Diffusive transport and self-consistent dynamics in coupled maps

The study of diffusion in Hamiltonian systems has been a problem of interest for a number of years. In this paper we explore the influence of self-consistency on the diffusion properties of systems described by coupled symplectic maps. Self-consistency, i.e. the back-influence of the transported quantity on the velocity field of the driving flow, despite of its critical importance, is usually overlooked in the description of realistic systems, for example in plasma physics. We propose a class of self-consistent models consisting of an ensemble of maps globally coupled through a mean field. Depending on the kind of coupling, two different general types of self-consistent maps are considered: maps coupled to the field only through the phase, and fully coupled maps, i.e. through the phase and the amplitude of the external field. The analogies and differences of the diffusion properties of these two kinds of maps are discussed in detail.Comment: 13 pages, 14 figure

Composite infrared bolometers with Si_3N_4 micromesh absorbers

We report the design and performance of 300-mK composite bolometers that use micromesh absorbers and support structures patterned from thin films of low-stress silicon nitride. The small geometrical filling factor of the micromesh absorber provides 20× reduction in heat capacity and cosmic ray cross section relative to a solid absorber with no loss in IR-absorption efficiency. The support structure is mechanically robust and has a thermal conductance, G < 2 × 10^(−11) W/K, which is four times smaller than previously achieved at 300 mK. The temperature rise of the bolometer is measured with a neutron transmutation doped germanium thermistor attached to the absorbing mesh. The dispersion in electrical and thermal parameters of a sample of 12 bolometers optimized for the Sunyaev–Zel’dovich Infrared Experiment is ±7% in R (T), ±5% in optical efficiency, and ±4% in G

The influence of fractional diffusion in Fisher-KPP equations

We study the Fisher-KPP equation where the Laplacian is replaced by the generator of a Feller semigroup with power decaying kernel, an important example being the fractional Laplacian. In contrast with the case of the stan- dard Laplacian where the stable state invades the unstable one at constant speed, we prove that with fractional diffusion, generated for instance by a stable L\'evy process, the front position is exponential in time. Our results provide a mathe- matically rigorous justification of numerous heuristics about this model

Paisaje urbano, sostenibilidad e inmigración en Santiago de Chile

Las bases de la sostenibilidad urbana se estructuran sobre la complejidad, la diversidad y la mixtura de actividades. Sin embargo, en Chile el paisaje urbano se encuentra sometido a las reglas de la oportunidad económica que crean estructuras urbanas. Además, la movilidad, la inmigración y la transculturalidad y están construyendo un nuevo layer que favorece la complejidad del paisaje urbano. Este trabajo describe un método para cartografiar las relaciones intangibles de la inmigración en una ciudad poco habituada a la mixtura, como es Santiago de Chile. Aquí se presenta el marco teórico que mueve la investigación y los primeros resultados sobre la visualización de este nuevo layer urbano

Fenomenologia: uma visão para a pesquisa em enfermagem

La disciplina de enfermería necesita identificarse con una filosofía que le permita otorgar un sentido interpretativo a los fenómenos sociales o individuales; y la investigación cualitativa ofrece la metodología necesaria para llevar a cabo la interpretación de los significados bajo un análisis crítico y reflexivo. El objetivo del presente trabajo fue reflexionar sobre diferentes tradiciones filosóficas en torno a la fenomenología, al explorar los pensamientos de Edmund Husserl, Martin Heidegger y Alfred Schütz. Se realizó un ensayo teórico cuyo insumo literario se obtuvo de repositorios y fuentes de datos electrónicas, se incluyeron artículos publicados de los años 2010 al 2014, se utilizaron combinaciones de ocho palabras clave y se excluyeron aquellos artículos que no mencionaron el enfoque teórico de los filósofos de interés. Se concluye que las tres perspectivas filosóficas plantean una estrategia metodológica factible de ser utilizada dentro de la investigación cualitativa en enfermería, ya sea bajo la escuela descriptiva de Husserl, la postura interpretativa de Heidegger o la visión social de Schütz.The discipline of nursing needs to identify with a philosophy that allows give an interpretive sense of social or individual phenomena; and qualitative research provides the necessary methodology to perform the interpretation of the meanings under a critical and reflective analysis. The aim of this study was to reflect on different philosophical traditions around phenomenology, exploring the thoughts of Edmund Husserl, Martin Heidegger and Alfred Schütz. A theoretical essay whose literary input was obtained from repositories and electronic data sources was conducted, published in the years 2010 to 2014 were included combinations of eight key words were used and those items not mentioned the theoretical approach of philosophers were excluded of interest. It is concluded that the three philosophical perspectives pose a feasible methodological strategy to be used in qualitative research in nursing, either under the descriptive school of Husserl, Heidegger interpretive stance or the social vision of Schütz.A disciplina de enfermagem precisa identificar-se com uma filosofia que permite dar um sentido interpretativo dos fenômenos sociais ou individuais; e pesquisa qualitativa fornece a metodologia necessária para realizar a interpretação dos significados sob uma análise crítica e reflexiva. O objetivo deste estudo foi refletir sobre diferentes tradições filosóficas em torno de fenomenologia, explorando os pensamentos de Edmund Husserl, Heidegger e Alfred Martin Schütz. Um ensaio teórico cuja entrada literária foi obtida a partir de repositórios e fontes de dados eletrônicos foram realizadas, publicado nos anos de 2010 a 2014 foram incluídos foram utilizadas combinações de oito palavras-chave e esses itens não mencionou a abordagem teórica de filósofos foram excluídos juros. Conclui-se que as três perspectivas filosóficas representam uma estratégia metodológica viável para ser utilizado na pesquisa qualitativa em enfermagem, seja sob a escola descritiva de Husserl, Heidegger postura interpretativa ou a visão social de Schütz

Strain-induced martensite decay in bearing steels under rolling contact fatigue: Modelling and atomic-scale characterisation

Martensite decay in bearing steels manifested as dark etching regions (DERs) under rolling contact fatigue (RCF) is modelled. The proposed model is established based on a dislocation-assisted carbon migration mechanism. The proposed model is capable of predicting the progress of DER formation and the corresponding mechanical property evolution with increasing number of cycles, in good agreement with the experimental data reported throughout seventy years. The effects of RCF testing conditions on DER formation are studied and a useful tool, DER% maps, is developed for illustrating the temperature, contact pressure and number of cycles for DER occurrence. Moreover, an atom probe tomography study is carried out, revealing the nature of DER ferrite and obtaining strong evidence supporting the postulated DER formation mechanism. The successful application of the dislocation assisted carbon migration mechanism to DER formation provides a plausible explanation to the phenomenon of martensite decay under rolling contact fatigue

COMPUTATION OF THE REFLECTANCE AND TRANSMITTANCE FOR AN INHOMOGENEOUS LAYERED MEDIUM WITH TURNING POINT S USING THE WKB AND SPPS METHODS

Electromagnetic wave propagation is currently present in the vast majority of situations which occur in veryday life, whether in mobile communications, DTV, satellite tracking, broadcasting, etc. Because of this the study of increasingly complex means of propagation of lectromagnetic waves has become necessary in order to optimize resources and increase the capabilities of the devices as required by the growing demand for such services. Within the electromagnetic wave propagation different parameters are considered that characterize it under various circumstances and of particular importance are the reflectance and transmittance. There are several methods or the analysis of the reflectance and transmittance such as the method of approximation by boundary condition, the plane wave expansion method (PWE), etc., but this work focuses on the WKB and SPPS methods. The implementation of the WKB method is relatively simple but is found to be relatively efficient only when working at high frequencies. The SPPS method (Spectral Parameter Powers Series) based on the theory of pseudoanalytic functions, is used to solve this problem through a new representation for solutions of Sturm Liouville equations and has recently proven to be a powerful tool to solve different boundary value and eigenvalue problems. Moreover, it has a very suitable structure for numerical implementation, which in this case took place in the Matlab software for the valuation of both conventional and turning points profiles. The comparison between the two methods allows us to obtain valuable information about their perfor mance which is useful for determining the validity and propriety of their application for solving problems where these parameters are calculated in real life applications

Geometrothermodynamics

We present the fundamentals of geometrothermodynamics, an approach to study the properties of thermodynamic systems in terms of differential geometric concepts. It is based, on the one hand, upon the well-known contact structure of the thermodynamic phase space and, on the other hand, on the metric structure of the space of thermodynamic equilibrium states. In order to make these two structures compatible we introduce a Legendre invariant set of metrics in the phase space, and demand that their pullback generates metrics on the space of equilibrium states. We show that Weinhold's metric, which was introduced {\it ad hoc}, is not contained within this invariant set. We propose alternative metrics which allow us to redefine the concept of thermodynamic length in an invariant manner and to study phase transitions in terms of curvature singularities.Comment: Revised version, to be published in Jour. Math. Phy