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L'inversion de phase des émulsions est un processus employé dans de nombreux procédés industriels, pour obtenir des émulsions très fines. Le suivi de l'inversion et la compréhension des phénomènes physico-chimiques mis en jeu constituent donc des enjeux majeurs pour maîtriser la formation et la stabilité des émulsions. Notre travail a porté sur l'étude de l'inversion de phase induite par le changement de température de systèmes de type CiEj / n-alcane / Eau (+NaCl). En premier lieu, nous avons mis au point une méthode de détection de l'inversion par mesure du signal de rétrodiffusion de lumière. D'autre part, nous avons étudié des diagrammes de phase afin de les corréler avec la carte formulation-composition, en s'appuyant sur un système simple. La rétrodiffusion de lumière permet de caractériser des systèmes SEH même exempts d'électrolytes. De plus, elle fournit un signal lorsque la phase continue est huileuse contrairement à d'autres techniques comme la conductimétrie. Elle apporte également une information sur la taille des gouttes, qualitative certes, mais plus significative que la mesure de viscosité. La construction et l'analyse physicochimique et géométrique détaillée des différents diagrammes de phase formant le prisme SEH - Température d'un système défini (C10E4 / n-octane / NaCl 10-2M) a permis de mettre en évidence certaines zones de diagrammes non explorées et de présenter des interprétations novatrices des diagrammes de phases. La confrontation des résultats obtenus par les processus d'inversion standard et dynamique souligne la relation étroite existant entre les diagrammes de phases et les cartes formulation - composition obtenues après émulsification. / The phase inversion of emulsions is used in many industrial processes to obtain very fine emulsions. The tracking of inversion and the understanding of the implied physico-chemical phenomena are thus major issues to control the formation and stability of emulsions. We have been studying the phase inversion induced by a temperature change in CiEj/n-alkane/Water(+NaCl) systems. ln the first place, a method to detect the phase inversion by measuring the backscatterîng signal has been developed. On the other hand, we have studied phase diagrams in order to correlate them with the formulation-composition map, by using a simple system. Light backscattering allows characterizing SOW systems, even free from electrolytes. Moreover, ît gives a signal when the continuous phase is oily, contrarily to other techniques like conductimetry. It also gives some information about the droplet size, although qualitatively, but more significantly than viscosity does. The construction and the physico-chemical and geometrical analyses of the different phase diagrams forming the SOW - Temperature prism for a defined system (C10E4 / n-octane / NaCI 10-2M) has put forward some unexplored zones of the diagrams and allowed to present novel interpretations of the phase diagrams. The comparison of the results obtained with the standard and dynamic inversion processes underlines the tight relation existing between the phase diagrams and the fommlation-composition maps obtained after emulsification.

A 10 km x 10 km study area in the western Bushveld Complex, south of the Pilanesberg Complex, was selected for testing the inversion of vertical component gravity (Gz) data to determine the geometry of the Bushveld Complex/Transvaal Supergroup contact. This contact has a density contrast of ~0.350 g.cm-3 making it a suitable target for gravity inversion. The resulting 3D gravity model agrees well with the 3D seismic interpretation, indicating that the depths determined from the seismic data are appropriate. The gravity inversion could be extended laterally to investigate regions without seismic data coverage. This methodology may prove useful where upwellings in the floor of the Bushveld Complex distort seismic data, but can be imaged by gravity inversions. The Gz dataset was created from converted Airborne Gradient Gravity (AGG) data, combined with upward continued ground Gz gravity data, providing extensive coverage. This combined dataset was used in an interactive, iterative 3D gravity inversion methodology used to model the geometry of the Bushveld Complex/Transvaal Supergroup contact and densities of the Bushveld Complex, Transvaal Supergroup and Iron-Rich Ultramafic Pegmatoids (IRUPs). The resulting 3D gravity model provides an acceptable first-pass model of the Bushveld Complex/Transvaal Supergroup contact. In the shallow south-west region of the study area, the steeply dipping contact was determined from borehole intersections. 3D seismic data was the only constraint towards the north-east, where the contact flattens out to a sub-parallel contact, at ~2 000 m depth. In the north-western section, the Bushveld Complex/Transvaal Supergroup contact is fault-bounded by a conjugate set of the Rustenburg Fault, causing the Bushveld to onlap the Transvaal sediments. In the southern region, the contact changes as the conjugate fault dies out, and the Bushveld Complex becomes layered/sub-parallel to Transvaal sediments. This, and other geological features (e.g. faulting, folding, dykes), can be explained in relation to the regional tectonic history, relating to motion along the Thabazimbi-Murchison Lineament (TML). Pre-Bushveld emplacement NW-SE far-field stress caused NW trending extensional features in the region (e.g. Rustenburg Fault). Re-orientation of the compressive force to NE-SW, in syn- to post-emplacement, caused compressive features in the region (e.g. open folds with axes trending NW). Ground gravity data (100 m x 100 m station- and line-spacing) were also inverted to obtain a 3D model of the overburden, constrained by borehole data. However, the inversion failed to satisfy the gravity data and borehole data simultaneously, relating to difficulties in modelling the regional gravity field and the gradational nature of the weathered contact. Several rapid variations in overburden thickness were mapped, with particular success in the high frequency ground gravity survey (30 m x 30 m station- and line-spacing) with the identification of a deeply weathered (~10 m deep) channel relating to an mapped fault.

Typescript, etc. / Digitized by Kansas Correctional Industries

The reflection seismic experiment results in a measurement(reflection seismic data) of the seismic wavefield. The linear Born approximation to the seismic wavefield leads to a forward modelling operator that we use to approximate reflection seismic data in terms of a scattering potential. We consider approximations to the scattering potential using two methods: the adjoint of the forward modelling operator (migration), and regularized numerical inversion using the forward and adjoint operators. We implement two parameterizations of the forward modelling and migration operators: source-receiver and shot-profile. For both parameterizations, we find requisite Green's function using the split-step approximation. We first develop the forward modelling operator, and then find the adjoint (migration) operator by recognizing a Fredholm integral equation of the first kind. The resulting numerical system is generally under-determined, requiring prior information to find a solution. In source-receiver migration, the parameterization of the scattering potential is understood using the migration imaging condition, and this encourages us to apply sparse prior models to the scattering potential. To that end, we use both a Cauchy prior and a mixed Cauchy-Gaussian prior, finding better resolved estimates of the scattering potential than are given by the adjoint. In shot-profile migration, the parameterization of the scattering potential has its redundancy in multiple active energy sources (i.e. shots). We find that a smallest model regularized inverse representation of the scattering potential gives a more resolved picture of the earth, as compared to the simpler adjoint representation. The shot-profile parameterization allows us to introduce a joint inversion to further improve the estimate of the scattering potential. Moreover, it allows us to introduce a novel data reconstruction algorithm so that limited data can be interpolated/extrapolated. The linearized operators are expensive, encouraging their parallel implementation. For the source-receiver parameterization of the scattering potential this parallelization is non-trivial. Seismic data is typically corrupted by various types of noise. Sparse coding can be used to suppress noise prior to migration. It is a method that stems from information theory and that we apply to noise suppression in seismic data. / Geophysics

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 87-88).

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In this thesis, we study the Stieltjes transforms of the probability distribution functions and compare them with the characteristic functions of the probability distribution functions simultaneously. In section 1 and section 2, we introduce briefly the Stieltjes transforms. In section 3, we conclude that the Stieltjes transform is similar to the complexion of symmetry under the condition of symmetric probability distribution functions. In section 4, we discuss the relation between Stieltjes transforms of probability distribution functions and the density of probability distribution functions. We also show that the nth derivative of Stieltjes transform is uniformly continuous on the upper complex plane.

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