Resonance Frequency Of Oscillations Research Articles

A Research on Principle and Parameter Design about a Kind of Antenna Working in Water

Magnetic antenna has many advantages such as small volume, high SNR and no grounding needed. Especially in some special environment such as water, the superiority is more obvious. According to its basic principle, this article discusses the structure characteristics, pivotal parameter and fundamental devising thinking. Its operational principle is simple. There will be a response current when the magnetic line of flux passes through the hoop. Its resonance oscillation frequency is decided by the inductance and the electric capacity in the circuit. The coiling way and circle are the critical factors to its receiving feature except the permeability, the length and the thickness of magnetic material. The design must be sure impedance matching in order to keep the signal out in the most power.

Dynamics of Carbon Nanotube Tipped Atomic Force Microscopy in Liquid

Carbon nanotubes (CNT) are proper tips for atomic force microscopes (AFMs) as a result of their small tip diameter, high aspect ratio, and high flexibility. For nanoscale imaging of soft biological specimens, a CNT tipped AFM is an ideal tool. In this article we review the application of CNTs as AFM tips and present related research about the forces applied from liquids on nanotubes. Then a dynamic mode CNT tipped AFM in liquid is modeled and simulated. The simulation results are compared with experimental results. For modeling and simulation, a continuous beam model and a forward-time simulation method are used. The simulation results show that when a CNT tip vibrates in liquid, the oscillation amplitude and resonance frequency are changed compared to the state of oscillation in air. The small structure of CNTs reduces the hydrodynamic forces, and the liquid environment reduces the adhesive forces between the CNT tip and the sample. These two factors make CNTs a good choice as an AFM tip.

Intensity noise of erbium-doped fiber laser based on full quantum theory

Traditionally, by means of full quantum theory, we present the intensity noise transfer function of an Er-doped fiber laser, on the basis of which we analyze the spectrum of the intensity noise. Our theoretical results are in agreement with the existing experiment results. This model explains not only how the noise is produced, but also how the spontaneous emission and dipole fluctuations have an effect on the output noise, which cannot be explained via rate equation theory. We analyze the physical sources of various contributions to the noise spectrum as well. The simulation results show that the noise of the Er-doped fiber laser mainly consists of the vacuum noise resulting from the output coupling, dipole fluctuation noise, the pump source intensity noise, and the spontaneous emission from the upper level to the ground level, which provides the theoretical basis for noise suppression. Compared to the solid laser, the Er-doped fiber laser shows lower resonant relaxation oscillation frequency.

Chronic Ketamine Reduces the Peak Frequency of Gamma Oscillations in Mouse Prefrontal Cortex Ex vivo

Abnormalities in EEG gamma band oscillations (GBO, 30–80 Hz) serve as a prominent biomarker of schizophrenia (Sz), associated with positive, negative, and cognitive symptoms. Chronic, subanesthetic administration of antagonists of N-methyl-D-aspartate receptors (NMDAR), such as ketamine, elicits behavioral effects, and alterations in cortical interneurons similar to those observed in Sz. However, the chronic effects of ketamine on neocortical GBO are unknown. Thus, here we examine the effects of chronic (five daily i.p. injections) application of ketamine (5 and 30 mg/kg) and the more specific NMDAR antagonist, MK-801 (0.02, 0.5, and 2 mg/kg), on neocortical GBO ex vivo. Oscillations were generated by focal application of the glutamate receptor agonist, kainate (KA), in coronal brain slices containing the prelimbic cortex. This region constitutes the rodent analog of the human dorsolateral prefrontal cortex, a brain region strongly implicated in Sz-pathophysiology. Here we report the novel finding that chronic ketamine elicits a reduction in the peak oscillatory frequency of KA-elicited oscillations (from 47 to 40 Hz at 30 mg/kg). Moreover, the power of GBO in the 40–50 Hz band was reduced. These findings are reminiscent of both the reduced resonance frequency and power of cortical oscillations observed in Sz clinical studies. Surprisingly, MK-801 had no significant effect, suggesting care is needed when equating Sz-like behavioral effects elicited by different NMDAR antagonists to alterations in GBO activity. We conclude that chronic ketamine in the mouse mimics GBO abnormalities observed in Sz patients. Use of this ex vivo slice model may be useful in testing therapeutic compounds which rescue these GBO abnormalities.

利用弛豫振荡频率和输出功率测量单频钛宝石激光器的腔内损耗

利用弛豫振荡频率和输出功率测量单频钛宝石激光器的腔内损耗

On the nature of global plasma oscillations in a tokamak. Part II: Spatial structure and propagation of perturbations observed at the T-10 tokamak

Large-scale plasma oscillations (so-called MHD oscillations) observed at the T-10 tokamak are investigated. The central electron cyclotron heating was used to enhance oscillations at the m/n = 1/1 mode with the goal of determining the internal characteristics of the process. The spatially resolved electron cyclotron emission diagnostics allowed analyzing the propagation characteristics of plasma perturbations. The experiments have revealed that excitation of oscillations in a particular mode occur simultaneously in the entire area located within the corresponding rational magnetic surface. The propagation of plasma perturbations along the torus is found to be inhomogeneous. The electron cyclotron emission diagnostics allowed finding eigen (resonance) frequencies of plasma oscillations from the parameters of their inhomogeneous propagation in the plasma core and comparing them with spectra of oscillations of the magnetic field induced by the plasma current in the edge plasma, which were recorded by magnetic probes. It is established that the frequencies of eigenmodes are independent of the electron temperature, plasma density, and auxiliary heating power. Even spatial harmonics of the principal magnetic surface are observed under strong excitation of oscillations. The rational magnetic surfaces that determine oscillation harmonics retain their position during the entire steady-state phase of the total plasma current in spite of the strong sharpening of the temperature profile due to central heating.

Nature of the diamagnetic maximum in the temperature dependences of the magnetic susceptibility of crystals of (Bi2 − x Sb x )Te3 alloys (0 < x < 1)

The temperature dependences of the magnetic susceptibility χ of crystals of (Bi2 − xSbx)Te3 alloys (0 < x < 1) are studied using a SQUID magnetometer in the temperature range from 2 to 400 K with the parallel and perpendicular orientations of the vector of magnetic field strength H relative to the trigonal axis of the crystal C3 (H ‖ C3 and H ⊥ C3). It is found that the diamagnetic susceptibility of the samples with x = 0.2 (Bi1.8Sb0.2Te3) and x = 0.5 (Bi1.5Sb0.5Te3) increases in the range from 50 K to temperatures preceding the emergence of intrinsic conductivity (250 K). It is found that the diamagnetic maximum manifests itself in the same temperature range, in which an anomalous increase in the Hall coefficient is observed. It is shown that the nature of the diamagnetic maximum is associated with the nonparabolicity of the energy spectrum of light diamagnetic holes, a decrease in whose concentration is accompanied by a decrease in their effective masses, which provides an increase in the diamagnetic susceptibility with increasing temperature. These results are confirmed by the dynamics of the temperature variation in the resonance frequency of plasma oscillations of free charge carriers.

Electron Fluctuation Induced Resonance Broadening in Nano Electromechanical Systems: The Origin of Shear Force in Vacuum

This article presents a study of the poorly understood "shear-force" used in an important class of near-field instruments that use mechanical resonance feedback detection. In the case of a metallic probe near a metallic surface in vacuum, we show that in the 10-60 nm range there is no such a thing as a shear-force in the sense of the nonconservative friction force. Fluctuations of the oscillator resonance frequency, likely induced by local charge variations, could account for the reported effects in the literature without introducing a dissipative force.

Piezoelectric Transformer with Magnetic Feedback on Gain and Efficiency

Development of sensors technology steady trends toward miniaturization and multifunctionality. The presented in this work new sensor configurations, fabricated from subsequent layers of piezoelectric ceramics and magnetostrictor, was realised by superposition two different effects - piezoelectric and magnetostrictive in one compact structure of piezoelectric transformer. This construction exhibits many interesting and unusual piezoelectric and magnetic properties. The oscillation amplitude, phase and resonance frequency are modified by magnetic field induced interaction forces. Additional advantage of this device is simplified construction, in which the vibration detection is realized avoiding any additional coil for magnetic field generation as in previous solutions. A demonstration of voltage gain and efficiency, as well as gain reversal via the application of magnetic field across a multiferroic heterostructure is presented.

The effect of rotation on resonant frequency of interfacial oscillation of a droplet using electrostatic levitator

Under the microgravity environment, liquid can be treated without container due to weightlessness. Therefore physical properties of a material are expected to be measured with a high accuracy. In surface tension measurement of levitated droplet, it is calculated by using the formula derived under the assumption of linearity of the resonant frequency. However, it is indicated that the resonant frequency of a droplet changes due to oscillation and rotation. And mechanism of frequency shift has not been revealed yet. The final goal of this study is to make clear the mechanism of frequency shift. A droplet is levitated by using electrostatic levitator, and induced to oscillate and rotate. Resonant frequency, amplitude, angular velocity and aspect ratio are measured from droplet motion. It is confirmed oscillation and rotation effect on resonant frequency. And the frequency shift becomes zero under the appropriate combination of amplitude and angular velocity. It is experimentally clarified that the resonant frequency is strongly related with time average of aspect ratio.

Normal mode splitting and ground state cooling in a Fabry—Perot optical cavity and transmission line resonator

Optomechanical dynamics in two systems which are a transmission line resonator and Fabrya—Perot optical cavity via radiation—pressure are investigated by linearized quantum Langevin equation. We work in the resolved sideband regime where the oscillator resonance frequency exceeds the cavity linewidth. Normal mode splittings of the mechanical resonator as a pure result of the coupling interaction in the two optomechanical systems is studied, and we make a comparison of normal mode splitting of mechanical resonator between the two systems. In the optical cavity, the normal mode splitting of the movable mirror approaches the latest experiment very well. In addition, an approximation scheme is introduced to demonstrate the ground state cooling, and we make a comparison of cooling between the two systems dominated by two key factors, which are the initial bath temperature and the mechanical quality factor. Since both the normal mode splitting and cooling require working in the resolved sideband regime, whether the normal mode splitting influences the cooling of the mirror is considered. Considering the size of the mechanical resonator and precooling the system, the mechanical resonator in the transmission line resonator system is easier to achieve the ground state cooling than in optical cavity.

Вдосконалення методів визначення частотно-інерційних та кінематичних властивостей систем з розподіленими параметрами шляхом аналізу їх власних коливань

Free vibrations of the thin disc are studied. The equation for thick discs which include the inertia of rotation and the slide is determined. The dependencies of the resonant frequency of oscillation with knotty circles are made.

Research on Performance of Interdigitated Electrodes Piezoelectric Oscillator

A new type of oscillator is presented in paper which integrates the interdigitated electrode (IDE) into conventional piezoceramic oscillator. Some IDE piezoelectric oscillators are prepared from PZT-5 with length=56mm, width=15mm and thickness=1mm. The dimensions of IDE are 0.75mm space and 0.5mm. The conventional piezoelectric oscillators are also prepared with the same material and dimensions for comparison. The HP4294A High-frequency Impedance Analyzer and DU-20 Temperature-controlled Oil Bath are applied to explore the impedance of oscillator. The effect of temperature on the frequency of oscillator is researched. The results show that IDE piezoelectric oscillators have more resonant frequencies including overtone frequency and anti-resonance frequency. The resonant frequency of oscillators decreases as the temperature increase. The temperature coefficient of resonance frequency of conventional piezoelectric oscillators is -14%. The temperature coefficient of resonance frequency of IDE piezoelectric oscillators is -21%. The temperature stability of conventional piezoelectric oscillators is a little high.

Fine structure of one-dimensional periodic stratified flows

The stability of boundary flows occurring near an inclined plane or a cylinder executing longitudinal periodic oscillations is studied within the framework of a system of embedded models (homogeneous fluid, stratified viscous fluid, and fluid in the presence of diffusion). It is shown that in a stratified fluid the resonance boundary-oscillation frequency, at which the boundary layer thickness increases without bound, exists not only in the problem with a plane boundary but also in the case of oscillations of an inclined cylinder. Taking diffusion into account leads to the boundary layer splitting into viscous and diffusion sublayers with considerably different thicknesses and properties. Nevertheless, the fact itself of the existence of the resonance oscillation frequency turns out to be stable and the resonance takes place also in the models of stratified flows with allowance for diffusion.

Direct detection of Salmonella typhimurium on fresh produce using phage-based magnetoelastic biosensors

Current bacterial detection methods require the collection of samples followed by preparation and analysis in the laboratory, both time and labour consuming steps. More importantly, because of cost, only a limited number of samples can be taken and analyzed. This paper presents the results of an investigation to directly detect Salmonella typhimurium on fresh tomato surfaces using phage-based magnetoelastic (ME) biosensors. The biosensor is composed of a ME resonator platform coated with filamentous E2 phage, engineered to bind with S. typhimurium. The ME biosensors are wireless sensors, whose resonance oscillation and resonance frequency are actuated and detected through magnetic fields. The sensors used in this study were 0.028 mm × 0.2 mm × 1 mm in size. In this study, the tomato surface was spiked with S. typhimurium suspensions with concentrations ranging from 5 × 10 1 to 5 × 10 8 CFU/ml and then allowed to dry in air. The detection was conducted by directly placing ME measurement biosensors and control sensors on the spiked surface for 30 min in a humid environment. The control sensors were identical to the measurement biosensors, but without phage. Both measurement and control sensors were blocked with BSA to reduce non-specific binding. The resonance frequencies of both measurement and control sensors were measured prior to and after the placement of the sensors on the tomato. Shifts in the resonance frequency of the measurement biosensors were observed, while the control sensors showed negligible change. Scanning electron microscopy (SEM) was used to verify the specific binding of S. typhimurium to the biosensor. Results of multiple biosensor detection and corresponding analyzes showed statistically different responses between the measurement and control sensors for tomatoes spiked with S. typhimurium suspensions with concentrations of 5 × 10 2 CFU/ml and greater. This study demonstrates the direct detection of food-borne bacteria on fresh produce.

Resonance method of measuring shear viscoelastic properties of liquid media based on excitation of torsional oscillations in tubes

Possibilities of using torsional oscillations for measuring viscoelastic properties of liquids are discussed. The theory of torsional oscillations of an elastic tube filled with the media to be investigated possessing viscosity and shear elasticity is developed. It is shown that to determine a complex shear modulus it is sufficient to determine the resonance frequency and Q-factor of torsional oscillations. An experimental installation and the results of measurements of viscoelastic modulus of glycerin and oil of one oilfield within the temperature range from −10° to 60°C are given. The experimental installation allows measuring a viscoelastic modulus within the range of acoustic logging frequencies (10–20 kHz). The obtained results are compared with the results of rheometric measurements.

Analysis of Fringing Effect on Resonant Plasma Frequency in Plasma Wave Devices

The effect of fringing electric field due to the nonideality of the gate two-dimensional electron gas (2DEG) channel capacitance on the fundamental resonant frequency of plasma waves in a high-electron-mobility transistor (HEMT) channel was investigated. The spatial distribution of sheet electron density in the fringed region of the 2DEG channel and the expression for the fundamental resonant frequency of plasma oscillation were obtained. A cascaded transmission line (TL) equivalent circuit model was developed to represent the gated and ungated fringed regions of the HEMT 2DEG channel. Results of calculation and IsSpice simulation show that fringing effects can be the cause of the fundamental plasma frequency reduction. Thus, the developed fringing effect model improves the deviation between theoretical and experimental data.

Patterns by time diffraction grating in resonant oscillation spectrum of piezoelectric powders

Plastic deformation was induced in piezoelectric powders, whose resonant frequencies were moderately and widely spread, by applying large amplitude radio-frequency (RF) pulse sequences. The traces of them in the spectrum were described with the absolute values of the Fourier component of the applied pulses. The large amplitude oscillation brought about the change of oscillation characteristics of powders, the damping constants and the resonant oscillation frequencies. We tried to describe these results with the crystal dislocation contributions. And the readout of the changed absorption spectrum by the coherent pulses was experimentally achieved, which is expected by the inverse Fourier transformation of the resonant absorption spectrum induced.

Dependence of vortex phase transitions in mesoscopic Bi2Sr2CaCuO8 superconductor at tilted magnetic fields

A micron sized single crystal of the superconductor Bi2Sr2CaCuO8 was studied using silicon mechanical micro-oscillators at various tilt angles of the dc magnetic field with respect to the c axis of the sample. Different phases of the vortex matter were detected by measuring changes in the value and sign of the oscillator resonant frequency variation with temperature. We could explain the change in the sign of this variation at high temperatures as the transition from the 2D liquid of decoupled pancakes to a reversible 3D vortex lattice. The data indicates that this transition only depends on the magnetic field perpendicular to the superconducting layers while the dissipation involved in this process depends on the component parallel to them.

Dynamical Backaction of Microwave Fields on a Nanomechanical Oscillator

We measure the response and thermal motion of a high-Q nanomechanical oscillator coupled to a superconducting microwave cavity in the resolved-sideband regime where the oscillator's resonance frequency exceeds the cavity's linewidth. The coupling between the microwave field and mechanical motion is strong enough for radiation pressure to overwhelm the intrinsic mechanical damping. This radiation-pressure damping cools the fundamental mechanical mode by a factor of 5 below the thermal equilibrium temperature in a dilution refrigerator to a phonon occupancy of 140 quanta.