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Study of rheological properties of alternative electro insulating fluids
Botlová, Simona ; Jirák, Josef (referee) ; Frk, Martin (advisor)
This master thesis deals with clasification of electrical insulating liquids and analysis their reological properties. Theoretical part describes viscosity and possibilities of its measurement, electrical and non-electricl properties of electrical insulating liquids and themselves electrical insulating liquids. Practical part describes measurement of viscosity and density of chosen vegetable oils, their components and transformer oils in wide temperature range. At the conclusion of the thesis, analysis of measurement results is done.
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Evaluation of structures of solder joint with printed board circuit
Jakubec, Jiří ; Jirák, Josef (referee) ; Černoch, Pavel (advisor)
The theoretical part of the diploma thesis deals with the basic principles of the scanning electron microscope and the environmental scanning electron microscope. A description of the signals generated by an electrons incidence onto a specimen and detection options of these signals in the mentioned microscopes is included in the work. The experimental part of the work concerns an examination of a quality of several joints soldered by different methods on the printed circuit boards after different stresses by use of a visual check and the instruments of the light microscope and the environmental scanning electron microscope. The acquired data are evaluated and summarized.
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Electromagnetic pulse accelerator of projectiles
Žamberský, Jan ; Jirák, Josef (referee) ; Frk, Martin (advisor)
Tato práce se zabývá použitím magnetického pole k urychlení projektilů v zařízení zvaném coilgun. Je složena ze dvou částí, z nichž první je teoretická diskuze o magnetismu a jeho využití, druhá část je o vlastním coilgunu, jeho výhodách a nevýhodách. Následuje série měření na dvou experimentálně postavených coilgunech a jejich optimalizace pro dosažení co nejlepších výsledků. První část probírá více témat. Na začátku je krátká kapitola, ve které se definuje magnetické pole a s ním související konstanty a jevy. Další dvě kapitoly jsou zaměřeny na různé typy materiálů, především feromagnetik, jak reagují na přítomnost magnetického pole a jakými parametry jsou specifikovány. Dále je výčet některých aplikací magnetizmu napříč lidskou společností. V druhé části se popíše princip coilunu a jak byly prototypy vyrobeny. Měření na prvním prototypu je zaměřeno na testování různých materiálů projektilu, jeho rozměrů a přínosy externího magnetického obvodu okolo cívky. Taktéž je tam kapitola pojednávající o způsobu měření rychlosti projektilu. Druhý prototyp se snaží eliminovat nedostatky zjištěné na prvním a prozkoumat výhody vícenásobného urychlení na dalších stupních.
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Scintillation Secondary Electrons Detector for ESEM
Čudek, Pavel ; Kadlec, Jaromír (referee) ; Rek, Antonín (referee) ; Jirák, Josef (advisor)
The thesis deals with the scintillation secondary electron detector for environmental scanning electron microscope, its design and construction. The starting point was numerical simulation of electrostatic fields and electron trajectories in the electrode system of the detector and simulation of pressure distribution and flow of gases in different parts of the detector. On the basis of modeling and simulation, construction changes of the detector were gradually implemented. Detection efficiency of each version of the detector was determined by the method described in the work. This method enables to evaluate signal level from the captured images of the specimen, quality of images was stated from signal to noise ratio. The thesis describes the whole process of the detector improvement from initial state, when the detector operated with lower efficiency in the pressure range from 300 to 900 Pa, to final version that enables usage of the detector in the range from vacuum up to 1000 Pa of water vapors in the specimen chamber of the microscope.
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Scintillation SE Detector for Variable Pressure SEM
Tihlaříková, Eva ; Neděla, Vilém (referee) ; Jirák, Josef (advisor)
This project deals with the theme of environmental scanning electron microscopy (EREM). This method allows the examination of insulators and wet specimens without pretreatment and modification like drying and metallization. The principle of this method consists in using higher pressure in a specimen chamber. The pressure is within the range of 100 – 200 Pa. However, the pressure in the specimen chamber restricts the signal detection interference. The objective of the work is to explore the possibility of interference in secondary electron route detection by way of electrostatic field. The electrostatic field was realized with the system consisting of four electrodes located in front of the scintillation detector. It should have interfered the secondary electron´s trajectory to the detector chamber. The optimization of voltage on the electrodes was made by simulation program called SIMION. The simulation results were experimentally verified with laboratory EREM.
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Multi-electrode system of ionization detector for environmental scanning electrone microscope
Uhlář, Vít ; Špinka, Jiří (referee) ; Jirák, Josef (advisor)
Thesis deals with environmental scanning electron microscopy and with detection of signal electrons by using ionization detector. First part talks about the principle of environmental scanning electron microscope. Second part describes signals generated by interaction of primary electron beam with sample. Third section explains the principle of impact ionization and ionization detector. Experimental part deals with usage of segmental ionization detector and with measuring of signal amplification from copper and platinum. Thesis also examines arrangement of electrodes of ionisation detector on material contrast and examines also on influence of voltage contrast on base - emitter junction of an NPN bipolar transistor. All experiments were carried out in dependency on saturated water vapour pressure in sample chamber.
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Inorganic fillers effect on electrical properties of the epoxy resins
Doležel, Tomáš ; Jirák, Josef (referee) ; Frk, Martin (advisor)
This thesis deals with problems of electrical insulation materials based on epoxy composites used in the electronics industry. This thesis is divided into theoretical part focused on composite materials, their technological processing and diagnostics. It also describes dielectric materials, their properties and events taking place in their structure. The experimental section describes the measurement of electrical properties of samples of electrical insulating materials with different types of fillers.
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Logistic process optimization in expedition of electrical enterprise
Reboková, Lenka ; Jirák, Josef (referee) ; Špinka, Jiří (advisor)
Logistics as a process of planning, realization and controlling of effective and powerful workflow and commodities warehousing, services and related information with the goal of costumers satisfaction, became highly important and inseparable part of every company. The essential part of the planning process is an analysis of the current company situation, which tries to find all the limiting factors, and which serves as a basis for the process of making a company more effective. This diploma thesis analyses the current state of the expedition division of the ModusLink Czech Republic s.r.o. company – it analyses all its working operations in detail and using chronometrical analysis method evaluates division‘s theoretical and feasible throughput capacity. The feasible throughput capacity is then confronted with division’s real throughput capacity achieved during the monitored months, and depending on the results of the comparison there are some conclusions and recommendations for future improvements mentioned.
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Signal Detection by Segmental Ionization Detector in Environmental SEM
Černoch, Pavel ; Jirák, Josef (advisor)
The dissertation thesis deals with signal detection by an ionization detector in the environmental scanning electron microscope and utilization of this detector to gain required information in a specimen image. Main interest is focused on the detector containing several electrodes with a varied geometry arrangement and voltages on these electrodes. The detector was named segmental ionization detector. Detection capabilities of the segmental ionization detector were studied through computer simulations and experiments in the microscope utilizing knowledge from a technical literature background. On the base of the accomplished experiments, the segmental ionization detector has been optimized for the secondary electron detection improvement and at another configuration optimized for a high material contrast acquisition of the specimen image. Consideration of benefits of the examined segmental ionization detectors is included in the work.
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Scintillation SE detector for ESEM
Odehnal, Adam ; Špinka, Jiří (referee) ; Jirák, Josef (advisor)
Thesis deals with theoretical knowledge about scanning electron microscopy and environmental scanning electron microscopy. It describes principle of operation, signals generated by interaction between primary electron beam and specimen and means of detection of secondary electron signal in environmental conditions using scintillation detector. Furthermore, thesis focuses on optimization of detection od secondary electrons by adjusting electrode system of scintillation detector. Computer program Simion is used for modelling signal electron trajectories for proper adjustments. Simulation were starting-point for adjusting the design of the detector. Detection efficiency of adjusted detector was determined by evaluating signal magnitude from captured images, secondary electron detection capability from voltage contrast and quality of the captured images from signal/noise ratio.
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