1,578 research outputs found
Detecting a prey in a spider orb-web from in-plane vibration
No full textSpiders perform a task similar to solving an inverse problem when detecting the position of a prey, a mate, or a predator perturbing the orb-web. Recent work has advanced in the study of the orb-web as a sensor when it is subjected to small transverse vibrations, using a continuous membrane model for the orb-web. However, in-plane vibrations have not been investigated yet as data for the prey detection problem. In the present work, we develop the structure of the small in-plane vibratory response of an axially symmetric orb-web supported at the boundary. Additionally, we prove that knowledge of the in-plane dynamic response inside an annulus centered at the origin of the orb-web, where the spider is assumed to stay for a sufficiently large registration time, allows us to determine uniquely the in-plane distributed load simulating the prey's impact. The theoretical outcome is illustrated with a numerical implementation of the reconstruction method.This work was supported by Fapesp, the Sao Paulo Research Foundation (2017/07189-2, Visiting Researcher Program, and 2017/06452-1). The work ofthe second author was supported by National Research Project PRIN 2015TTJN95
La prevenció de la violencia. L’esport com a instrument de resolució de conflictes, cohesió i convivència social entre els infants i els joves
Get PDFEn aquest article es recull la recerca elaborada en el marc de la Càtedra Ethos de la Universitat Ramon Llull sobre l’esport com a eina d’integració social. El fenomen de l’esport és una de les manifestacions més polièdriques de la societat contemporània que permet múltiples abordatges. En aquest article s’exposen les conclusions d’una recerca empírica que demostra com la pràctica esportiva és un poderós instrument d’integració social en el món dels joves.In this article you can read the research elaborated in the framework of the Ethos Chair of the Ramon Llull University on the sport as an instrument of social inclusion. The sport is one of the most multifaceted manifestations of contemporary society that permits multiple approaches. In this article, the author exposes the conclusions of an empirical research that demonstrates the sports practice is a power instrument of social integration in the world of youth
La prevenció de la violencia. L’esport com a instrument de resolució de conflictes, cohesió i convivència social entre els infants i els joves
Get PDFEn aquest article es recull la recerca elaborada en el marc de la Càtedra Ethos de la Universitat Ramon Llull sobre l’esport com a eina d’integració social. El fenomen de l’esport és una de les manifestacions més polièdriques de la societat contemporània que permet múltiples abordatges. En aquest article s’exposen les conclusions d’una recerca empírica que demostra com la pràctica esportiva és un poderós instrument d’integració social en el món dels joves.In this article you can read the research elaborated in the framework of the Ethos Chair of the Ramon Llull University on the sport as an instrument of social inclusion. The sport is one of the most multifaceted manifestations of contemporary society that permits multiple approaches. In this article, the author exposes the conclusions of an empirical research that demonstrates the sports practice is a power instrument of social integration in the world of youth
Experimental and numerical analysis on the martensitic transformation in AISI 304 steel sheets subjected to perforation by conical and hemispherical projectiles
Get PDFLien vers la version éditeur: http://www.sciencedirect.com/science/article/pii/S0020768312004039In this work, an experimental and numerical analysis of the martensitic transformation in AISI 304 steel sheets subjected to perforation by conical and hemispherical projectiles is conducted. Experiments are performed using a pneumatic gas gun for with the impact velocities in the range of 35 m=s < V0 < 200 m=s. Two target thicknesses are examined, t1 ¼ 0:5 mm and t2 ¼ 1:0 mm. The experimental setup enabled the determination of the impact velocity, the residual velocity and the failure mode of the steel sheets. The effect of the projectile nose shape on the target’s capacity for energy absorption is evaluated. Moreover, martensite is detected in all the impacted samples, and the role played by the projectile nose shape on the transformation is highlighted. A three-dimensional model is developed in ABAQUS/Explicit to simulate the perforation tests. The material is defined via the constitutive model developed by Zaera et al. (2012) to describe the strain-induced martensitic transformation occurring in metastable austenitic steels at high strain rates. The finite element results are compared with the experimental evidence, and satisfactory matching is observed over the entire range of impact velocities tested and for both projectile configurations and target thicknesses considered. The numerical model succeeds in describing the perforation mechanisms associated with each projectile-target configuration analyzed. The roles played by impact velocity, target thickness and projectile nose shape on the martensitic transformation are properly captured.Project CCG10-UC3M/DPI-5596 (Comunidad Autónoma de Madrid) et DPI2011-24068 (Ministerio de Ciencia e Innovación de España
La prevenció de la violencia. L’esport com a instrument de resolució de conflictes, cohesió i convivència social entre els infants i els joves
No full textEn aquest article es recull la recerca elaborada en el marc de la Càtedra Ethos de la Universitat Ramon Llull sobre l’esport com a eina d’integració social. El fenomen de l’esport és una de les manifestacions més polièdriques de la societat contemporània que permet múltiples abordatges. En aquest article s’exposen les conclusions d’una recerca empírica que demostra com la pràctica esportiva és un poderós instrument d’integració social en el món dels joves.In this article you can read the research elaborated in the framework of the Ethos Chair of the Ramon Llull University on the sport as an instrument of social inclusion. The sport is one of the most multifaceted manifestations of contemporary society that permits multiple approaches. In this article, the author exposes the conclusions of an empirical research that demonstrates the sports practice is a power instrument of social integration in the world of youth
Desarrollo de una nueva herramienta basada en redes neuronales para el diseño de protecciones ligeras cerámica-metal frente a impacto de alta velocidad
Get PDFSe ha desarrollado una nueva herramienta para el diseño de protecciones ligeras cerámica-metal frente a impacto de alta velocidad basada en Redes Neuronales Artificiales. La herramienta predice, en tiempo real, el comportamiento de la protección frente a un impacto de alta velocidad, determinando si se produce la parada del cuerpo impactador o la perforación de la protección, y en ese caso, la velocidad y la masa residuales del cuerpo.
Para el entrenamiento y verifiación de la Red Neuronal se ha generado, mediante simulación numérica, un amplio conjunto de casos de impacto abarcando diferentes geométricas y materiales del cuerpo impactador y de la protección y diferentes velocidades de impacto, dentro del rango habitual de variación de estas variables en los problemas de impacto de alta velocidad.
Para la simulación del comportamiento frente a impacto de la cerámica se han modificado las ecuaciones constitutivas del modelo de Cortés et al. y se han implementado éstas, junto con un algoritmo de integración desarrollado a tal efecto, en un código comercial de simulación numérica. Posteriormente se han ajustado los parámetros del modelo para diferentes materiales cerámicos y por último se ha validado éste, junto con el algoritmo de integración y el modelo de elementos finitos, para un amplio rango de energías de impacto.
La Red Neuronal desarrollada ha mostrado una muy notable capacidad de predicción del comportamiento de protecciones ligeras frente a impacto, por lo que su uso puede
constituir una alternativa para el diseño de estos sistemas.
____________________________________________A new tool based on Artificial Neural Networks (ANNs) has been developed for the
design of lightweight ceramic-metal armors against high velocity impact of solids. The
developed tool predicts, in real-time, the response of the armor: impact body arrest or
target perforation are determined and, in the last case, the residual mass and velocity of
the impacting body are obtained.
A large set of impact cases has been generated, by numerical simulation, in order to train and test the ANN. The impact cases consider different impacting body and target
geometries, materials and impact velocities, all these parameters varying in a wide range
that covers common impact situations.
In order to simulate the behavior of the ceramic material under impact, the constitutive model proposed by Cortés et al. has been modified and a new algorithm to integrate it has been developed and implemented in a finite element code.
The parameters of the material model have been determined by inverse analysis for
different ceramic materials and finally, the modified constitutive model, its integration
algorithm and the finite element model have been validated for a large range of impact
energies.
The ANN developed has shown a remarkable prediction ability of the impact behavior of lightweight ceramic-metal armors and therefore it could be an alternative to the
conventional design methodologies
Raonament intel·lectual i materialitat del text: el cas de l'Ars inventiva veritatis de Ramon Llull
Get PDFRamon Llull's Ars inventiva veritatis (1290) is conserved in a manuscript closely connected with the author. The peculiar and complex disposition of the text of this codex permits us to study the careful organization of the work, revealing Llull's desire to guide the reader in certain specific directions. This makes evident, once again, the interrelation between the materiality and significance of the text
Mass detection in nanobeams from bending resonant frequency shifts
Get PDFanobeams are frequently used as vibration based-sensors to detect mass changes caused, for instance, by attachment of foreign atoms/molecules or chemical/molecular absorption. This paper deals with the bending vibration of a uniform nanobeam carrying a single point mass (direct problem) as well as the identification of the attached mass (inverse problem). The nanobeam is described using the modified strain energy theory adapted to the Euler-Bernoulli beam model, and the natural vibration frequencies have been obtained. Under the assumption of small intensity of the concentrated mass, a solution of the inverse problem based on the measurement of the mass-induced shifts in the first two eigenfrequencies is proposed. Both the cases of simply supported and cantilever end conditions are discussed in detail. The theoretical method is verified by numerical simulation and numerical tests agree well with analytical results
A constitutive model for analyzing martensite formation in austenitic steels deforming at high strain rates
Get PDFThis study presents a constitutive model for steels exhibiting SIMT, based on previous seminal works, and the corresponding methodology to estimate their parameters. The model includes temperature effects in the phase transformation kinetics, and in the softening of each solid phase through the use of a homogenization technique. The model was validated with experimental results of dynamic tensile tests on AISI 304 sheet steel specimens, and their predictions correlate well with the experimental evidence in terms of macroscopic stress–strain curves and martensite volume fraction formed at high strain rates. The work shows the value of considering temperature effects in the modeling of metastable austenitic steels submitted to impact conditions. Regarding most of the works reported in the literature on SIMT, modeling of the martensitic transformation at high strain rates is the distinctive feature of the present paper.The researchers of the University Carlos III of Madrid are indebted to the Comunidad Autónoma de Madrid (Project CCG10-UC3M/DPI-5596)) and to the Ministerio de Ciencia e Innovación de España (Project DPI/2008-06408) for the financial support received which allowed conducting part of this work. The authors express their thanks to Mr. Philippe and Mr. Tobisch from the company Zwick for the facilities provided to perform the tensile tests at high strain rates
What Makes Help Helpful? Some Thoughts on Ethics of Solidarity Through George Orwell’s Writings
Get PDFOrganisations that offer personal services, whether this be
a law firm or a hospital, may be extremely good at offering technical
solutions to people, but when it comes to offering recognition, this is
much more of a challenge. These institutions often lack the ability to ‘be
respectful of each individual’.
Recognition is a central topic –often overseen– in the works of George
Orwell, the English journalist and writer who, after taking part in the
colonial system for five years, decided to ‘expiate his guilt’ by consecutively becoming homeless, taking part in agricultural labor, writing on the living conditions of the English working class and fighting as a militiaman in the Republican side during the Spanish Civil War. It was a process that spanned over several years, in which a well-educated, intellectually brilliant person, confronted and interacted with people of different countries and social backgrounds. The paper examines both failed and successful recognition experiences in Orwell’s life and work, hoping to draw some insights in how recognition works in practice.
The analysis reveals two dramatic points and leads to a pessimistic conclusion: the first point, already presented in the first part of the article, is that without recognition, no act of help will be really helpful. And secondly, real recognition only takes place between individuals. Which leads the author to conclude, confirming the initial suggestion of the paper, that full help cannot be given by any standardized procedure, and depends almost exclusively on the ability, commitment and willingness of individuals.info:eu-repo/semantics/publishedVersio
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