Coupled Ostrovsky equations for internal waves in a shear flow

In the context of fluid flows, the coupled Ostrovsky equations arise when two distinct linear long wave modes have nearly coincident phase speeds in the presence of background rotation. In this paper, nonlinear waves in a stratified fluid in the presence of shear flow are investigated both analytically, using techniques from asymptotic perturbation theory, and through numerical simulations. The dispersion relation of the system, based on a three-layer model of a stratified shear flow, reveals various dynamical behaviours, including the existence of unsteady and steady envelope wave packets.Comment: 47 pages, 39 figures, accepted to Physics of Fluid

Transformation of a shoaling undular bore

We consider the propagation of a shallow-water undular bore over a gentle monotonic bottom slope connecting two regions of constant depth, in the framework of the variable-coefficient Korteweg-de Vries equation. We show that, when the undular bore advances in the direction of decreasing depth, its interaction with the slowly varying topography results, apart from an adiabatic deformation of the bore itself, in the generation of a sequence of isolated solitons - an expanding large-amplitude modulated solitary wavetrain propagating ahead of the bore. Using nonlinear modulation theory we construct an asymptotic solution describing the formation and evolution of this solitary wavetrain. Our analytical solution is supported by direct numerical simulations. The presented analysis can be extended to other systems describing the propagation of undular bores (dispersive shock waves) in weakly non-uniform environments

Anonymity and its Prospects in the Digital World

"This work­ing paper traces the changes under­gone by anonymity - and by the dis­courses sur­rounding it - in liberal Western societies. The author asks whether the current politi­cization of the issue is likely to have any impact on the gra­dual dis­appearance of oppor­tunities for anonymity that we are currently witnes­sing and argues that anonymity is an ambi­valent but critical feature of the demo­cratic public sphere. The argu­ment proceeds in three stages. It begins with a number of concep­tual ob­ser­vations on anonymity. From these, a heuristic frame­work emerges with which the changes in anony­mous communi­cation, and in the role this communi­cation plays in society, can be described. The author then analyses the extent to which options for anonymity have been affected by the rev­olution in infor­mation and communi­cation techno­logies and concludes by con­sidering how anonymity is framed in public dis­course and what impacts this has." (author's abstract)"Das Working Paper unter­sucht die Ver­änderungen von Anonymität und den Diskursen über Anonymität in liberalen west­lichen Gesell­schaften. Der Autor fragt, in­wiefern die gegen­wärtige Politi­sierung des Themas einen Einfluss auf das gra­duelle Ver­schwinden der Möglich­keiten anonymer Kom­munikation haben wird und welche Be­deutung Anonymität für die demo­kratische Öffen­tlich­keit hat. Die Analyse voll­zieht sich in drei Schritten: Zunächst wird konzep­tuell ge­klärt, was Anonymität ist und darauf auf­bauend ein heur­istisches Instru­ment ent­wickelt mittels dessen sich die Ver­änderung anonymer Kom­muni­kations­mög­lich­keiten in der Gesell­schaft be­schreiben lassen. Im zweiten Schritt wird dieses Instru­ment zur An­wendung gebracht, um die sich wandelnden Möglich­keiten anonymer Komm­uni­kation im digitalen Struktur­wandel zu porträtieren. Der dritte Teil des Papiers fragt schließ­lich nach der Art und Weise, wie Anonymität im öffent­lichen Diskurs politi­siert wird - und sucht die Erfolgs­aus­sichten ab­zu­schätzen, die diese Thema­tisierung hat, der Ent­wicklung zu be­gegnen oder sie gar um­zu­kehren." (Autorenreferat

Steady transcritical flow over an obstacle: Parametric map of solutions of the forced extended Korteweg-de Vries equation

Transcritical flow of a stratified fluid over an obstacle is often modeled by the forced Korteweg-de Vries equation, which describes a balance among weak nonlinearity, weak dispersion, and small forcing effects. However, in some special circumstances, it is necessary to add an additional cubic nonlinear term, so that the relevant model is the forced extended Korteweg-de Vries equation. Here we seek steady solutions with constant, but different amplitudes upstream and downstream of the forcing region. Our main interest is in the case when the forcing has negative polarity, which represents a hole. The effects of the width of the hole and the amplitude of the hole on these steady solutions are then investigated. © 2011 American Institute of Physics.published_or_final_versio

Language and the development of intercultural competence in an 'internationalised' university: staff and student perspectives

Within the currently diverse UK higher education environment, one important aspect of learning is the development of intercultural competence. The study that informs this paper investigated the ways intercultural competence was perceived as being enhanced or inhibited through current language and educational practices at a university that positions itself as internationally engaged and globally recognised. The project employed a multiple-case study design, examining eight academic programmes drawn from four different broad disciplinary groupings: social sciences, science, engineering, and management. Data were collected through individual, focus group and stimulated recall interviews, the latter using class observation recordings as a stimulus. The study revealed the ways in which language was exploited by both staff and students to convey particular meanings within an intercultural context. It was found that language choices, register and style were perceived as contributing to the pragmatic impact of either reinforcing barriers to or promoting intercultural competence development

Transformation of a shoaling undular bore

We consider the propagation of a shallow-water undular bore over a gentle monotonic bottom slope connecting two regions of constant depth, in the framework of the variablecoefficient Korteweg – de Vries equation. We show that, when the undular bore advances in the direction of decreasing depth, its interaction with the slowly varying topography results, apart from an adiabatic deformation of the bore itself, in the generation of a sequence of isolated solitons — an expanding large-amplitude modulated solitary wavetrain propagating ahead of the bore. Using nonlinear modulation theory we construct an asymptotic solution describing the formation and evolution of this solitary wavetrain. Our analytical solution is supported by direct numerical simulations. The presented analysis can be extended to other systems describing the propagation of undular bores (dispersive shock waves) in weakly non-uniform environments