Design and implementation of a cognitive node for heterogeneous wireless ad-hoc

In this thesis, the design of a cognitive network layer solution for a scenario with mobile devices is presented. Cognitive networks are able to sense the environment and adapt in order to find the best performance of the network at any moment. The final objective is to carry out a design of a node of the network which has incorporated in it up to three different technologies, which are WLAN, Bluetooth and ZigBee. The node is able to determine whether a technology should be used or not based on the network state. In order to find out the network state, a routing protocol based on Link State to provide the full view of the network is designed. Adaptive routing metrics have been designed in order to determine the best performance of the network to meet the QoS requirements considering what service is being required by the application and therefore to choose what technology is more appropriated for the connection. Those metrics are based on the capacity of the link, which takes into account the technology, the delay and the packet error rate of itself, and the utilization level. Then, Dijkstras’ algorithm is computed to solve the routing problem based on the adaptive weights instead of using the traditional hop-based count as a cost function. Furthermore, a heterogeneous cognitive wireless ad-hoc network testbed is implemented to analyze the behavior of the cognitive network when different types of services are used. On top of the cognitive network layer, an application to arrange meetings is implemented. Meeting rooms offer two different type of service for the guests, video and data service. Thus, clients are able to configure a video conference with the meeting room in case they cannot attend the meeting

Design and validation of rockfall protection systems by numerical modeling with discrete elements

Rockfall protection systems are installed in order to preserve civil infrastructures against landslides and falling rocks. For the evaluation of these systems,one of the main problems is the difficulty to develop laboratory tests, since landslides and falling rocks are unpredictable events that involve the movement of large masses of material over several meters or evenkil-ometers. For this reason, the use of numerical methods, which allows reproducing full-scale situations without the need of laboratory devices or sliding materials, has become more popular. The study presented in this document shows theapplication of the Discrete Element Method (DEM) for the analysis of the behavior of one of the most popular rockfall protection systems, flexible metallic fences.Postprint (published version

Los fondos fotográficos del Instituto de Historia del Consejo Superior de Investigaciones Científicas (España): Iniciativas para una nueva gestión

XIV Coloquio del Seminario de Estudio y Conservación del Patrimonio Cultural: La fotografía: imagen y materia, Oaxaca, del 28 al 31 de mayo, 2006 . Universidad Nacional Autonónoma de México. Instituto de Investigaciones EstéticasPeer reviewe

Accurate Approximation of the Matrix Hyperbolic Cosine Using Bernoulli Polynomials

[EN] This paper presents three different alternatives to evaluate the matrix hyperbolic cosine using Bernoulli matrix polynomials, comparing them from the point of view of accuracy and computational complexity. The first two alternatives are derived from two different Bernoulli series expansions of the matrix hyperbolic cosine, while the third one is based on the approximation of the matrix exponential by means of Bernoulli matrix polynomials. We carry out an analysis of the absolute and relative forward errors incurred in the approximations, deriving corresponding suitable values for the matrix polynomial degree and the scaling factor to be used. Finally, we use a comprehensive matrix testbed to perform a thorough comparison of the alternative approximations, also taking into account other current state-of-the-art approaches. The most accurate and efficient options are identified as results.This research was supported by the Vicerrectorado de Investigacion de la Universitat Politecnica de Valencia (PAID-11-21).Alonso Abalos, JM.; Ibáñez González, JJ.; Defez Candel, E.; Alvarruiz Bermejo, F. (2023). Accurate Approximation of the Matrix Hyperbolic Cosine Using Bernoulli Polynomials. Mathematics. 11(3):1-22. https://doi.org/10.3390/math1103052012211

Realidad aumentada en cirugía: una aproximación semántica mediante aprendizaje profundo

En este proyecto se ha desarrollado una herramienta que combina técnicas clásicas de visión por computador para tomar medidas precisas junto con técnicas de aprendizaje profundo. Esto permite crear un sistema capaz de entender la escena que está viendo, a la vez que la posiciona en el espacio de manera precisa, permitiendo incluso tomar medidas en verdadera magnitud. La fusión de estos dos tipos de tecnología permite abrir una nueva línea de trabajo, estableciendo las bases para la extracción semántica del interior de un paciente en un entorno quirúrgico.El principal reto abordado en el proyecto es la identificación de las regiones internas del paciente (el hígado en este caso) a partir de imágenes planas tomadas con cámaras monoculares estándar, como un endoscopio. El objetivo final es la estimación de la pose (posición con respecto a la cámara, compuesta de traslación y rotación) del hígado, que se utilizará para localizar partes internas no visibles, como vasos sanguíneos o tumores, sobre el órgano en realidad aumentada durante una intervención quirúrgica.Para el entrenamiento de la red neuronal se ha utilizado un modelo sintético del hígado, obtenido a partir de un simulador quirúrgico desarrollado en el Grupo AMB del Instituto de Investigación en Ingeniería de Aragón (I3A). La principal dificultad del proyecto radica en el entrenamiento de la red para la obtención de la pose de forma precisa. Para ello, se ha reentrenado un modelo de red neuronal con imágenes del hígado, tanto sobre fondos homogéneos como sobre fondos simulando una intervención laparoscópica, con el objetivo de realizar predicciones en condiciones lo más realistas posibles.Finalmente, la información obtenida mediante la red neuronal se ha incorporado a ORB-SLAM, para la obtención de resultados en tiempo real.La principal novedad introducida en este proyecto es el uso conjunto de redes neuronales con ORB-SLAM. Esto permite realizar estimaciones de pose y escalado automáticamente sin la necesidad de utilizar información adicional, de modo que la herramienta se puede utilizar directamente con cámaras de laparoscopia, sin tener que recurrir a sensores adicionales como acelerómetros o LIDAR.<br /

Shockwaves in spillways with the particle finite element method

The final publication is available at Springer via http://dx.doi.org/10.1007/s40571-019-00252-1.Changes in direction and cross section in supercritical hydraulic channels generate shockwaves which result in an increase in flow depth with regard to that for uniform regime. These disturbances are propagated downstream and need to be considered in the design of the chute walls. In dam spillways, where flow rates are often high, this phenomenon can have significant implications for the cost and complexity of the solution. It has been traditionally analysed by means of reduced-scale experimental tests, as it has a clear three-dimensional character and therefore cannot be approached with two-dimensional numerical models. In this work, the ability of the particle finite element method (PFEM) to reproduce this phenomenon is analysed. PFEM has been successfully applied in previous works to problems involving high irregularities in free surface. First, simple test cases available in the technical bibliography were selected to be reproduced with PFEM. Subsequently, the method was applied in two spillways of real dams. The results show that PFEM is capable of capturing the shockwave fronts generated both in the contractions and in the expansions that occur behind the spillway piers. This suggests that the method may be useful as a complement to laboratory test campaigns for the design and hydraulic analysis of dam spillways with complex geometries.Peer ReviewedPostprint (author's final draft

Experimentos en ciencias sociales: energías renovables y pobreza energética en el sur de la provincia de Buenos Aires-Argentina

The existence, at home, of deprivations in access to basic services becomes especially relevant in the current context of the pandemic due to the coronavirus disease 2019 (COVID19). This paper presents the results obtained in the first stage of the Renewable Energies project as a tool for reducing energy poverty. A pilot test in vulnerable neighborhoods in Bahía Blanca. It aims to implement solar collectors to provide households in vulnerable neighborhoods with sanitary hot water and evaluate its impact based on a methodology of randomized controlled trials. A socioeconomic characterization of the target population is presented considering previous surveys and advances in new surveys. The methodological planning of the intervention is also detailed, with special emphasis on the modifications that had to be made due to the context of social isolation. The results suggest that households in the 9 de Noviembre neighborhood lag far behind in terms of development and well-being in relation to the city average. This situation is a constant as it arises from at least two household surveys (2016 and 2020). In the implementation of controlled trials in Economics, the explicit consideration of those factors not controllable by the researcher is essential.La existencia, en el hogar, de privaciones en el acceso a servicios básicos se torna especialmente relevante en el actual contexto de pandemia por la enfermedad del coronavirus 2019 (COVID-19). En este trabajo se presentan los resultados obtenidos en la primera etapa del proyecto Energías renovables como herramienta de reducción de la pobreza energética. Una prueba piloto en barrios vulnerables de Bahía Blanca. El mismo tiene por objetivo la implementación de colectores solares para brindar, a hogares en barrios vulnerables, agua caliente sanitaria y evaluar su impacto a partir de una metodología de ensayos aleatorios controlados. Se presenta una caracterización socioeconómica de la población objetivo considerando relevamientos previos y avances en nuevos relevamientos. También se detalla la planificación metodológica de la intervención, con especial énfasis en las modificaciones que debieron realizarse debido al contexto de aislamiento social. Los resultados sugieren que los hogares del barrio 9 de Noviembre se encuentran ampliamente rezagados en términos de desarrollo y bienestar en relación al promedio de la ciudad. Esta situación es una constante según surge de, al menos, dos relevamientos de hogares (2016 y 2020). En la implementación de ensayos controlados en Economía, se concibe esencial la consideración explícita de aquellos factores no controlables por el investigador

Analysis of fluid soil-structure interaction problems with the particle finite element method (PFEM)

We present some developments in the Particle Finite Element Method (PFEM) for analysis of coupled problems in mechanics involving fluid-soil-structure interaction (FSSI). The PFEM uses an updated Lagrangian description to model the motion of material points in both the fluid and the solid domains (the later including soil/rocks and structures). A mesh connects the particles (nodes) defining the discretized domain where the governing equations for each of the constituent materials are solved as in the standard FEM. The procedure to model frictional contact conditions and material erosion at fluid-solid and solid-solid interfaces is described. We present several examples of application of the PFEM to solve FSSI problems such as the motion of rocks by water streams, the erosion of river beds, the stability of breakwaters and constructions under sea waves, the falling of landslides on houses and into a reservoir and the failure of rockfill dams in overspill situations.Preprin