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The study of the refractory concrete binding system based on phosphoric acid and aluminous cement
Pavlík, Tomáš ; Švec, Jiří (referee) ; Šiler, Pavel (advisor)
This thesis deals with refractory concrete binding system based on aluminous cement and phosphoric acid. The prepared refractory concretes were fired at 1 000 °C. Various effects on compressive strength of refractory concrete were studied. The influence of aluminous cement content and phosphoric acid content, the influence of various admixtures, the influence of plasticizers and the influence of time and method of sample storage were studied. Simultaneous thermogravimetry and differential thermal analysis of the basic unfired sample were performed. Finally, selected refractory concretes were fired at 110, 200, 400, 600, 800, 900, 1 000 and 1 100 °C. The compressive strength of these samples was measured and powder X ray diffraction analysis was performed. The compressive strength of refractory concretes under intermediate temperatures (800–1 100 °C) was most increased in samples with metakaolin and gray microsilica.
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Characterization of portland cement hydration products by thermal dilatometric analysis
Dvořáková, Tereza ; Švec, Jiří (referee) ; Šoukal, František (advisor)
The paper presents the results of thermal dilatometric analysis of cement pastes during the heating at high temperatures. Volume changes were observed in samples of cement paste at selected time intervals during the hydration. Based on the measured data the dTDAc urves course has been described and the results have been compared with the curves of differential thermal analysis. To characterize the microstructure of the cement paste during the considerable shrinkage at higher temperatures the images by scanning electron microscope have been acquired.
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Personal Voice Activity Detection
Sedláček, Šimon ; Landini, Federico Nicolás (referee) ; Švec, Ján (advisor)
Cílem této práce je implementovat, otestovat a vyhodnotit řečníkem podmíněnou metodu pro detekci hlasu ( Voice Activity Detection , VAD) nazvanou Personal VAD. Pro detekci využívá tato metoda LSTM neuronových sítí a jejím účelem je vytvoření systému schopného spolehlivě detekovat řečové signály cílového řečníka při zachování vlastností typického VAD systému co se velikosti modelu, odezvy a nízkých nároků na zdroje týče. Systém je trénován pro klasifikaci řečových rámců do tří tříd: neřeč, řeč necílového a řeč cílového řečníka. Za tímto účelem využívá metoda speaker embedding vektory pro reprezentaci cílového řečníka jako součást vstupních příznaků. Některé z náročnějších variant systému využívají skórování rámců systémem pro verifikaci řečníka, což vede ke zvýšení spolehlivosti klasifikace. Vedle základní metody skórování představené v originálním článku byly navrženy dvě modifikace, jež základní metodu překonaly a zlepšily spolehlivost výsledného systému i v akusticky náročných prostředích.
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Recognition of Multi-Talker Overlapping Speech Using Neural Networks
Hradil, Jaromír ; Švec, Ján (referee) ; Žmolíková, Kateřina (advisor)
Tato práce se zabývá rozpoznáváním řeči překrývajících se řečníků pomocí neuronové sítě. Zkoumá problém rozpoznávání řečí od vícero řečníků a způsoby, jimiž se tento daný problém řeší. Jedná se konkrétně o aplikaci kromě tradičních komponentů jako konvoluční neuronové sítě, LSTM atd. také speciálních komponentů: attention mechanismus a gated konvoluce. A dále také aplikace techniky zvanou permutation invariant training. Součástí této práce je aplikování těchto přístupů na přidělená trénovací data, která jsou tvořena uměle vytvořenými směsmi dvou řečníků předčítající články z Wall Street Journal. Dalším krokem bylo natrénování příslušných architektur používající kombinující prvky zmíněné nahoře. Modely v této práci nahrazují akustický model. Jednalo se o dvě architektury užívající různé typy attention mechanismu a o jednu bez něj. Experimenty ukázaly, že architektury užívající attention mechanismus v tomto typu úlohy něpřekonaly tradičnější architekturu s užitím gated konvolucí. Přesto ale ukázaly potenciál.
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Magnetic classification of fly ashes and application of products
Červený, Ľuboš ; Švec, Jiří (referee) ; Šoukal, František (advisor)
Submitted bachelor thesis is dealing with problematics of magnetic separation of fly ash and utilization of the products of the separation in production of refractory ceramic materials. High temperature fly ash from power station Mělník was used in this thesis.Thesis evaluates results of magnetic separation at different setting of magnetic separator. It proves, that fraction of particles rich in iron as well as fraction depleted by this iron can be obtained by magnetic separation. In this thesis are presented results of volumetric weight, mineralogic element composition, measurments by heating microscope and results of particle size distribution of unseparated fly ash, but also its both separates. The thesis is focusing on possibilities of utilization as additive in refractory ceramic materials and comparison of their refractory properties. It evaluates results of characterisation of the products using XRD analysis and scanning electron microscopy.
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Inorganic thermal insulation material for masonry elements
Sedlačík, Martin ; Švec, Jiří (referee) ; Opravil, Tomáš (advisor)
This master’s thesis deals with preparation of foam glass and explores the possibilies of utilization of this material as an inorganic thermal insulating filler of fired hollow bricks. Foam glass was prepared via powder sintering method from waste packaging glass, using limestone and graphite as foaming agents. After inital analysis of raw materials, the effect of mixture composition and different processing parameters on bulk density, pore size and morphology of foam glass was investigated. Last but not least, different ways of manufacturing thermal insulating bricks, by preparation of foam glass directly in the cavities of fired hollow bricks, were tested.
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New Techniques in Neural Networks Training - Connectionist Temporal Classification
Gajdár, Matúš ; Švec, Ján (referee) ; Karafiát, Martin (advisor)
This bachelor’s thesis deals with neural network and their use in speech recognition. Firstly,there is some theory about speech recognition, afterwards we show theory around neural networks in connection with connectionist temporal classification method. In next chapter we introduce toolkits, which were used for training of neural networks and also experiments done by them to find out impact of connectionist temporal classification method on precisionin phoneme decoding. The last chapter include summarization of work and overall evaluation of experiments.
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Effect of Cement Bypass Dust on Cracking Tendency of Alkali-Activated Slag during Drying
Krejčová, Marie ; Švec, Jiří (referee) ; Bílek, Vlastimil (advisor)
This bachelor thesis deals with the influence of bypass cement dust on cracking of alkali activated slag. Significant shrinkage and cracking prevent greater use of alkali activated slag. The length changes and strength of the mixtures with different amount of bypass cement dust were measured at various curing conditions. In these mixtures, cracks were observed and their amount was evaluated by image analysis. It has been found that the addition of dust can reduce the amount of cracks. Treating the prisms in a humid environment leads to a reduction of cracks, especially during long-term treatment. In order to improve flexural and compressive strength, it is preferable to use dust as a replacement for part of aggregates and not as a partial slag replacement.
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Possibilities of utilization of brick-grind-dust in alternative binding systems based on fluidized ash
Tušla, Václav ; Švec, Jiří (referee) ; Opravil, Tomáš (advisor)
This bachelor´s thesis deals with usage of brick-grind-dust in alternative binding systems based on ashes of fluid combustion. Specifically it deals with fly ashes and softly milled bed ashes of brown coal combustion. Primarily thanks of content of free lime, anhydrite and other components, fluid ashes have binding properities. Brick-grind-dust arise in end formation of burned bricks. The aim of thesis is to verify, possibilities to create composite of appropriate abilities with high or even exclusive amount of fluid ashes and brick-grind-waste. The paper also deals with influence of some chemical modifying additive on this alternative systems.
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Possibilities of using plasticizers and superplasticizers in alkali-activated systems
Langová, Markéta ; Švec, Jiří (referee) ; Kalina, Lukáš (advisor)
Bachelor thesis deals with the preparation and properties alkali activated blast furnace slag after addition of the different types of plasticizers and superplasticizers with the different weight percentage amount. The aim of this thesis is to find suitable plasticizers or superplasticizers which would improve both workability and mechanical properties of alkali activated blast furnace slag. The effect of these admixtures on compressive and flexural strength was determined. In conclusion the behaviour of plasticizing admixtures in alkaline environment through the infrared spectrometry is studied.
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