Modelling Structural Flexure Effects in CPV Sun Trackers

Nowadays CPV trends mostly based in lens parqueted flat modules, enable the separate design of the sun tracker. To enable this possibility a set of specifications is to be prescribed for the tracker design team, which take into account fundamental requisites such as the maximum service loads both permanent and variable, the sun tracking accuracy and the tracker structural stiffness required to maintain the CPV array acceptance angle loss below a certain threshold. In its first part this paper outlines the author’s approach to confront these issues. Next, a method is introduced to estimate the acceptance angle losses due to the tracker’s structural flexure, which in last instance relies in the computation of the minimum enclosing circle of a set of points in the plane. This method is also useful to simulate the drifts in the tracker’s pointing vector due to structural deformation as a function of the aperture orientation angle. Results of this method when applied to the design of a two axis CPV pedestal tracker are presented.

Utzon and the sun path as an organizing element of life in a house

The present text intends to analyze the hypothesis stating that the path of the sun can be an organizing element for how you live in the houses designed by Jørn Utzon. To do so, I have selected twenty houses and building complexes designed by him between the years 1950-94, in Denmark, Sweden, The United Kingdom and Spain. In these projects I will look for elements which are repeated and their possible meaning. The aim is to reach practical conclusions that could help us decide how to orientate a house.

Where is photonics going? Reflections under the sun

After a short personal view of the first years of the photonics in Spain, some references about its present situation are given. As a possible future, the first steps towards a Photonics based on the study of the employed mechanisms in the visual system of the living beings are presented.

Change factors that may influence sun and beach destinations in a low-growth scenario

Análisis de los principales factores de cambio que previsiblemente incidirán en los destinos turísticos de sol y playa en un escenario de bajo crecimiento.

EL AIRE SE SERENA Y VISTE DE HERMOSURA Y LUZ NO USADA. De cómo el espacio arquitectónico es como el instrumento musical. Dedicado a Luis Suñén.

Se intenta en este texto establecer un paralelismo entre el instrumento musical y el espacio arquitectónico. El instrumento musical mediante el aire produce el regalo de la música. El espacio arquitectónico mediante la luz produce ese algo inefable que es la arquitectura.

Foresight in designing sun-beach destinations

Planteamiento de un Nuevo enfoque metodológico para incorporar la prospectiva en la planificación de destinos turísticos de sol y playa.

Reseña. Architecture of the Sun: Los Angeles Modernism 1900-1970

Reseña bibliográfica de Architecture of the Sun: Los Angeles Modernism 1900-1970

Magnetic Attitude Control for Satellites in Polar or Sun-Synchronous Orbits

In this work, a new law for magnetic control of satellites in near-polar orbits is presented. This law has been developed for the UMPSat-2 microsatellite, which has been designed and manufactured by Universidad Politécnica de Madrid, Madrid. The control law is a modification of the B-dot strategy that enables the satellite to control the rotation rate. Besides, the satellite?s equilibrium state is characterized by having the rotation axis perpendicular to the orbit?s plane. The control law described in the present work only needs magnetometers and magnetorquers, as sensors and actuators, respectively, to carry out a successful attitude control on the spacecraft. A description of the analysis is included. Performance and applicability of the proposed method have been demonstrated by control dynamics together with Monte Carlo techniques and by implementing the control law in the UPMSat-2 mission simulator. Results show good performance in terms of acquisition and stability of the satellite rotation rate and orientation with respect to its orbit?s plane.

Magnetic activity and differential rotation in the young Sun-like stars KIC 7985370 and KIC 7765135

Aims. We present a detailed study of the two Sun-like stars KIC 7985370 and KIC 7765135, to determine their activity level, spot distribution, and differential rotation. Both stars were previously discovered by us to be young stars and were observed by the NASA Kepler mission. Methods. The fundamental stellar parameters (vsini, spectral type, T_eff, log g, and [Fe/H]) were derived from optical spectroscopy by comparison with both standard-star and synthetic spectra. The spectra of the targets allowed us to study the chromospheric activity based on the emission in the core of hydrogen Hα and Ca ii infrared triplet (IRT) lines, which was revealed by the subtraction of inactive templates. The high-precision Kepler photometric data spanning over 229 days were then fitted with a robust spot model. Model selection and parameter estimation were performed in a Bayesian manner, using a Markov chain Monte Carlo method. Results. We find that both stars are Sun-like (of G1.5 V spectral type) and have an age of about 100–200 Myr, based on their lithium content and kinematics. Their youth is confirmed by their high level of chromospheric activity, which is comparable to that displayed by the early G-type stars in the Pleiades cluster. The Balmer decrement and flux ratio of their Ca ii-IRT lines suggest that the formation of the core of these lines occurs mainly in optically thick regions that are analogous to solar plages. The spot model applied to the Kepler photometry requires at least seven persistent spots in the case of KIC 7985370 and nine spots in the case of KIC 7765135 to provide a satisfactory fit to the data. The assumption of the longevity of the star spots, whose area is allowed to evolve with time, is at the heart of our spot-modelling approach. On both stars, the surface differential rotation is Sun-like, with the high-latitude spots rotating slower than the low-latitude ones. We found, for both stars, a rather high value of the equator-to-pole differential rotation (dΩ ≈ 0.18 rad d^-1), which disagrees with the predictions of some mean-field models of differential rotation for rapidly rotating stars. Our results agree instead with previous works on solar-type stars and other models that predict a higher latitudinal shear, increasing with equatorial angular velocity, that can vary during the magnetic cycle.