963 research outputs found
A consistent interface element formulation for geometrical and material nonlinearities
Decohesion undergoing large displacements takes place in a wide range of
applications. In these problems, interface element formulations for large
displacements should be used to accurately deal with coupled material and
geometrical nonlinearities. The present work proposes a consistent derivation
of a new interface element for large deformation analyses. The resulting
compact derivation leads to a operational formulation that enables the
accommodation of any order of kinematic interpolation and constitutive behavior
of the interface. The derived interface element has been implemented into the
finite element codes FEAP and ABAQUS by means of user-defined routines. The
interplay between geometrical and material nonlinearities is investigated by
considering two different constitutive models for the interface (tension
cut-off and polynomial cohesive zone models) and small or finite deformation
for the continuum. Numerical examples are proposed to assess the mesh
independency of the new interface element and to demonstrate the robustness of
the formulation. A comparison with experimental results for peeling confirms
the predictive capabilities of the formulation.Comment: 14 pages, 11 figure
What You Don\u27t Know About Motivational Laptop Stickers
Mental health problems are on the rise among young adults in the U.S. (Kingkade, 2016). At the same time, today’s U.S. young adults are significantly more invested than their older counterparts in portraying themselves as “positive” (self-confident, easy-going, and happy; Berenson et al., 2018). Although many have begun to speculate that these two trends may be linked (e.g., Fagan, 2017), little empirical research on this issue exists
Temporal characterization of the requests to Wikipedia
This paper presents an empirical study about the temporal patterns
characterizing the requests submitted by users to Wikipedia.
The study is based on the analysis of the log lines registered by the
Wikimedia Foundation Squid servers after having sent the appropriate
content in response to users' requests. The
analysis has been conducted regarding the ten most visited editions of
Wikipedia and has involved more than 14,000 million log lines
corresponding to the traffic of the entire year 2009. The conducted methodology
has mainly consisted in the parsing and filtering
of users' requests according to the study directives. As a result, relevant information
fields have been finally stored in a database for persistence and further
characterization. In this way, we, first, assessed, whether the traffic to Wikipedia could serve
as a reliable estimator of the overall traffic to all the Wikimedia Foundation
projects. Our subsequent analysis of the temporal evolutions corresponding to
the different types of requests to Wikipedia revealed interesting differences
and similarities among them that can be related to the users' attention to the Encyclopedia.
In addition, we have performed separated characterizations of each Wikipedia edition
to compare their respective evolutions over time
A quantitative examination of the impact of featured articles in Wikipedia
This paper presents a quantitative examination of the impact of the presentation of featured articles as quality content in the main page of several Wikipedia editions. Moreover, the paper also presents the analysis performed to determine the number of visits received by the articles promoted to the featured status. We have analyzed the visits not only in the month when articles awarded the promotion or were included in the main page, but also in the previous and following ones. The main aim for this is to assess the attention attracted by the featured content and the different dynamics exhibited by each community of users in respect to the promotion process. The main results of this paper are twofold: it shows how to extract relevant information related to the use of Wikipedia, which is an emerging research topic, and it analyzes whether the featured articles mechanism achieve to attract more attention
Análisis de controladores por realimentación de estados, control óptimo y lógica difusa, para un péndulo de Furuta
Este trabajo presenta el desarrollo y control de un
péndulo invertido rotacional (péndulo de Furuta) mediante
controladores en el espacio de estados, control
Ăłptimo y lĂłgica difusa. Este tipo de sistemas son las
aeronaves, vehĂculos espaciales, vehĂculos submarinos,
barcos, satélites y robots, construidos por barras y
uniones articuladas, pasivas y activas. Estos sistemas
generalmente están desafiando a la gravedad y deben
mantenerse en equilibrio, por lo tanto, las plantas
de estos sistemas son no lineales y se hace necesario
controlarlo mediante leyes de control no lineales; sin
embargo, debido al aparecimiento de la lĂłgica difusa,
este tipo de control tiene una gran ventaja que
radica en que no es necesario saber con exactitud
las caracterĂsticas de la planta; el control puede ser
adaptado para sistemas SISO y MIMO; la clave del
control difuso radica especialmente en el conocimiento
que debe tener el experto para plantear los rangos
de las funciones de inferencia y su tipo de funciones,
además, plantear el método de inferencia de la máquina
de inferencia; por lo tanto, para este tipo de
control se debe hacer varias pruebas hasta conseguir
los objetivos planteados en el sistema de control.This paper presents the development and control of
a rotational inverted pendulum (Furuta pendulum)
by controllers in the state space, optimal control and
fuzzy logic. Such systems are aircraft, spacecraft, underwater
vehicles, ships, satellites and robots, built
by rods and articulated joints, passive and active.
These systems generally are defying gravity to stay
in balance so plants such systems are nonlinear and
will need to be monitored by nonlinear control laws
however due to the appearance of fuzzy logic, this
control has great advantage is that it is not necessary
to know exactly the characteristics of the plant
and control systems can be adapted to Simple Simple
Input Output (SISO) or Multiple Input Multiple Output
(MIMO), the key lies especially fuzzy control in
the knowledge that you need to ask the expert ranges
inference functions and features such well raise the
inference method of inference engine, so for this type
of control should be done several tests to get the goals
set in the control system
Preliminary check-list of the bryophytes of Extremadura (Spain)
A list of all bryophytes recorded for Extremadura in the literature from 1802 to 2010 is provided. It includes
390 taxa (4 hornworts, 87 liverworts and 299 mosses). Information on the presence of these taxa in each of
the Extremaduran provinces (Cáceres and Badajoz) is included. In addition, the conservation status of these
species is added
Fracture of solar-grade anisotropic polycrystalline Silicon: A combined phase field–cohesive zone model approach
ArtĂculo Open Access en el sitio web del editor. Pago por publicar en abierto. This work presents a novel computational framework to simulate fracture events in brittle anisotropic polycrystalline materials at the microscopical level, with application to solar-grade polycrystalline Silicon. Quasi-static failure is modeled by combining the phase field approach of brittle fracture (for transgranular fracture) with the cohesive zone model for the grain boundaries (for intergranular fracture) through the generalization of the recent FE-based technique published in [M. Paggi, J. Reinoso, Comput. Methods Appl. Mech. Engrg., 31 (2017) 145–172] to deal with anisotropic polycrystalline microstructures. The proposed model, which accounts for any anisotropic constitutive tensor for the grains depending on their preferential orientation, as well as an orientation-dependent fracture toughness, allows to simulate intergranular and transgranular crack growths in an efficient manner, with or without initial defects. One of the advantages of the current variational method is the fact that complex crack patterns in such materials are triggered without any user-intervention, being possible to account for the competition between both dissipative phenomena. In addition, further aspects with regard to the model parameters identification are discussed in reference to solar cells images obtained from transmitted light source. A series of representative numerical simulations is carried out to highlight the interplay between the different types of fracture occurring in solar-grade polycrystalline Silicon, and to assess the role of anisotropy on the crack path and on the apparent tensile strength of the material. UniĂłn Europea FP/2007–2013/ERC 306622 Ministerio de EconomĂa y Competitividad MAT2015–71036-P y MAT2015–71309-P Junta de AndalucĂa P11-TEP-7093 y P12-TEP- 105
- …