1,135 research outputs found

    Towards Efficient Data Valuation Based on the Shapley Value

    Full text link
    "How much is my data worth?" is an increasingly common question posed by organizations and individuals alike. An answer to this question could allow, for instance, fairly distributing profits among multiple data contributors and determining prospective compensation when data breaches happen. In this paper, we study the problem of data valuation by utilizing the Shapley value, a popular notion of value which originated in coopoerative game theory. The Shapley value defines a unique payoff scheme that satisfies many desiderata for the notion of data value. However, the Shapley value often requires exponential time to compute. To meet this challenge, we propose a repertoire of efficient algorithms for approximating the Shapley value. We also demonstrate the value of each training instance for various benchmark datasets

    Double-loop sliding mode control of reentry hypersonic vehicle with RCS

    Get PDF
    In order to solve the problem of insufficient aerodynamic moment caused by thin air in the re-entry stage of hypersonic vehicle, this paper establishes an attitude angle model of hypersonic vehicle with reaction control system (RCS), and derives its affine linear model to decoupled the internal and external loop. According to the dead zone and saturation characteristics of RCS thruster, a control method to convert continuous moment into discrete switching instruction using pulse width modulation (PWM) is proposed. Since the number of thrusters is usually redundant, the installation matrix of thrusters in the body coordinate is established, and the command moment is coordinately distributed to the individual thrusters. Then a double-loop sliding mode controller (DSMC) is designed to achieve attitude stability and trajectory tracking. Finally, the simulation results show that DSMC has higher maneuverability, fewer thruster switches and stronger robustness to interference

    ψ(3770)\psi(3770) and BB meson exclusive decay Bψ(3770)KB \to \psi(3770) K in QCD factorization

    Full text link
    Belle has observed surprisingly copious production of ψ(3770)\psi(3770) in BB meson decay Bψ(3770)KB\to \psi(3770)K, of which the rate is comparable to that of Bψ(3686)KB\to \psi(3686)K. We study this puzzling process in the QCD factorization approach with the effect of S-D mixing considered. We find that the soft scattering effects in the spectator interactions play an essential role. With a proper parametrization for the higher twist soft end-point singularities associated with kaon, and with the S-D mixing angle θ=12\theta=-12^{\circ}, the calculated decay rates can be close to the data. Implications of these soft spectator effects to other charmonium production in BB exclusive decays are also emphasized.Comment: journal versio
    corecore