Resonant Oscillations Research Articles

Imbricated chaos in rough potential [formula omitted]-Rayleigh-Duffing oscillator

In this paper, a new ϕ6 - Rayleigh–Duffing system with dual potential is examined. Research is being done on the effect of roughness on forced dynamical systems. To evaluate the performance of the system parameters, the resonance oscillations are investigated using the multiple scale method. Both equilibrium points and local stability are calculated, while abrupt changes in the topological characteristics of attractors’ phase portraits are treated as bifurcation-Lyapunov parameters.

Microwave wireless power transfer system using a dual-dielectric resonator oscillator

Non-radiating wireless power transfer (WPT) systems have found extensive applications in science and technology. This paper reports the design, simulation, and implementation of a compact single-port (DC to RF) WPT system composed of two coupled dielectric resonators (DR). The DR on the transmitter side, in combination with a transistor amplifier and a series feedback circuit, forms a dielectric resonator oscillator for microwave power generation. The DR on the receiver side is coupled to the transmitter DR such that the circuit can be considered as a dual-dielectric resonator oscillator or DDRO. The DDRO is designed for optimum power transfer to the output port. The measured RF output power of the proposed WPT system at 7.5 GHz for a 10 mm spacing between the transmitting and receiving DR is measured to be 13.07dBm at a DC voltage of 3.3 V and a supply current of 32.3 mA, which shows a good agreement with our proposed method of analysis. The available bandwidth at the operating frequency of 7.5 GHz is measured to be 150 MHz which provide a relatively wide bandwidth for simultaneous data transmission.

A cryogenic sapphire resonator oscillator with 10−16 mid-term fractional frequency stability

We report in this Letter the outstanding frequency stability performance of an autonomous cryogenic sapphire oscillator (CSO) presenting a flicker frequency noise floor below 2×10−16 near 1000 s of integration time and a long-term Allan deviation limited by a random walk process of ∼1×10−18τ. The frequency stability qualification at this level called for the implementation of sophisticated instrumentation associated with ultra-stable frequency references. This result is technologically sound as it demonstrates the potentiality of the CSO technology. From the physical point of view, it sets an upper limit to the ultimate noise floor of the cryogenic microwave resonator that is competitive to that of the ultra-stable optical Fabry–Pérot cavities.

Dual Heteroatoms-Induced defect engineering in graphene towards metacomposites with epsilon-near-zero response

In this paper, the effect of diatomic doping on negative permittivity and epsilon-near-zero (ENZ) properties of graphene (GR)/polyvinylidene difluoride (PVDF) composites were investigated for the first time. Nitrogen (N) and phosphorus (P) atoms were doped into the GR lattice, and the doping sites and ratio of N and P atoms in the GR lattice were studied in detail. The results showed that introducing N and P atoms controlled the composite's percolation structure and carrier concentration. The dual atom synergy modulated the value of negative permittivity, and a stable weak negative permittivity between −30 and −40 was obtained. With further regulation of the diatomic doping ratio, an ENZ response in the kHz region was successfully acquired under synergistic effects. The ENZ response appeared at 170 kHz and exhibited a zero-crossing behavior. After the permittivity shifted to negative, the maximum negative permittivity was only −11.92 up to 1 MHz. The negative permittivity obtained for N/P co-doped GR/PVDF composites could all be perfectly fitted by Lorentz and/or Drude model. Further analysis revealed that plasma oscillation and dielectric resonance work in concert were necessary to produce a steady ENZ response in the kHz range.

Nanorobot-Mediated Synchronized Neuron Activation.

Interactions between active materials lead to collective behavior and even intelligence beyond the capability of individuals. Such behaviors are prevalent in nature and can be observed in animal colonies, providing these species with diverse capacities for communication and cooperation. In artificial systems, however, collective intelligence systems interacting with biological entities remains unexplored. Herein, we describe black (B)-TiO2@N/Au nanorobots interacting through photocatalytic pure water splitting-induced electrophoresis that exhibit periodic swarming oscillations under programmed near-infrared light. The periodic chemical-electric field generated by the oscillating B-TiO2@N/Au nanorobot swarm leads to local neuron activation in vitro. The field oscillations and neurotransmission from synchronized neurons further trigger the resonance oscillation of neuron populations without synaptic contact (about 2 mm spacing), in different ways from normal neuron oscillation requiring direct contact. We envision that the oscillating nanorobot swarm platforms will shed light on contactless communication of neurons and offer tools to explore interactions between neurons.

A Swing Self‐Regulated Triboelectric Nanogenerator for High‐Entropy Ocean Breaking Waves Energy Harvesting

AbstractMultidirectional irregular breaking wave is the most prominent feature of the ocean surface and bears tremendous amounts of sustainable high‐entropy energy. However, the commercial utilization and harvesting efficiency are very limited low due to its low‐frequency and low‐amplitude. Here, a swing self‐regulated triboelectric nanogenerator (SSR‐TENG) is proposed, which can convert collected low‐grade breaking waves energy into electrical energy by regulating the oscillation frequency and resonance effect. Benefiting from simple and efficient structural strategy, SSR‐TENG outputs a peak power of 0.14 mW under wave height range of 6–11 cm, that the open‐circuit voltage, short‐circuit current and transferred charge increases is 5.8, 4, and 3.7 times compared to without self‐regulated design, respectively. This work gives a practical solution to the problems faced by harvesting high‐entropy ocean breaking waves energy, which exhibits large potential for building the self‐powered ocean assessment and meteorology system in the future.

Harmonic oscillations of point soliton (Bloch point) in cylindrical ferromagnetic nanowire

Harmonic oscillations of a point magnetic soliton (Bloch point) located in a domain wall (DW) of a cylindrical ferromagnetic nanowire along the spatial directions of a primitive vortex cell formed by the magnetization vectors at the boundary between the core and the transition zone of the soliton are considered. The possibility of experimental implementation of Bloch point resonant oscillations excited by external alternating magnetic field is shown. In the case of weak attenuation, the maximum values of the resonant frequencies of Bloch points in iron and nickel nanowires are determined, which are 10 and 3 GHz, respectively. These results can be applied in the modern nanotechnologies based on the use of the magnetic properties of ferromagnetic nanowires whose DWs contain Bloch points.

Widely tunable near-infrared optical parametric oscillator based on a 5%MgO:PPLN partial cylinder pumped at 1064 nm by a 1-kHz sub-nanosecond microchip laser.

We report the implementation of a singly resonant optical parametric oscillator using a 5%MgO:PPLN partial cylinder pumped by a sub-nanosecond microchip laser emitting 1064 nm at a repetition rate of 1 kHz. It is continuously tunable from 1410 nm up to 4330 nm by rotating the cylinder and a total energy of several microjoules is emitted with a beam quality factor M2 lower than 3.

Investigation of dynamic behaviour of one complex steel structure

This paper deals with dynamic analysis of a steel structure, constructed by steel beams and pillars which are connected by bolts. This structure is designed to serve as an acoustic barrier to one rotating machine which generates an air borne and structure borne sound and vibrations on a certain frequencies. This excitation energy is transmitted to the steel structure and might cause the oscillations of the structure. Depending on the frequency of the source of excitation, oscillations of the structure may occur at one of its natural frequencies, which depends on the physical characteristics of the structure - shape, dimensions, materials, grounding conditions, as well as other structural parameters. If it happens that excitation frequencies and the natural frequencies of the structure coincide to each other, a resonant oscillation of the structure will occur. To avoid the resonant oscillation of the structure, it is necessary the structure be designed such a way that its natural frequencies are not in the operating frequency range of the source of vibration. The investigated steel structure is subjected to mass and stiffness changes due to inserting some additional elements. The change of these physical characteristics of the structure can lead to change of its natural frequencies. To investigate dynamic behaviour of overall structure, a numerical model was set by FEM analysis and experimental analysis was done using modal test and bump test.

Fabrication and characterization of (Mg0.8Zn0.2)(Ti0.99Sn0.01)O3 ceramics as a 4.0 GHz resonator in dielectric resonator oscillator module

Fabrication and characterization of (Mg0.8Zn0.2)(Ti0.99Sn0.01)O3 ceramics as a 4.0 GHz resonator in dielectric resonator oscillator module

Methods of reducing the negative impact of resonant oscillations on the quality of concrete products during their vibration compaction

Problem. Most of the equipment for vibroforming of concrete in the production of concrete construction products uses a "over-resonant" mode of operation. The system goes through resonance during acceleration and also before a complete stop. This is detrimental to the products, as newly formed products suffer from resonant oscillations. Goal. The goal of the research was to investigate ways to reduce the negative impact of negative resonance oscillations on products by reducing the time spent in the resonance mode and reducing the amplitude of oscillations. Methodology. The computational and analytical method of finding dependence, a comparative analysis of engine designs and experimental strain-metric studies of two designs of vibration platforms were applied. Results. The value of the angle forming the sector unbalance is substantiated both for the variant without the hub on the unbalance and with it. From the standpoint of minimizing the moment of inertia of the rotor, the expediency and perspective of using a hydraulic motor instead of an electric asynchronous motor has been proven. Other advantages of the hydraulic motor over the electric motor for vibrating machines and vibropresses with frequent transient processes (start-stop) are substantiated. It has been proven that the use of rubber elastic elements instead of steel springs in systems with frequent transient processes may be more appropriate. The amplitude of resonant oscillations in a vibration system with rubber elastic elements is smaller, and the transition through resonance occurs faster. Originality. Ways to reduce the negative impact due to resonance are considered comprehensively. Vibration studies were performed on two vibration platforms with different types of elastic elements. Practical value. Reducing the intensity and duration of resonant oscillations in over-resonant technological equipment for forming building products will positively affect the quality of products. The application of the proposed design features will improve the working conditions of workers and the reliability of equipment.

On the effect of vibrational capture of rotation of an unbalanced rotor

The dynamics of an unbalanced rotor with a vibrating suspension axis and driven by an asynchronous electric motor of limited power is considered. Stationary (near stationary) modes of rotation of the rotor with a frequency equal to the vibration frequency of the axis are investigated. An explanation of the phenomenon of vibrational capture of rotation of an unbalanced rotor is given. The proposed mechanical interpretation of the effect allows deeper understanding of the classical results and conclusions. The obtained condition for the existence of a stationary mode allows us to estimate the frequency capture interval of the rotor. The case when the mode of vibration capture of rotation is not set is considered. For such a case, an expression for the vibrational moment is obtained, as well as an equation for slow motions. Attention is drawn to the possibility of occurrence in the considered modes of motion of slow (relative to the rotation frequency) rotor oscillations with sufficiently large amplitudes. It is demonstrated that the vibrational capture mode has the property of self-regulation; allows to stabilize the rotation frequency of an unbalanced rotor during load oscillations. Attention is drawn to the fact that in this mode of motion, there is certainly a transfer of energy either from the source of vibration to the rotor, or vice versa. The Sommerfeld effect in an oscillatory system with an inertial vibration exciter is represented by vibration capture of rotation of the vibration exciter by resonant oscillations of the carrier body. The theoretical results are confirmed by numerical modelling.

Tunable double split-ring resonator for quantum sensing using nitrogen-vacancy centers in diamond

For quantum sensing based on nitrogen-vacancies (NV) ensembles, microwave antennas can couple the microwave field to the NV center, which leads it to becoming the core of spin manipulation and can directly affect the sensitivity of quantum sensing. The double split-ring resonator is a widely used microwave device for NV ensembles due to the advantages of high radiation efficiency and uniform magnetic field in millimeter-scale areas. But the bandwidth (30 MHz) is quite narrow which limits the application in quantum sensing with NV ensembles. Here, we experimentally achieve continuous tuning of the resonant frequency of the double split-ring resonator by changing the copper sheet position on the edge of the outer ring. The frequency tuning range can reach 80 MHz, up to 2-3 times the bandwidth, which can cover the transition of the electron spin under different magnetic field conditions. The performance of the tunable antenna in the quantum operation of NV centers is verified by optically detected magnetic resonance and Rabi oscillation. This tunable antenna is promising in the fabrication of integrated and arrayed quantum sensors based on NV ensembles.

DYNAMIC ANALYSIS OF A HELICOPTER BLADE WITH DAHL FRICTION IN A VERTICAL HINGE

A one-dimensional model of a helicopter main rotor blade in the plane of rotation with a vertical hinge (VSH) is considered. The friction in the VH corresponds to the Dahl model. The resonant frequency, free oscillations and phase trajectories of the model are analyzed depending on the value of the contact stiffness of Dahl friction.

Elastic and electron capture processes in slow He+–He collision

Aims. The elastic and electron-capture processes of He+ ions with ground helium atoms are very important for studies in astrophysics. It is essential to have reliable state-selective charge transfer, elastic, and transport cross-sections, along with the corresponding reaction rate coefficient data, especially for low collision energies. Methods. We investigated the elastic and non-radiative electron-capture processes in He+(1s)–He(1s2) collisions are investigated employing the full quantum-mechanical molecular orbital close-coupling method. The adopted ab initio adiabatic potentials and coupling matrix elements were obtained by a multi-reference single- and double-excitation configuration interaction approach. Results. We computed the elastic, charge-transfer, and transport cross-sections in the energy range of 0.01–2500eVamu−1 and the reaction rate coefficient in the temperature range of 10–109 K. Good agreement was achieved when compared to the available experimental and theoretical results. Shape resonance, Regge, and Glory oscillations were also found in the elastic and charge transfer cross-sections in the energy region considered here.

Temporal evolution of the magmatic system at Nevado del Ruiz Volcano (Colombia) inferred from long-period seismic events in 2003–2020

Long-period (LP) seismic events have been broadly assumed to be generated by oscillations of crack fluid-filled resonators. We investigated the waveforms and spectral characteristics of LP seismic events recorded by five stations at Nevado del Ruiz Volcano, Colombia. The observed event types of LP events exhibited decaying harmonic oscillations with either monochromatic or polychromatic spectral features (NLP events) or events characterized by non-decaying harmonic oscillations (BLP events). The NLP events occurred over four periods: September 2003 (period I), January 2004–October 2004 (period II), October 2010–March 2012 (period III), and October 2019–April 2020 (period IV). Their source locations were determined to be within the first kilometer of the conduit placed below the Arenas crater. Their locations involved a distinct resonator for each of the four periods but a single resonator for all the events during a single period. Assuming a crack geometry at their sources and based on their locations, we considered a dusty gas (mixture of ash and water vapor) filling a crack resonator. We estimated the crack model parameters to investigate the temporal processes generating variations in frequency and quality factor Q. Then, the estimated parameters indicate that NLP events were triggered by magma fragmentation. We found that events from period III preceded phreatomagmatic eruptions, increased ash and gas emissions and SO2 flux, and increased overall seismic activity. Three years after this period III, a dome was emplaced at the base of the Arenas crater. Besides, events from period IV also preceded by ~3 years a significant increase in the overall seismic activity, which led to a change in alert activity at the volcano. We argue that BLP events were driven by resonances provoked by the unstable degassing through the uppermost magma plug's open cracks (tuffisite veins).In contrast, NLP events occurred by overpressure released through fractures along the conduit's walls (shear fractures). The shear fractures at the conduit wall were in a region of high strain rate where a decrease in confining pressure triggered fragmentation, resulting in dusty gas and, subsequently, a resonance of the crack. NLP and BLP events were in a narrow relationship with the ascent of vesiculated magma to the surface. Our results show that the LP events help diagnose the state of magmatic fluids and understand the eruption processes of Nevado del Ruiz Volcano. LP events are not always followed by explosive eruptions, but they do indicate significant overpressure developing in the shallow conduit.

Unusual Mooring Oscillations: Apparent Foucault–Wheatstone Device in the Deep Ocean?

A pressure sensor, located for four months in the middle of a 1275 m-long taut deep-ocean mooring in 2380 m water depth above a seamount with sub-surface top-buoys and seafloor anchor-weight, demonstrates narrow-band spectral peaks of deterministic well-predictable signals with equivalent 0.5 m amplitudes at uncommon sub-harmonic frequencies f*/4, f*/2, 3f*/4 of the local near-inertial frequency f* = 1.085f, where f denotes the Coriolis parameter. None of these sub-harmonics can be associated with oceanographic motions, which are dominated by super-inertial internal waves that are more broadband and less predictable. No corresponding peaks are found in spectra of other observables like current velocity (differences), temperature, and pressure in the top buoy of the mooring. The mid-cable pressure sensor was mounted on a nearly 1 kN weighing non-swiveled frame. Its data are hypothesized to reflect a resonant mechanical oscillation of the high-tensioned elastic steel mooring cable under repeated short-scale Strouhal cable vibrations induced by vortex-shedding due to water-flow drag and/or possibly by tidal baroclinic motions that are about 50% larger near the sloping seafloor of the seamount than mid-depth thereby modifying the mooring-cable in a helical shape. Cable dynamics and mooring-motion considerations yield inconclusive results to explain the observations. Hypothesizing, the observations suggest, cable dynamically, sub-harmonic drainage of helix-shape source at non-tidal semidiurnal center-frequency (M2 + S2)/2 = 3f*/2, physically, the measurement of Earth rotation thereby mimicking a Foucault–Wheatstone device, and, oceanographically, the relative vortex-rotation ζ/2 = 0.085f being possibly induced by water-flow interacting quasi-permanently with the nearby seamount by a topographic obstruction, so that total local near-inertial frequency f* = f + ζ/2.

(Digital Presentation) Internal Friction, Mechanical Spectroscopy in SiO2/Si Wafers

In this work, after X-ray and electron irradiation, the outcomes of the evaluation dynamic characteristics of interstitial atoms Sij , vacancy V, and O-complexes were evaluated to account for the annealing conditions to derive specific structural defects in the SiO2/Si wafer. A non-destructive method, which allows the determination of the internal friction difference ΔQ-1/Q-1 0 of the elastic vibration structure defect density Nd and the depth of the broken layer hb , is offered for the SiO2/Si wafer. The method was developed, the installation was designed and manufactured for the excitation and registration of damped bending resonant oscillations in a SiO2/Si disc-shaped wafer with a thickness hSiO2 ≈ 100 nm, his = 300÷500×103 nm, and diameter D = 60÷100×10-3 m to measure the structurally sensitive internal friction Q-1 . Measurement of the internal friction background Q-1 0 at harmonic frequencies f0 and f2 allowed us to experimentally determine the nodal lines of the oscillating disks.

Wake-structure interaction of flow over a freely rotating hydrofoil in the wake of a cylinder

The two-dimensional flow characteristics of the wake-structure interference between a cylinder and a freely rotating hydrofoil are analysed using the unsteady Reynolds-averaged Navier–Stokes method. The effects of different rotation centres and spacing ratios on the mechanical properties, flow-field structures, surface pressure distributions, turbulent fluctuations, vortex shedding and interference, and the resultant radiated noise and fluid resonant oscillation of the cylinder–hydrofoil system are systematically investigated. The results show that the hydrofoil decreases the shedding frequency of the cylinder wake vortex, whereas the cylinder accelerates the steady flow on the hydrofoil surface through the backward movement of the rotation centre, enhancing the dynamic stall characteristics. The turbulent vortex structures have a major suppression effect in the interaction region. At small spacing ratios, the mechanical properties of the system fluctuate considerably. As the spacing increases, the cylinder Karman vortex street is gradually released and plays a dominant role in generating turbulent fluctuations. The surface pressure increasingly recovers, and the turbulent kinetic energy and vortex intensity show jump peaks at the leading edge of the hydrofoil due to wake impingement. The primary-vortex shedding behind the cylinder impacts the hydrofoil surface, resulting in alternating shedding of the large-scale vortex street with a gradual loss in strength and coherence. This periodic variation in the hydrodynamic characteristics is reflected in the radiated noise, which is confirmed by employing a feedback model, as the system sound pressure level becomes stronger at spacing ratios of L/d=1.0, 1.5, and 3.0 due to the flow resonant oscillation.

Resonant Oscillations of Gas in Tubes with Different Tips

Resonant Oscillations of Gas in Tubes with Different Tips