Influence of noise on Josephson junctions dynamics with a BCS theory-based model

We developed a weak-linked Josephson junction time-domain simulation tool based on the Bardeen-Cooper-Schrieffer (BCS) theory to account for the electrodynamics of Cooper pairs and quasiparticles in the presence of thermal noise. The model, based on Werthamer and Harris formalisms, allows us to describe the behavior of Josephson junctions for various current and/or voltage input waveforms, analog or digital, and for any operating temperature below the critical temperature of the superconducting materials. We show a good agreement between experimental and simulated IV curves of Josephson junctions, as well as a relative increase of the grey zone width of an SFQ balanced comparator between 4 and 20% due to the presence of quasiparticles, for McCumber parameters comprised between 0.1 and 1, respectively.Comment: Presented at the European Conference on Applied Superconductivity (EUCAS 2023), Bologna, Italy, 03-07 September 2023. 5 pages, 6 figures, 21 reference

Sound and Automated Synthesis of Digital Stabilizing Controllers for Continuous Plants

Modern control is implemented with digital microcontrollers, embedded within a dynamical plant that represents physical components. We present a new algorithm based on counter-example guided inductive synthesis that automates the design of digital controllers that are correct by construction. The synthesis result is sound with respect to the complete range of approximations, including time discretization, quantization effects, and finite-precision arithmetic and its rounding errors. We have implemented our new algorithm in a tool called DSSynth, and are able to automatically generate stable controllers for a set of intricate plant models taken from the literature within minutes.Comment: 10 page

Global linear stability analysis of flow in a lined duct

Eigenmodes of the linearised Euler equations are computed in order to study lined flow duct global stability. A simplified configuration is considered and the governing equations are discretised by means of the discontinuous Galerkin method. A biorthogonal technique is used to decompose the global eigenfunctions into local eigenmodes. The system dynamics switches from noise amplifier to resonator as the length of the liner is increased. The global mode in the liner region is shown to be mainly composed of a hydrodynamic unstable wave and a left-running acoustic mode

A New Implementation of the Extended Helmholtz Resonator Acoustic Liner Impedance Model in Time Domain CAA

The application of wall acoustic lining is a major factor in the reduction of aircraft engine noise. The Extended Helmholtz Resonator impedance model is widely used since it is representative of the behavior of realistic liners over a wide range of frequencies. Its application in time domain CAA methods by means of z-transform has been the subject of several papers. In contrast to standard liner modeling in time domain CAA, which consists in imposing a boundary condition modelling both the cavities and the perforated sheet of the liner, an alternative approach involves adding the cavities to the computational domain and imposing a condition between these cavities and the duct domain to model the resistive sheet. However, the original method may not be used for broadband acoustics since it implements an impedance condition with frequency independent resistance. This paper describes an extension of this method to implement the extended Helmholtz Resonator impedance model in a time domain CAA method

Semantic and Visual Similarities for Efficient Knowledge Transfer in CNN Training

International audienceIn recent years, representation learning approaches have disrupted many multimedia computing tasks. Among those approaches, deep convolutional neural networks (CNNs) have notably reached human level expertise on some constrained image classification tasks. Nonetheless, training CNNs from scratch for new task or simply new data turns out to be complex and time-consuming. Recently, transfer learning has emerged as an effective methodology for adapting pre-trained CNNs to new data and classes, by only retraining the last classification layer. This paper focuses on improving this process, in order to better transfer knowledge between CNN architectures for faster trainings in the case of fine tuning for image classification. This is achieved by combining and transfering supplementary weights, based on similarity considerations between source and target classes. The study includes a comparison between semantic and content-based similarities, and highlights increased initial performances and training speed, along with superior long term performances when limited training samples are available

Asymptotic stability of the linearised Euler equations with long-memory impedance boundary condition

This work focuses on the well-posedness and stability of the linearised Euler equations (1) with impedance boundary condition (2,3). The first part covers the acoustical case ($u_0 = 0$), where the complexity lies solely in the chosen impedance model. The existence of an asymptotically stable $C_0$-semigroup of contractions is shown when the passive impedance admits a dissipative realisation; the only source of instability is the time-delay $\tau$. The second part discusses the more challenging aeroacoustical case($u_0 \neq 0$), which is the subject of ongoing research. A discontinuous Galerkin discretisation is used to investigate both cases

Simulation temporelle d'un modèle d'impédance de liner en utilisant la représentation diffusive d'opérateurs

Une nouvelle condition aux limites temporelle de type impédance (TDIBC), adaptée à la simulation large-bande d’un liner, est présentée. Elle se base sur des modèles physiques existants, qui séparent impédance de cavité et de perforation. Pour la cavité, une approximation du nombre d’onde aboutit à un modèle EHR. Pour la perforation, une analyse temporelle théoriquement exacte du terme en dérivée fractionnaire mène à une formulation équivalente par équations différentielles, sans convolution récursive, qui se couple à tout schéma numérique dès le niveau semi-discret. Une étude numérique dans une méthode Galerkin Discontinu, qui résout les équations d’Euler linéarisées monodimensionelles, met en évidence la neutralité de la TDIBC vis à vis du CFL

Lactic Acid Bacteria as Microbial Silage Additives: Current Status and Future Outlook

Silage making is not a novel technique. However, the agricultural industry has made great strides in improving our understanding of—and efficiency in—producing high-quality silage for livestock. Silage microbiology research has been using the newest molecular techniques to study microbial diversity and metabolic changes. This chapter reviews important research that has laid the foundation for field-based utilization of silage inoculants. We also outline areas of current, and future, research that will improve global livestock production through the use of silage