343 research outputs found

    Helium Cryostat for Experimental Study of Natural Turbulent Convection

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    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.The thesis focuses on the design of a helium cryostat with an experimental convection cell for the study of natural turbulent convection in the range of Rayleigh numbers Ra up to 1015 and Nusselt numbers Nu up to 104. Cryogenic 4He gas is used as a working fluid for experimental studies due to its advantageous properties that allow reaching very high Ra numbers. The cryostat design is based on the conception of low-loss NMR magnet cryostats. In the centre of the cryostat a cylindrical convection cell of 300 mm in diameter and 300 mm in height is placed. The cell is made of middle, top and bottom parts. These are jointed together by flanges sealed by indium wires. The middle part is exchangeable and allows the geometry of the cell to be modified. The cell is designed for measurements at pressures up to 250 kPa. The main advantage of this cryostat is the minimal influence of the cell design and materials on the studied convection.

    Broadband Spectrum Survey Measurements for Cognitive Radio Applications

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    It is well known that the existing spectrum licensing system results in a gross under-utilization of the frequency spectrum. Spectrum background measurements – spectrum surveys – provide useful data for spectrum regulation, planning or finding frequency niches for spectrum sharing. Dynamic spectrum sharing as a main goal of cognitive radio (CR) is the modern option on how to optimize usage of the frequency spectrum. A spectrum survey measurement system is introduced with results obtained from a variety of markedly different scenarios allowing us, unlike other studies, to focus on wideband and fast spectrum scans. The sensitivity of the receiver is no worse than -113 dBm in the whole band. The utilization of the frequency spectrum is analyzed to prove its under-utilization and to show spectrum sharing opportunities. This was shown to be true in the frequency band higher than 2.5 GHz. A comparison with other spectrum survey campaigns is provided

    OTPLINJAVANJE RUDNIKA KAO TEMELJNI SIGURNOSNI ELEMENT U PODZEMNIM DIJELOVIMA PLINOVITIH RUDNIKA UGLJENA NA UGLJENONOSNOM PODRUČJU OSTRAVA - KARVINÁ

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    In the article, degasification methods to drain the gas from the underground parts of coal mines in the Czech Republic are described. The authors are concerned with the possibilities of and new trends in ensuring safety by means of drilling operations. Examples of applications of degasification in mine plants in the Czech Republic, above all in a hard coal deposit in the Ostrava-Karviná Coalfield in the Upper Silesian Basin are presented.U članku su opisane metode otplinjavanja podzemnih dijelova rudnika ugljena u Republici Češkoj. Autori se bave mogućnostima i novim trendovima u osiguranju sigurnosti primjenom bušačkih operacija. Prikazani su primjeri primjene otplinjavanja rudnika u Republici Češkoj i to posebno u ležištima kamenog ugljena na eksploatacijskim poljima Ostrava-Karviná u ugljenom bazenu gornje Šleske

    The Study of the Contract Award in Selected Company

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    Hlavní téma této bakalářské práce je zpracování návrhu průběhu zakázky podnikem k maximální spokojenosti se zaměřením na dodací termíny, jakost a náklady. Konkrétně v podniku Cimbria HMD, s.r.o. Litomyšl, který se zabývá výrobou a servisem posklizňových strojů. V teoretické části se práce zabývá informacemi o projektovém řízení. Podle zjištěných nedostatků z analýzy současného stavu zakázky, se v práci věnuji na jejím zlepšení.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.

    The Project of Educational cycle trail in the protected landscape area in Broumovsko

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    Název Projekt cyklistické naučné stezky v Chráněné krajinné oblasti Broumovsko Cíl práce Cílem této práce je vytvořit projekt cyklistické naučné stezky v turisticky opomíjených částech CHKO Broumovsko, který bude prostřednictvím informační brožury distribuován v informačních centrech regionu a rovněž bude k dispozici na internetových stránkách institucí a zařízeních působících v oblasti těchto cyklistických naučných stezek. Metoda První část práce analyzuje dostupné informace získané z tištěných a elektronických zdrojů a konzultací s odborníky CHKO Broumovsko. Poté byl získaný materiál uspořádán a byl proveden výběr materiálu pro zastávky naučné cyklostezky a definována její trasa. Ve druhé části jsem se zabýval hodnocením naučné cyklostezky formou dotazníku, který byl rozdán respondentům, kteří cyklistické naučné stezky absolvovali. Výsledky Výsledkem této práce jsou návrhy dvou cyklistických naučných stezek, z nichž obě mají dvě varianty. Tyto návrhy jsou zpracované do dvou informačních brožur, které jsou připraveny k použití a které si následně mohou návštěvníci oblasti volně vzít v informačních centrech, ubytovacích a stravovacích zařízeních v regionu, či si jej mohou stáhnout z webových stránek některé z institucí této oblasti. 2 Klíčová slova Cykloturistika, naučná stezka, cyklotrasa,...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...Sporty v příroděFaculty of Physical Education and SportFakulta tělesné výchovy a sport

    Occupational Diseases in the Automotive Industry in Czechia – Geographic and Medical Context

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    Objectives: The automotive industry represents the most important industrial sector in Czechia. The objective of this study has been to analyze the occurrence of occupational diseases (OD) in the automotive industry during the period from 2001 till 2014. Material and Methods: Data on OD cases was retrieved from the National Registry of OD. Further, we conducted a survey in automotive companies with focus on occupational health services and positions of the companies in global production networks (GPNs). An analysis of OD distribution in the automotive industry was performed (age, gender, company size and its role in GPNs, regional distribution of studied companies, and regional unemployment rate), and was accompanied by assessment of the quality and range of occupational health services. Results: Employees older than 40 years old have nearly 2.5 times higher probability of OD occurrence as compared with employees younger than 40 years old (odds ratio (OR) = 2.41, 95% confidence interval (CI): 2.05–2.85). Occupational diseases occurrence probability was 3 times higher for women than for men (OR = 3.01, 95% CI: 2.55–3.55). Occupational diseases incidence rates increased with the size of the company (0 OD/10 000 employees in micro enterprises to 57 OD/10 000 employees in large enterprises). A particularly steep rise in OD incidents in the automotive industry was observed in the Plzeň Region between 2001 and 2011. An association between OD incidents and the unemployment rate was not statistically confirmed. Conclusions: A statistically significant increase in OD incidents dependent on company size may be arguably attributed to a higher quality of occupational medical services in bigger companies, which ensures better detection and diagnosis of OD. In the Plzeň Region, the rapid increase in OD incidents was mainly caused by a change in the production process of automobile textiles in one factory due to the introduction of a glue containing isocyanates, which are potent allergising agents. This led to an increase in occupational allergic diseases – bronchial asthma in particular
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