A Fractional Model of Complex Permittivity of Conductor Media with Relaxation: Theory vs. Experiments

Moving from the study of plasmonic materials with relaxation, in this work we propose a fractional Abraham-Lorentz-like model of the complex permittivity of conductor media. This model extends the Ciancio-Kluitenberg, based on the Mazur-de Groot non-equilibrium thermodynamics theory (NET). The approach based on NET allows us to link the phenomenological function of internal variables and electrodynamics variables for a large range of frequencies. This allows us to closer reproduce experimental data for some key metals, such as Cu, Au and Ag. Particularly, our fitting significantly improves those obtained by Rakic and coworkers and we were able to operate in a larger range of energy values. Moreover, in this work we also provide a definition of a substantial fractional derivative, and we extend the fractional model proposed by Flora et al

Thermomechanics of Interstitial Working at Liquid Boundaries

A model of material interface, for which the metric tensor is regarded as an internal variable, is considered. Both a local and a non-local evolution equation for such a variable are analyzed. The consequences of the second law of thermodynamics are derived in both cases

Architectural self-fabrication

The paper will focus on the role of computational design and digital fabrication in the processes of urban and architectural self-regeneration of existing infrastructures and buildings. The Architectural Fabrication research agenda takes inspiration from some of the concepts mentioned in Christopher Alexander’s essay ‘Systems generating systems’ (1968). It aims at introducing ways in which systems thinking and computer aided manufacturing can be most directly applied to the built environment. Hacking architectural spaces, by evolving their genetic spatial and structural codes, is developing the idea of optimizing resources involving inhabitants rather than generating other top down architectural solutions. During the last decades (starting from the book of Mario Carpo, ‘The Digital Turn in Architecture’) the digital shift in architectural design has generated a new discipline with the aim to define an innovative way to bridge the notion of nature with the one of teknè. From such a cultural milieu many research agenda were focusing on the concepts of morphogenesis and evolutionary thinking inspired by the work of French philosophers Gilles Deleuze and Felix Guattari based on the theory of complex systems. Despite this interest in bridging an evolutionary approach with the notion of emergent technologies in architecture (well described in the book ‘The Architecture of Emergence’ of Michael Weinstock) only a very few researchers have investigated on the potential of computational design as a driver for the ecological rehabilitation of existing infrastructures. As a matter of fact, the computational designers were so worried to claim for a new aesthetical identity of their discipline while a new opportunity was emerging for applying this evolutionary approach in order to hack existing structures. The idea of living infrastructures is related to the possibility of developing contextual algorithms in order to customize standard solutions with a post-human process that creates diversified spatial configurations out of very rigid organizational systems. Therefore, the paper will also talk about the Hacking Gomorra project as a possible paradigm of experimenting a 3D printing protocol for the environmental rehabilitation of a mega-structural housing building in Naples (Italy)

On a mathematical model of immune competition

AbstractThis work deals with the qualitative analysis of a nonlinear integro-differential model of immune competition with special attention to the dynamics of tumor cells contrasted by the immune system. The analysis gives evidence of how initial conditions and parameters influence the asymptotic behavior of the solutions

Dynamic behavior of anisotropic plates with various combinations of edge conditions

En el presente trabajo se determinan las frecuencias naturales de vibración en placas delgadas rectangulares anisótropas, sustentadas en sus cuatro bordes por combinaciones diferentes de las clásicas condiciones de vínculos. Se consideran tres conjuntos de condiciones de contorno: 1) un par de bordes opuestos empotrado-empotrado y el otro par de bordes empotrado-simplemente apoyado, 2) tres bordes empotrados y el restante libre, 3) ambos pares de bordes empotrado-simplemente apoyado. Se considera la incidencia de la anisotropía del material, examinando el efecto de esta variable sobre las frecuencias naturales y formas modales de placas cuadrangulares con distintas relaciones de lados. Se utiliza el método variacional de Ritz, empleando como funciones aproximantes del desplazamiento las denominadas “funciones viga” en cada dirección coordenada principal. Es importante destacar el hecho de que en un trabajo pionero sobre el tema del cual son autores Mohan and Kingsbury5 se realiza un grave error desde el punto de vista matemático, ya que se utiliza el método variacional de Galerkin para obtener el algoritmo de cálculo siendo que las funciones coordenadas utilizadas no satisfacen condiciones naturales en varios casos. Por consiguiente, los resultados obtenidos no son lícitos en la mayoría de los casos tratados en el trabajo mencionado. Se realiza una implementación computacional que permite optimizar los tiempos para la obtención de re-sultados. A partir de la condición de anisotropía se efectúa la particularización al caso isótropo y ortótropo. Para validar la metodología empleada se comparan los resultados obtenidos con los disponibles en la literatura científica. Los resultados de este trabajo muestran que las frecuencias naturales son afectadas directamente por las condiciones de contorno y por la anisotropía del material y que el comportamiento dinámico de las mismas no puede predecirse sobre la base del análisis convencional de placas isótropas y ortótropas.Peer Reviewe

Modeling of shock absorption in athletics track surfaces

In this work, the possibility of predicting the force reduction (FR) characterizing the shock absorption capability of track surfaces by finite element modeling was investigated. The mechanical responses of a typical sport surface and of a reference material were characterized by quasi-static uniaxial compression experiments and fitted by Neo-Hookean and Mooney–Rivlin’s hyperelastic models to select the more appropriate one. Furthermore, in order to examine the materials behavior at strain rates typical of athletics applications, the rate dependence of the constitutive parameters was investigated. A finite element model, taking into consideration the post-impact nonlinear dynamics of the track surface and of the system (track surface + artificial athlete), was developed and validated through comparison with the results of FR tests. The simulations showed a very good agreement with the experiments and allowed to interpret the experimentally observed combined effect of track thickness and material intrinsic properties on the overall surface behavior

Superconductivity in Sr2RuO4-Sr3Ru2O7 eutectic crystals

Superconducting behavior has been observed in the Sr2RuO4-Sr3Ru2O7 eutectic system as grown by the flux-feeding floating zone technique. A supercurrent flows across a single interface between Sr2RuO4 and Sr3Ru2O7 areas at distances that are far beyond those expected in a conventional proximity scenario. The current-voltage characteristics within the Sr3Ru2O7 macrodomain, as extracted from the eutectic, exhibit signatures of superconductivity in the bilayered ruthenate. Detailed microstructural, morphological and compositional analyses address issues on the concentration and the size of Sr2RuO4 inclusions within the Sr3Ru2O7 matrix. We speculate on the possibility of inhomogeneous superconductivity in the eutectic Sr3Ru2O7 and exotic pairing induced by the Sr2RuO4 inclusions.Comment: Pages 4, figures 3, submitted to Phys. Rev. Let