Multimode Oscillator Research Articles

Anomalous Temperature-Dependent Exciton–Phonon Coupling in Cesium Lead Bromide Perovskite Nanosheets

The role of exciton–phonon coupling in light emission in cesium lead bromide (CsPbBr3) nanosheets is investigated with combined photoluminescence spectroscopy and the multimode Brownian oscillator ...

Stochastic variability and transitions to chaos in a hierarchical three-species population model

A variability of the dynamic behavior in stochastically forced multi-species population models is studied. We address how noise can generate complex oscillatory regimes with transitions between attractors and order-chaos transformations. For the parametric analysis of noise-induced transitions, we utilize a semi-analytical technique based on the stochastic sensitivity analysis of attractors and confidence domains method. This approach is used in the study of the fairly realistic three-species population model describing the interaction of prey, predator and top predator. We consider in detail the parametric zone where the system is monostable with excitable limit cycle, or bistable with coexisting limit cycle and chaotic attractor. These zones are separated by the crisis bifurcation point. Noise-induced transitions between regular and chaotic attractors in the bistability zone are analysed by the confidence ellipses method. In the monostability zone, a mechanism of the transition from regular periodic to multimodal chaotic oscillations is studied.

On developing a framework for detection of oscillations in data

Oscillation is a phenomenon very commonly observed in systems, ranging from simple ones to complex distributed network. Several techniques have been proposed in the literature for detecting oscillations to study their importance in domains ranging from physiology to climate studies. However, there is a lack of a common framework accommodative of important features of data such as non-stationarity, intermittent oscillations, measurement noise, multimodal oscillations, and the like. In this article, we outline a framework that addresses these challenges, the results of which can then be analyzed along with appropriate knowledge about the underlying system. We present results of an extensive simulation study that establishes the robustness and reliability of the proposed technique and demonstrate its applicability to real datasets in climate and in industrial datasets.

Systematic Methodology for the Global Stability Analysis of Nonlinear Circuits

A new methodology for the detection of Hopf, flip, and turning-point bifurcations in nonlinear circuits analyzed with harmonic balance (HB) is presented. It enables a systematic determination of bifurcation loci in terms of relevant parameters, such as input power, input frequency, and bias voltages, for instance. It does not rely on the use of continuation techniques and is able to globally provide the entire loci, often containing multivalued sections and/or disconnected curves, in a single simulation. The calculation of Hopf and flip bifurcations is based on the extraction of a small-signal admittance/impedance function from HB and the calculation of its zeros through a geometrical procedure. The method is ideally suited for the investigation of the global stability properties of power amplifiers and other nonlinear circuits. The turning-point locus, associated with either jump phenomena or synchronization, is obtained by taking into account the annihilation/generation of steady-state solutions that is inherent to this type of bifurcation. A technique is also presented for the exhaustive calculation of oscillation modes in multidevice oscillators and oscillators loaded with multiresonance networks. The new methodologies are illustrated through their application to a power amplifier and a multimode oscillator.

Adaptive Damping Control Strategy of Wind Integrated Power System

Random variation of grid-connected wind power can cause stochastic variation of the power system operating point. This paper proposes a new scheme to design an adaptive damping controller by tracking the variation of system operating points and updating the controller’s functions to achieve a robust damping control effect. Firstly, the operating space is classified into different modes according to the classification of wind power outputs. Multiple power system stabilizers (PSSs) are then designed. Secondly, the method of optimal classification and regression decision tree (CART) is utilized for classifying subspaces of system operating point and it is proposed that the on-line measurements from wide area measurement system (WAMS) are used for tracking the dynamic behaviors of stochastic drifting point and thus guide the updating of appropriate PSSs be switched on adaptively. A 16-generator-68-bus power system integrated with wind power is presented as a test system to demonstrate that the adaptive control scheme by use of the CART can damp multi-mode oscillations effectively when the wind power output changes.

Random Bragg-gratings-based narrow linewidth random fiber laser with a π-phase-shifted FBG

A new structure of short-cavity random fiber laser (RFL) with narrow linewidth lasing is proposed. A π-phase-shifted fiber Bragg grating (FBG) loop mirror was used in the RFL for spectral filtering and to suppress multi-mode oscillation due to the narrow transmission window. The random feedback of the RFL was implemented by a randomly dispersed weak reflection FBG array. The high gain of the erbium-doped fiber and a half-open cavity design results in a low lasing threshold. The linewidth of the laser was 225 Hz with 58 dB side-mode-suppression ratio. The laser threshold was 4.5 mW, and the optical signal-to-noise ratio was up to 63 dB.

Realization of a 101 W single-frequency continuous wave all-solid-state 1064 nm laser by means of mode self-reproduction.

We realized a 101W single-frequency continuous wave (CW) all-solid-state 1064nm laser by means of mode self-reproduction in this Letter. Two identical laser crystals were placed into a resonator to relax the thermal lens of the laser crystals, and an imaging system was employed to realize cavity mode self-reproduced at the places of the laser crystals. Single-frequency operation of the resonator was realized by employing a new kind of high extinction ratio optical diode based on the terbium scandium aluminum garnet crystal to realize a stable unidirectional operation of the laser, together with introducing a large enough nonlinear loss to the resonator to effectively suppress the multi-mode oscillation and mode hopping of the laser. As a result, a 101W single-frequency 1064nm laser in a single-ring resonator was achieved with 42.3% optical efficiency. The measured power stability for 8h and the beam quality were better than ±0.73% and 1.2, respectively.

Uniform continuity bounds for information characteristics of quantum channels depending on input dimension and on input energy

We obtain continuity bounds for basic information characteristics of quantum channels depending on their input dimension (if it is finite) and on the input energy bound (if the input dimension is infinite). We pay special attention to the case in which a multimode quantum oscillator is an input system.First, we prove continuity bounds for the output conditional mutual information for a single channel and for copies of a channel.Then we obtain estimates for the variation of the output Holevo quantity with respect to simultaneous variations of a channel and of an input ensemble.As a result, tight and close-to-tight continuity bounds for basic capacities of quantum channels, which depend on the input dimension, are obtained. They complement the Leung–Smith continuity bounds, which depend on the output dimension.Finally, we obtain tight and close-to-tight continuity bounds for basic capacities of infinite-dimensional energy-constrained channels with respect to the energy-constrained Bures distance generating the strong convergence of quantum channels.

An 802.11ax 4 <inline-formula> <tex-math notation="LaTeX">$\times$ </tex-math> </inline-formula> 4 High-Efficiency WLAN AP Transceiver SoC Supporting 1024-QAM With Frequency-Dependent IQ Calibration and Integrated Interference Analyzer

A fully integrated 4 $\times $ 4 802.11abgn/ac/ax transceiver system-on-chip (SoC) with integrated interference analyzer and frequency-dependent in-phase and quadrature (IQ) (FD-IQ) calibration is presented. The FD-IQ technique helps meeting the extremely strict IQ imbalance requirement for 1-K quadratic-amplitude modulation (QAM). The pure current-mode TX baseband (BB) improves SNR to better than 50 dB, and a multi-mode local oscillator (LO) distribution circuit provides non-contiguous operation with the error vector magnitude (EVM) of less than −37 dB. The integrated interference analyzer achieves the highly reliable connection in the presence of the undesired signal and hence improves the frequency usage efficiency by identifying the wireless LAN (WLAN) and other signals in the 2G/5G band.

Control of flexible single-link manipulators having Duffing oscillator dynamics

Abstract Unwanted vibrations caused by the commanded motions lower the positioning accuracy and degrade the control performance of flexible link manipulators. Much work has been devoted to the dynamics and control of flexible link manipulators. However, there are few studies dedicated to the flexible link manipulators having Duffing oscillator dynamics. This paper develops a new model for a flexible single-link manipulator by assuming large mechanical impedance in the drives or large inertia of the motor hub and by considering the flexibility of the single-link manipulator. The derived model includes an infinite number of uncoupled Duffing oscillators by ignoring the modal coupling effects. Two new methods are presented for controlling the vibrations of the flexible manipulator governed by Duffing oscillators. One is designed for the single-mode Duffing oscillator, and the other is for the multi-mode Duffing oscillators. A comparison of these two methods is made using the results of numerical simulations and experimental measurements. Experimental investigations are also performed on a flexible single-link manipulator to validate the dynamic behavior of Duffing oscillators and the effectiveness of the new control methods.

Multimode oscillation Q-switched erbium-doped fiber laser with a few-mode fiber cavity

We propose and demonstrate experimentally a multimode oscillation Q-switched erbium-doped fiber laser with a few-mode fiber cavity. The different coupling processes of reflection peaks of fiber Bragg gratings (FBGs) which act as cavity mirrors allow the different oscillating states. We obtain microsecond light pulse output states whose oscillation and output beams have different mode compositions, including high order mode. Such a structure enables the high order mode oscillation in the whole cavity with an all-fiber structure, which has potential applications in mode-division multiplexed systems and research of multimode nonlinear effect.

Analysis of multimode oscillations caused by subsynchronous resonance on generator shaft

Analysis of multimode oscillations caused by subsynchronous resonance on generator shaft

Super-mode noise suppression for coupled optoelectronic oscillator with optoelectronic hybrid filter

A novel scheme to implement the super-mode noise suppression for coupled optoelectronic oscillator (COEO) utilizing an optoelectronic hybrid filter (OEF) is proposed and experimentally demonstrated. The OEF is made up of a multi-mode optoelectronic oscillator, incorporated in the COEO loop to serve as a channelized RF filter, while the fiber laser in the COEO can be viewed as another channelized RF filter of high Q. The cascading of the two equivalent channelized RF filters can greatly improve the out-of-band rejection ratio of the combined filter and restrain the adjacent mismatched modes in the oscillating loop. In the experiment, a 9.955 GHz RF signal with the side mode suppression ratio of larger than 82.6 dB is obtained, and the super-mode noise spur at an offset frequency of 5.9 MHz is suppressed 15 dB to -145 dBc/Hz level compared with the conventional COEO.

Quantized pseudomodes for plasmonic cavity QED.

We present a quantized pseudomode theory for solving system-level cavity quantum electrodynamics with quantum emitters coupled to plasmonic resonators. Exploiting the Green function response of a silver nanoparticle and an exact solution for the input-output coupling, we study the non-Markovian coupling regimes of multi-mode vacuum Rabi oscillations and coherently pumped multi-photon resonances from the higher lying ladder states of collective plasmon modes. The nonlinear pumping regime also facilitates pronounced population inversion of a single two-level atom through multiphoton resonances dominated by dark plasmons.

Relationships between music training, speech processing, and word learning: a network perspective.

Numerous studies have documented the behavioral advantages conferred on professional musicians and children undergoing music training in processing speech sounds varying in the spectral and temporal dimensions. These beneficial effects have previously often been associated with local functional and structural changes in the auditory cortex (AC). However, this perspective is oversimplified, in that it does not take into account the intrinsic organization of the human brain, namely, neural networks and oscillatory dynamics. Therefore, we propose a new framework for extending these previous findings to a network perspective by integrating multimodal imaging, electrophysiology, and neural oscillations. In particular, we provide concrete examples of how functional and structural connectivity can be used to model simple neural circuits exerting a modulatory influence on AC activity. In addition, we describe how such a network approach can be used for better comprehending the beneficial effects of music training on more complex speech functions, such as word learning.

Filterless low-phase-noise frequency-quadrupled microwave generation based on a multimode optoelectronic oscillator

Filterless low-phase-noise frequency-quadrupled microwave generation based on a multimode optoelectronic oscillator

Spectral properties and breathing dynamics of a few-body Bose–Bose mixture in a 1D harmonic trap

We investigate a few-body mixture of two bosonic components, each consisting of two particles confined in a quasi one-dimensional harmonic trap. By means of exact diagonalization with a correlated basis approach we obtain the low-energy spectrum and eigenstates for the whole range of repulsive intra- and inter-component interaction strengths. We analyse the eigenvalues as a function of the inter-component coupling, covering hereby all the limiting regimes, and characterize the behaviour in-between these regimes by exploiting the symmetries of the Hamiltonian. Provided with this knowledge we study the breathing dynamics in the linear-response regime by slightly quenching the trap frequency symmetrically for both components. Depending on the choice of interactions strengths, we identify 1 to 3 monopole modes besides the breathing mode of the centre of mass coordinate. For the uncoupled mixture each monopole mode corresponds to the breathing oscillation of a specific relative coordinate. Increasing the inter-component coupling first leads to multi-mode oscillations in each relative coordinate, which turn into single-mode oscillations of the same frequency in the composite-fermionization regime.

A Two-Level Forced Oscillations Source Location Method Based on Phasor and Energy Analysis

Forced oscillations (FOs), which are caused by sustained cyclic disturbances, threaten the safe and stable operation of power system. The most effective way to eliminate FOs is to locate the oscillation source and take corresponding measures. In this paper, a two-level method for forced oscillations source location is proposed. First, the energy structure of the generator is analyzed based on Hamiltonian function. The energy injected into generator is divided into two parts, i.e., energy injected by the prime mover system and excitation system. Then, as to the energy injected into power grid, the phasor relation between the variances of branch variables is analyzed to identify the energy flow direction. Based on the former analysis, the proposed method includes two levels. The bus level location of the oscillation source is realized according to the energy flow direction obtained with phasor analysis. Furthermore, the control device level location within the generator is realized according to the injected energy of the prime mover system and excitation system of generator. This method has good robustness for the measurement of data quality issue and is able to locate multimode oscillations with multiple disturbances. The simulation results in four-machine two-area system, East China power grid and the WECC 179-bus system as well as the comparison with classic energy-based method demonstrate the effectiveness and improvement of the proposed method.

Temporal Variation of Atmospheric Static Electric Field and Air Ions and their Relationships to Pollution in Shanghai

ABSTRACT Atmospheric electric field (EF) and air ions were measured in Shanghai from December 2014 to December 2015 to examine the influence of particulate pollutants. Fair-weather EF exhibits a diurnal variation of multi-modal oscillations in spring, summer, and autumn. Linear correlation analyses show that the local meteorological conditions of relative humidity, temperature, pressure and wind affect atmospheric electric field, with wind direction exhibiting the highest correlation coefficient. Atmospheric EF is significantly higher in the west compared with that in the east, as the air mass from inland areas carries more polluted aerosols. Air ion concentrations are generally higher in the daytime than at night and correlate with meteorological factors. Atmospheric EF undergoes a substantial fluctuation in polluted periods, but remains flat under clean conditions. Overall, in areas with pollution, the atmospheric EF gradually increases with increased pollution or increased particle loading (e.g., PM2.5), a useful indicator of air pollution. The concentration of PM2.5 is positively correlated with the atmospheric electric field under polluted conditions, because as the concentration of aerosol particles declines, the concentrations of small ions and the atmospheric conductivity decrease accordingly, thus causing an increase in the electric field. Overall, aerosol particles, air ions, and their interactions in the presence of various meteorological parameters can have local effects on the atmospheric electric field.

Investigation of vibration machine movement with a multimode oscillation spectrum

The necessity of solving the problem of increasing the efficiency and reducing the energy intensity of the working process of the vibration machine movement is substantiated. A new principle is proposed for transferring energy from the shape-forming surfaces to the processing medium by implementing highly effective modes and parameters. A constructive scheme and a definite mathematical model of the frame of the vibration machine have been developed, realizing complex spatial oscillations. The oscillations of this shape-forming surface are investigated using the finite element method. The finite element model is composed by approximating all load-bearing elements of the frame with beam end elements. Loads created by pneumatic centrifugal exciters of high-frequency oscillations are determined. The basic waveforms of the shape-forming surfaces that are realized at 18.79 Hz, 18.89 Hz and 19.71 Hz, respectively, are investigated and determined. The distribution of the vibration amplitudes along the perimeter of the frame is estimated at the excitation frequency of 182.5 Hz. The rational values of the amplitude of oscillations for the realization of an effective process of concrete mixture compaction are found. The amplitude of the oscillations is 0.0002...0.0005 m. The obtained vibrations show the presence of the multimode operation of the vibration machine. A definite direction of the purposeful use of one of the forms of natural oscillations is the shape-forming surfaces. The approach for creating high-performance vibration machines of a new generation is proposed. The ideology of implementing such regimes can be successfully applied in road construction for the construction of concrete roads