of the radical polymerization initiation system. Calculated profiles of functional groups conversion and polymerization rate were used as a basis for understanding and interpretation of mechanisms of networks morphogenesis and comparison with known models. Furthermore, kinetics of thermal degradation process was studied because it is closely related to the morphology of the networks. Then, temperature dependence of viscoelastic modulus was determined and the relationship between supramolecular structure of dimethacrylate networks and their viscoelastic response within the given temperature range was quantified. Polymerization kinetics was studied by differential photo-calorimetry (DPC) and infrared spectroscopy (FTIR). Process of thermal degradation was analyzed using thermo-gravimetric analysis (TGA). Viscoelastic parameters were measured using dynamic-mechanical analysis (DMA). Reactivity of dimethacrylate systems is derived from the molecular structure of monomers, because it affects mobility of reacting species during polymerization. Kinetics of polymerization is controlled by diffusion. Rate of diffusion is given by the monomer rigidity, concentration of functional groups, and an impact of physical interactions. The mobility restrictions, affecting growing chains, pendant side chains and free monomers, lead to monomolecular termination of macroradicals and limited degree of conversion. Since the mobility is restricted severely from the early phases of the reaction, i.e. from the gel point, phase separation is suppressed despite any potential thermodynamic instability, and the copolymerization process is random. This was confirmed by identification of single glass transition temperature in DMA experiments of copolymers. Heterogeneous character of morphogenesis is related to a varying reactivity of pendant functional groups. In the early phases of the polymerization, propagation proceeds via intramolecular attack of the radical site to the pendant, leading to the primary cycle formation. Probability of the cyclization is increased by flexibility of the monomer backbone. Heterogeneity of the curing reaction is characterized by formation of internally crosslinked structures, i.e. microgels, followed by their interconnections. On contrary, rigidity of the monomer leads to a higher effectivity of crosslinking and more homogeneous morphology of the corresponding networks. Presence of the inhomogeneities, characterized by coexistence of structurally distinct regions, is related to a two-step mechanism of thermal decomposition. Progress of the storage modulus and the glass transition temperature correlate with the network stiffness, effectivity of crosslinking, and the presence of physical interactions that reinforce the structure beyond the scope of covalent crosslinking. Structural heterogeneity is manifested by broad transition region indicating wide variations in relaxation times. Experimental data are in qualitative correlation with the numerical models that simulates kinetics of free radical network polymerization.
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