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DDC: 530 × Subject: Numerical methods ×

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Now showing 1 - 3 of 3
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    Enhanced reliability of drift-diffusion approximation for electrons in fluid models for nonthermal plasmas
    (New York, NY : American Inst. of Physics, 2013) Becker, M.M.; Loffhagen, D.
    Common fluid models used for the description of electron transport in nonthermal discharge plasmas are subject to substantial restrictions if the electron energy transport significantly influences the discharge behaviour. A drift-diffusion approach is presented which is based on a multiterm approximation of the electron velocity distribution function and overcomes some of these restrictions. It is validated using a benchmark model and applied for the analysis of argon discharge plasmas at low and atmospheric pressure. The results are compared to those of common drift-diffusion models as well as to experimental data. It is pointed out that fluid models are able to describe nonlocal phenomena caused by electron energy transport, if the energy transport is consistently described. Numerical difficulties that frequently occur when the conventional drift-diffusion model is consistently applied are avoided by the proposed method.
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    Potentials and limits to basin stability estimation
    (Bristol : Institute of Physics Publishing, 2017) Schultz, P.; Menck, P.J.; Heitzig, J.; Kurths, J.
    Stability assessment methods for dynamical systems have recently been complemented by basin stability and derived measures, i.e. probabilistic statements whether systems remain in a basin of attraction given a distribution of perturbations. Their application requires numerical estimation via Monte Carlo sampling and integration of differential equations. Here, we analyse the applicability of basin stability to systems with basin geometries that are challenging for this numerical method, having fractal basin boundaries and riddled or intermingled basins of attraction. We find that numerical basin stability estimation is still meaningful for fractal boundaries but reaches its limits for riddled basins with holes.
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    Improved accuracy in high-frequency AC transport measurements in pulsed high magnetic fields
    ([S.l.] : American Institute of Physics, 2020) Mitamura, Hiroyuki; Watanuki, Ryuta; Kampert, Erik; Förster, Tobias; Matsuo, Akira; Onimaru, Takahiro; Onozaki, Norimichi; Amou, Yuta; Wakiya, Kazuhei; Yamamoto, Isao; Matsumoto, Keisuke T.; Suzuki, Kazuya; Zherlitsyn, Sergei; Wosnitza, Joachim; Tokunaga, Masashi; Kindo, Koichi; Sakakibara, Toshiro
    We show theoretically and experimentally that accurate transport measurements are possible even within the short time provided by pulsed magnetic fields. For this purpose, a new method has been devised, which removes the noise component of a specific frequency from the signal by taking a linear combination of the results of numerical phase detection using multiple integer periods. We also established a method to unambiguously determine the phase rotation angle in AC transport measurements using a frequency range of tens of kilohertz. We revealed that the dominant noise in low-frequency transport measurements in pulsed magnetic fields is the electromagnetic induction caused by mechanical vibrations of wire loops in inhomogeneous magnetic fields. These results strongly suggest that accurate transport measurements in short-pulsed magnets are possible when mechanical vibrations are well suppressed. © 2020 Author(s).