Approximation of Non-Linear Rotor Dynamic Resonance Behavior of Vertically Aligned Hydro-Units Guided by Tilting-Pad Bearings

Dynamic analyses of vertical hydro power plant rotors require the consideration of the non-linear bearing characteristics. This study investigates the vibrational behavior of a typical vertical machine using a time integration method that considers non-linear bearing forces. Thereby, the influence of support stiffness and unbalance magnitude is examined. The results show a rising influence of unbalance on resonance speed with increasing support stiffness. Furthermore, simulations reveal that the shaft orbit in the bearing is nearly circular for typical design constellations. This property is applied to derive a novel approximation procedure enabling the examination of non-linear resonance behavior, using linear rotor dynamic theory. The procedure considers the dynamic film pressure for determining the pad position. In addition, it is time-efficient compared to a time integration method, especially at high amplitudes when damping becomes small.

Effects of substrate phonon absorption on the resonance behavior of metal-insulator-metal metamaterial terahertz absorbers

We have investigated effects of substrate phonon absorption on the resonance behavior of metal-insulator-metal double layer metamaterial absorbers in the terahertz frequency range. A sharp resonant absorption dip is clearly observed for a metamaterial-on-ground-plane structure fabricated on a GaAs substrate when THz radiation is incident from the surface metamaterials side. However, when the THz is incident from the substrate side to the ground-plane-on-metamaterial structures fabricated on a GaAs substrate, the resonance dip is almost merged into the broad background of acoustic phonon absorption. The resonant absorption is recovered when the GaAs substrate is replaced with a high-resistivity Si substrate.

High-temperature behavior of housed piezoelectric resonators based on CTGS

A temperature sensor based on piezoelectric single crystals allowing stable operation in harsh environments such as extreme temperatures and highly reducing or oxidizing atmospheres is presented. The temperature dependence of the mechanical stiffness of thickness shear mode resonators is used to determine temperature changes. The sensor is based on catangasite (Ca3TaGa3Si2O14 – CTGS), a member of a langasite crystal family. CTGS exhibits an ordered crystal structure and low acoustic losses, even at 1000 ∘C. The resonance frequency and quality factor of unhoused and of housed CTGS resonators are measured up to about 1030 ∘C. A temperature coefficient of the resonance frequency of about 200 Hz K−1 for a 5 MHz device is found and enables determination of temperature changes as small as 0.04 K. Housed CTGS resonators do not show any significant change in the resonance behavior during a 30 d, long-term test at 711 ∘C.

Features in the Resonance Behavior of Magnetization in Arrays of Triangular and Square Nanodots

Collective modes of the gyrotropic motion of a magnetic vortex core in ordered arrays of triangular and square ferromagnetic film nanodots have been theoretically investigated. The dispersion relations have been derived. The dipole–dipole interaction of the magnetic moments of the magnetic vortex cores of elements has been taken into account in the approximation of a small shift from the equilibrium position. It is shown that the effective rigidity of the magnetic subsystem of triangular elements is noticeably higher than that of the subsystem of square elements of the same linear sizes. The potential application of the polygonal film nanodisks as nanoscalpels for noninvasive tumor cell surgery is discussed

On the Self-Shielding in the Unresolved Resonance Range

Resonance behavior is a feature of nuclear reaction cross sections. Resonance density increases with increasing incident particle energy and they begin to overlap, until they can no longer be resolved experimentally, but they still contribute to self-shielding and must be accounted for. This is usually done by representing them with statistical average parameters according to methods and approximations described in standard text-books. Self-shielding factors are commonly used in deterministic transport codes, while statistical Monte Carlo codes use probability tables or multi-band parameters. An exercise was conducted at the International Atomic Energy Agency (IAEA) to validate codes and methods for generating data that account for self-shielding in deterministic and Monte Carlo codes. A simple numerical model problem was defined, considering a sphere of 1 m radius with a 20 MeV isotropic neutron source at the center. The chosen material for testing was 139La from the ENDF/B-VIII.0 library, which clearly showed anomalous behavior.

Stochastic dynamic behavior of FitzHugh–Nagumo neurons stimulated by white noise

Stochastic noise exists widely in the nervous system, and noise plays an extremely important role in the information processing of the nervous system. Noise can enhance the ability of neurons to process information as well as decrease it. For the dynamic behavior of stochastic resonance and coherent resonance shown by neurons under the action of stochastic noise, this paper uses Fourier coefficient and coherence resonance coefficient to measure the behavior of stochastic resonance and coherence resonance, respectively, and some conclusions are drawn by analyzing the effects of additive noise and multiplicative noise. Appropriate noise can make the nonlinear system exhibit stochastic resonance behavior and enhance the detection ability of external signals. It can also make the coherent resonance behavior of the nonlinear system reach its optimal state, and the system becomes more orderly. By comparing the effects of additive and multiplicative noise on the stochastic resonance behavior and coherent resonance behavior of the system, it is found that additive and multiplicative noise can both make the system appear the phenomenon of stochastic resonance and have almost identical discharge state at the same noise intensity. However, with the increase of noise intensity, the coherent resonance of the system occurs, the multiplicative noise intensity is smaller than that of additive noise, but the coherent resonance coefficient of additive noise is smaller and the coherent resonance effect is better. The system whose system parameters are located near the bifurcation point is more prone to coherent resonance, and the closer the bifurcation point is, the more obvious the coherent resonance phenomenon is, and the more regular the system becomes. When the parameters of the system are far away from the bifurcation point, the coherent resonance will hardly appear. Besides, when additive and multiplicative noise interact together, the stochastic resonance and coherent resonance phenomena are more likely to appear at small noise, and the behavior of stochastic resonance and coherent resonance that the system shown is better in the local range.

Stochastic Resonance Behavior of DNA Translocation with an Oscillatory Electric Field

Stochastic resonance (SR) describes the synchronization between noise of a system and an applied oscillating field to achieve an optimized response signal. In this work, we use simulations to investigate the phenomenon of SR of a single stranded DNA driven through a nanopore when an oscillating electric field is added. The system is comprised of a MspA protein nanopore embedded in a membrane and different lengths of DNA is driven from one end of the pore to the other via a constant potential difference. We superimposed an oscillating electric field on top of the existing electric field. The source of noise is due to thermal fluctuations, since the system is immersed in solution at room temperature. Here, the signal optimization we seek is the increase in translocation time of DNA through the protein nanopore. Normally, translocation time scales linearly with DNA length and inversely with driving force in a drift dominanted regime. We found a non monotonic dependence of the mean translocation time with the frequency of the oscillating field. This non-monotonic behavior of the translocation time is observed for all lengths of DNA, but SR occurs only for longer DNA. Furthermore, we also see evidence of DNA extension being influenced by the oscillating field while moving through the nanopore.