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Ultra-low-energy STEM in SEM
Frank, Luděk ; Nebesářová, J. ; Müllerová, Ilona
Examination of thin samples in TEM or STEM has been performed at hundreds of keV. This energy range offered high resolution but low contrasts which meant that tissue sections had to be contrasted with heavy metal salts. Recent TEM with aberration correctors preserve an acceptable resolution down to 20 keV and provide enhanced contrasts. The LVTEM device is operated at 5 keV on samples thinner than 20 nm. STEM attachments to SEMs have become widespread [3] profiting from an image contrast substantially increasing even for light elements at tens or units of keV. The methods for the preparation of ultrathin sections of various substances are capable of producing layers at and even below 10 nm which enables one to further decrease the energy of the electrons provided the image resolution is maintained. When using the STEM technique virtually all transmitted electrons can be utilised for imaging, while in TEM we are restricted to using electrons capable of forming the final image at acceptable quality. This forces us to narrow the ranges of the angular and energy spreads of electrons that enter the image-forming lenses. Consequently, the STEM technique promises higher contrasts at comparable resolutions. Unlimited reduction of the energy of the illuminating electrons is possible by employing the cathode lens principle. This consists of biasing the sample together with its holder (made flat on both sides) to a high negative potential that retards the incident electrons before they land on the sample surface and accelerates backscattered and transmitted electrons to their respective detectors above and below the sample. Calculations have shown a final spot size only moderately extended even at units of eV so that quality-consistent micrographs can be recorded over the full energy scale.
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CREDIT RISK MEASUREMENT: The case study of Mongolian Small and Medium sized firms
Togtokh, Enkhjargal ; Rippel, Milan (advisor) ; Teplý, Petr (referee)
This thesis presents credit risk measurement approaches and some empirical results of predicting firm's failure by using various financial ratios. It aims to re-examine Altman's Z-score model and build a comparable method by logistic regression, a credit scoring model technique. The small and medium sized enterprises' empirical data used in the research work is provided from a Mongolian commercial bank. We analyzed forty two firms' financial statements, including bankrupted and non-bankrupted firms, for the period of 2007-2008. At first, financial ratios of selected sample have been analyzed through Altman's Z-score model. Overall, prediction accuracy of Altman Z-score model was significantly high, 71 percent. In terms of logistic regression method, we estimated fifteen financial ratios through the model and come to conclusion that two ratios, namely cash to total asset ratio and retained earning to total asset ratio, are significant predictor for firm's bankruptcy in Mongolian SMEs. If we compare the prediction power of the two methods, model derived from logistic regression is slightly lower than in Altman Z score model. Keywords: Credit Risk measurement, bankruptcy, Altman Z score, logistic regression
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Higher Heating Value of Sewage Sludge
Mikluš, Michal ; Bělohradský, Petr (referee) ; Houdková, Lucie (advisor)
The thesis is focused on problems of thermal treatment of sludge from wastewater treatment plants. The main objective is to establish a formula for calculating higher heating value (HHV) and lower heating value (LHV) of sludge based on its chemical analysis. The work is divided into two main parts: The theoretical part deals with the characteristics of sludge, thermal treatment of sludge, it isn´t omitted higher heating value and lower heating value. The main topic of a practical part is formulation of eguations for HHV and LHV calculation. Chemical analysis of sludge samples were supplied by TÜV NORD Czech s.r.o., together with the values of HHV and LHV. The calculations were verified by the program MINITAB.
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Optimisation of experimental parameters for double-pulse LIBS
Roščák, Michal ; Novotný, Karel (referee) ; Kaiser, Jozef (advisor)
Diploma thesis presents the description of laser induced breakdown spectroscopy (LIBS) analytical method. The possibility to decrease LIBS detection limits using double pulse LIBS (DP-LIBS) is also detailed. Properties of laser induced plasma (LIP) are discussed. Thesis describes the optimisation process of DP-LIBS setup at laser spectroscopy laboratory of Faculty of Mechanical Engineering, Brno University of Technology. Optimisation was carried out for detection of chrome in steel with respect to detection limits and ablation crater size. Optimised DP-LIBS setup is appropriate for mapping chrome distribution in steel samples.
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Stress-strain analysis of arterial aneurysms
Tesařová, Petra ; Skácel, Pavel (referee) ; Burša, Jiří (advisor)
The diploma thesis is focused on the creation of the aneurysm finite element model and the making of the aneurysm wall stess-strain analysis using ANSYS software. The model of abdominal aortic aneurysm geometry starts from the CT scan of the particular patient. In the thesis there are compared two chosen constitutive models, each of them appears from different mechanical tests done on human arterial fibre samples. Furthermore, a limiting condition for aneurysm wall structure damage is expressed. On the basis of the results of stress calculation in the aneurysm wall and the limiting condition, the safety coefficient and rupture factors risk are worked out.
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Manipulator with sheet metal samples for mechanical tests
Glogar, Matěj ; Plachký, Pavel (referee) ; Laurinec, Marián (advisor)
This thesis deals with a solution of lifting equipment for sheet metal samples handling. Facility will be part of an automatic production line for semi-finished test specimens for testing the mechanical properties of sheet metals. The options of solutions discussed in this thesis is performed that choice which should be the concept of lifting equipment. Course work cycle of the selected concept is designed, so that material flow provided by the facility meets requirements of the production line. Calculations for the design parts of the main cylinder and the running gear are carried out using a set of parameters and then strength check of steel construction follows. The 3D model of the manipulator, the manipulator assembly drawings and layout drawings of the production line are annexes of this work.
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Thermal Effects in Physics and Dynamics of Small Bodies of the Solar System
Čapek, David
Thermal Effects in Physics and Dynamics of Small Bodies of the Solar System Abstract of the Ph.D. thesis \s David Capek It has been shown, that the thermal effects are very important in the dynamics of small Solar System bodies. A phenomenon which is known as the Yarkovsky effect is able to secularly change the semimajor axis of an orbit, while the YORP effect affects the rotation state of a body. The Yarkovsky effect and the YORP effect were previously calculated with many constraining assumptions like spherical shapes of asteroids, circular orbits, small variations of the surface temperature, principal axis rotation, constant thermal parameters, etc. We developed a sophisticated numerical model of the Yarkovsky/YORP effect without such simplifications. With this model, we have been able to describe the shape, the orbit, the rotation and the thermal behaviour of an asteroid in a very precise way. The YORP effect was studied on a sample of artificially generated shapes, roughly resembling Main Belt asteroids, and also on several shapes of real asteroids. The depen- dence of YORP on the obliquity and the thermal parameters of the surface were studied (Vokrouhlicky and Capek, 2002; Capek and Vokrouhlicky, 2004). A wide variety of pos- sible YORP evolution paths of the spin state was found. The possibility of...
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Technology of product machining on CNC machines
Brázda, Jiří ; Kalivoda, Milan (referee) ; Osička, Karel (advisor)
This diploma thesis deals with a technology of production milling of sample component “ending of generator shaft” by CNC milling in environment of small company. At first common aspects of CNC machines, technology of CNC milling and technology of construction are introduced. Possible problems with milling of sample component are analyzed and their possible solutions are presented. Next technology of CNC milling with operating program for CNC lathe (HAAS SL20) and CNC milling machine (HAAS VF3), production of component in small company with necessary documentation in technology procedure are projected. Using of operating systems HAAS, Fanuc and HEIDEHAIN are compared. Using of cutting tools and cutting condition for component milling is projected. Finally timing of operations and financial calculations necessary for small production of sample component is proposed.
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Diffusion of carbon in welding joints of low alloys and high alloy steels.
Zdvořáček, Marek ; Rek, Antonín (referee) ; Stránský, Karel (advisor)
Content of a document result measurements and analysis carbon´s diffusion at welding joint created from hight alloyed austenitic steel CSN 417242 and not alloyed steel CSN 412 050. Samples have been put throught isothermal anneal in a temperature range 500 °C up to 1100°C. Aim one´s effort to metalographyic quantification carburized and uncarburized zone. The next part of the document content measuring x-ray energy through microanalysis, where has been record course of a carbon disintegration and selected replacements elements at whole length of the welding joint . At the end of experimental part has been gauged course microhardness HV 0,05 at whole lenght of welding joint, from an acquired data has been chose the most optimal temperature of isothermal anneal, to produce the smallest structural notch.
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