Beat Phenomenon Research Articles

Characterization of photo-induced anomalous Hall effect in the two-dimensional MoS2

We report the observation of a small but finite valley Hall effect (VHE) signal in two-dimensional MoS2 channels which is grown on SiO2/Si substrates under the circularly polarized light. And the angular dependence of VHE in two-dimensional MoS2 is studied. The VHE signal is a periodic function (period π) but with a phase shift, which confirms the presence of strong coupling between spin and valley. Furthermore, using a weak measurement under the condition of the optical circular dichroism, we find resembling beating phenomena, which suggests that a static electric field can induce oscillations. It is interesting that the interval time of the peak starts from an certain value, which is related to carrier densities. We suppose that this certain value is explained by a quasi-two-dimensional electron gas model, which is based on the Hall conductance quantized value of e2/h. To our knowledge, it is the first experiment that realizes such quantized values.

富山湾沿岸における長周期水位変動について

It is known that there are periodic water level fluctuations off the coast of Toyama Wan. Investigation on the periodic water level fluctuations was carried out to prevent wave disasters by wave observations and wave generating experiment. Water levels were observed at three points of Toyama New Port, Iwasehama and Iida Wan. The water level fluctuations with the periods of about 10 minutes or more were investigated using the water level data observed at the three points and wave generating experiment data.The results of this investigation are:(1)The water level fluctuations with the periods from about 10 minutes to about 1 hour are proper oscillations driven by water level fluctuations due to moving low atmospheric pressure or earthquake, in horizontal shallow water off the coast.(2)Proper oscillation with the period of about 36 minutes between the Toyama coast and the southern coast of apex of Noto peninsula, causes a beat phenomenon with the same period as the proper oscillation period to swells which invade Toyama Wan from north.(3)There is greater tsunami risk on the coast of Iida Wan as compared with the Toyama coast.

Seismo-ionospheric anomalies and implications from recent GNSS observations in India and South-East Asia

The lithosphere and the atmosphere/ionosphere, continuously exchange energy through various coupling mechanisms. Earthquake creates waves of energy, e.g. direct shock acoustic waves (SAWs) and Rayleigh wave induced acoustic waves (RAWs). In the event of an earthquake occurring beneath the sea, atmospheric gravity waves (AGWs) are also generated. If the earthquake is large enough (Mw > 6), SAWs, RAWs and AGWs induce detectable ionospheric plasma perturbations. Inferring the seismological information from these seismo-ionospheric manifestations is the subject that pertains to ionospheric seismology. Both ground and satellite based advanced radio techniques are being used in monitoring ionospheric plasma perturbations. In this study, seismo-ionospheric anomalies and implications from recent GNSS observations in India and South-East Asia are discussed, mainly pertaining to the following. (1) From the ionospheric plasma response to 2015 Nepal earthquake, the estimated group velocity for Andaman and Indian shield regions are 2100 ms−1 and 3900 ms−1 respectively and validated from ground measurements. (2) Atmospheric acoustic resonance at 4.0 mHz and a train of wave packet of TEC variation resulting from the beat phenomenon observed at the site ‘umlh’ and (3) GNSS-based tsunami warning which is going to be promising tool in augmenting the existing tsunami warning systems.

Limiting Phase Trajectories as an Alternative to Nonlinear Normal Modes

We discuss a recently developed concept of limiting phase trajectories (LPTs) allowing a unified description of resonance, highly non-stationary processes for a wide range of classical and quantum dynamical systems with constant and varying parameters. This concept provides a far going extension and adequate mathematical description of the well-known linear beating phenomenon to a diverse variety of nonlinear systems ranging from classical multi-particle models to nonlinear quantum tunneling. While stationary (and non-stationary, but non-resonant) oscllations can be described in the framework of non-linear normal modes (NNMs) concept, it is not so in the considered case of resonant non-stationary processes. In the latter case which is characterized by intense energy exchange between different parts of a system, an additiional slow time scale appears. The energy exchange proceeds in this time scale and can be identified as strong modulation of the fast oscillations. The aforementioned resonant non-staionary prcesses include, e.g., targeted energy transfer, non-stationary vibrations of carbon nanotubes, quantum tunneling, auto-resonance and non-conventional synchronization. Besides the non-linear beating, the LPT concept allows one to find the conditions of transition from intense energy exchange to strongly localized (e.g. breather-like) excitations. A special mathematical technique based on the non- smooth temporal transformations leads to the clear and simple description of strongly modulated regimes. The role of LPTs in the theory of resonance non-stationary processes turns out to be similar to that of NNMs in stationary case.As an example we present results of analytical and numerical study of planar dynamics of a string with uniformly distributed discrete masses without a preliminary stretching. Each mass is also affected by grounding support with cubic characteristic (which is equivalent to transversal unstretched string). We consider the most important case of low-energy transversal dynamics. This example is especially instructive because the considered system cannot be linearized. Adequate analytical description of resonance non-stationary processes which correspond to intensive energy exchange between different parts of the system (clusters) in low frequency domain was obtained in terms of LPTs. We have revealed also in these terms the conditions of energy localization on the initially excited cluster. Analytical results are in agreement with the results of numerical simulations. It is shown that the considered system can be used as an efficient energy sink.

The brain responses to different frequencies of binaural beat sounds on QEEG at cortical level.

Beat phenomenon is occurred when two slightly different frequency waves interfere each other. The beat can also occur in the brain by providing two slightly different frequency waves separately each ear. This is called binaural beat. The brain responses to binaural beat are in discussion process whether the brain side and the brain area. Therefore, this study aims to figure out the brain responses to binaural beat by providing different binaural beat frequencies on 250 carrier tone continuously for 30 minutes to participants and using quantitative electroencephalography (QEEG) to interpret the data. The result shows that different responses appear in different beat frequency. Left hemisphere dominance occur in 3 Hz beat within 15 minutes and 15 Hz beat within 5 minutes. Right hemisphere dominance occurs in 10 Hz beat within 25 minute. 6 Hz beat enhances all area of the brain within 10 minutes. 8 Hz and 25 Hz beats have no clearly responses while 40 Hz beat enhances the responses in frontal lobe. These brain responses can be used for brain modulation application to induce the brain activity in further studies.

징의 타격 위치와 강도에 따른 음향 분석

본 논문은 다양한 타격 강도와 위치에 따른 징의 음향 차이를 소프닝과 맥놀이 분석을 통해 살펴본다. 타격 강도는 아주 강하게, 강하게, 약하게로 구분하였고 타격 위치는 가운데, 위, 오른쪽으로 구분하였으며 분석에는 스펙트로그램을 사용하였다. 소프닝은 징의 가운데를 강하게 타격할수록 명확하게 관측되었고 주파수 이동 폭은 타격 강도와 주파수에 비례하였다. 이러한 현상은 배음에서 두드러졌으며 다른 부분음에서는 불규칙적으로 발생하였다. 맥놀이는 초기 맥놀이와 후기 맥놀이로 분류할 수 있었으며 가운데를 타격할 때보다 측면을 타격할 때 더 넓은 주파수 대역에서 더 많은 맥놀이가 발생한다는 것을 알 수 있었다. 또한 가운데를 타격한 경우 초기 맥놀이에 영향을 주는 배음 주변의 성분들이 있음을 밝혔다. This paper describes an acoustic analysis of a Jing, Korean percussion instrument, according to different drive point and blow strength, and this analysis is focused on the softening and beat phenomena. Three kinds of blow strength (very strong, strong, and weak) and three locations of drive point (center, up, and right) are applied, and the spectrogram function built in Matlab is utilized to analyzing the softening and beat of target sounds. The stronger blow you drive to the center of the Jing, the more clearly softening is observed. Frequency shifting is increased proportionally to the blow strength and frequency and it is stand out on the harmonics in contrast with that of other partials. Beat of the Jing can be classified into the early beat and late beat. The beats by the outside driven Jing are distributed in wider frequency band than the beats by the center driven Jing. In addition, it is observed that the early beat is affected by few specific partials developed around harmonics for the center driven Jing.

Coupling of transit time instabilities in electrostatic confinement fusion devices

A model of the behavior of transit time instabilities in an electrostatic confinement fusion reactor is presented in this letter. It is demonstrated that different modes are excited within the spherical cathode of a Farnsworth fusor. Each of these modes is dependent on the fusion products as well as the acceleration voltage applied between the two electrodes and they couple to a resulting oscillation showing non-linear beat phenomena. This type of instability is similar to the transit time instability of electrons between two resonant surfaces but the presence of ions and the occurring fusion reactions alter the physics of this instability considerably. The physics of this plasma instability is examined in detail for typical physical parameter ranges of electrostatic confinement fusion devices.

Wideband Modeling, Field Measurement, and Simulation of a 420-kV Variable Shunt Reactor

A 420-kV gapped-core five-legged variable shunt reactor is modeled in the frequency range 5 Hz-10 MHz based on frequency sweep measurements and curve fitting using rational functions. Comparison with time-domain measurements at reduced voltage shows that the model can accurately predict the transient behavior of the shunt reactor, both for impinging overvoltages and circuit-breaker transient recovery voltages. Among the observations is that mutual coupling between the phases leads to a beat phenomenon in the reactor voltage following disconnection. Representing the shunt reactor by an LC parallel circuit leads to unrealistic results for steep-fronted incoming waves and high-frequency oscillating overvoltages, and for the attenuation of the transient recovery voltage following disconnection.

Control of chaos in a semiconductor laser using the Faraday effect

We present a novel laser system with an external cavity delay feedback semiconductor laser under the control of Faraday effect. To study the chaos-control and chaos-anti-control of the laser system, we construct two types of optical path structures as two control systems of the negative feedback and the ring cavity by using the combination of the Faraday effect controller, the polarizer and the mirror. We give a physical model of laser dynamics with the delayed negative feedback or the delayed positive feedback under the control of Faraday effect. Using the Faraday effect principle of magnetic rotation and the characteristics of the system, we can achieve the double parameter control of the laser. We can shift the optical rotation angle by operating Faraday effect controller and modulate the optical delay time by performing the mirror to vary the double parameter. The laser can be controlled to a double-cycle, a tri-cycle, a multi-cycle, and beat phenomenon by using the control system of the negative feedback, etc. The periodic laser can be anti-controlled to chaos by using the control system of the ring cavity. Some control and anti-control areas formed with the distribution of magnetic rotation angular are found in the laser. For the negative feedback system under the some control cases, the chaotic laser can be controlled to some tri-cycle states between π/14 and π/9. By shifting the control parameters, the chaotic laser can be controlled to some cycle-7 states between 10π/133 and 10π/108 and another tri-cycle region is found from 10π/96 to π/8. Under other control parameters, the chaotic laser can be controlled to some cycle-8 or cycle-9 states. For the ring cavity system under the some control cases, the dual-cycle region is between π/10 and π/30, the cycle-6 region is between π/4 and π/5, the cycle-13 region is found to be from π/6 to 10π/76. In another control case, the large chaos-anti-control region is found to exist between 0 and π/12. Dynamic controls of the chaotic laser and the periodic laser are also studied while the transformation and evolution of laser states are discussed. It is found that it takes about 10 ns for one state to change into another state when the control operation is applied to the laser. The control method is very useful for studying chaos-control, new laser system and its application.

Numerical Study of Self-Induced Rotary Sloshing Caused by an Upward Periodic Jet in a Cylindrical Container

Jet-induced rotary sloshing caused by an upward periodic jet in a partially filled cylindrical container is computationally simulated for investigating a stable sloshing condition and its basic characteristics under various values of AQ, Tjet and QL0 in a given function of the inlet jet: QL(t) = AQ sin[(2π /Tjet)t] + QL0. Then, the stable rotary sloshing is found not to be observed when either the minimum or maximum flow rate of QL(t) reaches a threshold value of the sloshing-occurrence boundary. The free surface motion like a beat phenomenon caused by interference between the sloshing wave and the periodicity of the inlet jet is also observed in the signal of the free surface elevation. Furthermore, the period of the envelope seems to match with Tjet, and this phenomenon is successfully formulated by the superposition between the sloshing wave and the free surface wave due to the periodic inlet jet.

Study on the relationship between coherent population beating signal and the coherence of ground-state hyperfine sublevels

Coherent population beating (CPB) phenomenon occurs in a typical three-level system. When the frequency difference between two coherent pumping laser fields has a certain detuning from the ground-state hyperfine splitting, the excited state population will experience a transient oscillation before reaching equilibrium, and the oscillation frequency is equal to the detuning. The CPB phenomenon enables us to directly obtain the beat frequency between the measured radio frequency (RF) signal and the atomic transition frequency. Then we can get the standard frequency by compensating the beat frequency to the RF. We propose a scheme to implement atomic clock based on the CPB phenomenon in 2009, and the scheme has been implemented. When this effect is used to achieve an atomic clock, the frequency stability is directly related to the amplitude and SNR (signal to noise ratio) of the CPB signal. Influence of the ground-state hyperfine sublevels' coherence on CPB signal is theoretically simulated and experimentally investigated in this paper. A formula of the CPB signal is derived by using the semi-classical model of the interaction of atoms with light, and the theoretical simulation is done using the formula obtained. In the experiment two coherent pumping laser fields are used to interact with 87Rb atoms. A CPB process includes the coherence build-up and the CPB stimulation. The coherence of the ground-state hyperfine sublevels is achieved by controlling the pumping time of the coherent laser fields that are resonant to the ground-state hyperfine sublevels. With this method, the relationship between CPB signal and coherence of the ground-state hyperfine sublevels can be observed. Result shows that the amplitude of CPB signal is proportional to the ground-state hyperfine sublevels' coherence. The hign quality CPB signal can be achieved when the CPB stimulation is started with a pure coherent population trapping (CPT) state. In the CPB process, the coherence build-up rate is approximately equal to the coherence decay rate. So a 50% duty cycle square wave can be used to modulate the RF, and the period of the square wave had better be twice of the decay time of the ground-state hyperfine sublevels' coherence. To improve the SNR of CPB signal and the stability of atomic frequency standard, the ground-state hyperfine sublevels' coherence must be built up, improved, and maintained before the CPB stimulation. The feasibility of applying CPB phenomenon to the weak magnetic field measurement and other applications is also discussed in this paper.

A concept of limiting phase trajectories and description of highly non-stationary resonance processes

We discuss a recently developed concept of limiting phase trajectories (LPTs) allowing a unified description of resonance, highly non-stationary processes for a wide range of classical and quantum dynamical systems with constant and varying parameters. This concept provides a far going extension and adequate mathematical description of the well-known linear beating phenomenon to a diverse variety of nonlinear systems ranging from classical multi-particle models up to nonlinear quantum tunneling. Contrary to stationary and non-stationary, but non-resonance oscillations, described in the framework of nonlinear normal modes (NNMs) concept, the non-stationary processes under consideration are characterized by strong modulation and intense energy exchange between different parts of the system. They include, e.g. targeted energy transfer, non-stationary vibrations of carbon nanotubes, quantum tunneling, auto-resonance and non-conventional synchronization. Besides the non-linear beating, the LPT concept allows to find the conditions of transition from intense energy exchange to strongly localized (e.g. breather-like) excitations. A special mathematical technique based on the non-smooth temporal transformations leads to the clear and simple description of strongly modulated regimes. The role of LPTs in the theory of resonance non-stationary processes turns out to be similar to that of NNMs in stationary case.

Quantum Interference of Surface-Induced Friedel Oscillations Enhanced by Fermi-Surface Nesting in Layered Manganites

Imbalance of Mn3+ and Mn4+ ions between surface and bulk in layered manganites is investigated on the basis of an orbital degenerate double-exchange model with surfaces. For two types of t2g spin structures, the number of Mn4+ ions on the surface is found to be larger than that in the bulk, explained by the surface-induced Friedel oscillation. In particular, for the sheet-type antiferromagnetic state, quantum beat phenomenon appears due to the interference among Friedel oscillations and the number of Mn4+ ions tends to increase on the surface. The present results are believed to be useful to develop high-efficient cathodes in Li-ion batteries and catalysts.

Dynamic Modeling of an Insect Wing Subject to Three-Dimensional Rotation

A dynamic model of an insect wing is developed treating the wing as a deformable body subject to three-dimensional finite rotation about a fixed point at the base of the wing. Discretization of a stationary wing is first conducted via finite element analysis to determine the natural frequencies and mode shapes of the wing. By formulating and discretizing the kinetic and potential energy, we derive the equation of motion governing the modal response of a flapping wing using Lagrange's equation. The equation of motion indicates Coriolis, Euler, and centrifugal forces resulting from the finite rotation are responsible for the wings elastic deformation. Numerical integration reveals a beat phenomenon that arises from the Coriolis excitation in the first vibration mode. The beat phenomenon is insensitive to yaw amplitudes and nonzero initial conditions but diminishes in the presence of damping. The beat phenomenon can potentially be used to estimate gyroscopic forces.

Nonlinear lateral vibrations of a deploying Euler–Bernoulli beam with a spinning motion

The nonlinear lateral vibrations of a beam deploying from a fixed rigid hub are analyzed when the beam has a spinning motion. Previous studies do not consider the nonlinear coupled effect between axial and lateral displacements when analyzing the vibration behavior of a deploying beam with spin. In contrast, the present study considers the nonlinear coupling effect of the axial and lateral displacements for a deploying beam with spin to investigate the vibration behavior more exactly and comprehensively. The Euler–Bernoulli beam theory and von Karman nonlinear strain theory are used together to develop a new nonlinear model. The differences in dynamic response between the linear and nonlinear models are compared, and the effects of physical parameters on the differences are investigated. In addition, the beat phenomenon of a deploying beam with spin is studied. Significant differences in dynamic responses are observed between the proposed nonlinear and previous linear models. It is found that the beat phenomenon is caused by the interference of two close natural frequencies: the first and second natural frequencies of a spinning beam.

Tunable Fano Resonance in Rod-Ring Plasmonic Nanocavities

Tunable Fano resonances in the gold rod-ring plasmonic nanocavities with strong coherent coupling are demonstrated by finite-difference time-domain (FDTD) method. For one rod-one ring nanocavity, symmetry breaking activates the high-order plasmon modes in the ring and causes a Fano resonance with a dip in the extinction spectrum of the cavity by the coherent coupling between the bright rod mode and dark ring mode. The addition of a non-resonant rod introduces a second dark mode, which could be successively excited by the first dark ring mode, and produces double Fano resonances. By adjusting the rod number and configuration of the nanocavity, the extinction line shape can be controlled and the near-field distribution can be dramatically modified. An intriguing phenomenon of superposition beats in the plasmon damping process is revealed, which induces an energy swap between the rod and ring. The antenna effect of the resonant rod as well as the energy transfer and distribution in the nanocavities are also discussed.

Beat: A Nonlinear Thermoacoustic Instability in Rijke Burners

A beat phenomenon has been observed in Rijke burners with premixed flames. This oscillation is distinguished from the stable limit cycles and has very low frequency (~ 1 Hz) amplitude modulation in acoustic pressure fluctuations. The beat in the thermo-acoustic system is a nonlinear and self-excited oscillation. To understand the mechanisms of self-excited beat, a forced beat by superimposing external acoustic perturbations on a stable limit cycle has been measured, and the pressure oscillations and heat release rate fluctuations in the forced beat are compared with those in the self-excited beats. The power spectrums and the joint time-frequency diagrams highlight the differences of these two types of beats. For the self-excited beat, the low frequency flames pulsations and the corresponding heat release rates have been investigated. The pulsation effects on the acoustic pressure amplitude variation and the fundamental frequency variation are discussed. Finally, the effects of heat powers and equivalence...

43.3: Electrostatic Tactile Display Using Beat Phenomenon of Voltage Waveforms

AbstractWe propose an electrostatic tactile display, which presents regional stimulation. The 240‐Hz electrostatic force is generated by the beat phenomenon in a region where excited X electrodes cross excited Y electrodes, which presents tactile sensation to users. This display can accommodate multi‐touch tactile interaction with visual information.

Analyzing the acoustic beat with mobile devices

In this column, we have previously presented various examples of how physical relationships can be examined by analyzing acoustic signals using smartphones or tablet PCs.1–3 In this example, we will be exploring the acoustic phenomenon of small beats, which is produced by the overlapping of two tones with a low difference in frequency Δf. The resulting auditory sensation is a tone with a volume that varies periodically. Acoustic beats can be perceived repeatedly in day-to-day life and have some interesting applications. For example, string instruments are still tuned with the help of an acoustic beat, even with modern technology. If a reference tone (e.g., 440 Hz) and, for example, a slightly out-of-tune violin string produce a tone simultaneously, a beat can be perceived. The more similar the frequencies, the longer the duration of the beat. In the extreme case, when the frequencies are identical, a beat no longer arises. The string is therefore correctly tuned. Using the Oscilloscope app,4 it is possible to capture and save acoustic signals of this kind and determine the beat frequency fS of the signal, which represents the difference in frequency Δf of the two overlapping tones (for Android smartphones, the app OsciPrime Oscilloscope can be used).

Social Modulation of Circadian Synchronization and Temporal Perception in Complete Isolation

Social Modulation of Circadian Synchronization and Temporal Perception in Complete Isolation