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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.
351

Explosion en temps fini de solutions d’équations dispersives ou dissipatives non-linéaires / Finite time blowup of solutions of dispersive or dissipative nonlinear equations

Cortez, Manuel Fernando 15 October 2015 (has links)
Le sujet de cette thèse est la formation de singularités pour certaines équations d'évolution dispersives et/ou dissipatives non-linéaires. Notre travail est axé sur les problèmes de Cauchy, généralement avec des conditions aux limites périodiques ou dans tout $\mathbb{R}^n$. Notre objectif est de fournir les conditions nécessaires ou suffisantes (ou les deux) sur les données initiales $u_0(x)$, garantissant que la durée de vie $T^{*}$ de la solution résultant de $u_0$ est finie ou non. Nous étudions deux types d'équations : une équation parabolique non linéaires et une classe d'équations d'ondes dispersives. La première équation étudiée est un modèle $1D$ de propagation d’ondes non-linéaires, qui apparaît par exemple dans l'étude des vagues dans un canal ou des déformations d’une barre hyper-élastique. L'une des contributions décisives de notre travail sera celle-ci : la seule solution forte globale périodique du problème de Cauchy de la barre hyper-élastique qui s’annule en au moins un point est la solution identiquement nulle. Nous établissons également l'analogue de ce résultat dans le cas des solutions non-périodiques définies sur toute la droite réelle, avec limite nulle à l'infini. Notre analyse repose sur l'application de nouveaux critères d'explosion "locaux en espace” (local-in-space blowup criteria). Une deuxième équation étudiée est une généralisation de l'équation de la barre hyperélastique qui a été proposée par H. Holden et X. Raynaud. Cette généralisation peut couvrir de nombreux autres types d'équations avec des propriétés mathématiques intéressantes. Nous établirons alors des critères d'explosion locaux en espace pour les solutions de ce modèle. Plus précisément, il s'agira de critères qui ne font intervenir que les propriétés de la condition initiale $u_0$ au voisinage d'un seul point. Ils simplifient et étendent de précédents critères d'explosion pour cette équation. Ensuite, nous nous sommes intéressés à une famille d'équations connue dans la littérature sous le nom $b$-family equations. L'un des cas les plus notables de cette famille d'équations est l'équation de Degasperis-Procesi. Pour cette famille, nous avons obtenu des résultats similaires à ceux décris précédemment. Enfin, dans la dernière partie, il s'agit d'étudier le caractère bien posé, local ou global en temps, dans des espaces fonctionnels issus de l'analyse harmonique et ayant les bonnes propriétés d'invariance par rapport aux changements d'échelle. Nous étudions le problème de Cauchy non linéaire de l'équation de la chaleur. Après avoir établi une extension du résultat d'Y. Meyer sur l’existence de solutions globales à données petites dans les espaces de Besov homogènes $\dot{B}_{p}^{-\sigma, \infty}(\mathbb{R}^{3})$, où $3 < p < 9$ et $\sigma=1-3/p$, nous prouvons que les données initiales $u_0\in \mathcal{S}(\mathbb{R}^{3})$, arbitrairement petites dans ${\dot B^{-2/3,\infty}_{9}}(\mathbb{R}^{3})$, peuvent produire des solutions qui explosent en temps fini. En outre, cette explosion peut se produire après un temps arbitrairement court / The subject of this thesis is the formation of singularities for some nonlinear evolution equations of dissipative and/or dispersive type. Our work is focused on the Cauchy problems, usually with periodic boundary conditions or on the whole $\mathbb{R}^{n}$. Our aim is to provide the necessary or sufficient conditions (or both) on the initial data $u_0 (x)$, ensuring that the lifetime $T^{*}$ of the solution resulting from $u_0$ is finite or not. We study two types of equations: a nonlinear parabolic equation and a class of dispersive wave equations. In the first case, we study a one-dimensional model which describe the propagation of nonlinear waves in a channel or the deformations of a hyper-elastic rod. One decisive contibutions of our work will be this: the only global strong periodic solution of the rod equation vanishing in at least one point is the identically zero solution. We also establish the analogue of this result in the case of non-periodic solutions defined on the whole real line which vanish at infinity. Our analysis is based on the application of new local-in-space blowup criteria. The second equation that we consider is a generalization of the rod equation which was proposed by H. Holden and X. Raynaud. This generalization covers many other equations with interesting mathematical properties. We will establish criteria for the blowup in finite time that involve only the properties of the data $u_0$ in a neighborhood of a single point, thus simplifying and extending earlier blowup criteria for this equation. After, we study family of equations known in the literature as the $b$-family equations. One of the most notable cases of this family of equations is the Degasperis-Procesi equation. For this family we obtain similar results as those described above. Finally, the last part, we study the well-posedness, locally or globally in time of the nonlinear heat equation, in functional spaces having appropriate invariance properties relative to scale changes. After extending Y. Meyer's result establishing the existence of global solutions, under a smallness condition of the initial data in the homogeneous Besov spaces $\dot{B}_{p}^{-\sigma, \infty}(\mathbb{R}^{3})$, where $3 < p < 9$ and $\sigma=1-3/p$, we prove that initial data $u_0\in \mathcal{S}(\mathbb{R}^{3})$, arbitrarily small in ${\dot B^{-2/3,\infty}_{9}}(\mathbb{R}^{3})$, can produce solutions that explode in finite time. In addition, the blowup may occur after an arbitrarily short time.
352

Ultra-large sheet formation by 1D to 2D hierarchical self-assembly of a “rod–coil” graft copolymer with a polyphenylene backbone

Huang, Yinjuan, Yuan, Rui, Xu, Fugui, Mai, Yiyong, Feng, Xinliang, Yan, Deyue 17 July 2017 (has links)
This communication reports a unique ultra-large sheet formation through hierarchical self-assembly of a rod–coil graft copolymer containing a rigid polyphenylene backbone and flexible poly(ethylene oxide) (PEO) side chains. The hierarchical self-assembly process involved a distinctive morphological transition of 1D helical to 2D superstructures. The graft copolymer offers a new chance for the challenging bottom-up fabrication of ultra-large self-assembled nanosheets in solution, as well as a novel system for fundamental studies on 2D self-assembly of polymers.
353

Zrádná slova v češtině a polštině a práce s nimi ve výuce češtiny jako cizího jazyka / Czech-Polish false friends and their use in teaching Czech as a Foreign Language

Pohorská, Iva January 2021 (has links)
The diploma thesis focuses on the so called "false friends" in contemporary Czech and Polish. Both languages are first introduced in the context of their linguistic and typological features as relevant to the subject of the thesis. Particular attention is paid to the differences between the two languages, and therefore possible language interferences. Furthermore, the paper discusses the issue of so called "false friends" and, based on the studies of E. Lotko, there were selected four types of false friends (grammatical (according to the grammatical gender of the noun), lexicographical, stylistic and valency false friends) and discussed more. Those lexical units are first characterized in general terms, and are then focused on the apecific "false friends" contained in the Common European Framework of Reference (levels A1-B1 for Czech as a foreign language). The second part of the thesis (based on the acquired theoretical knowledge) tries to design and recommend a methodology for working with so called "false friends" in the teaching of Czech as a foreign language to the target group of native Polish speakers. This includes worksheets for students as well as the methodology for teachers. Key words False friends, Interlanguage homonymity, Czech language, Polish language, Common European Framework of...
354

Hnací mechanismus Stirlingova motoru / Crankshaft mechanism of Stirling engine

Valčík, Martin January 2018 (has links)
This diploma thesis is focused on the design of the driving mechanism of Stirling engine, where was chosen modification of these engines with rhombic drive. Subsequently is constructed kinematical, dynamical and thermomechanical mathematical model. Finally, is going from these models for execution strength control and drawing documentation.
355

Zážehový pětiválcový hvězdicový letecký motor / Petrol five-cylinder radial aircraft engine

Donutil, Jan January 2019 (has links)
This thesis deals with configuration of radial five-cylinder engine with attention to crank mechanism. Covered topics are motion of crank mechanism with articulated connecting rod, force analysis and balancing of inertial forces. The second part discusses FEM analysis and calculation of safety factor of selected component.
356

Přestavba zavěšení předních kol automobilu / Conversion of Car Front Suspension

Chaura, Václav January 2019 (has links)
This diploma thesis is focused on the design of the conversion of the car front suspension for racing purpose. Existing suspension solution is described by analyse static and kinematic quantities. Furthermore, a change of suspension is proposed to improve the driving characteristics of the vehicle, where the kinematic, dynamic and strength analysis of the newly designed suspension is performed. The conclusion summarizes the comparison of the original and the new suspension design.
357

Příprava DNA v kvalitě vhodné pro polymerázovou řetězovou reakci / Preparation of PCR-ready DNA

Čuta, Robert January 2011 (has links)
In these days are probiotic lactic acid bacteria (LAB) very often used in food processing industry, such as milk products, cheese and fermented salami production. As well as the food conservation agent. Except of the industry usage of the LAB there are microbiological aspects. Identification of the bacterial species methods based on the isolation and amplification of DNA are very often used last few years. Diploma thesis deal with the bacterial cell of Lactobacillus species lysis and it´s optimalization. At first it was tested the optimal concentration of lysozyme (3mg/ml, 5mg/ml, 10mg/ml) and the exposure times (3, 5 a 10 hours). Another testing was aimed to the use and suitability of washing powder to the bacterial cell of Lactobacillus species lysis. I tested the Amway washing powder optimal concentration (1%, 2%, 3% a 4%). Four of another comercial washing powders were tested too. All these tests were performed at the pure Lactobacillus bacterial culture. To ensure the results I tested the washing powders at the real food matrix (Acidified milk, yogurt mango, yogurt white). All the methods were evaluated at the amplification method PCR with specific primers for the Lactobacillus genus. The DNA isolation was performed with the paramagnetic microsperes P(HEMA-co-GMA) and the amount of the DNA was quantified spectrophotometrically. The PCR products detection was performed with the agarose gel electrophoresis.
358

Návrh přepěťové ochrany pro objekt s nebezpečím výbuchu / Design of overvoltage protection for the object with explosive risk

Polášek, Roman January 2014 (has links)
This master´s thesis deals with the designing process of surge protection for the object potentially explosive atmospheres and according to a set of standards ČEN EN 62305 and ČSN EN 60079. This work consists of four main parts. The first part deals with the theory of lightning and surges. Subsequently, in the second part is devoted to the theory of protection against these phenomena and proposals for external and internal lightning protection and surge. This chapter also deals with more demands on electrical installations in hazardous areas. The third part deals with the analysis of the risks to the subject paint and according to ČSN EN 62305-2 ed.2 and at the conclusion of the study is a proposal for external lightning protection and internal surge protection.
359

Nosná konstrukce jízdárny / Load carring structure of a riding hall

Kubíček, Michal January 2013 (has links)
Master's thesis describes the design and check of the construction of the riding hall. Here are compared two versions the steel structure riding hall. For select version is here technical report, design calculation, statement of material and design documentation. Next is prepared specialization in the field of building construction.
360

Most v obci Návsí přes řeku Olši / Bridge over the Olše river in Návsí

Mendroková, Magda January 2013 (has links)
The diploma thesis deals with design and assessment of steel arched bridge with the semi through bridge deck placed on the third-class road. This steel structure is drawn up to bridge water barrier – the river Olše in Návsí. The distance between axes lay on abutments is 48,5 meters. The bridge´s supporting structure consists of two steel arches angled towards each other and fastened to the foundation blocks. The supporting beam of the bridge deck is tied to the arch by tie-rods. The tie-rods are designed to the V-shaped system.

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