Encontrado(s) 2242214 resultado(s)
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Design of injection locked frequency divider in 65nm CMOS technology for mmW applications

  • Brandano, Davide
  • González Jiménez, José Luis
In this paper, an Injection Locking Frequency Divider (ILFD) in 65 nm RF CMOS Technology for applications in millimeter-wave (mm-W) band is presented. The proposed circuit achieves 12.69% of locking range without any tuning mechanism and it can cover the entire mm-W band in presence of Process, Voltage and Temperature (PVT) variations by changing the Injection Locking Oscillator (ILO) voltage control. A design methodology flow is proposed for ILFD design and an overview regarding CMOS capabilities and opportunities for mm-W transceiver implementation is also exposed.

Mapas de la ciencia UPC : representación visual de la actividad investigadora de la UPC a partir de los datos del repositorio institucional y el CRIS (FUTUR)

  • Clavero Campos, Javier
Presentació exposada al XV Workshop de Rebiun, celebrat a la Universitat Jaume I de Castelló els dies 29 i 30 de setembre de 2016, Peer Reviewed

A unified approach to explain contrary effects of hysteresis and smoothing in nonsmooth systems

  • Bonet Revés, Carles
  • Martínez-Seara Alonso, M. Teresa
  • Fossas Colet, Enric
  • Jeffrey, Mike R.
Piecewise smooth dynamical systems make use of discontinuities to model switching between regions of smooth evolution. This introduces an ambiguity in prescribing dynamics at the discontinuity: should the dynamics be given by a limiting value on one side or other of the discontinuity, or a member of some set containing those values? One way to remove the ambiguity is to regularize the discontinuity, the most common being either to smooth it out, or to introduce a hysteresis between switching in one direction or the other across it. Here we show that the two can in general lead to qualitatively different dynamical outcomes. We then define a higher dimensional model with both smoothing and hysteresis, and study the competing limits in which hysteretic or smoothing effects dominate the behaviour, only the former of which correspond to Filippov’s standard ‘sliding modes’., Peer Reviewed

Motion capture based on RGBD data from multiple sensors for avatar animation

  • Vico Moya, Miguel Ángel
With recent advances in technology and emergence of affordable RGB-D sensors for a wider range of users, markerless motion capture has become an active field of research both in computer vision and computer graphics. In this thesis, we designed a POC (Proof of Concept) for a new tool that enables us to perform motion capture by using a variable number of commodity RGB-D sensors of different brands and technical specifications on constraint-less layout environments. The main goal of this work is to provide a tool with motion capture capabilities by using a handful of RGB-D sensors, without imposing strong requirements in terms of lighting, background or extension of the motion capture area. Of course, the number of RGB-D sensors needed is inversely proportional to their resolution, and directly proportional to the size of the area to track to. Built on top of the OpenNI 2 library, we made this POC compatible with most of the nonhigh-end RGB-D sensors currently available in the market. Due to the lack of resources on a single computer, in order to support more than a couple of sensors working simultaneously, we need a setup composed of multiple computers. In order to keep data coherency and synchronization across sensors and computers, our tool makes use of a semi-automatic calibration method and a message-oriented network protocol. From color and depth data given by a sensor, we can also obtain a 3D pointcloud representation of the environment. By combining pointclouds from multiple sensors, we can collect a complete and animated 3D pointcloud that can be visualized from any viewpoint. Given a 3D avatar model and its corresponding attached skeleton, we can use an iterative optimization method (e.g. Simplex) to find a fit between each pointcloud frame and a skeleton configuration, resulting in 3D avatar animation when using such skeleton configurations as key frames.

3D numerical simulation of experiments on masonry arch bridges

  • Brunet Coll, Ignacio
Masonry arch bridges are one of the oldest civil engineering heritage preserved until today. Besides having great historical and engineering value, most are still functional and come to be approximately 60% of the total European masonry railway bridge stock. Most of these structures have to withstand increased axle loads higher than the designed ones. Consequently, many masonry bridges are damaged and need to be refurbished and in worst cases replaced. The Construction Engineering Department of the Polytechnic University of Catalonia carried out a real-scale masonry arch bridge aiming to improve the understanding of these types of structures. Since this experimental test, and based on previous studies of the same case of study, this dissertation has the objective to set up a three-dimensional numerical model to reproduce the same results obtained in the laboratory. First, a current state of the art about these types of structures is presented including a brief description of the main structural elements and their typologies, the main characteristics of masonry and a brief history of the analysis of these structures, from its beginnings in the seventeenth century till the implementation of finite element method. Moreover, the construction, material characterization and test instrumentation of the experimental test is described. The results are analysed and compared with previous analytical and numerical predictions. Finally, a non-linear analysis of a new three-dimensional model including all the main structural elements and interactions between them through the use of interface elements is performed., Los puentes en arco de obra de fábrica son una de las formas de paso más antiguas que se conservan hoy en día. Además de tener gran valor patrimonial e ingenieril, la mayoría aún son funcionales y llegan a representar hasta el 60% del total de los puentes de ferrocarril en Europa. La mayor parte de estas estructuras han visto aumentar considerablemente sus cargas en los últimos años. En consecuencia, muchos puentes de obra de fábrica se encuentran deteriorados y necesitan ser analizados y en el peor de los casos rehabilitados. En el Departamento de Ingeniería de la Construcción de la Universidad Politécnica de Cataluña se llevó a cabo un ensayo de un puente en arco de obra de fábrica a escala real enfocado a la mejora del entendimiento del funcionamiento de este tipo de estructuras. A partir de este ensayo y de varios estudios previos del mismo, esta tesina tiene como principal objetivo realizar un modelo numérico tridimensional que permita reproducir los mismos resultados obtenidos en el laboratorio. Primero, se presenta un estado actual del conocimiento detallado sobre este tipo de estructuras incluyendo una breve descripción de los principales elementos estructurales y sus principales tipologías, principales rasgos de la obra de fábrica como material y una breve historia del análisis de este tipo de estructuras, desde sus inicios en el siglo XVII hasta la actualidad con la implementación del método de los elementos finitos. Después, se describe la construcción y ejecución del ensayo realizado en el laboratorio. Se analizan los resultados y se contrastan con diversos modelos numéricos que fueron realizados posteriormente. Finalmente, se realiza un análisis no-lineal de un nuevo modelo tridimensional incluyendo todos los principales elementos estructurales y sus interacciones entre ellos por medio de elementos de interfaz.

Hope un curt d'animació 3D

  • Chiva Matamoros, Àlex
Hope és un projecte en el qual es pretén crear un curtmetratge d’animació per computadora. Des de la conceptualització d’una idea inicial fins a la creació d’un curt d’animació, passant per totes les etapes que això comporta. Portant a terme cadascuna de les fases en preproducció, producció i postproducció es vol entendre la importància i l’organització que requereix la creació d’una peça audiovisual d’aquestes característiques. En aquest document, s’explicaran tots els passos seguits, des dels objectius inicials fins al resultat final i les conclusions.

Influence of fish swimming on the flow pattern of circular tanks

  • Masaló Llorà, Ingrid
  • Oca Baradad, Joan
The effect of swimming fish on the average velocity and velocity profile of a circular tank was studied. Working with different inlet diameters and flow rates, nine different impulse forces (configurations) were evaluated. Each configuration was tested with and without fish, and the effects of two different fish sizes were compared. The velocity profiles in experiments with fish presented a considerable reduction in velocity in the centre of the tank near the outlet, which was a consequence of the increase in the kinematic eddy viscosity due to the turbulence introduced by fish swimming. A flattening of the angular velocity profile was observed in the central area of the tank, which had a radius of about 0.3 m (18% of the total volume of the tank). A previous model proposed by Oca and Masaló (2013) was modified in order to better describe the distribution of velocities in the central volume of a tank with swimming fish. The proposed modification was based on Burgers¿ proposal for a bathtub vortex, which implies the determination of the parameter (1¿e¿ar2)(1¿e¿ar2), where r is the radius and the a values were experimentally obtained for each tank configuration, in which they increased with the impulse force. The average velocities in the tank were proportional to the square root of the impulse force in experiments with and without fish. Experiments with fish presented lower average velocities, which imply higher tank resistance coefficients. At similar stocking densities (14.6 kg/m3), the increase in the tank resistance coefficients obtained with small fish sizes (154 g) were slightly higher than those obtained with bigger fish sizes (330 g)., This work was funded by Spanish Ministerio de Educación y Ciencia (AGL2009-1655).

Advanced computationally efficient modeling of RC structures nonlinear cyclic behavior

  • Alfarah, Bashar
Under severe seismic excitation, structural behavior of buildings and other constructions is highly complex. It involves, among other issues, soil-structure interaction, large strains and displacements, damage, plasticity, and near-collapse behavior. Moreover, in reinforced concrete structures, there are several coupled degradation and failure modes: cracking, crushing and spalling of concrete, yielding and pull-out of tensioned reinforcement, yielding and buckling of compressed reinforcement. Furthermore, another circumstance makes the situation more alarming: given the increasing awareness and concern on the huge worldwide seismic risk, earthquake engineering has experienced in last years substantial advances. New design and analysis strategies have been proposed, leading to relevant developments. These developments rely on extensive testing and numerical simulation mainly based on oversimplified models referred in this work as structural component-based models, as a result of their moderate computational cost. Therefore, there is a strong need of verifying the reliability of the new developments by comparison with analyses performed using more advanced simulation tools and with experiments. This work is organized in two parts. First part presents an accurate model, while the second part deals with a more simplified model, although highly computational efficient. First part. This research clarifies the aforementioned issues by developing a new continuum mechanics-based model for simulating the monotonic and cyclic behavior of reinforced concrete structures. The developed model combines a new methodology for calculating the damage variables in Concrete Plastic Damage Models "CPDM", and a new approach to integrate CPDM with a 3-D interface bond-slip model developed by other researchers. A new scheme to implement the interface model in a continuum FEM model of regions with crossing reinforcement bars is also presented in this research. Mesh-insensitivity, accuracy and reliability of the proposed model are verified by simulating several monotonic and cyclic tests; the obtained results are compared with experimental ones, satisfactory agreement has been accomplished. Second part. The developed model is the First Part is compared with simplified structural component-based models that are commonly used in earthquake engineering; results has shown the superiority of the proposed model to predict the actual behavior of highly damaged RC elements and frames, capturing strength reduction, stiffness degradation and pinching phenomena. However, some of the structural component-based models have shown an acceptable performance considering the law computationally cost in comparison with the advanced continuum mechanics-based model. After this conclusion, this part presents a numerical study on the relation among the non-simulated deterioration modes of the elements in non-ductile RC frames and their final capacity. A structural component-based model has been developed for simulating the nonlinear dynamic behavior of non-ductile reinforced structures, accounting for flexure, shear and axial deterioration modes. The developed model is numerically efficient, thus being suitable for day use in earthquake engineering. The capacity of the developed model is verified by simulating the nonlinear dynamic behavior of an existing non-ductile building and the prototype building. Obtained results shows that the developed model, despite its moderate computational cost, detects and reproduces accurately the nonlinear dynamic behavior of non-ductile RC structures, as well, capturing the deterioration modes that are blind to the simplified models. Comparison with results from more simplified models highlights the importance of hidden failure modes in the behavior of each element and in the overall collapse mechanisms. The relation between the non-simulated failure modes and the so-called "Structural Resurrection" is addressed, El comportamiento estructural de edificios y otras construcciones bajo severas excitaciones sísmicas es muy complejo e implica temas como, la interacción suelo-estructura, grandes esfuerzos y desplazamientos, daños, plasticidad y el comportamiento de la estructura cerca del colapso. Por otra parte, en estructuras de hormigón armado, existen varios modos de fallo y de degradación: agrietamiento, aplastamiento y desprendimiento del hormigón, plastificación y extracción de las armaduras traccionadas y plastificación y pandeo de las armaduras comprimidas. Además, otras circunstancias hacen que la situación sea más alarmante: dada la creciente conciencia y preocupación por el enorme riesgo sísmico mundial, la ingeniería sísmica ha experimentado en los últimos años avances sustanciales, para lo cual se han propuesto nuevas estrategias de análisis y diseño, lo que conduce a desarrollos relevantes. Estos desarrollos se basan en pruebas y simulaciones numéricas basadas principalmente en modelos simplificados referidos en este trabajo como modelo basados en la estructura, resultando un costo computacional moderado. Por lo tanto, existen una gran necesidad de verificar la fiabilidad de los nuevos desarrollos en comparación con los análisis realizados utilizando herramientas de simulación más avanzadas y con ensayos. Este trabajo se organiza en dos partes; en la primera se describe un modelo preciso basado en la mecánica del medio continuo y en la segunda se presenta otro modelo más simplificado basado en los componentes de la estructura. Primera parte. En esta parte se desarrolla un nuevo modelo basado en la mecánica del medio continuo para simular el comportamiento monotónico y cíclico de estructuras de hormigón armado. El modelo desarrollado combina una nueva metodología para el cálculo de las variables del daño en el Modelo de Daño Plástico del Hormigón “CPDM”, y un nuevo enfoque para integrar el CPDM con un modelo de interface de 3-D desarrollado en otra investigación. También se presenta un nuevo esquema para implementar la interfaz del modelo en un modelo FEM continuo de regiones con armaduras que se cruzan en varias direcciones. La precisión, la fiabilidad y la insensibilidad a la malla del modelo propuesto se verifican simulando varias pruebas incrementales y cíclicas; los resultados obtenidos se comparan con experimentales, lográndose un ajuste satisfactorio. Segunda parte. El modelo desarrollado in el Primer Parte ha sido comparado con modelos simplificados basados en los componentes estructurales de uso común en la ingeniería sísmica, los resultados mostraron la superioridad del modelo pro-puesto para predecir el comportamiento real de los elementos y pórticos RC altamente dañados, capturando la reducción de la resistencia, la degradación de la rigidez y el efecto pinzamiento (“pinching”). Sin embargo, algunos de los modelos basados en componentes estructurales han mostrado un desempeño aceptable teniendo en cuenta el costo computacional de la ley en comparación con el modelo avanzado basado en la mecánica del medio continuo. Con de esta conclusión, este parte de este trabajo presenta un estudio numérico sobre la relación entre los modos de deterioro no-simulados de pórticos de hormigón sin ductilidad y su capacidad última. Se ha desarrollado un modelo avanzado basado en los componentes de la estructura para simular el comportamiento dinámico no lineal de las estructuras sin ductilidad, teniendo en cuenta los modos de deterioro de flexión, corte y axial. El modelo desarrollado es numéricamente eficiente, siendo pues adecuado para el uso profesional en ingeniería sísmica. La capacidad del modelo desarrollado se verifica mediante la simulación del comportamiento dinámico no lineal de un edificio no dúctil existente y del edificio prototipo.

Rodeados por la red

  • Barceló Garcia, Miquel

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