Tortuosity Perturbations Induced by Defects in Porous Media

In this chapter, we describe the effects of defects in a homogeneous saturated porous medium. Defects are modelized by inclusions which disturb the motion of the viscous fluid flowing in the pore space of the medium. The seepage rate of the fluid in the host medium and in the inclusion is given by the Darcy’s law. Disturbances thus produced modify the shape of the stream lines from which we establish the tortuosity induced by the defects and its implications on the acoustic waves propagation in saturated porous media

What is Nature Tourism? Case Study: University Students

On the one hand in recent years nature tourism (turystyka przyrodnicza) has constituted a significant part of the tourism industry, on the other it has caused many problems for researchers attempting to define the phenomenon. Should the tourism destination or its primary motivation determine its categorisation? Is there indeed a need when considering practice as well as theory? The authors of the article have attempted a discourse with both foreign and domestic literature and subsequently sought to find the perceived meaning of turystyka przyrodnicza (nature tourism) amongst students of Poznań University particularly those associated with the natural environment on their degree courses. The present article should be considered as a contribution to further work in this field theoretically as well as practically

Dynamika i kierunki zmian funkcji turystycznej województwa wielkopolskiego w latach 1995– 2009

Przedmiotem badań  niniejszego opracowania jest funkcja turystyczna województwa wielkopolskiego, omówiona na podstawie analizy istniejącego ruchu oraz osadnictwa turystycznego w ujęciu dynamicznym i przestrzennym – przy wykorzystaniu najczęściej stosowanych mierników określających tę  funkcję  (FISCHBACH 1989) oraz dostępnych materiałów statystycznych dotyczących lat 1995–2009

Vérification formelle des systèmes multi-agents auto-adaptatifs

A major challenge for the development of self-organizing MAS is to guarantee the convergence of the system to the overall function expected by an external observer and to ensure that agents are able to adapt to changes. In the literature, several works were based on simulation and model-checking to study self-organizing MAS. The simulation allows designers to experiment various settings and create some heuristics to facilitate the system design. Model checking provides support to discover deadlocks and properties violations. However, to cope with the complexity of self-organizing MAS, the designer also needs techniques that support not only verification, but also the development process itself. Moreover, such techniques should support disciplined development and facilitate reasoning about various aspects of the system behavior at different levels of abstraction. In this thesis, three essential contributions were made in the field of formal development and verification of self-organizing MAS: a formalization with the Event-B language of self-organizing MAS key concepts into three levels of abstraction, an experimentation of a top-down refinement strategy for the development of self-organizing MAS and the definition of a bottom-up refinement process based on refinement patterns.Un des défis majeurs pour le développement des Systèmes Multi-Agents (SMA) auto-organisateurs est de garantir la convergence du système vers la fonction globale attendue par un observateur externe et de garantir que les agents sont capables de s'adapter face aux perturbations. Dans la littérature, plusieurs travaux se sont basés sur la simulation et le model-checking pour analyser les SMA auto-organisateurs. La simulation permet aux concepteurs d'expérimenter plusieurs paramètres et de créer certaines heuristiques pour faciliter la conception du système. Le model-checking fournit un support pour découvrir les blocages et les violations de propriétés. Cependant, pour faire face à la complexité de la conception des SMA auto-organisateurs, le concepteur a également besoin de techniques qui prennent en charge non seulement la vérification, mais aussi le processus de développement lui-même. En outre, ces techniques doivent permettre un développement méthodique et faciliter le raisonnement sur divers aspects du comportement du système à différents niveaux d'abstraction. Dans cette thèse, trois contributions essentielles ont été apportées dans le cadre du développement et la vérification formelle des SMA auto-organisateurs: une formalisation à l'aide du langage B-événementiel des concepts clés de ces systèmes en trois niveaux d'abstraction (micro, méso et macro), une expérimentation d'une stratégie de raffinement descendante pour le développement des SMA auto-organisateurs et la proposition d'un processus de raffinement ascendant basé sur des patrons de raffinement

spatial and temporal predictions for positive vectors

Predicting a given pixel from surrounding neighboring pixels is of great interest for several image processing tasks. To model images, many researchers use Gaussian distributions. However, some data are obviously non-Gaussian, such as the image clutter and texture. In such cases, predictors are hard to derive and to obtain. In this thesis, we analytically derive a new non-linear predictor based on an inverted Dirichlet mixture. The non-linear combination of the neighbouring pixels and the combination of the mixture parameters demonstrate a good efficiency in predicting pixels. In order to prove the efficacy of our predictor, we use two challenging tasks, which are; object detection and image restoration. We also develop a pixel prediction framework based on a finite generalized inverted Dirichlet (GID) mixture model that has proven its efficiency in several machine learning applications. We propose a GID optimal predictor, and we learn its parameters using a likelihood-based approach combined with the Newton-Raphson method. We demonstrate the efficiency of our proposed approach through a challenging application, namely image inpainting, and we compare the experimental results with related-work methods. Finally, we build a new time series state space model based on inverted Dirichlet distribution. We use the power steady modeling approach and we derive an analytical expression of the model latent variable using the maximum a posteriori technique. We also approximate the predictive density using local variational inference, and we validate our model on the electricity consumption time series dataset of Germany. A comparison with the Generalized Dirichlet state space model is conducted, and the results demonstrate the merits of our approach in modeling continuous positive vectors

Syndrome d’interruption de la tige pituitaire à révélation tardive

Le syndrome d'interruption de la tige pituitaire est une cause assez fréquente de déficit en hormone de croissance et d'hypopituitarisme souvent révélé pendant la période néonatale et l'enfance. Cette observation illustre les particularités d'une révélation tardive de ce syndrome. Il s'agit d'une patiente âgée de 17ans hospitalisée pour aménorrhée primaire et impubérisme. Elle n'a pas d'antécédent d'incident néonatal. L'examen clinique révèle un retard de croissance sévère. L'hypophysiogramme a montré un hypopituitarisme complet sans diabète insipide. L'imagerie par résonnance magnétique a montré une interruption de la tige pituitaire avec une post hypophyse ectopique. Une malformation rénale a été objectivée, ce qui est en faveur d'une origine congénitale malformative de ce syndrome. Une substitution hormonale a été administrée à cette patiente. Cette forme clinique tardive souligne la nécessité de diagnostic précoce d'impubérisme et/ou de retard de croissance révélant une pathologie à potentiel de gravité important.Pan African Medical Journal 2016; 2

Obstructive sleep apnea presenting as pseudopheochromocytoma

A 52-year-old female with a history of poorly controlled resistant hypertension was admitted to our hospital with severe hypertension. She had a history of fatigue and intermittent episodes of palpitations. Laboratory evaluation was significant for elevated 24-h urinary catecholamine levels (3,5 times the upper normal levels). This case was presenting with a clinical and biochemical picture indistinguishable from that of pheochromocytoma. However, neither computed tomography nor meta-iodo-benzyl-guanidine scintigraphy detected any catecholamine-producing tumor in or outside the adrenal glands. Our patient was screened with full polysomnography because of heavy snoring, daytime somnolence and obesity. It revealed severe obstructive sleep apnea syndrome. After three months of continuous positive airway pressure therapy, the patient experienced resolution of his presenting symptoms, improved blood pressure control and normalization of his urinary catecholamine levels. This case highlights sleep disordered breathing as a potentially reversible cause of pseudo-pheochromocytoma.Pan African Medical Journal 2016; 2