Effect of the exothermic mixture humidity on the metal solidification in the feeders

Práce se zabývá rešeršní činností v oblasti nálitkování odlitků a dále i podstatou a principem exotermických nálitků. Dále byl navržen experiment pomocí, kterého byly zkoumány účinky vlhkosti na exotermické směsi a její dosazovací schopnosti. Na experiment byly použity nálitky s různým stupněm vlhkosti zaformované do Bentonitových forem. Dále byly zhodnoceny křivky tuhnutí získané během tuhnutí taveniny v nálitku a staženiny, které v nálitku vznikly.The work deals with research activities in the field of casting and also the nature and principle of exothermic castings. Furthermore, an experiment was designed to investigate the effects of moisture on the exothermic mixture and its settling ability. For the experiment, risers with different degrees of humidity formed into bentonite molds were used. Furthermore, the solidification curves obtained during the melt in the riser and the shrinkage which were formed in the riser were evaluated.

Transmitters for fiberless optical diffusive networks

Tato práce se zabývá mobilními bezvláknovými optickými komunikacemi. V rámci této rozsáhlé problematiky je práce zaměřena primárně na využití komunikace pomocí nově navrhovaného modelu RGBY. Ten umožňuje komunikaci pomocí 4 různých vlnových délek ve viditelném světelném spektru současně a přitom zachovává na výstupu bílé světlo, které může současně sloužit pro potřeby osvětlování. Přenos dat pomocí bezdrátových technologií v současnosti představuje významnou oblast vědeckého zájmu. Požadavky na mobilitu a objemy přenášených dat se u koncových uživatelů každým dnem zvyšují. Díky velké hustotě zalidnění se ve městech dostává rádiová komunikace na hranici svých přenosových schopností. Velikost buněk mobilních operátorů se neustále zmenšuje, aby obsáhla rostoucí počet mobilních koncových zařízení. Možnosti připojení pomocí bezdrátových rádiových technologií začínají být, především v pásmu 2,4 GHz, výrazným problémem. V pokrývaných oblastech bývá ve většině případů více přístupových bodů než dostupných kanálů. To způsobuje, že se kanály začínají opakovat a vzájemně se tak rušit. Neustále se tak zvyšuje potřeba dalších komunikačních technologií, které by dokázaly eliminovat problémy s rušením a poskytovaly vysoké přenosové rychlosti při zachování mobility. Jednou z možností řešení se ukazuje právě využití bezvláknových optických sítí, které poskytují transportní nezávislost, pracují v bezlicenčním pásmu a se současným rozvojem LED technologií je lze snadněji implementovat pro potřeby koncových uživatelů. Aktuálně navrhované možnosti komunikačního systému pomocí bílých LED, nebo kombinace barev RGB se ukázaly jako nedostatečné, takže byla pro komunikaci dodatečně přidána ještě barva žlutá. Výstupem je komunikační model RGBY, který lépe využívá rozsah viditelného spektra a umožňuje vytvářet buňkové systémy pro pokrývání větších prostorů. Teoretická část práce se zabývá základy systémů komunikací ve viditelném spektru (VLC), jejich možnostmi, problémy a využitím. Praktická část pak klade důraz na návrh RGBY komunikačního systému a jeho realizaci pro potřeby ověření použitelnosti v reálných podmínkách.This work deals with mobile fiberless optical communications. Due to the huge area of this technology, this work is primarily fucused on use of the RGBY model. This model can communicate with 4 separate wavelenghts in visible spectrum and keep white light at the output, so it can be used also for illumination pusposes. Wireless data transmission is a huge area of interest today. The demand of user mobility and amount of transmitted data is increasing every day. Due to the high density of city population are radio technologies on the edge of the usability. The cell sizes of mobile operators are steadily decreasing to obtain the growing numbers of mobile phone users. Connecting via Wi-Fi is nowadays the significant problem, especially in 2,4 GHz band. Number of access points in the areas is usually higher than number of available channels. This leads to problem that channels are starting to repeat and mutually interfere with each other. Need for other technologies, that could eliminate this problems are constantly increasing. One of possible solutions are fiberless optical netwotks, which offers communication transparency, unlicensed band and thanks to the actual development of LED technologies also easier implementation to users needs. Instead of white LEDs this work uses multiple individual colors and diffuser to create white light. The current system capabilities with use of RGB (red, green and blue) model are insufficient so the system was extended with yellow. As a result we get RGBY system which better utilizes the visible spectrum and it is capable to create huge cellular systems for wide area coverage. Theoretical part of this work deals with the theory of visible light communication systems (VLC), their possibilities, challenges and applications. The practical part is focused on the design of RGBY communication system and its realization. In the final part the system functionality in the real conditions is validated.440 - Katedra telekomunikační technikyvyhově

Fundamentals of photonics

OstravaE-vyuk

Základy fotoniky

OstravaE-vyuk

Effect of Biochar Application Rate on Physical and Hydro-physical Properties of A Dystric Cambisol

The field trial evaluating the effect of biochar on physical and hydro-physical properties of a Dystric Cambisol was carried out at the Research Grassland Station Vatín. The observed variants of the biochar experiment were as follows: 1) the control without biochar, 2) the biochar rate of 15 t/ha applied to the topsoil, 3) the biochar rate of 30 t/ha applied to the topsoil and 4) the biochar rate of 45 t/ha applied to the topsoil. It was found out that even the highest rate of biochar 45 t/ha did not affect saturated hydraulic conductivity of the topsoil at the depth of 0.05-0.20 m. When monitoring bulk density, it was confirmed that the biochar rate of 45 t/ha significantly reduced bulk density from 1218 kg/m3 to 1169 kg/m3. In the crop rotation without manure and clover growing the application of biochar at the rate of 45 t/ha resulted in the relevant decline in the average value of bulk density from 1197 kg/m3 to 1138 kg/m3. In the Norfolk crop rotation there were the inconclusive differences in bulk density. The rate of 45 t/ha had a highly noticeable impact on porosity. It increased from 53.75% (0 t/ha) to 55.60%. The biochar doses did not affect the value of field capacity. The application of biochar at the rate of 45 t/ha caused the significant increase in the average value of aeration from 31.90% to 34.45%.O

Simple and universal current modulator circuit for indoor mobile free-space-optical communications testing

The use of LED for illumination and communication together is more and more interesting with the increasing deployment of LEDs to our homes and industrial buildings. Modulation of this kind of light sources is difficult because of high voltage and current demands. Since the LED configurations and values of current and voltage are different, our universal modulator has to be able to operate even under these circumstances. This paper proposes simple and universal current modulator for LED lighting modulation for frequencies around 1MHz. Main objective is to allow initial testing of different types of High Power LEDs and different photodetector configurations and circuits in diffusive based Free-Space-Optical networks. In the experimental part we also compare results for some different types of LED light sources

Real Measurements and Evaluation of the Influence of Atmospheric Phenomena on FSO Combined with Modulation Formats

The influence of atmospheric environment is fundamental for Free-Space Optical link (FSO). The atmosphere can significantly degrade the communication quality of FSO up to so low received power/RSSI level that it can lead to the loss of communication. For this reason, authors used a professional weather station built on site of FSO link for measurement of real atmospheric conditions such as wind speed, temperature, relative air humidity, air pressure and solar radiation. Random changing of these atmosphere parameters creates atmospheric turbulences, absorption and dispersion centers. It is necessary to specify the value of refractive index structure parameter Cn^2 because it determines the influence of atmosphere on the FSO. The first part of this article includes the theoretical calculation of Cn^2, there are used two models PAMELA and Macroscale Meteorological model. The evaluation of the atmospheric influences and the RSSI value of received power level and also simulation of different types of modulation formats OOK-RZ, OOK-NRZ and BPSK in Optiwave is integral part of this article

Purposeful Suppression and Reconstruction of White Light from LED for Improvement of Communication Properties

Visible Light Communication (VLC) technology uses white Light Emitting Diodes (LED) for providing illumination and communication at the same time. White LEDs have excellent illumination properties but their communication properties need improvement. This article proposes a way how to evade the communication limitations of white LEDs. A part of original white LED spectrum is suppressed by an optical filter. Then the suppressed part is replaced by another LED. The correct choice of suitable LED enables to reconstruct the original spectrum. This solution removes the limitations because the white LED emits continuously. Data are carried by the communication LED only. The evaluation of reconstruction of original white light is measurement of the colour coordinates x and y. Furthermore, the communication properties of this transmitter were tested and obtained results are shown in this paper. EVM parameter was measured

Evaluation of the ECOSSE Model for Estimating Soil Respiration from Eight European Permanent Grassland Sites

Acknowledgments We are grateful to Lukas Hörtnagl, Keller Sabina, Shiva Ghiasi and people from other investigated sites for providing us with the data. Funding This work is funded by the Super-G project (funded under EU Horizon 2020 programme: project number 774124).Peer reviewedPublisher PD