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Schim Valve of Hydraulic Suspension Damper
Reisch, Martin ; Blaťák, Ondřej (referee) ; Hejtmánek, Petr (advisor)
This bachelor thesis is focusing on the problem of the shim valve in a hydraulic suspension damper, its pressure drops and the effect of different modifications of the valve on the properties of the complete damper. In the first part, an overview of the shim assemblies used on the shim valve is made and the influence of the different assemblies on the damping properties of the shock absorber is described. The effect of the different parameters of the shims (thickness, radius, position) on the overall stiffness of the shim assembly is described. In the next section, an overview of analytical models for the calculation of stiffness and pressure drops on the shim valve is developed and a FEM methodology for the calculation of valve stiffness is established. All computational methods are compared with measured data on a real damper throughout the paper.
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Methods of provenance determination of marbles
Dontová, Kateřina ; Přikryl, Richard (advisor) ; Kuchařová, Aneta (referee)
Determination of provenance of marble from sculptures or architecture, which make part of our cultural heritage, make some of the principal goals of material investigation of artefact and/or archaeological findings. Light-coloured marbles used in antiquity are amongst the most studied types of natural stone. Various methods and approaches, employed for marble provenance, rank to the most developer. Moreover, antique marbles take advantage of having the largest datasets for provenance determination. This bachelor thesis focuses on the review of the main scientific methods which have been used for marble provenance studies during past 130 years. Mineralogical-petrographic description together with thin-section microscopy makes the basis of such studies. Traditional qualitative description has evolved into more precise quantitative study with the help of computer-based image analysis methods allowing for obtaining sound quantitative data (grains size, grain shape etc.). After-2WW period is characterised by adoption of various analytical methods, which employ different chemical characteristics of marbles. Along with trace elements studies (e.g. by INAA, LA-IC-MS), most of the recently used analytical methods focus on the C and O stable isotopes. Each of the methods has also some limitations, therefore...
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Studium flavonoidů u bílých vín
Mráz, David
Phenolic substances are synthesized in plants, where they help in their defense against fungal diseases, are used as a significant source of substances by the human population. Phenolic substances are not a human organism capable of producing themselves and it is therefore necessary to take these health benefits in the diet. Grape vines, berries, are very rich in natural phenolic substances. We divide these natural phenolic substances into two basic groups: flavonoid and non-flavonoid, which, thanks to the technology of grapevine processing, pass into wine. Thanks to different grape processing technology, red wine is richer in phenolic content, but the content of these antioxidant components is not negligible even in white wines. Grape vines and their wine products are constantly being studied for the content of antioxidant components and their importance for human health, thanks to the development of modern analytical methods. The results of scientific studies are constantly updated and accepted not only by human health experts but also by the general public.
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Methodology for determining the chemical composition of water glasses
Flídrová, Michaela ; Bartoníčková, Eva (referee) ; Kalina, Lukáš (advisor)
The bachelor thesis deals with the methodology of determination of the chemical composition of water glasses. The aim was to find a more suitable method than the colorimetric analysis used by one of the domestic water glass manufacturers. The current procedure can be used to determine the content of Me2O (Na2O, K2O, Li2O), however, in the determination of SiO2 the method is inaccurate since the color change of the indicator during the second titration is very slow and therefore the equivalence point is ambiguous. The main aim of this work was to find a suitable method for the complex determination of the chemical composition of water glasses, which is compared with other methods used in the analytical chemistry of silicate materials. A very promising method is the conductometric titration with a volumetric hydrochloric acid solution, which provides an accurate, fast and instrumentally inexpensive method of chemical determination.
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Advanced Magnesium Alloys Surface Modification by Ni-P Based Coatings
Kosár, Petr ; Pacal, Bohumil (referee) ; Nový,, František (referee) ; Havlica, Jaromír (advisor)
The dissertation thesis deals with the modification of the surface of advanced magnesium alloys with Ni-P based coatings. At the beginning of the theoretical part, the structures of the used magnesium alloys and the influence of individual alloying elements on their properties are characterized. In the following part of the thesis the current knowledge in the field of electroless deposition on metal substrates is summarized. The theoretical part of the thesis is closed with contemporary research study in the field of clarification and determination of possible mechanism of electroless deposition. For the subsequent investigation of the mechanism of electroless deposition on magnesium alloys, it was necessary to characterize the microstructure and composition of individual magnesium alloys in the first phase of the experimental part. The exact composition of elements was determined using glow discharge optical emission spectroscopy and scanning electron microscopy with EDS was used for composition of phases of magnesium alloys. Using scanning electron microscopy and detailed elemental analysis of the coated magnesium substrate, it was found that for optimal Ni-P coating deposition on magnesium alloys, acid pickling prior coating is required in a mixture of acetic acid and sodium nitrate. Using the XPS method, it was found that the phosphorus atom in the sodium dihydride-diphosphate reducing agent has a + V charge. 4 At the end of the experimental part scanning electron microscopy and detailed elemental analyses were used for monitoring of the Ni-P particles nucleation and growth in the first 120 seconds of the coating process.
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Obsah přiboudliny v ovocných destilátech
Borko, Jozef
Fusel typical compounds for fruit juices, but also for distillate fractions (Luther head, heart, tail). Of the varieties TOPAZ was ready to leaven, which was converted by distillation to the mentioned distillate fractions. Samples of fresh apple juice and distillate stocks were stored in a cooling box at - 18 ° C. Analysis of fusel oils and other ingredients of fabric were determined SPME / GC / MS. Analytical treated sample (captured in the hollow fiber), followed by desorption of the liquid was divided column. The mass spectrometer analytical peaks quantified according to the standard for which is a recognized m / z. Of the amount of the analyte for each analytical unit (juice - boiling fraction) were separated substance of analytical chemical group of the alcohols, branched alcohols, aldehydes, ketones, esters and terpenes.
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Studium vlivu teploty na obsah antioxidantů při přípravě zelených čajů
Blažková, Lucie
Tea is one of the most popular beverages worldwide. It was demonstrated that the beverage prepared by leaching of leaves of Camellia sinensis in hot water, has a positive effect on human organism in many cases. The substances found in green tea have antioxidant properties and positive effects on the prevention of many diseases. The beneficial effects are attributed mainly due to plant phenols whose antioxidative activity protects the body against free radicals. In this work the content of selected biologically active compounds in extracts of loose green teas was determined using modern bioanalytical methods. The amount of natural antioxidants determined in tea from Japan and China at different preparation temperatures of the tea extract solution were compared.
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Charakteristika a metody stanovení vitaminů v masozeleninových přesnídávkách určených pro dětskou výživu
Piechowiczová, Markéta
Bachelor thesis Characteristics and methods for determination of vitamins in meat-vegetables purées intended for baby food was focused on acquiring general knowledge about child nutrition, with regard to adequate intake of vitamins in the diet, which are then characterized, together with methods of their determination. In the first part there are described particular periods of nourishment until 12th month of life. Nourishment recommendations are summarized here, more specifically required nutrients in this age, but also issues concerning allergies, alternative nourishment and some diseases, which can lead to hypovitaminosis. The second part is devoted to the characteristics of vitamins. Chemical properties, effect on the body, occurrence in foods and the recommended daily intake are included. The chapter about occurrence in food is always accompanied by the recommendation of ingredients with a high content of vitamins, which are appropriate to add to complementary food. In the last part of thesis the methodology for determination of vitamins are summarized in the light of the newest trends. These methods include chromatographic methods, spectrophotometric,fluorimetric, polarographic, microbiological and capillary electrophoresis.
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Acrylamide in potato products
Jiruška, Jan ; Sedláková, Vladimíra (advisor) ; Dvořák, Petr (referee)
This thesis provides a review describing acrylamide (AA), its detection and reduction. Botanical description and list of registered varieties of Solanum tuberosum in the Czech Republic is provided. Attention is payed to chemical composition of tubers. Next step is about AA. AA can cause carcinogenic and neurotoxic effects, particularly because it can be converted to a more reactive compound glycidamide in a human body. Thanks to animal experiments, we can reveal negative effects on the human body.
AA is formed by heat treatment over 120 °C in potatoes. Therefore, it is in potato chips and crisps. It is reaction of the free amino acids (especially asparagine) and reducing sugars (mostly glucose or fructose). It is all about several consecutive reactions that are included in the Maillard reaction. This reaction causes typical taste and aroma in products. Unfortunately, AA is one of the byproducts.
Today, formation of acrylamide has growing attention, because scientists want to reduce it as much as possible. Growing, industrial processing of potatoes and addition of additives during heat treatment is included. Antioxidants can significantly prevent formation of AA in food. There are also gathered informations on advanced analytical methods to detect AA in food. Rapid methods of detection are becoming more popular by scientits, that is why they are also included.
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Analytické a senzorické možnosti kontroly falšování pravosti révového vína
Rozek, Kamil
The diploma thesis deals with analytical and sensorial possibilities of control of grape wine adulteration. In the first, theoretical part of the thesis, the author introduces valid legislation regulating authorized substances in wine, as well as the wine production processes itself. The reader is acquainted with the means of wine adulteration in the Czech Republic that ensued from an analysis of unsatisfactory samples of wine, collected between 2012 -- 2015 by the SZPI (Czech Agriculture and Food Inspection Authority). The second, practical part of the thesis, describes not only grape wine and SZPI samples imitation production processes, but also methods used for their subsequent sensorial and analytical study. Besides, it interprets measured data, and compares and contrasts the possibilities and appropriateness of the sensorial evaluation and analytical study for the detection of wine adulteration.
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