Level Crossing Rate and Average Fade Duration of the Multihop Rayleigh Fading Channel

We present a novel analytical framework for the evaluation of important second order statistical parameters, as the level crossing rate (LCR) and the average fade duration (AFD) of the amplify-and-forward multihop Rayleigh fading channel. More specifically, motivated by the fact that this channel is a cascaded one, which can be modelled as the product of N fading amplitudes, we derive novel analytical expressions for the average LCR and AFD of the product of N Rayleigh fading envelopes, or of the recently so-called N*Rayleigh channel. Furthermore, we derive simple and efficient closed-form approximations to the aforementioned parameters, using the multivariate Laplace approximation theorem. It is shown that our general results reduce to the specific dual-hop case, previously published. Numerical and computer simulation examples verify the accuracy of the presented mathematical analysis and show the tightness of the proposed approximations

Políticas públicas y ganadería familiar en Uruguay: los desafíos ambientales y de ordenamiento territorial

Las políticas públicas recientes en favor de la agricultura familiar en Uruguay enfrentan varias tensiones con la lógica neoliberal dominante en la economía y la agricultura uruguaya. Este artículo analiza innovaciones en las políticas públicas de gestión de los recursos naturales, uso de la tierra y descentralización del desarrollo rural examinando sus efectos, sobre todo en el área de la ganadería familiar. Uruguay sigue el proceso de integración de las normas internacionales en las políticas ambientales —conservación de agua y suelo— y de desarrollo regional sostenible. Pero la implementación de esos nuevos instrumentos de regulación —territorial, ambiental, de tierra, agua y suelos, entre otros— entra en tensión o en conflicto con los intereses del sector empresarial de un lado y con la identidad de los ganaderos familiares en campo natural por otro. (Résumé d'auteur

MEASUREMENT OF ADHESIVE-ADHEREND INTERLAYER PROPERTIES USING ACOUSTIC MICROSCOPY

There is considerable uncertainty about the mechanism of adhesive bonding and, in particular, the changes occurring during environmental attack which greatly reduce the bond strength [1]. This lack of understanding hampers the development of better adhesive systems and also makes the development of non-destructive evaluation methods very difficult since it is not certain what properties should ideally be measured

Continental-scale water-level response to a large earthquake

Coseismic groundwater-level changes induced by earthquakes have been reported for thousands of years. The M8.0 Wenchuan earthquake caused coseismic groundwater-level responses across the Chinese mainland. Three types of changes were recorded in 197 monitoring wells: coseismic oscillations ranging in amplitude from 0.004 to 1.1m, immediate coseismic step changes ranging from 0.0039 to 9.188 m, and more gradual postseismic changes ranging from 0.014 to 1.087 m. Hydrogeological and tectonic settings are dominant factors in determining the coseismic response. Wells located near the boundaries of active blocks can have large coseismic responses even when the epicenter distance is large. Both the sign and amplitude of water-level changes are random at the continental scale. Poroelastic response to the coseismic static strain cannot explain most of the coseismic changes. Permeability changes caused by stress changes may explain the large variability of the coseismic response amplitude