Spherical wave near-field imaging and radar cross-section measurement

The paper presents a new inverse synthetic aperture radar (ISAR) algorithm intended for radar cross-section (RCS) imaging and measurement from scattered fields. The method, based on a spherical-wave near-field illumination of the target, overcomes the requirement for an expensive compact range facility to produce a plane wave illumination. The formulation and the implementation of the algorithm are described. Some experimental results obtained in an anechoic chamber are presented to show RCS results similar to the conventional plane wave methods.Peer Reviewe

Thermal response of Sanabria lake to global change (NW Spain)

Are large water bodies able to act as sensors of global change? As accumulators of water and heat, some of their thermal characteristics might be altered by long term (decadal) hydrometeorological changes and thus may be used as indicators of the effects of global change on fluvial ecosystems. This work focuses on the effect of global change (climate change plus water quantity and land use changes) in the internal organization of Sanabria Lake, specifically in its thermal annual cycle. The existence of temporal trends in the thermal behaviour of the lake was investigated based on the water temperature profiles are available since 1986. Data analyses include the non-parametric Mann-Kendall trend test and the Sen slope estimate to evaluate long term and seasonal patterns of hydrometeorological and in-lake thermal variables. The main results surprisingly point to a net lake cooling that could be explained by a stronger thermocline and a weaker vertical transfer of heat to the hypolimnion during the stratification period. These results contribute to understand and quantify the effects of global change on Iberian freshwater bodies.Peer ReviewedPostprint (published version

Movements and dispersal of brown trout (Salmo trutta Linnaeus, 1758) in Mediterranean streams: influence of habitat and biotic factors

Dispersal is a critical determinant of animal distribution and population dynamics, and is essential information for management planning. We studied the movement patterns and the influence of habitat and biotic factors on Mediterranean brown trout (Salmo trutta) by mark-recapture methods in three headwater streams of the Ebro Basin (NE Iberian Peninsula). Fish were sampled by electrofishing on five occasions over 18–24 months and movements of over 3,000 individually tagged trout (age 1+ onwards) were recorded. Most of the tagged fish exhibited limited movement and were recaptured within 100 m from the initial capture section. Small seasonal differences in the movement pattern were observed, but in two of the streams, displacement distances increased prior the spawning period in autumn. The frequency distributions of dispersal distances were highly leptokurtic and skewed to the right and fitted well to a two-group exponential model, thus trout populations were composed of mobile and stationary individuals, the latter being the predominant component in the populations (71.1–87.5% of individuals). The mean dispersal distances, for fish captured at least in three sampling events, ranged 20.7–45.4 m for the stationary group and 229.4–540.5 m for the mobile group. Moving brown trout were larger than non-moving individuals and exhibited higher growth rates in two of the streams. Habitat features were not consistently linked to movement rates, but there were some interaction effects between stream and habitat characteristics such as depth, cover and water velocity

Movements and dispersal of brown trout (Salmo trutta Linnaeus, 1758) in Mediterranean streams: influence of habitat and biotic factors

Dispersal is a critical determinant of animal distribution and population dynamics, and is essential information for management planning. We studied the movement patterns and the influence of habitat and biotic factors on Mediterranean brown trout (Salmo trutta) by mark-recapture methods in three headwater streams of the Ebro Basin (NE Iberian Peninsula). Fish were sampled by electrofishing on five occasions over 18–24 months and movements of over 3,000 individually tagged trout (age 1+ onwards) were recorded. Most of the tagged fish exhibited limited movement and were recaptured within 100 m from the initial capture section. Small seasonal differences in the movement pattern were observed, but in two of the streams, displacement distances increased prior the spawning period in autumn. The frequency distributions of dispersal distances were highly leptokurtic and skewed to the right and fitted well to a two-group exponential model, thus trout populations were composed of mobile and stationary individuals, the latter being the predominant component in the populations (71.1–87.5% of individuals). The mean dispersal distances, for fish captured at least in three sampling events, ranged 20.7–45.4 m for the stationary group and 229.4–540.5 m for the mobile group. Moving brown trout were larger than non-moving individuals and exhibited higher growth rates in two of the streams. Habitat features were not consistently linked to movement rates, but there were some interaction effects between stream and habitat characteristics such as depth, cover and water velocity.info:eu-repo/semantics/publishedVersio

Evaluación de las posibilidades de remoción de macrófitos mediante avenidas controladas

La problemática asociada al crecimiento masivo de macrófitos en el Bajo Ebro ha llevado a autoridades y gestores a examinar la posibilidad de paliar los efectos negativos que producen sobre el sistema hídrico, y los usos del agua, mediante la realización de avenidas controladas periódicas que provoquen su remoción. El presente trabajo tiene como objetivo principal evaluar la capacidad erosiva de las avenidas controladas en el tramo del río Ebro comprendido entre la presa de Flix y la CN de Ascó. Este tramo se encuentra colonizado casi en su totalidad por macrófitos, un tipo de flora acuática que modifica considerablemente la morfodinámica del río. Empleando técnicas de modelización hidráulica (modelo Iber) se pudo contrastar cómo los macrófitos tienen una alta capacidad de fijación del sedimento, dificultando su eliminación. Además, fue posible determinar, para el tramo analizado, el caudal umbral a partir del cual se produciría movilización de sedimentos de manera generalizada, y previsiblemente de los macrófito

Evaluación de las posibilidades de remoción de macrófitos mediante avenidas controladas

La problemática asociada al crecimiento masivo de macrófitos en el Bajo Ebro ha llevado a autoridades y gestores a examinar la posibilidad de paliar los efectos negativos que producen sobre el sistema hídrico, y los usos del agua, mediante la realización de avenidas controladas periódicas que provoquen su remoción. El presente trabajo tiene como objetivo principal evaluar la capacidad erosiva de las avenidas controladas en el tramo del río Ebro comprendido entre la presa de Flix y la CN de Ascó. Este tramo se encuentra colonizado casi en su totalidad por macrófitos, un tipo de flora acuática que modifica considerablemente la morfodinámica del río. Empleando técnicas de modelización hidráulica (modelo Iber) se pudo contrastar cómo los macrófitos tienen una alta capacidad de fijación del sedimento, dificultando su eliminación. Además, fue posible determinar, para el tramo analizado, el caudal umbral a partir del cual se produciría movilización de sedimentos de manera generalizada, y previsiblemente de los macrófitosPostprint (published version

Evaluación de las posibilidades de remoción de macrófitos mediante avenidas controladas

La problemática asociada al crecimiento masivo de macrófitos en el Bajo Ebro ha llevado a autoridades y gestores a examinar la posibilidad de paliar los efectos negativos que producen sobre el sistema hídrico, y los usos del agua, mediante la realización de avenidas controladas periódicas que provoquen su remoción. El presente trabajo tiene como objetivo principal evaluar la capacidad erosiva de las avenidas controladas en el tramo del río Ebro comprendido entre la presa de Flix y la CN de Ascó. Este tramo se encuentra colonizado casi en su totalidad por macrófitos, un tipo de flora acuática que modifica considerablemente la morfodinámica del río. Empleando técnicas de modelización hidráulica (modelo Iber) se pudo contrastar cómo los macrófitos tienen una alta capacidad de fijación del sedimento, dificultando su eliminación. Además, fue posible determinar, para el tramo analizado, el caudal umbral a partir del cual se produciría movilización de sedimentos de manera generalizada, y previsiblemente de los macrófito

Spherical wave near-field imaging and radar cross-section measurement

The paper presents a new inverse synthetic aperture radar (ISAR) algorithm intended for radar cross-section (RCS) imaging and measurement from scattered fields. The method, based on a spherical-wave near-field illumination of the target, overcomes the requirement for an expensive compact range facility to produce a plane wave illumination. The formulation and the implementation of the algorithm are described. Some experimental results obtained in an anechoic chamber are presented to show RCS results similar to the conventional plane wave methods.Peer Reviewe

Medida de RCS con onda esférica en campo próximo

Peer ReviewedPostprint (published version

Medida de RCS con onda esférica en campo próximo

Peer Reviewe