Two approaches for effective modelling of rain-rate time-series for radiocommunication system simulations

The paper presents a model which allows to synthetically generate rain rate time-series for a fixed location. Rain rate time-series are very much correlated with signal attenuation in Ka band and above and, thus, enable to realistically simulate propagation effects on Earth-satellite links. The model presented are based on Markov chains

Ionic behavior assessment of surface-active compounds from corn steep liquor by exchange resins

Depending on their ionic nature, biosurfactants can be classified as nonionic, anionic, cationic, or amphoteric. The ionic behavior of biosurfactants is an important characteristic that dictates their use in industrial applications. In this work, a biosurfactant extract obtained from corn steep liquor was subjected to anionic or cationic resins, in order to study the ionic behavior under different operational conditions using response surface methodology. The independent variables included in the study are the dilution of biosurfactant solution, the amount of cationic or anionic resin, and the extraction time, whereas the dependent variables studied consisted of the surface tension of biosurfactant aqueous solution, after contacting with anionic or cationic resin. The results showed that biosurfactant extracted from corn steep liquor is amphoteric, since both resins were able to entrap this biosurfactant, making it particularly suited for use in personal care preparations for sensitive skin.Peer ReviewedPostprint (author's final draft

Optimum sizing of launching nose of prestressed concrete bridges

El diseño del pico de lanzamiento de un puente lanzado determina su proceso constructivo y, por lo tanto, también sus dimensiones. La optimización del pico de lanzamiento puede plantearse como primer paso para la mejora del diseño de un puente lanzado. El procedimiento convencional de diseño del pico de lanzamiento se basa en emplear la técnica de prueba y error para reducir el momento flector sobre el apoyo frontal del tablero de hormigón pretensado durante el proceso de lanzamiento. Esta forma de trabajo en ningún caso garantiza alcanzar la mejor de entre todas las soluciones posibles, pues se basa en la experiencia e intuición del proyectista, además de limitarse necesariamente a escasos tanteos. Dado que los puentes lanzados constituyen una tipología constructiva importante, deben incorporar todas las capacidades disponibles de innovación del diseño, entre las que se encuentra la optimización matemática. Este trabajo propone una formulación objetiva y rigurosa para optimizar el pico de lanzamiento de un puente lanzado adaptada a los condicionantes reales que tienen en la práctica los proyectistas de puentes. Comparando los resultados obtenidos mediante procedimientos convencionales y con técnicas de optimización se puede comprobar el grado de validez de algunas afirmaciones, que se dan por supuestas en los métodos clásicos de diseño de picos de lanzamiento, pero que en realidad no se sustentan en fundamento teórico alguno, demostrándose la utilidad de la optimización matemática para la mejora del diseño.The design of the launching nose of an incrementally launched bridge determines its constructive process and, therefore, also its dimensions. The optimization of the launching nose can raise as a first step to improve the design of a launched bridge. The conventional design process of a launching nose is based on trial and error method to reduce bending moment of prestressed concrete deck at the foremost support during launch. In this way, there is no guarantee that the obtained solution is the best among all the possible solutions since they all depend on the experience and intuition of a designer, and they are also restricted by a limited number of possible iterations. Given that launched bridges constitute an important constructive typology, all the available capacities of design innovation should be incorporated, among which it can be found numerical optimization. This research work proposes an objective and rigorous formulation to optimize a launching nose of launched bridge under real constraints that a bridge designer can encounter in practice. Comparing the results obtained by conventional process and that by optimization techniques, it can be verified that some of the assumptions, considered in classical design methods of a launching nose, are not based on any theoretical foundation. This fact demonstrates the utility of numerical optimization to improve a design.Peer Reviewe

Combined beach - inner shelf erosion in short and medium term (Maspalomas, Canary Islands)

The analysis of the accurate topo-bathymetric digital elevation model (DEM), the cartography of the submarine sedimentary cover and the monitoring of short (seasonal) and medium-term (2000-2009) morphological changes have permitted depicting the erosional trend in the short and medium-term of the Maspalomas sedimentary system. Short-term analysis showed intense sedimentary fluxes between the beaches and the inner shelf, and sedimentary exchanges with other sectors of the inner shelf, while the steep slope inner shelf fronting La Bajeta cape was identified as a sink area. In the medium-term the sediment budget showed high erosion of the supratidal and intertidal sectors of the beaches due to storm waves in the 2005-2006 winter, followed by accretion over the next four years, but which did not reach the initial sedimentary state. The inner shelf and subtidal sector of the beaches showed negative budgets in the short and medium-term. Interannual variability of the wave and wind regimes determines decadal beach erosion-accretion cycles, while long-term climatic change, evidenced at the study area by a decrease of trade winds and NE wave intensity in 2005, is expected to produce a possible increase of erosion at the El Inglés inner shelf and consequently a decrease in sediment inputs to the El Inglés beach and Maspalomas dune field. Finally, the influence of the geological heritage is depicted by the Fataga gully’s control of the present coastal morphology, and by the island relief control of the wind, waves and current directions in the study area