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Choice of measure source terms in interface coupling for a model problem in gas dynamics.
No full textInternational audienceThis paper is devoted to the mathematical and numerical analysis of a coupling procedure for one-dimensional Euler systems. The two systems have different closure laws and are coupled through a thin fixed interface. Following the work of [5], we propose to couple these systems by a bounded vector-valued Dirac measure, concentrated at the coupling interface, which in the applications may have a physical meaning. We show that the proposed framework allows to control the coupling conditions and we propose an approximate Riemann solver based on a relaxation approach preserving equilibrium solutions of the coupled problem. Numerical experiments in constrained optimization problems are then presented to assess the performances of the present method. 1. Introduction The study of large-scale and complex problems exhibiting a wide range of physical space and time scales (see for instance [62, 35, 14]), usually requires separate solvers adapted to the resolution of specific scales. This is the case of many industrial flows. Let us quote, for example, the numerical simulation of two-phase flows applied to the burning liquid oxygen-hydrogen gas in rocket engines [58]. This kind of flow contains both separated and dispersed two-phase flows, due to atomization and evaporation phenomena. This requires appropriate models and solvers for separated and dispersed phases that have to be appropriately coupled. Another example concerns turbomachine flows which can be modeled by the Euler equations of gas dynamics with different closure laws between the stages of the turbine, where the conditions of temperature and pressure are strongly heterogeneous. The coupling of these different systems is thus necessary to give a complete description of the flow inside the whole turbine. The method of interface coupling allows to represent the evolution of such flows, where different models are separated by fixed interfaces. First, coupling conditions are specified at the interface to exchange information between the systems. The definition of transmission conditions generally results from physical consideration, e.g. the conservation or the continuity of given variables. Then, the transmission conditions are represented at the discrete level. The study of interface coupling for nonlinear hyperbolic systems has received attention for several years. In [43], the authors study the scalar case from both mathematical and numerical points of view
A simple explicit bijection between (n, 2) Gog and Magog trapezoids
No full textInternational audienceA sub-problem of the open problem of finding an explicit bijection between alternating sign matrices and totally symmetric self-complementary plane partitions consists in finding an explicit bijection between so-called (n, k) Gog trapezoids and (n, k) Magog trapezoids. A quite involved bijection was found by Biane and Cheballah in the case k = 2. We give here a simpler bijection for this case
Measurement of muon anti-neutrino oscillations with an accelerator-produced off-axis beam
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Search for narrow resonances decaying to dijets in proton-proton collisions at sqrt(s) = 13 TeV
No full textSubmitted to Phys. Rev. Lett ; see paper for full list of authorsInternational audienceA search for narrow resonances in proton-proton collisions at sqrt(s) = 13 TeV is presented. The invariant mass distribution of the two leading jets is measured with the CMS detector using a data set corresponding to an integrated luminosity of 2.4 inverse femtobarns. The highest observed dijet mass is 6.1 TeV. The distribution is smooth and no evidence for resonant particles is observed. Upper limits at 95 % confidence level are set on the production cross section for narrow resonances with masses above 1.5 TeV. When interpreted in the context of specific models, the limits exclude string resonances with masses below 7.0 TeV, scalar diquarks below 6.0 TeV, axigluons and colorons below 5.1 TeV, excited quarks below 5.0 TeV, color-octet scalars below 3.1 TeV, and W' bosons below 2.6 TeV. These results significantly extend previously published limits
Measurement of t-tbar production with additional jet activity, including b quark jets, in the dilepton channel using pp collisions at sqrt(s) = 8TeV
No full textSubmitted to Eur. Phys. J. C, see paper for full list of authorsInternational audienceJet multiplicity distributions in top quark pair (t-tbar) events are measured in pp collisions at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC using a data set corresponding to an integrated luminosity of 19.7 inverse-femtobarns. The measurement is performed in the dilepton decay channels (e+ e-, mu+ mu-, and e+/- mu-/+). The absolute and normalized differential cross sections for t-tbar production are measured as a function of the jet multiplicity in the event for different jet transverse momentum thresholds and the kinematic properties of the leading additional jets. The differential t-tbar-b and t-tbar-b-bbar cross sections are presented for the first time as a function of the kinematic properties of the leading additional b jets. Furthermore, the fraction of events without additional jets above a threshold is measured as a function of the transverse momenta of the leading additional jets and the scalar sum of the transverse momenta of all additional jets. The data are compared and found to be consistent with predictions from several perturbative quantum chromodynamics event generators and a next-to-leading order calculation
Triangulating stable laminations
No full textInternational audienceWe study the asymptotic behavior of random simply generated noncrossing planar trees in the space of compact subsets of the unit disk, equipped with the Hausdorff distance. Their distributional limits are obtained by triangulating at random the faces of stable laminations, which are random compact subsets of the unit disk made of non-intersecting chords coded by stable Lévy processes. We also study other ways to ``fill-in'' the faces of stable laminations, which leads us to introduce the iteration of laminations and of trees
Search for single production of scalar leptoquarks in proton-proton collisions at sqrt(s) = 8 TeV
No full textSubmitted to Phys. Rev. D ; see paper for full list of authorsInternational audienceA search is presented for the production of both first- and second- generation scalar leptoquarks with a final state of either two electrons and one jet or two muons and one jet. A data sample of proton-proton collisions at center-of-mass energy sqrt(s) = 8 TeV recorded with the CMS detector corresponds to an integrated luminosity of 19.6 inverse-femtobarns. Upper limits are set on both the first- and second- generation leptoquark production cross sections as functions of the leptoquark mass and the leptoquark couplings to a lepton and a quark. Results are compared with theoretical predictions to obtain lower limits on the leptoquark mass. At 95\% confidence level, single production of first-generation leptoquarks with a coupling and branching fraction of 1.0 is excluded for masses below 1730 GeV, and second-generation leptoquarks with a coupling and branching fraction of 1.0 is excluded for masses below 530 GeV. These are the best overall limits on the production of first-generation leptoquarks to date
NectarCAM : a camera for the medium size telescopes of the Cherenkov Telescope Array
No full textInternational audienceNectarCAM is a camera proposed for the medium-sized telescopes of the Cherenkov Telescope Array (CTA) covering the central energy range of ~100 GeV to ~30 TeV. It has a modular design and is based on the NECTAr chip, at the heart of which is a GHz sampling Switched Capacitor Array and a 12-bit Analog to Digital converter. The camera will be equipped with 265 7-photomultiplier modules, covering a field of view of 8 degrees. Each module includes the photomultiplier bases, high voltage supply, pre-amplifier, trigger, readout and Ethernet transceiver. The recorded events last between a few nanoseconds and tens of nanoseconds. The camera trigger will be flexible so as to minimize the read-out dead-time of the NECTAr chips. NectarCAM is designed to sustain a data rate of more than 4 kHz with less than 5\% dead time. The camera concept, the design and tests of the various subcomponents and results of thermal and electrical prototypes are presented. The design includes the mechanical structure, cooling of the electronics, read-out, clock distribution, slow control, data-acquisition, triggering, monitoring and services
Numerical simulation of electrocardiograms for full cardiac cycles in healthy and pathological conditions
No full textInternational audienceThis work is dedicated to the simulation of full cycles of the electrical activity of the heart and the corresponding body surface potential. The model is based on a realistic torso and heart anatomy, including ventricles and atria. One of the specificities of our approach is to model the atria as a surface, which is the kind of data typically provided by medical imaging for thin volumes. The bidomain equations are considered in their usual formulation in the ventricles, and in a surface formulation on the atria. Two ionic models are used: the Courtemanche-Ramirez-Nattel model on the atria, and the " Minimal model for human Ventricular action potentials " (MV) by Bueno-Orovio, Cherry and Fenton in the ventricles. The heart is weakly coupled to the torso by a Robin boundary condition based on a resistor-capacitor transmission condition. Various ECGs are simulated in healthy and pathological conditions (left and right bundle branch blocks, Bachmann's bundle block, Wolff-Parkinson-White syndrome). To assess the numerical ECGs, we use several qualitative and quantitative criteria found in the medical literature. Our simulator can also be used to generate the signals measured by a vest of electrodes. This capability is illustrated at the end of the article
A general Doob-Meyer-Mertens decomposition for g-supermartingale systems
No full textInternational audienceWe provide a general Doob-Meyer decomposition for g-supermartingale systems, which does not require any right-continuity on the system. In particular, it generalizes the Doob-Meyer decomposition of Mertens for classical supermartingales, as well as Peng's version for right-continuous g-supermartingales. As examples of application, we prove an optional decomposition theorem for g-supermartingale systems, and also obtain a general version of the well-known dual formation for BSDEs with constraint on the gains-process, using very simple arguments