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Σκοπός της εργασίας αυτής είναι να αναδείξει την σπουδαιότητα του ΔΛΠ 7 για τις Ταμειακές Ροές στην χρηματοοικονομική ανάλυση καθώς επίσης να παραθέσει μια καταγραφή της διεθνής έρευνας σχετικά με το πληροφοριακό περιεχόμενο των Ταμειακών Ροών. Εν συνεχεία γίνεται μια προσπάθεια να αποτιμηθεί η χρησιμότητα των Ταμειακών Ροών από Λειτουργικές, Επενδυτικές και Χρηματοοικονομικές Δραστηριότητες και δίνεται ένα παράδειγμα εμπέδωσης της Κατάστασης Ταμειακών Ροών με την άμεση και την έμμεση μέθοδο. Στην εμπειρική έρευνα, αναλύονται δεδομένα από το Χρηματιστήριο Αθηνών την περίοδο 2005-2007 με έμφαση στα Κέρδη προ Φόρων και στις Λειτουργικές Ταμειακές Ροές. Ειδικότερα εξετάζεται συσχέτιση στα πρόσημα των δύο μεταβλητών με το πρόσημο των αποδόσεων των μετοχών. Τέλος, εξετάζεται η προβλεπτική ικανότητα των Ταμειακών Ροών από Λειτουργικές Δραστηριότητες στα μελλοντικά κέρδη προ φόρων. / Purpose of this assignment is to highlight the importance of the IAS 7 for the Cash Flows Statements on the financial analysis as well to quote a notation of the international research for the “value relevance” of the Cash Flows. In addition to this, there is an attempt to evaluate the usefulness of the Cash Flows from Operating, Investing and Financial Activities and an example of Cash Flow Statement reporting with direct and indirect method is given. In the empirical research, data from the Stock market of Athens for the period of 2005-2007 is analyzed with emphasis to Earnings before Taxes and the Cash Flows from Operating Activities. Specifically a correlation among the operator of the above figures with the operator of the stock returns is examined. In the final part it is investigated the predicted capability of the Cash Flows from Operating Activities to future earnings before taxes.

We investigate flows generated by bacteria near boundaries which are ubiquitous in biological systems. A bacterium such as \textit{Escherichia coli} is equipped with a number of rotary motors on its surface. Every motor has a helical flagellum attached to it and by rotating these motors the bacterium can move the fluid. We consider these flows in four different systems. Firstly, we explore a chiral flow which is always in the clockwise direction (when viewed from above) ahead of a dense suspension of bacteria on a moist surface. We quantitatively test a hypothesis that this flow is due to the action of cells stalled at the edge of a colony which extend their flagella outwards, moving fluid over a substrate. The model provides insight on the flagella orientations and their spatial distributions. Secondly, inspired by experiments which proposed to use confined bacteria in order to generate flows near surfaces, we develop a theoretical model of this fluid transport using a superposition of fundamental flow singularities. The rotation of a helical bacterial flagellum induces both a force and a torque on the surrounding fluid, both of which lead to a net flow along the surface. We investigate the optimal helical shapes to be used as micropumps near surfaces and show that bacterial flagella are nearly optimal. Thirdly, we build a theoretical model on a reorientation of peritrichous bacteria at the edge of a liquid drop on a Petri dish. Bacteria are more likely to turn clockwise because of the interaction between counterclockwise rotating flagella and boundaries which causes them to self-organise and circle clockwise (when viewed from above) around the outer edge of the colony. Finally, motivated by problems in biological physics occurring near corners, we derive the asymptotic behaviour for the Stokeslet (a flow due to a point force at low Reynolds number) both near and far from a corner geometry by using complex analysis on a known double integral solution for corner flows. We analyse flows in acute, obtuse and salient three-dimensional corners. We also use experiments on beads sedimenting in corn syrup to qualitatively test our results. The fundamental understanding of Stokes flows near boundaries is important for future developments in biophysics and bioengineering including applications to bacterial micropumps, steering microswimmers near corners, and preventing biofilm formation.

Tesis para optar al grado de Magíster en Finanzas / This paper investigates the e ect of capital ows shocks such as Sudden Stops on industry level data and how the di erent sources of external nance can imply di erent outcomes.

Dans le but d’améliorer le rendement des propulseurs aérospatiaux, on s’intéresse à l’utilisation de ladétonation dans le cycle moteur. Cette thèse porte sur le développement et l’utilisation d’un codepour la compréhension du fonctionnement d’un moteur à détonation continue (CDWE). Le 1erchapitre place le cadre de l’étude, et positionne le CDWE par rapport à différents concepts demoteurs à détonation. Un état des lieux des simulations numériques concernant le fonctionnementd’un CDWE est établi afin de justifier l’approche numérique à utiliser. Cette approche numérique estdétaillée dans le 2e chapitre. Les équations d’Euler, les modèles thermochimiques, ainsi que lesschémas cinétiques utilisés dans cette étude y sont présentés. Le 3e chapitre décrit les méthodesnumériques implémentées dans le code. Le schéma WENO d’ordre 5 est utilisé pour l’évaluation desflux numériques. L’avancement temporel est assuré par le schéma semi-implicite d’ordre 2 ASIRK2Cou explicite d’ordre 3 RK3. Le 4e chapitre est consacré à la technique de raffinement adaptatif demaillage (AMR) et à la bibliothèque choisie. Le code est testé dans le 5e chapitre sur différents cas etappliqué à la simulation d’une onde de détonation afin de préparer les simulations présentées dans ledernier chapitre. Le 6e chapitre présente les résultats des simulations d’un CDWE. La structure 2Dd’une onde de détonation continue est présentée et comparée avec la structure 3D. L’influence durayon de courbure du canal et l’effet d’une injection par une fente sur la structure de l’écoulementsont étudiés. / In order to improve the performance of aerospace propulsion systems, it is interesting to use detonation in the engine cycle. This thesis focuses on the development and use of a code for understanding the operation of a continuous detonation wave engine (CDWE). The first chapter establishes the framework of the study and compares the CDWE with different concepts of detonation engines. An overview of numerical simulations concerning the operation of a CDWE is made to justify the numerical approach to use. This numerical approach is detailed in the second chapter. The Euler equations, thermochemical models and kinetic mechanisms used in this study are presented. The third chapter describes the numerical methods implemented in the code. The 5th order WENO scheme is used for the evaluation of numerical fluxes. The time-stepping is provided by the 2nd order semi-implicit ASIRK2C scheme or the 3rd order explicit RK3 scheme. The fourth chapter describes the technique of adaptive mesh refinement (AMR) and the selected library. The code is tested in the fifth chapter on different cases and applied to the simulation of a detonation wave in order to prepare the simulations presented in the last chapter. The sixth chapter presents the results of simulations of a CDWE. The 2D structure of a continuous detonation wave is presented and compared with the 3D structure. The influence of the radius of the curvature of the duct and the effect of a slot injection on the structure of the flowfield are discussed.

Lava flows are common at volcanoes around the world and on other terrestrial planets, but their behavior is not fully understood. In Hawai`i, advances in remote sensing are offering new insights into lava flow emplacement. In this dissertation, I develop new techniques using satellite-based synthetic aperature radar, aerial photographs, and airborne lidar to produce three-dimensional high-resolution maps of lava flows from data collected before, during, and after emplacement. These new datasets highlight complex lava channel networks within these flows, which are not incorporated into current predictive or probabilistic lava flow models yet may affect flow behavior. I investigate the origin and influence of these channel networks through morphologic analysis of underlying topography, network topology, and flow morphology and volume. Channel network geometries range from distributary systems dominated by flow branching around local obstacles to tributary systems constricted by topography. I find that flow branching occurs where the flow thins over steeper slopes and that the degree of flow branching, network connectivity, and longevity of flow segments all influence the final flow morphology. Furthermore, because channel networks govern the distribution of lava supply within a flow, changes in the channel topology can dramatically alter the effective volumetric flux in any one branch, which affects both flow length and advance rate. Specifically, branching will slow and shorten flows, while merging can accelerate and lengthen them. To test these observations from historic eruptions and morphologic analysis, I use analogue experiments to simulate the interaction of a lava flow with a topographic obstacle and determine the conditions under which the flow branches and the effects of the bifurcation on flow advance rate. These experiments support the earlier results but also demonstrate the importance of flow dynamics and obstacle morphology on governing when flows may overtop obstacles. Consideration of channel networks is thus important for predicting lava flow behavior and mitigating flow hazards with diversion barriers. One video of Kilauea lava flow activity from 2003-2010 accompanies this dissertation as a supplemental file. This dissertation includes both previously published and unpublished co-authored material.

No description available.

Today’s aerospace industry continues to exploit liquid hydrocarbon fossil fuels. Motivated by operational considerations, continued availability and cost, this is likely to be the case for many years, despite the obvious environmental concerns. The interplay of liquid atomisation, spray vaporisation and the combustion process are intricately linked. However, the physical process of fuel injection and its atomisation into tiny droplets prior to combustion remains poorly understood. Because atomisation governs the size of the fuel droplets, and therefore their subsequent evaporation rate, adjusting the injection sequence is of paramount importance and will have far-reaching repercussions on many aspects of the combustion process, for example pollutant formation. In the context of jet engines, kerosene is usually injected in its liquid form via an airblast-type fuel injector. A coflowing high-speed airstream destabilises the liquid fuel, which is thus sprayed into fine droplets into the combustion chamber. The prediction of this phenomenon for various operating conditions relevant to the aeronautical industry requires a deeper understanding of the mechanisms involved in the interaction of the two fluids. A key element in predicting the complex behaviour of spray formation and evolution in jet engines is accurate modelling of fuel atomisation. Atomisation represents one of the key challenges that remains to be undertaken to make predictive computational simulations possible. However, the inherent multi-physics and multi-scale nature of this process limits numerical investigations. Thanks to the steady progress in computer power and Computational Fluid Dynamics (CFD) methods, computational modelling of injection systems emerges as a promising tool that can drive the design of future devices. This research project sets out to investigate the atomisation process in detail, in particular in providing physical insight into the fundamental physics of the phenomenon, in conjunction with an analysis on wetting behaviours and liquid droplet tracking. High-fidelity numerical simulations are performed using a novel in-house state-of-the-art multiphase flow modelling capability, RCLSFoam. The performance of the numerical scheme is demonstrated on typical two-dimensional and three-dimensional benchmark test cases relevant to both multiphase flow modelling and atomisation, and validated against other computational methods. An informed and systematic qualitative assessment of the topological variations of the phase interface during primary atomisation of a liquid film is made through dynamical analysis, while investigating an extensive domain of operating conditions at ambient and aero-engine injection conditions relevant to industry. This analysis demonstrated the influence of shear-driven instabilities on the atomisation process. The shear stress and difference in inertia between liquid and gas are observed to play a significant role in the atomisation process. In addition, the key physical mechanisms and their competing effects have been mapped out in order to predict the evolution of the process according to the operating conditions of the injection system. The proposed cartography gathers four different atomisation mechanisms. In particular, for sufficiently high liquid injection speeds, three-dimensional wave modes were observed to co-exist (the “3-D wave mode” regime). For very low liquid flow rates, accumulated liquid at the atomising edge undergoes deformation by which droplets are generated (the “accumulation” regime). For an increasing gas injection speed and a fixed liquid velocity, the effects of surface tension were observed to result in the generation of streamwise ligaments only, which tend to pair up (the “ligament-merging” regime). Finally, “vortex action” is another observed mechanism by which the liquid film is fragmented. Overall, this research project culminated in (i) the study of dynamic wetting behaviours, with the implementation and validation against experimental data of the Kistler dynamic contact model; and (ii) the demonstration of an algorithm for droplet capture and subsequent post-processing analysis of the droplet characteristics.

abstract: The three-dimensional flow contained in a rapidly rotating circular split cylinder is studied numerically solving the Navier--Stokes equations. The cylinder is completely filled with fluid and is split at the midplane. Three different types of boundary conditions were imposed, leading to a variety of instabilities and complex flow dynamics. The first configuration has a strong background rotation and a small differential rotation between the two halves. The axisymmetric flow was first studied identifying boundary layer instabilities which produce inertial waves under some conditions. Limit cycle states and quasiperiodic states were found, including some period doubling bifurcations. Then, a three-dimensional study was conducted identifying low and high azimuthal wavenumber rotating waves due to G\"ortler and Tollmien–-Schlichting type instabilities. Over most of the parameter space considered, quasiperiodic states were found where both types of instabilities were present. In the second configuration, both cylinder halves are in exact counter-rotation, producing an O(2) symmetry in the system. The basic state flow dynamic is dominated by the shear layer created in the midplane. By changing the speed rotation and the aspect ratio of the cylinder, the flow loses symmetries in a variety of ways creating static waves, rotating waves, direction reversing waves and slow-fast pulsing waves. The bifurcations, including infinite-period bifurcations, were characterized and the flow dynamics was elucidated. Additionally, preliminary experimental results for this case are presented. In the third set up, with oscillatory boundary conditions, inertial wave beams were forced imposing a range of frequencies. These beams emanate from the corner of the cylinder and from the split at the midplane, leading to destructive/constructive interactions which produce peaks in vorticity for some specific frequencies. These frequencies are shown to be associated with the resonant Kelvin modes. Furthermore, a study of the influence of imposing a phase difference between the oscillations of the two halves of the cylinder led to the interesting result that different Kelvin modes can be excited depending on the phase difference. / Dissertation/Thesis / Doctoral Dissertation Applied Mathematics 2017

Comment appréhender le sens socio-politique de l'officialisation de la catégorie d'inspiration démographique « immigré » dans le cadre du lancement de la politique d'intégration au début des années 1990 ? Telle est question à laquelle cette thèse s'efforce de répondre au travers d'une sociologie foucaldienne de la quantification de l'immigration en tant que population. Ce travail en vient ainsi notamment à formuler l'hypothèse selon laquelle l'enrôlement du savoir démographique participe, dans le cadre du travail de réorganisation de la production des statistiques publiques en matière d'immigration entrepris entre 1990 et 1997 au sein du groupe « Statistiques » attaché au HCI (Haut Conseil à l'intégration), à la formalisation statistique d'une représentation cognitive de l'immigration en tant que séries d'agrégats totalisés et temporalisés d'individus par et dans leur mobilité juridico-légale. Replaçant notamment le processus de mise en catégorie de l'« immigré » en vis-à-vis de l'élaboration d'une méthode comptable de mesure des flux annuels d'immigrations et des tentatives de pré-formater l'exploitation d'AGDREF (Application nationale pour la gestion des dossiers des ressortissants étrangers en France du ministère de l'Intérieur), cette recherche suppose et propose de substituer à l'analyse du processus socio-historique d'objectivation du critère de l'« origine », celle des logiques dispositives de sécurisation (statistique) des flux. / What is the socio-political meaning of the category of “immigrant” that the French integration policy officialised in 1990? The thesis uses a foucaldian sociology of quantification of immigration as a population to answer this question. The mobilization of a demographic knowledge, in the context of the reform of immigration statistics by the “Statistic” Group of the HIC between 1990 and 1997, leads to the formalization of a cognitive representation of immigration, as series of totalized and temporalized aggregates of individuals, from and in their juridical and legal mobility. In particular, we compare the process of categorization of the “immigrant” to a calculative method measurement of annuals flows of immigrations, as well as to the attempts to format the processing of AGDREF. This allows to switch from the analysis of socio-historical processes that objectivates the “origin” criteria, to an analysis in terms of (statistical) securitization of flows.