Multi-terminal HVDC grids with inertia mimicry capability

The high-voltage multi-terminal dc (MTDC) systems are foreseen to experience an important development in the next years. Currently, they have appeared to be a prevailing technical and economical solution for harvesting offshore wind energy. In this study, inertia mimicry capability is added to a voltage-source converter-HVDC grid-side station in an MTDC grid connected to a weak ac grid, which can have low inertia or even operate as an islanded grid. The presented inertia mimicry control is integrated in the generalised voltage droop strategy implemented at the primary level of a two-layer hierarchical control structure of the MTDC grid to provide higher flexibility, and thus controllability to the network. Besides, complete control framework from the operational point of view is developed to integrate the low-level control of the converter stations in the supervisory control centre of the MTDC grid. A scaled laboratory test results considering the international council on large electric systems (CIGRE) B4 MTDC grid demonstrate the good performance of the converter station when it is connected to a weak islanded ac grid.Peer ReviewedPostprint (author's final draft

Special geometry of Euclidean supersymmetry II: hypermultiplets and the c-map

We construct two new versions of the c-map which allow us to obtain the target manifolds of hypermultiplets in Euclidean theories with rigid N =2 supersymmetry. While the Minkowskian para-c-map is obtained by dimensional reduction of the Minkowskian vector multiplet lagrangian over time, the Euclidean para-c-map corresponds to the dimensional reduction of the Euclidean vector multiplet lagrangian. In both cases the resulting hypermultiplet target spaces are para-hyper-Kahler manifolds. We review and prove the relevant results of para-complex and para-hypercomplex geometry. In particular, we give a second, purely geometrical construction of both c-maps, by proving that the cotangent bundle N=T^*M of any affine special (para-)Kahler manifold M is para-hyper-Kahler.Comment: 36 pages, 1 figur

Tachoastrometry: astrometry with radial velocities

Spectra of composite systems (e.g., spectroscopic binaries) contain spatial information that can be retrieved by measuring the radial velocities (i.e., Doppler shifts) of the components in four observations with the slit rotated by 90 degrees in the sky. By using basic concepts of slit spectroscopy we show that the geometry of composite systems can be reliably retrieved by measuring only radial velocity differences taken with different slit angles. The spatial resolution is determined by the precision with which differential radial velocities can be measured. We use the UVES spectrograph at the VLT to observe the known spectroscopic binary star HD 188088 (HIP 97944), which has a maximum expected separation of 23 milli-arcseconds. We measure an astrometric signal in radial velocity of 276 \ms, which corresponds to a separation between the two components at the time of the observations of 18 $\pm2$ milli-arcseconds. The stars were aligned east-west. We describe a simple optical device to simultaneously record pairs of spectra rotated by 180 degrees, thus reducing systematic effects. We compute and provide the function expressing the shift of the centroid of a seeing-limited image in the presence of a narrow slit.The proposed technique is simple to use and our test shows that it is amenable for deriving astrometry with milli-arcsecond accuracy or better, beyond the diffraction limit of the telescope. The technique can be further improved by using simple devices to simultaneously record the spectra with 180 degrees angles.With tachoastrometry, radial velocities and astrometric positions can be measured simultaneously for many double line system binaries in an easy way. The method is not limited to binary stars, but can be applied to any astrophysical configuration in which spectral lines are generated by separate (non-rotational symmetric) regions.Comment: Accepted for publication in A&

Completeness in supergravity constructions

We prove that the supergravity r- and c-maps preserve completeness. As a consequence, any component H of a hypersurface {h=1} defined by a homogeneous cubic polynomial such that -d^2 h is a complete Riemannian metric on H defines a complete projective special Kahler manifold and any complete projective special Kahler manifold defines a complete quaternionic Kahler manifold of negative scalar curvature. We classify all complete quaternionic Kahler manifolds of dimension less or equal to 12 which are obtained in this way and describe some complete examples in 16 dimensions.Comment: 29 page

STANDARDIZED CATCH RATES OF SAILFISH (ISTIOPHORUS ALBICANS) CAUGHT AS BYCATCH OF THE SPANISH SURFACE LONGLINE FISHERY TARGETING SWORDFISH (XIPHIAS GLADIUS) IN THE ATLANTIC OCEAN

Standardized catch rates of the sailfish (Istiophorus albicans) were obtained from 10615 trip observations of surface longline fishing targeting swordfish during the period 2001-2014. In roughly 28% of these trips at least one individual belonging to this species was found. Because of the low prevalence of this species in this fishery, the standardized CPUE was developed using a Generalized Linear Mixed Model assuming a delta-lognormal error distribution. The results obtained indicate that the overall trend of the standardized CPUE was similar for the total Atlantic areas and for the East and West stocks. An overall increasing trend was identified for the total Atlantic areas and for the East and West stock for the whole 2001-2014 period with some fluctuations in the most recent years

El papel de las Redes Virtuales de Aprendizaje en la formación y actualización docente

La ponencia recoge los resultados del proyecto de Investigación realizado en la ciudad de Pasto (Colombia), con el propósito de llevar a cabo la implantación y dinamización de las redes virtuales de aprendizaje de docentes de las instituciones educativas de la ciudad. Su propósito fue el de proporcionar a los docentes de los diferentes establecimientos educativos, un espacio donde puedan interactuar, entablar comunicación, fortalecer las relaciones académicas, profesionales y laborales, con el objetivo principal de hacer una adecuada incorporación de las nuevas tecnologías de la información y comunicación en su labor educativa, encaminando todo el proceso hacia el mejoramiento de la calidad educativa de todos los participantes. En el proyecto participaron profesores de diez establecimientos educativos y contó con la colaboración de la Alcaldía Municipal, la Secretaria de Educación Municipal y el Sistema Tecnológico de Pasto, como organismo encargado del seguimiento del proceso. El presente documento incluye una breve descripción de las actividades desarrolladas y los resultados obtenidos en cada etapa del proceso investigativo, además se analiza en evaluación realizada a todo el proyecto, así como las conclusiones y recomendaciones más importantes para la continuidad del proceso de fortalecimiento de estas redes de aprendizaje

Radiative decay Z_H-> \gamma A_H in the little Higgs model with T-parity

In the little Higgs model with T-parity (LHTM), the only tree-level kinematically allowed two-body decay of the Z_H boson is Z_H-> A_H H and thus one-loop induced two-body decays may have a significant rate. We study the Z_H-> \gamma A_H decay, which is induced at the one-loop level by a fermion triangle and is interesting as it depends on the mechanism of anomaly cancellation of the model. All the relevant two- and three-body decays of the Z_H gauge boson arising at the tree-level are also calculated. We consider a small region of the parameter space where the scale of the symmetry breaking f is still allowed to be as low as 500 GeV by electroweak precision data. We first analyze the scenario of a Higgs boson with a mass of 120 GeV. We found that the Z_H->\gamma A_H branching ratio can be of the order of a tree-level three-body decay and may be at the reach of detection at the LHC for f close to 500 GeV, but it may be difficult to detect for f=1 TeV. There is also an scenario where the Higgs boson has an intermediate mass such that the Z_H-> A_H H decay is closed, the Z_H-> \gamma A_H gets considerably enhanced and the chances of detection get a large boost.Comment: 19 pages, 9 figures, 2 table

Revisión de la tipología geométrica de la cúpula del Palau Güell

The Palau Güell, by Antoni Gaudí, is a UNESCO World Heritage Site. Architects and historians commonly claim that the surface of the dome in Palau Güell’s Central Hall is a paraboloid. In this study, using photogrammetrical and geometrical techniques, we prove this claim to be wrong and we define the quadric surface which best fits the dome. Besides, we provide an objective measure of that fit and we state the geometric parameters defining this surface.El Palau Güell de Antoni Gaudí está catalogado por la UNESCO como World Heritage. Es comúnmente afirmado por arquitectos e historiadores que la superficie del diseño de la cúpula que cubre el Salón Central del Palau Güell es un paraboloide. Mediante técnicas fotogramétricas y geométricas mostramos que tal afirmación no es cierta. Esta investigación determina cual es la superficie cuádrica que mejor ajusta a la cúpula. Además, damos una medida de ese ajuste, y mostramos cuáles son los parámetros geométricos que configuran esa superficie