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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.
821

Studie vlivu složitosti Chabocheho modelu plasticity na napjatost a deformaci u vysokotlaké nádoby / Study of the Chaboche´s plasticity model complexity influence on the stress and deformation at the high pressure vessel

Paraska, Boris January 2014 (has links)
The main aim of this thesis is to define material parameters of Chaboche model of plasticity. Adjustment of the parameters has to correspond to the experimental datas. These datas are represented by an uniaxial strain controlled test curve for fewer than two cycles and also by cyclic stress-strain curve. After that, an cyclic tension-compresion test for various parameters of Chaboche´s model of plasticity is simulated in an ANSYS software. Finally, the most suitable configuration of Chaboche´s model of plasticity is used for cylindrical thick-walled body. Cylindrical body represents a simplified model of high-pressure tank of fuel (diesel) – rail in Common Rail system.
822

Kryptoanalýza postranními kanály / Side Channel Cryptanalysis

Martinásek, Zdeněk January 2013 (has links)
Side channels fundamentally changes the view of the cryptographic system security in cryptography. It is not enough to analyze the security algorithm only from a mathematical point of view using abstract models but it is necessary to focus on the implementation of the algorithms. The introduction of the thesis deals with the basic terms, principles of side channel attacks and basic clasification of side channels. The following chapter describes the objectives of the thesis. The main goal of the thesis is to propose and experimentally verify a new power analysis method whish will use the neural network. This main goal was based on the realized analyzes presented in the following chapters. These chapters contain a detailed analysis of currently used power analysis and analysis of AES encryption algorithm. AES was selected becouse the algorithm is resistant to the conventional cryptoanalysis. The following section describes the experimental results of the optimization of existing methods, the influence of the parameters affecting power consumption and the results of the proposed analysis using neural networks. This section includes the discussion of the results. This type of side channel attack has not been published yet thus it is a completely new idea. The final goal of the thesis was to summarize the possible countermeasures protecting against the side channel attacks.
823

Webový portál pro správu a klasifikaci informací z distribuovaných zdrojů / Web Application for Managing and Classifying Information from Distributed Sources

Vrána, Pavel January 2011 (has links)
This master's thesis deals with data mining techniques and classification of the data into specified categories. The goal of this thesis is to implement a web portal for administration and classification of data from distributed sources. To achieve the goal, it is necessary to test different methods and find the most appropriate one for web articles classification. From the results obtained, there will be developed an automated application for downloading and classification of data from different sources, which would ultimately be able to substitute a user, who would process all the tasks manually.
824

Návrh silničního spřaženého mostu na obchvatu Bytomi / Design of steel-concrete composite structure of road bridge on by-road of Bytom

Uhl, Milan January 2016 (has links)
The task of the thesis is to design composite steel-concrete bridge consisting of four spans. Student will design two versions – continuous beam and four simple supported beams.
825

Lávka pro pěší a cyklisty ve městě Zvolen / The footbridge for pedestrians and cyclists in Zvolen

Hric, Fedor January 2017 (has links)
Diploma´s thesis is about timber structure of footbridge for pedestrians and cyclists over the Slatina river in the city of Zvolen as cast of alternatives. In the first alternative is footbridge designed as a simple arched beam, made of glued laminated timber. Footbridge is also designed with semi through bridge deck, made of structural timber. The second alternative is designed as a tied arch structure. At this alternative is the bridge deck left unchanged(material, sizes of members). Both alternatives are attested by currents standarts.
826

Improved REBa₂Cu₃O₇₋ₓ (RE ═ Y, Gd) structure and superconducting properties by addition of acetylacetone in TFA-MOD precursor solutions

Erbe, Manuela, Hänisch, Jens, Freudenberg, Thomas, Kirchner, Anke, Kaskel, Stefan, Mönch, Ingolf, Schultz, Ludwig, Holzapfel, Bernhard 02 December 2019 (has links)
For developing commercially utilized high-performance high-temperature superconductors, the fabrication of biaxially textured (RE)Ba₂Cu₃O₇₋ₓ (REBCO, RE ═ Y, Gd) coated conductors via metal–organic decomposition of trifluoroacetate precursors (TFA-MOD) has become an interesting strategy for industrial scale-up due to low costs and simple operation. However, the hygroscopic nature of commonly used precursor solutions makes them very sensitive to water pollution through air humidity. This can lead to a degradation of the final microstructure, which in return deteriorates critical current densities. Here, we present a new method to overcome that problem by using a moderator of 2,4-pentanedione (acac) in a pre-existing REBCO precursor solution. Our results show that even initially low-performance solutions can be enhanced to such an extent that they finally outperform standard high-performance solutions and the temperature window for their optimal growth widens significantly. Scanning electron microscopy gives evidence of considerable microstructural improvements, e.g. avoidance of pore formation and grooves, reduction of buckling and surface granularity. X-ray investigations indicate texture improvements, and electrical measurements reveal that transport critical current densities (Jc) increase in self-field and applied magnetic fields. For YBCO, a molar ratio of acac/RE ═ 0.64 is most effective and leads to an increase of the maximum pinning force density Fmaxp from 1.0 to 2.4 GN mˉ³ at 77 K. For GdBCO, a broad window of annealing temperatures (790–840°C) is possible for films with Jc values above 2.9 MA cmˉ² and Fmaxp above 3 GN mˉ³ at 77 K.
827

Vliv věku, pohlaví a pohybové aktivity na úroveň reakčních schopností dolních končetin u pubescentů / The Influence of age, gender and movement activity on the reaction abilities of lower limbs by pubescents

Brychta, Petr January 2015 (has links)
Title: The influence of age, gender and movement activity on the reaction abilities of lower limbs. Objectives: The main objective of this dissertation was to find the reaction abilities of pubescent's (aged 10 - 15years) lower limbs on the basis of age, gender and movement activity. The further aim was to determine the pubescence period (age) when the most noticeable decrease of the visual disjunctive motor response time of lower limbs occurs. Methods: 214 boys and girls aged 10-15 years (157.8 ± 10.8 cm; 47.2 ± 10.7 kg) participated in this research. Simple, choice and disjunctive reaction time of lower limbs was measured through the Fitro Agility Check test. The results processing, including statistical procedures, was carried out using the Matlab (MathWorks, Inc.) programming environment, an IBM SPSS Statistics 22. Three-way ANOVA and Tukey post-hoc tests (α=0.05) were used to determine the individual parameters connection. Results: With increasing age, year over year, we found important differences and reaction time decreases of all types of reaction speeds. Testing brings to light the fact that the most noticeable decrease of both selection and disjunctive reaction time of lower limbs are between groups of 11 year olds (11.00-11.99) and 12 year olds (12.00-12.99). The most noticeable decrease...
828

Einführung in die Ökonometrie

Huschens, Stefan 30 March 2017 (has links)
Die Kapitel 1 bis 6 im ersten Teil dieses Skriptes beruhen auf einer Vorlesung Ökonometrie I, die zuletzt im WS 2001/02 gehalten wurde, die Kapitel 7 bis 16 beruhen auf einer Vorlesung Ökonometrie II, die zuletzt im SS 2006 gehalten wurde. Das achte Kapitel enthält eine komprimierte Zusammenfassung der Ergebnisse aus dem Teil Ökonometrie I.
829

Transient Dynamics of Compound Drops in Shear and Pressure Driven Flow

Sang Kyu Kim (8099576) 09 December 2019 (has links)
Multiphase flows abound in nature and enterprises. Our daily interactions with fluids - washing, drinking, and cooking, for example - occur at a free surface and within the realm of multiphase flows. The applications of multiphase flows within the context of emulsions, which are caused by mixing two immiscible fluids, have been of interest since the nineteenth century: compartmentalizing one fluid in another is particularly of interest in applications in pharmaceutical, materials, microfluidics, chemical, and biological engineering. Even more control in compartmentalization and delivery can be obtained through the usage of double emulsions, which are emulsions of smaller drops (i.e., inner drop) within larger drops (i.e., outer drop). The goal of this work is to understand the dynamic behavior of compound drops in confined flow at low Reynolds numbers. These behaviors include the migration patterns, limit cycles, and equilibrium locations in confined flows such as channel flows.<br> <br>Firstly, we look at non-concentric compound drops that are subject to simple shear flows. The eccentricity in the inner drop is either within the place of shear, normal to the plane of shear, or mixed. We show unreported motions that persist throughout time regardless of the initial eccentricity, given that the deformations of the inner and outer drops are small. Understanding the temporal dynamics of compound drops within the simple shear flow, one of the simplest background flows that may be imposed, allows us to probe at the dynamics of more complicated background flows.<br> <br>Secondly, we look at the lateral migration of compound drops in a Poiseuille flow. Depending on the initial condition, we show that there are multiple equilibria. We also show that the majority of initial configurations results in the compound drop with symmetry about the short wall direction. We then show the time it takes for the interfaces to merge if a given initial configuration does not reach the aforementioned symmetry.<br> <br>Thirdly, while the different equilibria of compound drops offer some positional differences at different radii ratio, we show that the lift force profiles at non-equilibrium locations offer distinctly different results for compound drops with different radii ratio. We then look at how this effect is greater than changes that arise due to viscosity ratio changes, and offer insights on what may create such a change in the lift force profile.
830

Sequential and non-sequential hypertemporal classification and change detection of Modis time-series

Grobler, Trienko Lups 10 June 2013 (has links)
Satellites provide humanity with data to infer properties of the earth that were impossible a century ago. Humanity can now easily monitor the amount of ice found on the polar caps, the size of forests and deserts, the earth’s atmosphere, the seasonal variation on land and in the oceans and the surface temperature of the earth. In this thesis, new hypertemporal techniques are proposed for the settlement detection problem in South Africa. The hypertemporal techniques are applied to study areas in the Gauteng and Limpopo provinces of South Africa. To be more specific, new sequential (windowless) and non-sequential hypertemporal techniques are implemented. The time-series employed by the new hypertemporal techniques are obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor, which is on board the earth observations satellites Aqua and Terra. One MODIS dataset is constructed for each province. A Support Vector Machine (SVM) [1] that uses a novel noise-harmonic feature set is implemented to detect existing human settlements. The noise-harmonic feature set is a non-sequential hypertemporal feature set and is constructed by using the Coloured Simple Harmonic Oscillator (CSHO) [2]. The CSHO consists of a Simple Harmonic Oscillator (SHO) [3], which is superimposed on the Ornstein-Uhlenbeck process [4]. The noise-harmonic feature set is an extension of the classic harmonic feature set [5]. The classic harmonic feature set consists of a mean and a seasonal component. For the case studies in this thesis, it is observed that the noise-harmonic feature set not only extends the harmonic feature set, but also improves on its classification capability. The Cumulative Sum (CUSUM) algorithm was developed by Page in 1954 [6]. In its original form it is a sequential (windowless) hypertemporal change detection technique. Windowed versions of the algorithm have been applied in a remote sensing context. In this thesis CUSUM is used in its original form to detect settlement expansion in South Africa and is benchmarked against the classic band differencing change detection approach of Lunetta et al., which was developed in 2006 [7]. In the case of the Gauteng study area, the CUSUM algorithm outperformed the band differencing technique. The exact opposite behaviour was seen in the case of the Limpopo dataset. Sequential hypertemporal techniques are data-intensive and an inductive MODIS simulator was therefore also developed (to augment datasets). The proposed simulator is also based on the CSHO. Two case studies showed that the proposed inductive simulator accurately replicates the temporal dynamics and spectral dependencies found in MODIS data. / Thesis (PhD(Eng))--University of Pretoria, 2012. / Electrical, Electronic and Computer Engineering / unrestricted

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