abstract: In this work, I worked on the synthesis and characterization of nanowires and belts, grown using different materials, in Chemical Vapor Deposition (CVD) system with catalytic growth method. Through this thesis, I utilized the Photoluminescence (PL), Secondary Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) analyses to find out the properties of Erbium Chloride Silicate (ECS) and two segment CdS-CdSe samples. In the first part of my research, growth of very new material, Erbium Chloride Silicate (ECS), in form of core/shell Si/ECS and pure ECS nanowires, was demonstrated. This new material has very fascinating properties for new Si based photonic devices. The Erbium density in those nanowires is which is very high value compared to the other Erbium doped materials. It was shown that the luminescence peaks of ECS nanowires are very sharp and stronger than their counterparts. Furthermore, both PL and XRD peaks get sharper and stronger as growth temperature increases and this shows that crystalline quality of ECS nanowires gets better with higher temperature. In the second part, I did a very detail research for growing two segment axial nanowires or radial belts and report that the structure type mostly depends on the growth temperature. Since our final step is to create white light LEDs using single axial nanowires which have three different regions grown with distinct materials and give red, green and blue colors simultaneously, we worked on growing CdS-CdSe nanowires or belts for the first step of our aim. Those products were successfully grown and they gave two luminescence peaks with maximum 160 nm wavelength separation depending on the growth conditions. It was observed that products become more likely belt once the substrate temperature increases. Also, dominance between VLS and VS is very critical to determine the shape of the products and the substitution of CdS by CdSe is very effective; hence, CdSe growth time should be chosen accordingly. However, it was shown two segmented products can be synthesized by picking the right conditions and with very careful analyses. We also demonstrated that simultaneous two colors lasing from a single segmented belt structures is possible with strong enough-pumping-power. / Dissertation/Thesis / M.S. Electrical Engineering 2012

We study heat transfer in one dimension with and without convection, also called advection-diffusion. This is done using the Finite Element Method (FEM) to discretise the mathematical model, i.e. the heat equation. The results are compared to analytic Fourier series solutions. Our main result is that the FEM could be used to better model the heat transfer which allow for more accurate models than today's use of steady state models.

One-dimensional (1D) nanomaterials are of great importance for a number of potential applications. However, in order to realize this potential a thorough understanding of the charge-carrier dynamics in these materials is required, since these largely determine the optoelectronic properties of the materials in question. This thesis investigates the charge-carrier dynamics of two 1D nanomaterials, single-walled carbon nanotubes (CNTs) and tungsten-oxide nanowires (WOxNWs), with the goal of better understanding the nature of their optoelectronic responses, and how nanomaterial geometry and morphology influence these responses. We do this using terahertz time-domain spectroscopy (THz-TDS) and optical pump - terahertz probe time-domain spectroscopy (OPTP). Firstly, we discuss how to properly analyse and interpret the data obtained from these experiments when measuring 1D nanomaterials. While the data obtained from THz-TDS is fairly straight-forward to analyse, OPTP experimental data can be far from trivial. Depending on the relative size of the sample geometry compared to the probe wavelength, various approximations can be used to simplify the extraction of their ultrafast response. We present a general method, based on the transfer matrix method, for evaluating the applicability of these approximations for a given multilayer structure, and show the limitations of the most commonly used approximations. We find that these approximations are only valid in extreme cases where the thickness of the sample is several orders of magnitude smaller or larger than the wavelength, which highlight the danger originating from improper use of these approximations. We then move on to investigate how the charge-carrier dynamics of our CNTs is influenced by nanotube length and density. This is done through studying the nature of the broad THz resonance observed in finite-length CNTs, and how the nanotube length and density affects this resonance. We do this by measuring the conductivity spectra of thin films comprising bundled CNTs of different average lengths in the frequency range 0.3-1000 THz and temperature interval 10-530 K. From this we show that the observed temperature-induced changes in the terahertz conductivity spectra depend strongly on the average CNT length, with a conductivity around 1 THz that increases/decreases as the temperature increases for short/long tubes. This behaviour originates from the temperature dependence of the electron scattering rate, which results in a subsequent broadening of the observed THz conductivity peak at higher temperatures and a shift to lower frequencies for increasing CNT length. Finally, we show that the change in conductivity with temperature depends not only on tube length, but also varies with tube density. We record the effective conductivities of composite films comprising mixtures of WS2 nanotubes and CNTs vs CNT density for frequencies in the range 0.3-1 THz, finding that the conductivity increases/decreases for low/high density films as the temperature increases. This effect arises due to the density dependence of the effective length of conducting pathways in the composite films, which again leads to a shift and temperature dependent broadening of the THz conductivity peak. Next, we investigate the conflicting reports regarding the ultrafast photoconductive response of films of CNTs, which apparently exhibit photoconductivities that can vastly differ, even in sign. Here we observe explicitly that the THz photoconductivity of CNT films is a highly variable quantity which correlates with the length of the CNTs, while the specific type of CNT has little influence. Moreover, by comparing the photo-induced change in THz conductivity with heat-induced changes, we show that both occur primarily due to heat-generated modification of the Drude electron relaxation rate, resulting in a broadening of the plasmonic resonance present in finite-length metallic and doped semiconducting CNTs. This clarifies the nature of the photo-response of CNT films and demonstrates the need to carefully consider the geometry of the CNTs, specifically the length, when considering them for application in optoelectronic devices. We then move on to consider our WOxNWs. We measure the terahertz conductivity and photoconductivity spectra of thin films compromising tungsten-oxide (WOx) nanowires of average diameters 4 nm and 100 nm, and oxygen deficiencies WO2.72 and WO3 using THz-TDS and OPTP. From this we present the first experimental evidence of a metal-to-insulator transition in WOx nanowires, which occurs when the oxygen content is increased from x=2.72 -> 3 and manifests itself as a massive drop in the THz conductivity due to a shift in the Fermi level from the conduction band down into the bandgap. Furthermore we present the first experimental measurements of the photoexcited charge-carrier dynamics of WOx nanowires on a picosecond timescale and map the influence of oxygen-content and nanowire diameter. From this we show that the decay-dynamics of the nanowires is characterized by a fast decay of < 1 ps, followed by slow decay of 3-10 ps, which we attribute to saturable carrier trapping at the surface of the nanowires.

La contraction périodique du coeur est à l’origine de l’onde de pouls qui, de part son interaction avec les artères élastiques, le sang et le réseau artériel lui-même, devient le signal observé quotidiennement par les médecins. Cette dynamique ondulatoire est d’une importance primordiale dans la compréhension de la genèse de nombreuses maladies cardiovasculaires. En effet, ce sont souvent des facteurs hémodynamiques qui sont à l’origine de la croissance de ces pathologies. Malheureusement, les mesures non-invasives et l’imagerie médicale sont souvent insuffisantes pour appréhender la complexité des écoulements sanguins. La simulation numérique est donc en plein essor car celle-ci permet d’obtenir des données précises dans des régions vasculaires difficiles d’accès. Bien que les modèles sanguins tridimensionnels soient très précis et permettent de reproduire fidèlement la géométrie vasculaire, leur coût, à la fois numérique et paramétrique, est trop important pour que ceux-ci soient utilisés dans de grands réseaux vasculaires. Nous avons donc choisi d’utiliser des modèles simplifiés qui permettent d’accéder à cette dynamique de réseau si importante. Premièrement, nous nous sommes intéressés aux modèles unidimensionnels et nous avons développé de nouvelles approches permettant de prendre en compte l’aspect non-Newtonien du sang et la viscoélasticité des parois artérielles. Secondement, nous avons proposé un modèle bidimensionnel, que nous avons utilisé pour simuler l’écoulement dans des sténoses et anévrismes. Finalement, nous avons utilisé ces modèles pour décrire l’écoulement du sang dans de grands réseaux artériels et pour optimiser un pontage extracorporel. / Every cardiac cycle, the heart contracts and ejects blood into the vascular network. This periodic inflow translates into the propagation of a pulse wave, which, through interactions with the elastic arterial wall, the blood and the complex arterial network, shapes itself into the pulsatile signal clinicians observe on a daily basis. Understanding these complex wave propagation dynamics is of great clinical relevance as large arteries are a breeding ground for many common cardiovascular pathologies which are often triggered by hemodynamical factors. Unfortunately, hemodynamics in large arteries are too complex to be apprehended using only non-invasive measurements and medical imaging techniques. Patient-specific numerical simulations of blood flow have therefore been developed to provide clinicians with valuable insights on pathogenesis and the outcome of surgeries. As three-dimensional models are usually used only in small portions of the cardiovascular system due to their high modeling and computational costs, we have used reduced-order models to reproduce complex wave propagation behaviors in large networks of arteries. We have first focused on one-dimensional models for blood flow and developed novel approaches that take into account the non-Newtonian behavior of blood and the viscoelastic response of the arterial wall. Next, we have proposed a fluid-structure interaction twodimensional blood flow model to capture the complex flow patterns in stenoses and aneurysms unavailable to classical one-dimensional models. Finally, we have applied these models to compute the flow in large arterial networks and to predict the outcome of bypass surgeries.

Dicelis, G. E., Estudo Integrado da Camada de Basalto em Bebedouro SP, Bacia do Paraná: Relocalização dos sismos induzidos por poços tubulares, 2011. Dissertação de Mestrado Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, SP. A partir de 2004, a população do distrito de Andes, Bebedouro (SP), passou a sentir pequenos tremores de terra. Uma rede sismográfica instalada em 2005 mostrou que os sismos locais são induzidos por poços tubulares profundos usados para irrigação de lavouras (Assumpção et al., 2007). Neste projeto de pesquisa foi melhorada a localização desses sismos, usando análise da forma de onda e os tempos de chegada das ondas P e S, com o propósito de efetuar uma melhor análise da sismicidade induzida. Para isto foram aproveitados resultados de estudos anteriores como sísmica de refração, dispersão de ondas de superfície, sondagem elétrica vertical, função do receptor e TDEM. Para obter o melhor modelo de velocidades 1D, foram testados diferentes algoritmos de localização e técnicas de relocalização de hipocentros, para aproximadamente 3000 microtremores gravados pela rede sismográfica no período 2005 2010. Os resultados mostraram que as profundidades focais dos sismos relocalizados ficaram em sua maioria dentro da camada de basalto, a menos de 500m de profundidade. Este resultado confirma que os sismos estão relacionados com a perturbação do equilíbrio de tensões (pressões) geológicas, em zonas de fraturas já existentes dentro da camada de basalto. Foi usada uma combinação de correlação cruzada e tempos de chegada para analisar um conjunto de sismos, baseada na similaridade dos seus sismogramas. Foi melhorada a distribuição hipocentral o que permitiu determinar claramente uma solução do plano focal de um cluster, o que indicou a existência de uma falha normal de orientação WNW-ESSE e mergulho para o norte, com extensão NNE-SSW (eixo-T). Este mecanismo pode complementar os dados de esforços na região sudeste. / Dicelis, G. E., Integrated Study of the basalt layer in Bebedouro SP, Paraná Basin: Relocation of earthquakes induced by wells, 2011. Master dissertation - Institute of Astronomy, Geophysics and Atmospheric Sciences of the University of Sao Paulo, Brazil. Since 2004 the population of the district of Andes, Bebedouro SP, began to feel small earthquakes. A seismograph network installed in 2005 showed that earthquakes are caused by local deep wells used for irrigation of crops (Assumpção et al., 2007). In this research project we improved the location of these earthquakes, using analysis of waveform and the arrival times of P and S waves, in order to make a better analysis of the induced seismicity. To better relocate the events we determined a velocit model using results of previous studies such as seismic refraction, surface wave dispersion, vertical electrical sounding, receiver function and TDEM. The best fit 1D model was achieved testing different localization algorithms and techniques for relocation of hypocenters for approximately 3000 microtremors recorded by seismograph network to the period 2005 2010. The results showed that the focal depths of the relocated earthquakes are mostly within the basalt layer, less than 500m depth. This confirms that the earthquakes are related with disturbance of geological stresses (pressures) in pre-existing fracture zones within the basalt layer. We used a combination of cross-correlation and arrival times for analyze a set of earthquakes, based on the similarity of their recorded seismograms. The hypocentral distribution was improved allowing a clear determination of the best fit fault plane solution for one cluster, which indicates the existence of a normal fault with direction WNW-ESE and dip to the north, with NNE-SSW extension (T-axis). This mechanism may complement the stress data in the Southeast Brazil.

Pseudorandom sequences have many applications in fields such as wireless communication, cryptography and built-in self test of integrated circuits. Maximal length sequences (m-sequences) are commonly employed pseudorandom sequences because they have ideal randomness properties like balance, run and autocorrelation. However, the linear complexity of m-sequences is poor. This thesis considers the use of one-dimensional Cellular Automata (CA) to generate pseudorandom sequences that have high linear complexity and good randomness. The properties of these sequences are compared with those of the corresponding m-sequences to determine their suitability. / Graduate

L'aorte conduit le sang oxygéné aux organes et amortit l'onde pulsatile cardiaque. Au cours du vieillissement, elle est exposée à des altérations hémodynamiques et à une rigidité augmentée, elle-même associée à la mortalité.L'objectif de ma thèse est de proposer, à partir de l'IRM et des simulations, des indices non-invasifs de l'hémodynamique aortique locale, qui soient simples, rapides et complémentaires aux indices IRM de géométrie et de fonction aortiques établis.Un premier volet est consacré au développement et la personnalisation d'un modèle 1D de l'aorte descendante, validé qualitativement et quantitativement avec des données IRM sur 7 sujets, afin d'extraire des paramètres de pression, vitesse et surface.Un second volet, dédié aux données IRM, est centré sur :la comparaison de 7 méthodes d'évaluation de la pulsatilité aortique et leur validation avec la référence sur 70 sujets sainsla quantification du flux réverse aortique et l'étude de sa variation avec l'âge, ainsi que l'identification de ses déterminants sur 96 sujets sainsl'estimation automatique d'indices hémodynamiques de la sténose valvulaire aortique (SVA) et leur comparaison à l'échocardiographie Doppler sur 53 patients avec une SVA et 21 contrôles.Ainsi, le modèle aortique pourrait aider à identifier les déterminants des altérations aortiques et à consolider les observations in vivo. Par ailleurs, les outils mis au point pour l'analyse reproductible des données d'IRM fournissent des indices caractéristiques du vieillissement, qui pourraient être étudiés vis-à-vis des organes cibles (coeur, cerveau, rein, etc.) dans les pathologies cardiovasculaires (hypertension artérielle, drépanocytose). / The aorta conducts oxygenated blood to organs and also cushions the cardiac pulse wave. Such artery is exposed to age-related hemodynamic alterations and increased stiffness, which is associated with mortality. The objective of my PhD thesis is to propose, using MRI and numerical simulations, non-invasive indices of local aortic hemodynamics, which would be simple, fast and complementary to established aortic geometry and function MRI indices. A first work aims at developing and personalizing a 1D model of the descending aorta, as well as validating such model both qualitatively and quantitatively against MRI data acquired in 7 subjects, to eventually extract pressure, velocity and area parameters. A second work, which is based on MRI data, focuses on: the comparison of 7 methods for the evaluation of aortic pulsatility and their validation against the reference method in 70 healthy subjects, the quantification of aortic reverse flow and its variation with age, as well as the identification of its prime determinants in 96 healthy subjects, : the automated estimation of hemodynamic indices in aortic valve stenosis (AVS) as well as their comparison with the reference Doppler echocardiography, in 53 patients with AVS and 21 controls. Thus, the aortic model could help to identify determinants of aortic alterations and to strengthen in vivo observations. Besides, software tools developed for the reproducible analysis of MRI data provide indices that are characteristic of aging, and which could be studied in relation to end-target organs damage (heart, brain, kidney, etc.) in the setting of cardiovascular pathologies (hypertension, sickle cell disease).

The current global scenario, in which an ever increasing population with an ever growing transportation needs is coupled with a reduction in the fossil fuel production and increasing human-made pollution derived problems, leads automotive engine manufacturers to constant struggles for fuel consumption and emission reductions while keeping engine performance. One-dimensional simulation codes have become a key tool towards these objectives, but require continued accuracy refinements. Phenomena that were previously thought of a limited importance and could be extremely easily modelled now require the development of new methods to be accounted for. Among these phenomena are the turbocharger mechanical losses and the turbine behaviour under highly pulsating boundary conditions. This work is focused on the improvement of current one-dimensional models, for both mechanical losses prediction and high frequency pulsating flow turbine performance. After reviewing the state-of-the-art in experimental measurement and fast simulation of automotive turbochargers, this work presents first a experimental study of several turbochargers working under both steady-state and unsteady operating conditions, focusing on the general performance of the turbine and the losses in the power transmission between it and the compressor, even including internal pressure measurements in one of the tested units. All the measurements are corrected due to heat transfer, getting the purely adiabatic behaviour. Furthermore, a CFD simulation campaign of a radial turbine has been performed, thus obtaining a detailed description of its internal behaviour under highly pulsating flow. In the light of both the experimental and CFD-simulated results, a quasi-steady mechanical losses and a quasi-bidimensional turbine model have been developed. Both models have been validated using all the experimental and simulated data, proving a prediction accuracy improvements from the results of previous methods. The mechanical losses model offers a clear advantage over the usual practice of using a constant mechanical efficiency value for correcting the manufacturer’s turbocharger map, whereas the turbine model has demonstrated potential for turbine map extrapolation and has improved the instantaneous results over classic onedimensional turbine volute models for frequencies higher than 1000 Hz. Both models have been developed trying to keep a reduced computational cost, ensuring to exploit the specific characteristics of the processors where they are going to be run. / García-Cuevas González, LM. (2014). Experiments and Modelling of Automotive Turbochargers under Unsteady Conditions [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48458 / TESIS

The diploma thesis deals with the proposal of measures on the Svratka stream in the cadastral area Český Herálec and Herálec na Moravě. The aim of the diploma thesis is to propose appropriate flood protection in the Herálec urban area and to elaborate proposals of nature friendly measures outside the municipality’s built up area, which will enable the renewal of the ecological functions of Svratka in the spring area. In the diploma thesis the assessment of the current state of the watercourse in the analyzed locality was caried out and also the assessment of the capacity of the watercourse and the objects on there. Furthermore, the flood levels and its areas were determined. Hydraulic water flow calculations were performed using the 1D and 1D/2D numerical model. For calculation, HEC-RAS 5.0.3 was used. When processing a 1D/2D numerical model, a manual describing the progress of work in the HEC-RAS 5.0.3 program was also created. On the basis of the results from the numerical model, a proposal for flood protection measures in the urban area and nature friendly measures in the extravilan was carried out.

The master’s thesis deals with the hydraulic analysis of the water flow capacity for the flood flow on the river Litava in the river kilometres 11,550 – 18,315 using the HEC-RAS 5.0.5 specifically 1D-2D numerical model. On the basic of flood areas, depths and speeds the results were evaluated and subsequently was created own proposal flood protection.