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A data assimilation (DA) strategy was developed for accurate prediction of the flow-acoustic resonant fields within a channel-branch system. The challenges of numerical simulation of such internal aeroacoustic systems are primarily associated with determination of the transfer loss between the acoustic waves and the shear layer vortices. Thus, a data-assimilated momentum loss model that comprises a viscous loss item and an inertial loss item was established and embedded into the Navier-Stokes equations. During the DA, the acoustic pressure pulsations measured from a dynamic pressure array served as the observational data, the ensemble Kalman filter served as the optimization algorithm, and a three-dimensional transient computational fluid dynamics method comprising an explicit algebraic Reynolds stress model (EARSM) served as the predictive model system. EARSM was used because its ability to predict internal flow-acoustic resonances was superior to that of other eddy viscosity models and Reynolds stress models. The data-assimilated flow-acoustic resonant fields were then comprehensively validated in terms of their acoustic fields, time-averaged flow fields, and phase-dependent flow fields. The time-averaged flow fields were obtained from planar particle-image velocimetry (PIV) measurements, and the phase-dependent flow fields were obtained from field programmable gate array-based phase-locking PIV measurements. The results demonstrate that the use of DA afforded an optimal simulation that efficiently decreased the numerical errors in the frequencies and amplitudes of the acoustic pressure pulsations, thereby achieving better agreement between time-averaged flow distributions and fluctuations. In addition, the data-assimilated numerical simulation completely reproduced the spatiotemporal evolution of the shear layer vortices, that is, their formation, developing, transport, and collapsing regions.

In this study, the Pb(Zr0.65Ti0.35)O3 (PZT) structure was produced by the solid state reaction method, and a new polarization geometry was used to obtain the radial and thickness modes in cylindrical samples with more efficiency. The polarization procedure was investigated by varying the temperature from 30°C to 80°C. The experimental excitation of radial and thickness modes was observed, and a comparative study was performed with numerical simulations. The comparative analysis of the acoustic response of the cylindrical PZT samples under theoretical and experimental conditions was validated by COMSOL Multiphysics® software. The new polarization geometry technique was used to generate radial thickness and acoustic mixed modes with more efficiency. The results show that the resonance frequency and antiresonance, as well as the impedance mode and phase angle are well adjusted, showing the validation of the technique presented between the theoretical and experimental measurements.

Nowadays, the size reduction of electronic devices based on magnetoelectric (ME) effects is an important task. This will provide an opportunity for the wide integration of ME devices into modern microsystem technology. In this letter, the effects of in-plane sizes of planar heterostructures containing a ferromagnetic Ni film and a piezoelectric lead zirconate titanate (PZT) substrate on characteristics of the direct resonance ME effect are investigated. The Ni films of 10 μm in thickness were electrodeposited on the PZT substrates that were 200-μm-thick and 1.2-23 mm in length. The structures were placed in a permanent magnetic field and excited with an ac magnetic field. The generated ME voltage was measured at frequencies near planar acoustic resonances of the structures. For a 1.2 mm long structure, a frequency of 1380 kHz for in-plane acoustic resonance was achieved. A drop in the amplitude of the ME voltage was observed when the length of the structure became less than a critical value. Various mechanisms are discussed that lead to a voltage drop with a reduction of sizes of the structure, including the demagnetization effect, relaxation losses due to frequency dependence of the capacitance and resistance of the PZT layer, and an increase in acoustic losses.

An investigation is conducted on the acoustic resonance that develops in rectangular and cylindrical cavities with rigid walls. An analytical model for the small amplitude acoustic perturbations inside an enclosure with rigid walls is developed from classical linerized acoustics. The method is first applied to a rectangular geometry and the normalized mode shapes and frequencies of the first six standing wave modes are given. The results are used to diagnose whether coupling is likely to occur between the first two Rossiter modes and the acoustic standing waves, which may lead to a reinforcement of the flow instability. At the selected test conditions, the method indicates that the second Rossiter mode can couple with the first longitudinal acoustic mode. The acoustic resonant mode predictions for a cylindrical cavity of length to depth ratios 0.71 and 2.5, tested at near-incompressible speeds, suggest that the acoustic resonant modes and the main fluid dynamic instability in the enclosure are sufficiently apart in frequency not to strongly interact with one another. The parametrized analytical solutions developed in this study enable the aero-acoustic engineer to diagnose whether coupling between a given fluid dynamic instability and acoustic resonance is likely to affect a rectangular or cylindrical cavity component.

A gas compressor station only had its about 35% design processing capacity as a result of the abnormal piping vibrations on the inlet pipelines. Characterization, diagnostics, analysis, and elimination of piping vibration were performed. The root causes and sources of the abnormal vibration were investigated by on-site measurements and analysis of vibration and pulsation under various load conditions of compressors. The results revealed that it was not mechanical resonance, but the high pressure pulsation and acoustic resonance occurred on the inlet pipelines, which resulted in the severe vibration. Three different modification models against vibration were proposed by shortening the length of the pipe to avoid acoustic resonance, enlarging the volume of the gathering manifold to buffer pressure pulsation, and adding supports to increase the stiffness. A better modification model was applied by performing modal analysis and fluid-structure interaction (FSI) vibration analysis using the finite element method. The effect of countermeasures was evaluated by vibration and pulsation measurements during operation after modifications, which results showed the level of piping vibration and pressure pulsation was within the allowable limits. The processing capacity of the gas station has reached its design requirement as a result of the desired reduction in vibrations.

Introduction.Petroleum is a complex mixture of hydrocarbons. Sulphur is the most common heteroatom in pe-troleum and petroleum products. Its content in oil can reach 14 %. The determination of sulphur in oil and its removal is of great importance, since sulphur compounds adversely affect the quality of petroleum products and pollute the environment. Desulphurization of hydrocarbons is important in the processing of petroleum products, which needs in usage of accurate and simple methods for the sulphur-containing components determination. Most of developed methods are difficult to apply for flow online analysis, which can create difficulties in using them to monitor the content of sulphur-containing heteroatomic components in real time. Acoustic sensors are one of the possible solutions. In term of sensing of flammable liquids, the use of the acoustic methods is attractive since the analyte is not a part of an electrical measuring circuit and it is only acoustically coupled that prevents an occurrence of a spark.Objective.The purpose of the work is to study the possibilities of online flow analysis of sulphur-containing heteroatomic components using acoustic measurements. The challenge is the development of a resonator system integrated with the pipe.Materials and methods. Thiophene and oil fraction with the boundary boiling point of 100–140 oC were used to prepare the mixtures. Thiophene is a representative of sulphur-containing components, which may be included in the composition of petroleum and its derivatives. Experimental measuring equipment includes impedance analyzer, a developed sensor structure integrated with a liquid-filled pipe, a pump and a tank with a measured liquid. A theoretical analysis of sensor structure was carried out on the basis of numerical simulation using COMSOL Multiphysics software.Results.The sensor structure was designed as a combination of 2D and 1D pipe periodic arrangements to achieve high Q-factor of acoustic resonance in the flow system. The eigenmodes of the sensor structure with a liquid analyte were carried out. The characteristic of sensor structure is determined. The sensor shows good sensitivity to the thiophene content with high resolution in-line analysis. This result is achieved by limiting the energy losses of acoustic resonance in radiation along the pipe by creating a periodic structure.Conclusion. The study of acoustic properties of solutions prepared on the basis of thiophene and oil fraction with boundary boiling point 100–140 °C was performed. It shows that methods based on acoustic spectroscopy make it possible to accurately determine the concentration of heteroatomic components in gasoline mixtures, since the presence of heteroatomic components leads to a change in mechanical properties of liquid hydrocarbons mixtures. Possible applications for developed acoustic sensor are flow analysis for monitoring the quality of oil products.

In this work the feasibility of a NO 2 detection system based on photoacoustic effect is presented. The developed system takes advantage of low-cost components such as a commercial UV-LED as excitation source and a MEMS microphone as acoustic transducer. A cylindrical shaped structure has been used as a photoacoustic resonant cell and the light source modulated near its acoustic resonance frequency. Acoustic simulations have been carried out to investigate the acoustic coupling between the considered medium and the mechanical structure, and to determine the requirements of the readout electronic system. Preliminary gas measurement results are shown, obtained by exploiting an ad hoc realized characterization system. The gas sensing performances of the system have been tested in the range 0-50 ppm of NO 2 concentration.

A novel method of acoustic resonance laser calorimetry (ARLC) for the determination of low optical absorption coefficients of crystals and glasses is introduced. It is based on measurements of the kinetics of the equivalent temperature of the sample irradiated by the pulse laser radiation. The equivalent temperature of the sample is directly obtained by measuring the frequency changes of its temperature-calibrated acoustic resonances excited by the laser radiation with a corresponding pulse repetition rate. In contrast to the conventional resonant photoacoustic spectroscopy, where the resonance is used for the enhancement of the registered signal, in ARLC, the laser-excited acoustic resonance of the sample acts as a high-sensitivity temperature probe for measurements of its heating kinetics. The ARLC approach was verified by measuring the optical absorption coefficient of the potassium dihydrogen phosphate crystal ( α = 4.2 ⋅ 1 0 − 2 c m − 1 ) at 1064 nm wavelength.

Barium strontium titanate (BST) thin-film varactors promise very good performance in RF frontends in terms of low loss and high tunability. However, their application is commonly limited to lower GHz frequencies. For higher frequencies, acoustic resonances drastically reduce the device quality in metal-insulator-metal (MIM) structures under bias voltage. In this work, this limitation is overcome by replacing the metal electrodes with conducting oxides that structurally match to BST and, therefore, avoid acoustic impedance mismatch. A detailed analytic model is derived, incorporating electric and acoustic behavior. Four samples with an oxide bottom electrode and varying BST thickness are characterized and fitted by the derived model with very high accuracy. Each shows a significantly reduced degradation due to acoustic loss. A model-wise comparison of stacks with metal and oxide electrodes demonstrates the strong benefit of all-oxide varactors, the possibility of complete suppression of acoustic resonances.

The experimentally determined normal incident mass-air-mass resonance frequency for a double leaf cavity stud building element is significantly greater than the theoretically predicted frequency for wood studs and steel studs manufactured from thicker sheet steel. This paper gives a method for calculating the effective mass-air-mass resonance frequency as the root mean square sum of the mass-air-mass resonance frequency and the resonance frequency of the first bending wave mode of the leaves between the studs. This calculation should use the isothermal mass-air-mass resonance frequency if the building element cavity contains porous sound absorbing material. If the cavity does not contain porous sound absorbing material, the usual adiabatic mass-air-mass resonance frequency should be used in the calculation. Because the exact boundary conditions of the building element leaves at the studs and the effective in situ damping are unknown, the paper gives empirical correction factors to determine the actual resonance frequency and the depth of the dip in the predicted sound insulation. This paper also gives empirically derived formulae for the line and point equivalent translational compliances of steel studs manufactured from different sheet steel gauges and compares them with formulae derived by other authors for the case of 25 gauge steel studs.

In this study, we compare different machine learning approaches applied to acoustic resonance recognition of coins. Euro-cents and Euro-coins were classified by the sound emerging when throwing the coins onto a hard surface.The used dataset is a representative example of a small data which was collected in carefully prepared experiments.Due to the small number of coin specimens and the count of the collected observations, it was interesting to see whether deep learning methods can achieve similarly or maybe even better classification performances compared with more traditional methods.The results of the multi-class prediction of coin denominations are presented and compared in terms of balanced accuracy and Matthews Correlation Coefficient metrics. The feature analysis methods combined with the employed classifiers achieved acceptable results, despite the relatively small dataset.

In recent years, 3D-printing technology has become widely accessible to non-experts and hobbyists, enabling them to fabricate objects of varying geometries. In contrast to this new ease of producing new forms, fabricating objects that can sense user input traditionally requires the assembly of complex circuits and physical parts. With my work, I explore what I call \pap: 3D-printed interactive objects without requiring any post-print activities such as assembly or calibration. I approach this by by externally sensing how the user's actions interact with well-studied physical phenomena (e.g., acoustic resonance and fluid dynamics). I have developed two novel techniques using this principle: , a blow-based interaction technique for fabricated objects using acoustic resonance; and , a technique for fabricating touch-sensitive objects using pneumatic sensing and fluid dynamics principles.

Bubble formation plays an important role in industries concerned with mineral flotation, food, cosmetics, and materials, which requires additional energy to produce the liquid–gas interfaces. A naturally observed fact is, owing to the effect of surface tension, a bubble film tends to retract to reduce its surface area. Here we show a “reverse” phenomenon whereby a drop is transformed into a bubble using acoustic levitation via acoustic resonance. Once the volume of the cavity encapsulated by the buckled film reaches a critical value V*, resonance occurs and an abrupt inflation is triggered, leading to the formation of a closed bubble. Experiments and simulations both reveal that V* decreases with increasing acoustic frequency, which agrees well with acoustic resonance theory. The results afford enlightening insights into acoustic resonance and highlight its role in manipulating buckled fluid–fluid interfaces, providing a reference for fabricating unique core–shell-like materials., Bubbles tend to burst and retract into droplets. Here the authors show how a droplet can be turned into a bubble by levitating the droplets acoustically and exploiting their buckling to form gas bubbles.

A structure for an underwater sound absorber with subwavelength thickness and a quasi-perfect absorption property at multiple frequency bands is reported. This absorber consists of a viscoelastic coating layer embedded with periodically distributed plate scatterers (PSs). The embedded PSs cannot only slow sound waves in the coating, leading to a down-shifted resonance frequency where the absorption is maximized, but also introduce multiple local bending modes and local longitudinal modes in the coating. Via proper selection of the parameters of the PSs and the PS array, multiple local resonance modes of different types in a coating unit can be excited, resulting in quasi-perfect absorption of incident sound at multiple frequencies whose wavelengths are much longer than the thickness of the coating layer. For example, absorption (89%) of underwater sound at 462.9 Hz is achieved by such a layer with a thickness of 6 cm, which is 1.9% of the wavelength of the incident sound. Broadband quasi-perfect absorption can also be realized by coupling of those multiple local resonant modes. This quasi-perfect absorption property can also be observed for sound waves with different incident angles, because a large number of local intrinsic modes could still be excited.

Cast iron foundries have historically utilized ultrasonic methods to determine nodularity levels in ductile iron parts. The foundries have begun to search for an alternative that would provide a test of the whole part, while eliminating part preparation, consumables, rust and plating issues and safety hazards. Progress has been made in the application and performance evaluation of resonant acoustic method as an alternative tool for detecting unacceptable levels of nodularity in ductile iron. This paper covers other aspects of cast iron microstructure, namely graphite shape, graphite size and matrix microstructure. To identify cast iron microstructure variation within a thick section, samples from different locations of a thick section (2″) were studied. Finally, a preliminary study of effect of having casting skin on resonant frequency was also conducted. Step block castings were produced with above-mentioned variables. Rectangular samples for resonant inspection were machined. The cast iron samples were excited by a calibrated hammer, and the resonant frequencies (RF) were recorded with an accelerometer. The RF measurements were normalized to eliminate weight change affect. Finite element analysis (FEA) was done to show the minimum level of shift in RF due to dimensional variability. The design of experiment analysis showed that the variations in graphite shape and matrix microstructure are identifiable. The graphite size variation due to section sizes is detectable to a certain extent, i.e., variation between 5/8″ and 1″. However, the result obtained in this study does not support the use of resonant frequency shift to identify samples from section sizes 1″, 2″ and 4″. The RF response showed that the samples with surface condition (presence of skin) variation can be identified for a known graphite shape.

This work addresses the piezoelectric induced reduction of quality factor in fully-printed metal-insulator-metal (MIM) barium strontium titanate (BST) thick film varactors designed for high power operation. An acoustically optimized varactor design is presented and compared to a non-optimized high-power varactor. The design is utilized to present a narrowband acoustic suppression technique based on defined weights. The acoustically optimized varactor consists of 162 varactor cells in a capacitive matrix. The cells in the matrix are interconnectable allowing for a variable unbiased capacitance and power rating. Due to this setup, surface acoustic waves are interrupted, and the reduced size of the cells allows for a reduced BST layer thickness, shifting the acoustic resonance away from the operational frequency. Therefore, an inverted behavior in comparison to the high-power varactor is observed with an increasing quality factor with biasing voltage. Compared to the high-power varactor, the acoustically optimized varactor design shows a 40% increased quality factor in biased state. By applying the narrowband acoustic suppression technique, an increase in quality factor of 145% is achieved compared to the unsuppressed design. In comparison to the high-power varactor, the acoustical suppressed design shows an increase in quality factor of 480% at the first acoustic resonance frequency.

Acoustic signals passing through a material gather a great deal of analytical information. Such information act as a signature for classification of the materials. Therefore, the paper proposes a novel method for classification of oils by extracting spectral features from acoustic signals. A developed acoustic resonance spectrometry system has been used for the acquisition of acoustic signals from different oils. The system has a quartz V-tube and two similar piezoelectric transducers, attached at the two ends of the tube. One of the transducer acts as a transmitter and the others as a receiver. The transmitter generates the vibrations with the excitation of white noise. The vibrations transmitted through the tube along with oil from the transmitter end to the receiver end. At the receiver end, vibrations translated into the acoustic signal that has been recorded and analyzed. The experiments were performed on six different oils samples namely: Castor, Mustard, Olive, D.Almond, Petrol, and Tarpin. The Burg spectral analysis was carried out on acoustic signals and eight resonance peaks frequency were recorded. The principal component analysis was done on the collected resonance frequencies datasets. The first three principal components were given as input to ECOC SVM classifier using radial basic function kernel in five different output coding schemes one versus one (1VS1), one versus all (1VSA), ordinal (ORD), and binary complete (BNC). The accuracies of SVM_1VS1, SVM_1VSA, SVM_ORD, and SVM_BNC are found to be 100% in classifying Castor, Mustard, Olive, and Tarpin. The best classifier in classifying D.Almond and Petrol is SVM_ORD that has accuracies of 96.75% and 91.47% respectively. The total classification accuracies of classifiers SVM_1VS1, SVM_1VSA, SVM_ORD, and SVM_BNC are 95.71%, 93.08%, 98.03%, and 95.47% respectively. Hence, the variation in resonant peaks in the Burg autoregressive spectrum of acoustic signals showed significant potential in classifying the oils.

Mechanical strain plays a key role in the physics and operation of nanoscale semiconductor systems, including quantum dots and single-dopant devices. Here we describe the design of a nanoelectronic device where a single nuclear spin is coherently controlled via nuclear acoustic resonance (NAR) through the local application of dynamical strain. The strain drives spin transitions by modulating the nuclear quadrupole interaction. We adopt an AlN piezoelectric actuator compatible with standard silicon metal-oxide-semiconductor processing, and optimize the device layout to maximize the NAR drive. We predict NAR Rabi frequencies of order 200 Hz for a single $^{123}$Sb nucleus in a wide region of the device. Spin transitions driven directly by electric fields are suppressed in the center of the device, allowing the observation of pure NAR. Using electric field gradient-elastic tensors calculated by density-functional theory, we extend our predictions to other high-spin group-V donors in silicon, and to the isoelectronic $^{73}$Ge atom., 6 pages, 5 figures

In this study an approach is proposed to probabilistically evaluate wall thickness and the probability of pipe failure when subjected to wall thinning based on the results of periodic non-destructive evaluations. Electromagnetic acoustic resonance (EMAR) has been adopted as a specific non-destructive method to evaluate pipe wall thickness. A probabilistic model correlating the true and evaluated thicknesses was proposed on the basis of the results of laboratory experiments to measure 38 artificially corroded carbon steel plates. A Bayesian approach was proposed to estimate the probability of true thickness and the probability of failure from results of multiple non-destructive evaluations at certain time intervals. The approach was applied to the analyses of several virtual periodic EMAR evaluations of pipe wall thickness that gradually became thinner, whose results demonstrate that the proposed approach is effective regardless of the variability of corrosion rates.

A planar magnetoelectric voltage transformer based on a layered composite structure containing layers of amorphous ferromagnet and piezoelectric lead zirconate-titanate has been fabricated and investigated. The transformer uses a coilless system (the so-called "magnetic capacitor") to excite the direct magnetoelectric effect at the frequency of the acoustic resonance of the structure, which made it possible to significantly simplify the design. The voltage transformation ratio of the magnetoelectric transformer, in contrast to the known electromagnetic or piezoelectric transformers, can be tuned by an external magnetic field from zero to 13.2 with an increase in the field from zero to 30 Oe. The operating range of the output voltage of the transformer is 0−400 mV, and the output power reaches 9 μW at optimal load resistance. The technique for calculating the characteristics of the transformer is described.

In general, the aerosols mixed in air medium can be regularly manipulated by means of the interactions between the aerosols and the acoustic field. The manipulable properties of aerosols can be engineered through geometric parameter and acoustic resonance condition of the underlying device. The aerosols manipulated by modulated multiple acoustic wavepackets (MAWP) in acoustic resonance condition is proposed and demonstrated in this paper, whose application belongs to an efficient aerosol removal technique. The experimental results indicated that the removal efficiency of aerosols was mainly influenced by the different harmonic order. The technique and process proposed in this paper was feasible for industrial application. The MAWP is modulated by means of the synthetic standing wave field at the resonant frequency 1.268 kHz. The aerosol manipulation processes through MAWP consist of the aerosol shift, collision aggregation and deposition between the dot and the anti-neck of a single wavepacket. As a visual inspection confirming standing wave, the processes may also be applied in modulating the MAWP simultaneously. The manipulation efficiency can be increased due to the increase of wavepacket amount under the same operating conditions. The acoustic radiation force causes shift and accumulation of aerosol in waveguide and the secondary radiation force enhances collision aggregation and deposition thereof. The initial number concentration of particles

Acoustic resonance (AR) occurs in metal halide (MH) lamps and could cause light flicker, lamp arc bending and rotation, lamp extinction and arc tube explosion in the worst situations. This study takes place in the context of developing electronic ballasts with a low-cost and robust AR detection and avoidance mechanism. In this case, a lock-in amplifier is used to obtain the variations of lamp voltage envelope. A mathematical criterion is proposed to classify AR presence and severity. This criterion is based upon the short-term standard variation of voltage envelope and it was tested over a set of MH lamps with different powers and manufacturers. By varying the operation frequency of the high-frequency ballast, it was experimentally possible to control the average electrical power and the level of AR occurrence in the lamps. A data set consisting of healthy (without AR or AR-free) and faulty (with AR) cases was constructed by varying these parameters. The proposed criterion permitted to classify the observed waveforms in a two-dimensional (2D) plane. It was observed that AR-free and AR cases are separated. The results of this study show that the voltage envelope variations and the defined criterion are significantly correlated with AR presence whatever the lamp of the operation power.

This study proposes an acoustic theory that describes the resonance phenomena in a resonator made of acoustic composite right/left-handed (CRLH) metamaterials, and verifies it through numerical simulation. The established theory for a microwave CRLH metamaterial resonator is adapted to explain the resonance phenomena in an acoustic CRLH metamaterial resonator. In particular, attention is focused on the zeroth-order resonance phenomenon which has several interesting properties. When a resonator is composed of a CRLH metamaterial, a resonance with a flat acoustic field distribution may occur at one of the frequencies where the wavenumber becomes zero. This resonance is called zeroth-order resonance. Through numerical simulation, such unusual resonance phenomenon in acoustics is observed in more detail and the proposed theory is verified. The results of the theory and the numerical simulation clearly show that zeroth-order resonance can exist at those frequencies where the acoustic field distribution is flat due to infinite wavelength. It is also shown that the resonance frequency and the Q factor of this resonance depend on the boundary condition at both ends of the resonator, and they basically do not change even when the number of units is reduced or increased.

Here, an efficient acoustic energy harvester is proposed that is suitable for low-frequency bands. It is composed of a tunable Helmholtz resonator with a flexible bottom, with affixed piezo disk and proof mass. The proof mass can lower the mechanical resonance frequency of the bottom, while increasing the harvested sound power. The proposed Helmholtz resonator was designed for sound pressure amplification. Furthermore, it is tunable, enabling adjustment of the acoustic resonance frequency to the mechanical resonance frequency. The designed tunable Helmholtz resonator has been fabricated and its function was experimentally verified. Furthermore, the acoustic energy harvesting study was conducted under 100 dB sound pressure level excitation. Experimental results show that the proposed harvester can generate 3.49 μW (at optimal load) when both resonance frequencies are matched, and the energy conversion efficiency can reach up to 38.4%.

Pressure relief valves (PRVs) in systems supporting constant vessel pressure are required to operate over a wide range of valve strokes, of set pressures and external impacts such as adjacent components vibration, ambient temperature, etc. At the same time, valve operation should be stable, reliable and precise. The aim of this work is to broaden the current knowledge of the PRV self-excited oscillation mechanism. The methods employed during the study are time history review with further spectrogram post processing of the valve input and output parameters in its opening and closing modes. Furthermore, the experimental investigations include valve tests under external vibration conditions. Additionally, an experimental verified mathematical model has been developed that can explain the nature of the valve self-excited oscillation onset. The model represents a one-dimensional approach to predict valve dynamics enhanced with a three-dimensional simulation of the flow choked through the valve. The experimental investigation demonstrated low-frequency self-excited oscillation in the range of 1–10 Hz (amounting to 0.04–0.4 of the valve spring-mass eigenfrequency) throughout the valves, but a number of the valves showed their failure proneness at high-frequency self-excited oscillations within the range of 100–120 Hz (amounting to 4.0 to 4.8 of the valve spring-mass eigenfrequency). The experiments have shown that the reasons of this kind of damage are low-frequency self-excited oscillation as well as external vibration coupled with acoustic resonance of the vessel with an attached the pipe leading to fleeting reduction of drag force in the valve and to high-frequency valve chatter. To prevent of high-frequency self-excited oscillation, the developed design features allow constant and appropriate value of friction force required for chatter elimination in all operating modes of the valve.

In order to reduce the electric consumption for high intensity discharge lamps (HID), the use of high frequencies electronic ballasts represents both a solution and many advantages such as, the decrease in the congestion, low costs and weak losses, approximately 10%. However it is not regarded as perfectly reliable, this is due in a great part to the appearance of Acoustic Resonances inside the arc tube which can result in low frequency light flicker and even lamp destruction. Experimentally we used a HID lamp of 50 W and we determined, light flicker frequencies and the arc motion frequencies using a photodiode which detects the light intensity fluctuation and a camera to record the arc motion. The experiment was done in the Department of Mechanical Engineering and Production, Hamburg University of Applied Sciences.

Resonant ultrasound spectroscopy (RUS) was used in this paper to measure shifts in resonant frequency that arise from the presence of cracks in barium-titanate-based multilayer ceramic capacitors (MLCCs). This paper was motivated by an industrial need for a nondestructive quality-control technique with enhanced capabilities for detecting dielectric cracks that have no initial effect on electrical characteristics of MLCCs. In this quality-control application, no information will generally be available on acoustic spectra of capacitors prior to the introduction of cracks during manufacture or mounting in devices. However, information on the distribution of frequencies of a specified resonant acoustic mode of a population of uncracked MLCCs could serve as a reference for determining whether the resonant frequency of an individual MLCC is within an acceptable range. In this paper, acoustic spectra were obtained from sets of MLCCs before and after thermal quenching that generated surface-breaking cracks in a fraction of the specimens. Three resonant modes below 1000 kHz were studied. The largest of these three resonant peaks, in the range of 575 kHz to 595 kHz in MLCCs before heat treatment, was found to be most sensitive to the presence of visible cracks. An analysis of Gaussian fits of the frequency distributions for this mode before and after heat treatment shows that approximately 71% of the visibly cracked MLCCs and less than 1% of the uncracked quenched MLCCs are rejected when the criterion for rejection is that the frequency is more than two standard deviations different than the mean frequency before heat treatment. These results show that RUS is a promising approach for nondestructive screening for the presence of cracks in MLCCs.

A theoretical study of resonant photoacoustic spectroscopy (PAS) for glucose noninvasive detection was performed by rigorously taking into account the spatial distribution of the photothermal source and the acoustic resonance mode in a cavity. The sensitivity of the dual-wavelength differential PA technique is derived when glucose with weak optical absorption is detected in solution with high optical absorption. The sensitivity dependence of acoustic resonance modes was evaluated by both analysis and experiment with pure water. The analytical results show good agreement with the experiment. The sensitivity against the concentration of the target molecules can be enhanced approximately twofold by choosing the optimum acoustic resonance mode. The results indicate that this method has the potential to detect glucose in a physiological range comparable to that of invasive blood glucose monitoring.

This letter analytically and numerically examines sound transmission through a metasurface of hybrid resonances in the presence of thermoviscous dissipation. The metasurface unit of a subwavelength thickness consists of a slit and series of sided resonators embedded in air. Both wall friction and thermoviscous diffusivity in the unit are taken into account. The results reveal that the dissipation has a weak influence on phases even when there is a large loss. The dissipation reduces the transmission by 28% when the thermoviscous boundary layer thickness is only around 2.3% of the slit width. Optimal designs for minimal dissipation are addressed.

In this paper, acoustic resonance testing on glass intravenous (IV) bottles is presented. Different machine learning methods were applied to distinguish acoustic observations of bottles with defects from the intact ones. Due to the very limited amount of available specimens, the question arises whether the deep learning methods can achieve similar or even better detection performance compared with traditional methods.

A novel quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor based on a micro quartz tuning fork (QTF) is reported. As a photoacoustic transducer, a novel micro QTF was 3.7 times smaller than the usually used standard QTF, resulting in a gas sampling volume of ~0.1 mm3. As a proof of concept, water vapor in the air was detected by using 1.39 &mu, m distributed feedback (DFB) laser. A detailed analysis of the performance of a QEPAS sensor based on the micro QTF was performed by detecting atmosphere H2O. The laser focus position and the laser modulation depth were optimized to improve the QEPAS excitation efficiency. A pair of acoustic micro resonators (AmRs) was assembled with the micro QTF in an on-beam configuration to enhance the photoacoustic signal. The AmRs geometry was optimized to amplify the acoustic resonance. With a 1 s integration time, a normalized noise equivalent absorption coefficient (NNEA) of 1.97 &times, 10&minus, 8 W&middot, cm&minus, 1&middot, Hz&minus, 1/2 was achieved when detecting H2O at less than 1 atm.

In this study, 145 poplar (Populus &times, euramericana cv.&rsquo, 74/76&rsquo, ) seedlings, a common plantation tree species in China, were selected and their ultrasonic velocities were measured at four timepoints during the first growth year. After that, 60 poplar seedlings were randomly selected and cut down to determine their acoustic velocity, using the acoustic resonance method. The effects of influencing factors such as wood green density, microfibril angle, growth days, and root-collar diameter on acoustic speed in seedlings and the relationship between ultrasonic speed and acoustic resonance speed were investigated and analyzed in this work. The number of specimens used for investigating growth days and root-collar diameter was 145 in both cases, while 60 and two specimens were used for investigating wood density and the microfibril angle, respectively. The results of this study showed that the ultrasonic speed of poplar seedlings significantly and linearly increased with growth days, within 209 growing days. The ultrasonic velocity of poplar seedlings has a high and positive correlation with growth days, and the correlation was 0.99. However, no significant relationship was found between the ultrasonic velocity and root-collar diameter of poplar seedlings. Furthermore, a low and negative relationship was found between wood density and ultrasonic speed (R2 = 0.26). However, ultrasonic velocity significantly decreased with increasing microfibril angle (MFA) in two seedlings, and thus MFA may have an impact on ultrasonic speed in poplar seedlings. In addition, ultrasonic velocity was found to have a strong correlation with acoustic resonance velocity (R2 = 0.81) and a good correlation, R2 = 0.75, was also found between the dynamic moduli of elasticity from ultrasonic and acoustic resonance tests. The results of this study indicate that the ultrasonic technique can possibly be used to measure the ultrasound speed of young seedlings, and thus early screen seedlings for their stiffness properties in the future.

This paper presents preliminary experimental results on the influence of the flow approach angle on the acoustic resonance excitation of in-line tube bundles in cross-flow. The pitch-to-diameter ratio (P/D) of the in-line tube bundles investigated is P/D = 1.733. The flow approach angle was investigated by physically rotating the tube bundle clockwise relative to the flow direction. The tube bundles are capable of rotating with increments of 5° up to an angle of 45°. For brevity, only the results for the 0° and 30° orientation will be presented herein. For the 0° orientation, two Strouhal frequencies (St1 = 0.437 and St2 = 0.252) were observed. However, only one of these frequencies (St1 = 0.437) was capable of exciting resonance. During resonance, a peak sound pressure level (SPL) of 170 dB was achieved. The Strouhal frequencies and peak SPL agrees well with what has been presented in the literature. For the 30° orientation, only one Strouhal frequency (St1 = 0.98) was measured. At this orientation, the lock-in phenomenon occurred at a much lower flow velocity compared to the 0° orientation with a peak SPL reaching 153 dB. Jumps in the lock-in frequency were observed at the 30° orientation. This phenomenon is associated with two reasons. The first reason is a partial lock-in with an acoustic resonant mode, due to the acoustic energy not being fully trapped within the tube bundle. The second reason is related to the changes in the apparent speed of sound resulting in variations in the acoustic cross-mode frequency depending on where the excitation source is emanating from within the tube bundle. A brief summary of the results is presented in this paper.

Piping vibration had been observed in one of our refinery’s reactor inlet piping for several decades. Vibration levels in inlet piping for reactor ‘D’ and ‘E’ were highest, relative to those in reactor ‘A’, ‘B’, and ‘C’. To cope with the vibration, design changes to small-bore branch connections had been implemented to reduce susceptibility to the vibration. A recent increase in production demand made the vibration levels more evident and a production constraint was imposed after an MOV gas seal failure. Analysis identified the root-cause as flow-excited acoustic resonance of (almost) coaxial closed side branches in the flow path. The selected vibration mitigation solution involved installing a perforated annulus in the main line, in front of the mouth of the (almost) coaxial closed side branch acoustic resonator. Before fabricating and installing the perforated annulus, it was decided to evaluate its expected performance by means of computational fluid dynamics (CFD) and structural stress finite element analysis (FEA). This paper gives an account of the selection of the perforated annulus as the preferred vibration mitigation solution and its evaluation by means of high-performance computing CFD and FEA. The CFD and FEA analysis showed that the perforated annulus would perform as intended and mitigate the piping vibration. The perforated annulus was fabricated and installed in the inlet piping for reactor ‘D’. Piping vibration was observed to be mitigated, even when flowing above the design rate. The perforated annulus vibration mitigation solution was replicated in the inlet piping for reactor ‘E’. The production constraint has since been lifted.

The characterization of buried nanoscale structures nondestructively is an important challenge in a number of applications, such as defect detection and metrology in the semiconductor industry. A promising technique is Subsurface Scanning Probe Microscopy (SSPM), which combines ultrasound with Atomic Force Microscopy (AFM). Initially, SSPM was used to measure the viscoelastic contrast between a subsurface feature and its surrounding medium. However, by increasing the ultrasonic frequency to >1 GHz, it has been shown that SSPM can also measure acoustic impedance based contrasts. At these frequencies, it becomes difficult to reliably couple the sound into the sample such that the AFM is able to pick up the scattered sound field. The cause is the existence of strong acoustic resonances in the sample, the transducer, and the coupling layer-the liquid layer used to couple the sound energy from the transducer into the sample-in combination with the nonlinearity of the tip-sample interaction. Thus, it is essential to control and measure the thickness of the coupling layer with nanometer accuracy. Here, we present the design of a mechanical clamp to ensure a stable acoustic coupling. Moreover, an acoustic method is presented to measure the coupling layer thickness in real-time. Stable coupling layers with thicknesses of 700 ± 2 nm were achieved over periods of 2-4 h. Measurements of the downmixed AFM signals showed stable signal intensities for >1 h. The clamp and monitoring method introduced here makes scattering based SSPM practical, robust, and reliable and enables measurement periods of hours.

This paper proposes a novel single-stage high-power-factor electronic ballast for high-pressure sodium (HPS) lamps suitable for streetlight applications; this ballast integrates an interleaved buck-boost converter with coupled inductors and a full-bridge inverter for supplying low-frequency square-wave sources to the HPS lamp without incurring acoustic resonance. A 250W-rated prototype HPS lamp ballast circuit operating with 110V-rms input utility-line voltage has been successfully implemented and tested. The functionalities of the presented ballast are demonstrated through satisfactory experimental results in terms of high power factor (>0.99), low utility-line current total harmonic distortion 89%).

Radiation pressure within engineered structures has recently been used to couple the motion of nanomechanical objects with high sensitivity to optical and microwave electromagnetic fields. Here, we demonstrate a form of electromechanical crystal for coupling microwave photons and hypersonic phonons by embedding the vacuum-gap capacitor of a superconducting resonator within a phononic crystal acoustic cavity. Utilizing a two-photon resonance condition for efficient microwave pumping and a phononic bandgap shield to eliminate acoustic radiation, we demonstrate large cooperative coupling ($C \approx 30$) between a pair of electrical resonances at $10$GHz and an acoustic resonance at $0.425$GHz. Electrical read-out of the phonon occupancy shows that the hypersonic acoustic mode has an intrinsic energy decay time of $2.3$ms and thermalizes close to its quantum ground-state of motion (occupancy $1.5$) at a fridge temperature of $10$mK. Such an electromechanical transducer is envisioned as part of a hybrid quantum circuit architecture, capable of interfacing to both superconducting qubits and optical photons., Comment: 16 pages, 12 figures, 8 appendices

This paper describes a new concept to monitor the temperature of water utilizing the acoustic resonance, which occurs when ultrasound passes through a thin layer. In the ultrasonic transmission system that comprises of the reflection plate, thin film, and water, the reflection coefficient of the ultrasound at the plate/film/water interface depends on the frequency and takes its minimum value at the resonant frequency. Notably, this is closely related to the acoustic impedance of the water; moreover, it is a known fact that the acoustic impedance of the water demonstrates temperature dependence. Against this background, the present study aims to develop a technique in order to monitor the temperature of water utilizing the aforementioned correlation between the reflection coefficient and water temperature. First, a theoretical model was developed to determine the acoustic impedance of water from the difference in the amplitude spectra of echoes reflected at the back of the plate in the cases both with and without the film. It was found that the ratio of the amplitude spectrum of the echo recorded in the case with the film to that in the case without the film clearly decreased with a drop in water temperature. From this, we obtained the equation for determining water temperature experimentally. Finally, the temperature of water, which was brought down by air or ice cooling, was monitored by the proposed method. It was found that the behavior of temperature determined by the proposed method was congruent with that which was measured by a thermocouple.

A fast and reliable photoacoustic (PA) sensor for trace gas detection is reported. The sensor is based on a 3D-printed resonant cell in combination with a continuous wave mode-hop-free external cavity quantum cascade laser to rapidly acquire gas absorption data in the midinfrared range. The cell is designed so as to minimize the window PA background at a selected acoustic resonance. The goal is a resonant PA cell capable of detecting the traces of gases using wavelength modulation of the laser source and second harmonic detection. The versatility and enhancement of the limit of detection at sub-ppm levels are investigated by monitoring specific lines of hydrogen sulfide (H2S). The noise-equivalent absorption normalized to laser-beam power and detection bandwidth is 1.07×10-8 W cm-1 Hz-1/2 for H2S targeting the absorption line at 1247.2 cm−1. These properties make the sensor suitable for various practical sensors for water quality applications.

Scanning ultra-short pulse laser ablation is a very flexible technology that can be used for the subtractive manufacturing of complex three-dimensional structures with precision requirements on micrometer level. In our studies, inadvertent periodic deviations at the bottom of ablated cavities in silicon were observed after laser ablation with ultra-short laser pulses. We introduce the hypothesis of an interdependency between the ablation process and ultrasonic resonant acoustic waves, also known as standing waves, forming in the air within the ablated volume. Using basic acoustic wave equations, the corresponding periodicity of the deviations at the bottom surface of the cavities is described with good agreement to our experimental data.

To design an instrumentation system for evaluating contrast agents of photoacoustic imaging, the optimal pulse width of the excitation laser is discussed in this paper. A pulsed semiconductor laser with a moderate pulse width (15–129 ns) and low peak power (1 W) is adopted in the proposed system. Black ink is selected as the reference sample, which is filled in a glass capillary embedded in a soft phantom. Our aim is that the pulse width matches the acoustic resonance of the target and the center frequency of the receiving transducer (5 MHz) to obtain sufficient strength of the ultrasonic signal with minimal laser power. A series of experiments reveal a clear relationship between the laser pulse width and the maximal amplitude of the resonance mode. Acoustic resonance occurs inside the capillary whose frequencies can be precisely predicted as the radial eigen mode. The laser pulse width and concentration of the sample showed little influence on these resonance frequencies as expected. To efficiently utilize the signal enhancement effect due to the resonance, several resonance mode candidates are investigated and discussed. It then becomes clear that the second angular and zeroth radial order mode is useful for capillaries with sub-millimeter inner diameters. It was demonstrated that the concentration of samples had very limited influence on the frequencies. Finally, consideration based on two delayed attenuating vibrations is successfully conducted to explain the experimental results.

Noise-like quasi-continuous-wave background (qCWB) in a mode-locked fiber laser mediates various multi-pulse dynamics via long-range inter-pulse interactions. This raises a possibility to control multi-pulse phenomena through manipulation of the qCWB, while it has been rarely studied yet. Here, we investigate the qCWB engineering by imposing optomechanically induced impulsive intensity modulations on the qCWB. The mode-locked pulses excite electrostrictively several transverse acoustic resonance modes inside the fiber cavity, which eventually leads to the formation of sharp qCWB modulations regularly spaced in the time domain. In particular, we experimentally demonstrate that the characteristics of the optomechanical qCWB modulations can be adjusted by controlling the in-fiber optomechanical interactions via changing the structure of the fiber core, cladding, and coating. Our observations are supported by directly measured forward stimulated Brillouin scattering spectra of the intracavity fibers.

In this paper, we investigate the femtosecond-optical-pulse-induced strain dynamics in relatively thin (100 nm) and thick (10 000 nm) silicon plates based on finite-element simulations. In the thin sample, almost spatially homogeneous excitation by the optical pulse predominantly generates a standing wave of the lowest-order acoustic resonance mode along the out-of-plane direction. At the same time, laterally propagating plate waves are emitted at the sample edge through the open edge deformation. Fourier transformation analysis reveals that the plate waves in the thin sample are mainly composed of two symmetric Lamb waves, reflecting the spatially uniform photoexcitation. In the thick sample, on the other hand, only the near surface region is photo-excited and thus a strain pulse that propagates along the out-of-plane direction is generated, accompanying the laterally propagating pulse-like strain dynamics through the edge deformation. These lateral strain pulses consist of multiple Lamb waves, including asymmetric and higher-order symmetric modes. Our simulations quantitatively demonstrate the out-of-plane and in-plane photoinduced strain dynamics in realistic silicon plates, ranging from the plate wave form to pulse trains, depending on material parameters such as sample thickness, optical penetration depth, and sound velocity.

In the context of sound incident upon a metamaterial plate, explicit formulas for sound transmission loss (STL) are derived in the presence of external mean flow. Metamaterial plate, consisting of homogeneous plate and lateral local resonators (LLRs), is homogenized by using effective medium method to obtain the effective mass density and facilitate the calculation of STL. Results show that (a) vigorously oscillating LLRs lead to higher STL compared with bare plate, (b) increasing Mach number of the external mean flow helps obtain higher STL below the coincidence frequency but decreases STL above the coincidence frequency due to the added mass effect of light fluid loading and aerodynamic damping effect, (c) the coincidence frequency shifts to higher frequency range for the refracted effect of the external mean flow. However, effects of the flow on STL within negative mass density range can be neglected because of the lateral local resonance occurring. Moreover, hysteretic damping from metamaterial can only smooth the transmission curves by lowering higher peaks and filling dips. Effects of incident angles on STL are also examined. It is demonstrated that increasing elevation angle can improve the sound insulation, while the azimuth angle does not.

This paper discusses the diagnostic signs used to monitor the technical condition of GCU (gas compressor units) in operation. The problem of detecting the impact of GCU design on their wave gas dynamics is solved, as well as detecting diagnostic signs of defects in engines during operation. To solve the problem, numerical methods for modeling of wave processes in conjunction with the methods of research of vibrating are used. A technique is created to detect signs of acoustic vibrations in the gas-dynamic flows of gas turbines, and estimate their effect on engine components. To improve the reliability of resonance detection in engine components, authors used numeric methods to estimate probability of resonances in various operating modes of GCUs. The methods involve a 3D modeling of input and output gas channels. Operating maps are plotted for individual engine components (high- and low-pressure compressors and turbines, combustion chamber). It was revealed that the design of the GCU affects aerodynamic vibrations, causing vibration and resonance in engine components at particular operating conditions. This may contribute to increased vibration in engine components, which leads to increased cyclic load values, and as a result decreases MTBF (mean time between failures) due to failure of the components. The developed technique allows monitoring the emergence of acoustic resonance zones when changing operating modes of gas pumping engines. Opportunities are emerging to assess the impact of vibration on technical condition of engine components, and to develop recommendations on altering the geometry of gas channels for the purpose of eliminating low-frequency pulsations of their working fluid.

Extraordinarily rapid mixing has surprisingly been achieved in confined mixing layers by active forcing within an optimal narrow frequency band (Wang, PhD Dissertation, 1999; Wang, Chem. Eng. Sci., 2003; Wang, AIChE J., 2006). However, the corresponding mechanism of the large receptivity and rapid mixing is still unclear so far. Since it is found that the optimal frequency that corresponds to the rapid mixing is independent of Reynolds number or bulk flow velocity, we postulate that some type of resonance of the experimental setup or fluid-structure interaction might be the cause. In this manuscript, the possible influence of acoustic resonance and fluid-structure interactions are investigated by both parametric study through flow visualization and finite element method (FEM). The results reveal the optimal forcing frequency of the fast mixing is tightly related to a complicated acoustic resonance mechanism of the entire water tunnel system, and when the confined mixing layers are forced under the resonance frequency, ultrafast mixing can be observed. This finding may lead to new technology for mixing and heat transfer enhancement.

Variants of the resonance excitation of a narrow intense acoustic beam are described for a special geometry of the propagation of an incident pump wave in tetragonal and cubic crystals. Resonances arise when the excited reflected beam propagates at a narrow angle to the surface and has a structure close to the bulk eigenmode. Relations between elastic moduli are established that ensure that the reflection is close to conversion and minimizes the energy loss upon the reflection of a parasitic leakage wave. A number of crystals are found in which these relations can be observed.

The effect of electronic tuning of acoustic resonances in an acousto-optic mode locker is studied theoretically and experimentally. The tuning is implemented by means of changing a matching inductance connected to the transducer in parallel. Experimental investigations are carried out with a mode locker made of a fused quartz with a lithium niobate transducer. Varying magnitude of the inductor from 0.025 to 0.25 mH has made it possible to retune the acoustic resonance frequency by 0.19 MHz, i.e. wider than the acoustic resonance half-width.

We have performed a detailed analysis of the temperature field in a turbulent swirl flame operating with a self-excited thermo-acoustic instability. The temperature field was measured using 5 kHz chirped-probe-pulse (CPP) femtosecond (fs) coherent anti-Stokes Raman scattering (CARS). The measurements are described in detail in the part 1 companion article. In this paper, part 2, a detailed analysis of the time-resolved temperature measurements and simultaneous pressure measurements is performed to provide insight into the dynamics and structure of the swirl-stabilized flame. This work is the first to capture the dynamics of the flame, flow, and coupled flow-flame processes using high-fidelity, spatially- and temporally-resolved thermometry in a flame of practical relevance. The time-averaged contour plot of the temperature field indicates that the flame is very flat and stabilizes approximately 10 mm downstream of the burner face. In this region, there are very significant temperature fluctuations indicating a very high level of unsteadiness. The temperature probability distribution functions (PDFs) are clearly bimodal in this region near the injector face. A Fourier analysis of the temperature time series revealed multiple coherent oscillatory modes. The strongest oscillation was found to be coherent and in-phase with an acoustic resonance at 314 Hz, as expected from the Rayleigh criteria for the unstable flame. An analysis of the phase-conditioned average temperature fields clearly shows an axial pumping of low-temperature reactants, which are consumed after a convective delay and result in a spike in the global heat-release rate. Continued analysis also revealed a 438 Hz oscillation that was found to correspond with the dynamics of convective transport by a helical precessing vortex core (PVC). The structure of the PVC, and its interaction with the flame, were studied based on the presence of this characteristic frequency in the power spectral densities computed throughout the flow. The precision and time-resolution of the CPP fsCARS measurements was also sufficient to enable computation of the integral time-scales as well as the PDFs of the temporal temperature gradients. A sample of state space trajectories were used to provide insight into the nature of coupling between the narrowband acoustic resonance and the broadband spectrum of turbulent flame processes.