Differential interferometry for multi-frequency ground-based SAR systems

Ground-Based Synthetic Aperture Radars (GB-SAR) are a type of Synthetic Aperture Radars (SAR) with a higher flexibility and lower cost than their satellite counterparts. The effectiveness of GB-SAR terrain displacement monitoring has already been proven with bare soils. There is interest in studying their effectiveness in areas covered by vegetation. The Multi-Frequency GB-SAR system developed by Balamis is able to operate in bands X, C, L and P. A measurement campaign took place in the "Castell de Subirats" to study an area covered by vegetation. Two Trihedral Corner Reflectors (TCR) were placed in the area, one of them surrounded by vegetation. Can we consider the reflectors stable? A big Rock is present in the area but is covered by vegetation. Can it be used as natural reflector for low bands? Is it possible to monitor displacements in the reflectors in all bands? In X-band the reflectors are not stable because of the surrounding vegetation. In C-band the TCRs are stable. In L-band one of the TCR and the Rock are stable. In P-band only the Rock is stable. The Rock can be used as a reflector and a calibrator for bands L and P as those frequencies can penetrate vegetation. It is possible to monitor the displacements, except in band X because of the phase shifts caused by the vegetation.Los Radares de Apertura Sintética Terrestres (GB-SAR en inglés) son un tipo de Radares de Apertura Sintética (SAR) con una mayor flexibilidad y un coste más bajo que sus homólogos de satélite. La eficacia de la monitorización de desplazamientos del terreno con sistemas GB-SAR ya se ha demostrado con suelos desnudos. Hay interés por estudiar su efectividad en zonas cubiertas de vegetación. El sistema Multi-Frecuencia GB-SAR desarrollado por Balamis es capaz de operar en las bandas X, C, L y P. Se realizó una campaña de medida en el "Castillo de Subirats" para estudiar una zona cubierta de vegetación. Se colocaron en la zona dos Reflectores de Esquinas Triédricas (TCR), uno de ellos rodeado de vegetación. Podemos considerar los reflectores estables? Hay una gran Piedra presente en la zona pero está cubierta de vegetación. Se puede utilizar como reflector natural para bandas bajas? Es posible medir los desplazamientos en los reflectores en todas las bandas? En banda X, los reflectores no son estables debido a la vegetación circundante. En banda C, los TCR son estables. En banda L, uno de los TCR y la Piedra son estables. En banda P, sólo la Piedra es estable. La Piedra se puede utilizar como reflector y calibrador para las bandas L y P, ya que estas frecuencias pueden penetrar en la vegetación. Es posible medir los desplazamientos, excepto en banda X debido a las inestabilidades de fase provocadas por la vegetación.Els Radars d'Obertura Sintètica Terrestres (GB-SAR en anglès) són un tipus de Radars d'Obertura Sintètica (SAR) amb una major flexibilitat i un cost més baix que els seus homòlegs de satèl·lit. L'eficàcia de la monitorització de desplaçaments del terreny amb sistemes GB-SAR ja s'ha demostrat amb sòls nus. Hi ha interès per estudiar la seva efectivitat en zones cobertes de vegetació. El sistema Multi-Freqüència GB-SAR desenvolupat per Balamis és capaç d'operar a les bandes X, C, L i P. Es va realitzar una campanya de mesura al "Castell de Subirats" per estudiar una zona coberta de vegetació. Es van col·locar a la zona dos Reflectors de Cantonades Trièdriques (TCR), un d'ells envoltat de vegetació. Podem considerar els reflectors estables? Hi ha una gran Pedra present a la zona però està coberta de vegetació. Es pot utilitzar com a reflector natural per a bandes baixes? És possible mesurar els desplaçaments als reflectors a totes les bandes? A banda X, els reflectors no són estables a causa de la vegetació circumdant. A banda C, els TCR són estables. A banda L, un dels TCR i la Pedra són estables. A banda P, només la Pedra és estable. La Pedra es pot utilitzar com a reflector i calibrador per a les bandes L i P, ja que aquestes freqüències poden penetrar la vegetació. És possible mesurar els desplaçaments, excepte a la banda X a causa de les inestabilitats de fase provocades per la vegetació

Predicting wind power from wind speed data

The search for renewable and sustainable energy sources is a global concern. One way to produce renewable energy is by making use of wind turbines. However, wind speed is a stochastic process which fluctuates considerably. This means that energy cannot be produced at a constant rate. For many years, the most used probability density function has beenthe Weibull distribution. Experimental research is made in this report, in which Nakagami, Normal,and Rician distributionsarecompared to Weibull distribution usingthe Kullback-Leibler divergence for different time frames.The resultsreveal that the four distributionsareall numerically acceptablefor analysing wind speed data for different time frames.Since Weibull distribution is the commonly used distribution, wind generation companies can continue using this distribution as the standard one.However, almost everytime frame manifestmultimodal distributed wind speed data. Future research can focus onstudyingmultimodal distributions instead of unimodal.OutgoingObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminan

Association entre l'élastographie vasculaire non invasive et l'indice de masse corporelle chez les enfants

Sachant que l’Athérosclérose commence durant l’enfance par des marqueurs subcliniques, cette étude explore l’association entre l’indice de masse corporelle (IMC) et l’élastographie vasculaire non-invasive (NIVE) des artères carotides communes chez les enfants. On compare aussi les techniques de mesure de l’intima-média (IMT) des artères carotides en se basant sur le mode-B et la radiofréquence (RF) chez les enfants avec IMC normal et élevé. Il s’agit d’une étude prospective effectuée entre 2005 et 2011. Les paramètres de « NIVE » ont été comparés pour deux groupes d’IMC (normal et élevé) de 60 enfants respectivement, faisant tous partie de la cohorte de l’étude QUebec Adipose and Lifestyle Investigation in Youth (QUALITY). Les paramètres de NIVE incluent la contrainte axiale cumulative (CAS) en %, la translation axiale cumulative (CAT) en mm. L’épaisseur de l’intima-média est calculée selon trois méthodes : logiciel «M’ath-Std» (mode-B), « echotracking » des signaux de RF et probabilité de distribution des signaux de RF sur la plateforme NIVE. Une analyse ANOVA et corrélation Pearson ont été effectuées sur le logiciel SAS version 9.3. Une corrélation intra-class (ICC) a été effectuée sur un logiciel MedCalc version 17.2. L’âge moyen était 11,4 ans pour le groupe IMC normal et 12 pour le groupe IMC élevé. Cinquante-huit pourcent étaient des garçons dans le groupe IMC normal et 63% dans le groupe IMC élevé. Les deux groupes étaient différents selon l’âge, stade de Tanner, tension artérielle (systolique et diastolique), et LDL mais similaire pour le sexe. En contrôlant pour les variables confondantes, la CAS n’est pas différente entre les deux groupes. La CAT est plus basse chez les enfants avec IMC normal (CAT=0.51 +/-0.17 mm pour le groupe « IMC normal » et 0.67+/-0.24 mm pour le groupe « IMC élevé » (p<0.001)). Il y a une très faible corrélation entre les trois techniques de mesure d’IMT ICC=0,34 (95% intervalle de confiance 0,27-0,39). L’IMT est significativement plus élevé dans le groupe d’enfants « IMC élevé ». Mode-B (0.55 mm « IMC normal » vs. 0.57 mm « IMC élevé »; p=0.02); IMT RF (0.45 mm « IMC normal » vs. 0.48 mm « IMC élevé »; p=0.03) et IMT probabilité de distribution des signaux RF (0.32 mm « IMC normal » vs. 0.35 mm « IMC élevé »; p=0.010). La NIVE montre une différence significative dans la CAT de l'artère carotide commune des enfants avec un IMC normal par rapport à l'IMC élevé. Des variations significatives de la mesure des IMT ont été observées entre les différentes techniques. Cependant, les enfants avec IMC élevé ont des valeurs IMT plus élevées, indépendamment de la méthode utilisée. Les deux marqueurs subcliniques peuvent être utilisés pour la stratification des enfants à risque de maladies cardiovasculaires. La même méthode devrait toujours être utilisée.Knowing that cardiovascular disease risk factors are present in asymptomatic children, this study explores the association between non-invasive vascular elastography (NIVE) as a subclinical marker of atherosclerosis and obesity in children. In the absence of a gold standard, we also compare B-mode and Radiofrequency (RF) based ultrasound measurements of intima-media thickness (IMT) in children with normal and increased body mass index (BMI). This is a prospective study between 2005 and 2011. NIVE parameters and IMT of the common carotid artery were compared between 60 children with normal BMI and 60 children with increased BMI enrolled in the QUebec Adipose and Lifestyle Investigation in Youth cohort (QUALITY). NIVE parameters included cumulated axial strain (CAS) (%) and cumulated axial translation (CAT) in mm. The three methods of IMT measurements included M’ath Std (B-mode), RF echotracking system and RF probability distribution using NIVE platform. ANOVA analysis and Pearson correlation were calculated using SAS version 9.3. Intra-class correlation coefficient (ICC) and regression analysis was done on MedCalc software version 17.2. The mean age was 11.4 years for the normal BMI group and 12 years for the increased BMI group. Fifty-eight percent were boys in the normal BMI group and 63% in the increased BMI group. The two groups were significantly different with respect to age, Tanner stage, systolic and diastolic blood pressure and were similar with respect to sex. After controlling for confounders, the results show no difference in CAS between the two groups and a significantly lower CAT in the normal BMI group (CAT=0.51+/-0.17 mm for the normal BMI group and 0.67+/-0.24 mm for the increased BMI group (p<0.001)). There is a weak correlation among the three techniques. ICC=0.34 (95% confidence interval (CI): 0.27-0.39). There is however significantly increased IMT in children with increased BMI according to all three techniques. The results were as follow: for B-mode IMT (0.55 mm (normal BMI group) vs. 0.57 mm (increased BMI group); p=0.02); for RF echotracking IMT (0.45 mm (normal BMI group) vs. 0.48 mm (increased BMI group); p=0.03) and for RF probability distribution IMT (0.32 mm (normal BMI group) vs. 0.35 mm (increased BMI group); p=0.010).NIVE is a one-step technique for IMT and CAT measurement in children at risk. Significant IMT measurement variation is observed between the three techniques. However, children with increased BMI tend to have higher IMT values regardless of the technique. Both subclinical markers can be used for optimal stratification of children with cardiovascular disease risk factors. The same technique should be used throughout

Doctor of Philosophy

dissertationWireless communication has become an essential part of everyday life. The hunger for more data, more phone calls, more video, and more access in more places, including vehicles, is growing massively. Communication in vehicles is particularly challenging because of their extremely high multipath environment. In addition, there is significant interest in reducing the number of wires in vehicles to reduce weight, complexity, maintenance, etc. and replace them with wireless systems. Preliminary research shows that MIMO systems take advantage of the extreme multipath environment found in aircraft and other vehicles and also provides more consistent channel capacity than SISO systems. The purpose of this research was to quantify complex channels (including the aircraft/vehicle environment) and their relation to other environments, evaluate MIMO in aircraft, provide design constraints for accurately modeling complex channels, and provide information to predict optimum antenna type and location to enable communication in aircraft/cars/buses/ships/trains/etc. and other extreme channels. The ability to evaluate and design MIMO technologies from the guidelines in this paper is potentially transformative for aircraft safety - enabling a new generation of location specific monitoring and maintenance. Average measured capacity was found to be between 18 and 21 bits/s/Hz using a 4x4 array of antennas, and had no direct relation to the size of the channel. Site-specific capacity showed a multipath rich channel, varying between 15 to 23 bits/s/Hz. The capacity decreased for increasing measurement distance, with exceptions near reflective objects that increase multipath. Due to these special circumstances for site-specific locations within complex channels, it is recommended that 3D ray tracing be used for modeling as it is more accurate than commonly used statistical models, within 1.1 bits/s/Hz. This showed that our 3D ray tracing is adaptable to various environments and gives a more accurate depiction than statistical models that average channel variations. This comes at the cost of greater model complexity. If increased complexity is not desirable, Nakagami 1.4 could be used as the next most accurate model. Design requirements for modeling different complex channels involve a detailed depiction of channel geometry, including height, width, length, shape (square, cylindrical, slanted walls, etc.), large windows, and reflective objects inside the channel space, especially those near the transmitter. Overall, the multipath rich channel found in vehicles is an excellent environment for MIMO systems. These complex channels can be simulated accurately without measurement and before they are even built using our sitespecific 3D ray tracing software combined with a detailed signal model to incorporate antenna effects

Advances in Sensors and Sensing for Technical Condition Assessment and NDT

The adequate assessment of key apparatus conditions is a hot topic in all branches of industry. Various online and offline diagnostic methods are widely applied to provide early detections of any abnormality in exploitation. Furthermore, different sensors may also be applied to capture selected physical quantities that may be used to indicate the type of potential fault. The essential steps of the signal analysis regarding the technical condition assessment process may be listed as: signal measurement (using relevant sensors), processing, modelling, and classification. In the Special Issue entitled “Advances in Sensors and Sensing for Technical Condition Assessment and NDT”, we present the latest research in various areas of technology