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The Technology of Manufacture of a Positive Lens of Achromatic Dublet
Rail, Zdeněk ; Melich, Zbyněk ; Šrajer, Bohdan ; Šípová, Gabriela ; Ulrichová, Iva ; Franců, Helena ; Melich, Radek ; Vápenka, David ; Tomka, David ; Thoř, Tomáš
This paper deals with manufacturing of a positive lens of achromatic dublet. Diameter of the dublet is 158 mm and its focal length about 2500 mm. The glass material of the former lens was inhomogeneous and the dublet provided bad images. This is why we decided to manufacture new lens. The process was made by means of former machines of our workshop. The telescope with this dublet is placed at the Observatory of Turnov and serves for public astronomical observation.
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High temperature corrosion studies of HVOF sprayed coatings in molten sulphate salts environment
Lencová, K. ; Česánek, Z. ; Houdková, Š. ; Lukáč, František ; Mušálek, Radek
The generally applied requirements on lowering of emission production in the field of power industry have led, among others, into the application of low-emission combustion process of coal fired power plants. Besides the emissions reduction, this process has led to an increase of boilers parts corrosion degradation due to the reducing atmosphere in low-emission boilers, responsible for sulphide corrosion and molten salt attack. In such environment, the protection of the exposed surfaces gains importance. Among others, the thermal spraying technology can offer a suitable way of surface corrosion protection. In the present work, the high temperature corrosion behaviour of CoCrAlYTaCSi and Cr3C2-25%NiCr High Pressure/High Velocity Oxygen Fuel (HP/HVOF) sprayed coatings is evaluated and compared to the behaviour of bare structural steel (SPT360) substrate. The specimens were exposed to a molten salt environment, i. e., 12% Na2SO4 + 82% Fe2(SO4)3 at 690 °C under cyclic condition, simulating the working environment in low-emission boilers of coal-fired power plants. The thermogravimetric method was used to establish the kinetics of corrosion. X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) techniques were used to analyse the corrosion products and determine the corrosion mechanism. The thermogravimetric measurement shows high oxidation rate of SPT360 steel. Cr3C2-25%NiCr coating provides slightly better performance compared to CoCrAlYTaCSi coating. Based on the obtained results, both coatings were found to have higher corrosion resistance than the SPT360 steel substrate, offering a sufficient surface protection in a given environment.
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Tungsten-steel and tungsten-chromium composites prepared by RF plasma spraying
Matějíček, Jiří ; Klečka, Jakub ; Čížek, Jan ; Veverka, Jakub ; Vilémová, Monika ; Chráska, Tomáš ; Ganesh, V.
For future fusion reactors, materials able to withstand harsh environments are needed. In particular, this concerns the plasma-facing components which are foreseen to consist of tungsten based plasma-facing armor and structural and cooling part made of steel. Currently, joining of these materials presents a significant challenge. The stress concentration at their interface, which arises due to thermal exposure and the difference in thermal and mechanical properties, can be reduced by composite/graded interlayers. Plasma spraying is among the prospective technologies for their preparation. In this work, tungsten-steel and tungsten-chromium composites were prepared by radio-frequency inductively coupled plasma (RF-ICP) spraying. Initial optimization of the spraying process for pure materials as well as their mixtures was carried out. Basic characterization of the layers for their structure, porosity and composition is presented.
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Disposal of antibiotics from waste water
Mastný, L. ; Brožek, Vlastimil ; Slavětínská, R.
The work is focused on the removal of a broad-spectrum tetracycline antibiotic intended for mass therapeutic and preventive application in animals. The veterinary drug, which contains tetracycline and its derivatives, reaches the waste water at a high concentration after completion of the production campaign. A method based on the oxidation of an antibiotic with an acidified solution of potassium permanganate is used for the disposal of organic waste. The method of disposal will be introduced in the company TEKRO, Ltd.
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The Digitalisation of the Maksutov Camera 350/840 of the Observatory in Úpice
Rail, Zdeněk ; Melich, Zbyněk
The Maksutov chamber with a diameter of 350 mm and a focal length of 840 mm was manufactured in Turnov in the early 1980s. At the Úpice Observatory it was used to photograph the sky for photographic film. Currently, we have been asked to convert it to a digital device. It was necessary to design and manufacture a correction element for the chamber to straighten its focal surface and to equip it with a suitable digital camera. In this work we present description of modification of this device.
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