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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Sledování odolnosti proti mrazu a vodě stmelených směsí do pozemních komunikací / Resistance to freezing and thawing of hydraulically bound mixtures to roads

Švantner, Lukáš January 2014 (has links)
The theoretical part of this master’s thesis contain comparing the methods of endurance hydraulic bound mixtures of concrete recycles against influence of water and freeze in Czech republic and some other states of The European Union. The practical part is dedicated about laboratory testing concrete recycles with mixtures of binders and its endurance against the water and freeze cycles in Czech republic. In made rollers is compared the strength in pure compression with the strength in pure compression after freezing cycles. From the results of the exams is considered about suitability of using these hydraulic bound mixtures to road construction depending on the kind of use binder, amount of the binder and water. Results of this thesis will be used to revision of national postscript of technological norm ČSN 73 6124-1.
32

Výzkum fázového rozhraní zrno - geopolymerní pojivo u křemenných i nekřemenných ostřiv / Research of interface between quartz and non quartz mould materials grains and geopolymer binder

Skřivánková, Vendula January 2014 (has links)
Presented thesis deals with monitoring of the properties of the interface between opening materials and geopolymer binder using three quartz and four non quartz opening materials. There is observed mainly the type of destruction of connective bridges. The theoretical part of the thesis briefly summarizes commonly used methods in foundries and monitors experience with implementation of geopolymers in different foundries. The practical part monitors shape of the grains of the chosen opening materials. There are writed down the results from the measurement of the bending strength and workability and there is observed the type of destruction of connective bridges.
33

Využití numerické simulace k optimalizaci výroby voskových modelů / Use of Numerical Simulation to Optimize Wax Patterns Production

Kosour, Vojtěch January 2013 (has links)
Production of wax pattern model by injection machine is a one of the key phases of Investment casting process. The thesis deals with the development of numerical simulation wax blend injection in to metal die. The possibilities of selection simulation software – ProCast and Cadmould are described in the relation to numerical predictions of wax injection. Creating of material database of selected wax blends is described. The prototype simulations of die filling are made. The special testing die are designed a used for created simulations. The measurements of initial conditions are mentioned.
34

Optimalizace technologických vlastností cementových formovacích směsí / Optimalization of Technological Properties of Cement Sand Mixtures

Burianová, Klára January 2017 (has links)
The work deals with optimization of the technological properties of cement-sand mixtures. The main objective is to find the correct mixture of the individual components which contribute to the rapid solidification of the mixture, hence shorter dismantling. The content is also of a method of measuring and recording during the plasticity of the mixture. Also assessment of the velocity of hydration heat cement mixture in the initial stage of the solidification process in the course of the strength properties of the mixture. To assess these phenomena was used calorimetric method used for measuring hydration heat cement mixture. Further measurements plasticity mixtures and mechanical and physical methods for measuring the compressive strength with the help of a measuring instrument LRU-D.
35

Modifikace polymerních směsí na bázi polyhydroxybutyrátu a jejich vlastnosti / Modification of polymer blends based on polyhydroxybutyrate and their properties

Melčová, Veronika January 2017 (has links)
Teoretická část této diplomové práce popisuje vlastnosti a možnosti modifikace poly(3-hydroxybutyrátu) (PHB) a amorfní poly(mléčné kyseliny) (PLA) a jejich směsí. V experimentální části je studována reaktivita Joncrylu, Raschigu a fosfitových činidel trifenylfosfitu, tris(nonylfenyl) fosfitu a difenylisodecylfosfitu s čistým PLA a PHB. Raschig, oligomerní aditivum na bázi polykarbodiimidu, prokázal v množství 2hm. % zvýšení viskozity taveniny obou polymerů, a proto byl použit k přípravě směsí o pěti hmotnostních poměrech PHB/(PHB+PLA). Vzorky s Raschigem a odpovídajícími nereaktivními vzorky byly studovány pomocí reologie, gelové permeační chromatografie a modulované diferenční kompenzační kalorimetrie. Výsledky naznačily reakce Raschigu v PHB/PLA směsích vedoucí k rozvětveným strukturám. Rychlost reakce však není nedostatečná ke kompenzaci poklesu viskozity v důsledku degradace při zpracování. Následně zůstává nezreagované množství Raschigu v matrici. Na základě těchto zjištění se dospělo k závěru, že Raschig se chová spíše jako relativně účinný stabilizátor reologických vlastností, než jako činidlo pro záměrnou modifikaci struktury směsí PHB/PLA. Za účelem studia mechanických vlastností těchto směsí byly ve dvoušnekovém extrudéru připraveny vzorky plastifikovány acetyltributylcitrátem.
36

STUDIUM BIOGENNÍCH POJIV / STUDY OF BIOGENOUS BINDERS

Cupák, Petr January 2011 (has links)
oundry production, which forms an integral part of the engineering industry, is a source of waste with a negative impact on the working and living environment. The pressure on greening the production in all production branches of industry does not dodge the foundry industry and technical engineers seek out possibilities of decreasing the negative impact of the production of casting on the environment. An important source of environmentally dangerous waste in foundry operation is the use of organic compounds during the preparation of shaping and core mixtures. Their substitution with materials that would ensure similar technological features of the shaping and core mixtures as the organic materials used hitherto and at the same time decrease the amount of solid, liquid and gaseous ecologically undesirable compounds used in or arising during the preparation and use of shaping and core mixtures, would be significant for decreasing the ecological burden connected to casting production. A promising group of materials usable as components of shaping and core mixtures are the biopolymer materials which can substitute the organic connective systems used in the production of foundry cores by the means of the so-called hot processes – Hot-Box and Warm-Box. This work focuses on the exploration of the technological and ecological features of several biopolymer materials available on the domestic market which have the potential to become a full alternative of the binders used so far on the basis of urea-formaldehyde, melamine-formaldehyde, phenol-formaldehyde and furan resins.
37

OPTIMALIZACE TECHNOLOGICKÝCH VLASTNOSTÍ CEMENTOVÝCH FORMOVACÍCH SMĚSÍ / OPTIMIZATION OF TECHNOLOGICAL PROPERTIES OF CEMENT SAND MIXTURES

Burianová, Klára January 2017 (has links)
The work deals with optimization of the technological properties of cement-sand mixtures. The main objective is to find the correct mixture of the individual components which contribute to the rapid solidification of the mixture, hence shorter dismantling. The content is also of a method of measuring and recording during the plasticity of the mixture. Also assessment of the velocity of hydration heat cement mixture in the initial stage of the solidification process in the course of the strength properties of the mixture. To assess these phenomena was used calorimetric method used for measuring hydration heat cement mixture. Further measurements plasticity mixtures and mechanical and physical methods for measuring the compressive strength with the help of a measuring instrument LRU-D.
38

Ekonomické zhodnocení vlivu vybraného biologického doplňku ve výkrmu brojlerových kuřat / Economical evaluation of choice biological supplement effect in broiler chicken fattening

LANKAŠOVÁ, Jana January 2007 (has links)
The influence of biological supplement AEN 700 in broiler chicken fattening was traced in operating conditions of broiler houses Kladruby.This influence was analysed economically.Compared to year 2005 when the antibiotic stimulators of growth were used there are well-balanced zootechnical and economical results.The results of development confirmed that the biological supplement AEN 700 has minimally equivalent effect in production and in economical effect compared to antibiotic stimulators of growth.
39

Charakterizace vyfukovaných fólií z měkčeného polylaktidu / Characterization of blowing films from softened polylactide

Kubíček, Václav January 2020 (has links)
The master's thesis focuses on preparation of blown films from polylactid acid (PLA) which was blended with selected polyesteres – poly(butylene adipate-co-terephtalate) (PBAT), polycaprolactone (PCL) and polybutylene succinate (PBS) – and thermoplastic starch (TPS) in amount of 30% in order to soften PLA films. The influence of the aditives on static and mechanical tensile properties, on structure, morphology and thermal properties of the films was determined and the obtained parameters were compared to properties of films prepared from neat PLA and high density polyethylene (HDPE). The results showed that the additives increased crystalinity of PLA and thus significantly influenced the properties of the films. In contrast to the film from neat PLA, softening in terms of lowering glass transition temperature occured only by adding PBS and TPS, in terms of increasing ductility only by adding PBAT. All PLA films showed nearly constant elastic modulus up to the beginning of glass transition enabling their potential application till 50 °C. Preparation of the film with TPS was problematic and the film showed the worst mechanical properties. Preparation of other films was without any problems. The most promising additive from the tested ones was PBAT which showed comparable mechanical properties as the film from HDPE.
40

Možnosti využití slévárenských odprachů / The possibilities of using of foundry filter ash

Solik, Jaroslav January 2012 (has links)
This thesis explores the posibility of using of foundry filter ash for production of inorganic composite materials, that could be used primary in the construction industry. The thesis is divided into theoretical and experimental section, where theoretical section contain literature review of used materials and the experimental section summarizes the results of laboratory tests performed on tested mixture based on portland and alumina cement with various content of foundry filter ash. For comparison was also used another foundry waste - foundry sand. Prepared test bodies with dimension of 40 x 40x 160 mm was subjected to mechanical strength tests and the influence of amount of foundry waste on the strenght of the prepared mixtures was monitored. Next the thesis deals with possibilities of alkaline activation of foundry waste, where sodium water glass, sodium hydroxide and commercially supplied baucis L 160 component B were used as alkaline activator. These test mixtures were also subjected to mechanical strenght tests and the influence of amount of foundry waste on the strenght was observed too. The analysis of input materials were performed by XRF, TG – DTA – EGA and XRD powder diffraction methods. All strength tests were tested by testing equipment desttest 4310.

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