http://hdl.handle.net/2117/222 2013-05-20T15:49:24Z http://hdl.handle.net/2117/14928 Title: Modelling shoreline sand waves: application to the coast of Namibia Authors: Falqués Serra, Albert; Van den Berg, Niels; Ribas Prats, Francesca; Caballeria Suriñach, Miquel Abstract: The SW coast of Africa (Namibia and part of Angola) features very long sandy beaches and a wave climate dominated by energetic swells from the SSW, therefore approaching the coast with a very high obliquity. Satellite images reveal that along that coast there are many shoreline sand waves with wavelengths ranging from 2 to 8 km. A more detailed study, including a Fourier analysis of the shoreline position, confirms a high spectral density concentration at these lengths scales. Also, it becomes apparent that at least some of the sand waves are dynamically active rather than being controlled by the geological setting. A morphodynamic model is used to test the hypothesis that these sand waves could emerge as free morphodynamic instabilities of the coastline due to the obliquity in wave incidence. It is found that the wave period, Tp, is crucial to establish the tendency to stability or instability, instability increasing for decreasing period, whilst there is some discrepancy in the observed periods. Model results for Tp = 7 s clearly show the tendency for the coast to develop free sand waves at 2 km wavelength within a few years, which migrate to the north at rates of 0.6-0.7 km/yr. For Tp = 8 s, instability is weaker and rather sensitive to other factors as the underlying bathymetry. In this case, the coast seems to be nearly at neutral stability so that sand waves originated from other mechanisms can propagate downdrift with little decay. http://hdl.handle.net/2117/16259 Title: Rehabilitación energética de edificios escolares en clima mediterráneo: caso de estudio, Barcelona Authors: Bosch González, Montserrat; Rodríguez Cantalapiedra, Inma; Álvarez del Castillo, Javier Abstract: necesidad de reducir el consumo energético se hace cada día más evidente, especialmente en Europa debido a su situación de dependencia energética de países externos a la Unión y también por razones relacionadas con el impacto ambiental y las emisiones asociadas. En este contexto, la rehabilitación energética de edificios es una línea de trabajo prioritaria que actúa sobre el parque edificado, y los edificios públicos deben ser un modelo o ejemplo para impulsar este tipo de actuaciones. Los centros docentes, con un potencial de ahorro muy importante y con unos consumos energéticos asociados básicamente a dos grandes conceptos, la iluminación y la climatización, pueden considerarse como un laboratorio de investigación en cuanto a eficiencia energética. A partir de las experiencias adquiridas durante más de 10 años se ha desarrollado una metodología de análisis para la intervención en edificios docentes en Barcelona con los siguientes objetivos: definir los indicadores estratégicos para identificar las oportunidades de ahorro, evaluar las posibles medidas de reducción de consumos a partir de la limitación de la demanda, analizar y dar contenido al papel de cada uno de los actores que intervienen en las estrategias de uso y gestión de los edificios escolares y establecer los criterios que deben considerarse para realizar las futuras intervenciones de rehabilitación energética. El método, como manera de pensar ordenadamente, ha de permitir optimizar los recursos y descubrir les rutas de trabajo que nos conduzcan al objetivo final: reducir el consumo energético del parque edificado http://hdl.handle.net/2117/19335 Title: Focalization of evanescent beams Authors: Botey Cumella, Muriel; Cheng, Yu Chieh; Herrero Simon, Ramon; Romero García, V.; Pico, R.; Sánchez Morcillo, V. J.; Staliunas, Kestutis Abstract: We predict and show the existence of unlocked evanescent waves in two dimensional periodic structures. In a one dimensional periodic structure an evanescent mode are located either at the center or at the boundary of the Brillouin Zone, and the real part of wave-vectors is locked either to zero or to the modulation vector of the periodicity. However, we report an unexpected observation that this is not the case in 2D or 3D PhCs where "unlocked" complex modes can be predicted. As an interesting consequence, due to their “complex” character, or, equivalently, due to their phase freedom, beams constructed from such evanescent waves can show focalization effects. Indeed, we numerically simulate the propagation of such beams in the bandgap of PhC slabs, and we find significant focalization. 2013-05-17T12:44:37Z http://hdl.handle.net/2117/19318 Title: Percolation experiments in complex fractal media Authors: Redondo Apraiz, José Manuel; Tarquis, Ana Maria; Cherubini, Claudia; Lopez Gonzalez-Nieto, Pilar; Vila, Teresa 2013-05-16T16:20:33Z http://hdl.handle.net/2117/19317 Title: SAR measurements of coastal features in the NW Mediterranean Authors: Redondo Apraiz, José Manuel; Martínez Benjamín, Juan José; Díez Rilova, Margarita; Lopez Gonzalez-Nieto, Pilar 2013-05-16T16:15:04Z http://hdl.handle.net/2117/19289 Title: White dwarf mergers and the origin of R coronae borealis stars Authors: Lorén Aguilar, Pablo; Longland, Richard Leigh; José Pont, Jordi; García-Berro Montilla, Enrique; Althaus, Leandro G.; Isern-Fontanet, J. Abstract: We present a nucleosynthesis study of the merger of a 0.4 M⊙ helium white dwarf with a 0.8 M⊙ carbon-oxygen white dwarf, coupling the thermodynamic history of Smoothed Particle Hydrodynamics particles with a post-processing code. The resulting chemical abundance pattern, particularly for oxygen and fluorine, is in qualitative agreement with the observed abundances in R Coronae Borealis stars. 2013-05-16T11:56:45Z http://hdl.handle.net/2117/19286 Title: Interaction of Supernovae remnants: From the circumstellar medium to the terrestrial laboratory Authors: Velarde, P; García Senz, Domingo; Bravo Guil, Eduardo; Ogando, F; Relaño, A; Oliva, E Abstract: The evolution of supernova remnants (SNRs) represents a useful and natural laboratory for gasdynamics studies. In this paper the results of several hydrodynamical simulations of the propagation and early phases of interaction of two SNRs embedded in a homogeneous interstellar environment are shown. In particular, the hydrodynamic evolution and collision of twin SNRs during their self-similar stage has been simulated using a two-dimensional Lagrangian hydrocode. In addition, the results of a detailed simulation that attempts to set the adequate conditions to reproduce the same phenomenon through laser ablation of two plastic plugs at the laboratory scale are presented. These results indicate that both large-scale and small-scale simulations display several common features that can be used to design an experiment aimed to validate the hydrodynamical codes. Of particular interest are the structures found around the juncture of the two colliding shells produced by the interaction of the remnants. 2013-05-16T10:41:34Z http://hdl.handle.net/2117/19284 Title: Production of intermediate-mass and heavy nuclei Authors: Thielemann, F. K.; Frölich, Carla; Hirschi, R.; Liebendörfer, M.; Dillmann, I.; Mocelj, D.; Rauscher, t.; Martínez Pinedo, Gabriel; Langanke, K; Farouqi, K; Kratz, K.L.; Pfeiffer, B.; Panov, I.; Nadyozhin, D.K.; Blinnikov, S.; Bravo Guil, Eduardo; Hix, W.R.; Höflich, P.; Zinner, Ernst 2013-05-16T10:33:12Z http://hdl.handle.net/2117/19257 Title: Spatial noise reduction in broad area semiconductors Authors: Herrero Simon, Ramon; Botey Cumella, Muriel; Pradeep Kumar, Nikhil; Staliunas, Kestutis 2013-05-15T14:13:50Z http://hdl.handle.net/2117/19253 Title: Dispersion management in spatially modulated broad band semiconductors Authors: Herrero Simon, Ramon; Botey Cumella, Muriel; Khumar, N.P.; Staliunas, Kestutis 2013-05-15T13:44:05Z http://hdl.handle.net/2117/19248 Title: Phase transitions with infinitely many absorbing states in complex networks Authors: Sander, Renan; Ferreira, Silvio C.; Pastor Satorras, Romualdo Abstract: We investigate the properties of the threshold contact process (TCP), a process showing an absorbing-state phase transition with infinitely many absorbing states, on random complex networks. The finite-size scaling exponents characterizing the transition are obtained in a heterogeneous mean-field (HMF) approximation and compared with extensive simulations, particularly in the case of heterogeneous scale-free networks. We observe that the TCP exhibits the same critical properties as the contact process, which undergoes an absorbing-state phase transition to a single absorbing state. The accordance among the critical exponents of different models and networks leads to conjecture that the critical behavior of the contact process in a HMF theory is a universal feature of absorbing-state phase transitions in complex networks, depending only on the locality of the interactions and independent of the number of absorbing states. The conditions for the applicability of the conjecture are discussed considering a parallel with the susceptible-infected-susceptible epidemic spreading model, which in fact belongs to a different universality class in complex networks. 2013-05-15T12:52:57Z http://hdl.handle.net/2117/19244 Title: Consequences of the Collision Between the Gas Ejected in the Collapse of a White Dwarf and a Low-Mass Star Authors: Serichol Augué, Núria; García Senz, Domingo; Bravo Guil, Eduardo 2013-05-15T11:07:44Z http://hdl.handle.net/2117/19243 Title: Recovery and treatment of spirulina platensis cells cultured in a continous photobioreactor to be used as food Authors: Morist, A; Montesinos, J L; Cusidó Fàbregas, Joan Antoni; Godia, F Abstract: he development of auto-regenerative biological life support systems for men in Space will be based on photosynthetic organisms, such as higher plants and algae, providing edible material. In this work, Spirulina platensis grown in a continuous photobioreactor was used to design a process for its recovery and further treatment to be used as food. Two different possibilities are studied (liquid or dry food). In each case, different steps are considered in the design of the process and further characterised: cell harvesting, washing, pasteurisation and spry-drying. Special emphasis is made on biomass quality, both in terms of potential microbial contamination and changes in its composition during the different steps of the process. Cell harvesting was conducted with a net recovery of solids and water higher than 95% with a solids concentration factor about 20–30. Biomass quality was shown as satisfactory in all the treatments tested. 2013-05-15T11:03:46Z http://hdl.handle.net/2117/19238 Title: Unified one-dimensional simulations of gamma-ray line emission from type Ia supernovae Authors: Milne, P A; Hungerford, A L; Fryer, C L; Evans, T M; Urbatsch, T J; Boggs, S E; Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Hirschmann, A; Kumagai, S; Pinto, P A; The, L S Abstract: The light curves of Type Ia supernovae (SNe Ia) are powered by gamma rays emitted by the decay of radioactive elements such as 56Ni and its decay products. These gamma rays are downscattered, absorbed, and eventually reprocessed into the optical emission that makes up the bulk of all SN observations. Detection of the gamma rays that escape the expanding star provide the only direct means to study this power source for SN Ia light curves. Unfortunately, disagreements between calculations for the gamma-ray lines have made it difficult to interpret any gamma-ray observations. Here we present a detailed comparison of the major gamma-ray line transport codes for a series of one-dimensional SN Ia models. Discrepancies in past results were due to errors in the codes, and the corrected versions of the seven different codes yield very similar results. This convergence of the simulation results allows us to infer more reliable information from the current set of gamma-ray observations of SNe Ia. The observations of SN 1986G, SN 1991T, and SN 1998bu are consistent with explosion models based on their classification: subluminous, superluminous, and normally luminous, respectively. 2013-05-15T10:29:56Z http://hdl.handle.net/2117/19233 Title: Bounds on the possible evolution of the gravitational constant from cosmological type-Ia supernovae Authors: Gaztañaga, E; García-Berro Montilla, Enrique; Isern Vilaboy, Jordi; Bravo Guil, Eduardo; Domínguez, I Abstract: Recent high-redshift type-Ia supernovae results can be used to set new bounds on a possible variation of the gravitational constant G. If the local value of G at the space-time location of distant supernovae is different, it would change both the kinetic energy release and the amount of 56Ni synthesized in the supernova outburst. Both effects are related to a change in the Chandrasekhar mass MCh∝G-3/2. In addition, the integrated variation of G with time would also affect the cosmic evolution and therefore the luminosity distance relation. We show that the later effect in the magnitudes of type-Ia supernovae is typically several times smaller than the change produced by the corresponding variation of the Chandrasekhar mass. We investigate in a consistent way how a varying G could modify the Hubble diagram of type-Ia supernovae and how these results can be used to set upper bounds to a hypothetical variation of G. We find G/G0≲1.1 and Ġ/G≲10-11yr-1 at redshifts z≃0.5. These new bounds extend the currently available constraints on the evolution of G all the way from solar and stellar distances to typical scales of Gpc/Gyr, i.e., by more than 15 orders of magnitude in time and distance. 2013-05-15T10:00:45Z