Exploring advanced techniques capable of probing nanometric acoustic waves in nanostructures is critically important for the development of miniaturized acoustic devices.In this study,we probe the optically-excited ac...Exploring advanced techniques capable of probing nanometric acoustic waves in nanostructures is critically important for the development of miniaturized acoustic devices.In this study,we probe the optically-excited acoustic waves in a single silicon nanowire(NW)using the time-resolved(tr-)high-order Laue-zone(HOLZ)lines under convergent-beam electron diffraction(CBED)conditions in an ultrafast transmission electron microscope(UTEM).We devise an experimental scheme to obtain tr-HOLZ lines under off-zone-axis CBED conditions.We also propose a geometric description of HOLZ line formation and use this alternative description to quantitatively evaluate the dynamics of optically-excited silicon NW.Using part of the deformation gradient tensor,our simulations of the dynamics of Si NW reproduce the experimental results.We further discuss the feasibility of a full retrieval of the deformation gradient tensor by using a set of HOLZ lines from three zone axes.Our findings illustrate a strategy for the quantitative access to dynamical acoustic waves optically excited in micro-and nano-structures using UTEM.展开更多
Nonplanar electron acoustic waves(NEAWs)with double spectral index-distributed hot electrons are studied under the two-temperature electrons model in a collisionless unmagnetized plasma.Using this model,the Korteweg–...Nonplanar electron acoustic waves(NEAWs)with double spectral index-distributed hot electrons are studied under the two-temperature electrons model in a collisionless unmagnetized plasma.Using this model,the Korteweg–de Vries(KdV)equation is derived in nonplanar geometry.On the basis of the solutions of KdV equation,alterations of velocity,width,and amplitude of acoustic waves having various plasma factors are investigated.Nonlinear and dispersion coefficients obtained rely on double spectral index parameters r and q,and particle densityα.The combined influence of these factors significantly alters the features of electron acoustic waves in nonplanar geometry.This study is expected to contribute to the understanding of nonlinear principles that underlie nonplanar electrostatic waves in laboratory plasmas as well as in space.展开更多
Based on the Burgers equation and Manley-Rowe equation, the derivation about nonlinear interaction of the acoustic waves has been done in this paper. After nonlinear interaction among the low-frequency weak waves and ...Based on the Burgers equation and Manley-Rowe equation, the derivation about nonlinear interaction of the acoustic waves has been done in this paper. After nonlinear interaction among the low-frequency weak waves and the pump wave, the analytical solutions of acoustic waves＇ amplitude in the field are deduced. The relationship between normalized energy of high-frequency and the change of acoustic energy before and after the nonlinear interaction of the acoustic waves is analyzed. The experimental results about the changes of the acoustic energy are presented. The study shows that new frequencies are generated and the energies of the low-frequency are modulated in a long term by the pump waves, which leads the energies of the low-frequency acoustic waves to change in the pulse trend in the process of the nonlinear interaction of the acoustic waves. The increase and decrease of the energies of the low-frequency are observed under certain typical conditions, which lays a foundation for practical engineering applications.展开更多
We investigate the surface acoustic wave(SAW)modulation of the exchange bias field(H_(EB))in Py/IrMn films deposited on LiNbO_(3)substrates.We measured the anisotropic magnetoresistance(AMR)of the multilayer film when...We investigate the surface acoustic wave(SAW)modulation of the exchange bias field(H_(EB))in Py/IrMn films deposited on LiNbO_(3)substrates.We measured the anisotropic magnetoresistance(AMR)of the multilayer film when continuous SAW or pulsed SAW were applied and obtained H_(EB).With continuous SAW,the H_(EB)decreases continuously with power.While in the case of pulsed SAW,the H_(EB)first decreases and then stabilizes.Compared to pulsed SAW,the thermal effects from the continuous SAW lead to the continuous decrease of H_(EB)at higher SAW power,which is verified by the measurement of H_(EB)at different temperatures and input currents.Furthermore,our results show that pulsed SAW can effectively avoid thermal effects.The decrease of H_(EB)at smaller power in both continuous and pulsed SAW is mainly due to the SAW-induced dynamic strain field,which leads to a small perturbation in the magnetic moment of the FM layer.Combined with the AMR values measured at different angles during the saturation field,we believe that the SAW-induced dynamic strain field causes a 15°angle between the magnetic moment and the easy axis.Our experiments provide a different approach to manipulating H_(EB),opening up a potential avenue for future manipulation of antiferromagnetic moments.展开更多
The propagation of surface acoustic waves in layered piezoelectric structureswith initial stresses is investigated. The phase velocity equations are obtained for electricallyfree and shorted cases, respectively. Effec...The propagation of surface acoustic waves in layered piezoelectric structureswith initial stresses is investigated. The phase velocity equations are obtained for electricallyfree and shorted cases, respectively. Effects of the initial stresses on the phase velocity and theelectromechanical coupling coefficient for the fundamental mode of the layered piezoelectricstructures are discussed. Numerical results for the c-axis oriented film of LiNbO_3 on a sapphiresubstrate are given. It is found that the fractional change in phase velocity is a linear functionwith the initial stresses, and the electromechanical coupling factor increases with an increase ofthe absolute values of the compressive initial stresses. The results are useful for the design ofsurface acoustic wave devices.展开更多
Cylindrical and spherical (nonplanar) solitary waves (SWs) and double layers (DLs) in a multi-ion plasma system (containing inertial positively as well as negatively charged ions, non-inertial degenerate electrons, an...Cylindrical and spherical (nonplanar) solitary waves (SWs) and double layers (DLs) in a multi-ion plasma system (containing inertial positively as well as negatively charged ions, non-inertial degenerate electrons, and negatively charged static dust) are studied by employing the standard reductive perturbation method. The modified Gardner (MG) equation describing the nonlinear propagation of the dust ion-acoustic (DIA) waves is derived, and its nonplanar SWs and DLs solutions are numerically analyzed. The parametric regimes for the existence of SWs, which are associated with both positive and negative potential, and DLs which are associated with negative potential, are obtained. The basic features of nonplanar DIA SWs, and DLs, which are found to be different from planar ones, are also identified.展开更多
The application of surface acoustic waves（SAWs） for thickness measurement is presented. By studying the impact of film thickness h on the dispersion phenomenon of surface acoustic waves, a method for thickness deter...The application of surface acoustic waves（SAWs） for thickness measurement is presented. By studying the impact of film thickness h on the dispersion phenomenon of surface acoustic waves, a method for thickness determination based on theoretical dispersion curve v（ fh） and experimental dispersion curve v（ f） is developed. The method provides a series of thickness values at different frequencies f, and the mean value is considered as the final result of the measurement. The thicknesses of six interconnect films are determined by SAWs, and the results are compared with the manufacturer＇s data.The relative differences are in the range from 0.4% to 2.18%, which indicates that the surface acoustic wave technique is reliable and accurate in the nondestructive thickness determination for films. This method can be generally used for fast and direct determination of film thickness.展开更多
In the backward propagation of acoustic waves, the direction of phase velocity is anti-parallel to that of group velocity. We propose a scheme to manipulate the backward propagation using a periodicM structure. The dy...In the backward propagation of acoustic waves, the direction of phase velocity is anti-parallel to that of group velocity. We propose a scheme to manipulate the backward propagation using a periodicM structure. The dynamic backward propagation process is further experimentally observed. It is demonstrated that the oblique incident plane wave moves backward when it travels through the periodical structure and the backward shift can be controlled within a certain range.展开更多
In a biomimetic approach the feasibility of liquid flow actuation by vibrating protruding structures excited via guided acoustic waves is investigated.Inspired by periodically beating cilia the loop part of a punched ...In a biomimetic approach the feasibility of liquid flow actuation by vibrating protruding structures excited via guided acoustic waves is investigated.Inspired by periodically beating cilia the loop part of a punched metallic hook-and-loop tape with tilted protruding loops was used as a waveguide for plate waves in water.Such waves were excited in the frequency range of 110 Hz to 220 Hz by directly coupling the tape to a loudspeaker membrane.A flow generated in the tilt direction of the loops with velocities up to 60 mm s 1 was visualized by ink droplets deposited on the tape.The phenomenon persisted,when the protruding length of the loops was reduced by decreasing the protrusion angle.However,after closing the punch holes near the loops with sticking tape streaming could not be observed any longer.The same happened with open punch holes when the ink was replaced by glycerol.Low-frequency acoustic streaming around vibrating sharp edges is proposed as an explanation for the observed phenomena.Applications are expected with respect to the modification of flow profiles and the enhancement of transport processes along and across liquid-solid boundaries.展开更多
Apnoea,a major sleep disorder,affects many adults and causes several issues,such as fatigue,high blood pressure,liver conditions,increased risk of type II diabetes,and heart problems.Therefore,advanced monitoring and ...Apnoea,a major sleep disorder,affects many adults and causes several issues,such as fatigue,high blood pressure,liver conditions,increased risk of type II diabetes,and heart problems.Therefore,advanced monitoring and diagnosing tools of apnoea disorders are needed to facilitate better treatment,with advantages such as accuracy,comfort of use,cost effectiveness,and embedded computation capabilities to recognise,store,process,and transmit time series data.In this work we present an adaptation of our apnoea-Pi open-source surface acoustic wave(SAW)platform(Apnoea-Pi)to monitor and recognise apnoea in patients.The platform is based on a thin-film SAW device using bimorph ZnO and Al structures,including those fabricated as Al foils or plates,to achieve breath tracking based on humidity and temperature changes.We applied open-source electronics and provided embedded computing characteristics for signal processing,data recognition,storage,and transmission of breath signals.We show that the thin-film SAW device out-performed standard and off-the-shelf capacitive electronic sensors in terms of their response and accuracy for human breath-tracking purposes.This in combination with embedded electronics makes a suitable platform for human breath monitoring and sleep disorder recognition.展开更多
The nonlinear dust acoustic waves in two-dimensional dust plasma with dust charge variation is analytically investigated by using the formally variable separation approach. New analytical solutions for the governing e...The nonlinear dust acoustic waves in two-dimensional dust plasma with dust charge variation is analytically investigated by using the formally variable separation approach. New analytical solutions for the governing equation of this system have been obtained for dust acoustic waves in a dust plasma for the first time. We derive exact analytical expressions for the general case of the nonlinear dust acoustic waves in two-dimensional dust plasma with dust charge variation.展开更多
This paper studied the propagating characteristics of(2+1)-dimensional nonlinear ion acoustic waves in a multicomponent plasma with nonthermal electrons,positrons,and bipolar ions.The dispersion relations are initiall...This paper studied the propagating characteristics of(2+1)-dimensional nonlinear ion acoustic waves in a multicomponent plasma with nonthermal electrons,positrons,and bipolar ions.The dispersion relations are initially explored by using the small amplitude wave's dispersion relation.Then,the Sagdeev potential method is employed to study large amplitude ion acoustic waves.The analysis involves examining the system's phase diagram,Sagdeev potential function,and solitary wave solutions through numerical solution of an analytical process in order to investigate the propagation properties of nonlinear ion acoustic waves under various parameters.It is found that the propagation of nonlinear ion acoustic waves is subject to the influence of various physical parameters,including the ratio of number densities between the unperturbed positrons,electrons to positive ions,nonthermal parameters,the mass ratio of positive ions to negative ions,and the charge number ratio of negative ions to positive ions,the ratio of the electrons'temperature to positrons'temperature.In addition,the multicomponent plasma system has a compressive solitary waves with amplitude greater than zero or a rarefactive solitary waves with amplitude less than zero,in the meantime,compressive and rarefactive ion acoustic wave characteristics depend on the charge number ratio of negative ions to positive ions.展开更多
Using the reductive perturbation method, we investigate the small amplitude nonlinear acoustic wave in a collisional self-gravitating dusty plasma. The result shows that the small amplitude dust acoustic wave can be e...Using the reductive perturbation method, we investigate the small amplitude nonlinear acoustic wave in a collisional self-gravitating dusty plasma. The result shows that the small amplitude dust acoustic wave can be expressed by a modified Korteweg-de Vries equation, and the nonlinear wave is instable because of the collisions between the neutral gas molecules and the charged particles.展开更多
Acoustic wave exhibits inherently different characters of propagation, excitation and coupling in phonon band-gap materials in which its elastic, piezoelectric constants are modulated in order of acoustic wavelength. ...Acoustic wave exhibits inherently different characters of propagation, excitation and coupling in phonon band-gap materials in which its elastic, piezoelectric constants are modulated in order of acoustic wavelength. These kinds of novel materials were exampled by phononic crystals with elastic constants modulation, acoustic superlattice and ionic-type phononic crystals with piezoelectric constants modulation. In this talk, phonic crystals were constructed with steel rods embedded in air. Negative refraction of acoustic wave was both experimentally and theoretically established in the phononic crystals. The propagation of acoustic wave in the crystals show acoustic band structures because the waves are strong scattered at the Brillouin Zone Boundaries, analogy to electron band structure in real crystals and photonic band structure in photonic crystals. In the acoustic superlattice, ultrasonic waves could be excited by applied alternative electric fields by piezoelectric effect. The frequency, mode and amplitude of the excited wave are determined by the microstructured parameters of the acoustic superlattice at the condition of phase matching. Ionic-type phononic crystals describe the coupling between superlattice phonon and electromagnetic wave. The coupling process resulted in the polariton with a dispersion relation totally different from that of both superlattice phonon and E-M waves, analogy to the polariton of the ionic crystals but in microwave instead of infrared light. These microstructural dielectric materials show artificial abnormal properties and will find novel application in ultrasonic devices and microwave devices.展开更多
The nonlinear propagation of quantum ion acoustic wave（QIAW） is investigated in a four-component plasma composed of warm classical positive ions and negative ions,as well as inertialess relativistically degenerate e...The nonlinear propagation of quantum ion acoustic wave（QIAW） is investigated in a four-component plasma composed of warm classical positive ions and negative ions,as well as inertialess relativistically degenerate electrons and positrons.A nonlinear Schrodinger equation is derived by using the reductive perturbation method,which governs the dynamics of QIAW packets.The modulation instability analysis of QIAWs is considered based on the typical parameters of the white dwarf.The results exhibit that both in the weakly relativistic limit and in the ultrarelativistic limit,the modulational instability regions are sensitively dependent on the ratios of temperature and number density of negative ions to those of positive ions respectively,and on the relativistically degenerate effect as well.展开更多
Large amplitude (1+1)-dimensional nonlinear ion acoustic waves are theoretically studied in multicomponent plasma consisting of positively charged ions and negatively charged ions, ion beam, kappa-distributed electron...Large amplitude (1+1)-dimensional nonlinear ion acoustic waves are theoretically studied in multicomponent plasma consisting of positively charged ions and negatively charged ions, ion beam, kappa-distributed electrons, and dust grains,respectively. By using the Sagdeev potential method, the dynamical system and the Sagdeev potential function are obtained.The important influences of system parameters on the phase diagram of this system are investigated. It is found that the linear waves, the nonlinear waves and the solitary waves are coexistent in the multicomponent plasma system. Meanwhile,the variations of Sagdeev potential with parameter can also be obtained. Finally, it seems that the propagating characteristics of (1+1)-dimensional nonlinear ion acoustic solitary waves and ion acoustic nonlinear shock wave can be influenced by different parameters of this system.展开更多
Langatate( LGT) is a novel piezoelectric crystal; its structure is similar to quartz. A numerical analysis of the most important propagation characteristics of surface acoustic waves( SAW) on LGT and quartz is present...Langatate( LGT) is a novel piezoelectric crystal; its structure is similar to quartz. A numerical analysis of the most important propagation characteristics of surface acoustic waves( SAW) on LGT and quartz is presented in this paper. The results show that the phase velocity on LGT is slower than that on quartz.Similar to quartz,there are zero temperature cuts and pure module orientations on LGT. The electro-mechanical coupling constant( k2)of LGT is larger than that of quartz. The characteristics of SAW on LGT with different material constants are calculated and compared.The results show that there are somewhat deviations with different material constants. Especially, the temperature coefficient of frequency( TCF) shows a relatively high difference.展开更多
This research investigates the possibility of convergent acoustic waves generation in the liquid by means of the sotmd waves reflection from the solid cylindrical surface, emerged in the pulsed electric discharge. The...This research investigates the possibility of convergent acoustic waves generation in the liquid by means of the sotmd waves reflection from the solid cylindrical surface, emerged in the pulsed electric discharge. The spectra of pulse discharge plasma emission in the water and in the air-water mixture were obtained. The temperature of cuprum and oxygen atoms electronic excitation levels and the temperature tendencies during the discharge current existence were calculated.展开更多
In this paper, by using functional analysis and integral equation method, we obtain some results about the properties of far field of acoustic waves in an inhomogeneous medium. And we also discuss some ill-posed inver...In this paper, by using functional analysis and integral equation method, we obtain some results about the properties of far field of acoustic waves in an inhomogeneous medium. And we also discuss some ill-posed inverse scattering problems by Tikhonov regularization method.展开更多
In this work, aqueous glycerol solutions are atomized to investigate the influence of the viscosity on the droplet size and the general atomization behavior in a setup using standing surface acoustic waves (sSAW) and ...In this work, aqueous glycerol solutions are atomized to investigate the influence of the viscosity on the droplet size and the general atomization behavior in a setup using standing surface acoustic waves (sSAW) and a fluid supply at the boundary of the acoustic path. Depending on the fluid viscosity, the produced aerosols have a monomodal or polymodal size distribution. The mean droplet size in the dominant droplet fraction, however, decreases with increasing viscosity. Our results also indicate that the local wavefield conditions are crucial for the atomization process.展开更多
基金supported by the Guangxi Natural Science Foundation(Grant No.2024GXNSFDA010014)the National Natural Science Foundation of China(Grant Nos.12364018 and U22A6005)+1 种基金the Guangxi Science and Technology Major Program(Grant No.AA23073019)the Innovation Project of Guangxi Graduate Education(Grant Nos.YCBZ2022049 and YCBZ2023015)。
文摘Exploring advanced techniques capable of probing nanometric acoustic waves in nanostructures is critically important for the development of miniaturized acoustic devices.In this study,we probe the optically-excited acoustic waves in a single silicon nanowire(NW)using the time-resolved(tr-)high-order Laue-zone(HOLZ)lines under convergent-beam electron diffraction(CBED)conditions in an ultrafast transmission electron microscope(UTEM).We devise an experimental scheme to obtain tr-HOLZ lines under off-zone-axis CBED conditions.We also propose a geometric description of HOLZ line formation and use this alternative description to quantitatively evaluate the dynamics of optically-excited silicon NW.Using part of the deformation gradient tensor,our simulations of the dynamics of Si NW reproduce the experimental results.We further discuss the feasibility of a full retrieval of the deformation gradient tensor by using a set of HOLZ lines from three zone axes.Our findings illustrate a strategy for the quantitative access to dynamical acoustic waves optically excited in micro-and nano-structures using UTEM.
基金funded by the Scientific Research Deanship at the University of Ha'il-Saudi Arabia through project number RG-23183.
文摘Nonplanar electron acoustic waves(NEAWs)with double spectral index-distributed hot electrons are studied under the two-temperature electrons model in a collisionless unmagnetized plasma.Using this model,the Korteweg–de Vries(KdV)equation is derived in nonplanar geometry.On the basis of the solutions of KdV equation,alterations of velocity,width,and amplitude of acoustic waves having various plasma factors are investigated.Nonlinear and dispersion coefficients obtained rely on double spectral index parameters r and q,and particle densityα.The combined influence of these factors significantly alters the features of electron acoustic waves in nonplanar geometry.This study is expected to contribute to the understanding of nonlinear principles that underlie nonplanar electrostatic waves in laboratory plasmas as well as in space.
基金financially supported by the Scientific Research Fund of Heilongjiang Provincial Education Department(Grant No.12541132)the Natural Science Youth Foundation of Heilongjiang Province of China(Grant No.QC2015082)
文摘Based on the Burgers equation and Manley-Rowe equation, the derivation about nonlinear interaction of the acoustic waves has been done in this paper. After nonlinear interaction among the low-frequency weak waves and the pump wave, the analytical solutions of acoustic waves＇ amplitude in the field are deduced. The relationship between normalized energy of high-frequency and the change of acoustic energy before and after the nonlinear interaction of the acoustic waves is analyzed. The experimental results about the changes of the acoustic energy are presented. The study shows that new frequencies are generated and the energies of the low-frequency are modulated in a long term by the pump waves, which leads the energies of the low-frequency acoustic waves to change in the pulse trend in the process of the nonlinear interaction of the acoustic waves. The increase and decrease of the energies of the low-frequency are observed under certain typical conditions, which lays a foundation for practical engineering applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.12174166 and 12304144)the Fund from Beijing National Laboratory for Condensed Matter Physics(Grant No.2024BNLCMPKF013)the Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2024-22).
文摘We investigate the surface acoustic wave(SAW)modulation of the exchange bias field(H_(EB))in Py/IrMn films deposited on LiNbO_(3)substrates.We measured the anisotropic magnetoresistance(AMR)of the multilayer film when continuous SAW or pulsed SAW were applied and obtained H_(EB).With continuous SAW,the H_(EB)decreases continuously with power.While in the case of pulsed SAW,the H_(EB)first decreases and then stabilizes.Compared to pulsed SAW,the thermal effects from the continuous SAW lead to the continuous decrease of H_(EB)at higher SAW power,which is verified by the measurement of H_(EB)at different temperatures and input currents.Furthermore,our results show that pulsed SAW can effectively avoid thermal effects.The decrease of H_(EB)at smaller power in both continuous and pulsed SAW is mainly due to the SAW-induced dynamic strain field,which leads to a small perturbation in the magnetic moment of the FM layer.Combined with the AMR values measured at different angles during the saturation field,we believe that the SAW-induced dynamic strain field causes a 15°angle between the magnetic moment and the easy axis.Our experiments provide a different approach to manipulating H_(EB),opening up a potential avenue for future manipulation of antiferromagnetic moments.
基金Project supported by the National Natural Science Foundation of China(Nos.10132010 and 10072033)
文摘The propagation of surface acoustic waves in layered piezoelectric structureswith initial stresses is investigated. The phase velocity equations are obtained for electricallyfree and shorted cases, respectively. Effects of the initial stresses on the phase velocity and theelectromechanical coupling coefficient for the fundamental mode of the layered piezoelectricstructures are discussed. Numerical results for the c-axis oriented film of LiNbO_3 on a sapphiresubstrate are given. It is found that the fractional change in phase velocity is a linear functionwith the initial stresses, and the electromechanical coupling factor increases with an increase ofthe absolute values of the compressive initial stresses. The results are useful for the design ofsurface acoustic wave devices.
文摘Cylindrical and spherical (nonplanar) solitary waves (SWs) and double layers (DLs) in a multi-ion plasma system (containing inertial positively as well as negatively charged ions, non-inertial degenerate electrons, and negatively charged static dust) are studied by employing the standard reductive perturbation method. The modified Gardner (MG) equation describing the nonlinear propagation of the dust ion-acoustic (DIA) waves is derived, and its nonplanar SWs and DLs solutions are numerically analyzed. The parametric regimes for the existence of SWs, which are associated with both positive and negative potential, and DLs which are associated with negative potential, are obtained. The basic features of nonplanar DIA SWs, and DLs, which are found to be different from planar ones, are also identified.
基金Project supported by the National Natural Science Foundation of China(Grant No.61571319)
文摘The application of surface acoustic waves（SAWs） for thickness measurement is presented. By studying the impact of film thickness h on the dispersion phenomenon of surface acoustic waves, a method for thickness determination based on theoretical dispersion curve v（ fh） and experimental dispersion curve v（ f） is developed. The method provides a series of thickness values at different frequencies f, and the mean value is considered as the final result of the measurement. The thicknesses of six interconnect films are determined by SAWs, and the results are compared with the manufacturer＇s data.The relative differences are in the range from 0.4% to 2.18%, which indicates that the surface acoustic wave technique is reliable and accurate in the nondestructive thickness determination for films. This method can be generally used for fast and direct determination of film thickness.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11404245 and 11374231the National High-Tech Research and Development Program of China under Grant No 2012AA022606+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education under Grant No 20130091130004the National Key Scientific Instrument and Equipment Development Project of China under Grant No 2012YQ15021306
文摘In the backward propagation of acoustic waves, the direction of phase velocity is anti-parallel to that of group velocity. We propose a scheme to manipulate the backward propagation using a periodicM structure. The dynamic backward propagation process is further experimentally observed. It is demonstrated that the oblique incident plane wave moves backward when it travels through the periodical structure and the backward shift can be controlled within a certain range.
基金This research was supported by the European Fund of Regional Development(EFRE)within the project“InnoTerm”and from“Technologieallianz Oberfranken(TAO)”.
文摘In a biomimetic approach the feasibility of liquid flow actuation by vibrating protruding structures excited via guided acoustic waves is investigated.Inspired by periodically beating cilia the loop part of a punched metallic hook-and-loop tape with tilted protruding loops was used as a waveguide for plate waves in water.Such waves were excited in the frequency range of 110 Hz to 220 Hz by directly coupling the tape to a loudspeaker membrane.A flow generated in the tilt direction of the loops with velocities up to 60 mm s 1 was visualized by ink droplets deposited on the tape.The phenomenon persisted,when the protruding length of the loops was reduced by decreasing the protrusion angle.However,after closing the punch holes near the loops with sticking tape streaming could not be observed any longer.The same happened with open punch holes when the ink was replaced by glycerol.Low-frequency acoustic streaming around vibrating sharp edges is proposed as an explanation for the observed phenomena.Applications are expected with respect to the modification of flow profiles and the enhancement of transport processes along and across liquid-solid boundaries.
基金financially supported by the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/P018998/1the UK Fluidic Network Special Interest Group of Acoustofluidics (EP/N032861/1).
文摘Apnoea,a major sleep disorder,affects many adults and causes several issues,such as fatigue,high blood pressure,liver conditions,increased risk of type II diabetes,and heart problems.Therefore,advanced monitoring and diagnosing tools of apnoea disorders are needed to facilitate better treatment,with advantages such as accuracy,comfort of use,cost effectiveness,and embedded computation capabilities to recognise,store,process,and transmit time series data.In this work we present an adaptation of our apnoea-Pi open-source surface acoustic wave(SAW)platform(Apnoea-Pi)to monitor and recognise apnoea in patients.The platform is based on a thin-film SAW device using bimorph ZnO and Al structures,including those fabricated as Al foils or plates,to achieve breath tracking based on humidity and temperature changes.We applied open-source electronics and provided embedded computing characteristics for signal processing,data recognition,storage,and transmission of breath signals.We show that the thin-film SAW device out-performed standard and off-the-shelf capacitive electronic sensors in terms of their response and accuracy for human breath-tracking purposes.This in combination with embedded electronics makes a suitable platform for human breath monitoring and sleep disorder recognition.
文摘The nonlinear dust acoustic waves in two-dimensional dust plasma with dust charge variation is analytically investigated by using the formally variable separation approach. New analytical solutions for the governing equation of this system have been obtained for dust acoustic waves in a dust plasma for the first time. We derive exact analytical expressions for the general case of the nonlinear dust acoustic waves in two-dimensional dust plasma with dust charge variation.
文摘This paper studied the propagating characteristics of(2+1)-dimensional nonlinear ion acoustic waves in a multicomponent plasma with nonthermal electrons,positrons,and bipolar ions.The dispersion relations are initially explored by using the small amplitude wave's dispersion relation.Then,the Sagdeev potential method is employed to study large amplitude ion acoustic waves.The analysis involves examining the system's phase diagram,Sagdeev potential function,and solitary wave solutions through numerical solution of an analytical process in order to investigate the propagation properties of nonlinear ion acoustic waves under various parameters.It is found that the propagation of nonlinear ion acoustic waves is subject to the influence of various physical parameters,including the ratio of number densities between the unperturbed positrons,electrons to positive ions,nonthermal parameters,the mass ratio of positive ions to negative ions,and the charge number ratio of negative ions to positive ions,the ratio of the electrons'temperature to positrons'temperature.In addition,the multicomponent plasma system has a compressive solitary waves with amplitude greater than zero or a rarefactive solitary waves with amplitude less than zero,in the meantime,compressive and rarefactive ion acoustic wave characteristics depend on the charge number ratio of negative ions to positive ions.
基金Project supported by the Initial Research Fund of Shihezi University,China (Grant Nos. RCZX200742 and RCZX200743)
文摘Using the reductive perturbation method, we investigate the small amplitude nonlinear acoustic wave in a collisional self-gravitating dusty plasma. The result shows that the small amplitude dust acoustic wave can be expressed by a modified Korteweg-de Vries equation, and the nonlinear wave is instable because of the collisions between the neutral gas molecules and the charged particles.
文摘Acoustic wave exhibits inherently different characters of propagation, excitation and coupling in phonon band-gap materials in which its elastic, piezoelectric constants are modulated in order of acoustic wavelength. These kinds of novel materials were exampled by phononic crystals with elastic constants modulation, acoustic superlattice and ionic-type phononic crystals with piezoelectric constants modulation. In this talk, phonic crystals were constructed with steel rods embedded in air. Negative refraction of acoustic wave was both experimentally and theoretically established in the phononic crystals. The propagation of acoustic wave in the crystals show acoustic band structures because the waves are strong scattered at the Brillouin Zone Boundaries, analogy to electron band structure in real crystals and photonic band structure in photonic crystals. In the acoustic superlattice, ultrasonic waves could be excited by applied alternative electric fields by piezoelectric effect. The frequency, mode and amplitude of the excited wave are determined by the microstructured parameters of the acoustic superlattice at the condition of phase matching. Ionic-type phononic crystals describe the coupling between superlattice phonon and electromagnetic wave. The coupling process resulted in the polariton with a dispersion relation totally different from that of both superlattice phonon and E-M waves, analogy to the polariton of the ionic crystals but in microwave instead of infrared light. These microstructural dielectric materials show artificial abnormal properties and will find novel application in ultrasonic devices and microwave devices.
基金supported by the National Natural Science Foundation of China(Grant No.11104012)the Fundamental Research Funds for the Central Universities(Grant Nos.FRF-TP-09-019A and FRF-BR-11-031B)
文摘The nonlinear propagation of quantum ion acoustic wave（QIAW） is investigated in a four-component plasma composed of warm classical positive ions and negative ions,as well as inertialess relativistically degenerate electrons and positrons.A nonlinear Schrodinger equation is derived by using the reductive perturbation method,which governs the dynamics of QIAW packets.The modulation instability analysis of QIAWs is considered based on the typical parameters of the white dwarf.The results exhibit that both in the weakly relativistic limit and in the ultrarelativistic limit,the modulational instability regions are sensitively dependent on the ratios of temperature and number density of negative ions to those of positive ions respectively,and on the relativistically degenerate effect as well.
文摘Large amplitude (1+1)-dimensional nonlinear ion acoustic waves are theoretically studied in multicomponent plasma consisting of positively charged ions and negatively charged ions, ion beam, kappa-distributed electrons, and dust grains,respectively. By using the Sagdeev potential method, the dynamical system and the Sagdeev potential function are obtained.The important influences of system parameters on the phase diagram of this system are investigated. It is found that the linear waves, the nonlinear waves and the solitary waves are coexistent in the multicomponent plasma system. Meanwhile,the variations of Sagdeev potential with parameter can also be obtained. Finally, it seems that the propagating characteristics of (1+1)-dimensional nonlinear ion acoustic solitary waves and ion acoustic nonlinear shock wave can be influenced by different parameters of this system.
基金Leading Academic Discipline Project of Shanghai Municipal Education Commission,China(No.J513032)Innovation Program of Shanghai Municipal Education Commission,China(No.09YZ343)
文摘Langatate( LGT) is a novel piezoelectric crystal; its structure is similar to quartz. A numerical analysis of the most important propagation characteristics of surface acoustic waves( SAW) on LGT and quartz is presented in this paper. The results show that the phase velocity on LGT is slower than that on quartz.Similar to quartz,there are zero temperature cuts and pure module orientations on LGT. The electro-mechanical coupling constant( k2)of LGT is larger than that of quartz. The characteristics of SAW on LGT with different material constants are calculated and compared.The results show that there are somewhat deviations with different material constants. Especially, the temperature coefficient of frequency( TCF) shows a relatively high difference.
文摘This research investigates the possibility of convergent acoustic waves generation in the liquid by means of the sotmd waves reflection from the solid cylindrical surface, emerged in the pulsed electric discharge. The spectra of pulse discharge plasma emission in the water and in the air-water mixture were obtained. The temperature of cuprum and oxygen atoms electronic excitation levels and the temperature tendencies during the discharge current existence were calculated.
基金Shanghai Youth Science FoundationSupported in Part by Shanghai ScienceTechnology Development Foundation
文摘In this paper, by using functional analysis and integral equation method, we obtain some results about the properties of far field of acoustic waves in an inhomogeneous medium. And we also discuss some ill-posed inverse scattering problems by Tikhonov regularization method.
文摘In this work, aqueous glycerol solutions are atomized to investigate the influence of the viscosity on the droplet size and the general atomization behavior in a setup using standing surface acoustic waves (sSAW) and a fluid supply at the boundary of the acoustic path. Depending on the fluid viscosity, the produced aerosols have a monomodal or polymodal size distribution. The mean droplet size in the dominant droplet fraction, however, decreases with increasing viscosity. Our results also indicate that the local wavefield conditions are crucial for the atomization process.
