Magister Scientiae - MSc / The spectroscopic, SEM and Raman measurements on carbon nanotubes under the exact conditions of which OES analysis were made showed that at a pressure of 400 Torr and a flow rate of 200 sccm, the quality and quantity of single-walled carbon nanotubes was the highest. / South Africa

The present work is concerned with fundamental studies on the liquid fuel transport in the intake manifold of small carburetted engines. This work is motivated by the need for development of technologies to meet the stringent cold-start emission norms that are to be prescribed for two-wheelers in particular. More specifically, visualization studies conducted in a transparent manifold made of quartz in a small four-stroke 110-cc two-wheeler engine have shown the presence of gasoline films on the walls of the inlet manifold under cold start conditions. Advanced Laser diagnostic techniques such as Planar Laser Induced Fluorescence (PLIF) have been utilized to measure the thickness of the fuel films. The Sauter Mean Diameter for the fuel droplets at the carburettor exit is measured using Laser Shadowgraphy technique. It is observed that the films are present both at idling conditions and under load. This large amount of liquid fuel entering the engine leads to incomplete combustion and higher emissions of unburned hydrocarbons. A detailed analysis of the effects of heating the inlet manifold has been performed. The potential of this manifold heating strategy in reducing hydrocarbon emissions has been assessed and found to be promising. In addition, a need of proper control of the fuel exiting the carburettor is shown to reduce emissions and increase fuel efficiency.

An isolated wing-tip vortex from a square-tipped NACA 0012 wing at an angle of attack of 5 degrees was studied in a water tunnel at a chord based Reynolds number of approximately 24000. Measurements were taken using stereo particle image velocimetry at three measurement planes downstream of the wing under each of three freestream turbulence conditions. The amplitude of wandering of the vortex axis increased with increasing distance downstream of the wing and with increasing freestream turbulence intensity. The magnitude of the peak azimuthal velocity decreased with increasing distance from the wing as well as with increases in the freestream turbulence intensity. The streamwise velocity in the vortex core was less than the freestream velocity in all cases. Time resolved histories of the instantaneous waveform shape and location of the vortex axis were determined from sequences of images of fluorescent dye released from the wing.

La fluorescence induite par laser multibande est une technique non intrusive permettant d’accéder à la température de la phase liquide dans des milieux complexes. L’application de cette technique dans des liquides monophasiques où le chemin optique est variable (produit de la concentration moléculaire du traceur et de la distance dans le milieu liquide entre le volume de mesure et l’optique de détection) a été considérée. Le rapport des intensités de fluorescence collectées sur deux bandes spectrales permet de s’affranchir de la concentration en traceur fluorescent, de l’intensité laser incidente et du volume de mesure. Une troisième bande spectrale de détection permet de prendre en compte le terme de ré-absorption de la fluorescence dans le cas de chemins optiques non-négligeables et variables. Puis l’application de la technique à la mesure de la température de la phase liquide d’un spray est présentée. Un traitement spécifique du signal a été développé afin de tenir compte de la nature aléatoire du signal de fluorescence liée à la présence de gouttes dans le volume de mesure. De plus, ce traitement a été adapté afin de rendre possible le couplage des données de fluorescence avec des mesures granulométriques effectuées par la technique phase Doppler dans la perspective finale d’obtenir des températures de goutte par classe de taille. Cependant plusieurs phénomènes perturbateurs ont été mis en évidence : - une dépendance inattendue et non linéaire à la taille de goutte du rapport des intensités de fluorescence collectées sur deux bandes spectrales. - une forte diffusion de la lumière laser incidente par le nuage de gouttelettes induit une fluorescence bien au delà de la zone d’excitation laser. Cette fluorescence parasite est néanmoins détectée dans la profondeur de champ du dispositif optique et se conjugue avec l’effet non-linéaire de la taille des gouttes. Une stratégie de correction de ces différents phénomènes est proposée et une expérience de validation est réalisée sur un spray chauffé injecté dans une cellule saturée en vapeur / Multiband laser-induced fluorescence is a non-intrusive technique able to provide a measurement of the liquid phase of complex media. The application of this technique in single phase liquids, with a variable optical path (product of the fluorescent tracer molecular concentration by the distance between the probe volume and the collection optics in the liquid) was considered. The ratio of the fluorescence intensities collected on two spectral bands allows removing the influence of the fluorescence tracer concentration, incident laser intensity and probe volume. A third spectral band of detection is used to take into account the re-absorption of the fluorescence in the case of non negligible and variable optical paths. Then, the application of this technique to the measurement of the temperature of the liquid phase of a spray is presented. A specific data processing was developed in order to take into account the random presence of droplets in the probe volume. Moreover, the processing was adapted to achieve combined fluorescence and droplet size measurements using the phase Doppler technique. The overall foreseen goal is to measure temperature per droplet size class. However, several disturbing phenomena were highlighted: - an unexpected non-linear dependence on the droplet size of the ratio of the fluorescence intensities collected on two spectral bands, - a strong incident laser light scattering by the droplets cloud, which induces a fluorescence beyond the excitation zone. This fluorescence is also collected in the depth of field of the optical device and combines with the non-linear size dependence. A correction strategy of these phenomena was implemented and a validation experiment on a heated spray injected in a vapour-saturated cell was performed

L’étude des transferts de chaleur et de masse lors de l’évaporation de gouttes en mouvement et en interaction est un domaine complexe à cause des nombreux phénomènes en jeu. Les principaux paramètres influençant l’évaporation ont pu être étudiés indépendamment grâce à l’utilisation de diagnostics optiques de mesure non-intrusifs sur un train de gouttes monodisperse. Une technique basée sur la fluorescence induite par laser (LIF) à deux couleurs a été développée afin d’obtenir la température moyenne de gouttes de combustible mono et multicomposant. Afin de supprimer l'effet optique parasite engendré par des résonances morphologiquement dépendantes, un absorbeur non fluorescent a été ensemencé à faible concentration. L’évolution de la vitesse et de la taille des gouttes ont été investiguées grâce à une technique par ombroscopie quantitative qui permis la mesure très précise des taux d’évaporation. Une enceinte à haute température a été conçue afin de générer des conditions ambiantes maitrisées et propices à la formation d’une forte évaporation. Ainsi, les nombres de Nusselt et Sherwood ont été déterminés expérimentalement pour plusieurs combustibles dans diverses conditions d'injection. L'étude sur différents combustibles et à différentes températures d'injection a confirmé l’influence de la volatilité du combustible sur les transferts. L’influence du nombre de Reynolds a aussi été mise en évidence. L’étude de gouttes multicomposant a permis de montrer différentes phases d’échauffement et d’évaporation lors du temps de transit de la goutte liées aux différences de volatilité des combustibles du mélange. Les effets de différentes compositions ont aussi été investigués / The study of heat and mass transfers during the evaporation of moving and interacting droplets remain a complex field because of the various mechanisms in action. The main parameters influencing the evaporation of droplets have been studied separately thanks to non intrusive optical diagnostics that have been used on a monodisperse droplet stream. A technique based on two colors laser induced fluorescence (LIF) was developed to measure the temperature of mono and multicomponent evaporating fuel droplets. The liquid fuel is seeded by a non-fluorescent absorber to eliminate the effect of morphological dependant resonances. The size evolution was obtained thanks to shadow imaging which allowed precise measurements of evaporation rates. A hot chamber was conceived to create controlled ambient conditions around the droplets. Thereby, the Nusselt and Sherwood numbers, characterizing the heat and mass transfers, were deduced from the experimental data for various experimental conditions. The studies allowed confirming the influence of the volatility of the fuel regarding heat and mass transfers. The results also exhibit an influence of the Reynolds number. Finally, the study of multicomponent droplets had shown different heating and evaporating phases during the droplet transit time. Effects of various compositions have also been investigated

Tato diplomová práce je zaměřena na analýzu lehkých prvků (tj. uhlík, sýra a fosfor) v železných slitinách pomocí metody laserem indukovaného plazmatu (LIBS). Hlavním cílem je vyvinout a implementovat nový modul, který bude umožňovat analýzu v hluboké ultrafialové oblasti (VUV), což je nezbytné jak pro stanovení chemického složení lehkých prvků v ocelích tak pro mnoho dalších aplikací metody LIBS. V první části je vytvořen přehled moderních přístupů optické emisní spektroskopie (OES) a rovněž jsou shrnuty tradiční techniky používané v metalurgii pro analýzu ocelí. Teorie absorpce ultrafialového záření vzduchem a optickými skly byla důkladně studována a shrnuta k získání potřebného teoretického základu k vývoji modulu. Před návrhem finální verze modulu byl navržen experimentální modul s cílem otestovat navržený koncept analýzy ve VUV oblasti metodou LIBS. Na základě testování byla navrhnuta finální verze založená na unikátním klínovém mechanismu. Funkční vzorek byl vyroben ve spolupráci s extérním výrobcem a vlastnosti modulu byly následně demonstrovány naměřením pěti certifikovaných ocelových standardů. Experiment určil limity detekce pro uhlík jako 0.028 hm.%. Nicméně, síra ani fosfor nebyly detekovány v žádném ze vzorků. Tato práce vytvořila modul nezbytný pro budoucí zkoumání metody LIBS v oblasti VUV v Laboratoři laserové spektroskopie v Brně.

Laser-induced breakdown spectroscopy (LIBS) is a fast analytical method, but can also be complicated. This spectroscopic method is used to provide a qualitative and quantitative analysis of a sample. The analysis is carried out by capturing the emission radiation of the generated plasma. The accuracy and stability of the measurement is affected by several parameters, such as stability of the laser, physical and chemical properties of the sample, its homogeneity and others, that can not always be eliminated. For this reason other methods are being added to the LIBS experiment that could improve the quality of this analysis. This diploma thesis is focused on a research of the literature on the standardization of laser-induced plasma signal and the possibility of using an acoustic signal for this purpose. For this reason , it is necessary to perform basic experiments and to verify if the acoustic signal correlates with the emission signal. If these signals correlate together, it would be possible to use the acoustic signal for standardization og the LIBS data, which would improve the accuracy of the analysis. In the theoretical part at the beginning other spectroscopic methods are summarised. Then the work is focused on the description of the LIBS method, possible ways of the analysis, standardization of emission signals and its review in the literature. The experimental part is aimed at the study of the acoustic signal that was performed in the framework of this study. At the beginning, there are introduced results of the basic measurements on steel and brass samples. These results were important for an optimization of the experiment. The following section shows the results obtained from the measurements of the acoustic signal on the samples with the same chemical composition but different hardness. At the end the correlation between the acoustic and emission signals is discussed.

This diploma thesis deals with evaluation of toxicity and bioaccumulation of photon-upconversion nanoparticles (UCNPs) in model plant maize (Zea mays). Lanthanide-doped UCNPs with different composition and size were tested in three different concentrations in this work. The exposure took place for 168 hours. Toxicity was assessed based on four macroscopic toxicological endpoints (mortality, the length of belowground part of the plants, the length of aboveground part of the plants and whole plants length). Spatial distribution of elements yttrium, ytterbium, erbium and gadolinium in model plants was determined using laser induced breakdown spectroscopy with spatial resolution of 100 m and 26 m. Distribution of UCNPs in plants was further studied with photon-upconversion microscanning with spatial resolution of 40 m. Stability of UCNPs during and after the plant exposure was also discussed in this thesis.

The presented diploma thesis deals with the elemental composition of hard tissues – human and murine jaws studied by laser-induced plasma spectroscopy (LIBS). Samples of human teeth contained a disease called ankylosis and the difference in elemental composition of healthy and diseased tissue was observed to localize ankylosis in the tooth. When evaluating the map of the spatial distribution of phosphorus and calcium, a decrease in the concentration of these elements in the ankylosis infected area was observed. Furthermore, murine jaws containing lead were analyzed. When assessing the spatial distribution of lead in tissue, it was found that lead was incorporated in murine teeth in the enamel at the tip of the incisor and molars. In conclusion, LIBS method achieved good results considering the detection of the elemental distribution of hard tissues. It enables to differentiate parts of the tooth in terms of elemental composition and tissue hardness and also to detect changes in the matrix caused by a disease or bioaccumulation of heavy metals.

The thesis studies detection of fluorescein for coloration experiments in surface and underground water. The first part of the work deals with the adsorption of fluorescein on active charcoal from water and desorption by means of different desorption solutions. The results of measurements are used for practice of coloration experiments in karst research. In the second part of thesis it is researched the option of automated record of fluorescence concentration and its detection by means of laser induced fluorescence with confocal microscope.