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Sample records for acoustic waves excited

  1. Observation of self-excited acoustic vortices in defect-mediated dust acoustic wave turbulence.

    PubMed

    Tsai, Ya-Yi; I, Lin

    2014-07-01

    Using the self-excited dust acoustic wave as a platform, we demonstrate experimental observation of self-excited fluctuating acoustic vortex pairs with ± 1 topological charges through spontaneous waveform undulation in defect-mediated turbulence for three-dimensional traveling nonlinear longitudinal waves. The acoustic vortex pair has helical waveforms with opposite chirality around the low-density hole filament pair in xyt space (the xy plane is the plane normal to the wave propagation direction). It is generated through ruptures of sequential crest surfaces and reconnections with their trailing ruptured crest surfaces. The initial rupture is originated from the amplitude reduction induced by the formation of the kinked wave crest strip with strong stretching through the undulation instability. Increasing rupture causes the separation of the acoustic vortex pair after generation. A similar reverse process is followed for the acoustic vortex annihilating with the opposite-charged acoustic vortex from the same or another pair generation.

  2. Synchronization of self-excited dust acoustic waves

    NASA Astrophysics Data System (ADS)

    Suranga Ruhunusiri, W. D.; Goree, John

    2012-10-01

    Synchronization is a nonlinear phenomenon where a self-excited oscillation, like a wave in a plasma, interacts with an external driving, resulting in an adjustment of the oscillation frequency. Dust acoustic wave synchronization has been experimentally studied previously in laboratory and in microgravity conditions, e.g. [Pilch PoP 2009] and [Menzel PRL 2010]. We perform a laboratory experiment to study synchronization of self-excited dust acoustic waves. An rf glow discharge argon plasma is formed by applying a low power radio frequency voltage to a lower electrode. A 3D dust cloud is formed by levitating 4.83 micron microspheres inside a glass box placed on the lower electrode. Dust acoustic waves are self-excited with a natural frequency of 22 Hz due to an ion streaming instability. A cross section of the dust cloud is illuminated by a vertical laser sheet and imaged from the side with a digital camera. To synchronize the waves, we sinusoidally modulate the overall ion density. Differently from previous experiments, we use a driving electrode that is separate from the electrode that sustains the plasma, and we characterize synchronization by varying both driving amplitude and frequency.

  3. EXCITATION OF ACOUSTIC WAVES BY VORTICES IN THE QUIET SUN

    SciTech Connect

    Kitiashvili, I. N.; Kosovichev, A. G.; Mansour, N. N.; Wray, A. A.

    2011-02-01

    The five-minute oscillations are one of the basic properties of solar convection. Observations show a mixture of a large number of acoustic wave fronts propagating from their sources. We investigate the process of acoustic waves excitation from the point of view of individual events, by using a realistic three-dimensional radiative hydrodynamic simulation of the quiet Sun. The results show that the excitation events are related to the dynamics of vortex tubes (or swirls) in intergranular lanes of solar convection. These whirlpool-like flows are characterized by very strong horizontal velocities (7-11 km s{sup -1}) and downflows ({approx}7 km s{sup -1}), and are accompanied by strong decreases of temperature, density, and pressure at the surface and 0.5-1 Mm below the surface. High-speed whirlpool flows can attract and capture other vortices. According to our simulation results the processes of vortex interaction, such as vortex annihilation, can cause excitation of acoustic waves on the Sun.

  4. Excitation of nonlinear ion acoustic waves in CH plasmas

    NASA Astrophysics Data System (ADS)

    Feng, Q. S.; Zheng, C. Y.; Liu, Z. J.; Xiao, C. Z.; Wang, Q.; He, X. T.

    2016-08-01

    Excitation of nonlinear ion acoustic wave (IAW) by an external electric field is demonstrated by Vlasov simulation. The frequency calculated by the dispersion relation with no damping is verified much closer to the resonance frequency of the small-amplitude nonlinear IAW than that calculated by the linear dispersion relation. When the wave number k λ D e increases, the linear Landau damping of the fast mode (its phase velocity is greater than any ion's thermal velocity) increases obviously in the region of T i / T e < 0.2 in which the fast mode is weakly damped mode. As a result, the deviation between the frequency calculated by the linear dispersion relation and that by the dispersion relation with no damping becomes larger with k λ D e increasing. When k λ D e is not large, such as k λ D e = 0.1 , 0.3 , 0.5 , the nonlinear IAW can be excited by the driver with the linear frequency of the modes. However, when k λ D e is large, such as k λ D e = 0.7 , the linear frequency cannot be applied to exciting the nonlinear IAW, while the frequency calculated by the dispersion relation with no damping can be applied to exciting the nonlinear IAW.

  5. Particle-Wave Micro-Dynamics in Nonlinear Self-Excited Dust Acoustic Waves

    SciTech Connect

    Tsai, C.-Y.; Teng, L.-W.; Liao, C.-T.; I Lin

    2008-09-07

    The large amplitude dust acoustic wave can be self-excited in a low-pressure dusty plasma. In the wave, the nonlinear wave-particle interaction determines particle motion, which in turn determines the waveform and wave propagation. In this work, the above behaviors are investigated by directly tracking particle motion through video-microscopy. A Lagrangian picture for the wave dynamics is constructed. The wave particle interaction associated with the transition from ordered to disordered particle oscillation, the wave crest trapping and wave heating are demonstrated and discussed.

  6. Directional excitation of the designer surface acoustic waves

    NASA Astrophysics Data System (ADS)

    Lu, Jiuyang; Qiu, Chunyin; Ke, Manzhu; Liu, Zhengyou

    2015-05-01

    We propose an efficient design route to realize directional excitation of the structure-induced surface waves for airborne sound. The whole system consists of a periodically corrugated rigid plate combining with a pair of asymmetric narrow slits. The directional excitation of the mimicked surface waves stems from the destructive interference between the evanescent waves emitted from the double slits. The directionality can be switched conveniently by tuning the external frequency. The theoretical prediction is validated well by simulations and experiments. Promising applications can be anticipated such as in designing compact devices for airborne sound.

  7. HF Doppler observations of acoustic waves excited by the earthquake

    NASA Technical Reports Server (NTRS)

    Ichinose, T.; Takagi, K.; Tanaka, T.; Okuzawa, T.; Shibata, T.; Sato, Y.; Nagasawa, C.; Ogawa, T.

    1985-01-01

    Ionospheric disturbances caused by the earthquake of a relatively small and large epicentral distance have been detected by a network of HF-Doppler sounders in central Japan and Kyoto station, respectively. The HF-Doppler data of a small epicentral distance, together with the seismic data, have been used to formulate a mechanism whereby ionospheric disturbances are produced by the Urakawa-Oki earthquake in Japan. Comparison of the dynamic spectra of these data has revealed experimentally that the atmosphere acts as a low-pass filter for upward-propagating acoustic waves. By surveying the earthquakes for which the magnitude M is larger than 6.0, researchers found the ionospheric effect in 16 cases of 82 seismic events. As almost all these effects have occurred in the daytime, it is considered that it may result from the filtering effect of the upward-propagating acoustic waves.

  8. Experimental study of propagation of instability waves in a submerged jet under transverse acoustic excitation

    NASA Astrophysics Data System (ADS)

    Mironov, A. K.; Krasheninnikov, S. Yu.; Maslov, V. P.; Zakharov, D. E.

    2016-07-01

    An experimental study was conducted on the specific features of instability wave propagation in the mixing layer of a turbulent jet when the jet is excited by an external acoustic wave. We used the technique of conditional phase averaging of data obtained by particle image velocimetry using the reference signal of a microphone placed near the jet. The influence of the excitation frequency on the characteristics of large-scale structures in the mixing layer was investigated. It is shown that the propagation patterns of the instability waves agree well with previously obtained data on the localization of acoustic sources in turbulent jets.

  9. Collective lipid bilayer dynamics excited by surface acoustic waves.

    PubMed

    Reusch, T; Schülein, F J R; Nicolas, J D; Osterhoff, M; Beerlink, A; Krenner, H J; Müller, M; Wixforth, A; Salditt, T

    2014-09-12

    We use standing surface acoustic waves to induce coherent phonons in model lipid multilayers deposited on a piezoelectric surface. Probing the structure by phase-controlled stroboscopic x-ray pulses we find that the internal lipid bilayer electron density profile oscillates in response to the externally driven motion of the lipid film. The structural response to the well-controlled motion is a strong indication that bilayer structure and membrane fluctuations are intrinsically coupled, even though these structural changes are averaged out in equilibrium and time integrating measurements. Here the effects are revealed by a timing scheme with temporal resolution on the picosecond scale in combination with the sub-nm spatial resolution, enabled by high brilliance synchrotron x-ray reflectivity.

  10. Probing thermomechanics at the nanoscale: impulsively excited pseudosurface acoustic waves in hypersonic phononic crystals.

    PubMed

    Nardi, Damiano; Travagliati, Marco; Siemens, Mark E; Li, Qing; Murnane, Margaret M; Kapteyn, Henry C; Ferrini, Gabriele; Parmigiani, Fulvio; Banfi, Francesco

    2011-10-12

    High-frequency surface acoustic waves can be generated by ultrafast laser excitation of nanoscale patterned surfaces. Here we study this phenomenon in the hypersonic frequency limit. By modeling the thermomechanics from first-principles, we calculate the system's initial heat-driven impulsive response and follow its time evolution. A scheme is introduced to quantitatively access frequencies and lifetimes of the composite system's excited eigenmodes. A spectral decomposition of the calculated response on the eigemodes of the system reveals asymmetric resonances that result from the coupling between surface and bulk acoustic modes. This finding allows evaluation of impulsively excited pseudosurface acoustic wave frequencies and lifetimes and expands our understanding of the scattering of surface waves in mesoscale metamaterials. The model is successfully benchmarked against time-resolved optical diffraction measurements performed on one-dimensional and two-dimensional surface phononic crystals, probed using light at extreme ultraviolet and near-infrared wavelengths.

  11. Probing Thermomechanics at the Nanoscale: Impulsively Excited Pseudosurface Acoustic Waves in Hypersonic Phononic Crystals

    PubMed Central

    2011-01-01

    High-frequency surface acoustic waves can be generated by ultrafast laser excitation of nanoscale patterned surfaces. Here we study this phenomenon in the hypersonic frequency limit. By modeling the thermomechanics from first-principles, we calculate the system’s initial heat-driven impulsive response and follow its time evolution. A scheme is introduced to quantitatively access frequencies and lifetimes of the composite system’s excited eigenmodes. A spectral decomposition of the calculated response on the eigemodes of the system reveals asymmetric resonances that result from the coupling between surface and bulk acoustic modes. This finding allows evaluation of impulsively excited pseudosurface acoustic wave frequencies and lifetimes and expands our understanding of the scattering of surface waves in mesoscale metamaterials. The model is successfully benchmarked against time-resolved optical diffraction measurements performed on one-dimensional and two-dimensional surface phononic crystals, probed using light at extreme ultraviolet and near-infrared wavelengths. PMID:21910426

  12. Superior analytical sensitivity of electromagnetic excitation compared to contact electrode instigation of transverse acoustic waves.

    PubMed

    Ballantyne, Scott M; Thompson, Michael

    2004-03-01

    Quartz disks incorporated into an electrolyte flow-through configuration have been excited by both direct electrode contact and electromagnetic fields to generate propagating transverse acoustic waves in to the fluid. The conventional thickness-mode device was operated at the first harmonic (9 MHz) whereas the EM excited structure functioned successfully at 453 MHz (nominal 49th harmonic). The nature of signals produced by the two devices and potential contributions to noise are evaluated. A comparison of the response of the higher frequency sensor to the introduction of the protein neutravidin to the system reveals at least a seven times higher signal-to-noise ratio than is the result for the conventional bulk-acoustic wave structure. This increase in sensitivity coupled with the possibilities for tuning the frequency of the electromagnetic device and its potential for non-contact excitation offer significant advantages in terms of analytical sensor technology.

  13. Development of an electromagnetic acoustic transducer (EMAT) for the noncontact excitation of guided ultrasonic waves

    NASA Astrophysics Data System (ADS)

    Fromme, P.

    2015-03-01

    Fatigue damage can develop in aerospace structures at locations of stress concentration, such as fasteners. For the safe operation of the aircraft fatigue cracks need to be detected before reaching a critical length. Guided ultrasonic waves offer an efficient method for the detection and characterization of such defects in large aerospace structures. Noncontact excitation of guided waves was achieved using electromagnetic acoustic transducers (EMAT). The transducer development for the specific excitation of the A0 Lamb wave mode is explained. The radial and angular dependency of the excited guided wave pulses at different frequencies were measured using a noncontact laser interferometer. Based on the induced eddy currents in the plate a theoretical model was developed and reasonably good agreement with the measured transducer performance was achieved. The developed transducers were employed for defect detection in aluminum components using fully noncontact guided wave measurements. Excitation of the A0 Lamb wave mode was achieved using the developed EMAT transducer and the guided wave propagation and scattering was measured using a noncontact laser interferometer. These results provide the basis for the defect characterization in aerospace structures using noncontact guided wave sensors.

  14. Noncontact excitation of guided waves (A0 mode) using an electromagnetic acoustic transducer (EMAT)

    NASA Astrophysics Data System (ADS)

    Fromme, Paul

    2016-02-01

    Fatigue damage can develop in aircraft structures at locations of stress concentration, such as fasteners, and has to be detected before reaching a critical size to ensure safe aircraft operation. Guided ultrasonic waves offer an efficient method for the detection and characterization of such defects in large aerospace structures. Electromagnetic acoustic transducers (EMAT) for the noncontact excitation of guided ultrasonic waves were developed. The transducer development for the specific excitation of the A0 Lamb wave mode with an out-of-plane Lorentz force is explained. The achieved radial and angular dependency of the excited guided wave pulses were measured using a noncontact laser interferometer. Based on the induced eddy currents in the plate a theoretical model was developed. The application of the developed transducers for defect detection in aluminum components using fully noncontact guided wave measurements was demonstrated. Excitation of the A0 Lamb wave mode was achieved using the developed EMAT transducer and the guided wave propagation and scattering was measured using a noncontact laser interferometer.

  15. Selective excitation of eigenmodes in a multilayer thin film resonator on bulk acoustic waves

    NASA Astrophysics Data System (ADS)

    Mikhailov, A. K.; Ptashnik, S. V.; Kozyrev, A. B.

    2016-08-01

    We consider a method of control over the operating frequency of a resonator on bulk acoustic waves, which is based on the selective excitation of eigenmodes. The frequency switching is achieved by using several layers of a ferroelectric in the paraelectric state and applying a control voltage of appropriate magnitude and polarity to each layer. The principle of selectivity is formulated and the criterion function is defined, which ensure the most effective excitation of a selected eigenmode with the possible suppression of parasitic modes. An example of using this function for a resonator switched between four eigenmodes is presented.

  16. The transmission of acoustic energy by a finite cylindrical shell excited by external plane waves

    NASA Astrophysics Data System (ADS)

    Cacciolati, C.; Gotteland, M.; Barbe, M.

    A qualitative method is presented for sensitivity analyses of acoustic coupling between cylindrical shells such as found in aerospace structures. The shells are excited by an exterior plane wave. The analysis is carried out in terms of coupling among the exterior and structural natural modes and the structural and cavity natural modes. Strong coupling is shown to be limited to cases of coincidence of resonance frequencies and when numerous identical incident waves arrive from multiple directions. Coupling will in any case be confined to low frequencies. Limits are defined for the necessary number of frequencies which must be considered when predicting whether or not coupling will occur.

  17. Excitation and Damping of Acoustic Waves in Three-Dimensional Accretion Disks

    NASA Astrophysics Data System (ADS)

    Mosqueira, I.; Houben, H.

    2002-09-01

    The damping of acoustic waves plays a key role in determining the criterion for gap opening (see Estrada and Mosqueira, this conference). Because of the potential significance of gap-opening in regulating the rate of accretion and of radial migration, it is important to investigate all sources of wave damping in an accretion disk. Here we mainly discuss damping mechanisms arising from 3-D effects in disks with aspect ratio H/r ~ 0.1. A 2-D treatment is valid when the response of the disk is locally isothermal with adiabatic index γ = 1 and the vertical forcing is ignored. In that case, tidal forcing will generate a 2-D wave which is likely to damp due to wave steepening in a lengthscale of order ~ rL (with weak dependence on the mass of the pertuber), where rL is the radial location of the Lindblad resonance where the acoustic wave is launched (Goodman and Rafikov 2001; Rafikov 2002). On the other hand, vertically thermally stratified disks, as may be the case for active disks with high-optical depth, generate 3-D waves which damp due to non-linear dissipation in a lengthscale of order ~ rL/m, where m is the azimuthal wavenumber (Lubow and Ogilvie 1998). In this case, most of the angular momentum flux is carried by the f-mode; however, tidal forcing also excites other modes. Finally, in a vertically isothermal (but not radially) disk with γ = 5/3 horizontal tidal forcing excites buoyancy g waves that receive ~ 20 per cent of the energy flux for a m = 0 mode (Bate et al. 2002). These g-waves have non-zero vertical group velocity, and are excited primarily away from the midplane, where non-linear dissipation is more readily attained. The radial damping length for these waves is likely to be ~ H and only weakly dependent on the mass of the perturber. We generalize the problem to include the effects of vertical tidal forcing in a vertically isothermal atmosphere with γ > 1, and calculate the vertical flux of angular momentum of acoustic waves with m < r/H. The

  18. Circumferential resonance modes of solid elastic cylinders excited by obliquely incident acoustic waves.

    PubMed

    Fan, Ying; Honarvar, Farhang; Sinclair, Anthony N; Jafari, Mohammad-Reza

    2003-01-01

    When an immersed solid elastic cylinder is insonified by an obliquely incident plane acoustic wave, some of the resonance modes of the cylinder are excited. These modes are directly related to the incidence angle of the insonifying wave. In this paper, the circumferential resonance modes of such immersed elastic cylinders are studied over a large range of incidence angles and frequencies and physical explanations are presented for singular features of the frequency-incidence angle plots. These features include the pairing of one axially guided mode with each transverse whispering gallery mode, the appearance of an anomalous pseudo-Rayleigh in the cylinder at incidence angles greater than the Rayleigh angle, and distortional effects of the longitudinal whispering gallery modes on the entire resonance spectrum of the cylinder. The physical explanations are derived from Resonance Scattering Theory (RST), which is employed to determine the interior displacement field of the cylinder and its dependence on insonification angle.

  19. Excitation of kinetic geodesic acoustic modes by drift waves in nonuniform plasmas

    SciTech Connect

    Qiu, Z.; Chen, L.; Zonca, F.

    2014-02-15

    Effects of system nonuniformities and kinetic dispersiveness on the spontaneous excitation of Geodesic Acoustic Mode (GAM) by Drift Wave (DW) turbulence are investigated based on nonlinear gyrokinetic theory. The coupled nonlinear equations describing parametric decay of DW into GAM and DW lower sideband are derived and then solved both analytically and numerically to investigate the effects on the parametric decay process due to system nonuniformities, such as nonuniform diamagnetic frequency, finite radial envelope of DW pump, and kinetic dispersiveness. It is found that the parametric decay process is a convective instability for typical tokamak parameters when finite group velocities of DW and GAM associated with kinetic dispersiveness and finite radial envelope are taken into account. When, however, nonuniformity of diamagnetic frequency is taken into account, the parametric decay process becomes, time asymptotically, a quasi-exponentially growing absolute instability.

  20. Wave-particle dynamics of waveform and defect evolutions in undulated nonlinear self-excited dust acoustic waves

    NASA Astrophysics Data System (ADS)

    Tsai, Jun-Yi; Tsai, Ya-Yi; I, Lin

    2015-01-01

    The wave-particle dynamics for the evolutions of defects and surrounding pitchfork type waveforms of a weakly disordered self-excited dust acoustic wave is experimentally investigated in an rf dusty plasma system. Particle trajectories are tracked and correlated with waveform evolution to construct an Eulerian-Lagrangian wave-particle dynamical picture. It is found that the local accumulation and depletion of particles in the wave crest and rear, respectively, determines the local crest speed, and the growth and decay of the local crest height, which in turn determine the waveform evolution. The local crest height and the focusing and defocusing of particle trajectories due to the transverse force fields from the tilted wave crest and the non-uniform crest height along the wave crest are the key factors to determine the above particle accumulation and depletion. It explains the observations such as the lower speed of smaller crests, the straightening of the leading front of the pitchfork waveform associated with the transverse motion of defect to the open side, and the vertical defect gliding in the wave frame through the detachment of the strongly kinked pitchfork branch followed by its reconnection with the trailing crest.

  1. Wave-particle dynamics of waveform and defect evolutions in undulated nonlinear self-excited dust acoustic waves

    SciTech Connect

    Tsai, Jun-Yi; Tsai, Ya-Yi; I, Lin

    2015-01-15

    The wave-particle dynamics for the evolutions of defects and surrounding pitchfork type waveforms of a weakly disordered self-excited dust acoustic wave is experimentally investigated in an rf dusty plasma system. Particle trajectories are tracked and correlated with waveform evolution to construct an Eulerian-Lagrangian wave-particle dynamical picture. It is found that the local accumulation and depletion of particles in the wave crest and rear, respectively, determines the local crest speed, and the growth and decay of the local crest height, which in turn determine the waveform evolution. The local crest height and the focusing and defocusing of particle trajectories due to the transverse force fields from the tilted wave crest and the non-uniform crest height along the wave crest are the key factors to determine the above particle accumulation and depletion. It explains the observations such as the lower speed of smaller crests, the straightening of the leading front of the pitchfork waveform associated with the transverse motion of defect to the open side, and the vertical defect gliding in the wave frame through the detachment of the strongly kinked pitchfork branch followed by its reconnection with the trailing crest.

  2. Prediction of the thermal sensitivity of surface acoustic waves excited under a periodic grating of electrodes.

    PubMed

    Pastureaud, Thomas; Lardat, Raphael; Chamaly, Stéphane; Pénavaire, Louis; Ballandras, Sylvain

    2005-08-01

    The prediction of the temperature sensitivity of surface acoustic wave (SAW) devices still requires improvement because the nature of the implemented surface modes and the devices' complexity strongly change from the early basic Rayleigh-wave-based devices. To address this problem, a theoretical analysis and a numerical tool have been developed to predict the thermal dispersion of general electro-acoustic devices. The proposed model accounts for the electrode contribution to the frequency-temperature law. The computed thermal sensitivities are compared to experimental results for different kinds of substrates and waves.

  3. Excitation of Kinetic Geodesic Acoustic Modes by Drift Waves in Nonuniform Plasmas

    NASA Astrophysics Data System (ADS)

    Qiu, Zhiyong; Chen, Liu; Zonca, Fulvio

    2015-11-01

    Spontaneous excitation of geodesic acoustic mode (GAM) by drift wave turbulence (DW), which is expected to play an important role in the DW saturation process, is investigated including effects of system nonuniformities and kinetic plasma response. The coupled equations describing the fully nonlinear interaction between GAM and DW are derived based on the nonlinear gyrokinetic theory, and then we solved both analytically and numerically to investigate the spatial-temporal evolution of the coupled DW-GAM system. Kinetic effects as well as nonuniformities due to diamagnetic frequency profile, finite radial envelope width of DW pump and GAM continuum are systematically included in the analysis. It is found that the parametric decay process is a convective instability for typical tokamak parameters, when finite group velocities of DW and GAM associated with kinetic effects and finite radial envelope width are taken into account. The nonlinearly driven GAM propagates at a group velocity, that, due to coupling with DW, is typically much larger than that predicted by the linear theory of GAM. When, however, nonuniformity of diamagnetic frequency is taken into account, the parametric decay process becomes, time asymptotically, a quasi-exponentially growing absolute instab Work supported by US DoE, ITER-CN, NSFC and EUROfusion projects.

  4. Excitation of ion-acoustic perturbations by incoherent kinetic Alfven waves in plasmas

    SciTech Connect

    Mendonca, J. T.; Shukla, P. K.

    2007-12-15

    The dispersion relation for ion-acoustic perturbations (IAPs) in the presence of incoherent kinetic Alfven waves (KAWs) in plasmas is derived. The wave-kinetic-approach is used to study the nonlinear interactions between an ensemble of random phase KAWs and IAPs. It is found that incoherent KAW spectrum is unstable against IAPs. The instability growth rates for particular cases are obtained. The present instability offers the possibility of heating ions in a turbulent magnetoplasma composed of incoherent KAWs.

  5. Excitation of ion-acoustic perturbations by incoherent kinetic Alfvén waves in plasmas

    NASA Astrophysics Data System (ADS)

    Mendonça, J. T.; Shukla, P. K.

    2007-12-01

    The dispersion relation for ion-acoustic perturbations (IAPs) in the presence of incoherent kinetic Alfvén waves (KAWs) in plasmas is derived. The wave-kinetic-approach is used to study the nonlinear interactions between an ensemble of random phase KAWs and IAPs. It is found that incoherent KAW spectrum is unstable against IAPs. The instability growth rates for particular cases are obtained. The present instability offers the possibility of heating ions in a turbulent magnetoplasma composed of incoherent KAWs.

  6. Modulational excitation of low-frequency dust acoustic waves in the Earth's lower ionosphere

    NASA Astrophysics Data System (ADS)

    Kopnin, S. I.; Popel, S. I.; Yu, M. Y.

    2007-04-01

    During the observation of Perseid, Leonid, Gemenid, and Orionid meteor showers, stable low-frequency lines in the frequency range of 20-60 Hz were recorded against the radio-frequency noise background. A physical mechanism for this effect is proposed, and it is established that the effect itself is related to the modulational interaction between electromagnetic and dust acoustic waves. The dynamics of the components of a complex (dusty) ionospheric plasma with dust produced from the evolution of meteoric material is described. The conditions for the existence of dust acoustic waves in the ionosphere are considered, and the waves are shown to dissipate energy mainly in collisions of neutral particles with charged dust grains. The modulational instability of electromagnetic waves in a complex (dusty) ionospheric plasma is analyzed and is found to be driven by the nonlinear Joule heating, the ponderomotive force, and the processes governing dust charging and dynamics. The conditions for the onset of the modulational instability of electromagnetic waves, as well as its growth rate and threshold, are determined for both daytime and nighttime. It is shown that low-frequency perturbations generated in the modulational interaction are related to dust acoustic waves.

  7. Modulational excitation of low-frequency dust acoustic waves in the Earth's lower ionosphere

    SciTech Connect

    Kopnin, S. I.; Popel, S. I.; Yu, M. Y.

    2007-04-15

    During the observation of Perseid, Leonid, Gemenid, and Orionid meteor showers, stable low-frequency lines in the frequency range of 20-60 Hz were recorded against the radio-frequency noise background. A physical mechanism for this effect is proposed, and it is established that the effect itself is related to the modulational interaction between electromagnetic and dust acoustic waves. The dynamics of the components of a complex (dusty) ionospheric plasma with dust produced from the evolution of meteoric material is described. The conditions for the existence of dust acoustic waves in the ionosphere are considered, and the waves are shown to dissipate energy mainly in collisions of neutral particles with charged dust grains. The modulational instability of electromagnetic waves in a complex (dusty) ionospheric plasma is analyzed and is found to be driven by the nonlinear Joule heating, the ponderomotive force, and the processes governing dust charging and dynamics. The conditions for the onset of the modulational instability of electromagnetic waves, as well as its growth rate and threshold, are determined for both daytime and nighttime. It is shown that low-frequency perturbations generated in the modulational interaction are related to dust acoustic waves.

  8. Photo-acoustic excitation and detection of guided ultrasonic waves in bone samples covered by a soft coating layer

    NASA Astrophysics Data System (ADS)

    Zhao, Zuomin; Moilanen, Petro; Karppinen, Pasi; Määttä, Mikko; Karppinen, Timo; Hæggström, Edward; Timonen, Jussi; Myllylä, Risto

    2012-12-01

    Photo-acoustic (PA) excitation was combined with skeletal quantitative ultrasound (QUS) for multi-mode ultrasonic assessment of human long bones. This approach permits tailoring of the ultrasonic excitation and detection so as to efficiently detect the fundamental flexural guided wave (FFGW) through a coating of soft tissue. FFGW is a clinically relevant indicator of cortical thickness. An OPO laser with tunable optical wavelength, was used to excite a photo-acoustic source in the shaft of a porcine femur. Ultrasonic signals were detected by a piezoelectric transducer, scanning along the long axis of the bone, 20-50 mm away from the source. Five femurs were measured without and with a soft coating. The coating was made of an aqueous gelatin-intralipid suspension that optically and acoustically mimicked real soft tissue. An even coating thickness was ensured by using a specific mold. The optical wave length of the source (1250 nm) was tuned to maximize the amplitude of FFGW excitation at 50 kHz frequency. The experimentally determined FFGW phase velocity in the uncoated samples was consistent with that of the fundamental antisymmetric Lamb mode (A0). Using appropriate signal processing, FFGW was also identified in the coated bone samples, this time with a phase velocity consistent with that theoretically predicted for the first mode of a fluid-solid bilayer waveguide (BL1). Our results suggest that photo-acoustic quantitative ultrasound enables assessment of the thickness-sensitive FFGW in bone through a layer of soft tissue. Photo-acoustic characterization of the cortical bone thickness may thus become possible.

  9. Excitation and detection of shear horizontal waves with electromagnetic acoustic transducers for nondestructive testing of plates

    NASA Astrophysics Data System (ADS)

    Ma, Qingzeng; Jiao, Jingpin; Hu, Ping; Zhong, Xi; Wu, Bin; He, Cunfu

    2014-03-01

    The fundamental shear horizontal(SH0) wave has several unique features that are attractive for long-range nondestructive testing(NDT). By a careful design of the geometric configuration, electromagnetic acoustic transducers(EMATs) have the capability to generate a wide range of guided wave modes, such as Lamb waves and shear-horizontal(SH) waves in plates. However, the performance of EMATs is influenced by their parameters. To evaluate the performance of periodic permanent magnet(PPM) EMATs, a distributed-line-source model is developed to calculate the angular acoustic field cross-section in the far-field. Numerical analysis is conducted to investigate the performance of such EMATs with different geometric parameters, such as period and number of magnet arrays, and inner and outer coil widths. Such parameters have a great influence on the directivity of the generated SH0 waves that arises mainly in the amplitude and width of both main and side lobes. According to the numerical analysis, these parameters are optimized to obtain better directivity. Optimized PPM EMATs are designed and used for NDT of strip plates. Experimental results show that the lateral boundary of the strip plate has no perceivable influence on SH0-wave propagation, thus validating their used in NDT. The proposed model predicts the radiation pattern of PPM EMATs, and can be used for their parameter optimization.

  10. Excitation of Ion Acoustic Waves in Confined Plasmas with Untrapped Electrons

    NASA Astrophysics Data System (ADS)

    Schamis, Hanna; Dow, Ansel; Carlsson, Johan; Kaganovich, Igor; Khrabrov, Alexander

    2015-11-01

    Various plasma propulsion devices exhibit strong electron emission from the walls either as a result of secondary processes or due to thermionic emission. To understand the electron kinetics in plasmas with strong emission, we have performed simulations using a reduced model with the LSP particle-in-cell code. This model aims to show the instability generated by the electron emission, in the form of ion acoustic waves near the sheath. It also aims to show the instability produced by untrapped electrons that propagate across the plasma, similarly to a beam, and can drive ion acoustic waves in the plasma bulk. This work was made possible by funding from the Department of Energy for the Summer Undergraduate Laboratory Internship (SULI) program. This work is supported by the US DOE Contract No.DE-AC02-09CH11466.

  11. Dynamics of sessile and pendant drops excited by surface acoustic waves: Gravity effects and correlation between oscillatory and translational motions

    NASA Astrophysics Data System (ADS)

    Bussonnière, A.; Baudoin, M.; Brunet, P.; Matar, O. Bou

    2016-05-01

    When sessile droplets are excited by ultrasonic traveling surface acoustic waves (SAWs), they undergo complex dynamics with both oscillations and translational motion. While the nature of the Rayleigh-Lamb quadrupolar drop oscillations has been identified, their origin and their influence on the drop mobility remains unexplained. Indeed, the physics behind this peculiar dynamics is complex with nonlinearities involved both at the excitation level (acoustic streaming and radiation pressure) and in the droplet response (nonlinear oscillations and contact line dynamics). In this paper, we investigate the dynamics of sessile and pendant drops excited by SAWs. For pendant drops, so-far unreported dynamics are observed close to the drop detachment threshold with the suppression of the translational motion. Away from this threshold, the comparison between pendant and sessile drop dynamics allows us to identify the role played by gravity or, more generally, by an initial or dynamically induced stretching of the drop. In turn, we elucidate the origin of the resonance frequency shift, as well as the origin of the strong correlation between oscillatory and translational motion. We show that for sessile drops, the velocity is mainly determined by the amplitude of oscillation and that the saturation observed is due to the nonlinear dependence of the drop response frequency on the dynamically induced stretching.

  12. Dynamics of sessile and pendant drops excited by surface acoustic waves: Gravity effects and correlation between oscillatory and translational motions.

    PubMed

    Bussonnière, A; Baudoin, M; Brunet, P; Matar, O Bou

    2016-05-01

    When sessile droplets are excited by ultrasonic traveling surface acoustic waves (SAWs), they undergo complex dynamics with both oscillations and translational motion. While the nature of the Rayleigh-Lamb quadrupolar drop oscillations has been identified, their origin and their influence on the drop mobility remains unexplained. Indeed, the physics behind this peculiar dynamics is complex with nonlinearities involved both at the excitation level (acoustic streaming and radiation pressure) and in the droplet response (nonlinear oscillations and contact line dynamics). In this paper, we investigate the dynamics of sessile and pendant drops excited by SAWs. For pendant drops, so-far unreported dynamics are observed close to the drop detachment threshold with the suppression of the translational motion. Away from this threshold, the comparison between pendant and sessile drop dynamics allows us to identify the role played by gravity or, more generally, by an initial or dynamically induced stretching of the drop. In turn, we elucidate the origin of the resonance frequency shift, as well as the origin of the strong correlation between oscillatory and translational motion. We show that for sessile drops, the velocity is mainly determined by the amplitude of oscillation and that the saturation observed is due to the nonlinear dependence of the drop response frequency on the dynamically induced stretching. PMID:27300977

  13. Dynamics of sessile and pendant drops excited by surface acoustic waves: Gravity effects and correlation between oscillatory and translational motions.

    PubMed

    Bussonnière, A; Baudoin, M; Brunet, P; Matar, O Bou

    2016-05-01

    When sessile droplets are excited by ultrasonic traveling surface acoustic waves (SAWs), they undergo complex dynamics with both oscillations and translational motion. While the nature of the Rayleigh-Lamb quadrupolar drop oscillations has been identified, their origin and their influence on the drop mobility remains unexplained. Indeed, the physics behind this peculiar dynamics is complex with nonlinearities involved both at the excitation level (acoustic streaming and radiation pressure) and in the droplet response (nonlinear oscillations and contact line dynamics). In this paper, we investigate the dynamics of sessile and pendant drops excited by SAWs. For pendant drops, so-far unreported dynamics are observed close to the drop detachment threshold with the suppression of the translational motion. Away from this threshold, the comparison between pendant and sessile drop dynamics allows us to identify the role played by gravity or, more generally, by an initial or dynamically induced stretching of the drop. In turn, we elucidate the origin of the resonance frequency shift, as well as the origin of the strong correlation between oscillatory and translational motion. We show that for sessile drops, the velocity is mainly determined by the amplitude of oscillation and that the saturation observed is due to the nonlinear dependence of the drop response frequency on the dynamically induced stretching.

  14. [Thermoelastic excitation of acoustic waves in biological models under the effect of the high peak-power pulsed electromagnetic radiation of extremely high frequency].

    PubMed

    Gapeev, A B; Rubanik, A V; Pashovkin, T N; Chemeris, N K

    2007-01-01

    The capability of high peak-power pulsed electromagnetic radiation of extremely high frequency (35,27 GHz, pulse widths of 100 and 600 ns, peak power of 20 kW) to excite acoustic waves in model water-containing objects and muscular tissue of animals has been experimentally shown for the first time. The amplitude and duration of excited acoustic pulses are within the limits of accuracy of theoretical assessments and have a complex nonlinear dependence on the energy input of electromagnetic radiation supplied. The velocity of propagation of acoustic pulses in water-containing models and isolated muscular tissue of animals was close to the reference data. The excitation of acoustic waves in biological systems under the action of high peak-power pulsed electromagnetic radiation of extremely high frequency is the important phenomenon, which essentially contributes to the understanding of the mechanisms of biological effects of these electromagnetic fields.

  15. Time interval measurement device based on surface acoustic wave filter excitation, providing 1 ps precision and stability

    SciTech Connect

    Panek, Petr; Prochazka, Ivan

    2007-09-15

    This article deals with the time interval measurement device, which is based on a surface acoustic wave (SAW) filter as a time interpolator. The operating principle is based on the fact that a transversal SAW filter excited by a short pulse can generate a finite signal with highly suppressed spectra outside a narrow frequency band. If the responses to two excitations are sampled at clock ticks, they can be precisely reconstructed from a finite number of samples and then compared so as to determine the time interval between the two excitations. We have designed and constructed a two-channel time interval measurement device which allows independent timing of two events and evaluation of the time interval between them. The device has been constructed using commercially available components. The experimental results proved the concept. We have assessed the single-shot time interval measurement precision of 1.3 ps rms that corresponds to the time of arrival precision of 0.9 ps rms in each channel. The temperature drift of the measured time interval on temperature is lower than 0.5 ps/K, and the long term stability is better than {+-}0.2 ps/h. These are to our knowledge the best values reported for the time interval measurement device. The results are in good agreement with the error budget based on the theoretical analysis.

  16. Time interval measurement device based on surface acoustic wave filter excitation, providing 1 ps precision and stability

    NASA Astrophysics Data System (ADS)

    Panek, Petr; Prochazka, Ivan

    2007-09-01

    This article deals with the time interval measurement device, which is based on a surface acoustic wave (SAW) filter as a time interpolator. The operating principle is based on the fact that a transversal SAW filter excited by a short pulse can generate a finite signal with highly suppressed spectra outside a narrow frequency band. If the responses to two excitations are sampled at clock ticks, they can be precisely reconstructed from a finite number of samples and then compared so as to determine the time interval between the two excitations. We have designed and constructed a two-channel time interval measurement device which allows independent timing of two events and evaluation of the time interval between them. The device has been constructed using commercially available components. The experimental results proved the concept. We have assessed the single-shot time interval measurement precision of 1.3ps rms that corresponds to the time of arrival precision of 0.9ps rms in each channel. The temperature drift of the measured time interval on temperature is lower than 0.5ps/K, and the long term stability is better than ±0.2ps/h. These are to our knowledge the best values reported for the time interval measurement device. The results are in good agreement with the error budget based on the theoretical analysis.

  17. Modulational instability and envelope excitation of ion-acoustic waves in quantum electron-positron-ion plasmas

    NASA Astrophysics Data System (ADS)

    Misra, A. P.; Bhowmik, C.; Shukla, P. K.

    2009-07-01

    The theoretical study of modulational instability (MI) and localized envelope excitations of finite amplitude ion-acoustic waves (IAWs) is revisited in an unmagnetized quantum electron-positron-ion plasma. For this purpose, a one-dimensional nonlinear Schrödinger equation, which governs the slow modulation of IAW packets, is derived by using the standard reductive perturbations technique. Two parameters, defining the ratio of the electron to ion number density (μ) and the quantum coupling parameter (H) describing the ratio of the "plasmonic energy density" to the Fermi energy density, are shown to play crucial roles in determining the modulational stability/MI domains, as well as for the existence of both bright and dark envelope solitons. It is found that the stability region increases (decreases) with increasing μ(H ), whereas the MI region for the IAW mode shifts to larger (smaller) wave number k as the value of μ(H ) increases. Moreover, the parameter H is shown to suppress the MI growth rate of the IAWs. The present results may be relevant to dense astrophysical plasmas (e.g., white dwarfs, where the electron-positron annihilation can be important, and where the particle density is of the order of 1034-1035 m-3) as well as to the next generation intense laser solid density plasma experiments.

  18. Acoustically excited heated jets. 1: Internal excitation

    NASA Technical Reports Server (NTRS)

    Lepicovsky, J.; Ahuja, K. K.; Brown, W. H.; Salikuddin, M.; Morris, P. J.

    1988-01-01

    The effects of relatively strong upstream acoustic excitation on the mixing of heated jets with the surrounding air are investigated. To determine the extent of the available information on experiments and theories dealing with acoustically excited heated jets, an extensive literature survey was carried out. The experimental program consisted of flow visualization and flowfield velocity and temperature measurements for a broad range of jet operating and flow excitation conditions. A 50.8-mm-diam nozzle was used for this purpose. Parallel to the experimental study, an existing theoretical model of excited jets was refined to include the region downstream of the jet potential core. Excellent agreement was found between theory and experiment in moderately heated jets. However, the theory has not yet been confirmed for highly heated jets. It was found that the sensitivity of heated jets to upstream acoustic excitation varies strongly with the jet operating conditions and that the threshold excitation level increases with increasing jet temperature. Furthermore, the preferential Strouhal number is found not to change significantly with a change of the jet operating conditions. Finally, the effects of the nozzle exit boundary layer thickness appear to be similar for both heated and unheated jets at low Mach numbers.

  19. Excited waves in shear layers

    NASA Technical Reports Server (NTRS)

    Bechert, D. W.

    1982-01-01

    The generation of instability waves in free shear layers is investigated. The model assumes an infinitesimally thin shear layer shed from a semi-infinite plate which is exposed to sound excitation. The acoustical shear layer excitation by a source further away from the plate edge in the downstream direction is very weak while upstream from the plate edge the excitation is relatively efficient. A special solution is given for the source at the plate edge. The theory is then extended to two streams on both sides of the shear layer having different velocities and densities. Furthermore, the excitation of a shear layer in a channel is calculated. A reference quantity is found for the magnitude of the excited instability waves. For a comparison with measurements, numerical computations of the velocity field outside the shear layer were carried out.

  20. Self-excited dust-acoustic waves in an electron-depleted nanodusty plasma

    SciTech Connect

    Tadsen, Benjamin Greiner, Franko; Groth, Sebastian; Piel, Alexander

    2015-11-15

    A dust density wave field is observed in a cloud of nanodust particles confined in a radio frequency plasma. Simultaneous measurements of the dust properties, grain size and density, as well as the wave parameters, frequency and wave number, allow for an estimate of the ion density, ion drift velocity, and the dust charge using a hybrid model for the wave dispersion. It appears that the charge on the dust grains in the cloud is drastically reduced to tens of elementary charges compared with isolated dust particles in a plasma. The charge is much higher at the cloud's periphery, i.e., towards the void in the plasma center and also towards the outer edge of the cloud.

  1. Nonlinear Excitation of Acoustic Modes by Large-Amplitude Alfvén Waves in a Laboratory Plasma

    NASA Astrophysics Data System (ADS)

    Dorfman, S.; Carter, T. A.

    2013-05-01

    The nonlinear three-wave interaction process at the heart of the parametric decay process is studied by launching counterpropagating Alfvén waves from antennas placed at either end of the Large Plasma Device. A resonance in the beat wave response produced by the two launched Alfvén waves is observed and is identified as a damped ion acoustic mode based on the measured dispersion relation. Other properties of the interaction including the spatial profile of the beat mode and response amplitude are also consistent with theoretical predictions for a three-wave interaction driven by a nonlinear ponderomotive force.

  2. Non-linear Alfvén wave interaction leading to resonant excitation of an acoustic mode in the laboratory

    SciTech Connect

    Dorfman, S.; Carter, T. A.

    2015-05-15

    The nonlinear three-wave interaction process at the heart of the parametric decay process is studied by launching counter-propagating Alfvén waves from antennas placed at either end of the Large Plasma Device [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)]. A resonance in the beat wave response produced by the two launched Alfvén waves is observed and is identified as a damped ion acoustic mode based on the measured dispersion relation. Other properties of the interaction including the spatial profile of the beat mode and response amplitude are also consistent with theoretical predictions for a three-wave interaction driven by a nonlinear ponderomotive force. A simple damped, driven oscillator model making use of the MHD equations well-predicts most of the observations, but the width of the resonance curve is still under investigation.

  3. Non-linear Alfvén wave interaction leading to resonant excitation of an acoustic mode in the laboratorya)

    NASA Astrophysics Data System (ADS)

    Dorfman, S.; Carter, T. A.

    2015-05-01

    The nonlinear three-wave interaction process at the heart of the parametric decay process is studied by launching counter-propagating Alfvén waves from antennas placed at either end of the Large Plasma Device [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)]. A resonance in the beat wave response produced by the two launched Alfvén waves is observed and is identified as a damped ion acoustic mode based on the measured dispersion relation. Other properties of the interaction including the spatial profile of the beat mode and response amplitude are also consistent with theoretical predictions for a three-wave interaction driven by a nonlinear ponderomotive force. A simple damped, driven oscillator model making use of the MHD equations well-predicts most of the observations, but the width of the resonance curve is still under investigation.

  4. Line-focus probe excitation of Scholte acoustic waves at the liquid-loaded surfaces of periodic structures

    SciTech Connect

    Every, A.G.; Vines, R.E.; Wolfe, J.P.

    1999-10-01

    A model is introduced to explain our observation of Scholte-like ultrasonic waves traveling at the water-loaded surfaces of solids with periodically varying properties. The observations pertain to two two-dimensional superlattices: a laminated solid of alternating 0.5-mm-thick layers of aluminum and a polymer, and a hexagonal array of polymer rods of lattice spacing 1 mm in an aluminum matrix. The surface waves are generated and detected by line focus acoustic lenses aligned parallel to each other, and separated by varying distances. The acoustic fields of these lenses may be considered a superposition of plain bulk waves with wave normals contained within the angular apertures of the lenses. For homogeneous solids, phase matching constraints do not allow the Scholte wave to be coupled into with an experimental configuration of this type. This is not true for a spatially periodic solid, where coupling between bulk waves and the Scholte surface wave takes place through Umklapp processes involving a change in the wave-vector component parallel to the surface by a reciprocal lattice vector. In the experiments, the source pulse is broadband, extending up to about 6 MHz, whereas the spectrum of the observed Scholte wave is peaked at around 4 and 4.5 MHz for the layered solid and hexagonal lattice, respectively. We attribute this to a resonance in the surface response of the solid, possibly associated with a critical point in the dispersion relation of the superlattice. On rotating the solid about its surface normal, the Scholte wave displays dramatic variation in phase arrival time and, to a lesser extent, also group arrival time. This variation is well accounted for by our model. {copyright} {ital 1999} {ital The American Physical Society}

  5. Excitation of dust acoustic waves by an ion beam in a plasma cylinder with negatively charged dust grains

    SciTech Connect

    Sharma, Suresh C.; Kaur, Daljeet; Gahlot, Ajay; Sharma, Jyotsna

    2014-10-15

    An ion beam propagating through a plasma cylinder having negatively charged dust grains drives a low frequency electrostatic dust acoustic wave (DAW) to instability via Cerenkov interaction. The unstable wave frequencies and the growth rate increase with the relative density of negatively charged dust grains. The growth rate of the unstable mode scales to the one-third power of the beam density. The real part of the frequency of the unstable mode increases with the beam energy and scales to almost one-half power of the beam energy. The phase velocity, frequency, and wavelength results of the unstable mode are in compliance with the experimental observations.

  6. Surface Acoustic Wave Microfluidics

    NASA Astrophysics Data System (ADS)

    Yeo, Leslie Y.; Friend, James R.

    2014-01-01

    Fluid manipulations at the microscale and beyond are powerfully enabled through the use of 10-1,000-MHz acoustic waves. A superior alternative in many cases to other microfluidic actuation techniques, such high-frequency acoustics is almost universally produced by surface acoustic wave devices that employ electromechanical transduction in wafer-scale or thin-film piezoelectric media to generate the kinetic energy needed to transport and manipulate fluids placed in adjacent microfluidic structures. These waves are responsible for a diverse range of complex fluid transport phenomena - from interfacial fluid vibration and drop and confined fluid transport to jetting and atomization - underlying a flourishing research literature spanning fundamental fluid physics to chip-scale engineering applications. We highlight some of this literature to provide the reader with a historical basis, routes for more detailed study, and an impression of the field's future directions.

  7. Ion heating via turbulent ion acoustic waves.

    NASA Technical Reports Server (NTRS)

    Taylor, R. J.; Coroniti, F. V.

    1972-01-01

    The ion acoustic turbulence in the turbulent-heating experiment reported is excited by the ion-ion beam instability. Graphs are presented, showing the spatial evolution of the parallel ion beam energy and the spatial evolution of the ion acoustic turbulent wave spectrum. The observed characteristics of test waves in a turbulent beam-plasma imply that wave saturation is a dynamic balance between the emission of waves by the beam and the destruction or damping of wave coherence by the turbulent diffusion of particle orbits.

  8. Splitting a droplet with oil encapsulation using surface acoustic wave excited by electric signal with low power

    NASA Astrophysics Data System (ADS)

    Zhang, Anliang; Zha, Yan; Fu, Xingting

    2013-07-01

    A new method for splitting a droplet with oil encapsulation is presented. An interdigital transducer and a reflector are fabricated on a 128° yx-LiNbO3 piezoelectric substrate using microelectric technology. An electric signal with the power of 12.3 dBm is applied to the interdigital transducer to generate surface acoustic wave, which is radiated into a droplet with oil encapsulation, leading to surface acoustic wave streaming force. When the electric signal is suddenly moved off, the breakup of the droplet occurs due to inertial force. Color dye solution droplets encapsulated by oil droplets are demonstrated. The effects of electric power, the volume ratio of color dye solution to oil, and the volume of mother droplet on the breakup of droplets are studied. As applications, the presented method is successfully applied to mixture operation and color development reaction of two droplets. The method provides a new sample preparation technique, which is helpful for microfluidic biochemical analysis in a piezoelectric microfluidic system.

  9. Quantum positron acoustic waves

    SciTech Connect

    Metref, Hassina; Tribeche, Mouloud

    2014-12-15

    Nonlinear quantum positron-acoustic (QPA) waves are investigated for the first time, within the theoretical framework of the quantum hydrodynamic model. In the small but finite amplitude limit, both deformed Korteweg-de Vries and generalized Korteweg-de Vries equations governing, respectively, the dynamics of QPA solitary waves and double-layers are derived. Moreover, a full finite amplitude analysis is undertaken, and a numerical integration of the obtained highly nonlinear equations is carried out. The results complement our previously published results on this problem.

  10. Imaging feedback for histotripsy by characterizing dynamics of acoustic radiation force impulse (ARFI)-induced shear waves excited in a treated volume.

    PubMed

    Wang, Tzu-Yin; Hall, Timothy L; Xu, Zhen; Fowlkes, J Brian; Cain, Charles A

    2014-07-01

    Our previous study indicated that shear waves decay and propagate at a lower speed as they propagate into a tissue volume mechanically fractionated by histotripsy. In this paper, we hypothesize that the change in the shear dynamics is related to the degree of tissue fractionation, and can be used to predict histotripsy treatment outcomes. To test this hypothesis, lesions with different degrees of tissue fractionation were created in agar-graphite tissue phantoms and ex vivo kidneys with increasing numbers of therapy pulses, from 0 to 2000 pulses per treatment location. The therapy pulses were 3-cycle 750-kHz focused ultrasound delivered at a peak negative/positive pressure of 17/108 MPa and a repetition rate of 50 Hz. The shear waves were excited by acoustic radiation force impulse (ARFI) focused at the center of the lesion. The spatial and temporal behavior of the propagating shear waves was measured with ultrasound plane wave imaging. The temporal displacement profile at a lateral location 10 mm offset to the shear excitation region was detected with M-mode imaging. The decay and delay of the shear waves were quantitatively characterized on the temporal displacement profile. Results showed significant changes in two characteristics on the temporal displacement profile: the peak-to-peak displacement decayed exponentially with increasing numbers of therapy pulses; the relative time-to-peak displacement increased with increasing numbers of therapy pulses, and appeared to saturate at higher numbers of pulses. Correspondingly, the degree of tissues fractionation, as indicated by the percentage of structurally intact cell nuclei, decreased exponentially with increasing numbers of therapy pulses. Strong linear correlations were found between the two characteristics and the degree of tissue fractionation. These results suggest that the characteristics of the shear temporal displacement profile may provide useful feedback information regarding the treatment outcomes.

  11. Ion acoustic traveling waves

    NASA Astrophysics Data System (ADS)

    Webb, G. M.; Burrows, R. H.; Ao, X.; Zank, G. P.; Zank

    2014-04-01

    Models for traveling waves in multi-fluid plasmas give essential insight into fully nonlinear wave structures in plasmas, not readily available from either numerical simulations or from weakly nonlinear wave theories. We illustrate these ideas using one of the simplest models of an electron-proton multi-fluid plasma for the case where there is no magnetic field or a constant normal magnetic field present. We show that the traveling waves can be reduced to a single first-order differential equation governing the dynamics. We also show that the equations admit a multi-symplectic Hamiltonian formulation in which both the space and time variables can act as the evolution variable. An integral equation useful for calculating adiabatic, electrostatic solitary wave signatures for multi-fluid plasmas with arbitrary mass ratios is presented. The integral equation arises naturally from a fluid dynamics approach for a two fluid plasma, with a given mass ratio of the two species (e.g. the plasma could be an electron-proton or an electron-positron plasma). Besides its intrinsic interest, the integral equation solution provides a useful analytical test for numerical codes that include a proton-electron mass ratio as a fundamental constant, such as for particle in cell (PIC) codes. The integral equation is used to delineate the physical characteristics of ion acoustic traveling waves consisting of hot electron and cold proton fluids.

  12. Guided acoustic wave inspection system

    DOEpatents

    Chinn, Diane J.

    2004-10-05

    A system for inspecting a conduit for undesirable characteristics. A transducer system induces guided acoustic waves onto said conduit. The transducer system detects the undesirable characteristics of the conduit by receiving guided acoustic waves that contain information about the undesirable characteristics. The conduit has at least two sides and the transducer system utilizes flexural modes of propagation to provide inspection using access from only the one side of the conduit. Cracking is detected with pulse-echo testing using one transducer to both send and receive the guided acoustic waves. Thinning is detected in through-transmission testing where one transducer sends and another transducer receives the guided acoustic waves.

  13. Dust-Acoustic Waves: Visible Sound Waves

    SciTech Connect

    Merlino, Robert L.

    2009-11-10

    A historical overview of some of the early theoretical and experimental work on dust acoustic waves is given. The basic physics of the dust acoustic wave and some of the theoretical refinements that have been made, including the effects of collisions, plasma absorption, dust charge fluctuations, particle drifts and strong coupling effects are discussed. Some recent experimental findings and outstanding problems are also presented.

  14. Laboratory Observations of Self-Excited Dust Acoustic Shocks

    SciTech Connect

    Heinrich, J.; Kim, S.-H.; Merlino, R. L.

    2009-09-11

    Repeated, self-excited dust acoustic shock waves (DASWs) have been observed in a dc glow discharge dusty plasma using high-speed video imaging. Two major observations are reported: (1) The self-steepening of a nonlinear dust acoustic wave (DAW) into a saw-tooth wave with sharp gradient in dust density, very similar to those found in numerical solutions of the fully nonlinear fluid equations for a nondispersive DAW [B. Eliasson and P. K. Shukla, Phys. Rev. E 69, 067401 (2004)], and (2) the collision and confluence of two DASWs.

  15. Targeted energy transfers and passive acoustic wave redirection in a two-dimensional granular network under periodic excitation

    SciTech Connect

    Zhang, Yijing Moore, Keegan J.; Vakakis, Alexander F.; McFarland, D. Michael

    2015-12-21

    We study passive pulse redirection and nonlinear targeted energy transfer in a granular network composed of two semi-infinite, ordered homogeneous granular chains mounted on linear elastic foundations and coupled by weak linear stiffnesses. Periodic excitation in the form of repetitive half-sine pulses is applied to one of the chains, designated as the “excited chain,” whereas the other chain is initially at rest and is regarded as the “absorbing chain.” We show that passive pulse redirection and targeted energy transfer from the excited to the absorbing chain can be achieved by macro-scale realization of the spatial analog of the Landau-Zener quantum tunneling effect. This is realized by finite stratification of the elastic foundation of the excited chain and depends on the system parameters (e.g., the percentage of stratification) and on the parameters of the periodic excitation. Utilizing empirical mode decomposition and numerical Hilbert transforms, we detect the existence of two distinct nonlinear phenomena in the periodically forced network; namely, (i) energy localization in the absorbing chain due to sustained 1:1 resonance capture leading to irreversible pulse redirection from the excited chain, and (ii) continuous energy exchanges in the form of nonlinear beats between the two chains in the absence of resonance capture. Our results extend previous findings of transient passive energy redirection in impulsively excited granular networks and demonstrate that steady state passive pulse redirection in these networks can be robustly achieved under periodic excitation.

  16. Active micromixer using surface acoustic wave streaming

    SciTech Connect

    Branch; Darren W. , Meyer; Grant D. , Craighead; Harold G.

    2011-05-17

    An active micromixer uses a surface acoustic wave, preferably a Rayleigh wave, propagating on a piezoelectric substrate to induce acoustic streaming in a fluid in a microfluidic channel. The surface acoustic wave can be generated by applying an RF excitation signal to at least one interdigital transducer on the piezoelectric substrate. The active micromixer can rapidly mix quiescent fluids or laminar streams in low Reynolds number flows. The active micromixer has no moving parts (other than the SAW transducer) and is, therefore, more reliable, less damaging to sensitive fluids, and less susceptible to fouling and channel clogging than other types of active and passive micromixers. The active micromixer is adaptable to a wide range of geometries, can be easily fabricated, and can be integrated in a microfluidic system, reducing dead volume. Finally, the active micromixer has on-demand on/off mixing capability and can be operated at low power.

  17. Surface acoustic wave microfluidics

    PubMed Central

    Ding, Xiaoyun; Li, Peng; Lin, Sz-Chin Steven; Stratton, Zackary S.; Nama, Nitesh; Guo, Feng; Slotcavage, Daniel; Mao, Xiaole; Shi, Jinjie; Costanzo, Francesco; Huang, Tony Jun

    2014-01-01

    The recent introduction of surface acoustic wave (SAW) technology onto lab-on-a-chip platforms has opened a new frontier in microfluidics. The advantages provided by such SAW microfluidics are numerous: simple fabrication, high biocompatibility, fast fluid actuation, versatility, compact and inexpensive devices and accessories, contact-free particle manipulation, and compatibility with other microfluidic components. We believe that these advantages enable SAW microfluidics to play a significant role in a variety of applications in biology, chemistry, engineering, and medicine. In this review article, we discuss the theory underpinning SAWs and their interactions with particles and the contacting fluids in which they are suspended. We then review the SAW-enabled microfluidic devices demonstrated to date, starting with devices that accomplish fluid mixing and transport through the use of travelling SAW; we follow that by reviewing the more recent innovations achieved with standing SAW that enable such actions as particle/cell focusing, sorting, and patterning. Finally, we look forward and appraise where the discipline of SAW microfluidics could go next. PMID:23900527

  18. Surface acoustic wave microfluidics.

    PubMed

    Ding, Xiaoyun; Li, Peng; Lin, Sz-Chin Steven; Stratton, Zackary S; Nama, Nitesh; Guo, Feng; Slotcavage, Daniel; Mao, Xiaole; Shi, Jinjie; Costanzo, Francesco; Huang, Tony Jun

    2013-09-21

    The recent introduction of surface acoustic wave (SAW) technology onto lab-on-a-chip platforms has opened a new frontier in microfluidics. The advantages provided by such SAW microfluidics are numerous: simple fabrication, high biocompatibility, fast fluid actuation, versatility, compact and inexpensive devices and accessories, contact-free particle manipulation, and compatibility with other microfluidic components. We believe that these advantages enable SAW microfluidics to play a significant role in a variety of applications in biology, chemistry, engineering and medicine. In this review article, we discuss the theory underpinning SAWs and their interactions with particles and the contacting fluids in which they are suspended. We then review the SAW-enabled microfluidic devices demonstrated to date, starting with devices that accomplish fluid mixing and transport through the use of travelling SAW; we follow that by reviewing the more recent innovations achieved with standing SAW that enable such actions as particle/cell focusing, sorting and patterning. Finally, we look forward and appraise where the discipline of SAW microfluidics could go next.

  19. Canonical Acoustics and Its Application to Surface Acoustic Wave on Acoustic Metamaterials

    NASA Astrophysics Data System (ADS)

    Shen, Jian Qi

    2016-08-01

    In a conventional formalism of acoustics, acoustic pressure p and velocity field u are used for characterizing acoustic waves propagating inside elastic/acoustic materials. We shall treat some fundamental problems relevant to acoustic wave propagation alternatively by using canonical acoustics (a more concise and compact formalism of acoustic dynamics), in which an acoustic scalar potential and an acoustic vector potential (Φ ,V), instead of the conventional acoustic field quantities such as acoustic pressure and velocity field (p,u) for characterizing acoustic waves, have been defined as the fundamental variables. The canonical formalism of the acoustic energy-momentum tensor is derived in terms of the acoustic potentials. Both the acoustic Hamiltonian density and the acoustic Lagrangian density have been defined, and based on this formulation, the acoustic wave quantization in a fluid is also developed. Such a formalism of acoustic potentials is employed to the problem of negative-mass-density assisted surface acoustic wave that is a highly localized surface bound state (an eigenstate of the acoustic wave equations). Since such a surface acoustic wave can be strongly confined to an interface between an acoustic metamaterial (e.g., fluid-solid composite structures with a negative dynamical mass density) and an ordinary material (with a positive mass density), it will give rise to an effect of acoustic field enhancement on the acoustic interface, and would have potential applications in acoustic device design for acoustic wave control.

  20. Electron Acoustic Waves in Pure Ion Plasmas

    NASA Astrophysics Data System (ADS)

    Anderegg, F.; Affolter, M.; Driscoll, C. F.; O'Neil, T. M.; Valentini, F.

    2012-10-01

    Electron Acoustic Waves (EAWs) are the low-frequency branch of near-linear Langmuir (plasma) waves: the frequency is such that the complex dielectric function (Dr, Di) has Dr= 0; and ``flattening'' of f(v) near the wave phase velocity vph gives Di=0 and eliminates Landau damping. Here, we observe standing axisymmetric EAWs in a pure ion column.footnotetextF. Anderegg, et al., Phys. Rev. Lett. 102, 095001 (2009). At low excitation amplitudes, the EAWs have vph˜1.4 v, in close agreement with near-linear theory. At moderate excitation strengths, EAW waves are observed over a range of frequencies, with 1.3 v < vph< 2.1 v. Here, the final wave frequency may differ from the excitation frequency since the excitation modifies f (v); and recent theory analyzes frequency shifts from ``corners'' of a plateau at vph.footnotetextF. Valentini et al., arXiv:1206.3500v1. Large amplitude EAWs have strong phase-locked harmonic content, and experiments will be compared to same-geometry simulations, and to simulations of KEENfootnotetextB. Afeyan et al., Proc. Inertial Fusion Sci. and Applications 2003, A.N.S. Monterey (2004), p. 213. waves in HEDLP geometries.

  1. Acoustic spin pumping in magnetoelectric bulk acoustic wave resonator

    NASA Astrophysics Data System (ADS)

    Polzikova, N. I.; Alekseev, S. G.; Pyataikin, I. I.; Kotelyanskii, I. M.; Luzanov, V. A.; Orlov, A. P.

    2016-05-01

    We present the generation and detection of spin currents by using magnetoelastic resonance excitation in a magnetoelectric composite high overtone bulk acoustic wave (BAW) resonator (HBAR) formed by a Al-ZnO-Al-GGG-YIG-Pt structure. Transversal BAW drives magnetization oscillations in YIG film at a given resonant magnetic field, and the resonant magneto-elastic coupling establishes the spin-current generation at the Pt/YIG interface. Due to the inverse spin Hall effect (ISHE) this BAW-driven spin current is converted to a dc voltage in the Pt layer. The dependence of the measured voltage both on magnetic field and frequency has a resonant character. The voltage is determined by the acoustic power in HBAR and changes its sign upon magnetic field reversal. We compare the experimentally observed amplitudes of the ISHE electrical field achieved by our method and other approaches to spin current generation that use surface acoustic waves and microwave resonators for ferromagnetic resonance excitation, with the theoretically expected values.

  2. Creating and studying ion acoustic waves in ultracold neutral plasmas

    SciTech Connect

    Killian, T. C.; Castro, J.; McQuillen, P.; O'Neil, T. M.

    2012-05-15

    We excite ion acoustic waves in ultracold neutral plasmas by imprinting density modulations during plasma creation. Laser-induced fluorescence is used to observe the density and velocity perturbations created by the waves. The effect of expansion of the plasma on the evolution of the wave amplitude is described by treating the wave action as an adiabatic invariant. After accounting for this effect, we determine that the waves are weakly damped, but the damping is significantly faster than expected for Landau damping.

  3. Acoustic-Gravity Waves from Bolide Sources

    NASA Astrophysics Data System (ADS)

    Revelle, Douglas O.

    2008-06-01

    We have developed a new approach to modeling the acoustic-gravity wave (AGW) radiation from bolide sources. This first effort involves entry modeling of bolide sources that have available satellite data through procedures developed in ReVelle (Earth Moon Planets 95, 441-476, 2004a; in: A. Milani, G. Valsecchi, D. Vokrouhlicky (eds) NEO Fireball Diversity: Energetics-based Entry Modeling and Analysis Techniques, Near-earth Objects: Our Celestial Neighbors (IAU S236), 2007b). Results from the entry modeling are directly coupled to AGW production through line source blast wave theory for the initial wave amplitude and period at x=10 (at 10 blast wave radii and perpendicular to the trajectory). The second effort involves the prediction of the formation and or dominance of the propagation of the atmospheric Lamb, edge-wave composite mode in a viscous fluid (Pierce, J. Acoust. Soc. Amer. 35, 1798-1807, 1963) as a function of the source energy, horizontal range and source altitude using the Lamb wave frequency that was deduced directly during the entry modeling and that is used as a surrogate for the source energy. We have also determined that Lamb wave production by bolides at close range decreases dramatically as either the source energy decreases or the source altitude increases. Finally using procedures in Gill ( Atmospheric-Ocean Dynamics, 1982) and in Tolstoy ( Wave Propagation, 1973), we have analyzed two simple dispersion relationships and have calculated the expected dispersion for the Lamb edge-wave mode and for the excited, propagating internal acoustic waves. Finally, we have used the above formalism to fully evaluate these techniques for four large bolides, namely: the Tunguska bolide of June 30, 1908; the Revelstoke bolide of March 31, 1965; the Crete bolide of June 6, 2002 and the Antarctic bolide of September 3, 2004. Due to page limitations, we will only present results in detail for the Revelstoke bolide.

  4. Marble Ageing Characterization by Acoustic Waves

    NASA Astrophysics Data System (ADS)

    Boudani, Mohamed El; Wilkie-Chancellier, Nicolas; Martinez, Loïc; Hébert, Ronan; Rolland, Olivier; Forst, Sébastien; Vergès-Belmin, Véronique; Serfaty, Stéphane

    In cultural heritage, statue marble characterization by acoustic waves is a well-known non-destructive method. Such investigations through the statues by time of flight method (TOF) point out sound speeds decrease with ageing. However for outdoor stored statues as the ones in the gardens of Chateau de Versailles, ageing affects mainly the surface of the Carrara marble. The present paper proposes an experimental study of the marble acoustic properties variations during accelerated laboratory ageing. The surface degradation of the marble is reproduced in laboratory for 29 mm thick marble samples by using heating/cooling thermal cycles on one face of a marble plate. Acoustic waves are generated by 1 MHz central frequency contact transducers excited by a voltage pulse placed on both sides of the plate. During the ageing and by using ad hoc transducers, the marble samples are characterized in transmission, along their volume by shear, compressional TOF measurements and along their surface by Rayleigh waves measurements. For Rayleigh waves, both TOF by transducers and laser vibrometry methods are used to detect the Rayleigh wave. The transmission measurements point out a deep decrease of the waves speeds in conjunction with a dramatic decrease of the maximum frequency transmitted. The marble acts as a low pass filter whose characteristic frequency cut decreases with ageing. This pattern occurs also for the Rayleigh wave surface measurements. The speed change in conjunction with the bandwidth translation is shown to be correlated to the material de-structuration during ageing. With a similar behavior but reversed in time, the same king of phenomena have been observed trough sol-gel materials during their structuration from liquid to solid state (Martinez, L. et all (2004). "Chirp-Z analysis for sol-gel transition monitoring". Ultrasonics, 42(1), 507-510.). A model is proposed to interpret the acoustical measurements

  5. Dual excitation acoustic paramagnetic logging tool

    DOEpatents

    Vail, III, William B.

    1989-01-01

    New methods and apparatus are disclosed which allow measurement of the presence of oil and water in gelogical formations using a new physical effect called the Acoustic Paramagnetic Logging Effect (APLE). The presence of petroleum in formation causes a slight increase in the earth's magnetic field in the vicinity of the reservoir. This is the phenomena of paramagnetism. Application of an acoustic source to a geological formation at the Larmor frequency of the nucleous present causes the paramagnetism of the formation to disappear. This results in a decrease in the earth's magnetic field in the vicinity of the oil bearing formation. Repetitively frequency sweeping the acoustic source through the Larmor frequency of the nucleons present (approx. 2 kHz) causes an amplitude modulation of the earth's magnetic field which is a consequence of the APLE. The amplitude modulation of the earth's magnetic field is measured with an induction coil gradiometer and provides a direct measure of the amount of oil and water in the excitation zone of the formation. The phase of the signal is used to infer the longitudinal relaxation times of the fluids present, which results in the ability in general to separate oil and water and to measure the viscosity of the oil present. Such measurements may be preformed in open boreholes and in cased well bores. The Dual Excitation Acoustic Paramagnetic Logging Tool employing two acoustic sources is also described.

  6. Dual excitation acoustic paramagnetic logging tool

    DOEpatents

    Vail, W.B. III.

    1989-02-14

    New methods and apparatus are disclosed which allow measurement of the presence of oil and water in geological formations using a new physical effect called the Acoustic Paramagnetic Logging Effect (APLE). The presence of petroleum in formation causes a slight increase in the earth's magnetic field in the vicinity of the reservoir. This is the phenomena of paramagnetism. Application of an acoustic source to a geological formation at the Larmor frequency of the nucleons present causes the paramagnetism of the formation to disappear. This results in a decrease in the earth's magnetic field in the vicinity of the oil bearing formation. Repetitively frequency sweeping the acoustic source through the Larmor frequency of the nucleons present (approx. 2 kHz) causes an amplitude modulation of the earth's magnetic field which is a consequence of the APLE. The amplitude modulation of the earth's magnetic field is measured with an induction coil gradiometer and provides a direct measure of the amount of oil and water in the excitation zone of the formation. The phase of the signal is used to infer the longitudinal relaxation times of the fluids present, which results in the ability in general to separate oil and water and to measure the viscosity of the oil present. Such measurements may be performed in open boreholes and in cased well bores. The Dual Excitation Acoustic Paramagnetic Logging Tool employing two acoustic sources is also described. 6 figs.

  7. Acoustic-gravity waves, theory and application

    NASA Astrophysics Data System (ADS)

    Kadri, Usama; Farrell, William E.; Munk, Walter

    2015-04-01

    Acoustic-gravity waves (AGW) propagate in the ocean under the influence of both the compressibility of sea water and the restoring force of gravity. The gravity dependence vanishes if the wave vector is normal to the ocean surface, but becomes increasingly important as the wave vector acquires a horizontal tilt. They are excited by many sources, including non-linear surface wave interactions, disturbances of the ocean bottom (submarine earthquakes and landslides) and underwater explosions. In this introductory lecture on acoustic-gravity waves, we describe their properties, and their relation to organ pipe modes, to microseisms, and to deep ocean signatures by short surface waves. We discuss the generation of AGW by underwater earthquakes; knowledge of their behaviour with water depth can be applied for the early detection of tsunamis. We also discuss their generation by the non-linear interaction of surface gravity waves, which explains the major role they play in transforming energy from the ocean surface to the crust, as part of the microseisms phenomenon. Finally, they contribute to horizontal water transport at depth, which might affect benthic life.

  8. On fast radial propagation of parametrically excited geodesic acoustic mode

    SciTech Connect

    Qiu, Z.; Chen, L.; Zonca, F.

    2015-04-15

    The spatial and temporal evolution of parametrically excited geodesic acoustic mode (GAM) initial pulse is investigated both analytically and numerically. Our results show that the nonlinearly excited GAM propagates at a group velocity which is, typically, much larger than that due to finite ion Larmor radius as predicted by the linear theory. The nonlinear dispersion relation of GAM driven by a finite amplitude drift wave pump is also derived, showing a nonlinear frequency increment of GAM. Further implications of these findings for interpreting experimental observations are also discussed.

  9. Acoustical scattering cross section of gas bubbles under dual-frequency acoustic excitation.

    PubMed

    Zhang, Yuning; Li, Shengcai

    2015-09-01

    The acoustical scattering cross section is a paramount parameter determining the scattering ability of cavitation bubbles when they are excited by the incident acoustic waves. This parameter is strongly related with many important applications of acoustic cavitation including facilitating the reaction of chemical process, boosting bubble sonoluminescence, and performing non-invasive therapy and drug delivery. In present paper, both the analytical and numerical solutions of acoustical scattering cross section of gas bubbles under dual-frequency excitation are obtained. The validity of the analytical solution is shown with demonstrating examples. The nonlinear characteristics (e.g., harmonics, subharmonics and ultraharmonics) of the scattering cross section curve under dual-frequency approach are investigated. Compared with single-frequency approach, the dual-frequency approach displays more resonances termed as "combination resonances" and could promote the acoustical scattering cross section significantly within a much broader range of bubble sizes due to the generation of more resonances. The influence of several paramount parameters (e.g., acoustic pressure amplitude, power allocations between two acoustic components, and the ratio of the frequencies) in the dual-frequency system on the predictions of scattering cross section has been discussed.

  10. Multi-reflective acoustic wave device

    DOEpatents

    Andle, Jeffrey C.

    2006-02-21

    An acoustic wave device, which utilizes multiple localized reflections of acoustic wave for achieving an infinite impulse response while maintaining high tolerance for dampening effects, is disclosed. The device utilized a plurality of electromechanically significant electrodes disposed on most of the active surface. A plurality of sensors utilizing the disclosed acoustic wave mode device are also described.

  11. Acoustically levitated dancing drops: Self-excited oscillation to chaotic shedding

    NASA Astrophysics Data System (ADS)

    Lin, Po-Cheng; I, Lin

    2016-02-01

    We experimentally demonstrate self-excited oscillation and shedding of millimeter-sized water drops, acoustically levitated in a single-node standing waves cavity, by decreasing the steady acoustic wave intensity below a threshold. The perturbation of the acoustic field by drop motion is a possible source for providing an effective negative damping for sustaining the growing amplitude of the self-excited motion. Its further interplay with surface tension, drop inertia, gravity and acoustic intensities, select various self-excited modes for different size of drops and acoustic intensity. The large drop exhibits quasiperiodic motion from a vertical mode and a zonal mode with growing coupling, as oscillation amplitudes grow, until falling on the floor. For small drops, chaotic oscillations constituted by several broadened sectorial modes and corresponding zonal modes are self-excited. The growing oscillation amplitude leads to droplet shedding from the edges of highly stretched lobes, where surface tension no longer holds the rapid expanding flow.

  12. Acoustically levitated dancing drops: Self-excited oscillation to chaotic shedding.

    PubMed

    Lin, Po-Cheng; I, Lin

    2016-02-01

    We experimentally demonstrate self-excited oscillation and shedding of millimeter-sized water drops, acoustically levitated in a single-node standing waves cavity, by decreasing the steady acoustic wave intensity below a threshold. The perturbation of the acoustic field by drop motion is a possible source for providing an effective negative damping for sustaining the growing amplitude of the self-excited motion. Its further interplay with surface tension, drop inertia, gravity and acoustic intensities, select various self-excited modes for different size of drops and acoustic intensity. The large drop exhibits quasiperiodic motion from a vertical mode and a zonal mode with growing coupling, as oscillation amplitudes grow, until falling on the floor. For small drops, chaotic oscillations constituted by several broadened sectorial modes and corresponding zonal modes are self-excited. The growing oscillation amplitude leads to droplet shedding from the edges of highly stretched lobes, where surface tension no longer holds the rapid expanding flow. PMID:26986279

  13. Acoustically levitated dancing drops: Self-excited oscillation to chaotic shedding.

    PubMed

    Lin, Po-Cheng; I, Lin

    2016-02-01

    We experimentally demonstrate self-excited oscillation and shedding of millimeter-sized water drops, acoustically levitated in a single-node standing waves cavity, by decreasing the steady acoustic wave intensity below a threshold. The perturbation of the acoustic field by drop motion is a possible source for providing an effective negative damping for sustaining the growing amplitude of the self-excited motion. Its further interplay with surface tension, drop inertia, gravity and acoustic intensities, select various self-excited modes for different size of drops and acoustic intensity. The large drop exhibits quasiperiodic motion from a vertical mode and a zonal mode with growing coupling, as oscillation amplitudes grow, until falling on the floor. For small drops, chaotic oscillations constituted by several broadened sectorial modes and corresponding zonal modes are self-excited. The growing oscillation amplitude leads to droplet shedding from the edges of highly stretched lobes, where surface tension no longer holds the rapid expanding flow.

  14. Constraining shallow slip and tsunami excitation in megathrust ruptures using seismic and ocean acoustic waves recorded on ocean-bottom sensor networks

    NASA Astrophysics Data System (ADS)

    Kozdon, Jeremy E.; Dunham, Eric M.

    2014-06-01

    Great earthquakes along subduction-zone plate boundaries, like the 2011 magnitude 9.0 Tohoku-Oki, Japan, event, deform the seafloor to generate massive tsunamis. Tsunami wave heights near shore are greatest when excitation occurs far offshore near the trench, where water depths are greatest and fault slip is shallow. The Tohoku event, featuring over 30 m of slip near the trench, exemplifies this hazard. Unfortunately the rupture process that far offshore is poorly constrained with land-based geodetic and even most seafloor deformation measurements, and seismic inferences of shallow slip are often nonunique. Here we demonstrate, through dynamic rupture simulations of the Tohoku event, that long-period guided waves in the ocean (specifically, leaking oceanic P-wave modes known as PL waves) can resolve the shallow rupture process and tsunami excitation near the trench. With predicted pressure changes of ∼0.1-1 MPa along most of the seafloor landward of the trench, and periods of several seconds, these PL waves should be observable with ocean-bottom pressure sensors and/or seismometers. With cabled sensor networks like those being deployed offshore Japan and in other subduction zones, these waves could be used to rapidly quantify shallow slip and near-trench seafloor uplift and improve local tsunami early warning systems.

  15. An experimental investigation of an acoustically excited laminar premixed flame

    SciTech Connect

    Kartheekeyan, S.; Chakravarthy, S.R.

    2006-08-15

    A two-dimensional laminar premixed flame is stabilized over a burner in a confined duct and is subjected to external acoustic forcing from the downstream end. The equivalence ratio of the flame is 0.7. The flame is stabilized in the central slot of a three-slotted burner. The strength of the shear layer of the cold reactive mixture through the central slot is controlled by the flow rate of cold nitrogen gas through the side slots. The frequency range of acoustic excitation is 400-1200 Hz, and the amplitude levels are such that the acoustic velocity is less than the mean flow velocity of the reactants. Time-averaged chemiluminescence images of the perturbed flame front display time-mean changes as compared to the unperturbed flame shape at certain excitation frequencies. Prominent changes to the flame front are in the form of stretching or shrinkage, asymmetric development of its shape, increased/preferential lift-off of one or both of the stabilization points of the flame, and nearly random three-dimensional fluctuations over large time scales under some conditions. The oscillations of the shear layer and the response of the confined jet of the hot products to the acoustic forcing, such as asymmetric flow development and jet spreading, are found to be responsible for the observed mean changes in the flame shape. A distinct low-frequency component ({approx}60-90 Hz) relative to the excitation frequency is observed in the fluctuations of the chemiluminescent intensity in the flame under most conditions. It is observed that fluctuations in the flame area predominantly contribute to the origin of the low-frequency component. This is primarily due to the rollup of vortices and the generation of enthalpy waves at the burner lip. Both of these processes are excited at the externally imposed acoustic time scale, but convect/propagate downstream at the flow time scale, which is much larger. (author)

  16. Millimeter Waves: Acoustic and Electromagnetic

    PubMed Central

    Ziskin, Marvin C.

    2012-01-01

    This article is the presentation I gave at the D'Arsonval Award Ceremony on June 14, 2011 at the Bioelectromagnetics Society Annual Meeting in Halifax, Nova Scotia. It summarizes my research activities in acoustic and electromagnetic millimeter waves over the past 47 years. My earliest research involved acoustic millimeter waves, with a special interest in diagnostic ultrasound imaging and its safety. For the last 21 years my research expanded to include electromagnetic millimeter waves, with a special interest in the mechanisms underlying millimeter wave therapy. Millimeter wave therapy has been widely used in the former Soviet Union with great reported success for many diseases, but is virtually unknown to Western physicians. I and the very capable members of my laboratory were able to demonstrate that the local exposure of skin to low intensity millimeter waves caused the release of endogenous opioids, and the transport of these agents by blood flow to all parts of the body resulted in pain relief and other beneficial effects. PMID:22926874

  17. Millimeter waves: acoustic and electromagnetic.

    PubMed

    Ziskin, Marvin C

    2013-01-01

    This article is the presentation I gave at the D'Arsonval Award Ceremony on June 14, 2011 at the Bioelectromagnetics Society Annual Meeting in Halifax, Nova Scotia. It summarizes my research activities in acoustic and electromagnetic millimeter waves over the past 47 years. My earliest research involved acoustic millimeter waves, with a special interest in diagnostic ultrasound imaging and its safety. For the last 21 years my research expanded to include electromagnetic millimeter waves, with a special interest in the mechanisms underlying millimeter wave therapy. Millimeter wave therapy has been widely used in the former Soviet Union with great reported success for many diseases, but is virtually unknown to Western physicians. I and the very capable members of my laboratory were able to demonstrate that the local exposure of skin to low intensity millimeter waves caused the release of endogenous opioids, and the transport of these agents by blood flow to all parts of the body resulted in pain relief and other beneficial effects.

  18. Surface acoustic wave oxygen sensor

    NASA Technical Reports Server (NTRS)

    Collman, James P.; Oglesby, Donald M.; Upchurch, Billy T.; Leighty, Bradley D.; Zhang, Xumu; Herrmann, Paul C.

    1994-01-01

    A surface acoustic wave (SAW) device that responds to oxygen pressure was developed by coating a 158 MHz quartz surface acoustic wave (SAW) device with an oxygen binding agent. Two types of coatings were used. One type was prepared by dissolving an oxygen binding agent in a toluene solution of a copolymer containing the axial ligand. A second type was prepared with an oxygen binding porphyrin solution containing excess axial ligand without a polymer matrix. In the polymer based coatings, the copolymer served to provide the axial ligand to the oxygen binding agent and as a coating matrix on the surface of the SAW device. The oxygen sensing SAW device has been shown to bind oxygen following a Langmuir isotherm and may be used to measure the equilibrium constant of the oxygen binding compound in the coating matrix.

  19. Nonlinear positron acoustic solitary waves

    SciTech Connect

    Tribeche, Mouloud; Aoutou, Kamel; Younsi, Smain; Amour, Rabia

    2009-07-15

    The problem of nonlinear positron acoustic solitary waves involving the dynamics of mobile cold positrons is addressed. A theoretical work is presented to show their existence and possible realization in a simple four-component plasma model. The results should be useful for the understanding of the localized structures that may occur in space and laboratory plasmas as new sources of cold positrons are now well developed.

  20. Convective Excitation of Internal Waves

    NASA Astrophysics Data System (ADS)

    Lecoanet, Daniel; Le Bars, Michael; Burns, Keaton; Vasil, Geoffrey; Quataert, Eliot; Brown, Benjamin; Oishi, Jeffrey

    2015-11-01

    We will present a joint experimental & computational study of internal wave generation by convection. First we describe an experiment using the peculiar property of water that its density maximum is at 4° C . A tank of water cooled from below and heated from above develops a cold, convective layer near 4° C at the bottom of the tank, adjacent to a hot stably stratified layer at the top of the tank. We simulate this setup in 2D using the open-source Dedalus code (dedalus-project.org). Our simulations show that waves are excited from within the convection zone, opposed to at the interface between the convective and stably stratified regions. Finally, we will present 3D simulations of internal wave excitation by convection in a fully compressible atmosphere with multiple density scaleheights. These simulations provide greater freedom in choosing the thermal equilibrium of the system, and are run at higher Rayleigh number. The simulated waves are then compared to analytic predictions of the bulk excitation model.

  1. Acoustics of Excited Jets: A Historical Perspective

    NASA Technical Reports Server (NTRS)

    Brown, Cliffard A.

    2005-01-01

    The idea that a jet may be excited by external forcing is not new. The first published demonstration of a jet responding to external pressure waves occurred in the mid-1800's. It was not, however, until the 1950's, with the advent of commercial jet aircraft, that interest in the subject greatly increased. Researchers first used excited jets to study the structure of the jet and attempt to determine the nature of the noise sources. The jet actuators of the time limited the range (Reynolds and Mach numbers) of jets that could be excited. As the actuators improved, more realistic jets could be studied. This has led to a better understanding of how jet excitation may be used not only as a research tool to understand the flow properties and noise generation process, but also as a method to control jet noise.

  2. Pseudo-continuous-wave acoustic instrument

    NASA Technical Reports Server (NTRS)

    Heyman, J. S.; Stone, F. D.

    1978-01-01

    Simple, inexpensive, and portable ultrasonic device accurately measures acoustic properties of liquids, gases, and solids, using pseudo-continuous wave responses from samples to measure change in resonant frequency or amplitude in acoustic signal.

  3. Acoustic Waves in Medical Imaging and Diagnostics

    PubMed Central

    Sarvazyan, Armen P.; Urban, Matthew W.; Greenleaf, James F.

    2013-01-01

    Up until about two decades ago acoustic imaging and ultrasound imaging were synonymous. The term “ultrasonography,” or its abbreviated version “sonography” meant an imaging modality based on the use of ultrasonic compressional bulk waves. Since the 1990s numerous acoustic imaging modalities started to emerge based on the use of a different mode of acoustic wave: shear waves. It was demonstrated that imaging with these waves can provide very useful and very different information about the biological tissue being examined. We will discuss physical basis for the differences between these two basic modes of acoustic waves used in medical imaging and analyze the advantages associated with shear acoustic imaging. A comprehensive analysis of the range of acoustic wavelengths, velocities, and frequencies that have been used in different imaging applications will be presented. We will discuss the potential for future shear wave imaging applications. PMID:23643056

  4. Acoustic waves in medical imaging and diagnostics.

    PubMed

    Sarvazyan, Armen P; Urban, Matthew W; Greenleaf, James F

    2013-07-01

    Up until about two decades ago acoustic imaging and ultrasound imaging were synonymous. The term ultrasonography, or its abbreviated version sonography, meant an imaging modality based on the use of ultrasonic compressional bulk waves. Beginning in the 1990s, there started to emerge numerous acoustic imaging modalities based on the use of a different mode of acoustic wave: shear waves. Imaging with these waves was shown to provide very useful and very different information about the biological tissue being examined. We discuss the physical basis for the differences between these two basic modes of acoustic waves used in medical imaging and analyze the advantages associated with shear acoustic imaging. A comprehensive analysis of the range of acoustic wavelengths, velocities and frequencies that have been used in different imaging applications is presented. We discuss the potential for future shear wave imaging applications.

  5. Nonlinear Wave-particle Interaction and Particle Trapping in Large Amplitude Dust Acoustic Waves

    SciTech Connect

    Chang, Mei-Chu; Teng, Lee-Wen; Lin, I.

    2011-11-29

    Large amplitude dust acoustic wave can be self-excited by the strong downward ion flow in a dusty plasma liquid formed by negatively charged dusts suspended in a weakly ionized low pressure discharge. In this work, we investigate experimentally the wave-particle phase space dynamics of the large amplitude dust acoustic wave by connecting the Lagrangian and Eulerian views, through directly tracking particle motion and measuring local dust density fluctuations. The microscopic pictures of wave steepening and breaking, resonant particle-wave crest trapping, and the absence of trough trapping observed in our experiment are constructed.

  6. A passively tunable acoustic metamaterial lens for selective ultrasonic excitation

    SciTech Connect

    Zhu, H.; Semperlotti, F.

    2014-09-07

    In this paper, we present an approach to ultrasonic beam-forming and beam-steering in structures based on the concept of embedded acoustic metamaterial lenses. The lens design exploits the principle of acoustic drop-channel that enables the dynamic coupling of multiple ultrasonic waveguides at selected frequencies. In contrast with currently available technology, the embedded lens allows exploiting the host structure as a key component of the transducer system therefore enabling directional excitation by means of a single ultrasonic transducer. The design and the performance of the lens are numerically investigated by using Plane Wave Expansion and Finite Difference Time Domain techniques applied to bulk structures. Then, the design is experimentally validated on a thin aluminum plate waveguide where the lens is implemented by through-holes. The dynamic response of the embedded lens is estimated by reconstructing, via Laser Vibrometry, the velocity field induced by a single source located at the center of the lens.

  7. Wave-Particle Interactions in Electron Acoustic Waves in Pure Ion Plasmas

    SciTech Connect

    Anderegg, F.; Driscoll, C. F.; Dubin, D. H. E.; O'Neil, T. M.

    2009-03-06

    Electron acoustic waves (EAW) with a phase velocity less than twice the plasma thermal velocity are observed on pure ion plasma columns. At low excitation amplitudes, the EAW frequencies agree with theory, but at moderate excitation the EAW is more frequency variable than typical Langmuir waves, and at large excitations resonance is observed over a broad range. Laser induced fluorescence measurements of the wave-coherent ion velocity distribution show phase reversals and wave-particle trapping plateaus at {+-}v{sub ph}, as expected, and corroborate the unusual role of kinetic pressure in the EAW.

  8. Manipulate acoustic waves by impedance matched acoustic metasurfaces

    NASA Astrophysics Data System (ADS)

    Wu, Ying; Mei, Jun; Aljahdali, Rasha

    We design a type of acoustic metasurface, which is composed of carefully designed slits in a rigid thin plate. The effective refractive indices of different slits are different but the impedances are kept the same as that of the host medium. Numerical simulations show that such a metasurface can redirect or reflect a normally incident wave at different frequencies, even though it is impedance matched to the host medium. We show that the underlying mechanisms can be understood by using the generalized Snell's law, and a unified analytic model based on mode-coupling theory. We demonstrate some simple realization of such acoustic metasurface with real materials. The principle is also extended to the design of planar acoustic lens which can focus acoustic waves. Manipulate acoustic waves by impedance matched acoustic metasurfaces.

  9. Tropospheric Response to Modulational Excitation of Dust Acoustic Perturbartions in Earth's Ionosphere

    NASA Astrophysics Data System (ADS)

    Kopnin, S. I.; Popel, S. I.; Yu, M. Y.

    2011-11-01

    It is shown that, during Perseid, Geminid, Orionid, and Leonid meteor showers, the excitation of low-frequency dust acoustic perturbations by modulational instability in the Earth's ionosphere can lead to the generation of infrasonic waves. The processes accompanying the propagation of these waves in Earth's troposphere are considered, and the possibility of observing the waves from the Earth's surface is discussed, as well as the possible onset of acoustic gravitational vortex structures in the region of dust acoustic perturbations. The generation of such structures during Perseid, Geminid, Orionid, and Leonid meteor showers can show up as an increase in the intensity of green nightglow by an amount on the order of 10% and can be attributed to the formation of nonlinear (vortex) structures at altitudes of 110-120 km. Thus the modulational excitation of the dust acoustic perturbations in the ionosphere has tropospherical response: it influences physical processes and observations in Earth's troposphere.

  10. Thermo-acoustic engineering of silicon microresonators via evanescent waves

    SciTech Connect

    Tabrizian, R.; Ayazi, F.

    2015-06-29

    A temperature-compensated silicon micromechanical resonator with a quadratic temperature characteristic is realized by acoustic engineering. Energy-trapped resonance modes are synthesized by acoustic coupling of propagating and evanescent extensional waves in waveguides with rectangular cross section. Highly different temperature sensitivity of propagating and evanescent waves is used to engineer the linear temperature coefficient of frequency. The resulted quadratic temperature characteristic has a well-defined turn-over temperature that can be tailored by relative energy distribution between propagating and evanescent acoustic fields. A 76 MHz prototype is implemented in single crystal silicon. Two high quality factor and closely spaced resonance modes, created from efficient energy trapping of extensional waves, are excited through thin aluminum nitride film. Having different evanescent wave constituents and energy distribution across the device, these modes show different turn over points of 67 °C and 87 °C for their quadratic temperature characteristic.

  11. Thermo-acoustic engineering of silicon microresonators via evanescent waves

    NASA Astrophysics Data System (ADS)

    Tabrizian, R.; Ayazi, F.

    2015-06-01

    A temperature-compensated silicon micromechanical resonator with a quadratic temperature characteristic is realized by acoustic engineering. Energy-trapped resonance modes are synthesized by acoustic coupling of propagating and evanescent extensional waves in waveguides with rectangular cross section. Highly different temperature sensitivity of propagating and evanescent waves is used to engineer the linear temperature coefficient of frequency. The resulted quadratic temperature characteristic has a well-defined turn-over temperature that can be tailored by relative energy distribution between propagating and evanescent acoustic fields. A 76 MHz prototype is implemented in single crystal silicon. Two high quality factor and closely spaced resonance modes, created from efficient energy trapping of extensional waves, are excited through thin aluminum nitride film. Having different evanescent wave constituents and energy distribution across the device, these modes show different turn over points of 67 °C and 87 °C for their quadratic temperature characteristic.

  12. Picosecond Surface Acoustic Waves Using A Suboptical Wavelength Absorption Grating

    SciTech Connect

    Hurley, David Howard; Telschow, Kenneth Louis

    2002-10-01

    We have demonstrated laser generation and detection of Rayleigh surface acoustic waves (SAW’s) with acoustic wavelengths that are smaller than the optical wavelength of both the excitation and the detection beams. SAW generation was achieved using electron beam lithography to modulate the surface reflectivity and hence the lateral thermal gradients on a suboptical wavelength scale. The generation and detection characteristics of two material systems were investigated (aluminum absorption gratings on Si and GaAs substrates). The polarization sensitive absorption characteristics of the suboptical wavelength lithographic grating were exploited in order to explore various acoustic generation and detection schemes.

  13. Subwavelength acoustic focusing by surface-wave-resonance enhanced transmission in doubly negative acoustic metamaterials

    SciTech Connect

    Zhou, Xiaoming; Badreddine Assouar, M. Oudich, Mourad

    2014-11-21

    We present analytical and numerical analyses of a yet unseen lensing paradigm that is based on a solid metamaterial slab in which the wave excitation source is attached. We propose and demonstrate sub-diffraction-limited acoustic focusing induced by surface resonant states in doubly negative metamaterials. The enhancement of evanescent waves across the metamaterial slab produced by their resonant coupling to surface waves is evidenced and quantitatively determined. The effect of metamaterial parameters on surface states, transmission, and wavenumber bandwidth is clearly identified. Based on this concept consisting of a wave source attached on the metamaterial, a high resolution of λ/28.4 is obtained with the optimum effective physical parameters, opening then an exciting way to design acoustic metamaterials for ultrasonic focused imaging.

  14. Probing Acoustic Nonlinearity by Mixing Surface Acoustic Waves

    SciTech Connect

    Hurley, David Howard; Telschow, Kenneth Louis

    2000-07-01

    Measurement methods aimed at determining material properties through nonlinear wave propagation are sensitive to artifacts caused by background nonlinearities inherent in the ultrasonic generation and detection methods. The focus of this paper is to describe our investigation of nonlinear mixing of surface acoustic waves (SAWs) as a means to decrease sensitivity to background nonlinearity and increase spatial sensitivity to acoustic nonlinearity induced by material microstructure.

  15. Surface acoustic wave stabilized oscillators

    NASA Technical Reports Server (NTRS)

    Parker, T. E.; Lee, D. L.; Leja, I.

    1979-01-01

    Four areas of surface acoustic wave (SAW) controlled oscillators were investigated and a number of 401.2 MHz oscillators were constructed that showed improved performance. Aging studies on SAW devices packaged in HC36/U cold weld enclosures produced frequency drifts as low as 0.4 ppm in 35 weeks and drift rates well under 0.5 ppm/year. Temperature compensation circuits have substantially improved oscillator temperature stability, with a deviation of + or - 4 ppm observed over the range -45 C to + 40 C. High efficiency amplifiers were constructed for SAW oscillators and a dc to RF efficiency of 44 percent was obtained for an RF output of 25 mW. Shock and vibration tests were made on four oscillators and all survived 500 G shock pulses unchanged. Only when white noise vibration (20 Hz to 2000 Hz) levels of 20 G's rms were applied did some of the devices fail.

  16. Swimming using surface acoustic waves.

    PubMed

    Bourquin, Yannyk; Cooper, Jonathan M

    2013-01-01

    Microactuation of free standing objects in fluids is currently dominated by the rotary propeller, giving rise to a range of potential applications in the military, aeronautic and biomedical fields. Previously, surface acoustic waves (SAWs) have been shown to be of increasing interest in the field of microfluidics, where the refraction of a SAW into a drop of fluid creates a convective flow, a phenomenon generally known as SAW streaming. We now show how SAWs, generated at microelectronic devices, can be used as an efficient method of propulsion actuated by localised fluid streaming. The direction of the force arising from such streaming is optimal when the devices are maintained at the Rayleigh angle. The technique provides propulsion without any moving parts, and, due to the inherent design of the SAW transducer, enables simple control of the direction of travel. PMID:23431358

  17. Swimming using surface acoustic waves.

    PubMed

    Bourquin, Yannyk; Cooper, Jonathan M

    2013-01-01

    Microactuation of free standing objects in fluids is currently dominated by the rotary propeller, giving rise to a range of potential applications in the military, aeronautic and biomedical fields. Previously, surface acoustic waves (SAWs) have been shown to be of increasing interest in the field of microfluidics, where the refraction of a SAW into a drop of fluid creates a convective flow, a phenomenon generally known as SAW streaming. We now show how SAWs, generated at microelectronic devices, can be used as an efficient method of propulsion actuated by localised fluid streaming. The direction of the force arising from such streaming is optimal when the devices are maintained at the Rayleigh angle. The technique provides propulsion without any moving parts, and, due to the inherent design of the SAW transducer, enables simple control of the direction of travel.

  18. Swimming Using Surface Acoustic Waves

    PubMed Central

    Bourquin, Yannyk; Cooper, Jonathan M.

    2013-01-01

    Microactuation of free standing objects in fluids is currently dominated by the rotary propeller, giving rise to a range of potential applications in the military, aeronautic and biomedical fields. Previously, surface acoustic waves (SAWs) have been shown to be of increasing interest in the field of microfluidics, where the refraction of a SAW into a drop of fluid creates a convective flow, a phenomenon generally known as SAW streaming. We now show how SAWs, generated at microelectronic devices, can be used as an efficient method of propulsion actuated by localised fluid streaming. The direction of the force arising from such streaming is optimal when the devices are maintained at the Rayleigh angle. The technique provides propulsion without any moving parts, and, due to the inherent design of the SAW transducer, enables simple control of the direction of travel. PMID:23431358

  19. Surface acoustic wave stabilized oscillators

    NASA Technical Reports Server (NTRS)

    Parker, T. E.

    1978-01-01

    A number of 401.2 MHz surface acoustic wave (SAW) controlled oscillators were built and tested. The performance of these oscillators was evaluated for possible use as stable oscillators in communication systems. A short term frequency stability of better than 1 x 10 to the minus 9th power for one second was measured for the SAW oscillators. Long term frequency drift was measured and was found to be dependent on SAW design and packaging. Drift rates ranging from 15 ppm in twenty weeks to 2.5 ppm in twenty weeks were observed. Some further improvement was required. The temperature dependence of the saw oscillators was evaluated and it was concluded that some form of temperature compensation will be necessary to meet the requirements of some communication systems.

  20. INTERFERENCE FRINGES OF SOLAR ACOUSTIC WAVES AROUND SUNSPOTS

    SciTech Connect

    Chou, Dean-Yi; Zhao Hui; Yang, Ming-Hsu; Liang, Zhi-Chao

    2012-10-20

    Solar acoustic waves are scattered by a sunspot due to the interaction between the acoustic waves and the sunspot. The sunspot, excited by the incident wave, generates the scattered wave. The scattered wave is added to the incident wave to form the total wave around the sunspot. The interference fringes between the scattered wave and the incident wave are visible in the intensity of the total wave because the coherent time of the incident wave is of the order of a wave period. The strength of the interference fringes anti-correlates with the width of temporal spectra of the incident wave. The separation between neighboring fringes increases with the incident wavelength and the sunspot size. The strength of the fringes increases with the radial order n of the incident wave from n = 0 to n = 2, and then decreases from n = 2 to n = 5. The interference fringes play a role analogous to holograms in optics. This study suggests the feasibility of using the interference fringes to reconstruct the scattered wavefields of the sunspot, although the quality of the reconstructed wavefields is sensitive to the noise and errors in the interference fringes.

  1. Temperature-controlled acoustic surface waves

    NASA Astrophysics Data System (ADS)

    Cselyuszka, Norbert; Sečujski, Milan; Engheta, Nader; Crnojević-Bengin, Vesna

    2016-10-01

    Conventional approaches to the control of acoustic waves propagating along boundaries between fluids and hard grooved surfaces are limited to the manipulation of surface geometry. Here we demonstrate for the first time, through theoretical analysis, numerical simulation as well as experimentally, that the velocity of acoustic surface waves, and consequently the direction of their propagation as well as the shape of their wave fronts, can be controlled by varying the temperature distribution over the surface. This significantly increases the versatility of applications such as sound trapping, acoustic spectral analysis and acoustic focusing, by providing a simple mechanism for modifying their behavior without any change in the geometry of the system. We further discuss that the dependence between the behavior of acoustic surface waves and the temperature of the fluid can be exploited conversely as well, which opens a way for potential application in the domain of temperature sensing.

  2. High-frequency shear-horizontal surface acoustic wave sensor

    SciTech Connect

    Branch, Darren W

    2013-05-07

    A Love wave sensor uses a single-phase unidirectional interdigital transducer (IDT) on a piezoelectric substrate for leaky surface acoustic wave generation. The IDT design minimizes propagation losses, bulk wave interferences, provides a highly linear phase response, and eliminates the need for impedance matching. As an example, a high frequency (.about.300-400 MHz) surface acoustic wave (SAW) transducer enables efficient excitation of shear-horizontal waves on 36.degree. Y-cut lithium tantalate (LTO) giving a highly linear phase response (2.8.degree. P-P). The sensor has the ability to detect at the pg/mm.sup.2 level and can perform multi-analyte detection in real-time. The sensor can be used for rapid autonomous detection of pathogenic microorganisms and bioagents by field deployable platforms.

  3. High-frequency shear-horizontal surface acoustic wave sensor

    SciTech Connect

    Branch, Darren W

    2014-03-11

    A Love wave sensor uses a single-phase unidirectional interdigital transducer (IDT) on a piezoelectric substrate for leaky surface acoustic wave generation. The IDT design minimizes propagation losses, bulk wave interferences, provides a highly linear phase response, and eliminates the need for impedance matching. As an example, a high frequency (.about.300-400 MHz) surface acoustic wave (SAW) transducer enables efficient excitation of shear-horizontal waves on 36.degree. Y-cut lithium tantalate (LTO) giving a highly linear phase response (2.8.degree. P-P). The sensor has the ability to detect at the pg/mm.sup.2 level and can perform multi-analyte detection in real-time. The sensor can be used for rapid autonomous detection of pathogenic microorganisms and bioagents by field deployable platforms.

  4. Surface acoustic wave dust deposition monitor

    DOEpatents

    Fasching, G.E.; Smith, N.S. Jr.

    1988-02-12

    A system is disclosed for using the attenuation of surface acoustic waves to monitor real time dust deposition rates on surfaces. The system includes a signal generator, a tone-burst generator/amplifier connected to a transmitting transducer for converting electrical signals into acoustic waves. These waves are transmitted through a path defining means adjacent to a layer of dust and then, in turn, transmitted to a receiving transducer for changing the attenuated acoustic wave to electrical signals. The signals representing the attenuated acoustic waves may be amplified and used in a means for analyzing the output signals to produce an output indicative of the dust deposition rates and/or values of dust in the layer. 8 figs.

  5. Chromospheric heating by acoustic shock waves

    NASA Technical Reports Server (NTRS)

    Jordan, Stuart D.

    1993-01-01

    Work by Anderson & Athay (1989) suggests that the mechanical energy required to heat the quiet solar chromosphere might be due to the dissipation of weak acoustic shocks. The calculations reported here demonstrate that a simple picture of chromospheric shock heating by acoustic waves propagating upward through a model solar atmosphere, free of both magnetic fields and local inhomogeneities, cannot reproduce their chromospheric model. The primary reason is the tendency for vertically propagating acoustic waves in the range of allowed periods to dissipate too low in the atmosphere, providing insufficient residual energy for the middle chromosphere. The effect of diverging magnetic fields and the corresponding expanding acoustic wavefronts on the mechanical dissipation length is then discussed as a means of preserving a quasi-acoustic heating hypothesis. It is argued that this effect, in a canopy that overlies the low chromosphere, might preserve the acoustic shock hypothesis consistent with the chromospheric radiation losses computed by Anderson & Athay.

  6. Microfabricated bulk wave acoustic bandgap device

    DOEpatents

    Olsson, Roy H.; El-Kady, Ihab F.; McCormick, Frederick; Fleming, James G.; Fleming, legal representative, Carol

    2010-11-23

    A microfabricated bulk wave acoustic bandgap device comprises a periodic two-dimensional array of scatterers embedded within the matrix material membrane, wherein the scatterer material has a density and/or elastic constant that is different than the matrix material and wherein the periodicity of the array causes destructive interference of the acoustic wave within an acoustic bandgap. The membrane can be suspended above a substrate by an air or vacuum gap to provide acoustic isolation from the substrate. The device can be fabricated using microelectromechanical systems (MEMS) technologies. Such microfabricated bulk wave phononic bandgap devices are useful for acoustic isolation in the ultrasonic, VHF, or UHF regime (i.e., frequencies of order 1 MHz to 10 GHz and higher, and lattice constants of order 100 .mu.m or less).

  7. Microfabricated bulk wave acoustic bandgap device

    DOEpatents

    Olsson, Roy H.; El-Kady, Ihab F.; McCormick, Frederick; Fleming, James G.; Fleming, Carol

    2010-06-08

    A microfabricated bulk wave acoustic bandgap device comprises a periodic two-dimensional array of scatterers embedded within the matrix material membrane, wherein the scatterer material has a density and/or elastic constant that is different than the matrix material and wherein the periodicity of the array causes destructive interference of the acoustic wave within an acoustic bandgap. The membrane can be suspended above a substrate by an air or vacuum gap to provide acoustic isolation from the substrate. The device can be fabricated using microelectromechanical systems (MEMS) technologies. Such microfabricated bulk wave phononic bandgap devices are useful for acoustic isolation in the ultrasonic, VHF, or UHF regime (i.e., frequencies of order 1 MHz to 10 GHz and higher, and lattice constants of order 100 .mu.m or less).

  8. A New Wave of Acoustics.

    ERIC Educational Resources Information Center

    Beyer, Robert

    1981-01-01

    Surveys 50 years of acoustical studies by discussing selected topics including the ear, nonlinear representations, underwater sound, acoustical diagnostics, absorption, electrolytes, phonons, magnetic interaction, and superfluidity and the five sounds. (JN)

  9. Dynamics of coupled light waves and electron-acoustic waves.

    PubMed

    Shukla, P K; Stenflo, L; Hellberg, M

    2002-08-01

    The nonlinear interaction between coherent light waves and electron-acoustic waves in a two-electron plasma is considered. The interaction is governed by a pair of equations comprising a Schrödinger-like equation for the light wave envelope and a driven (by the light pressure) electron-acoustic wave equation. The newly derived nonlinear equations are used to study the formation and dynamics of envelope light wave solitons and light wave collapse. The implications of our investigation to space and laser-produced plasmas are pointed out.

  10. Making structured metals transparent for ultrabroadband electromagnetic waves and acoustic waves

    SciTech Connect

    Fan, Ren-Hao; Peng, Ru-Wen; Huang, Xian-Rong; Wang, Mu

    2015-07-15

    In this review, we present our recent work on making structured metals transparent for broadband electromagnetic waves and acoustic waves via excitation of surface waves. First, we theoretically show that one-dimensional metallic gratings can become transparent and completely antireflective for extremely broadband electromagnetic waves by relying on surface plasmons or spoof surface plasmons. Second, we experimentally demonstrate that metallic gratings with narrow slits are highly transparent for broadband terahertz waves at oblique incidence and high transmission efficiency is insensitive to the metal thickness. Further, we significantly develop oblique metal gratings transparent for broadband electromagnetic waves (including optical waves and terahertz ones) under normal incidence. In the third, we find the principles of broadband transparency for structured metals can be extended from one-dimensional metallic gratings to two-dimensional cases. Moreover, similar phenomena are found in sonic artificially metallic structures, which present the transparency for broadband acoustic waves. These investigations provide guidelines to develop many novel materials and devices, such as transparent conducting panels, antireflective solar cells, and other broadband metamaterials and stealth technologies. - Highlights: • Making structured metals transparent for ultrabroadband electromagnetic waves. • Non-resonant excitation of surface plasmons or spoof surface plasmons. • Sonic artificially metallic structures transparent for broadband acoustic waves.

  11. Internal waves excited by the marangoni effect

    PubMed

    Wierschem; Linde; Velarde

    2000-11-01

    Traveling periodic internal wave trains are generated in liquid layers during the absorption process of a miscible surface-active substance out of the vapor phase. In our nonstationary experimental runs, internal waves are excited by surface waves, which had been previously generated by a surface-tension-gradient-driven instability. The internal wave trains adjust their wave number by an Eckhaus instability. Close to the instability threshold narrow and extended pulses are observed. Furthermore, the wave trains can alter their traveling direction, i.e., one wave train traveling in one direction yields to another train, in general of different wave number, traveling in the opposite direction. PMID:11101989

  12. Interaction of acoustic waves generated by coupled plate

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.

    1990-01-01

    When two substructures are coupled, the acoustic field generated by the motion of each of the substructures will interact with the motion of the other substructure. This would be the case of a structure enclosing an acoustic cavity. A technique to model the interaction of the generated sound fields from the two components of a coupled structure, and the influence of this interaction on the vibration of the structural components is presented. Using a mobility power flow approach, each element of the substructure is treated independently both when developing the structural response and when determining the acoustic field generated by this component. The presence of the other substructural components is introduced by assuming these components to be rigid baffles. The excitation of one of the substructures is assumed to be by an incident acoustic wave which is dependent of the motion of the substructure. The sound field generated by the motion of the substructure is included in the solution of the response.

  13. Writing magnetic patterns with surface acoustic waves

    SciTech Connect

    Li, Weiyang; Buford, Benjamin; Jander, Albrecht; Dhagat, Pallavi

    2014-05-07

    A novel patterning technique that creates magnetization patterns in a continuous magnetostrictive film with surface acoustic waves is demonstrated. Patterns of 10 μm wide stripes of alternating magnetization and a 3 μm dot of reversed magnetization are written using standing and focusing acoustic waves, respectively. The magnetization pattern is size-tunable, erasable, and rewritable by changing the magnetic field and acoustic power. This versatility, along with its solid-state implementation (no moving parts) and electronic control, renders it as a promising technique for application in magnetic recording, magnonic signal processing, magnetic particle manipulation, and spatial magneto-optical modulation.

  14. Tunable damper for an acoustic wave guide

    DOEpatents

    Rogers, S.C.

    1982-10-21

    A damper for tunably damping acoustic waves in an ultrasonic waveguide is provided which may be used in a hostile environment such as a nuclear reactor. The area of the waveguide, which may be a selected size metal rod in which acoustic waves are to be damped, is wrapped, or surrounded, by a mass of stainless steel wool. The wool wrapped portion is then sandwiched between tuning plates, which may also be stainless steel, by means of clamping screws which may be adjusted to change the clamping force of the sandwiched assembly along the waveguide section. The plates are preformed along their length in a sinusoidally bent pattern with a period approximately equal to the acoustic wavelength which is to be damped. The bent pattern of the opposing plates are in phase along their length relative to their sinusoidal patterns so that as the clamping screws are tightened a bending stress is applied to the waveguide at 180/sup 0/ intervals along the damping section to oppose the acoustic wave motions in the waveguide and provide good coupling of the wool to the guide. The damper is tuned by selectively tightening the clamping screws while monitoring the amplitude of the acoustic waves launched in the waveguide. It may be selectively tuned to damp particular acoustic wave modes (torsional or extensional, for example) and/or frequencies while allowing others to pass unattenuated.

  15. Tunable damper for an acoustic wave guide

    DOEpatents

    Rogers, Samuel C.

    1984-01-01

    A damper for tunably damping acoustic waves in an ultrasonic waveguide is provided which may be used in a hostile environment such as a nuclear reactor. The area of the waveguide, which may be a selected size metal rod in which acoustic waves are to be damped, is wrapped, or surrounded, by a mass of stainless steel wool. The wool wrapped portion is then sandwiched between tuning plates, which may also be stainless steel, by means of clamping screws which may be adjusted to change the clamping force of the sandwiched assembly along the waveguide section. The plates are preformed along their length in a sinusoidally bent pattern with a period approximately equal to the acoustic wavelength which is to be damped. The bent pattern of the opposing plates are in phase along their length relative to their sinusoidal patterns so that as the clamping screws are tightened a bending stress is applied to the waveguide at 180.degree. intervals along the damping section to oppose the acoustic wave motions in the waveguide and provide good coupling of the wool to the guide. The damper is tuned by selectively tightening the clamping screws while monitoring the amplitude of the acoustic waves launched in the waveguide. It may be selectively tuned to damp particular acoustic wave modes (torsional or extensional, for example) and/or frequencies while allowing others to pass unattenuated.

  16. Excitation of Love waves in a thin film layer by a line source.

    NASA Technical Reports Server (NTRS)

    Tuan, H.-S.; Ponamgi, S. R.

    1972-01-01

    The excitation of a Love surface wave guided by a thin film layer deposited on a semiinfinite substrate is studied in this paper. Both the thin film and the substrate are considered to be elastically isotropic. Amplitudes of the surface wave in the thin film region and the substrate are found in terms of the strength of a line source vibrating in a direction transverse to the propagating wave. In addition to the surface wave, the bulk shear wave excited by the source is also studied. Analytical expressions for the bulk wave amplitude as a function of the direction of propagation, the acoustic powers transported by the surface and bulk waves, and the efficiency of surface wave excitation are obtained. A numerical example is given to show how the bulk wave radiation pattern depends upon the source frequency, the film thickness and other important parameters of the problem. The efficiency of surface wave excitation is also calculated for various parameter values.

  17. Asymptotic wave propagation in excitable media.

    PubMed

    Bernus, Olivier; Vigmond, Edward

    2015-07-01

    Wave shape and velocity are important issues in reaction-diffusion systems, and are often the result of competition in media with heterogeneous conduction properties. Asymptotic wave front propagation at maximal conduction velocity has been previously reported in the context of anisotropic cardiac tissue, but it is unknown whether this is a universal property of excitable tissues where conduction velocity can be locally modulated by mechanisms other than anisotropy. Here, we investigate the impact of conduction heterogeneities and boundary effects on wave propagation in excitable media. Following a theoretical analysis, we find that wave-front cusps occur where local velocity is reduced and that asymptotic wave fronts propagate at the maximal translational conduction velocity. Simulations performed in different reaction-diffusion systems, including cardiac tissue, confirm our theoretical findings. We conclude that this property can be found in a wide range of reaction-diffusion systems with excitable dynamics and that asymptotic wave-front shapes can be predicted.

  18. Ion Acoustic Waves in Ultracold Neutral Plasmas

    SciTech Connect

    Castro, J.; McQuillen, P.; Killian, T. C.

    2010-08-06

    We photoionize laser-cooled atoms with a laser beam possessing spatially periodic intensity modulations to create ultracold neutral plasmas with controlled density perturbations. Laser-induced fluorescence imaging reveals that the density perturbations oscillate in space and time, and the dispersion relation of the oscillations matches that of ion acoustic waves, which are long-wavelength, electrostatic, density waves.

  19. Classical acoustic waves in damped media.

    PubMed

    Albuquerque, E L; Mauriz, P W

    2003-05-01

    A Green function technique is employed to investigate the propagation of classical damped acoustic waves in complex media. The calculations are based on the linear response function approach, which is very convenient to deal with this kind of problem. Both the displacement and the gradient displacement Green functions are determined. All deformations in the media are supposed to be negligible, so the motions considered here are purely acoustic waves. The damping term gamma is included in a phenomenological way into the wave vector expression. By using the fluctuation-dissipation theorem, the power spectrum of the acoustic waves is also derived and has interesting properties, the most important of them being a possible relation with the analysis of seismic reflection data.

  20. Precise rainbow trapping for low-frequency acoustic waves with micro Mie resonance-based structures

    NASA Astrophysics Data System (ADS)

    Zhou, Chen; Yuan, Baoguo; Cheng, Ying; Liu, Xiaojun

    2016-02-01

    We have realized the acoustic rainbow trapping in the low frequency region (200-500 Hz) through micro Mie resonance-based structures. The structure has eight channels with a high refractive index obtained by coiling space, that can excite strong interactions with incident waves and support various orders of multipoles due to the Mie resonances of the microstructure. By utilizing the structure, the precise spatial modulation of the acoustic wave is demonstrated both theoretically and experimentally. The effect of trapping broadband acoustic waves and spatially separating different frequency components are ascribed to the monopolar Mie resonances of the structures. The trapping frequency is derived and the trapping positions can be tuned arbitrarily. With enhanced wave-structure interactions and tailored frequency responses, such micro structures show precise spectral-spatial control of acoustic waves and open a diverse venue for high performance acoustic wave detection, sensing, filtering, and a nondestructive test.

  1. Nonlinear excited waves on the interventricular septum

    NASA Astrophysics Data System (ADS)

    Bekki, Naoaki; Harada, Yoshifumi; Kanai, Hiroshi

    2012-11-01

    Using a novel ultrasonic noninvasive imaging method, we observe some phase singularities in propagating excited waves on a human cardiac interventricular septum (IVS) for a healthy young male. We present a possible physical model explaining one-dimensional dynamics of phase singularities in nonlinearly excited waves on the IVS. We show that at least one of the observed phase singularities in the excited waves on the IVS can be explained by the Bekki-Nozaki hole solution of the complex Ginzburg-Landau equation without any adjustable parameters. We conclude that the complex Ginzburg-Landau equation is such a suitable model for one-dimensional dynamics of cardiac phase singularities in nonlinearly excited waves on the IVS.

  2. Excitation of gravity waves in common envelopes

    NASA Technical Reports Server (NTRS)

    Soker, Noam

    1992-01-01

    We study the excitation of gravity waves by a low-mass companion orbiting inside the envelope of a giant star, concentrating on brown dwarfs inside the envelope of asymptotic giant branch stars. Efficient g-wave excitations occur only after the brown dwarf has spiraled-in to the radiative zone, well inside the envelope, of the asymptotic giant branch star. The brown dwarf excites g-waves when its orbital radius is about 3-10 solar radii. At this stage of the evolution the envelope mass is below 0.1 solar mass. The g-waves propagate inward from the secondary orbit, carrying angular momentum and energy. We find that the angular momentum transport leads to an efficient spin-up of the inner envelopes. The differential rotation between the envelope and core and nonlinear wave effects, can cause a mixing of heavy elements from the core to the envelope.

  3. Exciton transport by surface acoustic waves

    NASA Astrophysics Data System (ADS)

    Rudolph, J.; Hey, R.; Santos, P. V.

    2007-05-01

    Long-range acoustic transport of excitons in GaAs quantum wells (QWs) is demonstrated. The mobile strain field of a surface acoustic wave creates a dynamic lateral type I modulation of the conduction and valence bands in a double-quantum-well (DQW) structure. This mobile potential modulation transports long-living indirect excitons in the DQW over several hundreds of μm.

  4. Synchronization of the dust acoustic wave under microgravity

    NASA Astrophysics Data System (ADS)

    Ruhunusiri, W. D. Suranga; Goree, J.

    2013-10-01

    Synchronization is a nonlinear phenomenon where a self-excited oscillation, like a wave in a plasma, interacts with an external driving, resulting in an adjustment of the oscillation frequency. To prepare for experiments under microgravity conditions using the PK-4 facility on the International Space Station, we perform a laboratory experiment to observe synchronization of the self-excited dust acoustic wave. An rf glow discharge argon plasma is formed by applying a low power radio frequency voltage to a lower electrode. A 3D dust cloud is formed by levitating 4.83 micron microspheres inside a glass box placed on the lower electrode. The dust acoustic wave is self-excited with a natural frequency of 22 Hz due to an ion streaming instability. A cross section of the dust cloud is illuminated by a vertical laser sheet and imaged from the side with a digital camera. To synchronize the wave, we sinusoidally modulate the overall ion density. Differently from previous experiments, we use a driving electrode that is separate from the electrode that sustains the plasma, and we characterize synchronization by varying both driving amplitude and frequency. Supported by NASA's Physical Science Research Program.

  5. Ultrafast microfluidics using surface acoustic waves

    PubMed Central

    Yeo, Leslie Y.; Friend, James R.

    2009-01-01

    We demonstrate that surface acoustic waves (SAWs), nanometer amplitude Rayleigh waves driven at megahertz order frequencies propagating on the surface of a piezoelectric substrate, offer a powerful method for driving a host of extremely fast microfluidic actuation and micro∕bioparticle manipulation schemes. We show that sessile drops can be translated rapidly on planar substrates or fluid can be pumped through microchannels at 1–10 cm∕s velocities, which are typically one to two orders quicker than that afforded by current microfluidic technologies. Through symmetry-breaking, azimuthal recirculation can be induced within the drop to drive strong inertial microcentrifugation for micromixing and particle concentration or separation. Similar micromixing strategies can be induced in the same microchannel in which fluid is pumped with the SAW by merely changing the SAW frequency to rapidly switch the uniform through-flow into a chaotic oscillatory flow by exploiting superpositioning of the irradiated sound waves from the sidewalls of the microchannel. If the flow is sufficiently quiescent, the nodes of the transverse standing wave that arises across the microchannel also allow for particle aggregation, and hence, sorting on nodal lines. In addition, the SAW also facilitates other microfluidic capabilities. For example, capillary waves excited at the free surface of a sessile drop by the SAW underneath it can be exploited for micro∕nanoparticle collection and sorting at nodal points or lines at low powers. At higher powers, the large accelerations off the substrate surface as the SAW propagates across drives rapid destabilization of the drop free surface giving rise to inertial liquid jets that persist over 1–2 cm in length or atomization of the entire drop to produce 1–10 μm monodispersed aerosol droplets, which can be exploited for ink-jet printing, mass spectrometry interfacing, or pulmonary drug delivery. The atomization of polymer∕protein solutions

  6. Imaging of Acoustic Waves in Sand

    SciTech Connect

    Deason, Vance Albert; Telschow, Kenneth Louis; Watson, Scott Marshall

    2003-08-01

    There is considerable interest in detecting objects such as landmines shallowly buried in loose earth or sand. Various techniques involving microwave, acoustic, thermal and magnetic sensors have been used to detect such objects. Acoustic and microwave sensors have shown promise, especially if used together. In most cases, the sensor package is scanned over an area to eventually build up an image or map of anomalies. We are proposing an alternate, acoustic method that directly provides an image of acoustic waves in sand or soil, and their interaction with buried objects. The INEEL Laser Ultrasonic Camera utilizes dynamic holography within photorefractive recording materials. This permits one to image and demodulate acoustic waves on surfaces in real time, without scanning. A video image is produced where intensity is directly and linearly proportional to surface motion. Both specular and diffusely reflecting surfaces can be accomodated and surface motion as small as 0.1 nm can be quantitatively detected. This system was used to directly image acoustic surface waves in sand as well as in solid objects. Waves as frequencies of 16 kHz were generated using modified acoustic speakers. These waves were directed through sand toward partially buried objects. The sand container was not on a vibration isolation table, but sat on the lab floor. Interaction of wavefronts with buried objects showed reflection, diffraction and interference effects that could provide clues to location and characteristics of buried objects. Although results are preliminary, success in this effort suggests that this method could be applied to detection of buried landmines or other near-surface items such as pipes and tanks.

  7. Topological charge pump by surface acoustic waves

    NASA Astrophysics Data System (ADS)

    Yi, Zheng; Shi-Ping, Feng; Shi-Jie, Yang

    2016-06-01

    Quantized electron pumping by the surface acoustic wave across barriers created by a sequence of split metal gates is interpreted from the viewpoint of topology. The surface acoustic wave serves as a one-dimensional periodical potential whose energy spectrum possesses the Bloch band structure. The time-dependent phase plays the role of an adiabatic parameter of the Hamiltonian which induces a geometrical phase. The pumping currents are related to the Chern numbers of the filled bands below the Fermi energy. Based on this understanding, we predict a novel effect of quantized but non-monotonous current plateaus simultaneously pumped by two homodromous surface acoustic waves. Project supported by the National Natural Science Foundation of China (Grant No. 11374036) and the National Basic Research Program of China (Grant No. 2012CB821403).

  8. Faraday Waves under Time-Reversed Excitation

    NASA Astrophysics Data System (ADS)

    Pietschmann, Dirk; Stannarius, Ralf; Wagner, Christian; John, Thomas

    2013-03-01

    Do parametrically driven systems distinguish periodic excitations that are time mirrors of each other? Faraday waves in a Newtonian fluid are studied under excitation with superimposed harmonic wave forms. We demonstrate that the threshold parameters for the stability of the ground state are insensitive to a time inversion of the driving function. This is a peculiarity of some dynamic systems. The Faraday system shares this property with standard electroconvection in nematic liquid crystals [J. Heuer , Phys. Rev. E 78, 036218 (2008)PLEEE81539-3755]. In general, time inversion of the excitation affects the asymptotic stability of a parametrically driven system, even when it is described by linear ordinary differential equations. Obviously, the observed symmetry has to be attributed to the particular structure of the underlying differential equation system. The pattern selection of the Faraday waves above threshold, on the other hand, discriminates between time-mirrored excitation functions.

  9. Excitation of a slow wave structure

    SciTech Connect

    Zhang Peng; Lau, Y. Y.; Hoff, Brad; French, D. M.; Luginsland, J. W.

    2012-12-15

    The Green's function on a slow wave structure is constructed. The Green's function includes all radial modes, and for each radial mode, all space harmonics. We compare the analytic solution of the frequency response on the slow wave structure with that obtained from a particle-in-cell code. Favorable comparison is obtained when the first few lower order modes are resonantly excited. This gives some confidence in the prediction of converting a pulse train into radiation using a slow wave structure.

  10. Optically tunable acoustic wave band-pass filter

    SciTech Connect

    Swinteck, N.; Lucas, P.; Deymier, P. A.

    2014-12-15

    The acoustic properties of a hybrid composite that exhibits both photonic and phononic behavior are investigated numerically with finite-element and finite-difference time-domain simulations. The structure is constituted of a periodic array of photonic resonant cavities embedded in a background superlattice. The resonant cavities contain a photo-elastic chalcogenide glass that undergoes atomic-scale structural reorganization when irradiated with light having energy close to its band-gap. Photo-excitation of the chalcogenide glass changes its elastic properties and, consequently, augments the acoustic transmission spectrum of the composite. By modulating the intensity of light irradiating the hybrid photonic/phononic structure, the position and spectral width of phonon passing-bands can be controlled. This demonstration offers the technological platform for optically-tunable acoustic wave band-pass filters.

  11. Optically tunable acoustic wave band-pass filter

    NASA Astrophysics Data System (ADS)

    Swinteck, N.; Lucas, P.; Deymier, P. A.

    2014-12-01

    The acoustic properties of a hybrid composite that exhibits both photonic and phononic behavior are investigated numerically with finite-element and finite-difference time-domain simulations. The structure is constituted of a periodic array of photonic resonant cavities embedded in a background superlattice. The resonant cavities contain a photo-elastic chalcogenide glass that undergoes atomic-scale structural reorganization when irradiated with light having energy close to its band-gap. Photo-excitation of the chalcogenide glass changes its elastic properties and, consequently, augments the acoustic transmission spectrum of the composite. By modulating the intensity of light irradiating the hybrid photonic/phononic structure, the position and spectral width of phonon passing-bands can be controlled. This demonstration offers the technological platform for optically-tunable acoustic wave band-pass filters.

  12. High-temperature bulk acoustic wave sensors

    NASA Astrophysics Data System (ADS)

    Fritze, Holger

    2011-01-01

    Piezoelectric crystals like langasite (La3Ga5SiO14, LGS) and gallium orthophosphate (GaPO4) exhibit piezoelectrically excited bulk acoustic waves at temperatures of up to at least 1450 °C and 900 °C, respectively. Consequently, resonant sensors based on those materials enable new sensing approaches. Thereby, resonant high-temperature microbalances are of particular interest. They correlate very small mass changes during film deposition onto resonators or gas composition-dependent stoichiometry changes of thin films already deposited onto the resonators with the resonance frequency shift of such devices. Consequently, the objective of the work is to review the high-temperature properties, the operation limits and the measurement principles of such resonators. The electromechanical properties of high-temperature bulk acoustic wave resonators such as mechanical stiffness, piezoelectric and dielectric constant, effective viscosity and electrical conductivity are described using a one-dimensional physical model and determined accurately up to temperatures as close as possible to their ultimate limit. Insights from defect chemical models are correlated with the electromechanical properties of the resonators. Thereby, crucial properties for stable operation as a sensor under harsh conditions are identified to be the formation of oxygen vacancies and the bulk conductivity. Operation limits concerning temperature, oxygen partial pressure and water vapor pressure are given. Further, application-relevant aspects such as temperature coefficients, temperature compensation and mass sensitivity are evaluated. In addition, approximations are introduced which make the exact model handy for routine data evaluation. An equivalent electrical circuit for high-temperature resonator devices is derived based on the one-dimensional physical model. Low- and high-temperature approximations are introduced. Thereby, the structure of the equivalent circuit corresponds to the Butterworth

  13. Acoustic and elastic waves in metamaterials for underwater applications

    NASA Astrophysics Data System (ADS)

    Titovich, Alexey S.

    Elastic effects in acoustic metamaterials are investigated. Water-based periodic arrays of elastic scatterers, sonic crystals, suffer from low transmission due to the impedance and index mismatch of typical engineering materials with water. A new type of acoustic metamaterial element is proposed that can be tuned to match the acoustic properties of water in the quasi-static regime. The element comprises a hollow elastic cylindrical shell fitted with an optimized internal substructure consisting of a central mass supported by an axisymmetric distribution of elastic stiffeners, which dictate the shell's effective bulk modulus and density. The derived closed form scattering solution for this system shows that the subsonic flexural waves excited in the shell by the attachment of stiffeners are suppressed by including a sufficiently large number of such stiffeners. As an example of refraction-based wave steering, a cylindrical-to-plane wave lens is designed by varying the bulk modulus in the array according to the conformal mapping of a unit circle to a square. Elastic shells provide rich scattering properties, mainly due to their ability to support highly dispersive flexural waves. Analysis of flexural-borne waves on a pair of shells yields an analytical expression for the width of a flexural resonance, which is then used with the theory of multiple scattering to accurately predict the splitting of the resonance frequency. This analysis leads to the discovery of the acoustic Poisson-like effect in a periodic wave medium. This effect redirects an incident acoustic wave by 90° in an otherwise acoustically transparent sonic crystal. An unresponsive "deaf" antisymmetric mode locked to band gap boundaries is unlocked by matching Bragg scattering with a quadrupole flexural resonance of the shell. The dynamic effect causes normal unidirectional wave motion to strongly couple to perpendicular motion, analogous to the quasi-static Poisson effect in solids. The Poisson

  14. Wideband excitation in nonlinear vibro-acoustic modulation for damage detection

    NASA Astrophysics Data System (ADS)

    Klepka, A.; Adamczyk, M.; Pieczonka, L.; Staszewski, W. J.

    2016-04-01

    The paper discusses the use of wideband excitation in nonlinear vibro-acoustic modulation technique (VAM) used for damage detection. In its original form, two mono-harmonic signals (low and high frequency) are used for excitation. The low frequency excitation is typically selected based on a modal analysis test and high frequency excitation is selected arbitrarily in the ultrasonic frequency range. This paper presents a different approach with use of wideband excitation signals. The proposed approach gives the possibility to simplify the testing procedure by omitting the modal test used to determine the value of low frequency excitation. Simultaneous use of wideband excitation for high frequency solves the ambiguity related to the selection of the frequency of acoustic wave. Broadband excitation signals require, however, more elaborate signal processing methods to determine the intensity of modulation for a given bandwidth. The paper discusses the proposed approach and the related signal processing procedure. Experimental validation of the proposed technique is performed on a laminated composite plate with a barely visible impact damage that was generated in an impact test. Piezoceramic actuators are used for vibration excitation and a scanning laser vibrometer is used for noncontact data acquisition.

  15. Dust acoustic solitary and shock excitations in a Thomas-Fermi magnetoplasma

    NASA Astrophysics Data System (ADS)

    Rahim, Z.; Ali, S.; Qamar, A.

    2014-07-01

    The linear and nonlinear properties of dust-acoustic waves are investigated in a collisionless Thomas-Fermi magnetoplasma, whose constituents are electrons, ions, and negatively charged dust particles. At dust time scale, the electron and ion number densities follow the Thomas-Fermi distribution, whereas the dust component is described by the classical fluid equations. A linear dispersion relation is analyzed to show that the wave frequencies associated with the upper and lower modes are enhanced with the variation of dust concentration. The effect of the latter is seen more strongly on the upper mode as compared to the lower mode. For nonlinear analysis, we obtain magnetized Korteweg-de Vries (KdV) and Zakharov-Kuznetsov (ZK) equations involving the dust-acoustic solitary waves in the framework of reductive perturbation technique. Furthermore, the shock wave excitations are also studied by allowing dissipation effects in the model, leading to the Korteweg-de Vries-Burgers (KdVB) and ZKB equations. The analysis reveals that the dust-acoustic solitary and shock excitations in a Thomas-Fermi plasma are strongly influenced by the plasma parameters, e.g., dust concentration, dust temperature, obliqueness, magnetic field strength, and dust fluid viscosity. The present results should be important for understanding the solitary and shock excitations in the environments of white dwarfs or supernova, where dust particles can exist.

  16. Dust acoustic solitary and shock excitations in a Thomas-Fermi magnetoplasma

    SciTech Connect

    Rahim, Z.; Qamar, A.; Ali, S.

    2014-07-15

    The linear and nonlinear properties of dust-acoustic waves are investigated in a collisionless Thomas-Fermi magnetoplasma, whose constituents are electrons, ions, and negatively charged dust particles. At dust time scale, the electron and ion number densities follow the Thomas-Fermi distribution, whereas the dust component is described by the classical fluid equations. A linear dispersion relation is analyzed to show that the wave frequencies associated with the upper and lower modes are enhanced with the variation of dust concentration. The effect of the latter is seen more strongly on the upper mode as compared to the lower mode. For nonlinear analysis, we obtain magnetized Korteweg-de Vries (KdV) and Zakharov-Kuznetsov (ZK) equations involving the dust-acoustic solitary waves in the framework of reductive perturbation technique. Furthermore, the shock wave excitations are also studied by allowing dissipation effects in the model, leading to the Korteweg-de Vries-Burgers (KdVB) and ZKB equations. The analysis reveals that the dust-acoustic solitary and shock excitations in a Thomas-Fermi plasma are strongly influenced by the plasma parameters, e.g., dust concentration, dust temperature, obliqueness, magnetic field strength, and dust fluid viscosity. The present results should be important for understanding the solitary and shock excitations in the environments of white dwarfs or supernova, where dust particles can exist.

  17. Broadband acoustic cloak for ultrasound waves.

    PubMed

    Zhang, Shu; Xia, Chunguang; Fang, Nicholas

    2011-01-14

    Invisibility devices based on coordinate transformation have opened up a new field of considerable interest. We present here the first practical realization of a low-loss and broadband acoustic cloak for underwater ultrasound. This metamaterial cloak is constructed with a network of acoustic circuit elements, namely, serial inductors and shunt capacitors. Our experiment clearly shows that the acoustic cloak can effectively bend the ultrasound waves around the hidden object, with reduced scattering and shadow. Because of the nonresonant nature of the building elements, this low-loss (∼6  dB/m) cylindrical cloak exhibits invisibility over a broad frequency range from 52 to 64 kHz. Furthermore, our experimental study indicates that this design approach should be scalable to different acoustic frequencies and offers the possibility for a variety of devices based on coordinate transformation.

  18. Radial wave crystals: radially periodic structures from anisotropic metamaterials for engineering acoustic or electromagnetic waves.

    PubMed

    Torrent, Daniel; Sánchez-Dehesa, José

    2009-08-01

    We demonstrate that metamaterials with anisotropic properties can be used to develop a new class of periodic structures that has been named radial wave crystals. They can be sonic or photonic, and wave propagation along the radial directions is obtained through Bloch states like in usual sonic or photonic crystals. The band structure of the proposed structures can be tailored in a large amount to get exciting novel wave phenomena. For example, it is shown that acoustical cavities based on radial sonic crystals can be employed as passive devices for beam forming or dynamically orientated antennas for sound localization.

  19. Acoustic excitation of droplet combustion in microgravity and normal gravity

    SciTech Connect

    Dattarajan, S.; Lutomirski, A.; Lobbia, R.; Smith, O.I.; Karagozian, A.R.

    2006-01-01

    This experimental study focused on methanol droplet combustion characteristics during exposure to external acoustical perturbations in both normal gravity and microgravity. Emphasis was placed on examination of excitation conditions in which the droplet was situated (1) at or near a velocity antinode (pressure node), where the droplet experienced the greatest effects of velocity perturbations, or (2) at a velocity node (pressure antinode), where the droplet was exposed to minimal velocity fluctuations. Acoustic excitation had a significantly greater influence on droplet-burning rates and flame structures in microgravity than in normal gravity. In normal gravity, acoustic excitation of droplets situated near a pressure node produced only very moderate increases in burning rate (about 11-15% higher than for nonacoustically excited, burning droplets) and produced no significant change in burning rate near a pressure antinode. In microgravity, for the same range in sound pressure level, droplet burning rates increased by over 75 and 200% for droplets situated at or near pressure antinode and pressure node locations, respectively. Observed flame deformation for droplets situated near pressure nodes or antinodes were generally consistent with the notion of acoustic radiation forces arising in connection with acoustic streaming, yet both velocity and pressure perturbations were seen to affect flame behavior, even when the droplet was situated precisely at or extremely close to node or antinode locations. Displacements of the droplet with respect to node or antinode locations were observed to have a measureable effect on droplet burning rates, yet acoustic accelerations associated with such displacements, as an analogy to gravitational acceleration, did not completely explain the significant increases in burning rate resulting from the excitation.

  20. Acoustic wave levitation: Handling of components

    NASA Astrophysics Data System (ADS)

    Vandaele, Vincent; Delchambre, Alain; Lambert, Pierre

    2011-06-01

    Apart from contact micromanipulation, there exists a large variety of levitation techniques among which standing wave levitation will be proposed as a way to handle (sub)millimetric components. This paper will compare analytical formulas to calculate the order of magnitude of the levitation force. It will then describe digital simulation and experimental levitation setup. Stable levitation of various components (cardboard, steel washer, ball, ceramic capacity, water droplet) was shown along 5 degrees of freedom: The only degree of freedom that could not be mastered was the rotation about the symmetry axis of the acoustic field. More importantly, the present work will show the modification of the orientation of the radial force component in the presence of an object disturbing the acoustic field. This property can be used as a new feeding strategy as it means that levitating components are spontaneously pushed toward grippers in an acoustic plane standing wave.

  1. Modified dust-acoustic waves in dusty plasma with Lennard-Jones potential

    NASA Astrophysics Data System (ADS)

    Qian, Y. Z.; Chen, H.; Yang, X. S.; Liu, S. Q.

    2015-10-01

    Dust-acoustic waves in a dusty plasma are investigated by solving the Vlasov equation including the effect of dust-dust interaction modeled by a Lennard-Jones-like potential. The latter contains a potential well and is applicable when thermionic or photo emission processes are important. It is shown that the excitation and linear dispersion of the dust-acoustic waves are strongly modified. In fact, the phase of the dust acoustic waves is shifted and a cut-off for the long-wavelength modes appears, leading to a purely growing instability.

  2. Dust-ion-acoustic wave oscillation in metallic multiwalled carbon nanotubes

    SciTech Connect

    Fathalian, Ali; Nikjo, Shahram

    2010-10-15

    In this paper, a charged multiwalled carbon nanotube (MWCNT), which is surrounded by charged nanoparticles, is modeled as a cylindrical shell of electron-ion-dust plasma. By employing the classical electrodynamics formulations and linearized hydrodynamic model, the dispersion relation of the dust-ion-acoustic wave oscillations in the composed system is investigated. We obtain a new low-frequency electrostatic excitation in the MWCNTs, i.e., dust-ion-acoustic wave oscillations.

  3. Measuring Acoustic Nonlinearity by Collinear Mixing Waves

    NASA Astrophysics Data System (ADS)

    Liu, M.; Tang, G.; Jacobs, L. J.; Qu, J.

    2011-06-01

    It is well known that the acoustic nonlinearity parameter β is correlated to fatigue damage in metallic materials. Various methods have been developed to measure β. One of the most often used methods is the harmonic generation technique, in which β is obtained by measuring the magnitude of the second order harmonic waves. An inherent weakness of this method is the difficulty in distinguishing material nonlinearity from the nonlinearity of the measurement system. In this paper, we demonstrate the possibility of using collinear mixing waves to measure β. The wave mixing method is based on the interaction between two incident waves in a nonlinear medium. Under certain conditions, such interactions generate a third wave of different frequency. This generated third wave is also called resonant wave, because its amplitude is unbounded if the medium has no attenuation. Such resonant waves are less sensitive to the nonlinearity of the measurement system, and have the potential to identify the source location of the nonlinearity. In this work, we used a longitudinal wave and a shear wave as the incident waves. The resonant shear wave is measured experimentally on samples made of aluminum and steel, respectively. Numerical simulations of the tests were also performed using a finite difference method.

  4. Direct acoustic phonon excitation by intense and ultrashort terahertz pulses

    NASA Astrophysics Data System (ADS)

    Manceau, J.-M.; Loukakos, P. A.; Tzortzakis, S.

    2010-12-01

    We report on the direct and resonant excitation of acoustic phonons in an AlGaAs intrinsic semiconductor using intense coherent and single cycle terahertz pulses created by two-color femtosecond laser pulse filamentation in air. While the electrons are left unperturbed, we follow the lattice dynamics with time-delayed optical photons tuned to the interband transition.

  5. Wave instabilities in an excitable electrochemical system

    NASA Astrophysics Data System (ADS)

    Otterstedt, R. D.; Jaeger, N. I.; Plath, P. J.; Hudson, J. L.

    1998-11-01

    Spatiotemporal pattern formation under potentiostatic control in the excitable potential range at the active/passive transition of cobalt in buffered phosphoric acid has been investigated in a ribbon electrode geometry. The propagation of an active area with modulation and wave splitting has been observed, depending on the parameters potential and time of passivation prior to excitation. The modulation and wave splitting are influenced both by the kinetics of repassivation on the electrode surface and by long-range coupling and positive feedback through the electric field. Modulation in the vicinity of the system boundary gives rise to an apparent reflection of the active area at the boundary.

  6. Standing wave acoustic levitation on an annular plate

    NASA Astrophysics Data System (ADS)

    Kandemir, Mehmet Hakan; Çalışkan, Mehmet

    2016-11-01

    In standing wave acoustic levitation technique, a standing wave is formed between a source and a reflector. Particles can be attracted towards pressure nodes in standing waves owing to a spring action through which particles can be suspended in air. This operation can be performed on continuous structures as well as in several numbers of axes. In this study an annular acoustic levitation arrangement is introduced. Design features of the arrangement are discussed in detail. Bending modes of the annular plate, known as the most efficient sound generation mechanism in such structures, are focused on. Several types of bending modes of the plate are simulated and evaluated by computer simulations. Waveguides are designed to amplify waves coming from sources of excitation, that are, transducers. With the right positioning of the reflector plate, standing waves are formed in the space between the annular vibrating plate and the reflector plate. Radiation forces are also predicted. It is demonstrated that small particles can be suspended in air at pressure nodes of the standing wave corresponding to a particular bending mode.

  7. Coded excitation plane wave imaging for shear wave motion detection.

    PubMed

    Song, Pengfei; Urban, Matthew W; Manduca, Armando; Greenleaf, James F; Chen, Shigao

    2015-07-01

    Plane wave imaging has greatly advanced the field of shear wave elastography thanks to its ultrafast imaging frame rate and the large field-of-view (FOV). However, plane wave imaging also has decreased penetration due to lack of transmit focusing, which makes it challenging to use plane waves for shear wave detection in deep tissues and in obese patients. This study investigated the feasibility of implementing coded excitation in plane wave imaging for shear wave detection, with the hypothesis that coded ultrasound signals can provide superior detection penetration and shear wave SNR compared with conventional ultrasound signals. Both phase encoding (Barker code) and frequency encoding (chirp code) methods were studied. A first phantom experiment showed an approximate penetration gain of 2 to 4 cm for the coded pulses. Two subsequent phantom studies showed that all coded pulses outperformed the conventional short imaging pulse by providing superior sensitivity to small motion and robustness to weak ultrasound signals. Finally, an in vivo liver case study on an obese subject (body mass index = 40) demonstrated the feasibility of using the proposed method for in vivo applications, and showed that all coded pulses could provide higher SNR shear wave signals than the conventional short pulse. These findings indicate that by using coded excitation shear wave detection, one can benefit from the ultrafast imaging frame rate and large FOV provided by plane wave imaging while preserving good penetration and shear wave signal quality, which is essential for obtaining robust shear elasticity measurements of tissue.

  8. Helicon wave excitation with helical antennas

    SciTech Connect

    Light, M.; Chen, F.F.

    1995-04-01

    Components of the wave magnetic field in a helicon discharge have been measured with a single-turn, coaxial magnetic probe. Left- and right-handed helical antennas, as well as plane-polarized antennas, were used; and the results were compared with the field patterns computed for a nonuniform plasma. The results show that the right-hand circularly polarized mode is preferentially excited with all antennas, even those designed to excite the left-hand mode. For right-hand excitation, the radial amplitude profiles are in excellent agreement with computations. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  9. Acoustic wave-equation-based earthquake location

    NASA Astrophysics Data System (ADS)

    Tong, Ping; Yang, Dinghui; Liu, Qinya; Yang, Xu; Harris, Jerry

    2016-04-01

    We present a novel earthquake location method using acoustic wave-equation-based traveltime inversion. The linear relationship between the location perturbation (δt0, δxs) and the resulting traveltime residual δt of a particular seismic phase, represented by the traveltime sensitivity kernel K(t0, xs) with respect to the earthquake location (t0, xs), is theoretically derived based on the adjoint method. Traveltime sensitivity kernel K(t0, xs) is formulated as a convolution between the forward and adjoint wavefields, which are calculated by numerically solving two acoustic wave equations. The advantage of this newly derived traveltime kernel is that it not only takes into account the earthquake-receiver geometry but also accurately honours the complexity of the velocity model. The earthquake location is obtained by solving a regularized least-squares problem. In 3-D realistic applications, it is computationally expensive to conduct full wave simulations. Therefore, we propose a 2.5-D approach which assumes the forward and adjoint wave simulations within a 2-D vertical plane passing through the earthquake and receiver. Various synthetic examples show the accuracy of this acoustic wave-equation-based earthquake location method. The accuracy and efficiency of the 2.5-D approach for 3-D earthquake location are further verified by its application to the 2004 Big Bear earthquake in Southern California.

  10. Love waves excited by a moving source

    NASA Astrophysics Data System (ADS)

    Zaslavskii, Yu. M.

    2016-01-01

    The study analyzes the characteristics of surface Love waves excited by the moment of an oscillating torsional force with a point of action that moves uniformly and rectilinearly along the free flat boundary of a medium having the structure of a "layer on a half-space." The azimuthal-angular distribution of the amplitude and Doppler shift in frequency of the wave modes is studied as a function of the motion velocity of a vibrating source and the parameters of the medium.

  11. Extraordinary transmission of gigahertz surface acoustic waves.

    PubMed

    Mezil, Sylvain; Chonan, Kazuki; Otsuka, Paul H; Tomoda, Motonobu; Matsuda, Osamu; Lee, Sam H; Wright, Oliver B

    2016-09-19

    Extraordinary transmission of waves, i.e. a transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths λ ~ 3-50 μm, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Several resonant modes of the structure, both one- and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e. intensity enhancements, up to ~23 and ~8 in the two respective cases. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. Applications include new metamaterials and subwavelength imaging.

  12. Extraordinary transmission of gigahertz surface acoustic waves

    NASA Astrophysics Data System (ADS)

    Mezil, Sylvain; Chonan, Kazuki; Otsuka, Paul H.; Tomoda, Motonobu; Matsuda, Osamu; Lee, Sam H.; Wright, Oliver B.

    2016-09-01

    Extraordinary transmission of waves, i.e. a transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths λ ~ 3–50 μm, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Several resonant modes of the structure, both one- and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e. intensity enhancements, up to ~23 and ~8 in the two respective cases. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. Applications include new metamaterials and subwavelength imaging.

  13. Extraordinary transmission of gigahertz surface acoustic waves.

    PubMed

    Mezil, Sylvain; Chonan, Kazuki; Otsuka, Paul H; Tomoda, Motonobu; Matsuda, Osamu; Lee, Sam H; Wright, Oliver B

    2016-01-01

    Extraordinary transmission of waves, i.e. a transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths λ ~ 3-50 μm, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Several resonant modes of the structure, both one- and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e. intensity enhancements, up to ~23 and ~8 in the two respective cases. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. Applications include new metamaterials and subwavelength imaging. PMID:27640998

  14. Extraordinary transmission of gigahertz surface acoustic waves

    PubMed Central

    Mezil, Sylvain; Chonan, Kazuki; Otsuka, Paul H.; Tomoda, Motonobu; Matsuda, Osamu; Lee, Sam H.; Wright, Oliver B.

    2016-01-01

    Extraordinary transmission of waves, i.e. a transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths λ ~ 3–50 μm, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Several resonant modes of the structure, both one- and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e. intensity enhancements, up to ~23 and ~8 in the two respective cases. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. Applications include new metamaterials and subwavelength imaging. PMID:27640998

  15. Nonlinear acoustic wave propagation in atmosphere

    NASA Technical Reports Server (NTRS)

    Hariharan, S. I.

    1985-01-01

    A model problem that simulates an atmospheric acoustic wave propagation situation that is nonlinear is considered. The model is derived from the basic Euler equations for the atmospheric flow and from the regular perturbations for the acoustic part. The nonlinear effects are studied by obtaining two successive linear problems in which the second one involves the solution of the first problem. Well posedness of these problems is discussed and approximations of the radiation boundary conditions that can be used in numerical simulations are presented.

  16. Nonlinear acoustic wave propagation in atmosphere

    NASA Technical Reports Server (NTRS)

    Hariharan, S. I.

    1986-01-01

    In this paper a model problem is considered that simulates an atmospheric acoustic wave propagation situation that is nonlinear. The model is derived from the basic Euler equations for the atmospheric flow and from the regular perturbations for the acoustic part. The nonlinear effects are studied by obtaining two successive linear problems in which the second one involves the solution of the first problem. Well-posedness of these problems is discussed and approximations of the radiation boundary conditions that can be used in numerical simulations are presented.

  17. Generation mechanism for electron acoustic solitary waves

    SciTech Connect

    Kakad, A. P.; Singh, S. V.; Reddy, R. V.; Lakhina, G. S.; Tagare, S. G.; Verheest, F.

    2007-05-15

    Nonlinear electron acoustic solitary waves (EASWs) are studied in a collisionless and unmagnetized plasma consisting of cold background electrons, cold beam electrons, and two different temperature ion species. Using pseudopotential analysis, the properties of arbitrary amplitude EASWs are investigated. The present model supports compressive as well as rarefactive electron acoustic solitary structures. Furthermore, there is an interesting possibility of the coexistence of compressive and rarefactive solitary structures in a specific plasma parameter range. The application of our results in interpreting the salient features of the broadband electrostatic noise in the plasma sheet boundary layer is discussed.

  18. Brillouin light scattering from surface acoustic waves in a subwavelength-diameter optical fibre

    PubMed Central

    Beugnot, Jean-Charles; Lebrun, Sylvie; Pauliat, Gilles; Maillotte, Hervé; Laude, Vincent; Sylvestre, Thibaut

    2014-01-01

    Brillouin scattering in optical fibres is a fundamental interaction between light and sound with important implications ranging from optical sensors to slow and fast light. In usual optical fibres, light both excites and feels shear and longitudinal bulk elastic waves, giving rise to forward-guided acoustic wave Brillouin scattering and backward-stimulated Brillouin scattering. In a subwavelength-diameter optical fibre, the situation changes dramatically, as we here report with the first experimental observation of Brillouin light scattering from surface acoustic waves. These Rayleigh-type surface waves travel the wire surface at a specific velocity of 3,400 m s−1 and backscatter the light with a Doppler shift of about 6 GHz. As these acoustic resonances are sensitive to surface defects or features, surface acoustic wave Brillouin scattering opens new opportunities for various sensing applications, but also in other domains such as microwave photonics and nonlinear plasmonics. PMID:25341638

  19. Parametric excitation of whistler waves by HF heater

    NASA Technical Reports Server (NTRS)

    Kuo, S. P.; Lee, M. C.

    1989-01-01

    Possible generation of whistler waves by Tromso HF heater is investigated. It is shown that the HF heater wave can parametrically decay into a whistler wave and a Langmuir wave. Since whistler waves may have a broad range of frequency, the simultaneously excited Langmuir waves can have a much broader frequency bandwidth than those excited by the parametric decay instability.

  20. Acoustic Remote Sensing of Rogue Waves

    NASA Astrophysics Data System (ADS)

    Parsons, Wade; Kadri, Usama

    2016-04-01

    We propose an early warning system for approaching rogue waves using the remote sensing of acoustic-gravity waves (AGWs) - progressive sound waves that propagate at the speed of sound in the ocean. It is believed that AGWs are generated during the formation of rogue waves, carrying information on the rogue waves at near the speed of sound, i.e. much faster than the rogue wave. The capability of identifying those special sound waves would enable detecting rogue waves most efficiently. A lot of promising work has been reported on AGWs in the last few years, part of which in the context of remote sensing as an early detection of tsunami. However, to our knowledge none of the work addresses the problem of rogue waves directly. Although there remains some uncertainty as to the proper definition of a rogue wave, there is little doubt that they exist and no one can dispute the potential destructive power of rogue waves. An early warning system for such extreme waves would become a demanding safety technology. A closed form expression was developed for the pressure induced by an impulsive source at the free surface (the Green's function) from which the solution for more general sources can be developed. In particular, we used the model of the Draupner Wave of January 1st, 1995 as a source and calculated the induced AGW signature. In particular we studied the AGW signature associated with a special feature of this wave, and characteristic of rogue waves, of the absence of any local set-down beneath the main crest and the presence of a large local set-up.

  1. Multi Reflection of Lamb Wave Emission in an Acoustic Waveguide Sensor

    PubMed Central

    Schmitt, Martin; Olfert, Sergei; Rautenberg, Jens; Lindner, Gerhard; Henning, Bernd; Reindl, Leonhard Michael

    2013-01-01

    Recently, an acoustic waveguide sensor based on multiple mode conversion of surface acoustic waves at the solid—liquid interfaces has been introduced for the concentration measurement of binary and ternary mixtures, liquid level sensing, investigation of spatial inhomogenities or bubble detection. In this contribution the sound wave propagation within this acoustic waveguide sensor is visualized by Schlieren imaging for continuous and burst operation the first time. In the acoustic waveguide the antisymmetrical zero order Lamb wave mode is excited by a single phase transducer of 1 MHz on thin glass plates of 1 mm thickness. By contact to the investigated liquid Lamb waves propagating on the first plate emit pressure waves into the adjacent liquid, which excites Lamb waves on the second plate, what again causes pressure waves traveling inside the liquid back to the first plate and so on. The Schlieren images prove this multi reflection within the acoustic waveguide, which confirms former considerations and calculations based on the receiver signal. With this knowledge the sensor concepts with the acoustic waveguide sensor can be interpreted in a better manner. PMID:23447010

  2. Influence of surface acoustic waves induced acoustic streaming on the kinetics of electrochemical reactions

    NASA Astrophysics Data System (ADS)

    Tietze, Sabrina; Schlemmer, Josefine; Lindner, Gerhard

    2013-12-01

    The kinetics of electrochemical reactions is controlled by diffusion processes of charge carriers across a boundary layer between the electrode and the electrolyte, which result in a shielding of the electric field inside the electrolyte and a concentration gradient across this boundary layer. In accumulators the diffusion rate determines the rather long time needed for charging, which is a major drawback for electric mobility. This diffusion boundary can be removed by acoustic streaming in the electrolyte induced by surface acoustic waves propagating of the electrode, which results in an increase of the charging current and thus in a reduction of the time needed for charging. For a quantitative study of the influence of acoustic streaming on the charge transport an electropolishing cell with vertically oriented copper electrodes and diluted H3PO4-Propanol electrolytes were used. Lamb waves with various excitation frequencies were exited on the anode with different piezoelectric transducers, which induced acoustic streaming in the overlaying electrolytic liquid. An increase of the polishing current of up to approximately 100 % has been obtained with such a set-up.

  3. Observation of multifractal intermittent dust-acoustic-wave turbulence

    NASA Astrophysics Data System (ADS)

    Tsai, Ya-Yi; Chang, Mei-Chu; I, Lin

    2012-10-01

    Intermittent dust acoustic wave turbulence self-excited by downward ion flow in dissipative dusty plasma is experimentally observed and investigated. The power spectra of the temporal dust density fluctuation show distinct bumps in the low-frequency regime and power-law scaling in the high-frequency regime. The structure-function analysis demonstrates the multifractal dynamics of the wave turbulence. Decreasing dissipation by decreasing neutral pressure leads to a more turbulent state with a less distinct low-frequency bump in the power spectrum, more stretched non-Gaussian tails in the histogram of the wave-height increment at a small time interval τ, and a higher degree of multifractality. The loss of long time memory with increasing τ for a more turbulent state causes a change from the distribution with stretched non-Gaussian tails to Gaussian with increasing τ.

  4. Langasite Surface Acoustic Wave Gas Sensors: Modeling and Verification

    SciTech Connect

    Zheng, Peng; Greve, David W; Oppenheim, Irving J

    2013-01-01

    We report finite element simulations of the effect of conductive sensing layers on the surface wave velocity of langasite substrates. The simulations include both the mechanical and electrical influences of the conducting sensing layer. We show that three-dimensional simulations are necessary because of the out-of-plane displacements of the commonly used (0, 138.5, 26.7) Euler angle. Measurements of the transducer input admittance in reflective delay-line devices yield a value for the electromechanical coupling coefficient that is in good agreement with the three-dimensional simulations on bare langasite substrate. The input admittance measurements also show evidence of excitation of an additional wave mode and excess loss due to the finger resistance. The results of these simulations and measurements will be useful in the design of surface acoustic wave gas sensors.

  5. Resonant coupling of Rayleigh waves through a narrow fluid channel causing extraordinary low acoustic transmission.

    PubMed

    Garcia-Chocano, Victor M; Nagaraj; Lòpez-Rios, Tomàs; Gumen, Lyudmila; Sànchez-Dehesa, Josè; Krokhin, Arkadii

    2012-10-01

    Coupling of Rayleigh waves propagating along two metal surfaces separated by a narrow fluid channel is predicted and experimentally observed. Although the coupling through a fluid (water) is weak, a strong synchronization in propagation of Rayleigh waves even for the metals with sufficiently high elastic contrast (brass and aluminum) is observed. Dispersion equation for two polarizations of the coupled Rayleigh waves is derived and experimentally confirmed. Excitation of coupled Rayleigh waves in a channel of finite length leads to anomalously low transmission of acoustic energy at discrete set of resonant frequencies. This effect may find useful applications in the design of acoustic metamaterial screens and reflectors.

  6. Mobility power flow analysis of coupled plate structure subjected to mechanical and acoustic excitation

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.

    1992-01-01

    The mobility power flow approach that was previously applied in the derivation of expressions for the vibrational power flow between coupled plate substructures forming an L configuration and subjected to mechanical loading is generalized. Using the generalized expressions, both point and distributed mechanical loads on one or both of the plates can be considered. The generalized approach is extended to deal with acoustic excitation of one of the plate substructures. In this case, the forces (acoustic pressures) acting on the structure are dependent on the response of the structure because of the scattered pressure component. The interaction between the plate structure and the acoustic fluid leads to the derivation of a corrected mode shape for the plates' normal surface velocity and also for the structure mobility functions. The determination of the scattered pressure components in the expressions for the power flow represents an additional component in the power flow balance for the source plate and the receiver plate. This component represents the radiated acoustical power from the plate structure. For a number of coupled plate substrates, the acoustic pressure generated by one substructure will interact with the motion of another substructure. That is, in the case of the L-shaped plate, acoustic interaction exists between the two plate substructures due to the generation of the acoustic waves by each of the substructures. An approach to deal with this phenomena is described.

  7. Acoustic excitation: A promising new means of controlling shear layers

    NASA Technical Reports Server (NTRS)

    Stone, J. R.; Mckinzie, D. J., Jr.

    1984-01-01

    Techniques have long been sought for the controlled modification of turbulent shear layers, such as in jets, wakes, boundary layers, and separated flows. Relatively recently published results of laboratory experiments have established that coherent structures exist within turbulent flows. These results indicate that even apparently chaotic flow fields can contain deterministic, nonrandom elements. Even more recently published results show that deliberate acoustic excitation of these coherent structures has a significant effect on the mixing characteristics of shear layers. Therefore, we have initiated a research effort to develop both an understanding of the interaction mechanisms and the ability to use it to favorably modify various shear layers. Acoustic excitation circumvents the need for pumping significant flow rates, as required by suction or blowing. Control of flows by intentional excitation of natural flow instabilities involves new and largely unexplored phenomena and offers considerable potential for improving component performance. Nonintrusive techniques for flow field control may permit much more efficient, flexible propulsion systems and aircraft designs, including means of stall avoidance and recovery. The techniques developed may also find application in many other areas where mixing is important, such as reactors, continuous lasers, rocket engines, and fluidic devices. It is the objective of this paper to examine some potential applications of the acoustic excitation technique to various shear layer flows of practical aerospace systems.

  8. High-Temperature Surface-Acoustic-Wave Transducer

    NASA Technical Reports Server (NTRS)

    Zhao, Xiaoliang; Tittmann, Bernhard R.

    2010-01-01

    Aircraft-engine rotating equipment usually operates at high temperature and stress. Non-invasive inspection of microcracks in those components poses a challenge for the non-destructive evaluation community. A low-profile ultrasonic guided wave sensor can detect cracks in situ. The key feature of the sensor is that it should withstand high temperatures and excite strong surface wave energy to inspect surface/subsurface cracks. As far as the innovators know at the time of this reporting, there is no existing sensor that is mounted to the rotor disks for crack inspection; the most often used technology includes fluorescent penetrant inspection or eddy-current probes for disassembled part inspection. An efficient, high-temperature, low-profile surface acoustic wave transducer design has been identified and tested for nondestructive evaluation of structures or materials. The development is a Sol-Gel bismuth titanate-based surface-acoustic-wave (SAW) sensor that can generate efficient surface acoustic waves for crack inspection. The produced sensor is very thin (submillimeter), and can generate surface waves up to 540 C. Finite element analysis of the SAW transducer design was performed to predict the sensor behavior, and experimental studies confirmed the results. One major uniqueness of the Sol-Gel bismuth titanate SAW sensor is that it is easy to implement to structures of various shapes. With a spray coating process, the sensor can be applied to surfaces of large curvatures. Second, the sensor is very thin (as a coating) and has very minimal effect on airflow or rotating equipment imbalance. Third, it can withstand temperatures up to 530 C, which is very useful for engine applications where high temperature is an issue.

  9. Condition of resonant break-up of gas bubbles by an acoustic wave in liquid

    NASA Astrophysics Data System (ADS)

    Vanovskiy, V. V.; Petrov, A. G.

    2016-07-01

    The linear theory of damping of radial vibrations of a bubble in a liquid is constructed by taking into account the key dissipative mechanisms: thermal, viscous, and acoustic. The basic approximation of homobaricity made helps to obtain the results in a convenient and simple form. The results obtained for damping are used further in the description of the forced resonant oscillations of a bubble in an acoustic wave with the frequency equal to the eigenfrequency of the radial oscillation mode and twice as high as the frequency of the deformation oscillation mode (resonance 2:2:1). It is shown that the amplitude of deformation oscillations, which is reasonably large for breaking, is developed at a relatively small pressure amplitude of the exciting acoustic wave, and subharmonics arise in the acoustic-emission spectrum. The condition of bubble break-up is obtained for a fast and slow start of the acoustic wave.

  10. Support minimized inversion of acoustic and elastic wave scattering

    SciTech Connect

    Safaeinili, A.

    1994-04-24

    This report discusses the following topics on support minimized inversion of acoustic and elastic wave scattering: Minimum support inversion; forward modelling of elastodynamic wave scattering; minimum support linearized acoustic inversion; support minimized nonlinear acoustic inversion without absolute phase; and support minimized nonlinear elastic inversion.

  11. Visualization of Surface Acoustic Waves in Thin Liquid Films

    PubMed Central

    Rambach, R. W.; Taiber, J.; Scheck, C. M. L.; Meyer, C.; Reboud, J.; Cooper, J. M.; Franke, T.

    2016-01-01

    We demonstrate that the propagation path of a surface acoustic wave (SAW), excited with an interdigitated transducer (IDT), can be visualized using a thin liquid film dispensed onto a lithium niobate (LiNbO3) substrate. The practical advantages of this visualization method are its rapid and simple implementation, with many potential applications including in characterising acoustic pumping within microfluidic channels. It also enables low-cost characterisation of IDT designs thereby allowing the determination of anisotropy and orientation of the piezoelectric substrate without the requirement for sophisticated and expensive equipment. Here, we show that the optical visibility of the sound path critically depends on the physical properties of the liquid film and identify heptane and methanol as most contrast rich solvents for visualization of SAW. We also provide a detailed theoretical description of this effect. PMID:26917490

  12. Visualization of Surface Acoustic Waves in Thin Liquid Films.

    PubMed

    Rambach, R W; Taiber, J; Scheck, C M L; Meyer, C; Reboud, J; Cooper, J M; Franke, T

    2016-01-01

    We demonstrate that the propagation path of a surface acoustic wave (SAW), excited with an interdigitated transducer (IDT), can be visualized using a thin liquid film dispensed onto a lithium niobate (LiNbO3) substrate. The practical advantages of this visualization method are its rapid and simple implementation, with many potential applications including in characterising acoustic pumping within microfluidic channels. It also enables low-cost characterisation of IDT designs thereby allowing the determination of anisotropy and orientation of the piezoelectric substrate without the requirement for sophisticated and expensive equipment. Here, we show that the optical visibility of the sound path critically depends on the physical properties of the liquid film and identify heptane and methanol as most contrast rich solvents for visualization of SAW. We also provide a detailed theoretical description of this effect. PMID:26917490

  13. Wireless Multiplexed Surface Acoustic Wave Sensors Project

    NASA Technical Reports Server (NTRS)

    Youngquist, Robert C.

    2014-01-01

    Wireless Surface Acoustic Wave (SAW) Sensor is a new technology for obtaining multiple, real-time measurements under extreme environmental conditions. This project plans to develop a wireless multiplexed sensor system that uses SAW sensors, with no batteries or semiconductors, that are passive and rugged, can operate down to cryogenic temperatures and up to hundreds of degrees C, and can be used to sense a wide variety of parameters over reasonable distances (meters).

  14. The Foley Acoustic Wave Front Slides

    NASA Astrophysics Data System (ADS)

    Greenslade, Thomas B.

    2004-04-01

    In 1912 Arthur L. Foley of Indiana University published an article in Physical Review about his technique for photographing acoustic wave fronts. Subsequently, the Central Scientific Company published a series of glass lantern slides of his illustrations. These have been unavailable for about 60 years. Here I discuss how Foley made his slides and give examples of use to the present-day physics teacher.

  15. Radio wave propagation and acoustic sounding

    NASA Astrophysics Data System (ADS)

    Singal, S. P.

    Radio wave propagation of the decimetric and centimetric waves depends to a large extent on the boundary layer meteorological conditions which give rise to severe fadings, very often due to multipath propagation. Sodar is one of the inexpensive remote sensing techniques which can be employed to probe the boundary layer structure. In the paper a historical perspective has been given of the simultaneously conducted studies on radio waves and sodar at various places. The radio meteorological information needed for propagation studies has been clearly spelt out and conditions of a ray path especially in the presence of a ducting layer have been defined as giving rise to fading or signal enhancement conditions. Finally the potential of the sodar studies to obtain information about the boundary layer phenomena has been stressed, clearly spelling out the use of acoustic sounding in radio wave propagation studies.

  16. Nonlinear ion acoustic waves scattered by vortexes

    NASA Astrophysics Data System (ADS)

    Ohno, Yuji; Yoshida, Zensho

    2016-09-01

    The Kadomtsev-Petviashvili (KP) hierarchy is the archetype of infinite-dimensional integrable systems, which describes nonlinear ion acoustic waves in two-dimensional space. This remarkably ordered system resides on a singular submanifold (leaf) embedded in a larger phase space of more general ion acoustic waves (low-frequency electrostatic perturbations). The KP hierarchy is characterized not only by small amplitudes but also by irrotational (zero-vorticity) velocity fields. In fact, the KP equation is derived by eliminating vorticity at every order of the reductive perturbation. Here, we modify the scaling of the velocity field so as to introduce a vortex term. The newly derived system of equations consists of a generalized three-dimensional KP equation and a two-dimensional vortex equation. The former describes 'scattering' of vortex-free waves by ambient vortexes that are determined by the latter. We say that the vortexes are 'ambient' because they do not receive reciprocal reactions from the waves (i.e., the vortex equation is independent of the wave fields). This model describes a minimal departure from the integrable KP system. By the Painlevé test, we delineate how the vorticity term violates integrability, bringing about an essential three-dimensionality to the solutions. By numerical simulation, we show how the solitons are scattered by vortexes and become chaotic.

  17. Excitation of instability waves in a two-dimensional shear layer by sound

    NASA Technical Reports Server (NTRS)

    Tam, C. K. W.

    1978-01-01

    The excitation of instability waves in a plane compressible shear layer by sound waves is studied. The problem is formulated mathematically as an inhomogeneous boundary-value problem. A general solution for abitrary incident sound wave is found by first constructing the Green's function of the problem. Numerical values of the coupling constants between incident sound waves and excited instability waves for a range of flow Mach number are calculated. The effect of the angle of incidence in the case of a beam of acoustic waves is analyzed. It is found that for moderate subsonic Mach numbers a narrow beam aiming at an angle between 50 to 80 deg to the flow direction is most effective in exciting instability waves.

  18. Mobility power flow analysis of an L-shaped plate structure subjected to acoustic excitation

    NASA Technical Reports Server (NTRS)

    Cuschieri, J. M.

    1989-01-01

    An analytical investigation based on the Mobility Power Flow method is presented for the determination of the vibrational response and power flow for two coupled flat plate structures in an L-shaped configuration, subjected to acoustical excitation. The principle of the mobility power flow method consists of dividing the global structure into a series of subsystems coupled together using mobility functions. Each separate subsystem is analyzed independently to determine the structural mobility functions for the junction and excitation locations. The mobility functions, together with the characteristics of the junction between the subsystems, are then used to determine the response of the global structure and the power flow. In the coupled plate structure considered here, mobility power flow expressions are derived for excitation by an incident acoustic plane wave. In this case, the forces (acoustic pressures) acting on the structure are dependent on the response of the structure because of the scattered pressure component. The interaction between the structure and the fluid leads to the derivation of a corrected mode shape for the plates' normal surface velocity and also for the structure mobility functions. The determination of the scattered pressure components in the expressions for the power flow represents an additional component in the power flow balance for the source plate and the receiver plate. This component represents the radiated acoustical power from the plate structure.

  19. Acoustic and vibration response of a structure with added noise control treatment under various excitations.

    PubMed

    Rhazi, Dilal; Atalla, Noureddine

    2014-02-01

    The evaluation of the acoustic performance of noise control treatments is of great importance in many engineering applications, e.g., aircraft, automotive, and building acoustics applications. Numerical methods such as finite- and boundary elements allow for the study of complex structures with added noise control treatment. However, these methods are computationally expensive when used for complex structures. At an early stage of the acoustic trim design process, many industries look for simple and easy to use tools that provide sufficient physical insight that can help to formulate design criteria. The paper presents a simple and tractable approach for the acoustic design of noise control treatments. It presents and compares two transfer matrix-based methods to investigate the vibroacoustic behavior of noise control treatments. The first is based on a modal approach, while the second is based on wave-number space decomposition. In addition to the classical rain-on-the-roof and diffuse acoustic field excitations, the paper also addresses turbulent boundary layer and point source (monopole) excitations. Various examples are presented and compared to a finite element calculation to validate the methodology and to confirm its relevance along with its limitations. PMID:25234878

  20. Controlling plume deflection by acoustic excitation - An experimental demonstration

    NASA Astrophysics Data System (ADS)

    Ahuja, K. K.

    1990-10-01

    Effect of imposing an external sound field on a Coanda jet was investigated experimentally. It was found that the exhaust angle of a Coanda plume can be varied by changing the level of excitation. Limited experiments were also performed in a wind tunnel to study the effects of flight simulation on plume deflection controllability by sound using a hollow airfoil fitted with a Coanda jet. Pressure coefficients are measured over this airfoil with and without acoustic excitation of the Coanda Jet. This exploratory study provided a number of new ideas for future work for controlling flow over curved surfaces.

  1. Propagation characteristics of acoustic waves in snow

    NASA Astrophysics Data System (ADS)

    Capelli, Achille; Kapil, Jagdish Chandra; Reiweger, Ingrid; Schweizer, Jürg; Or, Dani

    2015-04-01

    Acoustic emission analysis is a promising technique for monitoring snow slope stability with potential for application in early warning systems for avalanches. Current research efforts focus on identification and localization of acoustic emission features preceding snow failure and avalanches. However, our knowledge of sound propagation characteristics in snow is still limited. A review of previous studies showed that significant gaps exist and that the results of the various studies are partly contradictory. Furthermore, sound velocity and attenuation have been determined for the frequency range below 10 kHz, while recent snow failure experiments suggest that the peak frequency is in the ultrasound range between 30 kHz to 500 kHz. We therefore studied the propagation of pencil lead fracture (PLF) signals through snow in the ultrasound frequency range. This was achieved by performing laboratory experiments with columns of artificially produced snow of varying density and temperature. The attenuation constant was obtained by varying the size of the columns to eliminate possible influences of the snow-sensor coupling. The attenuation constant was measured for the entire PLF burst signal and for single frequency components. The propagation velocity was calculated from the arrival time of the acoustic signal. We then modelled the sound propagation for our experimental setup using Biot's model for wave propagation in porous media. The Model results were in good agreement with our experimental results. For the studied samples, the acoustic signals propagated as fast and slow longitudinal waves, but the main part of the energy was carried by the slow waves. The Young's modulus of our snow samples was determined from the sound velocity. This is highly relevant, as the elastic properties of snow are not well known.

  2. Effect of surface acoustic waves on the catalytic decomposition of ethanol employing a comb transducer for ultrasonic generation

    SciTech Connect

    S. J. Reese; D. H. Hurley; H.W. Rollins

    2006-04-01

    The effect of surface acoustic waves, generated on a silver catalyst using a comb transducer, on the catalytic decomposition of ethanol is examined. The comb transducer employs purely mechanical means for surface acoustic wave (SAW) transduction. Unlike interdigital SAW transducers on piezoelectric substrates, the complicating effects of heat generation due to electromechanical coupling, high electric fields between adjacent electrodes, and acoustoelectric currents are avoided. The ethanol decomposition reactions are carried out at 473 K. The rates of acetaldehyde and ethylene production are retarded when acoustic waves are applied. The rates recover to varying degrees when acoustic excitation ceases.

  3. Twisted electron-acoustic waves in plasmas

    NASA Astrophysics Data System (ADS)

    Aman-ur-Rehman, Ali, S.; Khan, S. A.; Shahzad, K.

    2016-08-01

    In the paraxial limit, a twisted electron-acoustic (EA) wave is studied in a collisionless unmagnetized plasma, whose constituents are the dynamical cold electrons and Boltzmannian hot electrons in the background of static positive ions. The analytical and numerical solutions of the plasma kinetic equation suggest that EA waves with finite amount of orbital angular momentum exhibit a twist in its behavior. The twisted wave particle resonance is also taken into consideration that has been appeared through the effective wave number qeff accounting for Laguerre-Gaussian mode profiles attributed to helical phase structures. Consequently, the dispersion relation and the damping rate of the EA waves are significantly modified with the twisted parameter η, and for η → ∞, the results coincide with the straight propagating plane EA waves. Numerically, new features of twisted EA waves are identified by considering various regimes of wavelength and the results might be useful for transport and trapping of plasma particles in a two-electron component plasma.

  4. Excitation of terahertz nanoantennas by Rabi waves

    SciTech Connect

    Slepyan, G. Ya.; Yerchak, Y. D.; Maksimenko, S. A.; Hoffmann, A.; Bass, F. G.

    2011-10-03

    Theoretical model of quantum dot ring, strongly coupled with classical electromagnetic field, is developed. We demonstrate, that tunnel current in the QD-ring has low-frequency component, excited by Rabi waves, propagating into the ring, and the ring can be considered as a candidate for role of terahertz magnetic loop antenna. The low-frequency current is inspired by the asymmetry of electron tunneling.

  5. Research on ponderomotive driven Vlasov–Poisson system in electron acoustic wave parametric region

    SciTech Connect

    Xiao, C. Z.; Huang, T. W.; Liu, Z. J.; Zheng, C. Y.; He, X. T.; Qiao, B.

    2014-03-15

    Theoretical analysis and corresponding 1D Particle-in-Cell (PIC) simulations of ponderomotive driven Vlasov–Poisson system in electron acoustic wave (EAW) parametric region are demonstrated. Theoretical analysis identifies that under the resonant condition, a monochromatic EAW can be excited when the wave number of the drive ponderomotive force satisfies 0.26≲k{sub d}λ{sub D}≲0.53. If k{sub d}λ{sub D}≲0.26, nonlinear superposition of harmonic waves can be resonantly excited, called kinetic electrostatic electron nonlinear waves. Numerical simulations have demonstrated these wave excitation and evolution dynamics, in consistence with the theoretical predictions. The physical nature of these two waves is supposed to be interaction of harmonic waves, and their similar phase space properties are also discussed.

  6. Linear excitation of the trapped waves by an incident wave

    NASA Astrophysics Data System (ADS)

    Postacioglu, Nazmi; Sinan Özeren, M.

    2016-04-01

    The excitation of the trapped waves by coastal events such as landslides has been extensively studied. The events in the open sea have in general larger magnitude. However the incident waves produced by these events in the open sea can only excite the the trapped waves through no linearity if the isobaths are straight lines that are in parallel with the coastline. We will show that the imperfections of the coastline can couple the incident and trapped waves using only linear processes. The Coriolis force is neglected in this work . Accordingly the trapped waves are consequence of uneven bathimetry. In the bathimetry we consider, the sea is divided into zones of constant depth and the boundaries between the zones are a family of hyperbolas. The boundary conditions between the zones will lead to an integral equation for the source distribution on the boundaries. The solution will contain both radiating and trapped waves. The trapped waves pose a serious threat for the coastal communities as they can travel long distances along the coastline without losing their energy through geometrical spreading.

  7. Interfacial destabilization and atomization driven by surface acoustic waves

    NASA Astrophysics Data System (ADS)

    Qi, Aisha; Yeo, Leslie Y.; Friend, James R.

    2008-07-01

    Surface acoustic wave atomization is a rapid means for generating micron and submicron aerosol droplets. Little, however, is understood about the mechanisms by which these droplets form due to the complex hydrodynamic processes that occur across widely varying length and time scales. Through experiments, scaling theory, and simple numerical modeling, we elucidate the interfacial destabilization mechanisms that lead to droplet formation. Using a millimeter-order fluid drop exposed to surface acoustic waves as it sits atop a single-crystal lithium niobate piezoelectric substrate, large aerosol droplets on the length scale of the parent drop dimension are ejected through a whipping and pinch-off phenomenon, which occurs at the asymmetrically formed crest of the drop due to leakage of acoustic radiation at the Rayleigh angle. Smaller micron order droplets, on the other hand, are formed due to the axisymmetric breakup of cylindrical liquid jets that are ejected as a consequence of interfacial destabilization. The 10μm droplet dimension correlates with the jet radius and the instability wavelength, both determined from a simple scaling argument involving a viscous-capillary dominant force balance. The results are further supported by numerical solution of the evolution equation governing the interfacial profile of a sessile drop along which an acoustic pressure wave is imposed. Viscous and capillary forces dominate in the bulk of the parent drop, but inertia is dominant in the ejected jets and within a thin boundary layer adjacent to the substrate where surface and interfacial accelerations are large. With the specific exception of parent drops that spread into thin films with thicknesses on the order of the boundary layer dimension prior to atomization, the free surface of the drop is always observed to vibrate at the capillary-viscous resonance frequency—even if the exciting frequency of the surface acoustic wave is several orders of magnitude larger—contrary to

  8. Acoustic field distribution of sawtooth wave with nonlinear SBE model

    SciTech Connect

    Liu, Xiaozhou Zhang, Lue; Wang, Xiangda; Gong, Xiufen

    2015-10-28

    For precise prediction of the acoustic field distribution of extracorporeal shock wave lithotripsy with an ellipsoid transducer, the nonlinear spheroidal beam equations (SBE) are employed to model acoustic wave propagation in medium. To solve the SBE model with frequency domain algorithm, boundary conditions are obtained for monochromatic and sawtooth waves based on the phase compensation. In numerical analysis, the influence of sinusoidal wave and sawtooth wave on axial pressure distributions are investigated.

  9. Chemotaxis to Excitable Waves in Dictyostelium Discoideum

    NASA Astrophysics Data System (ADS)

    Bhowmik, Arpan; Rappel, Wouter-Jan; Levine, Herbert

    In recent years, there have been significant advances in our understanding of the mechanisms underlying chemically directed motility by eukaryotic cells such as Dictyostelium. In particular, the LEGI model has proven capable of providing a framework for quantitatively explaining many experiments that present Dictyostelium cells with tailored chemical stimuli and monitor their subsequent polarization. Here, we couple the LEGI approach to an excitable medium model of the cAMP wave-field that is self-generated by the cells and investigate the extent to which this class of models enables accurate chemotaxis to the cAMP waveforms expected in vivo. Our results indicate that the ultra-sensitive version of the model does an excellent job in providing natural wave rectification, thereby providing a compelling solution to the ``back-of-the-wave paradox'' during cellular aggregation. This work was supported by National Institutes of Health Grant P01 GM078586.

  10. Instability of interfaces of gas bubbles in liquids under acoustic excitation with dual frequency.

    PubMed

    Zhang, Yuning; Du, Xiaoze; Xian, Haizhen; Wu, Yulin

    2015-03-01

    Instability of interfaces of gas bubbles in liquids under acoustic excitation with dual frequency is theoretically investigated. The critical bubble radii dividing stable and unstable regions of bubbles under dual-frequency acoustic excitation are strongly affected by the amplitudes of dual-frequency acoustic excitation rather than the frequencies of dual-frequency excitation. The limitation of the proposed model is also discussed with demonstrating examples.

  11. Coupling of an acoustic wave to shear motion due to viscous heating

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Goree, J.

    2016-07-01

    Viscous heating due to shear motion in a plasma can result in the excitation of a longitudinal acoustic wave, if the shear motion is modulated in time. The coupling mechanism is a thermal effect: time-dependent shear motion causes viscous heating, which leads to a rarefaction that can couple into a longitudinal wave, such as an acoustic wave. This coupling mechanism is demonstrated in an electrostatic three-dimensional (3D) simulation of a dusty plasma, in which a localized shear flow is initiated as a pulse, resulting in a delayed outward propagation of a longitudinal acoustic wave. This coupling effect can be profound in plasmas that exhibit localized viscous heating, such as the dusty plasma we simulated using parameters typical of the PK-4 experiment. We expect that a similar phenomenon can occur with other kinds of plasma waves.

  12. Observation of dust acoustic shock wave in a strongly coupled dusty plasma

    NASA Astrophysics Data System (ADS)

    Sharma, Sumita K.; Boruah, A.; Nakamura, Y.; Bailung, H.

    2016-05-01

    Dust acoustic shock wave is observed in a strongly coupled laboratory dusty plasma. A supersonic flow of charged microparticles is allowed to perturb a stationary dust fluid to excite dust acoustic shock wave. The evolution process beginning with steepening of initial wave front and then formation of a stable shock structure is similar to the numerical results of the Korteweg-de Vries-Burgers equation. The measured Mach number of the observed shock wave agrees with the theoretical results. Reduction of shock amplitude at large distances is also observed due to the dust neutral collision and viscosity effects. The dispersion relation and the spatial damping of a linear dust acoustic wave are also measured and compared with the relevant theory.

  13. Acoustic clouds: Standing sound waves around a black hole analogue

    NASA Astrophysics Data System (ADS)

    Benone, Carolina L.; Crispino, Luís C. B.; Herdeiro, Carlos; Radu, Eugen

    2015-05-01

    Under certain conditions sound waves in fluids experience an acoustic horizon with analogue properties to those of a black hole event horizon. In particular, a draining bathtub-like model can give rise to a rotating acoustic horizon and hence a rotating black hole (acoustic) analogue. We show that sound waves, when enclosed in a cylindrical cavity, can form stationary waves around such rotating acoustic holes. These acoustic perturbations display similar properties to the scalar clouds that have been studied around Kerr and Kerr-Newman black holes; thus they are dubbed acoustic clouds. We make the comparison between scalar clouds around Kerr black holes and acoustic clouds around the draining bathtub explicit by studying also the properties of scalar clouds around Kerr black holes enclosed in a cavity. Acoustic clouds suggest the possibility of testing, experimentally, the existence and properties of black hole clouds, using analog models.

  14. Dual-mode acoustic wave biosensors microarrays

    NASA Astrophysics Data System (ADS)

    Auner, Gregory W.; Shreve, Gina; Ying, Hao; Newaz, Golam; Hughes, Chantelle; Xu, Jianzeng

    2003-04-01

    We have develop highly sensitive and selective acoustic wave biosensor arrays with signal analysis systems to provide a fingerprint for the real-time identification and quantification of a wide array of bacterial pathogens and environmental health hazards. We have developed an unique highly sensitive dual mode acoustic wave platform prototype that, when combined with phage based selective detection elements, form a durable bacteria sensor. Arrays of these new real-time biosensors are integrated to form a biosensor array on a chip. This research and development program optimizes advanced piezoelectric aluminum nitride wide bandgap semiconductors, novel micromachining processes, advanced device structures, selective phage displays development and immobilization techniques, and system integration and signal analysis technology to develop the biosensor arrays. The dual sensor platform can be programmed to sense in a gas, vapor or liquid environment by switching between acoustic wave resonate modes. Such a dual mode sensor has tremendous implications for applications involving monitoring of pathogenic microorganisms in the clinical setting due to their ability to detect airborne pathogens. This provides a number of applications including hospital settings such as intensive care or other in-patient wards for the reduction of nosocomial infections and maintenance of sterile environments in surgical suites. Monitoring for airborn pathogen transmission in public transportation areas such as airplanes may be useful for implementation of strategies for redution of airborn transmission routes. The ability to use the same sensor in the liquid sensing mode is important for tracing the source of airborn pathogens to local liquid sources. Sensing of pathogens in saliva will be useful for sensing oral pathogens and support of decision-making strategies regarding prevention of transmission and support of treatment strategies.

  15. Acoustic excitation of liquid fuel droplets and coaxial jets

    NASA Astrophysics Data System (ADS)

    Rodriguez, Juan Ignacio

    This experimental study focuses on two important problems relevant to acoustic coupling with condensed phase transport processes, with special relevance to liquid rocket engine and airbreathing engine combustion instabilities. The first part of this dissertation describes droplet combustion characteristics of various fuels during exposure to external acoustical perturbations. Methanol, ethanol, a liquid synthetic fuel derived from coal gasification via the Fischer-Tropsch process, and a blend of aviation fuel and the synthetic fuel are used. During acoustic excitation, the droplet is situated at or near a pressure node condition, where the droplet experiences the largest velocity perturbations, and at or near a pressure antinode condition, where the droplet is exposed to minimal velocity fluctuations. For unforced conditions, the values of the droplet burning rate constant K of the different fuels are consistent with data in the literature. The location of the droplet with respect to a pressure node or antinode also has a measurable effect on droplet burning rates, which are different for different fuels and in some cases are as high as 28% above the unforced burning rate value. Estimates of flame extinction due to acoustic forcing for different fuels are also obtained. The second part of this work consists of an experimental study on coaxial jet behavior under non-reactive, cryogenic conditions, with direct applications to flow mixing and unstable behavior characterization in liquid rocket engines. These experiments, conducted with nitrogen, span a range of outer to inner jet momentum flux ratios from 0.013 to 23, and explore subcritical, nearcritical and supercritical pressure conditions, with and without acoustic excitation, for two injector geometries. Acoustic forcing at 3 kHz is utilized to maximize the pressure fluctuations within the chamber acting on the jet, reaching maximum values of 4% of the mean chamber pressure. The effect of the magnitude and phase

  16. Surface acoustic wave propagation in graphene film

    SciTech Connect

    Roshchupkin, Dmitry Plotitcyna, Olga; Matveev, Viktor; Kononenko, Oleg; Emelin, Evgenii; Irzhak, Dmitry; Ortega, Luc; Zizak, Ivo; Erko, Alexei; Tynyshtykbayev, Kurbangali; Insepov, Zinetula

    2015-09-14

    Surface acoustic wave (SAW) propagation in a graphene film on the surface of piezoelectric crystals was studied at the BESSY II synchrotron radiation source. Talbot effect enabled the visualization of the SAW propagation on the crystal surface with the graphene film in a real time mode, and high-resolution x-ray diffraction permitted the determination of the SAW amplitude in the graphene/piezoelectric crystal system. The influence of the SAW on the electrical properties of the graphene film was examined. It was shown that the changing of the SAW amplitude enables controlling the magnitude and direction of current in graphene film on the surface of piezoelectric crystals.

  17. Nonextensive dust-acoustic solitary waves

    SciTech Connect

    Tribeche, M.; Merriche, A.

    2011-03-15

    The seminal paper of Mamun et al. [Phys. Plasmas 3, 702 (1996)] is revisited within the theoretical framework of the Tsallis statistical mechanics. The nonextensivity may originate from the correlation or long-range interactions in the dusty plasma. It is found that depending on whether the nonextensive parameter q is positive or negative, the dust-acoustic (DA) soliton exhibits compression for q<0 and rarefaction for q>0. The lower limit of the Mach number for the existence of DA solitary waves is greater (smaller) than its Maxwellian counterpart in the case of superextensivity (subextensivity).

  18. Twisted dust acoustic waves in dusty plasmas

    SciTech Connect

    Shukla, P. K.

    2012-08-15

    We examine linear dust acoustic waves (DAWs) in a dusty plasma with strongly correlated dust grains, and discuss possibility of a twisted DA vortex beam carrying orbital angular momentum (OAM). For our purposes, we use the Boltzmann distributed electron and ion density perturbations, the dust continuity and generalized viscoelastic dust momentum equations, and Poisson's equation to obtain a dispersion relation for the modified DAWs. The effects of the polarization force, strong dust couplings, and dust charge fluctuations on the DAW spectrum are examined. Furthermore, we demonstrate that the DAW can propagate as a twisted vortex beam carrying OAM. A twisted DA vortex structure can trap and transport dust particles in dusty plasmas.

  19. Acoustic microfluidics: Capillary waves and vortex currents in a spherical fluid drop

    NASA Astrophysics Data System (ADS)

    Lebedev-Stepanov, P. V.; Rudenko, O. V.

    2016-07-01

    We calculate the radiation forces in a spherical drop lying on a solid substrate. The forces form as a result of the action of a capillary wave on a fluid as it propagates along the free spherical surface. We study the structure of acoustic currents excited by the radiation forces.

  20. Simulating acoustic waves in spotted stars

    NASA Astrophysics Data System (ADS)

    Papini, Emanuele; Birch, Aaron C.; Gizon, Laurent; Hanasoge, Shravan M.

    2015-05-01

    Acoustic modes of oscillation are affected by stellar activity, however it is unclear how starspots contribute to these changes. Here we investigate the nonmagnetic effects of starspots on global modes with angular degree ℓ ≤ 2 in highly active stars, and characterize the spot seismic signature on synthetic light curves. We perform 3D time-domain simulations of linear acoustic waves to study their interaction with a model starspot. We model the spot as a 3D change in the sound speed stratification with respect to a convectively stable stellar background, built from solar Model S. We perform a parametric study by considering different depths and perturbation amplitudes. Exact numerical simulations allow the investigation of the wavefield-spot interaction beyond first order perturbation theory. The interaction of the axisymmetric modes with the starspot is strongly nonlinear. As mode frequency increases, the frequency shifts for radial modes exceed the value predicted by linear theory, while the shifts for the ℓ = 2,m = 0 modes are smaller than predicted by linear theory, with avoided-crossing-like patterns forming between the m = 0 and m = 1 mode frequencies. The nonlinear behavior increases with increasing spot amplitude and/or decreasing depth. Linear theory still reproduces the correct shifts for nonaxisymmetric modes. In the nonlinear regime the mode eigenfunctions are not pure spherical harmonics, but rather a mixture of different spherical harmonics. This mode mixing, together with the frequency changes, may lead to misidentification of the modes in the observed acoustic power spectra.

  1. Microfluidic plug steering using surface acoustic waves.

    PubMed

    Sesen, Muhsincan; Alan, Tuncay; Neild, Adrian

    2015-07-21

    Digital microfluidic systems, in which isolated droplets are dispersed in a carrier medium, offer a method to study biological assays and chemical reactions highly efficiently. However, it's challenging to manipulate these droplets in closed microchannel devices. Here, we present a method to selectively steer plugs (droplets with diameters larger than the channel's width) at a specially designed Y-junction within a microfluidic chip. The method makes use of surface acoustic waves (SAWs) impinging on a multiphase interface in which an acoustic contrast is present. As a result, the liquid-liquid interface is subjected to acoustic radiation forces. These forces are exploited to steer plugs into selected branches of the Y-junction. Furthermore, the input power can be finely tuned to split a plug into two uneven plugs. The steering of plugs as a whole, based on plug volume and velocity is thoroughly characterized. The results indicate that there is a threshold plug volume after which the steering requires elevated electrical energy input. This plug steering method can easily be integrated to existing lab-on-a-chip devices and it offers a robust and active plug manipulation technique in closed microchannels.

  2. Microfluidic plug steering using surface acoustic waves.

    PubMed

    Sesen, Muhsincan; Alan, Tuncay; Neild, Adrian

    2015-07-21

    Digital microfluidic systems, in which isolated droplets are dispersed in a carrier medium, offer a method to study biological assays and chemical reactions highly efficiently. However, it's challenging to manipulate these droplets in closed microchannel devices. Here, we present a method to selectively steer plugs (droplets with diameters larger than the channel's width) at a specially designed Y-junction within a microfluidic chip. The method makes use of surface acoustic waves (SAWs) impinging on a multiphase interface in which an acoustic contrast is present. As a result, the liquid-liquid interface is subjected to acoustic radiation forces. These forces are exploited to steer plugs into selected branches of the Y-junction. Furthermore, the input power can be finely tuned to split a plug into two uneven plugs. The steering of plugs as a whole, based on plug volume and velocity is thoroughly characterized. The results indicate that there is a threshold plug volume after which the steering requires elevated electrical energy input. This plug steering method can easily be integrated to existing lab-on-a-chip devices and it offers a robust and active plug manipulation technique in closed microchannels. PMID:26079216

  3. The secondary Bjerknes force between two gas bubbles under dual-frequency acoustic excitation.

    PubMed

    Zhang, Yuning; Zhang, Yuning; Li, Shengcai

    2016-03-01

    The secondary Bjerknes force is one of the essential mechanisms of mutual interactions between bubbles oscillating in a sound field. The dual-frequency acoustic excitation has been applied in several fields such as sonochemistry, biomedicine and material engineering. In this paper, the secondary Bjerknes force under dual-frequency excitation is investigated both analytically and numerically within a large parameter zone. The unique characteristics (i.e., the complicated patterns of the parameter zone for sign change and the combination resonances) of the secondary Bjerknes force under dual-frequency excitation are revealed. Moreover, the influence of several parameters (e.g., the pressure amplitude, the bubble distance and the phase difference between sound waves) on the secondary Bjerknes force is also investigated numerically.

  4. Solar wind implication on dust ion acoustic rogue waves

    NASA Astrophysics Data System (ADS)

    Abdelghany, A. M.; Abd El-Razek, H. N.; Moslem, W. M.; El-Labany, S. K.

    2016-06-01

    The relevance of the solar wind with the magnetosphere of Jupiter that contains positively charged dust grains is investigated. The perturbation/excitation caused by streaming ions and electron beams from the solar wind could form different nonlinear structures such as rogue waves, depending on the dominant role of the plasma parameters. Using the reductive perturbation method, the basic set of fluid equations is reduced to modified Korteweg-de Vries (KdV) and further modified (KdV) equation. Assuming that the frequency of the carrier wave is much smaller than the ion plasma frequency, these equations are transformed into nonlinear Schrödinger equations with appropriate coefficients. Rational solution of the nonlinear Schrödinger equation shows that rogue wave envelopes are supported by the present plasma model. It is found that the existence region of rogue waves depends on the dust-acoustic speed and the streaming temperatures for both the ions and electrons. The dependence of the maximum rogue wave envelope amplitude on the system parameters has been investigated.

  5. Porous silicon bulk acoustic wave resonator with integrated transducer

    PubMed Central

    2012-01-01

    We report that porous silicon acoustic Bragg reflectors and AlN-based transducers can be successfully combined and processed in a commercial solidly mounted resonator production line. The resulting device takes advantage of the unique acoustic properties of porous silicon in order to form a monolithically integrated bulk acoustic wave resonator. PMID:22776697

  6. Excited and enhanced twinborn acoustic-induced mutual forces in oblique grating structures

    NASA Astrophysics Data System (ADS)

    Lu, Shuifang; Zhang, Xin; Wu, Fugen; Yao, Yuanwei; Chen, Zongwang

    2016-07-01

    We propose a water-immersed geometrically oblique grating structure patterned with a 1D periodic array of oblique rhombuses. Twin acoustic-induced mutual forces (both repulsive and attractive) between coupled steel plates were realized in this system when the external plane wave normally impacted the plates. Calculations showed that the emerging forces are more than an order of magnitude larger than the corresponding induced force of a conventional grating structure. We also found that the strong acoustic-induced mutual forces stem from the resonant excitation of nonleaky flexural Lamb modes in the coupled plates, and that these forces couple more strongly with the external incident acoustic waves. Furthermore, the amplitudes and resonant wavelengths of these forces can be coarsely controlled by changing the symmetry of the system and finely adjusted by varying the slant angle and the edge-length of the oblique rhombus. The proposed acoustic system could potentially be applied in sensors and in the ultrasonic detection of weak signals in water.

  7. Waves Excited by Noise: Applications to Helioseismology and Beyond

    NASA Astrophysics Data System (ADS)

    Duvall, Thomas L.

    2014-06-01

    The vigorous granular convection just beneath the solar photosphere excites acoustic waves. The resultant normal modes of the whole Sun are analogous to the ringing of a bell in a sandstorm. In classical helioseismology, the normal modes are used to study global solar properties, including the sound speed versus radius throughout the Sun and the rotation rate versus depth and latitude in the outer half of the Sun. But solar astronomers wished to better understand the subphotospheric 3-d structure of smaller scale features observed in the photosphere and were hence not satisfied studying only these global properties. One would like to have something akin to seismology, in which the waves from an earthquake traveling from a source through the interior to a distant receiver depend only on the properties along the path. However, the random nature of the solar convective wave sources generally prevents such a simple analogy. It was discovered that the temporal cross correlation of the solar oscillation signal between two locations averaged over many wave periods does mostly contain information about the properties along the path connecting the two locations. This discovery is the basis for time-distance helioseismology, in which travel times are extracted from the temporal cross correlations and mapped for different pairs of locations on the solar surface. A subsequent 3-d tomography aims to map the solar interior. This technique has been used to study the depth variation of a variety of solar photospheric features from small spatial scales (granulation) to larger scales (sunspots and supergranulation) to the largest scales (meridional circulation and rotation). The technique of temporal cross correlation of noise signals from two locations has subsequently been adopted successfully in a number of other fields including seismology, ultrasound, infrasound, ocean acoustics, structural engineering, lunar seismology, and medical diagnostics.

  8. Excitation of turbulence by density waves

    NASA Technical Reports Server (NTRS)

    Tichen, C. M.

    1985-01-01

    A nonlinear system describes the microdynamical state of turbulence that is excited by density waves. It consists of an equation of propagation and a master equation. A group-scaling generates the scaled equations of many interacting groups of distribution functions. The two leading groups govern the transport processes of evolution and eddy diffusivity. The remaining sub-groups represent the relaxation for the approach of diffusivity to equilibrium. In strong turbulence, the sub-groups disperse themselves and the ensemble acts like a medium that offers an effective damping to close the hierarchy. The kinetic equation of turbulence is derived. It calculates the eddy viscosity and identifies the effective damping of the assumed medium self-consistently. It formulates the coupling mechanism for the intensification of the turbulent energy at the expense of the wave energy, and the transfer mechanism for the cascade. The spectra of velocity and density fluctuations find the power law k sup-2 and k sup-4, respectively.

  9. Fast excitation of geodesic acoustic mode by energetic particle beams

    SciTech Connect

    Cao, Jintao; Qiu, Zhiyong; Zonca, Fulvio

    2015-12-15

    A new mechanism for geodesic acoustic mode (GAM) excitation by a not fully slowed down energetic particle (EP) beam is analyzed to explain experimental observations in Large Helical Device. It is shown that the positive velocity space gradient near the lower-energy end of the EP distribution function can strongly drive the GAM unstable. The new features of this EP-induced GAM (EGAM) are: (1) no instability threshold in the pitch angle; (2) the EGAM frequency can be higher than the local GAM frequency; and (3) the instability growth rate is much larger than that driven by a fully slowed down EP beam.

  10. Helioseismology and asteroseismology: looking for gravitational waves in acoustic oscillations

    SciTech Connect

    Lopes, Ilídio; Silk, Joseph E-mail: ilopes@uevora.pt

    2014-10-10

    Current helioseismology observations allow the determination of the frequencies and surface velocity amplitudes of solar acoustic modes with exceptionally high precision. In some cases, the frequency accuracy is better than one part in a million. We show that there is a distinct possibility that quadrupole acoustic modes of low order could be excited by gravitational waves (GWs), if the GWs have a strain amplitude in the range 10{sup –20} h {sub –20} with h {sub –20} ∼ 1 or h {sub –20} ∼ 10{sup 3}, as predicted by several types of GW sources, such as galactic ultracompact binaries or extreme mass ratio inspirals and coalescence of black holes. If the damping rate at low order is 10{sup –3}η {sub N} μHz, with η {sub N} ∼ 10{sup –3}-1, as inferred from the theory of stellar pulsations, then GW radiation will lead to a maximum rms surface velocity amplitude of quadrupole modes of the order of h{sub −20}η{sub N}{sup −1}∼ 10{sup –9}-10{sup –3} cm s{sup –1}, on the verge of what is currently detectable via helioseismology. The frequency and sensitivity range probed by helioseismological acoustic modes overlap with, and complement, the capabilities of eLISA for the brightest resolved ultracompact galactic binaries.

  11. Helioseismology and Asteroseismology: Looking for Gravitational Waves in Acoustic Oscillations

    NASA Astrophysics Data System (ADS)

    Lopes, Ilídio; Silk, Joseph

    2014-10-01

    Current helioseismology observations allow the determination of the frequencies and surface velocity amplitudes of solar acoustic modes with exceptionally high precision. In some cases, the frequency accuracy is better than one part in a million. We show that there is a distinct possibility that quadrupole acoustic modes of low order could be excited by gravitational waves (GWs), if the GWs have a strain amplitude in the range 10-20 h -20 with h -20 ~ 1 or h -20 ~ 103, as predicted by several types of GW sources, such as galactic ultracompact binaries or extreme mass ratio inspirals and coalescence of black holes. If the damping rate at low order is 10-3η N μHz, with η N ~ 10-3-1, as inferred from the theory of stellar pulsations, then GW radiation will lead to a maximum rms surface velocity amplitude of quadrupole modes of the order of h_{-20}\\eta _N^{-1}\\sim 10-9-10-3 cm s-1, on the verge of what is currently detectable via helioseismology. The frequency and sensitivity range probed by helioseismological acoustic modes overlap with, and complement, the capabilities of eLISA for the brightest resolved ultracompact galactic binaries.

  12. Spatial selective manipulation of microbubbles by tunable surface acoustic waves

    PubMed Central

    Zhou, Wei; Niu, Lili; Cai, Feiyan; Li, Fei; Wang, Chen; Huang, Xiaowei; Wang, Jingjing; Wu, Junru; Meng, Long; Zheng, Hairong

    2016-01-01

    A microfluidic device based on a pair of slant-finger interdigital transducers (SFITs) is developed to achieve a selective and flexible manipulation of microbubbles (MBs) by surface acoustic waves (SAWs). The resonance frequency of SAWs generated by the SFITs depends on the location of its parallel pathway; the particles at different locations of the SAWs' pathway can be controlled selectively by choosing the frequency of the excitation signal applied on the SFITs. By adjusting the input signal continuously, MBs can be transported along the acoustic aperture precisely. The displacement of MBs has a linear relationship with the frequency shift. The resolution of transportation is 15.19 ± 2.65 μm when the shift of input signal frequency is at a step of 10 kHz. In addition, the MBs can be controlled in a two-dimensional plane by combining variations of the frequency and the relative phase of the excitation signal applied on the SFITs simultaneously. This technology may open up the possibility of selectively and flexibly manipulating MBs using a simple one-dimensional device. PMID:27462381

  13. MODE CONVERSION BETWEEN DIFFERENT RADIAL ORDERS FOR SOLAR ACOUSTIC WAVES SCATTERED BY SUNSPOTS

    SciTech Connect

    Zhao, Hui; Chou, Dean-Yi

    2013-11-20

    We study the mode conversion between different radial orders for solar acoustic waves interacting with sunspots. Solar acoustic waves are modified in the presence of sunspots. The modification in the wave can be viewed as that the sunspot, excited by the incident wave, generates the scattered wave, and the scattered wave is added to the incident wave to form the total wave inside and around the sunspot. The wavefunction of the acoustic wave on the solar surface is computed from the cross-correlation function. The wavefunction of the scattered wave is obtained by subtracting the wavefunction of the incident wave from that of the total wave. We use the incident waves of radial order n = 0-5 to measure the scattered wavefunctions from n to another radial order n' for NOAAs 11084 and 11092. The strength of scattered waves decreases rapidly with |Δn|, where Δn ≡ n' – n. The scattered waves of Δn = ±1 are visible for n ≤ 1, and significant for n ≥ 2. For the scattered wave of Δn = ±2, only few cases are visible. None of the scattered waves of Δn = ±3 are visible. The properties of scattered waves for Δn = 0 and Δn ≠ 0 are different. The scattered wave amplitude relative to the incident wave amplitude decreases with n for Δn = 0, while it increases with n for Δn ≠ 0. The scattered wave amplitudes of Δn = 0 are greater for the larger sunspot, while those of Δn ≠ 0 are insensitive to the sunspot size.

  14. A conductive liquid-based surface acoustic wave device.

    PubMed

    Nam, Jeonghun; Lim, Chae Seung

    2016-10-01

    Surface acoustic wave-based microfluidic devices are popular for fluid and particle manipulation because of their noninvasiveness, low energy consumption, and easy integration with other systems. However, they have been limited by the use of patterned metal electrodes on a piezoelectric substrate, which requires expensive and complicated fabrication processes. Herein, we show a simpler and more cost-effective method for generating surface acoustic waves using eutectic gallium indium as a conductive liquid which can replace conventional patterned metal electrodes. We also demonstrate the comparable performance for acoustic streaming and mixing using conductive liquid-based surface acoustic wave devices. PMID:27528442

  15. A conductive liquid-based surface acoustic wave device.

    PubMed

    Nam, Jeonghun; Lim, Chae Seung

    2016-10-01

    Surface acoustic wave-based microfluidic devices are popular for fluid and particle manipulation because of their noninvasiveness, low energy consumption, and easy integration with other systems. However, they have been limited by the use of patterned metal electrodes on a piezoelectric substrate, which requires expensive and complicated fabrication processes. Herein, we show a simpler and more cost-effective method for generating surface acoustic waves using eutectic gallium indium as a conductive liquid which can replace conventional patterned metal electrodes. We also demonstrate the comparable performance for acoustic streaming and mixing using conductive liquid-based surface acoustic wave devices.

  16. Wave envelopes method for description of nonlinear acoustic wave propagation.

    PubMed

    Wójcik, J; Nowicki, A; Lewin, P A; Bloomfield, P E; Kujawska, T; Filipczyński, L

    2006-07-01

    A novel, free from paraxial approximation and computationally efficient numerical algorithm capable of predicting 4D acoustic fields in lossy and nonlinear media from arbitrary shaped sources (relevant to probes used in medical ultrasonic imaging and therapeutic systems) is described. The new WE (wave envelopes) approach to nonlinear propagation modeling is based on the solution of the second order nonlinear differential wave equation reported in [J. Wójcik, J. Acoust. Soc. Am. 104 (1998) 2654-2663; V.P. Kuznetsov, Akust. Zh. 16 (1970) 548-553]. An incremental stepping scheme allows for forward wave propagation. The operator-splitting method accounts independently for the effects of full diffraction, absorption and nonlinear interactions of harmonics. The WE method represents the propagating pulsed acoustic wave as a superposition of wavelet-like sinusoidal pulses with carrier frequencies being the harmonics of the boundary tone burst disturbance. The model is valid for lossy media, arbitrarily shaped plane and focused sources, accounts for the effects of diffraction and can be applied to continuous as well as to pulsed waves. Depending on the source geometry, level of nonlinearity and frequency bandwidth, in comparison with the conventional approach the Time-Averaged Wave Envelopes (TAWE) method shortens computational time of the full 4D nonlinear field calculation by at least an order of magnitude; thus, predictions of nonlinear beam propagation from complex sources (such as phased arrays) can be available within 30-60 min using only a standard PC. The approximate ratio between the computational time costs obtained by using the TAWE method and the conventional approach in calculations of the nonlinear interactions is proportional to 1/N2, and in memory consumption to 1/N where N is the average bandwidth of the individual wavelets. Numerical computations comparing the spatial field distributions obtained by using both the TAWE method and the conventional approach

  17. Wave envelopes method for description of nonlinear acoustic wave propagation.

    PubMed

    Wójcik, J; Nowicki, A; Lewin, P A; Bloomfield, P E; Kujawska, T; Filipczyński, L

    2006-07-01

    A novel, free from paraxial approximation and computationally efficient numerical algorithm capable of predicting 4D acoustic fields in lossy and nonlinear media from arbitrary shaped sources (relevant to probes used in medical ultrasonic imaging and therapeutic systems) is described. The new WE (wave envelopes) approach to nonlinear propagation modeling is based on the solution of the second order nonlinear differential wave equation reported in [J. Wójcik, J. Acoust. Soc. Am. 104 (1998) 2654-2663; V.P. Kuznetsov, Akust. Zh. 16 (1970) 548-553]. An incremental stepping scheme allows for forward wave propagation. The operator-splitting method accounts independently for the effects of full diffraction, absorption and nonlinear interactions of harmonics. The WE method represents the propagating pulsed acoustic wave as a superposition of wavelet-like sinusoidal pulses with carrier frequencies being the harmonics of the boundary tone burst disturbance. The model is valid for lossy media, arbitrarily shaped plane and focused sources, accounts for the effects of diffraction and can be applied to continuous as well as to pulsed waves. Depending on the source geometry, level of nonlinearity and frequency bandwidth, in comparison with the conventional approach the Time-Averaged Wave Envelopes (TAWE) method shortens computational time of the full 4D nonlinear field calculation by at least an order of magnitude; thus, predictions of nonlinear beam propagation from complex sources (such as phased arrays) can be available within 30-60 min using only a standard PC. The approximate ratio between the computational time costs obtained by using the TAWE method and the conventional approach in calculations of the nonlinear interactions is proportional to 1/N2, and in memory consumption to 1/N where N is the average bandwidth of the individual wavelets. Numerical computations comparing the spatial field distributions obtained by using both the TAWE method and the conventional approach

  18. Selection of Spiral Waves in Excitable Media with a Phase Wave at the Wave Back

    NASA Astrophysics Data System (ADS)

    Zykov, V. S.; Oikawa, N.; Bodenschatz, E.

    2011-12-01

    Universal relationships between the medium excitability and the angular velocity and the core radius of rigidly rotating spiral waves in excitable media are derived for situations where the wave front is a trigger wave and the wave back is a phase wave. Two universal limits restricting the region of existence of spiral waves in the parameter space are demonstrated. The predictions of the free-boundary approach are in good quantitative agreement with results from numerical reaction-diffusion simulations performed on the Kessler-Levine model.

  19. A four-quadrant PVDF transducer for surface acoustic wave detection.

    PubMed

    Lu, Zimo; Dorantes-Gonzalez, Dante J; Chen, Kun; Yang, Fei; Jin, Baoyin; Li, Yanning; Chen, Zhi; Hu, Xiaotang

    2012-01-01

    In this paper, a polyvinylidene fluoride (PVDF) piezoelectric transducer was developed to detect laser-induced surface acoustic waves in a SiO(2)-thin film-Si-substrate structure. In order to solve the problems related to, firstly, the position of the probe, and secondly, the fact that signals at different points cannot be detected simultaneously during the detection process, a four-quadrant surface acoustic wave PVDF transducer was designed and constructed for the purpose of detecting surface acoustic waves excited by a pulse laser line source. The experimental results of the four-quadrant piezoelectric detection in comparison with the commercial nanoindentation technology were consistent, the relative error is 0.56%, and the system eliminates the piezoelectric surface wave detection direction deviation errors, improves the accuracy of the testing system by 1.30%, achieving the acquisition at the same time at different testing positions of the sample. PMID:23112612

  20. Excitation of parametric instabilities by radio waves in the ionosphere.

    NASA Technical Reports Server (NTRS)

    Fejer, J. A.; Leer, E.

    1972-01-01

    The excitation of parametric instabilities by radio waves in a magnetoplasma is discussed. A uniform medium is assumed and linear approximations are used. Excitation by a pump wave of ordinary polarization is hardly affected by the magnetic field. Low or zero frequency ion waves and high frequency Langmuir waves are excited simultaneously. For an extraordinary pump wave, the excited high frequency electrostatic waves are in the Bernstein mode. The threshold is slightly higher and excitation can occur only within certain 'allowed' frequency bands. A new type of parametric instability in which the excited waves are electromagnetic in nature and which is more strongly affected by the inhomogeneous nature of the medium is discussed qualitatively.

  1. Excitation and propagation of exchange spin waves in films of yttrium iron garnet

    SciTech Connect

    Zil`berman, P.E.; Temiryazev, A.G.; Tikhomirova, M.P.

    1995-07-01

    We investigate resonant microwave absorption in films of yttrium iron garnet (YIG) with magneetic properties varying through the film thickness. Using measurements of the spin-wave resonant absorption spectra for two different directions of the external magnetic field, we calculate the profile of this nonuniformity. In our investigation of the response of nonuniform films to a pulsed microwave signal, we observed the appearance of delayed pulses, which we interpret to be the result of propagation of exchange spin waves transversely through the film. We analyze the dependence of the time delay on frequency for various nonuniformity profiles, and compare the data obtained with the results of experiment. Our investigation of the spin-wave resonance spectra, as well as the results of our pulsed measurements, show that propagation of spin waves is accompanied by the excitation of acoustic waves. We conclude that ferrite films that vary in the transverse direction can on the one hand be used to efficiently excite short-wavelength exchange spin waves with wave numbers 1{approximately}3 {center_dot}10{sup 5} cm{sup {minus}1}, and on the other hand to excite very high-frequency acoustic waves. 25 refs., 15 figs.

  2. Wave-wave interactions and deep ocean acoustics.

    PubMed

    Guralnik, Z; Bourdelais, J; Zabalgogeazcoa, X; Farrell, W E

    2013-10-01

    Deep ocean acoustics, in the absence of shipping and wildlife, is driven by surface processes. Best understood is the signal generated by non-linear surface wave interactions, the Longuet-Higgins mechanism, which dominates from 0.1 to 10 Hz, and may be significant for another octave. For this source, the spectral matrix of pressure and vector velocity is derived for points near the bottom of a deep ocean resting on an elastic half-space. In the absence of a bottom, the ratios of matrix elements are universal constants. Bottom effects vitiate the usual "standing wave approximation," but a weaker form of the approximation is shown to hold, and this is used for numerical calculations. In the weak standing wave approximation, the ratios of matrix elements are independent of the surface wave spectrum, but depend on frequency and the propagation environment. Data from the Hawaii-2 Observatory are in excellent accord with the theory for frequencies between 0.1 and 1 Hz, less so at higher frequencies. Insensitivity of the spectral ratios to wind, and presumably waves, is indeed observed in the data.

  3. Acoustic wave characterization of silicon phononic crystal plate

    NASA Astrophysics Data System (ADS)

    Feng, Duan; Jiang, Wanli; Xu, Dehui; Xiong, Bin; Wang, Yuelin

    2015-08-01

    In this paper, characterization of megahertz Lamb waves in a silicon phononic crystal based asymmetry filter by laser Doppler vibrometer is demonstrated. The acoustic power from a piezoelectric substrate was transmitted into the silicon superstrate by fluid coupling method, and measured results show that the displacement amplitude of the acoustic wave in the superstrate was approximately one fifth of that in the piezoelectric substrate. Effect of the phononic bandgap on the propagation of Lamb wave in the silicon superstrate is also measured, and the result shows that the phononic crystal structure could reflect part of the acoustic waves back.

  4. Comparison of acoustic and seismic excitation, propagation, and scattering at an air-ground interface containing a mine-like inclusion.

    PubMed

    Muir, Thomas G; Costley, R Daniel; Sabatier, James M

    2014-01-01

    Finite element methods are utilized to model and compare the use of both a remote loudspeaker and a vertical shaker in the generation of sound and shear and interface waves in an elastic solid containing an imbedded elastic scatterer, which is resonant. Results for steady state and transient insonification are presented to illustrate excitation, propagation, and scattering mechanisms and effects. Comparisons of acoustic and vibratory excitation of the solid interface are made, with a view towards remote sensing of induced vibratory motion through optical measurement of the ground interface motion above the imbedded inclusion. Some advantages of the acoustic excitation method for exciting plate mode resonances in the target are observed. PMID:24437744

  5. Comparison of acoustic and seismic excitation, propagation, and scattering at an air-ground interface containing a mine-like inclusion.

    PubMed

    Muir, Thomas G; Costley, R Daniel; Sabatier, James M

    2014-01-01

    Finite element methods are utilized to model and compare the use of both a remote loudspeaker and a vertical shaker in the generation of sound and shear and interface waves in an elastic solid containing an imbedded elastic scatterer, which is resonant. Results for steady state and transient insonification are presented to illustrate excitation, propagation, and scattering mechanisms and effects. Comparisons of acoustic and vibratory excitation of the solid interface are made, with a view towards remote sensing of induced vibratory motion through optical measurement of the ground interface motion above the imbedded inclusion. Some advantages of the acoustic excitation method for exciting plate mode resonances in the target are observed.

  6. Ion-acoustic cnoidal waves in a quantum plasma

    SciTech Connect

    Mahmood, S.; Haas, F.

    2014-10-15

    Nonlinear ion-acoustic cnoidal wave structures are studied in an unmagnetized quantum plasma. Using the reductive perturbation method, a Korteweg-de Vries equation is derived for appropriate boundary conditions and nonlinear periodic wave solutions are obtained. The corresponding analytical solution and numerical plots of the ion-acoustic cnoidal waves and solitons in the phase plane are presented using the Sagdeev pseudo-potential approach. The variations in the nonlinear potential of the ion-acoustic cnoidal waves are studied at different values of quantum parameter H{sub e} which is the ratio of electron plasmon energy to electron Fermi energy defined for degenerate electrons. It is found that both compressive and rarefactive ion-acoustic cnoidal wave structures are formed depending on the value of the quantum parameter. The dependence of the wavelength and frequency on nonlinear wave amplitude is also presented.

  7. Effect of Forcing Function on Nonlinear Acoustic Standing Waves

    NASA Technical Reports Server (NTRS)

    Finkheiner, Joshua R.; Li, Xiao-Fan; Raman, Ganesh; Daniels, Chris; Steinetz, Bruce

    2003-01-01

    Nonlinear acoustic standing waves of high amplitude have been demonstrated by utilizing the effects of resonator shape to prevent the pressure waves from entering saturation. Experimentally, nonlinear acoustic standing waves have been generated by shaking an entire resonating cavity. While this promotes more efficient energy transfer than a piston-driven resonator, it also introduces complicated structural dynamics into the system. Experiments have shown that these dynamics result in resonator forcing functions comprised of a sum of several Fourier modes. However, previous numerical studies of the acoustics generated within the resonator assumed simple sinusoidal waves as the driving force. Using a previously developed numerical code, this paper demonstrates the effects of using a forcing function constructed with a series of harmonic sinusoidal waves on resonating cavities. From these results, a method will be demonstrated which allows the direct numerical analysis of experimentally generated nonlinear acoustic waves in resonators driven by harmonic forcing functions.

  8. Raising Photoemission Efficiency with Surface Acoustic Waves

    SciTech Connect

    A. Afanasev, F. Hassani, C.E. Korman, V.G. Dudnikov, R.P. Johnson, M. Poelker, K.E.L. Surles-Law

    2012-07-01

    We are developing a novel technique that may help increase the efficiency and reduce costs of photoelectron sources used at electron accelerators. The technique is based on the use of Surface Acoustic Waves (SAW) in piezoelectric materials, such as GaAs, that are commonly used as photocathodes. Piezoelectric fields produced by the traveling SAW spatially separate electrons and holes, reducing their probability of recombination, thereby enhancing the photoemission quantum efficiency of the photocathode. Additional advantages could be increased polarization provided by the enhanced mobility of charge carriers that can be controlled by the SAW and the ionization of optically-generated excitons resulting in the creation of additional electron-hole pairs. It is expected that these novel features will reduce the cost of accelerator operation. A theoretical model for photoemission in the presence of SAW has been developed, and experimental tests of the technique are underway.

  9. Ionospheric acoustic and gravity waves associated with midlatitude thunderstorms

    SciTech Connect

    Lay, Erin H.; Shao, Xuan -Min; Kendrick, Alexander K.; Carrano, Charles S.

    2015-07-30

    Acoustic waves with periods of 2–4 min and gravity waves with periods of 6–16 min have been detected at ionospheric heights (25–350 km) using GPS total electron content measurements. The area disturbed by these waves and the wave amplitudes have been associated with underlying thunderstorm activity. A statistical study comparing Next Generation Weather Radar thunderstorm measurements with ionospheric acoustic and gravity waves in the midlatitude U.S. Great Plains region was performed for the time period of May–July 2005. An increase of ionospheric acoustic wave disturbed area and amplitude is primarily associated with large thunderstorms (mesoscale convective systems). Ionospheric gravity wave disturbed area and amplitude scale with thunderstorm activity, with even small storms (i.e., individual storm cells) producing an increase of gravity waves.

  10. Interactions between a spherical elastic shell and acoustic waves from a water-entry moving source

    NASA Astrophysics Data System (ADS)

    Lee, M.

    2004-05-01

    A possible interaction between the acoustic waves, which are generated from a water-entry body (moving source), and a submerged elastic shell is investigated theoretically within the scope of linear theory. The incident wave is defined from the ballistic wave model. The transient interaction is solved through extension of a method formulated for the excitation from a stationary source in an infinite domain. Numerical examples for the incident wave forms and corresponding shell responses are given to illustrate the effect of a moving source on the structure response.

  11. Reverberant Acoustic Testing and Direct Field Acoustic Testing Acoustic Standing Waves and their Impact on Structural Responses

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R.; Doty, Benjamin; Chang, Zensheu

    2012-01-01

    The aerospace industry has been using two methods of acoustic testing to qualify flight hardware: (1) Reverberant Acoustic Test (RAT), (2) Direct Field Acoustic Test (DFAT). The acoustic field obtained by RAT is generally understood and assumed to be diffuse, expect below Schroeder cut-of frequencies. DFAT method of testing has some distinct advantages over RAT, however the acoustic field characteristics can be strongly affected by test setup such as the speaker layouts, number and location of control microphones and control schemes. In this paper the following are discussed based on DEMO tests performed at APL and JPL: (1) Acoustic wave interference patterns and acoustic standing waves, (2) The structural responses in RAT and DFAT.

  12. Unstable resonators with excited converging wave

    SciTech Connect

    Hodgson, N. ); Weber, H. )

    1990-04-01

    This paper reports the properties of unstable resonators with an additional mirror inside or outside the resonator investigated, both experimentally and theoretically. The additional mirror excites the converging wave, and by this, output coupling is decreased without affecting beam quality. Experiments were performed with a pulsed Nd:YAG system. The theoretical model was based on the coupled Kirchhoff integrals and solved numerically. Agreement between theory and experiments indicates that this kind of resonator provides high focusability and maximum extraction efficiency simultaneously, even with low-gain media. This enables one to apply unstable resonators to solid-state lasers with low small-signal gain, like alexandrite or CW-pumped Nd:YAG.

  13. Generation of infrasonic waves by low-frequency dust acoustic perturbations in the Earth's lower ionosphere

    NASA Astrophysics Data System (ADS)

    Kopnin, S. I.; Popel, S. I.

    2008-06-01

    It is shown that, during Perseid, Geminid, Orionid, and Leonid meteor showers, the excitation of low-frequency dust acoustic perturbations by modulational instability in the Earth’s ionosphere can lead to the generation of infrasonic waves. The processes accompanying the propagation of these waves are considered, and the possibility of observing the waves from the Earth’s surface is discussed, as well as the possible onset of acoustic gravitational vortex structures in the region of dust acoustic perturbations. The generation of such structures during Perseid, Geminid, Orionid, and Leonid meteor showers can show up as an increase in the intensity of green nightglow by an amount on the order of 10% and can be attributed to the formation of nonlinear (vortex) structures at altitudes of 110-120 km.

  14. Generation of infrasonic waves by low-frequency dust acoustic perturbations in the Earth's lower ionosphere

    SciTech Connect

    Kopnin, S. I.; Popel, S. I.

    2008-06-15

    It is shown that, during Perseid, Geminid, Orionid, and Leonid meteor showers, the excitation of low-frequency dust acoustic perturbations by modulational instability in the Earth's ionosphere can lead to the generation of infrasonic waves. The processes accompanying the propagation of these waves are considered, and the possibility of observing the waves from the Earth's surface is discussed, as well as the possible onset of acoustic gravitational vortex structures in the region of dust acoustic perturbations. The generation of such structures during Perseid, Geminid, Orionid, and Leonid meteor showers can show up as an increase in the intensity of green nightglow by an amount on the order of 10% and can be attributed to the formation of nonlinear (vortex) structures at altitudes of 110-120 km.

  15. Picosecond x-ray strain rosette reveals direct laser excitation of coherent transverse acoustic phonons

    PubMed Central

    Lee, Sooheyong; Williams, G. Jackson; Campana, Maria I.; Walko, Donald A.; Landahl, Eric C.

    2016-01-01

    Using a strain-rosette, we demonstrate the existence of transverse strain using time-resolved x-ray diffraction from multiple Bragg reflections in laser-excited bulk gallium arsenide. We find that anisotropic strain is responsible for a considerable fraction of the total lattice motion at early times before thermal equilibrium is achieved. Our measurements are described by a new model where the Poisson ratio drives transverse motion, resulting in the creation of shear waves without the need for an indirect process such as mode conversion at an interface. Using the same excitation geometry with the narrow-gap semiconductor indium antimonide, we detected coherent transverse acoustic oscillations at frequencies of several GHz. PMID:26751616

  16. Picosecond x-ray strain rosette reveals direct laser excitation of coherent transverse acoustic phonons.

    PubMed

    Lee, Sooheyong; Williams, G Jackson; Campana, Maria I; Walko, Donald A; Landahl, Eric C

    2016-01-01

    Using a strain-rosette, we demonstrate the existence of transverse strain using time-resolved x-ray diffraction from multiple Bragg reflections in laser-excited bulk gallium arsenide. We find that anisotropic strain is responsible for a considerable fraction of the total lattice motion at early times before thermal equilibrium is achieved. Our measurements are described by a new model where the Poisson ratio drives transverse motion, resulting in the creation of shear waves without the need for an indirect process such as mode conversion at an interface. Using the same excitation geometry with the narrow-gap semiconductor indium antimonide, we detected coherent transverse acoustic oscillations at frequencies of several GHz. PMID:26751616

  17. Weakly nonlinear ion-acoustic excitations in a relativistic model for dense quantum plasma.

    PubMed

    Behery, E E; Haas, F; Kourakis, I

    2016-02-01

    The dynamics of linear and nonlinear ionic-scale electrostatic excitations propagating in a magnetized relativistic quantum plasma is studied. A quantum-hydrodynamic model is adopted and degenerate statistics for the electrons is taken into account. The dispersion properties of linear ion acoustic waves are examined in detail. A modified characteristic charge screening length and "sound speed" are introduced, for relativistic quantum plasmas. By employing the reductive perturbation technique, a Zakharov-Kuznetzov-type equation is derived. Using the small-k expansion method, the stability profile of weakly nonlinear slightly supersonic electrostatic pulses is also discussed. The effect of electron degeneracy on the basic characteristics of electrostatic excitations is investigated. The entire analysis is valid in a three-dimensional as well as in two-dimensional geometry. A brief discussion of possible applications in laboratory and space plasmas is included. PMID:26986431

  18. Picosecond x-ray strain rosette reveals direct laser excitation of coherent transverse acoustic phonons.

    PubMed

    Lee, Sooheyong; Williams, G Jackson; Campana, Maria I; Walko, Donald A; Landahl, Eric C

    2016-01-11

    Using a strain-rosette, we demonstrate the existence of transverse strain using time-resolved x-ray diffraction from multiple Bragg reflections in laser-excited bulk gallium arsenide. We find that anisotropic strain is responsible for a considerable fraction of the total lattice motion at early times before thermal equilibrium is achieved. Our measurements are described by a new model where the Poisson ratio drives transverse motion, resulting in the creation of shear waves without the need for an indirect process such as mode conversion at an interface. Using the same excitation geometry with the narrow-gap semiconductor indium antimonide, we detected coherent transverse acoustic oscillations at frequencies of several GHz.

  19. Stabilized wave segments in an excitable medium with a phase wave at the wave back

    NASA Astrophysics Data System (ADS)

    Zykov, V. S.; Bodenschatz, E.

    2014-04-01

    The propagation velocity and the shape of a stationary propagating wave segment are determined analytically for excitable media supporting excitation waves with trigger fronts and phase backs. The general relationships between the medium's excitability and the wave segment parameters are obtained in the framework of the free boundary approach under quite usual assumptions. Two universal limits restricting the region of existence of stabilized wave segments are found. The comparison of the analytical results with numerical simulations of the well-known Kessler-Levine model demonstrates their good quantitative agreement. The findings should be applicable to a wide class of systems, such as the propagation of electrical waves in the cardiac muscle or wave propagation in autocatalytic chemical reactions, due to the generality of the free-boundary approach used.

  20. Amplification of Pressure Waves during Vibrational Equilibration of Excited Chemical Reaction Products

    SciTech Connect

    Tarver, C M

    2004-05-11

    The Non-Equilibrium Zeldovich - von Neumann - Doring (NEZND) theory of self-sustaining detonation identified amplification of pressure wavelets during equilibration of vibrationally excited reaction products in the reaction zone as the physical mechanism by which exothermic chemical energy release sustains detonation waves. This mechanism leads to the formation of the well-known, complex three-dimensional structure of a self-sustaining detonation wave. This amplification mechanism is postulated to be a general property of subsonic and supersonic reactive flows occurring during: shock to detonation transition (SDT); hot spot ignition and growth; deflagration to detonation transition (DDT); flame acceleration by shock or compression waves; and acoustic (sound) wave amplification. The existing experimental and theoretical evidence for pressure wave amplification by chemical energy release into highly vibrationally excited product molecules under these reactive flow conditions is reviewed in this paper.

  1. Surface acoustic wave induced particle manipulation in a PDMS channel--principle concepts for continuous flow applications.

    PubMed

    Johansson, Linda; Enlund, Johannes; Johansson, Stefan; Katardjiev, Ilia; Yantchev, Ventsislav

    2012-04-01

    A device for acoustic particle manipulation in the 40 MHz range for continuous-flow operation in a 50 μm wide PDMS channel has been evaluated. Unidirectional interdigital transducers on a Y-cut Z-propagation lithium nixobate wafer were used to excite a surface acoustic wave that generated an acoustic standing wave inside the microfluidic channel. It was shown that particle alignment nodes with different inter-node spacing could be obtained, depending on device design and driving frequency. The observed inter-node spacing differed from the standard half-wavelength inter-node spacing generally employed in bulk acoustic transducer excited resonant systems. This effect and the related issue of acoustic node positions relative the channel walls, which is fundamental for most continuous flow particle manipulation operations in channels, was evaluated in measurements and simulations. Specific applications of particle separation and alignment where these systems can offer benefits relative state-of the art designs were identified.

  2. A Schamel equation for ion acoustic waves in superthermal plasmas

    SciTech Connect

    Williams, G. Kourakis, I.; Verheest, F.; Hellberg, M. A.; Anowar, M. G. M.

    2014-09-15

    An investigation of the propagation of ion acoustic waves in nonthermal plasmas in the presence of trapped electrons has been undertaken. This has been motivated by space and laboratory plasma observations of plasmas containing energetic particles, resulting in long-tailed distributions, in combination with trapped particles, whereby some of the plasma particles are confined to a finite region of phase space. An unmagnetized collisionless electron-ion plasma is considered, featuring a non-Maxwellian-trapped electron distribution, which is modelled by a kappa distribution function combined with a Schamel distribution. The effect of particle trapping has been considered, resulting in an expression for the electron density. Reductive perturbation theory has been used to construct a KdV-like Schamel equation, and examine its behaviour. The relevant configurational parameters in our study include the superthermality index κ and the characteristic trapping parameter β. A pulse-shaped family of solutions is proposed, also depending on the weak soliton speed increment u{sub 0}. The main modification due to an increase in particle trapping is an increase in the amplitude of solitary waves, yet leaving their spatial width practically unaffected. With enhanced superthermality, there is a decrease in both amplitude and width of solitary waves, for any given values of the trapping parameter and of the incremental soliton speed. Only positive polarity excitations were observed in our parametric investigation.

  3. Ionospheric acoustic and gravity waves associated with midlatitude thunderstorms

    DOE PAGES

    Lay, Erin H.; Shao, Xuan -Min; Kendrick, Alexander K.; Carrano, Charles S.

    2015-07-30

    Acoustic waves with periods of 2–4 min and gravity waves with periods of 6–16 min have been detected at ionospheric heights (25–350 km) using GPS total electron content measurements. The area disturbed by these waves and the wave amplitudes have been associated with underlying thunderstorm activity. A statistical study comparing Next Generation Weather Radar thunderstorm measurements with ionospheric acoustic and gravity waves in the midlatitude U.S. Great Plains region was performed for the time period of May–July 2005. An increase of ionospheric acoustic wave disturbed area and amplitude is primarily associated with large thunderstorms (mesoscale convective systems). Ionospheric gravity wavemore » disturbed area and amplitude scale with thunderstorm activity, with even small storms (i.e., individual storm cells) producing an increase of gravity waves.« less

  4. The dynamic behaviour of postbuckled composite plates under acoustic excitation

    NASA Technical Reports Server (NTRS)

    Ng, C. F.; White, R. G.

    1988-01-01

    The Rayleigh-Ritz method was used to find the postbuckling static displacement pattern of a composite plane (CFRP) under uniaxial in-plane compression of uniform edge-shortening. The resonance frequencies and mode shapes at various postbuckled states are then evaluated by eigenvalue analysis of the dynamical matrix equation consisting of up-dated tangential stiffness matrix at corresponding static configuration. The theoretical results are compared with experimental results obtained in 16-layered CFRP laminate of aspect ratio 1.5. The resonance frequencies and mode shapes obtained are used to interpret the multimodal and nonlinear strain responses to high level of acoustic excitation. The dominance of second-mode contribution and softening-spring behavior are found in the strain response of postbuckled plates.

  5. Irregular Reflection of Acoustical Shock Waves and von Neumann Paradox

    NASA Astrophysics Data System (ADS)

    Baskar, S.; Coulouvrat, F.; Marchiano, R.

    2006-05-01

    We investigate the reflection of weak acoustical shock waves grazing over a rigid surface. We define a critical parameter and examine the different types of reflection structure depending on this parameter. The study of the step shock is then extended to both N-waves and periodic saw-tooth waves, which are more realistic from an acoustical point of view. The numerical simulations reveal new reflection structures for these two waves which are not observed for step shocks. The results of the model are finally compared for periodic saw-tooth waves to ultrasonic experiments.

  6. Waveform inversion of acoustic waves for explosion yield estimation

    NASA Astrophysics Data System (ADS)

    Kim, K.; Rodgers, A.

    2016-07-01

    We present a new waveform inversion technique to estimate the energy of near-surface explosions using atmospheric acoustic waves. Conventional methods often employ air blast models based on a homogeneous atmosphere, where the acoustic wave propagation effects (e.g., refraction and diffraction) are not taken into account, and therefore, their accuracy decreases with increasing source-receiver distance. In this study, three-dimensional acoustic simulations are performed with a finite difference method in realistic atmospheres and topography, and the modeled acoustic Green's functions are incorporated into the waveform inversion for the acoustic source time functions. The strength of the acoustic source is related to explosion yield based on a standard air blast model. The technique was applied to local explosions (<10 km) and provided reasonable yield estimates (<˜30% error) in the presence of realistic topography and atmospheric structure. The presented method can be extended to explosions recorded at far distance provided proper meteorological specifications.

  7. False Paradoxes of Superposition in Electric and Acoustic Waves.

    ERIC Educational Resources Information Center

    Levine, Richard C.

    1980-01-01

    Corrected are several misconceptions concerning the apparently "missing" energy that results when acoustic or electromagnetic waves cancel by destructive interference and the wave impedance reflected to the sources of the wave energy changes so that the input power is reduced. (Author/CS)

  8. Forced response sound radiation from acoustically or mechanically excited small plates

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.

    1992-01-01

    Sound radiation from an acoustically excited, clamped aluminum plate is measured and expressed in terms of noise reduction to take into account the incident acoustic excitation field. Its mode shapes and modal frequencies are measured and show good agreement with the predictions from a finite element MSC/NASTRAN model. Noise reduction is measured at 15 points behind the plate and demonstrate good agreement with predictions employing the SYSNOISE numerical analysis system for acoustic-structure interaction.

  9. Effect of acoustic field parameters on arc acoustic binding during ultrasonic wave-assisted arc welding.

    PubMed

    Xie, Weifeng; Fan, Chenglei; Yang, Chunli; Lin, Sanbao

    2016-03-01

    As a newly developed arc welding method, power ultrasound has been successfully introduced into arc and weld pool during ultrasonic wave-assisted arc welding process. The advanced process for molten metals can be realized by utilizing additional ultrasonic field. Under the action of the acoustic wave, the plasma arc as weld heat source is regulated and its characteristics make an obvious change. Compared with the conventional arc, the ultrasonic wave-assisted arc plasma is bound significantly and becomes brighter. To reveal the dependence of the acoustic binding force on acoustic field parameters, a two-dimensional acoustic field model for ultrasonic wave-assisted arc welding device is established. The influences of the radiator height, the central pore radius, the radiator radius, and curvature radius or depth of concave radiator surface are discussed using the boundary element method. Then the authors analyze the resonant mode by this relationship curve between acoustic radiation power and radiator height. Furthermore, the best acoustic binding ability is obtained by optimizing the geometric parameters of acoustic radiator. In addition, three concave radiator surfaces including spherical cap surface, paraboloid of revolution, and rotating single curved surface are investigated systematically. Finally, both the calculation and experiment suggest that, to obtain the best acoustic binding ability, the ultrasonic wave-assisted arc welding setup should be operated under the first resonant mode using a radiator with a spherical cap surface, a small central pore, a large section radius and an appropriate curvature radius.

  10. Effect of acoustic field parameters on arc acoustic binding during ultrasonic wave-assisted arc welding.

    PubMed

    Xie, Weifeng; Fan, Chenglei; Yang, Chunli; Lin, Sanbao

    2016-03-01

    As a newly developed arc welding method, power ultrasound has been successfully introduced into arc and weld pool during ultrasonic wave-assisted arc welding process. The advanced process for molten metals can be realized by utilizing additional ultrasonic field. Under the action of the acoustic wave, the plasma arc as weld heat source is regulated and its characteristics make an obvious change. Compared with the conventional arc, the ultrasonic wave-assisted arc plasma is bound significantly and becomes brighter. To reveal the dependence of the acoustic binding force on acoustic field parameters, a two-dimensional acoustic field model for ultrasonic wave-assisted arc welding device is established. The influences of the radiator height, the central pore radius, the radiator radius, and curvature radius or depth of concave radiator surface are discussed using the boundary element method. Then the authors analyze the resonant mode by this relationship curve between acoustic radiation power and radiator height. Furthermore, the best acoustic binding ability is obtained by optimizing the geometric parameters of acoustic radiator. In addition, three concave radiator surfaces including spherical cap surface, paraboloid of revolution, and rotating single curved surface are investigated systematically. Finally, both the calculation and experiment suggest that, to obtain the best acoustic binding ability, the ultrasonic wave-assisted arc welding setup should be operated under the first resonant mode using a radiator with a spherical cap surface, a small central pore, a large section radius and an appropriate curvature radius. PMID:26558995

  11. Anisotropic Swirling Surface Acoustic Waves from Inverse Filtering for On-Chip Generation of Acoustic Vortices

    NASA Astrophysics Data System (ADS)

    Riaud, Antoine; Thomas, Jean-Louis; Charron, Eric; Bussonnière, Adrien; Bou Matar, Olivier; Baudoin, Michael

    2015-09-01

    From radio-electronics signal analysis to biological sample actuation, surface acoustic waves (SAWs) are involved in a multitude of modern devices. However, only the most simple standing or progressive waves such as plane and focused waves have been explored so far. In this paper, we expand the SAW toolbox with a wave family named "swirling surface acoustic waves" which are the 2D anisotropic analogue of bulk acoustic vortices. Similarly to their 3D counterpart, they appear as concentric structures of bright rings with a phase singularity in their center resulting in a central dark spot. After the rigorous mathematical definition of these waves, we synthesize them experimentally through the inverse filtering technique revisited for surface waves. For this purpose, we design a setup combining arrays of interdigitated transducers and a multichannel electronic that enables one to synthesize any prescribed wave field compatible with the anisotropy of the substrate in a region called the "acoustic scene." This work opens prospects for the design of integrated acoustic vortex generators for on-chip selective acoustic tweezing.

  12. Excitation of Standing Waves by an Electric Toothbrush

    ERIC Educational Resources Information Center

    Cros, Ana; Ferrer-Roca, Chantal

    2006-01-01

    There are a number of ways of exciting standing waves in ropes and springs using non-commercial vibrators such as loudspeakers, jigsaws, motors, or a simple tuning fork, including the rhythmical shaking of a handheld Slinky. We have come up with a very simple and cheap way of exciting stationary waves in a string, which anyone, particularly…

  13. Laser Excitation of a Fracture Source for Elastic Waves

    SciTech Connect

    Blum, Thomas E.; Wijk, Kasper van; Snieder, Roel; Willis, Mark E.

    2011-12-30

    We show that elastic waves can be excited at a fracture inside a transparent sample by focusing laser light directly onto this fracture. The associated displacement field, measured by a laser interferometer, has pronounced waves that are diffracted at the fracture tips. We confirm that these are tip diffractions from direct excitation of the fracture by comparing them with tip diffractions from scattered elastic waves excited on the exterior of the sample. Being able to investigate fractures - in this case in an optically transparent material - via direct excitation opens the door to more detailed studies of fracture properties in general.

  14. Nonlinear propagation and control of acoustic waves in phononic superlattices

    NASA Astrophysics Data System (ADS)

    Jiménez, Noé; Mehrem, Ahmed; Picó, Rubén; García-Raffi, Lluís M.; Sánchez-Morcillo, Víctor J.

    2016-05-01

    The propagation of intense acoustic waves in a one-dimensional phononic crystal is studied. The medium consists in a structured fluid, formed by a periodic array of fluid layers with alternating linear acoustic properties and quadratic nonlinearity coefficient. The spacing between layers is of the order of the wavelength, therefore Bragg effects such as band gaps appear. We show that the interplay between strong dispersion and nonlinearity leads to new scenarios of wave propagation. The classical waveform distortion process typical of intense acoustic waves in homogeneous media can be strongly altered when nonlinearly generated harmonics lie inside or close to band gaps. This allows the possibility of engineer a medium in order to get a particular waveform. Examples of this include the design of media with effective (e.g., cubic) nonlinearities, or extremely linear media (where distortion can be canceled). The presented ideas open a way towards the control of acoustic wave propagation in nonlinear regime. xml:lang="fr"

  15. Effects of abnormal excitation on the dynamics of spiral waves

    NASA Astrophysics Data System (ADS)

    Min-Yi, Deng; Xue-Liang, Zhang; Jing-Yu, Dai

    2016-01-01

    The effect of physiological and pathological abnormal excitation of a myocyte on the spiral waves is investigated based on the cellular automaton model. When the excitability of the medium is high enough, the physiological abnormal excitation causes the spiral wave to meander irregularly and slowly. When the excitability of the medium is low enough, the physiological abnormal excitation leads to a new stable spiral wave. On the other hand, the pathological abnormal excitation destroys the spiral wave and results in the spatiotemporal chaos, which agrees with the clinical conclusion that the early after depolarization is the pro-arrhythmic mechanism of some anti-arrhythmic drugs. The mechanisms underlying these phenomena are analyzed. Project supported by the National Natural Science Foundation of China (Grant Nos. 11365003 and 11165004).

  16. Estimating propagation velocity through a surface acoustic wave sensor

    DOEpatents

    Xu, Wenyuan; Huizinga, John S.

    2010-03-16

    Techniques are described for estimating the propagation velocity through a surface acoustic wave sensor. In particular, techniques which measure and exploit a proper segment of phase frequency response of the surface acoustic wave sensor are described for use as a basis of bacterial detection by the sensor. As described, use of velocity estimation based on a proper segment of phase frequency response has advantages over conventional techniques that use phase shift as the basis for detection.

  17. Demonstration of a directional sonic prism in two dimensions using an air-acoustic leaky wave antenna

    SciTech Connect

    Naify, Christina J. Rohde, Charles A.; Calvo, David C.; Orris, Gregory J.; Guild, Matthew D.

    2015-09-28

    Analysis and experimental demonstration of a two-dimensional acoustic leaky wave antenna is presented for use in air. The antenna is comprised of a two-dimensional waveguide patterned with radiating acoustic shunts. When excited using a single acoustic source within the waveguide, the antenna acts as a sonic prism that exhibits frequency steering. This design allows for control of acoustic steering angle using only a single source transducer and a patterned aperture. Aperture design was determined using transmission line analysis and finite element methods. The designed antenna was fabricated and the steering angle measured. The performance of the measured aperture was within 9% of predicted angle magnitudes over all examined frequencies.

  18. Evolution of nonlinear ion-acoustic solitary wave propagation in rotating plasma

    SciTech Connect

    Das, G. C.; Nag, Apratim

    2006-08-15

    A simple unmagnetized plasma rotating around an axis at an angle {theta} with the propagation direction of the acoustic mode has been taken. The nonlinear wave mode has been derived as an equivalent Sagdeev potential equation. A special procedure, known as the tanh method, has been developed to study the nonlinear wave propagation in plasma dynamics. Further, under small amplitude approximation, the nonlinear plasma acoustic mode has been exploited to study the evolution of soliton propagation in the plasma. The main emphasis has been given to the interaction of Coriolis force on the changes of coherent structure of the soliton. The solitary wave solution finds the different nature of solitons called compressive and rarefactive solitons as well as its explosions or collapses along with soliton dynamics and these have been showing exciting observations in exhibiting a narrow wave packet with the generation of high electric pressure and the growth of high energy which, in turn, yields the phenomena of radiating soliton in dynamics.

  19. Experimental validation of acoustic radiation force induced shear wave interference patterns.

    PubMed

    Hoyt, Kenneth; Hah, Zaegyoo; Hazard, Chris; Parker, Kevin J

    2012-01-01

    A novel elasticity imaging system founded on the use of acoustic radiation forces from a dual beam arrangement to generate shear wave interference patterns is described. Acquired pulse-echo data and correlation-based techniques were used to estimate the resultant deformation and to visualize tissue viscoelastic response. The use of normal versus axicon focal configurations was investigated for effects on shear wave generation. Theoretical models were introduced and shown in simulation to accurately predict shear wave propagation and interference pattern properties. In a tissue-mimicking phantom, experimental results are in congruence with theoretical predictions. Using dynamic acoustic radiation force excitation, results confirm that shear wave interference patterns can be produced remotely in a particular tissue region of interest (ROI). Overall, preliminary results are encouraging and the system described may prove feasible for interrogating the viscoelastic properties of normal and diseased tissue types.

  20. Excitation of fundamental shear horizontal wave by using face-shear (d36) piezoelectric ceramics

    NASA Astrophysics Data System (ADS)

    Miao, Hongchen; Dong, Shuxiang; Li, Faxin

    2016-05-01

    The fundamental shear horizontal (SH0) wave in plate-like structures is extremely useful for non-destructive testing (NDT) and structural health monitoring (SHM) as it is non-dispersive. However, currently, the SH0 wave is usually excited by electromagnetic acoustic transducers (EMAT) whose energy conversion efficiency is fairly low. The face-shear ( d 36 ) mode piezoelectrics is more promising for SH0 wave excitation, but this mode cannot appear in conventional piezoelectric ceramics. Recently, by modifying the symmetry of poled PbZr1-xTixO3 (PZT) ceramics via ferroelastic domain engineering, we realized the face-shear d 36 mode in both soft and hard PZT ceramics. In this work, we further improved the face-shear properties of PZT-4 and PZT-5H ceramics via lateral compression under elevated temperature. It was found that when bonded on a 1 mm-thick aluminum plate, the d 36 type PZT-4 exhibited better face-shear performance than PZT-5H. We then successfully excite SH0 wave in the aluminum plate using a face-shear PZT-4 square patch and receive the wave using a face-shear 0.72[Pb(Mg1/3Nb2/3)O3]-0.28[PbTiO3] (PMN-PT) patch. The frequency response and directionality of the excited SH0 wave were also investigated. The SH0 wave can be dominated over the Lamb waves (S0 and A0 waves) from 160 kHz to 280 kHz. The wave amplitude reaches its maxima along the two main directions (0° and 90°). The amplitude can keep over 80% of the maxima when the deviate angle is less than 30°, while it vanishes quickly at the 45° direction. The excited SH0 wave using piezoelectric ceramics could be very promising in the fields of NDT and SHM.

  1. Surface acoustic wave (SAW) vibration sensors.

    PubMed

    Filipiak, Jerzy; Solarz, Lech; Steczko, Grzegorz

    2011-01-01

    In the paper a feasibility study on the use of surface acoustic wave (SAW) vibration sensors for electronic warning systems is presented. The system is assembled from concatenated SAW vibration sensors based on a SAW delay line manufactured on a surface of a piezoelectric plate. Vibrations of the plate are transformed into electric signals that allow identification of the sensor and localization of a threat. The theoretical study of sensor vibrations leads us to the simple isotropic model with one degree of freedom. This model allowed an explicit description of the sensor plate movement and identification of the vibrating sensor. Analysis of frequency response of the ST-cut quartz sensor plate and a damping speed of its impulse response has been conducted. The analysis above was the basis to determine the ranges of parameters for vibrating plates to be useful in electronic warning systems. Generally, operation of electronic warning systems with SAW vibration sensors is based on the analysis of signal phase changes at the working frequency of delay line after being transmitted via two circuits of concatenated four-terminal networks. Frequencies of phase changes are equal to resonance frequencies of vibrating plates of sensors. The amplitude of these phase changes is proportional to the amplitude of vibrations of a sensor plate. Both pieces of information may be sent and recorded jointly by a simple electrical unit.

  2. Surface acoustic wave devices for sensor applications

    NASA Astrophysics Data System (ADS)

    Bo, Liu; Xiao, Chen; Hualin, Cai; Mohammad, Mohammad Ali; Xiangguang, Tian; Luqi, Tao; Yi, Yang; Tianling, Ren

    2016-02-01

    Surface acoustic wave (SAW) devices have been widely used in different fields and will continue to be of great importance in the foreseeable future. These devices are compact, cost efficient, easy to fabricate, and have a high performance, among other advantages. SAW devices can work as filters, signal processing units, sensors and actuators. They can even work without batteries and operate under harsh environments. In this review, the operating principles of SAW sensors, including temperature sensors, pressure sensors, humidity sensors and biosensors, will be discussed. Several examples and related issues will be presented. Technological trends and future developments will also be discussed. Project supported by the National Natural Science Foundation of China (Nos. 60936002, 61025021, 61434001, 61574083), the State Key Development Program for Basic Research of China (No. 2015CB352100), the National Key Project of Science and Technology (No. 2011ZX02403-002) and the Special Fund for Agroscientific Research in the Public Interest of China (No. 201303107). M.A.M is additionally supported by the Postdoctoral Fellowship (PDF) program of the Natural Sciences and Engineering Research Council (NSERC) of Canada and the China Postdoctoral Science Foundation (CPSF).

  3. Surface acoustic wave (SAW) vibration sensors.

    PubMed

    Filipiak, Jerzy; Solarz, Lech; Steczko, Grzegorz

    2011-01-01

    In the paper a feasibility study on the use of surface acoustic wave (SAW) vibration sensors for electronic warning systems is presented. The system is assembled from concatenated SAW vibration sensors based on a SAW delay line manufactured on a surface of a piezoelectric plate. Vibrations of the plate are transformed into electric signals that allow identification of the sensor and localization of a threat. The theoretical study of sensor vibrations leads us to the simple isotropic model with one degree of freedom. This model allowed an explicit description of the sensor plate movement and identification of the vibrating sensor. Analysis of frequency response of the ST-cut quartz sensor plate and a damping speed of its impulse response has been conducted. The analysis above was the basis to determine the ranges of parameters for vibrating plates to be useful in electronic warning systems. Generally, operation of electronic warning systems with SAW vibration sensors is based on the analysis of signal phase changes at the working frequency of delay line after being transmitted via two circuits of concatenated four-terminal networks. Frequencies of phase changes are equal to resonance frequencies of vibrating plates of sensors. The amplitude of these phase changes is proportional to the amplitude of vibrations of a sensor plate. Both pieces of information may be sent and recorded jointly by a simple electrical unit. PMID:22247694

  4. Investigations of droplet movement excited by Lamb waves on a non-piezoelectric substrate

    NASA Astrophysics Data System (ADS)

    Liang, Wei; Lindner, Gerhard

    2013-07-01

    A model for the numerical simulation of the movement of liquid droplets excited by Lamb waves propagating on non-piezoelectric substrates was developed, and the results of simulation calculations based on this model were compared with experimental observations. In the experiments antisymmetrical zero order Lamb waves with 1 MHz center frequency were excited on a 1 mm thick glass substrate by piezoelectric single phase transducers, which caused the propulsion of microliter water droplets. The acoustic streaming within the droplet was calculated by solving the incompressible Navier-Stokes equations with an inhomogeneous acoustic streaming force field. These calculations were validated by optical measurements of the streaming effects in the droplet and by measurements of the displacement amplitudes of the Lamb waves with a laser-Doppler-vibrometer. Another part of the numerical simulations was related to the transient motion of acoustically driven droplets by solving the incompressible Navier-Stokes equations using the moving mesh application mode of the comsol software including a weak formulation for the calculation of the surface tension. The corresponding measurements with a high-speed camera revealed a silkworm-like movement of the droplet resulting from the interaction with acoustic force, surface tension, gravity, and inertial force, which was reproduced by the numerical simulations.

  5. Nanoliter-droplet acoustic streaming via ultra high frequency surface acoustic waves.

    PubMed

    Shilton, Richie J; Travagliati, Marco; Beltram, Fabio; Cecchini, Marco

    2014-08-01

    The relevant length scales in sub-nanometer amplitude surface acoustic wave-driven acoustic streaming are demonstrated. We demonstrate the absence of any physical limitations preventing the downscaling of SAW-driven internal streaming to nanoliter microreactors and beyond by extending SAW microfluidics up to operating frequencies in the GHz range. This method is applied to nanoliter scale fluid mixing.

  6. Mechanically robust microfluidics and bulk wave acoustics to sort microparticles

    NASA Astrophysics Data System (ADS)

    Dauson, Erin R.; Gregory, Kelvin B.; Greve, David W.; Healy, Gregory P.; Oppenheim, Irving J.

    2016-04-01

    Sorting microparticles (or cells, or bacteria) is significant for scientific, medical and industrial purposes. Research groups have used lithium niobate SAW devices to produce standing waves, and then to align microparticles at the node lines in polydimethylsiloxane (PDMS, silicone) microfluidic channels. The "tilted angle" (skewed) configuration is a recent breakthrough producing particle trajectories that cross multiple node lines, making it practical to sort particles. However, lithium niobate wafers and PDMS microfluidic channels are not mechanically robust. We demonstrate "tilted angle" microparticle sorting in novel devices that are robust, rapidly prototyped, and manufacturable. We form our microfluidic system in a rigid polymethyl methacrylate (PMMA, acrylic) prism, sandwiched by lead-zirconium-titanate (PZT) wafers, operating in through-thickness mode with inertial backing, that produce standing bulk waves. The overall configuration is compact and mechanically robust, and actuating PZT wafers in through-thickness mode is highly efficient. Moving to this novel configuration introduced new acoustics questions involving internal reflections, but we show experimental images confirming the intended nodal geometry. Microparticles in "tilted angle" devices display undulating trajectories, where deviation from the straight path increases with particle diameter and with excitation voltage to create the mechanism by which particles are sorted. We show a simplified analytical model by which a "phase space" is constructed to characterize effective particle sorting, and we compare our experimental data to the predictions from that simplified model; precise correlation is not expected and is not observed, but the important physical trends from the model are paralleled in the measured particle trajectories.

  7. Strategies for reliable second harmonic of nonlinear acoustic wave through cement-based materials

    NASA Astrophysics Data System (ADS)

    Xie, Fan; Guo, Zhiwei; Zhang, Jinwei

    2014-07-01

    The strategies for retrieving reliable nonlinear second harmonic in cement-based materials are proposed in this paper using high-performance test system, piezoelectric transducers with central frequency in MHz, monochromatic tone-burst excitation and robust data process method.The Fundamental and second-order harmonics are measured to retrieve reliable acoustic nonlinearity with the input power level increased from ∼50 V to ∼280 V. About 173 times repeatable measurements are conducted to verify the stability of the experimental system. Specimens with three distinct aggregate sizes are used to measure the acoustic nonlinearity under uniaxial load. The results show a decrease in the measured acoustic nonlinearity at early damage stage, then a slight increase when large cracks coalesce. The rapid increase in acoustic nonlinearity at the final stage indicates the imminent failure. Our results also suggest that the nonlinear ultrasonic method is more sensitive than P-wave velocity for damage evaluation.

  8. Piezoelectric Shunt Vibration Damping of F-15 Panel under High Acoustic Excitation

    NASA Technical Reports Server (NTRS)

    Wu, Shu-Yau; Turner, Travis L.; Rizzi, Stephen A.

    2000-01-01

    At last year's SPIE symposium, we reported results of an experiment on structural vibration damping of an F-15 underbelly panel using piezoelectric shunting with five bonded PZT transducers. The panel vibration was induced with an acoustic speaker at an overall sound pressure level (OASPL) of about 90 dB. Amplitude reductions of 13.45 and 10.72 dB were achieved for the first and second modes, respectively, using single- and multiple-mode shunting. It is the purpose of this investigation to extend the passive piezoelectric shunt-damping technique to control structural vibration induced at higher acoustic excitation levels, and to examine the controllability and survivability of the bonded PZT transducers at these high levels. The shunting experiment was performed with the Thermal Acoustic Fatigue Apparatus (TAFA) at the NASA Langley Research Center using the same F-15 underbelly panel. The TAFA is a progressive wave tube facility. The panel was mounted in one wall of the TAFA test section using a specially designed mounting fixture such that the panel was subjected to grazing-incidence acoustic excitation. Five PZT transducers were used with two shunt circuits designed to control the first and second modes of the structure between 200 and 400 Hz. We first determined the values of the shunt inductance and resistance at an OASPL of 130 dB. These values were maintained while we gradually increased the OASPL from 130 to 154 dB in 6-dB steps. During each increment, the frequency response function between accelerometers on the panel and the acoustic excitation measured by microphones, before and after shunting, were recorded. Good response reduction was observed up to the 148dB level. The experiment was stopped at 154 dB due to wire breakage from vibration at a transducer wire joint. The PZT transducers, however, were still bonded well on the panel and survived at this high dB level. We also observed shifting of the frequency peaks toward lower frequency when the OASPL

  9. Influences of non-uniform pressure field outside bubbles on the propagation of acoustic waves in dilute bubbly liquids.

    PubMed

    Zhang, Yuning; Du, Xiaoze

    2015-09-01

    Predictions of the propagation of the acoustic waves in bubbly liquids is of great importance for bubble dynamics and related applications (e.g. sonochemistry, sonochemical reactor design, biomedical engineering). In the present paper, an approach for modeling the propagation of the acoustic waves in dilute bubbly liquids is proposed through considering the non-uniform pressure field outside the bubbles. This approach is validated through comparing with available experimental data in the literature. Comparing with the previous models, our approach mainly improves the predictions of the attenuation of acoustic waves in the regions with large kR0 (k is the wave number and R0 is the equilibrium bubble radius). Stability of the oscillating bubbles under acoustic excitation are also quantitatively discussed based on the analytical solution.

  10. Acoustic waves in gases with strong pressure gradients

    NASA Technical Reports Server (NTRS)

    Zorumski, William E.

    1989-01-01

    The effect of strong pressure gradients on the acoustic modes (standing waves) of a rectangular cavity is investigated analytically. When the cavity response is represented by a sum of modes, each mode is found to have two resonant frequencies. The lower frequency is near the Viaesaela-Brundt frequency, which characterizes the buoyant effect, and the higher frequency is above the ordinary acoustic resonance frequency. This finding shows that the propagation velocity of the acoustic waves is increased due to the pressure gradient effect.

  11. Flow profiling of a surface-acoustic-wave nanopump

    NASA Astrophysics Data System (ADS)

    Guttenberg, Z.; Rathgeber, A.; Keller, S.; Rädler, J. O.; Wixforth, A.; Kostur, M.; Schindler, M.; Talkner, P.

    2004-11-01

    The flow profile in a capillary gap and the pumping efficiency of an acoustic micropump employing surface acoustic waves is investigated both experimentally and theoretically. Ultrasonic surface waves on a piezoelectric substrate strongly couple to a thin liquid layer and generate a quadrupolar streaming pattern within the fluid. We use fluorescence correlation spectroscopy and fluorescence microscopy as complementary tools to investigate the resulting flow profile. The velocity was found to depend on the applied power approximately linearly and to decrease with the inverse third power of the distance from the ultrasound generator on the chip. The found properties reveal acoustic streaming as a promising tool for the controlled agitation during microarray hybridization.

  12. Acoustic excitations in glassy sorbitol and their relation with the fragility and the boson peak

    NASA Astrophysics Data System (ADS)

    Ruta, B.; Baldi, G.; Scarponi, F.; Fioretto, D.; Giordano, V. M.; Monaco, G.

    2012-12-01

    We report a detailed analysis of the dynamic structure factor of glassy sorbitol by using inelastic X-ray scattering and previously measured light scattering data [B. Ruta, G. Monaco, F. Scarponi, and D. Fioretto, Philos. Mag. 88, 3939 (2008), 10.1080/14786430802317586]. The thus obtained knowledge on the density-density fluctuations at both the mesoscopic and macroscopic length scale has been used to address two debated topics concerning the vibrational properties of glasses. The relation between the acoustic modes and the universal boson peak (BP) appearing in the vibrational density of states of glasses has been investigated, also in relation with some recent theoretical models. Moreover, the connection between the elastic properties of glasses and the slowing down of the structural relaxation process in supercooled liquids has been scrutinized. For what concerns the first issue, it is here shown that the wave vector dependence of the acoustic excitations can be used, in sorbitol, to quantitatively reproduce the shape of the boson peak, supporting the relation between BP and acoustic modes. For what concerns the second issue, a proper study of elasticity over a wide spatial range is shown to be fundamental in order to investigate the relation between elastic properties and the slowing down of the dynamics in the corresponding supercooled liquid phase.

  13. Mesoscale variations in acoustic signals induced by atmospheric gravity waves.

    PubMed

    Chunchuzov, Igor; Kulichkov, Sergey; Perepelkin, Vitaly; Ziemann, Astrid; Arnold, Klaus; Kniffka, Anke

    2009-02-01

    The results of acoustic tomographic monitoring of the coherent structures in the lower atmosphere and the effects of these structures on acoustic signal parameters are analyzed in the present study. From the measurements of acoustic travel time fluctuations (periods 1 min-1 h) with distant receivers, the temporal fluctuations of the effective sound speed and wind speed are retrieved along different ray paths connecting an acoustic pulse source and several receivers. By using a coherence analysis of the fluctuations near spatially distanced ray turning points, the internal wave-associated fluctuations are filtered and their spatial characteristics (coherences, horizontal phase velocities, and spatial scales) are estimated. The capability of acoustic tomography in estimating wind shear near ground is shown. A possible mechanism describing the temporal modulation of the near-ground wind field by ducted internal waves in the troposphere is proposed.

  14. System and method for characterizing voiced excitations of speech and acoustic signals, removing acoustic noise from speech, and synthesizing speech

    DOEpatents

    Burnett, Greg C.; Holzrichter, John F.; Ng, Lawrence C.

    2006-08-08

    The present invention is a system and method for characterizing human (or animate) speech voiced excitation functions and acoustic signals, for removing unwanted acoustic noise which often occurs when a speaker uses a microphone in common environments, and for synthesizing personalized or modified human (or other animate) speech upon command from a controller. A low power EM sensor is used to detect the motions of windpipe tissues in the glottal region of the human speech system before, during, and after voiced speech is produced by a user. From these tissue motion measurements, a voiced excitation function can be derived. Further, the excitation function provides speech production information to enhance noise removal from human speech and it enables accurate transfer functions of speech to be obtained. Previously stored excitation and transfer functions can be used for synthesizing personalized or modified human speech. Configurations of EM sensor and acoustic microphone systems are described to enhance noise cancellation and to enable multiple articulator measurements.

  15. System and method for characterizing voiced excitations of speech and acoustic signals, removing acoustic noise from speech, and synthesizing speech

    DOEpatents

    Burnett, Greg C.; Holzrichter, John F.; Ng, Lawrence C.

    2004-03-23

    The present invention is a system and method for characterizing human (or animate) speech voiced excitation functions and acoustic signals, for removing unwanted acoustic noise which often occurs when a speaker uses a microphone in common environments, and for synthesizing personalized or modified human (or other animate) speech upon command from a controller. A low power EM sensor is used to detect the motions of windpipe tissues in the glottal region of the human speech system before, during, and after voiced speech is produced by a user. From these tissue motion measurements, a voiced excitation function can be derived. Further, the excitation function provides speech production information to enhance noise removal from human speech and it enables accurate transfer functions of speech to be obtained. Previously stored excitation and transfer functions can be used for synthesizing personalized or modified human speech. Configurations of EM sensor and acoustic microphone systems are described to enhance noise cancellation and to enable multiple articulator measurements.

  16. System and method for characterizing voiced excitations of speech and acoustic signals, removing acoustic noise from speech, and synthesizing speech

    DOEpatents

    Burnett, Greg C.; Holzrichter, John F.; Ng, Lawrence C.

    2006-02-14

    The present invention is a system and method for characterizing human (or animate) speech voiced excitation functions and acoustic signals, for removing unwanted acoustic noise which often occurs when a speaker uses a microphone in common environments, and for synthesizing personalized or modified human (or other animate) speech upon command from a controller. A low power EM sensor is used to detect the motions of windpipe tissues in the glottal region of the human speech system before, during, and after voiced speech is produced by a user. From these tissue motion measurements, a voiced excitation function can be derived. Further, the excitation function provides speech production information to enhance noise removal from human speech and it enables accurate transfer functions of speech to be obtained. Previously stored excitation and transfer functions can be used for synthesizing personalized or modified human speech. Configurations of EM sensor and acoustic microphone systems are described to enhance noise cancellation and to enable multiple articulator measurements.

  17. System And Method For Characterizing Voiced Excitations Of Speech And Acoustic Signals, Removing Acoustic Noise From Speech, And Synthesizi

    DOEpatents

    Burnett, Greg C.; Holzrichter, John F.; Ng, Lawrence C.

    2006-04-25

    The present invention is a system and method for characterizing human (or animate) speech voiced excitation functions and acoustic signals, for removing unwanted acoustic noise which often occurs when a speaker uses a microphone in common environments, and for synthesizing personalized or modified human (or other animate) speech upon command from a controller. A low power EM sensor is used to detect the motions of windpipe tissues in the glottal region of the human speech system before, during, and after voiced speech is produced by a user. From these tissue motion measurements, a voiced excitation function can be derived. Further, the excitation function provides speech production information to enhance noise removal from human speech and it enables accurate transfer functions of speech to be obtained. Previously stored excitation and transfer functions can be used for synthesizing personalized or modified human speech. Configurations of EM sensor and acoustic microphone systems are described to enhance noise cancellation and to enable multiple articulator measurements.

  18. Experimental source characterization techniques for studying the acoustic properties of perforates under high level acoustic excitation.

    PubMed

    Bodén, Hans

    2011-11-01

    This paper discusses experimental techniques for obtaining the acoustic properties of in-duct samples with non-linear acoustic characteristic. The methods developed are intended both for studies of non-linear energy transfer to higher harmonics for samples only accessible from one side such as wall treatment in aircraft engine ducts or automotive exhaust systems and for samples accessible from both sides such as perforates or other top sheets. When harmonic sound waves are incident on the sample nonlinear energy transfer results in sound generation at higher harmonics at the sample (perforate) surface. The idea is that these sources can be characterized using linear system identification techniques similar to one-port or two-port techniques which are traditionally used for obtaining source data for in-duct sources such as IC-engines or fans. The starting point will be so called polyharmonic distortion modeling which is used for characterization of nonlinear properties of microwave systems. It will be shown how acoustic source data models can be expressed using this theory. Source models of different complexity are developed and experimentally tested. The results of the experimental tests show that these techniques can give results which are useful for understanding non-linear energy transfer to higher harmonics.

  19. Slow Wave Excitation in the ICRF and HHFW Regimes

    NASA Astrophysics Data System (ADS)

    Phillips, C. K.; Jaeger, E. F.; Berry, L. A.; Bonoli, P. T.; Valeo, E. J.; Hosea, J. C.; LeBlanc, B. P.; Ryan, P. M.; Smithe, D. N.; Wilson, J. R.; Wright, J. C.

    2011-12-01

    Theoretical considerations and high spatial resolution numerical simulations of radio frequency (rf) wave heating in tokamaks and in spherical toruses (ST) indicate that fast waves launched into tokamaks in the ion cyclotron range of frequencies (ICRF) or into spherical toruses in the high harmonic fast wave (HHFW) regime may excite a short wavelength slow mode inside of the plasma discharge due to the presence of hot electrons that satisfy the condition ωwave frequency, k∥ is the local parallel component of the wave vector, and vte is the local electron thermal speed. This excited slow wave may be related to the electrostatic ion cyclotron wave that propagates for frequencies above the fundamental ion cyclotron frequency [1] in warm plasmas or to a high frequency version of a kinetic Alfvén wave [2]. This slow wave, if physically real, would provide another path for rf power absorption in tokamaks and ST devices.

  20. Comparison with Analytical Solution: Generation and Radiation of Acoustic Waves from a 2-D Shear Layer

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.

    2000-01-01

    An acoustic source inside of a 2-D jet excites an instability wave in the shear layer resulting in sound radiating away from the shear layer. Solve the linearized Euler equations to predict the sound radiation outside of the jet. The jet static pressure is assumed to be constant. The jet flow is parallel and symmetric about the x-axis. Use a symmetry boundary condition along the x-axis.

  1. Optical control of excitation waves in cardiac tissue

    NASA Astrophysics Data System (ADS)

    Burton, Rebecca A. B.; Klimas, Aleksandra; Ambrosi, Christina M.; Tomek, Jakub; Corbett, Alex; Entcheva, Emilia; Bub, Gil

    2015-12-01

    In nature, macroscopic excitation waves are found in a diverse range of settings including chemical reactions, metal rust, yeast, amoeba and the heart and brain. In the case of living biological tissue, the spatiotemporal patterns formed by these excitation waves are different in healthy and diseased states. Current electrical and pharmacological methods for wave modulation lack the spatiotemporal precision needed to control these patterns. Optical methods have the potential to overcome these limitations, but to date have only been demonstrated in simple systems, such as the Belousov-Zhabotinsky chemical reaction. Here, we combine dye-free optical imaging with optogenetic actuation to achieve dynamic control of cardiac excitation waves. Illumination with patterned light is demonstrated to optically control the direction, speed and spiral chirality of such waves in cardiac tissue. This all-optical approach offers a new experimental platform for the study and control of pattern formation in complex biological excitable systems.

  2. Application of surface acoustic wave devices to radio telemetry

    NASA Technical Reports Server (NTRS)

    Strasilla, U.

    1983-01-01

    Three experimental Surface Acoustic Wave Resonators (SAWR) are developed and evaluated. A desired center frequency is obtained by correct spacing of the Inter-Digital Transducers (IDT). Transmitting and receiving IDT's must be close for adequate coupling and a sufficient number of reflectors are required to create a high quality standing wave. A review of oscillator theory is given and current technology evaluated.

  3. Quantum ion-acoustic wave oscillations in metallic nanowires

    SciTech Connect

    Moradi, Afshin

    2015-05-15

    The low-frequency electrostatic waves in metallic nanowires are studied using the quantum hydrodynamic model, in which the electron and ion components of the system are regarded as a two-species quantum plasma system. The Poisson equation as well as appropriate quantum boundary conditions give the analytical expressions of dispersion relations of the surface and bulk quantum ion-acoustic wave oscillations.

  4. Surface wave patterns on acoustically levitated viscous liquid alloys

    NASA Astrophysics Data System (ADS)

    Hong, Z. Y.; Yan, N.; Geng, D. L.; Wei, B.

    2014-04-01

    We demonstrate two different kinds of surface wave patterns on viscous liquid alloys, which are melted and solidified under acoustic levitation condition. These patterns are consistent with the morphologies of standing capillary waves and ensembles of oscillons, respectively. The rapid solidification of two-dimensional liquid alloy surfaces may hold them down.

  5. Nonlinear scattering of acoustic waves by vibrating obstacles

    NASA Astrophysics Data System (ADS)

    Piquette, J. C.

    1983-06-01

    The problem of the generation of sum- and difference-frequency waves produced via the scattering of an acoustic wave by an obstacle whose surface vibrates harmonically was studied both theoretically and experimentally. The theoretical approach involved solving the nonlinear wave equation, subject to appropriate boundary conditions, by the use of a perturbation expansion of the fields and a Green's function method. In addition to ordinary rigid-body scattering, Censor predicted nongrowing waves at frequencies equal to the sum and to the difference of the frequencies of the primary waves. The solution to the nonlinear wave equation also yields scattered waves at the sum and difference frequencies. However, the nonlinearity of the medium causes these waves to grow with increasing distance from the scatter's surface and, after a very small distance, dominate those predicted by Censor. The simple-source formulation of the second-order nonlinear wave equation for a lossless fluid medium has been derived for arbitrary primary wave fields. This equation was used to solve the problem of nonlinear scattering of acoustic waves by a vibrating obstacle for three geometries: (1) a plane-wave scattering by a vibrating plane, (2) cylindrical-wave scattering by a vibrating cylinder, and (3) plane-wave scattering by a vibrating cylinder. Successful experimental validation of the theory was inhibited by previously unexpected levels of nonlinearity in the hydrophones used. Such high levels of hydrophone nonlinearity appeared in hydrophones that, by their geometry of construction, were expected to be fairly linear.

  6. Resonance reflection of elastic waves at the interface between two crystals with sliding contact: II. Plane waves and acoustic beams in structures with hexagonal symmetry

    SciTech Connect

    Alshits, V.I.; Darinskii, A.N.; Radovich, A.

    1995-05-01

    The specific features of acoustic wave reflection are analyzed at the interface between two hexagonal crystals with a sliding contact between them. Attention is focused on the angles of incidence corresponding to excitation of the leaky wave. The conditions supporting the existence of leaky waves are found. The expressions illustrating the behavior of plane wave transformation coefficients for reflection, refraction, and excitation of interfacial oscillations are found in analytic form. In addition, the features of nonmirror reflection are studied for a slightly diverging acoustic beam having initially a rectangular profile. The study deals with the case when the tangential projection of the {open_quotes}mean{close_quotes} wavevector for the beam is close to or coincides with the real part of the wavevector of the leaky wave. 9 refs., 10 figs.

  7. Linear and nonlinear acoustic wave propagation in the atmosphere

    NASA Technical Reports Server (NTRS)

    Hariharan, S. I.; Yu, Ping

    1988-01-01

    The investigation of the acoustic wave propagation theory and numerical implementation for the situation of an isothermal atmosphere is described. A one-dimensional model to validate an asymptotic theory and a 3-D situation to relate to a realistic situation are considered. In addition, nonlinear wave propagation and the numerical treatment are included. It is known that the gravitational effects play a crucial role in the low frequency acoustic wave propagation. They propagate large distances and, as such, the numerical treatment of those problems become difficult in terms of posing boundary conditions which are valid for all frequencies.

  8. Femtosecond optical excitation of coherent acoustic phonons in a piezoelectric p-n junction

    NASA Astrophysics Data System (ADS)

    Wen, Yu-Chieh; Chern, Gia-Wei; Lin, Kung-Hsuan; Yeh, Jeffrey Jarren; Sun, Chi-Kuang

    2011-11-01

    We present a theoretical model for the photogeneration of coherent acoustic phonons in a piezoelectric p-n junction. In our model, the transport of photoexcited carriers is governed by the drift-diffusion equation, whereas the dynamics of acoustic phonons obeys a loaded string equation. Among various mechanisms, the piezoelectric coupling is found to dominate the acoustic-phonon generation process. The waveform of the photogenerated acoustic pulse is strongly influenced by the various dynamics of the photoexcited carriers, especially the picosecond hole drifting. Our calculation also confirms the crucial role of the built-in electric field in the formation of coherent acoustic phonons under optical excitations.

  9. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, B.T.; Chou, C.H.

    1990-03-20

    A shear acoustic transducer-lens system is described in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens. 9 figs.

  10. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, Butrus T.; Chou, Ching H.

    1990-01-01

    A shear acoustic transducer-lens system in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens.

  11. Standing wave pressure fields generated in an acoustic levitation chamber

    NASA Astrophysics Data System (ADS)

    Hancock, Andrew; Allen, John S.; Kruse, Dustin E.; Dayton, Paul A.; Kargel, Christian M.; Insana, Michael F.

    2001-05-01

    We are developing an acoustic levitation chamber for measuring adhesion force strengths among biological cells. Our research has four phases. Phase I, presented here, is concerned with the design and construction of a chamber for trapping cell-sized microbubbles with known properties in acoustic standing waves, and examines the theory that describes the standing wave field. A cylindrical chamber has been developed to generate a stable acoustic standing wave field. The pressure field was mapped using a 0.4-mm needle hydrophone, and experiments were performed using 100 micron diameter unencapsulated air bubbles, 9 micron diameter isobutane-filled microbubbles, and 3 micron diameter decafluorobutane (C4F10)-filled microbubbles, confirming that the net radiation force from the standing wave pressure field tends to band the microbubbles at pressure antinodes, in accordance with theory.

  12. Acoustic waves in random ensembles of magnetic fluxes

    SciTech Connect

    Ryutova, M.P.

    1995-10-10

    To analyze the observational data and provide the appropriate diagnostic procedure for photospheric manifestation of solar oscillations it is necessary to take into account strong inhomogeneity of solar atmosphere with respect to distribution of magnetic fields. We study the collective phenomena in the propagation of acoustic waves and unsteady wave-packets through quite regions, sunspots and plages, including time-dependent response of these regions to solar oscillations, the energy transfer mechanisms, frequency shift effects and reradiation of the acoustic waves in higher layers of atmosphere. We show that the dynamics of differently magnetized regions, their dispersion properties, and their response to the propagation of acoustic waves are completely different. We describe the effects caused by the specific distribution and randomness of magnetic flux tubes, which can be observed and which can provide the tools for diagnostic goals.

  13. Separation of acoustic waves in isentropic flow perturbations

    SciTech Connect

    Henke, Christian

    2015-04-15

    The present contribution investigates the mechanisms of sound generation and propagation in the case of highly-unsteady flows. Based on the linearisation of the isentropic Navier–Stokes equation around a new pathline-averaged base flow, it is demonstrated for the first time that flow perturbations of a non-uniform flow can be split into acoustic and vorticity modes, with the acoustic modes being independent of the vorticity modes. Therefore, we can propose this acoustic perturbation as a general definition of sound. As a consequence of the splitting result, we conclude that the present acoustic perturbation is propagated by the convective wave equation and fulfils Lighthill’s acoustic analogy. Moreover, we can define the deviations of the Navier–Stokes equation from the convective wave equation as “true” sound sources. In contrast to other authors, no assumptions on a slowly varying or irrotational flow are necessary. Using a symmetry argument for the conservation laws, an energy conservation result and a generalisation of the sound intensity are provided. - Highlights: • First splitting of non-uniform flows in acoustic and non-acoustic components. • These result leads to a generalisation of sound which is compatible with Lighthill’s acoustic analogy. • A closed equation for the generation and propagation of sound is given.

  14. Broadband enhanced transmission of acoustic waves through serrated metal gratings

    NASA Astrophysics Data System (ADS)

    Qi, Dong-Xiang; Fan, Ren-Hao; Deng, Yu-Qiang; Peng, Ru-Wen; Wang, Mu; Jiangnan University Collaboration

    In this talk, we present our studies on broadband properties of acoustic waves through metal gratings. We have demonstrated that serrated metal gratings, which introduce gradient coatings, can give rise to broadband transmission enhancement of acoustic waves. Here, we have experimentally and theoretically studied the acoustic transmission properties of metal gratings with or without serrated boundaries. The average transmission is obviously enhanced for serrated metal gratings within a wide frequency range, while the Fabry-Perot resonance is significantly suppressed. An effective medium hypothesis with varying acoustic impedance is proposed to analyze the mechanism, which was verified through comparison with finite-element simulation. The serrated boundary supplies gradient mass distribution and gradient normal acoustic impedance, which could efficiently reduce the boundary reflection. Further, by increasing the region of the serrated boundary, we present a broadband high-transmission grating for wide range of incident angle. Our results may have potential applications to broadband acoustic imaging, acoustic sensing and new acoustic devices. References: [1] Dong-Xiang Qi, Yu-Qiang Deng, Di-Hu Xu, Ren-Hao Fan, Ru-Wen Peng, Ze-Guo Chen, Ming-Hui Lu, X. R. Huang and Mu Wang, Appl. Phys. Lett. 106, 011906 (2015); [2] Dong-Xiang Qi, Ren-Hao Fan, Ru-Wen Peng, Xian-Rong Huang, Ming-Hui Lu, Xu Ni, Qing Hu, and Mu Wang, Applied Physics Letters 101, 061912 (2012).

  15. Artificial cochlea and acoustic black hole travelling waves observation: Model and experimental results

    NASA Astrophysics Data System (ADS)

    Foucaud, Simon; Michon, Guilhem; Gourinat, Yves; Pelat, Adrien; Gautier, François

    2014-07-01

    An inhomogeneous fluid structure waveguide reproducing passive behaviour of the inner ear is modelled with the help of the Wentzel-Kramers-Brillouin method. A physical setup is designed and built. Experimental results are compared with a good correlation to theoretical ones. The experimental setup is a varying width plate immersed in fluid and terminated with an acoustic black hole. The varying width plate provides a spatial repartition of the vibration depending on the excitation frequency. The acoustic black hole is made by decreasing the plate's thickness with a quadratic profile and by covering this region with a thin film of viscoelastic material. Such a termination attenuates the flexural wave reflection at the end of the waveguide, turning standing waves into travelling waves.

  16. Acoustic resonance excitation of turbulent heat transfer and flow reattachment downstream of a fence

    NASA Astrophysics Data System (ADS)

    Selcan, Claudio; Cukurel, Beni; Shashank, Judah

    2015-12-01

    The current work investigates the aero-thermal impact of standing sound waves, excited in a straight channel geometry, on turbulent, separating and reattaching flow over a fence. Effects of distinct frequency resonant forcing (ReH = 10,050 and f = 122 Hz) are quantified by wall static pressure measurements and detailed convective heat transfer distributions via liquid crystal thermometry. Acoustic boundary conditions are numerically predicted and the computed longitudinal resonance mode shapes are experimentally verified by surface microphone measurements. Findings indicate the presence of a resonant sound field to exert strong influence on local heat transfer downstream of the fence, whereas the boundary layer upstream of the obstacle remains notable unaffected. Upstream shift of the maximum heat transfer location and an earlier pressure recovery indicate a reduction in time averaged flow reattachment length of up to 37 %. Although the streamwise peak Nusselt increased by only 5 %, the heat transfer level in the vicinity of the unexcited reattachment zone was locally enhanced up to 25 %. Despite prominent impact of resonant forcing on the fence wake flow, the total pressure drop penalty remained invariant. Observations demonstrate the significant aero-thermal implications of shear layer excitation by standing sound waves superimposed on the channel flow field.

  17. Acoustic resonance excitation of turbulent heat transfer and flow reattachment downstream of a fence

    NASA Astrophysics Data System (ADS)

    Selcan, Claudio; Cukurel, Beni; Shashank, Judah

    2016-10-01

    The current work investigates the aero-thermal impact of standing sound waves, excited in a straight channel geometry, on turbulent, separating and reattaching flow over a fence. Effects of distinct frequency resonant forcing (ReH = 10,050 and f = 122 Hz) are quantified by wall static pressure measurements and detailed convective heat transfer distributions via liquid crystal thermometry. Acoustic boundary conditions are numerically predicted and the computed longitudinal resonance mode shapes are experimentally verified by surface microphone measurements. Findings indicate the presence of a resonant sound field to exert strong influence on local heat transfer downstream of the fence, whereas the boundary layer upstream of the obstacle remains notable unaffected. Upstream shift of the maximum heat transfer location and an earlier pressure recovery indicate a reduction in time averaged flow reattachment length of up to 37 %. Although the streamwise peak Nusselt increased by only 5 %, the heat transfer level in the vicinity of the unexcited reattachment zone was locally enhanced up to 25 %. Despite prominent impact of resonant forcing on the fence wake flow, the total pressure drop penalty remained invariant. Observations demonstrate the significant aero-thermal implications of shear layer excitation by standing sound waves superimposed on the channel flow field.

  18. The dispersion of parametrically excited surface waves in viscous ferrofluids

    NASA Astrophysics Data System (ADS)

    Müller, Hanns Walter

    1999-07-01

    Surface waves on a ferrofluid, which is exposed to a normal magnetic field, may exhibit a non-monotonous behavior. Stationary standing waves can be excited mechanically by a vertical vibration of the vessel, or magnetically by a modulation of the applied field. A linear stability analysis for the onset of these parametrically excited waves is presented. It will be shown that a careful choice of the filling depth allows for a detection of the anomalous dispersion branch. Furthermore, a theoretical confirmation is provided for the synchronous wave response, recently observed in a magnetic Faraday experiment.

  19. Infrasonic acoustic waves generated by fast air heating in sprite cores

    NASA Astrophysics Data System (ADS)

    Silva, Caitano L.; Pasko, Victor P.

    2014-03-01

    Acceleration, expansion, and branching of sprite streamers can lead to concentration of high electrical currents in regions of space, that are observed in the form of bright sprite cores. Driven by this electrical current, a series of chemical processes take place in the sprite plasma. Excitation, followed by quenching of excited electronic states leads to energy transfer from charged to neutral species. The consequence is heating and expansion of air leading to emission of infrasonic acoustic waves. Results indicate that ≳0.01 Pa pressure perturbations on the ground, observed in association with sprites, can only be produced by exceptionally strong currents in sprite cores, exceeding 2 kA.

  20. Optical excitation of narrowband Rayleigh surface waves for second harmonic generation

    NASA Astrophysics Data System (ADS)

    Swacek, C. B.; Kim, J.-Y.; Jacobs, L. J.

    2013-01-01

    Conventional fluid-coupled contact ultrasonic methods suffer from large variability, which is known to originate from a number of sources such as the coupling variation and the surface roughness at the transducer/specimen interface. The inherently small higherharmonic signals can be significantly influenced by these changes in contact conditions, especially in nonlinear ultrasonic measurements. For this reason, the noncontact generation and detection techniques are very attractive. This research first focuses on the noncontact optical generation of tone-burst surface acoustic wave signals in a metallic specimen. Two methods that use laser light as an optical source are compared for generating surface acoustics waves in 5 MHz range. Both the shadow mask and diffraction grating are used to convert the circular laser beam into a periodic excitation pattern on the specimen. The generated signals are detected by a wedge transducer at a fixed location while the location of the excitation is varied. Then the harmonic contents in the generated signals and the repeatability of the methods are evaluated. Finally, the developed method is used to characterize the acoustic nonlinearity of aluminum (Al 6061) and steel (A36). The results on the aluminum samples show that the measurements based on the shadow mask excitation are repeatable in the ablative regime.

  1. Anomalous Refraction of Acoustic Guided Waves in Solids with Geometrically Tapered Metasurfaces.

    PubMed

    Zhu, Hongfei; Semperlotti, Fabio

    2016-07-15

    The concept of a metasurface opens new exciting directions to engineer the refraction properties in both optical and acoustic media. Metasurfaces are typically designed by assembling arrays of subwavelength anisotropic scatterers able to mold incoming wave fronts in rather unconventional ways. The concept of a metasurface was pioneered in photonics and later extended to acoustics while its application to the propagation of elastic waves in solids is still relatively unexplored. We investigate the design of acoustic metasurfaces to control elastic guided waves in thin-walled structural elements. These engineered discontinuities enable the anomalous refraction of guided wave modes according to the generalized Snell's law. The metasurfaces are made out of locally resonant toruslike tapers enabling an accurate phase shift of the incoming wave, which ultimately affects the refraction properties. We show that anomalous refraction can be achieved on transmitted antisymmetric modes (A_{0}) either when using a symmetric (S_{0}) or antisymmetric (A_{0}) incident wave, the former clearly involving mode conversion. The same metasurface design also allows achieving structure embedded planar focal lenses and phase masks for nonparaxial propagation.

  2. Anomalous Refraction of Acoustic Guided Waves in Solids with Geometrically Tapered Metasurfaces.

    PubMed

    Zhu, Hongfei; Semperlotti, Fabio

    2016-07-15

    The concept of a metasurface opens new exciting directions to engineer the refraction properties in both optical and acoustic media. Metasurfaces are typically designed by assembling arrays of subwavelength anisotropic scatterers able to mold incoming wave fronts in rather unconventional ways. The concept of a metasurface was pioneered in photonics and later extended to acoustics while its application to the propagation of elastic waves in solids is still relatively unexplored. We investigate the design of acoustic metasurfaces to control elastic guided waves in thin-walled structural elements. These engineered discontinuities enable the anomalous refraction of guided wave modes according to the generalized Snell's law. The metasurfaces are made out of locally resonant toruslike tapers enabling an accurate phase shift of the incoming wave, which ultimately affects the refraction properties. We show that anomalous refraction can be achieved on transmitted antisymmetric modes (A_{0}) either when using a symmetric (S_{0}) or antisymmetric (A_{0}) incident wave, the former clearly involving mode conversion. The same metasurface design also allows achieving structure embedded planar focal lenses and phase masks for nonparaxial propagation. PMID:27472114

  3. Anomalous Refraction of Acoustic Guided Waves in Solids with Geometrically Tapered Metasurfaces

    NASA Astrophysics Data System (ADS)

    Zhu, Hongfei; Semperlotti, Fabio

    2016-07-01

    The concept of a metasurface opens new exciting directions to engineer the refraction properties in both optical and acoustic media. Metasurfaces are typically designed by assembling arrays of subwavelength anisotropic scatterers able to mold incoming wave fronts in rather unconventional ways. The concept of a metasurface was pioneered in photonics and later extended to acoustics while its application to the propagation of elastic waves in solids is still relatively unexplored. We investigate the design of acoustic metasurfaces to control elastic guided waves in thin-walled structural elements. These engineered discontinuities enable the anomalous refraction of guided wave modes according to the generalized Snell's law. The metasurfaces are made out of locally resonant toruslike tapers enabling an accurate phase shift of the incoming wave, which ultimately affects the refraction properties. We show that anomalous refraction can be achieved on transmitted antisymmetric modes (A0) either when using a symmetric (S0) or antisymmetric (A0) incident wave, the former clearly involving mode conversion. The same metasurface design also allows achieving structure embedded planar focal lenses and phase masks for nonparaxial propagation.

  4. Acoustic tweezers via sub–time-of-flight regime surface acoustic waves

    PubMed Central

    Collins, David J.; Devendran, Citsabehsan; Ma, Zhichao; Ng, Jia Wei; Neild, Adrian; Ai, Ye

    2016-01-01

    Micrometer-scale acoustic waves are highly useful for refined optomechanical and acoustofluidic manipulation, where these fields are spatially localized along the transducer aperture but not along the acoustic propagation direction. In the case of acoustic tweezers, such a conventional acoustic standing wave results in particle and cell patterning across the entire width of a microfluidic channel, preventing selective trapping. We demonstrate the use of nanosecond-scale pulsed surface acoustic waves (SAWs) with a pulse period that is less than the time of flight between opposing transducers to generate localized time-averaged patterning regions while using conventional electrode structures. These nodal positions can be readily and arbitrarily positioned in two dimensions and within the patterning region itself through the imposition of pulse delays, frequency modulation, and phase shifts. This straightforward concept adds new spatial dimensions to which acoustic fields can be localized in SAW applications in a manner analogous to optical tweezers, including spatially selective acoustic tweezers and optical waveguides. PMID:27453940

  5. DE-1 and COSMOS 1809 observations of lower hybrid waves excited by VLF whistler mode waves

    NASA Technical Reports Server (NTRS)

    Bell, T. F; Inan, U. S.; Lauben, D.; Sonwalkar, V. S.; Helliwell, R. A.; Sobolev, Ya. P.; Chmyrev, V. M.; Gonzalez, S.

    1994-01-01

    Past work demostrates that strong lower hybrid (LH) waves can be excited by electromagnetic whistler mode waves throughout large regions of the topside ionosphere and magnetosphere. The effects of the excited LH waves upon the suprathermal ion population in the topside ionosphere and magnetosphere depend upon the distribution of LH wave amplitude with wavelength lambda. The present work reports plasma wave data from the DE-1 and COSMOS 1809 spacecraft which suggests that the excited LH wave spectrum has components for which lambda less than or equal to 3.5 m when excitation occurs at a frequency roughly equal to the local lower hybrid resonance frequency. This wavelength limit is a factor of approximately 3 below that reported in past work and suggests that the excited LH waves can interact with suprathermal H(+) ions with energy less than or equal to 6 eV. This finding supports recent work concerning the heating of suprathermal ions above thunderstorm cells.

  6. DE-1 and COSMOS 1809 observations of lower hybrid waves excited by VLF whistler mode waves

    SciTech Connect

    Bell, T.F.; Inan, U.S.; Lauben, D.; Sonwalkar, V.S.; Helliwell, R.A.; Sobolev, Ya.P.; Chmyrev, V.M.; Gonzalez, S.

    1994-04-15

    Past work demonstrates that strong lower hybrid (LH) waves can be excited by electromagnetic whistler mode waves throughout large regions of the topside ionosphere and magnetosphere. The effects of the excited LH waves upon the suprathermal ion population in the topside ionosphere and magnetosphere depend upon the distribution of LH wave amplitude with wavelength {lambda}. The present work reports plasma wave data from the DE-1 and COSMOS 1809 spacecraft which suggests that the excited LH wave spectrum has components for which {lambda} {le} 3.5 m when excitation occurs at a frequency roughly equal to the lower hybrid resonance frequency. This wavelength limit is a factor of {approximately} 3 below that reported in past work and suggests that the excited LH waves can interact with suprathermal H{sup +} ions with energy {le} 6 eV. This finding supports recent work concerning the heating of suprathermal ions above thunderstorm cells. 19 refs., 3 figs.

  7. Effect of nonadiabaticity of dust charge variation on dust acoustic waves: generation of dust acoustic shock waves.

    PubMed

    Gupta, M R; Sarkar, S; Ghosh, S; Debnath, M; Khan, M

    2001-04-01

    The effect of nonadiabaticity of dust charge variation arising due to small nonzero values of tau(ch)/tau(d) has been studied where tau(ch) and tau(d) are the dust charging and dust hydrodynamical time scales on the nonlinear propagation of dust acoustic waves. Analytical investigation shows that the propagation of a small amplitude wave is governed by a Korteweg-de Vries (KdV) Burger equation. Notwithstanding the soliton decay, the "soliton mass" is conserved, but the dissipative term leads to the development of a noise tail. Nonadiabaticity generated dissipative effect causes the generation of a dust acoustic shock wave having oscillatory behavior on the downstream side. Numerical investigations reveal that the propagation of a large amplitude dust acoustic shock wave with dust density enhancement may occur only for Mach numbers lying between a minimum and a maximum value whose dependence on the dusty plasma parameters is presented. PMID:11308955

  8. Dissipation of acoustic-gravity waves: an asymptotic approach.

    PubMed

    Godin, Oleg A

    2014-12-01

    Acoustic-gravity waves in the middle and upper atmosphere and long-range propagation of infrasound are strongly affected by air viscosity and thermal conductivity. To characterize the wave dissipation, it is typical to consider idealized environments, which admit plane-wave solutions. Here, an asymptotic approach is developed that relies instead on the assumption that spatial variations of environmental parameters are gradual. It is found that realistic assumptions about the atmosphere lead to rather different predictions for wave damping than do the plane-wave solutions. A modification to the Sutherland-Bass model of infrasound absorption is proposed. PMID:25480091

  9. Dissipation of acoustic-gravity waves: an asymptotic approach.

    PubMed

    Godin, Oleg A

    2014-12-01

    Acoustic-gravity waves in the middle and upper atmosphere and long-range propagation of infrasound are strongly affected by air viscosity and thermal conductivity. To characterize the wave dissipation, it is typical to consider idealized environments, which admit plane-wave solutions. Here, an asymptotic approach is developed that relies instead on the assumption that spatial variations of environmental parameters are gradual. It is found that realistic assumptions about the atmosphere lead to rather different predictions for wave damping than do the plane-wave solutions. A modification to the Sutherland-Bass model of infrasound absorption is proposed.

  10. Excitation of sound waves upon propagation of laser pulses in optical fibres

    SciTech Connect

    Biryukov, A S; Sukharev, M E; Dianov, Evgenii M

    2002-09-30

    A revised, more comprehensive model of excitation and propagation of acoustic vibrations, electrostrictively induced in optical fibres by laser pulses, is presented. An analytic expression for the acoustic response function of the refractive index in a standard single-mode fibre is derived. Response functions are found for a standard fibre as well as for a single-mode double-clad fibre, which offers much promise for fibreoptic communication lines and where the effective area of mode-field cross section is increased with respect to a standard fibre. It is shown that the intensity of excited sound waves in double-clad fibres is usually several times higher than that in standard fibres. This intensity is determined mainly by the shape of the radial distribution of the electromagnetic field in the pulse, which is different for the fibres considered in this paper. (invited paper)

  11. Artificial excitation of ELF waves with frequency of Schumann resonance

    NASA Astrophysics Data System (ADS)

    Streltsov, A. V.; Guido, T.; Tulegenov, B.; Labenski, J.; Chang, C.-L.

    2014-11-01

    We report results from the experiment aimed at the artificial excitation of extremely low-frequency (ELF) electromagnetic waves with frequencies corresponding to the frequency of Schumann resonance. Electromagnetic waves with these frequencies can form a standing pattern inside the spherical cavity formed by the surface of the Earth and the ionosphere. In the experiment the ELF waves were excited by heating the ionosphere with X-mode HF electromagnetic waves generated at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. The experiment demonstrates that heating of the ionosphere can excite relatively large-amplitude electromagnetic waves with frequencies in the range 7.8-8.0 Hz when the ionosphere has a strong F layer, the frequency of the HF radiation is in the range 3.20-4.57 MHz, and the electric field greater than 5 mV/m is present in the ionosphere.

  12. Stochastic excitation of seismic waves by a hurricane

    NASA Astrophysics Data System (ADS)

    Tanimoto, Toshiro; Valovcin, Anne

    2015-11-01

    We investigate how a tropical cyclone (Hurricane Isaac in 2012) generated seismic ground motions using seismic and barometric data from the Earthscope network. In the frequency band 0.01-0.02 Hz, seismic and surface pressure amplitudes show a systematic decreasing trend with distance from the center of the hurricane. However, the decreasing rate is much higher for seismic waves than for pressure. We develop a stochastic theory of seismic wave excitation by surface pressure that connects these two observed data sets; surface pressure is the excitation source, and seismic data are the resulting seismic wave field. This theory contains two parameters: (i) the pressure power spectral density (Sp) and (ii) the correlation length in the pressure field (L). Using the formula, we solve for the spatial variation of correlation lengths. The solution shows that longer correlation lengths in pressure are near the hurricane center. Because seismic wave excitation is proportional to L2Sp, the excitation for seismic waves becomes effectively more localized closer to the center. Also, the scaling relation between L and Sp leads to an excitation source which is approximately proportional to the third power of surface pressure. This centralized source for seismic wave excitation explains why the decreasing rate with distance is higher for seismic data than for barometric data. However, this spatial coherence mechanism may not be the only process, as strong turbulence near the center may cause transient bursts of pressure and also induce higher temporal correlation. These alternative mechanisms need to be carefully analyzed in the future.

  13. Electron-acoustic solitary waves in a nonextensive plasma

    SciTech Connect

    Tribeche, Mouloud; Djebarni, Lyes

    2010-12-15

    The problem of arbitrary amplitude electron-acoustic solitary waves (EASWs) in a plasma having cold fluid electrons, hot nonextensive electrons, and stationary ions is addressed. It is found that the 'Maxwellianization' process of the hot nonextensive component does not favor the propagation of the EASWs. In contrast to superthermality, nonextensivity makes the electron-acoustic solitary structure less spiky. Our theoretical analysis brings a possibility to develop more refined theories of nonlinear solitary structures in astrophysical plasmas.

  14. The behavior of acoustic waves in the lakes bottom sediments.

    NASA Astrophysics Data System (ADS)

    Krylov, Pavel; Nourgaliev, Danis; Yasonov, Pavel

    2016-04-01

    Seismic studies are used for various tasks, such as the study of the bottom sediments properties, finding sunken objects, reconstruction the reservoir history, etc. Multiple acoustic waves are an enormous obstacle in obtaining full seismic record. Multiples from the bottom of a body of water (the surface of the base of water and the rock or sediment beneath it) and the air-water surface are common in lake seismic data. Multiple reflections on the seismic cross-sections are usually located on the double distance from the air/water surface. However, sometime multiple reflections from liquid deposits cannot be generated or they reflected from the deeper horizons. It is observed the phenomenon of changes in reflectance of the water/weakly consolidated sediments acoustic boundary under the influence of the acoustic wave. This phenomenon lies in the fact that after the first acoustic impact and reflection of acoustic wave for some time the reflectance of this boundary remains close to 0. This event on a cross-section can explain by the short-term changes in the properties of bottom sediments under the influence of shock? acoustic wave, with a further reduction of these properties to the next wave generation (generation period of 2 seconds). Perhaps in these deposits occurs thixotropic process. The paper presents the seismic acoustic cross-sections of Lake Balkhash (Kazakhstan), Turgoyak (Russia). The work was carried out according to the Russia Government's Program of Competitive Growth of Kazan Federal University, supported by the grant provided to the Kazan State University for performing the state program in the field of scientific research, and partially supported by the Russian Foundation for Basic research (grants № 14-05-00785, 16-35-00452).

  15. Controllable optical transparency using an acoustic standing-wave device

    NASA Astrophysics Data System (ADS)

    Moradi, Kamran; El-Zahab, Bilal

    2015-09-01

    In this paper, a suspended-particle device with controllable light transmittance was developed based on acoustic stimuli. Using a glass compartment and carbon particle suspension in an organic solvent, the device responded to acoustic stimulation by alignment of particles. The alignment of light-absorbing carbon particles afforded an increase in light transmittance as high as 84.5% and was controllable based on the control of the frequency and amplitude of the acoustic waves. The device also demonstrated alignment memory rendering it energy-efficient.

  16. Unique flow transitions and particle collection switching phenomena in a microchannel induced by surface acoustic waves

    NASA Astrophysics Data System (ADS)

    Tan, Ming K.; Yeo, Leslie Y.; Friend, James R.

    2010-12-01

    We present an experimental approach for controlled switching between uniform flow for pumping and vortical flow for mixing in a microchannel fabricated onto a piezoelectric substrate. For particle laden fluids, this arrangement permits a choice between transport and alignment of microparticles. Using surface acoustic waves with amplitudes beyond 1 nm, the transition from uniform to mixing flows occurs when the acoustic wavelength in the fluid is reduced to a dimension smaller than the channel width, i.e., λf≥Wch for uniform flow and λfacoustic waves with amplitudes below 1 nm, particles in an initially homogeneous suspension agglomerate into equally spaced lines with a separation of λf/2. Switching the transducer between its fundamental resonant frequency f0 and its first harmonic frequency f1+˜2f0 causes a switch between uniform and mixing flow, while switching between large and small amplitude excitation allows one to choose whether to collect the particles in the flow along nodal lines parallel to the channel. These results are uniquely achieved without requiring the microfabrication of complex microchannel architectures and control schemes; the switching is simply achieved by adjusting two parameters: the acoustic excitation frequency and amplitude.

  17. Frequent excitations of T waves by earthquakes in the South Mariana Arc

    NASA Astrophysics Data System (ADS)

    Chen, Po-Fei; Chen, Kai-Xun; Cheng, Hui-Yun

    2015-02-01

    We used broadband stations in Taiwan and on the Ryukyu Arc islands to investigate T waves induced by earthquakes in the Izu-Bonin-Mariana subduction zone. Of the 48 earthquakes that took place in 2005, 17 earthquakes exhibited T-wave signals consistent with predicted arrival times at stations. Of theses T-excited events, 13 were located in the South Mariana Arc, where the isobaths exhibit strong concave curvature, and were predominantly of normal faulting type. The energies of observed T waves were used quantitatively to evaluate the relative efficiency of receiver-side acoustic-elastic conversions by Gamma calculations. Results show that the steep slopes of offshore bathymetry together with nearly perpendicular angles of back azimuth relative to local isobaths are suitable conditions for T waves observations. In 2010, two clusters of repeated moderate earthquakes in the north and south ends of the Mariana Arc displayed stark contrasts in terms of T-wave excitations despite their normal faulting type. Examining of this discrepancy indicate that a specific curvature together with a specific radiation pattern accounts for the frequent excitations of T waves from shallow earthquakes in the South Mariana Arc.

  18. Randomly driven acoustic-gravity waves in the solar atmosphere: cutoff period and its observational verification

    NASA Astrophysics Data System (ADS)

    Murawski, K.; Musielak, Z. E.

    2016-09-01

    We study the propagation of acoustic-gravity waves in the solar atmosphere. The waves are excited by a space- and time-dependent random driver, whose action mimics turbulence in the upper part of the solar convection zone. Our main goal is to find vertical variations of wave periods of these waves and compare the obtained results to the recent observations of Wiśniewska et al. (2016). We solve numerically the hydrodynamic equations in the solar atmosphere whose temperature is given by the semi-empirical model of Avrett & Loeser (2008). The obtained numerical results show that wave periods vary along vertical direction in agreement with the recent observational data. We discuss physical consequences of our theoretical results.

  19. Excitation of Banded Whistler Waves in the Magnetosphere

    SciTech Connect

    Gary, S. Peter; Liu, Kaijun; Winske, Dan

    2012-07-13

    Banded whistler waves can be generated by the whistler anisotropy instability driven by two bi-Maxwellian electron components with T{sub {perpendicular}}/T{sub {parallel}} > 1 at different T{sub {parallel}} For typical magnetospheric condition of 1 < {omega}{sub e}/{Omega}{sub e} < 5 in regions associated with strong chorus, upper-band waves can be excited by anisotropic electrons below {approx} 1 keV, while lower-band waves are excited by anisotropic electrons above {approx} 10 keV. Lower-band waves are generally field-aligned and substantially electromagnetic, while upper-band waves propagate obliquely and have quasi-electrostatic fluctuating electric fields. The quasi-electrostatic feature of upper-band waves suggests that they may be more easily identified in electric field observations than in magnetic field observations. Upper-band waves are liable to Landau damping and the saturation level of upperband waves is lower than lower-band waves, consistent with observations that lower-band waves are stronger than upper-band waves on average. The oblique propagation, the lower saturation level, and the more severe Landau damping together would make upper-band waves more tightly confined to the geomagnetic equator (|{lambda}{sub m}| < {approx}10{sup o}) than lower-band waves.

  20. Acoustic waves switch based on meta-fluid phononic crystals

    NASA Astrophysics Data System (ADS)

    Zhu, Xue-Feng

    2012-08-01

    The acoustic waves switch based on meta-fluid phononic crystals (MEFL PCs) is theoretically investigated. The MEFL PCs consist of fluid matrix and fluid-like inclusions with extremely anisotropic-density. The dispersion relations are calculated via the plane wave expansion method, which are in good agreement with the transmitted sound pressure level spectra obtained by the finite element method. The results show that the width of absolute band gap in MEFL PCs depends sensitively upon the orientation of the extremely anisotropic-density inclusions and reaches maximum at the rotating angle of 45°, with the gap position nearly unchanged. Also, the inter-mode conversion inside anisotropic-density inclusions can be ignored due to large acoustic mismatch. The study gives a possibility to realize greater flexibility and stronger effects in tuning the acoustic band gaps, which is very significant in the enhanced control over sound waves and has potential applications in ultrasonic imaging and therapy.

  1. Surface acoustic wave devices for harsh environment wireless sensing

    DOE PAGES

    Greve, David W.; Chin, Tao -Lun; Zheng, Peng; Ohodnicki, Paul; Baltrus, John; Oppenheim, Irving J.

    2013-05-24

    In this study, langasite surface acoustic wave devices can be used to implement harsh environment wireless sensing of gas concentration and temperature. This paper reviews prior work on the development of langasite surface acoustic wave devices, followed by a report of recent progress toward the implementation of oxygen gas sensors. Resistive metal oxide films can be used as the oxygen sensing film, although development of an adherent barrier layer will be necessary with the sensing layers studied here to prevent interaction with the langasite substrate. Experimental results are presented for the performance of a langasite surface acoustic wave oxygen sensormore » with tin oxide sensing layer, and these experimental results are correlated with direct measurements of the sensing layer resistivity.« less

  2. On acoustic wave generation in uniform shear flow

    NASA Astrophysics Data System (ADS)

    Gogoberidze, G.

    2016-07-01

    The linear dynamics of acoustic waves and vortices in uniform shear flow is studied. For flows with very low shear rates, the dynamics of perturbations is adiabatic and can be described by the WKB approximation. However, for flows with moderate and high shear rates the WKB approximation is not appropriate, and alternative analysis shows that two important phenomena occur: acoustic wave over-reflection and wave generation by vortices. The later phenomenon is a known linear mechanisms for sound generation in shear flows, a mechanism that is related to the continuous spectrum that arises in linear shear flow dynamics. A detailed analytical study of these phenomena is performed and the main quantitative and qualitative characteristics of the radiated acoustic field are obtained and analyzed.

  3. Surface Acoustic Wave Devices for Harsh Environment Wireless Sensing

    PubMed Central

    Greve, David W.; Chin, Tao-Lun; Zheng, Peng; Ohodnicki, Paul; Baltrus, John; Oppenheim, Irving J.

    2013-01-01

    Langasite surface acoustic wave devices can be used to implement harsh-environment wireless sensing of gas concentration and temperature. This paper reviews prior work on the development of langasite surface acoustic wave devices, followed by a report of recent progress toward the implementation of oxygen gas sensors. Resistive metal oxide films can be used as the oxygen sensing film, although development of an adherent barrier layer will be necessary with the sensing layers studied here to prevent interaction with the langasite substrate. Experimental results are presented for the performance of a langasite surface acoustic wave oxygen sensor with tin oxide sensing layer, and these experimental results are correlated with direct measurements of the sensing layer resistivity. PMID:23708273

  4. Surface acoustic wave devices for harsh environment wireless sensing

    SciTech Connect

    Greve, David W.; Chin, Tao -Lun; Zheng, Peng; Ohodnicki, Paul; Baltrus, John; Oppenheim, Irving J.

    2013-05-24

    In this study, langasite surface acoustic wave devices can be used to implement harsh environment wireless sensing of gas concentration and temperature. This paper reviews prior work on the development of langasite surface acoustic wave devices, followed by a report of recent progress toward the implementation of oxygen gas sensors. Resistive metal oxide films can be used as the oxygen sensing film, although development of an adherent barrier layer will be necessary with the sensing layers studied here to prevent interaction with the langasite substrate. Experimental results are presented for the performance of a langasite surface acoustic wave oxygen sensor with tin oxide sensing layer, and these experimental results are correlated with direct measurements of the sensing layer resistivity.

  5. Effect of Thermal Conduction on Acoustic Waves in Coronal Loops

    NASA Astrophysics Data System (ADS)

    Bogdan, T. J.

    2006-05-01

    The influence of classical (Spitzer) thermal conduction on longitudinal acoustic waves in a coronal loop is determined through an idealized but exactly solvable model. The model consists of an isothermal, stratified (constant gravity) atmosphere in which a monochromatic acoustic wave, traveling in the direction of decreasing density, is imposed throughout the lower half of the atmosphere. Based on the linearized equations of motion, the complete steady state (t-->∞) solution is obtained. In addition to the imposed driving wave, the solution also contains reflected and transmitted acoustic and thermal conduction waves. The mode transformation and mixing occurs in the vicinity of the atmospheric layer where the gas pressure passes through a critical value set by the magnitude of the thermal conduction and other model parameters. For 5 minute waves in a million degree loop, this critical pressure is on the order of 8×10-4 in cgs units. Since the apex gas pressure of many coronal loops of current interest is thought to be comfortably in excess of this value, mode mixing and transformation is not likely to be a relevant factor for understanding acoustic waves in these structures. On the other hand, enhanced thermal conductivity as a result of plasma instabilities, for example, could revive the importance of this mechanism for coronal loops. If this mixing layer is present, the calculations show that the pair of thermal conduction waves invariably gains the overwhelming majority of the energy flux of the incoming acoustic wave. This energy is rapidly dissipated in the neighborhood of the mixing layer.

  6. Observations of acoustic surface waves in outdoor sound propagation

    NASA Astrophysics Data System (ADS)

    Albert, Donald G.

    2003-05-01

    Acoustic surface waves have been detected propagating outdoors under natural conditions. Two critical experimental conditions were employed to ensure the conclusive detection of these waves. First, acoustic pulses rather than a continuous wave source allowed an examination of the waveform shape and avoided the masking of wave arrivals. Second, a snow cover provided favorable ground impedance conditions for surface waves to exist. The acoustic pulses were generated by blank pistol shots fired 1 m above the snow. The resultant waveforms were measured using a vertical array of six microphones located 60 m away from the source at heights between 0.1 and 4.75 m. A strong, low frequency ``tail'' following the initial arrival was recorded near the snow surface. This tail, and its exponential decay with height (z) above the surface (~e-αz), are diagnostic features of surface waves. The measured attenuation coefficient α was 0.28 m-1. The identification of the surface wave is confirmed by comparing the measured waveforms with waveforms predicted by the theoretical evaluation of the explicit surface wave pole term using residue theory.

  7. Mechanical back-action of a spin-wave resonance in a magnetoelastic thin film on a surface acoustic wave

    NASA Astrophysics Data System (ADS)

    Gowtham, P. G.; Labanowski, D.; Salahuddin, S.

    2016-07-01

    Surface acoustic waves (SAWs) traveling on the surface of a piezoelectric crystal can, through the magnetoelastic interaction, excite traveling spin-wave resonance in a magnetic film deposited on the substrate. This spin-wave resonance in the magnetic film creates a time-ynamic surface stress of magnetoelastic origin that acts back on the surface of the piezoelectric and modifies the SAW propagation. Unlike previous analyses that treat the excitation as a magnon-phonon polariton, here the magnetoelastic film is treated as a perturbation modifying boundary conditions on the SAW. We use acoustical perturbation theory to find closed-form expressions for the back-action surface stress and strain fields and the resultant SAW velocity shifts and attenuation. We demonstrate that the shear stres fields associated with this spin-wave back-action also generate effective surface currents on the piezoelectric both in phase and out of phase with the driving SAW potential. Characterization of these surface currents and their applications in determination of the magnetoelastic coupling are discussed. The perturbative calculation is carried out explicitly to first order (a regime corresponding to many experimental situations of current interest) and we provide a sketch of the implications of the theory at higher order.

  8. Excitation of parasitic waves near cutoff in forward-wave amplifiers

    SciTech Connect

    Nusinovich, Gregory S.; Sinitsyn, Oleksandr V.; Antonsen, Thomas M. Jr.

    2010-10-15

    In this paper, excitation of parasitic waves near cutoff in forward-wave amplifiers is studied in a rather general form. This problem is important for developing high-power sources of coherent, phase controlled short-wavelength electromagnetic radiation because just the waves which can be excited near cutoff have low group velocities. Since the wave coupling to an electron beam is inversely proportional to the group velocity, these waves are the most dangerous parasitic waves preventing stable amplification of desired signal waves. Two effects are analyzed in the paper. The first one is the effect of signal wave parameters on the self-excitation conditions of such parasitic waves. The second effect is the role of the beam geometry on excitation of these parasitic waves in forward-wave amplifiers with spatially extended interaction space, such as sheet-beam devices. It is shown that a large-amplitude signal wave can greatly influence the self-excitation conditions of the parasitic waves which define stability of operation. Therefore the effect described is important for accurate designing of high-power amplifiers of electromagnetic waves.

  9. Influence of acoustoelastic coefficient on wave time of flight in stress measurement in piezoelectric self-excited system

    NASA Astrophysics Data System (ADS)

    Kwaśniewki, Janusz; Dominik, Ireneusz; Lalik, Krzysztof; Holewa, Karolina

    2016-10-01

    This paper presents the Self-excited Acoustical System (SAS) in elastic construction stress change measurement. The system is based on the acoustical autoresonance phenomena and enables an indirect measurement of the construction effort level. The essence of the SAS system is to use a piezoelectric vibration emitter and a piezoelectric vibration receiver placed at a distance, which are coupled with a proper power amplifier, and which are operating in a closed loop with a positive feedback. This causes the excitation of the system. The change of the velocity of wave propagation, which is associated with the change of the resonance frequency in the system is caused by the stress change in the examined material. A variable, which determines the change of the acoustic wave velocity, is called an acoustoelastic coefficient β. Such a coefficient allows to determine the absolute stress value in the tested material.

  10. An experimental investigation of the generation and consequences of acoustic waves in an axial flow compressor Large axial spacings between blade rows

    NASA Astrophysics Data System (ADS)

    Parker, R.; Stoneman, S. A. T.

    1985-03-01

    The excitation of acoustic waves by vortex shedding from the inlet guide vanes in the annulus of a single-stage, low-speed axial-flow compressor test rig is investigated experimentally, in an effort to examine the assumptions made in the study of Parker (1984) and to provide data for mathematical models of these phenomena. The experimental setup and the transducers used to measure the operating and acoustic parameters are described in detail and illustrated with photographs and drawings, and the results are presented graphically. It is found that each mode excited can be associated with several excitation frequencies of the rotor blades, indicating forced blade vibration due to acoustic resonances.

  11. A metasurface carpet cloak for electromagnetic, acoustic and water waves.

    PubMed

    Yang, Yihao; Wang, Huaping; Yu, Faxin; Xu, Zhiwei; Chen, Hongsheng

    2016-01-29

    We propose a single low-profile skin metasurface carpet cloak to hide objects with arbitrary shape and size under three different waves, i.e., electromagnetic (EM) waves, acoustic waves and water waves. We first present a metasurface which can control the local reflection phase of these three waves. By taking advantage of this metasurface, we then design a metasurface carpet cloak which provides an additional phase to compensate the phase distortion introduced by a bump, thus restoring the reflection waves as if the incident waves impinge onto a flat mirror. The finite element simulation results demonstrate that an object can be hidden under these three kinds of waves with a single metasurface cloak.

  12. A metasurface carpet cloak for electromagnetic, acoustic and water waves

    PubMed Central

    Yang, Yihao; Wang, Huaping; Yu, Faxin; Xu, Zhiwei; Chen, Hongsheng

    2016-01-01

    We propose a single low-profile skin metasurface carpet cloak to hide objects with arbitrary shape and size under three different waves, i.e., electromagnetic (EM) waves, acoustic waves and water waves. We first present a metasurface which can control the local reflection phase of these three waves. By taking advantage of this metasurface, we then design a metasurface carpet cloak which provides an additional phase to compensate the phase distortion introduced by a bump, thus restoring the reflection waves as if the incident waves impinge onto a flat mirror. The finite element simulation results demonstrate that an object can be hidden under these three kinds of waves with a single metasurface cloak. PMID:26822429

  13. A metasurface carpet cloak for electromagnetic, acoustic and water waves

    NASA Astrophysics Data System (ADS)

    Yang, Yihao; Wang, Huaping; Yu, Faxin; Xu, Zhiwei; Chen, Hongsheng

    2016-01-01

    We propose a single low-profile skin metasurface carpet cloak to hide objects with arbitrary shape and size under three different waves, i.e., electromagnetic (EM) waves, acoustic waves and water waves. We first present a metasurface which can control the local reflection phase of these three waves. By taking advantage of this metasurface, we then design a metasurface carpet cloak which provides an additional phase to compensate the phase distortion introduced by a bump, thus restoring the reflection waves as if the incident waves impinge onto a flat mirror. The finite element simulation results demonstrate that an object can be hidden under these three kinds of waves with a single metasurface cloak.

  14. A metasurface carpet cloak for electromagnetic, acoustic and water waves.

    PubMed

    Yang, Yihao; Wang, Huaping; Yu, Faxin; Xu, Zhiwei; Chen, Hongsheng

    2016-01-01

    We propose a single low-profile skin metasurface carpet cloak to hide objects with arbitrary shape and size under three different waves, i.e., electromagnetic (EM) waves, acoustic waves and water waves. We first present a metasurface which can control the local reflection phase of these three waves. By taking advantage of this metasurface, we then design a metasurface carpet cloak which provides an additional phase to compensate the phase distortion introduced by a bump, thus restoring the reflection waves as if the incident waves impinge onto a flat mirror. The finite element simulation results demonstrate that an object can be hidden under these three kinds of waves with a single metasurface cloak. PMID:26822429

  15. Coupling between hydrodynamics, acoustics, and heat release in a self-excited unstable combustor

    NASA Astrophysics Data System (ADS)

    Harvazinski, Matthew E.; Huang, Cheng; Sankaran, Venkateswaran; Feldman, Thomas W.; Anderson, William E.; Merkle, Charles L.; Talley, Douglas G.

    2015-04-01

    The unsteady gas dynamic field in a closed combustor is determined by the nonlinear interactions between chamber acoustics, hydrodynamics, and turbulent combustion that can energize these modes. These interactions are studied in detail using hybrid RANS/large eddy simulations (RANS = Reynolds Averaged Navier-Stokes) of a non-premixed, high-pressure laboratory combustor that produces self-excited longitudinal instabilities. The main variable in the study is the relative acoustic length between the combustion chamber and the tube that injects oxidizer into the combustor. Assuming a half-wave (closed-closed) combustion chamber, the tube lengths approximately correspond to quarter-, 3/8-, and half-wave resonators that serve to vary the phasing between the acoustic modes in the tube and the combustion chamber. The simulation correctly predicts the relatively stable behavior measured with the shortest tube and the very unstable behavior measured with the intermediate tube. Unstable behavior is also predicted for the longest tube, a case for which bifurcated stability behavior was measured in the experiment. In the first (stable) configuration, fuel flows into the combustor uninterrupted, and heat release is spatially continuous with a flame that remains attached to the back step. In the second (unstable) configuration, a cyclic process is apparent comprising a disruption in the fuel flow, subsequent detachment of the flame from the back step, and accumulation of fuel in the recirculation zone that ignites upon arrival of a compression wave reflected from the downstream boundary of the combustion chamber. The third case (mixed stable/unstable) shares features with both of the other cases. The major difference between the two cases predicted to be unstable is that, in the intermediate length tube, a pressure wave reflection inside the tube pushes unburnt fuel behind the back step radially outward, leading to a post-coupled reignition mechanism, while in the case of the

  16. Precessional magnetization switching by a surface acoustic wave

    NASA Astrophysics Data System (ADS)

    Thevenard, L.; Camara, I. S.; Majrab, S.; Bernard, M.; Rovillain, P.; Lemaître, A.; Gourdon, C.; Duquesne, J.-Y.

    2016-04-01

    Precessional switching allows subnanosecond and deterministic reversal of magnetic data bits. It relies on triggering a large-angle, highly nonlinear precession of magnetic moments around a bias field. Here we demonstrate that a surface acoustic wave (SAW) propagating on a magnetostrictive semiconducting material produces an efficient torque that induces precessional switching. This is evidenced by Kerr microscopy and acoustic behavior analysis in a (Ga,Mn)(As,P) thin film. Using SAWs should therefore allow remote and wave control of individual magnetic bits at potentially GHz frequencies.

  17. A surface acoustic wave /SAW/ charge transfer imager

    NASA Technical Reports Server (NTRS)

    Papanicolauo, N. A.; Lin, H. C.

    1981-01-01

    An 80 MHz, 2-microsecond surface acoustic wave charge transfer device (SAW-CTD) has been fabricated in which surface acoustic waves are used to create traveling longitudinal electric fields in the silicon substrate and to replace the multiphase clocks of charge coupled devices. The traveling electric fields create potential wells which will carry along charges that may be stored in the wells; the charges may be injected into the wells by light. An optical application is proposed where the SAW-CTD structure is used in place of a conventional interline transfer design.

  18. Surface acoustic wave/silicon monolithic sensor/processor

    NASA Technical Reports Server (NTRS)

    Kowel, S. T.; Kornreich, P. G.; Nouhi, A.; Kilmer, R.; Fathimulla, M. A.; Mehter, E.

    1983-01-01

    A new technique for sputter deposition of piezoelectric zinc oxide (ZnO) is described. An argon-ion milling system was converted to sputter zinc oxide films in an oxygen atmosphere using a pure zinc oxide target. Piezoelectric films were grown on silicon dioxide and silicon dioxide overlayed with gold. The sputtered films were evaluated using surface acoustic wave measurements, X-ray diffraction, scanning electron microscopy, Auger electron spectroscopy, and resistivity measurements. The effect of the sputtering conditions on the film quality and the result of post-deposition annealing are discussed. The application of these films to the generation of surface acoustic waves is also discussed.

  19. Anisotropic diffraction of bulk acoustic wave beams in lithium niobate.

    PubMed

    Naumenko, Natalya F; Chizhikov, Sergey I; Molchanov, Vladimir Ya; Yushkov, Konstantin B

    2015-12-01

    The formalism of planar diffraction tensor was applied to the analysis of anisotropy of bulk acoustic wave diffraction and to build a full map of anisotropic diffractional coefficients for three bulk acoustic wave modes propagating in lithium niobate. For arbitrary propagation direction the diffractional coefficients derived allow estimation of ultrasonic beam divergence in far-field. Analysis of obtained data revealed that the maxima of acousto-optic figure of merit for anisotropic diffraction in the YZ plane correspond to moderate diffractional spreading of the beams exceeding isotropic diffraction 2-3 times. PMID:26150402

  20. Switching in multicore fibers using flexural acoustic waves.

    PubMed

    Fernandes, Gil M; Muga, Nelson J; Rocha, Ana M; Pinto, Armando N

    2015-10-01

    We propose an in-line wavelength selective core switch for multicore fiber (MCF) transmission systems, based on the acousto-optic effect. A theoretical model addressing the interaction between flexural acoustic waves and the optical signal in MCFs is developed. We show that an optical signal propagating in a particular core can be switched to any other core or distributed over all the cores. By tuning the acoustic wave amplitude, we can adjust the amount of optical power transferred between the cores. PMID:26480145

  1. Longitudinal spin dynamics in ferrimagnets: Multiple spin wave nature of longitudinal spin excitations

    NASA Astrophysics Data System (ADS)

    Krivoruchko, V. N.

    2016-08-01

    Motivated by the existing controversy about the physical mechanisms that govern longitudinal magnetization dynamics under the effect of ultrafast laser pulses, in this paper we study the microscopic model of longitudinal spin excitations in a two-sublattice ferrimagnet using the diagrammatic technique for spin operators. The diagrammatic approach provides us with an efficient procedure to derive graphical representations for perturbation expansion series for different spin Green's functions and thus to overcome limitations typical for phenomenological approaches. The infinite series involving all distinct loops built from spin wave propagators are summed up. These result in an expression for the longitudinal spin susceptibility χz z(q ,ω ) applicable in all regions of frequency ω and wave vector q space beyond the hydrodynamical and critical regimes. A strong renormalization of the longitudinal spin oscillations due to processes of virtual creation and annihilation of transverse spin waves has been found. We have shown that the spectrum of longitudinal excitations consists of a quasirelaxation mode forming a central peak in χz z(q ,ω ) and two (acoustic and exchange) precessionlike modes. As the main result, it is predicted that both acoustic and exchange longitudinal excitations are energetically above similar modes of transverse spin waves at the same temperature and wave vector. The existence of the exchange longitudinal mode at such frequencies can result in a new form of excitation behavior in ferrimagnetic system, which could be important for understanding the physics of nonequilibrium magnetic dynamics under the effect of ultrafast laser pulses in multisublattice magnetic materials.

  2. Speech coding, reconstruction and recognition using acoustics and electromagnetic waves

    DOEpatents

    Holzrichter, J.F.; Ng, L.C.

    1998-03-17

    The use of EM radiation in conjunction with simultaneously recorded acoustic speech information enables a complete mathematical coding of acoustic speech. The methods include the forming of a feature vector for each pitch period of voiced speech and the forming of feature vectors for each time frame of unvoiced, as well as for combined voiced and unvoiced speech. The methods include how to deconvolve the speech excitation function from the acoustic speech output to describe the transfer function each time frame. The formation of feature vectors defining all acoustic speech units over well defined time frames can be used for purposes of speech coding, speech compression, speaker identification, language-of-speech identification, speech recognition, speech synthesis, speech translation, speech telephony, and speech teaching. 35 figs.

  3. Speech coding, reconstruction and recognition using acoustics and electromagnetic waves

    DOEpatents

    Holzrichter, John F.; Ng, Lawrence C.

    1998-01-01

    The use of EM radiation in conjunction with simultaneously recorded acoustic speech information enables a complete mathematical coding of acoustic speech. The methods include the forming of a feature vector for each pitch period of voiced speech and the forming of feature vectors for each time frame of unvoiced, as well as for combined voiced and unvoiced speech. The methods include how to deconvolve the speech excitation function from the acoustic speech output to describe the transfer function each time frame. The formation of feature vectors defining all acoustic speech units over well defined time frames can be used for purposes of speech coding, speech compression, speaker identification, language-of-speech identification, speech recognition, speech synthesis, speech translation, speech telephony, and speech teaching.

  4. Antenna excitation of drift wave in a toroidal plasma

    SciTech Connect

    Diallo, A.; Ricci, P.; Fasoli, A.; Furno, I.; Labit, B.; Mueller, S. H.; Podesta, M.; Poli, F. M.; Skiff, F.

    2007-10-15

    In a magnetized toroidal plasma, an antenna tunable in vertical wave number is used to excite density perturbations. Coherent detection is performed by means of Langmuir probes to directly determine both the wave vector and the plasma response induced by the antenna. Comparison between the theoretical density response predicted by the generalized Hasegawa-Wakatani model, and the experimentally determined density response enables us the identification of one peak of the plasma response as a drift wave.

  5. Linear coupling of acoustic and cyclotron waves in plasma flows

    SciTech Connect

    Rogava, Andria; Gogoberidze, Grigol

    2005-05-15

    It is found that in magnetized electrostatic plasma flows the velocity shear couples ion-acoustic waves with ion-cyclotron waves and leads, under favorable conditions, to their efficient reciprocal transformations. It is shown that in a two-dimensional setup this coupling has a remarkable feature: it is governed by equations that are mathematically equal to the ones describing coupling of sound waves with internal gravity waves [Rogava and Mahajan, Phys. Rev. E 55, 1185 (1997)] in neutral fluids. For flows with low shearing rates a fully analytic, quantitative description of the coupling efficiency, based on a noteworthy quantum-mechanical analogy, is given and transformation coefficients are calculated.

  6. Pulsed-laser excitation of acoustic modes in open high-Q photoacoustic resonators for trace gas monitoring: results for C2H4

    NASA Astrophysics Data System (ADS)

    Brand, Christian; Winkler, Andreas; Hess, Peter; Miklós, András; Bozóki, Zoltán; Sneider, János

    1995-06-01

    The pulsed excitation of acoustic resonances was studied with a continuously monitoring photoacoustic detector system. Acoustic waves were generated in C2H4/N 2 gas mixtures by light absorption of the pulses from a transversely excited atmospheric CO2 laser. The photoacoustic part consisted of high-Q cylindrical resonators (Q factor 820 for the first radial mode in N2) and two adjoining variable acoustic filter systems. The time-resolved signal was Fourier transformed to a frequency spectrum of high resolution. For the first radial mode a Lorentzian profile was fitted to the measured data. The outside noise suppression and the signal-to-noise ratio were investigated in a normal laboratory environment in the flow-through mode. The acoustic and electric filter system combined with the

  7. Excitability of guided waves in composites with PWAS transducers

    NASA Astrophysics Data System (ADS)

    Shen, Yanfeng; Giurgiutiu, Victor

    2015-03-01

    Piezoelectric Wafer Active Sensors (PWAS) are convenient enablers for generating and receiving ultrasonic guided waves. The wide application of composite structures has put new challenges for the Structural Health Monitoring (SHM) and Nondestructive Evaluation (NDE) community due to the general anisotropic behaviors and complicated guided wave features in composites. The excitability of guided waves in composite structures directly influences the implementation of active sensing systems to achieve the best interrogation of certain sensing directions. This paper presents a hybrid modeling technique for studying the excitably of guided waves in composite structures with PWAS transducers. This hybrid technique comprehensively covers local finite element model (FEM), semi-analytical finite element (SAFE) method, and analytical guided wave solutions. Harmonic analysis of a small-size local FEM with non-reflective boundaries (NRB) was carried out for obtaining guided wave generation features in plate structures. The PWAS transducers were modeled with coupled filed elements. Thus, the FEM can fully capture the geometry and material property effects of PWAS transducers and their influence on the guided wave excitation. SAFE method was used to obtain the complicated guided wave features in composites such as dispersion curves and modeshapes. The SAFE procedure was coded into MATLAB Graphical User Interface (GUI), and the software SAFE-DISPERSION was developed. To study the excitability of each wave mode, we considered all the possible wave modes being generated simultaneously and propagating independently. The analytical wave expressions based on the exact guided wave solution with Hankel functions were used to join the SAFE method and the local FEM. Formulated in frequency domain, the hybrid model is highly efficient, providing an over determined equation system for the calculation of mode participation factors. Case studies were carried out: (1) the Lamb wave excitability

  8. Chromospheric Heating by Acoustic Waves Compared to Radiative Cooling

    NASA Astrophysics Data System (ADS)

    Sobotka, M.; Heinzel, P.; Švanda, M.; Jurčák, J.; del Moro, D.; Berrilli, F.

    2016-07-01

    Acoustic and magnetoacoustic waves are among the possible candidate mechanisms that heat the upper layers of the solar atmosphere. A weak chromospheric plage near the large solar pore NOAA 11005 was observed on 2008 October 15, in the Fe i 617.3 nm and Ca ii 853.2 nm lines of the Interferometric Bidimemsional Spectrometer attached to the Dunn Solar Telescope. In analyzing the Ca ii observations (with spatial and temporal resolutions of 0.″4 and 52 s) the energy deposited by acoustic waves is compared to that released by radiative losses. The deposited acoustic flux is estimated from the power spectra of Doppler oscillations measured in the Ca ii line core. The radiative losses are calculated using a grid of seven one-dimensional hydrostatic semi-empirical model atmospheres. The comparison shows that the spatial correlation of the maps of radiative losses and acoustic flux is 72%. In a quiet chromosphere, the contribution of acoustic energy flux to radiative losses is small, only about 15%. In active areas with a photospheric magnetic-field strength between 300 and 1300 G and an inclination of 20°-60°, the contribution increases from 23% (chromospheric network) to 54% (a plage). However, these values have to be considered as lower limits and it might be possible that the acoustic energy flux is the main contributor to the heating of bright chromospheric network and plages.

  9. Waveform inversion of acoustic waves for explosion yield estimation

    DOE PAGES

    Kim, K.; Rodgers, A. J.

    2016-07-08

    We present a new waveform inversion technique to estimate the energy of near-surface explosions using atmospheric acoustic waves. Conventional methods often employ air blast models based on a homogeneous atmosphere, where the acoustic wave propagation effects (e.g., refraction and diffraction) are not taken into account, and therefore, their accuracy decreases with increasing source-receiver distance. In this study, three-dimensional acoustic simulations are performed with a finite difference method in realistic atmospheres and topography, and the modeled acoustic Green's functions are incorporated into the waveform inversion for the acoustic source time functions. The strength of the acoustic source is related to explosionmore » yield based on a standard air blast model. The technique was applied to local explosions (<10 km) and provided reasonable yield estimates (<~30% error) in the presence of realistic topography and atmospheric structure. In conclusion, the presented method can be extended to explosions recorded at far distance provided proper meteorological specifications.« less

  10. Characterization of surface acoustic waves by stroboscopic white-light interferometry.

    PubMed

    Kokkonen, Kimmo; Lipiäinen, Lauri; Shavrin, Igor; Novotny, Steffen; Kaivola, Matti; Ludvigsen, Hanne

    2015-04-20

    We present phase-sensitive absolute amplitude measurements of surface acoustic wave fields obtained using a stroboscopic white-light interferometer. The data analysis makes use of the high resolution available in the measured interferometric phase data, enabling the characterization of the out-of-plane surface vibration fields in electrically excited microstructures with better than 100 pm amplitude resolution. The setup uses a supercontinuum light source with tailored spectral properties for obtaining the high amplitude resolution. The duration of the light pulses is less than 300 ps to allow the detection of high frequencies. These capabilities enabled a detailed measurement of the focusing of surface acoustic waves by an annular interdigital transducer structure operating at 74 MHz, featuring a maximum vibration amplitude of 3 nm.

  11. Acoustic plane waves incident on an oblique clamped panel in a rectangular duct

    NASA Technical Reports Server (NTRS)

    Unz, H.; Roskam, J.

    1980-01-01

    The theory of acoustic plane waves incident on an oblique clamped panel in a rectangular duct was developed from basic theoretical concepts. The coupling theory between the elastic vibrations of the panel (plate) and the oblique incident acoustic plane wave in infinite space was considered in detail, and was used for the oblique clamped panel in the rectangular duct. The partial differential equation which governs the vibrations of the clamped panel (plate) was modified by adding to it stiffness (spring) forces and damping forces. The Transmission Loss coefficient and the Noise Reduction coefficient for oblique incidence were defined and derived in detail. The resonance frequencies excited by the free vibrations of the oblique finite clamped panel (plate) were derived and calculated in detail for the present case.

  12. Linear models of acoustic waves in sunspot umbrae

    NASA Technical Reports Server (NTRS)

    Gurman, J. B.; Leibacher, J. W.

    1984-01-01

    The two-dimensional, linear hydrodynamics of quiet solar and umbral model atmospheres in a plane-parallel, adiabatic approximation are investigated. The 5.5-8.5 mHz oscillations observed in umbral chromospheres and transition regions are interpreted as acoustic waves propagating parallel, or nearly parallel, to the temperature gradient. These waves are not totally internally reflected by the steep temperature gradient and, thus, are not trapped. Partial reflections, however, are effective in modulating the transmission as a function of frequency. The resonant transmission mechanism of Zugzda, Locans, and Staude (1983) is found to produce a spectrum of resonances in the transmission of acoustic waves in any atmosphere with a temperature minimum. Since the observed umbral oscillations display power in only a narrow range of frequencies, characteristics of the umbral models, wave propagation, and observations that would tend to suppress the higher frequency resonances are examined.

  13. Chromospheric extents predicted by time-dependent acoustic wave models

    NASA Technical Reports Server (NTRS)

    Cuntz, Manfred

    1990-01-01

    Theoretical models for chromospheric structures of late-type giant stars are computed, including the time-dependent propagation of acoustic waves. Models with short-period monochromatic shock waves as well as a spectrum of acoustic waves are discussed, and the method is applied to the stars Arcturus, Aldebaran, and Betelgeuse. Chromospheric extent, defined as the monotonic decrease with height of the time-averaged electron densities, are found to be 1.12, 1.13, and 1.22 stellar radii for the three stars, respectively; this corresponds to a time-averaged electron density of 10 to the 7th/cu cm. Predictions of the extended chromospheric obtained using a simple scaling law agree well with those obtained by the time-dependent wave models; thus, the chromospheres of all stars for which the scaling law is valid consist of the same number of pressure scale heights.

  14. Reflection and Transmission of Acoustic Waves at Semiconductor - Liquid Interface

    NASA Astrophysics Data System (ADS)

    Sharma, J. N.; Sharma, A.

    2011-09-01

    The study of reflection and transmission characteristics of acoustic waves at the interface of a semiconductor halfspace underlying an inviscid liquid has been carried out. The reflection and transmission coefficients of reflected and transmitted waves have been obtained for quasi-longitudinal (qP) wave incident at the interface from fluid to semiconductor. The numerical computations of reflection and transmission coefficients have been carried out with the help of Gauss elimination method by using MATLAB programming for silicon (Si), germanium (Ge) and silicon nitride (Si3N4) semiconductors. In order to interpret and compare, the computer simulated results are plotted graphically. The study may be useful in semiconductors, seismology and surface acoustic wave (SAW) devices in addition to engines of the space shuttles.

  15. Coherence of acoustic modes propagating through shallow water internal waves

    NASA Astrophysics Data System (ADS)

    Rouseff, Daniel; Turgut, Altan; Wolf, Stephen N.; Finette, Steve; Orr, Marshall H.; Pasewark, Bruce H.; Apel, John R.; Badiey, Mohsen; Chiu, Ching-Sang; Headrick, Robert H.; Lynch, James F.; Kemp, John N.; Newhall, Arthur E.; von der Heydt, Keith; Tielbuerger, Dirk

    2002-04-01

    The 1995 Shallow Water Acoustics in a Random Medium (SWARM) experiment [Apel et al., IEEE J. Ocean. Eng. 22, 445-464 (1997)] was conducted off the New Jersey coast. The experiment featured two well-populated vertical receiving arrays, which permitted the measured acoustic field to be decomposed into its normal modes. The decomposition was repeated for successive transmissions allowing the amplitude of each mode to be tracked. The modal amplitudes were observed to decorrelate with time scales on the order of 100 s [Headrick et al., J. Acoust. Soc. Am. 107(1), 201-220 (2000)]. In the present work, a theoretical model is proposed to explain the observed decorrelation. Packets of intense internal waves are modeled as coherent structures moving along the acoustic propagation path without changing shape. The packets cause mode coupling and their motion results in a changing acoustic interference pattern. The model is consistent with the rapid decorrelation observed in SWARM. The model also predicts the observed partial recorrelation of the field at longer time scales. The model is first tested in simple continuous-wave simulations using canonical representations for the internal waves. More detailed time-domain simulations are presented mimicking the situation in SWARM. Modeling results are compared to experimental data.

  16. Ion-Acoustic Waves in Self-Gravitaing Dusty Plasma

    SciTech Connect

    Kumar, Nagendra; Kumar, Vinod; Kumar, Anil

    2008-09-07

    The propagation and damping of low frequency ion-acoustic waves in steady state, unmagnetised, self-gravitating dusty plasma are studied taking into account two important damping mechanisms creation damping and Tromso damping. It is found that imaginary part of wave number is independent of frequency in case of creation damping. But when we consider the case of creation and Tromso damping together, an additional contribution to damping appears with the increase in frequency attributed to Tromso effect.

  17. Dust acoustic shock waves in two temperatures charged dusty grains

    SciTech Connect

    El-Shewy, E. K.; Abdelwahed, H. G.; Elmessary, M. A.

    2011-11-15

    The reductive perturbation method has been used to derive the Korteweg-de Vries-Burger equation and modified Korteweg-de Vries-Burger for dust acoustic shock waves in a homogeneous unmagnetized plasma having electrons, singly charged ions, hot and cold dust species with Boltzmann distributions for electrons and ions in the presence of the cold (hot) dust viscosity coefficients. The behavior of the shock waves in the dusty plasma has been investigated.

  18. Ion-acoustic solitary waves in relativistic plasmas

    SciTech Connect

    Das, G.C.; Paul, S.N.

    1985-03-01

    This is a sequel to our earlier study on ion-acoustic waves studied through the augmentation to a modified Korteweg--deVries (K--dV) equation. We have derived a K--dV equation in a plasma, taking account of weakly relativistic effects, and the result shows that the solitary wave does exhibit the relativistic effect in the presence of ion streaming.

  19. S-Band Shallow Bulk Acoustic Wave (SBAW) microwave source

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Techniques necessary to fabricate a high performance S-band microwave single source using state-of-the-art shallow bulk acoustic wave (SBAW) were explored. The bulk wave structures of the AlN/Al 2O3 were investigated for both the R plane and basal plane of sapphire. A 1.072 GHz SBAW delay line and oscillators were developed. A method of selecting and setting oscillator output frequency by selecting substrate orientation angle was also established.

  20. Standing surface acoustic wave (SSAW)-based cell washing

    PubMed Central

    Li, Sixing; Ding, Xiaoyun; Mao, Zhangming; Chen, Yuchao; Nama, Nitesh; Guo, Feng; Li, Peng; Wang, Lin; Cameron, Craig E.; Huang, Tony Jun

    2014-01-01

    Cell/bead washing is an indispensable sample preparation procedure used in various cell studies and analytical processes. In this article, we report a standing surface acoustic wave (SSAW)-based microfluidic device for cell and bead washing in a continuous flow. In our approach, the acoustic radiation force generated in a SSAW field is utilized to actively extract cells or beads from their original medium. A unique configuration of tilted-angle standing surface acoustic wave (taSSAW) is employed in our device, enabling us to wash beads with >98% recovery rate and >97% washing efficiency. We also demonstrate the functionality of our device by preparing high-purity (>97%) white blood cells from lysed blood samples through cell washing. Our SSAW-based cell/bead washing device has the advantages of label-free manipulation, simplicity, high biocompatibility, high recovery rate, and high washing efficiency. It can be useful for many lab-on-a-chip applications. PMID:25372273

  1. Protein adsorption to organosiloxane surfaces studied by acoustic wave sensor.

    PubMed

    Cavic, B A; Thompson, M

    1998-10-01

    Surfaces of the two organosiloxanes, polymercaptopropylmethylsiloxane and octaphenylcyclotetrasiloxane, were prepared on the gold electrodes of thickness-shear mode acoustic wave sensors. Compounds containing the siloxane bond are important in the fabrication of medical implants. The flow-through adsorption of the proteins: human serum albumin, alpha-chymotripsinogen A, cytochrome c, fibrinogen, hemoglobin, immunoglobulin G and apo-transferrin to the two siloxane surfaces and a gold electrode were detected by acoustic network analysis. With the exception of minor wash-off by buffer flow, the adsorption of all proteins to the three surfaces is irreversible. Differences observed for the magnitudes of adsorption for the various cases are ascribed to the role played by molecular interactions at the liquid/solid interface. The results confirm that changes in series resonant frequencies caused by macromolecular adsorption differ significantly from the widely accepted "mass based" model usually employed to characterize the response of this type of acoustic wave device.

  2. Numerical modelling of nonlinear full-wave acoustic propagation

    SciTech Connect

    Velasco-Segura, Roberto Rendón, Pablo L.

    2015-10-28

    The various model equations of nonlinear acoustics are arrived at by making assumptions which permit the observation of the interaction with propagation of either single or joint effects. We present here a form of the conservation equations of fluid dynamics which are deduced using slightly less restrictive hypothesis than those necessary to obtain the well known Westervelt equation. This formulation accounts for full wave diffraction, nonlinearity, and thermoviscous dissipative effects. A two-dimensional, finite-volume method using Roe’s linearisation has been implemented to obtain numerically the solution of the proposed equations. This code, which has been written for parallel execution on a GPU, can be used to describe moderate nonlinear phenomena, at low Mach numbers, in domains as large as 100 wave lengths. Applications range from models of diagnostic and therapeutic HIFU, to parametric acoustic arrays and nonlinear propagation in acoustic waveguides. Examples related to these applications are shown and discussed.

  3. Yellow Sea ocean-acoustic solitary wave modeling studies

    NASA Astrophysics Data System (ADS)

    Warn-Varnas, A. C.; Chin-Bing, S. A.; King, D. B.; Hawkins, J. A.; Lamb, K. G.; Teixeira, M.

    2005-08-01

    This study is in an area south of the Shandong peninsula, near the region where Zhou et al. (1991) observed anomalous drops in acoustical intensity. Solitary wave generation and propagation simulations are performed using the Lamb (1994) nonhydrostatic model. The model simulations show that, for summer conditions, the existing semi-diurnal tidal flow over the topographic variations formed internal bores and solitary waves. For the Shandong area, we analyzed summer observations from Synthetic Aperture Radar (SAR) that tracked solitary wave trains from their surface roughness signatures. The images contained seven events consisting of internal bores and solitary waves that traveled in a well-defined direction for 2.5 days. The origin of the trains appeared at a well-defined point along a steep topographic drop. The SAR observations guided and tuned the model simulations, by comparing spectra of observed and modeled wavelengths. The tuned model yields wavelengths within factors of 2, or less, of those derived from SAR data. Wavelength and amplitude dispersion analysis showed two dispersion regimes. Modeled phase speeds were at the lower limit of phase speeds deduced from SAR data, from about 0.8 to 1.0 m/s. Acoustical intensity calculations in the presence of solitary wave trains will be undertaken in a subsequent paper using a parabolic equation acoustical model along the path of solitary wave train propagation.

  4. Magnetically excited flexural plate wave apparatus

    DOEpatents

    Martin, S.J.; Butler, M.A.; Frye, G.C.; Smith, J.H.

    1998-11-17

    A non-piezoelectric flexural plate wave apparatus having meander-line transducers mounted on a non-piezoelectric membrane is disclosed. A static magnetic field is directed perpendicularly to the conductive legs of the transducers in the plane of the membrane. Single-port, two-port, resonant, non-resonant, eigenmode, and delay-line modes may be employed. 15 figs.

  5. Magnetically excited flexural plate wave apparatus

    DOEpatents

    Martin, Stephen J.; Butler, Michael A.; Frye, Gregory C.; Smith, James H.

    1998-01-01

    A non-piezoelectric flexural plate wave apparatus having meander-line transducers mounted on a non-piezoelectric membrane. A static magnetic field is directed perpendicularly to the conductive legs of the transducers in the plane of the membrane. Single-port, two-port, resonant, non-resonant, eigenmode, and delay-line modes may be employed.

  6. Monolithic ZnO SAW (Surface Acoustic Waves) structures

    NASA Astrophysics Data System (ADS)

    Gunshor, R. L.; Pierret, R. F.

    1983-07-01

    ZnO-on-silicon surface acoustic wave devices have been fabricated and tested. Electronic erasure of a stored correlator reference was demonstrated, the effect of laser annealing on propagation loss was examined, preliminary ageing studies were performed, and a conceptually new mode conversion resonator configuration was reported.

  7. Corrigendum and addendum. Modeling weakly nonlinear acoustic wave propagation

    DOE PAGES

    Christov, Ivan; Christov, C. I.; Jordan, P. M.

    2014-12-18

    This article presents errors, corrections, and additions to the research outlined in the following citation: Christov, I., Christov, C. I., & Jordan, P. M. (2007). Modeling weakly nonlinear acoustic wave propagation. The Quarterly Journal of Mechanics and Applied Mathematics, 60(4), 473-495.

  8. Gasoline identifier based on SH0 plate acoustic waves.

    PubMed

    Kuznetsova, Iren E; Zaitsev, Boris D; Seleznev, Eugenii P; Verona, Enrico

    2016-08-01

    The present paper is devoted to the development of gasoline identifier based on zero order shear-horizontal (SH0) acoustic wave propagating in piezoelectric plate. It has been found that the permittivity of gasoline is increased when its octane number rises. The development of such identifier is experimentally demonstrated to be possible. PMID:27125559

  9. Thermal Acoustic Waves from Wall with Temporal Temperature Change

    NASA Astrophysics Data System (ADS)

    Sakaguchi, G.; Tsukamoto, M.; Sakurai, A.

    2011-05-01

    Although phenomenon of thermo-acoustic wave has been known for many years in some familiar experiences such as "singing flame" from Bunsen burner, recent trends of utilizing it for the industrial applications urge the understandings of basic details of the phenomenon itself. Here we consider, in this connection, the problem of acoustic wave generation from a particular heat source of solid wall whose temperature changes with time and the phenomenon of temperature change by standing wave oscillating in closed tube. For these we set a hollow tube whose temperature at its one end wall changes with time, and compute flow field inside using the molecular kinetic model, which is found to be more convenient for the boundary value fitting than the ordinary acoustic theory system to this problem. In practice, we use the Boltzmann equation with the BGK approximation, and compute two cases above in monotonic and sinusoidal temperature changes with time. Results of both cases show propagating density wave from the wall almost in acoustic velocity to the first case and the temperature decreases in average to the second case.

  10. Gasoline identifier based on SH0 plate acoustic waves.

    PubMed

    Kuznetsova, Iren E; Zaitsev, Boris D; Seleznev, Eugenii P; Verona, Enrico

    2016-08-01

    The present paper is devoted to the development of gasoline identifier based on zero order shear-horizontal (SH0) acoustic wave propagating in piezoelectric plate. It has been found that the permittivity of gasoline is increased when its octane number rises. The development of such identifier is experimentally demonstrated to be possible.

  11. Characterization of Ion-Acoustic Wave Reflection Off A Plasma Chamber Wall

    NASA Astrophysics Data System (ADS)

    Berumen, Jorge; Chu, Feng; Hood, Ryan; Mattingly, Sean; Rogers, Anthony; Skiff, Fred

    2015-11-01

    We present an experimental characterization of the ion acoustic wave reflection coefficient off a plasma chamber wall. The experiment is performed in a cylindrical, magnetized, singly-ionized Argon inductively-coupled gas discharge plasma that is weakly collisional with typical conditions: n ~ 1010cm-3 Te ~ 3 eV and B ~ 1 kG. The main diagnostics are laser-induced fluorescence and Langmuir probe measurements. A survey of the ion velocity distribution function's zeroth and first order as well as density fluctuations at different wave excitation frequencies is obtained. Analysis of the reflection coefficient's dependence on the phase velocity and frequency of the wave is done through the characterization of waves utilizing Case-Van Kampen modes and the use of Morrison's G-transform. This research is supported by the Department of Energy under grant No. DOE DE-FG02-99ER54543.

  12. Measurement of Elastic Properties of Tissue by Shear Wave Propagation Generated by Acoustic Radiation Force

    NASA Astrophysics Data System (ADS)

    Marie Tabaru,; Takashi Azuma,; Kunio Hashiba,

    2010-07-01

    Acoustic radiation force (ARF) imaging has been developed as a novel elastography technology to diagnose hepatic disease and breast cancer. The accuracy of shear wave speed estimation, which is one of the applications of ARF elastography, is studied. The Young’s moduli of pig liver and foie gras samples estimated from the shear wave speed were compared with those measured the static Young’s modulus measurement. The difference in the two methods was 8%. Distance attenuation characteristics of the shear wave were also studied using finite element method (FEM) analysis. We found that the differences in the axial and lateral beam widths in pressure and ARF are 16 and 9% at F-number=0.9. We studied the relationship between two branch points in distance attenuation characteristics and the shape of ARF. We found that the maximum measurable length to estimate shear wave speed for one ARF excitation was 8 mm.

  13. Measurement of Elastic Properties of Tissue by Shear Wave Propagation Generated by Acoustic Radiation Force

    NASA Astrophysics Data System (ADS)

    Tabaru, Marie; Azuma, Takashi; Hashiba, Kunio

    2010-07-01

    Acoustic radiation force (ARF) imaging has been developed as a novel elastography technology to diagnose hepatic disease and breast cancer. The accuracy of shear wave speed estimation, which is one of the applications of ARF elastography, is studied. The Young's moduli of pig liver and foie gras samples estimated from the shear wave speed were compared with those measured the static Young's modulus measurement. The difference in the two methods was 8%. Distance attenuation characteristics of the shear wave were also studied using finite element method (FEM) analysis. We found that the differences in the axial and lateral beam widths in pressure and ARF are 16 and 9% at F-number=0.9. We studied the relationship between two branch points in distance attenuation characteristics and the shape of ARF. We found that the maximum measurable length to estimate shear wave speed for one ARF excitation was 8 mm.

  14. Acoustic omni meta-atom for decoupled access to all octants of a wave parameter space

    NASA Astrophysics Data System (ADS)

    Koo, Sukmo; Cho, Choonlae; Jeong, Jun-Ho; Park, Namkyoo

    2016-09-01

    The common behaviour of a wave is determined by wave parameters of its medium, which are generally associated with the characteristic oscillations of its corresponding elementary particles. In the context of metamaterials, the decoupled excitation of these fundamental oscillations would provide an ideal platform for top-down and reconfigurable access to the entire constitutive parameter space; however, this has remained as a conceivable problem that must be accomplished, after being pointed out by Pendry. Here by focusing on acoustic metamaterials, we achieve the decoupling of density ρ, modulus B-1 and bianisotropy ξ, by separating the paths of particle momentum to conform to the characteristic oscillations of each macroscopic wave parameter. Independent access to all octants of wave parameter space (ρ, B-1, ξ)=(+/-,+/-,+/-) is thus realized using a single platform that we call an omni meta-atom; as a building block that achieves top-down access to the target properties of metamaterials.

  15. Acoustic omni meta-atom for decoupled access to all octants of a wave parameter space

    PubMed Central

    Koo, Sukmo; Cho, Choonlae; Jeong, Jun-ho; Park, Namkyoo

    2016-01-01

    The common behaviour of a wave is determined by wave parameters of its medium, which are generally associated with the characteristic oscillations of its corresponding elementary particles. In the context of metamaterials, the decoupled excitation of these fundamental oscillations would provide an ideal platform for top–down and reconfigurable access to the entire constitutive parameter space; however, this has remained as a conceivable problem that must be accomplished, after being pointed out by Pendry. Here by focusing on acoustic metamaterials, we achieve the decoupling of density ρ, modulus B−1 and bianisotropy ξ, by separating the paths of particle momentum to conform to the characteristic oscillations of each macroscopic wave parameter. Independent access to all octants of wave parameter space (ρ, B−1, ξ)=(+/−,+/−,+/−) is thus realized using a single platform that we call an omni meta-atom; as a building block that achieves top–down access to the target properties of metamaterials. PMID:27687689

  16. Two-dimensional cylindrical ion-acoustic solitary and rogue waves in ultrarelativistic plasmas

    SciTech Connect

    Ata-ur-Rahman; Ali, S.; Moslem, W. M.; Mushtaq, A.

    2013-07-15

    The propagation of ion-acoustic (IA) solitary and rogue waves is investigated in a two-dimensional ultrarelativistic degenerate warm dense plasma. By using the reductive perturbation technique, the cylindrical Kadomtsev–Petviashvili (KP) equation is derived, which can be further transformed into a Korteweg–de Vries (KdV) equation. The latter admits a solitary wave solution. However, when the frequency of the carrier wave is much smaller than the ion plasma frequency, the KdV equation can be transferred to a nonlinear Schrödinger equation to study the nonlinear evolution of modulationally unstable modified IA wavepackets. The propagation characteristics of the IA solitary and rogue waves are strongly influenced by the variation of different plasma parameters in an ultrarelativistic degenerate dense plasma. The present results might be helpful to understand the nonlinear electrostatic excitations in astrophysical degenerate dense plasmas.

  17. Dust confinement and dust-acoustic waves in weakly magnetized anodic plasmas

    SciTech Connect

    Trottenberg, Thomas; Block, Dietmar; Piel, Alexander

    2006-04-15

    Experiments on dust-acoustic waves (DAW) in a magnetized anodic plasma are presented for the regime of low collisionality. The dust trapping and the self-excited and synchronized DAW dynamics are studied. Based on Langmuir and emissive probe measurements the dust confinement is found to be well described with respect to size, stability, and position of the dust cloud by an effective potential well formed by ion drag and Coulomb forces. Moreover, the measurements indicate the necessity for a kinetic model for the wave dispersion. By means of singular value decomposition the local wavelengths and growth rates of the waves are measured systematically. It is found that the measured mean wave number is well described by kinetic theory, while the theoretical growth rates overestimate the experiments. A novel observation for the DAW is a systematic variation of the wavelength inside the dust cloud.

  18. System and method for characterizing voiced excitations of speech and acoustic signals, removing acoustic noise from speech, and synthesizing speech

    DOEpatents

    Burnett, Greg C.; Holzrichter, John F.; Ng, Lawrence C.

    2002-01-01

    Low power EM waves are used to detect motions of vocal tract tissues of the human speech system before, during, and after voiced speech. A voiced excitation function is derived. The excitation function provides speech production information to enhance speech characterization and to enable noise removal from human speech.

  19. Impact of Acoustic Standing Waves on Structural Responses: Reverberant Acoustic Testing (RAT) vs. Direct Field Acoustic Testing (DFAT)

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R.; Doty, Benjamin; Chang, Zensheu

    2012-01-01

    Loudspeakers have been used for acoustic qualification of spacecraft, reflectors, solar panels, and other acoustically responsive structures for more than a decade. Limited measurements from some of the recent speaker tests used to qualify flight hardware have indicated significant spatial variation of the acoustic field within the test volume. Also structural responses have been reported to differ when similar tests were performed using reverberant chambers. To address the impact of non-uniform acoustic field on structural responses, a series of acoustic tests were performed using a flat panel and a 3-ft cylinder exposed to the field controlled by speakers and repeated in a reverberant chamber. The speaker testing was performed using multi-input-single-output (MISO) and multi-input-multi-output (MIMO) control schemes with and without the test articles. In this paper the spatial variation of the acoustic field due to acoustic standing waves and their impacts on the structural responses in RAT and DFAT (both using MISO and MIMO controls for DFAT) are discussed in some detail.

  20. Numerical simulation of the resonantly excited capillary-gravity waves

    NASA Astrophysics Data System (ADS)

    Hanazaki, Hideshi; Hirata, Motonori; Okino, Shinya

    2015-11-01

    Capillary gravity waves excited by an obstacle are investigated by a direct numerical simulation. In the flow without capillary effects, it is well known that large-amplitude upstream advancing solitary waves are generated periodically under the resonant condition, i.e., when the phase velocity of the long surface waves and the mean flow velocity agrees. With capillary effects, solutions of the Euler equations show the generation of very short waves further upstream of the solitary waves and also in the depression region downstream of the obstacle. The overall characteristics of these waves agree with the solutions of the forced fifth-order KdV equation, while the weakly nonlinear theory generally overestimates the wavelength of the short waves.

  1. Analyzing excitation forces acting on a plate based on measured acoustic pressure.

    PubMed

    Wu, Sean F; Zhou, Pan

    2016-07-01

    This paper presents a theoretical study on "seeing" through an elastic structure to uncover the root cause of sound and vibration by using nearfield acoustical holography (NAH) and normal modes expansion. This approach is of generality because vibro-acoustic responses on the surface of a vibrating structure can always be reconstructed, exactly or approximately. With these vibro-acoustic responses, excitation forces acting on the structure can always be determined, analytically or numerically, given any set of boundary conditions. As an example, the explicit formulations for reconstructing time-harmonic excitation forces, including point, line and surface forces, and their arbitrary combinations acting on a rectangular thin plate in vacuum mounted on an infinite baffle are presented. The reason for choosing this example is that the analytic solutions to vibro-acoustic responses are available, and in-depth analyses of results are possible. Results demonstrate that this approach allows one to identify excitation forces based on measured acoustic pressures and reveal their characteristics such as locations, types and amplitudes, as if one could "see" excitation forces acting behind the plate based on acoustic pressure measured on the opposite side. This approach is extendable to general elastic structures, except that in such circumstance numerical results must be sought. PMID:27475174

  2. Fabrication, Operation and Flow Visualization in Surface-acoustic-wave-driven Acoustic-counterflow Microfluidics

    PubMed Central

    Travagliati, Marco; Shilton, Richie; Beltram, Fabio; Cecchini, Marco

    2013-01-01

    Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we present the fabrication protocol for a multilayered SAW acoustic counterflow device. The device is fabricated starting from a lithium niobate (LN) substrate onto which two interdigital transducers (IDTs) and appropriate markers are patterned. A polydimethylsiloxane (PDMS) channel cast on an SU8 master mold is finally bonded on the patterned substrate. Following the fabrication procedure, we show the techniques that allow the characterization and operation of the acoustic counterflow device in order to pump fluids through the PDMS channel grid. We finally present the procedure to visualize liquid flow in the channels. The protocol is used to show on-chip fluid pumping under different flow regimes such as laminar flow and more complicated dynamics characterized by vortices and particle accumulation domains. PMID:24022515

  3. Extraction of the acoustic component of a turbulent flow exciting a plate by inverting the vibration problem

    NASA Astrophysics Data System (ADS)

    Lecoq, D.; Pézerat, C.; Thomas, J.-H.; Bi, W. P.

    2014-06-01

    characterized by the convection wavenumber [12] kconv={ω}/{Uc}, where Uc is the convection velocity, generally deduced from the relationship Uc=KU∞ with U∞ the fluid velocity in the laminar flow and K a coefficient between 0.6 and 0.8 [12,13]; the acoustic component related to waves generated by turbulence at the top of the plate and propagating in all directions with the acoustic wavenumber kac={ω}/{c0}, where c0 refers to the speed of sound. Note that this component may also contain contributions due to the plate vibration. This is particularly true if the problem is in the vicinity of the coincidence frequency and when the coupling effects between the plate and the fluid are not negligible. In this study, there is therefore no separation between the acoustic radiation of the plate and the acoustic part of the TBL. Generally, the wavenumber-frequency spectra S(kx,ky,ω) are used to analyze these excitations [12] S(kx,ky,ω)={1}/{4π2}∬-∞+∞S(rx,ry,ω)ee drx dry, where rx=x-x', ry=y-y', and S(rx,ry,ω) the cross-spectrum between the wall pressures p(x,y,t) and p(x',y',t) S(rx,ry,ω)=limT→∞ 2/πT E[P(x,y,ω)P*(x',y',ω)], where P(x,y,ω) is the finite Fourier transform of p(x,y,t) with T the duration of the signal P(x,y,ω)={12π∫}/{-T/2T/2p(x,y,t)e dt, and P*(x,y,ω) its complex conjugate.With this kind of representation, one can easily distinguish the two components: the acoustic component in the low wavenumbers and the aerodynamic component with very small wavelengths (see Fig. 3). In addition, the wavenumber representation allows one to study the vibration and the radiation of a plate under TBL conditions by introducing the flexural wavenumber kf[14]: kf=1/2ρ(1-ν2)Eh2}4√{ω}, where ρ, E, ν are respectively the mass density, Young's modulus, Poisson's ratio of the material and h is the thickness of the plate.Fig. 3 shows the evolution of this wavenumber as a function of frequency in parallel with that of the aerodynamic and the

  4. Surface acoustic wave mode conversion resonator

    NASA Astrophysics Data System (ADS)

    Martin, S. J.; Gunshor, R. L.; Melloch, M. R.; Datta, S.; Pierret, R. F.

    1983-08-01

    The fact that a ZnO-on-Si structure supports two distinct surface waves, referred to as the Rayleigh and the Sezawa modes, if the ZnO layer is sufficiently thick is recalled. A description is given of a unique surface wave resonator that operates by efficiently converting between the two modes at the resonant frequency. Since input and output coupling is effected through different modes, the mode conversion resonator promises enhanced out-of-band signal rejection. A Rayleigh wave traversing the resonant cavity in one direction is reflected as a Sezawa wave. It is pointed out that the off-resonance rejection of the mode conversion resonator could be enhanced by designing the transducers to minimize the level of cross coupling between transducers and propagating modes.

  5. Surface wave acoustics of granular packing under gravity

    SciTech Connect

    Clement, Eric; Andreotti, Bruno; Bonneau, Lenaic

    2009-06-18

    Due to the non-linearity of Hertzian contacts, the speed of sound in granular matter increases with pressure. For a packing under gravity and in the presence of a free surface, bulk acoustic waves cannot propagate due to the inherent refraction toward the surface (the mirage effect). Thus, only modes corresponding to surface waves (Raleigh-Hertz modes) are able to propagate the acoustic signal. First, based on a non-linear elasticity model, we describe the main features associated to these surface waves. We show that under gravity, a granular packing is from the acoustic propagation point of view an index gradient waveguide that selects modes of two distinct families i.e. the sagittal and transverse waves localized in the vicinity of the free surface. A striking feature of these surface waves is the multi-modal propagation: for both transverse and sagittal waves, we show the existence of a infinite but discrete series of propagating modes. In each case, we determine the mode shape and and the corresponding dispersion relation. In the case of a finite size system, a geometric waveguide is superimposed to the index gradient wave guide. In this later case, the dispersion relations are modified by the appearance of a cut-off frequency that scales with depth. The second part is devoted to an experimental study of surface waves propagating in a granular packing confined in a long channel. This set-up allows to tune a monomodal emission by taking advantage of the geometric waveguide features combined with properly designed emitters. For both sagittal and transverses waves, we were able to isolate a single mode (the fundamental one) and to plot the dispersion relation. This measurements agree well with the Hertzian scaling law as predicted by meanfield models. Furthermore, it allows us to determine quantitatively relations on the elastic moduli. However, we observe that our data yield a shear modulus abnormally weak when compared to several meanfield predictions.

  6. Nanometer stepping drives of surface acoustic wave motor.

    PubMed

    Shigematsu, Takashi; Kurosawa, Minoru Kuribayashi; Asai, Katsuhiko

    2003-04-01

    High resolution (from nanometer to subnanometer) stepping drives of a surface acoustic wave motor are presented. It was shown that step displacement was easily controlled by adjusting a number of driving waves, using a steel ball slider equipped with permanent magnet for preload. By means of this open loop control, the step displacement was controlled from centimeter-order to submicrometer-order. In this paper, using a silicon slider equipped with a ball bearing linear guide, the stepping motions of a surface acoustic wave motor were investigated. A laser interferometer equipped with a 2-picometer resolution displacement demodulator was introduced. Motions of the slider ranging from several hundreds of nanometers to several nanometers in each step displacement were observed. Reduction of the driving waves down to 25 cycles, under a 100 Vpeak driving voltage and a 30 N preload condition, generated about 2 nm stepping motion using our experimental setup under an open loop condition. We also demonstrated subnanometer step movements. These experimental results indicated that the surface acoustic wave motor has an ability of subnanometer positioning with a centimeter-level stroke. PMID:12744393

  7. Surface acoustic wave depth profiling of a functionally graded material

    SciTech Connect

    Goossens, Jozefien; Leclaire, Philippe; Xu Xiaodong; Glorieux, Christ; Martinez, Loic; Sola, Antonella; Siligardi, Cristina; Cannillo, Valeria; Van der Donck, Tom; Celis, Jean-Pierre

    2007-09-01

    The potential and limitations of Rayleigh wave spectroscopy to characterize the elastic depth profile of heterogeneous functional gradient materials are investigated by comparing simulations of the surface acoustic wave dispersion curves of different profile-spectrum pairs. This inverse problem is shown to be quite ill posed. The method is then applied to extract information on the depth structure of a glass-ceramic (alumina) functionally graded material from experimental data. The surface acoustic wave analysis suggests the presence of a uniform coating region consisting of a mixture of Al{sub 2}O{sub 3} and glass, with a sharp transition between the coating and the substrate. This is confirmed by scanning electron microscope with energy dispersive x-ray analysis.

  8. Langasite Surface Acoustic Wave Sensors: Fabrication and Testing

    SciTech Connect

    Zheng, Peng; Greve, David W.; Oppenheim, Irving J.; Chin, Tao-Lun; Malone, Vanessa

    2012-02-01

    We report on the development of harsh-environment surface acoustic wave sensors for wired and wireless operation. Surface acoustic wave devices with an interdigitated transducer emitter and multiple reflectors were fabricated on langasite substrates. Both wired and wireless temperature sensing was demonstrated using radar-mode (pulse) detection. Temperature resolution of better than ±0.5°C was achieved between 200°C and 600°C. Oxygen sensing was achieved by depositing a layer of ZnO on the propagation path. Although the ZnO layer caused additional attenuation of the surface wave, oxygen sensing was accomplished at temperatures up to 700°C. The results indicate that langasite SAW devices are a potential solution for harsh-environment gas and temperature sensing.

  9. Propagation of acoustic waves in the partly ionized interstellar medium

    NASA Astrophysics Data System (ADS)

    Chalov, S. V.

    2014-07-01

    The properties of linear acoustic waves propagating in the interstellar medium, which is a mixture of electron-proton plasma and hydrogen atoms, are studied analytically. The plasma component interacts with hydrogen atoms through resonant charge exchange between the atoms and protons. To make the problem tractable, only short-wavelength disturbances are considered. Namely, the wavelength is assumed to be small as compared with the mean free path of atoms with respect to charge exchange. It is shown that short waves are damped out due to the charge exchange process, and the magnitude of decrement increases with the cross-section for charge exchange, number density of atoms and sound speed. In the first approximation, decrement does not depend on the wavelength, and acoustic waves are dispersionless. The advantage of our model is fully kinetic treatment of the interstellar atom motion.

  10. Optimization of Surface Acoustic Wave-Based Rate Sensors

    PubMed Central

    Xu, Fangqian; Wang, Wen; Shao, Xiuting; Liu, Xinlu; Liang, Yong

    2015-01-01

    The optimization of an surface acoustic wave (SAW)-based rate sensor incorporating metallic dot arrays was performed by using the approach of partial-wave analysis in layered media. The optimal sensor chip designs, including the material choice of piezoelectric crystals and metallic dots, dot thickness, and sensor operation frequency were determined theoretically. The theoretical predictions were confirmed experimentally by using the developed SAW sensor composed of differential delay line-oscillators and a metallic dot array deposited along the acoustic wave propagation path of the SAW delay lines. A significant improvement in sensor sensitivity was achieved in the case of 128° YX LiNbO3, and a thicker Au dot array, and low operation frequency were used to structure the sensor. PMID:26473865

  11. Single crystal metal wedges for surface acoustic wave propagation

    DOEpatents

    Fisher, E.S.

    1980-05-09

    An ultrasonic testing device has been developed to evaluate flaws and inhomogeneities in the near-surface region of a test material. A metal single crystal wedge is used to generate high frequency Rayleigh surface waves in the test material surface by conversion of a slow velocity, bulk acoustic mode in the wedge into a Rayleigh wave at the metal-wedge test material interface. Particular classes of metals have been found to provide the bulk acoustic modes necessary for production of a surface wave with extremely high frequency and angular collimation. The high frequency allows flaws and inhomogeneities to be examined with greater resolution. The high degree of angular collimation for the outgoing ultrasonic beam permits precision angular location of flaws and inhomogeneities in the test material surface.

  12. Single crystal metal wedges for surface acoustic wave propagation

    DOEpatents

    Fisher, Edward S.

    1982-01-01

    An ultrasonic testing device has been developed to evaluate flaws and inhomogeneities in the near-surface region of a test material. A metal single crystal wedge is used to generate high frequency Rayleigh surface waves in the test material surface by conversion of a slow velocity, bulk acoustic mode in the wedge into a Rayleigh wave at the metal-wedge test material interface. Particular classes of metals have been found to provide the bulk acoustic modes necessary for production of a surface wave with extremely high frequency and angular collimation. The high frequency allows flaws and inhomogeneities to be examined with greater resolution. The high degree of angular collimation for the outgoing ultrasonic beam permits precision angular location of flaws and inhomogeneities in the test material surface.

  13. Separation of acoustic waves in isentropic flow perturbations

    NASA Astrophysics Data System (ADS)

    Henke, Christian

    2015-04-01

    The present contribution investigates the mechanisms of sound generation and propagation in the case of highly-unsteady flows. Based on the linearisation of the isentropic Navier-Stokes equation around a new pathline-averaged base flow, it is demonstrated for the first time that flow perturbations of a non-uniform flow can be split into acoustic and vorticity modes, with the acoustic modes being independent of the vorticity modes. Therefore, we can propose this acoustic perturbation as a general definition of sound. As a consequence of the splitting result, we conclude that the present acoustic perturbation is propagated by the convective wave equation and fulfils Lighthill's acoustic analogy. Moreover, we can define the deviations of the Navier-Stokes equation from the convective wave equation as "true" sound sources. In contrast to other authors, no assumptions on a slowly varying or irrotational flow are necessary. Using a symmetry argument for the conservation laws, an energy conservation result and a generalisation of the sound intensity are provided.

  14. Seismoelectric waves in a borehole excited by an external explosive source

    NASA Astrophysics Data System (ADS)

    Zhou, Jiu-Guang; Cui, Zhi-Wen; Lü, Wei-Guo; Zhang, Yu-Jun; Wang, Ke-Xie

    2014-01-01

    The conversion of energy between seismic and electromagnetic wave fields has been described by Pride's coupled equations in porous media. In this paper, the seismoelectric field excited by the explosive point source located at the outside of the borehole is studied. The scattering fields inside and outside a borehole are analyzed and deduced under the boundary conditions at the interface between fluid and porous media. The influences of the distance of the point source, multipole components of the eccentric explosive source, and the receiving position along the axis of vertical borehole, on the converted waves inside the borehole are all investigated. When the distance from the acoustic source to the axis of a borehole is far enough, the longitudinal and coseismic longitudinal wave packets dominate the acoustic and electric field, respectively. The three components of both electric field and magnetic field can be detected, and the radial electric field is mainly excited and converted by the dipole component. Owing to the existence of borehole, the electric fields and magnetic fields in the borehole are azimuthal. The distance from the point where the maximum amplitude of the axial components of electric field is recorded, to the origin of coordinate indicates the horizontal distance from the explosive source to the axis of vertical borehole.

  15. Surface acoustic wave devices as passive buried sensors

    NASA Astrophysics Data System (ADS)

    Friedt, J.-M.; Rétornaz, T.; Alzuaga, S.; Baron, T.; Martin, G.; Laroche, T.; Ballandras, S.; Griselin, M.; Simonnet, J.-P.

    2011-02-01

    Surface acoustic wave (SAW) devices are currently used as passive remote-controlled sensors for measuring various physical quantities through a wireless link. Among the two main classes of designs—resonator and delay line—the former has the advantage of providing narrow-band spectrum informations and hence appears compatible with an interrogation strategy complying with Industry-Scientific-Medical regulations in radio-frequency (rf) bands centered around 434, 866, or 915 MHz. Delay-line based sensors require larger bandwidths as they consists of a few interdigitated electrodes excited by short rf pulses with large instantaneous energy and short response delays but is compatible with existing equipment such as ground penetrating radar (GPR). We here demonstrate the measurement of temperature using the two configurations, particularly for long term monitoring using sensors buried in soil. Although we have demonstrated long term stability and robustness of packaged resonators and signal to noise ratio compatible with the expected application, the interrogation range (maximum 80 cm) is insufficient for most geology or geophysical purposes. We then focus on the use of delay lines, as the corresponding interrogation method is similar to the one used by GPR which allows for rf penetration distances ranging from a few meters to tens of meters and which operates in the lower rf range, depending on soil water content, permittivity, and conductivity. Assuming propagation losses in a pure dielectric medium with negligible conductivity (snow or ice), an interrogation distance of about 40 m is predicted, which overcomes the observed limits met when using interrogation methods specifically developed for wireless SAW sensors, and could partly comply with the above-mentioned applications. Although quite optimistic, this estimate is consistent with the signal to noise ratio observed during an experimental demonstration of the interrogation of a delay line buried at a depth of 5

  16. Acoustic Resonances in Helium Fluids Excited by Quartz Tuning Forks

    NASA Astrophysics Data System (ADS)

    Salmela, A.; Tuoriniemi, J.; Rysti, J.

    2011-03-01

    Ordinary quartz tuning fork resonators, operated at about 30 or 200 kHz frequency, couple to acoustic first and second sound resonances in helium fluids under certain conditions. We have studied acoustic resonances in supercritical 4He, normal and superfluid 4He, and in isotopic mixtures of helium. Suggestive temperature, pressure, and concentration dependences are given. Furthermore, we propose a thermometric reference point device based on second sound resonances in helium mixtures, and indicate possible differences in the nature of second sound resonances in superfluid 4He and helium mixtures.

  17. Resonant excitation of Rayleigh waves in a narrow fluid channel clad between two metal plates

    NASA Astrophysics Data System (ADS)

    Nagaraj, Nagaraj; Krokhin, Arkadii; Sánchez-Dehesa, José.; Garcia-Chocano, Victor M.

    2012-02-01

    We study extraordinary absorption of acoustic energy due to resonant excitation of Rayleigh waves in a narrow water channel clad between two unidentical metal plates with Brass plate on one side of the channel and Aluminium plate on the other. The extraordinary absorption is observed at discrete resonant frequencies. From the elastic properties of the metal plates we derive a dispersion equation for coupled Rayleigh waves. Two different types of resonances, corresponding to different polarizations of the coupled waves, are studied for different channel widths and are experimentally confirmed. We also present the experimental confirmation of coupling through measurements of change in transmission minima with channel aperture. Experimental, theoretical, and numerical results are in a good agreement.

  18. Triadic Resonance of Tidally Excited Internal Gravity Waves

    NASA Astrophysics Data System (ADS)

    Lecoanet, D.; Quataert, E.

    2013-12-01

    Tides can excite internal gravity waves in many different ways including, e.g., inducing flow over topography, linear resonance, and nonlinear coupling. These waves can then be unstable to triadic resonance instabilities, which can influence the rate of dissipation of the tidal energy. In this work, we simulate the full nonlinear interaction of many internal gravity waves in a 3D, triply periodic, Boussinesq box. To model the wave excitation due to the tide, we linearly force a specific mode. Diffusivity and the quantization of modes in the box determine which modes couple to the forced mode. For low forcing rates and high diffusivity, only a few modes interact, and we are able to predict the equilibrium amplitudes of the modes and dissipation rates. However, for higher forcing rates or low diffusivity, many modes interact with one another and the system becomes turbulent.

  19. An SU-8 liquid cell for surface acoustic wave biosensors

    NASA Astrophysics Data System (ADS)

    Francis, Laurent A.; Friedt, Jean-Michel; Bartic, Carmen; Campitelli, Andrew

    2004-08-01

    One significant challenge facing biosensor development is packaging. For surface acoustic wave based biosensors, packaging influences the general sensing performance. The acoustic wave is generated and received thanks to interdigital transducers and the separation between the transducers defines the sensing area. Liquids used in biosensing experiments lead to an attenuation of the acoustic signal while in contact with the transducers. We have developed a liquid cell based on photodefinable epoxy SU-8 that prevents the presence of liquid on the transducers, has a small disturbance effect on the propagation of the acoustic wave, does not interfere with the biochemical sensing event, and leads to an integrated sensor system with reproducible properties. The liquid cell is achieved in two steps. In a first step, the SU-8 is precisely patterned around the transducers to define 120 μm thick walls. In a second step and after the dicing of the sensors, a glass capping is placed manually and glued on top of the SU-8 walls. This design approach is an improvement compared to the more classical solution consisting of a pre-molded cell that must be pressed against the device in order to avoid leaks, with negative consequences on the reproducibility of the experimental results. We demonstrate the effectiveness of our approach by protein adsorption monitoring. The packaging materials do not interfere with the biomolecules and have a high chemical resistance. For future developments, wafer level bonding of the quartz capping onto the SU-8 walls is envisioned.

  20. Acoustic wave reflection from thermal gradient regions in a gas

    NASA Astrophysics Data System (ADS)

    Tarau, Calin; Otugen, Volkan; Sheverev, Valeri; Vradis, George

    2003-11-01

    Acoustic wave reflection from thermal gradient regions in a gas Calin Tarau, Volkan Otugen, Valery Sheverev and George Vradis Polytechnic University Six Metrotech Center Brooklyn, NY 11201 Temperature gradients in a gas medium can cause reflection and refraction of acoustic waves. For large incidence angles and sharp temperature gradients, sound reflection from the high (or low) temperature zone can be significant. The present report evaluates the effectiveness of using small regions of hot gas inside an ambient environment as a sound barrier. The behavior of sound wave in the two extreme cases where the acoustic wavelength is either much larger or much smaller than the gradient region is well known. In the latter case, the reflection coefficient tends to be negligible while the maximum reflection is obtained for the former situation. The present is the intermediate case where Ü l L (Ü and L are the acoustic wavelength and length of gradient region, respectively). The compressible unsteady Euler's equations together with the perfect gas state equation are solved using higher order (both time and space) finite volume approach. The numerical results are compared with previous theoretical analysis and recent experimental results of sound propagation through glow discharge.

  1. Propagation of three-dimensional electron-acoustic solitary waves

    SciTech Connect

    Shalaby, M.; El-Sherif, L. S.; El-Labany, S. K.; Sabry, R.

    2011-06-15

    Theoretical investigation is carried out for understanding the properties of three-dimensional electron-acoustic waves propagating in magnetized plasma whose constituents are cold magnetized electron fluid, hot electrons obeying nonthermal distribution, and stationary ions. For this purpose, the hydrodynamic equations for the cold magnetized electron fluid, nonthermal electron density distribution, and the Poisson equation are used to derive the corresponding nonlinear evolution equation, Zkharov-Kuznetsov (ZK) equation, in the small- but finite- amplitude regime. The ZK equation is solved analytically and it is found that it supports both solitary and blow-up solutions. It is found that rarefactive electron-acoustic solitary waves strongly depend on the density and temperature ratios of the hot-to-cold electron species as well as the nonthermal electron parameter. Furthermore, there is a critical value for the nonthermal electron parameter, which decides whether the electron-acoustic solitary wave's amplitude is decreased or increased by changing various plasma parameters. Importantly, the change of the propagation angles leads to miss the balance between the nonlinearity and dispersion; hence, the localized pulses convert to explosive/blow-up pulses. The relevance of this study to the nonlinear electron-acoustic structures in the dayside auroral zone in the light of Viking satellite observations is discussed.

  2. Effects of vibration excitation methodology and configuration of an acoustic needle on its tip vibration.

    PubMed

    Li, Ning; Hu, Junhui

    2013-04-01

    One of design purposes of an acoustic needle is to obtain a big vibration displacement at its tip. In this paper, vibration characteristics of the tip of the acoustic needle driven by a sandwich type ultrasonic transducer, is investigated to obtain the guidelines for increasing the tip vibration. It is found that the tip vibration can be increased by employing acoustic needles with proper vibration excitation structure and configuration. The effective measures include using a sandwich type piezoelectric transducer with flexurally vibrating end plates and an acoustic needle with conical tip section, decreasing the length of vibration excitation section at the needle root, bonding the needle root at a proper location of the transducer end plate, and tuning the length ratio of the conical tip section to the whole needle. PMID:23294988

  3. Electron acceleration by parametrically excited Langmuir waves. [in ionospheric modification

    NASA Technical Reports Server (NTRS)

    Fejer, J. A.; Graham, K. N.

    1974-01-01

    Simple physical arguments are used to estimate the downward-going energetic electron flux due to parametrically excited Langmuir waves in ionospheric modification experiments. The acceleration mechanism is a single velocity reversal as seen in the frame of the Langmuir wave. The flux is sufficient to produce the observed ionospheric airglow if focusing-type instabilities are invoked to produce moderate local enhancements of the pump field.

  4. A surface-acoustic-wave-based cantilever bio-sensor.

    PubMed

    De Simoni, Giorgio; Signore, Giovanni; Agostini, Matteo; Beltram, Fabio; Piazza, Vincenzo

    2015-06-15

    A scalable surface-acoustic-wave- (SAW-) based cantilevered device for portable bio-chemical sensing applications is presented. Even in the current, proof-of-principle implementation this architecture is shown to outperform commercial quartz-crystal microbalances in terms of sensitivity. Adhesion of analytes on a functionalized surface of the cantilever shifts the resonant frequency of a SAW-generating transducer due to the stress-induced variation of the speed of surface acoustic modes. We discuss the relevance of this approach for diagnostics applications based on miniaturized devices.

  5. Three-Dimensional Particle-in-Cell Simulations of Wave Excitation by Conventional and Parametric Antennas in the Ionospheric Plasma

    NASA Astrophysics Data System (ADS)

    Main, Daniel; Kim, Tony; Caplinger, James; Sotnokiv, Vladimir; Paraschiv, I.; Rose, David

    2015-11-01

    Conventional antennas immersed in a cold, magnetized plasma (CMP) and operating in the very low frequency (VLF) range (e.g. loop and dipole antennas) excite predominately the electrostatic part of the wave spectrum. For example, loop antennas excited in the frequency range ωLH < ω <ωce produce electrostatic lower oblique resonance (LOR) waves. The goal of our research is to increase power radiated into the electromagnetic part of the VLF wave spectrum. Electromagnetic whistler waves are generated due to a nonlinear coupling of LOR and ion acoustic (IA) waves inside a plasma volume around two conventional antennas. Ion acoustic type density perturbations can be excited by a conventional dipole antenna with frequencies in the range ωci < ω <ωLH . In this poster we show three-dimensional electric field patterns from the loop and dipole antennas and the EM spectrum excited due to the parametric interaction. (NOTE: LH = lower hybrid, ce = electron cyclotron,ci=ion cyclotron).

  6. EVIDENCE FOR THE PHOTOSPHERIC EXCITATION OF INCOMPRESSIBLE CHROMOSPHERIC WAVES

    SciTech Connect

    Morton, R. J.; Verth, G.; Fedun, V.; Erdelyi, R.; Shelyag, S.

    2013-05-01

    Observing the excitation mechanisms of incompressible transverse waves is vital for determining how energy propagates through the lower solar atmosphere. We aim to show the connection between convectively driven photospheric flows and incompressible chromospheric waves. The observations presented here show the propagation of incompressible motion through the quiet lower solar atmosphere, from the photosphere to the chromosphere. We determine photospheric flow vectors to search for signatures of vortex motion and compare results to photospheric flows present in convective simulations. Further, we search for the chromospheric response to vortex motions. Evidence is presented that suggests incompressible waves can be excited by the vortex motions of a strong magnetic flux concentration in the photosphere. A chromospheric counterpart to the photospheric vortex motion is also observed, presenting itself as a quasi-periodic torsional motion. Fine-scale, fibril structures that emanate from the chromospheric counterpart support transverse waves that are driven by the observed torsional motion. A new technique for obtaining details of transverse waves from time-distance diagrams is presented and the properties of transverse waves (e.g., amplitudes and periods) excited by the chromospheric torsional motion are measured.

  7. Electrostatic Generation of Bulk Acoustic Waves and Electrical Parameters of Si-MEMS Resonators.

    PubMed

    Dulmet, Bernard; Ivan, Mihaela Eugenia; Ballandras, Sylvain

    2016-02-01

    This paper proposes an analytical approach to model the generation of bulk acoustic waves in an electrostatically excited silicon MEMS structure, as well as its electromechanical response in terms of static and dynamic displacements, electromechanical coupling, and motional current. The analysis pertains to the single-port electrostatic drive of trapped-energy thickness-extensional (TE) modes in thin plates. Both asymmetric single-side and symmetric double-side electrostatic gap configurations are modeled. Green's function is used to describe the characteristic of the static displacement of the driven surface of the structure versus the dc bias voltage, which allows us to determine the electrical response of the resonator. Optical and electrical characterizations have been performed on resonator samples operating at 10.3 MHz on the fundamental of TE mode under single-side electrostatic excitation. The various figures of merit depend on the dc bias voltage. Typical values of 9000 for the Q-factor, and of 10(-5) for the electromechanical coupling factor k(2) have been obtained with [Formula: see text] for [Formula: see text]-thick gaps. Here-considered modes have a typical temperature coefficients of frequency (TCF) close to -30 ppm/(°)C. We conclude that the practical usability of such electrostatically excited bulk acoustic waves (BAW) resonators essentially depends on the efficiency of the compensation of feed-through capacitance.

  8. Electrostatic Generation of Bulk Acoustic Waves and Electrical Parameters of Si-MEMS Resonators.

    PubMed

    Dulmet, Bernard; Ivan, Mihaela Eugenia; Ballandras, Sylvain

    2016-02-01

    This paper proposes an analytical approach to model the generation of bulk acoustic waves in an electrostatically excited silicon MEMS structure, as well as its electromechanical response in terms of static and dynamic displacements, electromechanical coupling, and motional current. The analysis pertains to the single-port electrostatic drive of trapped-energy thickness-extensional (TE) modes in thin plates. Both asymmetric single-side and symmetric double-side electrostatic gap configurations are modeled. Green's function is used to describe the characteristic of the static displacement of the driven surface of the structure versus the dc bias voltage, which allows us to determine the electrical response of the resonator. Optical and electrical characterizations have been performed on resonator samples operating at 10.3 MHz on the fundamental of TE mode under single-side electrostatic excitation. The various figures of merit depend on the dc bias voltage. Typical values of 9000 for the Q-factor, and of 10(-5) for the electromechanical coupling factor k(2) have been obtained with [Formula: see text] for [Formula: see text]-thick gaps. Here-considered modes have a typical temperature coefficients of frequency (TCF) close to -30 ppm/(°)C. We conclude that the practical usability of such electrostatically excited bulk acoustic waves (BAW) resonators essentially depends on the efficiency of the compensation of feed-through capacitance. PMID:26642450

  9. Excitation of an electrostatic wave by a cold electron current sheet of finite thickness

    NASA Technical Reports Server (NTRS)

    Hwang, K. S.; Fontheim, E. G.; Ong, R. S. B.

    1983-01-01

    Calculations for the threshold of current-driven instabilities and the growth rates of ion acoustic and electrostatic ion cyclotron instabilities in a magnetized plasma driven a current sheet with a finite width are presented. Maxwellian equations are employed to model the velocity distributions of electrons and ions in a direction perpendicular to the sheet. A dispersion relation is defined for the regions of instability, and boundary conditions are characterized in order to obtain a set of eigenvalue equations. Thresholds are delineated for various regions, including ducted mode solutions where only ion-acoustic waves are excited in areas where the frequency range significantly exceeds the ion cyclotron frequency. When a constant electron drift velocity is present, a thick current sheet is more unstable than a thin one. Fewer modes become unstable with a thinner sheet.

  10. Observed features of acoustic gravity waves in the heterosphere

    NASA Astrophysics Data System (ADS)

    Fedorenko, A. K.; Kryuchkov, E. I.

    2014-01-01

    According to measurements on the Dynamic Explorer 2 satellite, features of the propagation of acoustic gravity waves (AGWs) in the multicomponent upper atmosphere have been investigated. In the altitude range 250-400 km in wave concentration variations of some atmospheric gases, amplitude and phase differences have been observed. Using the approach proposed in this paper, in different gases, AGW variations have been divided into components associated with elastic compression, adiabatic expansion, and the vertical background distribution. The amplitude and phase differences observed in different gases are explained on the basis of analyzing these components. It is shown how to use this effect in order to determine the wave propagation, the vertical displacement of the volume element, the wave frequency, and the spatial distribution of the wave energy density.

  11. Nonlinear electron acoustic waves in presence of shear magnetic field

    SciTech Connect

    Dutta, Manjistha; Khan, Manoranjan; Ghosh, Samiran; Chakrabarti, Nikhil

    2013-12-15

    Nonlinear electron acoustic waves are studied in a quasineutral plasma in the presence of a variable magnetic field. The fluid model is used to describe the dynamics of two temperature electron species in a stationary positively charged ion background. Linear analysis of the governing equations manifests dispersion relation of electron magneto sonic wave. Whereas, nonlinear wave dynamics is being investigated by introducing Lagrangian variable method in long wavelength limit. It is shown from finite amplitude analysis that the nonlinear wave characteristics are well depicted by KdV equation. The wave dispersion arising in quasineutral plasma is induced by transverse magnetic field component. The results are discussed in the context of plasma of Earth's magnetosphere.

  12. Inverse Scattering Problems for Acoustic Waves in AN Inhomogeneous Medium.

    NASA Astrophysics Data System (ADS)

    Kedzierawski, Andrzej Wladyslaw

    1990-01-01

    This dissertation considers the inverse scattering problem of determining either the absorption of sound in an inhomogeneous medium or the surface impedance of an obstacle from a knowledge of the far-field patterns of the scattered fields corresponding to many incident time -harmonic plane waves. First, we consider the inverse problem in the case when the scattering object is an inhomogeneous medium with complex refraction index having compact support. Our approach to this problem is the orthogonal projection method of Colton-Monk (cf. The inverse scattering problem for time acoustic waves in an inhomogeneous medium, Quart. J. Mech. Appl. Math. 41 (1988), 97-125). After that, we prove the analogue of Karp's Theorem for the scattering of acoustic waves through an inhomogeneous medium with compact support. We then generalize some of these results to the case when the inhomogeneous medium is no longer of compact support. If the acoustic wave penetrates the inhomogeneous medium by only a small amount then the inverse medium problem leads to the inverse obstacle problem with an impedance boundary condition. We solve the inverse impedance problem of determining the surface impedance of an obstacle of known shape by using both the methods of Kirsch-Kress and Colton-Monk (cf. R. Kress, Linear Integral Equations, Springer-Verlag, New York, 1989).

  13. A frequency selective acoustic transducer for directional Lamb wave sensing.

    PubMed

    Senesi, Matteo; Ruzzene, Massimo

    2011-10-01

    A frequency selective acoustic transducer (FSAT) is proposed for directional sensing of guided waves. The considered FSAT design is characterized by a spiral configuration in wavenumber domain, which leads to a spatial arrangement of the sensing material producing output signals whose dominant frequency component is uniquely associated with the direction of incoming waves. The resulting spiral FSAT can be employed both for directional sensing and generation of guided waves, without relying on phasing and control of a large number of channels. The analytical expression of the shape of the spiral FSAT is obtained through the theoretical formulation for continuously distributed active material as part of a shaped piezoelectric device. Testing is performed by forming a discrete array through the points of the measurement grid of a scanning laser Doppler vibrometer. The discrete array approximates the continuous spiral FSAT geometry, and provides the flexibility to test several configurations. The experimental results demonstrate the strong frequency dependent directionality of the spiral FSAT and suggest its application for frequency selective acoustic sensors, to be employed for the localization of broadband acoustic events, or for the directional generation of Lamb waves for active interrogation of structural health. PMID:21973344

  14. Analysis of Measured and Simulated Supraglottal Acoustic Waves.

    PubMed

    Fraile, Rubén; Evdokimova, Vera V; Evgrafova, Karina V; Godino-Llorente, Juan I; Skrelin, Pavel A

    2016-09-01

    To date, although much attention has been paid to the estimation and modeling of the voice source (ie, the glottal airflow volume velocity), the measurement and characterization of the supraglottal pressure wave have been much less studied. Some previous results have unveiled that the supraglottal pressure wave has some spectral resonances similar to those of the voice pressure wave. This makes the supraglottal wave partially intelligible. Although the explanation for such effect seems to be clearly related to the reflected pressure wave traveling upstream along the vocal tract, the influence that nonlinear source-filter interaction has on it is not as clear. This article provides an insight into this issue by comparing the acoustic analyses of measured and simulated supraglottal and voice waves. Simulations have been performed using a high-dimensional discrete vocal fold model. Results of such comparative analysis indicate that spectral resonances in the supraglottal wave are mainly caused by the regressive pressure wave that travels upstream along the vocal tract and not by source-tract interaction. On the contrary and according to simulation results, source-tract interaction has a role in the loss of intelligibility that happens in the supraglottal wave with respect to the voice wave. This loss of intelligibility mainly corresponds to spectral differences for frequencies above 1500 Hz. PMID:26377510

  15. Effects of dissipation on propagation of surface electromagnetic and acoustic waves

    NASA Astrophysics Data System (ADS)

    Nagaraj, Nagaraj

    With the recent emergence of the field of metamaterials, the study of subwavelength propagation of plane waves and the dissipation of their energy either in the form of Joule losses in the case of electomagnetic waves or in the form of viscous dissipation in the case of acoustic waves in different interfaced media assumes great importance. With this motivation, I have worked on problems in two different areas, viz., plasmonics and surface acoustics. The first part (chapters 2 & 3) of the dissertation deals with the emerging field of plasmonics. Researchers have come up with various designs in an effort to fabricate efficient plasmonic waveguides capable of guiding plasmonic signals. However, the inherent dissipation in the form of Joule losses limits efficient usage of surface plasmon signal. A dielectric-metal-dielectric planar structure is one of the most practical plasmonic structures that can serve as an efficient waveguide to guide electromagnetic waves along the metal-dielectric boundary. I present here a theoretical study of propagation of surface plasmons along a symmetric dielectric-metal-dielectric structure and show how proper orientation of the optical axis of the anisotropic substrate enhances the propagation length. An equation for propagation length is derived in a wide range of frequencies. I also show how the frequency of coupled surface plasmons can be modulated by changing the thickness of the metal film. I propose a Kronig-Penny model for the plasmonic crystal, which in the long wavelength limit, may serve as a homogeneous dielectric substrate with high anisotropy which do not exist for natural optical crystals. In the second part (chapters 4 & 5) of the dissertation, I discuss an interesting effect of extraordinary absorption of acoustic energy due to resonant excitation of Rayleigh waves in a narrow water channel clad between two metal plates. Starting from the elastic properties of the metal plates, I derive a dispersion equation that gives

  16. Generation of a reference radiation pattern of string instruments using automatic excitation and acoustic centering.

    PubMed

    Shabtai, Noam R; Behler, Gottfried; Vorländer, Michael

    2015-11-01

    Radiation patterns of musical instruments are important for the understanding of music perception in concert halls, and may be used to improve the plausibility of virtual acoustic systems. Many attempts have been performed to measure the spatial response of musical instruments using surrounding spherical microphone arrays with a limited number of microphones. This work presents a high-resolution spatial sampling of the radiation pattern of an electrically excited violin, and addresses technical problems that arise due to mechanical reasons of the excitation apparatus using acoustic centering.

  17. Generation of a reference radiation pattern of string instruments using automatic excitation and acoustic centering.

    PubMed

    Shabtai, Noam R; Behler, Gottfried; Vorländer, Michael

    2015-11-01

    Radiation patterns of musical instruments are important for the understanding of music perception in concert halls, and may be used to improve the plausibility of virtual acoustic systems. Many attempts have been performed to measure the spatial response of musical instruments using surrounding spherical microphone arrays with a limited number of microphones. This work presents a high-resolution spatial sampling of the radiation pattern of an electrically excited violin, and addresses technical problems that arise due to mechanical reasons of the excitation apparatus using acoustic centering. PMID:26627818

  18. Argon–oxygen dc magnetron discharge plasma probed with ion acoustic waves

    SciTech Connect

    Saikia, Partha Saikia, Bipul Kumar; Goswami, Kalyan Sindhu; Phukan, Arindam

    2014-05-15

    The precise determination of the relative concentration of negative ions is very important for the optimization of magnetron sputtering processes, especially for those undertaken in a multicomponent background produced by adding electronegative gases, such as oxygen, to the discharge. The temporal behavior of an ion acoustic wave excited from a stainless steel grid inside the plasma chamber is used to determine the relative negative ion concentration in the magnetron discharge plasma. The phase velocity of the ion acoustic wave in the presence of negative ions is found to be faster than in a pure argon plasma, and the phase velocity increases with the oxygen partial pressure. Optical emission spectroscopy further confirms the increase in the oxygen negative ion density, along with a decrease in the argon positive ion density under the same discharge conditions. The relative negative ion concentration values measured by ion acoustic waves are compared with those measured by a single Langmuir probe, and a similarity in the results obtained by both techniques is observed.

  19. Stable Vortex Generation in Liquid Filled Wells by Mode Conversion of Surface Acoustic Waves

    NASA Astrophysics Data System (ADS)

    Landskron, Johannes; Schmidt, Katrin; Kufner, Maria; Lindner, Gerhard

    The formation of stable vortex flow pattern has been observed at liquid filled aluminum wells of 15 to 30 mm diameter when Lamb waves are excited on the bottom of the wells by piezoelectric transducers operated at a frequency of 1 MHz. The shape of the vortex pattern changed with the position of the transducer. Strong differences in mixing times were observed between water and ethanol when the filling level was changed and a remarkable reduction of mixing time was achieved by the addition of a small amount of detergent to water at small filling levels. Besides mixing of liquids thermal equilibration within a liquid volume was accelerated by acoustic streaming.

  20. Numerical study of ion acoustic shock waves in dense quantum plasma

    SciTech Connect

    Hanif, M.; Mirza, Arshad M.; Ali, S.; Mukhtar, Q.

    2014-03-15

    Two fluid quantum hydrodynamic equations are solved numerically to investigate the propagation characteristics of ion acoustic shock waves in an unmagnetized dense quantum plasma, whose constituents are the electrons and ions. For this purpose, we employ the standard finite difference Lax Wendroff and relaxation methods, to examine the quantum effects on the profiles of shock potential, the electron/ion number densities, and velocity even for quantum parameter at H = 2. The effects of the latter vanish in a weakly non-linear limit while obeying the KdV theory. It is shown that the evolution of the wave depends sensitively on the plasma density and the quantum parameter. Numerical results reveal that the kinks or oscillations are pronounced for large values of quantum parameter, especially at H = 2. Our results should be important to understand the shock wave excitations in dense quantum plasmas, white dwarfs, neutron stars, etc.

  1. Theory of Seismic Noise Excitation by Ocean Waves

    NASA Astrophysics Data System (ADS)

    Tanimoto, T.

    2009-12-01

    It is becoming increasingly clear that seismic noise, recorded in continuous data, will be an important part of seismic data that will be used for seismic structure study. Causes of noise vary from frequency to frequency but the predominant noise, specifically in the microseismic frequency band (about 0.05-0.4 Hz), is now recognized to be ocean waves. The Hum, seismic noise in a lower frequency band about 0.003-0.015 Hz, may also be excited by this mechanism (Webb, 2007). The detailed excitation mechanism of microseisms by ocean waves is attributed to Longuet-Higgins (1950) (which credits earlier study by Miche, 1944) which beautifully explains one critical aspect of data, the double frequency noise peak. Longuet-Higgins (1950) basically showed how nonlinear advection term in the Navier-Stokes equation and the nonlinear term in the kinematic free-surface boundary condition lead to the generation of pressure when there are colliding ocean waves. In this paper, we will show that excitation of seismic noise can be formulated starting from the original nonlinear terms in the equations, basically skipping the intermediate pressure term derived by Longuet-Higgins. The equivalent body-force term by these nonlinear terms can be expressed in a compact formula and may be used to describe seismic wavefields. We will show 1. The equivalent Longuet-Higgins term arises from our approach but it is exact only for low frequencies below 0.1 Hz. At higher frequencies, depending on ocean depth, deviations up to a factor of 5-10 can arise. 2. At low frequencies (<0.005 Hz), a horizontal force term arises whose effects may become larger than pressure variations due to the Longuet-Higgins mechanism. Webb (2007) and Tanimoto (2007) pointed out this term. This term contains azimuthal effects (radiation pattern), as opposed to the isotropic vertical forcing by the Longuett-Higgins mechanism. 3. We also examine the excitation of the toroidal hum (Kurrle and Widmer, 2008). Infragravity waves

  2. Dust-acoustic solitary and rogue waves in a Thomas-Fermi degenerate dusty plasma

    NASA Astrophysics Data System (ADS)

    Irfan, M.; Ali, S.; Mirza, Arshad M.

    2014-10-01

    The formation and propagation of dust-acoustic (DA) solitary and rogue waves are studied in a non-relativistic degenerate Thomas-Fermi thermal dusty plasma incorporating transverse velocity perturbation effects. The electrons and ions are described by the Thomas-Fermi density distributions, whereas the dust grains are taken as dynamic and classical. By using the reductive perturbation technique, the cylindrical Kadomtsev-Petviashvili (CKP) equation is derived, which is then transformed into a Korteweg-deVries (KdV) equation by using appropriate variable transformations. The latter admits a solitary wave solution. However, when the carrier waves frequency is much smaller than the dust plasma frequency, the DA waves evolve into the nonlinear modulation instability, generating modulated wave packets in the form of Rogue waves. For the study of DA-rogue waves, the KdV equation is transformed into a self-focusing nonlinear Schrödinger equation. The variation of dust temperature and the electron density affects the nonlinearity and dispersion coefficients which suppress the amplitudes of the DA solitary and rogue waves. The present results aim to describe the nonlinear electrostatic excitations in astrophysical degenerate dense plasma.

  3. Excitation of coherent propagating spin waves by pure spin currents

    PubMed Central

    Demidov, Vladislav E.; Urazhdin, Sergei; Liu, Ronghua; Divinskiy, Boris; Telegin, Andrey; Demokritov, Sergej O.

    2016-01-01

    Utilization of pure spin currents not accompanied by the flow of electrical charge provides unprecedented opportunities for the emerging technologies based on the electron's spin degree of freedom, such as spintronics and magnonics. It was recently shown that pure spin currents can be used to excite coherent magnetization dynamics in magnetic nanostructures. However, because of the intrinsic nonlinear self-localization effects, magnetic auto-oscillations in the demonstrated devices were spatially confined, preventing their applications as sources of propagating spin waves in magnonic circuits using these waves as signal carriers. Here, we experimentally demonstrate efficient excitation and directional propagation of coherent spin waves generated by pure spin current. We show that this can be achieved by using the nonlocal spin injection mechanism, which enables flexible design of magnetic nanosystems and allows one to efficiently control their dynamic characteristics. PMID:26818232

  4. Vibro-acoustic analysis of the acoustic-structure interaction of flexible structure due to acoustic excitation

    NASA Astrophysics Data System (ADS)

    Djojodihardjo, Harijono

    2015-03-01

    The application of BE-FE acoustic-structure interaction on a structure subject to acoustic load is elaborated using the boundary element-finite element acoustic structural coupling and the utilization of the computational scheme developed earlier. The plausibility of the numerical treatment is investigated and validated through application to generic cases. The analysis carried out in the work is intended to serve as a baseline in the analysis of acoustic structure interaction for lightweight structures. Results obtained thus far exhibit the robustness of the method developed.

  5. Laser-generated acoustic wave studies on tattoo pigment

    NASA Astrophysics Data System (ADS)

    Paterson, Lorna M.; Dickinson, Mark R.; King, Terence A.

    1996-01-01

    A Q-switched alexandrite laser (180 ns at 755 nm) was used to irradiate samples of agar embedded with red, black and green tattoo dyes. The acoustic waves generated in the samples were detected using a PVDF membrane hydrophone and compared to theoretical expectations. The laser pulses were found to generate acoustic waves in the black and green samples but not in the red pigment. Pressures of up to 1.4 MPa were produced with irradiances of up to 96 MWcm-2 which is comparable to the irradiances used to clear pigment embedded in skin. The pressure gradient generated across pigment particles was approximately 1.09 X 1010 Pam-1 giving a pressure difference of 1.09 +/- 0.17 MPa over a particle with mean diameter 100 micrometers . This is not sufficient to permanently damage skin which has a tensile strength of 7.4 MPa.

  6. High-Temperature Piezoelectric Crystals for Acoustic Wave Sensor Applications.

    PubMed

    Zu, Hongfei; Wu, Huiyan; Wang, Qing-Ming

    2016-03-01

    In this review paper, nine different types of high-temperature piezoelectric crystals and their sensor applications are overviewed. The important materials' properties of these piezoelectric crystals including dielectric constant, elastic coefficients, piezoelectric coefficients, electromechanical coupling coefficients, and mechanical quality factor are discussed in detail. The determination methods of these physical properties are also presented. Moreover, the growth methods, structures, and properties of these piezoelectric crystals are summarized and compared. Of particular interest are langasite and oxyborate crystals, which exhibit no phase transitions prior to their melting points ∼ 1500 °C and possess high electrical resistivity, piezoelectric coefficients, and mechanical quality factor at ultrahigh temperature ( ∼ 1000 °C). Finally, some research results on surface acoustic wave (SAW) and bulk acoustic wave (BAW) sensors developed using this high-temperature piezoelectric crystals are discussed.

  7. Comparison of Transmission Line Methods for Surface Acoustic Wave Modeling

    NASA Technical Reports Server (NTRS)

    Wilson, William; Atkinson, Gary

    2009-01-01

    Surface Acoustic Wave (SAW) technology is low cost, rugged, lightweight, extremely low power and can be used to develop passive wireless sensors. For these reasons, NASA is investigating the use of SAW technology for Integrated Vehicle Health Monitoring (IVHM) of aerospace structures. To facilitate rapid prototyping of passive SAW sensors for aerospace applications, SAW models have been developed. This paper reports on the comparison of three methods of modeling SAWs. The three models are the Impulse Response Method (a first order model), and two second order matrix methods; the conventional matrix approach, and a modified matrix approach that is extended to include internal finger reflections. The second order models are based upon matrices that were originally developed for analyzing microwave circuits using transmission line theory. Results from the models are presented with measured data from devices. Keywords: Surface Acoustic Wave, SAW, transmission line models, Impulse Response Method.

  8. Microwave acoustics handbook. Volume 4: Bulk wave velocities: Numerical data

    NASA Astrophysics Data System (ADS)

    Slobodnik, A. J., Jr.; Delmonico, R. T.; Conway, E. D.

    1980-06-01

    Information useful for the design of acoustic delay lines, resonators, and other miniature, low-cost devices for use in communications and electronic sensing is given. Numerical data on bulk acoustic wave velocities and power flow angles are given for longitudinal, and two shear waves for various orientations of the following single crystalline materials: Ba2NaNb5O15, Bi12/geO20, CdS, Diamond, Eu3Fe5O15, GaAs, Gadolinium Gallium Garnet, Germanium, InSb, InAs, Lead Molybdate, PbS, LiNbO3, LiTaO3, MgO, Quartz, Rutile, Sapphire, Silicon, Spinel, TeO2, YAG, YGaG, YIG, and ZnO. This present volume is intended to be used as a supplement to Volume 3 whenever accurate numerical data is required rather than the more convenient graphical information.

  9. High-Temperature Piezoelectric Crystals for Acoustic Wave Sensor Applications.

    PubMed

    Zu, Hongfei; Wu, Huiyan; Wang, Qing-Ming

    2016-03-01

    In this review paper, nine different types of high-temperature piezoelectric crystals and their sensor applications are overviewed. The important materials' properties of these piezoelectric crystals including dielectric constant, elastic coefficients, piezoelectric coefficients, electromechanical coupling coefficients, and mechanical quality factor are discussed in detail. The determination methods of these physical properties are also presented. Moreover, the growth methods, structures, and properties of these piezoelectric crystals are summarized and compared. Of particular interest are langasite and oxyborate crystals, which exhibit no phase transitions prior to their melting points ∼ 1500 °C and possess high electrical resistivity, piezoelectric coefficients, and mechanical quality factor at ultrahigh temperature ( ∼ 1000 °C). Finally, some research results on surface acoustic wave (SAW) and bulk acoustic wave (BAW) sensors developed using this high-temperature piezoelectric crystals are discussed. PMID:26886982

  10. Impact of Acoustic Standing Waves on Structural Responses

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R.

    2014-01-01

    For several decades large reverberant chambers and most recently direct field acoustic testing have been used in the aerospace industry to test larger structures with low surface densities such as solar arrays and reflectors to qualify them and to detect faults in the design and fabrication. It has been reported that in reverberant chamber and direct acoustic testing, standing acoustic modes may strongly couple with the fundamental structural modes of the test hardware (Reference 1). In this paper results from a recent reverberant chamber acoustic test of a composite reflector are discussed. These results provide further convincing evidence of the acoustic standing wave and structural modes coupling phenomenon. The purpose of this paper is to alert test organizations to this phenomenon so that they can account for the potential increase in structural responses and ensure that flight hardware undergoes safe testing. An understanding of the coupling phenomenon may also help minimize the over and/or under testing that could pose un-anticipated structural and flight qualification issues.

  11. Surface acoustic wave probe implant for predicting epileptic seizures

    DOEpatents

    Gopalsami, Nachappa; Kulikov, Stanislav; Osorio, Ivan; Raptis, Apostolos C.

    2012-04-24

    A system and method for predicting and avoiding a seizure in a patient. The system and method includes use of an implanted surface acoustic wave probe and coupled RF antenna to monitor temperature of the patient's brain, critical changes in the temperature characteristic of a precursor to the seizure. The system can activate an implanted cooling unit which can avoid or minimize a seizure in the patient.

  12. Space manufacturing of surface acoustic wave devices, appendix D

    NASA Technical Reports Server (NTRS)

    Sardella, G.

    1973-01-01

    Space manufacturing of transducers in a vibration free environment is discussed. Fabrication of the masks, and possible manufacturing of the surface acoustic wave components aboard a space laboratory would avoid the inherent ground vibrations and the frequency limitation imposed by a seismic isolator pad. The manufacturing vibration requirements are identified. The concepts of space manufacturing are analyzed. A development program for manufacturing transducers is recommended.

  13. Decay of transverse acoustic waves in a pulsed gas laser

    SciTech Connect

    Kulkarny, V.A.

    1980-11-01

    The long-term characteristics of transverse acoustic waves in the cavity of a pulsed gaseous laser were studied by analyzing them in a straight duct configuration with nonlinear techniques used in sonic boom problems. A decaying sawtooth waveform containing a shockwave reverberated in the cavity transverse to the flow direction. In the asymptotic decay, the relative pressure perturbation of the wave varies as the 2/5 power of the product of the relative overpressure from the pulse and the speed of sound in the gas.

  14. Volumetric measurements of a spatially growing dust acoustic wave

    NASA Astrophysics Data System (ADS)

    Williams, Jeremiah D.

    2012-11-01

    In this study, tomographic particle image velocimetry (tomo-PIV) techniques are used to make volumetric measurements of the dust acoustic wave (DAW) in a weakly coupled dusty plasma system in an argon, dc glow discharge plasma. These tomo-PIV measurements provide the first instantaneous volumetric measurement of a naturally occurring propagating DAW. These measurements reveal over the measured volume that the measured wave mode propagates in all three spatial dimensional and exhibits the same spatial growth rate and wavelength in each spatial direction.

  15. Scanning Laser Doppler Vibrometry Application to Artworks: New Acoustic and Mechanical Exciters for Structural Diagnostics

    NASA Astrophysics Data System (ADS)

    Agnani, A.; Esposito, E.

    After first attempts some years ago, the scanning laser Doppler vibrometer has become an effective way of diagnosing different types of artworks; successful applications regard frescoes, icons, mosaics, ceramic artefacts and wood inlays. Also application to historical bridges has been successfully developed and a recently approved European Commission project will see the employment of scanning laser Doppler Vibrometry (SLDV) for the dynamical characterization of ancient buildings. However, a critical issue consists in the adequate excitation of the structure under test. Moreover different types of defects and different kinds of artworks require different types of excitation, so this topic needs a deep consideration. In this work we will present two new types of exciters developed at our Department, namely an acoustic exciter and a mechanical one. Acoustic exciters allow remote non-invasive loading but are limited in the lower frequency range and in the amount of vibrational energy input into the structure. The proposed automatic tapping device based on a commercial impact hammer overcomes these problems. Also another acoustic exciter, a HyperSonic Sound (HSS) source has been evaluated, showing interesting features as regards sound radiation.

  16. Surface acoustic waves enhance neutrophil killing of bacteria.

    PubMed

    Loike, John D; Plitt, Anna; Kothari, Komal; Zumeris, Jona; Budhu, Sadna; Kavalus, Kaitlyn; Ray, Yonatan; Jacob, Harold

    2013-01-01

    Biofilms are structured communities of bacteria that play a major role in the pathogenicity of bacteria and are the leading cause of antibiotic resistant bacterial infections on indwelling catheters and medical prosthetic devices. Failure to resolve these biofilm infections may necessitate the surgical removal of the prosthetic device which can be debilitating and costly. Recent studies have shown that application of surface acoustic waves to catheter surfaces can reduce the incidence of infections by a mechanism that has not yet been clarified. We report here the effects of surface acoustic waves (SAW) on the capacity of human neutrophils to eradicate S. epidermidis bacteria in a planktonic state and within biofilms. Utilizing a novel fibrin gel system that mimics a tissue-like environment, we show that SAW, at an intensity of 0.3 mW/cm(2), significantly enhances human neutrophil killing of S. epidermidis in a planktonic state and within biofilms by enhancing human neutrophil chemotaxis in response to chemoattractants. In addition, we show that the integrin CD18 plays a significant role in the killing enhancement observed in applying SAW. We propose from out data that this integrin may serve as mechanoreceptor for surface acoustic waves enhancing neutrophil chemotaxis and killing of bacteria.

  17. Energy scavenging system by acoustic wave and integrated wireless communication

    NASA Astrophysics Data System (ADS)

    Kim, Albert

    The purpose of the project was developing an energy-scavenging device for other bio implantable devices. Researchers and scientist have studied energy scavenging method because of the limitation of traditional power source, especially for bio-implantable devices. In this research, piezoelectric power generator that activates by acoustic wave, or music was developed. Follow by power generator, a wireless communication also integrated with the device for monitoring the power generation. The Lead Zirconate Titanate (PZT) bimorph cantilever with a proof mass at the free end tip was studied to convert acoustic wave to power. The music or acoustic wave played through a speaker to vibrate piezoelectric power generator. The LC circuit integrated with the piezoelectric material for purpose of wireless monitoring power generation. However, wireless monitoring can be used as wireless power transmission, which means the signal received via wireless communication also can be used for power for other devices. Size of 74 by 7 by 7cm device could generate and transmit 100mVp from 70 mm distance away with electrical resonant frequency at 420.2 kHz..

  18. RADIATIVE HYDRODYNAMIC SIMULATIONS OF ACOUSTIC WAVES IN SUNSPOTS

    SciTech Connect

    Bard, S.; Carlsson, M.

    2010-10-10

    We investigate the formation and evolution of the Ca II H line in a sunspot. The aim of our study is to establish the mechanisms underlying the formation of the frequently observed brightenings of small regions of sunspot umbrae known as 'umbral flashes'. We perform fully consistent NLTE radiation hydrodynamic simulations of the propagation of acoustic waves in sunspot umbrae and conclude that umbral flashes result from increased emission of the local solar material during the passage of acoustic waves originating in the photosphere and steepening to shock in the chromosphere. To quantify the significance of possible physical mechanisms that contribute to the formation of umbral flashes, we perform a set of simulations on a grid formed by different wave power spectra, different inbound coronal radiation, and different parameterized chromospheric heating. Our simulations show that the waves with frequencies in the range 4.5-7.0 mHz are critical to the formation of the observed blueshifts of umbral flashes while waves with frequencies below 4.5 mHz do not play a role despite their dominance in the photosphere. The observed emission in the Ca II H core between flashes only occurs in the simulations that include significant inbound coronal radiation and/or extra non-radiative chromospheric heating in addition to shock dissipation.

  19. Ion acoustic shock wave in collisional equal mass plasma

    SciTech Connect

    Adak, Ashish; Ghosh, Samiran; Chakrabarti, Nikhil

    2015-10-15

    The effect of ion-ion collision on the dynamics of nonlinear ion acoustic wave in an unmagnetized pair-ion plasma has been investigated. The two-fluid model has been used to describe the dynamics of both positive and negative ions with equal masses. It is well known that in the dynamics of the weakly nonlinear wave, the viscosity mediates wave dissipation in presence of weak nonlinearity and dispersion. This dissipation is responsible for the shock structures in pair-ion plasma. Here, it has been shown that the ion-ion collision in presence of collective phenomena mediated by the plasma current is the source of dissipation that causes the Burgers' term which is responsible for the shock structures in equal mass pair-ion plasma. The dynamics of the weakly nonlinear wave is governed by the Korteweg-de Vries Burgers equation. The analytical and numerical investigations revealed that the ion acoustic wave exhibits both oscillatory and monotonic shock structures depending on the frequency of ion-ion collision parameter. The results have been discussed in the context of the fullerene pair-ion plasma experiments.

  20. Characteristics of acoustic gravity waves obtained from Dynasonde data

    NASA Astrophysics Data System (ADS)

    Negrea, Cǎtǎlin; Zabotin, Nikolay; Bullett, Terrence; Fuller-Rowell, Tim; Fang, Tzu-Wei; Codrescu, Mihail

    2016-04-01

    Traveling ionospheric disturbances (TIDs) are ubiquitous in the thermosphere-ionosphere and are often assumed to be caused by acoustic gravity waves (AGWs). This study performs an analysis of the TID and AGW activity above Wallops Island, VA, during October 2013. The variations in electron density and ionospheric tilts obtained with the Dynasonde technique are used as primary indicators of wave activity. The temporal and spectral characteristics of the data are discussed in detail, using also results of the Whole Atmosphere Model (WAM) and the Global Ionosphere Plasmasphere Model (GIP). The full set of propagation parameters (frequency, and the vertical, zonal and meridional wave vector components) of the TIDs is determined over the 160-220 km height range. A test of the self-consistency of these results within the confines of the theoretical AGW dispersion relation is devised. This is applied to a sample data set of 24 October 2013. A remarkable agreement has been achieved for wave periods between 52 and 21 min, for which we can rigorously claim the TIDs are caused by underlying acoustic gravity waves. The Wallops Island Dynasonde can operate for extended periods at a 2 min cadence, allowing determination of the statistical distributions of propagation parameters. A dominant population of TIDs is identified in the frequency band below 1 mHz, and for it, the distributions of the horizontal wavelengths, vertical wavelengths, and horizontal phase speeds are obtained.

  1. Dual mode acoustic wave sensor for precise pressure reading

    NASA Astrophysics Data System (ADS)

    Mu, Xiaojing; Kropelnicki, Piotr; Wang, Yong; Randles, Andrew Benson; Chuan Chai, Kevin Tshun; Cai, Hong; Gu, Yuan Dong

    2014-09-01

    In this letter, a Microelectromechanical system acoustic wave sensor, which has a dual mode (lateral field exited Lamb wave mode and surface acoustic wave (SAW) mode) behavior, is presented for precious pressure change read out. Comb-like interdigital structured electrodes on top of piezoelectric material aluminium nitride (AlN) are used to generate the wave modes. The sensor membrane consists of single crystalline silicon formed by backside-etching of the bulk material of a silicon on insulator wafer having variable device thickness layer (5 μm-50 μm). With this principle, a pressure sensor has been fabricated and mounted on a pressure test package with pressure applied to the backside of the membrane within a range of 0 psi to 300 psi. The temperature coefficient of frequency was experimentally measured in the temperature range of -50 °C to 300 °C. This idea demonstrates a piezoelectric based sensor having two modes SAW/Lamb wave for direct physical parameter—pressure readout and temperature cancellation which can operate in harsh environment such as oil and gas exploration, automobile and aeronautic applications using the dual mode behavior of the sensor and differential readout at the same time.

  2. Ion acoustic shock wave in collisional equal mass plasma

    NASA Astrophysics Data System (ADS)

    Adak, Ashish; Ghosh, Samiran; Chakrabarti, Nikhil

    2015-10-01

    The effect of ion-ion collision on the dynamics of nonlinear ion acoustic wave in an unmagnetized pair-ion plasma has been investigated. The two-fluid model has been used to describe the dynamics of both positive and negative ions with equal masses. It is well known that in the dynamics of the weakly nonlinear wave, the viscosity mediates wave dissipation in presence of weak nonlinearity and dispersion. This dissipation is responsible for the shock structures in pair-ion plasma. Here, it has been shown that the ion-ion collision in presence of collective phenomena mediated by the plasma current is the source of dissipation that causes the Burgers' term which is responsible for the shock structures in equal mass pair-ion plasma. The dynamics of the weakly nonlinear wave is governed by the Korteweg-de Vries Burgers equation. The analytical and numerical investigations revealed that the ion acoustic wave exhibits both oscillatory and monotonic shock structures depending on the frequency of ion-ion collision parameter. The results have been discussed in the context of the fullerene pair-ion plasma experiments.

  3. Influences of shear in the ion parallel drift velocity and of inhomogeneous perpendicular electric field on generation of oblique ion acoustic waves

    NASA Astrophysics Data System (ADS)

    Ilyasov, Askar; Chernyshov, Alexander; Mogilevsky, Mikhail; Golovchanskaya, Irina; Kozelov, Boris

    2016-03-01

    It is well known that the broadband electrostatic turbulence observed in the topside auroral ionosphere can be identified with electrostatic ion cyclotron and/or oblique ion acoustic waves. Under certain conditions generation of the ion cyclotron modes is inhibited, so that the oblique ion acoustic waves become the prevailing part of the broadband noise. While generation of ion cyclotron waves by the inhomogeneous distribution of energy density (IEDD) instability has been actively studied in recent years, much less attention was paid to the excitation of ion acoustic waves by means of the IEDD instability. In this work, influence of shear in the ion parallel drift velocities and of inhomogeneous perpendicular electric field on generation of nonlocal oblique ion acoustic mode is studied. It is demonstrated that the shear of the ion parallel drift velocities can generate ion acoustic waves. It is shown that this mechanism of instability development provides broadband spectrum in the frequency range around 0.1 of ion gyrofrequency, and thus, this instability can be invoked to explain the observed broadband electrostatic turbulence in the auroral region. Effect of the main background plasma parameters on excitation of oblique ion acoustic waves is analyzed.

  4. Stimulated Brillouin side-scattering of the beat wave excited by two counter-propagating X-mode lasers in magnetized plasma

    NASA Astrophysics Data System (ADS)

    Verma, Kanika; Sajal, Vivek; Baliyan, Sweta; Kumar, Ravindra; Sharma, Navneet K.

    2015-06-01

    The stimulated Brillouin scattering (SBS) of nonresonant beat mode in the presence of static magnetic field is investigated in a plasma. Two counter-propagating lasers of frequencies ( ω 1 and ω 2 ) and wave vectors ( k 1 and k 2 ) drive a nonresonant space charge beat mode at the phase matching condition of frequency ω 0 ≈ ω 1 ˜ ω 2 and wave number k → 0 ≈ k → 1 + k → 2 . The driver wave parametrically excites a pair of ion acoustic wave ( ω , k → ) and a sideband electromagnetic wave ( ω 3 , k → 3 ) . The beat wave couples with the sideband electromagnetic wave to exert a nonlinear ponderomotive force at the frequency of ion acoustic wave. Density perturbations due to ion acoustic wave and ponderomotive force couple with the oscillatory motion of plasma electron due to velocity of beat wave to give rise to a nonlinear current (by feedback mechanism) responsible for the growth of sideband wave at resonance. The growth rate of SBS was reduced (from ˜ 10 12 s - 1 to 10 10 s - 1 ) by applying a transverse static magnetic field ˜ 90 T. The present study can be useful for the excitation of fast plasma waves (for the purpose of electron acceleration) by two counter-propagating laser beams.

  5. Second and third harmonic waves excited by focused Gaussian beams.

    PubMed

    Levy, Uri; Silberberg, Yaron

    2015-10-19

    Harmonic generation by tightly-focused Gaussian beams is finding important applications, primarily in nonlinear microscopy. It is often naively assumed that the nonlinear signal is generated predominantly in the focal region. However, the intensity of Gaussian-excited electromagnetic harmonic waves is sensitive to the excitation geometry and to the phase matching condition, and may depend on quite an extended region of the material away from the focal plane. Here we solve analytically the amplitude integral for second harmonic and third harmonic waves and study the generated harmonic intensities vs. focal-plane position within the material. We find that maximum intensity for positive wave-vector mismatch values, for both second harmonic and third harmonic waves, is achieved when the fundamental Gaussian is focused few Rayleigh lengths beyond the front surface. Harmonic-generation theory predicts strong intensity oscillations with thickness if the material is very thin. We reproduced these intensity oscillations in glass slabs pumped at 1550nm. From the oscillations of the 517nm third-harmonic waves with slab thickness we estimate the wave-vector mismatch in a Soda-lime glass as Δk(H)= -0.249μm(-1). PMID:26480441

  6. Acoustic Wave Stimulated Enhanced Oil Recovery

    NASA Astrophysics Data System (ADS)

    Reichmann, Sven; Giese, Rüdiger; Amro, Mohammed

    2013-04-01

    High demand and the finite oil deposits will be a problem in the future. To temper the impact of a shortage in crude oil, a lot of research in the field of enhanced oil recovery (EOR) is worldwide ongoing. Using seismic waves to stimulate recovery of oil is known as seismic-EOR. The development of a stimulation procedure using seismic sources and the evaluation of the obtained data in a real oil field is the aim of the project WAVE.O.R. The project is funded by the German scientific society for oil, gas and coal (DGMK). The Technical University of Freiberg (TUBAF) and the German Research Center for Geosciences (GFZ) in Potsdam developed a flooding cell connected with magnetostrictive actuators as sources for seismic energy. This device is eligible to survey the impact of different seismic stimulation parameter like frequency, alignment, amplitude and rock characteristics on oil recovery. The obtained laboratory data of flooding experiments using seismic waves were analyzed for key features like water breakthrough point, oil recovery and oil fraction. New approach has been developed, which consists of the connection of a principal component analysis with a clustering algorithm. This new technique allows us a better understanding and thus prediction of the recovery behavior of oil bearing sediments. The experiments show promising possibilities to enhance oil recovery with seismic stimulation. Especially the combination of different frequencies between 100 Hz and 4000 Hz had a positive impact on oil recovery. The responsible mechanisms were identified and discussed. Data obtained with the laboratory device will be applied in a field test using a borehole device developed by the GFZ in the project "Seismic Prediction While Drilling" (SPWD). For this purpose experiments are conducted to obtain the radiation pattern of the seismic sources used by the SPWD device in a borehole. In addition, the development of a control setup for the 1-D actuator array is an aim of the

  7. Resonant excitation of coupled Rayleigh waves in a short and narrow fluid channel clad between two identical metal plates

    SciTech Connect

    García-Chocano, Victor M.; López-Rios, Tomás; Krokhin, Arkadii; Sanchez-Dehesa, Jose

    2011-12-23

    Transmission of ultrasonic waves through a slit between two water immersed brass plates is studied for sub-wavelength plate thicknesses and slit apertures. Extraordinary high absorption is observed at discrete frequencies corresponding to resonant excitation of Rayleigh waves on the both sides of the channel. The coupling of the Rayleigh waves occurs through the fluid and the corresponding contribution to the dispersion has been theoretically derived and also experimentally confirmed. Symmetric and anti-symmetric modes are predicted but only the symmetric mode resonances have been observed. It follows from the dispersion equation that the coupled Rayleigh waves cannot be excited in a channel with apertures less than the critical one. The calculated critical aperture is in a good agreement with the measured acoustic spectra. These findings could be applied to design a broadband absorptive metamaterial.

  8. Resonant excitation of coupled Rayleigh waves in a short and narrow fluid channel clad between two identical metal plates

    DOE PAGES

    García-Chocano, Victor M.; López-Rios, Tomás; Krokhin, Arkadii; Sanchez-Dehesa, Jose

    2011-12-23

    Transmission of ultrasonic waves through a slit between two water immersed brass plates is studied for sub-wavelength plate thicknesses and slit apertures. Extraordinary high absorption is observed at discrete frequencies corresponding to resonant excitation of Rayleigh waves on the both sides of the channel. The coupling of the Rayleigh waves occurs through the fluid and the corresponding contribution to the dispersion has been theoretically derived and also experimentally confirmed. Symmetric and anti-symmetric modes are predicted but only the symmetric mode resonances have been observed. It follows from the dispersion equation that the coupled Rayleigh waves cannot be excited in amore » channel with apertures less than the critical one. The calculated critical aperture is in a good agreement with the measured acoustic spectra. These findings could be applied to design a broadband absorptive metamaterial.« less

  9. Acoustic and Cavitation Fields of Shock Wave Therapy Devices

    NASA Astrophysics Data System (ADS)

    Chitnis, Parag V.; Cleveland, Robin O.

    2006-05-01

    Extracorporeal shock wave therapy (ESWT) is considered a viable treatment modality for orthopedic ailments. Despite increasing clinical use, the mechanisms by which ESWT devices generate a therapeutic effect are not yet understood. The mechanistic differences in various devices and their efficacies might be dependent on their acoustic and cavitation outputs. We report acoustic and cavitation measurements of a number of different shock wave therapy devices. Two devices were electrohydraulic: one had a large reflector (HMT Ossatron) and the other was a hand-held source (HMT Evotron); the other device was a pneumatically driven device (EMS Swiss DolorClast Vet). Acoustic measurements were made using a fiber-optic probe hydrophone and a PVDF hydrophone. A dual passive cavitation detection system was used to monitor cavitation activity. Qualitative differences between these devices were also highlighted using a high-speed camera. We found that the Ossatron generated focused shock waves with a peak positive pressure around 40 MPa. The Evotron produced peak positive pressure around 20 MPa, however, its acoustic output appeared to be independent of the power setting of the device. The peak positive pressure from the DolorClast was about 5 MPa without a clear shock front. The DolorClast did not generate a focused acoustic field. Shadowgraph images show that the wave propagating from the DolorClast is planar and not focused in the vicinity of the hand-piece. All three devices produced measurable cavitation with a characteristic time (cavitation inception to bubble collapse) that varied between 95 and 209 μs for the Ossatron, between 59 and 283 μs for the Evotron, and between 195 and 431 μs for the DolorClast. The high-speed camera images show that the cavitation activity for the DolorClast is primarily restricted to the contact surface of the hand-piece. These data indicate that the devices studied here vary in acoustic and cavitation output, which may imply that the

  10. Guided wave opto-acoustic device

    DOEpatents

    Jarecki, Jr., Robert L.; Rakich, Peter Thomas; Camacho, Ryan; Shin, Heedeuk; Cox, Jonathan Albert; Qiu, Wenjun; Wang, Zheng

    2016-02-23

    The various technologies presented herein relate to various hybrid phononic-photonic waveguide structures that can exhibit nonlinear behavior associated with traveling-wave forward stimulated Brillouin scattering (forward-SBS). The various structures can simultaneously guide photons and phonons in a suspended membrane. By utilizing a suspended membrane, a substrate pathway can be eliminated for loss of phonons that suppresses SBS in conventional silicon-on-insulator (SOI) waveguides. Consequently, forward-SBS nonlinear susceptibilities are achievable at about 3000 times greater than achievable with a conventional waveguide system. Owing to the strong phonon-photon coupling achievable with the various embodiments, potential application for the various embodiments presented herein cover a range of radiofrequency (RF) and photonic signal processing applications. Further, the various embodiments presented herein are applicable to applications operating over a wide bandwidth, e.g. 100 MHz to 50 GHz or more.

  11. Acoustic Suppression Systems and Related Methods

    NASA Technical Reports Server (NTRS)

    Kolaini, Ali R. (Inventor); Kern, Dennis L. (Inventor)

    2013-01-01

    An acoustic suppression system for absorbing and/or scattering acoustic energy comprising a plurality of acoustic targets in a containment is described, the acoustic targets configured to have resonance frequencies allowing the targets to be excited by incoming acoustic waves, the resonance frequencies being adjustable to suppress acoustic energy in a set frequency range. Methods for fabricating and implementing the acoustic suppression system are also provided.

  12. Ion acoustic and dust acoustic waves at finite size of plasma particles

    SciTech Connect

    Andreev, Pavel A. Kuz'menkov, L. S.

    2015-03-15

    We consider the influence of the finite size of ions on the properties of classic plasmas. We focus our attention at the ion acoustic waves for electron-ion plasmas. We also consider the dusty plasmas where we account the finite size of ions and particles of dust and consider the dispersion of dust acoustic waves. The finite size of particles is a classical effect as well as the Coulomb interaction. The finite size of particles considerably contributes to the properties of the dense plasmas in the small wavelength limit. Low temperature dense plasmas, revealing the quantum effects, are also affected by the finite size of plasma particles. Consequently, it is important to consider the finite size of ions in the quantum plasmas as well.

  13. Acoustically induced tissue displacement for shear wave elasticity imaging using MRI

    NASA Astrophysics Data System (ADS)

    Haworth, Kevin; Kripfgans, Oliver; Steele, Derek; Swanson, Scott; Sutin, Alexander; Sarvazyan, Armen

    2005-09-01

    Palpitation detects tissue abnormalities by exploiting the vast range of elastic properties found in vivo. The method is limited by tactile sensitivity and the inability to probe tissues at depth. Recent efforts seek to remove these limitation by developing a medical imaging modality based on radiation force shear wave excitation. Our approach uses an acoustic source to launch a shear wave in a tissue-mimicking phantom and MRI to record microscopic displacements. Gelatin (10% wt/vol) was used for the tissue-mimicking phantom. Results for in situ elasticity were obtained using an air-backed 10-cm-diam piezoelectric crystal. To correct for future in vivo beam aberrations, we also employ a high-pressure 1-bit time-reversal cavity. Frequency and pulse duration were selected to optimize the TRA system for acoustic output pressure. Shear wave displacements were recorded by MRI in 1-ms time increments in a complete basis that allowed for 3-D reconstruction and analysis. The Lamé coefficients are then derived from the shear wave velocity and attenuation.

  14. Generation and Radiation of Acoustic Waves from a 2-D Shear Layer using the CE/SE Method

    NASA Technical Reports Server (NTRS)

    Loh, Ching Y.; Wang, Xiao Y.; Chang, Sin-Chung; Jorgenson, Philip C. E.

    2000-01-01

    In the present work, the generation and radiation of acoustic waves from a 2-D shear layer problem is considered. An acoustic source inside of a 2-D jet excites an instability wave in the shear layer, resulting in sound Mach radiation. The numerical solution is obtained by solving the Euler equations using the space time conservation element and solution element (CE/SE) method. Linearization is achieved through choosing a small acoustic source amplitude. The Euler equations are nondimensionalized as instructed in the problem statement. All other conditions are the same except that the Crocco's relation has a slightly different form. In the following, after a brief sketch of the CE/SE method, the numerical results for this problem are presented.

  15. Switchable and Tunable Ferroelectric Bulk Acoustic Wave Resonators and Filters

    NASA Astrophysics Data System (ADS)

    Saddik, George Nabih

    Ferroelectric materials such as barium titanate (BaTiO 3 or BTO), strontium titanate (SrTiO3 or STO), and their solid solution barium strontium titanate (BaxSr1-xTiO 3 or BST) have been under investigation for over 50 years. BTO, STO, and BST are high-k dielectric materials, with a field dependent permittivity and a perovskite crystal structure. At room temperature BTO is a ferroelectric with a ferroelectric to paraelectric transition temperature of about 116°C (Curie temperature), while STO has no ferroelectric phase. The formation of a solid solution between BTO and STO allows for the engineering of the Curie temperature; the Curie temperature decreses as the mole ratio of barium decreases. Extensive research went into understanding the properties of BST and developing RF circuits such as tunable capacitors, tunable matching networks, tunable filters, phase shifters and harmonic generators. BST tunable capacitors have always had anomalous resonances in the one port scattering parameter measurements, although they are very small they degrade the quality factor of the device, and research went into reducing these resonances as much as possible. The goal of this thesis is to investigate these anomalous resonances and exploit them into RF devices and circuits. Careful investigation showed that these resonances were field induced piezoelectric resonance. Piezoelectric materials such as AlN, ZnO, and PZT are used in many applications, such as resonators, and filters. Thin film bulk acoustic wave resonators (FBAR) have been in use by research and industry since the early 1980s, and in high volume production for cell phone duplexers since early 2000s. FBAR filters and duplexers have several advantages over surface acoustic wave (SAW) and ceramic devices such as high quality factors necessary for sharp filter skirts, small size, high performance, and ease of integration. There are two approaches to designing bulk acoustic wave resonators. The first is an FBAR where a

  16. Shear mode bulk acoustic wave resonator based on c-axis oriented AlN thin film

    NASA Astrophysics Data System (ADS)

    Milyutin, Evgeny; Gentil, Sandrine; Muralt, Paul

    2008-10-01

    A shear mode resonator based on bulk waves trapped in c-axis oriented AlN thin films was fabricated, simulated, and tested. The active 1.55 μm thick AlN layer was deposited on top of an acoustic Bragg reflector composed of SiO2/AlN λ /4 layer pairs. The resonance was excited by means of interdigitated electrodes consisting of 150 nm thick Al lines. Analytical and simulation calculations show that the in-plane electric field excites bulk acoustic wave shear modes that are trapped in such an AlN film slab. The experimental frequency corresponds well to the theoretical one. The evaluated resonance of the fundamental shear mode at 1.86 GHz revealed a coupling of 0.15% and Q-factor of 870 in air and 260 in silicon oil.

  17. Digital data-acquisition system for measuring the free decay of acoustical standing waves in a resonant tube

    NASA Technical Reports Server (NTRS)

    Meredith, R. W.; Zuckerwar, A. J.

    1984-01-01

    A low-cost digital system based on an 8-bit Apple II microcomputer has been designed to provide on-line control, data acquisition, and evaluation of sound absorption measurements in gases. The measurements are conducted in a resonant tube, in which an acoustical standing wave is excited, the excitation removed, and the sound absorption evaluated from the free decay envelope. The free decay is initiated from the computer keyboard after the standing wave is established, and the microphone response signal is the source of the analog signal for the A/D converter. The acquisition software is written in ASSEMBLY language and the evaluation software in BASIC. This paper describes the acoustical measurement, hardware, software, and system performance and presents measurements of sound absorption in air as an example.

  18. Simultaneous multipoint acoustic emission sensing using fibre acoustic wave grating sensors with identical spectrum

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Ryul; Lee, Seung-Seok; Yoon, Dong-Jin

    2008-08-01

    This paper introduces the development of a simultaneous multipoint acoustic emission (AE) sensing system using a narrowband tuneable laser with high power and fibre acoustic wave grating sensors (FAWGSs). The demodulation technique is the same as that used in existing methods where the narrowband laser peak is tuned to one mid-reflection point in the main lobe of a fibre Bragg grating (FBG) spectrum. However, the sensor head is changed to an FAWGS for which a FBG is installed in a strain-free configuration so that it can detect AE waves in a structure not directly but in the form of a fibre-guided acoustic wave. Therefore since the structural strain cannot make the Bragg wavelength change, multiple FBGs with identical spectrum can be connected with multiple optical paths realized by equal light intensity dividers. The possible temperature difference between the multiple FAWGSs is passively resolved by using short FBGs which provide a wider operating temperature region. Consequently, we can resolve the problem that the FBG spectrum is easily deviated from the lasing wavelength because of the strain. In addition, the simultaneous multipoint sensing capability based on a single laser improves the cost-performance ratio of the optical system as well as reducing the structural inspection time, and enabling in situ health monitoring of real structures exposed to large and dynamic strains. The feasibility of the system is demonstrated in typical applications of in situ structural health monitoring based on AE techniques.

  19. Particle simulation of Alfven waves excited at a boundary

    SciTech Connect

    Tsung, F.S.; Tonge, J.W.; Morales, G.J.

    2005-01-01

    A particle-in-cell (PIC) code has been developed that is capable of describing the propagation of compressional and shear Alfven waves excited from a boundary. The code is used to elucidate the properties of Alfven wave cones radiated from sources having transverse scale comparable to the electron skin depth. Good agreement between theoretical predictions and simulation results is found over a wide range of frequencies. An investigation has been undertaken of the effect of hot ions on the Alfven wave cones. The PIC simulations demonstrate that as the ion temperature is increased there is a reversal in the cone angle. The reversal implies that there is a cross-field focusing of the shear Alfven waves. This is a feature which is presently being considered in studies of field-line resonances in the earth's magnetic field. The PIC results also illustrate the damping of shear modes due to the Doppler-shifted cyclotron resonance with hot ions.

  20. Flow velocity measurement with the nonlinear acoustic wave scattering

    NASA Astrophysics Data System (ADS)

    Didenkulov, Igor; Pronchatov-Rubtsov, Nikolay

    2015-10-01

    A problem of noninvasive measurement of liquid flow velocity arises in many practical applications. To this end the most often approach is the use of the linear Doppler technique. The Doppler frequency shift of signal scattered from the inhomogeneities distributed in a liquid relatively to the emitted frequency is proportional to the sound frequency and velocities of inhomogeneities. In the case of very slow flow one needs to use very high frequency sound. This approach fails in media with strong sound attenuation because acoustic wave attenuation increases with frequency and there is limit in increasing sound intensity, i.e. the cavitation threshold. Another approach which is considered in this paper is based on the method using the difference frequency Doppler Effect for flows with bubbles. This method is based on simultaneous action of two high-frequency primary acoustic waves with closed frequencies on bubbles and registration of the scattered by bubbles acoustic field at the difference frequency. The use of this method is interesting since the scattered difference frequency wave has much lower attenuation in a liquid. The theoretical consideration of the method is given in the paper. The experimental examples confirming the theoretical equations, as well as the ability of the method to be applied in medical diagnostics and in technical applications on measurement of flow velocities in liquids with strong sound attenuation is described. It is shown that the Doppler spectrum form depends on bubble concentration velocity distribution in the primary acoustic beams crossing zone that allows one to measure the flow velocity distribution.

  1. Flow velocity measurement with the nonlinear acoustic wave scattering

    SciTech Connect

    Didenkulov, Igor; Pronchatov-Rubtsov, Nikolay

    2015-10-28

    A problem of noninvasive measurement of liquid flow velocity arises in many practical applications. To this end the most often approach is the use of the linear Doppler technique. The Doppler frequency shift of signal scattered from the inhomogeneities distributed in a liquid relatively to the emitted frequency is proportional to the sound frequency and velocities of inhomogeneities. In the case of very slow flow one needs to use very high frequency sound. This approach fails in media with strong sound attenuation because acoustic wave attenuation increases with frequency and there is limit in increasing sound intensity, i.e. the cavitation threshold. Another approach which is considered in this paper is based on the method using the difference frequency Doppler Effect for flows with bubbles. This method is based on simultaneous action of two high-frequency primary acoustic waves with closed frequencies on bubbles and registration of the scattered by bubbles acoustic field at the difference frequency. The use of this method is interesting since the scattered difference frequency wave has much lower attenuation in a liquid. The theoretical consideration of the method is given in the paper. The experimental examples confirming the theoretical equations, as well as the ability of the method to be applied in medical diagnostics and in technical applications on measurement of flow velocities in liquids with strong sound attenuation is described. It is shown that the Doppler spectrum form depends on bubble concentration velocity distribution in the primary acoustic beams crossing zone that allows one to measure the flow velocity distribution.

  2. Determination of hydrocarbon levels in water via laser-induced acoustics wave

    NASA Astrophysics Data System (ADS)

    Bidin, Noriah; Hossenian, Raheleh; Duralim, Maisarah; Krishnan, Ganesan; Marsin, Faridah Mohd; Nughro, Waskito; Zainal, Jasman

    2016-04-01

    Hydrocarbon contamination in water is a major environmental concern in terms of foreseen collapse of the natural ecosystem. Hydrocarbon level in water was determined by generating acoustic wave via an innovative laser-induced breakdown in conjunction with high-speed photographic coupling with piezoelectric transducer to trace acoustic wave propagation. A Q-switched Nd:YAG (40 mJ) was focused in cuvette-filled hydrocarbon solution at various concentrations (0-2000 ppm) to induce optical breakdown, shock wave generation and later acoustic wave propagation. A nitro-dye (ND) laser (10 mJ) was used as a flash to illuminate and frozen the acoustic wave propagation. Lasers were synchronised using a digital delay generator. The image of acoustic waves was grabbed and recorded via charged couple device (CCD) video camera at the speed of 30 frames/second with the aid of Matrox software version 9. The optical delay (0.8-10.0 μs) between the acoustic wave formation and its frozen time is recorded through photodetectors. A piezo-electric transducer (PZT) was used to trace the acoustic wave (sound signal), which cascades to a digital oscilloscope. The acoustic speed is calculated from the ratio of acoustic wave radius (1-8 mm) and optical time delay. Acoustic wave speed is found to linearly increase with hydrocarbon concentrations. The acoustic signal generation at higher hydrocarbon levels in water is attributed to supplementary mass transfer and impact on the probe. Integrated high-speed photography with transducer detection system authenticated that the signals indeed emerged from the laser-induced acoustic wave instead of photothermal processes. It is established that the acoustic wave speed in water is used as a fingerprint to detect the hydrocarbon levels.

  3. Direct visualization of surface acoustic waves along substrates using smoke particles

    NASA Astrophysics Data System (ADS)

    Tan, Ming K.; Friend, James R.; Yeo, Leslie Y.

    2007-11-01

    Smoke particles (SPs) are used to directly visualize surface acoustic waves (SAWs) propagating on a 128°-rotated Y-cut X-propagating lithium niobate (LiNbO3) substrate. By electrically exciting a SAW device in a compartment filled with SP, the SP were found to collect along the regions where the SAW propagates on the substrate. The results of the experiments show that SPs are deposited adjacent to regions of large vibration amplitude and form a clear pattern corresponding to the surface wave profile on the substrate. Through an analysis of the SAW-induced acoustic streaming in the air adjacent to the substrate and the surface acceleration measured with a laser Doppler vibrometer, we postulate that the large transverse surface accelerations due to the SAW ejects SP from the surface and carries them aloft to relatively quiescent regions nearby via acoustic streaming. Offering finer detail than fine powders common in Chladni figures [E. Chladni, Entdeckungen über die Theorie des Klanges (Weidmanns, Erben und Reich, Leipzig, Germany, 1787)] the approach is an inexpensive and a quick counterpart to laser interferometric techniques, presenting a means to explore the controversial phenomena of particle agglomeration on surfaces.

  4. Longitudinal spread of mechanical excitation through tectorial membrane traveling waves

    PubMed Central

    Sellon, Jonathan B.; Farrahi, Shirin; Ghaffari, Roozbeh; Freeman, Dennis M.

    2015-01-01

    The mammalian inner ear separates sounds by their frequency content, and this separation underlies important properties of human hearing, including our ability to understand speech in noisy environments. Studies of genetic disorders of hearing have demonstrated a link between frequency selectivity and wave properties of the tectorial membrane (TM). To understand these wave properties better, we developed chemical manipulations that systematically and reversibly alter TM stiffness and viscosity. Using microfabricated shear probes, we show that (i) reducing pH reduces TM stiffness with little change in TM viscosity and (ii) adding PEG increases TM viscosity with little change in TM stiffness. By applying these manipulations in measurements of TM waves, we show that TM wave speed is determined primarily by stiffness at low frequencies and by viscosity at high frequencies. Both TM viscosity and stiffness affect the longitudinal spread of mechanical excitation through the TM over a broad range of frequencies. Increasing TM viscosity or decreasing stiffness reduces longitudinal spread of mechanical excitation, thereby coupling a smaller range of best frequencies and sharpening tuning. In contrast, increasing viscous loss or decreasing stiffness would tend to broaden tuning in resonance-based TM models. Thus, TM wave and resonance mechanisms are fundamentally different in the way they control frequency selectivity. PMID:26438861

  5. Plane-wave analysis of solar acoustic-gravity waves: A (slightly) new approach

    NASA Technical Reports Server (NTRS)

    Bogart, Richard S.; Sa, L. A. D.; Duvall, Thomas L., Jr.; Haber, Deborah A.; Toomre, Juri; Hill, Frank

    1995-01-01

    The plane-wave decomposition of the acoustic-gravity wave effects observed in the photosphere provides a computationally efficient technique that probes the structure of the upper convective zone and boundary. In this region, the flat sun approximation is considered as being reasonably accurate. A technique to be used for the systematic plane-wave analysis of Michelson Doppler imager data, as part of the solar oscillations investigation, is described. Estimates of sensitivity are presented, and the effects of using different planar mappings are discussed. The technique is compared with previous approaches to the three dimensional plane-wave problem.

  6. Nonlinear vibration and radiation from a panel with transition to chaos induced by acoustic waves

    NASA Technical Reports Server (NTRS)

    Maestrello, Lucio; Frendi, Abdelkader; Brown, Donald E.

    1992-01-01

    The dynamic response of an aircraft panel forced at resonance and off-resonance by plane acoustic waves at normal incidence is investigated experimentally and numerically. Linear, nonlinear (period doubling) and chaotic responses are obtained by increasing the sound pressure level of the excitation. The response time history is sensitive to the input level and to the frequency of excitation. The change in response behavior is due to a change in input conditions, triggered either naturally or by modulation of the bandwidth of the incident waves. Off-resonance, bifurcation is diffused and difficult to maintain, thus the panel response drifts into a linear behavior. The acoustic pressure emanated by the panel is either linear or nonlinear as is the vibration response. The nonlinear effects accumulate during the propagation with distance. Results are also obtained on the control of the panel response using damping tape on aluminum panel and using a graphite epoxy panel having the same size and weight. Good agreement is obtained between the experimental and numerical results.

  7. Fluorescence excitation by enhanced plasmon upconversion under continuous wave illumination

    NASA Astrophysics Data System (ADS)

    Tasgin, Mehmet Emre; Salakhutdinov, Ildar; Kendziora, Dania; Abak, Musa Kurtulus; Turkpence, Deniz; Piantanida, Luca; Fruk, Ljiljana; Lazzarino, Marco; Bek, Alpan

    2016-09-01

    We demonstrate effective background-free continuous wave nonlinear optical excitation of molecules that are sandwiched between asymmetrically constructed plasmonic gold nanoparticle clusters. We observe that near infrared photons are converted to visible photons through efficient plasmonic second harmonic generation. Our theoretical model and simulations demonstrate that Fano resonances may be responsible for being able to observe nonlinear conversion using a continuous wave light source. We show that nonlinearity enhancement of plasmonic nanostructures via coupled quantum mechanical oscillators such as molecules can be several orders larger as compared to their classical counterparts.

  8. Excitation of knotted vortex lines in matter waves

    NASA Astrophysics Data System (ADS)

    Maucher, F.; Gardiner, S. A.; Hughes, I. G.

    2016-06-01

    We study the creation of knotted ultracold matter waves in Bose–Einstein condensates via coherent two-photon Raman transitions with a Λ level configuration. The Raman transition allows an indirect transfer of atoms from the internal state | a> to the target state | b> via an excited state | e> , that would be otherwise dipole-forbidden. This setup enables us to imprint three-dimensional knotted vortex lines embedded in the probe field to the density in the target state. We elaborate on experimental feasibility as well as on subsequent dynamics of the matter wave.

  9. Graphene-mediated microfluidic transport and nebulization via high frequency Rayleigh wave substrate excitation.

    PubMed

    Ang, Kar M; Yeo, Leslie Y; Hung, Yew M; Tan, Ming K

    2016-09-21

    The deposition of a thin graphene film atop a chip scale piezoelectric substrate on which surface acoustic waves are excited is observed to enhance its performance for fluid transport and manipulation considerably, which can be exploited to achieve further efficiency gains in these devices. Such gains can then enable complete integration and miniaturization for true portability for a variety of microfluidic applications across drug delivery, biosensing and point-of-care diagnostics, among others, where field-use, point-of-collection or point-of-care functionality is desired. In addition to a first demonstration of vibration-induced molecular transport in graphene films, we show that the coupling of the surface acoustic wave gives rise to antisymmetric Lamb waves in the film which enhance molecular diffusion and hence the flow through the interstitial layers that make up the film. Above a critical input power, the strong substrate vibration displacement can also force the molecules out of the graphene film to form a thin fluid layer, which subsequently destabilizes and breaks up to form a mist of micron dimension aerosol droplets. We provide physical insight into this coupling through a simple numerical model, verified through experiments, and show several-fold improvement in the rate of fluid transport through the film, and up to 55% enhancement in the rate of fluid atomization from the film using this simple method. PMID:27502324

  10. Fluid simulation of dispersive and nondispersive ion acoustic waves in the presence of superthermal electrons

    NASA Astrophysics Data System (ADS)

    Lotekar, Ajay; Kakad, Amar; Kakad, Bharati

    2016-10-01

    One-dimensional fluid simulation is performed for the unmagnetized plasma consisting of cold fluid ions and superthermal electrons. Such a plasma system supports the generation of ion acoustic (IA) waves. A standard Gaussian type perturbation is used in both electron and ion equilibrium densities to excite the IA waves. The evolutionary profiles of the IA waves are obtained by varying the superthermal index and the amplitude of the initial perturbation. This simulation demonstrates that the amplitude of the initial perturbation and the superthermal index play an important role in determining the time evolution and the characteristics of the generated IA waves. The initial density perturbation in the system creates charge separation that drives the finite electrostatic potential in the system. This electrostatic potential later evolves into the dispersive and nondispersive IA waves in the simulation system. The density perturbation with the amplitude smaller than 10% of the equilibrium plasma density evolves into the dispersive IA waves, whereas larger density perturbations evolve into both dispersive and nondispersive IA waves for lower and higher superthermal index. The dispersive IA waves are the IA oscillations that propagate with constant ion plasma frequency, whereas the nondispersive IA waves are the IA solitary pulses (termed as IA solitons in the stability region) that propagate with the constant wave speed. The characteristics of the stable nondispersive IA solitons are found to be consistent with the nonlinear fluid theory. To the best of our knowledge, this is the first fluid simulation study that has considered the superthermal distributions for the plasma species to model the electrostatic solitary waves.

  11. Surface modification on acoustic wave biosensors for enhanced specificity.

    PubMed

    Onen, Onursal; Ahmad, Asad A; Guldiken, Rasim; Gallant, Nathan D

    2012-01-01

    Changes in mass loading on the surface of acoustic biosensors result in output frequency shifts which provide precise measurements of analytes. Therefore, to detect a particular biomarker, the sensor delay path must be judiciously designed to maximize sensitivity and specificity. B-cell lymphoma 2 protein (Bcl-2) found in urine is under investigation as a biomarker for non-invasive early detection of ovarian cancer. In this study, surface chemistry and biofunctionalization approaches were evaluated for their effectiveness in presenting antibodies for Bcl-2 capture while minimizing non-specific protein adsorption. The optimal combination of sequentially adsorbing protein A/G, anti-Bcl-2 IgG and Pluronic F127 onto a hydrophobic surface provided the greatest signal-to-noise ratio and enabled the reliable detection of Bcl-2 concentrations below that previously identified for early stage ovarian cancer as characterized by a modified ELISA method. Finally, the optimal surface modification was applied to a prototype acoustic device and the frequency shift for a range of Bcl-2 concentration was quantified to demonstrate the effectiveness in surface acoustic wave (SAW)-based detection applications. The surface functionalization approaches demonstrated here to specifically and sensitively detect Bcl-2 in a working ultrasonic MEMS biosensor prototype can easily be modified to detect additional biomarkers and enhance other acoustic biosensors.

  12. Modeling Nonlinear Acoustic Standing Waves in Resonators: Theory and Experiments

    NASA Technical Reports Server (NTRS)

    Raman, Ganesh; Li, Xiaofan; Finkbeiner, Joshua

    2004-01-01

    The overall goal of the cooperative research with NASA Glenn is to fundamentally understand, computationally model, and experimentally validate non-linear acoustic waves in enclosures with the ultimate goal of developing a non-contact acoustic seal. The longer term goal is to transition the Glenn acoustic seal innovation to a prototype sealing device. Lucas and coworkers are credited with pioneering work in Resonant Macrosonic Synthesis (RMS). Several Patents and publications have successfully illustrated the concept of Resonant Macrosonic Synthesis. To utilize this concept in practical application one needs to have an understanding of the details of the phenomenon and a predictive tool that can examine the waveforms produced within resonators of complex shapes. With appropriately shaped resonators one can produce un-shocked waveforms of high amplitude that would result in very high pressures in certain regions. Our goal is to control the waveforms and exploit the high pressures to produce an acoustic seal. Note that shock formation critically limits peak-to-peak pressure amplitudes and also causes excessive energy dissipation. Proper shaping of the resonator is thus critical to the use of this innovation.

  13. Dust acoustic solitary waves in a quantum plasma

    SciTech Connect

    Ali, S.; Shukla, P.K.

    2006-02-15

    By employing one-dimensional quantum hydrodynamic (QHD) model for a three species quantum plasma, nonlinear properties of dust acoustic solitary waves are studied. For this purpose a Korteweg-de Vries (KdV) equation is derived, incorporating quantum corrections. The quantum mechanical effects are also examined numerically both on the profiles of the amplitude and the width of dust acoustic solitary waves. It is found that the amplitude remains constant but the width shrinks for different values of a dimensionless electron quantum parameter H{sub e}={radical}((Z{sub d0}({Dirac_h}/2{pi}){sup 2}{omega}{sub pd}{sup 2})/m{sub e}m{sub d}C{sub d}{sup 4}), where Z{sub d0} is the dust charge state, ({Dirac_h}/2{pi}) is the Planck constant divided by 2{pi}, {omega}{sub pd} is the dust plasma frequency, m{sub e} (m{sub d}) is the electron (dust) mass, and C{sub d} is the dust acoustic speed.

  14. Microwave acoustics handbook. Volume 3: Bulk wave velocities

    NASA Astrophysics Data System (ADS)

    Slobodnik, A. J., Jr.; Delmonico, R. T.; Conway, E. D.

    1980-05-01

    Information useful for the design of acoustic delay lines, resonators, and other miniature, low cost, reliable devices for use in communications and electronic sensing is given in this report. Computations of bulk acoustic wave velocities, power flow angles, and coupling to electric fields are plotted for various orientations of the following single crystalline materials: Ba2NaNb5O15, Bi12GeO20, CdS, Diamond, Eu3Fe5O15, Gadolinium Gallium Garnet, GaAs, Germanium, InSb, InAs, Lead Molybdate, PbS, LiNbO3, LiTaO3, MgO, Quartz, Rutile, Sapphire, Silicon, Spinel, TeO2, YAG, YGaG, YIG, and ZnO. Particular cuts of interest, including cases for common metals, are then chosen for more detailed numerical calculations of mechanical and electrical parameters governing acoustic wave propagation in these media. A list of material constants is also included.

  15. Longitudinal elastic wave propagation characteristics of inertant acoustic metamaterials

    NASA Astrophysics Data System (ADS)

    Kulkarni, Prateek P.; Manimala, James M.

    2016-06-01

    Longitudinal elastic wave propagation characteristics of acoustic metamaterials with various inerter configurations are investigated using their representative one-dimensional discrete element lattice models. Inerters are dynamic mass-amplifying mechanical elements that are activated by a difference in acceleration across them. They have a small device mass but can provide a relatively large dynamic mass presence depending on accelerations in systems that employ them. The effect of introducing inerters both in local attachments and in the lattice was examined vis-à-vis the propagation characteristics of locally resonant acoustic metamaterials. A simple effective model based on mass, stiffness, or their combined equivalent was used to establish dispersion behavior and quantify attenuation within bandgaps. Depending on inerter configurations in local attachments or in the lattice, both up-shift and down-shift in the bandgap frequency range and their extent are shown to be possible while retaining static mass addition to the host structure to a minimum. Further, frequency-dependent negative and even extreme effective-stiffness regimes are encountered. The feasibility of employing tuned combinations of such mass-delimited inertant configurations to engineer acoustic metamaterials that act as high-pass filters without the use of grounded elements or even as complete longitudinal wave inhibitors is shown. Potential device implications and strategies for practical applications are also discussed.

  16. Determination of particle size distributions from acoustic wave propagation measurements

    SciTech Connect

    Spelt, P.D.; Norato, M.A.; Sangani, A.S.; Tavlarides, L.L.

    1999-05-01

    The wave equations for the interior and exterior of the particles are ensemble averaged and combined with an analysis by Allegra and Hawley [J. Acoust. Soc. Am. {bold 51}, 1545 (1972)] for the interaction of a single particle with the incident wave to determine the phase speed and attenuation of sound waves propagating through dilute slurries. The theory is shown to compare very well with the measured attenuation. The inverse problem, i.e., the problem of determining the particle size distribution given the attenuation as a function of frequency, is examined using regularization techniques that have been successful for bubbly liquids. It is shown that, unlike the bubbly liquids, the success of solving the inverse problem is limited since it depends strongly on the nature of particles and the frequency range used in inverse calculations. {copyright} {ital 1999 American Institute of Physics.}

  17. Ion acoustic solitary waves in magneto-rotating plasmas

    NASA Astrophysics Data System (ADS)

    Mushtaq, A.

    2010-08-01

    Propagation of an ion acoustic wave (IAW) in a magnetized electron-ion plasma, which is rotating around an axis at an angle θ with the direction of magnetic field, is studied by incorporating the effects of trapped and untrapped electron distributions. Employing the perturbation scheme, Korteweg-deVries and Schamel's modified KdV equations are derived for the small angle θ which may support the nonlinear IAW on a slow time scale of ion motion. The amplitude and width of the solitary wave in both cases (trapped and untrapped electrons) have been discussed with the effects of oblique rotation and external magnetic field. It is shown that the nonlinear effects considerably influence the propagation of waves in rotating plasmas.

  18. Attenuation of 7 GHz surface acoustic waves on silicon

    NASA Astrophysics Data System (ADS)

    Li, Dongyao; Cahill, David G.

    2016-09-01

    We measured the attenuation of GHz frequency surface acoustic waves (SAWs) on the Si (001) surface using an optical pump-probe technique at temperatures between 300 and 600 K. SAWs are generated and detected by a 700 nm Al grating fabricated by nanoimprint lithography. The grating for SAW generation is separated from the grating for SAW detection by ≈150 μ m . The amplitude of SAWs is attenuated by coupling to bulk waves created by the Al grating, diffraction due to the finite size of the source, and the intrinsic relaxational Akhiezer damping of elastic waves in Si. Thermal phonon relaxation time and Grüneisen parameters are fitted using temperature-dependent measurement. The f Q product of a hypothetical micromechanical oscillator limited by Akhiezer damping at this frequency is ˜3 ×1013 Hz.

  19. Asymmetric wave transmission in a diatomic acoustic/elastic metamaterial

    NASA Astrophysics Data System (ADS)

    Li, Bing; Tan, K. T.

    2016-08-01

    Asymmetric acoustic/elastic wave transmission has recently been realized using nonlinearity, wave diffraction, or bias effects, but always at the cost of frequency distortion, direction shift, large volumes, or external energy. Based on the self-coupling of dual resonators, we propose a linear diatomic metamaterial, consisting of several small-sized unit cells, to realize large asymmetric wave transmission in low frequency domain (below 1 kHz). The asymmetric transmission mechanism is theoretically investigated, and numerically verified by both mass-spring and continuum models. This passive system does not require any frequency conversion or external energy, and the asymmetric transmission band can be theoretically predicted and mathematically controlled, which extends the design concept of unidirectional transmission devices.

  20. Underwater acoustic wave generation by filamentation of terawatt ultrashort laser pulses.

    PubMed

    Jukna, Vytautas; Jarnac, Amélie; Milián, Carles; Brelet, Yohann; Carbonnel, Jérôme; André, Yves-Bernard; Guillermin, Régine; Sessarego, Jean-Pierre; Fattaccioli, Dominique; Mysyrowicz, André; Couairon, Arnaud; Houard, Aurélien

    2016-06-01

    Acoustic signals generated by filamentation of ultrashort terawatt laser pulses in water are characterized experimentally. Measurements reveal a strong influence of input pulse duration on the shape and intensity of the acoustic wave. Numerical simulations of the laser pulse nonlinear propagation and the subsequent water hydrodynamics and acoustic wave generation show that the strong acoustic emission is related to the mechanism of superfilamention in water. The elongated shape of the plasma volume where energy is deposited drives the far-field profile of the acoustic signal, which takes the form of a radially directed pressure wave with a single oscillation and a very broad spectrum.

  1. Underwater acoustic wave generation by filamentation of terawatt ultrashort laser pulses.

    PubMed

    Jukna, Vytautas; Jarnac, Amélie; Milián, Carles; Brelet, Yohann; Carbonnel, Jérôme; André, Yves-Bernard; Guillermin, Régine; Sessarego, Jean-Pierre; Fattaccioli, Dominique; Mysyrowicz, André; Couairon, Arnaud; Houard, Aurélien

    2016-06-01

    Acoustic signals generated by filamentation of ultrashort terawatt laser pulses in water are characterized experimentally. Measurements reveal a strong influence of input pulse duration on the shape and intensity of the acoustic wave. Numerical simulations of the laser pulse nonlinear propagation and the subsequent water hydrodynamics and acoustic wave generation show that the strong acoustic emission is related to the mechanism of superfilamention in water. The elongated shape of the plasma volume where energy is deposited drives the far-field profile of the acoustic signal, which takes the form of a radially directed pressure wave with a single oscillation and a very broad spectrum. PMID:27415357

  2. Excitation and evolution of finite-amplitude plasma wave

    SciTech Connect

    Hou, Y. W.; Wu, Y. C.; Chen, M. X.; Yu, M. Y.; Wu, B.

    2015-12-15

    The evolution of a small spatially periodic perturbation in the electron velocity distribution function in collisionless plasma is reconsidered by numerically solving the Vlasov and Poisson equations. The short as well as long time behaviors of the excited oscillations and damping/modulation are followed. In the small but finite-amplitude excited plasma wave, resonant electrons become trapped in the wave potential wells and their motion affects the low-velocity electrons participating in the plasma oscillations, leading to modulation of the latter at an effective trapping frequency. It is found that the phase space of the resonant and low-velocity electrons becomes chaotic, but then self-organization takes place but remains fine-scale chaotic. It is also found that as long as particles are trapped, there is only modulation and no monotonic damping of the excited plasma wave. The modulation period/amplitude increases/decreases as the magnitude of the initial disturbance is reduced. For the initial and boundary conditions used here, linear Landau damping corresponds to the asymptotic limit of the modulation period becoming infinite, or no trapping of the resonant electrons.

  3. Observation of orbital waves as elementary excitations in a solid.

    PubMed

    Saitoh, E; Okamoto, S; Takahashi, K T; Tobe, K; Yamamoto, K; Kimura, T; Ishihara, S; Maekawa, S; Tokura, Y

    2001-03-01

    A basic concept in solid-state physics is that when some kind of symmetry in a solid is spontaneously broken, collective excitations will arise. For example, phonons are the collective excitations corresponding to lattice vibrations in a crystal, and magnons correspond to spin waves in a magnetically ordered compound. Modulations in the relative shape of the electronic clouds in an orbitally ordered state could in principle give rise to orbital waves, or 'orbitons', but this type of elementary excitation has yet to be observed experimentally. Systems in which the electrons are strongly correlated-such as high-temperature superconductors and manganites exhibiting colossal magnetoresistivity-are promising candidates for supporting orbital waves, because they contain transition-metal ions in which the orbital degree of freedom is important. Orbitally ordered states have been found in several transition-metal compounds, and orbitons have been predicted theoretically for LaMnO3. Here we report experimental evidence for orbitons in LaMnO3, using Raman scattering measurements. We perform a model calculation of orbiton resonances which provides a good fit to the experimental data.

  4. Theoretical study of the anisotropic diffraction of light waves by acoustic waves in lithium niobate crystals.

    PubMed

    Rouvaen, J M; Waxin, G; Gazalet, M G; Bridoux, E

    1990-03-20

    The anisotropic diffraction of light by high frequency longitudinal ultrasonic waves in the tangential phase matching configuration may present some definite advantages over the same interaction using transverse acoustic waves. A systematic search for favorable crystal cuts in lithium niobate was worked out. The main results of this study are reported here; they enable the choice of the best configuration for a given operating center frequency.

  5. High Temperature Shear Horizontal Electromagnetic Acoustic Transducer for Guided Wave Inspection.

    PubMed

    Kogia, Maria; Gan, Tat-Hean; Balachandran, Wamadeva; Livadas, Makis; Kappatos, Vassilios; Szabo, Istvan; Mohimi, Abbas; Round, Andrew

    2016-04-22

    Guided Wave Testing (GWT) using novel Electromagnetic Acoustic Transducers (EMATs) is proposed for the inspection of large structures operating at high temperatures. To date, high temperature EMATs have been developed only for thickness measurements and they are not suitable for GWT. A pair of water-cooled EMATs capable of exciting and receiving Shear Horizontal (SH₀) waves for GWT with optimal high temperature properties (up to 500 °C) has been developed. Thermal and Computational Fluid Dynamic (CFD) simulations of the EMAT design have been performed and experimentally validated. The optimal thermal EMAT design, material selection and operating conditions were calculated. The EMAT was successfully tested regarding its thermal and GWT performance from ambient temperature to 500 °C.

  6. High Temperature Shear Horizontal Electromagnetic Acoustic Transducer for Guided Wave Inspection

    PubMed Central

    Kogia, Maria; Gan, Tat-Hean; Balachandran, Wamadeva; Livadas, Makis; Kappatos, Vassilios; Szabo, Istvan; Mohimi, Abbas; Round, Andrew

    2016-01-01

    Guided Wave Testing (GWT) using novel Electromagnetic Acoustic Transducers (EMATs) is proposed for the inspection of large structures operating at high temperatures. To date, high temperature EMATs have been developed only for thickness measurements and they are not suitable for GWT. A pair of water-cooled EMATs capable of exciting and receiving Shear Horizontal (SH0) waves for GWT with optimal high temperature properties (up to 500 °C) has been developed. Thermal and Computational Fluid Dynamic (CFD) simulations of the EMAT design have been performed and experimentally validated. The optimal thermal EMAT design, material selection and operating conditions were calculated. The EMAT was successfully tested regarding its thermal and GWT performance from ambient temperature to 500 °C. PMID:27110792

  7. Absorption of surface acoustic waves by topological insulator thin films

    SciTech Connect

    Li, L. L.; Xu, W.

    2014-08-11

    We present a theoretical study on the absorption of the surface acoustic waves (SAWs) by Dirac electrons in topological insulator (TI) thin films (TITFs). We find that due to momentum and energy conservation laws, the absorption of the SAWs in TITFs can only be achieved via intra-band electronic transitions. The strong absorption can be observed up to sub-terahertz frequencies. With increasing temperature, the absorption intensity increases significantly and the cut-off frequency is blue-shifted. More interestingly, we find that the absorption of the SAWs by the TITFs can be markedly enhanced by the tunable subgap in the Dirac energy spectrum of the TI surface states. Such a subgap is absent in conventional two-dimensional electron gases (2DEGs) and in the gapless Dirac 2DEG such as graphene. This study is pertinent to the exploration of the acoustic properties of TIs and to potential application of TIs as tunable SAW devices working at hypersonic frequencies.

  8. Parallel acoustic wave propagation and generation of a seismic dataset

    SciTech Connect

    Oldfield, R.; Dyke, J.V.; Semeraro, B.D.

    1995-12-01

    The ultimate goal of this work is to construct a large seismic dataset that will be used to calibrate industrial seismic analysis codes. Seismic analysis is used in oil and gas exploration to deduce subterranean geological formations based on the reflection of acoustic waves from a source to an array of receivers placed on or near the surface. This work deals with the generation of a test set of acoustic data based on a known representative geological formation. Industrial users of the data will calibrate their codes by comparing their predicted geology to the know geology used to generate the test data. This is a cooperative effort involving Los Alamos, Sandia, Oak Ridge and Lawrence Livermore national labs as well as Institut Francais du Petrole and the Society of Exploration Geophysicists.

  9. Ion acoustic waves and related plasma observations in the solar wind

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Marsch, E.; Pilipp, W.; Schwenn, R.; Rosenbauer, H.

    1979-01-01

    The paper presents a study of the relationship between the interplanetary ion acoustic waves detected by Helios and the macroscopic and microscopic characteristics of the solar wind plasma. Two major mechanisms, an electron heat flux instability and a double-ion beam instability, are considered for generating the ion-acoustic-like waves observed in the solar wind. The results provide support to both mechanisms for generating the solar wind ion acoustic waves, although each mechanism has problems under certain conditions.

  10. Cylindrical and spherical ion acoustic waves in a plasma with nonthermal electrons and warm ions

    SciTech Connect

    Sahu, Biswajit; Roychoudhury, Rajkumar

    2005-05-15

    Using the reductive perturbation technique, nonlinear cylindrical and spherical Korteweg-de Vries (KdV) and modified KdV equations are derived for ion acoustic waves in an unmagnetized plasma consisting of warm adiabatic ions and nonthermal electrons. The effects of nonthermally distributed electrons on cylindrical and spherical ion acoustic waves are investigated. It is found that the nonthermality has a very significant effect on the nature of ion acoustic waves.

  11. Dynamic index modulation mechanism in polarization-maintained fiber Bragg gratings induced by transverse acoustic waves.

    PubMed

    Miao, Ren; Zhang, Wei; Feng, Xue; Zhao, Jianhui; Liu, Xiaoming

    2009-08-20

    A novel index modulation mechanism of polarization-maintained fiber Bragg gratings based on the microbend of stress members induced by a transverse acoustic wave is proposed and investigated experimentally. The index modulation leads to a series of ghost gratings with specific polarization, whose wavelengths can be tuned by the acoustic wave frequency and whose intensities depend on the vibration direction of the transverse acoustic wave. Our method provides a novel way to achieve polarization-dependent narrowband acousto-optic tunable filters.

  12. Molding acoustic, electromagnetic and water waves with a single cloak.

    PubMed

    Xu, Jun; Jiang, Xu; Fang, Nicholas; Georget, Elodie; Abdeddaim, Redha; Geffrin, Jean-Michel; Farhat, Mohamed; Sabouroux, Pierre; Enoch, Stefan; Guenneau, Sébastien

    2015-06-09

    We describe two experiments demonstrating that a cylindrical cloak formerly introduced for linear surface liquid waves works equally well for sound and electromagnetic waves. This structured cloak behaves like an acoustic cloak with an effective anisotropic density and an electromagnetic cloak with an effective anisotropic permittivity, respectively. Measured forward scattering for pressure and magnetic fields are in good agreement and provide first evidence of broadband cloaking. Microwave experiments and 3D electromagnetic wave simulations further confirm reduced forward and backscattering when a rectangular metallic obstacle is surrounded by the structured cloak for cloaking frequencies between 2.6 and 7.0 GHz. This suggests, as supported by 2D finite element simulations, sound waves are cloaked between 3 and 8 KHz and linear surface liquid waves between 5 and 16 Hz. Moreover, microwave experiments show the field is reduced by 10 to 30 dB inside the invisibility region, which suggests the multi-wave cloak could be used as a protection against water, sonic or microwaves.

  13. Molding acoustic, electromagnetic and water waves with a single cloak

    PubMed Central

    Xu, Jun; Jiang, Xu; Fang, Nicholas; Georget, Elodie; Abdeddaim, Redha; Geffrin, Jean-Michel; Farhat, Mohamed; Sabouroux, Pierre; Enoch, Stefan; Guenneau, Sébastien

    2015-01-01

    We describe two experiments demonstrating that a cylindrical cloak formerly introduced for linear surface liquid waves works equally well for sound and electromagnetic waves. This structured cloak behaves like an acoustic cloak with an effective anisotropic density and an electromagnetic cloak with an effective anisotropic permittivity, respectively. Measured forward scattering for pressure and magnetic fields are in good agreement and provide first evidence of broadband cloaking. Microwave experiments and 3D electromagnetic wave simulations further confirm reduced forward and backscattering when a rectangular metallic obstacle is surrounded by the structured cloak for cloaking frequencies between 2.6 and 7.0 GHz. This suggests, as supported by 2D finite element simulations, sound waves are cloaked between 3 and 8 KHz and linear surface liquid waves between 5 and 16 Hz. Moreover, microwave experiments show the field is reduced by 10 to 30 dB inside the invisibility region, which suggests the multi-wave cloak could be used as a protection against water, sonic or microwaves. PMID:26057934

  14. Novel limiting circle theory in acoustic wave scattering and absorption

    NASA Astrophysics Data System (ADS)

    Huang, Changzheng

    Wave scattering theory is the basis for many key technologies that have important military and commercial applications. The familiar examples are radar, sonar, and various ultrasound instruments commonly used in remote sensing, target identification, non-destructive evaluation, medical diagnosis, and many other areas. Their mathematical model involves the solution of the so- called inverse scattering problem where an incident wave is used to probe a remote or inaccessible object. From the scattered field measurement, the shape and/or the material composition of the object can be determined. A new wave scattering theory, termed limiting circle theory (LCT), has been developed in this dissertation based on a novel approach of decomposing the wave scattering matrix. LCT has rigorously proved that the scattered wave field from any penetrable object (of cylinder and sphere geometries) is composed of three contributions: a rigid background, a soft background, and a pure resonance. This is a significant modification to the existing resonance scattering theory (RST) which states that the scattered field is made up of only two components: a proper background (either rigid or soft), and a pure resonance. LCT formalism led to the discovery of the limiting circle patterns associated with all normal modes or partial waves. These patterns provide a clear understanding of the resonance behavior such as the resonance period and the resonance intensity. The analytical LCT approach could also be the key to solving the background problems for shell structures that have remained unsolved for many years in acoustics.

  15. System and method for sonic wave measurements using an acoustic beam source

    SciTech Connect

    Vu, Cung Khac; Sinha, Dipen N.; Pantea, Cristian

    2015-08-11

    A method and system for investigating structure near a borehole are described herein. The method includes generating an acoustic beam by an acoustic source; directing at one or more azimuthal angles the acoustic beam towards a selected location in a vicinity of a borehole; receiving at one or more receivers an acoustic signal, the acoustic signal originating from a reflection or a refraction of the acoustic wave by a material at the selected location; and analyzing the received acoustic signal to characterize features of the material around the borehole.

  16. Cell separation using tilted-angle standing surface acoustic waves.

    PubMed

    Ding, Xiaoyun; Peng, Zhangli; Lin, Sz-Chin Steven; Geri, Michela; Li, Sixing; Li, Peng; Chen, Yuchao; Dao, Ming; Suresh, Subra; Huang, Tony Jun

    2014-09-01

    Separation of cells is a critical process for studying cell properties, disease diagnostics, and therapeutics. Cell sorting by acoustic waves offers a means to separate cells on the basis of their size and physical properties in a label-free, contactless, and biocompatible manner. The separation sensitivity and efficiency of currently available acoustic-based approaches, however, are limited, thereby restricting their widespread application in research and health diagnostics. In this work, we introduce a unique configuration of tilted-angle standing surface acoustic waves (taSSAW), which are oriented at an optimally designed inclination to the flow direction in the microfluidic channel. We demonstrate that this design significantly improves the efficiency and sensitivity of acoustic separation techniques. To optimize our device design, we carried out systematic simulations of cell trajectories, matching closely with experimental results. Using numerically optimized design of taSSAW, we successfully separated 2- and 10-µm-diameter polystyrene beads with a separation efficiency of ∼ 99%, and separated 7.3- and 9.9-µm-polystyrene beads with an efficiency of ∼ 97%. We illustrate that taSSAW is capable of effectively separating particles-cells of approximately the same size and density but different compressibility. Finally, we demonstrate the effectiveness of the present technique for biological-biomedical applications by sorting MCF-7 human breast cancer cells from nonmalignant leukocytes, while preserving the integrity of the separated cells. The method introduced here thus offers a unique route for separating circulating tumor cells, and for label-free cell separation with potential applications in biological research, disease diagnostics, and clinical practice.

  17. Cell separation using tilted-angle standing surface acoustic waves

    PubMed Central

    Ding, Xiaoyun; Peng, Zhangli; Lin, Sz-Chin Steven; Geri, Michela; Li, Sixing; Li, Peng; Chen, Yuchao; Dao, Ming; Suresh, Subra; Huang, Tony Jun

    2014-01-01

    Separation of cells is a critical process for studying cell properties, disease diagnostics, and therapeutics. Cell sorting by acoustic waves offers a means to separate cells on the basis of their size and physical properties in a label-free, contactless, and biocompatible manner. The separation sensitivity and efficiency of currently available acoustic-based approaches, however, are limited, thereby restricting their widespread application in research and health diagnostics. In this work, we introduce a unique configuration of tilted-angle standing surface acoustic waves (taSSAW), which are oriented at an optimally designed inclination to the flow direction in the microfluidic channel. We demonstrate that this design significantly improves the efficiency and sensitivity of acoustic separation techniques. To optimize our device design, we carried out systematic simulations of cell trajectories, matching closely with experimental results. Using numerically optimized design of taSSAW, we successfully separated 2- and 10-µm-diameter polystyrene beads with a separation efficiency of ∼99%, and separated 7.3- and 9.9-µm-polystyrene beads with an efficiency of ∼97%. We illustrate that taSSAW is capable of effectively separating particles–cells of approximately the same size and density but different compressibility. Finally, we demonstrate the effectiveness of the present technique for biological–biomedical applications by sorting MCF-7 human breast cancer cells from nonmalignant leukocytes, while preserving the integrity of the separated cells. The method introduced here thus offers a unique route for separating circulating tumor cells, and for label-free cell separation with potential applications in biological research, disease diagnostics, and clinical practice. PMID:25157150

  18. Cell separation using tilted-angle standing surface acoustic waves.

    PubMed

    Ding, Xiaoyun; Peng, Zhangli; Lin, Sz-Chin Steven; Geri, Michela; Li, Sixing; Li, Peng; Chen, Yuchao; Dao, Ming; Suresh, Subra; Huang, Tony Jun

    2014-09-01

    Separation of cells is a critical process for studying cell properties, disease diagnostics, and therapeutics. Cell sorting by acoustic waves offers a means to separate cells on the basis of their size and physical properties in a label-free, contactless, and biocompatible manner. The separation sensitivity and efficiency of currently available acoustic-based approaches, however, are limited, thereby restricting their widespread application in research and health diagnostics. In this work, we introduce a unique configuration of tilted-angle standing surface acoustic waves (taSSAW), which are oriented at an optimally designed inclination to the flow direction in the microfluidic channel. We demonstrate that this design significantly improves the efficiency and sensitivity of acoustic separation techniques. To optimize our device design, we carried out systematic simulations of cell trajectories, matching closely with experimental results. Using numerically optimized design of taSSAW, we successfully separated 2- and 10-µm-diameter polystyrene beads with a separation efficiency of ∼ 99%, and separated 7.3- and 9.9-µm-polystyrene beads with an efficiency of ∼ 97%. We illustrate that taSSAW is capable of effectively separating particles-cells of approximately the same size and density but different compressibility. Finally, we demonstrate the effectiveness of the present technique for biological-biomedical applications by sorting MCF-7 human breast cancer cells from nonmalignant leukocytes, while preserving the integrity of the separated cells. The method introduced here thus offers a unique route for separating circulating tumor cells, and for label-free cell separation with potential applications in biological research, disease diagnostics, and clinical practice. PMID:25157150

  19. Excitation of Standing Waves by an Electric Toothbrush

    NASA Astrophysics Data System (ADS)

    Cros, Ana; Ferrer-Roca, Chantal

    2006-12-01

    There are a number of ways of exciting standing waves in ropes and springs using non-commercial vibrators such as loudspeakers, jigsaws,2 motors,3 or a simple tuning fork,4 including the rhythmical shaking of a handheld Slinky. We have come up with a very simple and cheap way of exciting stationary waves in a string, which anyone, particularly children, can try at home. It consists of using an electric toothbrush to produce a regular sideways motion that can be easily transmitted to an elastic cord. Most suitable for this experiment is the kind of unit that has a metal rod protruding from the front (see Fig. 1, which shows our Braun Oral-B®) to which a brush is normally affixed. The ends of the cord are attached to stands. Elastic cords that come with some school notebooks work well for this experiment, but a longer cord allows the observation of a larger number of modes. The toothbrush unit is placed near one end of the cord, which is wrapped once around the rod. As the toothbrush vibrates at a fixed frequency, standing waves (see Fig. 2) may be tuned by changing the tension of the cord while keeping its length constant. We have found up to five harmonics with a 150-cm cord. The toothbrush can be connected to a small potentiometer to reduce the dc voltage and hence the frequency of the motor, allowing the tuning of the standing waves with a fixed tension.

  20. Defects formation and wave emitting from defects in excitable media

    NASA Astrophysics Data System (ADS)

    Ma, Jun; Xu, Ying; Tang, Jun; Wang, Chunni

    2016-05-01

    Abnormal electrical activities in neuronal system could be associated with some neuronal diseases. Indeed, external forcing can cause breakdown even collapse in nervous system under appropriate condition. The excitable media sometimes could be described by neuronal network with different topologies. The collective behaviors of neurons can show complex spatiotemporal dynamical properties and spatial distribution for electrical activities due to self-organization even from the regulating from central nervous system. Defects in the nervous system can emit continuous waves or pulses, and pacemaker-like source is generated to perturb the normal signal propagation in nervous system. How these defects are developed? In this paper, a network of neurons is designed in two-dimensional square array with nearest-neighbor connection type; the formation mechanism of defects is investigated by detecting the wave propagation induced by external forcing. It is found that defects could be induced under external periodical forcing under the boundary, and then the wave emitted from the defects can keep balance with the waves excited from external forcing.