Acoustic transmission and reflection by a shear discontinuity separating hot and cold regions

Acoustic transmission and reflection is analyzed for plane waves propagating from a hot moving medium, impinging on a plane shear discontinuity into a cold stationary region. It is shown that incident waves originating in the hot region and propagating in the flow direction are transmitted into the cold region at almost right angles to the interface. The result is employed to examine the strong side radiation of internal noise transmitted through the exhaust duct of a turbojet engine

Acoustic radiation from the end of two-dimensional duct, effects of uniform flow and duct lining

A study is presented of the radiation of acoustic modes from the end of a duct immersed in a uniformly moving medium. It is shown that the uniform flow has roughly the same effect as an increase in frequency at constant mode number: the number of lobes of the radiation pattern increases, and the radiation maximum is slightly displaced towards the duct axis. When the mode is near cut-off the forward radiation for an inlet is enhanced. The acoustic radiation characteristics of ducts with soft or absorbing walls and hard, perfectly-reflecting walls are then compared. It is shown, and this is of technological interest, that the side radiation from the end of an acoustically soft duct is greatly reduced for lower-order modes

Preliminary Water Assessment Reports of The Test Basins of The Watch Project

This report presents the initial plans of the case studies how they link to rest of the Watch project and on which water resources they will focus. This report will function as the basis for further discussions on how to improve the integration of the case studies within the project and to develop a more general protocol for each of the case studies. Currently 5 catchments are used within the Watch project, they differ in climatic and hydro-geological features and expected climate changes: the Glomma River basin (Eastern Norway), the upper Guadiana basin (Central Spanish Plateau), the Nitra River basin (central Slovakia), the Upper-Elbe basin (part of the Elbe River) and the island of Crete. Also the water resources issues vary over these cases. Agricultural (and domestic) water use is under pressure in the Mediterranean catchments probably aggravating with the expected increase in drought frequency under future climate. The Norwegian catchment provides hydropower services under threat of precipitation increase rather than decrease. The central European catchments are threatened mainly by increased variability, i.e. increased frequencies of extremes in a densely populated environment, and river flow may need additional buffers (reservoirs) to reduce floodrisk and store water for dry period

Polar Smectic Films

We report on a new experimental procedure for forming and studying polar smectic liquid crystal films. A free standing smectic film is put in contact with a liquid drop, so that the film has one liquid crystal/liquid interface and one liquid crystal/air interface. This polar environment results in changes in the textures observed in the film, including a boojum texture and a previously unobserved spiral texture in which the winding direction of the spiral reverses at a finite radius from its center. Some aspects of these textures are explained by the presence of a Ksb term in the bulk elastic free energy density that favors a combination of splay and bend deformations.Comment: 4 pages, REVTeX, 3 figures, submitted to PR

Black Hole Entropy, Topological Entropy and the Baum-Connes Conjecture in K-Theory

We shall try to exhibit a relation between black hole entropy and topological entropy using the famous Baum-Connes conjecture for foliated manifolds which are particular examples of noncommutative spaces. Our argument is qualitative and it is based on the microscopic origin of the Beckenstein-Hawking area-entropy formula for black holes, provided by superstring theory, in the more general noncommutative geometric context of M-Theory following the Connes- Douglas-Schwarz article.Comment: 17 pages, Latex, contains an important paragraph in section 2 which gives a better understandin

Notes on the Third Law of Thermodynamics.I

We analyze some aspects of the third law of thermodynamics. We first review both the entropic version (N) and the unattainability version (U) and the relation occurring between them. Then, we heuristically interpret (N) as a continuity boundary condition for thermodynamics at the boundary T=0 of the thermodynamic domain. On a rigorous mathematical footing, we discuss the third law both in Carath\'eodory's approach and in Gibbs' one. Carath\'eodory's approach is fundamental in order to understand the nature of the surface T=0. In fact, in this approach, under suitable mathematical conditions, T=0 appears as a leaf of the foliation of the thermodynamic manifold associated with the non-singular integrable Pfaffian form $\delta Q_{rev}$. Being a leaf, it cannot intersect any other leaf $S=$ const. of the foliation. We show that (N) is equivalent to the requirement that T=0 is a leaf. In Gibbs' approach, the peculiar nature of T=0 appears to be less evident because the existence of the entropy is a postulate; nevertheless, it is still possible to conclude that the lowest value of the entropy has to belong to the boundary of the convex set where the function is defined.Comment: 29 pages, 2 figures; RevTex fil

Benthic foraminifera diversity from the south Atlantic Ocean: Tierra del Fuego and surrounding waters (South America)

Abstract The present study provides a detailed record of foraminiferal fauna and their ecological implications from surface sediments from Atlantic shelf of Tierra del Fuego, Argentina. The foraminiferal assemblage is mostly composed by four main hyaline genera, such as Cibicidoides, Cibicides, Globocassidulina and Buccella, which allowed the identification of three environmental zones. Zone 1 (Z1, 37 to 90 m) encompasses the eastern Beagle Channel and San Sebastian Bay. The assemblage reflected well-oxygenated marine inner shelf habitat, adapted to cold temperate waters. Zone 2 (Z2, up to 98.4 m), is located around the southern tip of Tierra del Fuego. The assemblage suggested a deeper marine environment, well oxygenated and with higher energy, probably due to the effect of tides and mainly by the influence of Malvinas Current. Finally, Zone 3 (Z3, up to 195 m) is located furthest from the Atlantic coast and the assemblage suggested an environment characteristic of outer shelf, with well-oxygenated cold waters and high-energy environment, reflected by species adhered to the substrate and coarse sediments. The distribution and abundance of certain species showed the influence of the Malvinas Current, while others evidenced a contribution of the Cape Horn waters

Resin tapping in Pinus pinaster: effects on growth and response function to climate

Dendrocronología sobre Pinus pinaster, como la recolección de resina y los factores climáticos han afectado a su crecimiento

Secondary LS category of measured laminations

In the author's Ph.D., a version of the tangential LS category for foliated spaces depending on a transverse invariant measure, called the measured category, was introduced. Unfortunately, the measured category vanishes easily. When it is zero, the rate of convergence to zero of the quantity involved in the definition, by taking arbitrarily large homotopies, gives a new invariant, called the secondary measured category. Several versions of classical results are proved for the secondary measured category. It is also shown that the secondary measured category is a transverse invariant related to the growth of (pseudo)groups. The equality between secondary category and the growth of a group is done in the case of free suspensions by Rohlin groups.Comment: 14 pages. arXiv admin note: substantial text overlap with arXiv:1112.500