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Sledování jakosti hovězího masa během zrání
Kavanová, Monika
The diploma thesis is dealing with the monitoring of quality of beef meat during the process of ageing. In the literary overview the terms beef meat and quality are defined, the consumption of beef meat is stated and the composition and attributes of the beef meat are described. The list of factors that influence the quality of beef meat follows. The factors are divided into intravital and postmortal. The postmortal processes are described more thoroughly; the possibilities and consequences of their abnormal progress and other quality defects are added. The practical part of the thesis is devoted to the comparison of chosen parameters of heifer meat (n = 6) of the Aberdeen Angus breed (AA) and Czech Fleckvieh breed (CS). In the cut-out parts Musculus longissimus dorsi (NR) and Musculus adductores (SŠ) the parameters of pH, electrical conductivity and color were observed for eight weeks of aging in the vacuum (1-2 °C). The color was measured spectrofometrically with the application of the CIELAB color space.
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Study of electrical and dielectric properties of conducting polymers
Varga, Martin ; Prokeš, Jan (advisor) ; Petzelt, Jan (referee) ; Pfleger, Jiří (referee)
Title: Study of electrical and dielectric properties of conducting polymers Author: Mgr. Martin Varga Department: Department of Macromolecular Physics Supervisor: RNDr. Jan Prokeš, CSc., Department of Macromolecular Physics Abstract: Charge transport in polyaniline (PANI) and polypyrrole (PPy) was studied in respect to various oxidants, dopants, morphology, and other modifica- tions in their synthesis. The mechanism of transport was discussed in the frame- work of combination of several models characteristic for disordered solids due to inherent heterogeneous structure of conducting polymers. Effect of drying on conductivity was studied and the long-time limit was explained with the diffusion- based model for bulk materials. For PPy nanotubes stability in strong alkaline media and aging were studied by AC and DC techniques. While conductivity of naturally aged samples after two years remained in the same order of magni- tude, after exposure to alkaline media or accelerated aging at high temperatures, conductivity decreased several orders of magnitude. Degraded material exhibited strong disorder and the transport model was completely changed. Despite severe treatment electrical properties were still comparable to other as-prepared mate- rials. Finally, an application example as ammonia sensor, the response of...
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Gel polymer electrolytes with fire retardands
Veselkova, Iuliia ; Jahn, Michal (referee) ; Sedlaříková, Marie (advisor)
This graduate work deals with the study and preparation of gel polymer electrolytes with flame retardants for lithium-ion batteries. The theoretical part describes the types of electrolytes, their features, benefits, how they differ and where they are used in detail. The basis of this section is gel electrolytes with flame retardants, to measure their electrical and electrochemical properties. The experimental part deals with the preparation of samples of gel electrolytes with different percentages of flame retardant, where varied species of flame retardants and measuring their electrical conductivity and potential windows. Impedance spectroscopy, cyclic voltammetry and dynamic-analytical thermal analysis were selected as measuring methods.
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Methodology of Determination of Electroinsulating Properties
Čanigová, Veronika ; Nevřivová, Lenka (referee) ; Sokolář, Radomír (advisor)
The core of this bachelor thesis is porcelain and electrical porcelain property specification accompanied by definition and explanation of electric conductivity. The theoretical section provides insight into electrical porcelain production from initial raw material exploitation to final stages of body baking. The experimental part compiles a number of electrical porcelain test methods based on current European standards and draft test procedures, which are followed in order to specify properties of conventional electrical porcelain as well as emerging anorthite porcelain based on aluminate cement.
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Silicate materials with enhanced electrical conductivity
Míková, Maria ; Kusák, Ivo (referee) ; Rovnaník, Pavel (advisor)
This bachelor thesis deals with electrical properties of cement- or aluminosilicate-based materials used in building industry. It presents the summary of the most commonly used functional fillers with ability to increase conduction of the composites and theirs characteristics. Thesis also deals with measured electrical properties and applications of composites with enhanced electrical conductivity. In the experimental part, the influence of graphite powder concentration on the characteristics of alkali activated slag was examined. Electrical, mechanical properties and microstructure was observed. Microstructure was examined by means of mercury porosimetry and scanning elektron microscopy.
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Monitoring properties of nanocomposites on base epoxy
Libra, Miroslav ; Rozsívalová, Zdenka (referee) ; Polsterová, Helena (advisor)
The present thesis deals with the study of nanotechnology in the field of composite materials (nanocomposites). Furthermore, the production, composition and electrical properties of these materials. Samples for the experiment are made of epoxy resin as matrix and titanium dioxide TiO2 as fillers with different benefits. Are the measurements the temperature dependence of permittivity, loss factor and internal resistivity.
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Mechanical and Electrical Properties of Thin Metal Films Deposited by Vacuum Evaporation
W. F. Yahya, Doaa ; Kolařík, Vladimír (referee) ; Štencl,, Jiří (referee) ; Šandera, Josef (advisor)
Thin layers are widely used in many fields of technology and today we can say that they are found in all modern technologies. Thin layers can be created in two ways, namely by chemical or physical means. This work focuses on the latter method, more particularly a technology of thermal evaporation of thin layers in a vacuum. The work focuses on the process principles during and after the evaporation. Much of the work focuses on the development and design of experiments. These experiments illustrate some of the phenomena that take place on thin films produced by the aforementioned technology. Work helps to better understand processes during formation of thin layers and properties that influence the quality and stability of thin films. In conclusion we describe results of experiments and new developments in the field of thin films deposition using evaporation under vakuum are summarized.
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Dielectric Properties of Thin Tantalum and Niobium Oxide Layers
Abuetwirat, Inas Faisel ; Chobola, Zdeněk (referee) ; Lelák, Jaroslav (referee) ; Liedermann, Karel (advisor)
Dielektrická relaxační spektroskopie je jednou z užitečných metod pro studium molekulární dynamiky materiálů. Díky nedávnému pokroku v přístrojové a měřicí technice je dnes možné získat dielektrické spektrum v širokém frekvenčním intervalu a pro velice rozdílné materiály. Cílem mé práce bylo studium dielektrických relaxačních spekter a vodivosti oxidů titanu, niobu, tantalu, lanthanu a hafnia pro katody pracující na principu studené emise. Cílem výzkumu bylo analyzovat frekvenční a teplotní chování těchto oxidů, včetně jejich vodivosti, v širokém frekvenčním a teplotním rozsahu, a pokusit se stanovit původ relaxačního mechanismu. Vzhledem k tomu, že původně zadaný rozsah oxidů byl dosti široký, soustředila se pozornost pouze na oxidy tantalu a niobu, rovněž s ohledem na jejich aplikace v elektrolytických kondenzátorech. Elektrické, tepelné a mechanické (při zpracování) vlastnosti oxidů tantalu a niobu jsou dnes již dobře prozkoumány. K dispozici je však jen málo poznatků o jejich dielektrických relaxačních mechanismech. Výsledky získané pro Ta2O5 ukazují existence relaxačního maxima, nacházejícího se v experimentálně dostupném teplotním a frekvenčním intervalu 187 K – 385 K a 1 Hz – 10 MHz. Frekvence ztrátového maxima se řídí Arrheniovým zákonem s aktivační energií 0.048 eV. Ve vodivostních spektrech vykazují tenké vrstvy Ta2O5 na nízkých frekvencích ustálenou hodnotu a při vysokých frekvencích monotónní nárůst, který závisí na teplotě. Pozorovanou vodivost lze popsat mocninnou funkcí s exponentem nepatrně větším než jedna (tzv. superlineární závislost). Výsledky získané pro Nb2O5 v podobné teplotní a frekvenční oblasti, 218 K – 373 K, 1 Hz – 1 MHz rovněž ukazují jedno relaxační maximum. Frekvence ztrátového maxima se opět řídí Arrheniovým zákonem s poněkud vyšší aktivační energií 0.055 eV. Niobové kondenzátory vykazují vodivostní mechanismus shodný s kondenzátory tantalovými.
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