Periodic-coefficient damping estimates, and stability of large-amplitude roll waves in inclined thin film flow

A technical obstruction preventing the conclusion of nonlinear stability of large-Froude number roll waves of the St. Venant equations for inclined thin film flow is the "slope condition" of Johnson-Noble-Zumbrun, used to obtain pointwise symmetrizability of the linearized equations and thereby high-frequency resolvent bounds and a crucial H s nonlinear damping estimate. Numerically, this condition is seen to hold for Froude numbers 2 \textless{} F 3.5, but to fail for 3.5 F. As hydraulic engineering applications typically involve Froude number 3 F 5, this issue is indeed relevant to practical considerations. Here, we show that the pointwise slope condition can be replaced by an averaged version which holds always, thereby completing the nonlinear theory in the large-F case. The analysis has potentially larger interest as an extension to the periodic case of a type of weighted "Kawashima-type" damping estimate introduced in the asymptotically-constant coefficient case for the study of stability of large-amplitude viscous shock waves

Whitham's equations for modulated roll-waves in shallow flows

This paper is concerned with the detailed behaviour of roll-waves undergoing a low-frequency perturbation. We rst derive the so-called Whitham's averaged modulation equations and relate the well-posedness of this set of equations to the spectral stability problem in the small Floquet-number limit. We then fully validate such a system and in particular, we are able to construct solutions to the shallow water equations in the neighbourhood of modulated roll-waves proles that exist for asymptotically large time

Invariant Measures for a Stochastic Fokker-Planck Equation

We study the kinetic Fokker-Planck equation perturbed by a stochastic Vlasov force term. When the noise intensity is not too large, we solve the Cauchy Problem in a class of well-localized (in velocity) functions. We also show that, when the noise intensity is sufficiently small, the system with prescribed mass admits a unique invariant measure which is exponentially mixing. The proof uses hypocoercive decay estimates and hypoelliptic gains of regularity. At last we also exhibit an explicit example showing that some restriction on the noise intensity is indeed required.Comment: Extended versio

Paradigm shift in the automotive market: how will premium brands deal with the innumerous challenges they will face? An analysis to their strategy, main challenges and a set of recommendations to maintain relevance

This work project focuses on the analysis of the automotive industry, more specifically, the premium segment. This assessment includes, not only the current outlook of the market, but also the future challenges that the industry will face. The motivation for this research lies in the key point in time which the market is, and in figuring out how brands can keep up with the revolutionary technological changes and challenges. Although the premium sector may seem a specific piece of the automotive industry, it appears like the one that not only can push forward the premium segment needs and desires but also the one that can better surpass future technological drivers and challenges and, in the end, influence the market as a whole. The automotive industry faces an unprecedented transformation, as such, there is the need to look at the current strategies, anticipate future changes, and elaborate a new strategy able to accommodate all challenges. The trends covered range from new engines to autonomous driving, connectivity, and new mobility solutions. In order to understand the current panorama and the main challenges the industry faces, the group started by conducting intensive secondary data research as well as expert interviews. The final goal of the Work Project is to develop a set of recommendations for premium brands to stay relevant in this industry

A novel olfactory receptor gene family in teleost fish:phylogenomics, cellular localization and comparison with other olfactory receptor gene families

While for two of four mammalian olfactory receptor families, all of them G protein-coupled receptors, ortholog teleost families have been identified and well-characterized (OR and V2R), two other families (V1R and TAAR) lack to date a systematic study in non-mammalian vertebrates. By data mining I identified a total of six V1R-like genes in five teleost species plus four orthologs in one jawless and one cartilaginous fish species each. In the phylogenetic analysis these ora genes (olfactory receptor, class A-related) form a single clade with three subclades, one of them including the entire mammalian V1R superfamily. The Ora family originates early in the vertebrate lineage, before the separation of the jawless from jawed fish. A similar search was performed also for taar genes in genomes of five teleosts, two basal fish and seven higher vertebrates. Taar genes segregate into three classes and their family size ranges from 18 to 112 genes in teleosts (pufferfish and zebrafish, respectively), while mammalian families contain at most 19 genes (opossum). The TAAR family originated in the common ancestor of bony and cartilaginous fishes, after its divergence from jawless fish. In these and other properties the ora and taar gene families turn out to be at opposite poles of the spectrum of olfactory receptor families. All the six teleost Ora family members are evolutionarily much older than the speciation events in the teleost lineage, while most extant teleost taar genes have emerged late in evolution, well after the split between basal teleosts (zebrafish) and neoteleostei (stickleback, medaka, pufferfish). Taar genes are largely arranged according to phylogenetic proximity in two big clusters (both syntenic to the single sarcopterygian gene cluster), whereas the ora genes are organized as singletons or symmetrical gene pairs. TAAR genes are mostly monoexonic, whereas two ora genes exhibit a highly conserved multi-exonic structure. Furthermore, the ora genes are under strong negative selection (minute dN/dS values), whereas the teleost taar genes display a relaxed pattern of global negative selection and an unprecedented degree of local positive selection. Taken together, the ora gene repertoire is highly conserved across teleosts, in striking contrast to the frequent species-specific expansions observed in mammalian V1Rs. The inverse is observed for the taar gene repertoire, which is rather conserved across mammalian species, but exhibits frequent and large species-specific expansions in teleosts. Thus, the transition from teleosts to tetrapods may parallel a transition in function as well as regulation of both the ora/V1R and TAAR gene families. Consistent with a function as olfactory receptors all zebrafish ora and all analyzed taar genes (except taar1) were expressed in sparse subsets of olfactory receptor neurons. The olfactory epithelium contains three subtypes of olfactory receptor neurons, ciliated, microvillous and crypt cells, the latter so far without known receptors, but with both cilia and microvilli. I found the ora genes to be expressed in the crypt cells, thereby deorphanizing this third type of OSN. Furthermore, the ora genes follow the monogenic rule of expression previously reported for members of other olfactory receptor gene families. Ora genes co-express both Gαi and Gαo, supporting the hypothesis that crypt cells might possess two distinct olfactory signaling pathways, one via their cilia and the other via microvilli

Sur le temps de vie de la turbulence bidimensionnelle

International audienceOn sait que toutes les solutions de l'équation de Navier-Stokes dans R^2 dont le tourbillon est intégrable convergent dans la limite des grands temps vers un écoulement autosimilaire appelé tourbillon d'Oseen. Dans cet article, nous donnons une estimation du temps nécessaire à la solution pour atteindre un voisinage du tourbillon d'Oseen à partir d'une donnée initiale arbitraire, mais bien localisée en espace. Nous obtenons ainsi une borne supérieure sur le temps de vie de la turbulence bidimensionnelle libre, en fonction du nombre de Reynolds de la donnée initiale. Deux cas particuliers sont discutés plus en détail : celui des solutions à tourbillon positif, et celui des petites perturbations d'un tourbillon d'Osee

Whitham's Modulation Equations and Stability of Periodic Wave Solutions of the Korteweg-de Vries-Kuramoto-Sivashinsky Equation

International audienceWe study the spectral stability of periodic wave trains of the Korteweg-de Vries-Kuramoto-Sivashinsky equation which are, among many other applications, often used to describe the evolution of a thin liquid film flowing down an inclined ramp. More precisely, we show that the formal slow modulation approximation resulting in the Whitham system accurately describes the spectral stability to side-band perturbations. Here, we use a direct Bloch expansion method and spectral perturbation analysis instead of Evans function computations. We first establish, in our context, the now usual connection between first order expansion of eigenvalues bifurcating from the origin (both eigenvalue 0 and Floquet parameter 0) and the first order Whitham's modulation system: the hyperbolicity of such a system provides a necessary condition of spectral stability. Under a condition of strict hyperbolicity, we show that eigenvalues are indeed analytic in the neighborhood of the origin and that their expansion up to second order is connected to a viscous correction of the Whitham's equations. This, in turn, provides new stability criteria. Finally, we study the Korteweg-de Vries limit: in this case the domain of validity of the previous expansion shrinks to nothing and a new modulation theory is needed. The new modulation system consists in the Korteweg-de Vries modulation equations supplemented with a source term: relaxation limit in such a system provides in turn some stability criteria

Modulated wave trains in generalized Kuramoto-Sivashinksi equations

This paper is concerned with the stability of periodic wave trains in a generalized Kuramoto-Sivashinski (gKS) equation. This equation is useful to describe the weak instability of low frequency perturbations for thin film flows down an inclined ramp. We provide a set of equations, namely Whitham's modulation equations, that determines the behaviour of low frequency perturbations of periodic wave trains. As a byproduct, we relate the spectral stability in the small wavenumber regime to properties of the modulation equations. This stability is always critical since 0 is a 0-Floquet number eigenvalue associated to translational invariance

The use of sighting data to analyse Iberian lynx habitat and distribution

1. Over a large part of its very restricted and fragmented range, Iberian lynx Lynx pardinus occur in remote mountainous country at low density, where the only information about the species comprises records of incidental sightings obtained by inquiry. In this study we developed an approach for quantifying lynx-habitat relationships and distribution patterns from sighting data, using records from western Algarve (Portugal) in 1990-95. 2. Habitat was described in terms of land cover, topography, human disturbance and rabbit abundance, in 25-km(2) cells surrounding lynx sightings and at random locations within the study area. 3. Lynx sightings were consistently associated with predictable habitat features. Sighting probabilities estimated from a logistic regression model increased with the abundance of rabbits and the proportion of land covered by tall Mediterranean maquis, and declined with road density and the amount of developed land. This model identified correctly 85.7% of lynx sightings; at the same time only 20.7% of the random locations were misclassified. 4. Indices of human presence were never associated positively with lynx sightings, suggesting that observation patterns were not influenced by the spatial distribution of potential observers. 5. Kriging was used to interpolate spatially between sighting probabilities derived from the logistic model in order to produce a map of sighting potential for the Iberian lynx in western Algarve. Jack-knife resampling assessed the accuracy of this map. Three well-defined areas of high sighting potential were identified, probably representing the lynx core areas in this region. 6. Our analysis of lynx sighting records suggests that these data may provide a first approximation to lynx habitat and distribution when further information is lacking. The application of this approach to other ran and reclusive species is discussed.This study was funded by the Instituto da Conservação da Natureza (ICN) and by the European Union (Project LIFE B4±3200/94/767)info:eu-repo/semantics/publishedVersio

Software asset management in an organization

This thesis presents a project conducted to assess software asset management (SAM) maturity, through the usage of a SAM maturity model, in a Portuguese group, composed of six companies of different business sectors, in order to understand if the group was taking all necessary measures to prevent software non-compliance risks whilst maximizing SAM benefits. The SAM maturity model adopted was based on the Microsoft SAM Optimization Model (SOM) and comprised the assessment of ten core competences, each considering a total of four different maturity levels. The results show that despite the recent group efforts to improve SAM maturity the overall conclusion is that the group is still at Basic Level and vision, goals and objectives to be achieved with a global SAM still need to be approved. This project was the first enterprise initiative to promote SAM awareness in the group under the sponsorship of the Board of Directors and has allowed to understand the current SAM maturity, for the group and each of the six companies, define the desired SAM maturity and also determine all initiatives that must be implemented to achieve the target maturity within the next twelve months.A presente tese consiste no projecto que foi efectuado para aferir a maturidade da gestão de activos de software, tendo por base um modelo de maturidade de gestão de activos de software, de um grupo Português, composto por seis empresas que actuam em diversos sectores da nossa economia, a fim de compreender se o grupo estava a tomar todas as medidas necessárias para prevenir os riscos de não cumprimento legal e regulamentar associados à temática do software e para obter o máximo de benefícios associados à gestão dos activos de software. O modelo de maturidade de gestão de activos de software adoptado teve por base o Microsoft SAM Optimization Model (SOM) que contempla um total de dez competências, cada um com quatro níveis de maturidade distintos. Os resultados obtidos permitem concluir que apesar dos recentes esforços por parte do grupo para melhorar a maturidade nesta área o grupo ainda está no nível Básico e não existe uma visão e objectivos a atingir aprovados que permitam definir o caminho a seguir. Este projecto foi, no entanto, a primeira iniciativa transversal para promover o tema de forma corporativa, com o apoio da Comissão Executiva, e permitiu aferir o nível de maturidade actual, no grupo e em cada uma das seis empresas, bem como o nível de maturidade desejado para o grupo e o conjunto de iniciativas a implementar no período de doze meses de modo a atingir o estágio pretendido