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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.
151

Technicko-ekonomické porovnání nekonvenčních technologií AWJ a LBM z hlediska potřeb firmy / Cost-effect and technical comparison of nonconventional technologies AWJ and LBM with the view of needs of a company

Malát, Jan January 2011 (has links)
This study deals with unconventional materials cutting technology with a fo-cus on abrasive water jet cutting and CO2 laser. The thesis is divided into theoretical and experimental section. The theoretical part describes principles and functions of nonconventional technologies, the basic division and practical applications. The practical part is focused on choosing the best technology with the production of samples and their subsequent comparison. The thesis recommends producer and type of the machine which best meets requirements on basis of the test results.
152

Spektroskopické studium dohasínajících výbojů v dusíku a jeho směsích / Spectroscopic Study of Post-Discharges in Nitrogen and its Mixtures

Mazánková, Věra January 2009 (has links)
Presented thesis gives results obtained during the spectroscopic observations of post –discharges of the pure nitrogen plasma with small oxygen admixture and in the nitrogen – argon mixture and the effect of the pink afterglow in it. The DC discharge in the flowing regime has been used for the plasma generation. The decaying plasma was study by optical emission spectroscopy, mainly in the range of 300–800 nm. The first positive, second positive, first negative nitrogen spectral system and NO spectral systems were observed in measured spectra. The band head intensities of these bands have been studied in the dependencies on experimental conditions. Simultaneously, the relative vibrational populations on the given nitrogen states have been calculated. Two discharge tubes made from different materials (PYREX glass and QUARTZ glass) were used in the case of nitrogen plasma containing low oxygen traces (up to 0.2 %). These experiments have been carried out at two wall temperatures for the determination of the temperature effect on the post-discharge. The discharge tube around the observation point was kept at the ambient temperature (300 K) or it was cooled down to 77 K by liquid nitrogen vapor. The total gas pressure of 1 000 Pa and the discharge current of 200 mA were conserved for all these experiments. The relative populations of electronic states were calculated in the dependence on the post-discharge time. The dependencies on oxygen concentration were given, too. The results showed no simple dependence of vibrational populations on oxygen concentration. Generally, slight increase of neutral nitrogen states populations was observed with the increase of oxygen concentration. These observations were well visible due to the intensity of nitrogen pink afterglow effect that was well visible at all oxygen concentrations. The pink afterglow maximal intensity was reached at about 5–10 ms at the wall temperature of 300 K in the PYREX tube. The molecular ion emission was strongly quenched by the oxygen and as this was dominant process for the pink afterglow emission the pink afterglow effect disappears at oxygen concentration of about 2000 ppm. The temperature and wall material influences were observed, too. The post-discharge in nitrogen argon mixtures was studied only in the PYREX tube at the ambient wall temperature of 300 K. The power dissipated in an active discharge was constant of 290 kW. The experimental studies had two new parameters – total gas pressure (500 Pa – 5 000 Pa) and the argon concentrations that were varied in the range of 0–83 %. Also in this case the dependencies of relative intensities of the bands given above were obtained and further the relative populations of electronic states as a function of decay time, total gas pressure and on argon concentration were obtained. The pink afterglow effect was observed at all applied discharge powers and total gas pressures. At the highest argon concentrations, especially at lower pressure, the pink afterglow effect disappeared. The presented experimental work is one of the hugest sets of experiments in the nitrogen with oxygen traces and in nitrogen-argon mixtures. These data can be used as a very good fundament for the further studies using wide numeric modeling of the post-discharge kinetic processes.
153

Radiační přenos energie v obloukovém plazmatu / Radiation Transfer of Energy in Arc Plasma

Bogatyreva, Naděžda January 2015 (has links)
Hlavním cílem práce je studium radiačního přenosu energie v termálním plazmatu pomocí aproximační metody sférických harmonických funkcí (PN-aproximace). Práce má teoretický charakter. Pozornost je věnována především P1-aproximaci. Spektrální závislost absorpčních koeficientů byla zpracována pomocí multigroup aproximace. Byl vytvořen výpočetní program pro výpočet radiačních charakteristik v izotermickém válcovém plazmatu a ve válcovém plazmatu s daným teplotním profilem, a vypočteny radiační charakteristiky pro plazma vzduchu a směsí SF6 a PTFE. Získané výsledky umožňují zahrnout radiační ztráty energie do celkové energetické bilance plazmatu elektrického oblouku. Jsou využívány v matematických modelech elektrického oblouku, které vytváří naši spolupracovníci z Ústavu fyziky plazmatu AV ČR v Praze a také ze zahraničních pracovišť (ABB Corporate Research ve Švýcarsku a Siemens AG Corporate Technology v Německu).
154

Rozšíření možností optické diagnostiky spínacího oblouku / Enhancement of optical diagnostics of the switching arc

Samohejl, Matěj January 2016 (has links)
This master´s thesis si focused on determinig methodology of optical diagnostics of the switching arc using the high-speed camera Photron SA-X2. The thesis contains basic rules for proper setup of the measurement system and the rules to adjust the camera exposure. The experiments were performed on the prototype of a parametric switching chambre, while the majority of source materials was derived from the requirements of another study which was aimed on the movement of the electode spots. The process of the first adjustment of the camera, a record edit options for the presentation purposes and the process of the 3D model design of the switching arc in SketchUp software was stated. Paper contains a comparsion of the spectral filter effect and neutral density filter effect on the final record as well. The part of the work outputs are the 3D model of the switching arc and the supporting record editing software. The paper results show a degree of the inaccuracies in a optical diagnostics made from only one direction caused by the lack of the information about third dimension.
155

Pokovování technických plastů pro výrobu odlehčených konstrukčních dílů pro dopravní průmysl / Metallization of technical plastics for lightweight traffic components with reduced fuel consumption

Sanetrníková, Dominika January 2017 (has links)
The beginning of this thesis is dedicated to polymeric materials, which include plastics an composites. Plastics are shortly divided into two groups, thermoplastics and thermosets. The following part is the use of plastics and composites in traffic industry and briefly this work focuses on techniques of recycling of this materials. This work also focuses on the techniques of thin film deposition, electroless plating, electrodeposition as well and plating in the vacuum environment. special techniques of thin film deposition are also mentioned shortly. The coatings of polymer including cleaning and surface activation is introduced using various techniques including plasma treatment. The surface treatment of polyetheretherketone (PEEK) is included too. The final part describes performed experiments and discussion of results.
156

Spektroskopické studium interakcí fokusovaného svazku rentgenového laseru s hmotou / The spectroscopy study of focused short-wavelength laser-matter interactions

Burian, Tomáš January 2019 (has links)
Title: The spectroscopy study of focused short-wavelength laser-matter interactions Author: Tomas Burian Department: Department of Surface and Plasma Science Supervisor: Ing. Libor Juha, CSc., Department of Radiation and Chemical Physics, Institute of Physics of the Czech Academy of Sciences, Prague Abstract: This thesis is focused on processes occurring during and immediately after an interaction of intense short-wavelength laser pulses with matter. Extreme states of matter (warm dense matter - WDM and hot dense matter - HDM), induced by EUV/SXR/X-ray lasers of two kinds, i.e., free-electron lasers (FEL) and plasma-based lasers, were investigated by emission spectroscopy over various spectral ranges and mass spectroscopic techniques. Absorption/transmission experiments revealed an effect of saturable absorption of soft X-ray laser radiation in aluminium WDM. Then, an ionisation potential depression (IPD) in dense plasmas was investigated by means of X-ray emission spectroscopy. Results obtained with the X-ray FEL-produced plasma exhibit very good agreement with computer simulations considering the Ecker-Kröll model. Analysis of optical emission spectra (OES) supports the key role played by fast recombination processes in the ablation plume created by focused short-wavelength laser beams on the solid target...
157

Vznik organických molekul iniciovaný procesy o vysoké hustotě energie v planetárních atmosférách / Formation of organics molecules initiated by high-power density energy events in planetary atmospheres

Kamas, Michal January 2010 (has links)
The focused laser beam delivered by the high-power laser system PALS was used for laboratory simulation of high-energy-density events in a planetary atmosphere. Several model gas mixtures were prepared to mimic the mildly reducing early Earth's atmosphere (CO-N2-H2O) as well as the atmosphere of Saturn's moon Titan and the strongly reducing early Earth's atmosphere (CH4-N2-H2O). In situ investigation of transient species generated by the laser-induced dielectric breakdown in the gaseous mixtures was performed by optical emission spectroscopy (OES). Final products of laser-plasma initiated chemical reactions were identified and determined by advanced mass-spectrometry (SIFT-MS) and absorption FT-IR spectroscopy. High-power laser system SOFIA was utilized to simulate in our laboratory a high-velocity impact into the icy satellites of the outer planets of the Solar system. OES was engaged in probing the plasmas produced by the SOFIA beam focused on ice surfaces (water, methanol, formamide), while final products were analyzed by means of gas chromatography (GC/MS) and mass-spectrometry (SIFT-MS).
158

Využitie extracelulárnych nukleových kyselín na neinvazívnu prenatálnu diagnostiku monogénne dedičných porúch, komplikácií tehotenstva asociovaných s placentárnou insuficienciou a Downovho syndrómu / The use of cell-free nucleic acids in maternal plasma for non-invasive prenatal diagnosis of monogenic diseases, placental insufficiency-related complications and Down syndrome

Veselovská, Lenka January 2011 (has links)
Since the discovery of cell-free fetal DNA in peripheral blood of pregnant women, cell-free nucleic acids in maternal plasma are explored in relation to non-invasive prenatal diagnosis of various fetal conditions and pregnancy complications. Non-invasive prenatal diagnosis of monogenic diseases represented by TSC1-linked tuberous sclerosis could be achieved by detection of paternally-inherited mutant allele in the pool of maternal alleles in plasma. Reliability of detection of mutant allele could be improved by simultaneous mutation haplotype analysis or detection of universal fetal marker. None of the 3 methods (allele- specific real-time PCR, SNaPshot minisequencing and quantitative fluorescent PCR) evaluated using artificial mixtures and maternal plasma samples reliably and accurately detected low-frequency allele distinguished by point mutation, SNP or microsatellite in TSC1 gene or in its close proximity. We developed a strategy for prediction of proportion of informative couples for panel of SNPs of interest that can be applied to any monogenic disease. Exploiting differential methylation of promoters of genes RASSF1A, HLCS and OLIG2 in maternal and fetal genome, we failed to establish functional fetal marker. MicroRNAs of placental origin released into plasma could serve as biomarkers of...
159

Determination of titanium dioxide nanoparticles in personal care products / Determination of titanium dioxide nanoparticles in personal care products

Košík, Juraj January 2016 (has links)
Předkládaná diplomová práce se zabývá extrakcí nanočástic oxidu titaničitého z produktů osobní péče, konkrétně opalovacích krémů a následnou charakterizací těchto částic. Počet komerčně dostupných produktů s obsahem nanočástic TiO2 se neustále zvyšuje a to se sebou přináší potřebu vyhodnotit potenciální osud a nepřímou expozici TiO2 nanošástic o různých velikostí a tvarů a zkoumat jejich celý životní cyklus. Bylo zkoumáno použití ultrafiltrace a ultracentrifugace jako extrakční metody. Dvě metody pro extrakci TiO2 nanočástic byly vyvinuty a aplikovány na vzorky opalovacích krémů. Extrahované částice mohou být použity pro ekotoxikologické studie, případně experimenty v mesokosmu. Velikost částic byla stanovena pomocí metody dynamického rozptylu světla a transmisní elektronové mikroskopie.
160

Stanovení vybraných komponent v lidské moči elektroforézou v krátké kapiláře. / Determination of selected components in human urine with electrophoresis in short capillary.

Makrlíková, Anna January 2015 (has links)
Capillary zone electrophoresis is frequently used in various analyses. In this diploma thesis a hydrodynamic sample introduction method controlled by pressure pulse has been proposed for short-capillary electrophoresis. The base electrolyte flushes sample from the loop of a six-way sampling valve and is carried to the injection end of the capillary. At the time when the sample zone reached the capillary, a short pressure impulse is generated in the electrolyte stream, which provides injection of the sample into the capillary. Then the electrolyte flow is stopped and the separation voltage is turned on. The amount of sample introduced to the capillary is controlled by the duration of the pressure pulse. This new sample introduction method was tested in the determination of ammonia, histidine, creatinine, uric acid and hippuric acid in human urine and for rapid screening of the contents of the inorganic ions in cerebrospinal fluid and blood plasma. The determination was performed in a capillary with an overall length of 10,5 cm and two base electrolytes was tested - 50 mM MES + 5 mM NaOH (pH 5,10) and 1 M acetic acid + 1,5 mM crown ether 18-crown-6 (pH 2,40). Using dual detection techniques contactless conductivity and UV spectrometric detection, anorganic and organic substances in the sample could...

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