Contributions to ionospheric determination with global positioning system: solar flare detection and prediction of global maps of total electron content

Two research studies have been addressed in this thesis. Both of them are of actual scientific interest and are based on processing GNSS data. The first part of this thesis is devoted to GNSS detection and monitoring of solar flares. The second one is devoted to GNSS prediction of ionospheric Total Electron Content. Regarding the first study, a new solar flare detector called SISTED has been designed and implemented. Its goal is to provide a simple and efficient way of detecting the most number of powerful X-class solar flares in real time operation. In addition, it can send early warning messages to prevent the harmful consequences of the increase of ejected particles from the Sun that may reach the Earth after a solar flare, especially in case of a Coronal Mass Ejection. The main benefit of SISTED regarding other detection techniques is that it does not require data from external providers out of the GNSS community. In addition, it can run in real-time operation and could provide value added data to GNSS users. The results show that SISTED was able to detect up to the 95% of the X-class flares reported by GOES for more than a half solar cycle. Regarding the second study, a new approach to predict Global Ionospheric vertical TEC Maps has been designed and implemented in the context of the IGS Ionosphere Working Group. The motivation to develop a UPC Predicted product was the interest of ESA's SMOS mission. A recent application using UPC Predicted products is the generation of real-time global VTEC maps as background model. In addition, the predicted VTEC maps are used to generate the combined IGS Predicted products. The results obtained in this thesis show that the model performs well when the results are compared with those obtained by the other IGS analysis centers. In addition, applying the prediction model leads to better results than the use of time-invariant ionosphere for two days ahead. In relation with this research, 4 publications in international journals indexed in JCR/ISI have been generated (and another one is under review process), and 7 presentations have been authored in international meetings, among the new UPC predicted product contributing to IGS, and the contribution to two competitive projects funded by the European Space Agency (AGIM and MONITOR)

Global distribution of ionospheric scintillations from the Real-Time GPS ROTI

A global real-time monitoring system has been implemented in the frame of ESA-ESTEC/EGNOS-POfunded project MONITOR. It is based on world-wide GNSS datastreams distributed by means of NTRIP and provides multiple ionospheric indices and products to the scientific community and industry. In particular, the Rate Of Total Electron Content Index (ROTI) proxy, which is correlated with scintillation activity and has been running for several years for real-time detection and monitoring. It shall also be pointed out that the multiple products, also aiming at the identification of Travelling Ionospheric Disturbances (TIDs), Solar Flares overionization, among other ionospheric perturbations, are useful to properly characterize scenarios where these could occur simultaneously to scintillations. In addition, there is also a new proxy suitable for radio-occultation GNSS measurements, named OSPI. In this context, a climatological ionospheric scintillation study has been conducted in different latitudinal regions from the UPC-IonSAT database of global ROTI. For this purpose, we have obtained results from several receivers in 30-degree latitudinal strips and distinguishing between North- and South-Hemisphere locations.Postprint (published version

West Nile Virus Encephalitis in Haematological Setting: Report of Two Cases and a Brief Review of the Literature

West Nile virus is a zoonotic agent causing life-threatening encephalitis in a proportion of infected patients. Older age, immunosuppression, and mutations in specific host genes (e.g., CCR5 delta-32 mutation) predispose to neuroinvasive infection. We report on two cases of severe West Nile encephalitis in recently-treated, different-aged, chronic lymphocytic leukemia patients. Both patients developed high-grade fever associated with severe neurological impairment. The younger one harboured germ-line CCR5 delta-32 mutation, which might have played a role in the pathogenesis of its neuroinvasive manifestations

UPC contributions to GNSS monitoring of ionosphere in the frame of the IGS Iono-WG

UPC has been acting as Ionosphere Associate Analysis Center (IAAC) from the beginning of the IGS Iono-WG activities on 1st June, 1998, providing multiple products on GNSS monitoring of ionosphere and also assuming its chairmanship for 5 years (2002 to 2007), as the result of the common work of the co-authors of this presentation. The recently formed UPC-IonSAT research group has not only continued providing rapid, final and 2-days ahead predicted Global Ionospheric Maps (GIMs) at 2-hour time resolution in IONEX format labelled UPCG, UPRG and U2PG respectively) but also real time GIMs (labelled URTG) and 15-minute and 1-hour time resolution GIMs considering rapid latencies (labelled UQRG and UHRG, respectively). Such products have been generated using the TOMION SW for ionospheric modelling and precise positioning. TOMION has evolved from 1998 until nowadays in order to provide the above-mentioned recent products but also to improve the performance of the previously existing ones. This also has led to a reprocessing campaign. It is also worth mentioning that an improved Kriging interpolation technique, combined with the global tomographic modelling ([Orús et al., 2005 and Hernández-Pajares et al.1999]) has recently enabled a boost in the performance for all existing products.Postprint (published version

Real time Ionospheric determination at global scale

The global ionospheric determination has been possible in the last 15 years thanks to the availability of a new type of ionospheric sensor with a very high spatial and temporal sampling: the dual-frequency GPS receivers. Indeed, several hundreds of them, worldwide distributed, are freely available, tracking typically 6+ GPS satellites in view, providing at every epoch several thousands of line-of-sight integrated free electron densities (Slant Total Electron Content, STEC). This has allowed in particular to compute and freely distribute global Vertical Total Electron Content (VTEC) maps, in the context of the open- product organization called International GNSS Service (IGS), which applications run from single frequency receivers (accurate mitigation of ionospheric delay), calibration of new altimeters (such as the SMOS mission) up to the potential use for increasing the performance of positioning based on carrier phase measurements. One of the next challenges, in particular in IGS, is computing the global VTEC maps, in real-time, which involves much less permanent receivers, increasing much more the di cult task of interpolating in a realistic way the electron content over large regions with few receivers (south hemisphere, oceans...). In this paper the actual status of the problem will be presented, from the perspective of gAGE/UPC, one of the four IGS Ionospheric Analysis Centers, participating in the Real-Time IGS Pilot Project.Peer ReviewedPostprint (published version

Contact Optimization for Non-Prehensile Loco-Manipulation via Hierarchical Model Predictive Control

Recent studies on quadruped robots have focused on either locomotion or mobile manipulation using a robotic arm. Legged robots can manipulate heavier and larger objects using non-prehensile manipulation primitives, such as planar pushing, to drive the object to the desired location. In this paper, we present a novel hierarchical model predictive control (MPC) for contact optimization of the manipulation task. Using two cascading MPCs, we split the loco-manipulation problem into two parts: the first to optimize both contact force and contact location between the robot and the object, and the second to regulate the desired interaction force through the robot locomotion. Our method is successfully validated in both simulation and hardware experiments. While the baseline locomotion MPC fails to follow the desired trajectory of the object, our proposed approach can effectively control both object's position and orientation with minimal tracking error. This capability also allows us to perform obstacle avoidance for both the robot and the object during the loco-manipulation task.Comment: 7 pages, 9 figure

Pérdida de peso en frutos de seis híbridos de pimiento tipo ancho (Capsicum annuum L.) bajo las condiciones de Casma

Universidad Nacional Agraria La Molina. Facultad de Agronomía. Departamento Académico de HorticulturaEl presente trabajo de investigación se realizó en los arenales cercanos a la zona agroindustrial de Casma cerca al Fundo “Santa Delfina” donde se cosecharon los pimientos Anchos a tratar, ubicado a 1.5 km. del Fundo y a 4 km. de la ciudad de Casma. Es allí donde se acondicionaron espacios de secado llamados “eras” para el secado respectivo de los pimientos anchos cosechados, con el objetivo de evaluar el ritmo de pérdida de peso de los frutos de seis híbridos de pimiento ancho en túneles de secado con el quemado de azufre y determinar cuál de estos pierden gran cantidad de agua y quien tiene mejor peso seco comercial (mayor materia seca) que es de interés al productor. El Factor en estudio fueron los híbridos y las variables evaluadas fueron: Peso fresco inicial de 10 frutos (gr.), Variación de peso y humedad de 10 frutos (gr. /día), Relación peso fresco/peso seco (PF/PS), Registro de Temperatura y Humedad, determinación por calidades y de la merma. El diseño estadístico fue un DBCA con cuatro bloques. Se realizó el ANVA y la prueba múltiple de Duncan. Hubo diferencias significativas en todas las variables evaluadas. Los híbridos que presentaron mayor peso fresco fueron Máncora y Amazonas con 194.65 gr/fruto y 186.98 gr/fruto respectivamente; los que mayor agua perdieron por frutos fueron Mancora y Fumagalli con 89.2% (173.65 gr. de H2O) y 88.8%(173.65 gr. de H2O) respectivamente de su peso fresco. La mejor relación PF/PS lo tuvo el híbrido Vencedor con 7.71. El Tiempo de secado para este tipo sistema de secado con azufre fue entre 12 a 17 díasTesi

Reconstrução de imagens de ultrassom utilizando regularização l1 através de mínimos quadrados iterativamente reponderados e gradiente conjugado

This work presents an inverse problem based method for ultrasound image reconstruction which uses the L2-norm (or euclidean norm) as a penalty for the error between the data and the solution, and the L1-norm as a regularization penalty. The motivation for the use of of L1 regularization is the sparsity promoting property of this type of regularization. The sparsity of L1 regularization circumvents the problem of excess of artifatcts that is observed in other approaches of inverse problem based reconstrucion in ultrasound. Such problem is mainly a consequence of the limitation in the discrete representation of a continuous object in the acquisition model. Due to this limitation, reflecting objects in the imaged area are often localized in positions that do not correspond precisely to one of the positions in the discrete model, therefore generating data that do not correspond to the model data. The formulations of the problem with L2 regularization and with L1 regularization are presented and compared in geometric and Bayesian terms. The optimization algorithm proposed is an implementation of Iteratively Reweighted Least Squares (IRLS) and uses the Conjugate Gradient (CG) method inside each iteration, thus being called IRLS-CG. Simulations with computer phantoms are realized showing that the proposed method allows for the reconstruction of images, without observable artifacts, from data with reflectors located in non-modeled positions. Simulations also show a better spatial resolution in the proposed method when compared to the delay-and-sum (DAS) algorithm. It was also observed better computational performance of CG when compared to the matrix inversion in the iterations of IRLS.Este trabalho apresenta um método de reconstrução de imagens de ultrassom por problemas inversos que tem como penalidade para o erro entre solução e dados a norma L2, ou euclidiana, e como penalidade de regularização a norma L1. A motivação para o uso da regularização L1 é que se trata de um tipo de regularização promotora de esparsidade na solução. A esparsidade da regularização L1 contorna o problema de excesso do artefatos, observado em outras implementações de reconstrução por problemas inversos em ultrassom. Este problema é consequência principalmente da limitação da representação discreta do objeto contínuo no modelo de aquisição. Por conta desta limitação, objetos refletores na área imageada quase sempre localizam-se em posições que não correspondem precisamente a uma das posições do modelo discreto, gerando dados que não correspondem aos dados modelados. As formulações do problema com regularização L2 e com regularização L1 são apresentadas e comparadas dos pontos de vista geométrico e Bayesiano. O algoritmo de otimização proposto é uma implementação do algoritmo Iteratively Reweighted Least Squares (IRLS) e utiliza o método do Gradiente Conjugado (CG - Conjugate Gradient) a cada iteração, sendo chamado de IRLS-CG. São realizadas simulações com phantoms computacionais que mostram que o método permite reconstruir imagens a partir da aquisição de dados com refletores em posições não modeladas sem a observação de artefatos. As simulações também mostram melhor resolução espacial do método proposto com relação ao algoritmo delay-and-sum (DAS). Também se observou melhor desempenho computacional do CG com relação à matriz inversa nas iterações do IRLS

Recent activities of IAG working group “Ionosphere Prediction”

Ionospheric disturbances pose, for instance, an increasing risk on economy, national security, satellite and airline operations, communications networks and the navigation systems. Constructing forecasted ionospheric products with a reliable accuracy is still an ongoing challenge. In this sense, a Working Group (WG) with the title “Ionosphere Prediction” within the International Association of Geodesy (IAG) under Sub-Commission 4.3 “Atmosphere Remote Sensing” of the Commission 4 “Positioning and Applications” has been created and is actively working since 2015 to encourage scientific collaborations on developing models and discussing challenges of the ionosphere prediction problem. Different centers contribute to the WG such as the German Aerospace Center (DLR), Universitat Politècnica de Catalunya (UPC), Technical University of Munich (TUM) and GMV. One of the main focus of the WG is to evaluate different ionosphere prediction approaches and products which are highly depending on solar and geomagnetic conditions as well as on data from different measurement techniques (e.g. GNSS) with varying spatial-temporal resolution, sensitivity and latency. In this contribution, the recent progress of the WG on ionosphere prediction studies including individual and cooperated activities will be presented.Postprint (published version

TEC forecasting based on manifold trajectories

In this paper, we present a method for forecasting the ionospheric Total Electron Content (TEC) distribution from the International GNSS Service’s Global Ionospheric Maps. The forecasting system gives an estimation of the value of the TEC distribution based on linear combination of previous TEC maps (i.e., a set of 2D arrays indexed by time), and the computation of a tangent subspace in a manifold associated to each map. The use of the tangent space to each map is justified because it allows modeling the possible distortions from one observation to the next as a trajectory on the tangent manifold of the map. The coefficients of the linear combination of the last observations along with the tangent space are estimated at each time stamp to minimize the mean square forecasting error with a regularization term. The estimation is made at each time stamp to adapt the forecast to short-term variations in solar activity.Peer ReviewedPostprint (published version