National Repository of Grey Literature 247 records found  1 - 10nextend  jump to record: Search took 0.04 seconds. 
The study of PET bottles in terms of the content of risk elements
Kryštofová, Petra ; Řezáčová, Veronika (referee) ; Komendová, Renata (advisor)
This bachelor thesis deals with the issue of PET bottles in terms of the possible content of risk elements. The contents of antimony, copper and lead were determined in the PET packaging material and in the beverages contained in the bottles. A total of 15 samples of bottled still and infant water available in the Czech sales network were analyzed. The PET material was decomposed in an acidic medium under the action of microwave radiation under optimized conditions. Atomic absorption spectrometric methods with flame or graphite cuvette atomization were used to determine selected risk elements based on the predicted analyte concentrations. In the PET packaging material, 159.35 to 265.68 mgkg-1 of antimony were determined, the determined values of lead concentration were in the range of 10.96-20.23 mg·kg-1 and the copper concentration in the range of 0.11-7,52 mg·kg-1. In bottled water and in bottled infant water, antimony was identified only in samples labeled 6a, 8a, 9a and 15a, all lead concentrations were measured below LODPb, copper was determined only in samples 2a, 6a and 8a. In none of the samples did the concentrations given by the valid legislation be exceeded. The limits of these metals are not set in legislation in the packaging materials, only specific migration limits and they have not been exceeded. However, the high concentration of antimony in PET poses a potential risk of contamination of the contents of these packages.
Temperature Profile in Reflow Soldering and Influence of Different PCBś and ComponentsThermal Capacities
Procházka, Martin ; Špinka, Jiří (referee) ; Starý, Jiří (advisor)
This thesis mainly deals with the prediction of temperature on the components and the PCB during reflow soldering. The theoretical part describes the particular solder reflow process, types of heat transfer and temperature profiles. The practical part is divided into forecasting temperatures if the conveyor is stopped and the temperature predictions when the conveyor is in motion. In both parts of the measured temperature is compared with the predicted temperatures, which show the success rate of prediction. The last part of this work is part of the simulation, which helps in proper understanding of the issues discussed.
The study of vertical mobility of heavy metals and their transfer to mushrooms
Jurnečka, Roman ; Doležalová Weissmannová, Helena (referee) ; Komendová, Renata (advisor)
This bachelor thesis deals with the issue of contamination of forest soils and edible mushrooms with lead, cadmium, copper and zinc in the Jeseníky Mountains, specifically in the Domašov and Vápenná forests. Sampling took place at 12 localities, divided into spruce and beech stands. Atomic absorption spectrometry AAS ContrAA 800D was chosen to determine the content of selected heavy metals. Based on the measured values of the concentrations of the studied metals and other soil properties, dependences were created to determine the vertical mobility of selected metals in the soil profile. Vertical mobility depends on the physico-chemical properties of the soil (pH, C and S content). The dependence of the content of selected heavy metals in the soil on the pH value of the soil was found. In the case of lead, the sorption capacity of the soil organic component was confirmed. The risk and above-limit content of Pb, Cd and Cu was found on the yellow-boletus mushroom. Cadmium shows the highest bioavailability. Lead was evaluated as the element with the lowest mobility.
Creation of Logistic Concept in the Selected Company
Kapusta, Vladimír ; Lahučký, Martin (referee) ; Jurová, Marie (advisor)
Master thesis named „Creation of logistic concept in the selected company“ is focused on detailed analysis of material flow of waste in manufacturing company. The main objective of thesis is proposal of new logistic concept of handling with copper waste, which is created during the manufacturing processes, which function will be to remove defects in material flow, to shorten the handling time with copper waste and more accurate information flow, considering work safety, costs and time.
Thick-film sensors for heavy metals detection
Gajdoš, Libor ; Majzlíková, Petra (referee) ; Prášek, Jan (advisor)
This project describes the possibilities of heavy metals detections in solutions using differential pulse voltammetry with tree-electrode electrochemical thick-film sensors. In the theoretical part, the thick-film technology is described as well as thick-film pastes’ types and compositions, followed by introduction to electrochemistry and electro-analytical methods of measurement. This project also describes the three measured heavy metals – cadmium, lead and copper. In the practical part, heavy metals’ ions detection in solutions using carbon working electrode and determination of the detection limit and sensitivity are described and discussed. Finally the evaluation of obtained results and results comparison to hygienic limits are included.
Corrosion layers removal in low-pressure plasma
Kujawa, Adam ; Grossmannová, Hana (referee) ; Krčma, František (advisor)
A plasmachemical reduction of corrosion layers on copper was studied. In this case two series of copper samples were prepared and putted in two corrosive environments for one week. The first corrosive environment contained a concentrated nitric acid and the second environment contained a concentrated sulfuric acid. Samples thus prepared were ready to be plasmachemicaly treated. The plasmachemical reductions took place in low-temperature, low-pressure, non-isothermal, high-frequency-inducted hydrogen plasma on the Faculty of Chemistry in University of Technology in Brno. The discharge was generated in continual or pulse mode with changeable pulse ratio. To monitor the reduction process an optical emission spectroscopy was used. The radiation from plasma discharge was measured by an optical spectrometer in the intervals of 1 to 10 minutes. An object of our concern in collected spectrum was the radiation of OH radicals with electromagnetical wavelenght in a range of 305 – 330 nm, and which were produced in a reaction between the hydrogen radicals and the oxygen atoms, contained in the corosion layers. A rotation temperature of plasma was calculated from the spectrums of OH radicals in a dependence of discharge conditions. Gathered findings will give us a better knowing of this conservation technique, that is used for treatment of the corroded surfaces of the archeological artifacts, and will also allow more provident appliance of this method on a copper historical objects.
Reconstruction of the town spa in Malé Svatoňovice
Macek, Štěpán ; Špiller, Martin (referee) ; Guzdek, Adam (advisor) ; Kalousek, Lubor (advisor)
The aim of the bachelor thesis was to prepare a documentation for building permits and a part of the documentation for the building construction on the basis of an architectural study, developed in the „AG35 – Monuments Restoration Studio“ module. The topic of the studio work was to think about the appropriate use of a listed building in the historic center of the village of Malé Svatoňovice and to create an architectural study. I have proposed the following concept. The building should serve as a municipal house, so I have concentrated the corresponding functions here: the municipal office, the ceremonial hall, the museum, doctors labs, cosmetics, the pharmacy and finally the spa, which had a long tradition here. When restoring an object, I proceed synthetically. I examine the quality and preservation of individual layers. Then I highlight the best of each one. If some layer have not been preserved, but still have had its qualities, I remind it in a new language. I think it was Tadao Ando who said, "If the genius loci is to be legible, it must be revived and provoked by inventive inputs." I combine modern with historical using timelessness.
Options for increasing the efficiency of small motors.
Kusý, Karel ; Janda, Marcel (referee) ; Hájek, Vítězslav (advisor)
This bachelor thesis concerns itself with the possibilities of achieving higher efficiency of small asynchronous motors and their manufacturing costs. The following chapters describe the design, function and principles of speed regulation of the asynchronous motor. Next, losses that occur during motor operation and ways of reducing them, are described. The last chapter of the thesis addreses factors that influence the manufacturing costs of the asynchornous motor and evaluates the material costs of one modified motor.
Recent Trends in Research and Development of Non-toxic Small Calibre Bullets
Macháček, Tomáš ; Komenda,, Jan (referee) ; Klakurková, Lenka (advisor)
This thesis focuses on finding equivalent replacement of toxic lead used in bullets with different non-toxic material. Bullets produced from copper, brass, zinc and lead were tested. The work contains information about chemical composition, a macro and mikro documentation and the hardness values of each bullet. Methods of light microscopy, scanning electron microscopy and microhardness measurements were used for this study.
Metals Transport in the System Soil/Plant. Comparison of the Active and Passive Sampling Method (The Diffusive Gradients in Thin Films Technique)
Trávníčková, Jana ; Janoš, Pavel (referee) ; Chýlková, Jaromíra (referee) ; Čelechovská, Olga (referee) ; Dočekalová, Hana (advisor)
The doctoral thesis deals with comparison between copper uptake by radish (Raphanus sativus L.) and concentration of copper measured by a DGT-device and concentration of copper obtained by extraction with generally used extraction agents (HNO3, NaNO3 and water). Plants were cultivated in pot experiments on a tested non-treated and gradually spiked soil. The amount of copper was determined in various part of radish (whole plant, above- and below-ground part) after mineralization in the APION mineralizer by ET – AAS. The highest concentration was in belowground part, especially in root tissues and sheel of root bulb. It confirms copper is associated with cell walls. The amount of copper taken by radish up does not pass beyond sanitary standards not even in spiked soils and consummation of radish is not unhealthy. Good correlations were found between copper concentration in radish and the amount of copper extracted with HNO3, NaNO3 and water and the amount found in soil solution. Results of extraction with HNO3 confirmed the amount of copper was stable in spiked soils during the pot experiments. The DGT experiments have shown that the rate of resupply from the solid phase to soil solution is constant during the deployment time. Whereas the release of copper decreases after 24 hours in natural soil. Copper added to soil in form of cupric ions is present in the different form after one month-equilibration than copper present in unspiked soils. The results obtained by DGT measurements were approximately up to two orders of magnitude lower than copper concentration obtained by leaching with sodium nitrate. The extraction with sodium nitrate does not provide true reflection of metal availability to plant root system and soil microorganism. High values of correlation coefficients (R2 > 0,9) were found between concentration of copper in radish plant and the concentration of copper in soil solution measured by DGT technique. Concentration of copper in soil solution was three times higher than concentration measured by DGT technique. Soil solution contains species of copper that are not measured by DGT technique and available to plants. Concentration of metals obtained by DGT measurements is more closely to real concentration of bioavailable forms of metal in soil. Therefore it is possible to recommend the DGT technique as a technique for determination of bioavailable forms of copper in soils.

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