Modelování viskoelastických materialů s teplotní závislostí

Materiály jako sklo, asfalt, polymery nebo zemská kůra vykazují chování, které nelze popsat modelem pro viskózní tekutinu ani modelem pro pevnou látku. Existují modely, které jsou schopny tyto tzv. viskoelastické jevy zachytit mnohem lépe, nicméně tyto modely většinou předpokládají konstantní teplotu. V mnoha případech, například ve sklářství nebo v geofyzice, vlastnosti viskoelastického materiálu silně závisí na teplotě a právě tyto změny je třeba popsat. V praxi se používají viskoelastické modely, které uvažují závislost materiálových parametrů na teplotě, nicméně při popisu evoluce teploty nezohledňují viskoelastickou povahu materiálu. Cílem této práce je odvození termodynamicky konzistentních viskoelastických modelů s materiálovými parametry závislými na teplotě a příslušnou evoluční rovnicí pro teplotu, implementace těchto modelů a provedení jednoduchých testových simulací. Powered by TCPDF (www.tcpdf.org)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)Matematický ústav UKMathematical Institute of Charles UniversityMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

Wearable textile electrodes for ECG measurement

The electrocardiogram (ECG) is one of the most important parameters for monitoring of the physiological state of a person. Currently available systems for ECG monitoring are both stationary and wearable, but the comfort of the monitored person is not at a satisfactory level because these systems are not part of standard clothing. This article is therefore devoted to the development and measurement of wearable textile electrodes for ECG measurement device with high comfort for the user. The electrode material is made of electrically conductive textile. This creates a textile composite that guarantees high comfort for the user while ensuring good quality of ECG measurements. The composite is implemented by a carrier (a T-shirt with flame retardant) and sensing electrodes embroidered with yarn based on a mixture of polyester coated with silver nanoparticles and cotton. The electrodes not only provide great comfort but are also antibacterial and antiallergic due to silver nanoparticles

A continuum model for yttria-stabilized zirconia incorporating triple phase boundary, lattice structure and immobile oxide ions

A continuum model for yttria-stabilized zirconia (YSZ) in the framework of non-equilibrium thermodynamics is developed. Particular attention is given to (i) modeling of the YSZ-metal-gas triple phase boundary, (ii) incorporation of the lattice structure and immobile oxide ions within the free energy model and (iii) surface reactions. A finite volume discretization method based on modified Scharfetter-Gummel fluxes is derived in order to perform numerical simulations. The model is used to study the impact of yttria and immobile oxide ions on the structure of the charged boundary layer and the double layer capacitance. Cyclic voltammograms of an air-half cell are simulated to study the effect of parameter variations on surface reactions, adsorption and anion diffusion. © 2019, The Author(s)

Symmetrization Method of AC Traction Substation with Power Balancer

the project OP VVV Electrical Engineering Technologies with High-Level of Embedded Intelligence CZ.02.1.01/0.0/0.0/18_069/0009855, project SGS-2021-021The paper describes the symmetrization method of power converter used in topology of AC traction substation with power balancer. This topology provides the three-phase current symmetrization and the reactive power compensation for AC traction substation feeding 25 kV / 50 Hz traction catenary. The described symmetrization method is based on principles of the Steinmetz symmetrizing circuit. The main paper contribution is a derivation and description of the symmetrization equations, which are used for the control algorithm of multilevel semiconductor converters in a delta connected circuit

Hydrotreating of waste plastic pyrolysis oil with increased chlorine and nitrogen content

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Model Study of Cooperating Traction Substations at 25 kV Traction Catenary without Superior Power Distribution Control

OP VVV Electrical Engineering Technologies with High-Level of Embedded Intelligence CZ.02.1.01/0.0/0.0/18_069/0009855 and under project SGS-2021-021This paper describes the results of the model study for traction system 25 kV / 50 Hz, which is built on an advanced traction substation with a rail active balancer and phase shifting device. The first part of this paper is described traction substation topology with a description of its properties. The following section describes the operation of the traction system in terms of interconnection with the distribution power grid. The important requirements for the behavior and used equipment of advanced traction stations are explained in more details here. The last part of this paper presents the proposed concept of control of individual traction substations, while superior power distribution control is not available. Therefore, each traction substation must have its own independent control algorithms, its behavior properties are presented and documented in the results of simulation models. In order to be able to explain the whole issue well, the created model is simplified only to the control of two independent traction substations

Limited validity of West and Yennie integral formula for elastic scattering of hadrons

The commonly used West and Yennie integral formula for the relative phase between the Coulomb and elastic hadronic amplitudes might be consistently applied to only if the hadronic amplitude had the constant ratio of the real to the imaginary parts al all kinematically allowed values of four momentum transfer squared.Comment: 5 page

Generalized Poisson--Nernst--Planck-based physical model of O2_2 I LSM I YSZ electrode

The paper presents a generalized Poisson-Nernst-Planck model of an yttria-stabilized zirconia electrolyte developed from first principles of nonequilibrium thermodynamics which allows for spatial resolution of the space charge layer. It takes into account limitations in oxide ion concentrations due to the limited availability of oxygen vacancies. The electrolyte model is coupled with a reaction kinetic model describing the triple phase boundary with electron conducting lanthanum strontium manganite and gaseous phase oxygen. By comparing the outcome of numerical simulations based on different formulations of the kinetic equations with results of EIS and CV measurements we attempt to discern the existence of separate surface lattice sites for oxygen adatoms and O2- from the assumption of shared ones. Furthermore, we discern mass-action kinetics models from exponential kinetics models

Carbonyl content determination in bio-oils with increased nitrogen content

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Interference between Coulomb and hadronic scattering in elastic high-energy nucleon collisions

The different models of elastic nucleon scattering amplitude will be discussed. Especially, the preference of the more general approach based on eikonal model will be summarized in comparison with the West and Yennie amplitude that played an important role in analyzing corresponding experimental data in the past.Comment: 13 pages, 2 figure