Processing and integrity of DC/DF GBAS for CAT II/III operations

In Civil Aviation domain, to cope with the increasing traffic demand, research activities are pointed toward the optimization of the airspace capacity. Researches are thus ongoing on all Civil Aviation areas: Communication, Navigation, Surveillance (CNS) and Air Traffic Management (ATM). Focusing on the navigation aspect, the goals are expected to be met by improving performances of the existing services through the developments of new NAVigation AIDS (NAVAIDS) and the definition of new procedures based on these new systems. The Global Navigation Satellite System (GNSS) is recognized as a key technology in providing accurate navigation services with a worldwide coverage. The GNSS concept was defined by the International Civil Aviation Organization (ICAO). A symbol of its importance, in civil aviation, can be observed in the avionics of new civil aviation aircraft since a majority of them are now equipped with GNSS receivers. The GNSS concept includes the provision of an integrity monitoring function by an augmentation system in addition to the core constellations. This is needed to meet all the required performance metrics of accuracy, integrity, continuity and availability which cannot be met by the stand-alone constellations such as GPS. Three augmentation systems have been developed within civil aviation: the GBAS (Ground Based Augmentation System), the SBAS (Satellite Based Augmentation System) and the ABAS (Aircraft Based Augmentation System). GBAS, in particular, is currently standardized to provide precision approach navigation services down to Category I (CAT I) using GPS or Glonass constellations and L1 band signals. This service is known as GBAS Approach Service Type-C (GAST-C). In order to extend this concept down to CAT II/III service, research activities is ongoing to define the new service called a GAST-D. Among other challenges, the monitoring of the ionospheric threat is the area where the integrity requirement is not met. Thanks to the deployment of new constellations, Galileo and Beidou, and the modernization process of the existing ones, GPS and Glonass, the future of GNSS is envisaged to be Multi-Constellation (MC) and Multi-frequency (MF). In Europe, research activities have been focused on a Dual-Constellation (DC) GNSS and DC GBAS services based on GPS and Galileo constellations. Moreover, to overcome the problems experienced by Single-Frequency (SF) GBAS due to ionosphere anomalies, the use of two frequencies (Dual Frequency, DF) has been selected as a mean to improve ionosphere anomalies detection and to mitigate ionosphere residual errors. Advantages in using a DC/DF GBAS (GAST-F) system are, however, not only related to the integrity monitoring performance improvement. Benefits, brought by DC and DF, are also related to •the robustness of the entire system against unintentional interference thanks to the use of measurements in two protected frequency bands, •the robustness against a constellation failure, •the accuracy improvement by using new signals with improved performance, and more satellites. However, the use of new signals and a new constellation, does not bring only benefits. It also raises a series of challenges that have to be solved to fully benefit from the new concept. In this thesis, some challenges, related to DC/DF GBAS, have been investigated. One of them, rising from the use of new GNSS signals, is to determine the impact of error sources that are uncorrelated between the ground station and the aircraft and that induce an error on the estimated position. Using two frequencies, there is the possibility to form measurement combinations like Divergence-free (D-free) and Ionosphere-free (I-free) for which the errors impact has to be analyzed. In this thesis, the impact of the uncorrelated errors (noise and multipath as main sources) on ground measurements is analyzed. The aim is to compare the derived performances with the curve proposed in (RTCA,Inc DO-253C, 2008) for th

catena-Poly[bis­(4-amino­pyridinium) [[tetra­aqua­nickel(II)]-μ-benzene-1,2,4,5-tetra­carboxyl­ato] dihydrate]

The asymmetric unit of the title compound, {(C5H7N2)2[Ni(C10H2O8)(H2O)4]·2H2O}n, contains an NiII atom, two water mol­ecules of coordination, one half of a benzene-1,2,4,5-tetra­carboxyl­ate (btec) anionic ligand, one 4-amino­pyridinium cation (papy) and an uncoordinated water mol­ecule. The metal center lies on an inversion center and adopts an octa­hedral geometry with the carboxyl­ate groups tilted out of the mean plane formed by the btec. In the crystal, mol­ecules are linked into one-dimensional coordination polymers running along the ac diagonal. The crystal structure is consolidated by N—H⋯O and O—H⋯O hydrogen bonds

Numerical Analysis for Reduced-scale Road Tunnel Model Equipped with Axial Jet Fan Ventilation System☆

Abstract In this paper a preliminary tridimensional CFD analysis is carried out for a future realization of a reduced-scale road tunnel experimental apparatus of 1/50 equipped with different impulsive fans, traditional and alternative. The alternative jet fan is provided of inlet/outlet sections inclined at a fixed pitch angle (α=6°) toward the tunnel floor. Typically, in the experimental scale tunnel model the air flow induced by ventilation system is provided by an external fan and fully developed flow field is considered. In this paper, the authors have simulated a realistic full and reduced-scale tunnel in order to evaluate the influence of ceiling and floor roughness height on the velocity field to identify an appropriate material for a future experimental apparatus. The jet fans are simulated as a simple momentum source. The fan is considered to be infinitely thin and the discontinuous pressure rise (pressure drop) across it is defined as a function of the air velocity through the fan. In order to create a reduced-scale model from a full scale, Froude method is applied to preserve geometrical, kinematical and dynamical similitude. The results, provided in terms of axial velocity profiles in different tunnel sections, show the overlapping between velocity profiles of full scale numerical model with those of the reduced-scale model, for the both ventilation systems

Computational analysis of cooling dynamics in photonic-crystal-based thermal switches

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Triorganotin(IV) derivatives of 7-amino-2-(methylthio)[1,2,4]triazolo [1,5-a]pyrimidine-6-carboxylic acid. Synthesis, spectroscopic characterization, in vitro antimicrobial activity and X-ray crystallography

Triorganotin(IV) complexes of the 7-amino-2-(methylthio)[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylic acid (HL), Me3SnL(H2O), (1), [n-Bu3SnL]2(H2O), (2), Ph3SnL(MeOH), (3), were synthesized by reacting the amino acid with organotin(IV) hydroxides or oxides in refluxing methanol. The complexes have been characterized by elemental analysis, 1H, 13C and 119Sn NMR, IR, Raman and 119Sn Mössbauer spectroscopic techniques. Single crystal X-ray diffraction data were obtained for compounds (2) and (3). Ph3SnL(MeOH) presents a trigonal bipyramidal structure with the organic groups on the equatorial plane and the axial positions occupied by a ligand molecule, coordinated to tin through the carboxylate, and a solvent molecule, MeOH. A similar structure is proposed for Me3SnL(H2O) on the basis of analytical and spectroscopic data. The tributyltin(IV) derivative, [n-Bu3SnL]2(H2O), is characterized by two different tin sites with similar tbp geometry featured by butyl groups on the equatorial plane. Sn(1) and Sn(2) atoms are axially bridged by a ligand molecule binding through the N(4) and the carboxylate group; the two coordination spheres are saturated by another ligand molecule, binding the metal through the carboxylate group, and a water molecule, respectively. Antimicrobial tests on compounds 1 and 2 showed in vitro activity against Gram-positive bacteria

catena-Poly[[[μ-aqua-penta­aqua­dizinc(II)]-μ4-benzene-1,2,4,5-tetra­carboxyl­ato] dihydrate]

The asymmetric unit of the title compound, {[Zn2(C10H2O8)(H2O)6]·2H2O}n, contains two distinct Zn atoms joined by a bridging water molecule and two bridging carboxyl­ate groups belonging to distinct halves of benzene-1,2,4,5-tetra­carboxyl­ate (tbec) tetra­anionic ligands, both lying on crystallographic inversion centres. The structure of this new isopolymorphic one-dimensional coordination polymer features asymmetric bimetallic octa­hedral knots. O—H⋯O hydrogen bonds between water molecules and carboxylate O atoms help to consolidate the crystal packing