Wave propagation in discontinuous media

Wave propagation in discontinuous media, which is of interest for design analysis of underground structures and geotechnical works in general, is studied in this paper with the scattering matrix method. This method determines the response of a system, i.e. the discontinuous medium, excited by an elastic wave. Both P, SV or SH waves can be applied to the model with any oblique angle of incidence. The scattering matrix is composed of reflection and transmission coefficients of a single joint or a set of parallel joints. The analytical solution is obtained in the frequency domain and allows one to consider multiple wave reflections between joints. Reflected and transmitted waves are calculated for one and more joints in dry or fluid filled conditions. The solutions obtained are compared with analytical and numerical solutions available in the literature or obtained independently by using the Distinct Element Metho

Multiple dielectric loaded perforated screens as frequency selective surfaces

Abstract: Perforated screens can be used as frequency selective surfaces when a high pass frequency response is required. In this paper, a spectral characterisation of perforated screens is presented. The analysis yields the generalised scattering matrix of each screen, which is a useful tool for studying composite structures. Numerical results, relative to single and double screens with periodical distributions of circular apertures, are discussed

Bimodal Resonance Phenomena. Part III: High-Contrast Grating Reflectors

The extraordinary broadband high-reflectivity features of high-contrast gratings are stimulating great interest in many opto-electronic applications. In view of obtaining a simple simulation framework, the analogy of high-contrast grating reflectors with bimodal Fabry-Pérot interferometers is proposed. The closed-form expressions of the interferometer reflectivity, obtained starting from a novel parametrization of the scattering matrices characterizing the bar-air interface, allow a complete exploration of the device parameter space, explaining and predicting the phenomenon of ultra-broadband quasi-100% reflectivity. In this paper an optimized and numerically efficient design procedure is described and compared with the standard rigorous coupled wave analysis, both for the classical "bar-in-air" configuration and for a more robust and practical one, with bars lying on a dielectric support. It is shown that the model can be applied also in the more realistic case of lossy gratings

Scattering from finite extent frequency selective surface illuminated by arbitrary sources

A method is proposed for the computation of the field scattered from a dichroic plate placed in the near-field region of the feeds. The primary pattern of the feed and dichroic plate assembly has been computed

Mastering Lateral Radiation Losses in Tunable VCSELs

This paper deals with the loss mechanisms in tunable vertical-cavity surface-emitting lasers (VCSELs). The strong increase of the threshold gain at the tuning range edges motivates the investigation of the degradation mechanisms presented in this paper. A campaign of simulations performed with our in-house VCSEL ELectroMagnetic (VELM) simulation code, combined with a novel approach based on the study of the Poynting vector, allowed to identify significant lateral radiation losses. The proposal of technology-affordable countermeasures rests on the proper understanding of these phenomena

Simulation of Spiral Phase Plate VCSELs

Several groups belonging to different scientific communities are focusing their efforts on the theoretical and applied research on the orbital angular momentum of light (OAM). Among the most significant examples in the field of ICT, the OAM-division multiplexing recently emerged as a viable approach for increasing the capacity of the next generation optical networks. Optical beams featuring an OAM are usually generated through the conversion of a standard laser mode; such techniques usually rely on bulk optical components such as computer-generated holograms, spatial light modulators or spiral phase plates (SPPs). In a recent paper Li et al. proposed the possibility to load a commercial GaAs VCSEL with a micro-SPP [1]. The resulting device, which can emit directly OAM modes, is extremely appealing in view of reducing manufacturing costs, even opening up the possibility to introduce it in mass market applications, with an eye to the “green technology” paradigm in which VCSELs perfectly fit, due to their well-known low consumption features. The experimental work described in [1] has been complemented by a theoretical study performed by means of our in-house Vcsel ELectroMagnetic simulator (VELM) [2]. The possibility to estimate the OAM mode efficiency with full-wave simulations allowed to perform a thorough analysis of the sensitivity of the device to the possible manufacturing issues. As an example of the several numerical results that will be presented during the conference, Fig. 1 shows the simulated field profiles for the unprocessed VCSEL and for three micro-SPP geometries producing various OAM orders. Furthermore, the flexibility of VELM opens up the possibility to explore alternative implementations of SPP-VCSELs. Such solutions, supported by a technological affordability study, may allow to further develop these devices, in view of improving the emitted OAM mode purity while lowering the manufacturing costs

Aplicación de un Programa Educativo Tendente a Mejorar el Control de Enfermedad Hipertensiva en Pacientes Hipertensos del Hospital I María Reiche Newman de ESSALUD Marcona Mayo - Julio 2002

Siendo la hipertensión arterial una enfermedad considerada como problema de salud público en los países en desarrollo y cuya incidencia y prevaléncia se encuentra en aumento a nivel mundial. Convencidos de que el adecuado control de la hipertensión arterial es necesario para disminuir las complicaciones en su mayoría de casos limitantes y que genera secuelas graves deteriorando la calidad de vida de los pacientes, es que nos motiva a realizar esta investigación. El presente trabajo fue realizado en el Hospital I Maria Reiche Neuman de Essalud Marcona - Ica Perú. En el periodo comprendido entre los meses de mayo a julio del año 2002, siendo una investigación de campo y de nivel explicativo, perteneciendo al campo general de ciencias de la salud, área especifica de Educación para la Salud y especialidad de medicina Interna. Teniendo como unidades de estudio 35 pacientes del programa de hipertensión arterial que cumplieron con el criterio de inclusión y no presentaron ninguno de los criterios de exclusión El Estudio cuenta con la variable independiente Programa educativo y como variable dependiente Control de enfermedad Hipertensiva, los objetivos del trabajo fueron determinar los valores de presión arterial e índice de masa corporal previo y posterior a la aplicación del programa educativo y valorar la efectividad 6 del programa educativo en la población en estudio; Planteándose como hipótesis “dado que la hipertensión arterial es uno de los principales problemas de salud pública y que el tratamiento de esta enfermedad, es básicamente no farmacológico. Es probable que la aplicación de un programa educativo orientado a modificar los estilos de vida, mejore el control de la enfermedad hipertensiva en los pacientes hipertensos del Hospital I María Reiche Neuman de EsSalud Marcona”. La Población de estudio fue compuesta por 35 pacientes, con edades entre 28 y 70 años de ambos sexos, a los que se les aplico un programa educativo de dos meses de duración en numero de ocho charlas ; realizándose la contrastación de resultados y la aplicación de pruebas estadísticas chi2, “t” de students comprobándose la hipótesis planteada y determinando que la aplicación del programa educativo disminuye significativamente los valores de presión arterial sistólica en 9 mm Hg.; los valores de presión arterial diastólica en 6.28 mm Hg. y disminuyendo el índice de masa corporal en 0.8117 Kg./m2 no siendo esta ultima estadísticamente significativa Se sugiere a la gerencia central de Essalud a través de la red asistencial de Ica, por medio del programa de hipertensión arterial la aplicación del programa educativo en forma permanente, a fin de lograr un mejor control de la hipertensión arterial, lo que disminuiría las complicaciones de dicha enfermedad. Se presenta una propuesta de capacitación para estos pacientes del hospital I María Reiche Neuman