Résolution de Conflits Aériens par Méthodes Exactes et Approchées

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A new framework for solving en-routes conflicts

International audienceThe en-route conflict resolution problem has been modelled in many different ways, generally depending on the tools that were proposed to solve it. For instance, with purely analytic mathematical solvers, models tend to be very restrictive (constant speeds, linear trajectories\dots) to respect the inherent limitations of the technology. This paper introduces a new framework that separates the model from the solver so as to be able to: first, enhance the model with as many refinements (e.g. wind and trajectory uncertainties) as necessary to comply with operational constraints; second, compare different resolution methods on the same data, which is one of the crucial aspects of scientific research. To this aim, our framework can generate a benchmark of conflict resolution problems built with various scenarios involving a given number of aircraft, level of uncertainties and number of manoeuvres. We then compare two different optimization paradigms, Evolutionary Algorithm and Constraint Programming, which can efficiently solve difficult instances in near real time, to illustrate the usefulness of our approach

Assessing the Robustness of a UAS Detect & Avoid Algorithm

International audienceIn this article, we evaluate the robustness of a detect and avoid algorithm designed for the integration of UASs in terminal control areas. This assessment relies on a realistic modeling of navigation accuracy on positions and velocities and was carried out on thousands of scenarios built from recorded commercial traffic trajectories. The tested scenarios involved two different types of UASs – flying at 80 kts and 160 kts – with various missions, and three strategies for separation: one focussing on the separation distance, one focussing on the UAS mission and and combination of both. Fast-time simulation was used to evaluate each scenario against a wide range of accuracy levels corresponding to required navigation precision standards and linked to on-board navigation and communication systems. Experiments reveal a strong robustness of the separation algorithm up to relatively high uncertainty levels, indicating that UASs equipped with low accuracy navigation systems can still manage proper separation. However, the maneuvering cost for separation increases when the accuracy deteriorates. Nevertheless, a UAS with GPS-based navigation in a collaborative environment (e.g. aircraft providing their navigation parameters through ADS-B) can expect robustness at a reasonable cost

Departure Management with Robust Gate Allocation

International audienceThe Airport Collaborative Decision Making (A-CDM) concept yields concrete and promising solutions for airports, in terms of traffic punctuality and predictability, with possible delay, noise and pollution reduction. A key feature of A-CDM is the Departure Management (DMAN): runway takeoff sequences can be anticipated such that a significant part of the delay can be shifted at the gate, engines off, without penalizing the remaining traffic. During this process, an increase in the gate occupancy for delayed departures is unavoidable, therefore the airport layout must provide enough gates and their allocation must be robust enough w.r.t. departures delay. In this paper, we introduce a method to estimate the gate delays due to the DMAN pre-departure scheduling, then we propose a robust gate allocation algorithm and assess its performance with current and increased traffic at Paris-Charles-de-Gaulle international airport. Results show a significant reduction in the number of gate conflicts, when comparing such a robust gate allocation to current practice

Sea ice inertial oscillations in the Arctic Basin

International audienceAn original method to quantify the amplitude of inertial motion of oceanic and ice drifters, through the introduction of a non-dimensional parameter M defined from a spectral analysis, is presented. A strong seasonal dependence of the magnitude of sea ice inertial oscillations is revealed, in agreement with the corresponding annual cycles of sea ice extent, concentration, thickness, advection velocity, and deformation rates. The spatial pattern of the magnitude of the sea ice inertial oscillations over the Arctic Basin is also in agreement with the sea ice thickness and concentration patterns. This argues for a strong interaction between the magnitude of inertial motion on one hand, the dissipation of energy through mechanical processes, and the cohesiveness of the cover on the other hand. Finally, a significant multi-annual evolution towards greater magnitudes of inertial oscillations in recent years, in both summer and winter, is reported, thus concomitant with reduced sea ice thickness, concentration and spatial extent

Análisis multiparamétrico y validación de tres simulaciones globales en el Mediterráneo occidental

We analyse a hierarchy of three 1/4° global numerical simulations (ORCA-025.G70 (G70), ORCA-025.G85 (G85) and GLORYS1V1 (GLORYS)) by assessing their performance against observational data in the western Mediterranean. When compared with the EN3_v2a temperature and salinity database, the simulations are capable of reproducing surface layer temperature interannual variability but G70 is inaccurate with intermediate and deep-layer trends. This aspect is improved by the increased vertical resolution of G85 and by data assimilation in GLORYS. Salinity is the most problematic parameter because of the imbalance of the freshwater budget derived from inaccuracies in the atmospheric forcing parameters. Surface salinity restoring is needed in order to avoid salinity drift and inaccurate sea-level trends. G70, with a stronger relaxation, has a lower trend closer to altimetric measurements than G85. Mean surface circulation is well reproduced for relatively large-scale signals. We further show that G85 and GLORYS provide evidence of the 2004-2005 and 2005-2006 deep convection events in the Gulf of Lion. Finally, transports through the main straits of the western Mediterranean are correct in order of magnitude, direction and seasonal cycle when compared with observations. This study contributes to the improvement of the ORCA hierarchy of simulations and points out the strengths and weaknesses of these simulations in the Mediterranean Sea.Analizamos un conjunto de tres simulaciones numéricas globales de 1/4º (ORCA-025.G70 (G70), ORCA-025.G85 (G85) y GLORYS1V1 (GLORYS)) comparándolas con datos observacionales en el Mediterráneo Occidental (WMED). Contrastando con la base de datos de temperatura y salinidad EN3_v2a las simulaciones son capaces de reproducir la variabilidad superficial en temperatura sin embargo G70 exagera las tendencias en capas intermedias y profundas. Este aspecto es mejorado por la mayor resolución vertical de G85 y la asimilación de datos de GLORYS. La salinidad es el parámetro más problemático debido al desequilibrio del balance de agua dulce procedente de imprecisiones en los parámetros de forzamiento atmosférico. Relajación de salinidad superficial es necesaria para evitar derivas de salinidad y nivel del mar. De hecho G70 con su relajación más intensa tiene una tendencia más baja (y más cercana a mediciones altimétricas) que G85. La circulación promedio en superficie está bien reproducida para señales relativamente grandes. Además, demostramos que G85 y GLORYS muestran evidencia de los eventos de convección profunda de 2004-2005 y 2005-2006 en el Golfo de León. Finalmente, transportes a través de los principales canales y estrechos del Mediterráneo Occidental son correctos cuando se comparan con observaciones, tanto en orden de magnitud y dirección, como en el ciclo estacional. Este estudio contribuye a la mejora del conjunto de simulaciones ORCA y señala las fortalezas y debilidades de estas simulaciones en el Mar Mediterráneo

Efficacy of three innovative bacterin vaccines against experimental infection with Mycoplasma hyopneumoniae

International audienceAbstractNew vaccine formulations that include novel strains of Mycoplasma hyopneumoniae and innovative adjuvants designed to induce cellular immunity could improve vaccine efficacy against this pathogen. The aim of this experimental study was to assess the efficacy of three experimental bacterin formulations based on M. hyopneumoniae field strain F7.2C which were able to induce cellular immunity. The formulations included a cationic liposome formulation with the Mincle receptor ligand trehalose 6,6-dibehenate (Lipo_DDA:TDB), a squalene-in-water emulsion with Toll-like receptor (TLR) ligands targeting TLR1/2, TLR7/8 and TLR9 (SWE_TLR), and a poly(lactic-co-glycolic acid) micro-particle formulation with the same TLR ligands (PLGA_TLR). Four groups of 12 M. hyopneumoniae-free piglets were primo- (day (D) 0; 39 days of age) and booster vaccinated (D14) intramuscularly with either one of the three experimental bacterin formulations or PBS. The pigs were endotracheally inoculated with a highly and low virulent M. hyopneumoniae strain on D28 and D29, respectively, and euthanized on D56. The main efficacy parameters were: respiratory disease score (RDS; daily), macroscopic lung lesion score (D56) and log copies M. hyopneumoniae DNA determined with qPCR on bronchoalveolar lavage (BAL) fluid (D42, D56). All formulations were able to reduce clinical symptoms, lung lesions and the M. hyopneumoniae DNA load in the lung, with formulation SWE_TLR being the most effective (RDSD28–D56 −61.90%, macroscopic lung lesions −88.38%, M. hyopneumoniae DNA load in BAL fluid (D42) −67.28%). Further experiments raised under field conditions are needed to confirm these results and to assess the effect of the vaccines on performance parameters

Down selecting adjuvanted vaccine formulations: a comparative method for harmonized evaluation.

The need for rapid and accurate comparison of panels of adjuvanted vaccine formulations and subsequent rational down selection, presents several challenges for modern vaccine development. Here we describe a method which may enable vaccine and adjuvant developers to compare antigen/adjuvant combinations in a harmonized fashion. Three reference antigens: Plasmodium falciparum apical membrane antigen 1 (AMA1), hepatitis B virus surface antigen (HBsAg), and Mycobacterium tuberculosis antigen 85A (Ag85A), were selected as model antigens and were each formulated with three adjuvants: aluminium oxyhydroxide, squalene-in-water emulsion, and a liposome formulation mixed with the purified saponin fraction QS21. The nine antigen/adjuvant formulations were assessed for stability and immunogenicity in mice in order to provide benchmarks against which other formulations could be compared, in order to assist subsequent down selection of adjuvanted vaccines. Furthermore, mouse cellular immune responses were analyzed by measuring IFN-γ and IL-5 production in splenocytes by ELISPOT, and humoral responses were determined by antigen-specific ELISA, where levels of total IgG, IgG1, IgG2b and IgG2c in serum samples were determined. The reference antigens and adjuvants described in this study, which span a spectrum of immune responses, are of potential use as tools to act as points of reference in vaccine development studies. The harmonized methodology described herein may be used as a tool for adjuvant/antigen comparison studies

Systems Immunology Characterization of Novel Vaccine Formulations for Mycoplasma hyopneumoniae Bacterins

We characterized five different vaccine candidates and a commercial vaccine in terms of safety, immunogenicity and using a systems vaccinology approach, with the aim to select novel vaccine candidates against Mycoplasma hyopneumoniae. Seven groups of six M. hyopneumoniae-free piglets were primo- and booster vaccinated with the different experimental bacterin formulations, the commercial vaccine Hyogen® as a positive control or PBS as a negative control. The experimental bacterin was formulated with cationic liposomes + c-di-AMP (Lipo_AMP), cationic liposomes + Toll-like receptor (TLR) 2/1, TLR7, and TLR9 ligands (TLR ligands; Lipo_TLR), micro-particles + TLR ligands (PLGA_TLR), squalene-in-water emulsion + TLR ligands (SWE_TLR), or DDA:TDB liposomes (Lipo_DDA:TDB). Lipo_DDA:TDB and Lipo_AMP were the most potent in terms of serum antibody induction, and Lipo_DDA:TDB, Lipo_AMP, and SWE_TLR significantly induced Th1 cytokine-secreting T-cells. Only PLGA_TLR appeared to induce Th17 cells, but was unable to induce serum antibodies. The transcriptomic analyses demonstrated that the induction of inflammatory and myeloid cell blood transcriptional modules (BTM) in the first 24 h after vaccination correlated well with serum antibodies, while negative correlations with the same modules were found 7 days post-vaccination. Furthermore, many cell cycle and T-cell BTM upregulated at day seven correlated positively with adaptive immune responses. When comparing the delivery of the identical TLR ligands with the three formulations, we found SWE_TLR to be more potent in the induction of an early innate immune response, while the liposomal formulation more strongly promoted late cell cycle and T-cell BTM. For the PLGA formulation we found signs of a delayed and weak perturbation of these BTM. Lipo_AMP was found to be the most potent vaccine at inducing a BTM profile similar to that correlating with adaptive immune response in this and other studies. Taken together, we identified four promising vaccine candidates able to induce M. hyopneumoniae-specific antibody and T-cell responses. In addition, we have adapted a systems vaccinology approach developed for human to pigs and demonstrated its capacity in identifying early immune signatures in the blood relating to adaptive immune responses. This approach represents an important step in a more rational design of efficacious vaccines for pigs

An assessment of air-sea heat fluxes from ocean and coupled reanalyses

Sixteen monthly air–sea heat flux products from global ocean/coupled reanalyses are compared over 1993–2009 as part of the Ocean Reanalysis Intercomparison Project (ORA-IP). Objectives include assessing the global heat closure, the consistency of temporal variability, comparison with other flux products, and documenting errors against in situ flux measurements at a number of OceanSITES moorings. The ensemble of 16 ORA-IP flux estimates has a global positive bias over 1993–2009 of 4.2 ± 1.1 W m−2. Residual heat gain (i.e., surface flux + assimilation increments) is reduced to a small positive imbalance (typically, +1–2 W m−2). This compensation between surface fluxes and assimilation increments is concentrated in the upper 100 m. Implied steady meridional heat transports also improve by including assimilation sources, except near the equator. The ensemble spread in surface heat fluxes is dominated by turbulent fluxes (>40 W m−2 over the western boundary currents). The mean seasonal cycle is highly consistent, with variability between products mostly <10 W m−2. The interannual variability has consistent signal-to-noise ratio (~2) throughout the equatorial Pacific, reflecting ENSO variability. Comparisons at tropical buoy sites (10°S–15°N) over 2007–2009 showed too little ocean heat gain (i.e., flux into the ocean) in ORA-IP (up to 1/3 smaller than buoy measurements) primarily due to latent heat flux errors in ORA-IP. Comparisons with the Stratus buoy (20°S, 85°W) over a longer period, 2001–2009, also show the ORA-IP ensemble has 16 W m−2 smaller net heat gain, nearly all of which is due to too much latent cooling caused by differences in surface winds imposed in ORA-IP