Multiresolution hierarchy co-clustering for semantic segmentation in sequences with small variations

This paper presents a co-clustering technique that, given a collection of images and their hierarchies, clusters nodes from these hierarchies to obtain a coherent multiresolution representation of the image collection. We formalize the co-clustering as a Quadratic Semi-Assignment Problem and solve it with a linear programming relaxation approach that makes effective use of information from hierarchies. Initially, we address the problem of generating an optimal, coherent partition per image and, afterwards, we extend this method to a multiresolution framework. Finally, we particularize this framework to an iterative multiresolution video segmentation algorithm in sequences with small variations. We evaluate the algorithm on the Video Occlusion/Object Boundary Detection Dataset, showing that it produces state-of-the-art results in these scenarios.Comment: International Conference on Computer Vision (ICCV) 201

Type of view estimation in Football sequences

Due to the huge repercussion of football broadcast in society, an enormous number of applications can be derived to both analyze the match and enhance the visual experience of the spectator. These applications request semantical information about the content of the images. In particular, the type of view in a football image contains valuable information about the game. Thus, the type of view must be automatically computed to be able to process the large amount of information extracted from each football match. In this work, we propose a robust classification system that estimates the type of view in football images in real time. For each frame of the sequence, a set of descriptors is extracted to characterize a specific part of the scene: the grass field. Gathering all these descriptors and a few ones related with texture, a decision tree determines the view that is shown in that frame. In order to improve the robustness of the algorithm, the redundancy of the temporal domain is exploited. The validity of the proposed algorithm has been tested on a large amount of frames from broadcasted football sequences in a wide variety of scenarios (stadiums, light conditions, ...). Promising results have been obtained with a 96% of accuracy in the classification of these images

Estudio experimental y numérico del comportamiento de tanques integrados de combustible frente a impacto de alta velocidad

Los impactos a alta velocidad sobre tanques de combustible están considerados como amenazas de gran importancia en relación con la vulnerabilidad de las aeronaves, ya que dichos tanques ocupan una gran parte de las alas, y éstas representan la mayor superficie expuesta de todos los elementos estructurales susceptibles de recibir cualquier tipo de impacto. En esta Tesis Doctoral se ha estudiado el comportamiento de tanques de aluminio, conteniendo fluido, frente a impacto de alta velocidad. Se ha analizado, tanto por medio de una metodología experimental como numérica, la influencia de dos factores sobre la respuesta estructural del tanque: la velocidad de impacto y la fracción de llenado del tanque. Para la realización de los ensayos experimentales se ha empleado un sistema neumático de impulsión, a través del cual se han lanzado proyectiles a distintas velocidades, y una cámara de alta velocidad capaz de filmar el proceso de penetración del proyectil en el fluido. Las simulaciones numéricas se han realizado mediante un código comercial de elementos finitos, empleando dos técnicas diferentes (ALE y SPH) para evaluar la capacidad predictiva de cada una de ellas en este tipo de problemas de impacto. Mediante el análisis de los resultados se ha conseguido una mayor comprensión del fenómeno de Golpe Hidrodinámico, que puede contribuir a su atenuación en futuros diseños de tanques de combustible. En este sentido, el desarrollo y validación del modelo de simulación empleado permitirá facilitar el diseño y reducir el número de ensayos experimentales._______________________________________________________High speed impacts on fluid-filled tanks are considered as one of the most important threats in aircraft vulnerability, since the fuel tanks represent the largest exposed area of all the vulnerable components. In this Ph.D. Thesis the behavior of fluid-filled aluminium tanks subjected to high-velocity impact has been studied. An experimental and numerical methodology has been employed to analyze the influence of two different factors on the tank structural behavior: impact velocity and volume fraction. To perform the experimental tests, a pneumatic boost system, to launch projectiles at different velocities, and a high-speed camera, which is capable of record the penetration process of the projectile into de fluid, have been used. The numerical simulations have been carried on by means of a finite element commercial code, applying two different approaches (ALE and SPH) to evaluate its predictive capacity in this kind of impact problems. The results analysis have allowed a better understanding of the Hydrodynamic Ram phenomenon, which could contribute to attenuate it on future fuel tanks designs. On this way, the development and validation of the simulation model used will make the design process easier and reduce the number of experimental tests

Visibility estimation of advertising panels in football sequences

In this work, we propose a robust classification system that estimates the advertising panels visibility in real time. For each frame of the sequence, a set of descriptors is extracted to characterize a specific part of the scene: the grass field. Gathering all these descriptors, a decision tree determines whether the LED panels are visible in that frame. In order to improve the robustness of the algorithm, the redundancy of the temporal domain is exploited. The validity of the proposed algorithm has been tested on a large amount of frames representing 250 minutes of broadcasted football sequences in a wide variety of scenarios. Promising results have been obtained with a 95% of accuracy in the classification of these images

Experimental characterization framework for SLA additive manufacturing materials

This article belongs to the Special Issue Mechanical Performance of Polymeric Parts Obtained by Additive Manufacturing.Additive manufacturing (AM) is driving a change in the industry not only regarding prototyping but due to the ease of including printed parts in final designs. Engineers and designers can go deeper into optimization and improvements of their designs without drawbacks of long manufacturing times. However, some drawbacks such as the limited available materials or uncertainty about mechanical properties and anisotropic behavior of 3D printed parts prevent use in large-scale production. To gain knowledge and confidence about printed materials it is necessary to know how they behave under different stress states and strain-rate regimes, and how some of the printing parameters may affect them. The present work proposes an experimental methodology framework to study and characterize materials printed by stereolithography (SLA) to clarify certain aspects that must be taken into account to broaden the use of this kind of material. To this end, tensile and compression tests at different strain rates were carried out. To study the influence of certain printing parameters on the printed material behavior, samples with different printing angles (θ = [0–90]) and different printing resolution (layer height of 50 and 100 µm) were tested. In addition, the effects of curing time and temperature were also studied. The testing specimens were manufactured in the non-professional SLA machine Form 2 from Formlabs® using resin called Durable. Nevertheless, the proposed experimental methodology could be extended to any other resin.Ministerio de Asuntos Económicos y Transformación Digital, Gobierno de España grant number DPI2017-85073-R, and Vicerrectorado de Política Científica UC3M (Projects 2013/00413/003 and 2014/00006/003)

Experimental study of CFRP fluid-filled tubes subjected to high-velocity impact

In recent years, vulnerability against high-velocity impact loads has become an increasingly critical issue in the design of composite aerospace structures. The effects of Hydrodynamic Ram (HRAM), a phenomenon that occurs when a high-energy object penetrates a fluid-filled container, are of particular concern in the design of wing fuel tanks for aircraft because it has been identified as one of the important factors in aircraft vulnerability. The projectile transfers its momentum and kinetic energy through the fluid to the surrounding structure, increasing the risk of catastrophic failure and excessive structural damage. For the present work, water-filled CFRP square tubes were subjected to an impact of steel spherical projectiles (12.5 mm diameter) at impact velocities of 600–900 m/s. The CFRP tubes were filled to different volumes to examine how volume might influence the tank behavior. The composite test boxes were instrumented with six strain gauges and two pressure transducers, and the formation process of the cavity was recorded using a high-speed camera. The damage produced in the tubes was then analyzed, and differences were found according to the testing conditions. This work presents the results of these tests.The authors would like to acknowledge the Center for the Development of Industrial Technology (CDTI) of Spain and to the company AERNNOVA Aerospace for the financial support for this research.Publicad

Numerical modelling of the hydrodynamic ram phenomenon

12 pages, 16 figures.Hydrodynamic ram (HRAM) is a phenomenon that occurs when a high-kinetic energy object penetrates a fluid-filled container. The projectile transfers its momentum and kinetic energy through the fluid to the surrounding structure, increasing the risk of catastrophic failure and excessive structural damage. This is of particular concern in the design of wing fuel tanks for aircraft since it has been identified as one of the important factors in aircraft vulnerability. In the present paper, the commercial finite-element code LS-DYNA has been used to simulate an HRAM event created by a steel spherical projectile impacting a water-filled aluminium square tube. Two different formulations (ALE and SPH) are employed to reproduce the event. Experimental tests which indicate the pressure at different points of the fluid, displacement of the walls and cavity evolution for different impact velocities are compared with the numerical results in order to assess the validity and accuracy of both ALE and SPH techniques in reproducing such a complex phenomenon.Publicad

Experimental analysis of fluid-filled aluminium tubes subjected to high-velocity impact

11 pages, 20 figures.Hydrodynamic ram (HRAM) is a phenomenon that occurs when a high-energy object penetrates a fluid-filled container. The projectile transfers its momentum and kinetic energy through the fluid to the surrounding structure increasing the risk of catastrophic failure and excessive structural damage. It is of particular concern in the design of wing fuel tanks for aircraft since it has been identified as one of the important factors in aircraft vulnerability. For the present work, water-filled aluminium square tubes (6063-T5) were subjected to impact by steel spherical projectiles (12.5 mm diameter) at impact velocities of 600–900 m/s. The aluminium tubes were filled at different volumes to study how an air layer inside the tank might influence the impact behaviour. The test boxes were instrumented with five strain gauges and two pressure transducers. The formation process of the cavity was recorded with a high-speed camera. This work presents the results of these tests.This research was done with the financial support of the Spanish Ministry of Education under Project reference DPI2005-06769, and of the University Carlos III of Madrid and Comunidad Autónoma de Madrid under project reference CCG07-UC3M/DPI-3395.Publicad