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Results 431-440 of 2278 (Search time: 0.005 seconds).
    • Regularization by Noise of an Averaged Version of the Navier–Stokes Equations
    Authors: Theresa, Lange;  Advisor: -;  Co-Author: - (2023)

    In Tao 2016, the author constructs an averaged version of the deterministic three-dimensional Navier–Stokes equations (3D NSE) which experiences blow-up in finite time. In the last decades, various works have studied suitable perturbations of ill-behaved deterministic PDEs in order to prevent or delay such behavior. A promising example is given by a particular choice of stochastic transport noise closely studied in Flandoli et al. 2021. We analyze the model in Tao 2016 in view of these results and discuss the regularization skills of this noise in the context of the averaged 3D NSE.
    • Final state observability estimates and cost-uniform approximate null-controllability for bi-continuous semigroups
    Authors: Karsten, Kruse; Christian, Seifert;  Advisor: -;  Co-Author: - (2023)

    We consider final state observability estimates for bi-continuous semigroups on Banach spaces, i.e. for every initial value, estimating the state at a final time T>0 by taking into account the orbit of the initial value under the semigroup for t∈[0,T], measured in a suitable norm. We state a sufficient criterion based on an uncertainty relation and a dissipation estimate and provide two examples of bi-continuous semigroups which share a final state observability estimate, namely the Gauß–Weierstraß semigroup and the Ornstein–Uhlenbeck semigroup on the space of bounded continuous functions.
    • Strategies to parallelize a finite element mesh truncation technique on multi-core and many-core architectures
    Authors: Jose M., Badia; Adrian, Amor-Martin; Jose A., Belloch;  Advisor: -;  Co-Author: - (2023)

    Achieving maximum parallel performance on multi-core CPUs and many-core GPUs is a challenging task depending on multiple factors. These include, for example, the number and granularity of the computations or the use of the memories of the devices. In this paper, we assess those factors by evaluating and comparing different parallelizations of the same problem on a multiprocessor containing a CPU with 40 cores and four P100 GPUs with Pascal architecture. We use, as study case, the convolutional operation behind a non-standard finite element mesh truncation technique in the context of open region electromagnetic wave propagation problems.
    • Stabilization of a uniform rotating disk-beam-mass system with boundary input disturbance
    Authors: My Driss, Aouragh; Mohamed, Nahli; M’hamed, Segaoui;  Advisor: -;  Co-Author: - (2022)

    In this paper, we study the stabilization problem of a disk beam structure with disturbance. Specifically, the structure consists of a beam clamped at one end to the center of a rotating rigid disk, while the other end is attached to a tip mass subject to a non-uniform bounded disturbance. We start the investigation by designing the controller via the Active disturbance rejection control (ADRC) approach. The high gain extended state observer (ESO) is first designed to estimate the disturbance, then the feedback observer-based controller is designed to employ the estimation to cancel the disturbance effect.
    • Analysis on Trees with Nondoubling Flow Measures
    Authors: Matteo, Levi; Federico, Santagati; Anita, Tabacco;  Advisor: -;  Co-Author: - (2021)

    We consider trees with root at infinity endowed with flow measures, which are nondoubling measures of at least exponential growth and which do not satisfy the isoperimetric inequality. In this setting, we develop a Calderón–Zygmund theory and we define BMO and Hardy spaces, proving a number of desired results extending the corresponding theory as known in more classical settings.