Nonlinear optical techniques for ultrafast laser diagnostics : Development of femtosecond LIF, LIGS, CARS and backward lasing

The thesis work concerns development and application of four versatile nonlinear optical techniques, based on exploiting ultrashort laser pulses, for diagnostic purposes in gases and flames. The four techniques, all laser-based, are two-photon laser-induced fluorescence (TPLIF), hybrid femtosecond/nanosecond (fs/ns) rotational coherent anti-Stokes Raman scattering (fs/ns RCARS), fs-laser-induced grating spectroscopy (fs-LIGS), and backward lasing. Special characteristics of fs-laser pulses, such as short pulse duration, high peak power even at low pulse energy, and broad spectral bandwidth, advance the development of these techniques to a new level.In the TPLIF project, two-photon excited fluorescence of CO in CH_4/air flames was investigated and compared for ns, picosecond (ps), and fs-laser excitation. Moreover, based on fs-laser excitation, simultaneous interference-free two-photon excited fluorescence imaging of H and O atoms in turbulent flames was performed for the first time. In comparison with previous studies, it has been demonstrated that significantly larger measurement areas can be visualized in single-shot acquisitions.A concept for lasing in the backward direction, facilitated by fs-laser excitation, was developed and demonstrated for range-resolved detection of H atoms in flames. The technique shows great potential for stand-off measurements in devices with only one optical access. On the fundamental level, studies were performed to uncover the physical mechanism responsible for the lasing effect.With the developed hybrid fs/ns RCARS technique, the RCARS signal can be recorded with a high spectral and temporal resolution, simultaneously, allowing Raman linewidths to be measured on a single-shot basis. This capacity is of great importance for thermometry as it, in principle, eliminates the need for pre-knowledge about the chemical composition and availability of simulated linewidths. With increased fs-laser pulse energy, additional lines in the spectrum were observed due to Stark splitting.The pioneering work on fs-LIGS was performed in heated flows of N_2 gas with temperatures varying from room temperature to 750 K. The thermal grating was formed by resonant multi-photon absorption, based on 800-nm fs pulses, and the generated LIGS signals were detected time-resolved in single-shot acquisitions. The results show that the method works very well for single-shot thermometry in nitrogen, with a measurement uncertainty of ± 1 K for room temperatures and ± 14 K for 600 K, as an example. Increasing the laser pump energy above a certain threshold causes ionization and generates a plasma density grating.It is my hope and belief that the developed laser-based diagnostic techniques can contribute important tools for the larger research community in thermal energy conversion, and support the urgent transition to a sustainable energy system

ANALYSIS OF FOREIGN EXPERIENCE IN THE REGULATORY FRAMEWORK OF DISTRIBUTED LEDGERS AND ICO (INITIAL COIN OFFERING) WITHIN INNOVATIVE ECONOMY

Purpose: The article analyzes the content of economic and legal mechanisms of state control over the emerging market of ICO (Initial Coin Offering). Methodology: This was analytical-logical research based on content analysis. Result: Regarding the considered areas of legal regulation, it is worth noting that in regulating the protection of intellectual rights, counteracting legalization and laundering of money obtained by criminal means, as well as in regulating the protection of personal data, most states use the current legislation without any changes. Applications: This research can be used for universities, teachers, and students. Novelty/Originality: In this research, the model of the analysis of foreign experience in the regulatory framework of distributed ledgers and ICO (initial coin offering) within innovative economy is presented in a comprehensive and complete manner

Komentovaný překlad eseje o moderní české literatuře

Úkolem této diplomové práce byl překlad eseje Květoslava Chvatíka Romány Milana Kundery a krize lidské existence pozdní doby ze sborníku esejí Melancholie a vzdor a následný rozbor některých problematických stránek překladu. Z lexikálního hlediska bylo úsilí zaměřeno na zachování expresivních výrazů a odborných názvů, které leckdy představovaly jistá překladatelská úskalí. V některých situacích však zachování všech výrazových hodnot originálu nebylo možné, proto bylo třeba zvolit překlad pomocí výrazu s obecnějším významem nebo bylo třeba pro překlad jednoho slova v originále použít několik slov v cílovém jazyce, aby byla daná skutečnost popsána co nejvěrněji. Ze syntaktického hlediska jsme se snažili respektovat a zachovávat původní větnou skladbu originálu do té míry, aby to znělo přirozeně i v cílovém jazyce; jindy povaha cílového jazyka vyžadovala užití odlišných syntaktických struktur. Ze stylistického hlediska můžeme konstatovat, že tuto esej nelze přesně zařadit do publicistického stylu, ani do vědeckého, ani do vědecko- populárního, ke kterému má ale nejblíže. Vykazuje totiž jevy, které jsou příznačné pro všechny tyto styly. V překladu do cílového jazyka jsme se snažily tyto jevy zachovat a vyjádřit co nejadekvátněji. V popředí zájmu bylo zachování základní ideové a estetické hodnoty předlohy....The aim of this thesis was to outline some problematic issues of translating Květoslav Chvatík's essay "Romány Milana Kundery a krize lidské existence pozdní doby" (The Novels by Milan Kundera and the Crisis of Human Existence in Modern Times) from the essay collection "Melancholie a vzdor" (Melancholy and Resistence). From the lexical point of view we focused on conveying informal expressions and terms, which were often difficult to translate. In some cases we found ourselves in a situation when it was not possible to keep all the expressive values of the original and we had to opt for a more general word, in other cases we had to use more words in the target language to translate one word of the original in order to express the meaning accurately. From the syntactic point of view we can say that we tried to respect and follow the syntax of the original text in the translation, in so far as it sounds natural in the target language, in some cases the use of different syntactic structures was dictated by the nature of the target language. From the stylistic point of view we can say that this essay could be defined neither as publicistic style, nor scientific, nor popular-scientific style, which may be the closest. It contains features of all of these styles. When translating into the target language we tried...Institute of Translation StudiesÚstav translatologieFaculty of ArtsFilozofická fakult

Gain mechanism of femtosecond two-photon-excited lasing effect in atomic hydrogen

By aiming to establish single-ended standoff combustion diagnostics, bidirectional lasing emissions of atomic hydrogen at 656 nm wavelength have been generated via two-photon resonant excitation by focusing 205 nm femtosecond laser pulses into a premixed CH4/O2 flame. The forward lasing strength is approximately one order of magnitude stronger than that of the backward one, due to the geometry of traveling wave excitation over a 2-mm-long pencil-shaped gain volume and the short gain lifetime of 3.5 ps. The gain coefficient of hydrogen lasing was determined to approximate 52/cm. As for the underlying physics of hydrogen lasing, amplified spontaneous emission (ASE) occurs simultaneously with four-wave mixing (FWM), and ASE dominates in the forward direction, whereas the backward lasing is virtually only ASE

Single-shot coherent control of molecular rotation by fs/ns rotational coherent anti-Stokes Raman spectroscopy

We present a novel method, to our knowledge, to control the shape of the spectra using 2-beam hybrid femtosecond (fs)/nanosecond (ns) coherent anti-Stokes Raman scattering (RCARS). The method is demonstrated experimentally and theoretically by utilizing a species-selective excitation approach via a field-free molecular alignment as an illustrative example. Two non-resonant fs laser pulses with proper delay selectively create and then annihilate N2 resonances in a binary mixture with O2 molecules. The RCARS signal is simultaneously resolved in spectral and temporal domains within a single-shot acquisition. The method requires very low pulse energies for excitation, hence minimizing multiphoton ionization probability, allowing for coherent control at various temperatures and pressures, with spectroscopic applications in non-stationary and unpredictable reacting flows

Risks in Public Administration in the Context of Globalisation

The relevance of the study is conditioned by the fact that globalisation is accompanied by a conflict of interest, increasing contradictions, the emergence of new risks in various areas of public administration in particular. The paper investigates risks in public administration in the context of globalisation. According to the results of cluster analysis, the risks are grouped into the following clusters: socio-humanitarian, environmental, financial-economic, and information-technological. In the context of the conducted expert assessment, the risks in public administration in the context of globalisation were identified and a cluster analysis of the identified risks was performed; a map of risks is drawn up, and constructive and destructive factors influencing the processes of globalisation are determined. It was argued that the globalisation processes are already irreversible, but countries need to identify risks to minimise or neutralise them, to predict possible threats and consequences, as an indicator of these changes is security. The paper has theoretical and practical significance, because national and state security are leading in public administration, as almost any conflict becomes a global issue

FACTORS ANALYSES AND DETERMINATION OF THEIR INFLUENCE ON THE INDICATORS VALUE COMPETITIVENESS OF GOODS EXPORT

Abstract. The pertinence of the issue is because of the impact of fare aggressiveness elements of the Russian Alliance on the elements of remote exchange the development of merchandise outside the traditions region of the EAEU. The presence of such factors won't take into account the compelling usage of state trade approach and the advancement of the national economy. Thusly, it is important to distinguish such factors, their examination, to decide the level of their impact and to shape recommendations for taking measures on their disposal. In such manner, the reason for the article is to recognize the level of impact of fare aggressiveness factors on the fare intensity pointersproclaimed in Russian and worldwide reports. The main strategies for perception fundamental the investigation of this issue are examination, union and enlistment, permitting to distinguish the level of impact of fare intensity factors on fare aggressiveness pointers and to legitimize recommendations for their leveling. The fundamental aftereffect of the article is the development of a grid, which obviously demonstrates the impact of components on individual markers of fare aggressiveness, apportioned by global associations, which will figure out which factors have an increasingly negative effect on the execution of fare intensity in a bigger volume and, hence, should be tended to as a need. Thematerials of the article can be utilized to evaluate the fare aggressiveness of mechanical and different items; will decide further headings to improve the state arrangement in the field of Russian fares' advancement and increment the allure of the residential economy in remote markets.Keywords: export competitiveness, factors of export competitiveness, indicators, state support of export

Laser-induced thermal grating spectroscopy based on femtosecond laser multi-photon absorption

Laser-induced grating spectroscopy (LIGS) is for the first time explored in a configuration based on the crossing of two focused femtosecond (fs) laser pulses (800-nm wavelength) and a focused continuous-wave (cw) laser beam (532-nm wavelength). A thermal grating was formed by multi-photon absorption of the fs-laser pulses by N 2 with a pulse energy around 700 μ J (∼ 45 TW/cm 2). The feasibility of this LIGS configuration was investigated for thermometry in heated nitrogen gas flows. The temperature was varied from room temperature up to 750 K, producing strong single-shot LIGS signals. A model based on the solution of the linearized hydrodynamic equations was used to extract temperature information from single-shot experimental data, and the results show excellent agreement with the thermocouple measurements. Furthermore, the fluorescence produced by the fs-laser pulses was investigated. This study indicates an 8-photon absorption pathway for N 2 in order to reach the B 3Π g state from the ground state, and 8 + 5 photon excitation to reach the B2Σu+ state of the N2+ ion. At pulse energies higher than 1 mJ, the LIGS signal was disturbed due to the generation of plasma. Additionally, measurements in argon gas and air were performed, where the LIGS signal for argon shows lower intensity compared to air and N 2

Temporal dynamics of femtosecond-TALIF of atomic hydrogen and oxygen in a nanosecond repetitively pulsed discharge-assisted methane-air flame

The temporal dynamics of the spatial distribution of atomic hydrogen and oxygen in a lean methane-air flame, forced by a nanosecond repetitively pulsed discharge-induced plasma, are investigated via femtosecond two-photon absorption laser-induced fluorescence technique. Plasma luminescence that interferes with the fluorescence from H and O atoms was observed to decay completely within 15 ns, which is the minimum delay required for imaging measurements with respect to the discharge occurrence. During discharge, H atoms in the excited state rather than the ground state, produced by electron-impact dissociation processes, are detected at the flame front. It was found that the temporal evolution of H and O fluorescence intensity during a cycle of 100 µs between two discharge pulses remains constant. Finally, the decay time of O-atoms produced by the discharge in the fresh methane-air mixture was about 2 µs, which suggests a faster reaction between O-atoms and methane than in air