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Effect of thermal radiation on low temperature measurement for various types of temperature sensor installations
Urban, Pavel ; Hanzelka, Pavel ; Králík, Tomáš ; Vlček, Ivan ; Srnka, Aleš
We investigated an effect of thermal radiation (300 K) on precision of low temperature measurement of a sample holder (or sample) in an UHV SEM/SPM microscope working at range down to 20 K for various ways of temperature sensor mounting. We designed a special copper casing for installation of Lake Shore\ntemperature sensors (CernoxTM and Si diodes) encapsulated in SD packages. The sensor body is attached direct to the casing using indium solder. The current leads pertaining to the sensor are thermally anchored but electrically insulated from the casing. Quality of sensors installation in the casing was tested for various ways of mounting on a cooled plate. Insufficient thermal anchoring of electrical wires and thermal shielding were imitated. Comparative measurement was also performed with sensors in SD package mounted without\ncasing. The experiments proved that our special design of temperature sensors casing is adequate for intended application of temperature measurement of sample holder in UHV SEM/SPM microscope. In contrary, measurement precision of unprotected sensors was absolutely unsuitable.
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Effect of gold coating on emissivity and absorptivity of Ti-6Al-4V alloy
Frolec, Jiří ; Králík, Tomáš ; Musilová, Věra ; Urban, Pavel
The article provides experimental analysis of total hemispherical emissivity and absorptivity of Ti-6Al-4V alloy before and after deposition of 1-2 .pí.m gold layer. We measured their dependences on the temperature of thermal radiation (varying from 20 K to 320 K) and confronted these results with mechanically polished copper, i.e. with material known for extremely low emissivity and absorptivity. Galvanic deposition of pure gold resulted in significant lowering of original emissivity of Ti-6Al-4V bare surfaces from 15.8 percent to 3.4 percent at 300 K and from 4.1 percent to 1.1 percent at 20 K. Our findings about thermal-radiative properties have practical relevance for an improvement of a low temperature part of an ultra-high vacuum scanning probe microscope\n(UHV-SPM) designed by our group and could also be useful for other applications and low temperature systems.
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Business Plan for Nutrition Centre Establishment
Urban, Pavel ; Švec, Marek (referee) ; Bayerová, Vladimíra (advisor)
The diploma thesis deals with the elaboration of a business plan for the establishment of a nutrition center in Olomouc. In the first part, there are elaborated the theoretical starting points for the business plan, and then the thesis deals with analyses and a segmentation of the market. Based on this information the proposal of the business plan is elaborated.
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Attention training using EEG biofeedback in patients with brain injury
Gregorová, Iva ; Kulišťák, Petr (advisor) ; Kocourková, Jana (referee) ; Urban, Pavel (referee)
Celosvětové statistiky jsou pravidelně plněny varovnými čísly, která oznamují, kolik lidí každý rok podlehne následkům traumatu mozku. Díky zlepšující se lékařské péči se zvyšuje počet lidí, kteří přežívají i závažná poranění mozku. Tato poranění však sebou nesou řadu komplikací a to raných i pozdějších. Finanční prostředky vynakládané na léčbu pacientů po poranění mozku jsou značné. Přesná čísla nejsou známa, ale podle Smrčky (2001) v roce 1990 např. v USA dosáhly roční náklady na mozková traumata 25 miliard US dolarů. Tato částka zahrnuje náklady spojené jednak s přímou léčbou pacientů, ale i s následnou rehabilitací, rekvalifikačními kurzy atd. Řada pacientů je díky následkům úrazu v dlouhodobé pracovní neschopnosti nebo trvalé invaliditě. Častými následky po poranění mozku jsou mimo Jlne deficity kognitivních funkcí, zvláště pozornosti. Tato disertační práce se zaměřuje na možnost využití metody EEG biofeedback při tréninku pozornosti u pacientů po poranění mozku, Jednou z terapeutických aplikací metody EEG biofeedback jsou právě poruchy pozornosti. Metoda EEG biofeedback je mnohými opěvovaná a jinými zase zatracovaná. Využívána je při léčbě celé řady onemocnění. Původní projekt této disertační práce musel být změněn. Měla být ověřována efektivita metody EEG biofeedback u vzorku dětí s diagnózou ADHD, u...
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Design and verification of low temperature parts of UHV SEM/SPM stage
Pola, Tomáš ; Vlček, Ivan (referee) ; Urban, Pavel (advisor)
This thesis focuses on experimental verification and experimental-based improvements of designed low temperature parts of stage of the UHV SEM/SPM microscope, which operates in temperature range from 20 K to 700 K. The main focus is on the functionality verification of thermal insulation pad (InBallPad) as well as on the effect of length and contact quality of braid on minimal achievable temperature. The contact quality of sample holder with sample carrier realized with two springs is investigated together with influence of thermal contact resistances on achievable temperature. The thesis also contains a calculation model used for cooldown times and minimal temperature estimation. In the conclusion of this work several future experiments are suggested which could explain some of the observed, yet unexpected, phenomena.
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Visualization of cryogenic helium flow using of laser-induced-fluorescence
Drahotský, Jakub ; Šiler, Martin (referee) ; Urban, Pavel (advisor)
This work evaluates the laser induced fluorescence method (LIF) for the vizualization of the cryogenic helium flows for experimental study of the Rayleigh–Bénard convection at the Institute of Scientific Instruments (ISI) in Brno in the labs of Cryogenics and Superconductivity group. As the tracer particles, we considered the metastable molecules He2*, that are created by the ionization of helium with themfemtosecond laser pulse and then they are excited by the lasers with appropriate wavelengths for the invocation of the fluorescence. On the basis of the research study, I have evaluated the current laser equipment at the ISI as insufficient for the experiment realization. At the end of this work, there is a list of a laser technique and other devices which are necessary for the adaptation of the LIF method in the experiments at ISI.
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The Study of the Contract Award in Selected Company
Urban, Pavel ; Ing.Miloslav Krejbych (referee) ; Jurová, Marie (advisor)
The main topic of this bachelor thesis is to make a draft of process of contract in the company to maximum satisfaction with a focus on delivery schedules, quality and costs. Specifically in the company Cimbria HMD Ltd. Litomyšl which deals with manufacturing and servicing of after-harvest machinery. The theoretical part deals with information about project management. According to identified deficiencies from analysis of the current status of the contract, I deal with on its improvement.
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Helium Cryostat for Experimental Study of Natural Turbulent Convection
Urban, Pavel ; Jícha, Miroslav (referee) ; Rotter, Miloš (referee) ; Fedor,, Ján (referee) ; Musilová, Věra (advisor)
V disertační práci je popsán heliový kryostat s experimentální válcovou konvekční celou pro studium proudění při přirozené konvekci za velmi vysokých Rayleigho čísel Ra (až do řádu 10^15) a Nusseltových čísel Nu (až do řádu 10^4). Pracovní látkou je studené 4He, které umožňuje díky výhodným fyzikálním vlastnostem dosažení velmi vysokých hodnot čísel Ra. Návrh kryostatu je založen na koncepci lázňových NMR kryostatů s nízkým odparem kryokapalin. Ve středu kryostatu je umístěna konvekční cela o průměru 300 mm a výšce 300 mm. Celu tvoří horní a spodní dno a výměnná střední část. Tyto díly jsou spojeny rozebíratelnými přírubami těsněnými indiovým drátem. Výměnná část umožňuje snadnou modifikaci geometrie cely. Hlavní přednost kryostatu spočívá v minimálním vlivu konstrukce cely a použitých materiálů na studovanou konvekci. Cela kryostatu je navržena pro pracovní tlaky do 250 kPa.
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Design and verification of low temperature part of UHV – STM microscope
Voňka, Jakub ; Rotter, Miloš (referee) ; Urban, Pavel (advisor)
The diploma thesis addresses the design and experimental verification of cooling system and low temperature part of UHV - STM working in temperature range of 20K - 300K. Due to the demand of variable temperature, the flow cooling system with cryogenic (~5 K) helium (He) is used. Two variants of the low temperature part of the microscope are studied. First the version with cooling only the sample holder, and second with cooling of the whole STM. Designed cooling system consists of He flow cryostat allowing to connect it to the Dewar vessel with liquid helium (LHe) using a low-loss transfer line. The cryostat consists of He inlet and outlet, heat exchangers and copper strains (i.e. braids) for the thermal connection of the sample holder/STM and radiation shield around the STM with the heat exchangers. The thesis describes the design of the flow cryostat and its initial tests in the designed vacuum chamber. Heat flow through a spot contact is also discussed to estimate thermal conductance of insulation supports based on thermal resistance of spherical contacts. The thesis was elaborated in collaboration with the Institute of Scientific Instruments of the ASCR, v.v.i.
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