A limitation on Long's model in stratified fluid flows

The flow of a continuously stratified fluid into a contraction is examined, under the assumptions that the dynamic pressure and the density gradient are constant upstream (Long's model). It is shown that a solution to the equations exists if and only if the strength of the contraction does not exceed a certain critical value which depends on the internal Froude number. For the flow of a stratified fluid over a finite barrier in a channel, it is further shown that, if the barrier height exceeds this same critical value, lee-wave amplitudes increase without bound as the length of the barrier increases. The breakdown of the model, as implied by these arbitrarily large amplitudes, is discussed. The criterion is compared with available experimental results for both geometries

A note on the motion of surfaces

We study the motion of surfaces in an intrinsic formulation in which the surface is described by its metric and curvature tensors. The evolution equations for the six quantities contained in these tensors are reduced in number in two cases: (i) for arbitrary surfaces, we use principal coordinates to obtain two equations for the two principal curvatures, highlighting the similarity with the equations of motion of a plane curve; and (ii) for surfaces with spatially constant negative curvature, we use parameterization by Tchebyshev nets to reduce to a single evolution equation. We also obtain necessary and sufficient conditions for a surface to maintain spatially constant negative curvature as it moves. One choice for the surface's normal motion leads to the modified-Korteweg de Vries equation,the appearance of which is explained by connections to the AKNS hierarchy and the motion of space curves.Comment: 10 pages, compile with AMSTEX. Two figures available from the author

The Korteweg-de Vries equation and water waves. Part 2. Comparison with experiments

The Korteweg-de Vries (KdV) equation is tested experimentally as a model for moderate amplitude waves propagating in one direction in relatively shallow water of uniform depth. For a wide range of initial data, comparisons are made between the asymptotic wave forms observed and those predicted by the theory in terms of the number of solitons that evolve, the amplitude of the leading soliton, the asymptotic shape of the wave and other qualitative features. The KdV equation is found to predict accurately the number of evolving solitons and their shapes for initial data whose asymptotic characteristics develop in the test section of the wave tank. The accuracy of the leading-soliton amplitudes computed by the KdV equation could not be conclusively tested owing to the viscous decay of the measured wave amplitudes; however, a procedure is presented for estimating the decay in amplitude of the leading wave. Computations suggest that the KdV equation predicts the amplitude of the leading soliton to within the expected error due to viscosity (12%) when the non-decayed amplitudes are less than about a quarter of the water depth. Indeed, agreement to within about 20% is observed over the entire range of experiments examined, including those with initial data for which the non-decayed amplitudes of the leading soliton exceed half the fluid depth

On the asymptotic expansion of the solutions of the separated nonlinear Schroedinger equation

Nonlinear Schr\"odinger equation (with the Schwarzian initial data) is important in nonlinear optics, Bose condensation and in the theory of strongly correlated electrons. The asymptotic solutions in the region $x/t={\cal O}(1)$, $t\to\infty$, can be represented as a double series in $t^{-1}$ and $\ln t$. Our current purpose is the description of the asymptotics of the coefficients of the series.Comment: 11 pages, LaTe

An Analysis of Techniques Used to Manage Historic Open Spaces on Two Suburban American University Campuses

As more and more Americans are attending higher educational institutions, the built environment of these places is becoming relevant to a larger number of people. To many graduates familiar with a university, its ensemble of buildings and spaces have the ability to stir up a sense of personal meaning associated with a past era in their life. It is important to preserve these campuses, by maintaining resources that already exist and protecting them from inappropriate change that would diminish their integrity. The physical environment of a university is often an icon of the school. The school\u27s community as well as the public associates the architecture and landscape of a school as part of its identity. In fact, the emblem of many universities is an historic architectural landmark, open space or ensemble of buildings that can be found on their campus. Such buildings and spaces are often used by the school to create a distinct identity

Another integrable case in the Lorenz model

A scaling invariance in the Lorenz model allows one to consider the usually discarded case sigma=0. We integrate it with the third Painlev\'e function.Comment: 3 pages, no figure, to appear in J. Phys.

Une situation expérimentale de réception des images télévisuelles: la mise en œuvre d'EARS

Resorting to experimental situation offers the possibility to study media messages reception. In particular, Real Time Response Systems allow investigations that don’t need words: researchers don’t have to ask people to phrase their reactions. However, the use of such a device requires taking into account methodological limits. Indeed, it is necessary to question the results given, between undoubted and restricted contributions. Within this framework we present the results of a reception study about immigration TV images, lead in 2003 at University de Lorraine by a research team from Centre de recherche sur les mediations. These results are the starting point from which an introducing and open question is initiated: within communication studies, what kind of experimental situation is it possible to settle, and what kind of results can be expected

El árbol urbano como pilar fundamental en la estrategia para la adaptación al cambio climático de El Gran Lyon

[ES] Desde hace 20 años, el Gran Lyon está involucrado en una mejor integración de los árboles en su territorio. Esta política está simbolizada por una “Carta de Árbol” que hace que los actores públicos, privados y las asociaciones profesionales trabajen de forma conjunta. También se ha duplicado el número de árboles en zonas públicas durante estos veinte años, así como mejorar la protección y el desarrollo del patrimonio privado. Esta carta tiene ocho grandes principios. Uno de ellos se centra en la innovación y quiere aprovechar los grandes proyectos urbanos como una oportunidad para promover la investigación y el desarrollo. El tema central de esta investigación es la adaptación de la ciudad a los cambios climáticos, especialmente para disminuir el efecto de isla de calor urbano y las olas de calor estivales. Esta investigación ayuda a probar soluciones innovadoras que crean un vínculo entre la gestión alternativa del agua de lluvia y el desarrollo de las plantaciones urbanas con el fin de mejorar el confort térmico de los habitantes. El enfoque interdisciplinario da un nuevo punto de vista sobre la planificación y el desarrollo urbano, y soluciones prácticas en materia de calidad de vida en las ciudades masificadas.Segur, F. (2014). El árbol urbano como pilar fundamental en la estrategia para la adaptación al cambio climático de El Gran Lyon. En XVI CONGRESO NACIONAL DE ARBORICULTURA. Editorial Universitat Politècnica de València. 157-162. http://hdl.handle.net/10251/91331OCS15716