Trading off Complexity With Communication Costs in Distributed Adaptive Learning via Krylov Subspaces for Dimensionality Reduction

In this paper, the problemof dimensionality reduction in adaptive distributed learning is studied. We consider a network obeying the ad-hoc topology, in which the nodes sense an amount of data and cooperate with each other, by exchanging information, in order to estimate an unknown, common, parameter vector. The algorithm, to be presented here, follows the set-theoretic estimation rationale; i.e., at each time instant and at each node of the network, a closed convex set is constructed based on the received measurements, and this defines the region in which the solution is searched for. In this paper, these closed convex sets, known as property sets, take the form of hyperslabs. Moreover, in order to reduce the number of transmitted coefficients, which is dictated by the dimension of the unknown vector, we seek for possible solutions in a subspace of lower dimension; the technique will be developed around the Krylov subspace rationale. Our goal is to find a point that belongs to the intersection of this infinite number of hyperslabs and the respective Krylov subspaces. This is achieved via a sequence of projections onto the property sets and the Krylov subspaces. The case of highly correlated inputs that degrades the performance of the algorithm is also considered. This is overcome via a transformation whichwhitens the input. The proposed schemes are brought in a decentralized form by adopting the combine-adapt cooperation strategy among the nodes. Full convergence analysis is carried out and numerical tests verify the validity of the proposed schemes in different scenarios in the context of the adaptive distributed system identification task

Distributed Signal Processing Algorithms for Wireless Networks

Distributed signal processing algorithms have become a key approach for statistical inference in wireless networks and applications such as wireless sensor networks and smart grids. It is well known that distributed processing techniques deal with the extraction of information from data collected at nodes that are distributed over a geographic area. In this context, for each specific node, a set of neighbor nodes collect their local information and transmit the estimates to a specific node. Then, each specific node combines the collected information together with its local estimate to generate an improved estimate. In this thesis, novel distributed cooperative algorithms for inference in ad hoc, wireless sensor networks and smart grids are investigated. Low-complexity and effective algorithms to perform statistical inference in a distributed way are devised. A number of innovative approaches for dealing with node failures, compression of data and exchange of information are proposed and summarized as follows: Firstly, distributed adaptive algorithms based on the conjugate gradient (CG) method for distributed networks are presented. Both incremental and diffusion adaptive solutions are considered. Secondly, adaptive link selection algorithms for distributed estimation and their application to wireless sensor networks and smart grids are proposed. Thirdly, a novel distributed compressed estimation scheme is introduced for sparse signals and systems based on compressive sensing techniques. The proposed scheme consists of compression and decompression modules inspired by compressive sensing to perform distributed compressed estimation. A design procedure is also presented and an algorithm is developed to optimize measurement matrices. Lastly, a novel distributed reduced-rank scheme and adaptive algorithms are proposed for distributed estimation in wireless sensor networks and smart grids. The proposed distributed scheme is based on a transformation that performs dimensionality reduction at each agent of the network followed by a reduced–dimension parameter vector

Efficient material characterization by means of the Doppler effect in microwaves

Subject of this thesis is the efficient material characterization and defects detection by means of the Doppler effect with microwaves. The first main goal of the work is to develop a prototype of a microwave Doppler system for Non-Destructive Testing (NDT) purposes. Therefore it is necessary that the Doppler system satisfies the following requirements: non-expensive, easily integrated into industrial process, allows fast measurements. The Doppler system needs to include software for hardware control, measurements, and fast signal processing. The second main goal of the thesis is to establish and experimentally confirm possible practical applications of the Doppler system. The Doppler system consists of the following parts. The hardware part is designed in a way to ensure fast measurement and easy adjustment to the different radar types. The software part of the system contains tools for: hardware control, data acquisition, signal processing and representing data to the user. In this work firstly a new type of 2D Doppler amplitude imaging was developed and formalized. Such a technique is used to derive information about the measured object from several angles of view. In the thesis special attention was paid to the frequency analysis of the mea- sured signals as a means to improve spatial resolution of the radar. In the context of frequency analysis we present 2D Doppler frequency imaging and compare it with amplitude imaging. In the thesis the spatial resolution ability of CW radars is examined and im- proved. We show that the joint frequency and the amplitude signal processing allows to significantly increase the spatial resolution of the radar.Das Thema dieser Dissertation ist die effiziente Materialcharakterisierung und Fehlerdetektion durch Nutzung des Dopplereffektes mittels Mikrowellen. Das erste Hauptziel der Arbeit ist die Entwicklung eines Prototyps eines Mikrowellen-Doppler-Systems im Bereich der zerstörungsfreien Prüfung. Das Doppler-System muss folgenden Voraussetzungen erfüllen: es sollte preisgünstig sein, leicht in industrielle Prozesse integrierbar sein und schnelle Messungen erlauben. Das Doppler-System muss die Software für die Hardware-Kontrolle, den Messablauf und die schnelle Signalverarbeitung beinhalten. Das zweite Hauptziel der Dissertation ist es, mögliche praktische Anwendungsfelder des Doppler-Systems zu identifizieren und experimentell zu bearbeiten. Das Doppler-System besteht aus zwei Teilen. Der Hardware-Teil ist so konstruiert, dass er schnelle Messungen und leichte Anpassungen an verschiedene Sensor- und Radartypen zulässt. Der Software-Teil des Systems beinhaltet Werkzeuge für: Hardware-Kontrolle, Datenerfassung, Signalverarbeitung und Programme, um die Daten für den Benutzer zu präsentieren. In dieser Arbeit wurde zuerst ein neuer Typ der 2D-Doppler-Amplitudenbildgebung entwickelt und formalisiert. Dieser Technik wird dafür benutzt, Informationen über die gemessenen Objekte von verschiedenen Blickpunkten aus zu erhalten. In dieser Doktorarbeit wird der Frequenzanalyse der gemessenen Signale besondere Aufmerksamkeit geschenkt, um die Ortsauflösung des Radars zu verbessern. Im Kontext der Frequenzanalyse wird die 2D-Doppler-Frequenzbildgebung präsentiert und mit der Amplitudenbildgebung vergleichen. In dieser Dissertation werden die räumliche Auflösungsmöglichkeiten von CW-Radaren untersucht und verbessert. Es wird gezeigt, dass es die Frequenz- und Amplitudensignalverarbeitung erlaubt, die Ortsauflösung des Radars erheblich zu erhöhen

Segmentation and Scene Content in Moving Images

The problem of scene content in moving images was brought by Aralia. The goal in this study group was to consider two problems. The first was image segmentation and the second is the context of the scene. These problems were explored in different areas, namely the Bayesian approach to image segmentation, shadow detection, shape recognition and background separation

Advanced capabilities for planar X-ray systems

Mención Internacional en el título de doctorThe past decades have seen a rapid evolution towards the use of digital detectors in radiology and a more flexible robotized movement of the system components, X-ray tube and detector. This evolution opened the possibility for incorporating advanced capabilities in these planar X-ray systems, and for providing new valuable diagnostic information compared to the previous technology. Some of the current challenges for radiography are to obtain more quantitative images and to reduce the inherent superposition of tissues because of the 2D nature of the technique. Dual energy radiography, based on the acquisition of two images at different source voltages, enables a separate characterization of soft tissue and bone structures. Its benefits over conventional radiography have been proven in different applications, since it improves information content without adding significant extra acquisition time or radiation dose. In a different direction, a really disruptive advance would be to obtain 3D imaging with systems designed just for planar images. The incorporation of tomographic capabilities into these systems would have to deal with the acquisition of a limited number of projections, with non-standard geometrical configurations. This thesis presents original contributions in these two directions: dual energy radiography and 3D imaging with X-ray systems designed for planar imaging. The work is framed in a line of research of the Biomedical Imaging and Instrumentation Group from the Bioengineering and Aerospace Department of University Carlos III de Madrid working jointly with the University Hospital Gregorio Marañón, focused on the advance of radiology systems. This research line is carried out in collaboration with the group of Computer Architecture, Communications and Systems (ARCOS), from the same university, the Imaging Research Laboratory (IRL) of the University of Washington and the research center CREATIS, France. The research has a clear focus on technology transfer to the industry through the company Sedecal, a Spanish multinational among the 10 best world companies in the medical imaging field. The first contribution of this thesis is a complete novel protocol to incorporate dual energy capabilities that enable quantitative planar studies. The proposal is based on the use of a preliminary calibration with a very simple and low-cost phantom formed by two parts that represent soft tissue and bone equivalent materials. This calibration is performed automatically with no strict placement requirements. Compared to current Dual-energy X-ray Absorptiometry (DXA) systems, 1) it provides real mass-thickness values directly, enabling quantitative planar studies instead of relative comparisons, and 2) it is based on an automatic preliminary calibration without the need of interaction of an experienced technician. The second contribution is a novel protocol for the incorporation of tomographic capabilities into X-ray systems originally intended for planar imaging. For this purpose, we faced three main challenges. First, the geometrical trajectory of equipment follows non-standard circular orbits, thus posing severe difficulties for reconstruction. To handle this, the proposed protocol comprises a new geometrical calibration procedure that estimates all the system parameters per-projection. Second, the reconstruction of a limited number of projections from a reduced angular span leads to severe artifacts when using conventional reconstruction methods. To deal with these limited-view data, the protocol includes a novel advanced reconstruction method that incorporates the surface information of the sample, which can be extracted with a 3D light surface scanner. These data are introduced as an imposed constraint following the Split Bregman formulation. The restriction of the search space by exploiting the surface-based support becomes crucial for a complete recovery of the external contour of the sample and surroundings when the angular span is extremely reduced. The modular, efficient and flexible design followed for its implementation allows for the reconstruction of limited-view data with non-standard trajectories. Third, the optimization of the acquisition protocols has not yet explored with these systems. This thesis includes a study of the optimum acquisition protocols that allowed us to identify the possibilities and limitations of these planar systems. Using the surface-constrained method, it is possible to reduce the total number of projections up to 33% and the angular span down to 60 degrees. The contributions of this thesis open the way to provide depth and quantitative information very valuable for the improvement of radiological diagnosis. This could impact considerably the clinical practice, where conventional radiology is still the imaging modality most used, accounting for 80-90% of the total medical imaging exams. These advances open the possibility of new clinical applications in scenarios where 1) the reduction of the radiation dose is key, such as lung cancer screening or Pediatrics, according to the ALARA criteria (As Low As Reasonably Achievable), 2) a CT system is not usable due to movement limitations, such as during surgery or in an ICU and 3) where costs issues complicate the availability of CT systems, such as rural areas or underdeveloped countries. The results of this thesis has a clear application in the industry, since it is part of a proof of concept of the new generation of planar X-ray systems that will be commercialized worldwide by the company SEDECAL (Madrid, Spain).Los últimos años están viendo un rápido avance de los sistemas de radiología hacia el uso de detectores digitales y a una mayor flexibilidad de movimientos de los principales componentes del sistema, el tubo de rayos X y el detector. Esta evolución abre la posibilidad de incorporar capacidades avanzadas en sistemas de imagen plana por rayos X proporcionando nueva información valiosa para el diagnóstico. Dos retos en radiografía son obtener imágenes cuantitativas y reducir la superposición de tejidos debida a la naturaleza proyectiva de la técnica. La radiografía de energía dual, basada en la adquisición de dos imágenes a diferente kilovoltaje, permite obtener imágenes de tejido blando y hueso por separado. Los beneficios de esta técnica que aumenta la cantidad de información sin añadir un tiempo de adquisición o de dosis de radiación extra significativos frente al uso de radiografía convencional, han sido demostrados en diferentes aplicaciones. En otra dirección, un avance realmente disruptivo sería la obtención de imagen 3D con sistemas diseñados únicamente para imagen plana. La incorporación de capacidades tomográficas en estos sistemas tendría que lidiar con la adquisición de un número limitado de proyecciones siguiendo trayectorias no estándar. Esta tesis presenta contribuciones originales en esas dos direcciones: radiografía de energía dual e imagen 3D con sistemas de rayos X diseñados para imagen plana. El trabajo se encuadra en una línea de investigación del grupo de Imagen Biomédica e Instrumentación del Departamento de Bioingeniería e Ingeniería Aerospacial de la Universidad Carlos III de Madrid junto con el Hospital Universitario Gregorio Marañon, centrada en el avance de sistemas de radiología. Esta línea de investigación se desarollada en colaboración con el grupo Computer Architecture, Communications and Systems (ARCOS), de la misma universidad, el grupo Imaging Research Laboratory (IRL) de la Universidad de Washington y el centro de investigación CREATIS, de Francia. Se trata de una línea de investigación con un claro enfoque de transferencia tecnológica a la industria a través de la compañía SEDECAL, una multinacional española de entre las 10 líderes del mundo en el campo de la radiología. La primera contribución de esta tesis es un protocolo completo para incorporar capacidades de energía dual que permitan estudios cuantitativos de imagen plana. La propuesta se basa en una calibración previa con un maniquí simple y de bajo coste formado por dos materiales equivalentes de tejido blando y hueso respectivamente. Comparado con los sistemas actuales DXA (Dual-energy X-ray Absorptiometry), 1) proporciona valores reales de tejido atravesado, 2) se basa en una calibración automática que no requiere la interacción de un técnico con gran experiencia. La segunda contribución es un protocolo nuevo para la incorporación de capacidades tomográficas en sistemas de rayos X originariamente diseñados para imagen plana. Para ello, nos enfrentamos a tres principales dificultades. En primer lugar, las trayectorias que pueden seguir la fuente y el detector en estos sistemas no constituyen órbitas circulares estándares, lo que plantea retos importantes en la caracterización geométrica. Para solventarlo, el protocolo propuesto incluye una calibración geométrica que estima todos los parámetros geométricos del sistema para cada proyección. En segundo lugar, la reconstrucción de un número limitado de proyecciones adquiridas en un rango angular reducido da lugar a artefactos graves cuando se reconstruye con algoritmos convencionales. Para lidiar con estos datos de ángulo limitado, el protocolo incluye un nuevo método avanzado de reconstrucción que incorpora la información de superficie de la muestra, que se puede se obtener con un escáner 3D. Esta información se impone como una restricción siguiendo la formulación de Split Bregman, para compensar la falta de datos. La restricción del espacio de búsqueda a través de la explotación del soporte basado en superficie, es crucial para una recuperación completa del contorno externo de la muestra cuando el rango angular es extremadamente pequeño. El diseño modular, eficiente y flexible de la implementación propuesta permite reconstruir datos de ángulo limitado obtenidos con posiciones de fuente y detector no estándar. En tercer lugar, hasta la fecha, no se ha explorado la optimización del protocolo de adquisición con estos sistemas. Esta tesis incluye un estudio de los protocolos óptimos de adquisición que permitió identificar las posibilidades y limitaciones de estos sistemas de imagen plana. Gracias al método de reconstrucción basado en superficie, es posible reducir el número total de proyecciones hasta el 33% y el rango angular hasta 60 grados. Las contribuciones de esta tesis abren la posibilidad de proporcionar información de profundidad y cuantitativa muy valiosa para la mejora del diagnóstico radiológico. Esto podría impactar considerablemente en la práctica clínica, donde la radiología convencional es todavía la modalidad de imagen más utilizada, abarcando el 80- 90% del total de los exámenes de imagen médica. Estos avances abren la posibilidad de nuevas aplicaciones clínicas en escenarios donde 1) la reducción de la dosis de radiación es clave, como en screening de cáncer de pulmón, de acuerdo con el criterio ALARA (As Low As Reasonably Achievable), 2) no se puede usar un sistema TAC por limitaciones de movimiento como en cirugía o UCI, o 3) el coste limita la disponibilidad de sistemas TAC, como en zonas rurales o en países subdesarrollados. Los resultados de esta tesis presentan una clara aplicación industrial, ya que son parte de un prototipo de la nueva generación de sistemas planos de rayos X que serán distribuidos mundialmente por la compañía SEDECAL.This thesis has been developed as part of several research projects with public funding: - DPI2016-79075-R. ”Nuevos escenarios de tomografía por rayos X”, IP: Mónica Abella García, Ministerio de Economía y Competitividad, 01/01/2017-31/12/2019, 147.620 e. - ”Nuevos escenarios de tomografía por rayos X (NEXT) DPI2016-79075-R. Ministerio de Economía”, Industria y Competitividad. (Universidad Carlos III de Madrid). 30/12/2016-29/12/2019. 147.620 e. (…) - FP7-IMI-2012 (GA-115337), ”PreDict-TB: Model-based preclinical development of anti-tuberculosis drug combinations”. FP7-IMI - Seventh Framework Programme (EC-EFPIA). Unión Europea. (Universidad Carlos III de Madrid). 01/05/2012-31/10/2017. (…) - TEC2013-47270-R, ”Avances en Imagen Radiológica (AIR)”, Ministerio de Economía y Competitividad”, 01/01/2014-31/12/2016. IP: Mónica Abella Garcia and Manuel Desco Menéndez. 160.204 e (…) - RTC-2014-3028-1, ”Nuevos Escenarios Clínicos con Radiología Avanzada (NECRA)”, Ministerio de Economía y Competitividad, 01/06/2014-31/12/2016 IP: Mónica Abella García. 2014-2016. 219.458,96 e - IDI-20130301, ”Nuevo sistema integral de radiografía (INNPROVE: INNovative image PROcessing in medicine and VEterinary)”, IP: Mónica Abella García and Manuel Desco Menéndez. Ministerio de Economía y Competitividad. Subcontratación CDTI, 14/01/2013-31/03/2015. Total: 1.860.629e (UC3M: 325.000e). (Art. 83) - IPT-2012-0401-300000 INNPACTO 2012, ”Tecnologías para Procedimientos Intraoperatorios Seguros y Precisos. XIORT. MINECO. (Universidad Carlos III de Madrid). 01/01/2013-31/12/2015.Programa Oficial de Doctorado en Ingeniería MatemáticaPresidente: Doménec Ros Puig.- Secretario: Cyril Riddell.- Vocal: Yannick Boursie

Model Order Reduction

An increasing complexity of models used to predict real-world systems leads to the need for algorithms to replace complex models with far simpler ones, while preserving the accuracy of the predictions. This three-volume handbook covers methods as well as applications. This third volume focuses on applications in engineering, biomedical engineering, computational physics and computer science

Anomaly detection & object classification using multi-spectral LiDAR and sonar

In this thesis, we present the theory of high-dimensional signal approximation of multifrequency signals. We also present both linear and non-linear compressive sensing (CS) algorithms that generate encoded representations of time-correlated single photon counting (TCSPC) light detection and ranging (LiDAR) data, side-scan sonar (SSS) and synthetic aperture sonar (SAS). The main contributions of this thesis are summarised as follows: 1. Research is carried out studying full-waveform (FW) LiDARs, in particular, the TCSPC data, capture, storage and processing. 2. FW-LiDARs are capable of capturing large quantities of photon-counting data in real-time. However, the real-time processing of the raw LiDAR waveforms hasn’t been widely exploited. This thesis answers some of the fundamental questions: • can semantic information be extracted and encoded from raw multi-spectral FW-LiDAR signals? • can these encoded representations then be used for object segmentation and classification? 3. Research is carried out into signal approximation and compressive sensing techniques, its limitations and the application domains. 4. Research is also carried out in 3D point cloud processing, combining geometric features with material spectra (spectral-depth representation), for object segmentation and classification. 5. Extensive experiments have been carried out with publicly available datasets, e.g. the Washington RGB Image and Depth (RGB-D) dataset [108], YaleB face dataset1 [110], real-world multi-frequency aerial laser scans (ALS)2 and an underwater multifrequency (16 wavelengths) TCSPC dataset collected using custom-build targets especially for this thesis. 6. The multi-spectral measurements were made underwater on targets with different shapes and materials. A novel spectral-depth representation is presented with strong discrimination characteristics on target signatures. Several custom-made and realistically scaled exemplars with known and unknown targets have been investigated using a multi-spectral single photon counting LiDAR system. 7. In this work, we also present a new approach to peak modelling and classification for waveform enabled LiDAR systems. Not all existing approaches perform peak modelling and classification simultaneously in real-time. This was tested on both simulated waveform enabled LiDAR data and real ALS data2 . This PhD also led to an industrial secondment at Carbomap, Edinburgh, where some of the waveform modelling algorithms were implemented in C++ and CUDA for Nvidia TX1 boards for real-time performance. 1http://vision.ucsd.edu/~leekc/ExtYaleDatabase/ 2This dataset was captured in collaboration with Carbomap Ltd. Edinburgh, UK. The data was collected during one of the trials in Austria using commercial-off-the-shelf (COTS) sensors