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Investigation of Reliability for Solder Joints in Nitrogen Atmosphere
Vala, Martin ; Adámek, Martin (referee) ; Szendiuch, Ivan (advisor)
This thesis examines the influence of nitrogen atmosphere on the quality of the solder joint lead-free solder paste. For the solder paste were measured and set temperature profiles. Thesis includes the implementation and measurement of samples in a protective nitrogen atmosphere and without a protective atmosphere. These measurements are compared, and the conclusions were drawn for the influence of nitrogen atmosphere. The reliability and the quality of the soldered joints were investigated.
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Influence of Inert Atmosphere on Surface Wetting in Lead Free Soldering
Nestrojil, Michal ; Špinka, Jiří (referee) ; Starý, Jiří (advisor)
This master´s thesis dealing with study of influence of inert atmosphere on the wettability of soldered surfaces. The theoretical part is discussed the issue of the soldering, solder joint, oxidation, and inert atmosphere. The glass cover with internal inert gas preheating for the wetting balance testing was prepared in the practical part. With this adjustment were realised tests, in which was examined the effect of the inert gases on the wettability of different materials combination. Further experiments were focused on plasma surface cleaning as possible flux substitution. The evaluation of these experiments were discussed in the end of this master´s thesis. Some of topics were designed for further experiments.
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Testing of Solders in Protection Atmosphere
Vala, Radek ; Jankovský, Jaroslav (referee) ; Szendiuch, Ivan (advisor)
The project deals with the overall design and construction of equipment called the desiccators for brazing in a protective atmosphere. The device was designed and manufactured cooling and heating element. For the soldering various temperature profiles have been defined and adjusted, as for SnPb as well for lead-free solders. There was a realization of samples were measured and analyzed. Finally were realized micro sections for lead free solder.
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Investigation of Reliability for Solder Joints
Toufar, Michal ; Somer, Jakub (referee) ; Szendiuch, Ivan (advisor)
It evaluates the importance of soldering in a protective atmosphere. Factors influencing the process of reflow soldering in a protective atmosphere of nitrogen. Evaluates the quality of solder joints due to a defined residual oxygen during the soldering proces. According finishes used on the resulting quality connections for two types of lead free solder.
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Optimization of the radiofrequency atomic source for deposition of GaN
Kern, Michal ; Wertheimer, Pavel (referee) ; Mach, Jindřich (advisor)
This thesis is focused on construction and optimization of radiofrequency atomic dissociation source of atomic nitrogen for depostion of GaN. The theoretical part deals with atomic sources, growth of ultrathin layers and the issue of radiofrequency circuits, with emphasis on their design using Smith chart. Methods for synthesis of GaN ultrathin layers and deposition are also discussed. In the experimental part, design and realization of various congurations of the impedance matching network is described. Using the impedance matching network a nitrogen plasma discharge was successfuly created and its spectrum was analysed. Afterwards, design and realization of a stepper motor control for the impedance matching network is described.
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The dynamics of non-structural saccharides accumulation and Rubisco activity under the elevated carbon dioxide concentration and sink manipulation at beech
Uhrová, Lucie ; Vítová, Eva (referee) ; Hrstka, Miroslav (advisor)
This diploma thesis deals with dynamic of accumulation of non-structural carbohydrates and activity of Rubisco enzyme at elevated concentration of CO2 on beech (Fagus sylvatica L.). Three years old seedlings of beech were cultivated in minisphere with ambient (385 µmol•mol-1, variant A), and with elevated concentration CO2 (700 µmol•mol-1, variant E) for four months. In every variant the first half of plants was fertilized by nitrogen (variant N+) and the second half was control (variant N-). Plants used for experiment were at first adapted for darkness for 12 hours. Subsequently tested leaves were cut off, leafstalk including short segment of branch (approximately 1 cm) was inserted into 0.7 M solution of sucrose (variant S) or water (variant V) and exposed to radiation 200 mol•m-2•s-1 for 0, 30, 60, 120, 180 minutes. Then leaf area and fresh mass of leaf blade were established, samples were fixed in liquid nitrogen and stored in deep freezer to analysis in –70 °C. Rubisco content was determined by SDS-PAGE method, Rubisco activity spectrofotometrically and content of non-structural carbohydrates by anthrone method and HPLC method. Rubisco content was significantly lower in the N- variant than in N+ variant. Rubisco content was also significantly lower in E than in A variant, which is an evidence of down-regulation. Rubisco activity is moderately stimulated at E variant with time, but differences between variant A and E are not statistically significant. Influence of sucrose feeding to Rubisco activity was not proved. Significant differences were detected by anthrone method in non-structural carbohydrates content between variants S and V, but not between variants A and E. Statistically significant increase of sucrose content with time was detected by HPLC method at variant AS, but not at variant ES.
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Characteristic parameters of combustion of low calorific fuels
Kvapil, Matěj ; Bělohradský, Petr (referee) ; Hudák, Igor (advisor)
The diploma thesis is focused on the combustion of the low calorific gaseous fuels. The first part is devoted to the characterization and usage of low calorific fuels. Then combustion theory focused mainly on emissions and thermodynamics. Next characterization of burners and their modifications for low calorific value fuels is described. Safe storage and handling of chosen gases is also included in the last chapter of the theoretical part. Practical part includes the description of the laboratory experiment, which was a part of this thesis. It consists of the experiment description, experimental plan, calculation and evaluation of emissions, high and low heating value, density, flame temperatures and heat flux. Laboratory experiment was carried out with different fuels. Low calorific fuels were simulated by gradual increase of the concentration of inert gasses in the natural gas. Increased concentration of inert gasses had positive effect on the emissions. Measurement of the flame temperatures confirmed that the decrease of emissions corresponds to the inert gas addition to the noble fuel. Heat flux and thermal efficiency of the combustion was almost identical for each configuration.
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Optimization of heavy steel castings manufacture
Procházka, Zdeněk ; Čech, Jan (referee) ; Šenberger, Jaroslav (advisor)
The Master’s thesis was conducted under the project FR-TI1/070 “Optimalization of heavy steel casting manufacture” in cooperation with ŽĎAS a. s. foundry. It evaluates rate of conchoidal fracture in samples extracted from experimental castings. The testing bar for the static tensile test were extracted from thermal axis of casting. The research part describes ways of deoxidating the liquid metal and usage of separate deoxidating chemical parts, followed by summary of research knowledge on conchoidal fractures. In the practical part, the process of sample evaluation is described. The conchoidal fracture, the surface of which was evaluated on the fracture surfaces, influences mechanical qualities of cast steel. Simultaneously, impacts of metallurgical factors on rate of conchoidal fracture were examined
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Zhodnocení jakosti vody vybraných přítoků Oslavy
Michálková, Barbora
The bachelor thesis deals with water quality of selected Oslava river tributaries. The goal was to conduct literature search dealing with the issue of water quality by using scientific database and to determine and evaluate quality of selected tributaries. This was achieved by annual monitoring in the field and subsequent laboratory analyses. The data was evaluated using ČSN 75 7221 and Environmental Quality Standards. Thanks to the data provided by Povodí Moravy, s. p. from the monitoring of the river Oslava, an overall view of the water quality in the vicinity of the target basins was created. The results showed phosphorus and nitrogen pollution of the inflows. Phosphorus was measured in higher concentrations especially in more urbanized basins without wastewater treatment plants. Nitrogen pollution came from livestock and crop production, but was also measured in other tributaries, even in places identified as nitrate vulnerable areas. The conclusions show that there is a need to focus, for example, on the management of wastewater in small municipalities, compliance with the rules of the nitrate directive or complex anti-erosion measures.
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Mineral nutrients dynamics of hemiparasite Viscum album L. and its host Tilia cordata Mill
Nikitina, Tatiana
The presence of hemiparasitic plants can potentially harm urban trees, which are valuable resources due to their aesthetic and environmental functions. Therefore, this study examines the nutrient dynamics of European mistletoe (Viscum album L. subsp. album) and its host tree small-leaved linden (Tilia cordata Mill.) during the vegetation season. The concentration of all macronutrients was higher in mistletoe compared to the host tree, except for calcium. Deficiencies in phosphorus and potassium were observed in Tilia leaves during the vegetation season. The concentration of soluble non-structural carbohydrates in Tilia leaves was significantly higher than that of Viscum. Leaf spectral reflectance showed differing outcomes for the two species, with Tilia displaying a quicker senescence rate than Viscum's current-year leaves and slower and prolonged development of current-year Viscum leaves. The study emphasizes the accumulation of macronutrients by mistletoe at the expense of hot tree resources.
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