A family of well-balanced WENO and TENO schemes for atmospheric flows

We herein present a novel methodology to construct very high order well-balanced schemes for the computation of the Euler equations with gravitational source term, with application to numerical weather prediction (NWP). The proposed method is based on augmented Riemann solvers, which allow preserving the exact equilibrium between fluxes and source terms at cell interfaces. In particular, the augmented HLL solver (HLLS) is considered. Different spatial reconstruction methods can be used to ensure a high order of accuracy in space (e.g. WENO, TENO, linear reconstruction), being the TENO reconstruction the preferred method in this work. To the knowledge of the authors, the TENO method has not been applied to NWP before, although it has been extensively used by the computational fluid dynamics community in recent years. Therefore, we offer a thorough assessment of the TENO method to evidence its suitability for NWP considering some benchmark cases which involve inertia and gravity waves as well as convective processes. The TENO method offers an enhanced behavior when dealing with turbulent flows and underresolved solutions, where the traditional WENO scheme proves to be more diffusive. The proposed methodology, based on the HLLS solver in combination with a very high-order discretization, allows carrying out the simulation of meso- and micro-scale atmospheric flows in an implicit Large Eddy Simulation manner. Due to the HLLS solver, the isothermal, adiabatic and constant Brunt-Väisälä frequency hydrostatic equilibrium states are preserved with machine accuracy

Evaluación de cementos obtenidos por activación alcalina de ceniza de carbón con NaOH curados a bajas temperaturas

The temperature at which the alkaline activation process takes place is a significant factor in the evolution of the mechanical properties of coal ash cementitious base material. In this work, the influence of temperature (8 a 38 °C) and curing time (3 and 28 days) on the mechanical properties of the alkaline synthesis of two coal ashes was evaluated through the study of the mineralogical evolution of the cementitious phases by XRD and FTIR. We found that the type of zeolite, a synthesis product, depends on the study factors. For values above 28 °C and at least 7 days, alkalinely activated cements with compressive strength above 20 MPa were achieved. Other parameters, such as SiO2/Al2O3 ratio, percentage of unburned coal and particle-size distribution, should be taken into account in the variation of mechanical performance.La temperatura a la cual se desarrolla el proceso de activación alcalina es un factor significativo en la evolución de las propiedades mecánicas de material cementante base ceniza de carbón. En este trabajo se evaluó, a través del estudio de la evolución mineralógica de las fases cementantes por DRX y FTIR, la influencia de la temperatura (8 a 38 °C) y tiempo (3 y 28 días) de curado sobre las propiedades mecánicas de la síntesis alcalina de dos cenizas de carbón. Se encontró que el tipo de zeolita, producto de la síntesis, depende de los factores de estudio. Para valores superiores a 28 °C y mínimo 7 días, se lograron cementos activados alcalinamente con resistencias superiores a 20 MPa. Otros parámetros, como la relación SiO2/Al2O3, el porcentaje de carbón inquemado y la distribución del tamaño de partícula, se deben de tener en cuenta en la variación del desempeño mecánico

Synthesis and structural characterization of homochiral 2D coordination polymers of zinc and copper with conformationally flexible ditopic imidazolium-based dicarboxylate ligands

Different novel coordination polymers containing zinc, 1–4, and copper, 5–8, metals, connected via chiral imidazolium-based dicarboxylate ligands, [LR]−, were isolated by reaction between zinc acetate or copper acetate and enantiomerically pure HLR compounds. They were characterised and structurally identified by X-ray diffraction methods (single crystal and powder). These compounds are twodimensional homochiral coordination polymers, [M(LR)2]n, in which the metal ions are coordinated by the two carboxylate groups of [LR]− anions in a general bridging monodentate μ2–κ1-O1,κ1-O3 fashion that afforded tetrahedral metal coordination environments for zinc, 1–4, and square planar for copper, 5–8, complexes. In all the compounds the 3D supramolecular architecture is constructed by non-covalent interactions between the hydrophobic parts (R groups) of the homochiral 2D coordination polymers and, in some cases, by weak C–H⋯O non-classical hydrogen bonds that provided, in general, a dense crystal packing. DFT calculations on the [LR]− anions confirmed their conformational flexibility as ditopic linkers and this fact makes possible the formation of different coordination polymers for four-coordinated metal centers. Preliminary studies on the Zn-catalyzed synthesis of chiral α-aminophosphonates were carried out and, unfortunately, no enantioselectivity was observed in these reactions.Proyecto de la Junta de Andalucía FQM-707

Optimization of time data codification and transmission schemes: Application to Gaia

Gaia is an ambitious space observatory devoted to obtain the largest and most precise astrometric catalogue of astronomical objects from our Galaxy and beyond. On-board processing and transmission of the huge amount of data generated by the instruments is one of its several technological challenges. The measurement time tags are critical for the scientific results of the mission, so they must be measured and transmitted with the highest precision - leading to an important telemetry channel occupation. In this paper we present the optimisation of time data, which has resulted in a useful software tool. We also present how time data is adapted to the Packet Telemetry standard. The several communication layers are illustrated and a method for coding and transmitting the relevant data is described as well. Although our work is focused on Gaia, the timing scheme and the corresponding tools can be applied to any other instrument or mission with similar operational principles

Interpolation of the magnetic field at the test masses in eLISA

A feasible design for a magnetic diagnostics subsystem for eLISA will be based on that of its precursor mission, LISA Pathfinder. Previous experience indicates that magnetic field estimation at the positions of the test masses has certain complications. This is due to two reasons. The first is that magnetometers usually back-act due to their measurement principles (i.e., they also create their own magnetic fields), while the second is that the sensors selected for LISA Pathfinder have a large size, which conflicts with space resolution and with the possibility of having a sufficient number of them to properly map the magnetic field around the test masses. However, high-sensitivity and small-sized sensors that significantly mitigate the two aforementioned limitations exist, and have been proposed to overcome these problems. Thus, these sensors will be likely selected for the magnetic diagnostics subsystem of eLISA. Here we perform a quantitative analysis of the new magnetic subsystem, as it is currently conceived, and assess the feasibility of selecting these sensors in the final configuration of the magnetic diagnostic subsystem.Peer ReviewedPostprint (author's final draft

2D experiments and numerical simulation of the oscillatory shallow flow in an open channel lateral cavity

Steady shallow flows past an open channel lateral cavity can induce the excitation of an eigenmode of a gravity standing wave inside the cavity, called seiche, which may be coupled with the shedding of vortices at the opening of the cavity. The presence of the seiche is of fundamental interest as it enhances the mass exchange between the main channel and the cavity. Measurements of the time evolution of the water surface are not often found in the literature for this type of flows. In this work, an experimental and numerical study of a shallow flow past a channel lateral cavity is carried out. The main novelty is the use of a pioneering non-intrusive experimental technique to measure the water surface at the channel-cavity region. This optical technique offers high resolution 2D data in time and space of the water surface evolution, allowing to determine the relevant features of the seiche oscillation. Such data are supplemented with Particle Image Velocimetry measurements. Furthermore, the experiments are numerically reproduced using a high-resolution depth-averaged URANS shallow water model, under the assumption that shallow water turbulence is mainly horizontal. The experimental and numerical results are analyzed in the frequency domain. High-resolution two-dimensional amplitude oscillation maps of the seiche phenomenon, as well as velocity fields, are presented. The high quality of the experimental data reported in this work makes this data set a suitable benchmark for numerical simulation models in order to evaluate their performance in the resolution of turbulent resonant shallow flows

FIRI - a Far-Infrared Interferometer

Half of the energy ever emitted by stars and accreting objects comes to us in the FIR waveband and has yet to be properly explored. We propose a powerful Far-InfraRed Interferometer mission, FIRI, to carry out high-resolution imaging spectroscopy in the FIR. This key observational capability is essential to reveal how gas and dust evolve into stars and planets, how the first luminous objects in the Universe ignited, how galaxies formed, and when super-massive black holes grew. FIRI will disentangle the cosmic histories of star formation and accretion onto black holes and will trace the assembly and evolution of quiescent galaxies like our Milky Way. Perhaps most importantly, FIRI will observe all stages of planetary system formation and recognise Earth-like planets that may harbour life, via its ability to image the dust structures in planetary systems. It will thus address directly questions fundamental to our understanding of how the Universe has developed and evolved - the very questions posed by ESA's Cosmic Vision.Comment: Proposal developed by a large team of astronomers from Europe, USA and Canada and submitted to the European Space Agency as part of "Cosmic Vision 2015-2025

Valores antropométricos en niños con celiaquía diagnosticados precozmente

Peer Reviewe