1,095 research outputs found

    Large and small-scale structures and the dust energy balance problem in spiral galaxies

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    The interstellar dust content in galaxies can be traced in extinction at optical wavelengths, or in emission in the far-infrared. Several studies have found that radiative transfer models that successfully explain the optical extinction in edge-on spiral galaxies generally underestimate the observed FIR/submm fluxes by a factor of about three. In order to investigate this so-called dust energy balance problem, we use two Milky Way-like galaxies produced by high-resolution hydrodynamical simulations. We create mock optical edge-on views of these simulated galaxies (using the radiative transfer code SKIRT), and we then fit the parameters of a basic spiral galaxy model to these images (using the fitting code FitSKIRT). The basic model includes smooth axisymmetric distributions along a S\'ersic bulge and exponential disc for the stars, and a second exponential disc for the dust. We find that the dust mass recovered by the fitted models is about three times smaller than the known dust mass of the hydrodynamical input models. This factor is in agreement with previous energy balance studies of real edge-on spiral galaxies. On the other hand, fitting the same basic model to less complex input models (e.g. a smooth exponential disc with a spiral perturbation or with random clumps), does recover the dust mass of the input model almost perfectly. Thus it seems that the complex asymmetries and the inhomogeneous structure of real and hydrodynamically simulated galaxies are a lot more efficient at hiding dust than the rather contrived geometries in typical quasi-analytical models. This effect may help explain the discrepancy between the dust emission predicted by radiative transfer models and the observed emission in energy balance studies for edge-on spiral galaxies.Comment: 9 pages, 5 figures, accepted for publication in A&

    Industrialización en la vivienda social de Madrid

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    The use of industrialized systems often clashes with the inertia of traditional construction methods, the lack of technical knowledge and fear of a budget increase of all those agents involved in the process of design, construction and dwelling. This article stresses the relevance of systematize and rationalize the entire process. The promotion of industrial systems requires a wide understanding of the industrial context and the need of changing construction habits. It is an strategic and conscious effort to boost the construction industry, as well as a means to achieve higher quality in the product, and safer construction sites. To support the implementation of industrialized construction systems, is important to stress the environmental benefits of their use, such as recyclability, energetic efficiency of their production and the smaller amount of waste material. At last, never forget the satisfaction and participation in the whole process of the final user.El empleo de sistemas industrializados a menudo se enfrenta a las inercias de formas de construir tradicionales, al desconocimiento técnico y a la desconfianza sobre los costes de todos los implicados en el proceso de promoción, construcción y habitación. Este artículo insiste en la necesidad de sistematizar y racionalizar todo el proceso. La promoción de sistemas industriales requiere una comprensión amplia del tejido industrial y de la necesidad de modificar hábitos constructivos. Se debe entender como una apuesta estratégica consciente para impulsar la industria de la construcción, así como un medio para conseguir un producto de más calidad y mayor seguridad en obra. Para reforzar la implantación de sistemas industrializados, es importante incidir en los beneficios medioambientales de su utilización, tales como reciclaje, eficiencia energética de su producción y menor generación de residuos. También considerar como fundamental la satisfacción y participación en el proceso del que será su usuario final

    Los documentos de idoneidad técnica como potenciales incentivadotes de la industrialización de la construcción.

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    Los documentos de idoneidad técnica como potenciales incentivadotes de la industrialización de la construcción

    Gaps analysis and requirements specification for the evolution of Copernicus system for polar regions monitoring: addressing the challenges in the horizon 2020-2030

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    This work was developed as part of the European H2020 ONION (Operational Network of Individual Observation Nodes) project, aiming at identifying the technological opportunity areas to complement the Copernicus space infrastructure in the horizon 2020–2030 for polar region monitoring. The European Earth Observation (EO) infrastructure is assessed through of comprehensive end-user need and data gap analysis. This review was based on the top 10 use cases, identifying 20 measurements with gaps and 13 potential EO technologies to cover the identified gaps. It was found that the top priority is the observation of polar regions to support sustainable and safe commercial activities and the preservation of the environment. Additionally, an analysis of the technological limitations based on measurement requirements was performed. Finally, this analysis was used for the basis of the architecture design of a potential polar mission.Peer ReviewedPostprint (published version

    A Black Ring with two Angular Momenta in Taub-NUT

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    We use the recently-constructed explicit duality transformation that relates a rotating anti-D6-D4-D2-D0 black hole solution to a rotating M5-M2-P black string to construct a non-supersymmetric black ring in Taub-NUT that has two angular momenta, as well as M2 charges and M5 dipole moments. This is the first black ring solution that has both dipole charges and rotation along the S^2 of the horizon, and hence can be thought of as the "Pomeransky-Senkov" version of the M5-M2 black ring in Taub-NUT. Its physics should provide a testing ground for the applicability of the blackfold approach to charged rotating black branes, and should elucidate the phase space of charged dipole rings in various backgrounds.Comment: 20 pages, LaTe

    Electric field inversion asymmetry: Rashba and Stark effects for holes in resonant tunneling devices

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    We report experimental evidence of excitonic spin-splitting, in addition to the conventional Zeeman effect, produced by a combination of the Rashba spin-orbit interaction, Stark shift and charge screening. The electric-field-induced modulation of the spin-splitting are studied during the charging and discharging processes of p-type GaAs/AlAs double barrier resonant tunneling diodes (RTD) under applied bias and magnetic field. The abrupt changes in the photoluminescence, with the applied bias, provide information of the charge accumulation effects on the device.Comment: 4 pages, 2 figure

    Ultrafocused electromagnetic field pulses with a hollow cylindrical waveguide

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    We theoretically show that a dipole externally driven by a pulse with a lower-bounded temporal width, and placed inside a cylindrical hollow waveguide, can generate a train of arbitrarily short and focused electromagnetic pulses. The waveguide encloses vacuum with perfect electric conducting walls. A dipole driven by a single short pulse, which is properly engineered to exploit the linear spectral filtering of the cylindrical hollow waveguide, excites longitudinal waveguide modes that are coherently refocused at some particular instances of time, thereby producing arbitrarily short and focused electromagnetic pulses. We numerically show that such ultrafocused pulses persist outside the cylindrical waveguide at distances comparable to its radius

    Los documentos de idoneidad técnica como potenciales incentivadores de la industrialización de la construcción

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    The first part of this work2 proceeds to determine the relative weight of a series of functional elements in convention building construction as a preliminary to a study of two residential buildings, simulating the intensive application of sistems, products and/or components certified with DIT, DIT Plus and ETA (Spanish technical approvals, Spanish technical approvals plus and European technical approvals) on them. The work concludes highlighting that the number of approvals (DIT, DIT Plus and ETA) issued and the availability of industrialised construction products (fachades, inside partitions, roofing...), available for an estimated 70% of the value of functional elements in residential buildings. The relatively scant use of industrialised elements (understanding in this point –only in this work context- as the ones approved with the mentioned ‘documents’) in residential construction in Spain cannot, therefore, be attributed to a market scarcity of such elements, components or subsystems.En la primera parte de este trabajo1 se desglosa la incidencia de los elementos funcionales en la edificación, como paso previo para el estudio de dos edificios de viviendas, en los que se ha simulado la aplicación intensiva de sistemas, productos y/o componentes acreditados con DIT, DIT Plus o DITE. El trabajo concluye destacando que hay una relación directa entre el número de ‘documentos’ (DIT, DIT Plus o DITE) otorgados y la disponibilidad de productos industrializados para la construcción (fachadas, cerramientos interiores, cubiertas…), estimado en un 70% del valor los elementos funcionales de los edificios de viviendas. Así, la relativamente escasa utilización de elementos industrializados (entendido en este caso –a efectos únicamente de este trabajo- como los que cuentan con los ‘documentos’ aludidos) en la construcción de viviendas en España, no puede imputarse a una carencia de elementos, componentes o subsistemas industrializados de mercado
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