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

Stability of periodic waves in Hamiltonian PDEs of either long wavelength or small amplitude

Stability criteria have been derived and investigated in the last decades for many kinds of periodic traveling wave solutions to Hamiltonian PDEs. They turned out to depend in a crucial way on the negative signature of the Hessian matrix of action integrals associated with those waves. In a previous paper (Nonlinearity 2016), the authors addressed the characterization of stability of periodic waves for a rather large class of Hamiltonian partial differential equations that includes quasilinear generalizations of the Korteweg--de Vries equation and dispersive perturbations of the Euler equations for compressible fluids, either in Lagrangian or in Eulerian coordinates. They derived a sufficient condition for orbital stability with respect to co-periodic perturbations, and a necessary condition for spectral stability, both in terms of the negative signature - or Morse index - of the Hessian matrix of the action integral. Here the asymptotic behavior of this matrix is investigated in two asymptotic regimes, namely for small amplitude waves and for waves approaching a solitary wave as their wavelength goes to infinity. The special structure of the matrices involved in the expansions makes possible to actually compute the negative signature of the action Hessian both in the harmonic limit and in the soliton limit. As a consequence, it is found that nondegenerate small amplitude waves are orbitally stable with respect to co-periodic perturbations in this framework. For waves of long wavelength, the negative signature of the action Hessian is found to be exactly governed by the second derivative with respect to the wave speed of the Boussinesq momentum associated with the limiting solitary wave

Promoting Physical Exercise Participation: The Role of Interpersonal Behaviors for Practical Implications

he number of people engaging in physical exercise has been decreasing every year. These behaviors are known to be related with non-communicable chronic diseases and to drastically increase premature morbidity and mortality. Since “the lack of motivation” has been pointed out as one of the main reasons for not engaging in physical exercise, several theoretical and empirical studies have been conducted aimed at understanding what influences behavior regulation. According to literature, gym exercisers who perceive exercise instructors as supportive are more likely to maintain physical exercise participation over the long-run. Supporting autonomy, competence, and relatedness should be carefully considered when interacting with health club clients as a way to promote more autonomous motivation. Overall, it seems that exercise instructors should foster a supportive environment for gym exercisers, in order to encourage exercise as a habitual behavior.info:eu-repo/semantics/publishedVersio

The mirror of the black body: Colonial desires and civilizing missions

Richard Burton’s The Lake Regions of Central Africa (1860), Volume I has been studied as an example of British Imperial values regarding the settling in Africa in the late nineteenth century. Broadly speaking, most works have focused on how the text expresses these ideas and very little work has been carried out on researching the meanings of the imagery used in the text. In this short piece, I look at how the original frontispiece of The Lake Regions of Central Africa (1860), Volume I is revealing of colonial desires and civilizing missions. Particularly, I argue that the image reveals a projection of white through the expression of sexual desires towards the black body, settling fantasies and civilizing mission goals.Richard Burton na sua obra The Lake Regions of Central Africa (1860), Volume I é um autor bastante estudado para entender os valores do Imperialismo Britânico no século XIX. A maior parte do trabalho de análise do seu trabalgo foca-se no seu texto e não nas imagens do texto. Neste artigo, eu analiso a imagem da capa do livro The Lake Regions of Central Africa (1860), Volume I e argumento que a capa reflete desejos sexuais e fantasias de missão civilizadora no imaginário branco em relação aos corpos negros

Refinement by interpretation in {\pi}-institutions

The paper discusses the role of interpretations, understood as multifunctions that preserve and reflect logical consequence, as refinement witnesses in the general setting of pi-institutions. This leads to a smooth generalization of the refinement-by-interpretation approach, recently introduced by the authors in more specific contexts. As a second, yet related contribution a basis is provided to build up a refinement calculus of structured specifications in and across arbitrary pi-institutions.Comment: In Proceedings Refine 2011, arXiv:1106.348

Stakeholders perspectives on time horizon and quantification of enterprise architectures benefits/value drivers

Enterprise Architectures are being used by many organizations as a strategic tool for framing and managing key business and IT initiatives and activities. However, given the complexity and costs associated with building an Enterprise Architecture, there is a growing need to demonstrate the importance and usefulness in terms of the value that it represents to an organization. Without an adequate justification for the investment in Enterprise Architecture projects, organizations either do not to start or tend to abandon their Enterprise Architectures. In this paper, we present the stakeholders perspectives on two key dimensions of the Enterprise Architectures benefits/value drivers: the time horizon (time needed for the realization of the benefits) and its quantification (measurement of the realization of the benefits). In our view, these two dimensions are fundamental to realize how much effort will be required to assess the value of an Enterprise Architecture.- (undefined