This paper presents an alternative analysis of obtaining radiated electromagnetic (EM) fields in a dielectric prolate spheroid using the perturbation technique. A circular loop antenna is used as a radiator on the top...
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This paper presents an alternative analysis of obtaining radiated electromagnetic (EM) fields in a dielectric prolate spheroid using the perturbation technique. A circular loop antenna is used as a radiator on the top of the spheroid. The spheroid is approximated by the first a few terms of the Taylor series expansion (higher-order approximation), and coefficients for transmission and scattered EM fields are found using the perturbation method where the coefficients are also expanded into Taylor series and determined by matching the boundary conditions on the spheroidal dielectric surface. After the approximated coefficients and EM fields are obtained, validity of the approach is discussed and limitations are also addressed.
Relying on well known technology for microbending sensors largely used in high sensitivity pressure measurements, an optoelectronic sensor for temperature measurements was devised and successfully tested. It can prove...
Microcavities are a class of optical structures providing a versatile approach to engineering light matter interactions. In light of recent developments in materials processing technologies, in particular for organic ...
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Microcavities are a class of optical structures providing a versatile approach to engineering light matter interactions. In light of recent developments in materials processing technologies, in particular for organic and hybrid ones, and of the need for high efficiency optical systems, there has been extensive innovation and improvement in their design and realization leading to a multitude of structures and materials. Among these, closed multi-material microcavities or microresonators based on the effect of dielectric contrast have been attractive for their low losses, applicability in a wide spectral range, and customizability. High-dielectric contrast microcavities based on distributed Bragg reflectors have been adapted early on for their highly controlled fabrication and strong light confinement and proved to be essential in current technologies including lasers and light emitting diodes. In this review, we map their evolution from planar one-dimensional inorganic structures to more sophisticated designs incorporating various categories of organic and hybrid materials. Additionally, we provide an overview of state-of-the-art developments and limitations of this class of structures.
MANY NEW developments to meet modern requirements have been applied to the renewable expulsion-fuse and oil-fuse cut-outs for a-c. distribution systems of 15,000 volts and below. While there are several different type...
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MANY NEW developments to meet modern requirements have been applied to the renewable expulsion-fuse and oil-fuse cut-outs for a-c. distribution systems of 15,000 volts and below. While there are several different types of fuse cut-outs, the universal design problem is the interruption of an arc formed when the current carrying element melts. Both expulsion-fuse and oil-fuse cut-outs depend for this interruption upon the gas pressure generated by the current in the arc.
The optimisation of the support structure of heliostats in concentrating solar power plants is a fundamental task aimed at attempting to reduce the high levelised cost of energy (LCOE) of current configurations. In th...
The optimisation of the support structure of heliostats in concentrating solar power plants is a fundamental task aimed at attempting to reduce the high levelised cost of energy (LCOE) of current configurations. In this work, an integrated multi-objective optimisation framework is presented, which relies on the combination of a lean and fast structural model with a genetic algorithm to simultaneously minimise both the overall mass of the support structure and the mean angle of rotation of the mirror surface, which directly affects the optical efficiency of the component. A particular feature of the proposed framework is that it represents an integrated solution, i.e., it allows to simultaneously optimise the main components of the heliostat support structure, i.e., the pedestal, the truss and the back support structure, assuming they are off-the-shelf components easily available on the market. The optimisation problem is set up selecting as design variables (i) the number of elements in the back support structure and (ii) the relevant characteristics of all the components considered, i.e., section shape and dimensions, according to the components commercial datasheets. At each iteration of the optimisation process, the structural model is fed with the currentdesign variables values and, according to some computed aerodynamic loads, it allows evaluating the displacement and rotation of the points of interest within the mirror surface. An aerodynamic model present in the literature based on experimental wind tunnel tests is used to estimate the wind forces acting on the heliostat as a function both of the mirror inclination angle with respect to the ground and of the wind direction with respect to the mirror orientation. In this work, the proposed methodology is demonstrated on a realistic case study and the results commented in detail, highlighting possible future developments and the limitations of the framework.
Over the last decade, the vector-apodizing phase plate (vAPP) coronagraph has been developed from concept to on-sky application in many high-contrast imaging systems on 8-m class telescopes. The vAPP is an geometric-p...
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