Resonance Frequency Of Oscillations Research Articles

Cure State Sensing of Polymethylmethacrylate Using a Vibrating Axial Probe.

A new axially vibrating sensor based on an audio voice coil transducer and a lead zirconate titanate (PZT) piezoelectric disc microphone was developed as a probe for the measurement of in vitro rheological fluid properties, including curing progress for polymethylmethacrylate (PMMA) mixtures with important uses as bone cement in the field of orthopedics. The measurement of the vibrating axial sensor's acoustic spectra in PMMA undergoing curing can be described by a damped harmonic oscillator formalism and resonant frequency (ca. 180 Hz) shift can be used as an indicator of curing progress, with shifts to the blue by as much as 14 Hz. The resonant frequency peak was measured in 19 different 4.0 g PMMA samples to have a rate of shift of 0.0462 ± 0.00624 Hz·s-1 over a period of 400 s while the PMMA was in a dough state and before the PMMA transitioned to a hard-setting phase. This transition is unambiguously indicated by this sensor technology through the generation of a distinct circa 5 kHz high-Q under-damped ring-down response.

Optical injection locking and optical-fiber data transmission by directly modulated wavelength tunable laser transmitters

Enhancement of the small- and large-signal modulation performance of wavelength tunable laser diode (TLD) transmitters under strong optical injection locking (OIL) is investigated numerically in back-to-back and optical-fiber transmission schemes. Our model is based on the spatiotemporal description of laser dynamics as due to the composite cavity design of TLDs, the usual rate equation formalism is not directly applicable. We demonstrate that TLD transmission strongly depends on wavelength tuning, which was investigated over a 21-nm range between 1529 and 1550 nm emission wavelengths. The best performance for both free-running (FR) and OIL TLDs is achieved at shorter wavelengths, 1529 nm for our device. Although in both cases this is due to larger differential material gain at shorter wavelengths, the underlying physics of the effect is completely different. For an FR TLD, it is the resonance oscillation frequency (ROF) that defines the best modulation speed, while for an OIL TLD, the achievable modulation speed depends on the cavity mode shift due to optical injection. Both the ROF and the cavity mode shift increase when the differential gain increases. However, the ROF is the device’s fixed parameter, while the cavity mode shift is defined by the OIL conditions, and thus, it can be optimized. The superior performance of the optical fiber digital data transmission with the OIL TLD is demonstrated at around 20-Gb/s modulation speed for standard fibers. This result is attributed to an enhanced modulation response and suppressed frequency chirping of the OIL TLD, and it is important for practical utilization of TLD transmitters.

ACOUSTIC METHODS FOR MEASURING THE THICKNESS OF DEPOSITS ON THE INNER WALL OF PIPELINES

Wax deposits on the inner walls of pipelines and technological equipment are a serious problem in the petroleum industry. This is not a new problem and it appeared at the dawn of oil production, but it still remains relevant, especially today, when most of petroleum fields are moving to a late stage of their development. Wax deposits lead to complications in the transportation of petroleum products, which leads to economic losses, and deposits can also cause equipment failure.For timely planning and implementation of treatment activities, information on the current thickness of wax deposits is required. However, there is currently no simple and effective method for measuring thickness of deposits.The paper considers the existing acoustic methods for measuring the thickness of deposits: through-transmission method, echo-method andmethod based on attenuation of acoustic signal. Experimental studies were carried out to determine the applicability of the proposed methods. An analysis of the literature was carried out and we proposed a new method for measuring the thickness of wax deposits, based on the analysis parameters of frequency of natural vibrations of the pipeline wall.An experimental study and computer modeling have been carried out, confirming the existence of a relationship between the resonant frequency of the pipeline wall oscillations and the thickness of the deposits. This dependence can be used as the basis for a new device for measuring the thickness of wax deposits.

On the influence of internal oscillators on the performance of metastructures: Modelling and tuning conditions

A longitudinally excited metastructure with periodically distributed internal oscillators is considered with a view to determining how the tuning condition between their frequency and the frequency of the metastructure as a whole affects vibration attenuation. First, the mechanical model is created, and the tuning condition related to the first resonance frequency of the metastructure with blocked internal oscillators and the first resonance frequency of internal oscillators themselves is obtained in an original analytical form. Then, this condition is used to design the stiffness of the internal oscillators and they are allowed to oscillate in the metastructure, yielding vibration attenuation around the first resonance. The influence of the number of internal oscillators as well as the mass ratio between the mass of one internal oscillator and external oscillator of the metastructure is investigated. Experimental validations, accompanied with numerical results, of these theoretical results are provided subsequently. In addition, the theoretical concept is extended to other resonances, demonstrating its adaptivity and generality, and these cases are then validated via numerical experiments in FEM simulations.

Characterization of Mechanical Oscillations in Bismuth Selenide Nanowires at Low Temperatures.

A single transistor preamplifier circuit was designed to facilitate electrical detection of mechanical oscillations in nanoelectromechanical systems (NEMSs) at low temperatures. The amplifier was integrated in the close vicinity of the nanowire inside the cryostat to minimize cabling load and interference. The function of the circuit was impedance conversion for current flow measurements in NEMSs with a high internal resistance. The circuit was tested to operate at temperatures as low as 5 K and demonstrated the ability to detect oscillations in double-clamped bismuth selenide nanowires upon excitation by a 0.1 MHz-10 MHz AC signal applied to a mechanically separated gate electrode. A strong resonance frequency dependency on temperature was observed. A relatively weak shift in the oscillation amplitude and resonance frequency was measured when a DC bias voltage was applied to the gate electrode at a constant temperature.

Influence of the laser crystal temperature on the intensity noise performance of solid-state lasers

The influence of the laser crystal boundary temperature on the intensity noise performance of solid-state lasers is theoretically investigated in this paper. The intensity noise spectra of a Nd:YVO4 laser with various laser crystal boundary temperatures are numerically simulated. The simulation results are qualitatively analyzed by normalizing the intensity noise spectra to the output powers of the laser upon considering the influence of the laser crystal temperature on the laser parameters. It is found that the intensity noise spectra of the laser below shot noise limit (SNL) moves to low frequency range and the resonant relation oscillation (RRO) frequency of the laser decreases from 765.93 to 524.61 kHz when tuning the laser crystal boundary temperature from 20 to 80 °C with a step of 10 °C. However, the amplitude of the RRO peak increases from 43.08 to 51.69 dB/Hz above the SNL, which can be ascribed to an enhanced non-radiation transition induced by the decreased stimulated radiation rate and the increased energy transfer upconversion process of the laser.

Teragertsevaya spektroskopiya s vremennym razresheniem (THZ–TDS) svetodiodnykh geterostruktur s tremya i pyat'yu kvantovymiyamami InxGa1−xN/GaN

Using terahertz time-domain spectroscopy (THz-TDS), we have detected resonance frequencies of plasmon oscillations excited in heterostructures with multiple InxGa1 – xN/GaN quantum wells by laser pulses with a duration of 130 fs in the temperature range from 90 to 170 K. The fast Fourier transform of temporal forms of terahertz pulses has made it possible to obtain frequency spectra of the power and of the phase shift of terahertz radiation, the interpretation of which has allowed us to estimate the quasi-momentum relaxation time (τ = 10–12 s), mobility (μ = 4 × 103 cm2/(V s)), and effective mass (m* = 0.45m) of majority charge carriers in these heterostructures. Based on the frequency spectra of power and phase shift of terahertz radiation, we have obtained the temperature dependences of the effective mass and relaxation time of the quasi-momentum of a 2D electron gas (2DEG). The 2DEG mobility value obtained by the THz-TDS method is in good agreement with the Hall measurement data.

Quantum state purity versus average phonon number for characterization of mechanical oscillators in cavity optomechanics

Quantum oscillators in Gaussian states are often characterized by average occupation numbers that refer to a basis of eigenstates of the non-interacting oscillator Hamiltonian. We argue that quantum state purity is a more appropriate characteristic of such states, which can be applied to oscillators of any dimensionality. For a one-dimensional oscillator, the state purity is directly related to a thermal occupation number defined with respect to the number state basis in which the oscillator's quantum state is thermal. Thus, it naturally introduces a more versatile definition of an average occupation number. We study optomechanical sideband cooling of one- and two-dimensional mechanical oscillators in particular, and derive exact analytical expressions for the maximal mechanical state purity achievable in the quantum backaction limit. In the case of a one-dimensional oscillator, we show that the thermal occupation number related to purity can be well approximated by the average phonon number in the weak-coupling regime, but that the two differ in the regime of ultrastrong optomechanical coupling or in cases where the oscillator's resonance frequency is strongly renormalized.

STUDY OF THE INFLUENCE OF CHANGING THE PARAMETERS OF BRUSHLESS MAGNETOELECTRIC MOTORS OF THE RETURN-ROTARY MOTION ON THEIR CHARACTERISTICS

The paper presents the results of studies on the influence of changing the parameters of a specialized brushless magne-toelectric motor on its characteristics in the mode of return-rotary motion. The frequency dependencies of the amplitude of the rotor oscillation angle, the effective value of the stator current, the efficiency index of the motor operation mode, the amplitude of the angular speed of the rotor oscillations, the amplitude of the stator voltage, the total value of losses in the motor are given. The dependences of the resonant frequency of mechanical oscillations on the changing values of the elasticity coefficient, the moment of inertia, and temperature-dependent parameters are determined. The depend-ence of the maximum value of the efficiency of the return-rotary motion motor on the viscosity coefficient of the me-chanical load is obtained. It is shown that the most economical mode of operation of the motor is provided under the condition of resonance of mechanical oscillations. Ref. 11, fig. 5.

Application of Heat-Enhancement for Improving the Sensitivity of Quartz Crystal Microbalance.

The use of quartz crystal microbalance in trace mass detection is restricted by unsatisfactory sensitivity, especially in damping media, due to the worsening of the quality factor of the damping resonator. The enhancement of the sensor performance could be realized by increasing the innate resonant frequency of quartz oscillators. Herein, increased working temperature of QCM systems was proved to bring an enhancement of the original resonant frequency. In addition, the measurement of ion osmotic pressure, single layer formation and single nucleotide polymorphism (SNP) at different temperatures demonstrated that an increased working temperature could enhance the sensitivity and accuracy, suggesting a potential application in a series of trace detections.

Active micromixer platform based on Lorentz force for lab-on-a-chip application.

Mixing in an active micromixer was achieved using Lorentz force-assisted actuation of an enameled copper wire. A single-step template-assisted soft lithography technique was used to construct the mixing chamber. The chamber had a volume of 1.86 µl. The application of a square wave alternating current in tandem with tension in the wire provided the necessary conditions for the resonant oscillation frequency of the wire. The repeatability of the ratio of higher harmonics to the fundamental frequencies of the oscillating wire conforms to standardization of the device fabrication, assembly, and functionality. Simulations and experiments were performed to validate uniform temperature distribution in the mixing chamber. Real-time optical detection of the sample assisted in sensing the completion of chemical reactions in the chamber. Mixing of various aqueous based chemical reactions was performed. It was found that mixing efficiency was greater than 95 percent. Multiple devices were fabricated to show the usability and reproducibility of the system.

Experimental study of the oscillatory process in cylindrical pipes filled with gas-bubble liquid

In hydraulic systems, undamped oscillations often occur, the frequencies of which coincide with the natural frequencies of the elements of hydraulic systems. The resulting pressure pulsations in the liquid are harmful and can disrupt the operation of hydraulic systems and elements of its automation. The search for ways and methods to reduce the impact of wave and vibration processes on pipelines, as well as the creation of devices that ensure their implementation, is an urgent scientific and technical task. The paper proposes an original method of damping resonant vibrations by feeding gas bubbles into the acoustic circuit. The aim of the work was to evaluate the effectiveness of the proposed method for reducing the sound level in water at the resonant frequencies of the main harmonics and overtones. To test the proposed method, an experimental stand was developed, the resonant frequencies and sound levels in a liquid medium bounded by a pipe closed on one side were determined by an experimental method, the influence of the supplied gas with different volume flow rates on the sound level in the pipe at the resonant frequencies of the main harmonics and overtones was investigated. The experimental results obtained allow us to conclude that the gas supply to a liquid medium leads to a change in the properties of the medium and, as a consequence, to a decrease in the sound pressure level in the liquid from the resonant (natural) oscillation frequencies of cylindrical pipes closed at one end.

Частотний аналіз вала електромеханічного приводу малого мобільного робота

Problem statement and the research purpose. The implementation and use of mobile robots in the most diverse spheres of human activity is currently an urgent task. At the same time, ensuring their reliable operation and functioning determines their effectiveness to a certain extent. Using the appropriate calculations during the designing process of various machines, in particular of mobile robots, it is possible to increase the reliability and reduce the material consumption of the developed machine prototypes, and therefore to reduce the cost of its production and maintenance. Methodology of the study. For a small mobile robot with an electromechanical transmission, a number of calculations were carried out according to the developed methodology. The latter contains geometric, kinematic, dynamic, energy, technical and economic calculations, strength and rigidity analysis, and modal analysis of resonance frequencies of oscillations of the workpiece being designed. Results of the investigations. On the basis of the kinematic diagram of the robot’s electromechanical transmission, a solid-state model of the traction (driving) sprocket shaft of the crawler (track-type, caterpillar) drive was developed, for which the necessary safety assurance factor of the shaft material was determined on the basis of the schematized (linearized) Serensen-Kinasoshvili diagram of the critical stresses. Scientific novelty. The article presents an example of a modal analysis of a designed robot’s transmission shaft and determines the resonance frequencies of its oscillations. It was established that the most dangerous resonant frequencies for the designed shaft are equal to 11 Hz, 170 Hz, and 914 Hz. Practical value of the results. The developed technique can be effectively implemented while designing new experimental and industrial prototypes of mobile robots. Scopes of further investigations on the subject of the paper. Further research can be focused on the development of a complex methodology for calculating and designing the electromechanical drives of mobile robots taking into account geometric, kinematic, dynamic, energy, technical and economic calculations.

Joint voltage and frequency predictive controllers for distributed generation plants

The paper determines the effect of proposed joint voltage and frequency predictive controllers for distributed generation (DG) plants on quality indicators characterizing the control process in different operating modes of power supply systems. The studies are conducted in the MatLab environment (Simulink and SimPowerSystems simulation packages) employing control engineering methods. It is proposed to design and adjust joint predictive controllers by determining the resonant frequency of oscillations for the master generator rotor. This approach provides better quality indicators of voltage and frequency control in power supply systems while maintaining the same settings for the controllers of DG plants. With an additional load in an isolated power supply system, the maximum voltage sag is found to be 1.75 times lower than for local predictive control and 3.5 times lower as compared to the use of conventional controllers. For the specified mode, predictive controllers enable a threefold reduction in the transient time between rotor rotational speeds in a synchronous generator. In the start mode of a powerful electric motor, the predictive controllers of synchronous generators in the power supply system enable a 1.5 times reduction in voltage sag, with a 1.4 times reduction in overvoltage following its start. In the case of a short-term three phase short-circuit, joint predictive controllers allow a 1.5 times decrease in transient time and a 2.3 times decrease in the overshoot of power line frequency as compared to local control. In addition, frequency oscillation in the power system is also reduced. Similar effects are observed in other operating modes of the considered power supply systems equipped with DG plants. The performed dynamic simulation confirms the effectiveness of using joint voltage and frequency predictive controllers for DG plants, which consists in a positive impact on the quality of processes involved in controlling the parameters of power supply systems in various operating modes.

Fundamental limits and optimal estimation of the resonance frequency of a linear harmonic oscillator

All physical oscillators are subject to thermodynamic and quantum perturbations, fundamentally limiting measurement of their resonance frequency. Analyses assuming specific ways of estimating frequency can underestimate the available precision and overlook unconventional measurement regimes. Here we derive a general, estimation-method-independent Cramer Rao lower bound for a linear harmonic oscillator resonance frequency measurement uncertainty, seamlessly accounting for the quantum, thermodynamic and instrumental limitations, including Fisher information from quantum backaction- and thermodynamically driven fluctuations. We provide a universal and practical maximum-likelihood frequency estimator reaching the predicted limits in all regimes, and experimentally validate it on a thermodynamically limited nanomechanical oscillator. Low relative frequency uncertainty is obtained for both very high bandwidth measurements (≈10−5 for τ = 30 μs) and measurements using thermal fluctuations alone (<10−6). Beyond nanomechanics, these results advance frequency-based metrology across physical domains.

Multistability and Fano resonances in a hybrid optomechanical photonic crystal microcavity

We investigate the optical response of a hybrid cavity quantum-electrodynamics system consisting of a quantum dot embedded in an optomechanical photonic crystal cavity. The system is coupled to an auxiliary cavity via a waveguide that can support a single optical mode. We demonstrate the possibility of generating tunable optical bistability, double-bistabilty and tristability which can be utilized to design all-optical-switch and multi-valued logic circuits eventually forming a part of a large scale quantum communication platform. The proposed system has also found to exhibit the Mollow triplet and the Fano resonances modified by an optomechanical interaction. The optomechanically induced transparency (OMIT) is superimposed on the Fano resonance (OMIT-Fano resonance) having the transparency window occurring exactly at the point where the probe detuning becomes equal to the mechanical oscillator's resonant frequency.

Ultraviolet Radiation Sensor Based on ZnO Nanorods/La3Ga5SiO14 Microbalance.

The possibility of creating resonant ultraviolet (UV) sensors based on the structure of ZnO nanorods/La3Ga5SiO14 microbalance (LCM) has been investigated. The principle of sensor operation is based on the desorption of oxygen from the surface of ZnO nanorods upon irradiation with UV light and an increase in the concentration of charge carriers that leads to an increase in the capacitance of the structure of ZnO nanorods/LCM. It has been shown that UV radiation intensity affects the resonance oscillation frequency of the LCM sensor. After the end of irradiation, the reverse process of oxygen adsorption on the surface of ZnO nanorods occurs, and the resonance frequency of the sensor oscillations returns to the initial value.

Sensitivity and Accuracy of Dielectric Measurements of Liquids Significantly Improved by Coupled Capacitive-Dependent Quartz Crystals

A method to measure complex permittivity of liquids by using a capacitive-dependent quartz crystal and two quartz oscillators for temperature compensation in the frequency range of 4–10 MHz is described. Complex permittivity can be detected with high precision and sensitivity through a small change of capacitance and conductance, because a change in reactance in series with the quartz crystal impacts its resonant oscillation frequency. The temperature compensation in the range below 0.1 ppm is achieved by using two quartz oscillators that are made of elements of the same quality and have a temperature–frequency pair of quartz crystals. With the help of a reference oscillator, measurements of frequency are more accurate, because the frequency difference is in the kHz region, which also enables further processing of the signal by a microcontroller. With a proper calibration, the accuracy of this highly sensitive quartz crystal method is ±0.05%, which is an order of magnitude lower than that for a capacitance method without quartz crystals. The improved accuracy is of significant importance in the field of power engineering to monitor coolants and lubricants, oils, liquid fuels and other liquids, the dielectric properties of which are crucial for proper operation of devices.

Зонная структура и процессы в электронной системе кристаллов (Bi-=SUB=-2-x-=/SUB=-Sb-=SUB=-x-=/SUB=-)Te-=SUB=-3-=/SUB=- (0&amp;lt;x&amp;lt;2) по данным оптических исследований в инфракрасном диапазоне

The decrease in the resonance frequency of plasma oscillations of free charge carriers omegap with increasing temperature observed in Bi2-xSbx (0 &lt;x &lt;2) p-type crystals can only be partially explained by an increase in the polarization background of the crystal ε-infinity. Analysis of the experimental data suggests that the temperature change in omegap observed in the range from 80 to 300 K is also due to a decrease in the ratio of the concentration of free charge carriers to their effective mass p / m *. This can be explained by an increase in the effective mass of carriers with increasing temperature, as well as by the process of hole redistribution between nonequivalent extrema of the valence band, the existence of which is confirmed by the regularities of the temperature change in the optical band gap observed in the reflection spectra of infrared radiation. Key words: semiconductors, plasma resonance, concentration, effective mass of free charge carriers, electrical conductivity, thermal and optical band gap.

Investigation of the influence of the geometric parameters of AFM cantilevers on the resonant frequency of their oscillations

This paper presents the results of theoretical and experimental studies aimed at studying the influence of the basic geometric parameters of micromechanical cantilevers on the resonant frequency of their oscillations. The dependences of the oscillation frequency on the length of the cantilever beam, obtained based on mathematical modeling are theoretically investigated by the finite element method. In experimental studies that used AFM cantilever beams, the beams were shortened stepwise by the method of local ion beam etching by focused ion beam (FIB) Ga+. After each step, the change in the resonant frequency of oscillations was monitored. It was found that the application of the FIB method allows you to accurately change the geometric parameters of the probe beams, which, in turn, allows you to change the resonant frequency of cantilever oscillations with high accuracy. During the analysis of the obtained dependences of the resonant frequency of oscillations on the geometric parameters of the beams, it was found that a decrease in the length of the cantilever from 110 to 80 μm leads to an approximately twofold increase in the resonant frequency of oscillations of the cantilever from 320 to 620 kHz. The obtained graphs of the theoretical and experimental dependencies are compared, which showed a good correlation of the results.