1,008 research outputs found
Absorption and Direct Processes in Chaotic Wave Scattering
Recent results on the scattering of waves by chaotic systems with losses and
direct processes are discussed. We start by showing the results without direct
processes nor absorption. We then discuss systems with direct processes and
lossy systems separately. Finally the discussion of systems with both direct
processes and loses is given. We will see how the regimes of strong and weak
absorption are modified by the presence of the direct processes.Comment: 8 pages, 4 figures, Condensed Matter Physics (IV Mexican Meeting on
Mathematical and Experimental Physics), Edited by M. Martinez-Mares and J. A.
Moreno-Raz
Scattering of Elastic Waves in a Quasi-one-dimensional Cavity: Theory and Experiment
We study the scattering of torsional waves through a quasi-one-dimensional
cavity both, from the experimental and theoretical points of view. The
experiment consists of an elastic rod with square cross section. In order to
form a cavity, a notch at a certain distance of one end of the rod was grooved.
To absorb the waves, at the other side of the rod, a wedge, covered by an
absorbing foam, was machined. In the theoretical description, the scattering
matrix S of the torsional waves was obtained. The distribution of S is given by
Poisson's kernel. The theoretical predictions show an excellent agreement with
the experimental results. This experiment corresponds, in quantum mechanics, to
the scattering by a delta potential, in one dimension, located at a certain
distance from an impenetrable wall
Electromagnetic prompt response in an elastic wave cavity
A rapid, or prompt response, of an electromagnetic nature, is found in an
elastic wave scattering experiment. The experiment is performed with torsional
elastic waves in a quasi-one-dimensional cavity with one port, formed by a
notch grooved at a certain distance from the free end of a beam. The stationary
patterns are diminished using a passive vibration isolation system at the other
end of the beam. The measurement of the resonances is performed with
non-contact electromagnetic-acoustic transducers outside the cavity. In the
Argand plane, each resonance describes a circle over a base impedance curve
which comes from the electromagnetic components of the equipment. A model,
based on a variation of Poisson's kernel is developed. Excellent agreement
between theory and experiment is obtained.Comment: 4 pages, 5 figure
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A Collaborative Research Framework to Collect Data for the Understanding of Coastal and Marine Ecosystems and Fisheries
Combined Effects of the North Atlantic Oscillation and the Arctic Oscillation on Sea Surface Temperature in the Alborán Sea
We explored the possible effects of the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) on interannual sea
surface temperature (SST) variations in the Albora´n Sea, both separately and combined. The probability of observing mean
annual SST values higher than average was related to NAO and AO values of the previous year. The effect of NAO on SST
was negative, while that of AO was positive. The pure effects of NAO and AO on SST are obscuring each other, due to the
positive correlation between them. When decomposing SST, NAO and AO in seasonal values, we found that variation in
mean annual SST and mean winter SST was significantly related to the mean autumn NAO of the previous year, while mean
summer SST was related to mean autumn AO of the previous year. The one year delay in the effect of the NAO and AO on
the SST could be partially related to the amount of accumulated snow, as we found a significant correlation between the
total snow in the North Albora´n watershed for a year with the annual average SST of the subsequent year. A positive AO
implies a colder atmosphere in the Polar Regions, which could favour occasional cold waves over the Iberian Peninsula
which, when coupled with precipitations favoured by a negative NAO, may result in snow precipitation. This snow may be
accumulated in the high peaks and melt down in spring-summer of the following year, which consequently increases the
runoff of freshwater to the sea, which in turn causes a diminution of sea surface salinity and density, and blocks the local
upwelling of colder water, resulting in a higher SST.CGL2009-11316 (Ministerio de Ciencia e Innovación, Spain, and FEDER
On the potential biases of scientific estimates of catches of tropical tunas of purse seiners the EU and other countries report to the ICCAT and IOTC
This document represents a first attempt to explore potential differences between the catches of
tropical tunas estimated using the EU software T3 and those recorded on sale slips completed by
the canning factories purchasing fish from vessels registered with OPAGAC in the Atlantic and
Indian oceans, over the period 2011-16. The analysis identified potential sources of bias
estimates of catch of tropical tunas may be subject to, of different magnitude depending on the
ocean, fleet, and size category. The largest bias was recorded in the Indian Ocean. In the Atlantic
Ocean the catches of yellowfin and bigeye tunas seem to be also underestimated, with
underestimation of both large and small fish. Although the study is preliminary, the results
obtained indicate that the system the EU is using to sample purse seine landings and estimate
catches may be subject to bias which, if confirmed, could have consequences on the statistics,
stock assessments, management advice, and management measures adopted by ICCAT and IOT
The nature of women, peace and security: a Colombian perspective
On 12 November 2019, the Special Jurisdiction for Peace (JEP), handed down a landmark decision in the case of ‘Katsa Su’ concerning the Awa indigenous group in Colombia. The Colombian conflict has particularly affected indigenous groups, such as the Awa people, and has also affected the territory in which they live. In this article, we explore the decision of the JEP, within a broader analysis of the Colombian peace agreement and consider how it might help us to think about the place of the environment in the Women, Peace and Security agenda and in international law. We call for a gendered and intersectional approach to environmental peacebuilding which is attentive to the importance of gender and different groups. Further, we highlight how the Colombian example shows how concepts such as relief, recovery and reparations are often confined in international law to women's recovery and redress with respect to sexual violence and yet, this conceptualization should be much broader. The Katsa Su case provides an example of the fact that reparations and redress must address other forms of violence, spiritual and ecological, which women also suffer in times of conflict
Recent Approaches for the Determination of Forming Limits by Necking and Fracture in Sheet Metal Forming
Forming limit diagrams (FLD’s) are used to evaluate the workability of metal sheets. FLD’s provide the failure locus at which
plastic instability occurs and localized necking develops (commonly designated as the forming limit curve - FLC), and the failure
loci at the onset of fracture by tension (FFL) or by in-plane shear (SFFL). The interest of metal formers in controlling localized
necking is understandable because the consequence of plastic instability is an undesirable surface blemish in components.
However, because under certain loading conditions fracture can precede necking in sheet metal forming processes, there is a
growing interest in characterizing the forming limits by necking and fracture in the FLD’s. This paper gathers together a number
of recently developed methodologies for detecting the onset of local necking and fracture by in-plane tension or in-plane shear,
and discusses their applicability to determine experimentally the FLC’s, FFL’s and SFFL’s.Ministerio de Economía y Competitividad DPI2012-3291
ESTIMATION OF POTENTIAL EVAPOTRANSPIRATION WITH HARGREAVES-SAMANI MODEL AT VARIOUS LOCATIONS IN PUERTO RICO
ESTIMATION OF POTENTIAL EVAPOTRANSPIRATION WITH HARGREAVES-SAMANI MODEL AT VARIOUS LOCATIONS IN PUERTO RIC
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