An efficient ‘a priori’ model reduction for boundary element models

The Boundary Element Method (BEM) is a discretisation technique for solving partial differential equations, which offers, for certain problems, important advantages over domain techniques. Despite the high CPU time reduction that can be achieved, some 3D problems remain today untreatable because the extremely large number of degrees of freedom—dof—involved in the boundary description. Model reduction seems to be an appealing choice for both, accurate and efficient numerical simulations. However, in the BEM the reduction in the number of degrees of freedom does not imply a significant reduction in the CPU time, because in this technique the more important part of the computing time is spent in the construction of the discrete system of equations. In this way, a reduction also in the number of weighting functions, seems to be a key point to render efficient boundary element simulations.

A Novel Method for Radio Propagation Simulation Based on Automatic 3D Environment Reconstruction

In this paper, a novel method to simulate radio propagation is presented. The method consists of two steps: automatic 3D scenario reconstruction and propagation modeling. For 3D reconstruction, a machine learning algorithm is adopted and improved to automatically recognize objects in pictures taken from target regions, and 3D models are generated based on the recognized objects. The propagation model employs a ray tracing algorithm to compute signal strength for each point on the constructed 3D map. Our proposition reduces, or even eliminates, infrastructure cost and human efforts during the construction of realistic 3D scenes used in radio propagation modeling. In addition, the results obtained from our propagation model proves to be both accurate and efficient

Comparison of dynamic effects of high-speed traffic load on ballasted track using a simplified two-dimensional and full three-dimensional model.

The vertical dynamic actions transmitted by railway vehicles to the ballasted track infrastructure is evaluated taking into account models with different degree of detail. In particular, we have studied this matter from a two-dimensional (2D) finite element model to a fully coupled three-dimensional (3D) multi-body finite element model. The vehicle and track are coupled via a non-linear Hertz contact mechanism. The method of Lagrange multipliers is used for the contact constraint enforcement between wheel and rail. Distributed elevation irregularities are generated based on power spectral density (PSD) distributions which are taken into account for the interaction. The numerical simulations are performed in the time domain, using a direct integration method for solving the transient problem due to the contact nonlinearities. The results obtained include contact forces, forces transmitted to the infrastructure (sleeper) by railpads and envelopes of relevant results for several track irregularities and speed ranges. The main contribution of this work is to identify and discuss coincidences and differences between discrete 2D models and continuum 3D models, as wheel as assessing the validity of evaluating the dynamic loading on the track with simplified 2D models

Finite Element Analysis Model of a Contactless Transformer for Battery Chargers in Electric Vehicles

A contactless transformer model is proposed in this paper using Finite Element Analysis (FEA). This model can be used to simulate Inductive Coupling Power Transfer (ICPT) systems with good accuracy of the transformer and reduce the fabrication time of these systems. The model not only takes into account the geometry of the windings but also the frequency effects in them. As the transformer does not have a magnetic core, it is complicated to model because the flux is expanded in the area around the windings. In order to obtain a very accurate model, it is necessary to use a 2D/3D field solver.

A novel method for radio propagation simulation based on automatic 3D environment reconstruction

In this paper, a novel method to simulate radio propagation is presented. The method consists of two steps: automatic 3D scenario reconstruction and propagation modeling. For 3D reconstruction, a machine learning algorithm is adopted and improved to automatically recognize objects in pictures taken from target region, and 3D models are generated based on the recognized objects. The propagation model employs a ray tracing algorithm to compute signal strength for each point on the constructed 3D map. By comparing with other methods, the work presented in this paper makes contributions on reducing human efforts and cost in constructing 3D scene; moreover, the developed propagation model proves its potential in both accuracy and efficiency.

Development of a 3-Dimensional Mathematical Collision Risk Model Based on Recorded Aircraft Trajectories to Estimate the Safety Level in High Density En-Route Airspaces

Como en todos los medios de transporte, la seguridad en los viajes en avión es de primordial importancia. Con los aumentos de tráfico aéreo previstos en Europa para la próxima década, es evidente que el riesgo de accidentes necesita ser evaluado y monitorizado cuidadosamente de forma continúa. La Tesis presente tiene como objetivo el desarrollo de un modelo de riesgo de colisión exhaustivo como método para evaluar el nivel de seguridad en ruta del espacio aéreo europeo, considerando todos los factores de influencia. La mayor limitación en el desarrollo de metodologías y herramientas de monitorización adecuadas para evaluar el nivel de seguridad en espacios de ruta europeos, donde los controladores aéreos monitorizan el tráfico aéreo mediante la vigilancia radar y proporcionan instrucciones tácticas a las aeronaves, reside en la estimación del riesgo operacional. Hoy en día, la estimación del riesgo operacional está basada normalmente en reportes de incidentes proporcionados por el proveedor de servicios de navegación aérea (ANSP). Esta Tesis propone un nuevo e innovador enfoque para evaluar el nivel de seguridad basado exclusivamente en el procesamiento y análisis trazas radar. La metodología propuesta ha sido diseñada para complementar la información recogida en las bases de datos de accidentes e incidentes, mediante la provisión de información robusta de los factores de tráfico aéreo y métricas de seguridad inferidas del análisis automático en profundidad de todos los eventos de proximidad. La metodología 3-D CRM se ha implementado en un prototipo desarrollado en MATLAB © para analizar automáticamente las trazas radar y planes de vuelo registrados por los Sistemas de Procesamiento de Datos Radar (RDP) e identificar y analizar todos los eventos de proximidad (conflictos, conflictos potenciales y colisiones potenciales) en un periodo de tiempo y volumen del espacio aéreo. Actualmente, el prototipo 3-D CRM está siendo adaptado e integrado en la herramienta de monitorización de prestaciones de Aena (PERSEO) para complementar las bases de accidentes e incidentes ATM y mejorar la monitorización y proporcionar evidencias de los niveles de seguridad. ABSTRACT As with all forms of transport, the safety of air travel is of paramount importance. With the projected increases in European air traffic in the next decade and beyond, it is clear that the risk of accidents needs to be assessed and carefully monitored on a continuing basis. The present thesis is aimed at the development of a comprehensive collision risk model as a method of assessing the European en-route risk, due to all causes and across all dimensions within the airspace. The major constraint in developing appropriate monitoring methodologies and tools to assess the level of safety in en-route airspaces where controllers monitor air traffic by means of radar surveillance and provide aircraft with tactical instructions lies in the estimation of the operational risk. The operational risk estimate normally relies on incident reports provided by the air navigation service providers (ANSPs). This thesis proposes a new and innovative approach to assessing aircraft safety level based exclusively upon the process and analysis of radar tracks. The proposed methodology has been designed to complement the information collected in the accident and incident databases, thereby providing robust information on air traffic factors and safety metrics inferred from the in depth assessment of proximate events. The 3-D CRM methodology is implemented in a prototype tool in MATLAB © in order to automatically analyze recorded aircraft tracks and flight plan data from the Radar Data Processing systems (RDP) and identify and analyze all proximate events (conflicts, potential conflicts and potential collisions) within a time span and a given volume of airspace. Currently, the 3D-CRM prototype is been adapted and integrated in AENA’S Performance Monitoring Tool (PERSEO) to complement the information provided by the ATM accident and incident databases and to enhance monitoring and providing evidence of levels of safety.

Posibilidades del motor 3D de la Nintendo DS

La consola portátil Nintendo DS es una plataforma de desarrollo muy presente entre la comunidad de desarrolladores independientes, con una extensa y nutrida escena homebrew. Si bien las capacidades 2D de la consola están muy aprovechadas, dado que la mayor parte de los esfuerzos de los creadores amateur están enfocados en este aspecto, el motor 3D de ésta (el que se encarga de representar en pantalla modelos tridimensionales) no lo está de igual manera. Por lo tanto, en este proyecto se tiene en vista determinar las capacidades gráficas de la Nintendo DS. Para ello se ha realizado una biblioteca de funciones en C que permite aprovechar las posibilidades que ofrece la consola en el terreno 3D y que sirve como herramienta para la comunidad homebrew para crear aplicaciones 3D de forma sencilla, dado que se ha diseñado como un sistema modular y accesible. En cuanto al proceso de renderizado se han sacado varias conclusiones. En primer lugar se ha determinado la posibilidad de asignar varias componentes de color a un mismo vértice (color material reactivo a la iluminación, color por vértice directo y color de textura), tanto de forma independiente como simultáneamente, pudiéndose utilizar para aplicar diversos efectos al modelo, como iluminación pre-calculada o simulación de una textura mediante color por vértice, ahorrando en memoria de video. Por otro lado se ha implementado un sistema de renderizado multi-capa, que permite realizar varias pasadas de render, pudiendo, de esta forma, aplicar al modelo una segunda textura mezclada con la principal o realizar un efecto de reflexión esférica. Uno de los principales avances de esta herramienta con respecto a otras existentes se encuentra en el apartado de animación. El renderizador desarrollado permite por un lado animación por transformación, consistente en la animación de mallas o grupos de vértices del modelo mediante el movimiento de una articulación asociada que determina su posición y rotación en cada frame de animación. Por otro lado se ha implementado un sistema de animación por muestreo de vértices mediante el cual se determina la posición de éstos en cada instante de la animación, generando frame a frame las poses que componen el movimiento (siendo este último método necesario cuando no se puede animar una malla por transformación). Un mismo modelo puede contener diferentes esqueletos, animados independientemente entre sí, y cada uno de ellos tener definidas varias costumbres de animación que correspondan a movimientos contextuales diferentes (andar, correr, saltar, etc). Además, el sistema permite extraer cualquier articulación para asociar su transformación a un objeto estático externo y que éste siga el movimiento de la animación, pudiendo así, por ejemplo, equipar un objeto en la mano de un personaje. Finalmente se han implementado varios efectos útiles en la creación de escenas tridimensionales, como el billboarding (tanto esférico como cilíndrico), que restringe la rotación de un modelo para que éste siempre mire a cámara y así poder emular la apariencia de un objeto tridimensional mediante una imagen plana, ahorrando geometría, o emplearlo para realizar efectos de partículas. Por otra parte se ha implementado un sistema de animación de texturas por subimágenes que permite generar efectos de movimiento mediante imágenes, sin necesidad de transformar geometría. ABSTRACT. The Nintendo DS portable console has received great interest within the independent developers’ community, with a huge homebrew scene. The 2D capabilities of this console are well known and used since most efforts of the amateur creators has been focused on this point. However its 3D engine (which handles with the representation of three-dimensional models) is not equally used. Therefore, in this project the main objective is to assess the Nintendo DS graphic capabilities. For this purpose, a library of functions in C programming language has been coded. This library allows the programmer to take advantage of the possibilities that the 3D area brings. This way the library can be used by the homebrew community as a tool to create 3D applications in an easy way, since it has been designed as a modular and accessible system. Regarding the render process, some conclusions have been drawn. First, it is possible to assign several colour components to the same vertex (material colour, reactive to the illumination, colour per vertex and texture colour), independently and simultaneously. This feature can be useful to apply certain effects on the model, such as pre-calculated illumination or the simulation of a texture using colour per vertex, providing video memory saving. Moreover, a multi-layer render system has been implemented. This system allows the programmer to issue several render passes on the same model. This new feature brings the possibility to apply to the model a second texture blended with the main one or simulate a spherical reflection effect. One of the main advances of this tool over existing ones consists of its animation system. The developed renderer includes, on the one hand, transform animation, which consists on animating a mesh or groups of vertices of the model by the movement of an associated joint. This joint determines position and rotation of the mesh at each frame of the animation. On the other hand, this tool also implements an animation system by vertex sampling, where the position of vertices is determined at every instant of the animation, generating the poses that build up the movement (the latter method is mandatory when a mesh cannot be animated by transform). A model can contain multiple skeletons, animated independently, each of them being defined with several animation customs, corresponding to different contextual movements (walk, run, jump, etc). Besides, the system allows extraction of information from any joint in order to associate its transform to a static external object, which will follow the movement of the animation. This way, any object could be equipped, for example, on the hand of a character. Finally, some useful effects for the creation of three-dimensional scenes have been implemented. These effects include billboarding (both spherical and cylindrical), which constraints the rotation of a model so it always looks on the camera's direction. This feature can provide the ability to emulate the appearance of a three-dimensional model through a flat image (saving geometry). It can also be helpful in the implementation of particle effects. Moreover, a texture animation system using sub-images has also been implemented. This system allows the generation of movement by using images as textures, without having to transform geometry.

Massively parallelizable list-mode reconstruction using a Monte Carlo-based elliptical Gaussian model

Purpose: A fully three-dimensional (3D) massively parallelizable list-mode ordered-subsets expectation-maximization (LM-OSEM) reconstruction algorithm has been developed for high-resolution PET cameras. System response probabilities are calculated online from a set of parameters derived from Monte Carlo simulations. The shape of a system response for a given line of response (LOR) has been shown to be asymmetrical around the LOR. This work has been focused on the development of efficient region-search techniques to sample the system response probabilities, which are suitable for asymmetric kernel models, including elliptical Gaussian models that allow for high accuracy and high parallelization efficiency. The novel region-search scheme using variable kernel models is applied in the proposed PET reconstruction algorithm. Methods: A novel region-search technique has been used to sample the probability density function in correspondence with a small dynamic subset of the field of view that constitutes the region of response (ROR). The ROR is identified around the LOR by searching for any voxel within a dynamically calculated contour. The contour condition is currently defined as a fixed threshold over the posterior probability, and arbitrary kernel models can be applied using a numerical approach. The processing of the LORs is distributed in batches among the available computing devices, then, individual LORs are processed within different processing units. In this way, both multicore and multiple many-core processing units can be efficiently exploited. Tests have been conducted with probability models that take into account the noncolinearity, positron range, and crystal penetration effects, that produced tubes of response with varying elliptical sections whose axes were a function of the crystal's thickness and angle of incidence of the given LOR. The algorithm treats the probability model as a 3D scalar field defined within a reference system aligned with the ideal LOR. Results: This new technique provides superior image quality in terms of signal-to-noise ratio as compared with the histogram-mode method based on precomputed system matrices available for a commercial small animal scanner. Reconstruction times can be kept low with the use of multicore, many-core architectures, including multiple graphic processing units. Conclusions: A highly parallelizable LM reconstruction method has been proposed based on Monte Carlo simulations and new parallelization techniques aimed at improving the reconstruction speed and the image signal-to-noise of a given OSEM algorithm. The method has been validated using simulated and real phantoms. A special advantage of the new method is the possibility of defining dynamically the cut-off threshold over the calculated probabilities thus allowing for a direct control on the trade-off between speed and quality during the reconstruction.

Damage mechanisms of 3D woven hybrid composites in tension. Testing, inspection and simulation

Delamination reduces the strenght of the composites, mainly in compression. Several methods exist to overcome this problem, but they are either not feasible for large scale production or too expensive. 3D composites are a promising solution.

Traffic sign detection and tracking using robust 3D analysis

In this paper we present an innovative technique to tackle the problem of automatic road sign detection and tracking using an on-board stereo camera. It involves a continuous 3D analysis of the road sign during the whole tracking process. Firstly, a color and appearance based model is applied to generate road sign candidates in both stereo images. A sparse disparity map between the left and right images is then created for each candidate by using contour-based and SURF-based matching in the far and short range, respectively. Once the map has been computed, the correspondences are back-projected to generate a cloud of 3D points, and the best-fit plane is computed through RANSAC, ensuring robustness to outliers. Temporal consistency is enforced by means of a Kalman filter, which exploits the intrinsic smoothness of the 3D camera motion in traffic environments. Additionally, the estimation of the plane allows to correct deformations due to perspective, thus easing further sign classification.

Accurate depth-color scene modeling for 3D contents generation with low cost depth cameras

In this paper, we present a depth-color scene modeling strategy for indoors 3D contents generation. It combines depth and visual information provided by a low-cost active depth camera to improve the accuracy of the acquired depth maps considering the different dynamic nature of the scene elements. Accurate depth and color models of the scene background are iteratively built, and used to detect moving elements in the scene. The acquired depth data is continuously processed with an innovative joint-bilateral filter that efficiently combines depth and visual information thanks to the analysis of an edge-uncertainty map and the detected foreground regions. The main advantages of the proposed approach are: removing depth maps spatial noise and temporal random fluctuations; refining depth data at object boundaries, generating iteratively a robust depth and color background model and an accurate moving object silhouette.

Fast human pose estimation using 3D Zernike descriptors

Markerless video-based human pose estimation algorithms face a high-dimensional problem that is frequently broken down into several lower-dimensional ones by estimating the pose of each limb separately. However, in order to do so they need to reliably locate the torso, for which they typically rely on time coherence and tracking algorithms. Their losing track usually results in catastrophic failure of the process, requiring human intervention and thus precluding their usage in real-time applications. We propose a very fast rough pose estimation scheme based on global shape descriptors built on 3D Zernike moments. Using an articulated model that we configure in many poses, a large database of descriptor/pose pairs can be computed off-line. Thus, the only steps that must be done on-line are the extraction of the descriptors for each input volume and a search against the database to get the most likely poses. While the result of such process is not a fine pose estimation, it can be useful to help more sophisticated algorithms to regain track or make more educated guesses when creating new particles in particle-filter-based tracking schemes. We have achieved a performance of about ten fps on a single computer using a database of about one million entries.

Creación de personajes autónomos animados en la herramienta de desarrollo de entornos virtuales Unity 3D

Este trabajo se centra en la construcción de la parte física del personaje virtual. El desarrollo muestra téecnicas de modelado 3D, cinemática y animación usadas para la creación de personajes virtuales. Se incluye además una implementación que está dividida en: modelado del personaje virtual, creación de un sistema de cinemática inversa y la creación de animaciones utilizando el sistema de cinemática. Primero, crear un modelo 3D exacto al diseño original, segundo, el desarrollo de un sistema de cinemática inversa que resuelva con exactitud las posiciones de las partes articuladas que forman el personaje virtual, y tercero, la creación de animaciones haciendo uso del sistema de cinemática para conseguir animaciones fluidas y depuradas. Como consecuencia, se ha obtenido un componente 3D animado, reutilizable, ampliable, y exportable a otros entornos virtuales. ---ABSTRACT---This article is pointed in the making of the physical part of the virtual character. Development shows modeling 3D, kinematic and animation techniques used for create the virtual character. In addition, an implementation is included, and it is divided in: to model the 3D character, to create an inverse kinematics system, and to create animations using a kinematic system. First, creating an exact 3D model from the original design, second, developing an inverse kinematics system that resolves the positions of the articulated pieces that compose the virtual character, and third, creating animation using the inverse kinematics system to get fluid and refined animations in realtime. As consequence, a 3D animated, reusable, extendable and to other virtual environments exportable component has been obtained.

Mechanical behavior and failure micromechanisms of hybrid 3D woven composites in tension

The deformation and failure micromechanisms of a hybrid 3D woven composite were studied in tension. Plain and open-hole composite coupons were tested in tension until failure in the fill and warp directions, as well as fiber tows extracted from the dry fabric and impregnated with the matrix. The macroscopic evolution of damage in the composite coupons was assessed by means of periodic unloading–reloading (to obtain the elastic modulus and the residual strain), whereas the microscopic mechanism were established by means of X-ray computed microtomography. To this end, specimens were periodically removed from the mechanical testing machine and infiltrated with ZnI-containing liquid to assess the main damage modes as a function of the applied strain. The experimental observations and the predictions of an isostrain model were used to understand the key factors controlling the elastic modulus, strength and notch sensitivity of hybrid 3D woven composites in tension. It was found that the full contribution of the glass fibers to the composite strength was not employed, due to the premature fracture of the carbon fibers, but their presence increased the fracture strain and the energy dissipated during fracture. Thus, hybridization of the 3D woven composite led to a notch-insensitive behavior as demonstrated by open-hole tests

Perceptual distortion modeling for side-by-side 3D video delivery

A frame-level distortion model based on perceptual features of the human visual system is proposed to improve the performance of unequal error protection strategies and provide better quality of experience to users in Side-by-Side 3D video delivery systems.