A significant amount of Viscous Oil (e.g., heavy oil, extra heavy oil, and bitumen) is trapped in Naturally Fractured Carbonate Reservoirs also known as NFCRs. The word VO endowment in NFCRs is estimated at ~ 2 Trillion barrels mostly reported in Canada, the USA, Russia, and the Middle East. To date, contributions to the world daily oil production from this immense energy resource remains negligible mainly due to the lack of appropriate production technologies. Implementation of a VO production technology such as steam injection is expensive (high capital investment), time-consuming, and people-intensive. Hence, before selecting a production technology for detailed economic analysis, use of cursory or broad screening tools or guides is a convenient means of gaining a quick overview of the technical feasibility of the various possible production technologies applied to a particular reservoir. Technical screening tools are only available for the purpose of evaluation of the reservoir performance parameters in oil sands for various thermal VO exploitation technologies such as Steam Assisted Gravity Drainage (SAGD), Cyclic Steam Stimulation (CSS), Horizontal well Cyclic steam Stimulation (HCS), and so on. Nevertheless, such tools are not applicable for VO NFCRs assessment without considerable modifications due to the different nature of these two reservoir types (e.g., presence and effects of fracture network on reservoir behavior, wettability, lithology, fabric, pore structure, and so on) and also different mechanisms of energy and mass transport. Considering the lack of robust and rapid technical reservoir screening tools for the purpose of quick assessment and performance prediction for VO NFCRs under thermal stimulation (e.g., steamflooding), developing such fast and precise tools seems inevitable and desirable. In this dissertation, an attempt was made to develop new screening tools for the purpose of reservoir performance prediction in VO NFCRs using all the field and laboratory available data on a particular thermal technology (vertical well steamflooding). Considering the complex and heterogeneous nature of the NFCRs, there is great uncertainty associated with the geological nature of the NFCRs such as fracture and porosity distribution in the reservoir which will affect any modeling tasks aiming at modeling of processes involved in thermal VO production from these types of technically difficult and economically unattractive reservoirs. Therefore, several modeling and analyses technqiues were used in order to understand the main parameters controlling the steamflooding process in NFCRs and also cope with the uncertainties associated with the nature of geologic, reservoir and fluid properties data. Thermal geomechanics effects are well-known in VO production from oil sands using thermal technologies such as SAGD and cyclic steam processes. Hence, possible impacts of thermal processes on VO NFCRs performance was studied despite the lack of adequate field data. This dissertation makes the following contributions to the literature and the oil industry: Two new statistical correlations were developed, introduced, and examined which can be utilized for the purpose of estimation of Cumulative Steam to Oil Ratio (CSOR) and Recovery Factor (RF) as measures of process performance and technical viability during vertical well steamflooding in VO Naturally Fractured Carbonate Reservoirs (NFCRs). The proposed correlations include vital parameters such as in situ fluid and reservoir properties. The data used are taken from experimental studies and also field trials of vertical well steamflooding pilots in viscous oil NFCRs reported in the literature. The error percentage for the proposed correlations is < 10% for the worst case and contains fewer empirical constants compared with existing correlations for oil sands. The interactions between the parameters were also considered. The initial oil saturation and oil viscosity are the most important predictive factors. The proposed correlations successfully predicted steam/oil ratios and recovery factors in two heavy oil NFCRs. These correlations are reported for the first time in the literature for this type of VO reservoirs. A 3-D mathematical model was developed, presented, and examined in this research work, investigating various parameters and mechanisms affecting VO recovery from NFCRs using vertical well steamflooding. The governing equations are written for the matrix and fractured medium, separately. Uncertainties associated with the shape factor for the communication between the matrix and fracture is eliminated through setting a continuity boundary condition at the interface. Using this boundary condition, the solution method employed differs from the most of the modeling simulations reported in the literature. A Newton-Raphson approach was also used for solving mass and energy balance equations. RF and CSOR were obtained as a function of steam injection rate and temperature and characteristics of the fractured media such as matrix size and permeability. The numerical solution clearly shows that fractures play an important role in better conduction of heat into the matrix part. It was also concluded that the matrix block size and total permeability are the most important parameters affecting the dependent variables involved in steamflooding. A hybrid Artificial Neural Network model optimized by co-implementation of a Particle Swarm Optimization method (ANN-PSO) was developed, presented, and tested in this research work for the purpose of estimation of the CSOR and RF during vertical well steamflooding in VO NFCRs. The developed PSO-ANN model, conventional ANN models, and statistical correlations were examined using field data. Comparison of the predictions and field data implies superiority of the proposed PSO-ANN model with an absolute average error percentage < 6.5% , a determination coefficient (R2) > 0.98, and Mean Squared Error (MSE) < 0.06, a substantial improvement in comparison with conventional ANN model and empirical correlations for prediction of RF and CSOR. This indicates excellent potential for application of hybrid PSO-ANN models to screen VO NFCRs for steamflooding. This is the first time that the ANN technique has been applied for the purpose of performance prediction of steamflooding in VO NFCRs and also reported in the literature. The predictive PSO-ANN model and statistical correlations have strong potentials to be merged with heavy oil recovery modeling softwares available for thermal methods. This combination is expected to speed up their performance, reduce their uncertainty, and enhance their prediction and modeling capabilities. An integrated geological-geophysical-geomechanical approach was designed, presented, and applied in the case of a NFCR for the purpose of fracture and in situ stresses characterization in NFCRs. The proposed methodology can be applied for fracture and in situ stresses characterization which is beneficial to various aspects of asset development such as well placement, drilling, production, thermal reservoir modeling incorporating geomechanics effects, technology assessment and so on. A conceptual study was also conducted on geomechanics effects in VO NFCRs during steamflooding which is not yet well understood and still requires further field, laboratory, and theoretical studies. This can be considered as a small step forward in this area identifying positive potential of such knowledge to the design of large scale thermal operations in VO NFCRs.

Nano-particle aerosols are one of the major types of air pollutants in the urban indoor and outdoor environments. Therefore, determination of mechanisms of formation, dispersion, evolution, and transformation of combustion aerosols near the major source of this type of air pollution - busy roads and road networks - is one of the most essential and urgent goals. This Thesis addresses this particular direction of research by filling in gaps in the existing physical understanding of aerosol behaviour and evolution. The applicability of the Gaussian plume model to combustion aerosols near busy roads is discussed and used for the numerical analysis of aerosol dispersion. New methods of determination of emission factors from the average fleet on a road and from different types of vehicles are developed. Strong and fast evolution processes in combustion aerosols near busy roads are discovered experimentally, interpreted, modelled, and statistically analysed. A new major mechanism of aerosol evolution based on the intensive thermal fragmentation of nano-particles is proposed, discussed and modelled. A comprehensive interpretation of mutual transformations of particle modes, a strong maximum of the total number concentration at an optimal distance from the road, increase of the proportion of small nano-particles far from the road is suggested. Modelling of the new mechanism is developed on the basis of the theory of turbulent diffusion, kinetic equations, and theory of stochastic evaporation/degradation processes. Several new powerful statistical methods of analysis are developed for comprehensive data analysis in the presence of strong turbulent mixing and stochastic fluctuations of environmental factors and parameters. These methods are based upon the moving average approach, multi-variate and canonical correlation analyses. As a result, an important new physical insight into the relationships/interactions between particle modes, atmospheric parameters and traffic conditions is presented. In particular, a new definition of particle modes as groups of particles with similar diameters, characterised by strong mutual correlations, is introduced. Likely sources of different particle modes near a busy road are identified and investigated. Strong anti-correlations between some of the particle modes are discovered and interpreted using the derived fragmentation theorem. The results obtained in this thesis will be important for accurate prediction of aerosol pollution levels in the outdoor and indoor environments, for the reliable determination of human exposure and impact of transport emissions on the environment on local and possibly global scales. This work will also be important for the development of reliable and scientifically-based national and international standards for nano-particle emissions.

Zur Präparation von hochwertigen Heterostrukturen aus Übergangsmetallperowskiten wurde eine Anlage zur metallorganischen Aerosol-Deposition mit Wachstumskontrolle durch in-situ Ellipsometrie aufgebaut. Durch numerische Anpassung der in-situ Ellipsometrie kann man den beim Wachstum stattfindenden Transfer der $ e_{g} $-Elektronen zwischen unterschiedlich dotierten Perowskit-Manganaten erfassen. Im Verlauf des Wachstums von Übergittern aus $ \mathrm{LaMnO_{3}} $ (LMO) und $ \mathrm{SrMnO_{3}} $ (SMO) variiert die Längenskala, über die die $ e_{g} $-Elektronen delokalisieren, in einem Bereich von $ 0.4\, \mathrm{nm} $ bis $ 1.4 \, \mathrm{nm} $. Mit der neu eingeführten Atomlagenepitaxie (ALE) kann man die Chemie von Perowskit-Grenzflächen vollständig definieren. Am Beispiel von gestapelten $ \mathrm{SrO-SrTiO_{3}} $ (STO) Ruddlesden-Popper-Strukturen und LMO/SMO-Übergittern wird dieses Verfahren erprobt. Mit der in-situ Ellipsometrie kann man Defekte in der SrO-STO-Abfolge vorhersagen, die in anschließenden strukturellen Untersuchungen mit Transmissionselektronenmikroskopie (TEM) erkennbar sind. Außerdem lässt sich die Sr/Ti-Stöchiometrie mit einer Genauigkeit von $ 1.5\, \mathrm{\%} $ festlegen. In Bezug auf das Wachstum von LMO und SMO kann man über die in-situ Ellipsometrie Veränderungen der Mn-Valenzen erkennen und so auf ein zweidimensionales Wachstum jeder halben Perowskitlage schließen. Die in dieser Arbeit etablierte Depositionstechnologie erlaubt das systematische Studium der magnetischen Eigenschaften von Heterostrukturen aus verschieden dotierten Lanthan-Strontium-Manganaten ($ \mathrm{La_{1-x}Sr_{x}MnO_{3}} $ (LSMO(x)). Zunächst wird das magnetische Verhalten von Doppellagen aus dem ferromagnetischen LSMO(0.3) und verschiedenen antiferromagnetischen LSMO(x)-Lagen ($ x=0.6-1.0 $) untersucht. Für $ x>0.6 $ beobachtet man ein erhöhtes Koerzitivfeld und eine Verschiebung der Hysterese entlang der Feldachse (exchange bias (EB)). Als Funktion der Sr-Dotierung zeigen die durch das STO-Substrat verspannten LSMO(x)-Filme einen Übergang vom Antiferromagneten des G-Typs ($ x>0.95 $) zum Antiferromagneten des A-Typs ($ x \leq 0.95 $). Dieser Übergang wird von einer Halbierung der EB-Amplitude begleitet. Für LSMO(0.3)/SMO-Strukturen registriert man eine Abnahme der EB-Amplitude, wenn die epitaktischen Verzerrungen mit zunehmender Dicke der SMO-Lagen relaxieren. Bei Änderungen der tetragonalen Verzerrung der Manganat-Filme kommt es zu einer Modifikation der Balance zwischen den magnetischen Kopplungen in der Filmebene und senkrecht dazu. Dadurch verändern sich die Eigenheiten des Spin-Glases an der Grenzfläche und damit das magnetische Verhalten der Heterostruktur. LMO/SMO-Übergitter auf STO (001) zeigen eine zuvor noch nicht beobachtete Phänomenologie. Wenn die LMO/SMO-Bilagendicke $ \Lambda $ 8 Monolagen übersteigt, bemerkt man zwei separate ferromagnetische Signaturen. Die Tieftemperaturphase (LTP) hat eine Curie-Temperatur $ T_{C}^{L}=180\, \mathrm{K}-300 \, \mathrm{K} $, die mit $ \Lambda $ kontinuierlich abfällt, die Hochtemperaturphase (HTP) hat eine Curie-Temperatur $ T_{C}^{H}=345 \, \mathrm{K} \pm 10 \, \mathrm{K} $, die keine systematische Abhängigkeit von $ \Lambda $ besitzt. LTP und HTP sind magnetisch entkoppelt. Das Skalierungsverhalten des magnetischen Momentes der HTP mit der Bilagendicke und der Zahl von Wiederholungen der LMO/SMO-Einheit deutet auf einen Grenzflächencharakter der HTP. Außerdem besitzt die HTP eine große magnetische Anisotropieenergie, die Literaturwerte für dünne Manganatfilme um zwei Größenordnungen übersteigt. Beim Wachstum auf $ \mathrm{(La_{0.3}Sr_{0.7}) (Al_{0.65}Ta_{0.35})O_{3}} $ (LSAT), das eine kleinere Gitterkonstante als STO besitzt, verschwindet die HTP. Zur Erklärung der HTP stellt man ein Modell vor, bei dem die HTP an der chemisch scharfen SMO/LMO-Grenzfläche lokalisiert ist. Das STO-Substrat führt zu epitaktischen Zugspannungen, die die $ e_{g} $-Elektronen in den an den SMO/LMO-Grenzflächen befindlichen $ \mathrm{MnO_{2}} $-Lagen auf die $ d_{x^{2}−y^{2}} $-Orbitale zwingen. Dadurch ist der Austausch zu den in c-Richtung benachbarten $ \mathrm{MnO_{2}} $-Lagen sehr schwach und der magnetische Austausch findet vorwiegend in der Ebene statt. Durch den Ladungstransfer liegt in der $ \mathrm{MnO_{2}} $-Lage an der SMO/LMO-Grenzfläche ein $ \mathrm{Mn^{4+}} $-Anteil von $ x \approx 0.4 $ vor. Durch den Doppelaustausch bildet sich in dieser Ebene dann eine zweidimensionale ferromagnetische Phase, die die HTP darstellt.

Text in Afrikaans / The purpose of the research is to compare the quantity and quality of reporting on the employees of companies with the profitability and size of the top 100 companies over a four year period. The research is limited to the availability of quality information on employees in the financial statements of companies. A literature study is followed by an emperical inquiry into a comparison of the reporting on employees with the profitability and size of companies. The results reflect the following: * the quantity and quality of reporting on the employees of companies does not inevitably show an increase; * a significant relationship exist between the size and profitability of companies; * the role of reporting on the employees of companies is significant with regards to profit determination; and * some of the companies performed uniquely with regards to the quantity and quality of reporting on the employees of companies. / Accounting / M.Comm.(Accounting)

No description available.

This study tests for the market efficiency of the Nairobi Securities Exchange (NSE) after the year 2000 to determine the effect of technological advancements on market efficiency. Data that is used is the NSE 20 share index over the period 2001 to 2015; and the NSE All Share Index (NSE ASI) from its initiation during 2008 to 2015. We cannot accept the Efficient Market Hypothesis (EMH) for the NSE using the serial correlation test, the unit root tests and the runs test. However, we can accept the EMH for the more robust variance ratio test. Overall, the results of the market efficiency are mixed. The most significant finding is that the efficiency of the NSE has increased since the year 2000 which suggests that advancements in technology have contributed to the increase in the market efficiency of the NSE. / Business Management / M. Com. (Business Management)

Made available in DSpace on 2016-06-02T20:15:31Z (GMT). No. of bitstreams: 1 5792.pdf: 2150785 bytes, checksum: 967083b129be653705657afbcab00714 (MD5) Previous issue date: 2014-02-27 / Universidade Federal de Sao Carlos / This thesis consists of three studies in the context of cavity quantum electrodynam- ics. Firstly, we investigate the quantum-to-classical transition of a dissipative cavity .eld by measuring the correlations between two non-interacting atoms coupled to the cavity mode. We note that there is a time window in which the mode presents a classical be- havior, which depends on the cavity decay rate, the atom-.eld coupling strength and the number of atoms. Then, considering the steady state of two atoms inside the cavity, we note that the entanglement between the atoms disappears while the intracavity mean number of photons (ñ) increases. However, the mutual information, the classical corre- lations and the quantum discord reach asymptotic non-zero values even in the limit of (continue...) / Esta tese é constituída por três estudos no contexto de Eletrodinâmica Quântica de Cavidades. Primeiramente, investigamos a transição quântico-clássica de um campo de uma cavidade dissipativa através da geração de correlação entre dois átomos de dois níveis não interagentes acoplados a um modo da cavidade. Em primeiro lugar, mostramos que há uma janela de tempo na qual o modo da cavidade exibe um comportamento clássico, que depende da taxa de decaimento da cavidade, do acoplamento átomo-campo e do número de átomos. Em seguida, considerando o regime estacionário, vemos que o emaranhamento entre os átomos desaparece à medida que o número médio de fótons intracavidade (ñ) é aumentado. Entretanto, a informação mútua, as correlações clássicas e a discórdia quântica atingem valores assintóticos não nulos mesmo no limite (continua...)

I started writing this thesis not only to obtain a doctoral degree, but also to compile in a particular way all the work that I have done during this time. The articles published during these years can only give a short overview of my research task. I decided to give my own perspective of the things I have learned and the results I have obtained. Some sections are directly the published articles, but some other are not and contain a significant amount of unpublished data. Even in some cases the published plots have been modified / altered to provide more insight or to maintain consistency. Historical perspectives often provide a deep understanding of the problems and have been briefly discussed in some chapters. This thesis contains theoretical and computer simulation studies to under-stand effects of spatial correlation on dynamics in several complex systems. Based on the different phenomena studied, the thesis has been divided into three major parts: I. Pair hydrophobicity, composition-dependent anomalies and structural trans-formations in aqueous binary mixtures II. Microscopic analysis of hydrophobic force law in a two dimensional (2D) water-like model system III. Diffusion of a tagged particle on a rugged energy landscape with spatial correlations The three parts have been further divided into ten chapters. In the following we provide part-wise and chapter-wise outline of the thesis. Part I consists of six chapters, where we focus on several important aqueous binary mixtures of amphiphilic molecules. To start with, Chapter 1 provides an introduction to non-ideality often encountered in aqueous binary mixtures. Here we briefly discuss the existing ideas of structural transformations associated with solvation of a foreign molecule in water, with particular emphasis on the classic “iceberg” model. Over the last decade, several investigations, especially neutron scattering and diffraction experiments, have questioned the validity of existing theories and have given rise to an alternate molecular picture involving micro aggregation of amphiphilic co-solvents in their aqueous binary mixtures. Such microheterogeneity was also supported by other experiments and simulations. In Chapter 2, we present our calculation of the separation dependence of potential of mean force (PMF) between two methane molecules in water-dimethyl sulfoxide (DMSO) mixture, using constrained molecular dynamics simulation. It helps us to understand the composition-dependence of pair hydrophobicity in this binary solvent. We find that pair hydrophobicity in the medium is surprisingly enhanced at DMSO mole fraction xDMSO ≈ 0.15, which explains several anomalous properties of this binary mixture – including the age-old mystery of DMSO being a protein stabilizer at lower concentration and protein destabilizer at higher concentration. Chapter 3 starts with discussion of non-monotonic composition dependence of several other properties in water-DMSO binary mixture, like diffusion coefficient, local composition fluctuation and fluctuations in total dipole moment of the system. All these properties exhibit weak to strong anomalies at low solute concentration. We attempt to provide a physical interpretation of such anomalies. Previous analyses often suggested occurrence of a “structural transformation” (or, microheterogeneity) in aqueous binary mixtures of amphiphilic molecules. We show that this structural transformation can be characterized and better understood under the purview of percolation theory. We define the self-aggregates of DMSO as clusters. Analysis of fractal dimension and cluster size distribution with reference to corresponding “universal” scaling exponents, combined with calculation of weight-averaged fraction of largest cluster and cluster size weight average, reveal a percolation transition of the clusters of DMSO in the anomalous concentration range. The percolation threshold appears at xDMSO ≈ 0.15. The molecular picture suggests that DMSO molecules form segregated islands or micro-aggregates at concentrations below the percolation threshold. Close to the critical concentration, DMSO molecules start forming a spanning cluster which gives rise to a bi-continuous phase (of water-rich region and DMSO-rich region) beyond the threshold of xDMSO ≈ 0.15. This percolation transition might be responsible for composition-dependent anomalies of the binary mixture in this low concentration regime. Similar phenomenon is observed for another amphiphilic molecule – ethanol, as discussed in Chapter 4. We again find composition dependent anomalies in several thermophysical properties, such as local composition fluctuation, radial distribution function of ethyl groups and self-diffusion co-efficient of ethanol. Earlier experiments often suggested distinct structural regimes in water-ethanol mixture at different concentrations. Using the statistical mechanical techniques introduced in the previous chapter, we show that ethanol clusters undergo a percolation transition in the anomalous concentration range. Despite the lack of a precise determination of the percolation threshold, estimate lies in the ethanol mole fraction range xEtOH ≈ 0.075 - 0.10. This difficulty is probably due to transient nature of the clusters (as will be discussed in Chapter 6) and finite size of the system. The scaling of ethanol cluster size distribution and the fractal behavior of ethanol clusters, however, conclusively demonstrate their “spanning” nature. To develop a unified understanding, we further study the composition-dependent anomalies and structural transformations in another amphiphilic molecule, tertiary butyl alcohol (TBA) in Chapter 5. Similar to the above-mentioned aqueous binary mixtures of DMSO and ethanol, we demonstrate here that the anomalies occur due to local structural changes involving self-aggregation of TBA molecules and percolation transition of TBA clusters at xTBA ≈ 0.05. At this percolation threshold, we observe a lambda-type divergence in the fluctuation of the size of the largest TBA cluster, reminiscent of a critical point. Interestingly, water molecules themselves exhibit a reverse percolation transition at higher TBA concentration ≈ 0.45, where large spanning water clusters now break-up into small clusters. This is accompanied by significant divergence of the fluctuations in the size of the largest water cluster. This second transition gives rise to another set of anomalies around. We conclude this part of the thesis with Chapter 6, where we introduce a novel method for understanding the stability of fluctuating clusters of DMSO, ethanol and TBA in their respective aqueous binary mixtures. We find that TBA clusters are the most stable, whereas ethanol clusters are the most transient among the three representative amphiphilic co-solvents. This correlates well with the amplitude of anomalies observed in these three binary mixtures. Part II deals with the topic of hydrophobic force law in water. In the introductory Chapter 7 of this part, we briefly discuss the concept of hydrophobicity which is believed to be of importance in understanding / explaining the initial processes involved in protein folding. We also discuss the experimental observations of Israelachvili (on the force between hydrophobic plates) and the empirical hydrophobic force law. We briefly touch upon the theoretical back-ground, including Lum-Chandler-Weeks theory. We conclude this chapter with a brief account of relevant and important in silico studies so far. In Chapter 8, we present our studies on Mercedes-Benz (MB) model – a two dimensional model system where circular disks interact with an anisotropic potential. This model was introduced by Ben-Naim and was later parametrized by Dill and co-workers to reproduce many of the anomalous properties of water. Using molecular dynamics simulation, we show that hydrophobic force law is indeed observed in MB model, with a correlation length of ξ=3.79. The simplicity of the model enables us to unravel the underlying physics that leads to this long range force between hydrophobic plates. In accordance with Lum-Chandler-Weeks theory, density fluctuation of MB particles (leading to cavitation) between the hydrophobic rods is clearly distinguishable – but it is not sufficiently long ranged, with density correlation extending only up to ζ=2.45. We find that relative orientation of MB molecules plays an important role in the origin of the hydrophobic force in long range. We define appropriate order parameters to capture the role of orientation, and briefly discuss a plausible approach of an orientation-dependent theory to explain this phenomenon. Part III consists of two chapters and focuses on the diffusion of a Brownian particle on a Gaussian random energy landscape. We articulate the rich history of the problem in the introductory Chapter 9. Despite broad applicability and historical importance of the problem, we have little knowledge about the effect of ruggedness on diffusion at a quantitative level. Every study seems to use the expression of Zwanzig [Proc. Natl. Acad. U.S.A, 85, 2029 (1988)] who derived the effective diffusion coefficient, Deff =D0 exp (-β2ε2 )for a Gaussian random surface with variance ε, but validity of the same has never been tested rigorously. In Chapter 10, we introduce two models of Gaussian random energy surface – a discrete lattice and a continuous field. Using computer simulation and theoretical analyses, we explore many different aspects of the diffusion process. We show that the elegant expression of Zwanzig can be reproduced ex-actly by Rosenfeld diffusion-entropy scaling relationship. Our simulations show that Zwanzig’s expression overestimates diffusion in the uncorrelated Gaussian random lattice – differing even by more than an order of magnitude at moderately high ruggedness (ε>3.0). The disparity originates from the presence of “three-site traps” (TST) on the landscape – which are formed by deep minima flanked by high barriers on either side. Using mean first passage time (MFPT) formalism, we derive an expression for the effective diffusion coefficient, Deff =D0 exp ( -β2ε2)[1 +erf (βε/2)]−1 in the presence of TSTs. This modified expression reproduces the simulation results accurately. Further, in presence of spatial correlation we derive a general expression, which reduces to Zwanzig’s form in the limit of infinite spatial correlation and to the above-mentioned equation in absence of correlation. The Gaussian random field has an inherent spatial correlation. Diffusion coefficient obtained from the Gaussian field – both by simulations and analytical methods – establish the effect of spatial correlation on random walk. We make special note of the fact that presence of TSTs at large ruggedness gives rise to an apparent breakdown of ergodicity of the type often encountered in glassy liquids. We characterize the same using non-Gaussian order parameter, and show that this “breakdown” scales with ruggedness following an asymptotic power law. We have discussed the scope of future work at the end of each chapter when-ever appropriate.

Une des solutions envisagées par les motoristes pour améliorer le rendement des turbomoteurs consiste à réduire le jeu en fonctionnement dans les deux systèmes d’air des turbomachines. Plus particulièrement dans le système d’étanchéité d’air secondaire, la réduction du jeu entre les parties fixes et tournantes améliore le contrôle des étanchéités du moteur et les niveaux de refroidissement entre les différents modules des turbomoteurs, mais entraînent des interactions indésirables entre les différents composants. Les systèmes d’étanchéité dynamiques sont composés de joints labyrinthes couplés à un revêtement abradable sacrificiel en vis-à-vis, qui offre la particularité de s’user préférentiellement en préservant la majeure partie du système d’étanchéité en évitant une usure de la partie tournante. L’objectif de cette thèse est de reproduire et d’étudier, par l’intermédiaire d’un banc technologique haute vitesse spécialement conçu pour l’étude, les interactions labyrinthe-abradable appliquées au couple acier inoxydable/Al-Si 6%, dans des conditions de fonctionnement d’un turbomoteur. Une instrumentation spécifique est développée sur le banc et apporte à l’étude les données expérimentales manquantes visant à la caractérisation des interactions labyrinthe-abradable. Une analyse tribologique, basée sur le concept de troisième corps, est menée afin d’identifier les différents débits de matière puis de décrire les étapes successives des mécanismes d’usure (circuit tribologique) du revêtement Al-Si 6%. L’influence des paramètres de pilotage de l’interaction et de la géométrie du joint a été étudiée. Enfin, une étude statistique basée sur l’iconographie des corrélations, permet de modéliser le comportement global du système labyrinthe-abradable, d’identifier les paramètres influents du système et d’apporter des critères pour une potentielle surveillance des interactions. Ces travaux de thèse ont été réalisés dans le cadre d’une collaboration entre TURBOMECA Bordes (groupe SAFRAN), et le Laboratoire Génie Production (LGP) de Tarbes. / S of turbomachinery. Especially in the secondary air sealing system, the tight clearance between the stationary and rotating parts improves control of engine seals and cooling levels between the different modules of the engines but may cause undesirable interactions between the static and rotating components. Dynamic sealing systems are composed of labyrinth seals coupled to a sacrificial abradable coating, which can accommodate interactions to preserve the global geometrical seal integrity. The objective of this thesis is to study and reproduce, through a technological high speed test rig specifically designed for the study, the labyrinth-abradable interactions applied to stainless steel/Al-Si 6% couple, under similar turbo-engine operating conditions. A suitable instrumentation is developed on the test ring to complete missing experimental data to characterize abradable labyrinth interactions. A tribological study, based on the third body concept, is proposed to identify wear mechanisms process of the Al-Si 6% coating. The influence of interaction control parameters and the seal geometry was investigated. Finally, a statistical study, based on the iconography of the correlation, is proposed to model the overall labyrinth-abradable system behavior and to identify influential parameters of the system and provide suitable criteria to monitor labyrinth seal interactions. This work was achieved within the framework of cooperation between TURBOMECA Bordes (SAFRAN Group), and the Laboratoire Génie de Production (LGP) de Tarbes.

Alors qu’il existe de nombreux calculs microscopiques de barrières de fission pour des noyaux composés pair-pairs, il n’y a cependant que relativement peu de tels calculs pour des noyaux de masse impaire. Ceci est dû aux complications induites par la brisure de la symétric de reversement du sens du temps au niveau du champ moyen qui est engendrée par la présence d’un nucleon non apparié. Pour éviter cette difficulté, des calculs existants pour des noyaux de masse impaire ont tout simplement négligé ces effets de brisure de la symétrie de reversement du sens du temps.Dans ce travail, on se donne pour but d’améliorer la description des barrières de fission, aussi bien que des propriétés spectroscopiques du niveau fondamental et de l’état isomérique de fission,pour quelques isotopes de masse impaire dans la région des actinides en prenant en compte de tels effets. Ceci a été réalisé dans le cadre du formalisme de Skyrme–Hartree–Fock plus BCS avec blocking en adaptant ce formalisme à la brisure de la symétrie considérée. L’interaction résiduelle d’appariement a été approchée par une force de séniorité dont les paramètres ont été ajustés pour reproduire les différences de masse pair-impair de quelques noyaux de la région des actinides.Les énergies des têtes de bande rotationnelle de basse énergie ont été calculées dans le cadre du modèle unifié de Bohr-Mottelson pour quatre noyaux bien déformés (235U, 239Pu, 237Np, 241Am)produisant un bon accord qualitatif avec les données pour les noyaux impairs en neutrons. L’accord significativement moins bon obtenu pour les noyaux impairs en protons pourrait résulter de l’usage de l’approximation de Slater pour l’interaction d’échange de Coulomb. Les énergies de déformation de deux noyaux impairs en neutrons (235U, 239Pu) ont été calculées pour quelques configurations de particule individuelle, jusqu’après la barrières de fission externe. La symétrie axiale a été imposée tandis que la brisure de la symétrie droite-gauche (ou de parité intrinsèque) a été permise dans la région de la seconde barrière. Les hauteurs des barrières de fission pour ces noyaux impairs dépendent significativement des configurations de particule individuelle. Un accord qualitatif avec les données disponibles pour les hauteurs de barrières des noyaux impairs considérés et leurs voisins pair-pairs a été généralement obtenu. / While there have been numerous microscopic calculations on fission barriers of even-even compoundnuclei, there are however, relatively few such work dedicated to odd-mass nuclei. This is dueto the complications posed by the breaking of the time-reversal symmetry at the mean-field leveldue to the presence of an unpaired nucleon. In order to circumvent this difficulty, previous fission barriercalculations of odd-mass nuclei have been performed by neglecting the effect of time-reversalsymmetry breaking. This work aims to improve on the description of fission barriers as well asthe spectroscopic properties of ground and fission-isomeric state, of some odd-mass actinide nucleiby taking the effect of time-reversal symmetry breaking into account. This has been perfomedwithin a Skyrme-Hartree-Fock-plus-BCS framework with blocking, where the BCS formalism hasbeen adapted to accomodate this symmetry breaking. The Skyrme nucleon-nucleon effective forcehas been used with various sets of parameters (SIII, SkM*, SLy5*). The residual pairing interactionhas been approximated by seniority forces whose neutron and proton parameters have beenfitted to reproduce the odd-even mass differences of some actinide nuclei. The low-lying rotationalband-head energies evaluated within the Bohr-Mottelson unified model have been determined forfour well-deformed odd-nuclei (235U, 239Pu, 237Np, 241Am) yielding a good qualitative agreementto the data for odd-neutron nuclei. The agreement was significantly less good for the odd-protonnuclei, possibly due to the use of the Slater approximation for the exchange Coulomb interaction.The deformation energies of two odd-neutron nuclei (235U and 239Pu) have been calculated forsome single-particle configurations up to a point beyond the outer fission-barrier. Axial symmetrynuclear shape has been assumed while a breaking of the left-right (or intrinsic parity) symmetryhas been allowed around the outer fission-barrier. The fission-barrier heights of such odd-neutronnuclei depend significantly on the particle configurations. A special attention has been paid tothe very important rotational correction to deformation energies. In particular, the correction ofthe moment of inertia calculated from the usual Belyaev expression was considered. Overall, aqualitative agreement with available data on fission-barrier heights for the considered odd-neutronnuclei and their even neighbours has been obtained.