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  • Author: Jiří Moravec x
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Mixing system for highly concentrated fine-grained suspensions

The mixing equipment for highly concentrated fine-grained suspensions must be designed differently from the equipment in which a suspension with a low concentration of the solid phase or bigger particles is mixed. It is due to the different rheological properties of the suspensions. In this work we are trying to find a suitable mixing system for a highly concentrated fine-grained suspension. The aim was to determine an effect of particular geometrical parameters of the tested mixing systems on a suspension process, especially from the energetic viewpoint. The energetic costs of all the used mixing systems were compared on the basis of the power consumption which was necessary for reaching the state of sufficient suspension movement in the whole mixed bulk. As a result, it was confirmed that multistage impellers can be used even in standard vessels (with a liquid level height equal to a vessel diameter) with a profit. During experiments, the state of sufficient movement was determined by a visual observation of the suspension at the vessel bottom, at the wall and also at the suspension level.

Streszczenie

Kobaltové a niklové slitiny jsou běžně používaným materiálem v zubním lékařství. Jedním z důvodů použití je snaha o nahrazení slitin drahých kovů, jejichž cena neustále vzrůstá. Slitiny navíc v porovnání se zlatem a jeho slitinami dosahují vyšších modulů pružnosti, což umožňuje zmenšení hmotnosti dentálních prací při zachování stejných pevnostních charakteristik. Práce byla zaměřena na studium korozního chování komerčně dostupných slitin niklu a kobaltu užívaných v bioaplikacích. Byla studována náchylnost k nerovnoměrným formám koroze a posouzen vliv mikrostruktury na charakter korozního napadení. Korozní chování slitin bylo hodnoceno v modelových tělních tekutinách s použitím elektrochemických technik. Materiály s výjimkou niklové slitiny s obsahem ceru vykazovaly dobrou korozní odolnost při potenciálech odpovídajících oxidačně redukčním potenciálům prostředí lidského organizmu. Výrazná korozní aktivita niklové slitiny s obsahem ceru byla dána přítomností neušlechtilé fáze bohaté na cer. Bylo prokázáno, že mikrostrukturní heterogenita studovaných materiálů má vliv na korozní chování.

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Abstract

The new zoological exposition of the National Museum will be installed in eight exhibition halls on the second floor of the Historical Building. The exposition has the preliminary title Evolution and thematically, it will follow several significant evolutionary events, which enabled animals to occupy Earth. The first two exhibition halls will be devoted to invertebrates and their ability to occupy all kinds of environments. The following two exhibition halls will introduce fish-like vertebrates, amphibians, and reptiles and they will focus on the most important evolutionary step of vertebrates – stepping out of the water and onto land. The next hall will be devoted to the origin of flight and birds’ conquering of the skies. The last two halls will be dedicated to mammals and their origins and conquering of land, water, and air. The visitor will become acquainted with contemporary organisms as the results of a long evolutionary process. The exhibitions will be based on authentic collection items to the maximum possible extent, though models and multimedia will also be used on several occasions. The exposition should also include the restoration of the popular Pokoutník Gallery.