Transferencia de calor mediante la aplicación de RF sobre un modelo multicapa de tejido dérmico

HF radiation applied on the surface of the skin by an electrode is absorbed and it causes interior changes that redound into a smoother skin with less wrinkles. In this study, it is exposed a multiplayer method to determine absorbed radiation and increasing of temperature for each internal tissue. Each tissue is represented by a layer with certain parameters, such as permittivity, conductivity, density and specific heat. The model is applied to two different distributions of tissues: a fibrous and a fatty one. It is found that a fibrous distribution absorbs more energy than a fatty one, and also how the absorption could even be increased by previous humidification.Ingeniería, Industria y Construcció

Caracterización Electromagnética de Medios Quirales

Experimental techniques for chiral media characterization at microwave frequencies are reviewed. Free-wave, waveguide and resonators techniques found in the current literature and the author’s own experience are discussed. Some free-wave results are presented. Finally, a critical discussion about each technique feasibility is presented.Ingeniería, Industria y Construcció

Variación de la temperatura en las capas externas del cuerpo humano irradiado a alta frecuencia (HF)

The absorption of energy by human external tissue when HF irradiation and the physical consequences involved are the purposes of this study. When it is directed toward the surface of the skin, energy is transmitted to its inner layers causing an increase of the temperature. This process has experimentally been proved to be beneficial in many cases. Yet theoretically there is still a slightly hollow basis about it. Skin tissue is actually a multilayer tissue with a different characteristic in each layer. Each one of them is characterized by some parameters, such as permittivity, conductivity, density and specific heat. Two kinds of skin tissues will be analyzed: a fibrous and a fatty one, each of both with a different skin humidity. Our model takes into account the heating by HF radiation, the redistribution of energy through the tissues and the cooling rate by blood in order to predict the increasing of tissue temperature in differents situations.Ingeniería, Industria y Construcció

Caracterización experimental de medios quirales basados en inclusiones periódicas. El resonador de cuatro manivelas

The periodical distribution of elements forming a bi- or three-dimensional periodical lattice has provided a fundamental tool to develop new materials with exotic and, sometimes, amazing electromagnetic properties. Here we have analyzed the effects related to the electromagnetic activity produced by a 2D array of four crank resonators (4CR), which is composed by same handeness cranks in a packed configuration forming a parallelepiped. The sample has been built using printed circuit technology and the unit cell was designed to fit its electromagnetic response into the X band frequency range. Using a free-wave system and the corresponding reciprocal algorithms, we have characterized the material and determined the rotation angle, refraction index and chirality parameter.Ingeniería, Industria y Construcció

Algoritmo para la caracterización univoca de metamateriales basados en inclusiones quirales

Electromagnetic characterization is perfomed from the reflection and transmission coefficients by making use of retrieval algorithms. However, it is known the existence of uncertainties in the determination of these electromagnetic parameters. Here, we present a new algorithm that uses some techniques in order to avoid these uncertainities, some based on continuity conditions of physical magnitudes and some others based on causality relations, that is, exploiting Kramers-Kronig relations.Ingeniería, Industria y Construcció

Developing Chiral Media Based on the Inclusion of Metallic Cranks

A review of the manufacturing techniques for developing chiral media based on the inclusion of cranks is presented. Chirality is usually obtained by a randomdistribution of helices in a host medium. Here the chiral elements are obtained by bending thin metal-wires in three segments. We will show that a random distribution of cranks is able of rotate the polarization angle of the transmitted linearly polarized wave at microwave frequencies. This effect can be enhanced by the precise location of cranks forming a 2D periodic lattice. Several structures are analyzed looking for isotropy, reciprocity and homogeneity.Ingeniería, Industria y Construcció

Green's formulation for chirowaveguides

Green integral formulation of the boundary value problem in chirowaveguides with translational symmetry and the application to the rectangular case are presented in this paper. The Green equations for the two eigenmodes in unbounded chiral media, i.e. right and left circularly polarized waves, are formulated in terms of the Hankel functions. By splitting the waveguide contour into a finite number of intervals, the equations are discretized and a homogeneous system of equations can be obtained. The number of unknowns is reduced to the half by applying the relations between the longitudinal components and their normal derivatives at the metallic contours. The method has been used for modeling the rectangular waveguide and the dispersion diagram and the field structure for some propagation modes are presented.This work was supported by the Spanish Government (Research Projects TEC2014-55463-C3-1-P and TEC2014-55463-C3-2-P) and by the European Commission (ERDF)

Diseño de medios quirales basados en estructuras individuales bidimensionales

In this paper, we present a new way of constructing chiral media, in 8.2-12.4 GHz band, starting from achiral individual metallic elements (right angle). We showed that an appropriate distribution of such inclusions in a dielectric host responds in a manner consistent to that obtained with other media constructed using chiral metal inclusions. Appropriately modifying the size and spatial distribution of right angles is possible to model the response of these media. The media manufactured by the inclusion of right angles can be fabricated using technology printed circuit board (PCB).Ingeniería, Industria y Construcció

Diseño de medios quirales basados en la distribución ordenada de manivelas

In this communication, the experimental results obtained from the measurements of evenly distributed metallic cranks on a dielectric plate substrate is presented. The effect we have analyzed is the rotation of the polarization plane of an electromagnetic wave, both in free space and inside a circular waveguide. It is shown that the rotation of the polarization plane by some distributions of cranks, with specific symmetry properties, can be explicitly ascribed to a chirality effect.Ingeniería, Industria y Construcció

Actividad electromagnética de medios quirales basados en manivelas

Materials with electromagnetic activity are usually made by spreading helices inclusions into a host medium. In previous work, a new manufacturing technique based on the inclusion of few three segment wire hooks (cranks) was presented and the rotation of the polarisation angle in circular waveguide discussed. Here we present that the random inclusion of many cranks into a host medium produces electromagnetically active materials. Based on a free-wave experimental system, we have found that the transmitted wave through the material is rotated with respect to the incident one. First results seem to be in agreement with the typical behaviour of chiral media at the resonant frequency.Ingeniería, Industria y Construcció