Resonant frequencies of massless scalar field in rotating black-brane spacetime

This paper investigates the resonant frequencies of the massless scalar field in the near extremal Kerr-like black-brane spacetime. It is shown that the different angular quantum number will present different resonant frequencies. It is also shown that the real part of the resonant frequencies increases as the compact dimensions parameter μi increases, but the magnitude of the imaginary part decreases as μi increases.

Resonant frequencies of a piezoelectric drum transducer

This paper presents a piezoelectric-metal structure called a drum transducer. An equation for calculating the resonance frequency of the drum transducer is obtained based on thin plate elastic theory of piezoelectric and metal material combined with the Rayleigh-Ritz method. The finite element method (FEM) was used to predict the excitation frequency of the drum transducer. To verify the theoretical analysis, the input impedance characteristic of the drum transducer was measured using an experimental method. The results obtained from theoretical analysis were in very good agreement with those from the FEM and experimental results. The effect of geometrical changes to the thick-walled steel ring of the drum transducer at the first resonance frequency is also described. The calculated results were found to be in good agreement with the FEM results. The results indicate that the first resonance frequency of the drum decreases with the increasing inner diameter of the thick-walled steel ring.

TUNING THE RESONANT FREQUENCIES OF FLEXURE MODE FLEXOELECTRIC PIEZOELECTRIC COMPOSITES

The newly developed flexure mode flexoelectric composites have extremely high direct piezoelectric response around mechanical resonant frequency.Methods of tuning the resonant frequencies of the composites were studied in this paper.The resonant frequencies can be adjusted by changing dimensions of ferroelectric ceramic bars in the composites or by adding an additional mass on the composites.Design of flexure mode composites with multiple resonant frequencies was also studied.

Enhanced resonance frequency in Co2FeAl thin film with different thicknesses grown on flexible graphene substrate

The flexible materials exhibit more favorable properties than most rigid substrates in flexibility,weight saving,mechanical reliability,and excellent environmental toughness.Particularly,flexible graphene film with unique mechanical properties was extensively explored in high frequency devices.Herein,we report the characteristics of structure and magnetic properties at high frequency of Co2FeAl thin film with different thicknesses grown on flexible graphene substrate at room temperature.The exciting finding for the columnar structure of Co2FeAl thin film lays the foundation for excellent high frequency property of Co2FeAl/flexible graphene structure.In-plane magnetic anisotropy field varying with increasing thickness of Co2FeAl thin film can be obtained by measurement of ferromagnetic resonance,which can be ascribed to the enhancement of crystallinity and the increase of grain size.Meanwhile,the resonance frequency which can be achieved by the measurement of vector network analyzer with the microstrip method increases with increasing thickness of Co2FeAl thin film.Moreover,in our case with graphene film,the resonance magnetic field is quite stable though folded for twenty cycles,which demonstrates that good flexibility of graphene film and the stability of high frequency magnetic property of Co2FeAl thin film grown on flexible graphene substrate.These results are promising for the design of microwave devices and wireless communication equipment.

Modal Frequency Prediction of Chladni Patterns Using Machine Learning

The introduction of machine learning (ML) in the research domain is a new era technique. The machine learning algorithm is developed for frequency predication of patterns that are formed on the Chladni plate and focused on the application of machine learning algorithms in image processing. In the Chladni plate, nodes and antinodes are demonstrated at various excited frequencies. Sand on the plate creates specific patterns when it is excited by vibrations from a mechanical oscillator. In the experimental setup, a rectangular aluminum plate of 16 cm x 16 cm and 0.61 mm thickness was placed over the mechanical oscillator, which was driven by a sine wave signal generator. 14 Chladni patterns are obtained on a Chladni plate and validation is done with modal analysis in Ansys. For machine learning, a large number of data sets are required, as captured around 200 photos of each modal frequency and around 3000 photos with a camera of all 14 Chladni patterns for supervised learning. The current model is written in Python language and model has one convolution layer. The main modules used in this are Tensor Flow Keras, NumPy, CV2 and Maxpooling. The fed reference data is taken for 14 frequencies between 330 Hz to 3910 Hz. In the model, all the images are converted to grayscale and canny edge detected. All patterns of frequencies have an almost 80% - 99% correlation with test sample experimental data. This approach is to form a directory of Chladni patterns for future reference purpose in real-life application. A machine learning algorithm can predict the resonant frequency based on the patterns formed on the Chladni plate.

Non-contact evaluation of the resonant frequency of a microstructure using ultrasonic wave

This paper presents a novel non-contact method for evaluating the resonant frequency of a microstructure, Firstly, the microstructure under test is excited by ultrasonic waves. This excitation method does not impose any undefined load on the specimen like the electrostatic excitation and also this is the first actual use of ultrasonic wave for exciting a microstructure in the literature. Secondly, the amplitudes of the microstructure are determined by image edge detection using a Mexican hat wavelet transform on the vibrating images of the microstructure. The vibrating images are captured by a CCD camera when the microstructure is vibrated by ultrasonic waves at a series of discrete high frequencies （〉30 kHz）. Upon processing the vibrating images, the amplitudes at various excitation frequencies are obtained and an amplitude-frequency spectrum is obtained from which the resonant frequency is subsequently evaluated. A micro silicon structure consisting of a perforated plate （192 × 192 μm） and two cantilever beams （76 × 43 μm） which is about 4 μm thickness is tested. Since laser interferometry is not required, thermal effects on a test object can be avoided. Hence, the setup is relatively simple. Results show that the proposed method is a simple and effective approach for evaluating the dynamic characteristics of microstructures.

A Novel Resonant Frequency Tracking Control for Linear Compressor Based on MRAS Method

To optimize the efficiency of the linear compressor,its operating frequency must be controlled equal to the system resonant frequency.The traditional resonant frequency tracking control algorithm relies on the steady state characteristics of the system,which suffers from slow convergence speed,low accuracy and slow system response.In order to solve these problems,a novel resonant frequency tracking control for linear compressor based on model reference adaptive system(MRAS)is proposed in this paper,and the parameter adaptive rate is derived by the Popov's hyperstability theory,so that the system resonant frequency can be directly calculated through the parameter adaptive rate.Furthermore,the traditional algorithm needs to calculate the piston stroke signal by integrating the back-EMF,which has the problem of integral drift.The algorithm proposed in this paper only needs the velocity signal,and the accuracy of the velocity calculation can be ensured by utilizing the self-adaptive band-pass filter(SABPF),thereby greatly improving the accuracy of the resonance frequency calculation.Simulation results verify the effectiveness of the proposed algorithm.

Generation of self-oscillations from a singly resonant periodically poled potassium titanyl phosphate crystal frequency doubler

We report on the generation of self-oscillations from a continuously pumped singly resonant frequency doubler based on a periodically poled potassium titanyl phosphate crystal （PPKTP）. The sustained square-wave and staircase curve of self-oscillations are obtained when the incident pump powers are below and above the threshold of subharmonic-pumped parametric oscillation （SPO）, respectively. The self-oscillations can be explained by the competition between the phase shifts induced by cascading nonlinearity and thermal effect, and the influence of fundamental nonlinear phase shift by the generation of SPO. The simulation results are in good agreement with the experiment data.

Theoretical study on dynamic effective electroelastic properties of random piezoelectric composites with aligned inhomogeneities

The closed-form solutions of the dynamic problem of heterogeneous piezoelectric materials are formulated by introducing polarizations into a reference medium and using the generalized reciprocity theorem.These solutions can be reduced to the ones of an elastodynamic problem.Based on the effective medium method,these closedform solutions can be used to establish the self-consistent equations about the frequencydependent effective parameters,which can be numerically solved by iteration.Theoretical predictions are compared with the experimental results,and good agreement can be found.Furthermore,the analyses on the effects of microstructure and wavelength on the effective properties,resonance frequencies,and attenuation are also presented,which may provide some guidance for the microstructure design and analysis of piezoelectric composites.

Vibration of a Two-Layer“Metal+PZT”Plate Contacting with Viscous Fluid

The present work investigates the mechanically forced vibration of the hydro-elasto-piezoelectric system consisting of a two-layer plate“elastic+PZT”,a compressible viscous fluid,and a rigid wall.It is assumed that the PZT(piezoelectric)layer of the plate is in contact with the fluid and time-harmonic linear forces act on the free surface of the elastic-metallic layer.This study is valuable because it considers for the first time the mechanical vibration of the metal+piezoelectric bilayer plate in contact with a fluid.It is also the first time that the influence of the volumetric concentration of the constituents on the vibration of the hydro-elasto-piezoelectric system is studied.Another value of the present work is the use of the exact equations and relations of elasto-electrodynamics for elastic and piezoelectric materials to describe the motion of the plate layers within the framework of the piecewise homogeneous body model and the use of the linearized Navier-Stokes equations to describe the flow of the compressible viscous fluid.The plane-strain state in the plate and the plane flow in the fluid take place.For the solution of the corresponding boundary-value problem,the Fourier transform is used with respect to the spatial coordinate on the axis along the laying direction of the plate.The analytical expressions of the Fourier transform of all the sought values of each component of the system are determined.The origins of the searched values are determined numerically,after which numerical results on the stress on the fluid and plate interface planes are presented and discussed.These results are obtained for the case where PZT-2 is chosen as the piezoelectric material,steel and aluminum as the elastic metal materials,and Glycerin as the fluid.Analysis of these results allows conclusions to be drawn about the character of the problem parameters on the frequency response of the interfacial stress.In particular,it was found that after a certain value of the vibration frequency,the presence of the metal layer in the two-layer plate led to an increase in the absolute values of the above interfacial stress.

Detection of Frost-Resistance Property of Large-Size Concrete Based on Impact-Echo Method

The dynamic elasticity modulus(Ed)is the most commonly used indexes for nondestructive testing to represent the internal damage of hydraulic concrete.Samples with a specific size is required when the transverse resonance method was used to detect the Ed,resulting in a limitation for field tests.The impact-echo method can make up defects of traditional detection methods for frost-resistance testing,such as the evaluation via the loss of mass or strength.The feasibility of the impact-echo method to obtain the relative Ed is explored to detect the frost-resistance property of large-volume hydraulic concretes on site.Results show that the impact-echo method can replace the traditional resonance frequency method to evaluate the frost resistance of concrete,and has advantages of high accuracy,easy to operate,and not affecting by the aggregate size and size effect of samples.The dynamic elastic modulus of concrete detected by the impact-echo method has little difference with that obtained by the traditional resonance method.The one-dimensional elastic wave velocity of concrete has a good linear correlation with the transverse resonance frequency.The freeze-thaw damage occurred from the surface to the inner layer,and the surface is expected to be the most vulnerable part for the freeze-thaw damage.It is expected to monitor and track the degradation of the frost resistance of an actual structure by frequently detecting the P-wave velocity on site,which avoids coring again.

Simulation Study of CMUT for Pressure Sensing Applications

Capacitive micromechanical ultrasonic transducers(CMUTs)have been widely studied because they can be used as substitutes for piezoelectric ultrasonic transducers in imaging applications.However,it is unclear whether and how CMUTs can be developed for sensors incorporating other functions.For instance,researchers have proposed the use of CMUTs for pressure sensing,but fundamental and practical application issues remain unsolved.This study explored ways in which a pressure sensor can be properly developed based on a CMUT prototype using a simulation approach.A three-dimensional finite element model of CMUTs was designed using the COMSOL Multiphysics software by combining the working principle of CMUTs with pressure sensing characteristics in which the resonance frequency of the CMUT cell shifts accordingly when it is subjected to an external pressure.Simultaneously,when subjected to pressure,the CMUT membrane deforms,thus the pressure can be reflected by the change in the capacitance.

基于互补分裂谐振环的十字缝隙贴片天线

A compact patch antenna is designed, which is with structures of cross-shape slot, Complementary Split Ring Resonator(CSRR), and loaded transmission line. To implement the compactness in size, these structures are etched on the ground plane, then the input impedance has been improved. The CSRR is employed to improve impedance matching between the source and radiation patch, and the cross-shape slot on the radiation patch is utilized to increase the bandwidth. The design is validated by comparison of realistic field simulation with measurement results of an antenna prototype. The presented antenna is much smaller in size than conventional antennas with CSRR, showing good performances at the resonant frequency. The experimental results accord well with simulated results.

Influence of Phosphorus Content and Magnetic Annealing on Soft Magnetic Properties of Electrodeposited Amorphous FeMnP Alloy Films

In this work, we investigated the influence of phosphorus and magnetic anneal on the soft magnetic properties of electrodeposited FeMnP alloy films prepared by changing sodium hypophosphite concentrations. X-ray diffraction radiation patterns showed an amorphous structure of electrodeposited alloy films. The saturation magnetization and coercivity value decreased from 586 emu/cc to 346 emu/cc, and 52 Oe to 18 Oe, with the P content increased, respectively. The absorption resonance peak became broad as the P content increased, and the natural resonance frequency decreased from 1.8 GHz to 0.6 GHz, with the P content increasing. Magnetic annealing of samples reduced the magnetic damping, and natural resonance frequency increased by about 1.8 GHz and 3.5 GHz for the sample with lower and higher P content. The film structure with lower P content changed at 300˚C, while the structure remains unchanged for the films with higher P content. Thus, the crystallization temperature could depend on the P content in the film. FeMnP alloy films could be used in high-frequency devices.

Frequency response of a new kind of silicon nanoelectromechanical systems resonators

Diffraction effects will bring about more difficulties in actuating resonators,which are electrostatically actuated ones with sub-micrometer or nanometer dimensions,and in detecting the frequency of the resonator by optical detection.To avoid the effects of diffraction,a new type of nanoelectromechanical systems（NEMS） resonators is fabricated and actuated to oscillate.As a comparison,a doubly clamped silicon beam is also fabricated and studied.The smallest width and thickness of the resonators are 180 and 200 nm,respectively.The mechanical oscillation responses of these two kinds of resonators are studied experimentally.Results show that the resonant frequencies are from 6.8 to 20 MHz,much lower than the theoretical values.Based on the simulation,it is found that over-etching is one of the important factors which results in lower frequencies than the theoretical values.It is also found that the difference between resonance frequencies of two types of resonators decreases with the increase in beam length.The quality factor is improved greatly by lowering the pressure in the sample chamber at room temperature.

Electrode Location Efficiency and Equivalent Circuit for Flexure Vibration of Piezoelectric Beam

Aim To provide technical parameters for development of quartz gyro. Methods Theory of elastic beam was applied to piezoelectric beam. Based on the concept of equivalent volume force and energy conservation, the formula of electrode location efficiency was derived. And the electric system was compared with the dynamic one according to the principle of equivalent circuit for piezoelectric crystal, and the general formulae of the parameters for the equivalent circuit, R n L n C n , were derived. Results and Conclusion Optimum electrode location is chosen, and the derived equivalent circuit parameters are the theoretical base of the circuit design for quartz gyro.

Comparison of Mode Quality Factors for Equilateral Triangular, Square and Rhombus Optical Micro-Resonators

The mode frequencies and the quality factors for the equilateral triangular resonator (ETR), the square resonator (SR) and the rhombus resonator (RR) are numerically calculated by the finite difference time domain technique and the Padé approximation. The numerical results show that the resonant modes confined in an equilateral triangular cavity have much higher quality factors than those in the square or the rhombus cavities. The modes in the ETR are totally confined in transverse direction while those in the SR and RR are only partly confined. For the ETR with the side length of 4μm and the refractive index of 3 2, the mode quality factor of about 5 5×10 3 at the wavelength of 1 55μm has been obtained.

Testing an improved cymbal hydrophone

Cymbal hydrophones have small volume and high sensitivity, but their reception is not stable enough, and their reception is in too narrow a frequency band. In order to overcome these inadequacies, the structure of the cymbal hydrophone was improved. The single ceramic piezoelectric element was replaced with a double one, the radius of the ceramic piezoelectric element was reduced, and a parallel circuit was added. A static analysis of this new structure was developed, and then simulations were made of both the traditional and new hydrophone structure using finite element software. Tests were then conducted in a tank. The results showed that the improved hydrophone has reception in a wider frequency band, reception performance is stable within this frequency band, and sensitivity is still high.

INVESTIGATION OF SENSITIVITY FOR SILICON MICROMECHANICAL TUNING-FORK GYROSCOPE

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Space and Human Consciousness: The Great Whisper

Human Consciousness is one of most elusive issues in the scientific history. Its nature created major historical debate started thousands of years ago and still ongoing. Despite the explosive developments in the last century to explore its nature, the knowledge about it is still deficient. The important advances in the twentieth and 21st centuries in understanding cerebral cortex dynamics fortified by the dominant materialistic approach of the era dictated its impact on consciousness science, which is perceived as sole human brain function. This original review is a call for holistic perception of human consciousness incorporating the ancient wisdom of the human civilizations with the massive current era advances in different disciplines of applied sciences. The description of René Descartes in the 17th century of the Cartesian dualism is timely to revisit with new holistic perspective, in view of the major advances of our understanding of heart brain communications, astrophysical resonances with human heart ascending afferents to central nervous system, and signaling between humans and the space. Universal vibrations, frequencies and resonances as perceived by Nikola Tesla constitute the core of our new conceptual and experimental perspective on human consciousness. Neural and psychological correlates of human consciousness which dominate the consciousness research nowadays should undergo revolutionary conceptual understanding to perceive consciousness as a massive universal event expanding from human genes to galaxies. In the next discussion, we are going to navigate in the nature and fate of human consciousness with new innovative universal perspective based on heart rate variability of human heart and its cosmic resonances as represented by Schumann Resonances, Solar Wind Indices and Galactic Cosmic Rays. The interpretation of our existential secrets and biology without the space around us is a major gap in our scientific perception of life. The delicate orchestration between human heart and the space frequencies create the great whisper which in our perspective, encodes the secrets of human consciousness.