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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.
1

Zpracování obrazů při perfúzním zobrazování / Perfusion image processing

Dolníček, Petr January 2012 (has links)
The goal of this diploma thesis was to create a script in MATLAB, which is capable to load DICOM pictures, read the data in their headers and then select the right series for perfusion analysis. This analysis is based on detection of contrast fluid in bloodstream and tissue and right interpretation of concentration changes of this fluid in time. This work is trying to describe a way of building an ultimate system capable of autonomous tumor analysis and classification. In the end, there is an analysis of DICOM sample performed by created script.
2

Zobecnění metody analytického prodloužení ve vazbové konstantě / Generalization of the method of analytical continuation in coupling constant

Brožek, Pavel January 2014 (has links)
In the thesis we study a method for determining resonance energies - gen- eralization of the method of analytical continuation in the coupling constant, which is based on continuation of the coupling constant λ as a function of the momentum k. A formula for λ(k) is derived for spherically symmetric potential consisting of finite number of δ-functions and its Taylor series is studied. Taylor series of λ(k) and its asymptotic behavior is studied for sep- arable potential. Proper choice of added potential parameters is studied on examples. A method for determining λ(k) poles is described for spherically symmetric potential with added δ-function. It is tested whether the knowl- edge of λ(k) poles can be useful to improve the accuracy of the determination of the resonance parameters of the original potential.
3

Výpočet rezonančních šířek v kvadraticky integrabilních bázích / Computing resonance widths using square integrable basis

Votavová, Petra January 2016 (has links)
Four different non-orthogonal basis sets are studied and compared in order to obtain the resonance properties of a model scattering problem. In particular, two types of Gaussian basis sets, one B-spline basis set and one hybrid Gaussian - B-spline basis set. Their ability to represent the scattering continuum is investigated along with their numerical properties. Particular attention is paid to the energy range within which each basis set gives reasonably accurate values of the phase shift and the decay width. The radial Schrödinger equation is solved by the Löwdin's symmetric orthogonalization method and the decay width is extracted by the Stieltjes imaging procedure. The R-matrix method within the framework of Feshbach-Fano projection operator formalism with polynomial basis set is utilized as a numerically exact reference method.
4

Výpočetní tomografie v tkáňové charakteristice myokardu. / Computed tomography in tissue characterization of the myocardium.

Černý, Vladimír January 2020 (has links)
Introduction: Magnetic resonance (MR) represents still the gold standard in myocardial imaging. There are some studies suggesting that the computed tomography (CT) might be a valid alternative for some patients (especially the ones who are unable to undergo MR). Aims: We had two aims. Aim number 1: To evaluate the ability of CT in the evaluation of delayed contrast enhancement (DCE) in patients with dilated cardiomyopathy. Aim number 2: To assess the possibilities of CT originally performed for a different indication in myocardial tissue characterization. Methods: Part 1: We prospectively enrolled 17 patients with dilated cardiomyopathy. All the patients underwent both cardiac CT and cardiac MR. We compared the findings of DCE on CT with the findings of DCE on MR. Part 2: We retrospectively evaluated 96 patients who underwent both CT for any indication and cardiac MR. We compared the findings of a hypodense area in the myocardium with the findings of DCE on MR. Results: Part 1: CT detected DCE in 3 patients and MR detected DCE in 6 patients. The agreement between both modalities was in v 82% cases (kappa 0.56). The sensitivity and specificity of CT were 50% and 100%, respectively and the positive predictive value was 100%. In patients with positive findings on CT, the localization of DCE was almost...
5

Optimalizace pokusného NQR spektrometru / Optimization of the experimental NQR spectrometer

Segiňák, Ján January 2017 (has links)
The thesis deals with the NQR spectroscopy, which is one of the modern non-destructive measurement and diagnostic methods for the characterization of various materials. It is using a quadrupole moment - a property of atomic nuclei of certain isotopes. A method of nuclear quadrupole resonance (NQR) is in principle very similar to nuclear magnetic resonance (NMR). Thesis in the theoretical part analyse the principles of NMR and NQR, describes the possible use of this method to detect for example explosives, drugs, and other chemicals. In the following chapters are analysed the key parameters of NQR spectrometer and the principle of the chosen measurement method. The practical part deals with the individual components of NQR spectrometer, the design of possible improvements and programming of the measuring sequence. In the final chapter are processed the measurements of the submitted samples.
6

Nízkoenergetická excitace v orientovaném grafitu pomocí THz magnetooptické spektroskopie / Low energy excitations in oriented graphite by THz magneto-optical spectroscopy

Dubský, Jan January 2021 (has links)
This master’s thesis deals with the modelling of electronic properties of graphite crystal, which are measurable using a spectrometer based on high frequency electron paramagnetic resonance (HFEPR for short) located in laboratories of CEITEC BUT. This is especially the band structure of graphite and its Landau levels. The theoretical part of the thesis describes key effects and connections from quantum mechanics and definitions of important terms from solid state physics, which are used to describe the crystalline structure of graphite and its electronic properties. Furthermore, the project describes the HFEPR spectrometer and its functional principle. In the practical part of the thesis, there are numerical models of the band structure of graphite and of its Landau levels and description of the preparation of a graphite sample for measurement. At the end of the practical part there is the analysis of measurements results, namely the cyclotron resonance and Shubnikov-de Haas oscillations, thanks to which it is possible to determine physical parameters of the sample, such as effective mass of charge carriers and fundamental frequency.
7

Návrh a realizace klecové cívky pro MRI / Design and Realization of the Bird Cage Coil for MRI

Sedlář, Petr January 2016 (has links)
The work deals with the design and experimental production of the model type Birdcage coil used for magnetic resonance imaging system (MRI). The work deals with the design and behaviour of the model type Birdcage coil volume designed for imaging system for magnetic resonance imaging (MRI). Volume coils are generally very useful for use in MRI, because in transversal design allow easy access into the cavity when the flow vector of magnetization. The aim of the work was to construct a numerical model of transversal coil type Birdcage of the predefined dimensions. The created the coil tuned the desired resonant frequency having regard to maximize performance in the measured sample migrated. The modeling coil experimentally produced and measurements also confirm the accuracy of the numerical model.
8

Interakce migrujících obřích planet a malých těles sluneční soustavy / Interactions of migrating giant planets and small solar-system bodies

Chrenko, Ondřej January 2015 (has links)
Changes of semimajor axes of giant planets, which took place 4 billion years ago and evolved the Solar System towards its present state, affected various populations of minor Solar-System bodies. One of these populations was a group of dynamically stable asteroids in the 2:1 mean-motion resonance with Jupiter which reside in two islands of the phase space, denoted A and B, and exhibit lifetimes comparable to the age of the Solar System. The origin of stable asteroids has not been explained so far. Our main goal is to create a viable hypothesis of their origin. We update the resonant population and its physical properties on the basis of up-to-date observational data. Using an N-body model with seven giant planets and the Yarkovsky effect included, we demonstrate that the depletion of island A is faster compared to island B. We then investigate: (i) survivability of primordial resonant asteroids and (ii) capture of the population during planetary migration, using a recently described scenario with an escaping fifth giant planet and a jumping-Jupiter instability. We employ simulations with prescribed migration, smooth late migration and we statistically evaluate the results using dynamical maps. We also model collisions during the last 4 billion years. We conclude that the long-lived group was created by a...
9

Asteroidy vnitřního pásu ve spin-orbitální resonanci / Inner belt asteroids in the spin-orbital resonance

Vraštil, Jan January 2013 (has links)
Context: Slivan (2002) determined spin state of ten asteroids in the Koronis family. Surprisingly, all four asteroids with prograde sense of rotation were shown to have spin axes nearly parallel in the inertial space. All asteroids with retrograde sense of rotation had large obliquities and rotation periods either short or long. It was shown that Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect can explain all these peculiar facts. In particular, it drives spin axes of the prograde rotators to be captured in a secular spin-orbital resonance known as Cassini state 2. Vokrouhlický et al. (2002) dubbed these configurations "Slivan states". Aims: A question arises whether Slivan states could exist also in other regions of the main asteroid belt, in particular its inner part, where observations are most easily obtained. Here, however, dynamical difficulties arise due to convergence of the proper frequency s and the planetary frequency s6. We investigate possibilities of a long-term stable capture in the Slivan state in the inner part of the main belt. Method: We used SWIFT integrator to determine orbital evolution of selected asteroids in the inner part of the main belt. In the case of 20 Massalia, we observed the asteroid in 2011, and used these new data to help better solve the rotation state using the...
10

Rodiny planetek a jejich vztah k migraci planet / Asteroid families and their relation to planetary migration

Rozehnal, Jakub January 2013 (has links)
In this thesis, we study how the planetary migration affects asteroid families. We identify the families among the Trojans of Jupiter by analysing their properties in the space of resonant elements, the size-frequency distribution and the colour indices. The previously reported number of families (10) seems to be overestimated, our analysis indicates that there is only one collisional family among Trojans with the parent-body size DPB > 100 km. We also performed a simulation of the long-term orbital evolution of the Trojan families. We used a modified version of the SWIFT symplectic integrator where the migration is set analytically. We found that the families are unstable even in the late stages of the migration, when Jupiter and Saturn recede from their mutual 1:2 resonance. Hence, the families observed today must have been created after the planetary migration ended. In the last part of the work, we study a formation of asteroid families in the Main Belt during the Late Heavy Bombardement. We simulate perturbations induced by migrating planets in the "jumping Jupiter" scenario (Morbidelli et al., 2010) and we conclude that big families (DPB > 200 km) created during the bombardement should be observable today.

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