National Repository of Grey Literature 35 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Cryogenic cell for study of water ice in ESEM microscope
Krutil, Vojtěch ; Kubíček, Jaroslav (referee) ; Urban, Pavel (advisor)
The presented thesis focuses on designing a cryogenic cell for the study of water ice in an environmental scanning electron microscope (ESEM). This cell allows the study ice in the temperature range 80 K – 300 K in a nitrogen gas environment with a pressure of up to 400 Pa. The cell is cooled by a flow cooling system, where liquid or gaseous nitrogen is used as a refrigerant. The cell consists of a double-walled vessel with vacuum insulation, a flow-through heat exchanger, a sample well, and a cooled cell lid. The heat exchanger was designed to be able to dissipate the heat load at the level of 1 W. The exchanger is equipped with an electric resistance heater with an output of approximately 60 W, enabling heating of the sample at speeds of up to 100 K·min-1. The design also includes an LN2 gateway located on the door of the vacuum chamber of the microscope, to which the capillaries of the heat exchanger for the intake and outlet of refrigerant are connected. During the experimental verification of the cryogenic cell in the test vacuum chamber with a pressure of GN2 ~ 400 Pa, the limit temperature of 77.5 K on the sample well was reached.
Role of thermal near field in cryogenic Rayleigh-Bénard convection
Věžník, Tomáš ; Schmoranzer,, David (referee) ; Urban, Pavel (advisor)
This bachelor thesis is focused on the eect of the thermal near feld (NF) radiation on (i) the onset of Rayleigh-Bénard convection (RBC) and (ii) the thermal inuence on the temperature sensors used in RBC studies. In the frst part, the theoretic base for both studied areas, RBC and NF, is presented. Further, the ways of fnding the onset of RBC, the temperature profles, the basic equations for heat transfer in far feld and near feld and the description of the apparatus used for the measurements of radiative heat transfer are given too. In the practical part, the process of measurement is presented and the model that we obtained for describing the dependence of the coefcient of radiative heat transfer between two Cu surfaces is demonstrated. Afterwards, the data are used to analyse the eect of NF on the onset of convection, and to calculate the inuence on the temperature profle measurements with cryogenic temperature sensors and, at last, the comparison of total heat transferred over the experimental cell with NF heat transfer over the thermal boundary layers arising in RBC is done. A goal of this thesis was to fnd out whether the eect of NF can explain the contradictory results of determining the onset of convection in cryogenic RBC (expressed by critical Rac) based on the measurements of the heat transfer in RBC and of the eectivity of heat transfer at high values of Ra numbers in cryogenic experiments. The current evaluations clearly demonstrate that the eect of NF on studied phenomena is by several orders of magnitude smaller than other relevant eects and can thus justly be neglected.
Flow instabilities due to torsional oscillators in superfluid helium
Skokánková, Tamara ; Schmoranzer, David (advisor) ; Urban, Pavel (referee)
This Thesis is devoted to the investigation of superfluid helium flows due to torsional oscillators. In its first part, flow due to a torsionally oscillating disc suspended on a tungsten filament is studied (building upon the work of A. C. Hollis Hallett from 1952). Measurements of the motion of the torsionally oscillating disc were performed in superfluid helium at temperatures between 1.265 K and 2.157 K at saturated vapour pressure. Time traces of the disc angular deflection were obtained, and critical parameters related to the turbulent flow stability were determined. In laminar flow, scaling of drag forces with the dimensionless Donnelly number was verified. Based on these results, and comparison with the original work, a scenario of the decay of turbulent flow was suggested. The second part of this work is focused on the development and construction of a similar experiment for mK temperatures. A new type of oscillator was designed, a so-called "pillbox", and a series of testing measurements was performed both at room and mK temperatures.
Design of a sample holder with electrical contacts for UHV SEM/SPM
Krutil, Vojtěch ; Vlček, Ivan (referee) ; Urban, Pavel (advisor)
The presented thesis focuses on designing a sample holder for an UHV SEM/SPM microscope suitable for using in low temperature (20 K - 300 K) applications. This newly designed sample holder is equipped with ten spring-loaded contacts for electrical connection of a transport pallet to the sample holder, which will be equipped with a temperature sensor and a heating element. Two quadruples of contacts are reserved for the sample and the temperature sensor and the remaining pair for the heating element. A thorough research study of commercially available sample holders indicates that the holders for the intended use are not available on the market. In the low-temperature tests of the newly designed sample holder, the limit temperature of the 24 K was reached in a test vacuum chamber with a flow cooling system. The ambient temperature was 300 K. The contact function was successfully verified by measuring the transient electrical resistance at the fixed and the spring contact sections. Additionally, a modification of the sample holder for high temperature (300 K - 700 K) was suggested.
Temperature profiles and temperature fluctuations in turbulent Rayleigh-Bénard convection
Drahotský, Jakub ; Mantia,, Marco La (referee) ; Urban, Pavel (advisor)
Tato práce popisuje výzkum zaměřený na studium vertikálních teplotních profilů a fluktuací v turbulentní Rayleighově-Bénardově konvekci. Experiment byl proveden v "Barrel of Ilmenau" obsahující válcovou experimentální celu s průměrem 7,15 m a výškou 4,7 m ("the aspect ratio" = 1,5) naplněnou suchým vzduchem. Teplotní profily a fluktuace byly studovány podél vertikální osy cely mezi horní a spodní deskou spodní deskou v rozmezí Rayleighova čísla (Ra) 1E11 4E12. Teplotní profily byly změřeny novou metodou využívající systém s optickým vláknem Luna ODiSI-B, který byl pořízen týmem z Ilmenau. Systém umožňuje měřit teplotní profil ve všech bodech podél celého vlákna současně s prostorovým rozlišením 5 mm.
The Project of Educational cycle trail in the protected landscape area in Broumovsko
Urban, Pavel ; Šafránek, Jiří (advisor) ; Kuna, Petr (referee)
Title The Project of Educational cycle trail in the protected landscape area in Broumovsko. Objectives The aim of this work is to create project of Educational cycle trail in rarely visited areas in the protected landscape area in Broumovsko. The main outcome of this work is a brochure which should be easily accesible in Toutist Information Centres in the area as well as on the Internet, where the tourist are allowed to download this file for free. Method The first part of this work analyzes accessible information found in printed and internet sources and gained thanks to dialogues with specialists working in PLA Broumovsko. Afterwards these gained information and facts were organized and used for selecting material for two educational cycle trail and also the path was defined. In the second part I worked on the evaluation of these two paths in the form of questionnaire, which was distributed to those who rode their bikes along the educational cycle trails. On the basis of dialogues with experts dealing with the protected landscape area, such as people working in the administration of the PLA and people engaged in travel tourism organizations in this PLA, I made an analysis of the current situation in the protected area and afterwards, analysis of a possible contribution of this work. Then two...
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.
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.
Business Plan for Nutrition Centre Establishment
Urban, Pavel ; Švec, Marek (referee) ; Kučerová, 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.
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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