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  1. Free, publicly-accessible full text available January 1, 2023
  2. We examine the capacity of the Large Hadron Collider to determine the mean proper lifetime of long-lived particles assuming different decay final states. We mostly concentrate on the high luminosity runs of the LHC, and therefore, develop our discussion in light of the high amount of pile-up and the various upgrades for the HL-LHC runs. We employ model-dependent and model-independent methods in order to reconstruct the proper lifetime of neutral long- lived particles decaying into displaced leptons, potentially accompanied by missing energy, as well as charged long- lived particles decaying ihnto leptons and missing energy. We also present a discussionmore »for lifetime estimation of neu- tral long-lived particles decaying into displaced jets, along with the challenges in the high PU environment of HL-LHC. After a general discussion, we illustrate and discuss these methods using several new physics models. We conclude that the lifetime can indeed be reconstructed in many concrete cases. Finally, we discuss to which extent including timing information, which is an important addition in the Phase-II upgrade of CMS, can improve such an analysis.« less
  3. The successful deployment of autonomous real-time systems is contingent on their ability to recover from performance degradation of sensors, actuators, and other electro-mechanical subsystems with low latency. In this article, we introduce ALERA, a novel framework for real-time control law adaptation in nonlinear control systems assisted by system state encodings that generate an error signal when the code properties are violated in the presence of failures. The fundamental contributions of this methodology are twofold—first, we show that the time-domain error signal contains perturbed system parameters’ diagnostic information that can be used for quick control law adaptation to failure conditions andmore »second, this quick adaptation is performed via reinforcement learning algorithms that relearn the control law of the perturbed system from a starting condition dictated by the diagnostic information, thus achieving significantly faster recovery. The fast (up to 80X faster than traditional reinforcement learning paradigms) performance recovery enabled by ALERA is demonstrated on an inverted pendulum balancing problem, a brake-by-wire system, and a self-balancing robot.« less
  4. The residual shear strength of liquefied soil is a key parameter in evaluating liquefaction flow failures. Results from a series of dynamic centrifuge experiments where the shear strength of liquefied soil was inferred by measuring the force required to pull a thin metal plate (coupon) horizontally through the liquefied soil are assessed here using a computational fluid dynamics (CFD) based model. Viscosity is a key parameter for the Newtonian fluid constitutive model used in the simulations, and apparent viscosities of liquefied soil in the range of about 5,800 – 13,300 Pa·s were obtained when the CFD model was calibrated againstmore »coupons pulled through liquefied soil in dynamic centrifuge tests. These computational values agree reasonably with apparent viscosities of liquefied soil reported in the literature when the Reynold’s numbers exceeded 1.0. Importantly, the CFD simulations illustrated that in cases where Reynold’s numbers are < 1.0, apparent viscosities of liquefied soil back-calculated using simplistic closed-form solutions commonly applied in geotechnical literature are several orders of magnitude too large; and therefore, such closed-form solutions should not be used for these cases.« less