Interferometric SAR signal analysis in the presence of squint

This paper develops an analysis of the SAR impulse response function from the interferometric point of view, with the intention of studying its phase behavior in the presence of high squint angle values. It will be pointed out that in this case, a phase ramp is present in the range direction, which, in combination with a certain degree of misregistration between the two images induces an offset in the generated interferometric phase. This behavior, if not compensated, imposes strong limits on the performance of the interferometric techniques in a squinted case, especially for airborne SAR systems. The article proposes two new techniques, which are appropriate to correct the phase bias coming from this source. The first one is based on a modification of the azimuth compression filter, which cancels the phase ramp of the range impulse response function for one specific squint value. In case the SAR processing is performed with variable squint over range, the authors propose a second method oriented to estimating the expected misregistration and thus, the phase bias by means of an iterative approach. Simulated data as well as real corner reflector responses are used to show that the correct topography can be recovered precisely even in the presence of phase bias coming from the squinted geometry.Peer Reviewe

SAR interferometric coherence in wide band systems

This paper presents a study of the interferometric coherence aimed to the understanding of the main sources of phase error of an operative wide band system. This objective is accomplished by finding a theoretical expression of coherence based on a suitable model capable of including the roughness of the surface, which produces decorrelation besides the conventional spectral overlapping approach. The analysis is validated by means of numerical simulations and controlled experiments in anechoic chamber, with the aim of extrapolating the obtained results to airborne and spaceborne imaging radars.Peer Reviewe

Risk factors for reperfusion injury after lung transplantation

Objective: To assess the influence of recipient's and donor's factors as well as surgical events on the occurrence of reperfusion injury after lung transplantation. Design and setting: Retrospective study in the surgical intensive care unit (ICU) of auniversity hospital. Methods: We collected data on 60 lung transplantation donor/recipient pairs from June1993 to May2001, and compared the demographic, peri- and postoperative variables of patients who experienced reperfusion injury (35%) and those who did not. Results: The occurrence of high systolic pulmonary pressure immediately after transplantation and/or its persistence during the first 48 h after surgery was associated with reperfusion injury, independently of preoperative values. Reperfusion injury was associated with difficult hemostasis during transplantation (p = 0.03). Patients with reperfusion injury were more likely to require the administration of catecholamine during the first 48 h after surgery (p = 0.014). The extubation was delayed (p = 0.03) and the relative odds of ICU mortality were significantly greater (OR 4.8, 95% CI: 1.06, 21.8) in patients with reperfusion injury. Our analysis confirmed that preexisting pulmonary hypertension increased the incidence of reperfusion injury (p < 0.01). Conclusions: Difficulties in perioperative hemostasis were associated with reperfusion injury. Occurrence of reperfusion injury was associated with postoperative systolic pulmonary hypertension, longer mechanical ventilation and higher mortality. Whether early recognition and treatment of pulmonary hypertension during transplantation can prevent the occurrence of reperfusion injury needs to be investigate

Procesado de imágenes SAR (Radar de Apertura Sintética) aerotransportado con compensación de movimiento

An operational processor to obtain high resolution radar images of the Earth surface from an airborne platform is presented. The paper describes the problem, its geometry and the steps to obtain a reflectivity image from the echos received by an airborne SAR (Synthetic Aperture Radar) sensor, characterized by an unstable trajectory. The performance of the processor has been verified with real data from the DLR E-SAR system.Peer ReviewedPostprint (published version

H-α decomposition and unsupervised Wishart classification for dual-polarized polarimetric SAR data

En aquesta tesi s'ha aplicat el mètode de descomposició H-α juntament amb el classificador Wishart a un conjunt real de dades SAR (Synthetic Aperture Radar) utilitzant l'entorn MATLAB. El conjunt de dades va ser capturat a través del satèl·lit TerraSAR-X i correspon a la regió de Pangkalan Bun, a Indonèsia. L'objectiu de la tesi és analitzar i avaluar la precisió del classificador. S'ha pogut comprovar que les imatges SAR es poden segmentar utilitzant les propietats dels mecanismes de dispersió caracteritzats pels paràmetres d'entropia i alpha. Per tant, s'ha obtingut una bona segmentació de les diferents zones de la imatge a partir dels paràmetres d'entropia i alpha en combinació amb el classificador Wishart.En esta tesis se ha aplicado el método de descomposición H-α junto con el clasificador Wishart a un conjunto real de datos SAR (Synthetic Aperture Radar) utilizando el MATLAB. El conjunto de datos fue capturado a través del satélite TerraSAR-X y corresponde a la región de Pangkalan Bun, en Indonesia. El objetivo de la tesis es analizar y evaluar la precisión del clasificador. Se ha podido comprobar que la imágenes SAR se pueden segmentar utilizando las propiedades de los mecanismos de dispersión caracterizados por los parámetros de entropía y alpha. Por lo tanto, se ha obtenido una buena segmentación de las distintas zonas de la imagen a partir de los parámetros de entropía y alpha en combinación con el clasificador Wishart.In this thesis the H-α decomposition method and the unsupervised Wishart classifier have been applied to a dual-polarized polarimetric Synthetic Aperture Radar (SAR) dataset using MATLAB computing environment. The dataset was captured by TerraSAR-X satellite and corresponds to the region of Pangkalan Bun, Indonesia. The objective is to analyze and evaluate the precision of the classification. It has been proved that the SAR image can be segmented taking advantage of the properties of the scattering mechanism characterized by the entropy and alpha parameters. Hence, a robust segmentation of the different zones of the image has been obtained by means of the entropy and alpha parameters in combination with the Wishart classifier

Decomposition and unsupervised segmentation of dual-polarized polarimetric SAR data using fuzzy entropy and coherency clustering method

En aquesta tesi, el teorema de descomposició H-α i l'algorisme de segmentació fuzzy c-means s'apliquen a un conjunt de dades polarimètriques amb polarització dual d'un sistema SAR (Synthetic Aperture Radar) usant MATLAB i s'avalua la precisió de la segmentació. La segmentació es realitza amb l'objectiu de separar els diferents elements del paisatge emprant les característiques pròpies de cada mecanisme de dispersió. Com es veurà, els paràmetres d'entropia i d'alpha resulten molt valuosos per a diferenciar els diversos tipus d'objectius i l'algorisme fuzzy c-means proposat aplicat a l'entropia i a la matriu de coherència obté resultats robustos en el procés de segmentació. Ambdós algorismes s'apliquen sobre un conjunt de dades de Pangkalan Bun, Indonèsia, proporcionat pel satèl·lit radar TerraSAR-X.En esta tesis, el teorema de descomposición H-α y el algoritmo de segmentación fuzzy c-means se aplican a un conjunto de datos polarimétricos con polarización dual de un sistema SAR (Synthetic Aperture Radar) usando MATLAB y se evalúa la precisión de la segmentación. La segmentación separa los diferentes elementos del paisaje usando las características propias de cada mecanismo de dispersión. Como se verá, los parámetros de entropía y de alpha resultan muy valiosos para diferenciar los tipos de objetivos y el algoritmo fuzzy c-means propuesto aplicado a la entropía y a la matriz de coherencia proporciona resultados robustos en la segmentación. Ambos algoritmos se aplican sobre un conjunto de datos de Pangkalan Bun, Indonesia, proporcionado por el satélite TerraSAR-X.In this thesis, H-α decomposition theorem and fuzzy c-means segmentation algorithm are applied to dual-polarized polarimetric SAR (Synthetic Aperture Radar) data using MATLAB and the accuracy of segmentation is evaluated. The segmentation is done with the purpose of separating the different elements of the landscape using the characteristics of the scattering mechanisms. As it will be shown, entropy and alpha decomposition parameters are a valuable key to differentiate between diverse types of targets and the proposed fuzzy c-means algorithm applied to the entropy and coherency matrix provides robust results in the segmentation process. Both algorithms are applied on a dual-polarized SAR dataset of Pangkalan Bun, Indonesia, provided by TerraSAR-X radar Earth observation satellite

Módulo posterior del radiómetro Planck a 30 GHz: modelo de calificación

The Back End Module at 30 GHz for the Planck mission has been manufactured in its Qualification Model version. Design, integration and main performances are described. Electrical, thermal and vibration tests, already done for space qualification, are summarised. This module consists basically in four identical branches based on broadband low noise amplification, direct detection and video amplification

A Core Outcome Set for Efficacy of Acute Treatment of Hereditary Angioedema

BACKGROUND: Clinical trials investigating drugs for the acute treatment of hereditary angioedema attacks have assessed many different outcomes. This heterogeneity limits the comparability of trial results and may lead to selective outcome reporting bias and a high burden on trial participants. OBJECTIVE: To achieve consensus on a core outcome set composed of key outcomes that ideally should be used in all clinical efficacy trials involving the acute treatment of hereditary angioedema attacks. METHODS: We conducted a Delphi consensus study involving all relevant parties: patients with hereditary angioedema, hereditary angioedema expert clinicians and clinical researchers, pharmaceutical companies, and regulatory bodies. Two Internetbased survey rounds were conducted. In round 1, panelists indicated the importance of individual outcomes used in clinical trials on a 9 -point Likert scale. Based on these results, a core outcome set was developed and voted on by panelists in round 2. RESULTS: A total of 58 worldwide panelists completed both rounds. The fi rst round demonstrated high importance scores and substantial agreement among the panelists. In the second round, a consensus of 90% or greater was achieved on a core outcome set consisting of fi ve key outcomes: change in overall symptom severity at one predetermined time point between 15 minutes and 4 hours after treatment, time to end of progression of all symptoms, the need for rescue medication during the entire attack, impairment of daily activities, and treatment satisfaction. CONCLUSIONS: This international study obtained a high level of consensus on a core outcome set for the acute treatment of hereditary angioedema attacks, consisting of fi ve key outcomes. Crown Copyright (c) 2024 Published by Elsevier Inc. on behalf of the American Academy of Allergy, Asthma & Immunology. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). (J Allergy Clin Immunol Pract 2024;12:1614-21