Invertibility and weak continuity of the determinant for the modelling of cavitation and fracture in nonlinear elasticity

In this paper, we present and analyze a variational model in nonlinear elasticity that allows for cavitation and fracture. The main idea in unifying the theories of cavitation and fracture is to regard both cavities and cracks as phenomena of the creation of a new surface. Accordingly, we define a functional that measures the area of the created surface. This functional has relationships with the theory of Cartesian currents. We show that the boundedness of that functional implies sequential weak continuity of the determinant of the deformation gradient, and that the weak limit of one-to-one almost everywhere deformations is also one-to-one almost everywhere. We then use these results to obtain the existence of minimizers of variational models that incorporate elastic energy and this created surface energy, taking into account orientation-preserving and non-interpenetration conditions

Fracture Surfaces and the Regularity of Inverses for BV Deformations

Motivated by nonlinear elasticity theory, we study deformations that are approximately differentiable, orientation-preserving and one-to-one almost everywhere, and in addition have finite surface energy. This surface energy e{open} was used by the authors in a previous paper, and has connections with the theory of currents. In the present paper we prove that e{open} measures exactly the area of the surface created by the deformation. This is done through a proper definition of created surface, which is related to the set of discontinuity points of the inverse of the deformation. In doing so, we also obtain an SBV regularity result for the inverse

Multiplexing encrypted data by using polarized light

We investigate the feasibility of multiplexing, employing polarized light, a set of security encrypted data. The encryption approach is based on the double random pure-phase enciphering method. Phase conjugation operation is conducted in the reconstruction stage with the aid of a photorefractive crystal which stores the encrypted information. When storing each encrypted image, a polarization change is introduced in the system. This induces decorrelation on the speckle patterns inside the storing medium. We apply this approach for multiple image encryption. We show experimental results that confirm our approach

Serious game as support for the development of computational thinking for children with hearing impairment

Computational thinking (CT) has been a topic of interest in research, not only in the field of computer science, but also in education, since it allows the development of a set of competencies in the child related to problem-solving and decision-making. However, few studies on CT are focused on children with disabilities. Developing computational thinking skills for children with hearing problems is a challenge, even more so when their language skills are limited. Following a methodology for conception of serious games for children with hearing impairment called MECONESIS (Acronym in Spanish, MEtodología para CONcepción de juEgos Serios para nIños con discapacidad auditiva), we designed the serious game Perdi-Dogs for children between 7 and 11 years old with hearing impairment. We considered a set of aspects, such as challenges/learning, control, rules, feedback, interaction, rewards, surprise, communication/language, and fantasy. Perdi-Dogs involves both a physical and a digital interface, specifically a physical board together with digital interaction, by means of a QR (Quick Response) code and vibrotactile feedback system. Perdi-Dogs simulates a real environment, using physical elements able to interact simultaneously with technology. Evaluation was carried out with a group of seven children between 7 and 11 years old from the Institute for Deaf and Blind Children (Colombia). The results showed a high motivation to play for all of the children involved in the experiment

Influencia de algunas variables en el ensayo a compresión de probetas testigo en un hormigón autocompactante

La estimación de la resistencia a compresión a través de la evaluación de probetas testigo depende de numerosas variables, entre ellas, el diámetro de la probeta testigo, la dirección de extracción en relación con la dirección del hormigonado, el estado de humedad de la probeta testigo en el momento de ser ensayada, la esbeltez de la probeta testigo, la armadura embebida en la probeta testigo y la edad del hormigón investigado. El objetivo de este trabajo experimental ha sido evaluar, para un hormigón autocompactante, el efecto que presentan algunas de estas variables en el resultado de la resistencia a compresión de las probetas testigo. Estos efectos pueden ser muy diferentes de los que ocurren en el hormigón vibrado, debido a que no existe en este caso un procedimiento específico para la compactación de las probetas moldeadas. Igualmente se han analizado los posibles factores de corrección utilizados en la estimación de la resistencia a compresión de la probeta moldeada a través de la resistencia a compresión de la probeta testigo. Para ello se han fabricado 30 bloques de 50x50x100 cm en HAC cubriendo un amplio rango de resistencias (20 MPa - 80 MPa), de los cuales se extrajeron un total de 360 probetas testigo. Paralelamente a la ejecución de los bloques se han fabricado 90 probetas cilíndricas de 15 30 cm que posteriormente fueron ensayadas a compresión a la misma edad que las probetas testigo (28 días). Los resultados muestran que algunas de las variables incíden de forma muy diferente en estos hormigones que en los hormigones convencionales, en especial la dirección de extracción y el coeficiente de paso para considerar la resistencia en probeta moldeada

Passivity-based control applied of a reaction wheel pendulum: An IDA-PBC approach

This paper presents the development of a nonlinear controller for the reaction wheel pendulum (RWP) via an interconnection and damping assignment passivity-based control (IDA-PBC) approach. The IDA-PBC approach works with the port-Hamiltonian open-loop dynamics of the RWP to propose a nonlinear controller that preserves the Hamiltonian structure in closed-loop by guaranteeing stability properties in the sense of Lyapunov. Numerical results confirm the theoretical development presented throughout simulations in Simulink package from MATLAB. Comparison with a Lyapunov-based approach is also provide

Economic Dispatch of BESS and renewable generators in DC microgrids using voltage-dependent load models

This paper addresses the optimal dispatch problem for battery energy storage systems (BESSs) in direct current (DC) mode for an operational period of 24 h. The problem is represented by a nonlinear programming (NLP) model that was formulated using an exponential voltage-dependent load model, which is the main contribution of this paper. An artificial neural network was employed for the short-term prediction of available renewable energy from wind and photovoltaic sources. The NLP model was solved by using the general algebraic modeling system (GAMS) to implement a 30-node test feeder composed of four renewable generators and three batteries. Simulation results demonstrate that the cost reduction for a daily operation is drastically affected by the operating conditions of the BESS, as well as the type of load model used. © 2019 MDPI AG. All rights reserved

A variational model for fracture and debonding of thin films under in-plane loadings

We study fracture and debonding of a thin stiff film bonded to a rigid substrate through a thin compliant layer, introducing a two-dimensional variational fracture model in brittle elasticity. Fractures are naturally distinguished between transverse cracks in the film (curves in 2D) and debonded surfaces (2D planar regions). In order to study the mechanical response of such systems under increasing loads, we formulate a dimension-reduced, rate-independent, irreversible evolution law accounting for both transverse fracture and debonding. We propose a numerical implementation based on a regularized formulation of the fracture problem via a gradient damage functional, and provide an illustration of its capabilities exploring complex crack patterns, showing a qualitative comparison with geometrically involved real life examples. Moreover, we justify the underlying dimension-reduced model in the setting of scalar-valued displacement fields by a rigorous asymptotic analysis using Γ-convergence, starting from the three-dimensional variational fracture (free-discontinuity) problem under precise scaling hypotheses on material and geometric parameters. © 2014 Elsevier Ltd

SEOM guidelines on hydroelectrolytic disorders

Hydroelectrolytic disorders are one of the most common metabolic complications in cancer patients. Although often metabolic alterations affecting various ions are part of the manifestations of the oncological disease, even in the form of paraneoplastic syndrome, we must not forget that very often, these disorders could be caused by various drugs, including some of the antineoplastic agents most frequently used, such as platin derivatives or some biologics. These guidelines review major management of diagnosis, evaluation and treatment of the most common alterations of sodium, calcium, magnesium and potassium in cancer patients. Aside from life-sustaining treatments, we have reviewed the role of specific drug treatments aimed at correcting some of these disorders, such as intravenous bisphosphonates for hypercalcemia or V2 receptor antagonists in the management of syndrome of inappropriate antidiuretic hormone secretion-related hyponatremia