Browsing by Author "Voleský, Lukáš"

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    Analýza vlivu geometrie spojů na výslednou impedanci
    (2010-01-01) Voleský, Lukáš
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    Analýza vlivu geometrie spojů na výslednou impedanci
    (Technická Univerzita v Liberci, 2011-01-01) Voleský, Lukáš; Plíva, Zdeněk
    Tato diplomová práce se zabývá zkoumáním impedance vodičů vyrobených za pomoci řízené impedance. Zkoumané vodiče byly obsaženy v testovacích kupónech. Impedance vodičů na všech dodaných kupónech byla ověřena za pomoci měřící ústředny (kapitola 6.1.). Na základě měření byly vybrány dvě desky od každého motivu. U každé vybrané desky se provedly metalografické výbrusy na třech různých místech. U takto vzniklých vzorků se prozkoumaly rozměry vodiče a vzdálenosti vodiče od referencí pomocí mikroskopu (kapitola 6.3). Na základě tohoto zkoumání byly odhaleny chyby, u který se následně stanovily důvody vzniku.
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    CERAMIC 3D PRINTING: COMPARISON OF SLA AND DLP TECHNOLOGIES
    (MM SCIENCE, PRIPOCNI 1519-10A, PRAGUE 10, 10100, CZECH REPUBLIC, 2020-06-01) Truxová, Veronika; Šafka, Jiří; Seidl, Martin; Kovalenko, Iaroslav; Voleský, Lukáš; Ackermann, Michal
    Complex ceramic parts tend to be difficult or even impossible to produce by conventional methods. Therefore, the 3D printing technologies have started to spread widely in the area of ceramic parts production. The aim of this paper is to compare the efficiency of Stereolithography and Digital Light Processing technologies in 3D printing of ceramic parts. Firstly, indicative chemical analysis was performed on a chosen ceramic suspension. Secondly, sample parts of different shapes were designed and printed using both technologies. Next, printed samples were analyzed using thermogravimetric and optical analyses. Finally, printed parts were debound and sintered, and final ceramic parts were consequently reanalyzed. Both technologies show the best results in the printing of thin-walled and hollow models. The DLP was significantly faster, especially when the printing platform was close to full occupancy.
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    Composite Performance Evaluation of Basalt Textile-Reinforced Geopolymer Mortar
    (MDPI, 2019-07-01) Chi, Hiep Le; Louda, Petr; Van, Su Le; Voleský, Lukáš; Kovačič, Vladimír; Bakalova, Totka
    Basalt fiber is a novel type of inorganic fiber which is produced from the extrusion of natural vocalnic basalt rocks through their melting process at high temperature. So the quality and strength characteristics of basalt fiber depend mainly on both the quality of raw material and manufacturing processing. Basalt fabric-reinforced cementitious composites (FRCM) are a novel composite and an extensive scientific investigation is still ongoing for geopolymer composite. Based on three types of basalt textile with respect to various net sizes, the aim of this paper is to evaluate the flexural performance of basalt textile-reinforced geopolymer composite through the four-point bending test. The specimens of rectangular form with the dimension of 400 x 100 x 15 mm(3), reinforced with one to four layers of each type of basalt textile, were produced. They were then tested at the age of about 40 days after casting. On the other hand, the number of the specimens reinforced with four layers were considered to assess the mechanical strength of the specimens at longer periods of ageing time (60, 90, 150, 180 days). The experimental results showed that with the increasing number of reinforcing layers, the specimens significantly improved the mechanical strength, except for those reinforced with basalt textile of big net size. The specimens reinforced with basalt textile of big net size had no impact on post-crack mechanical strength, however, it helps to arrest the catastrophic brittle failure of the specimens; the failure of these specimens is due to localization of first crack. When the specimens were exposed to the further ageing times, the mechanical strength of the specimens were decreased over time. All the reinforced specimens have the same failure mode by flexural failure due to the rupture of fiber yarn in matrix, and no debonding of fiber yarn or a gradual peeling process of mortar matrix happened during testing.
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    Effect of nano silver coating on thermal protective performance of firefighter protective clothing
    (TAYLOR & FRANCIS LTD, 2-4 PARK SQUARE, MILTON PARK, ABINGDON OR14 4RN, OXON, ENGLAND, 2019-06-03) Naeem, Jawad; Mazari, Adnan; Voleský, Lukáš; Mazari, Funda
    The main aim of this experimental work is to find out possible improvement in thermal protective performance of firefighter protective clothing when subjected to different level of radiant heat flux density. Firefighter protective clothing normally consists of three layers: outer shell, moisture barrier and thermal liner. When thermal protective performance of firefighter protective clothing is enhanced, the time of exposure against radiant heat flux is increased, which will provide extra amount of time to firefighter to carry on their work without suffering from severe skin burn injuries. In this study, the exterior side of outer shell was coated with nano-silver metallic particle through magnetron sputtering technology. Coating of outer shell with nano-silver particles was performed at three level of thickness, i.e. 1, 2 and 3 mu m, respectively. All the uncoated and silver coated specimens were then characterized on air permeability tester, Permetest and radiant heat transmission machine. It was observed that coating has insignificant difference on the air and water vapor permeability of specimen and a significant decline was recorded for the value of transmitted heat flux density Q(c) (kW/m(2)) and percentage transmission factor (%TF Q(o)) as compared to uncoated specimen when subjected to 10 kW/m(2) and 20 kW/m(2) indicating improvement of thermal protective performance. These values go on further reduction with increase in thickness of coating layer of nano-silver particles.
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    Mechanical properties of geopolymer foam at high temperature
    (2020-01-01) Le, Van Su; Szczypinski, Michal M.; Hájková, Pavlína; Kovačič, Vladimír; Bakalova, Totka; Voleský, Lukáš; Hiep, Le Chi; Louda, Petr
    In this work, geopolymer foam composites containing waste basalt fibre (10, 30, and 50%wt) were exposed to elevated temperatures of 200, 400, 600, 800 and 1000 degrees C. With an increase in high temperature, the geopolymer foams material exhibits a decrease in compressive strength and bending strength. When heated above 600 degrees C, geopolymer foams materials exhibit a significant reduction in mechanical properties. It shows clearly with the naked eye that surface cracks in case of samples containing 10% of basalt filler. However, when increasing fillers with basalt fibres up to 30% and 50%, the cracking of the sample surface is no longer visible to the naked eye. Especially when the temperature increases, the mechanical properties also increase without decreasing in the sample of 50% by weighing to the binder. The results show that reinforcing the geopolymer foams with basalt ground fibre improves the mechanical properties at high temperatures.
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    Optická mikroskopie; Rastovací elektronová mikroskopie; mikroskopie atomových sil
    (2015-01-01) Voleský, Lukáš
    Výukový materiál vytvořený v průběhu projektu CZ.1.07/1.1.22/02.0006 na téma optická mikroskopie, rastrovací, elektronová mikroskopie a mikroskopie atomových sil. Materiál byl vytvořen v souladu s realizovanými kurzy a navazuje na středoškolskou výuku přírodovědných oborů.
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    Přípravek pro testování vlastností analogových a digitálních osciloskopů
    (Technická Univerzita v Liberci, 2013-12-20) Voleský, Lukáš; Slavík, Lubomír
    Cílem této bakalářské práce je návrh a praktická realizace elektronického zařízení, které je určeno pro testování osciloskopů a seznámení studentů s jednotlivými vlastnostmi osciloskopu. Zařízení má za úkol generovat signály (sinusový, obdélníkový, trojúhelníkový) vyskytující se v průmyslové praxi, včetně parazitních a chybových signálů. Přípravek simuluje zarušení užitečného signálu šumem, pravidelně i náhodně se vyskytujícími se pulzy, zákmity na hranách obdélníkového průběhu, snížení nebo výpadek amplitudy jedné periody sledovaného signálu. V možnostech moderních osciloskopů je analýza snímaného signálu včetně detekce chybových stavů na sběrnicích. Pomocí procesoru přípravek simuluje komunikaci na sériových rozhraních SPI, I2C a RS232 včetně komunikačních chyb.
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    Selective laser melting technology and manufacturing of accurate thin structures
    (Trans Tech Publications Ltd, 2016-01-01) Ackermann, Michal; Šafka, Jiří; Voleský, Lukáš
    This paper deals with finding the building parameters for manufacturing of fine structures with regard to their size precision and structural consistency. Practical use of these structures can be found in areas such as microelectronics, fine mechanics and automotive. Very fine structures with thickness lower than 0.3 mm are very hard to be manufactured due to the limitations of Selective Laser Melting (SLM) technology. These limitations lie in building parameters including mean size and shape of the powder particles, diameter of laser spot and scanning speed. Practical part of the work consists of printing the testing matrices from AlSi12 material with different building parameters for each element. Final products are then evaluated using scanning electron microscope in order to verify final size and structural properties of the specimens. Thanks to these tests, it was possible to find actual border of the technology for given type of powder. Structure with minimal thickness and sufficient strength was found to be 0.21 mm. Moreover, the method for finding parameters for manufacturing of fine structures is applicable for other types of materials. © 2016 Trans Tech Publications, Switzerland.
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    Studium degradačních procesů modifikovaných povrchů implantátů
    (2017-11-13) Voleský, Lukáš; ; Louda Petr, prof. Ing. CSc. Skolitel : 55456
    Tato práce je zaměřena na volbu různých typů tenkých vrstev s využitím v oblasti medicínských implantátů a na volbu jejich depozice na zvoleném substrátu při použití odlišných metod depozice. Teoretická část se zabývá materiály pro medicínské implantáty a jejich vlastnostmi, se zaměřením na tenké vrstvy. Experimentální část zahrnuje výrobu tenkých vrstev s různými parametry depozice testováním jejich vlastností vzhledem k aplikaci na medicínské implantáty, se zaměřením na jejich degradaci, biokompatibilitu a tribologické vlastnosti.
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    THERMAL CONDUCTIVITY OF REINFORCED GEOPOLYMER FOAMS
    (UNIV CHEMISTRY & TECHNOLOGY, PRAGUE, TECHNICKA 5, PRAGUE 6, DEJVICE 166 28, CZECH REPUBLIC, 2019-01-01) Le, Van Su; Hájková, Pavlína; Kovačič, Vladimír; Bakalova, Totka; Voleský, Lukáš; Le, Chi Hiep; Seifert, Kevin Ceccon; Peres, Amanda Pereira; Louda, Petr
    Reinforced geopolymer foams were studied in this work as potential building materials. It has been widely assumed that for a given thermal conductivity. [W center dot m(-1)center dot K-1], geopolymer foams can have a lighter density than other materials. The study sought to test this assumption by comparing the thermal conductivity between geopolymer foams. The thermal conductivity. was measured using an ISOMET 2014 device. In all the experiments, the geopolymer foams were obtained by adding aluminium powder and several combinations: silica fume and fine sand reinforced by short basalt fibres. Curing was carried out at room temperature and then in a furnace at 70 degrees C. After the curing process, the properties of the samples were tested at 7 and 28 days. The results show that the thermal conductivity, porosity, compressive strength, flexural strength and density for all of the tests ranged in the following values: 0.13 - 0.359 W center dot m(-1)center dot K-1; 41.8 - 62.5 %; 1.94 - 9 MPa; 0.96 - 2.93 MPa; 546 - 1028 kg center dot m(-3), respectively. It was proven that the filler in the geopolymer foams has a significant influence on the mechanical and physical properties of the tested samples.
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    Water Absorption Properties of Geopolymer Foam after Being Impregnated with Hydrophobic Agents
    (MDPI, 2019-01-01) Hájková, Pavlína; Louda, Petr; Voleský, Lukáš; Le Chi, Hiep; Le Van, Su
    Geopolymer foam is classified as a lightweight material with high porous in its matrix which has great offer for applications requiring fire-resistant, thermal, and acoustic properties. However, the high sensitivity to humid environments can be a major barrier of geopolymer foam that limits the variety of applications of this material. Based on this drawback, two types of hydrophobic agent (Lukosil M130 and Lukofob ELX) were used as an impregnator to treat the surface of geopolymer foam samples. This paper presented the results of water absorption properties of the untreated and treated geopolymer foam composites. The obtained properties were flexural strength, compressive strength, density, total water absorption, the rate of water absorption, and water absorption coefficient. The results showed that the samples after being impregnated with hydrophobic agents improved significantly their waterproof property especially using Lukosil M130. Moreover, the samples treated with Lukosil M130 had positive impact on their mechanical strength.