Národní úložiště šedé literatury Nalezeno 5 záznamů.  Hledání trvalo 0.02 vteřin. 
Material properties of lithium fluoride for predicting XUV laser ablation rate and threshold fluence
Blejchař, T. ; Nevrlý, V. ; Vašinek, M. ; Dostál, Michal ; Pečínka, L. ; Dlabka, J. ; Stachoň, M. ; Juha, Libor ; Bitala, P. ; Zelinger, Zdeněk ; Pira, P. ; Wild, J.
This paper deals with prediction of extreme ultraviolet (XUV) laser ablation of lithium fluoride at nanosecond timescales. Material properties of lithium fluoride were determined based on bibliographic survey. These data are necessary for theoretical estimation of surface removal rate in relevance to XUV laser desorption/ablation process. Parameters of XUV radiation pulses generated by the Prague capillary-discharge laser (CDL) desktop system were assumed in this context. Prediction of ablation curve and threshold laser fluence for lithium fluoride was performed employing XUV-ABLATOR code. Quasi-random sampling approach was used for evaluating its predictive capabilities in the means of variance and stability of model outputs in expected range of uncertainties. These results were compared to experimental data observed previously.
Hydroxyl radical measurement in atmospheric pressure dimethyl ether-air laminar premixed flat flame using tunable diode laser absorption spectroscopy
Nevrlý, V. ; Dostál, Michal ; Bitala, P. ; Zelinger, Zdeněk ; Suchánek, Jan ; Válek, V. ; Klečka, V. ; Kubát, Pavel ; Engst, Pavel ; Vašinek, M. ; Wild, J.
Spectroscopic detection of hydroxyl (OH) radical and determination of its concentration in flames have an elusive history and considerable influence on combustion research. Electronic transitions in ultraviolet spectral region were extensively studied in this context and until recent time chemiluminescence or laser induced fluorescence of excited hydroxyl (OH*) radical is broadly used for absolute concentration and temperature measurement in flames.\nHowever, number densities of molecular species and population of relevant quantum levels in ground electronic state can be directly estimated from intensities of absorption lines observed by probing rovibrational transitions in infrared spectral region. Application of near-infrared tunable diode laser absorption spectroscopy (NIR-TDLAS) for the given purpose was demonstrated in an earlier work of Aizawa et al. [1]. Following his pioneering studies summarized in [2], we further explored feasibility of NIR-TDLAS (especially 2f-WMS technique) for monitoring minor species within combustion experiments particularly when dealing with dimethyl ether (DME) flames. Here we report our first results of NIR-TDLAS measurements focused on hydroxyl radical detection in laminar premixed flame burning DME-air mixture under fuel-lean conditions.
High resolution infrared spectroscopy as diagnostic tool for combustion and plasma chemistry
Zelinger, Zdeněk ; Nevrlý, Václav ; Grigorová, Eva ; Bitala, P. ; Dostál, Michal ; Suchánek, Jan ; Kubát, Pavel ; Engst, Pavel ; Ferus, Martin ; Kubelík, Petr ; Civiš, Svatopluk
Monitoring of transient species within combustion experiments (laminar flames, shock-tubes, flow reactors, etc.) is still relatively challenging task especially if application of non-invasive, i.e. optical detection methods is required. High resolution infrared spectroscopy is based on observation of the fine rotation structure that accompanies vibration transitions and thus provides direct information essential to characterization of both molecular structure and reaction dynamics. Thanks to its outstanding advantage enabling unambiguous assignment of specific molecular system according to its spectral feature, it can serve as a helpful tool for exploring complex reaction mechanisms as well as chemical reactivity of individual species present in laboratory flames or plasmas.\nPrevious studies gaining new insights into combustion and plasma chemistry as well as our recent advances targeted towards application of high resolution infrared spectroscopy for species concentration measurement in laminar flames are summarized here below.
Wavelength modulation spectroscopy for multicomponent ana-lytics of biomass burning tracers
Dostál, Michal ; Válek, V. ; Suchánek, Jan ; Kristlová, E. ; Roupcová, P. ; Zelinger, Zdeněk ; Nevrlý, Václav ; Bitala, P. ; Vašinek, M. ; Kubát, Pavel ; Ferus, Martin ; Civiš, Svatopluk
The potential of Tunable Diode Laser Absorption Spectroscopy (TDLAS) for monitoring of several species produced by biomass burning is in focus of this work. The infrared spectra of selected molecules (HCOOH, C2H2, CH3CN, N2O, CH3OH, CH3COCH3) are measured in laboratory conditions and the selectivity and of this method is demonstrated.
Experimentální studie laminárního plamene: jsou hodnotné při zkoumání požáru a exploze?
Bitala, P. ; Nevrlý, Václav ; Filipi, B. ; Střižík, Michal ; Zelinger, Zdeněk ; Danihelka, P. ; Zavila, O. ; Jánošík, L.
Současného stupně poznání v oblasti výzkumu procesů plamenného hoření je dosaženo zejména díky spojení dvou komplementárních přístupů, tedy uplatněním experimentálních metod v rozdílných fyzikálních měřítcích a využitím nástrojů numerického modelování. Plameny simulované v laboratorním měřítku mohou zahrnovat některé aspekty uplatňující se i v reálných podmínkách při jevech spojených s procesy hoření (např. průmyslové požáry a exploze). Experimentální studie proto představují vhodný nástroj pro lepší pochopení těchto procesů a řešení dílčích problémů souvisejících s velkorozměrovými havarijními projevy.

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