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Influence of particle size on microreology experiments using fluorescence correlation spectroscopy
Valovič, Stela ; Sedláček, Petr (referee) ; Mravec, Filip (advisor)
This diploma thesis deals with microrheology measured via the fluorescence correlation spectroscopy. As microrheological probes, fluorescently marked nanoparticles of 5 sizes in the range of 10-100 nm, were used. The particles had been immersed in a variety of concentrated glycerol solutions and agarose gels of different concentrations, and the FCS measurement revealed a diffusion coefficient of individual particles in each environment. Based on the coefficient, the viscosity of the glycerol needed to stop the particles could be determined. Particles of 10 nm size were not stopped even by the 100 wt% glycerol. In the case of the agarose gels, a combination of higher agarose concentration and larger particles resulted in an increase in the diffusion coefficient to an unlikely high value. This was caused probably by an agarose autofluorescence and the value indicates stopping of the particles in the given agarose gel. Later, the data acquired by the FCS measurement were converted to MSD curves using MATLAB software. The thesis discusses the influence of the experimental parameters on the shape of the MSD curve. The results showed that the number of particles and autocorrelation function have the most significant effect.
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Experimentální určení tlumení nosníku
Fučík, Ondřej ; Hadraba, Petr (referee) ; Rubeš, Ondřej (advisor)
This bachelor thesis deals with structural damping of metallic materials. The first part is research of damping properties, ways how to discover damping properties and short description of how to simulate viscoelasticity of materials, using mathematical models. The second part is focused on an experiment with beams of different lengths and materials. Mathematical models making is also part of solution. The third, last part is focused on results processing. Using mathematical models, damping ratios of beams are determined.
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Viscoelastic deformation in geophysical applications
Sládková, Kateřina ; Čadek, Ondřej (advisor)
Our aim was to aid the viscoelasticity into the model for thermal convection by developing our own code in Fortran 90 and to study the role of viscoelasticity in this model. We should have included the viscoelasticity by Maxwell model; however, due to numerical instability we changed it for Oldroyd-B model. We were adding the terms of objective derivative into our code step by step and we were observing how they influence the behaviour of thermal convection. Partial time derivative and advective terms were included in whole complexity, the corrotational terms need more numerical testing. Our work suggest that the influence of viscoelasticity on thermal convection is noticeable. Powered by TCPDF (www.tcpdf.org)
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Static Analysis of Parts of Thermoplastic Pipe Systems
Plášek, Jan ; Kuklík,, Pavel (referee) ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Kytýr, Jiří (advisor)
Thermoplastic materials have significant nonlinear behaviour. The nonlinear behaviour is described by creep curves. The curves of creep modules are dependent on stress, temperature and time. The dissertation thesis deals with the approximation of the creep modules by Prony series. Subsequently three procedures are proposed to take account of creep modules. The proposed procedures are used in two applications. The first application deals with the ring stiffness value of a corrugated sewage pipe. The ring stiffness value is influenced by the creep modulus. The other one deals with a thermoplastic flange connection. The clamping force is dependent on the creep modulus of thermoplastics. The problems were solved by ANSYS program system.
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Maxwell-type viscoelasticity in small and large deformations of planetary mantles
Patočka, Vojtěch ; Čadek, Ondřej (advisor) ; Průša, Vít (referee) ; Tosi, Nicola (referee)
Title: Maxwell-type viscoelasticity in small and large deformations of planetary mantles Author: Mgr. RNDr. Vojtěch Patočka Department: Department of Geophysics Supervisor: prof. RNDr. Ondřej Čadek, CSc., Department of Geophysics Abstract: A present limitation of global-scale simulations of planetary interi- ors is that they assume a purely viscous or viscoplastic flow law for solid rock, i.e. elasticity is ignored. This is not a good assumption in the cold and strong outermost mantle layer known as the lithosphere, which seems to maintain its elastic properties even on time scales corresponding to the geological processes of subduction or sedimentation. Here we overcome such simplification and present a numerical tool for modelling visco-elasto-plastic mantle convection. The most promising new feature of the resulting models is related to the ability of vis- coelastic materials to remember deformation experienced in the past. Thus, the growing viscoelastic lithosphere of a cooling planet, when subject to internal or surface loading, can store information about its thickness at the time of loading. This phenomena is consistent with datasets of the effective elastic thicknesses determined in flexure studies and we label it here as the "stress memory effect". Attention is also paid to the theoretical foundations...
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Computational simulation of vibrations of rubber damper
Krupa, Lukáš ; Návrat, Tomáš (referee) ; Burša, Jiří (advisor)
This thesis deals with computational modelling of rubber damper using Finite element method (FEM). This thesis includes experimental measurement of material properties of rubber subjected to static and dynamic loading and their implementation into viscoelastic and hyperelastic material models with respect to given task. Dependance of dynamic stiffness on loading frequency obtained from the simulation is validated with experimental measurement. In the end the difference between results is investigated and possible causes of that are introduced.
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On the response of nonlinear dynamical systems to step input
Jiříček, David ; Průša, Vít (advisor) ; Tůma, Karel (referee)
We analyse response of a system, whose dynamic is governed by non- linear differential equations. In particular, we are interested in response to step input. Equation we are working with is constitutive relation of Maxwell type viscoelastic fluid. We motivate the constitutive relation, using one-dimensional Maxwell spring-dashpot model as a analogy to viscoelastic behaviour. The non- linear operator in the constitutive relation is an objective time derivative. We show why the constitutive relation contain such a operator. The essential char- acterization of viscoelastic fluid is their response in creep and stress relaxation tests. In these tests one is interested in the response to step input. This from the mathematical point of view means, that we need to solve a nonlinear differential equation in a generalized setting that allows one to work with jump discontinu- ities. We briefly introduce appropriate tool for solving the generalized equation. The mathematical tool is Colombeau algebra, which is a generalization of the- ory of distributions to nonlinear setting. We compare 4 different objective time derivatives of stress tensor in two different settings - simple shear and biaxial extension. We give explicit formula for the height of jump in stress as a response to jump in motion. 1
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Thixotropy test of semisolid preparations
Tenorová, Klára ; Šnejdrová, Eva (advisor) ; Drastík, Martin (referee)
CHARLES UNIVERSITY Faculty of Pharmacy in Hradec Kralove Department of Pharmaceutical technology Name: Klára Tenorová Title of diploma thesis: Thixotropy test of semisolid preparations Supervisor: PharmDr. Eva Snejdrova, Ph.D. This thesis deals with the study of thixotropic properties of selected semi-solid preparations such as Vaselinum album, Adep lanae, Adeps lanae cum aqua, Alcoholis cetylici unguentum and Alcoholis cetylici cremor. The theoretical part deals with characterization of semi-solid preparations and ointment bases, rheology, rheometry and description of the tests used in the measurement. The experimental part deals with the description of viscosity curves and with the measurement of time dependency of flow behaviour by thixotropic test. Model semi-solid samples show only partial recovery, i.e. false thixotropy. The highest recovery of the structure was shown by Adeps lanae, 83 % at 25 řC and 79 % at 32 řC. The flow behaviour are changed by incorporation of the water depending on the character of the semisolid preparation. At 25 ř C, the viscosity recovery rate was lower than at 32 ř C for all samples except Adeps lanae. After the emulsification of 25% water to Adeps lanae, the recovery rate at both temperatures was significantly reduced, which means that lanolin is slower to recover...
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Anelastic deformation of planetary bodies
Vach, Dominik ; Čadek, Ondřej (advisor) ; Běhounková, Marie (referee)
Observations indicate an existence of subsurface oceans for some of the icy moons in the Solar System which are heated by the tidal forces. In order to describe this anelastic deformation, the methods well-known from the continuum mechanics were employed, and thus the dissipation was calculated for various bodies. In the thesis, Maxwell and Kelvin-Voigt model were compared in their ability to predict the heating power of the bodies. In contrast to the Maxwell model, the Kelvin-Voigt model, which is generally not used in geophysics, repre- sents reversible processes, and thus could explain the effects which are otherwise explained only by the gravity. A program in Fortran was developed in order to compare the models by modelling 3D anelastic deformation of planetary bodies under the effect of tidal forces. The results indicate the predicted power can be various for both models and Kelvin-Voigt model could be used e.g. to describe short run deformation processes. 1
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Modelling of viscoelastic materials with temperature dependence
Miloš, Vojtěch ; Hron, Jaroslav (advisor) ; Tůma, Karel (referee)
Materials such as asphalt, polymers or the Earth's crust tend to behave in a way that can be described neither with a model of viscous fluid, nor a model from solid mechanics. There are indeed models capable of capturing these so called viscoelastic phenomena far better, but they are based on the presumption of constant temperature. In many cases, e.g. in the glass industry or in geophysics, the properties of a viscoelastic material strongly depend on temperature. That is why it is precisely these changes that need to be described. There are viscoelastic models used in practice that take into account the material parameters' dependence on temperature, however, they do not consider the viscoelastic nature of the material when describing the temperature evolution. The objective of this thesis is to derive thermodynamically consistent viscoelastic models with temperature dependent parameters and the appropriate evolution equation for temperature, implementation of the models and computing simple test simulations. Powered by TCPDF (www.tcpdf.org)
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