Search results for "Linear system"
showing 10 items of 1558 documents
Nonlinear SDE Excited by External Lévy White Noise Processes
2011
A numerical method for approximating the statistics of the solution of nonlinear stochastic systems excited by Gaussian and non-Gaussian external white noises is proposed. The differential equation governing the evolution in time of the characteristic function is resolved by the convolution quadrature method. This approach is especially suited for those problems in which the nonlinear drift term is not of polynomial form. In such cases the equation governing the evolution in time of the characteristic function is not a partial differential equation. Statistics are found by introducing an integral operator of Wiener-Hopf type, called the transformation operator, and applying the Lubich's con…
Static freezing transition at a finite temperature in a quasi-one-dimensional deuteron glass.
1996
The dipolar freezing process of a quasi-one-dimensional betaine deuteron glass was studied using linear and nonlinear dielectric spectroscopy. The linear response as measured for frequencies $5\mathrm{mHz}l\ensuremath{\nu}l200\mathrm{MHz}$ was analyzed using the recently invented $\ensuremath{\delta}$ plot, providing evidence for a static freezing transition near 30 K. Measurements of the ergodic to nonergodic transition as well as of the incipient divergence of the nonlinear susceptibility yield independent confirmation of this quasistatic freezing transition temperature. The critical exponent describing the nonlinear behavior is found to be $\ensuremath{\gamma}\phantom{\rule{0ex}{0ex}}=\p…
Incoherent Soliton Turbulence in Nonlocal Nonlinear Media
2011
The long-term behavior of a modulationally unstable nonintegrable system is known to be characterized by the soliton turbulence self-organization process: It is thermodynamically advantageous for the system to generate a large-scale coherent soliton in order to reach the (‘‘most disordered’’) equilibrium state. We show that this universal process of self-organization breaks down in the presence of a highly nonlocal nonlinear response. A wave turbulence approach based on a Vlasov-like kinetic equation reveals the existence of an incoherent soliton turbulence process: It is advantageous for the system to self-organize into a large-scale, spatially localized, incoherent soliton structure.
Influence of domain wall anisotropy on the current-induced hysteresis loop shift for quantification of the Dzyaloshinskii-Moriya interaction
2021
Using several material systems with various magnitudes of the interfacial Dzyaloshinskii-Moriya interaction (DMI), we elucidate a critical influence of domain wall (DW) anisotropy on the current-induced hysteresis loop shift scheme widely employed to determine the magnitude of the Dzyaloshinskii-Moriya effective field (${H}_{\mathrm{DMI}}$). Taking into account the DW anisotropy in the analysis of the hysteresis loop shift, which has not been included in the original model [Phys. Rev. B 93, 144409 (2016)], we show that it provides quantitative agreement of ${H}_{\mathrm{DMI}}$ with that determined from an asymmetric bubble expansion technique for small DMI material systems. For large DMI sy…
Nonlinear Evolution Equations, Quasi-Solitons and their Experimental Manifestation
1990
We review the typical experimental facts which characterize quasisolitons in one-dimensional real systems, in connection with their modeling by nonlinear partial differential equations.We consider these nonlinear waves or excitations in two different domains of the real world : the macroworld and the microworld. In the macroworld we examine typical one-dimensional devices : the electrical networks, the Josephson transmission lines and the optical fibers, where the localized waves or pulses can be simply and coherently created, easily observed and manipulated on a macroscopic scale. In the microworld, we consider the magnetic chains and polymers, where the indirect experimental signatures of…
Comment on "Highly nonlinear, sign-varying shift of hydrogen spectral lines in dense plasmas".
2004
The shift of hydrogen and hydrogenlike spectral lines in dense plasmas, calculated with the full computer simulation method, in nonquenching, classical path, dipole approximation for plasma-emitter interaction, is equal to zero. In the paper commented on, Escarguel et al., Phys. Rev. E 62, 2667 (2000) the electron concentrations ${N}_{e}$ and the corresponding temperature values T are shown to have been determined incorrectly.
KRYLOV-BOGOLIUBOV APPROACH TO NON-LINEAR HYSTERETIC INSTABILITY IN ROTORDYNAMICS
2012
The internal friction due to the shaft hysteresis or the shrink fitting release exerts a destabilizing effect on the overcritical rotor whirl, but may be counteracted by other external dissipative sources and/or by proper anisotropy of the support stiffness. The internal friction effect may be treated by either dry or viscous models, obtaining similar results in the hypothesis of small dissipation levels, provided that proper equivalence criteria are defined between the two approaches. The equivalence is here stated by imposing the same energy dissipation over a large number of shaft revolutions. Approximate closed-form autonomous solutions for a symmetric rotor arrangement subject to Coulo…
Dynamical effects and Terahertz harmonic generation in low-doped bulk semiconductors and submicron structures
2006
We present results obtained using a three-dimensional multivalleys Monte Carlo (MC) model to simulate the nonlinear carrier dynamics under the influence of an intense sub-terahertz electric field in a doped bulk semiconductor. By self-consistently coupling a one-dimensional Poisson solver to the ensemble MC code we simulate also the nonlinear carrier dynamics in n+nn+ structures operating under large-amplitude periodic signals and investigate the voltage-current characteristic hysteresis cycle and the high-order harmonic efficiency. For both cases we discuss the dependence of the nonlinearities and of the harmonic generation efficiency on the frequency and the intensity of the alternating s…
Nonlinear stopping power of an electron gas for slow ions
1986
Theoretical calculations of the stopping power of the electron gas for slow ions, v${v}_{F}$, are reviewed. New results are presented for stopping power and effective charge based on nonlinear density-functional calculations. Extensive comparisons with available experimental data show that these new theoretical results are clearly superior to earlier calculations based on linear theory.
Scaling and mean-field-like behaviour in phase separation processes
1985
Extensive Monte Carlo calculations are used to study the still not well understood process of phase separation in binary systems. The results show that for a separation dominated by long-wavelength fluctuations a mean-field description holds in certain concentration regions. This, however, is only true for short times after the system has been brought into a non-equilibrium state. A crucial parameter is the interaction range. It determines the region and the time where the mean field description is valid. At later times the structure factor exhibits dynamical scaling. Scaling is also investigated for the metastable states. The results are applicable to polymer blends with long chains or bin…