Science.gov

Sample records for acoustic radiation pressure

  1. Manipulating Liquids With Acoustic Radiation Pressure Phased Arrays

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C.

    1999-01-01

    High-intensity ultrasound waves can produce the effects of "Acoustic Radiation Pressure" (ARP) and "acoustic streaming." These effects can be used to propel liquid flows and to apply forces that can be used to move or manipulate floating objects or liquid surfaces. NASA's interest in ARP includes the remote-control agitation of liquids and the manipulation of bubbles and drops in liquid experiments and propellant systems. A high level of flexibility is attained by using a high-power acoustic phased array to generate, steer, and focus a beam of acoustic waves. This is called an Acoustic Radiation Pressure Phased Array, or ARPPA. In this approach, many acoustic transducer elements emit wavelets that converge into a single beam of sound waves. Electronically coordinating the timing, or "phase shift," of the acoustic waves makes it possible to form a beam with a predefined direction and focus. Therefore, a user can direct the ARP force at almost any desired point within a liquid volume. ARPPA lets experimenters manipulate objects anywhere in a test volume. This flexibility allow it to be used for multiple purposes, such as to agitate liquids, deploy and manipulate drops or bubbles, and even suppress sloshing in spacecraft propellant tanks.

  2. Modulated acoustic radiation pressure and stress-coupling projections

    NASA Astrophysics Data System (ADS)

    Marston, Philip L.; Thiessen, David B.

    2005-09-01

    Low-frequency deformation can be induced at a single frequency using radiation stress oscillations of double-sideband suppressed-carrier ultrasound [P. L. Marston and R. E. Apfel, J. Acoust. Soc. Am. 67, 27 (1980)]. The transducer voltage is proportional to a product of low- and high-frequency sine waves. To anticipate the shape and magnitude of induced deformations, it is helpful to expand the distribution of the radiation stress on the object to be deformed as a series of projections [P. L. Marston, J. Acoust. Soc. Am. 67, 15 (1980)]. Stress projections are also useful for unmodulated waves: the radiation force is an example. In addition to spherical and nearly spherical objects, recent experiments and calculations have concerned cylindrical objects [S. F. Morse, D. B. Thiessen, and P. L. Marston, Phys. Fluids 8, 3 (1996); W. Wei, D. B. Thiessen, and P. L. Marston, J. Acoust. Soc. Am. 116, 202 (2004)]. In standing waves the following projections are nonvanishing in the low acoustic frequency limit for appropriately situated dense objects: radial projection [M. J. Marr-Lyon, D. B. Thiessen, and P. L. Marston, Phys. Rev. Lett. 86, 2293 (2001)] and quadrupole projection [P. L. Marston et al., J. Acoust. Soc. Am. 69, 1499 (1981)].

  3. Effect of static pressure on acoustic energy radiated by cavitation bubbles in viscous liquids under ultrasound.

    PubMed

    Yasui, Kyuichi; Towata, Atsuya; Tuziuti, Toru; Kozuka, Teruyuki; Kato, Kazumi

    2011-11-01

    The effect of static pressure on acoustic emissions including shock-wave emissions from cavitation bubbles in viscous liquids under ultrasound has been studied by numerical simulations in order to investigate the effect of static pressure on dispersion of nano-particles in liquids by ultrasound. The results of the numerical simulations for bubbles of 5 μm in equilibrium radius at 20 kHz have indicated that the optimal static pressure which maximizes the energy of acoustic waves radiated by a bubble per acoustic cycle increases as the acoustic pressure amplitude increases or the viscosity of the solution decreases. It qualitatively agrees with the experimental results by Sauter et al. [Ultrason. Sonochem. 15, 517 (2008)]. In liquids with relatively high viscosity (∼200 mPa s), a bubble collapses more violently than in pure water when the acoustic pressure amplitude is relatively large (∼20 bar). In a mixture of bubbles of different equilibrium radius (3 and 5 μm), the acoustic energy radiated by a 5 μm bubble is much larger than that by a 3 μm bubble due to the interaction with bubbles of different equilibrium radius. The acoustic energy radiated by a 5 μm bubble is substantially increased by the interaction with 3 μm bubbles.

  4. Deformation of drop due to radiation pressure of acoustic standing wave

    NASA Astrophysics Data System (ADS)

    Yamanaka, T.; Saito, M.; Kamimura, H.

    To investigate the deformation of a liquid drop due to radiation pressure of acoustic standing waves, an analytical and experimental study was carried out. An approximate axisymmetric figure of equilibrium is obtained. The experimental study was carried out in the laboratory by using a triaxial acoustic chamber. An injection syringe was placed at the center of the triaxial acoustic resonance chamber. Holding a small liquid drop at the pointed end of the syringe, deformations of the liquid drop were measured. Assuming an oblate spheroid for the deformation, the experimental results were compared with theory.

  5. Manipulation of Liquids Using Phased Array Generation of Acoustic Radiation Pressure

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C. (Inventor)

    2000-01-01

    A phased array of piezoelectric transducers is used to control and manipulate contained as well as uncontained fluids in space and earth applications. The transducers in the phased array are individually activated while being commonly controlled to produce acoustic radiation pressure and acoustic streaming. The phased array is activated to produce a single pulse, a pulse burst or a continuous pulse to agitate, segregate or manipulate liquids and gases. The phased array generated acoustic radiation pressure is also useful in manipulating a drop, a bubble or other object immersed in a liquid. The transducers can be arranged in any number of layouts including linear single or multi- dimensional, space curved and annular arrays. The individual transducers in the array are activated by a controller, preferably driven by a computer.

  6. Three-dimensional visualization of shear wave propagation generated by dual acoustic radiation pressure

    NASA Astrophysics Data System (ADS)

    Mochizuki, Yuta; Taki, Hirofumi; Kanai, Hiroshi

    2016-07-01

    An elastic property of biological soft tissue is an important indicator of the tissue status. Therefore, quantitative and noninvasive methods for elasticity evaluation have been proposed. Our group previously proposed a method using acoustic radiation pressure irradiated from two directions for elastic property evaluation, in which by measuring the propagation velocity of the shear wave generated by the acoustic radiation pressure inside the object, the elastic properties of the object were successfully evaluated. In the present study, we visualized the propagation of the shear wave in a three-dimensional space by the synchronization of signals received at various probe positions. The proposed method succeeded in visualizing the shear wave propagation clearly in the three-dimensional space of 35 × 41 × 4 mm3. These results show the high potential of the proposed method to estimate the elastic properties of the object in the three-dimensional space.

  7. Stabilization and Low-Frequency Oscillation of Capillary Bridges with Modulated Acoustic Radiation Pressure

    NASA Technical Reports Server (NTRS)

    Marston, Philip L.; Marr-Lyon, Mark J.; Morse, S. F.; Thiessen, David B.

    1996-01-01

    In the work reported here it is demonstrated that acoustic radiation pressure may be used in simulated low gravity to produce stable bridges significantly beyond the Rayleigh limit with S as large as 3.6. The bridge (PDMS mixed with a dense liquid) has the same density as the surrounding water bath containing an ultrasonic standing wave. Modulation was first used to excite specific bridge modes. In the most recent work reported here the shape of the bridge is optically sensed and the ultrasonic drive is electronically adjusted such that the radiation stress distribution dynamically quenches the most unstable mode. This active control simulates passive stabilization suggested for low gravity. Feedback increases the mode frequency in the naturally stable region since the effective stiffness of the mode is increased.

  8. Shape oscillations of acoustically levitated drops in water: Early research with Bob Apfel on modulated radiation pressure

    NASA Astrophysics Data System (ADS)

    Marston, Philip L.

    2001-05-01

    In 1976, research in collaboration with Bob Apfel demonstrated that low-frequency shape oscillations of hydrocarbon drops levitated in water could be driven using modulated radiation pressure. While that response to modulated ultrasound was subsequently extended to a range of systems, the emphasis here is to recall the initial stages of development in Bob Apfel's laboratory leading to some publications [P. L. Marston and R. E. Apfel, J. Colloid Interface Sci. 68, 280-286 (1979); J. Acoust. Soc. Am. 67, 27-37 (1980)]. The levitation technology used at that time was such that it was helpful to develop a sensitive method for detecting weak oscillations using the interference pattern in laser light scattered by levitated drops. The initial experiments to verify this scattering method used shape oscillations induced by modulated electric fields within the acoustic levitator. Light scattering was subsequently used to detect shape oscillations induced by amplitude modulating a carrier having a high frequency (around 680 kHz) at a resonance of the transducer. Methods were also developed for quantitative measurements of the drop's response and with improved acoustic coupling drop fission was observed. The connection with research currently supported by NASA will also be noted.

  9. Coupling between plate vibration and acoustic radiation

    NASA Technical Reports Server (NTRS)

    Frendi, Abdelkader; Maestrello, Lucio; Bayliss, Alvin

    1992-01-01

    A detailed numerical investigation of the coupling between the vibration of a flexible plate and the acoustic radiation is performed. The nonlinear Euler equations are used to describe the acoustic fluid while the nonlinear plate equation is used to describe the plate vibration. Linear, nonlinear, and quasi-periodic or chaotic vibrations and the resultant acoustic radiation are analyzed. We find that for the linear plate response, acoustic coupling is negligible. However, for the nonlinear and chaotic responses, acoustic coupling has a significant effect on the vibration level as the loading increases. The radiated pressure from a plate undergoing nonlinear or chaotic vibrations is found to propagate nonlinearly into the far-field. However, the nonlinearity due to wave propagation is much weaker than that due to the plate vibrations. As the acoustic wave propagates into the far-field, the relative difference in level between the fundamental and its harmonics and subharmonics decreases with distance.

  10. Acoustic radiation and surface pressure characteristics of an airfoil due to incident turbulence

    NASA Technical Reports Server (NTRS)

    Paterson, R. W.

    1976-01-01

    A theoretical and experimental investigation of the noise and unsteady surface pressure characteristics of an isolated airfoil in a uniform mean velocity, homogeneous, nearly-isotropic turbulence field was conducted. Wind tunnel experiments were performed with a 23 cm chord, two dimensional NACA 0012 airfoil over a free stream Mach number range of 0.1 to 0.5. Far-field noise spectra and directivity were measured in an anechoic chamber that surrounded the tunnel open jet test section. Spanwise and chordwise distribution of unsteady airfoil surface pressure spectra and surface pressure cross-spectra were obtained. Incident turbulence intensities, length scales, spectra, and spanwise cross-spectra, required in the calculation of far-field noise and surface pressure characteristics were also measured.

  11. Correlation of signals of thermal acoustic radiation

    NASA Astrophysics Data System (ADS)

    Anosov, A. A.; Passechnik, V. I.

    2003-03-01

    The spatial correlation function is measured for the pressure of thermal acoustic radiation from a source (a narrow plasticine plate) whose temperature is made both higher and lower than the temperature of the receiver. The spatial correlation function of the pressure of thermal acoustic radiation is found to be oscillatory in character. The oscillation amplitude is determined not by the absolute temperature of the source but by the temperature difference between the source and the receiver. The correlation function changes its sign when a source heated with respect to the receiver is replaced by a cooled one.

  12. Pressure distribution based optimization of phase-coded acoustical vortices

    SciTech Connect

    Zheng, Haixiang; Gao, Lu; Dai, Yafei; Ma, Qingyu; Zhang, Dong

    2014-02-28

    Based on the acoustic radiation of point source, the physical mechanism of phase-coded acoustical vortices is investigated with formulae derivations of acoustic pressure and vibration velocity. Various factors that affect the optimization of acoustical vortices are analyzed. Numerical simulations of the axial, radial, and circular pressure distributions are performed with different source numbers, frequencies, and axial distances. The results prove that the acoustic pressure of acoustical vortices is linearly proportional to the source number, and lower fluctuations of circular pressure distributions can be produced for more sources. With the increase of source frequency, the acoustic pressure of acoustical vortices increases accordingly with decreased vortex radius. Meanwhile, increased vortex radius with reduced acoustic pressure is also achieved for longer axial distance. With the 6-source experimental system, circular and radial pressure distributions at various frequencies and axial distances have been measured, which have good agreements with the results of numerical simulations. The favorable results of acoustic pressure distributions provide theoretical basis for further studies of acoustical vortices.

  13. Methods for reconstructing acoustic quantities based on acoustic pressure measurements.

    PubMed

    Wu, Sean F

    2008-11-01

    This paper presents an overview of the acoustic imaging methods developed over the past three decades that enable one to reconstruct all acoustic quantities based on the acoustic pressure measurements taken around a target source at close distances. One such method that has received the most attention is known as near-field acoustical holography (NAH). The original NAH relies on Fourier transforms that are suitable for a surface containing a level of constant coordinate in a source-free region. Other methods are developed to reconstruct the acoustic quantities in three-dimensional space and on an arbitrary three-dimensional source surface. Note that there is a fine difference between Fourier transform based NAH and other methods that is largely overlooked. The former can offer a wave number spectrum, thus enabling visualization of various structural waves of different wavelengths that travel on the surface of a structure; the latter cannot provide such information, which is critical to acquire an in-depth understanding of the interrelationships between structural vibrations and sound radiation. All these methods are discussed in this paper, their advantages and limitations are compared, and the need for further development to analyze the root causes of noise and vibration problems is discussed.

  14. Turbofan Acoustic Propagation and Radiation

    NASA Technical Reports Server (NTRS)

    Eversman, Walter

    2000-01-01

    This document describes progress in the development of finite element codes for the prediction of near and far field acoustic radiation from the inlet and aft fan ducts of turbofan engines. The report consists of nine papers which have appeared in archival journals and conference proceedings, or are presently in review for publication. Topics included are: 1. Aft Fan Duct Acoustic Radiation; 2. Mapped Infinite Wave Envelope Elements for Acoustic Radiation in a Uniformly Moving Medium; 3. A Reflection Free Boundary Condition for Propagation in Uniform Flow Using Mapped Infinite Wave Envelope Elements; 4. A Numerical Comparison Between Multiple-Scales and FEM Solution for Sound Propagation in Lined Flow Ducts; 5. Acoustic Propagation at High Frequencies in Ducts; 6. The Boundary Condition at an Impedance Wall in a Nonuniform Duct with Potential Flow; 7. A Reverse Flow Theorem and Acoustic Reciprocity in Compressible Potential Flows; 8. Reciprocity and Acoustics Power in One Dimensional Compressible Potential Flows; and 9. Numerical Experiments on Acoustic Reciprocity in Compressible Potential Flows.

  15. Acoustic radiation from single and double ribbed circular cylindrical shells

    NASA Astrophysics Data System (ADS)

    Burroughs, C. B.; Hayek, S. I.; Hallander, J. E.; Bostian, D. A.

    1984-03-01

    Measurements of the acoustic radiation from single and double ribbed circular cylindrical shells were made on the NUSC Transducer Calibration Platform (TCP) in Lake Seneca, NY. Six different types of mechanical drives were used at each of three locations inside the inner shell. Measurements of the shell vibration and acoustic radiation were made with and without outer shells installed around the inner shell structure. For two types of drives, measurements were made with a pressure release layer installed between the inner and outer shell surfaces. Acoustic radiation measurements were made as a function of frequency from 20 to 5,000 Hz and as a function of observation direction at several frequencies for each shell and drive measurement configuration. Measured acoustic radiation data as a function of frequency have been processed. Analysis of the processed data is presented and discussed. It is shown that the location of the drive had a significant effect on the acoustic radiation. The outer shell reduced the acoustic radiation at shell resonant frequencies, but had little effect on other frequencies. The pressure release layer in the double shell had little effect on the acoustic radiation.

  16. Acoustic pressure-vector sensor array

    NASA Astrophysics Data System (ADS)

    Huang, Dehua; Elswick, Roy C.; McEachern, James F.

    2001-05-01

    Pressure-vector sensors measure both scalar and vector components of the acoustic field. December 2003 measurements at the NUWC Seneca Lake test facility verify previous observations that acoustic ambient noise spectrum levels measured by acoustic intensity sensors are reduced relative to either acoustic pressure or acoustic vector sensor spectrum levels. The Seneca measurements indicate a reduction by as much as 15 dB at the upper measurement frequency of 2500 Hz. A nonlinear array synthesis theory for pressure-vector sensors will be introduced that allows smaller apertures to achieve narrow beams. The significantly reduced ambient noise of individual pressure-vector elements observed in the ocean by others, and now at Seneca Lake, should allow a nonlinearly combined array to detect significantly lower levels than has been observed in previous multiplicative processing of pressure sensors alone. Nonlinear array synthesis of pressure-vector sensors differs from conventional super-directive algorithms that linearly combine pressure elements with positive and negative weights, thereby reducing the sensitivity of conventional super-directive arrays. The much smaller aperture of acoustic pressure-vector sensor arrays will be attractive for acoustic systems on underwater vehicles, as well as for other applications that require narrow beam acoustic receivers. [The authors gratefully acknowledge the support of ONR and NUWC.

  17. Acoustic radiation from weakly wrinkled premixed flames

    SciTech Connect

    Lieuwen, Tim; Mohan, Sripathi; Rajaram, Rajesh; Preetham,

    2006-01-01

    This paper describes a theoretical analysis of acoustic radiation from weakly wrinkled (i.e., u'/S{sub L}<1) premixed flames. Specifically, it determines the transfer function relating the spectrum of the acoustic pressure oscillations, P'({omega}), to that of the turbulent velocity fluctuations in the approach flow, U'({omega}). In the weakly wrinkled limit, this transfer function is local in frequency space; i.e., velocity fluctuations at a frequency {omega} distort the flame and generate sound at the same frequency. This transfer function primarily depends upon the flame Strouhal number St (based on mean flow velocity and flame length) and the correlation length, {lambda}, of the flow fluctuations. For cases where the ratio of the correlation length and duct radius {lambda}/a>>1, the acoustic pressure and turbulent velocity power spectra are related by P'({omega})-{omega}{sup 2}U'({omega}) and P'({omega})-U'({omega}) for St<<1 and St>>1, respectively. For cases where {lambda}/a<<1, the transfer functions take the form P'({omega})-{omega}{sup 2}({lambda}/a){sup 2}U'({omega}) and P'({omega})-{omega}{sup 2}({lambda}/a){sup 2}({psi}-{delta}ln({lambda}/a))U'({omega}) for St<<1 and St>>1, respectively, where (PS) and {delta} are constants. The latter result demonstrates that this transfer function does not exhibit a simple power law relationship in the high frequency region of the spectra. The simultaneous dependence of this pressure-velocity transfer function upon the Strouhal number and correlation length suggests a mechanism for the experimentally observed maximum in acoustic spectra and provides some insight into the controversy in the literature over how this peak should scale with the flame Strouhal number.

  18. 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.

  19. Acoustic radiation from lined, unflanged ducts: Acoustic source distribution program

    NASA Technical Reports Server (NTRS)

    Beckemeyer, R. J.; Sawdy, D. T.

    1971-01-01

    An acoustic radiation analysis was developed to predict the far-field characteristics of fan noise radiated from an acoustically lined unflanged duct. This analysis is comprised of three modular digital computer programs which together provide a capability of accounting for the impedance mismatch at the duct exit plane. Admissible duct configurations include circular or annular, with or without an extended centerbody. This variation in duct configurations provides a capability of modeling inlet and fan duct noise radiation. The computer programs are described in detail.

  20. Acoustics and Surface Pressure Measurements from Tandem Cylinder Configurations

    NASA Technical Reports Server (NTRS)

    Hutcheson, Florence V.; Brooks, Thomas F.; Lockard, David P.; Choudhari, Meelan M.; Stead, Daniel J.

    2014-01-01

    Acoustic and unsteady surface pressure measurements from two cylinders in tandem configurations were acquired to study the effect of spacing, surface trip and freestream velocity on the radiated noise. The Reynolds number ranged from 1.15x10(exp 5) to 2.17x10(exp 5), and the cylinder spacing varied between 1.435 and 3.7 cylinder diameters. The acoustic and surface pressure spectral characteristics associated with the different flow regimes produced by the cylinders' wake interference were identified. The dependence of the Strouhal number, peak Sound Pressure Level and spanwise coherence on cylinder spacing and flow velocity was examined. Directivity measurements were performed to determine how well the dipole assumption for the radiation of vortex shedding noise holds for the largest and smallest cylinder spacing tested.

  1. Spinning mode acoustic radiation from the flight inlet

    NASA Technical Reports Server (NTRS)

    Moss, W. F.

    1983-01-01

    A mathematical model was developed for spinning mode acoustic radiation from a thick wall duct without flow. This model is based on a series of experiments (with and without flow). A nearly pure azimuthal spinning mode was isolated and then reflection coefficients and far field pressure (amplitude and phase) were measured. In our model the governing boundary value problem for the Helmholtz equation is first converted into an integral equation for the unknown acoustic pressure over a disk, S1, near the mouth of the duct and over the exterior surface, S2, of the duct. Assuming a pure azimuthal mode excitation, the azimuthal dependence is integrated out which yields an integral equation over the generator C1 of S1 and the generator C2 of S2. The sound pressure on C1 was approximated by a truncated modal expansion of the interior acoustic pressure. Piecewise linear spline approximation on C2 was used.

  2. A Spectral Analysis Approach for Acoustic Radiation from Composite Panels

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Singh, Mahendra P.; Mei, Chuh

    2004-01-01

    A method is developed to predict the vibration response of a composite panel and the resulting far-field acoustic radiation due to acoustic excitation. The acoustic excitation is assumed to consist of obliquely incident plane waves. The panel is modeled by a finite element analysis and the radiated field is predicted using Rayleigh's integral. The approach can easily include other effects such as shape memory alloy (SMA) ber reinforcement, large detection thermal postbuckling, and non-symmetric SMA distribution or lamination. Transmission loss predictions for the case of an aluminum panel excited by a harmonic acoustic pressure are shown to compare very well with a classical analysis. Results for a composite panel with and without shape memory alloy reinforcement are also presented. The preliminary results demonstrate that the transmission loss can be significantly increased with shape memory alloy reinforcement. The mechanisms for further transmission loss improvement are identified and discussed.

  3. Correlation reception of thermal acoustic radiation

    NASA Astrophysics Data System (ADS)

    Anosov, A. A.; Barabanenkov, Yu. N.; Sel'Skii, A. G.

    2003-11-01

    Correlated signals of thermal acoustic radiation from heated sources extending in the transverse direction (a pair of narrow plasticine plates and a wide plasticine strip) are measured. The measurements are performed by multiplying together the signals that are shifted in time with respect to each other and detected by two piezoelectric transducers. The values of the correlated signals of thermal acoustic radiation are determined by the spatial variation of temperature in the medium under study.

  4. Nonlinear Bubble Interactions in Acoustic Pressure Fields

    NASA Technical Reports Server (NTRS)

    Barbat, Tiberiu; Ashgriz, Nasser; Liu, Ching-Shi

    1996-01-01

    The systems consisting of a two-phase mixture, as clouds of bubbles or drops, have shown many common features in their responses to different external force fields. One of particular interest is the effect of an unsteady pressure field applied to these systems, case in which the coupling of the vibrations induced in two neighboring components (two drops or two bubbles) may result in an interaction force between them. This behavior was explained by Bjerknes by postulating that every body that is moving in an accelerating fluid is subjected to a 'kinetic buoyancy' equal with the product of the acceleration of the fluid multiplied by the mass of the fluid displaced by the body. The external sound wave applied to a system of drops/bubbles triggers secondary sound waves from each component of the system. These secondary pressure fields integrated over the surface of the neighboring drop/bubble may result in a force additional to the effect of the primary sound wave on each component of the system. In certain conditions, the magnitude of these secondary forces may result in significant changes in the dynamics of each component, thus in the behavior of the entire system. In a system containing bubbles, the sound wave radiated by one bubble at the location of a neighboring one is dominated by the volume oscillation mode and its effects can be important for a large range of frequencies. The interaction forces in a system consisting of drops are much smaller than those consisting of bubbles. Therefore, as a first step towards the understanding of the drop-drop interaction subject to external pressure fluctuations, it is more convenient to study the bubble interactions. This paper presents experimental results and theoretical predictions concerning the interaction and the motion of two levitated air bubbles in water in the presence of an acoustic field at high frequencies (22-23 KHz).

  5. A general low frequency acoustic radiation capability for NASTRAN

    NASA Technical Reports Server (NTRS)

    Everstine, G. C.; Henderson, F. M.; Schroeder, E. A.; Lipman, R. R.

    1986-01-01

    A new capability called NASHUA is described for calculating the radiated acoustic sound pressure field exterior to a harmonically-excited arbitrary submerged 3-D elastic structure. The surface fluid pressures and velocities are first calculated by coupling a NASTRAN finite element model of the structure with a discretized form of the Helmholtz surface integral equation for the exterior fluid. After the fluid impedance is calculated, most of the required matrix operations are performed using the general matrix manipulation package (DMAP) available in NASTRAN. Far field radiated pressures are then calculated from the surface solution using the Helmholtz exterior integral equation. Other output quantities include the maximum sound pressure levels in each of the three coordinate planes, the rms and average surface pressures and normal velocities, the total radiated power and the radiation efficiency. The overall approach is illustrated and validated using known analytic solutions for submerged spherical shells subjected to both uniform and nonuniform applied loads.

  6. Ducted fan acoustic radiation including the effects of nonuniform mean flow and acoustic treatment

    NASA Technical Reports Server (NTRS)

    Eversman, Walter; Roy, Indranil Danda

    1993-01-01

    Forward and aft acoustic propagation and radiation from a ducted fan is modeled using a finite element discretization of the acoustic field equations. The fan noise source is introduced as equivalent body forces representing distributed blade loading. The flow in and around the nacelle is assumed to be nonuniform, reflecting the effects of forward flight and flow into the inlet. Refraction due to the fan exit jet shear layer is not represented. Acoustic treatment on the inlet and exhaust duct surfaces provides a mechanism for attenuation. In a region enclosing the fan a pressure formulation is used with the assumption of locally uniform flow. Away from the fan a velocity potential formulation is used and the flow is assumed nonuniform but irrotational. A procedure is developed for matching the two regions by making use of local duct modal amplitudes as transition state variables and determining the amplitudes by enforcing natural boundary conditions at the interface between adjacent regions in which pressure and velocity potential are used. Simple models of rotor alone and rotor/exit guide vane generated noise are used to demonstrate the calculation of the radiated acoustic field and to show the effect of acoustic treatment. The model has been used to assess the success of four techniques for acoustic lining optimization in reducing far field noise.

  7. Acoustic oscillatory pressure control for ramjet

    SciTech Connect

    Brown, R.S.; Dunlap, R.

    1988-08-02

    A method for controlling the acoustic oscillatory pressures generated by gas flow at the combustor inlet to a ramjet engine, the inlet including a sudden geometry expansion is described characterized by; restricting the inlet at the sudden expansion geometry such that the gas flow separates upstream and has a vena contracta downstream of the restricted inlet.

  8. Model helicopter rotor high-speed impulsive noise: Measured acoustics and blade pressures

    NASA Technical Reports Server (NTRS)

    Boxwell, D. A.; Schmitz, F. H.; Splettstoesser, W. R.; Schultz, K. J.

    1983-01-01

    A 1/17-scale research model of the AH-1 series helicopter main rotor was tested. Model-rotor acoustic and simultaneous blade pressure data were recorded at high speeds where full-scale helicopter high-speed impulsive noise levels are known to be dominant. Model-rotor measurements of the peak acoustic pressure levels, waveform shapes, and directively patterns are directly compared with full-scale investigations, using an equivalent in-flight technique. Model acoustic data are shown to scale remarkably well in shape and in amplitude with full-scale results. Model rotor-blade pressures are presented for rotor operating conditions both with and without shock-like discontinuities in the radiated acoustic waveform. Acoustically, both model and full-scale measurements support current evidence that above certain high subsonic advancing-tip Mach numbers, local shock waves that exist on the rotor blades ""delocalize'' and radiate to the acoustic far-field.

  9. Nucleation pressure threshold in acoustic droplet vaporization

    NASA Astrophysics Data System (ADS)

    Miles, Christopher J.; Doering, Charles R.; Kripfgans, Oliver D.

    2016-07-01

    We combine classical nucleation theory with superharmonic focusing to predict necessary pressures to induce nucleation in acoustic droplet vaporization. We show that linear acoustics is a valid approximation to leading order when particle displacements in the sound field are small relative to the radius of the droplet. This is done by perturbation analysis of an axisymmetric compressible inviscid flow about a droplet with small surface perturbations relative to the mean radius subjected to an incoming ultrasonic wave. The necessary nucleation pressure threshold inside the droplet is calculated to be -9.33 ± 0.30 MPa for typical experimental parameters by employing results from classical homogeneous nucleation theory. As a result, we are able to predict if a given incident pressure waveform will induce nucleation.

  10. Material fabrication using acoustic radiation forces

    DOEpatents

    Sinha, Naveen N.; Sinha, Dipen N.; Goddard, Gregory Russ

    2015-12-01

    Apparatus and methods for using acoustic radiation forces to order particles suspended in a host liquid are described. The particles may range in size from nanometers to millimeters, and may have any shape. The suspension is placed in an acoustic resonator cavity, and acoustical energy is supplied thereto using acoustic transducers. The resulting pattern may be fixed by using a solidifiable host liquid, forming thereby a solid material. Patterns may be quickly generated; typical times ranging from a few seconds to a few minutes. In a one-dimensional arrangement, parallel layers of particles are formed. With two and three dimensional transducer arrangements, more complex particle configurations are possible since different standing-wave patterns may be generated in the resonator. Fabrication of periodic structures, such as metamaterials, having periods tunable by varying the frequency of the acoustic waves, on surfaces or in bulk volume using acoustic radiation forces, provides great flexibility in the creation of new materials. Periodicities may range from millimeters to sub-micron distances, covering a large portion of the range for optical and acoustical metamaterials.

  11. Cascaded radiation pressure acceleration

    SciTech Connect

    Pei, Zhikun; Shen, Baifei E-mail: zhxm@siom.ac.cn; Zhang, Xiaomei E-mail: zhxm@siom.ac.cn; Wang, Wenpeng; Zhang, Lingang; Yi, Longqing; Shi, Yin; Xu, Zhizhan

    2015-07-15

    A cascaded radiation-pressure acceleration scheme is proposed. When an energetic proton beam is injected into an electrostatic field moving at light speed in a foil accelerated by light pressure, protons can be re-accelerated to much higher energy. An initial 3-GeV proton beam can be re-accelerated to 7 GeV while its energy spread is narrowed significantly, indicating a 4-GeV energy gain for one acceleration stage, as shown in one-dimensional simulations and analytical results. The validity of the method is further confirmed by two-dimensional simulations. This scheme provides a way to scale proton energy at the GeV level linearly with laser energy and is promising to obtain proton bunches at tens of gigaelectron-volts.

  12. Directional radiation pattern in structural-acoustic coupled system.

    PubMed

    Seo, Hee-Seon; Kim, Yang-Hann

    2005-07-01

    In this paper we demonstrate the possibility of designing a radiator using structural-acoustic interaction by predicting the pressure distribution and radiation pattern of a structural-acoustic coupling system that is composed by a wall and two spaces. If a wall separates spaces, then the wall's role in transporting the acoustic characteristics of the spaces is important. The spaces can be categorized as bounded finite space and unbounded infinite space. The wall considered in this study composes two plates and an opening, and the wall separates one space that is highly reverberant and the other that is unbounded without any reflection. This rather hypothetical circumstance is selected to study the general coupling problem between the finite and infinite acoustic domains. We developed an equation that predicts the energy distribution and energy flow in the two spaces separated by a wall, and its computational examples are presented. Three typical radiation patterns that include steered, focused, and omnidirected are presented. A designed radiation pattern is also presented by using the optimal design algorithm.

  13. Directional radiation pattern in structural-acoustic coupled system.

    PubMed

    Seo, Hee-Seon; Kim, Yang-Hann

    2005-07-01

    In this paper we demonstrate the possibility of designing a radiator using structural-acoustic interaction by predicting the pressure distribution and radiation pattern of a structural-acoustic coupling system that is composed by a wall and two spaces. If a wall separates spaces, then the wall's role in transporting the acoustic characteristics of the spaces is important. The spaces can be categorized as bounded finite space and unbounded infinite space. The wall considered in this study composes two plates and an opening, and the wall separates one space that is highly reverberant and the other that is unbounded without any reflection. This rather hypothetical circumstance is selected to study the general coupling problem between the finite and infinite acoustic domains. We developed an equation that predicts the energy distribution and energy flow in the two spaces separated by a wall, and its computational examples are presented. Three typical radiation patterns that include steered, focused, and omnidirected are presented. A designed radiation pattern is also presented by using the optimal design algorithm. PMID:16119333

  14. Measuring Acoustic-Radiation Stresses in Materials

    NASA Technical Reports Server (NTRS)

    Cantrell, John H.; Yost, W. T.

    1986-01-01

    System measures nonlinearity parameters of materials. Uses static strain generated by acoustic wave propagating in material. Since static strain is effectively "dc" component of waveform distortion, problems associated with phase-cancellation artifacts disappear. Further, sign of nonlinearity parameter obtained by simple inspection of measured signal polarity. These features make this system very amenable to use in field. System expected to become standard for acoustic-radiation-stress measurements for solids and liquids and for characterization of material properties related to strength and residual or applied stresses. Also expected to become standard for transducer calibration.

  15. Radiation directivity rotation by acoustic metamaterials

    SciTech Connect

    Jiang, Xue; Liang, Bin E-mail: jccheng@nju.edu.cn; Zou, Xin-ye; Cheng, Jian-chun E-mail: jccheng@nju.edu.cn; Zhang, Likun

    2015-08-31

    We use a metamaterial-based scheme to rotate the radiation directivity of sound radiated by a source surrounded by the structure. The rotation is demonstrated through both numerical simulations and experiments. The performance persists within a broadband and is entirely independent of the location and pattern of source inside, suggesting great potential in various practical scenarios where both the signal frequency and source position may vary significantly. We have also investigated the possibility to realize versatile controls of radiation direction by tailoring the structural parameters. Our design with special directivity-steering capability may open route to loudspeaker and auditorium acoustics designs and medical ultrasound applications.

  16. Radiation directivity rotation by acoustic metamaterials

    NASA Astrophysics Data System (ADS)

    Jiang, Xue; Zhang, Likun; Liang, Bin; Zou, Xin-ye; Cheng, Jian-chun

    2015-08-01

    We use a metamaterial-based scheme to rotate the radiation directivity of sound radiated by a source surrounded by the structure. The rotation is demonstrated through both numerical simulations and experiments. The performance persists within a broadband and is entirely independent of the location and pattern of source inside, suggesting great potential in various practical scenarios where both the signal frequency and source position may vary significantly. We have also investigated the possibility to realize versatile controls of radiation direction by tailoring the structural parameters. Our design with special directivity-steering capability may open route to loudspeaker and auditorium acoustics designs and medical ultrasound applications.

  17. Sound Pressure Level Gain in an Acoustic Metamaterial Cavity

    PubMed Central

    Song, Kyungjun; Kim, Kiwon; Hur, Shin; Kwak, Jun-Hyuk; Park, Jihyun; Yoon, Jong Rak; Kim, Jedo

    2014-01-01

    The inherent attenuation of a homogeneous viscous medium limits radiation propagation, thereby restricting the use of many high-frequency acoustic devices to only short-range applications. Here, we design and experimentally demonstrate an acoustic metamaterial localization cavity which is used for sound pressure level (SPL) gain using double coiled up space like structures thereby increasing the range of detection. This unique behavior occurs within a subwavelength cavity that is 1/10th of the wavelength of the incident acoustic wave, which provides up to a 13 dB SPL gain. We show that the amplification results from the Fabry-Perot resonance of the cavity, which has a simultaneously high effective refractive index and effective impedance. We also experimentally verify the SPL amplification in an underwater environment at higher frequencies using a sample with an identical unit cell size. The versatile scalability of the design shows promising applications in many areas, especially in acoustic imaging and underwater communication. PMID:25502279

  18. The acoustics and unsteady wall pressure of a circulation control airfoil

    NASA Astrophysics Data System (ADS)

    Silver, Jonathan C.

    A Circulation Control (CC) airfoil uses a wall jet exiting onto a rounded trailing edge to generate lift via the Coanda effect. The aerodynamics of the CC airfoil have been studied extensively. The acoustics of the airfoil are, however, much less understood. The primary goal of the present work was to study the radiated sound and unsteady surface pressures of a CC airfoil. The focus of this work can be divided up into three main categories: characterizing the unsteady surface pressures, characterizing the radiated sound, and understanding the acoustics from surface pressures. The present work is the first to present the unsteady surface pressures from the trailing edge cylinder of a circulation control airfoil. The auto-spectral density of the unsteady surface pressures at various locations around the trailing edge are presented over a wide range of the jets momentum coefficient. Coherence of pressure and length scales were computed and presented. Single microphone measurements were made at a range of angles for a fixed observer distance in the far field. Spectra are presented for select angles to show the directivity of the airfoil's radiated sound. Predictions of the acoustics were made from unsteady surface pressures via Howe's curvature noise model and a modified Curle's analogy. A summary of the current understanding of the acoustics from a CC airfoil is given along with suggestions for future work.

  19. Stirring and mixing of liquids using acoustic radiation force.

    PubMed

    Sarvazyan, Armen; Ostrovsky, Lev

    2009-06-01

    The possibility of using acoustic radiation force in standing waves for stirring and mixing small volumes of liquids is theoretically analyzed. The principle of stirring considered in this paper is based on moving the microparticles suspended in a standing acoustic wave by changing the frequency so that one standing wave mode is replaced by the other, with differently positioned minima of potential energy. The period-average transient dynamics of solid microparticles and gas microbubbles is considered, and simple analytical solutions are obtained for the case of standing waves of variable amplitude. It is shown that bubbles can be moved from one equilibrium position to another two to three orders of magnitude faster than solid particles. For example, radiation force in a standing acoustic wave field may induce movement of microbubbles with a speed of the order of a few m/s at a frequency of 1 MHz and ultrasound pressure amplitude of 100 kPa, whereas the speed of rigid particles does not exceed 1 cms under the same conditions. The stirring effect can be additionally enhanced due to the fact that the bubbles that are larger and smaller than the resonant bubbles move in opposite directions. Possible applications of the analyzed stirring mechanism, such as in microarrays, are discussed. PMID:19507936

  20. The patterning mechanism of carbon nanotubes using surface acoustic waves: the acoustic radiation effect or the dielectrophoretic effect

    NASA Astrophysics Data System (ADS)

    Ma, Zhichao; Guo, Jinhong; Liu, Yan Jun; Ai, Ye

    2015-08-01

    In this study, we present a simple technique capable of assembling and patterning suspended CNTs using a standing surface acoustic wave (SSAW) field. Individual CNTs could be assembled into larger CNT bundles and patterned in periodic positions on a substrate surface. The mechanism of the SSAW-based patterning technique has been investigated using both numerical simulation and experimental study. It has been found that the acoustic radiation effect due to the acoustic pressure field and the dielectrophoretic (DEP) effect induced by the electric field co-existing in the patterning process however play different roles depending on the properties of the suspended particles and the suspension medium. In the SSAW-based patterning of highly conductive CNTs with high aspect ratio geometry, the positive DEP effect dominates over the acoustic radiation effect. In contrast, the acoustic radiation effect dominates over the DEP effect when manipulating less conductive, spherical or low aspect ratio particles or biological cells. These results provide a meaningful insight into the mechanism of SSAW-based patterning, which is of great help to guide the effective use of this patterning technique for various applications.In this study, we present a simple technique capable of assembling and patterning suspended CNTs using a standing surface acoustic wave (SSAW) field. Individual CNTs could be assembled into larger CNT bundles and patterned in periodic positions on a substrate surface. The mechanism of the SSAW-based patterning technique has been investigated using both numerical simulation and experimental study. It has been found that the acoustic radiation effect due to the acoustic pressure field and the dielectrophoretic (DEP) effect induced by the electric field co-existing in the patterning process however play different roles depending on the properties of the suspended particles and the suspension medium. In the SSAW-based patterning of highly conductive CNTs with high

  1. Modal analysis and intensity of acoustic radiation of the kettledrum.

    PubMed

    Tronchin, Lamberto

    2005-02-01

    The acoustical features of kettledrums have been analyzed by means of modal analysis and acoustic radiation (p/v ratio) measurements. Modal analysis of two different kettledrums was undertaken, exciting the system both by a hammer and a shaker. Up to 15 vibrational modes were clearly identified. Acoustic radiation was studied using two ways. Based on previous experiments of other researchers, a new parameter, called intensity of acoustic radiation (IAR), has been defined and measured. Results show a strict relationship between IAR and the frequency response function (FRF, which is the v/F ratio), and IAR also strongly relates the modal pattern to acoustic radiation. Finally, IAR is proposed for vibro-acoustical characterization of kettledrums and other musical instruments such as strings, pianos, and harpsichords. PMID:15759711

  2. Inlet total pressure loss due to acoustic wall treatment

    NASA Technical Reports Server (NTRS)

    Miller, B. A.

    1977-01-01

    The effect of diffuser wall acoustic treatment on inlet total pressure loss was experimentally determined. Data were obtained by testing an inlet model with 10 different acoustically treated diffusers differing only in the design of the Helmholtz resonator acoustic treatment. Tests were conducted in a wind tunnel at forward velocities to 41 meters per second for inlet throat Mach numbers of .5 to .8 and angles of attack as high as 50 degrees. Results indicate a pressure loss penalty due to acoustic treatment that increases linearly with the porosity of the acoustic facing sheet. For a surface porosity of 14 percent the total pressure loss was 21 percent greater than that for an untreated inlet.

  3. Acoustics of the piezo-electric pressure probe

    NASA Technical Reports Server (NTRS)

    Dutt, G. S.

    1974-01-01

    Acoustical properties of a piezoelectric device are reported for measuring the pressure in the plasma flow from an MPD arc. A description and analysis of the acoustical behavior in a piezoelectric probe is presented for impedance matching and damping. The experimental results are presented in a set of oscillographic records.

  4. Development of acoustic agglomerator. Test plan for high temperature high pressure acoustic agglomerator

    NASA Astrophysics Data System (ADS)

    1985-08-01

    The design specifications for the HTHP AA Facility are listed. The facility is an open-loop, air flow system with subsystems and components to provide the high temperature, high pressure, residence time, dust loading and acoustic irradiation to simulate the aerosol and Hot Gas Cleanup (HGCU) AA system of a Pressurized Fluid Bed Combustor (PFBC), Combined Cycle Power Plant. Data sampling, instrumentation, and automatic controls and data analysis systems are also provided. This test plan describes the testing to be done on the high temperature, high pressure acoustic agglomerator (HTHP AA) at Pen State University's High Intensity Acoustic Laboratory.

  5. Experimental Robust Control of Structural Acoustic Radiation

    NASA Technical Reports Server (NTRS)

    Cox, David E.; Gibbs, Gary P.; Clark, Robert L.; Vipperman, Jeffrey S.

    1998-01-01

    This work addresses the design and application of robust controllers for structural acoustic control. Both simulation and experimental results are presented. H(infinity) and mu-synthesis design methods were used to design feedback controllers which minimize power radiated from a panel while avoiding instability due to unmodeled dynamics. Specifically, high order structural modes which couple strongly to the actuator-sensor path were poorly modeled. This model error was analytically bounded with an uncertainty model, which allowed controllers to be designed without artificial limits on control effort. It is found that robust control methods provide the control designer with physically meaningful parameters with which to tune control designs and can be very useful in determining limits of performance. Experimental results also showed, however, poor robustness properties for control designs with ad-hoc uncertainty models. The importance of quantifying and bounding model errors is discussed.

  6. 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.

  7. Acoustic radiation from the submerged circular cylindrical shell treated with active constrained layer damping

    NASA Astrophysics Data System (ADS)

    Yuan, Li-Yun; Xiang, Yu; Lu, Jing; Jiang, Hong-Hua

    2015-12-01

    Based on the transfer matrix method of exploring the circular cylindrical shell treated with active constrained layer damping (i.e., ACLD), combined with the analytical solution of the Helmholtz equation for a point source, a multi-point multipole virtual source simulation method is for the first time proposed for solving the acoustic radiation problem of a submerged ACLD shell. This approach, wherein some virtual point sources are assumed to be evenly distributed on the axial line of the cylindrical shell, and the sound pressure could be written in the form of the sum of the wave functions series with the undetermined coefficients, is demonstrated to be accurate to achieve the radiation acoustic pressure of the pulsating and oscillating spheres respectively. Meanwhile, this approach is proved to be accurate to obtain the radiation acoustic pressure for a stiffened cylindrical shell. Then, the chosen number of the virtual distributed point sources and truncated number of the wave functions series are discussed to achieve the approximate radiation acoustic pressure of an ACLD cylindrical shell. Applying this method, different radiation acoustic pressures of a submerged ACLD cylindrical shell with different boundary conditions, different thickness values of viscoelastic and piezoelectric layer, different feedback gains for the piezoelectric layer and coverage of ACLD are discussed in detail. Results show that a thicker thickness and larger velocity gain for the piezoelectric layer and larger coverage of the ACLD layer can obtain a better damping effect for the whole structure in general. Whereas, laying a thicker viscoelastic layer is not always a better treatment to achieve a better acoustic characteristic. Project supported by the National Natural Science Foundation of China (Grant Nos. 11162001, 11502056, and 51105083), the Natural Science Foundation of Guangxi Zhuang Autonomous Region, China (Grant No. 2012GXNSFAA053207), the Doctor Foundation of Guangxi

  8. Measurement of cochlear acoustic pressure in guinea pigs

    NASA Astrophysics Data System (ADS)

    Franke, R.; Dancer, A.

    1983-10-01

    Guinea pig cochlear acoustic pressure was measured in the 3 to 200 Hz range. The cochlear microphonic potential was recorded. The experimental results agree with the Peterson and Bogert model. The pressure transducers and the calibrating device are confirmed to be excellent tools for this type of research.

  9. Quantum fluctuations of radiation pressure

    SciTech Connect

    Wu, Chun-Hsien; Ford, L. H.

    2001-08-15

    Quantum fluctuations of electromagnetic radiation pressure are discussed. We use an approach based on the quantum stress tensor to calculate the fluctuations in velocity and position of a mirror subjected to electromagnetic radiation. Our approach reveals that radiation pressure fluctuations in the case of a coherent state are due to a cross term between vacuum and state dependent terms in a stress tensor operator product. Thus observation of these fluctuations would entail experimental confirmation of this cross term. We first analyze the pressure fluctuations on a single, perfectly reflecting mirror, and then study the case of an interferometer. This involves a study of the effects of multiple bounces in one arm, as well as the correlations of the pressure fluctuations between arms of the interferometer. In all cases, our results are consistent with those previously obtained by Caves using different methods. We argue that the agreement between the different methods supports the reality of the cross term and justifies the methods used in its evaluation.

  10. Acoustic intensity-based method for sound radiations in a uniform flow.

    PubMed

    Yu, Chao; Zhou, Zhengfang; Zhuang, Mei

    2009-11-01

    An acoustic intensity-based method (AIBM) is extended and verified for predicting sound radiation in a subsonic uniform flow. The method assumes that the acoustic propagation is governed by the modified Helmholtz equation on and outside of a control surface, which encloses all the noise sources and nonlinear effects. With acoustic pressure derivative and its co-located acoustic pressure as input from an open control surface, the unique solution of the modified Helmholtz equation is obtained by solving the least squares problem. The AIBM is coupled with near-field Computational Fluid Dynamics (CFD)/Computational Aeroacoustics (CAA) methods to predict sound radiation of model aeroacoustic problems. The effectiveness of this hybrid approach has been demonstrated by examples of both tonal and broadband noise. Since the AIBM method is stable and accurate based on the input acoustic data from an open surface in a radiated field, it is therefore advantageous for the far-field prediction of aerodynamics noise propagation when an acoustic input from a closed control surface, like the Ffowcs Williams-Hawkings surface, is not available [Philos. Trans. R. Soc. London, Ser. A 264, 321-342 (1969)]. PMID:19894800

  11. Acoustic Radiation from High-Speed Turbulent Boundary Layers in a Tunnel-Like Environment

    NASA Technical Reports Server (NTRS)

    Duan, Lian; Choudhari, Meelan M.; Zhang, Chao

    2015-01-01

    Direct numerical simulation of acoustic radiation from a turbulent boundary layer in a cylindrical domain will be conducted under the flow conditions corresponding to those at the nozzle exit of the Boeing/AFOSR Mach-6 Quiet Tunnel (BAM6QT) operated under noisy-flow conditions with a total pressure p(sub t) of 225 kPa and a total temperature of T(sub t) equal to 430 K. Simulations of acoustic radiation from a turbulent boundary layer over a flat surface are used as a reference configuration to illustrate the effects of the cylindrical enclosure. A detailed analysis of acoustic freestream disturbances in the cylindrical domain will be reported in the final paper along with a discussion pertaining to the significance of the flat-plate acoustic simulations and guidelines concerning the modeling of the effects of an axisymmetric tunnel wall on the noise field.

  12. Bubble-Based Acoustic Radiation Force Using Chirp Insonation to Reduce Standing Wave Effects

    PubMed Central

    Erpelding, Todd N.; Hollman, Kyle W.; O’Donnell, Matthew

    2007-01-01

    Bubble-based acoustic radiation force can measure local viscoelastic properties of tissue. High intensity acoustic waves applied to laser-generated bubbles induce displacements inversely proportional to local Young’s modulus. In certain instances, long pulse durations are desirable but are susceptible to standing wave artifacts, which corrupt displacement measurements. Chirp pulse acoustic radiation force was investigated as a method to reduce standing wave artifacts. Chirp pulses with linear frequency sweep magnitudes of 100, 200, and 300 kHz centered around 1.5 MHz were applied to glass beads within gelatin phantoms and laser-generated bubbles within porcine lenses. The ultrasound transducer was translated axially to vary standing wave conditions, while comparing displacements using chirp pulses and 1.5 MHz tone burst pulses of the same duration and peak rarefactional pressure. Results demonstrated significant reduction in standing wave effects using chirp pulses, with displacement proportional to acoustic intensity and bubble size. PMID:17306697

  13. Dynamics of Radiation Pressure Acceleration

    SciTech Connect

    Macchi, A.; Benedetti, C.; Pegoraro, F.; Veghini, S.

    2010-02-02

    We describe recent theoretical results on Radiation Pressure Acceleration of ions by ultraintense, circularly polarized laser pulses, giving an insight on the underlying dynamics and suggestions for the development of applications. In thick targets, we show how few-cycle pulses may generate single ion bunches in inhomogeneous density profiles. In thin targets, we present a refinement of the simple model of the accelerating mirror and a comparison of its predictions with simulation results, solving an apparent paradox.

  14. Acoustic manipulation of oscillating spherical bodies: Emergence of axial negative acoustic radiation force

    NASA Astrophysics Data System (ADS)

    Rajabi, Majid; Mojahed, Alireza

    2016-11-01

    In this paper, emergence of negative axial acoustic radiation force on a rigid oscillating spherical body is investigated for acoustic manipulation purposes. The problem of plane acoustic wave scattering from an oscillating spherical body submerged in an ideal acoustic fluid medium is solved. For the case of oscillating direction collinear with the wave propagation wave number vector (desired path), it has been shown that the acoustic radiation force, as a result of nonlinear acoustic wave interaction with bodies can be expressed as a linear function of incident wave field and the oscillation properties of the oscillator (i.e., amplitude and phase of oscillation). The negative (i.e., pulling effects) and positive (i.e., pushing effects) radiation force situations are divided in oscillation complex plane with a specific frequency-dependant straight line. This characteristic line defines the radiation force cancellation state. In order to investigate the stability of the mentioned manipulation strategy, the case of misaligned oscillation of sphere with the wave propagation direction is studied. The proposed methodology may suggest a novel concept of single-beam acoustic handling techniques based on smart carriers.

  15. Wall pressure fluctuations and acoustics in turbulent pipe flow

    NASA Astrophysics Data System (ADS)

    Daniels, M. A.; Lauchle, G. C.

    1986-09-01

    Measurements of the turbulent boundary layer (TBL) wall pressure spectrum and the facility's propagating acoustic field were conducted in the Boundary Layer Research Facility. Subminiature, piezoresistive-type pressure transducers were used. Detailed calibration of the pressure transducers was performed using a standing wave tube. Measured sensitivities of the transducers were within 0.5 dB of factory specifications and measured phase differences between individual transducers were insignificant. The TBL wall pressure spectrum was obtained using a novel signal-processing technique that allowed a minimization of both acoustic and vibration-induced noise. This technique uses pairs of transducer difference signals from an exisymmetric array of three flush-mounted pressure sensors and permits cancellation of the propagating acoustic and vibrationally induced pressure fields. A measurement involving the coherence function between these transducer signals was shown to validate the measured TBL wall pressure spectra and all assumptions used in developing the measurement technique. Non-dimensionalized spectra of the TBL fluctuating wall pressure measured in this investigation are compared to those measured previously. These comparisons substantiated a maximum, normalized transducer diameter for the complete resolution of the high-frequency part of the TBL wall pressure spectrum.

  16. 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.

  17. Acoustic radiation from a laminated composite plate reinforced by doubly periodic parallel stiffeners

    NASA Astrophysics Data System (ADS)

    Yin, X. W.; Gu, X. J.; Cui, H. F.; Shen, R. Y.

    2007-10-01

    Acoustic radiation from a point-driven, infinite fluid-loaded, laminated composite plate which is reinforced by doubly periodic parallel stiffeners is investigated theoretically. The stiffeners interact with the plate only through normal forces. Fourier transform is used for solving the responses of the plate, and the stationary phase approximate is then employed to find an expression for the far field pressure. Acoustic radiation from a stiffened uniform plate composed of multiple isotropic layers is calculated with the present stiffened, laminated composite plate theory, and with the stiffened uniform isotropic plate theory that Mace has proposed. Comparison of the numerical results reveals the validity of our work. Characteristics of the acoustic radiation from a stiffened laminated composite plate are examined through examples and some physical interpretations of significant features are also offered.

  18. Acoustic radiation force-based elasticity imaging methods

    PubMed Central

    Palmeri, Mark L.; Nightingale, Kathryn R.

    2011-01-01

    Conventional diagnostic ultrasound images portray differences in the acoustic properties of soft tissues, whereas ultrasound-based elasticity images portray differences in the elastic properties of soft tissues (i.e. stiffness, viscosity). The benefit of elasticity imaging lies in the fact that many soft tissues can share similar ultrasonic echogenicities, but may have different mechanical properties that can be used to clearly visualize normal anatomy and delineate pathological lesions. Acoustic radiation force-based elasticity imaging methods use acoustic radiation force to transiently deform soft tissues, and the dynamic displacement response of those tissues is measured ultrasonically and is used to estimate the tissue's mechanical properties. Both qualitative images and quantitative elasticity metrics can be reconstructed from these measured data, providing complimentary information to both diagnose and longitudinally monitor disease progression. Recently, acoustic radiation force-based elasticity imaging techniques have moved from the laboratory to the clinical setting, where clinicians are beginning to characterize tissue stiffness as a diagnostic metric, and commercial implementations of radiation force-based ultrasonic elasticity imaging are beginning to appear on the commercial market. This article provides an overview of acoustic radiation force-based elasticity imaging, including a review of the relevant soft tissue material properties, a review of radiation force-based methods that have been proposed for elasticity imaging, and a discussion of current research and commercial realizations of radiation force based-elasticity imaging technologies. PMID:22419986

  19. Finite Element Prediction of Acoustic Scattering and Radiation from Submerged Elastic Structures

    NASA Technical Reports Server (NTRS)

    Everstine, G. C.; Henderson, F. M.; Lipman, R. R.

    1984-01-01

    A finite element formulation is derived for the scattering and radiation of acoustic waves from submerged elastic structures. The formulation uses as fundamental unknowns the displacement in the structure and a velocity potential in the field. Symmetric coefficient matrices result. The outer boundary of the fluid region is terminated with an approximate local wave-absorbing boundary condition which assumes that outgoing waves are locally planar. The finite element model is capable of predicting only the near-field acoustic pressures. Far-field sound pressure levels may be determined by integrating the surface pressures and velocities over the wet boundary of the structure using the Helmholtz integral. Comparison of finite element results with analytic results show excellent agreement. The coupled fluid-structure problem may be solved with general purpose finite element codes by using an analogy between the equations of elasticity and the wave equation of linear acoustics.

  20. An improved method for the calculation of Near-Field Acoustic Radiation Modes

    NASA Astrophysics Data System (ADS)

    Liu, Zu-Bin; Maury, Cédric

    2016-02-01

    Sensing and controlling Acoustic Radiation Modes (ARMs) in the near-field of vibrating structures is of great interest for broadband noise reduction or enhancement, as ARMs are velocity distributions defined over a vibrating surface, that independently and optimally contribute to the acoustic power in the acoustic field. But present methods only provide far-field ARMs (FFARMs) that are inadequate for the acoustic near-field problem. The Near-Field Acoustic Radiation Modes (NFARMs) are firstly studied with an improved numerical method, the Pressure-Velocity method, which rely on the eigen decomposition of the acoustic transfers between the vibrating source and a conformal observation surface, including sound pressure and velocity transfer matrices. The active and reactive parts of the sound power are separated and lead to the active and reactive ARMs. NFARMs are studied for a 2D baffled beam and for a 3D baffled plate, and so as differences between the NFARMS and the classical FFARMs. Comparisons of the NFARMs are analyzed when varying frequency and observation distance to the source. It is found that the efficiencies and shapes of the optimal active ARMs are independent on the distance while that of the reactive ones are distinctly related on.

  1. Identifying Vulnerable Plaques with Acoustic Radiation Force Impulse Imaging

    NASA Astrophysics Data System (ADS)

    Doherty, Joshua Ryan

    The rupture of arterial plaques is the most common cause of ischemic complications including stroke, the fourth leading cause of death and number one cause of long term disability in the United States. Unfortunately, because conventional diagnostic tools fail to identify plaques that confer the highest risk, often a disabling stroke and/or sudden death is the first sign of disease. A diagnostic method capable of characterizing plaque vulnerability would likely enhance the predictive ability and ultimately the treatment of stroke before the onset of clinical events. This dissertation evaluates the hypothesis that Acoustic Radiation Force Impulse (ARFI) imaging can noninvasively identify lipid regions, that have been shown to increase a plaque's propensity to rupture, within carotid artery plaques in vivo. The work detailed herein describes development efforts and results from simulations and experiments that were performed to evaluate this hypothesis. To first demonstrate feasibility and evaluate potential safety concerns, finite- element method simulations are used to model the response of carotid artery plaques to an acoustic radiation force excitation. Lipid pool visualization is shown to vary as a function of lipid pool geometry and stiffness. A comparison of the resulting Von Mises stresses indicates that stresses induced by an ARFI excitation are three orders of magnitude lower than those induced by blood pressure. This thesis also presents the development of a novel pulse inversion harmonic tracking method to reduce clutter-imposed errors in ultrasound-based tissue displacement estimates. This method is validated in phantoms and was found to reduce bias and jitter displacement errors for a marked improvement in image quality in vivo. Lastly, this dissertation presents results from a preliminary in vivo study that compares ARFI imaging derived plaque stiffness with spatially registered composition determined by a Magnetic Resonance Imaging (MRI) gold standard

  2. Cosmic instability from radiation pressure

    NASA Technical Reports Server (NTRS)

    Hogan, Craig J.

    1990-01-01

    The Cosmic Background Explorer has recently confirmed the blackbody character of the microwave background to high accuracy (Mather et al., 1990), and will have the capability to detect other cosmic backgrounds throughout the infrared. A detection of cosmic background radiation dating from the pregalactic era would have important consequences for theories of cosmic structure. During the creation of such a background the pressure of the radiation itself causes an instability which leads inevitably to the growth of large-scale structure in the matter distribution. In contrast to conventional gravitational-instability models, the statistical properties of this structure are determined primarily by the self-organizing dynamics of the instability rather than details of cosmological initial conditions. The behavior of the instability is described here.

  3. 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.

  4. Acoustic Radiation From a Mach 14 Turbulent Boundary Layer

    NASA Technical Reports Server (NTRS)

    Zhang, Chao; Duan, Lian; Choudhari, Meelan M.

    2016-01-01

    Direct numerical simulations (DNS) are used to examine the turbulence statistics and the radiation field generated by a high-speed turbulent boundary layer with a nominal freestream Mach number of 14 and wall temperature of 0:18 times the recovery temperature. The flow conditions fall within the range of nozzle exit conditions of the Arnold Engineering Development Center (AEDC) Hypervelocity Tunnel No. 9 facility. The streamwise domain size is approximately 200 times the boundary-layer thickness at the inlet, with a useful range of Reynolds number corresponding to Re 450 ?? 650. Consistent with previous studies of turbulent boundary layer at high Mach numbers, the weak compressibility hypothesis for turbulent boundary layers remains applicable under this flow condition and the computational results confirm the validity of both the van Driest transformation and Morkovin's scaling. The Reynolds analogy is valid at the surface; the RMS of fluctuations in the surface pressure, wall shear stress, and heat flux is 24%, 53%, and 67% of the surface mean, respectively. The magnitude and dominant frequency of pressure fluctuations are found to vary dramatically within the inner layer (z/delta 0.< or approx. 0.08 or z+ < or approx. 50). The peak of the pre-multiplied frequency spectrum of the pressure fluctuation is f(delta)/U(sub infinity) approx. 2.1 at the surface and shifts to a lower frequency of f(delta)/U(sub infinity) approx. 0.7 in the free stream where the pressure signal is predominantly acoustic. The dominant frequency of the pressure spectrum shows a significant dependence on the freestream Mach number both at the wall and in the free stream.

  5. Transthoracic Cardiac Acoustic Radiation Force Impulse Imaging

    NASA Astrophysics Data System (ADS)

    Bradway, David Pierson

    This dissertation investigates the feasibility of a real-time transthoracic Acoustic Radiation Force Impulse (ARFI) imaging system to measure myocardial function non-invasively in clinical setting. Heart failure is an important cardiovascular disease and contributes to the leading cause of death for developed countries. Patients exhibiting heart failure with a low left ventricular ejection fraction (LVEF) can often be identified by clinicians, but patients with preserved LVEF might be undetected if they do not exhibit other signs and symptoms of heart failure. These cases motivate development of transthoracic ARFI imaging to aid the early diagnosis of the structural and functional heart abnormalities leading to heart failure. M-Mode ARFI imaging utilizes ultrasonic radiation force to displace tissue several micrometers in the direction of wave propagation. Conventional ultrasound tracks the response of the tissue to the force. This measurement is repeated rapidly at a location through the cardiac cycle, measuring timing and relative changes in myocardial stiffness. ARFI imaging was previously shown capable of measuring myocardial properties and function via invasive open-chest and intracardiac approaches. The prototype imaging system described in this dissertation is capable of rapid acquisition, processing, and display of ARFI images and shear wave elasticity imaging (SWEI) movies. Also presented is a rigorous safety analysis, including finite element method (FEM) simulations of tissue heating, hydrophone intensity and mechanical index (MI) measurements, and thermocouple transducer face heating measurements. For the pulse sequences used in later animal and clinical studies, results from the safety analysis indicates that transthoracic ARFI imaging can be safely applied at rates and levels realizable on the prototype ARFI imaging system. Preliminary data are presented from in vivo trials studying changes in myocardial stiffness occurring under normal and abnormal

  6. Introduction of acoustical diffraction in the radiative transfer method

    NASA Astrophysics Data System (ADS)

    Reboul, Emeline; Le Bot, Alain; Perret-Liaudet, Joël

    2004-07-01

    This Note presents an original approach to include diffraction in the radiative transfer method when applied to acoustics. This approach leads to a better spatial description of the acoustical energy. An energetic diffraction coefficient and some diffraction sources are introduced to model the diffraction phenomena. The amplitudes of these sources are determined by solving a linear sytem of equations resulting from the power balance between all acoustical sources. The approach is applied on bidimensional examples and gives good results except at geometrical boundaries. To cite this article: E. Reboul et al., C. R. Mecanique 332 (2004).

  7. Axial acoustic radiation force on a sphere in Gaussian field

    SciTech Connect

    Wu, Rongrong; Liu, Xiaozhou Gong, Xiufen

    2015-10-28

    Based on the finite series method, the acoustical radiation force resulting from a Gaussian beam incident on a spherical object is investigated analytically. When the position of the particles deviating from the center of the beam, the Gaussian beam is expanded as a spherical function at the center of the particles and the expanded coefficients of the Gaussian beam is calculated. The analytical expression of the acoustic radiation force on spherical particles deviating from the Gaussian beam center is deduced. The acoustic radiation force affected by the acoustic frequency and the offset distance from the Gaussian beam center is investigated. Results have been presented for Gaussian beams with different wavelengths and it has been shown that the interaction of a Gaussian beam with a sphere can result in attractive axial force under specific operational conditions. Results indicate the capability of manipulating and separating spherical spheres based on their mechanical and acoustical properties, the results provided here may provide a theoretical basis for development of single-beam acoustical tweezers.

  8. Acoustic Wave Propagation in Pressure Sense Lines

    NASA Technical Reports Server (NTRS)

    Vitarius, Patrick; Gregory, Don A.; Wiley, John; Korman, Valentin

    2003-01-01

    Sense lines are used in pressure measurements to passively transmit information from hostile environments to areas where transducers can be used. The transfer function of a sense line can be used to obtain information about the measured environment from the protected sensor. Several properties of this transfer function are examined, including frequency dependence, Helmholtz resonance, and time of flight delay.

  9. Neural network/acoustic emission burst pressure prediction for impact damaged composite pressure vessels

    SciTech Connect

    Walker, J.L.; Workman, G.L.; Russell, S.S.; Hill, E.V.K.

    1997-08-01

    Acoustic emission signal analysis has been used to measure the effect impact damage has on the burst pressure of 146 mm (5.75 in.) diameter graphite/epoxy and the organic polymer, Kevlar/epoxy filament wound pressure vessels. Burst pressure prediction models were developed by correlating the differential acoustic emission amplitude distribution collected during low level hydroproof tests to known burst pressures using backpropagation artificial neural networks. Impact damage conditions ranging from barely visible to obvious fiber breakage, matrix cracking, and delamination were included in this work. A simulated (inert) propellant was also cast into a series of the vessels from each material class, before impact loading, to provide boundary conditions during impact that would simulate those found on solid rocket motors. The results of this research effort demonstrate that a quantitative assessment of the effects that impact damage has on burst pressure can be made for both organic polymer/epoxy and graphite/epoxy pressure vessels. Here, an artificial neural network analysis of the acoustic emission parametric data recorded during low pressure hydroproof testing is used to relate burst pressure to the vessel`s acoustic signature. Burst pressure predictions within 6.0% of the actual failure pressure are demonstrated for a series of vessels.

  10. Acoustic power measurement of high-intensity focused ultrasound transducer using a pressure sensor.

    PubMed

    Zhou, Yufeng

    2015-03-01

    The acoustic power of high-intensity focused ultrasound (HIFU) is an important parameter that should be measured prior to each treatment to guarantee effective and safe outcomes. A new calibration technique was developed that involves estimating the pressure distribution, calculating the acoustic power using an underwater pressure blast sensor, and compensating the contribution of harmonics to the acoustic power. The output of a clinical extracorporeal HIFU system (center frequency of ~1 MHz, p+ = 2.5-57.2 MPa, p(-) = -1.8 to -13.9 MPa, I(SPPA) = 513-22,940 W/cm(2), -6 dB size of 1.6 × 10 mm: lateral × axial) was measured using this approach and then compared with that obtained using a radiation force balance. Similarities were found between each method at acoustic power ranging from 18.2 W to 912 W with an electrical-to-acoustic conversion efficiency of ~42%. The proposed method has advantages of low weight, smaller size, high sensitivity, quick response, high signal-to-noise ratio (especially at low power output), robust performance, and easy operation of HIFU exposimetry measurement.

  11. Acoustic power measurement of high-intensity focused ultrasound transducer using a pressure sensor.

    PubMed

    Zhou, Yufeng

    2015-03-01

    The acoustic power of high-intensity focused ultrasound (HIFU) is an important parameter that should be measured prior to each treatment to guarantee effective and safe outcomes. A new calibration technique was developed that involves estimating the pressure distribution, calculating the acoustic power using an underwater pressure blast sensor, and compensating the contribution of harmonics to the acoustic power. The output of a clinical extracorporeal HIFU system (center frequency of ~1 MHz, p+ = 2.5-57.2 MPa, p(-) = -1.8 to -13.9 MPa, I(SPPA) = 513-22,940 W/cm(2), -6 dB size of 1.6 × 10 mm: lateral × axial) was measured using this approach and then compared with that obtained using a radiation force balance. Similarities were found between each method at acoustic power ranging from 18.2 W to 912 W with an electrical-to-acoustic conversion efficiency of ~42%. The proposed method has advantages of low weight, smaller size, high sensitivity, quick response, high signal-to-noise ratio (especially at low power output), robust performance, and easy operation of HIFU exposimetry measurement. PMID:25659300

  12. Application of an ultrasonic focusing radiator for acoustic levitation of submillimeter samples

    NASA Technical Reports Server (NTRS)

    Lee, M. C.

    1981-01-01

    An acoustic apparatus has been specifically developed to handle samples of submillimeter size in a gaseous medium. This apparatus consists of an acoustic levitation device, deployment devices for small liquid and solid samples, heat sources for sample heat treatment, acoustic alignment devices, a cooling system and data-acquisition instrumentation. The levitation device includes a spherical aluminum dish of 12 in. diameter and 0.6 in. thickness, 130 pieces of PZT transducers attached to the back side of the dish and a spherical concave reflector situated in the vicinity of the center of curvature of the dish. The three lowest operating frequencies for the focusing-radiator levitation device are 75, 105 and 163 kHz, respectively. In comparison with other levitation apparatus, it possesses a large radiation pressure and a high lateral positional stability. This apparatus can be used most advantageously in the study of droplets and spherical shell systems, for instance, for fusion target applications.

  13. Application of an ultrasonic focusing radiator for acoustic levitation of submillimeter samples

    SciTech Connect

    Lee, M.C.

    1981-01-01

    An acoustic apparatus has been specifically developed to handle samples of submillimeter size in a gaseous medium. This apparatus consists of an acoustic levitation device, deployment devices for small liquid and solid samples, heat sources for sample heat treatment, acoustic alignment devices, a cooling system and data-acquisition instrumentation. The levitation device includes a spherical aluminum dish of 12'' diameter and 0.6'' thickness, 130 pieces of PZT tranducers attached to the back side of the dish and a spherical concave reflector situated in the vicinity of the center of curvature of the dish. The three lowest operating frequencies for the focusing-radiator levitation device are 75, 105 and 163 kHz, respectively. In comparison with other levitation apparatus, it possesses a large radiation pressure and a high lateral positional stability. This apparatus can be used most advantageously in the study of droplets and spherical shell systems, for instance, for fusion target applications.

  14. Acoustic Radiation Force Elasticity Imaging in Diagnostic Ultrasound

    PubMed Central

    Doherty, Joshua R.; Trahey, Gregg E.; Nightingale, Kathryn R.; Palmeri, Mark L.

    2013-01-01

    The development of ultrasound-based elasticity imaging methods has been the focus of intense research activity since the mid-1990s. In characterizing the mechanical properties of soft tissues, these techniques image an entirely new subset of tissue properties that cannot be derived with conventional ultrasound techniques. Clinically, tissue elasticity is known to be associated with pathological condition and with the ability to image these features in vivo, elasticity imaging methods may prove to be invaluable tools for the diagnosis and/or monitoring of disease. This review focuses on ultrasound-based elasticity imaging methods that generate an acoustic radiation force to induce tissue displacements. These methods can be performed non-invasively during routine exams to provide either qualitative or quantitative metrics of tissue elasticity. A brief overview of soft tissue mechanics relevant to elasticity imaging is provided, including a derivation of acoustic radiation force, and an overview of the various acoustic radiation force elasticity imaging methods. PMID:23549529

  15. Acoustic Radiation Force Impulse (ARFI) Imaging: a Review

    PubMed Central

    Nightingale, Kathy

    2012-01-01

    Acoustic radiation force based elasticity imaging methods are under investigation by many groups. These methods differ from traditional ultrasonic elasticity imaging methods in that they do not require compression of the transducer, and are thus expected to be less operator dependent. Methods have been developed that utilize impulsive (i.e. < 1 ms), harmonic (pulsed), and steady state radiation force excitations. The work discussed herein utilizes impulsive methods, for which two imaging approaches have been pursued: 1) monitoring the tissue response within the radiation force region of excitation (ROE) and generating images of relative differences in tissue stiffness (Acoustic Radiation Force Impulse (ARFI) imaging); and 2) monitoring the speed of shear wave propagation away from the ROE to quantify tissue stiffness (Shear Wave Elasticity Imaging (SWEI)). For these methods, a single ultrasound transducer on a commercial ultrasound system can be used to both generate acoustic radiation force in tissue, and to monitor the tissue displacement response. The response of tissue to this transient excitation is complicated and depends upon tissue geometry, radiation force field geometry, and tissue mechanical and acoustic properties. Higher shear wave speeds and smaller displacements are associated with stiffer tissues, and slower shear wave speeds and larger displacements occur with more compliant tissues. ARFI images have spatial resolution comparable to that of B-mode, often with greater contrast, providing matched, adjunctive information. SWEI images provide quantitative information about the tissue stiffness, typically with lower spatial resolution. A review these methods and examples of clinical applications are presented herein. PMID:22545033

  16. Sources and Radiation Patterns of Volcano-Acoustic Signals Investigated with Field-Scale Chemical Explosions

    NASA Astrophysics Data System (ADS)

    Bowman, D. C.; Lees, J. M.; Taddeucci, J.; Graettinger, A. H.; Sonder, I.; Valentine, G.

    2014-12-01

    We investigate the processes that give rise to complex acoustic signals during volcanic blasts by monitoring buried chemical explosions with infrasound and audio range microphones, strong motion sensors, and high speed imagery. Acoustic waveforms vary with scaled depth of burial (SDOB, units in meters per cube root of joules), ranging from high amplitude, impulsive, gas expansion dominated signals at low SDOB to low amplitude, longer duration, ground motion dominated signals at high SDOB. Typically, the sudden upward acceleration of the substrate above the blast produces the first acoustic arrival, followed by a second pulse due to the eruption of pressurized gas at the surface. Occasionally, a third overpressure occurs when displaced material decelerates upon impact with the ground. The transition between ground motion dominated and gas release dominated acoustics ranges between 0.0038-0.0018 SDOB, respectively. For example, one explosion registering an SDOB=0.0031 produced two overpressure pulses of approximately equal amplitude, one due to ground motion, the other to gas release. Recorded volcano infrasound has also identified distinct ground motion and gas release components during explosions at Sakurajima, Santiaguito, and Karymsky volcanoes. Our results indicate that infrasound records may provide a proxy for the depth and energy of these explosions. Furthermore, while magma fragmentation models indicate the possibility of several explosions during a single vulcanian eruption (Alidibirov, Bull Volc., 1994), our results suggest that a single explosion can also produce complex acoustic signals. Thus acoustic records alone cannot be used to distinguish between single explosions and multiple closely-spaced blasts at volcanoes. Results from a series of lateral blasts during the 2014 field experiment further indicates whether vent geometry can produce directional acoustic radiation patterns like those observed at Tungarahua volcano (Kim et al., GJI, 2012). Beside

  17. Quantitative measurement of acoustic pressure in the focal zone of acoustic lens-line focusing using the Schlieren method.

    PubMed

    Jiang, Xueping; Cheng, Qian; Xu, Zheng; Qian, Menglu; Han, Qingbang

    2016-04-01

    This paper proposes a theory and method for quantitative measurement of the acoustic lens-line focusing ultrasonic (ALLFU) field in its focal spot size and acoustic pressure using the Schlieren imaging technique. Using Fourier transformation, the relationship between the brightness of the Schlieren image and the acoustic pressure was introduced. The ALLFU field was simulated using finite element method and compared with the Schlieren acoustic field image. The measurement of the focal spot size was performed using the Schlieren method. The acoustic pressure in the focal zone of the ALLFU field and the transducer-transmitting voltage response were quantitatively determined by measuring the diffraction light fringe intensity. The results show that the brightness of the Schlieren image is a linear function of the acoustic intensity when the acousto-optic interaction length remains constant and the acoustic field is weak. PMID:27139646

  18. Propagation of waves in a medium with high radiation pressure

    NASA Technical Reports Server (NTRS)

    Bisnovatyy-Kogan, G. S.; Blinnikov, S. I.

    1979-01-01

    The propagation and mutual transformation of acoustic and thermal waves are investigated in media with a high radiative pressure. The equations of hydrodynamics for matter and the radiative transfer equations in a moving medium in the Eddington approximation are used in the investigation. Model problems of waves in a homogeneous medium with an abrupt jump in opacity and in a medium of variable opacity are presented. The characteristic and the times of variability are discussed. Amplitude for the brightness fluctuations for very massive stars are discussed.

  19. Modeling the effects of wind tunnel wall absorption on the acoustic radiation characteristics of propellers

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Eversman, W.

    1986-01-01

    Finite element theory is used to calculate the acoustic field of a propeller in a soft walled circular wind tunnel and to compare the radiation patterns to the same propeller in free space. Parametric solutions are present for a "Gutin" propeller for a variety of flow Mach numbers, admittance values at the wall, microphone position locations, and propeller to duct radius ratios. Wind tunnel boundary layer is not included in this analysis. For wall admittance nearly equal to the characteristic value of free space, the free field and ducted propeller models agree in pressure level and directionality. In addition, the need for experimentally mapping the acoustic field is discussed.

  20. Acoustic-radiation stress in solids. I - Theory

    NASA Technical Reports Server (NTRS)

    Cantrell, J. H., Jr.

    1984-01-01

    The general case of acoustic-radiation stress associated with quasi-compressional and quasi-shear waves propagating in infinite and semiinfinite lossless solids of arbitrary crystalline symmetry is studied. The Boussinesq radiation stress is defined and found to depend directly on an acoustic nonlinearity parameter which characterizes the radiation-induced static strain, a stress-generalized nonlinearity parameter which characterizes the stress nonlinearity, and the energy density of the propagating wave. Application of the Boltzmann-Ehrenfest principle of adiabatic invariance to a self-constrained system described by the nonlinear equations of motion allows the acoustic-radiation-induced static strain to be identified with a self-constrained variation in the time-averaged product of the internal energy density and displacement gradient. The time-averaged product is scaled by the acoustic nonlinearity parameter and represents the first-order nonlinearity in the virial theorem. Finally, the relationship between the Boussinesq and the Cauchy radiation stress is obtained in a closed three-dimensional form.

  1. Nonlinear Evolution of the Radiation-driven Magneto-acoustic Instability

    NASA Astrophysics Data System (ADS)

    Fernández, Rodrigo; Socrates, Aristotle

    2013-04-01

    We examine the nonlinear development of unstable magnetosonic waves driven by a background radiative flux—the radiation-driven magneto-acoustic instability (RMI, a.k.a. the "photon bubble" instability). The RMI may serve as a persistent source of density, radiative flux, and magnetic field fluctuations in stably stratified, optically thick media. The conditions for instability are present in a variety of astrophysical environments and do not require the radiation pressure to dominate or the magnetic field to be strong. Here, we numerically study the saturation properties of the RMI, covering three orders of magnitude in the relative strength of radiation, magnetic field, and gas energies. Two-dimensional, time-dependent radiation-magnetohydrodynamic simulations of local, stably stratified domains are conducted with Zeus-MP in the optically thick, highly conducting limit. Our results confirm the theoretical expectations of Blaes & Socrates in that the RMI operates even in gas-pressure-dominated environments that are weakly magnetized. The saturation amplitude is a monotonically increasing function of the ratio of radiation to gas pressure. Keeping this ratio constant, we find that the saturation amplitude peaks when the magnetic pressure is comparable to the radiation pressure. We discuss the implications of our results for the dynamics of magnetized stellar envelopes, where the RMI should act as a source of sub-photospheric perturbations.

  2. NONLINEAR EVOLUTION OF THE RADIATION-DRIVEN MAGNETO-ACOUSTIC INSTABILITY

    SciTech Connect

    Fernandez, Rodrigo; Socrates, Aristotle

    2013-04-20

    We examine the nonlinear development of unstable magnetosonic waves driven by a background radiative flux-the radiation-driven magneto-acoustic instability (RMI, a.k.a. the ''photon bubble'' instability). The RMI may serve as a persistent source of density, radiative flux, and magnetic field fluctuations in stably stratified, optically thick media. The conditions for instability are present in a variety of astrophysical environments and do not require the radiation pressure to dominate or the magnetic field to be strong. Here, we numerically study the saturation properties of the RMI, covering three orders of magnitude in the relative strength of radiation, magnetic field, and gas energies. Two-dimensional, time-dependent radiation-magnetohydrodynamic simulations of local, stably stratified domains are conducted with Zeus-MP in the optically thick, highly conducting limit. Our results confirm the theoretical expectations of Blaes and Socrates in that the RMI operates even in gas-pressure-dominated environments that are weakly magnetized. The saturation amplitude is a monotonically increasing function of the ratio of radiation to gas pressure. Keeping this ratio constant, we find that the saturation amplitude peaks when the magnetic pressure is comparable to the radiation pressure. We discuss the implications of our results for the dynamics of magnetized stellar envelopes, where the RMI should act as a source of sub-photospheric perturbations.

  3. Tongue-Palate Contact Pressure, Oral Air Pressure, and Acoustics of Clear Speech

    ERIC Educational Resources Information Center

    Searl, Jeff; Evitts, Paul M.

    2013-01-01

    Purpose: The authors compared articulatory contact pressure (ACP), oral air pressure (Po), and speech acoustics for conversational versus clear speech. They also assessed the relationship of these measures to listener perception. Method: Twelve adults with normal speech produced monosyllables in a phrase using conversational and clear speech.…

  4. Separation of Yeast Cells from MS2 Viruses Using Acoustic Radiation Force

    SciTech Connect

    Jung, B; Fisher, K; Ness, K; Rose, K A; Mariella, Jr., R P

    2008-03-27

    We report a rapid and robust separation of Saccharomyces cerevisiae and MS2 bacteriophage using acoustic focusing in a microfluidic device. A piezoelectric transducer (PZT) generates acoustic standing waves in the microchannel. These standing waves induce acoustic radiation force fields that direct microparticles towards the nodes (i.e., pressure minima) or the anti-nodes (i.e., pressure maxima) of the standing waves depending on the relative compressidensity between the particle and the suspending liquid.[1] For particles larger than 2 {micro}m, the transverse velocities generated by these force fields enable continuous, high throughput separation. Extensive work in the last decade [2-4] has demonstrated acoustic focusing for manipulating microparticles or biological samples in microfluidic devices. This prior work has primarily focused on experimental realization of acoustic focusing without modeling or with limited one-dimensional modeling estimates. We recently developed a finite element modeling tool to predict the two-dimensional acoustic radiation force field perpendicular to the flow direction in microfluidic devices.[1] Here we compare results from this model with experimental parametric studies including variations of the PZT driving frequencies and voltages as well as various particle sizes and compressidensities. These experimental parametric studies also provide insight into the development of an adjustable 'virtual' pore-size filter as well as optimal operating conditions for various microparticle sizes. Figure 1 shows a typical experimental acoustic focusing result for microparticles (diameter = 2.0 {micro}m) in a 500 {micro}m wide by 200 {micro}m deep microchannel. In this case, the PZT driving frequency and voltage are, respectively, 1.459 MHz and 6.6 V. The microparticles tightly focus (full width half maximum (FWHM) {approx}30 {micro}m) less than 30 s after the initiation of the acoustic field. We simulated the same geometry and operating

  5. Numerical calculation of acoustic radiation forces acting on a sphere in a viscous fluid

    NASA Astrophysics Data System (ADS)

    Sepehrirahnama, Shahrokh; Chau, Fook Siong; Lim, Kian-Meng

    2015-12-01

    In this work, a numerical scheme based on multipoles and Stokeslet is proposed for calculating the radiation force acting on a single rigid sphere in a viscous fluid. First-order velocity and pressure are obtained from the multipole series solution, and the volumetric force in the acoustic streaming is subsequently calculated from the first-order velocity and pressure. The acoustic streaming equations are solved using the Stokeslet method within a finite domain descretized by tetrahedral elements. The boundary conditions for streaming are imposed using the weighted residue method to obtain the unknown coefficients in the multipole series expansion for the second-order velocity potentials. The radiation forces obtained from this multipole-Stokeslet method match well with Doinikov's series solution, for a wide range of the sphere size. Compared to the complicated series solution, the multipole-Stokeslet method can be easily implemented without the evaluation of the semi-infinite integrals.

  6. Acoustic radiation damping of flat rectangular plates subjected to subsonic flows

    NASA Technical Reports Server (NTRS)

    Lyle, Karen Heitman

    1993-01-01

    The acoustic radiation damping for various isotropic and laminated composite plates and semi-infinite strips subjected to a uniform, subsonic and steady flow has been predicted. The predictions are based on the linear vibration of a flat plate. The fluid loading is characterized as the perturbation pressure derived from the linearized Bernoulli and continuity equations. Parameters varied in the analysis include Mach number, mode number and plate size, aspect ratio and mass. The predictions are compared with existing theoretical results and experimental data. The analytical results show that the fluid loading can significantly affect realistic plate responses. Generally, graphite/epoxy and carbon/carbon plates have higher acoustic radiation damping values than similar aluminum plates, except near plate divergence conditions resulting from aeroelastic instability. Universal curves are presented where the acoustic radiation damping normalized by the mass ratio is a linear function of the reduced frequency. A separate curve is required for each Mach number and plate aspect ratio. In addition, acoustic radiation damping values can be greater than or equal to the structural component of the modal critical damping ratio (assumed as 0.01) for the higher subsonic Mach numbers. New experimental data were acquired for comparison with the analytical results.

  7. A contactless methodology of picking up micro-particles from rigid surfaces by acoustic radiation force.

    PubMed

    Jia, Kun; Yang, Keji; Fan, Zongwei; Ju, Bing-Feng

    2012-01-01

    Controlled movement and pick up of small object from a rigid surface is a primary challenge in many applications. In this paper, a contactless methodology of picking up micro-particles within deionized water from rigid surfaces by acoustic radiation force is presented. In order to achieve this, an acoustic radiation force was generated by 1.75 MHz transducers. A custom built setup facilitates the optimization of the sound field by varying the parameters such as sound source size and source position. The three-dimensional pressure distributions are measured and its relative sound field is also characterized accordingly. The standing wave field has been formed and it is mainly composed of two obliquely incident plane waves and their reflectors. We demonstrated the gripping and positioning of silica beads, SiO(2), and aluminum micro-particles of 100 μm to 500 μm in size with this method using acoustic radiation force. The acoustic radiation force generated is well controlled, contactless, and in the tens of nano-Newton range which allowed us to manipulate relative big micro objects such as MEMS components as well as moving objects such as living cells. The proposed method provided an alternative form of contactless operating environment with scalable dimensions suitable for the manipulating of small objects. This permits high-throughput processing and reduction in time required for MEMS assembling, cell biomechanics, and biotechnology applications.

  8. A contactless methodology of picking up micro-particles from rigid surfaces by acoustic radiation force

    NASA Astrophysics Data System (ADS)

    Jia, Kun; Yang, Keji; Fan, Zongwei; Ju, Bing-Feng

    2012-01-01

    Controlled movement and pick up of small object from a rigid surface is a primary challenge in many applications. In this paper, a contactless methodology of picking up micro-particles within deionized water from rigid surfaces by acoustic radiation force is presented. In order to achieve this, an acoustic radiation force was generated by 1.75 MHz transducers. A custom built setup facilitates the optimization of the sound field by varying the parameters such as sound source size and source position. The three-dimensional pressure distributions are measured and its relative sound field is also characterized accordingly. The standing wave field has been formed and it is mainly composed of two obliquely incident plane waves and their reflectors. We demonstrated the gripping and positioning of silica beads, SiO2, and aluminum micro-particles of 100 μm to 500 μm in size with this method using acoustic radiation force. The acoustic radiation force generated is well controlled, contactless, and in the tens of nano-Newton range which allowed us to manipulate relative big micro objects such as MEMS components as well as moving objects such as living cells. The proposed method provided an alternative form of contactless operating environment with scalable dimensions suitable for the manipulating of small objects. This permits high-throughput processing and reduction in time required for MEMS assembling, cell biomechanics, and biotechnology applications.

  9. Measurement of the space-time correlation function of thermal acoustic radiation

    NASA Astrophysics Data System (ADS)

    Passechnik, V. I.; Anosov, A. A.; Barabanenkov, Yu. N.; Sel'Sky, A. G.

    2003-09-01

    The space-time correlation function of thermal acoustic radiation pressure is measured for a stationary heated source (a narrow plasticine plate). The correlation dependence is obtained by the multiplication of two signals shifted in time with respect to each other and measured by two receivers. The dependence exhibits an oscillating behavior and changes sign when the source is displaced by half the spatial period of the correlation function.

  10. Tunable acoustic radiation pattern assisted by effective impedance boundary

    NASA Astrophysics Data System (ADS)

    Qian, Feng; Quan, Li; Wang, Li-Wei; Liu, Xiao-Zhou; Gong, Xiu-Fen

    2016-02-01

    The acoustic wave propagation from a two-dimensional subwavelength slit surrounded by metal plates decorated with Helmholtz resonators (HRs) is investigated both numerically and experimentally in this work. Owing to the presence of HRs, the effective impedance of metal surface boundary can be manipulated. By optimizing the distribution of HRs, the asymmetric effective impedance boundary will be obtained, which contributes to generating tunable acoustic radiation pattern such as directional acoustic beaming. These dipole-like radiation patterns have high radiation efficiency, no fingerprint of sidelobes, and a wide tunable range of the radiation pattern directivity angle which can be steered by the spatial displacements of HRs. Project supported by the National Basic Research Program of China (Grant Nos. 2012CB921504 and 2011CB707902), the National Natural Science Foundation of China (Grant No.11474160), the Fundamental Research Funds for Central Universities, China (Grant No. 020414380001), the State Key Laboratory of Acoustics, Chinese Academy of Sciences (Grant No. SKLOA201401), the Priority Academic Program Development of Jiangsu Higher Education Institutions, and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry.

  11. 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.

  12. GPS satellites: Radiation pressure, attitude and resonance

    NASA Astrophysics Data System (ADS)

    Hugentobler, U.; Ineichen, D.; Beutler, G.

    2003-04-01

    At the altitude of the CPS satellites the most important non-gravitational perturbation is caused by the solar radiation pressure acting on the satellite body and its solar panels. The development of high-fidelity radiation pressure models may be motivated by the following observation: The GPS satellites are orbiting in a 2:1-commensurability with the Earth's rotation which causes resonance. The expected sensitivity to specific coefficients of the geopotential is, however, significantly reduced by strong correlations of these parameters with radiation pressure parameters. Sophisticated radiation pressure models rely on a precise knowledge of the satellite's attitude which does not only affects the location of the antenna phase center or the phase windup of the signal carrier but, through radiation pressure, also the orbital dynamics. PRN 23, whose attitudinal behaviour was modified early in 2002 is an interesting case. Due to this change an impressive improvement in the orbit quality could be achieved.

  13. Radiation-pressure-induced nonlinearity in microdroplets.

    PubMed

    Zhang, Peng; Jung, Sunghwan; Lee, Aram; Xu, Yong

    2015-12-01

    High quality (Q) factor whispering gallery modes (WGMs) can induce nonlinear effects in liquid droplets through mechanisms such as radiation pressure, Kerr nonlinearity, and thermal effects. However, such nonlinear effects, especially those due to radiation pressure, have yet to be thoroughly investigated and compared in the literature. In this study, we present an analytical approach that can exactly calculate the droplet deformation induced by the radiation pressure. The accuracy of the analytical approach is confirmed through numerical analyses based on the boundary element method. We show that the nonlinear optofluidic effect induced by the radiation pressure is stronger than the Kerr effect and the thermal effect under a large variety of realistic conditions. Using liquids with ultralow and experimentally attainable interfacial tension, we further confirm the prediction that it may only take a few photons to produce measurable WGM resonance shift through radiation-pressure-induced droplet deformation. PMID:26764829

  14. Physics of Acoustic Radiation from Jet Engine Inlets

    NASA Technical Reports Server (NTRS)

    Tam, Christopher K. W.; Parrish, Sarah A.; Envia, Edmane; Chien, Eugene W.

    2012-01-01

    Numerical simulations of acoustic radiation from a jet engine inlet are performed using advanced computational aeroacoustics (CAA) algorithms and high-quality numerical boundary treatments. As a model of modern commercial jet engine inlets, the inlet geometry of the NASA Source Diagnostic Test (SDT) is used. Fan noise consists of tones and broadband sound. This investigation considers the radiation of tones associated with upstream propagating duct modes. The primary objective is to identify the dominant physical processes that determine the directivity of the radiated sound. Two such processes have been identified. They are acoustic diffraction and refraction. Diffraction is the natural tendency for an acoustic wave to follow a curved solid surface as it propagates. Refraction is the turning of the direction of propagation of sound waves by mean flow gradients. Parametric studies on the changes in the directivity of radiated sound due to variations in forward flight Mach number and duct mode frequency, azimuthal mode number, and radial mode number are carried out. It is found there is a significant difference in directivity for the radiation of the same duct mode from an engine inlet when operating in static condition and in forward flight. It will be shown that the large change in directivity is the result of the combined effects of diffraction and refraction.

  15. Fast Pressure-Sensitive Paint for Flow and Acoustic Diagnostics

    NASA Astrophysics Data System (ADS)

    Gregory, James W.; Sakaue, Hirotaka; Liu, Tianshu; Sullivan, John P.

    2014-01-01

    The development and capabilities of fast-responding pressure-sensitive paint (fast PSP) are reviewed within the context of recent applications to aerodynamic and acoustic investigations. PSP is an optical technique for determining surface pressure distributions by measuring changes in the intensity of emitted light, whereas fast PSP is an extension applicable to unsteady flows and acoustics. Most fast PSP formulations are based on the development of porous binders that allow for rapid oxygen diffusion and interaction with the chemical sensor. This article reviews the development of porous binders, the selection of luminophore molecules suitable for unsteady testing, dynamic calibrations of PSP, data-acquisition methods, and noteworthy applications for flow and acoustic diagnostics. Calibrations of the dynamic response of fast PSP show a flat frequency response to at least 6 kHz, with some paint formulations exceeding a response of 1 MHz. Various applications of fast PSP are discussed that highlight the capabilities of the technique, and concluding remarks highlight the need for the future development of fast PSP.

  16. Acoustic radiation from a shell with internal structures

    NASA Technical Reports Server (NTRS)

    El-Raheb, M.; Wagner, P.

    1989-01-01

    A method is developed to compute frequency response and acoustic radiation of a complex shell. The axisymmetric geometry of the shell includes cylindrical, conical, and spherical segments stiffened by discrete rings and bulkheads. The shell is coupled to internal masses and elastic frames. Shell segments are treated by transfer matrices. Rings, bulkheads, frames, and concentrated masses are treated by impedances at junctions of segments. The shell is coupled to an external acoustic fluid treated by Green's function and curved surface elements. A major issue facing the method's treatment of the fluid would be lack of existence or uniqueness encountered in the uncoupled, external acoustic problem at characteristic wavenumbers. By using a simple spherical shell, without internal structures, this potential hindrance is shown not to arise. A fuller application of the method awaits subsequent results.

  17. Measurement and Applications of Radiation Pressure

    NASA Astrophysics Data System (ADS)

    Ma, Dakang; Garrett, Joseph; Murray, Joseph; Munday, Jeremy; Munday Lab Team

    Light reflected off a material or absorbed within it exerts radiation pressure through the transfer of momentum. Measuring and utilizing radiation pressure have aroused growing interest in a wide spectrum of research fields. Micromechanical transducers and oscillators are good candidates for measuring radiation pressure, but accompanying photothermal effects often obscure the measurement. In this work, we investigate the accurate measurement of the radiation force on microcantilevers in ambient conditions and ways to separate radiation pressure and photothermal effects. Further, we investigate an optically broadband switchable device based on polymer dispersed liquid crystal which has potential applications in solar sails and maneuvering spacecraft without moving parts. The authors would like to thank NASA Early Career Faculty Award and NASA Smallsat Technology Partnership Award for their funding support.

  18. Radiation force produced by time reversal acoustic focusing system

    NASA Astrophysics Data System (ADS)

    Sarvazyan, Armen; Sutin, Alexander

    2003-10-01

    An ultrasonic induced radiation force is an efficient tool for remote probing of internal anatomical structures and evaluating tissue viscoelastic properties, which are closely related to tissue functional state and abnormalities. Time Reversal Acoustic Focusing System (TRA FS) can provide efficient ultrasound focusing in highly inhomogeneous media. Furthermore, numerous reflections from boundaries, which distort focusing in conventional ultrasound focusing systems and are viewed as a significant technical hurdle, lead to an improvement of the focusing ability of the TRA system. In this work the TRA FS field structure and radiation force in a transcranial phantom were investigated. A simple TRA FS comprising a plane piezoceramic transducer attached to an external resonator such as an aluminum block was acoustically coupled to the tested transcranial phantom. A custom-designed compact electronic unit for TRA FS provided receiving, digitizing, storing, time reversing and transmitting of acoustic signals in a wide frequency range from 0.01 to 10 MHz. The radiation force produced by ultrasonic pulses was investigated as a function of the transmitted ultrasound temporal parameters. The simplest TRA FS provided focusing of 500 kHz ultrasound pulses and the generation of a radiation force with an efficacy hardly achievable using conventional sophisticated phased array transmitters. [Work supported by NIH.

  19. Validation of acoustic-analogy predictions for sound radiated by turbulence

    NASA Astrophysics Data System (ADS)

    Whitmire, Julia; Sarkar, Sutanu

    2000-02-01

    Predicting sound radiated by turbulence is of interest in aeroacoustics, hydroacoustics, and combustion noise. Significant improvements in computer technology have renewed interest in applying numerical techniques to predict sound from turbulent flows. One such technique is a hybrid approach in which the turbulence is computed using a method such as direct numerical simulation (DNS) or large eddy simulation (LES), and the sound is calculated using an acoustic analogy. In this study, sound from a turbulent flow is computed using DNS, and the DNS results are compared with acoustic-analogy predictions for mutual validation. The source considered is a three-dimensional region of forced turbulence which has limited extent in one coordinate direction and is periodic in the other two directions. Sound propagates statistically as a plane wave from the turbulence to the far field. The cases considered here have a small turbulent Mach number so that the source is spatially compact; that is, the turbulence integral scale is much smaller than the acoustic wavelength. The scaling of the amplitude and frequency of the far-field sound for the problem considered are derived in an analysis based on Lighthill's acoustic analogy. The analytical results predict that the far-field sound should exhibit "dipole-type" behavior; the root-mean-square pressure in the acoustic far field should increase as the cube of the turbulent Mach number. The acoustic power normalized by the turbulent dissipation rate is also predicted to scale as turbulent Mach number cubed. Agreement between the DNS results and the acoustic-analogy predictions is good. This study verifies the ability of the Lighthill acoustic analogy to predict sound generated by a three-dimensional, turbulent source containing many length and time scales.

  20. On the acoustic radiation of a pitching airfoil

    NASA Astrophysics Data System (ADS)

    Manela, A.

    2013-07-01

    We examine the acoustic far field of a thin elastic airfoil, immersed in low-Mach non-uniform stream flow, and actuated by small-amplitude sinusoidal pitching motion. The near-field fluid-structure interaction problem is analyzed using potential thin-airfoil theory, combined with a discrete vortex model to describe the evolution of airfoil trailing edge wake. The leading order dipole-sound signature of the system is investigated using Powell-Howe acoustic analogy. Compared with a pitching rigid airfoil, the results demonstrate a two-fold effect of structure elasticity on airfoil acoustic field: at actuation frequencies close to the system least stable eigenfrequency, elasticity amplifies airfoil motion amplitude and associated sound levels; however, at frequencies distant from this eigenfrequency, structure elasticity acts to absorb system kinetic energy and reduce acoustic radiation. In the latter case, and with increasing pitching frequency ωp, a rigid-airfoil setup becomes significantly noisier than an elastic airfoil, owing to an ω _p^{5/2} increase of its direct motion noise component. Unlike rigid airfoil signature, it is shown that wake sound contribution to elastic airfoil radiation is significant for all ωp. Remarkably, this contribution contains, in addition to the fundamental pitching frequency, its odd multiple harmonics, which result from nonlinear interactions between the airfoil and the wake. The results suggest that structure elasticity may serve as a viable means for design of flapping flight noise control methodologies.

  1. Deformation of red blood cells using acoustic radiation forces

    PubMed Central

    Mishra, Puja; Hill, Martyn; Glynne-Jones, Peter

    2014-01-01

    Acoustic radiation forces have been used to manipulate cells and bacteria in a number of recent microfluidic applications. The net force on a cell has been subject to careful investigation over a number of decades. We demonstrate that the radiation forces also act to deform cells. An ultrasonic standing wave field is created in a 0.1 mm glass capillary at a frequency of 7.9 MHz. Using osmotically swollen red-blood cells, we show observable deformations up to an aspect ratio of 1.35, comparable to deformations created by optical tweezing. In contrast to optical technologies, ultrasonic devices are potentially capable of deforming thousands of cells simultaneously. We create a finite element model that includes both the acoustic environment of the cell, and a model of the cell membrane subject to forces resulting from the non-linear aspects of the acoustic field. The model is found to give reasonable agreement with the experimental results, and shows that the deformation is the result of variation in an acoustic force that is directed outwards at all points on the cell membrane. We foresee applications in diagnostic devices, and in the possibility of mechanically stimulating cells to promote differentiation and physiological effects. PMID:25379070

  2. GUP assisted Hawking radiation of rotating acoustic black holes

    NASA Astrophysics Data System (ADS)

    Sakalli, I.; Övgün, A.; Jusufi, K.

    2016-10-01

    Recent studies (Steinhauer in Nat. Phys. 10:864, 2014, Phys. Rev. D 92:024043, 2015) provide compelling evidences that Hawking radiation could be experimentally proven by using an analogue black hole. In this paper, taking this situation into account we study the quantum gravitational effects on the Hawking radiation of rotating acoustic black holes. For this purpose, we consider the generalized uncertainty principle (GUP) in the phenomenon of quantum tunneling. We firstly take the modified commutation relations into account to compute the GUP modified Hawking temperature when the massive scalar particles tunnel from this black hole. Then, we find a remarkably instructive expression for the GUP entropy to derive the quantum gravity corrected Hawking temperature of the rotating acoustic black hole.

  3. A 3-D elasticity theory based model for acoustic radiation from multilayered anisotropic plates.

    PubMed

    Shen, C; Xin, F X; Lu, T J

    2014-05-01

    A theoretical model built upon three-dimensional elasticity theory is developed to investigate the acoustic radiation from multilayered anisotropic plates subjected to a harmonic point force excitation. Fourier transform technique and stationary phase method are combined to predict the far-field radiated sound pressure of one-side water immersed plate. Compared to equivalent single-layer plate models, the present model based on elasticity theory can differentiate radiated sound pressure between dry-side and wet-side excited cases, as well as discrepancies induced by different layer sequences for multilayered anisotropic plates. These results highlight the superiority of the present theoretical model especially for handling multilayered anisotropic structures. PMID:24815294

  4. Modelling of acoustic radiation problems associated with turbomachinery and rotating blades

    NASA Astrophysics Data System (ADS)

    Eversman, W.

    Finite element methods developed for computational predictions of turbofan and propeller acoustic radiation are presented. Account is taken of the disparate acoustic and geometric scales, the complex geometry, sound propagation in a nonuniformly flowing medium, the presence of a lining, and definition of bounds for calculations which are carried out in an unbounded domain. Density and pressure perturbations in the turbofan inlet are modeled with a linearized momentum equation. The sound radiation is represented by the Fourier components, i.e., angular modes. The same nacelle geometry is used for propeller noise, which requires inclusion of acoustic volume sources and forces. A forced convected wave equation for harmonic driving is obtained by combining continuity, momentum and state equations linearized for acoustic perturbations. The weak formulations for the two types of noise generation are solved by the Galerkin method modified with a frontal solver to reduce the required computer time. Model predictions show good agreement with experimental data for the directivity and amplitude of sound from the bellmouth inlet of the NASA-Langley Spinning Mode Synthesizer.

  5. Earth radiation pressure effects on satellites

    NASA Technical Reports Server (NTRS)

    Knocke, P. C.; Ries, J. C.; Tapley, B. D.

    1988-01-01

    A diffuse-earth radiation force model is presented, which includes a latitudinally varying representation of the shortwave and longwave radiation of the terrestrial sphere. Applications to various earth satellites indicate that this force, in particular the shortwave component, can materially affect the recovery of estimated parameters. Earth radiation pressure cannot explain the anomalous deceleration of LAGEOS, but can produce significant along track accelerations on satellites with highly eccentric orbits. Analyses of GEOS-1 tracking data confirm this result.

  6. Pressure Drop in Radiator Air Tubes

    NASA Technical Reports Server (NTRS)

    Parsons, S R

    1921-01-01

    This report describes a method for measuring the drop in static pressure of air flowing through a radiator and shows (1) a reason for the discrepancy noted by various observers between head resistance and drop in pressure; (2) a difference in degree of contraction of the jet in entering a circular cell and a square cell; (3) the ratio of internal frictional resistance to total head resistance for two representative types; (4) the effect of smoothness of surface on pressure gradient; and (5) the effects of supplying heat to the radiator on pressure gradient. The fact that the pressure gradients are found to be approximately proportional to the square of the rate of flow of air appears to indicate turbulent flow, even in the short tubes of the radiator. It was found that the drop in the static pressure in the air stream through a cellular radiator and the pressure gradient in the air tubes are practically proportional to the square of the air flow in a given air density; that the difference between the head resistance per unit area and the fall of static pressure through the air tubes in radiators is apparent rather than real; and that radiators of different types differ widely in the amount of contraction of the jet at entrance. The frictional resistance was found to vary considerably, and in one case to be two-thirds of the head resistance in the type using circular cells and one-half of the head resistance of the radiator type using square cells of approximately the same dimensions.

  7. Transient analysis of acoustically derived pressure and rate data

    SciTech Connect

    Kabir, C.S.; Kuchuk, F.J.; Hasan, A.R.

    1988-09-01

    A pressure-buildup test conducted on a sucker-rod pumping well is often by long-duration wellbore storage. In fact, this distortion could be so severe that even a week's shut-in period may not allow a semilog analysis. A longer shut-in period becomes economically discouraging because of lost production. Low energy and low transmissivity in the reservoir, coupled with increased fluid compressibility, contribute to this long-duration storage phenomenon. One way of reducing the storage effect clearly lies in the simultaneous analysis of downhole pressure and flow rate, estimated from casinghead pressure and rising annular liquid-level measurement made by acoustic well sounding (AWS). Ascertaining the quality of the indirectly measured pressure and rate data constitutes one of the objectives of this study. Several methods exist to translate the AWS measurement to downhole pressure and rate data for the subsequent transient analysis. The authors show that even an empirical hydrodynamic correlation provides satisfactory transient-pressure/flow-rate data for convolution and deconvolution analyses for moderate pumping-liquid columns. When long annular liquid columns are encountered, translating the AWS measurement with a mechanistically based hydrodynamic model appears to be a prudent approach. Interpretation of several transient tests show that automated convolved-type-curve or history matching of field data is a powerful tool for reservoir-parameter (total mobility, skin, fracture half-length, and storage coefficient) estimation. A simple algorithm for computing the Laplace transform of the wellbore pressure for an infinite-conductivity vertically fractured well in an infinite reservoir is developed in this work for a rapid, iterative-type computation used in automated convolved-type-curve analysis.

  8. Prediction of acoustic radiation from functionally graded shells of revolution in light and heavy fluids

    NASA Astrophysics Data System (ADS)

    Qu, Yegao; Meng, Guang

    2016-08-01

    This paper presents a semi-analytical method for the vibro-acoustic analysis of a functionally graded shell of revolution immersed in an infinite light or heavy fluid. The structural model of the shell is formulated on the basis of a modified variational method combined with a multi-segment technique, whereas a spectral Kirchhoff-Helmholtz integral formulation is employed to model the exterior fluid field. The material properties of the shell are estimated by using the Voigt's rule of mixture and the Mori-Tanaka's homogenization scheme. Displacement and sound pressure variables of each segment are expanded in the form of a mixed series using Fourier series and Chebyshev orthogonal polynomials. A set of collocation nodes distributed over the roots of Chebyshev polynomials are employed to establish the algebraic system of the acoustic integral equations, and the non-uniqueness solution is eliminated using a combined Helmholtz integral equation formulation. Loosely and strongly coupled schemes are implemented for the structure-acoustic interaction problem of a functionally graded shell immersed in a light and heavy fluid, respectively. The present method provides a flexible way to account for the individual contributions of circumferential wave modes to the vibration and acoustic responses of functionally graded shells of revolution in an analytical manner. Numerical tests are presented for sound radiation problems of spherical, cylindrical, conical and coupled shells. The individual contributions of the circumferential modes to the radiated sound pressure and sound power of functionally graded shells are observed. Effects of the material profile on the sound radiation of the shells are also investigated.

  9. 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.

  10. Application of the Spectral Element Method to Acoustic Radiation

    NASA Technical Reports Server (NTRS)

    Doyle, James F.; Rizzi, Stephen A. (Technical Monitor)

    2000-01-01

    This report summarizes research to develop a capability for analysis of interior noise in enclosed structures when acoustically excited by an external random source. Of particular interest was the application to the study of noise and vibration transmission in thin-walled structures as typified by aircraft fuselages. Three related topics are focused upon. The first concerns the development of a curved frame spectral element, the second shows how the spectral element method for wave propagation in folded plate structures is extended to problems involving curved segmented plates. These are of significance because by combining these curved spectral elements with previously presented flat spectral elements, the dynamic response of geometrically complex structures can be determined. The third topic shows how spectral elements, which incorporate the effect of fluid loading on the structure, are developed for analyzing acoustic radiation from dynamically loaded extended plates.

  11. Acoustic Radiation Force on a Finite-Sized Particle due to an Acoustic Field in a Viscous Compressible Fluid

    NASA Astrophysics Data System (ADS)

    Annamalai, Subramanian; Parmar, Manoj; Balachandar, S.

    2013-11-01

    Particles when subjected to acoustic waves experience a time-averaged second-order force known as the acoustic radiation force, which is of prime importance in the fields of microfluidics and acoustic levitation. Here, the acoustic radiation force on a rigid spherical particle in a viscous compressible medium due to progressive and standing waves is considered. The relevant length scales include: particle radius (a), acoustic wavelength (λ) and viscous penetration depth (δ). While a / λ and a / δ are arbitrary, δ << λ . A farfield derivation approach has been used in determining the radiated force. Expressing the flow-field as a sum of the incident and scattered fields, an analytical expression for the force is obtained as a summation over infinite series (monopole, dipole and higher sources). These results indicate that the contributions from monopole, dipole and their cross-interaction are sufficient to describe the acoustic radiation force. Subsequently, the monopole and dipole strengths are represented in terms of the particle surface and volume averages of the incoming velocity. This generalization allows one to evaluate the radiation force for an incoming wave of any functional form. However acoustic streaming effects are neglected.

  12. Active control of acoustic pressure fields using smart material technologies

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Smith, R. C.

    1993-01-01

    An overview describing the use of piezoceramic patches in reducing noise in a structural acoustics setting is presented. The passive and active contributions due to patches which are bonded to an Euler-Bernoulli beam or thin shell are briefly discussed and the results are incorporated into a 2-D structural acoustics model. In this model, an exterior noise source causes structural vibrations which in turn lead to interior noise as a result of nonlinear fluid/structure coupling mechanism. Interior sound pressure levels are reduced via patches bonded to the flexible boundary (a beam in this case) which generate pure bending moments when an out-of-phase voltage is applied. Well-posedness results for the infinite dimensional system are discussed and a Galerkin scheme for approximating the system dynamics is outlined. Control is implemented by using linear quadratic regulator (LQR) optimal control theory to calculate gains for the linearized system and then feeding these gains back into the nonlinear system of interest. The effectiveness of this strategy for this problem is illustrated in an example.

  13. Systems and methods of monitoring acoustic pressure to detect a flame condition in a gas turbine

    DOEpatents

    Ziminsky, Willy Steve; Krull, Anthony Wayne; Healy, Timothy Andrew , Yilmaz, Ertan

    2011-05-17

    A method may detect a flashback condition in a fuel nozzle of a combustor. The method may include obtaining a current acoustic pressure signal from the combustor, analyzing the current acoustic pressure signal to determine current operating frequency information for the combustor, and indicating that the flashback condition exists based at least in part on the current operating frequency information.

  14. Combining COMSOL modeling with acoustic pressure maps to design sono-reactors.

    PubMed

    Wei, Zongsu; Weavers, Linda K

    2016-07-01

    Scaled-up and economically viable sonochemical systems are critical for increased use of ultrasound in environmental and chemical processing applications. In this study, computational simulations and acoustic pressure maps were used to design a larger-scale sono-reactor containing a multi-stepped ultrasonic horn. Simulations in COMSOL Multiphysics showed ultrasonic waves emitted from the horn neck and tip, generating multiple regions of high acoustic pressure. The volume of these regions surrounding the horn neck were larger compared with those below the horn tip. The simulated acoustic field was verified by acoustic pressure contour maps generated from hydrophone measurements in a plexiglass box filled with water. These acoustic pressure contour maps revealed an asymmetric and discrete distribution of acoustic pressure due to acoustic cavitation, wave interaction, and water movement by ultrasonic irradiation. The acoustic pressure contour maps were consistent with simulation results in terms of the effective scale of cavitation zones (∼ 10 cm and <5 cm above and below horn tip, respectively). With the mapped acoustic field and identified cavitation location, a cylindrically-shaped sono-reactor with a conical bottom was designed to evaluate the treatment capacity (∼ 5 L) for the multi-stepped horn using COMSOL simulations. In this study, verification of simulation results with experiments demonstrates that coupling of COMSOL simulations with hydrophone measurements is a simple, effective and reliable scientific method to evaluate reactor designs of ultrasonic systems. PMID:26964976

  15. Oscillations of radiation pressure supported tori near black holes

    NASA Astrophysics Data System (ADS)

    Mazur, Grzegorz P.; Zanotti, Olindo; Sądowski, Aleksander; Mishra, Bhupendra; Kluźniak, Wlodek

    2016-03-01

    We study the dynamics of radiation pressure supported tori around Schwarzschild black holes, focusing on their oscillatory response to an external perturbation. Using KORAL, a general relativistic radiation-hydrodynamics code capable of modelling all radiative regimes from the optically thick to the optically thin, we monitor a sample of models at different initial temperatures and opacities, evolving them in two spatial dimensions for ˜165 orbital periods. The dynamics of models with high opacity is very similar to that of purely hydrodynamics models, and it is characterized by regular oscillations which are visible also in the light curves. As the opacity is decreased, the tori quickly and violently migrate towards the gas-pressure dominated regime, collapsing towards the equatorial plane. When the spectra of the L2 norm of the mass density are considered, high-frequency inertial-acoustic modes of oscillations are detected (with the fundamental mode at a frequency 68 M_BH^{-1} Hz), in close analogy to the phenomenology of purely hydrodynamic models. An additional mode of oscillation, at a frequency 129 M_BH^{-1} Hz, is also found, which can be unambiguously attributed to the radiation. The spectra extracted from the light curves are typically noisier, indicating that in a real observation such modes may not be easily detected.

  16. Nonlinear aspects of acoustic radiation force in biomedical applications

    SciTech Connect

    Ostrovsky, Lev; Tsyuryupa, Sergey; Sarvazyan, Armen

    2015-10-28

    In the past decade acoustic radiation force (ARF) became a powerful tool in numerous biomedical applications. ARF from a focused ultrasound beam acts as a virtual “finger” for remote probing of internal anatomical structures and obtaining diagnostic information. This presentation deals with generation of shear waves by nonlinear focused beams. Albeit the ARF has intrinsically nonlinear origin, in most cases the primary ultrasonic wave was considered in the linear approximation. In this presentation, we consider the effects of nonlinearly distorted beams on generation of shear waves by such beams.

  17. Enhanced acoustic sensing through wave compression and pressure amplification in anisotropic metamaterials

    NASA Astrophysics Data System (ADS)

    Chen, Yongyao; Liu, Haijun; Reilly, Michael; Bae, Hyungdae; Yu, Miao

    2014-10-01

    Acoustic sensors play an important role in many areas, such as homeland security, navigation, communication, health care and industry. However, the fundamental pressure detection limit hinders the performance of current acoustic sensing technologies. Here, through analytical, numerical and experimental studies, we show that anisotropic acoustic metamaterials can be designed to have strong wave compression effect that renders direct amplification of pressure fields in metamaterials. This enables a sensing mechanism that can help overcome the detection limit of conventional acoustic sensing systems. We further demonstrate a metamaterial-enhanced acoustic sensing system that achieves more than 20 dB signal-to-noise enhancement (over an order of magnitude enhancement in detection limit). With this system, weak acoustic pulse signals overwhelmed by the noise are successfully recovered. This work opens up new vistas for the development of metamaterial-based acoustic sensors with improved performance and functionalities that are highly desirable for many applications.

  18. Near and Far Field Acoustic Pressure Skewness in a Heated Supersonic Jet

    NASA Astrophysics Data System (ADS)

    Gutmark, Ephraim; Mora, Pablo; Kastner, Jeff; Heeb, Nick; Kailasanath, Kailas; Liu, Junhui; University of Cincinnati Collaboration; Naval Research Laboratory Collaboration

    2012-11-01

    The dominant component of turbulent mixing noise in high speed jets is the Mach wave radiation generated by large turbulent structures in the shear layer The Over-All Sound Pressure Level (OASPL) in the far field peaks in a direction near the Mach wave angle. ``Crackle'' is another important component of high speed jet noise. Crackle cannot be recognized in the spectrum of the acoustic pressure signal, but it appears in the temporal waveform of the pressure as sharply rising peaks. Skewness levels of the pressure and dP/dt have been used as a measure of crackle in high specific thrust engines and rockets. In this paper, we focus on recognizing a technique that identifies the impact of different test conditions on the near-field and far-field statistics of the pressure and dP/dt signals of a supersonic jet with a design Mach number of Md=1.5 produced by a C-D conical nozzle. Cold and hot jets, T0=300K and 600K, are tested at over, design, and under-expanded conditions, with NPRs=2.5, 3.671, 4.5, respectively. Second, Third and Forth order statistics are examined in the near and far fields. Rms, skewness and kurtosis intensity levels and propagation are better identified in the dP/dt than in the pressure signal. Statistics of the dP/dt demonstrate to be a better measure for crackle. Project funded by ONR grant.

  19. Study on demodulated signal distribution and acoustic pressure phase sensitivity of a self-interfered distributed acoustic sensing system

    NASA Astrophysics Data System (ADS)

    Shang, Ying; Yang, Yuan-Hong; Wang, Chen; Liu, Xiao-Hui; Wang, Chang; Peng, Gang-Ding

    2016-06-01

    We propose a demodulated signal distribution theory for a self-interfered distributed acoustic sensing system. The distribution region of Rayleigh backscattering including the acoustic sensing signal in the sensing fiber is investigated theoretically under different combinations of both the path difference and pulse width Additionally we determine the optimal solution between the path difference and pulse width to obtain the maximum phase change per unit length. We experimentally test this theory and realize a good acoustic pressure phase sensitivity of  -150 dB re rad/(μPa·m) of fiber in the frequency range from 200 Hz to 1 kHz.

  20. An efficient model for coupling structural vibrations with acoustic radiation

    NASA Technical Reports Server (NTRS)

    Frendi, Abdelkader; Maestrello, Lucio; Ting, LU

    1993-01-01

    The scattering of an incident wave by a flexible panel is studied. The panel vibration is governed by the nonlinear plate equations while the loading on the panel, which is the pressure difference across the panel, depends on the reflected and transmitted waves. Two models are used to calculate this structural-acoustic interaction problem. One solves the three dimensional nonlinear Euler equations for the flow-field coupled with the plate equations (the fully coupled model). The second uses the linear wave equation for the acoustic field and expresses the load as a double integral involving the panel oscillation (the decoupled model). The panel oscillation governed by a system of integro-differential equations is solved numerically and the acoustic field is then defined by an explicit formula. Numerical results are obtained using the two models for linear and nonlinear panel vibrations. The predictions given by these two models are in good agreement but the computational time needed for the 'fully coupled model' is 60 times longer than that for 'the decoupled model'.

  1. ISS Radiation Shielding and Acoustic Simulation Using an Immersive Environment

    NASA Technical Reports Server (NTRS)

    Verhage, Joshua E.; Sandridge, Chris A.; Qualls, Garry D.; Rizzi, Stephen A.

    2002-01-01

    The International Space Station Environment Simulator (ISSES) is a virtual reality application that uses high-performance computing, graphics, and audio rendering to simulate the radiation and acoustic environments of the International Space Station (ISS). This CAVE application allows the user to maneuver to different locations inside or outside of the ISS and interactively compute and display the radiation dose at a point. The directional dose data is displayed as a color-mapped sphere that indicates the relative levels of radiation from all directions about the center of the sphere. The noise environment is rendered in real time over headphones or speakers and includes non-spatial background noise, such as air-handling equipment, and spatial sounds associated with specific equipment racks, such as compressors or fans. Changes can be made to equipment rack locations that produce changes in both the radiation shielding and system noise. The ISSES application allows for interactive investigation and collaborative trade studies between radiation shielding and noise for crew safety and comfort.

  2. Acoustic Radiation Optimization Using the Particle Swarm Optimization Algorithm

    NASA Astrophysics Data System (ADS)

    Jeon, Jin-Young; Okuma, Masaaki

    The present paper describes a fundamental study on structural bending design to reduce noise using a new evolutionary population-based heuristic algorithm called the particle swarm optimization algorithm (PSOA). The particle swarm optimization algorithm is a parallel evolutionary computation technique proposed by Kennedy and Eberhart in 1995. This algorithm is based on the social behavior models for bird flocking, fish schooling and other models investigated by zoologists. Optimal structural design problems to reduce noise are highly nonlinear, so that most conventional methods are difficult to apply. The present paper investigates the applicability of PSOA to such problems. Optimal bending design of a vibrating plate using PSOA is performed in order to minimize noise radiation. PSOA can be effectively applied to such nonlinear acoustic radiation optimization.

  3. Resonances, radiation pressure and optical scattering phenomena of drops and bubbles

    NASA Technical Reports Server (NTRS)

    Marston, P. L.; Goosby, S. G.; Langley, D. S.; Loporto-Arione, S. E.

    1982-01-01

    Acoustic levitation and the response of fluid spheres to spherical harmonic projections of the radiation pressure are described. Simplified discussions of the projections are given. A relationship between the tangential radiation stress and the Konstantinov effect is introduced and fundamental streaming patterns for drops are predicted. Experiments on the forced shape oscillation of drops are described and photographs of drop fission are displayed. Photographs of critical angle and glory scattering by bubbles and rainbow scattering by drops are displayed.

  4. Theoretical models for duct acoustic propagation and radiation

    NASA Technical Reports Server (NTRS)

    Eversman, Walter

    1991-01-01

    The development of computational methods in acoustics has led to the introduction of analysis and design procedures which model the turbofan inlet as a coupled system, simultaneously modeling propagation and radiation in the presence of realistic internal and external flows. Such models are generally large, require substantial computer speed and capacity, and can be expected to be used in the final design stages, with the simpler models being used in the early design iterations. Emphasis is given to practical modeling methods that have been applied to the acoustical design problem in turbofan engines. The mathematical model is established and the simplest case of propagation in a duct with hard walls is solved to introduce concepts and terminologies. An extensive overview is given of methods for the calculation of attenuation in uniform ducts with uniform flow and with shear flow. Subsequent sections deal with numerical techniques which provide an integrated representation of duct propagation and near- and far-field radiation for realistic geometries and flight conditions.

  5. Effects of Non-Homogeneities on the Eigenmodes of Acoustic Pressure in Combustion Chambers

    NASA Astrophysics Data System (ADS)

    Kim, J. S.; Williams, F. A.

    1998-02-01

    Modifications to acoustic eigenmodes in combustion chambers such as those of liquid propellant rocket engines, produced by spatial variations of density and sound speed that arise mainly through progress of combustion processes, are analyzed by using a variational method. The variational principle shows that the eigenvalue is the ratio of a weighted acoustic kinetic energy to a weighted acoustic potential energy, and the eigenfunction is the minimizing function of this ratio. A sample calculation is made for the case in which variations of the properties occur dominantly in the longitudinal direction, with lower temperatures and higher densities prevailing near the injector. The results of the calculation exhibit two major characteristics: the longitudinal density variation aids transfer of acoustic kinetic energy from a lower mode to the adjacent higher mode, so that the pure transverse modes have substantially larger reductions (sometimes exceeding 50%) of their eigenvalues than the combined modes; and variations of the acoustic pressure gradients are found to be larger in high-density regions, so that the acoustic pressure amplitude for purely tangential modes is found to be much higher near the injector than near the nozzle. The higher head acoustic pressure may contribute to the greater sensitivity of acoustic instability to characteristics of the flames near the injectors, as commonly found in engine tests. The improved acoustic eigensolutions can also be helpful in sizing damping devices, such as baffles or acoustic liners.

  6. Predicting burst pressures in filament-wound composite pressure vessels by using acoustic emission data

    NASA Astrophysics Data System (ADS)

    Hill, Eric V. K.

    1992-12-01

    Multivariate statistical analysis was used to generate equations for predicting burst pressures in 14.6 cm dia. fiberglass-epoxy and 45.7 cm dia. graphite-epoxy pressure vessels from acoustic emission (AE) data taken during hydroproof. Using the AE energy and amplitude measurements as the primary independent variables, the less accurate of the two linear equations was able to predict burst pressures to within +/- 0.841 MPa of the value given by the 95 percent prediction interval. Moreover, this equation included the effects of two bottles that contained simulated manufacturing defects. Because the AE data used to generate the burst-pressure equations were both taken at or below 25 percent of the expected burst pressures, it is anticipated that by using this approach, it would be possible to lower proof pressures in larger filament-wound composite pressure vessels such as rocket motor cases. This would minimize hydroproof damage to the composite structure and the accompanying potential for premature failure in service.

  7. Acoustic black holes: massless scalar field analytic solutions and analogue Hawking radiation

    NASA Astrophysics Data System (ADS)

    Vieira, H. S.; Bezerra, V. B.

    2016-07-01

    We obtain the analytic solutions of the radial part of the massless Klein-Gordon equation in the spacetime of both three dimensional rotating and four dimensional canonical acoustic black holes, which are given in terms of the confluent Heun functions. From these solutions, we obtain the scalar waves near the acoustic horizon. We discuss the analogue Hawking radiation of massless scalar particles and the features of the spectrum associated with the radiation emitted by these acoustic black holes.

  8. Radiative Amplification of Acoustic Waves in Hot Stars

    NASA Technical Reports Server (NTRS)

    Wolf, B. E.

    1985-01-01

    The discovery of broad P Cygni profiles in early type stars and the detection of X-rays emitted from the envelopes of these stars made it clear, that a considerable amount of mechanical energy has to be present in massive stars. An attack on the problem, which has proven successful when applied to late type stars is proposed. It is possible that acoustic waves form out of random fluctuations, amplify by absorbing momentum from stellar radiation field, steepen into shock waves and dissipate. A stellar atmosphere was constructed, and sinusoidal small amplitude perturbations of specified Mach number and period at the inner boundary was introduced. The partial differential equations of hydrodynamics and the equations of radiation transfer for grey matter were solved numerically. The equation of motion was augmented by a term which describes the absorption of momentum from the radiation field in the continuum and in lines, including the Doppler effect and allows for the treatment of a large number of lines in the radiative acceleration term.

  9. Shear-layer acoustic radiation in an excited subsonic jet: experimental study

    NASA Astrophysics Data System (ADS)

    Fleury, Vincent; Bailly, Christophe; Juvé, Daniel

    2005-10-01

    The subharmonic acoustic radiation of a tone excited subsonic jet shear-layer has been investigated experimentally. Two jet velocities U=20 mṡs and U=40 mṡs were studied. For U=20 mṡs, the natural boundary-layer at the nozzle exit is laminar. When the perturbation is applied, the fluctuations of the first and the second subharmonics of the excitation frequency are detected in the shear-layer. In addition, the first subharmonic near pressure field along the spreading jet is constituted of two strong maxima of sinusoidal shape. The far-field directivity pattern displays two lobes separated by an extinction angle θ at around 85° from the jet axis. These observations follow the results of Bridges about the vortex pairing noise. On the other hand, for U=40 mṡs, the initial boundary-layer is transitional and only the first subharmonic is observed in the presence of the excitation. The near pressure field is of Gaussian shape in the jet periphery and the acoustic far-field is superdirective as observed by Laufer and Yen. The state of the initial shear-layer seems to be the key feature to distinguish these two different radiation patterns. To cite this article: V. Fleury et al., C. R. Mecanique 333 (2005).

  10. Experimental verification of theoretical equations for acoustic radiation force on compressible spherical particles in traveling waves

    NASA Astrophysics Data System (ADS)

    Johnson, Kennita A.; Vormohr, Hannah R.; Doinikov, Alexander A.; Bouakaz, Ayache; Shields, C. Wyatt; López, Gabriel P.; Dayton, Paul A.

    2016-05-01

    Acoustophoresis uses acoustic radiation force to remotely manipulate particles suspended in a host fluid for many scientific, technological, and medical applications, such as acoustic levitation, acoustic coagulation, contrast ultrasound imaging, ultrasound-assisted drug delivery, etc. To estimate the magnitude of acoustic radiation forces, equations derived for an inviscid host fluid are commonly used. However, there are theoretical predictions that, in the case of a traveling wave, viscous effects can dramatically change the magnitude of acoustic radiation forces, which make the equations obtained for an inviscid host fluid invalid for proper estimation of acoustic radiation forces. To date, experimental verification of these predictions has not been published. Experimental measurements of viscous effects on acoustic radiation forces in a traveling wave were conducted using a confocal optical and acoustic system and values were compared with available theories. Our results show that, even in a low-viscosity fluid such as water, the magnitude of acoustic radiation forces is increased manyfold by viscous effects in comparison with what follows from the equations derived for an inviscid fluid.

  11. Experimental verification of theoretical equations for acoustic radiation force on compressible spherical particles in traveling waves.

    PubMed

    Johnson, Kennita A; Vormohr, Hannah R; Doinikov, Alexander A; Bouakaz, Ayache; Shields, C Wyatt; López, Gabriel P; Dayton, Paul A

    2016-05-01

    Acoustophoresis uses acoustic radiation force to remotely manipulate particles suspended in a host fluid for many scientific, technological, and medical applications, such as acoustic levitation, acoustic coagulation, contrast ultrasound imaging, ultrasound-assisted drug delivery, etc. To estimate the magnitude of acoustic radiation forces, equations derived for an inviscid host fluid are commonly used. However, there are theoretical predictions that, in the case of a traveling wave, viscous effects can dramatically change the magnitude of acoustic radiation forces, which make the equations obtained for an inviscid host fluid invalid for proper estimation of acoustic radiation forces. To date, experimental verification of these predictions has not been published. Experimental measurements of viscous effects on acoustic radiation forces in a traveling wave were conducted using a confocal optical and acoustic system and values were compared with available theories. Our results show that, even in a low-viscosity fluid such as water, the magnitude of acoustic radiation forces is increased manyfold by viscous effects in comparison with what follows from the equations derived for an inviscid fluid. PMID:27300980

  12. Effect of Pressure Gradients on Plate Response and Radiation in a Supersonic Turbulent Boundary Layer

    NASA Technical Reports Server (NTRS)

    Frendi, Abdelkader

    1997-01-01

    Using the model developed by the author for zero-pressure gradient turbulent boundary layers, results are obtained for adverse and favorable pressure gradients. It is shown that when a flexible plate is located in an adverse pressure gradient area, it vibrates more than if it were in a favorable pressure gradient one. Therefore the noise generated by the plate in an adverse pressure gradient is much greater than that due to the plate in a favorable pressure gradient. The effects of Reynolds number and boundary layer thickness are also analyzed and found to have the same effect in both adverse and favorable pressure gradient cases. Increasing the Reynolds number is found to increase the loading on the plate and therefore acoustic radiation. An increase in boundary layer thickness is found to decrease the level of the high frequencies and therefore the response and radiation at these frequencies. The results are in good qualitative agreement with experimental measurements.

  13. Instability of sonoluminescing bubbles under a nonspherical symmetrical acoustic-pressure perturbation.

    PubMed

    An, Yu; Lu, Tao; Yang, Bing

    2005-02-01

    The perturbation of nonspherical symmetrical acoustic pressure is added to the equation governing the spherical stability of sonoluminescing bubbles. The numerical calculations of the shape instability of sonoluminescing bubbles with the modified equation are conducted and the results are illustrated accordingly in the p(a) - R0 phase diagrams. The calculated results indicate that the stability region vanishes as the amplitude of the driving acoustic pressure p(a) arrives at the upper threshold ( approximately 1.6 atm) due to the perturbation of a small nonspherical symmetrical acoustic pressure (about a few Pa), which is in consistence with the experimental observations.

  14. Neural Network Burst Pressure Prediction in Graphite/Epoxy Pressure Vessels from Acoustic Emission Amplitude Data

    NASA Technical Reports Server (NTRS)

    Hill, Eric v. K.; Walker, James L., II; Rowell, Ginger H.

    1995-01-01

    Acoustic emission (AE) data were taken during hydroproof for three sets of ASTM standard 5.75 inch diameter filament wound graphite/epoxy bottles. All three sets of bottles had the same design and were wound from the same graphite fiber; the only difference was in the epoxies used. Two of the epoxies had similar mechanical properties, and because the acoustic properties of materials are a function of their stiffnesses, it was thought that the AE data from the two sets might also be similar; however, this was not the case. Therefore, the three resin types were categorized using dummy variables, which allowed the prediction of burst pressures all three sets of bottles using a single neural network. Three bottles from each set were used to train the network. The resin category, the AE amplitude distribution data taken up to 25 % of the expected burst pressure, and the actual burst pressures were used as inputs. Architecturally, the network consisted of a forty-three neuron input layer (a single categorical variable defining the resin type plus forty-two continuous variables for the AE amplitude frequencies), a fifteen neuron hidden layer for mapping, and a single output neuron for burst pressure prediction. The network trained on all three bottle sets was able to predict burst pressures in the remaining bottles with a worst case error of + 6.59%, slightly greater than the desired goal of + 5%. This larger than desired error was due to poor resolution in the amplitude data for the third bottle set. When the third set of bottles was eliminated from consideration, only four hidden layer neurons were necessary to generate a worst case prediction error of - 3.43%, well within the desired goal.

  15. Considerations for acoustic emission monitoring of spherical Kevlar/epoxy composite pressure vessels

    NASA Technical Reports Server (NTRS)

    Hamstad, M. A.; Patterson, R. G.

    1977-01-01

    We are continuing to research the applications of acoustic emission testing for predicting burst pressure of filament-wound Kevlar 49/epoxy pressure vessels. This study has focused on three specific areas. The first area involves development of an experimental technique and the proper instrumentation to measure the energy given off by the acoustic emission transducer per acoustic emission burst. The second area concerns the design of a test fixture in which to mount the composite vessel so that the acoustic emission transducers are held against the outer surface of the composite. Included in this study area is the calibration of the entire test setup including couplant, transducer, electronics, and the instrument measuring the energy per burst. In the third and final area of this study, we consider the number, location, and sensitivity of the acoustic emission transducers used for proof testing composite pressure vessels.

  16. Optimization of Acoustic Pressure Measurements for Impedance Eduction

    NASA Technical Reports Server (NTRS)

    Jones, M. G.; Watson, W. R.; Nark, D. M.

    2007-01-01

    As noise constraints become increasingly stringent, there is continued emphasis on the development of improved acoustic liner concepts to reduce the amount of fan noise radiated to communities surrounding airports. As a result, multiple analytical prediction tools and experimental rigs have been developed by industry and academia to support liner evaluation. NASA Langley has also placed considerable effort in this area over the last three decades. More recently, a finite element code (Q3D) based on a quasi-3D implementation of the convected Helmholtz equation has been combined with measured data acquired in the Langley Grazing Incidence Tube (GIT) to reduce liner impedance in the presence of grazing flow. A new Curved Duct Test Rig (CDTR) has also been developed to allow evaluation of liners in the presence of grazing flow and controlled, higher-order modes, with straight and curved waveguides. Upgraded versions of each of these two test rigs are expected to begin operation by early 2008. The Grazing Flow Impedance Tube (GFIT) will replace the GIT, and additional capabilities will be incorporated into the CDTR. The current investigation uses the Q3D finite element code to evaluate some of the key capabilities of these two test rigs. First, the Q3D code is used to evaluate the microphone distribution designed for the GFIT. Liners ranging in length from 51 to 610 mm are investigated to determine whether acceptable impedance eduction can be achieved with microphones placed on the wall opposite the liner. This analysis indicates the best results are achieved for liner lengths of at least 203 mm. Next, the effects of moving this GFIT microphone array to the wall adjacent to the liner are evaluated, and acceptable results are achieved if the microphones are placed off the centerline. Finally, the code is used to investigate potential microphone placements in the CDTR rigid wall adjacent to the wall containing an acoustic liner, to determine if sufficient fidelity can be

  17. Computation of Generalized Modal Loads in an Acoustic Field Defined by a Distribution of Correlated Pressures

    NASA Technical Reports Server (NTRS)

    Sepcenko, Valentin

    1989-01-01

    This report is an aid to designers of structures with large area-to-mass ratios that are subject to high acoustic pressures during rocket launches. A means is provided for determining generalized modal loads using AJ-coefficients. AJ-coefficients are a measure of a vibroacoustic coupling between the structure and the acoustic field.

  18. Effects of viscosity and acoustic streaming on the interparticle radiation force between rigid spheres in a standing wave

    NASA Astrophysics Data System (ADS)

    Sepehrirahnama, Shahrokh; Chau, Fook Siong; Lim, Kian-Meng

    2016-02-01

    The total acoustic radiation force acting on interacting spheres in a viscous fluid consists of the primary and secondary forces. The primary force pushes rigid spheres to the pressure node due to the incident standing wave. The secondary force is the interparticle force caused by the interaction between spheres in the standing wave. In this study, an algorithm based on the multipole series expansion and Stokeslet method is proposed for calculating the primary and secondary radiation forces acting on a pair of spheres in a viscous fluid. It is concluded that the acoustical interaction between a pair of spheres is considerably stronger in a viscous fluid compared to the inviscid case due to the streaming effects in the viscous fluid. For spheres located far from each other, the interaction becomes considerably weak; thus, the spheres move mainly due to the primary radiation force.

  19. Acoustic wavefield and Mach wave radiation of flashing arcs in strombolian explosion measured by image luminance

    NASA Astrophysics Data System (ADS)

    Genco, Riccardo; Ripepe, Maurizio; Marchetti, Emanuele; Bonadonna, Costanza; Biass, Sebastien

    2014-10-01

    Explosive activity often generates visible flashing arcs in the volcanic plume considered as the evidence of the shock-front propagation induced by supersonic dynamics. High-speed image processing is used to visualize the pressure wavefield associated with flashing arcs observed in strombolian explosions. Image luminance is converted in virtual acoustic signal compatible with the signal recorded by pressure transducer. Luminance variations are moving with a spherical front at a 344.7 m/s velocity. Flashing arcs travel at the sound speed already 14 m above the vent and are not necessarily the evidence of a supersonic explosive dynamics. However, seconds later, the velocity of small fragments increases, and the spherical acousto-luminance wavefront becomes planar recalling the Mach wave radiation generated by large scale turbulence in high-speed jet. This planar wavefront forms a Mach angle of 55° with the explosive jet axis, suggesting an explosive dynamics moving at Mo = 1.22 Mach number.

  20. Structural acoustics model of the violin radiativity profile.

    PubMed

    Bissinger, George

    2008-12-01

    Violin radiativity profiles are dominated by the Helmholtz-like A0 cavity mode ( approximately 280 Hz), first corpus bending modes B1(-) and B1(+) ( approximately 500 Hz), and BH and bridge-filter peaks ( approximately 2.4 kHz and approximately 3.5 kHz, respectively), with falloff above approximately 4 kHz. The B1 modes-dependent on two low-lying free-plate modes--are proposed to excite A0 via coupling to B1-driven in-phase f-hole volume flows. VIOCADEAS data show that A0 radiativity increases primarily as A0-B1(-) frequency difference decreases, consistent with Meinel's 1937 experiment for too-thick/too-thin plate thicknesses, plus sound post removal and violin octet baritone results. The vibration-->acoustic energy filter, F(RAD), computed from shape-material-independent radiation and total damping, peaks at the critical frequency f(crit), estimated from a free-plate mode by analogy to flat-plate bending. Experimentally, f(crit) decreased as this plate mode (and B1(+)) frequency increased. Simulations show that increasing plate thicknesses lowers f(crit), reduces F(RAD), and moves the spectral balance toward lower frequencies. Incorporating string-->corpus filters (including bridge versus bridge-island impedances) provides a model for overall violin radiativity. This model-with B1 and A0-B1 couplings, and f(crit) (computed from a free-plate mode important to B1) strongly affecting the lowest and highest parts of the radiativity profile-substantiates prior empirical B1--sound quality linkages. PMID:19206824

  1. Structural acoustics model of the violin radiativity profile.

    PubMed

    Bissinger, George

    2008-12-01

    Violin radiativity profiles are dominated by the Helmholtz-like A0 cavity mode ( approximately 280 Hz), first corpus bending modes B1(-) and B1(+) ( approximately 500 Hz), and BH and bridge-filter peaks ( approximately 2.4 kHz and approximately 3.5 kHz, respectively), with falloff above approximately 4 kHz. The B1 modes-dependent on two low-lying free-plate modes--are proposed to excite A0 via coupling to B1-driven in-phase f-hole volume flows. VIOCADEAS data show that A0 radiativity increases primarily as A0-B1(-) frequency difference decreases, consistent with Meinel's 1937 experiment for too-thick/too-thin plate thicknesses, plus sound post removal and violin octet baritone results. The vibration-->acoustic energy filter, F(RAD), computed from shape-material-independent radiation and total damping, peaks at the critical frequency f(crit), estimated from a free-plate mode by analogy to flat-plate bending. Experimentally, f(crit) decreased as this plate mode (and B1(+)) frequency increased. Simulations show that increasing plate thicknesses lowers f(crit), reduces F(RAD), and moves the spectral balance toward lower frequencies. Incorporating string-->corpus filters (including bridge versus bridge-island impedances) provides a model for overall violin radiativity. This model-with B1 and A0-B1 couplings, and f(crit) (computed from a free-plate mode important to B1) strongly affecting the lowest and highest parts of the radiativity profile-substantiates prior empirical B1--sound quality linkages.

  2. Experimental study of acoustic radiation force of an ultrasound beam on absorbing and scattering objects

    SciTech Connect

    Nikolaeva, Anastasiia V. Kryzhanovsky, Maxim A.; Tsysar, Sergey A.; Kreider, Wayne; Sapozhnikov, Oleg A.

    2015-10-28

    Acoustic radiation force is a nonlinear acoustic effect caused by the transfer of wave momentum to absorbing or scattering objects. This phenomenon is exploited in modern ultrasound metrology for measurement of the acoustic power radiated by a source and is used for both therapeutic and diagnostic sources in medical applications. To calculate radiation force an acoustic hologram can be used in conjunction with analytical expressions based on the angular spectrum of the measured field. The results of an experimental investigation of radiation forces in two different cases are presented in this paper. In one case, the radiation force of an obliquely incident ultrasound beam on a large absorber (which completely absorbs the beam) is considered. The second case concerns measurement of the radiation force on a spherical target that is small compared to the beam diameter.

  3. Experimental study of acoustic radiation force of an ultrasound beam on absorbing and scattering objects

    NASA Astrophysics Data System (ADS)

    Nikolaeva, Anastasiia V.; Kryzhanovsky, Maxim A.; Tsysar, Sergey A.; Kreider, Wayne; Sapozhnikov, Oleg A.

    2015-10-01

    Acoustic radiation force is a nonlinear acoustic effect caused by the transfer of wave momentum to absorbing or scattering objects. This phenomenon is exploited in modern ultrasound metrology for measurement of the acoustic power radiated by a source and is used for both therapeutic and diagnostic sources in medical applications. To calculate radiation force an acoustic hologram can be used in conjunction with analytical expressions based on the angular spectrum of the measured field. The results of an experimental investigation of radiation forces in two different cases are presented in this paper. In one case, the radiation force of an obliquely incident ultrasound beam on a large absorber (which completely absorbs the beam) is considered. The second case concerns measurement of the radiation force on a spherical target that is small compared to the beam diameter.

  4. A system for acoustical and optical analysis of encapsulated microbubbles at ultrahigh hydrostatic pressures.

    PubMed

    Zhushma, Aleksandr; Lebedeva, Natalia; Sen, Pabitra; Rubinstein, Michael; Sheiko, Sergei S; Dayton, Paul A

    2013-05-01

    Acoustics are commonly used for borehole (i.e., oil well) imaging applications, under conditions where temperature and pressure reach extremes beyond that of conventional medical ultrasonics. Recently, there has been an interest in the application of encapsulated microbubbles as borehole contrast agents for acoustic assessment of fluid composition and flow. Although such microbubbles are widely studied under physiological conditions for medical imaging applications, to date there is a paucity of information on the behavior of encapsulated gas-filled microbubbles at high pressures. One major limitation is that there is a lack of experimental systems to assess both optical and acoustic data of micrometer-sized particles data at these extremes. In this paper, we present the design and application of a high-pressure cell designed for acoustical and optical studies of microbubbles at hydrostatic pressures up to 27.5 MPa (271 atm). PMID:23742587

  5. A system for acoustical and optical analysis of encapsulated microbubbles at ultrahigh hydrostatic pressures

    NASA Astrophysics Data System (ADS)

    Zhushma, Aleksandr; Lebedeva, Natalia; Sen, Pabitra; Rubinstein, Michael; Sheiko, Sergei S.; Dayton, Paul A.

    2013-05-01

    Acoustics are commonly used for borehole (i.e., oil well) imaging applications, under conditions where temperature and pressure reach extremes beyond that of conventional medical ultrasonics. Recently, there has been an interest in the application of encapsulated microbubbles as borehole contrast agents for acoustic assessment of fluid composition and flow. Although such microbubbles are widely studied under physiological conditions for medical imaging applications, to date there is a paucity of information on the behavior of encapsulated gas-filled microbubbles at high pressures. One major limitation is that there is a lack of experimental systems to assess both optical and acoustic data of micrometer-sized particles data at these extremes. In this paper, we present the design and application of a high-pressure cell designed for acoustical and optical studies of microbubbles at hydrostatic pressures up to 27.5 MPa (271 atm).

  6. Particle analysis in an acoustic cytometer

    DOEpatents

    Kaduchak, Gregory; Ward, Michael D

    2012-09-18

    The present invention is a method and apparatus for acoustically manipulating one or more particles. Acoustically manipulated particles may be separated by size. The particles may be flowed in a flow stream and acoustic radiation pressure, which may be radial, may be applied to the flow stream. This application of acoustic radiation pressure may separate the particles. In one embodiment, the particles may be separated by size, and as a further example, the larger particles may be transported to a central axis.

  7. The effects of acoustic radiation force on contrast agents: Experimental and theoretial analysis

    NASA Astrophysics Data System (ADS)

    Dayton, Paul Alexander

    The goal of this research is to understand the response of ultrasound contrast agents to acoustic radiation force. Ultrasound contrast agents are encapsulated microbubbles similar in size and rheologic behavior to human erythrocytes. A core of either air or a high- molecular weight gas makes these microbubbles extremely compressible and highly echogenic. Clinically, the detection of blood is difficult without contrast agents because the echoes from blood cells are typically 30-40 dB less than tissue echoes. Ultrasound contrast agents have been shown to be extremely useful in assisting delineation of perfused tissue in echocardiography, and are being increasingly used for tumor detection in radiology. The high compressibility of gas-filled contrast agents makes these microbubbles susceptible to translation due to radiation force. Thus, it is important to understand the effects of this force in order to avoid erroneous measurements based on the location and flow velocity of microbubbles. In addition, the ability to displace and concentrate microbubbles may be an advantage in targeted imaging, targeted therapy, or industrial applications where it is desired to localize microbubbles in a region. In this study, experimental and theoretical tools are combined to investigate the interaction between microbubbles and an acoustic pulse. Several unique experimental systems allow visualization and analysis of the radius-time curves of individual microbubbles, the displacement of individual microbubbles in-vitro, and the displacement of microbubbles in-vivo. Theoretical analysis illustrates that the effect of radiation force on microbubbles is directly proportional to the product of the bubble volume and the acoustic pressure gradient. A model designed to simulate the radius-time behavior of individual microbubbles is verified from experimental data, and used to estimate the magnitude of radiation force. The resulting bubble translation is determined using a second model

  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. Acoustic and elastic multiple scattering and radiation from cylindrical structures

    NASA Astrophysics Data System (ADS)

    Amirkulova, Feruza Abdukadirovna

    Multiple scattering (MS) and radiation of waves by a system of scatterers is of great theoretical and practical importance and is required in a wide variety of physical contexts such as the implementation of "invisibility" cloaks, the effective parameter characterization, and the fabrication of dynamically tunable structures, etc. The dissertation develops fast, rapidly convergent iterative techniques to expedite the solution of MS problems. The formulation of MS problems reduces to a system of linear algebraic equations using Graf's theorem and separation of variables. The iterative techniques are developed using Neumann expansion and Block Toeplitz structure of the linear system; they are very general, and suitable for parallel computations and a large number of MS problems, i.e. acoustic, elastic, electromagnetic, etc., and used for the first time to solve MS problems. The theory is implemented in Matlab and FORTRAN, and the theoretical predictions are compared to computations obtained by COMSOL. To formulate the MS problem, the transition matrix is obtained by analyzing an acoustic and an elastic single scattering of incident waves by elastic isotropic and anisotropic solids. The mathematical model of wave scattering from multilayered cylindrical and spherical structures is developed by means of an exact solution of dynamic 3D elasticity theory. The recursive impedance matrix algorithm is derived for radially heterogeneous anisotropic solids. An explicit method for finding the impedance in piecewise uniform, transverse-isotropic material is proposed; the solution is compared to elasticity theory solutions involving Buchwald potentials. Furthermore, active exterior cloaking devices are modeled for acoustic and elastic media using multipole sources. A cloaking device can render an object invisible to some incident waves as seen by some external observer. The active cloak is generated by a discrete set of multipole sources that destructively interfere with an

  10. Negative radiation pressure exerted on kinks

    NASA Astrophysics Data System (ADS)

    Forgács, Péter; Lukács, Árpád; Romańczukiewicz, Tomasz

    2008-06-01

    The interaction of a kink and a monochromatic plane wave in one dimensional scalar field theories is studied. It is shown that in a large class of models the radiation pressure exerted on the kink is negative, i.e. the kink is pulled towards the source of the radiation. This effect has been observed by numerical simulations in the ϕ4 model, and it is explained by a perturbative calculation assuming that the amplitude of the incoming wave is small. Quite importantly the effect is shown to be robust against small perturbations of the ϕ4 model. In the sine-Gordon (SG) model the time-averaged radiation pressure acting on the kink turns out to be zero. The results of the perturbative computations in the SG model are shown to be in full agreement with an analytical solution corresponding to the superposition of a SG kink with a cnoidal wave. It is also demonstrated that the acceleration of the kink satisfies Newton’s law.

  11. Negative radiation pressure exerted on kinks

    SciTech Connect

    Forgacs, Peter; Lukacs, Arpad; Romanczukiewicz, Tomasz

    2008-06-15

    The interaction of a kink and a monochromatic plane wave in one dimensional scalar field theories is studied. It is shown that in a large class of models the radiation pressure exerted on the kink is negative, i.e. the kink is pulled towards the source of the radiation. This effect has been observed by numerical simulations in the {phi}{sup 4} model, and it is explained by a perturbative calculation assuming that the amplitude of the incoming wave is small. Quite importantly the effect is shown to be robust against small perturbations of the {phi}{sup 4} model. In the sine-Gordon (SG) model the time-averaged radiation pressure acting on the kink turns out to be zero. The results of the perturbative computations in the SG model are shown to be in full agreement with an analytical solution corresponding to the superposition of a SG kink with a cnoidal wave. It is also demonstrated that the acceleration of the kink satisfies Newton's law.

  12. Generation of acoustic waves by cw laser radiation at the tip of an optical fiber in water

    NASA Astrophysics Data System (ADS)

    Yusupov, V. I.; Konovalov, A. N.; Ul'yanov, V. A.; Bagratashvili, V. N.

    2016-09-01

    We investigate the specific features of acoustic signals generated in water under the action of cw laser radiation with a power of 3 W at wavelengths of 0.97, 1.56, and 1.9 μm, emerging from an optical fiber. It is established that when a fiber tip without an absorbing coating is used, quasi-periodic pulse signals are generated according to the thermocavitation mechanism due to the formation and collapse of vapor-gas bubbles of millimeter size. In this case, the maximum energy of a broadband (up to 10 MHz) acoustic signal generated only at wavelengths of 1.56 and 1.9 μm is concentrated in the range of 4-20 kHz. It is shown that when there is no absorbing coating, an increase in the laser-radiation absorption coefficient in water leads to an increase in the frequency of generated acoustic pulses, while the maximum pressure amplitudes in them remain virtually constant. If there is an absorbing coating on the laser-fiber tip, a large number of small vapor-gas bubbles are generated at all laser-radiation wavelengths used. This leads to the appearance of a continuous amplitude-modulated acoustic signal, whose main energy is concentrated in the range of 8-15 kHz. It is shown that in this case, increasing the absorption coefficient of laser radiation in water leads to an increase in the power of an acoustic emission signal. The results can be used to explain the high therapeutic efficiency of moderate-power laser-fiber apparatus.

  13. 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.

  14. 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.

  15. Violin f-hole contribution to far-field radiation via patch near-field acoustical holography.

    PubMed

    Bissinger, George; Williams, Earl G; Valdivia, Nicolas

    2007-06-01

    The violin radiates either from dual ports (f-holes) or via surface motion of the corpus (top+ribs+back), with no clear delineation between these sources. Combining "patch" near-field acoustical holography over just the f-hole region of a violin with far-field radiativity measurements over a sphere, it was possible to separate f-hole from surface motion contributions to the total radiation of the corpus below 2.6 kHz. A0, the Helmholtz-like lowest cavity resonance, radiated essentially entirely through the f-holes as expected while A1, the first longitudinal cavity mode with a node at the f-holes, had no significant f-hole radiation. The observed A1 radiation comes from an indirect radiation mechanism, induced corpus motion approximately mirroring the cavity pressure profile seen for violinlike bowed string instruments across a wide range of sizes. The first estimates of the fraction of radiation from the f-holes F(f) indicate that some low frequency corpus modes thought to radiate only via surface motion (notably the first corpus bending modes) had significant radiation through the f-holes, in agreement with net volume changes estimated from experimental modal analysis. F(f) generally trended lower with increasing frequency, following corpus mobility decreases. The f-hole directivity (top/back radiativity ratio) was generally higher than whole-violin directivity. PMID:17552736

  16. Violin f-hole contribution to far-field radiation via patch near-field acoustical holography.

    PubMed

    Bissinger, George; Williams, Earl G; Valdivia, Nicolas

    2007-06-01

    The violin radiates either from dual ports (f-holes) or via surface motion of the corpus (top+ribs+back), with no clear delineation between these sources. Combining "patch" near-field acoustical holography over just the f-hole region of a violin with far-field radiativity measurements over a sphere, it was possible to separate f-hole from surface motion contributions to the total radiation of the corpus below 2.6 kHz. A0, the Helmholtz-like lowest cavity resonance, radiated essentially entirely through the f-holes as expected while A1, the first longitudinal cavity mode with a node at the f-holes, had no significant f-hole radiation. The observed A1 radiation comes from an indirect radiation mechanism, induced corpus motion approximately mirroring the cavity pressure profile seen for violinlike bowed string instruments across a wide range of sizes. The first estimates of the fraction of radiation from the f-holes F(f) indicate that some low frequency corpus modes thought to radiate only via surface motion (notably the first corpus bending modes) had significant radiation through the f-holes, in agreement with net volume changes estimated from experimental modal analysis. F(f) generally trended lower with increasing frequency, following corpus mobility decreases. The f-hole directivity (top/back radiativity ratio) was generally higher than whole-violin directivity.

  17. Acoustic Radiation Force Impulse (ARFI) Imaging-Based Needle Visualization

    PubMed Central

    Rotemberg, Veronica; Palmeri, Mark; Rosenzweig, Stephen; Grant, Stuart; Macleod, David; Nightingale, Kathryn

    2011-01-01

    Ultrasound-guided needle placement is widely used in the clinical setting, particularly for central venous catheter placement, tissue biopsy and regional anesthesia. Difficulties with ultrasound guidance in these areas often result from steep needle insertion angles and spatial offsets between the imaging plane and the needle. Acoustic Radiation Force Impulse (ARFI) imaging leads to improved needle visualization because it uses a standard diagnostic scanner to perform radiation force based elasticity imaging, creating a displacement map that displays tissue stiffness variations. The needle visualization in ARFI images is independent of needle-insertion angle and also extends needle visibility out of plane. Although ARFI images portray needles well, they often do not contain the usual B-mode landmarks. Therefore, a three-step segmentation algorithm has been developed to identify a needle in an ARFI image and overlay the needle prediction on a coregistered B-mode image. The steps are: (1) contrast enhancement by median filtration and Laplacian operator filtration, (2) noise suppression through displacement estimate correlation coefficient thresholding and (3) smoothing by removal of outliers and best-fit line prediction. The algorithm was applied to data sets from horizontal 18, 21 and 25 gauge needles between 0–4 mm offset in elevation from the transducer imaging plane and to 18G needles on the transducer axis (in plane) between 10° and 35° from the horizontal. Needle tips were visualized within 2 mm of their actual position for both horizontal needle orientations up to 1.5 mm off set in elevation from the transducer imaging plane and on-axis angled needles between 10°–35° above the horizontal orientation. We conclude that segmented ARFI images overlaid on matched B-mode images hold promise for improved needle visibility in many clinical applications. PMID:21608445

  18. Analysis of clot formation with acoustic radiation force

    NASA Astrophysics Data System (ADS)

    Viola, Francesco; Longo, Diane M.; Lawrence, Michael B.; Walker, William F.

    2002-04-01

    Inappropriate blood coagulation plays an important role in diseases including stroke, heart attack, and deep vein thrombosis (DVT). DVT arises when a blood clot forms in a large vein of the leg. DVT is detrimental because the blood flow may be partially or completely obstructed. More importantly, a potentially fatal situation may arise if part of the clot travels to the arteries in the lungs, forming a pulmonary embolism (PE). Characterization of the mechanical properties of DVT could improve diagnosis and suggest appropriate treatment. We are developing a technique to assess mechanical properties of forming thrombi. The technique uses acoustic radiation force as a means to produce small, localized displacements within the sample. Returned ultrasound echoes are processed to estimate the time dependent displacement of the sample. Appropriate mechanical modeling and signal processing produce plots depicting relative mechanical properties (relative elasticity and relative viscosity) and force-free parameters (time constant, damping ratio, and natural frequency). We present time displacement curves of blood samples obtained during coagulation, and show associated relative and force-free parameter plots. These results show that the Voigt model with added mass accurately characterizes blood behavior during clot formation.

  19. Investigations of High Pressure Acoustic Waves in Resonators with Seal-Like Features

    NASA Technical Reports Server (NTRS)

    Daniels, Christopher C.; Steinetz, Bruce M.; Finkbeiner, Joshua R.; Li, Xiao-Fan; Raman, Ganesh

    2004-01-01

    1) Standing waves with maximum pressures of 188 kPa have been produced in resonators containing ambient pressure air; 2) Addition of structures inside the resonator shifts the fundamental frequency and decreases the amplitude of the generated pressure waves; 3) Addition of holes to the resonator does reduce the magnitude of the acoustic waves produced, but their addition does not prohibit the generation of large magnitude non-linear standing waves; 4) The feasibility of reducing leakage using non-linear acoustics has been confirmed.

  20. Measured wavenumber: frequency spectrum associated with acoustic and aerodynamic wall pressure fluctuations.

    PubMed

    Arguillat, Blandine; Ricot, Denis; Bailly, Christophe; Robert, Gilles

    2010-10-01

    Direct measurements of the wavenumber-frequency spectrum of wall pressure fluctuations beneath a turbulent plane channel flow have been performed in an anechoic wind tunnel. A rotative array has been designed that allows the measurement of a complete map, 63×63 measuring points, of cross-power spectral densities over a large area. An original post-processing has been developed to separate the acoustic and the aerodynamic exciting loadings by transforming space-frequency data into wavenumber-frequency spectra. The acoustic part has also been estimated from a simple Corcos-like model including the contribution of a diffuse sound field. The measured acoustic contribution to the surface pressure fluctuations is 5% of the measured aerodynamic surface pressure fluctuations for a velocity and boundary layer thickness relevant for automotive interior noise applications. This shows that for aerodynamically induced car interior noise, both contributions to the surface pressure fluctuations on car windows have to be taken into account.

  1. Measurement of transient acoustic fields using a single-shot pressure-sensitive paint system.

    PubMed

    Disotell, Kevin J; Gregory, James W

    2011-07-01

    A pressure-sensitive paint (PSP) system capable of measuring high-frequency acoustic fields with non-periodic, acoustic-level pressure changes is described. As an optical measurement technique, PSP provides the experimenter with a global distribution of pressure on a painted surface. To demonstrate frequency response and enhanced sensitivity to pressure changes, a PSP system consisting of a polymer∕ceramic matrix binder with platinum tetra(pentafluorophenyl) porphyrin (PtTFPP) as the oxygen probe was applied to a wall inside an acoustic resonance cavity excited at 1.3 kHz. A data acquisition technique based on the luminescent decay lifetime of the oxygen sensors excited by a single pulse of light afforded the ability to capture instantaneous pressure fields with no phase-averaging. Superimposed wave-like structures were observed with a wavelength corresponding to a 4.7% difference from the theoretical value for a sound wave emanating from the speaker. High sound pressure cases upwards of 145 dB (re 20 μPa) exhibited skewed nodal lines attributed to a nonlinear acoustic field. The lowest sound pressure level of 125.4 dB--corresponding to an amplitude of 52.7 Pa, or approximately 0.05% of standard sea-level atmospheric pressure--showed that the paint could resolve the spatial details of the mode shape at the given resonance condition.

  2. Measurement of transient acoustic fields using a single-shot pressure-sensitive paint system.

    PubMed

    Disotell, Kevin J; Gregory, James W

    2011-07-01

    A pressure-sensitive paint (PSP) system capable of measuring high-frequency acoustic fields with non-periodic, acoustic-level pressure changes is described. As an optical measurement technique, PSP provides the experimenter with a global distribution of pressure on a painted surface. To demonstrate frequency response and enhanced sensitivity to pressure changes, a PSP system consisting of a polymer∕ceramic matrix binder with platinum tetra(pentafluorophenyl) porphyrin (PtTFPP) as the oxygen probe was applied to a wall inside an acoustic resonance cavity excited at 1.3 kHz. A data acquisition technique based on the luminescent decay lifetime of the oxygen sensors excited by a single pulse of light afforded the ability to capture instantaneous pressure fields with no phase-averaging. Superimposed wave-like structures were observed with a wavelength corresponding to a 4.7% difference from the theoretical value for a sound wave emanating from the speaker. High sound pressure cases upwards of 145 dB (re 20 μPa) exhibited skewed nodal lines attributed to a nonlinear acoustic field. The lowest sound pressure level of 125.4 dB--corresponding to an amplitude of 52.7 Pa, or approximately 0.05% of standard sea-level atmospheric pressure--showed that the paint could resolve the spatial details of the mode shape at the given resonance condition. PMID:21806232

  3. Radiation effects on reactor pressure vessel supports

    SciTech Connect

    Johnson, R.E.; Lipinski, R.E.

    1996-05-01

    The purpose of this report is to present the findings from the work done in accordance with the Task Action Plan developed to resolve the Nuclear Regulatory Commission (NRC) Generic Safety Issue No. 15, (GSI-15). GSI-15 was established to evaluate the potential for low-temperature, low-flux-level neutron irradiation to embrittle reactor pressure vessel (RPV) supports to the point of compromising plant safety. An evaluation of surveillance samples from the High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) had suggested that some materials used for RPV supports in pressurized-water reactors could exhibit higher than expected embrittlement rates. However, further tests designed to evaluate the applicability of the HFIR data to reactor RPV supports under operating conditions led to the conclusion that RPV supports could be evaluated using traditional method. It was found that the unique HFIR radiation environment allowed the gamma radiation to contribute significantly to the embrittlement. The shielding provided by the thick steel RPV shell ensures that degradation of RPV supports from gamma irradiation is improbable or minimal. The findings reported herein were used, in part, as the basis for technical resolution of the issue.

  4. Analytical and experimental investigations of gas turbine model combustor acoustics operated at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Richecoeur, Franck; Schuller, Thierry; Lamraoui, Ammar; Ducruix, Sébastien

    2013-01-01

    When coupled to acoustics, unsteady heat release oscillations may cause recurrent problems in many combustion chambers, potentially leading to dramatic damages to the structure. Accumulation of acoustic energy around the eigenmodes of the combustor results from the resonant coupling between pressure disturbances in the flame region with synchronized heat release rate perturbations. Predicting these frequencies and the corresponding sound pressure field is a key issue to design passive or active control systems to prevent the growth of these instabilities. In this study, an acoustically controlled combustion test bench CESAM is used to stabilize a partially premixed swirling propane-air flame. In the premixing tube, reactants are injected tangentially to generate the swirling flow, the flame being stabilized in the combustion chamber by a sudden expansion of the cross section. The premixer backplane is equipped with an Impedance Control System (ICS) allowing to adjust the acoustic reflection coefficient at this location. Acoustics of the coupled-cavity system formed by the premixer and the combustion chamber is investigated analytically by taking into account the measured acoustic impedances at the premixer backplane and in the feeding lines. The chamber length is also modified to examine the effects of the geometry on these predictions. It is shown that the premixer and combustion chamber can be considered as acoustically decoupled for small values of the acoustic coupling index, defined in the article. This offers flexible solutions to control the pressure distribution within the combustor, except when these frequencies match. When the frequencies are close to each other, only the analysis of the damping of the different cavities enables to indicate whether the system is coupled or not. Modifying either the acoustic coupling index or the damping values featuring the same frequency appears then as alternative solutions to decouple cavities.

  5. Measurement of transient acoustic fields using a single-shot pressure-sensitive paint system

    NASA Astrophysics Data System (ADS)

    Disotell, Kevin J.; Gregory, James W.

    2011-07-01

    A pressure-sensitive paint (PSP) system capable of measuring high-frequency acoustic fields with non-periodic, acoustic-level pressure changes is described. As an optical measurement technique, PSP provides the experimenter with a global distribution of pressure on a painted surface. To demonstrate frequency response and enhanced sensitivity to pressure changes, a PSP system consisting of a polymer/ceramic matrix binder with platinum tetra(pentafluorophenyl) porphyrin (PtTFPP) as the oxygen probe was applied to a wall inside an acoustic resonance cavity excited at 1.3 kHz. A data acquisition technique based on the luminescent decay lifetime of the oxygen sensors excited by a single pulse of light afforded the ability to capture instantaneous pressure fields with no phase-averaging. Superimposed wave-like structures were observed with a wavelength corresponding to a 4.7% difference from the theoretical value for a sound wave emanating from the speaker. High sound pressure cases upwards of 145 dB (re 20 μPa) exhibited skewed nodal lines attributed to a nonlinear acoustic field. The lowest sound pressure level of 125.4 dB—corresponding to an amplitude of 52.7 Pa, or approximately 0.05% of standard sea-level atmospheric pressure—showed that the paint could resolve the spatial details of the mode shape at the given resonance condition.

  6. Acoustic radiation force on a double-layer microsphere by a Gaussian focused beam

    NASA Astrophysics Data System (ADS)

    Wu, Rongrong; Cheng, Kaixuan; Liu, Xiaozhou; Liu, Jiehui; Mao, Yiwei; Gong, Xiufen

    2014-10-01

    A new model for calculating the radiation force on double-layer microsphere is proposed based on the ray acoustics approach. The axial acoustic radiation force resulting from a focused Gaussian beam incident on spherical shells immersed in water is examined theoretically in relation to its thickness and the contents of its double-layer. The attenuation both in the water and inside the sphere is considered in this method, which cannot be ignored while the high frequency ultrasonic is used. Results of numerical calculations are presented for fat and low density polyethylene materials, with the hollow region filled with animal oil, water, or air. These results show how the acoustic impedance and the sound velocity of both layers, together with the thickness of the shell, affect the acoustic radiation force.

  7. Acoustic radiation force on a double-layer microsphere by a Gaussian focused beam

    SciTech Connect

    Wu, Rongrong; Cheng, Kaixuan; Liu, Jiehui; Mao, Yiwei; Gong, Xiufen; Liu, Xiaozhou

    2014-10-14

    A new model for calculating the radiation force on double-layer microsphere is proposed based on the ray acoustics approach. The axial acoustic radiation force resulting from a focused Gaussian beam incident on spherical shells immersed in water is examined theoretically in relation to its thickness and the contents of its double-layer. The attenuation both in the water and inside the sphere is considered in this method, which cannot be ignored while the high frequency ultrasonic is used. Results of numerical calculations are presented for fat and low density polyethylene materials, with the hollow region filled with animal oil, water, or air. These results show how the acoustic impedance and the sound velocity of both layers, together with the thickness of the shell, affect the acoustic radiation force.

  8. Acousto-optic effect compensation for optical determination of the normal velocity distribution associated with acoustic transducer radiation.

    PubMed

    Foote, Kenneth G; Theobald, Peter D

    2015-09-01

    The acousto-optic effect, in which an acoustic wave causes variations in the optical index of refraction, imposes a fundamental limitation on the determination of the normal velocity, or normal displacement, distribution on the surface of an acoustic transducer or optically reflecting pellicle by a scanning heterodyne, or homodyne, laser interferometer. A general method of compensation is developed for a pulsed harmonic pressure field, transmitted by an acoustic transducer, in which the laser beam can transit the transducer nearfield. By representing the pressure field by the Rayleigh integral, the basic equation for the unknown normal velocity on the surface of the transducer or pellicle is transformed into a Fredholm equation of the second kind. A numerical solution is immediate when the scanned points on the surface correspond to those of the surface area discretization. Compensation is also made for oblique angles of incidence by the scanning laser beam. The present compensation method neglects edge waves, or those due to boundary diffraction, as well as effects due to baffles, if present. By allowing measurement in the nearfield of the radiating transducer, the method can enable quantification of edge-wave and baffle effects on transducer radiation. A verification experiment has been designed. PMID:26428801

  9. ACOUSTIC LOCATION OF LEAKS IN PRESSURIZED UNDER- GROUND PETROLEUM PIPELINES

    EPA Science Inventory

    Experiments were conducted at the Underground Storage Tank (UST) Test Apparatus Pipeline in which three acoustic sensors separated by a maximum distance of 38.1 m (125 ft) were used to monitor signals produced by 11.4-, 5.7-, and 3.8-L/h (3.0-, 1.5-, and 1.0-gal/h) leaks in th...

  10. Phase Aberration and Attenuation Effects on Acoustic Radiation Force-Based Shear Wave Generation.

    PubMed

    Carrascal, Carolina Amador; Aristizabal, Sara; Greenleaf, James F; Urban, Matthew W

    2016-02-01

    Elasticity is measured by shear wave elasticity imaging (SWEI) methods using acoustic radiation force to create the shear waves. Phase aberration and tissue attenuation can hamper the generation of shear waves for in vivo applications. In this study, the effects of phase aberration and attenuation in ultrasound focusing for creating shear waves were explored. This includes the effects of phase shifts and amplitude attenuation on shear wave characteristics such as shear wave amplitude, shear wave speed, shear wave center frequency, and bandwidth. Two samples of swine belly tissue were used to create phase aberration and attenuation experimentally. To explore the phase aberration and attenuation effects individually, tissue experiments were complemented with ultrasound beam simulations using fast object-oriented C++ ultrasound simulator (FOCUS) and shear wave simulations using finite-element-model (FEM) analysis. The ultrasound frequency used to generate shear waves was varied from 3.0 to 4.5 MHz. Results: The measured acoustic pressure and resulting shear wave amplitude decreased approximately 40%-90% with the introduction of the tissue samples. Acoustic intensity and shear wave displacement were correlated for both tissue samples, and the resulting Pearson's correlation coefficients were 0.99 and 0.97. Analysis of shear wave generation with tissue samples (phase aberration and attenuation case), measured phase screen, (only phase aberration case), and FOCUS/FEM model (only attenuation case) showed that tissue attenuation affected the shear wave generation more than tissue aberration. Decreasing the ultrasound frequency helped maintain a focused beam for creation of shear waves in the presence of both phase aberration and attenuation.

  11. Generation and Radiation of Acoustic Waves from a 2-D Shear Layer

    NASA Technical Reports Server (NTRS)

    Agarwal, Anurag; Morris, Philip J.

    2000-01-01

    A parallel numerical simulation of the radiation of sound from an acoustic source inside a 2-D jet is presented in this paper. This basic benchmark problem is used as a test case for scattering problems that are presently being solved by using the Impedance Mismatch Method (IMM). In this technique, a solid body in the domain is represented by setting the acoustic impedance of each medium, encountered by a wave, to a different value. This impedance discrepancy results in reflected and scattered waves with appropriate amplitudes. The great advantage of the use of this method is that no modifications to a simple Cartesian grid need to be made for complicated geometry bodies. Thus, high order finite difference schemes may be applied simply to all parts of the domain. In the IMM, the total perturbation field is split into incident and scattered fields. The incident pressure is assumed to be known and the equivalent sources for the scattered field are associated with the presence of the scattering body (through the impedance mismatch) and the propagation of the incident field through a non-uniform flow. An earlier version of the technique could only handle uniform flow in the vicinity of the source and at the outflow boundary. Scattering problems in non-uniform mean flow are of great practical importance (for example, scattering from a high lift device in a non-uniform mean flow or the effects of a fuselage boundary layer). The solution to this benchmark problem, which has an acoustic wave propagating through a non-uniform mean flow, serves as a test case for the extensions of the IMM technique.

  12. Influence of acoustic pressure and bubble sizes on the coalescence of two contacting bubbles in an acoustic field.

    PubMed

    Jiao, Junjie; He, Yong; Yasui, Kyuichi; Kentish, Sandra E; Ashokkumar, Muthupandian; Manasseh, Richard; Lee, Judy

    2015-01-01

    In this study, the coalescence time between two contacting sub-resonance size bubbles was measured experimentally under an acoustic pressure ranging from 10kPa to 120kPa, driven at a frequency of 22.4kHz. The coalescence time obtained under sonication was much longer compared to that calculated by the film drainage theory for a free bubble surface without surfactants. It was found that under the influence of an acoustic field, the coalescence time could be probabilistic in nature, exhibiting upper and lower limits of coalescence times which are prolonged when both the maximum surface approach velocity and secondary Bjerknes force increases. The size of the two contacting bubbles is also important. For a given acoustic pressure, bubbles having a larger average size and size difference were observed to exhibit longer coalescence times. This could be caused by the phase difference between the volume oscillations of the two bubbles, which in turn affects the minimum film thickness reached between the bubbles and the film drainage time. These results will have important implications for developing film drainage theory to account for the effect of bubble translational and volumetric oscillations, bubble surface fluctuations and microstreaming.

  13. Program for the feasibility of developing a high pressure acoustic levitator

    NASA Technical Reports Server (NTRS)

    Rey, Charles A.; Merkley, Dennis R.; Hammarlund, Gregory R.

    1988-01-01

    This is the final report for the program for the feasibility of developing a high-pressure acoustic levitator (HPAL). It includes work performed during the period from February 15, 1987 to October 26, 1987. The program was conducted for NASA under contract number NAS3-25115. The HPAL would be used for containerless processing of materials in the 1-g Earth environment. Results show that the use of increased gas pressure produces higher sound pressure levels. The harmonics produced by the acoustic source are also reduced. This provides an improvement in the capabilities of acoustic levitation in 1-g. The reported processing capabilities are directly limited by the design of the Medium Pressure Acoustic Levitator used for this study. Data show that sufficient acoustic intensities can be obtained to levitate and process a specimen of density 5 g/cu cm at 1500 C. However, it is recommended that a working engineering model of the HPAL be developed. The model would be used to establish the maximum operating parameters of furnace temperature and sample density.

  14. Hybrid optical and acoustic force based sorting

    NASA Astrophysics Data System (ADS)

    O'Mahoney, Paul; Brodie, Graham W.; Wang, Han; Demore, Christine E. M.; Cochran, Sandy; Spalding, Gabriel C.; MacDonald, Michael P.

    2014-09-01

    We report the combined use of optical sorting and acoustic levitation to give particle sorting. Differing sizes of microparticles are sorted optically both with and without the aid of acoustic levitation, and the results compared to show that the use of acoustic trapping can increase sorting efficiency. The use of a transparent ultrasonic transducer is also shown to streamline the integration of optics and acoustics. We also demonstrate the balance of optical radiation pressure and acoustic levitation to achieve vertical sorting.

  15. Experimental and numerical characterization of the sound pressure in standing wave acoustic levitators

    NASA Astrophysics Data System (ADS)

    Stindt, A.; Andrade, M. A. B.; Albrecht, M.; Adamowski, J. C.; Panne, U.; Riedel, J.

    2014-01-01

    A novel method for predictions of the sound pressure distribution in acoustic levitators is based on a matrix representation of the Rayleigh integral. This method allows for a fast calculation of the acoustic field within the resonator. To make sure that the underlying assumptions and simplifications are justified, this approach was tested by a direct comparison to experimental data. The experimental sound pressure distributions were recorded by high spatially resolved frequency selective microphone scanning. To emphasize the general applicability of the two approaches, the comparative studies were conducted for four different resonator geometries. In all cases, the results show an excellent agreement, demonstrating the accuracy of the matrix method.

  16. 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

  17. Theoretical Analysis of Shear Wave Interference Patterns by Means of Dynamic Acoustic Radiation Forces.

    PubMed

    Hoyt, Kenneth

    2011-03-01

    Acoustic radiation forces associated with high intensity focused ultrasound stimulate shear wave propagation allowing shear wave speed and shear viscosity estimation of tissue structures. As wave speeds are meters per second, real time displacement tracking over an extend field-of-view using ultrasound is problematic due to very high frame rate requirements. However, two spatially separated dynamic external sources can stimulate shear wave motion leading to shear wave interference patterns. Advantages are shear waves can be imaged at lower frame rates and local interference pattern spatial properties reflect tissue's viscoelastic properties. Here a theoretical analysis of shear wave interference patterns by means of dynamic acoustic radiation forces is detailed. Using a viscoelastic Green's function analysis, tissue motion due to a pair of focused ultrasound beams and associated radiation forces are presented. Overall, this paper theoretically demonstrates shear wave interference patterns can be stimulated using dynamic acoustic radiation forces and tracked using conventional ultrasound imaging.

  18. Full bandwidth calibration procedure for acoustic probes containing a pressure and particle velocity sensor.

    PubMed

    Basten, Tom G H; de Bree, Hans-Elias

    2010-01-01

    Calibration of acoustic particle velocity sensors is still difficult due to the lack of standardized sensors to compare with. Recently it is shown by Jacobsen and Jaud [J. Acoust. Soc. Am. 120, 830-837 (2006)] that it is possible to calibrate a sound pressure and particle velocity sensor in free field conditions at higher frequencies. This is done by using the known acoustic impedance at a certain distance of a spherical loudspeaker. When the sound pressure is measured with a calibrated reference microphone, the particle velocity can be calculated from the known impedance and the measured pressure. At lower frequencies, this approach gives unreliable results. The method is now extended to lower frequencies by measuring the acoustic pressure inside the spherical source. At lower frequencies, the sound pressure inside the sphere is proportional to the movement of the loudspeaker membrane. If the movement is known, the particle velocity in front of the loudspeaker can be derived. This low frequency approach is combined with the high frequency approach giving a full bandwidth calibration procedure which can be used in free field conditions using a single calibration setup. The calibration results are compared with results obtained with a standing wave tube.

  19. Acoustic travel time gauges for in-situ determination of pressure and temperature in multi-anvil apparatus

    SciTech Connect

    Wang, Xuebing; Chen, Ting; Qi, Xintong; Zou, Yongtao; Liebermann, Robert C.; Li, Baosheng; Kung, Jennifer; Yu, Tony; Wang, Yanbin

    2015-08-14

    In this study, we developed a new method for in-situ pressure determination in multi-anvil, high-pressure apparatus using an acoustic travel time approach within the framework of acoustoelasticity. The ultrasonic travel times of polycrystalline Al{sub 2}O{sub 3} were calibrated against NaCl pressure scale up to 15 GPa and 900 °C in a Kawai-type double-stage multi-anvil apparatus in conjunction with synchrotron X-radiation, thereby providing a convenient and reliable gauge for pressure determination at ambient and high temperatures. The pressures derived from this new travel time method are in excellent agreement with those from the fixed-point methods. Application of this new pressure gauge in an offline experiment revealed a remarkable agreement of the densities of coesite with those from the previous single crystal compression studies under hydrostatic conditions, thus providing strong validation for the current travel time pressure scale. The travel time approach not only can be used for continuous in-situ pressure determination at room temperature, high temperatures, during compression and decompression, but also bears a unique capability that none of the previous scales can deliver, i.e., simultaneous pressure and temperature determination with a high accuracy (±0.16 GPa in pressure and ±17 °C in temperature). Therefore, the new in-situ Al{sub 2}O{sub 3} pressure gauge is expected to enable new and expanded opportunities for offline laboratory studies of solid and liquid materials under high pressure and high temperature in multi-anvil apparatus.

  20. Toward Standardized Acoustic Radiation Force (ARF)-Based Ultrasound Elasticity Measurements With Robotic Force Control

    PubMed Central

    Kumar, Shalki; Lily, Kuo; Sen, H. Tutkun; Iordachita, Iulian; Kazanzides, Peter

    2016-01-01

    Objective Acoustic radiation force (ARF)-based approaches to measure tissue elasticity require transmission of a focused high-energy acoustic pulse from a stationary ultrasound probe and ultrasound-based tracking of the resulting tissue displacements to obtain stiffness images or shear wave speed estimates. The method has established benefits in biomedical applications such as tumor detection and tissue fibrosis staging. One limitation, however, is the dependence on applied probe pressure, which is difficult to control manually and prohibits standardization of quantitative measurements. To overcome this limitation, we built a robot prototype that controls probe contact forces for shear wave speed quantification. Methods The robot was evaluated with controlled force increments applied to a tissue-mimicking phantom and in vivo abdominal tissue from three human volunteers. Results The root-mean-square error between the desired and measured forces was 0.07 N in the phantom and higher for the fatty layer of in vivo abdominal tissue. The mean shear wave speeds increased from 3.7 to 4.5 m/s in the phantom and 1.0 to 3.0 m/s in the in vivo fat for compressive forces ranging from 2.5 to 30 N. The standard deviation of shear wave speeds obtained with the robotic approach were low in most cases (< 0.2 m/s) and comparable to that obtained with a semiquantitative landmark-based method. Conclusion Results are promising for the introduction of robotic systems to control the applied probe pressure for ARF-based measurements of tissue elasticity. Significance This approach has potential benefits in longitudinal studies of disease progression, comparative studies between patients, and large-scale multidimensional elasticity imaging. PMID:26552071

  1. Optical Verification of Microbubble Response to Acoustic Radiation Force in Large Vessels with In Vivo Results

    PubMed Central

    Wang, Shiying; Wang, Claudia Y.; Unnikrishnan, Sunil; Klibanov, Alexander L.; Hossack, John A.; Mauldin, F. William

    2015-01-01

    Objectives To optically verify the dynamic behaviors of adherent microbubbles in large blood vessel environments in response to a new ultrasound technique using modulated acoustic radiation force. Materials and Methods Polydimethylsiloxane (PDMS) flow channels coated with streptavidin were used in targeted groups to mimic large blood vessels. The custom modulated acoustic radiation force beam sequence was programmed on a Verasonics research scanner. In vitro experiments were performed by injecting a biotinylated lipid-perfluorobutane microbubble dispersion through flow channels. The dynamic response of adherent microbubbles was detected acoustically and simultaneously visualized using a video camera connected to a microscope. In vivo verification was performed in a large abdominal blood vessel of a murine model for inflammation with injection of biotinylated microbubbles conjugated with P-selectin antibody. Results Aggregates of adherent microbubbles were observed optically under the influence of acoustic radiation force. Large microbubble aggregates were observed solely in control groups without targeted adhesion. Additionally, the dispersion of microbubble aggregates were demonstrated to lead to a transient acoustic signal enhancement in control groups (a new phenomenon we refer to as “control peak”). In agreement with in vitro results, the “control peak” phenomenon was observed in vivo in a murine model. Conclusions This study provides the first optical observation of microbubble binding dynamics in large blood vessel environments with application of a modulated acoustic radiation force beam sequence. With targeted adhesion, secondary radiation forces were unable to produce large aggregates of adherent microbubbles. Additionally, the new phenomenon called “control peak” was observed both in vitro and in vivo in a murine model for the first time. The findings in this study provide us with a better understanding of microbubble behaviors in large blood

  2. A numerical method for the calculation of dynamic response and acoustic radiation from an underwater structure

    NASA Astrophysics Data System (ADS)

    Zhou, Q.; Joseph, P. F.

    2005-05-01

    An approach combining finite element with boundary element methods is proposed to calculate the elastic vibration and acoustic field radiated from an underwater structure. The FEM software NASTRAN is employed for computation of the structural vibration. An uncoupled boundary element method, based on the potential decomposition technique, is described to determine the acoustic added mass and damping coefficients that result due to fluid loading effects. The acoustic matrices of added mass and damping coefficients are then added to the structural mass and damping matrices, respectively, by the DMAP modules of NASTRAN. Numerical results are shown to be in good agreement with experimental data. The complex eigenvalue analyses of underwater structure are obtained by NASTRAN solution sequence SOL107. Results obtained from this study suggest that the natural frequencies of underwater structures are only weakly dependent on the acoustic frequency if the acoustic wavelength is roughly twice as large as the maximum structural dimension.

  3. Acoustic properties of pistonphones at low frequencies in the presence of pressure leakage and heat conduction

    NASA Astrophysics Data System (ADS)

    Zhang, Fan; He, Wen; He, Longbiao; Rong, Zuochao

    2015-12-01

    The wide concern on absolute pressure calibration of acoustic transducers at low frequencies prompts the development of the pistonphone method. At low frequencies, the acoustic properties of pistonphones are governed by the pressure leakage and the heat conduction effects. However, the traditional theory for these two effects applies a linear superposition of two independent correction models, which differs somewhat from their coupled effect at low frequencies. In this paper, acoustic properties of pistonphones at low frequencies in full consideration of the pressure leakage and heat conduction effects have been quantitatively studied, and the explicit expression for the generated sound pressure has been derived. With more practical significance, a coupled correction expression for these two effects of pistonphones has been derived. In allusion to two typical pistonphones, the NPL pistonphone and our developed infrasonic pistonphone, comparisons were done for the coupled correction expression and the traditional one, whose results reveal that the traditional one produces maximum insufficient errors of about 0.1 dB above the lower limiting frequencies of two pistonphones, while at lower frequencies, excessive correction errors with an explicit limit of about 3 dB are produced by the traditional expression. The coupled correction expression should be adopted in the absolute pressure calibration of acoustic transducers at low frequencies. Furthermore, it is found that the heat conduction effect takes a limiting deviation of about 3 dB for the pressure amplitude and a small phase difference as frequency decreases, while the pressure leakage effect remarkably drives the pressure amplitude to attenuate and the phase difference tends to be 90° as the frequency decreases. The pressure leakage effect plays a more important role on the low frequency property of pistonphones.

  4. The effect of the size of the opening on the acoustic power radiated by a reed woodwind instrument

    NASA Astrophysics Data System (ADS)

    Guilloteau, Alexis; Guillemain, Philippe; Kergomard, Jean; Jousserand, Michael

    2015-05-01

    For a given note, the maker of woodwind instruments can choose between different sizes for the toneholes under the condition that the location is appropriate. The present paper aims at analyzing the consequences of this choice on the power radiated by a hole, which depends on the coupling between the acoustic resonator and the excitation mechanism of the self-sustained oscillation, thus on the blowing pressure. For that purpose a simplified reed instrument is investigated, with a cylindrical pipe and a unique orifice at the pipe termination. The orifice diameter was varied between the pipe diameter and a size such that the instrument did not play. The pipe length was in each case adjusted to keep the resonance frequency constant. A simple analytical model predicts that, for a given mouth pressure of the instrumentalist, the radiated power does not depend on the size of the hole if it is wide enough and if resonator losses are ignored. Numerical solution of a model including losses confirms this result: the difference in radiated power between two diaphragm sizes remains smaller than the difference obtained if the radiated power would be proportional to the orifice cross section area. This is confirmed by experiments using an artificial mouth, but the results show that the linear losses are underestimated, and that significant nonlinear losses occur. The measurements are limited to the acoustic pressure at a given distance of the orifice. Experiments also show that rounding edges of the orifice reduces nonlinear losses resulting in an increase of the power radiated and of the extinction threshold, and resulting in a larger dynamical range.

  5. Experimental Study on Effects of Frequency and Mean Pressure on Heat Pumping by Acoustic Oscillation

    NASA Astrophysics Data System (ADS)

    Kawamoto, Akira; Ozawa, Mamoru; Kataoka, Masaki; Takifuji, Tomonari

    Experimental studies were conducted for the fundamental understanding of the thermoacoustic behavior in the simulated resonance-tube refrigerator with special reference to the effect of imposed frequency and mean pressure. The resonance frequency in the case of helium was lower by about 20% than the theoretical prediction, while the experimental value in the case of air was almost the same as the theoretical one. The temperature difference observed along the stack increased with the increase in the amplitude of acoustic pressure, and decreased with the increase in the mean pressure, Based on the simplified model of heat pumping process, the relationship between the temperature variation and the acoustic pressure field was formulated, and thus the characteristic parameter which represents overall heat transfer between gas and stack plates or heat exchangers was obtained.

  6. Correlation of combustor acoustic power levels inferred from internal fluctuating pressure measurements

    NASA Technical Reports Server (NTRS)

    Vonglahn, U. H.

    1978-01-01

    Combustion chamber acoustic power levels inferred from internal fluctuating pressure measurements are correlated with operating conditions and chamber geometries over a wide range. The variables include considerations of chamber design (can, annular, and reverse-flow annular) and size, number of fuel nozzles, burner staging and fuel split, airflow and heat release rates, and chamber inlet pressure and temperature levels. The correlated data include those obtained with combustion component development rigs as well as engines.

  7. Method for predicting pump-induced acoustic pressures in fluid-handling systems. [ACSTIC code

    SciTech Connect

    Schwirian, R.E.; Shockling, L.A.; Singleton, N.R.; Riddell, R.A.

    1982-01-01

    A method is described for predicting the amplitudes of pump-induced acoustic pressures in fluid-handling systems using a node-flow path discretization methodology and a harmonic analysis algorithm. A computer model of a Westinghouse test loop using the volumetric forcing function model of the pump is presented. Comparisons of measured pressure amplitude profiles in the loop with model prediction are shown to be in good agreement for both the first and second pump blade-passing frequencies. 10 refs.

  8. Nonlinear effects of flow unsteadiness on the acoustic radiation of a heaving airfoil

    NASA Astrophysics Data System (ADS)

    Manela, Avshalom

    2013-12-01

    The study considers the combined effects of boundary animation (small-amplitude heaving) and incoming flow unsteadiness (incident vorticity) on the vibroacoustic signature of a thin rigid airfoil in low-Mach number flow. The potential-flow problem is analysed using the Brown and Michael equation, yielding the incident vortex trajectory and time evolution of trailing edge wake. The dynamical description serves as an effective source term to evaluate the far-field sound using Powell-Howe analogy. The results identify the fluid-airfoil system as a dipole-type source, and demonstrate the significance of nonlinear eddy-airfoil interactions on the acoustic radiation. Based on the value of scaled heaving frequency ωa/U (with ω the dimensional heaving frequency, a the airfoil half-chord, and U the mean flow speed), the system behaviour can be divided into two characteristic regimes: (i) for ωa/U≪1, the effect of heaving is minor, and the acoustic response is well approximated by considering the interaction of a line vortex with a stationary airfoil; (ii) for ωa/U≫1, the impact of heaving is dominant, radiating sound through an “airfoil motion” dipole oriented along the direction of heaving. In between (for ωa/U~O(1)), an intermediate regime takes place. The results indicate that trailing edge vorticity has a two-fold impact on the acoustic far field: while reducing pressure fluctuations generated by incident vortex interaction with the airfoil, trailing edge vortices transmit sound along the mean-flow direction, characterized by airfoil heaving frequency. The “silencing” effect of trailing edge vorticity is particularly efficient when the incident vortex passes close to the airfoil trailing edge: at that time, application of the Kutta condition implies the release of a trailing edge vortex in the opposite direction to the incident vortex; the released vortex then detaches from the airfoil and follows the incident vortex, forming a “silent” vortex pair

  9. Generation of acoustic waves by focused infrared neodymium-laser radiation

    NASA Astrophysics Data System (ADS)

    Ward, Barry

    1991-02-01

    When the radiation from a sufficiently powerful pulsed laser is focused into the transparent gaseous, liquid or solid media, dielectric breakdown may occur around the beam waist giving rise to a short-lived high-temperature plasma which quickly heats the surrounding material. As a consequence of various energy-coupling mechanisms, this phenomenon causes the emission of one or more high-frequency ultrasonic acoustic waves whose speeds of propagation are dependent upon the physical properties of the host medium. In the high-speed photographic studies described, the 1.06 micron near-infrared radiation from an 8-ns, 10-mJ Q-switched Nd:YAG laser is focused in or onto a variety of fluid and solid materials. The rapid variations in density around the resulting plasma events are visualized using a Mach-Zehnder interferometer with a sub-nanosecond dye-laser light source and a video-imaging system. Calculations of the corresponding transient pressure distributions are then enacted from the digitally-recorded interferograms using a semi-automatic procedure under the control of a personal computer. Measurements of position, displacement, and velocity are also carried out using the same optical apparatus in schlieren and focused shadowgraph high-speed photographic measurements. The experimental work outlined in the following chapters is divided into three broad fields of interest. In the first of these, a study of the laser-generation of spherical shock waves in atmospheric air is carried out. In the second, the neodymium-laser beam is focused onto different solid-fluid interfaces resulting in the formation of bulk longitudinal and shear waves and surface acoustic waves. The interactions of these waves with various obstacles and defects are investigated with reference to their application to non-destructive testing. In the third and most important field, a detailed study of the dynamics of laser-induced cavitation bubbles in water is carried out. With regard to the associated

  10. Acoustic microscopy and nonlinear effects in pressurized superfluid helium. Technical report

    SciTech Connect

    Moulthrop, A.A.; Muha, M.S.; Kozlowski, G.C.; Silva, C.P.; Hadimioglu, B.

    1993-08-31

    The operation of an acoustic microscope having a resolution of 15 nm has been demonstrated. It uses as a coupling medium superfluid 4He colder than 0.9 K and pressurized to greater than 20 bar. The microscope is now being used to image objects that show little or no contrast on a scanning electron microscope. In addition, the acoustic microscope is being used to study the properties of sound propagation in the coupling fluid. At low acoustic intensities, the coupling fluid has very low acoustic attenuation at the microscope's operating frequency (15.3 GHz), but near the focal point the acoustic intensity can be high enough that the helium behaves with extreme nonlinearity. In fact, this medium is capable of entering new regimes of nonlinear interaction. Plots of the received signal versus input power display a nearly complete pump depletion at certain input power levels and a reconversion to the pump frequency at higher power levels. Such behavior has never before been observed. The authors present arguments that the process underlying this nonlinear behavior is harmonic generation. Cryogenic microscopy, Harmonic generation, Nonlinear acoustics.

  11. Radiation Pressure Measurements on Micron-Size Individual Dust Grains

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P. D.; Spann, J. F.; Witherow, W. K.; West, E. A.; Gallagher, D. L.; Adrian, M. L.; Fishman, G. J.; Tankosic, D.; LeClair, A.

    2003-01-01

    Measurements of electromagnetic radiation pressure have been made on individual silica (SiO2) particles levitated in an electrodynamic balance. These measurements were made by inserting single charged particles of known diameter in the 0.2- to 6.82-micron range and irradiating them from above with laser radiation focused to beam widths of approximately 175- 400 microns at ambient pressures particle due to the radiation force is balanced by the electrostatic force indicated by the compensating dc potential applied to the balance electrodes, providing a direct measure of the radiation force on the levitated particle. Theoretical calculations of the radiation pressure with a least-squares fit to the measured data yield the radiation pressure efficiencies of the particles, and comparisons with Mie scattering theory calculations provide the imaginary part of the refractive index of SiO2 and the corresponding extinction and scattering efficiencies.

  12. Acoustic Detection Of Loose Particles In Pressure Sensors

    NASA Technical Reports Server (NTRS)

    Kwok, Lloyd C.

    1995-01-01

    Particle-impact-noise-detector (PIND) apparatus used in conjunction with computer program analyzing output of apparatus to detect extraneous particles trapped in pressure sensors. PIND tester essentially shaker equipped with microphone measuring noise in pressure sensor or other object being shaken. Shaker applies controlled vibration. Output of microphone recorded and expressed in terms of voltage, yielding history of noise subsequently processed by computer program. Data taken at sampling rate sufficiently high to enable identification of all impacts of particles on sensor diaphragm and on inner surfaces of sensor cavities.

  13. 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.

  14. Tunable optical lens array using viscoelastic material and acoustic radiation force

    SciTech Connect

    Koyama, Daisuke Kashihara, Yuta; Matsukawa, Mami; Hatanaka, Megumi; Nakamura, Kentaro

    2015-10-28

    A movable optical lens array that uses acoustic radiation force was investigated. The lens array consists of a glass plate, two piezoelectric bimorph transducers, and a transparent viscoelastic gel film. A cylindrical lens array with a lens pitch of 4.6 mm was fabricated using the acoustic radiation force generated by the flexural vibration of the glass plate. The focal point and the positioning of the lenses can be changed using the input voltage and the driving phase difference between the two transducers, respectively.

  15. Confocal acoustic radiation force optical coherence elastography using a ring ultrasonic transducer

    SciTech Connect

    Qi, Wenjuan; Li, Rui; Ma, Teng; Kirk Shung, K.; Zhou, Qifa; Chen, Zhongping

    2014-03-24

    We designed and developed a confocal acoustic radiation force optical coherence elastography system. A ring ultrasound transducer was used to achieve reflection mode excitation and generate an oscillating acoustic radiation force in order to generate displacements within the tissue, which were detected using the phase-resolved optical coherence elastography method. Both phantom and human tissue tests indicate that this system is able to sense the stiffness difference of samples and quantitatively map the elastic property of materials. Our confocal setup promises a great potential for point by point elastic imaging in vivo and differentiation of diseased tissues from normal tissue.

  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. PMID:26627818

  17. The Dynamics of Vapor Bubbles in Acoustic Pressure Fields

    NASA Technical Reports Server (NTRS)

    Hao, Y.; Prosperetti, A.

    1999-01-01

    In spite of a superficial similarity with gas bubbles, the intimate coupling between dynamical and thermal processes confers to oscillating vapor bubbles some unique characteristics. This paper examines numerically the validity of some asymptotic-theory predictions such as the existence of two resonant radii and a limit size for a given sound amplitude and frequency. It is found that a small vapor bubble in a sound field of sufficient amplitude grows quickly through resonance and continues to grow thereafter at a very slow rate, seemingly indefinitely. Resonance phenomena therefore play a role for a few cycles at most, and reaching a limit size-if one exists at all-is found to require far more than several tens of thousands of cycles. It is also found that some small bubbles may grow or collapse depending on the phase of the sound field. The model accounts in detail for the thermo-fluid-mechanic processes in the vapor. In the second part of the paper, an approximate formulation valid for bubbles small with respect to the thermal penetration length in the vapor is derived and its accuracy examined, The present findings have implications for acoustically enhanced boiling heat transfer and other special applications such as boiling in microgravity.

  18. Nonlinear Response of Composite Panels Under Combined Acoustic Excitation and Aerodynamic Pressure

    NASA Technical Reports Server (NTRS)

    Abdel-Motagaly, K.; Duan, B.; Mei, C.

    1999-01-01

    A finite element formulation is presented for the analysis of large deflection response of composite panels subjected to aerodynamic pressure- at supersonic flow and high acoustic excitation. The first-order shear deformation theory is considered for laminated composite plates, and the von Karman nonlinear strain-displacement relations are employed for the analysis of large deflection panel response. The first-order piston theory aerodynamics and the simulated Gaussian white noise are employed for the aerodynamic and acoustic loads, respectively. The nonlinear equations of motion for an arbitrarily laminated composite panel subjected to a combined aerodynamic and acoustic pressures are formulated first in structure node degrees-of-freedom. The system equations are then transformed and reduced to a set of coupled nonlinear equations in modal coordinates. Modal participation is defined and the in-vacuo modes to be retained in the analysis are based on the modal participation values. Numerical results include root mean square values of maximum deflections, deflection and strain response time histories, probability distributions, and power spectrum densities. Results showed that combined acoustic and aerodynamic loads have to be considered for panel analysis and design at high dynamic pressure values.

  19. One-dimensional pressure transfer models for acoustic-electric transmission channels

    NASA Astrophysics Data System (ADS)

    Wilt, K. R.; Lawry, T. J.; Scarton, H. A.; Saulnier, G. J.

    2015-09-01

    A method for modeling piezoelectric-based ultrasonic acoustic-electric power and data transmission channels is presented. These channels employ piezoelectric disk transducers to convey signals across a series of physical layers using ultrasonic waves. This model decomposes the mechanical pathway of the signal into individual ultrasonic propagation layers which are generally independent of the layer's adjacent domains. Each layer is represented by a two-by-two traveling pressure wave transfer matrix which relates the forward and reverse pressure waves on one side of the layer to the pressure waves on the opposite face, where each face is assumed to be in contact with a domain of arbitrary reference acoustic impedance. A rigorous implementation of ultrasonic beam spreading is introduced and implemented within applicable domains. Compatible pressure-wave models for piezoelectric transducers are given, which relate the electric voltage and current interface of the transducer to the pressure waves on one mechanical interface while also allowing for passive acoustic loading of the secondary mechanical interface. It is also shown that the piezoelectric model's electrical interface is compatible with transmission line parameters (ABCD-parameters), allowing for connection of electronic components and networks. The model is shown to be capable of reproducing the behavior of realistic physical channels.

  20. Liver reserve function assessment by acoustic radiation force impulse imaging

    PubMed Central

    Sun, Xiao-Lan; Liang, Li-Wei; Cao, Hui; Men, Qiong; Hou, Ke-Zhu; Chen, Zhen; Zhao, Ya-E

    2015-01-01

    AIM: To evaluate the utility of liver reserve function by acoustic radiation force impulse (ARFI) imaging in patients with liver tumors. METHODS: Seventy-six patients with liver tumors were enrolled in this study. Serum biochemical indexes, such as aminotransferase (ALT), aspartate aminotransferase (AST), serum albumin (ALB), total bilirubin (T-Bil), and other indicators were observed. Liver stiffness (LS) was measured by ARFI imaging, measurements were repeated 10 times, and the average value of the results was taken as the final LS value. Indocyanine green (ICG) retention was performed, and ICG-K and ICG-R15 were recorded. Child-Pugh (CP) scores were carried out based on patient’s preoperative biochemical tests and physical condition. Correlations among CP scores, ICG-R15, ICG-K and LS values were observed and analyzed using either the Pearson correlation coefficient or the Spearman rank correlation coefficient. Kruskal-Wallis test was used to compare LS values of CP scores, and the receiver-operator characteristic (ROC) curve was used to analyze liver reserve function assessment accuracy. RESULTS: LS in the ICG-R15 10%-20% group was significantly higher than in the ICG-R15 < 10% group; and the difference was statistically significant (2.19 ± 0.27 vs 1.59 ± 0.32, P < 0.01). LS in the ICG-R15 > 20% group was significantly higher than in the ICG-R15 < 10% group; and the difference was statistically significant (2.92 ± 0.29 vs 1.59 ± 0.32, P < 0.01). The LS value in patients with CP class A was lower than in patients with CP class B (1.57 ± 0.34 vs 1.86 ± 0.27, P < 0.05), while the LS value in patients with CP class B was lower than in patients with CP class C (1.86 ± 0.27 vs 2.47 ± 0.33, P < 0.01). LS was positively correlated with ICG-R15 (r = 0.617, P < 0.01) and CP score (r = 0.772, P < 0.01). Meanwhile, LS was negatively correlated with ICG-K (r = -0.673, P < 0.01). AST, ALT and T-Bil were positively correlated with LS, while ALB was negatively

  1. Brillouin-scattering determination of the acoustic properties and their pressure dependence for three polymeric elastomers.

    PubMed

    Stevens, Lewis L; Orler, E Bruce; Dattelbaum, Dana M; Ahart, Muhtar; Hemley, Russell J

    2007-09-14

    The acoustic properties of three polymer elastomers, a cross-linked poly(dimethylsiloxane) (Sylgard 184), a cross-linked terpolymer poly(ethylene-vinyl acetate-vinyl alcohol), and a segmented thermoplastic poly(ester urethane) copolymer (Estane 5703), have been measured from ambient pressure to approximately 12 GPa by using Brillouin scattering in high-pressure diamond anvil cells. The Brillouin-scattering technique is a powerful tool for aiding in the determination of equations of state for a variety of materials, but to date has not been applied to polymers at pressures exceeding a few kilobars. For the three elastomers, both transverse and longitudinal acoustic modes were observed, though the transverse modes were observed only at elevated pressures (>0.7 GPa) in all cases. From the Brillouin frequency shifts, longitudinal and transverse sound speeds were calculated, as were the C(11) and C(12) elastic constants, bulk, shear, and Young's moduli, and Poisson's ratios, and their respective pressure dependencies. P-V isotherms were then constructed, and fit to several empirical/semiempirical equations of state to extract the isothermal bulk modulus and its pressure derivative for each material. Finally, the lack of shear waves observed for any polymer at ambient pressure, and the pressure dependency of their appearance is discussed with regard to instrumental and material considerations.

  2. Brillouin-scattering determination of the acoustic properties and their pressure dependence for three polymeric elastomers

    NASA Astrophysics Data System (ADS)

    Stevens, Lewis L.; Orler, E. Bruce; Dattelbaum, Dana M.; Ahart, Muhtar; Hemley, Russell J.

    2007-09-01

    The acoustic properties of three polymer elastomers, a cross-linked poly(dimethylsiloxane) (Sylgard® 184), a cross-linked terpolymer poly(ethylene-vinyl acetate-vinyl alcohol), and a segmented thermoplastic poly(ester urethane) copolymer (Estane® 5703), have been measured from ambient pressure to approximately 12GPa by using Brillouin scattering in high-pressure diamond anvil cells. The Brillouin-scattering technique is a powerful tool for aiding in the determination of equations of state for a variety of materials, but to date has not been applied to polymers at pressures exceeding a few kilobars. For the three elastomers, both transverse and longitudinal acoustic modes were observed, though the transverse modes were observed only at elevated pressures (>0.7GPa) in all cases. From the Brillouin frequency shifts, longitudinal and transverse sound speeds were calculated, as were the C11 and C12 elastic constants, bulk, shear, and Young's moduli, and Poisson's ratios, and their respective pressure dependencies. P-V isotherms were then constructed, and fit to several empirical/semiempirical equations of state to extract the isothermal bulk modulus and its pressure derivative for each material. Finally, the lack of shear waves observed for any polymer at ambient pressure, and the pressure dependency of their appearance is discussed with regard to instrumental and material considerations.

  3. Suppression of sound radiation to far field of near-field acoustic communication system using evanescent sound field

    NASA Astrophysics Data System (ADS)

    Fujii, Ayaka; Wakatsuki, Naoto; Mizutani, Koichi

    2016-01-01

    A method of suppressing sound radiation to the far field of a near-field acoustic communication system using an evanescent sound field is proposed. The amplitude of the evanescent sound field generated from an infinite vibrating plate attenuates exponentially with increasing a distance from the surface of the vibrating plate. However, a discontinuity of the sound field exists at the edge of the finite vibrating plate in practice, which broadens the wavenumber spectrum. A sound wave radiates over the evanescent sound field because of broadening of the wavenumber spectrum. Therefore, we calculated the optimum distribution of the particle velocity on the vibrating plate to reduce the broadening of the wavenumber spectrum. We focused on a window function that is utilized in the field of signal analysis for reducing the broadening of the frequency spectrum. The optimization calculation is necessary for the design of window function suitable for suppressing sound radiation and securing a spatial area for data communication. In addition, a wide frequency bandwidth is required to increase the data transmission speed. Therefore, we investigated a suitable method for calculating the sound pressure level at the far field to confirm the variation of the distribution of sound pressure level determined on the basis of the window shape and frequency. The distribution of the sound pressure level at a finite distance was in good agreement with that obtained at an infinite far field under the condition generating the evanescent sound field. Consequently, the window function was optimized by the method used to calculate the distribution of the sound pressure level at an infinite far field using the wavenumber spectrum on the vibrating plate. According to the result of comparing the distributions of the sound pressure level in the cases with and without the window function, it was confirmed that the area whose sound pressure level was reduced from the maximum level to -50 dB was

  4. Evaluation of Acoustic Emission SHM of PRSEUS Composite Pressure Cube Tests

    NASA Technical Reports Server (NTRS)

    Horne, Michael R.; Madaras, Eric I.

    2013-01-01

    A series of tests of the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) pressure cube were conducted during third quarter 2011 at NASA Langley Research Center (LaRC) in the Combined Loads Test facility (COLTS). This is a report of the analysis of the Acoustic Emission (AE) data collected during those tests. The AE signals of the later tests are consistent with the final failure progression through two of the pressure cube panels. Calibration tests and damage precursor AE indications, from preliminary checkout pressurizations, indicated areas of concern that eventually failed. Hence those tests have potential for vehicle health monitoring.

  5. Optical measurement of acoustic pressure amplitudes-at the sensitivity limits of Rayleigh scattering.

    PubMed

    Rausch, Anne; Fischer, André; Kings, Nancy; Bake, Friedrich; Roehle, Ingo

    2012-07-01

    Rayleigh scattering is a measurement technique applicable for the determination of density distributions in various technical or natural flows. The current sensitivity limits of the Rayleigh scattering technique were investigated experimentally. It is shown that it is possible to measure density oscillations caused by acoustic pressure oscillations noninvasively and directly. Acoustical standing waves in a rectangular duct were investigated using Rayleigh scattering and compared to microphone measurements. The comparison showed a sensitivity of the Rayleigh scattering technique of 75 Pa (7·10(-4) kg/m(3)) and a precision of 14 Pa (1·10(-4) kg/m(3)). Therefore, it was also shown that Rayleigh scattering is applicable for acoustic measurements. PMID:22743495

  6. Surprises and anomalies in acoustical and optical scattering and radiation forces

    NASA Astrophysics Data System (ADS)

    Marston, Philip L.

    2015-09-01

    Experiments on radiation torques and negative radiation forces by various researchers display how the underlying wave-field geometry influences radiation forces. Other situations strongly influenced by wave-field geometry include high-order caustics present in light-scattering patterns of objects as simple as oblate drops of water or oblate bubbles of air in water. Related theoretical and experimental investigations are considered. Acoustic scattering enhancements associated with various guided waves are also examined. These include guided waves having negative group velocities and guided wave radiating wavefronts having a vanishing Gaussian curvature.

  7. Core-Shell Particles that are Unresponsive to Acoustic Radiation Force

    NASA Astrophysics Data System (ADS)

    Leão-Neto, J. P.; Lopes, J. H.; Silva, G. T.

    2016-08-01

    We theoretically demonstrate that core-shell particles with a designed cloaking shell can be unresponsive to acoustic radiation force in an inviscid fluid. The core-shell particles' size is assumed to be much smaller than the incident wavelength, i.e., the long-wavelength limit. The cloaking shell should have an optimal thickness with which the radiation force is drastically attenuated or even totally suppressed. We show that absorbing shells (polymer type) do not yield neutrality under the radiation force of traveling waves. Such a restriction does not appear in the case of standing waves. In addition, we establish the conditions for the suppression of the acoustic interaction forces (secondary radiation forces) between two or more cloaked particles.

  8. Acoustical radiation torque and force for spheres and Bessel beam extinction efficiency

    NASA Astrophysics Data System (ADS)

    Marston, Philip L.; Zhang, Likun

    2014-11-01

    The scattering of optical and acoustical beams is relevant to the levitation and manipulation of drops. Here we examine theoretical developments in the acoustical case. We previously showed how the optical theorem for extinction can be extended to invariant beams. The example of a sphere in a Bessel beam facilitates the direct comparison with a circular disc computed using Babinet's principle and the Kirchhoff approximation. In related work, by considering traveling or standing wave first-order vortex beams we previously showed that the radiation torque is the ratio of the absorbed power and the radian acoustic frequency. By modifying the scattering to account for the viscosity of the surrounding fluid in the analysis of the absorbed power, approximations for radiation torque and force are obtained at long wavelengths in special cases and these can be compared with results published elsewhere.

  9. Acoustic manipulation of active spherical carriers: Generation of negative radiation force

    NASA Astrophysics Data System (ADS)

    Rajabi, Majid; Mojahed, Alireza

    2016-09-01

    This paper examines theoretically a novel mechanism of generating negative (pulling) radiation force for acoustic manipulation of spherical carriers equipped with piezoelectric actuators in its inner surface. In this mechanism, the spherical particle is handled by common plane progressive monochromatic acoustic waves instead of zero-/higher- order Bessel beams or standing waves field. The handling strategy is based on applying a spatially uniform harmonic electrical voltage at the piezoelectric actuator with the same frequency of handling acoustic waves, in order to change the radiation force effect from repulsive (away from source) to attractive (toward source). This study may be considered as a start point for development of contact-free precise handling and entrapment technology of active carriers which are essential in many engineering and medicine applications.

  10. SU-E-CAMPUS-T-02: Exploring Radiation Acoustics CT Dosimeter Design Aspects for Proton Therapy

    SciTech Connect

    Alsanea, F; Moskvin, V; Stantz, K

    2014-06-15

    Purpose: Investigate the design aspects and imaging dose capabilities of the Radiation Acoustics Computed Tomography (RA CT) dosimeter for Proton induced acoustics, with the objective to characterize a pulsed pencil proton beam. The focus includes scanner geometry, transducer array, and transducer bandwidth on image quality. Methods: The geometry of the dosimeter is a cylindrical water phantom (length 40cm, radius 15cm) with 71 ultrasound transducers placed along the length and end of the cylinder to achieve a weighted set of projections with spherical sampling. A 3D filtered backprojection algorithm was used to reconstruct the dosimetric images and compared to MC dose distribution. First, 3D Monte Carlo (MC) Dose distributions for proton beam energies (range of 12cm, 16cm, 20cm, and 27cm) were used to simulate the acoustic pressure signal within this scanner for a pulsed proton beam of 1.8x107 protons, with a pulse width of 1 microsecond and a rise time of 0.1 microseconds. Dose comparison within the Bragg peak and distal edge were compared to MC analysis, where the integrated Gaussian was used to locate the 50% dose of the distal edge. To evaluate spatial fidelity, a set of point sources within the scanner field of view (15×15×15cm3) were simulated implementing a low-pass bandwidth response function (0 to 1MHz) equivalent to a multiple frequency transducer array, and the FWHM of the point-spread-function determined. Results: From the reconstructed images, RACT and MC range values are within 0.5mm, and the average variation of the dose within the Bragg peak are within 2%. The spatial resolution tracked with transducer bandwidth and projection angle sampling, and can be kept at 1.5mm. Conclusion: This design is ready for fabrication to start acquiring measurements. The 15 cm FOV is an optimum size for imaging dosimetry. Currently, simulations comparing transducer sensitivity, bandwidth, and proton beam parameters are being evaluated to assess signal-to-noise.

  11. Integration of Acoustic Radiation Force and Optical Imaging for Blood Plasma Clot Stiffness Measurement

    PubMed Central

    Wang, Caroline W.; Perez, Matthew J.; Helmke, Brian P.; Viola, Francesco; Lawrence, Michael B.

    2015-01-01

    Despite the life-preserving function blood clotting serves in the body, inadequate or excessive blood clot stiffness has been associated with life-threatening diseases such as stroke, hemorrhage, and heart attack. The relationship between blood clot stiffness and vascular diseases underscores the importance of quantifying the magnitude and kinetics of blood’s transformation from a fluid to a viscoelastic solid. To measure blood plasma clot stiffness, we have developed a method that uses ultrasound acoustic radiation force (ARF) to induce micron-scaled displacements (1-500 μm) on microbeads suspended in blood plasma. The displacements were detected by optical microscopy and took place within a micro-liter sized clot region formed within a larger volume (2 mL sample) to minimize container surface effects. Modulation of the ultrasound generated acoustic radiation force allowed stiffness measurements to be made in blood plasma from before its gel point to the stage where it was a fully developed viscoelastic solid. A 0.5 wt % agarose hydrogel was 9.8-fold stiffer than the plasma (platelet-rich) clot at 1 h post-kaolin stimulus. The acoustic radiation force microbead method was sensitive to the presence of platelets and strength of coagulation stimulus. Platelet depletion reduced clot stiffness 6.9 fold relative to platelet rich plasma. The sensitivity of acoustic radiation force based stiffness assessment may allow for studying platelet regulation of both incipient and mature clot mechanical properties. PMID:26042775

  12. Intravascular Ultrasound Catheter to Enhance Microbubble-Based Drug Delivery via Acoustic Radiation Force

    PubMed Central

    Kilroy, Joseph P.; Klibanov, Alexander L.; Wamhoff, Brian R.; Hossack, John A.

    2015-01-01

    Previous research has demonstrated that acoustic radiation force enhances intravascular microbubble adhesion to blood vessels in the presence of flow for molecular-targeted ultrasound imaging and drug delivery. A prototype acoustic radiation force intravascular ultrasound (ARFIVUS) catheter was designed and fabricated to displace a microbubble contrast agent in flow representative of conditions encountered in the human carotid artery. The prototype ARFIVUS transducer was designed to match the resonance frequency of 1.4- to 2.6-μm-diameter microbubbles modeled by an experimentally verified 1-D microbubble acoustic radiation force translation model. The transducer element was an elongated Navy Type I (hard) lead zirconate titanate (PZT) ceramic designed to operate at 3 MHz. Fabricated devices operated with center frequencies of 3.3 and 3.6 MHz with −6-dB fractional bandwidths of 55% and 50%, respectively. Microbubble translation velocities as high as 0.86 m/s were measured using a high-speed streak camera when insonating with the ARFIVUS transducer. Finally, the prototype was used to displace microbubbles in a flow phantom while imaging with a commercial 45-MHz imaging IVUS transducer. A sustained increase of 31 dB in average video intensity was measured following insonation with the ARFIVUS, indicating microbubble accumulation resulting from the application of acoustic radiation force. PMID:23143566

  13. Integration of acoustic radiation force and optical imaging for blood plasma clot stiffness measurement.

    PubMed

    Wang, Caroline W; Perez, Matthew J; Helmke, Brian P; Viola, Francesco; Lawrence, Michael B

    2015-01-01

    Despite the life-preserving function blood clotting serves in the body, inadequate or excessive blood clot stiffness has been associated with life-threatening diseases such as stroke, hemorrhage, and heart attack. The relationship between blood clot stiffness and vascular diseases underscores the importance of quantifying the magnitude and kinetics of blood's transformation from a fluid to a viscoelastic solid. To measure blood plasma clot stiffness, we have developed a method that uses ultrasound acoustic radiation force (ARF) to induce micron-scaled displacements (1-500 μm) on microbeads suspended in blood plasma. The displacements were detected by optical microscopy and took place within a micro-liter sized clot region formed within a larger volume (2 mL sample) to minimize container surface effects. Modulation of the ultrasound generated acoustic radiation force allowed stiffness measurements to be made in blood plasma from before its gel point to the stage where it was a fully developed viscoelastic solid. A 0.5 wt % agarose hydrogel was 9.8-fold stiffer than the plasma (platelet-rich) clot at 1 h post-kaolin stimulus. The acoustic radiation force microbead method was sensitive to the presence of platelets and strength of coagulation stimulus. Platelet depletion reduced clot stiffness 6.9 fold relative to platelet rich plasma. The sensitivity of acoustic radiation force based stiffness assessment may allow for studying platelet regulation of both incipient and mature clot mechanical properties. PMID:26042775

  14. Active Path Selection of Fluid Microcapsules in Artificial Blood Vessel by Acoustic Radiation Force

    NASA Astrophysics Data System (ADS)

    Masuda, Kohji; Muramatsu, Yusuke; Ueda, Sawami; Nakamoto, Ryusuke; Nakayashiki, Yusuke; Ishihara, Ken

    2009-07-01

    Micrometer-sized microcapsules collapse upon exposure to ultrasound. Use of this phenomenon for a drug delivery system (DDS), not only for local delivery of medication but also for gene therapy, should be possible. However, enhancing the efficiency of medication is limited because capsules in suspension diffuse in the human body after injection, since the motion of capsules in blood flow cannot be controlled. To control the behavior of microcapsules, acoustic radiation force was introduced. We detected local changes in microcapsule density by producing acoustic radiation force in an artificial blood vessel. Furthermore, we theoretically estimated the conditions required for active path selection of capsules at a bifurcation point in the artificial blood vessel. We observed the difference in capsule density at both in the bifurcation point and in alternative paths downstream of the bifurcation point for different acoustic radiation forces. Comparing the experimental results with those obtained theoretically, the conditions for active path selection were calculated from the acoustic radiation force and fluid resistance of the capsules. The possibility of controlling capsule flow towards a specific point in a blood vessel was demonstrated.

  15. Acoustic radiation force impulse imaging of vulnerable plaques: a finite element method parametric analysis

    PubMed Central

    Doherty, Joshua R.; Dumont, Douglas M.; Trahey, Gregg E.; Palmeri, Mark L.

    2012-01-01

    Plaque rupture is the most common cause of complications such as stroke and coronary heart failure. Recent histopathological evidence suggests that several plaque features, including a large lipid core and a thin fibrous cap, are associated with plaques most at risk for rupture. Acoustic Radiation Force Impulse (ARFI) imaging, a recently developed ultrasound-based elasticity imaging technique, shows promise for imaging these features noninvasively. Clinically, this could be used to distinguish vulnerable plaques, for which surgical intervention may be required, from those less prone to rupture. In this study, a parametric analysis using Finite-Element Method (FEM) models was performed to simulate ARFI imaging of five different carotid artery plaques across a wide range of material properties. It was demonstrated that ARFI could resolve the softer lipid pool from the surrounding, stiffer media and fibrous cap and was most dependent upon the stiffness of the lipid pool component. Stress concentrations due to an ARFI excitation were located in the media and fibrous cap components. In all cases, the maximum Von Mises stress was < 1.2 kPa. In comparing these results with others investigating plaque rupture, it is concluded that while the mechanisms may be different, the Von Mises stresses imposed by ARFI are orders of magnitude lower than the stresses associated with blood pressure. PMID:23122224

  16. Reconstruction of an acoustic pressure field in a resonance tube by particle image velocimetry.

    PubMed

    Kuzuu, K; Hasegawa, S

    2015-11-01

    A technique for estimating an acoustic field in a resonance tube is suggested. The estimation of an acoustic field in a resonance tube is important for the development of the thermoacoustic engine, and can be conducted employing two sensors to measure pressure. While this measurement technique is known as the two-sensor method, care needs to be taken with the location of pressure sensors when conducting pressure measurements. In the present study, particle image velocimetry (PIV) is employed instead of a pressure measurement by a sensor, and two-dimensional velocity vector images are extracted as sequential data from only a one- time recording made by a video camera of PIV. The spatial velocity amplitude is obtained from those images, and a pressure distribution is calculated from velocity amplitudes at two points by extending the equations derived for the two-sensor method. By means of this method, problems relating to the locations and calibrations of multiple pressure sensors are avoided. Furthermore, to verify the accuracy of the present method, the experiments are conducted employing the conventional two-sensor method and laser Doppler velocimetry (LDV). Then, results by the proposed method are compared with those obtained with the two-sensor method and LDV.

  17. Evaluation of Acoustic Emission NDE of Kevlar Composite Over Wrapped Pressure Vessels

    NASA Technical Reports Server (NTRS)

    Horne, Michael R.; Madaras, Eric I.

    2008-01-01

    Pressurization and failure tests of small Kevlar/epoxy COPV bottles were conducted during 2006 and 2007 by Texas Research Institute Austin, Inc., at TRI facilities. This is a report of the analysis of the Acoustic Emission (AE) data collected during those tests. Results of some of the tests indicate a possibility that AE can be used to track the stress-rupture degradation of COPV vessels.

  18. PACT - a bottom pressure based, compact deep-ocean tsunameter with acoustic surface coupling

    NASA Astrophysics Data System (ADS)

    Macrander, A.; Gouretski, V.; Boebel, O.

    2009-04-01

    The German-Indonsian Tsunami Early Warning System (GITEWS) processes a multitude of information to comprehensively and accurately evaluate the possible risks inherent to seismic events around Indonesia. Within just a few minutes, measurements of the vibration and horizontal movements off the coastal regions of Indonesia provide a clear picture of the location and intensity of a seaquake. However, not every seaquake causes a tsunami, nor is every tsunami caused by a seaquake. To avoid nerve-wrecking and costly false alarms and to protect against tsunamis caused by landslides, the oceanic sea-level must be measured directly. This goal is pursued in the GITEWS work package "ocean instrumentation", aiming at a a highest reliability and redundancy by developing a set of independent instruments, which measure the sea-level both offshore in the deep ocean and at the coast on the islands off Indonesia. Deep ocean sea-level changes less than a centimetre can be detected by pressure gauges deployed at the sea floor. Based on some of the concepts developed as part of the US DART system, a bottom pressure based, acoustically coupled tsunami detector (PACT) was developed under the auspices of the AWI in collaboration with two German SME and with support of University of Bremen and University of Rhode Island. The PACT system records ocean bottom pressure, performs on-board tsunami detection and acoustically relays the data to the surface buoy. However, employing computational powers and communication technologies of the new millennium, PACT integrates the entire sea-floor package (pressure gauge, data logger and analyzer, acoustic modem, acoustic release and relocation aids) into a single unit, i.e. a standard benthos sphere. PACT thereby reduces costs, minimizes the deployment efforts, while maximizing reliability and maintenance intervals. Several PACT systems are scheduled for their first deployment off Indonesia during 2009. In this presentation, the technical specifications

  19. Acoustic radiation force on a rigid elliptical cylinder in plane (quasi)standing waves

    NASA Astrophysics Data System (ADS)

    Mitri, F. G.

    2015-12-01

    The acoustic radiation force on a 2D elliptical (non-circular) cylinder centered on the axis of wave propagation of plane quasi-standing and standing waves is derived, based on the partial-wave series expansion (PWSE) method in cylindrical coordinates. A non-dimensional acoustic radiation force function, which is the radiation force per unit length, per characteristic energy density and per unit cross-sectional surface of the ellipse, is defined in terms of the scattering coefficients that are determined by applying the Neumann boundary condition for an immovable surface. A system of linear equations involving a single numerical integration procedure is solved by matrix inversion. Numerical simulations showing the transition from the quasi-standing to the (equi-amplitude) standing wave behaviour are performed with particular emphasis on the aspect ratio a/b, where a and b are the ellipse semi-axes, as well as the dimensionless size parameter kb (where k is the wavenumber), without the restriction to a particular range of frequencies. It is found that at high kb values > 1, the radiation force per length with broadside incidence is larger, whereas the opposite situation occurs in the long-wavelength limit (i.e., kb < 1). The results are particularly relevant in acoustic levitation of elliptical cylinders, the acoustic stabilization of liquid columns in a host medium, acousto-fluidics devices, and other particle dynamics applications to name a few. Moreover, the formalism presented here may be effectively applied to compute the acoustic radiation force on other 2D surfaces of arbitrary shape such as super-ellipses, Chebyshev cylindrical particles, or other non-circular geometries.

  20. Acoustic radiation force on a rigid elliptical cylinder in plane (quasi)standing waves

    SciTech Connect

    Mitri, F. G.

    2015-12-07

    The acoustic radiation force on a 2D elliptical (non-circular) cylinder centered on the axis of wave propagation of plane quasi-standing and standing waves is derived, based on the partial-wave series expansion (PWSE) method in cylindrical coordinates. A non-dimensional acoustic radiation force function, which is the radiation force per unit length, per characteristic energy density and per unit cross-sectional surface of the ellipse, is defined in terms of the scattering coefficients that are determined by applying the Neumann boundary condition for an immovable surface. A system of linear equations involving a single numerical integration procedure is solved by matrix inversion. Numerical simulations showing the transition from the quasi-standing to the (equi-amplitude) standing wave behaviour are performed with particular emphasis on the aspect ratio a/b, where a and b are the ellipse semi-axes, as well as the dimensionless size parameter kb (where k is the wavenumber), without the restriction to a particular range of frequencies. It is found that at high kb values > 1, the radiation force per length with broadside incidence is larger, whereas the opposite situation occurs in the long-wavelength limit (i.e., kb < 1). The results are particularly relevant in acoustic levitation of elliptical cylinders, the acoustic stabilization of liquid columns in a host medium, acousto-fluidics devices, and other particle dynamics applications to name a few. Moreover, the formalism presented here may be effectively applied to compute the acoustic radiation force on other 2D surfaces of arbitrary shape such as super-ellipses, Chebyshev cylindrical particles, or other non-circular geometries.

  1. Effect of holed reflector on acoustic radiation force in noncontact ultrasonic dispensing of small droplets

    NASA Astrophysics Data System (ADS)

    Tanaka, Hiroki; Wada, Yuji; Mizuno, Yosuke; Nakamura, Kentaro

    2016-06-01

    We investigated the fundamental aspects of droplet dispensing, which is an important procedure in the noncontact ultrasonic manipulation of droplets in air. A holed reflector was used to dispense a droplet from a 27.4 kHz standing-wave acoustic field to a well. First, the relationship between the hole diameter of the reflector and the acoustic radiation force acting on a levitated droplet was clarified by calculating the acoustic impedance of the point just above the hole. When the hole diameter was half of (or equal to) the acoustic wavelength λ, the acoustic radiation force was ∼80% (or 50%) of that without a hole. The maximal diameters of droplets levitated above the holes through flat and half-cylindrical reflectors were then experimentally investigated. For instance, with the half-cylindrical reflector, the maximal diameter was 5.0 mm for a hole diameter of 6.0 mm, and droplets were levitatable up to a hole diameter of 12 mm (∼λ).

  2. Acoustic radiation force of a Bessel beam on a porous sphere.

    PubMed

    Azarpeyvand, Mahdi

    2012-06-01

    The possibility of using acoustic Bessel beams to produce an axial pulling force on porous particles is examined in an exact manner. The mathematical model utilizes the appropriate partial-wave expansion method in spherical coordinates, while Biot's model is used to describe the wave motion within the poroelastic medium. Of particular interest here is to examine the feasibility of using Bessel beams for (a) acoustic manipulation of fine porous particles and (b) suppression of particle resonances. To verify the viability of the technique, the radiation force and scattering form-function are calculated for aluminum and silica foams at various porosities. Inspection of the results has shown that acoustic manipulation of low porosity (<0.3) spheres is similar to that of solid elastic spheres, but this behavior significantly changes at higher porosities. Results have also shown a strong correlation between the backscattered form-function and the regions of negative radiation force. It has also been observed that the high-order resonances of the particle can be effectively suppressed by choosing the beam conical angle such that the acoustic contribution from that particular mode vanishes. This investigation may be helpful in the development of acoustic tweezers for manipulation of micro-porous drug delivery carrier and contrast agents.

  3. The trade-off characteristics of acoustic and pressure sensors for the NASP

    NASA Technical Reports Server (NTRS)

    Winkler, Martin; Bush, Chuck

    1992-01-01

    Results of a trade study for the development of pressure and acoustic sensors for use on the National Aerospace Plane (NASP) are summarized. Pressure sensors are needed to operate to 100 psia; acoustic sensors are needed that can give meaningful information about a 200 dB sound pressure level (SPL) environment. Both sensors will have to operate from a high temperature of 2000 F down to absolute zero. The main conclusions of the study are the following: (1) Diaphragm materials limit minimum size and maximum frequency response attainable. (2) No transduction is available to meet all the NASP requirements with existing technology. (3) Capacitive sensors are large relative to the requirement, have limited resolution and frequency response due to noise, and cable length is limited to approximately 20 feet. (4) Eddy current sensors are large relative to the requirement and have limited cable lengths. (5) Fiber optic sensors provide the possibility for a small sensor, even though present developments do not exhibit that characteristic. The need to use sapphire at high temperature complicates the design. Present high temperature research sensors suffer from poor resolution. A significant development effort will be required to realize the potential of fiber optics. (6) Short-term development seems to favor eddy current techniques with the penalty of larger size and reduced dynamic range for acoustic sensors. (7) Long-term development may favor fiber optics with the penalties of cost, schedule, and uncertainty.

  4. Numerical simulation of the processes in the normal incidence tube for high acoustic pressure levels

    NASA Astrophysics Data System (ADS)

    Fedotov, E. S.; Khramtsov, I. V.; Kustov, O. Yu.

    2016-10-01

    Numerical simulation of the acoustic processes in an impedance tube at high levels of acoustic pressure is a way to solve a problem of noise suppressing by liners. These studies used liner specimen that is one cylindrical Helmholtz resonator. The evaluation of the real and imaginary parts of the liner acoustic impedance and sound absorption coefficient was performed for sound pressure levels of 130, 140 and 150 dB. The numerical simulation used experimental data having been obtained on the impedance tube with normal incidence waves. At the first stage of the numerical simulation it was used the linearized Navier-Stokes equations, which describe well the imaginary part of the liner impedance whatever the sound pressure level. These equations were solved by finite element method in COMSOL Multiphysics program in axisymmetric formulation. At the second stage, the complete Navier-Stokes equations were solved by direct numerical simulation in ANSYS CFX in axisymmetric formulation. As the result, the acceptable agreement between numerical simulation and experiment was obtained.

  5. The trade-off characteristics of acoustic and pressure sensors for the NASP

    NASA Astrophysics Data System (ADS)

    Winkler, Martin; Bush, Chuck

    1992-09-01

    Results of a trade study for the development of pressure and acoustic sensors for use on the National Aerospace Plane (NASP) are summarized. Pressure sensors are needed to operate to 100 psia; acoustic sensors are needed that can give meaningful information about a 200 dB sound pressure level (SPL) environment. Both sensors will have to operate from a high temperature of 2000 F down to absolute zero. The main conclusions of the study are the following: (1) Diaphragm materials limit minimum size and maximum frequency response attainable. (2) No transduction is available to meet all the NASP requirements with existing technology. (3) Capacitive sensors are large relative to the requirement, have limited resolution and frequency response due to noise, and cable length is limited to approximately 20 feet. (4) Eddy current sensors are large relative to the requirement and have limited cable lengths. (5) Fiber optic sensors provide the possibility for a small sensor, even though present developments do not exhibit that characteristic. The need to use sapphire at high temperature complicates the design. Present high temperature research sensors suffer from poor resolution. A significant development effort will be required to realize the potential of fiber optics. (6) Short-term development seems to favor eddy current techniques with the penalty of larger size and reduced dynamic range for acoustic sensors. (7) Long-term development may favor fiber optics with the penalties of cost, schedule, and uncertainty.

  6. The effects of external acoustic pressure fields on a free-running supercavitating projectile.

    PubMed

    Cameron, Peter J K; Rogers, Peter H; Doane, John W

    2010-12-01

    Proliferation of supercavitating torpedoes has motivated research on countermeasures against them as well as on the fluid phenomenon which makes them possible. The goal of this research was to investigate an envisaged countermeasure, an acoustic field capable of slowing or diverting the weapon by disrupting the cavitation envelope. The research focused on the interactions between high pressure amplitude sound waves and a supercavity produced by a small free-flying projectile. The flight dynamics and cavity geometry measurements were compared to control experiments and theoretical considerations were made for evaluating the effects. Corrugations on the cavity/water interface caused by the pressure signal have been observed and characterized. Results also show that the accuracy of a supercavitating projectile can be adversely affected by the sound signal. This research concludes with results that indicate that it is acoustic cavitation in the medium surrounding the supercavity, caused by the high pressure amplitude sound, that is responsible for the reduced accuracy. A hypothesis has been presented addressing the means by which the acoustic cavitation could cause this effect. PMID:21218872

  7. A Novel Motion Compensation Algorithm for Acoustic Radiation Force Elastography

    PubMed Central

    Hsu, Stephen J.; Trahey, Gregg E.

    2009-01-01

    A novel method of physiological motion compensation for use with radiation force elasticity imaging has been developed. The method utilizes a priori information from finite element method models of the response of soft tissue to impulsive radiation force to isolate physiological motion artifacts from radiation force-induced displacement fields. The new algorithm is evaluated in a series of clinically realistic imaging scenarios, and its performance is compared to that achieved with previously described motion compensation algorithms. Though not without limitations, the new model-based motion compensation algorithm performs favorably in many circumstances and may be a logical choice for use with in vivo abdominal imaging. PMID:18519218

  8. Radiation and Maxwell Stress Stabilization of Liquid Bridges

    NASA Technical Reports Server (NTRS)

    Marr-Lyon, M. J.; Thiessen, D. B.; Blonigen, F. J.; Marston, P. L.

    1999-01-01

    The use of both acoustic radiation stress and the Maxwell stress to stabilize liquid bridges is reported. Acoustic radiation stress arises from the time-averaged acoustic pressure at the surface of an object immersed in a sound field. Both passive and active acoustic stabilization schemes as well as an active electrostatic method are examined.

  9. Pressure Measurement in Supersonic Air Flow by Differential Absorptive Laser-Induced Thermal Acoustics

    NASA Technical Reports Server (NTRS)

    Hart, Roger C.; Herring, Gregory C.; Balla, Robert J.

    2007-01-01

    Nonintrusive, off-body flow barometry in Mach-2 airflow has been demonstrated in a large-scale supersonic wind tunnel using seedless laser-induced thermal acoustics (LITA). The static pressure of the gas flow is determined with a novel differential absorption measurement of the ultrasonic sound produced by the LITA pump process. Simultaneously, stream-wise velocity and static gas temperature of the same spatially-resolved sample volume were measured with this nonresonant time-averaged LITA technique. Mach number, temperature and pressure have 0.2%, 0.4%, and 4% rms agreement, respectively, in comparison with known free-stream conditions.

  10. Acoustic Seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor)

    2006-01-01

    The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

  11. Acoustic seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor)

    2006-01-01

    The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

  12. Adjustable virtual pore-size filter for automated sample preparation using acoustic radiation force

    SciTech Connect

    Jung, B; Fisher, K; Ness, K; Rose, K; Mariella, R

    2008-05-22

    We present a rapid and robust size-based separation method for high throughput microfluidic devices using acoustic radiation force. We developed a finite element modeling tool to predict the two-dimensional acoustic radiation force field perpendicular to the flow direction in microfluidic devices. Here we compare the results from this model with experimental parametric studies including variations of the PZT driving frequencies and voltages as well as various particle sizes and compressidensities. These experimental parametric studies also provide insight into the development of an adjustable 'virtual' pore-size filter as well as optimal operating conditions for various microparticle sizes. We demonstrated the separation of Saccharomyces cerevisiae and MS2 bacteriophage using acoustic focusing. The acoustic radiation force did not affect the MS2 viruses, and their concentration profile remained unchanged. With optimized design of our microfluidic flow system we were able to achieve yields of > 90% for the MS2 with > 80% of the S. cerevisiae being removed in this continuous-flow sample preparation device.

  13. Acoustic radiation force expressed using complex phase shifts and momentum-transfer cross sections.

    PubMed

    Zhang, Likun; Marston, Philip L

    2016-08-01

    Acoustic radiation force is expressed using complex phase shifts of partial wave scattering functions and the momentum-transfer cross section, herein incorporated into acoustics from quantum mechanisms. Imaginary parts of the phase shifts represent dissipation in the object and/or in the boundary layer adjacent to the object. The formula simplifies the force as summation of functions of complex phase shifts of adjacent partial waves involving differences of real parts and sums of imaginary parts, providing an efficient way of exploring the force parameter-space. The formula for the force is proportional to a generalized momentum-transfer cross section for plane waves and no dissipation. PMID:27586777

  14. A Study of Standing Pressure Waves Within Open and Closed Acoustic Resonators

    NASA Technical Reports Server (NTRS)

    Daniels, C.; Steinetz, B.; Finkbeiner, J.; Raman, G.; Li, X.

    2002-01-01

    The first section of the results presented herein was conducted on an axisymmetric resonator configured with open ventilation ports on either end of the resonator, but otherwise closed and free from obstruction. The remaining section presents the results of a similar resonator shape that was closed, but contained an axisymmetric blockage centrally located through the axis of the resonator. Ambient air was used as the working fluid. In each of the studies, the resonator was oscillated at the resonant frequency of the fluid contained within the cavity while the dynamic pressure, static pressure, and temperature of the fluid were recorded at both ends of the resonator. The baseline results showed a marked reduction in the amplitude of the dynamic pressure waveforms over previous studies due to the use of air instead of refrigerant as the working fluid. A sharp reduction in the amplitude of the acoustic pressure waves was expected and recorded when the configuration of the resonators was modified from closed to open. A change in the resonant frequency was recorded when blockages of differing geometries were used in the closed resonator, while acoustic pressure amplitudes varied little from baseline measurements.

  15. Pressure and temperature dependences of the acoustic behaviors of biocompatible silk studied by using Brillouin spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Byoung Wan; Ryeom, Junho; Ko, Jae-Hyeon; Kim, Dong Wook; Park, Chan Hum; Park, Jaehoon; Ko, Young Ho; Kim, Kwang Joo

    2016-07-01

    The elastic properties of a biocompatible silk film were investigated under temperature and pressure variations by using Brillouin spectroscopy. The Brillouin frequency shift decreased monotonically upon heating and showed a sudden change at the glass transition temperature. The existence of water molecules in the film increased the longitudinal modulus by approximately 10% and induced a relaxation peak in the hypersonic damping at ~60 ◦ C. The pressure dependences of the sound velocities of the longitudinal and the transverse acoustic modes and the refractive index were determined for the first time at pressures up to ~15.5 GPa. All these properties increased upon compression; these changes indicated that the free volume in the silk film collapsed at a pressure of about 3 GPa.

  16. Modeling of Structural-Acoustic Interaction Using Coupled FE/BE Method and Control of Interior Acoustic Pressure Using Piezoelectric Actuators

    NASA Technical Reports Server (NTRS)

    Mei, Chuh; Shi, Yacheng

    1997-01-01

    A coupled finite element (FE) and boundary element (BE) approach is presented to model full coupled structural/acoustic/piezoelectric systems. The dual reciprocity boundary element method is used so that the natural frequencies and mode shapes of the coupled system can be obtained, and to extend this approach to time dependent problems. The boundary element method is applied to interior acoustic domains, and the results are very accurate when compared with limited exact solutions. Structural-acoustic problems are then analyzed with the coupled finite element/boundary element method, where the finite element method models the structural domain and the boundary element method models the acoustic domain. Results for a system consisting of an isotropic panel and a cubic cavity are in good agreement with exact solutions and experiment data. The response of a composite panel backed cavity is then obtained. The results show that the mass and stiffness of piezoelectric layers have to be considered. The coupled finite element and boundary element equations are transformed into modal coordinates, which is more convenient for transient excitation. Several transient problems are solved based on this formulation. Two control designs, a linear quadratic regulator (LQR) and a feedforward controller, are applied to reduce the acoustic pressure inside the cavity based on the equations in modal coordinates. The results indicate that both controllers can reduce the interior acoustic pressure and the plate deflection.

  17. Acoustics

    NASA Technical Reports Server (NTRS)

    Goodman, Jerry R.; Grosveld, Ferdinand

    2007-01-01

    The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

  18. Solar radiation pressure model for the relay satellite of SELENE

    NASA Astrophysics Data System (ADS)

    Kubo-Oka, T.; Sengoku, A.

    1999-09-01

    A new radiation pressure model of the relay satellite of SELENE has been developed. The shape of the satellite was assumed to be a combination of a regular octagonal pillar and a column. Radiation forces acting on each part of the spacecraft were calculated independently and summed vectorially to obtain the mean acceleration of the satellite center of mass. We incorporated this new radiation pressure model into the orbit analysis software GEODYN-II and simulated the tracking data reduction process of the relay satellite. We compared two models: one is the new radiation pressure model developed in this work and the other a so-called "cannonball model" where the shape of the satellite is assumed to be a sphere. By the analysis of simulated two-way Doppler tracking data, we found that the new radiation pressure model reduces the observation residuals compared to the cannonball model. Moreover, we can decrease errors in the estimated lunar gravity field coefficients significantly by use of the new radiation pressure model.

  19. Off-axial acoustic radiation force of repulsor and tractor bessel beams on a sphere.

    PubMed

    Silva, Glauber T; Lopes, J Henrique; Mitri, Farid G

    2013-06-01

    Acoustic Bessel beams are known to produce an axial radiation force on a sphere centered on the beam axis (on-axial configuration) that exhibits both repulsor and tractor behaviors. The repulsor and the tractor forces are oriented along the beam's direction of propagation and opposite to it, respectively. The behavior of the acoustic radiation force generated by Bessel beams when the sphere lies outside the beam's axis (off-axial configuration) is unknown. Using the 3-D radiation force formulas given in terms of the partial wave expansion coefficients for the incident and scattered waves, both axial and transverse components of the force exerted on a silicone- oil sphere are obtained for a zero- and a first-order Bessel vortex beam. As the sphere departs from the beam's axis, the tractor force becomes weaker. Moreover, the behavior of the transverse radiation force field may vary with the sphere's size factor ka (where k is the wavenumber and a is the sphere radius). Both stable and unstable equilibrium regions around the beam's axis are found, depending on ka values. These results are particularly important for the design of acoustical tractor beam devices operating with Bessel beams. PMID:25004483

  20. Radiation interactions in high-pressure gases

    SciTech Connect

    Christophorou, L.G. Tennessee Univ., Knoxville, TN )

    1990-01-01

    This article is on basic radiation interaction processes in dense fluids and on interphase studies aiming at the interfacing of knowledge on radiation interaction processes in the gaseous and the liquid state of matter. It is specifically focused on the effect of the density and nature of the medium on electron production in irradiated fluids and on the state, energy, transport, and attachment of slow excess electrons in dense fluids especially dielectric liquids which possess excess-electron conduction bands (V{sub 0} < 0 eV). Studies over the past two decades have shown that the interactions of low-energy electrons with molecules embedded in dense media depend not only on the molecules themselves and their internal state of excitation, but also on the electron state and energy in -- and the nature and density of -- the medium in which the interactions occur.

  1. Picosecond acoustics method for measuring the thermodynamical properties of solids and liquids at high pressure and high temperature.

    PubMed

    Decremps, F; Gauthier, M; Ayrinhac, S; Bove, L; Belliard, L; Perrin, B; Morand, M; Le Marchand, G; Bergame, F; Philippe, J

    2015-02-01

    Based on the original combination of picosecond acoustics and diamond anvils cell, recent improvements to accurately measure hypersonic sound velocities of liquids and solids under extreme conditions are described. To illustrate the capability of this technique, results are given on the pressure and temperature dependence of acoustic properties for three prototypical cases: polycrystal (iron), single-crystal (silicon) and liquid (mercury) samples. It is shown that such technique also enables the determination of the density as a function of pressure for liquids, of the complete set of elastic constants for single crystals, and of the melting curve for any kind of material. High pressure ultrafast acoustic spectroscopy technique clearly opens opportunities to measure thermodynamical properties under previously unattainable extreme conditions. Beyond physics, this state-of-the-art experiment would thus be useful in many other fields such as nonlinear acoustics, oceanography, petrology, in of view. A brief description of new developments and future directions of works conclude the article.

  2. Picosecond acoustics method for measuring the thermodynamical properties of solids and liquids at high pressure and high temperature.

    PubMed

    Decremps, F; Gauthier, M; Ayrinhac, S; Bove, L; Belliard, L; Perrin, B; Morand, M; Le Marchand, G; Bergame, F; Philippe, J

    2015-02-01

    Based on the original combination of picosecond acoustics and diamond anvils cell, recent improvements to accurately measure hypersonic sound velocities of liquids and solids under extreme conditions are described. To illustrate the capability of this technique, results are given on the pressure and temperature dependence of acoustic properties for three prototypical cases: polycrystal (iron), single-crystal (silicon) and liquid (mercury) samples. It is shown that such technique also enables the determination of the density as a function of pressure for liquids, of the complete set of elastic constants for single crystals, and of the melting curve for any kind of material. High pressure ultrafast acoustic spectroscopy technique clearly opens opportunities to measure thermodynamical properties under previously unattainable extreme conditions. Beyond physics, this state-of-the-art experiment would thus be useful in many other fields such as nonlinear acoustics, oceanography, petrology, in of view. A brief description of new developments and future directions of works conclude the article. PMID:24852260

  3. Temperature and Pressure Dependence of Signal Amplitudes for Electrostriction Laser-Induced Thermal Acoustics

    NASA Technical Reports Server (NTRS)

    Herring, Gregory C.

    2015-01-01

    The relative signal strength of electrostriction-only (no thermal grating) laser-induced thermal acoustics (LITA) in gas-phase air is reported as a function of temperature T and pressure P. Measurements were made in the free stream of a variable Mach number supersonic wind tunnel, where T and P are varied simultaneously as Mach number is varied. Using optical heterodyning, the measured signal amplitude (related to the optical reflectivity of the acoustic grating) was averaged for each of 11 flow conditions and compared to the expected theoretical dependence of a pure-electrostriction LITA process, where the signal is proportional to the square root of [P*P /( T*T*T)].

  4. Numerical simulation of acoustofluidic manipulation by radiation forces and acoustic streaming for complex particles.

    PubMed

    Hahn, Philipp; Leibacher, Ivo; Baasch, Thierry; Dual, Jurg

    2015-11-21

    The numerical prediction of acoustofluidic particle motion is of great help for the design, the analysis, and the physical understanding of acoustofluidic devices as it allows for a simple and direct comparison with experimental observations. However, such a numerical setup requires detailed modeling of the acoustofluidic device with all its components and thorough understanding of the acoustofluidic forces inducing the particle motion. In this work, we present a 3D trajectory simulation setup that covers the full spectrum, comprising a time-harmonic device model, an acoustic streaming model of the fluid cavity, a radiation force simulation, and the calculation of the hydrodynamic drag. In order to make quantitatively accurate predictions of the device vibration and the acoustic field, we include the viscous boundary layer damping. Using a semi-analytical method based on Nyborg's calculations, the boundary-driven acoustic streaming is derived directly from the device simulation and takes into account cavity wall vibrations which have often been neglected in the literature. The acoustic radiation forces and the hydrodynamic drag are calculated numerically to handle particles of arbitrary shape, structure, and size. In this way, complex 3D particle translation and rotation inside experimental microdevices can be predicted. We simulate the rotation of a microfiber in an amplitude-modulated 2D field and analyze the results with respect to experimental observations. For a quantitative verification, the motion of an alumina microdisk is compared to a simple experiment. Demonstrating the potential of the simulation setup, we compute the trajectory of a red blood cell inside a realistic microdevice under the simultaneous effects of acoustic streaming and radiation forces. PMID:26448531

  5. Numerical simulation of acoustofluidic manipulation by radiation forces and acoustic streaming for complex particles.

    PubMed

    Hahn, Philipp; Leibacher, Ivo; Baasch, Thierry; Dual, Jurg

    2015-11-21

    The numerical prediction of acoustofluidic particle motion is of great help for the design, the analysis, and the physical understanding of acoustofluidic devices as it allows for a simple and direct comparison with experimental observations. However, such a numerical setup requires detailed modeling of the acoustofluidic device with all its components and thorough understanding of the acoustofluidic forces inducing the particle motion. In this work, we present a 3D trajectory simulation setup that covers the full spectrum, comprising a time-harmonic device model, an acoustic streaming model of the fluid cavity, a radiation force simulation, and the calculation of the hydrodynamic drag. In order to make quantitatively accurate predictions of the device vibration and the acoustic field, we include the viscous boundary layer damping. Using a semi-analytical method based on Nyborg's calculations, the boundary-driven acoustic streaming is derived directly from the device simulation and takes into account cavity wall vibrations which have often been neglected in the literature. The acoustic radiation forces and the hydrodynamic drag are calculated numerically to handle particles of arbitrary shape, structure, and size. In this way, complex 3D particle translation and rotation inside experimental microdevices can be predicted. We simulate the rotation of a microfiber in an amplitude-modulated 2D field and analyze the results with respect to experimental observations. For a quantitative verification, the motion of an alumina microdisk is compared to a simple experiment. Demonstrating the potential of the simulation setup, we compute the trajectory of a red blood cell inside a realistic microdevice under the simultaneous effects of acoustic streaming and radiation forces.

  6. Location of acoustic radiators and inversion for energy density using radio-frequency sources and thunder recordings

    NASA Astrophysics Data System (ADS)

    Anderson, J.; Johnson, J. B.; Arechiga, R. O.; Edens, H. E.; Thomas, R. J.

    2011-12-01

    We use radio frequency (VHF) pulse locations mapped with the New Mexico Tech Lightning Mapping Array (LMA) to study the distribution of thunder sources in lightning channels. A least squares inversion is used to fit channel acoustic energy radiation with broadband (0.01 to 500 Hz) acoustic recordings using microphones deployed local (< 10 km) to the lightning. We model the thunder (acoustic) source as a superposition of line segments connecting the LMA VHF pulses. An optimum branching algorithm is used to reconstruct conductive channels delineated by VHF sources, which we discretize as a superposition of finely-spaced (0.25 m) acoustic point sources. We consider total radiated thunder as a weighted superposition of acoustic waves from individual channels, each with a constant current along its length that is presumed to be proportional to acoustic energy density radiated per unit length. Merged channels are considered as a linear sum of current-carrying branches and radiate proportionally greater acoustic energy. Synthetic energy time series for a given microphone location are calculated for each independent channel. We then use a non-negative least squares inversion to solve for channel energy densities to match the energy time series determined from broadband acoustic recordings across a 4-station microphone network. Events analyzed by this method have so far included 300-1000 VHF sources, and correlations as high as 0.5 between synthetic and recorded thunder energy were obtained, despite the presence of wind noise and 10-30 m uncertainty in VHF source locations.

  7. Layer contributions to the nonlinear acoustic radiation from stratified media.

    PubMed

    Vander Meulen, François; Haumesser, Lionel

    2016-12-01

    This study presents the thorough investigation of the second harmonic generation scenario in a three fluid layer system. An emphasis is on the evaluation of the nonlinear parameter B/A in each layer from remote measurements. A theoretical approach of the propagation of a finite amplitude acoustic wave in a multilayered medium is developed. In the frame of the KZK equation, the weak nonlinearity of the media, attenuation and diffraction effects are computed for the fundamental and second harmonic waves propagating back and forth in each of the layers of the system. The model uses a gaussian expansion to describe the beam propagation in order to quantitatively evaluate the contribution of each part of the system (layers and interfaces) to its nonlinearity. The model is validated through measurements on a water/aluminum/water system. Transmission as well as reflection configurations are studied. Good agreement is found between the theoretical results and the experimental data. The analysis of the second harmonic field sources measured by the transducers from outside the stratified medium highlights the factors that favor the cumulative effects.

  8. Radiation Pressure Measurements on Micron Size Individual Dust Grains

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P.D.; Spann, J. F.; Tankosic, D.; Witherow, W. K.; LeClair, A.; West, E.; Sheldon, R.; Gallagher, D. L.; Adrian, M. L.

    2003-01-01

    Measurements of electromagnetic radiation pressure have been made on individual silica (SiO2) particles levitated in an electrodynamic balance. These measurements were made by inserting single charged particles of known diameter in the 0.2 micron to 6.82 micron range and irradiating them from above with laser radiation focused to beam-widths of approx. 175-400 micron, at ambient pressures approx. 10(exp -3) to 10(exp -4) torr. The downward displacement of the particle due to the radiation force is balanced by the electrostatic force indicated by the compensating dc potential applied to the balance electrodes, providing a direct measure of the radiation force on the levitated particle. Theoretical calculations of the radiation pressure with a least-squares fit to the measured data yield the radiation pressure efficiencies of the particles, and comparisons with Mie scattering theory calculations provide the imaginary part of the refractive index of silica and the corresponding extinction and scattering efficiencies.

  9. Effect of particle-particle interactions on the acoustic radiation force in an ultrasonic standing wave

    NASA Astrophysics Data System (ADS)

    Lipkens, Bart; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.

    2015-10-01

    Ultrasonic standing waves are widely used for separation applications. In MEMS applications, a half wavelength standing wave field is generated perpendicular to a laminar flow. The acoustic radiation force exerted on the particle drives the particle to the center of the MEMS channel, where concentrated particles are harvested. In macro-scale applications, the ultrasonic standing wave spans multiple wavelengths. Examples of such applications are oil/water emulsion splitting [1], and blood/lipid separation [2]. In macro-scale applications, particles are typically trapped in the standing wave, resulting in clumping or coalescence of particles/droplets. Subsequent gravitational settling results in separation of the secondary phase. An often used expression for the radiation force on a particle is that derived by Gorkov [3]. The assumptions are that the particle size is small relative to the wavelength, and therefore, only monopole and dipole scattering contributions are used to calculate the radiation force. This framework seems satisfactory for MEMS scale applications where each particle is treated separately by the standing wave, and concentrations are typically low. In macro-scale applications, particle concentration is high, and particle clumping or droplet coalescence results in particle sizes not necessarily small relative to the wavelength. Ilinskii et al. developed a framework for calculation of the acoustic radiation force valid for any size particle [4]. However, this model does not take into account particle to particle effects, which can become important as particle concentration increases. It is known that an acoustic radiation force on a particle or a droplet is determined by the local field. An acoustic radiation force expression is developed that includes the effect of particle to particle interaction. The case of two neighboring particles is considered. The approach is based on sound scattering by the particles. The acoustic field at the location of

  10. Effect of particle-particle interactions on the acoustic radiation force in an ultrasonic standing wave

    SciTech Connect

    Lipkens, Bart; Ilinskii, Yurii A. Zabolotskaya, Evgenia A.

    2015-10-28

    Ultrasonic standing waves are widely used for separation applications. In MEMS applications, a half wavelength standing wave field is generated perpendicular to a laminar flow. The acoustic radiation force exerted on the particle drives the particle to the center of the MEMS channel, where concentrated particles are harvested. In macro-scale applications, the ultrasonic standing wave spans multiple wavelengths. Examples of such applications are oil/water emulsion splitting [1], and blood/lipid separation [2]. In macro-scale applications, particles are typically trapped in the standing wave, resulting in clumping or coalescence of particles/droplets. Subsequent gravitational settling results in separation of the secondary phase. An often used expression for the radiation force on a particle is that derived by Gorkov [3]. The assumptions are that the particle size is small relative to the wavelength, and therefore, only monopole and dipole scattering contributions are used to calculate the radiation force. This framework seems satisfactory for MEMS scale applications where each particle is treated separately by the standing wave, and concentrations are typically low. In macro-scale applications, particle concentration is high, and particle clumping or droplet coalescence results in particle sizes not necessarily small relative to the wavelength. Ilinskii et al. developed a framework for calculation of the acoustic radiation force valid for any size particle [4]. However, this model does not take into account particle to particle effects, which can become important as particle concentration increases. It is known that an acoustic radiation force on a particle or a droplet is determined by the local field. An acoustic radiation force expression is developed that includes the effect of particle to particle interaction. The case of two neighboring particles is considered. The approach is based on sound scattering by the particles. The acoustic field at the location of

  11. Single Bubble Sonoluminescence in Low Gravity and Optical Radiation Pressure Positioning of the Bubble

    NASA Technical Reports Server (NTRS)

    Thiessen, D. B.; Young, J. E.; Marr-Lyon, M. J.; Richardson, S. L.; Breckon, C. D.; Douthit, S. G.; Jian, P. S.; Torruellas, W. E.; Marston, P. L.

    1999-01-01

    Several groups of researchers have demonstrated that high frequency sound in water may be used to cause the regular repeated compression and luminescence of a small bubble of gas in a flask. The phenomenon is known as single bubble sonoluminescence (SBSL). It is potentially important because light emitted by the bubble appears to be associated with a significant concentration of energy within the volume of the bubble. Unfortunately, the detailed physical mechanisms causing the radiation of light by oscillating bubbles are poorly understood and there is some evidence that carrying out experiments in a weightless environment may provide helpful clues. In addition, the radiation pressure of laser beams on the bubble may provide a way of simulating weightless experiments in the laboratory. The standard model of SBSL attributes the light emission to heating within the bubble by a spherically imploding shock wave to achieve temperatures of 50,000 K or greater. In an alternative model, the emission is attributed to the impact of a jet of water which is required to span the bubble and the formation of the jet is linked to the buoyancy of the bubble. The coupling between buoyancy and jet formation is a consequence of the displacement of the bubble from a velocity node (pressure antinode) of the standing acoustic wave that drives the radial bubble oscillations. One objective of this grant is to understand SBSL emission in reduced buoyancy on KC-135 parabolic flights. To optimize the design of those experiments and for other reasons which will help resolve the role of buoyancy, laboratory experiments are planned in simulated low gravity in which the radiation pressure of laser light will be used to position the bubble at the acoustic velocity node of the ultrasonic standing wave. Laser light will also be used to push the bubble away from the velocity node, increasing the effective buoyancy. The original experiments on the optical levitation and radiation pressure on bubbles

  12. Acoustic radiation force due to arbitrary incident fields on spherical particles in soft tissue

    SciTech Connect

    Treweek, Benjamin C. Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F.

    2015-10-28

    Acoustic radiation force is of interest in a wide variety of biomedical applications ranging from tissue characterization (e.g. elastography) to tissue treatment (e.g. high intensity focused ultrasound, kidney stone fragment removal). As tissue mechanical properties are reliable indicators of tissue health, the former is the focus of the present contribution. This is accomplished through an investigation of the acoustic radiation force on a spherical scatterer embedded in tissue. Properties of both the scatterer and the surrounding tissue are important in determining the magnitude and the direction of the force. As these properties vary, the force computation shows changes in magnitude and direction, which may enable more accurate noninvasive determination of tissue properties.

  13. Acoustic radiation force due to arbitrary incident fields on spherical particles in soft tissue

    NASA Astrophysics Data System (ADS)

    Treweek, Benjamin C.; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F.

    2015-10-01

    Acoustic radiation force is of interest in a wide variety of biomedical applications ranging from tissue characterization (e.g. elastography) to tissue treatment (e.g. high intensity focused ultrasound, kidney stone fragment removal). As tissue mechanical properties are reliable indicators of tissue health, the former is the focus of the present contribution. This is accomplished through an investigation of the acoustic radiation force on a spherical scatterer embedded in tissue. Properties of both the scatterer and the surrounding tissue are important in determining the magnitude and the direction of the force. As these properties vary, the force computation shows changes in magnitude and direction, which may enable more accurate noninvasive determination of tissue properties.

  14. 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.

  15. Acoustic investigation of pressure-dependent resonance and shell elasticity of lipid-coated monodisperse microbubbles

    NASA Astrophysics Data System (ADS)

    Gong, Yanjun; Cabodi, Mario; Porter, Tyrone M.

    2014-02-01

    In this study, frequency-dependent attenuation was measured acoustically for monodisperse lipid-coated microbubble suspensions as a function of excitation pressure and radius. The resonance frequency was identified from the attenuation spectra and had an inverse relationship with mean microbubble diameter and excitation pressure. A reduction in the estimated shell elasticity constant from 0.50 N/m to 0.29 N/m was observed as the excitation pressure was increased from 25 kPa to 100 kPa, respectively, which suggests a nonlinear relationship exists between lipid shell stiffness and applied strain. These findings support the viewpoint that lipid shells coating microbubbles exist as heterogeneous mixtures that undergo dynamic and rapid variations in mechanical properties under applied strains.

  16. Near field acoustic holography based on the equivalent source method and pressure-velocity transducers.

    PubMed

    Zhang, Yong-Bin; Jacobsen, Finn; Bi, Chuan-Xing; Chen, Xin-Zhao

    2009-09-01

    The advantage of using the normal component of the particle velocity rather than the sound pressure in the hologram plane as the input of conventional spatial Fourier transform based near field acoustic holography (NAH) and also as the input of the statistically optimized variant of NAH has recently been demonstrated. This paper examines whether there might be a similar advantage in using the particle velocity as the input of NAH based on the equivalent source method (ESM). Error sensitivity considerations indicate that ESM-based NAH is less sensitive to measurement errors when it is based on particle velocity input data than when it is based on measurements of sound pressure data, and this is confirmed by a simulation study and by experimental results. A method that combines pressure- and particle velocity-based reconstructions in order to distinguish between contributions to the sound field generated by sources on the two sides of the hologram plane is also examined.

  17. Computation of the pressure field generated by surface acoustic waves in microchannels.

    PubMed

    Darinskii, A N; Weihnacht, M; Schmidt, H

    2016-07-01

    The high-frequency pressure induced by a surface acoustic wave in the fluid filling a microchannel is computed by solving the full scattering problem. The microchannel is fabricated inside a container attached to the top of a piezoelectric substrate where the surface wave propagates. The finite element method is used. The pressure found in this way is compared with the pressure obtained by solving boundary-value problems formulated on the basis of simplifications which have been introduced in earlier papers by other research studies. The considered example shows that the difference between the results can be significant, ranging from several tens of percent up to several times in different points inside the channel. PMID:27314212

  18. Radiation damage characterization in reactor pressure vessel steels with nonlinear ultrasound

    NASA Astrophysics Data System (ADS)

    Matlack, K. H.; Kim, J.-Y.; Wall, J. J.; Qu, J.; Jacobs, L. J.

    2014-02-01

    Nuclear generation currently accounts for roughly 20% of the US baseload power generation. Yet, many US nuclear plants are entering their first period of life extension and older plants are currently undergoing assessment of technical basis to operate beyond 60 years. This means that critical components, such as the reactor pressure vessel (RPV), will be exposed to higher levels of radiation than they were originally intended to withstand. Radiation damage in reactor pressure vessel steels causes microstructural changes such as vacancy clusters, precipitates, dislocations, and interstitial loops that leave the material in an embrittled state. The development of a nondestructive evaluation technique to characterize the effect of radiation exposure on the properties of the RPV would allow estimation of the remaining integrity of the RPV with time. Recent research has shown that nonlinear ultrasound is sensitive to radiation damage. The physical effect monitored by nonlinear ultrasonic techniques is the generation of higher harmonic frequencies in an initially monochromatic ultrasonic wave, arising from the interaction of the ultrasonic wave with microstructural features such as dislocations, precipitates, and their combinations. Current findings relating the measured acoustic nonlinearity parameter to increasing levels of neutron fluence for different representative RPV materials are presented.

  19. Radiation damage characterization in reactor pressure vessel steels with nonlinear ultrasound

    SciTech Connect

    Matlack, K. H.; Kim, J.-Y.; Wall, J. J.; Qu, J.; Jacobs, L. J.

    2014-02-18

    Nuclear generation currently accounts for roughly 20% of the US baseload power generation. Yet, many US nuclear plants are entering their first period of life extension and older plants are currently undergoing assessment of technical basis to operate beyond 60 years. This means that critical components, such as the reactor pressure vessel (RPV), will be exposed to higher levels of radiation than they were originally intended to withstand. Radiation damage in reactor pressure vessel steels causes microstructural changes such as vacancy clusters, precipitates, dislocations, and interstitial loops that leave the material in an embrittled state. The development of a nondestructive evaluation technique to characterize the effect of radiation exposure on the properties of the RPV would allow estimation of the remaining integrity of the RPV with time. Recent research has shown that nonlinear ultrasound is sensitive to radiation damage. The physical effect monitored by nonlinear ultrasonic techniques is the generation of higher harmonic frequencies in an initially monochromatic ultrasonic wave, arising from the interaction of the ultrasonic wave with microstructural features such as dislocations, precipitates, and their combinations. Current findings relating the measured acoustic nonlinearity parameter to increasing levels of neutron fluence for different representative RPV materials are presented.

  20. Theoretical estimation of the temperature and pressure within collapsing acoustical bubbles.

    PubMed

    Merouani, Slimane; Hamdaoui, Oualid; Rezgui, Yacine; Guemini, Miloud

    2014-01-01

    Formation of highly reactive species such as OH, H, HO2 and H2O2 due to transient collapse of cavitation bubbles is the primary mechanism of sonochemical reaction. The crucial parameters influencing the formation of radicals are the temperature and pressure achieved in the bubble during the strong collapse. Experimental determinations estimated a temperature of about 5000 K and pressure of several hundreds of MPa within the collapsing bubble. In this theoretical investigation, computer simulations of chemical reactions occurring in an O2-bubble oscillating in water irradiated by an ultrasonic wave have been performed for diverse combinations of various parameters such as ultrasound frequency (20-1000 kHz), acoustic amplitude (up to 0.3 MPa), static pressure (0.03-0.3 MPa) and liquid temperature (283-333 K). The aim of this series of computations is to correlate the production of OH radicals to the temperature and pressure achieved in the bubble during the strong collapse. The employed model combines the dynamic of bubble collapse in acoustical field with the chemical kinetics of single bubble. The results of the numerical simulations revealed that the main oxidant created in an O2 bubble is OH radical. The computer simulations clearly showed the existence of an optimum bubble temperature of about 5200±200 K and pressure of about 250±20 MPa. The predicted value of the bubble temperature for the production of OH radicals is in excellent agreement with that furnished by the experiments. The existence of an optimum bubble temperature and pressure in collapsing bubbles results from the competitions between the reactions of production and those of consumption of OH radicals at high temperatures. PMID:23769748

  1. Role of transient water pressure in quarrying: A subglacial experiment using acoustic emissions

    USGS Publications Warehouse

    Cohen, D.; Hooyer, T.S.; Iverson, N.R.; Thomason, J.F.; Jackson, M.

    2006-01-01

    Probably the most important mechanism of glacial erosion is quarrying: the growth and coalescence of cracks in subglacial bedrock and dislodgement of resultant rock fragments. Although evidence indicates that erosion rates depend on sliding speed, rates of crack growth in bedrock may be enhanced by changing stresses on the bed caused by fluctuating basal water pressure in zones of ice-bed separation. To study quarrying in real time, a granite step, 12 cm high with a crack in its stoss surface, was installed at the bed of Engabreen, Norway. Acoustic emission sensors monitored crack growth events in the step as ice slid over it. Vertical stresses, water pressure, and cavity height in the lee of the step were also measured. Water was pumped to the lee of the step several times over 8 days. Pumping initially caused opening of a leeward cavity, which then closed after pumping was stopped and water pressure decreased. During cavity closure, acoustic emissions emanating mostly from the vicinity of the base of the crack in the step increased dramatically. With repeated pump tests this crack grew with time until the step's lee surface was quarried. Our experiments indicate that fluctuating water pressure caused stress thresholds required for crack growth to be exceeded. Natural basal water pressure fluctuations should also concentrate stresses on rock steps, increasing rates of crack growth. Stress changes on the bed due to water pressure fluctuations will increase in magnitude and duration with cavity size, which may help explain the effect of sliding speed on erosion rates. Copyright 2006 by the American Geophysical Union.

  2. Hawking radiation from an acoustic black hole on an ion ring.

    PubMed

    Horstmann, B; Reznik, B; Fagnocchi, S; Cirac, J I

    2010-06-25

    In this Letter we propose to simulate acoustic black holes with ions in rings. If the ions are rotating with a stationary and inhomogeneous velocity profile, regions can appear where the ion velocity exceeds the group velocity of the phonons. In these regions phonons are trapped like light in black holes, even though we have a discrete field theory and a nonlinear dispersion relation. We study the appearance of Hawking radiation in this setup and propose a scheme to detect it. PMID:20867352

  3. Noise control using a plate radiator and an acoustic resonator

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor)

    1996-01-01

    An active noise control subassembly for reducing noise caused by a source (such as an aircraft engine) independent of the subassembly. A noise radiating panel is bendably vibratable to generate a panel noise canceling at least a portion of the source noise. A piezoceramic actuator plate is connected to the panel. A front plate is spaced apart from the panel and the first plate, is positioned generally between the source noise and the panel, and has a sound exit port. A first pair of spaced-apart side walls each generally abut the panel and the front plate so as to generally enclose a front cavity to define a resonator.

  4. Binding Dynamics of Targeted Microbubbles in Response to Modulated Acoustic Radiation Force

    PubMed Central

    Wang, Shiying; Hossack, John A; Klibanov, Alexander L; Mauldin, F William

    2014-01-01

    Detection of molecular targeted microbubbles plays a foundational role in ultrasound-based molecular imaging and targeted gene or drug delivery. In this paper, an empirical model describing the binding dynamics of targeted microbubbles in response to modulated acoustic radiation forces in large vessels is presented and experimentally verified using tissue-mimicking flow phantoms. Higher flow velocity and microbubble concentration led to faster detaching rates for specifically bound microbubbles (p < 0.001). Higher time-averaged acoustic radiation force intensity led to faster attaching rates and a higher saturation level of specifically bound microbubbles (p < 0.05). The level of residual microbubble signal in targeted experiments after cessation of radiation forces was the only response parameter that was reliably different between targeted and control experiments (p < 0.05). A related parameter, the ratio of residual-to-saturated microbubble signal (Rresid), is proposed as a measurement that is independent of absolute acoustic signal magnitude and therefore able to reliably detect targeted adhesion independently of control measurements (p < 0.01). These findings suggest the possibility of enhanced detection of specifically bound microbubbles in real-time, using relatively short imaging protocols (approximately 3 min), without waiting for free microbubble clearance. PMID:24374866

  5. Fan Noise Prediction System Development: Source/Radiation Field Coupling and Workstation Conversion for the Acoustic Radiation Code

    NASA Technical Reports Server (NTRS)

    Meyer, H. D.

    1993-01-01

    The Acoustic Radiation Code (ARC) is a finite element program used on the IBM mainframe to predict far-field acoustic radiation from a turbofan engine inlet. In this report, requirements for developers of internal aerodynamic codes regarding use of their program output an input for the ARC are discussed. More specifically, the particular input needed from the Bolt, Beranek and Newman/Pratt and Whitney (turbofan source noise generation) Code (BBN/PWC) is described. In a separate analysis, a method of coupling the source and radiation models, that recognizes waves crossing the interface in both directions, has been derived. A preliminary version of the coupled code has been developed and used for initial evaluation of coupling issues. Results thus far have shown that reflection from the inlet is sufficient to indicate that full coupling of the source and radiation fields is needed for accurate noise predictions ' Also, for this contract, the ARC has been modified for use on the Sun and Silicon Graphics Iris UNIX workstations. Changes and additions involved in this effort are described in an appendix.

  6. Radiation pressure on a dielectric wedge.

    PubMed

    Mansuripur, Masud; Zakharian, Armis; Moloney, Jerome

    2005-03-21

    The force of electromagnetic radiation on a dielectric medium may be derived by a direct application of the Lorentz law of classical electrodynamics. While the light's electric field acts upon the (induced) bound charges in the medium, its magnetic field exerts a force on the bound currents. We use the example of a wedge-shaped solid dielectric, immersed in a transparent liquid and illuminated at Brewster's angle, to demonstrate that the linear momentum of the electromagnetic field within dielectrics has neither the Minkowski nor the Abraham form; rather, the correct expression for momentum density has equal contributions from both. The time rate of change of the incident momentum thus expressed is equal to the force exerted on the wedge plus that experienced by the surrounding liquid.

  7. Determination of the viscous acoustic field for liquid drop positioning/forcing in an acoustic levitation chamber in microgravity

    NASA Technical Reports Server (NTRS)

    Lyell, Margaret J.

    1992-01-01

    The development of acoustic levitation systems has provided a technology with which to undertake droplet studies as well as do containerless processing experiments in a microgravity environment. Acoustic levitation chambers utilize radiation pressure forces to position/manipulate the drop. Oscillations can be induced via frequency modulation of the acoustic wave, with the modulated acoustic radiation vector acting as the driving force. To account for tangential as well as radial forcing, it is necessary that the viscous effects be included in the acoustic field. The method of composite expansions is employed in the determination of the acoustic field with viscous effects.

  8. Radiation Pressure on Fluffy Submicron-sized Grains

    NASA Astrophysics Data System (ADS)

    Silsbee, Kedron; Draine, Bruce T.

    2016-02-01

    We investigate the claim that the ratio β of radiation pressure force to gravitational force on a dust grain in our solar system can substantially exceed unity for some grain sizes, provided that grain porosity is high enough. For model grains consisting of random aggregates of silicate spherules, we find that the maximum value of β is almost independent of grain porosity, but for small (\\lt 0.3 μ {{m}}) grains, β actually decreases with increasing porosity. We also investigate the effect of metallic iron and amorphous carbon inclusions in the dust grains and find that while these inclusions do increase the radiation pressure cross-section, β remains below unity for grains with 3 pg of silicate material. These results affect the interpretation of the grain trajectories estimated from the Stardust mission, which were modeled assuming β values exceeding one. We find that radiation pressure effects are not large enough for particles Orion and Hylabrook captured by Stardust to be of interstellar origin given their reported impact velocities. We also consider the effects of solar radiation on transverse velocities and grain spin, and show that radiation pressure introduces both transverse velocities and equatorial spin velocities of several hundred meters per second for incoming interstellar grains at 2 au. These transverse velocities are not important for modeling trajectories, but such spin rates may result in centrifugal disruption of aggregates.

  9. Acoustic radiation force and torque exerted on a small viscoelastic particle in an ideal fluid.

    PubMed

    Leão-Neto, J P; Silva, G T

    2016-09-01

    We provide a detailed analysis on the acoustic radiation force and torque exerted on a homogeneous viscoelastic particle in the long-wave limit (i.e. the particle radius is much smaller than the incident wavelength) by an arbitrary wave. We assume that the particle behaves as a linear viscoelastic solid, which obeys the fractional Kelvin-Voigt model. Simple analytical expressions for the radiation force and torque are obtained. The developed theory is used to describe the interaction of acoustic waves (traveling and standing plane waves, and zero- and first-order Bessel beams) in the MHz-range with polymeric particles, namely lexan, low-density (LDPE) and high-density (HDPE) polyethylene. We found that particle absorption is chiefly the cause of the radiation force due to a traveling plane wave and zero-order Bessel beam when the frequency is smaller than 5MHz (HDPE), 3.9MHz (LDPE), and 0.9MHz (lexan). Whereas in a standing wave field, the radiation force is mildly changed due to dispersion inside the particle. We also show that the radiation torque caused by a first-order Bessel beam varies nearly quadratic with frequency. These findings may enable new possibilities of particle handling in acoustophoretic techniques. PMID:27254398

  10. Detecting leaks in gas-filled pressure vessels using acoustic resonances.

    PubMed

    Gillis, K A; Moldover, M R; Mehl, J B

    2016-05-01

    We demonstrate that a leak from a large, unthermostatted pressure vessel into ambient air can be detected an order of magnitude more effectively by measuring the time dependence of the ratio p/f(2) than by measuring the ratio p/T. Here f is the resonance frequency of an acoustic mode of the gas inside the pressure vessel, p is the pressure of the gas, and T is the kelvin temperature measured at one point in the gas. In general, the resonance frequencies are determined by a mode-dependent, weighted average of the square of the speed-of-sound throughout the volume of the gas. However, the weighting usually has a weak dependence on likely temperature gradients in the gas inside a large pressure vessel. Using the ratio p/f(2), we measured a gas leak (dM/dt)/M ≈ - 1.3 × 10(-5) h(-1) = - 0.11 yr(-1) from a 300-liter pressure vessel filled with argon at 450 kPa that was exposed to sunshine-driven temperature and pressure fluctuations as large as (dT/dt)/T ≈ (dp/dt)/p ≈ 5 × 10(-2) h(-1) using a 24-hour data record. This leak could not be detected in a 72-hour record of p/T. (Here M is the mass of the gas in the vessel and t is the time.).

  11. Detecting leaks in gas-filled pressure vessels using acoustic resonances

    NASA Astrophysics Data System (ADS)

    Gillis, K. A.; Moldover, M. R.; Mehl, J. B.

    2016-05-01

    We demonstrate that a leak from a large, unthermostatted pressure vessel into ambient air can be detected an order of magnitude more effectively by measuring the time dependence of the ratio p/f2 than by measuring the ratio p/T. Here f is the resonance frequency of an acoustic mode of the gas inside the pressure vessel, p is the pressure of the gas, and T is the kelvin temperature measured at one point in the gas. In general, the resonance frequencies are determined by a mode-dependent, weighted average of the square of the speed-of-sound throughout the volume of the gas. However, the weighting usually has a weak dependence on likely temperature gradients in the gas inside a large pressure vessel. Using the ratio p/f2, we measured a gas leak (dM/dt)/M ≈ - 1.3 × 10-5 h-1 = - 0.11 yr-1 from a 300-liter pressure vessel filled with argon at 450 kPa that was exposed to sunshine-driven temperature and pressure fluctuations as large as (dT/dt)/T ≈ (dp/dt)/p ≈ 5 × 10-2 h-1 using a 24-hour data record. This leak could not be detected in a 72-hour record of p/T. (Here M is the mass of the gas in the vessel and t is the time.)

  12. Detecting leaks in gas-filled pressure vessels using acoustic resonances.

    PubMed

    Gillis, K A; Moldover, M R; Mehl, J B

    2016-05-01

    We demonstrate that a leak from a large, unthermostatted pressure vessel into ambient air can be detected an order of magnitude more effectively by measuring the time dependence of the ratio p/f(2) than by measuring the ratio p/T. Here f is the resonance frequency of an acoustic mode of the gas inside the pressure vessel, p is the pressure of the gas, and T is the kelvin temperature measured at one point in the gas. In general, the resonance frequencies are determined by a mode-dependent, weighted average of the square of the speed-of-sound throughout the volume of the gas. However, the weighting usually has a weak dependence on likely temperature gradients in the gas inside a large pressure vessel. Using the ratio p/f(2), we measured a gas leak (dM/dt)/M ≈ - 1.3 × 10(-5) h(-1) = - 0.11 yr(-1) from a 300-liter pressure vessel filled with argon at 450 kPa that was exposed to sunshine-driven temperature and pressure fluctuations as large as (dT/dt)/T ≈ (dp/dt)/p ≈ 5 × 10(-2) h(-1) using a 24-hour data record. This leak could not be detected in a 72-hour record of p/T. (Here M is the mass of the gas in the vessel and t is the time.). PMID:27250456

  13. Survey of the Acoustic near Field of Three Nozzles at a Pressure Ratio of 30

    NASA Technical Reports Server (NTRS)

    Mull, Harold R; Erickson, John C , Jr

    1957-01-01

    The sound pressures radiating from the exhaust streams of two convergent-divergent and one convergent nozzle were measured. Exit diameters were 1.206 in. for the expanded nozzle and 0.625 in. for the convergent nozzle. The results are presented in a series of contour maps of overall and fine 1/3-octave-band sound pressures. The location of the source of the noise in each 1/3-octave band in the frequency range of 30 to 16,000 cps and the total power radiated were determined and compared with those of subsonic jets.

  14. The solar radiation pressure on the Mariner 9 Mars orbiter.

    NASA Technical Reports Server (NTRS)

    Georgevic, R. M.

    1973-01-01

    The refined mathematical model of the force created by the light pressure of the sun has been used to compute the solar radiation pressure force acting on the Mariner 9 (Mariner Mars 1971) spacecraft, taking into account the reflectivity characteristics of all its components. The results have been compared with values obtained from Mariner 9 observations during the cruise phase and are found to be in agreement within 0.1% of the values.

  15. Radiation-induced decomposition of PETN and TATB under pressure

    SciTech Connect

    Giefers, Hubertus; Pravica, Michael; Liermann, Hanns-Peter; Yang, Wenge

    2008-10-02

    We have investigated decomposition of PETN and TATB induced by white synchrotron X-ray radiation in a diamond anvil cell at ambient temperature and two pressures, nearly ambient and about 6 GPa. The decomposition rate of TATB decreases significantly when it is pressurized to 5.9 GPa. The measurements were highly reproducible and allowed us to obtain decomposition rates and the order parameters of the reactions.

  16. Active Control of Fan Noise-Feasibility Study. Volume 2: Canceling Noise Source-Design of an Acoustic Plate Radiator Using Piezoceramic Actuators

    NASA Technical Reports Server (NTRS)

    Pla, F. G.; Rajiyah, H.

    1995-01-01

    The feasibility of using acoustic plate radiators powered by piezoceramic thin sheets as canceling sources for active control of aircraft engine fan noise is demonstrated. Analytical and numerical models of actuated beams and plates are developed and validated. An optimization study is performed to identify the optimum combination of design parameters that maximizes the plate volume velocity for a given resonance frequency. Fifteen plates with various plate and actuator sizes, thicknesses, and bonding layers were fabricated and tested using results from the optimization study. A maximum equivalent piston displacement of 0.39 mm was achieved with the optimized plate samples tested with only one actuator powered, corresponding to a plate deflection at the center of over 1 millimeter. This is very close to the deflection required for a full size engine application and represents a 160-fold improvement over previous work. Experimental results further show that performance is limited by the critical stress of the piezoceramic actuator and bonding layer rather than by the maximum moment available from the actuator. Design enhancements are described in detail that will lead to a flight-worthy acoustic plate radiator by minimizing actuator tensile stresses and reducing nonlinear effects. Finally, several adaptive tuning methods designed to increase the bandwidth of acoustic plate radiators are analyzed including passive, active, and semi-active approaches. The back chamber pressurization and volume variation methods are investigated experimentally and shown to be simple and effective ways to obtain substantial control over the resonance frequency of a plate radiator. This study shows that piezoceramic-based plate radiators can be a viable acoustic source for active control of aircraft engine fan noise.

  17. Conditionally Increased Acoustic Pressures in Nonfetal Diagnostic Ultrasound Examinations Without Contrast Agents: A Preliminary Assessment.

    PubMed

    Nightingale, Kathryn R; Church, Charles C; Harris, Gerald; Wear, Keith A; Bailey, Michael R; Carson, Paul L; Jiang, Hui; Sandstrom, Kurt L; Szabo, Thomas L; Ziskin, Marvin C

    2015-07-01

    The mechanical index (MI) has been used by the US Food and Drug Administration (FDA) since 1992 for regulatory decisions regarding the acoustic output of diagnostic ultrasound equipment. Its formula is based on predictions of acoustic cavitation under specific conditions. Since its implementation over 2 decades ago, new imaging modes have been developed that employ unique beam sequences exploiting higher-order acoustic phenomena, and, concurrently, studies of the bioeffects of ultrasound under a range of imaging scenarios have been conducted. In 2012, the American Institute of Ultrasound in Medicine Technical Standards Committee convened a working group of its Output Standards Subcommittee to examine and report on the potential risks and benefits of the use of conditionally increased acoustic pressures (CIP) under specific diagnostic imaging scenarios. The term "conditionally" is included to indicate that CIP would be considered on a per-patient basis for the duration required to obtain the necessary diagnostic information. This document is a result of that effort. In summary, a fundamental assumption in the MI calculation is the presence of a preexisting gas body. For tissues not known to contain preexisting gas bodies, based on theoretical predications and experimentally reported cavitation thresholds, we find this assumption to be invalid. We thus conclude that exceeding the recommended maximum MI level given in the FDA guidance could be warranted without concern for increased risk of cavitation in these tissues. However, there is limited literature assessing the potential clinical benefit of exceeding the MI guidelines in these tissues. The report proposes a 3-tiered approach for CIP that follows the model for employing elevated output in magnetic resonance imaging and concludes with summary recommendations to facilitate Institutional Review Board (IRB)-monitored clinical studies investigating CIP in specific tissues.

  18. Conditionally Increased Acoustic Pressures in Nonfetal Diagnostic Ultrasound Examinations Without Contrast Agents: A Preliminary Assessment

    PubMed Central

    Nightingale, Kathryn R.; Church, Charles C.; Harris, Gerald; Wear, Keith A.; Bailey, Michael R.; Carson, Paul L.; Jiang, Hui; Sandstrom, Kurt L.; Szabo, Thomas L.; Ziskin, Marvin C.

    2016-01-01

    The mechanical index (MI) has been used by the US Food and Drug Administration (FDA) since 1992 for regulatory decisions regarding the acoustic output of diagnostic ultrasound equipment. Its formula is based on predictions of acoustic cavitation under specific conditions. Since its implementation over 2 decades ago, new imaging modes have been developed that employ unique beam sequences exploiting higher-order acoustic phenomena, and, concurrently, studies of the bioeffects of ultrasound under a range of imaging scenarios have been conducted. In 2012, the American Institute of Ultrasound in Medicine Technical Standards Committee convened a working group of its Output Standards Subcommittee to examine and report on the potential risks and benefits of the use of conditionally increased acoustic pressures (CIP) under specific diagnostic imaging scenarios. The term “conditionally” is included to indicate that CIP would be considered on a per-patient basis for the duration required to obtain the necessary diagnostic information. This document is a result of that effort. In summary, a fundamental assumption in the MI calculation is the presence of a preexisting gas body. For tissues not known to contain preexisting gas bodies, based on theoretical predications and experimentally reported cavitation thresholds, we find this assumption to be invalid. We thus conclude that exceeding the recommended maximum MI level given in the FDA guidance could be warranted without concern for increased risk of cavitation in these tissues. However, there is limited literature assessing the potential clinical benefit of exceeding the MI guidelines in these tissues. The report proposes a 3-tiered approach for CIP that follows the model for employing elevated output in magnetic resonance imaging and concludes with summary recommendations to facilitate Institutional Review Board (IRB)-monitored clinical studies investigating CIP in specific tissues. PMID:26112617

  19. Conditionally Increased Acoustic Pressures in Nonfetal Diagnostic Ultrasound Examinations Without Contrast Agents: A Preliminary Assessment.

    PubMed

    Nightingale, Kathryn R; Church, Charles C; Harris, Gerald; Wear, Keith A; Bailey, Michael R; Carson, Paul L; Jiang, Hui; Sandstrom, Kurt L; Szabo, Thomas L; Ziskin, Marvin C

    2015-07-01

    The mechanical index (MI) has been used by the US Food and Drug Administration (FDA) since 1992 for regulatory decisions regarding the acoustic output of diagnostic ultrasound equipment. Its formula is based on predictions of acoustic cavitation under specific conditions. Since its implementation over 2 decades ago, new imaging modes have been developed that employ unique beam sequences exploiting higher-order acoustic phenomena, and, concurrently, studies of the bioeffects of ultrasound under a range of imaging scenarios have been conducted. In 2012, the American Institute of Ultrasound in Medicine Technical Standards Committee convened a working group of its Output Standards Subcommittee to examine and report on the potential risks and benefits of the use of conditionally increased acoustic pressures (CIP) under specific diagnostic imaging scenarios. The term "conditionally" is included to indicate that CIP would be considered on a per-patient basis for the duration required to obtain the necessary diagnostic information. This document is a result of that effort. In summary, a fundamental assumption in the MI calculation is the presence of a preexisting gas body. For tissues not known to contain preexisting gas bodies, based on theoretical predications and experimentally reported cavitation thresholds, we find this assumption to be invalid. We thus conclude that exceeding the recommended maximum MI level given in the FDA guidance could be warranted without concern for increased risk of cavitation in these tissues. However, there is limited literature assessing the potential clinical benefit of exceeding the MI guidelines in these tissues. The report proposes a 3-tiered approach for CIP that follows the model for employing elevated output in magnetic resonance imaging and concludes with summary recommendations to facilitate Institutional Review Board (IRB)-monitored clinical studies investigating CIP in specific tissues. PMID:26112617

  20. Acoustic backscattering and radiation force on a rigid elliptical cylinder in plane progressive waves.

    PubMed

    Mitri, F G

    2016-03-01

    This work proposes a formal analytical theory using the partial-wave series expansion (PWSE) method in cylindrical coordinates, to calculate the acoustic backscattering form function as well as the radiation force-per-length on an infinitely long elliptical (non-circular) cylinder in plane progressive waves. The major (or minor) semi-axis of the ellipse coincides with the direction of the incident waves. The scattering coefficients for the rigid elliptical cylinder are determined by imposing the Neumann boundary condition for an immovable surface and solving a resulting system of linear equations by matrix inversion. The present method, which utilizes standard cylindrical (Bessel and Hankel) wave functions, presents an advantage over the solution for the scattering that is ordinarily expressed in a basis of elliptical Mathieu functions (which are generally non-orthogonal). Furthermore, an integral equation showing the direct connection of the radiation force function with the square of the scattering form function in the far-field from the scatterer (applicable for plane waves only), is noted and discussed. An important application of this integral equation is the adequate evaluation of the radiation force function from a bistatic measurement (i.e., in the polar plane) of the far-field scattering from any 2D object of arbitrary shape. Numerical predictions are evaluated for the acoustic backscattering form function and the radiation force function, which is the radiation force per unit length, per characteristic energy density, and per unit cross-sectional surface of the ellipse, with particular emphasis on the aspect ratio a/b, where a and b are the semi-axes, as well as the dimensionless size parameter kb, without the restriction to a particular range of frequencies. The results are particularly relevant in acoustic levitation, acousto-fluidics and particle dynamics applications. PMID:26726146

  1. Acoustic backscattering and radiation force on a rigid elliptical cylinder in plane progressive waves.

    PubMed

    Mitri, F G

    2016-03-01

    This work proposes a formal analytical theory using the partial-wave series expansion (PWSE) method in cylindrical coordinates, to calculate the acoustic backscattering form function as well as the radiation force-per-length on an infinitely long elliptical (non-circular) cylinder in plane progressive waves. The major (or minor) semi-axis of the ellipse coincides with the direction of the incident waves. The scattering coefficients for the rigid elliptical cylinder are determined by imposing the Neumann boundary condition for an immovable surface and solving a resulting system of linear equations by matrix inversion. The present method, which utilizes standard cylindrical (Bessel and Hankel) wave functions, presents an advantage over the solution for the scattering that is ordinarily expressed in a basis of elliptical Mathieu functions (which are generally non-orthogonal). Furthermore, an integral equation showing the direct connection of the radiation force function with the square of the scattering form function in the far-field from the scatterer (applicable for plane waves only), is noted and discussed. An important application of this integral equation is the adequate evaluation of the radiation force function from a bistatic measurement (i.e., in the polar plane) of the far-field scattering from any 2D object of arbitrary shape. Numerical predictions are evaluated for the acoustic backscattering form function and the radiation force function, which is the radiation force per unit length, per characteristic energy density, and per unit cross-sectional surface of the ellipse, with particular emphasis on the aspect ratio a/b, where a and b are the semi-axes, as well as the dimensionless size parameter kb, without the restriction to a particular range of frequencies. The results are particularly relevant in acoustic levitation, acousto-fluidics and particle dynamics applications.

  2. Low-frequency acoustic pressure, velocity, and intensity thresholds in a bottlenose dolphin (Tursiops truncatus) and white whale (Delphinapterus leucas)

    NASA Astrophysics Data System (ADS)

    Finneran, James J.; Carder, Donald A.; Ridgway, Sam H.

    2002-01-01

    The relative contributions of acoustic pressure and particle velocity to the low-frequency, underwater hearing abilities of the bottlenose dolphin (Tursiops truncatus) and white whale (Delphinapterus leucas) were investigated by measuring (masked) hearing thresholds while manipulating the relationship between the pressure and velocity. This was accomplished by varying the distance within the near field of a single underwater sound projector (experiment I) and using two underwater sound projectors and an active sound control system (experiment II). The results of experiment I showed no significant change in pressure thresholds as the distance between the subject and the sound source was changed. In contrast, velocity thresholds tended to increase and intensity thresholds tended to decrease as the source distance decreased. These data suggest that acoustic pressure is a better indicator of threshold, compared to particle velocity or mean active intensity, in the subjects tested. Interpretation of the results of experiment II (the active sound control system) was difficult because of complex acoustic conditions and the unknown effects of the subject on the generated acoustic field; however, these data also tend to support the results of experiment I and suggest that odontocete thresholds should be reported in units of acoustic pressure, rather than intensity.

  3. Radiation pressure and the linear momentum of the electromagnetic field.

    PubMed

    Mansuripur, Masud

    2004-11-01

    We derive the force of the electromagnetic radiation on material objects by a direct application of the Lorentz law of classical electrodynamics. The derivation is straightforward in the case of solid metals and solid dielectrics, where the mass density and the optical constants of the media are assumed to remain unchanged under internal and external pressures, and where material flow and deformation can be ignored. For metallic mirrors, we separate the contribution to the radiation pressure of the electrical charge density from that of the current density of the conduction electrons. In the case of dielectric media, we examine the forces experienced by bound charges and currents, and determine the contribution of each to the radiation pressure. These analyses reveal the existence of a lateral radiation pressure inside the dielectric media, one that is exerted at and around the edges of a finite-diameter light beam. The lateral pressure turns out to be compressive for s-polarized light and expansive for p-polarized light. Along the way, we derive an expression for the momentum density of the light field inside dielectric media, one that has equal contributions from the traditional Minkowski and Abraham forms. This new expression for the momentum density, which contains both electromagnetic and mechanical terms, is used to explain the behavior of light pulses and individual photons upon entering and exiting a dielectric slab. In all the cases considered, the net forces and torques experienced by material bodies are consistent with the relevant conservation laws. Our method of calculating the radiation pressure can be used in conjunction with numerical simulations to yield the distribution of fields and forces in diverse systems of practical interest.

  4. Radiation, propagtion, fluid-structure coupling; Colloquium on Aeronautical Acoustics, 9th, Compiegne, France, November 14-16, 1984, Reports. Parts 1 & 2

    NASA Astrophysics Data System (ADS)

    Analytical tools which have been devised for examination of acoustic phenomena of interest in aerospace applications are presented. The techniques include a finite element method for elasto-acoustic coupling in a surface, a finite difference model for acoustic propagation in ducts and a variational formulation for acoustic radiation from axisymmetric structures. The situations studied also cover acoustic energy transfer near the ring frequency in a cylinder and in a cylindrical shell excited by a plane wave. Finally, attention is devoted to the propagation of acoustic radiation in a turbomachinery duct.

  5. Numerical investigation of acoustic radiation from vortex-airfoil interaction

    NASA Astrophysics Data System (ADS)

    Legault, Anne; Ji, Minsuk; Wang, Meng

    2012-11-01

    Numerical simulations of vortices interacting with a NACA 0012 airfoil and a flat-plate airfoil at zero angle of attack are carried out to assess the applicability and accuracy of classical theories. Unsteady lift and sound are computed and compared with the predictions by theories of Sears and Amiet, which assume a thin-plate airfoil in an inviscid flow. A Navier-Stokes solver is used in the simulations, and therefore viscous effects are taken into consideration. For the thin-plate airfoil, the effect of viscosity is negligible. For a NACA 0012 airfoil, the viscous contribution to the unsteady lift and sound mainly comes from coherent vortex shedding in the wake of the airfoil and the interaction of the incoming vortices with the airfoil wake, which become stronger at higher Reynolds numbers for a 2-D laminar flow. When the flow is turbulent at chord Reynolds number of 4 . 8 ×105 , however, the viscous contribution becomes negligible as coherent vortex shedding is not present. Sound radiation from vortex-airfoil interaction at turbulent Reynolds numbers is computed numerically via Lighthill's theory and the result is compared with the predictions of Amiet and Curle. The effect of the airfoil thickness is also examined. Supported by ONR Grant N00014-09-1-1088.

  6. Strategies for single particle manipulation using acoustic radiation forces and external tools

    NASA Astrophysics Data System (ADS)

    Oberti, Stefano; Neild, Adrian; Möller, Dirk; Dual, Jurg

    2010-01-01

    The use of primary acoustic radiation forces has been shown to be a valid technique for the handling of micron sized suspended particles, such as beads or biological cells. These forces arise as a nonlinear effect when an acoustic wave or vibration, which is set up in the fluid by exciting to resonance the system containing the suspension, interacts with the particles. The typical frequencies (upper kHz - lower MHz range) and the periodicity (in the range of hundreds of micrometers) of the acoustic field make this technique particularly suited for the handling of particles within microfluidic systems. A variety of devices for separation, fractionation, trapping and positioning of beads or biological cells, working both in batch or fluid flow mode, have been proposed. With the exception of the ports used to inject or remove the sample or the carrier medium, these systems can be considered as closed systems. Nevertheless, access to the particles with external tools is sometimes needed after acoustic manipulation has been performed. For instance, particles or cells pre-positioned in a sequence along the centerline of a channel using acoustic radiation forces need to be removed from it using a microgripper for further handling. Furthermore, in the field of crystallography research protein crystals have to be placed one by one onto a nylon loop prior to X-ray analysis with synchrotron radiation. This is usually done using the loop to pick up the crystal from the solution where it has been growing with other ones. As this process is sometimes repeated for a large number of crystals there are efforts to automate it. To this purpose it would be advantageous to bring the crystals spatially separated into a known position where they than can be sequentially collected with the loop. Here strategies for single particle manipulation are presented combining the effects of acoustic fields, fluid flow, surface tension and external tools. They are discussed by means of numerical

  7. Acoustic radiation- and streaming-induced microparticle velocities determined by microparticle image velocimetry in an ultrasound symmetry plane.

    PubMed

    Barnkob, Rune; Augustsson, Per; Laurell, Thomas; Bruus, Henrik

    2012-11-01

    We present microparticle image velocimetry measurements of suspended microparticles of diameters from 0.6 to 10 μm undergoing acoustophoresis in an ultrasound symmetry plane in a microchannel. The motion of the smallest particles is dominated by the Stokes drag from the induced acoustic streaming flow, while the motion of the largest particles is dominated by the acoustic radiation force. For all particle sizes we predict theoretically how much of the particle velocity is due to radiation and streaming, respectively. These predictions include corrections for particle-wall interactions and ultrasonic thermoviscous effects and match our measurements within the experimental uncertainty. Finally, we predict theoretically and confirm experimentally that the ratio between the acoustic radiation- and streaming-induced particle velocities is proportional to the actuation frequency, the acoustic contrast factor, and the square of the particle size, while it is inversely proportional to the kinematic viscosity.

  8. Problems of applications of high power IR radiation in aquatic medium under high pressure

    NASA Astrophysics Data System (ADS)

    Sorokin, Yurii V.; Kuzyakov, Boris A.

    2004-06-01

    In this work the effects that appear in the optical breakdown are analyzed in water and the time dependences received also for the velocities and pressures at the wave fronts. The application of acoustic waves, generated by high power laser pulses in the aqueous medium, has quite serious perspectives for sounding. It is shown in the work that under comparatively low power density of radiation, as a result of a surface layer heating, the thermoelastic sresses arise, leading to the excitation of the acoustic waves. The analysis showed that the prognostic evaluations of the values of a light deflagration area are possible for a clear aqueous medium with the pressures up to 400 kg/cm2. With the presence of microinhomogeneities, it is necessary to know their total physical and chemical properties and detailed trustworthy data by their spatial distribution. A principally new approach was developed to the problem of videoinformation transmission from the object surfaces by the fiber-optic channel. The application of a precision measuring TV-camera with a color format in the range 0.3 - 0.98 μm allows to raise the information capacity of the transmitted information. The optimization of vision module choice are considered also.

  9. Improved Solar-Radiation-Pressure Models for GPS Satellites

    NASA Technical Reports Server (NTRS)

    Bar-Sever, Yoaz; Kuang, Da

    2006-01-01

    A report describes a series of computational models conceived as an improvement over prior models for determining effects of solar-radiation pressure on orbits of Global Positioning System (GPS) satellites. These models are based on fitting coefficients of Fourier functions of Sun-spacecraft- Earth angles to observed spacecraft orbital motions.

  10. Effects of Solar Radiation Pressure on Earth Satellite Orbits.

    PubMed

    Parkinson, R W; Jones, H M; Shapiro, I I

    1960-03-25

    Calculations show that, at a mean altitude of 1000 miles, radiation pressure can displace the orbit of the 100-foot Echo balloon at rates up to 3.7 miles per day, the orbit of the 12-foot Beacon satellite at 0.7 mile per day. For certain resonant conditions this effect accumulates, drastically affecting the satellite's lifetime.

  11. Ultrasonic Measurement of Strain Distribution Inside Object Cyclically Compressed by Dual Acoustic Radiation Force

    NASA Astrophysics Data System (ADS)

    Odagiri, Yoshitaka; Hasegawa, Hideyuki; Kanai, Hiroshi

    2008-05-01

    One possible way to evaluate acupuncture therapy quantitatively is to measure the change in the elastic property of muscle after application of the therapy. Many studies have been conducted to measure mechanical properties of tissues using ultrasound-induced acoustic radiation force. To assess mechanical properties, strain must be generated in an object. However, a single radiation force is not effective because it mainly generates translational motion when the object is much harder than the surrounding medium. In this study, two cyclic radiation forces are simultaneously applied to a muscle phantom from two opposite horizontal directions so that the object is cyclically compressed in the horizontal direction. By the horizontal compression, the object is expanded vertically based on its incompressibility. The resultant vertical displacement is measured using another ultrasound pulse. Two ultrasonic transducers for actuation were both driven by the sum of two continuous sinusoidal signals at two slightly different frequencies [1 MHz and (1 M + 5) Hz]. The displacement of several micrometers in amplitude, which fluctuated at 5 Hz, was measured by the ultrasonic phased tracking method. Increase in thickness inside the object was observed just when acoustic radiation forces increased. Such changes in thickness correspond to vertical expansion due to horizontal compression.

  12. Acoustic radiation force and torque on an absorbing compressible particle in an inviscid fluid.

    PubMed

    Silva, Glauber T

    2014-11-01

    Exact formulas of the acoustic radiation force and torque exerted by an arbitrary time-harmonic wave on an absorbing compressible particle that is suspended in an inviscid fluid are presented. It is considered that the particle diameter is much smaller than the incident wavelength, i.e., the so-called Rayleigh scattering limit. Moreover, the particle absorption assumed here is due to the attenuation of compressional waves only. Shear waves inside and outside the particle are neglected, since the inner and outer viscous boundary layer of the particle are supposed to be much smaller than the particle radius. The obtained radiation force formulas are used to establish the trapping conditions of a particle by a single-beam acoustical tweezer based on a spherically focused ultrasound transducer. In this case, it is shown that the particle absorption has a pivotal role in single-beam trapping at the transducer focal region. Furthermore, it is found that only the first-order Bessel vortex beam can generate the radiation torque on a small particle. In addition, numerical evaluation of the radiation force and torque exerted on a benzene and an olive oil droplet suspended in water are presented and discussed. PMID:25373943

  13. Acoustic radiation force and torque on an absorbing compressible particle in an inviscid fluid.

    PubMed

    Silva, Glauber T

    2014-11-01

    Exact formulas of the acoustic radiation force and torque exerted by an arbitrary time-harmonic wave on an absorbing compressible particle that is suspended in an inviscid fluid are presented. It is considered that the particle diameter is much smaller than the incident wavelength, i.e., the so-called Rayleigh scattering limit. Moreover, the particle absorption assumed here is due to the attenuation of compressional waves only. Shear waves inside and outside the particle are neglected, since the inner and outer viscous boundary layer of the particle are supposed to be much smaller than the particle radius. The obtained radiation force formulas are used to establish the trapping conditions of a particle by a single-beam acoustical tweezer based on a spherically focused ultrasound transducer. In this case, it is shown that the particle absorption has a pivotal role in single-beam trapping at the transducer focal region. Furthermore, it is found that only the first-order Bessel vortex beam can generate the radiation torque on a small particle. In addition, numerical evaluation of the radiation force and torque exerted on a benzene and an olive oil droplet suspended in water are presented and discussed.

  14. Generation of ultrasound radiation force with the use of time reversal acoustics principles

    NASA Astrophysics Data System (ADS)

    Sarvazyan, Armen; Sutin, Alexander

    2005-09-01

    There are numerous medical applications of ultrasound radiation force (RF) which could be made more effective using the time reversal acoustics (TRA) principles. This paper gives an overview of research into physical and technical bases of RF generation in heterogeneous biological media using TRA focusing systems. A custom-designed compact multichannel TRA system for receiving, digitizing, storing, time reversing, and transmitting acoustic signals in a wide frequency range from 0.01 to 10 MHz has been developed and extensively tested in model systems and ex vivo tissues and bones. Shear strain and shear waves remotely induced in soft tissues and bones by radiation force were detected using various acoustical and optical means. Experimental studies fully confirmed the feasibility of TRA generation of RF and demonstrated several advantages over conventional means of remotely inducing shear stress in biological media. These advantages include a possibility to create highly localized (close to diffraction limit) shear stress in heterogeneous media stir focused ultrasound beam in 3-D volume using very simple hardware. [Work supported by NIH grant.

  15. a Computational Method for the Analysis of Acoustic Radiation from Turbofan Inlets

    NASA Astrophysics Data System (ADS)

    Raviprakash, G. K.

    1992-01-01

    A computational method is presented for the analysis of the noise radiation from turbofan inlets. The method developed considers the effect of mean flow and can be used at high frequencies. The techniques for generating the grid, solving the acoustic equations, applying radiating conditions on the far-field boundary, imposing inlet-fan interface conditions as well as solving the steady compressible flow equations are embodied in the Inlet Acoustic Analysis Method. The theoretical basis, formulated for 3-D acoustics within an axisymmetric domain, considers the effect of non-uniform mean flow. The discretization of the field equations is done using a finite volume type differencing. This leads to a block tri-diagonal system of equations which is then efficiently solved. A new and powerful method is developed for the application of radiating conditions. A layer potential representation is used in obtaining numerically local radiating conditions. The locally radiating conditions, developed using the single layer source representation, can be used even at the interior eigenvalues. Using this technique, the radiating conditions can be applied very close to the inlet, and hence the computational efficiency can be significantly increased. The irrotationality conditions for the axisymmetric compressible flow are discretized for solving the mean flow field. An iterative scheme is developed to solve for the stream function, the density, and the speed of sound. The inlet-fan interface conditions are incorporated to properly specify the source of noise. The noise source is either directly specified or the interface potential distribution is split into a combination of an imposed right traveling disturbance and an unknown combination of left traveling disturbances, that come out as part of the solution process. The grid generation procedure utilizes algebraic transformations as well as the grid blending technique. This process is automated to accommodate variations in the grid

  16. A computational method for the analysis of acoustic radiation from turbofan inlets

    NASA Astrophysics Data System (ADS)

    Raviprakash, G. K.

    A computational method is presented for the analysis of the noise radiation from turbofan inlets. The method developed considers the effect of mean flow and can be used at high frequencies. The techniques for generating the grid, solving the acoustic equations, applying radiating conditions on the far-field boundary, imposing inlet-fan interface conditions as well as solving the steady compressible flow equations are embodied in the Inlet Acoustic Analysis Method. The theoretical basis, formulated for 3-D acoustics within an axisymmetric domain, considers the effect of non-uniform mean flow. The discretization of the field equations is done using a finite volume type differencing. This leads to a block tri-diagonal system of equations which is then efficiently solved. A new and powerful method is developed for the application of radiating conditions. A layer potential representation is used in obtaining numerically local radiating conditions. The locally radiating conditions, developed using the single layer source representation, can be used even at the interior eigenvalues. Using this technique, the radiating conditions can be applied very close to the inlet, and hence the computational efficiency can be significantly increased. The irrotationality conditions for the axisymmetric compressible flow are discretized for solving the mean flow field. An iterative scheme is developed to solve for the stream function, the density, and the speed of sound. The inlet-fan interface conditions are incorporated to properly specify the source of noise. The noise source is either directly specified or the interface potential distribution is split into a combination of an imposed right traveling disturbance and an unknown combination of left traveling disturbances, that come out as part of the solution process. The grid generation procedure utilizes algebraic transformations as well as the grid blending techniques. This process is automated to accommodate variations in the grid

  17. Indirect measurement of cylinder pressure from diesel engines using acoustic emission

    NASA Astrophysics Data System (ADS)

    El-Ghamry, M.; Steel, J. A.; Reuben, R. L.; Fog, T. L.

    2005-07-01

    Indirect measurement of the cylinder pressure from diesel engines is possible using acoustic emission (AE). A method is demonstrated for a large two-stroke marine diesel engine and a small four-stroke diesel engine, which involves reconstructing the cylinder crank angle domain diagram from the AE generated during the combustion phase. Raw AE was used for modelling and reconstructing the pressure waveform in the time domain but this could not be used to model the pressure rise (compression). To overcome this problem the signal was divided into two sections representing the compression part of the signal and the fuel injection/expansion stroke. The compression part of the pressure signal was reconstructed by using polynomial fitting. An auto-regressive technique was used during the injection/expansion stroke. The rms AE signal is well correlated with the pressure signal in the time and frequency domain and complex cepstrum analysis was used to model the pressure signal for the complete combustion phase (compression, injection and expansion). The main advantage of using cepstral analysis is that the model uses the frequency content of the rms AE signal rather than the energy content of the rms AE signal, which gives an advantage when the signal has lower energy content, during the compression process. By calculating the engine running speed from the rms AE signal and selecting the proper cepstrum model correlated to the combustion rms AE energy content, an analytical algorithm was developed to give a wide range of applicability over the different conditions of engine speed, engine type and load. The pressure reconstructed from both AE and acceleration data are compared. AE has the advantage of a much higher signal-to-noise ratio and improved time resolution and is shown to be better than the acceleration.

  18. Fluid displacement fronts in porous media: pore scale interfacial jumps, pressure bursts and acoustic emissions

    NASA Astrophysics Data System (ADS)

    Moebius, Franziska; Or, Dani

    2014-05-01

    The macroscopically smooth and regular motion of fluid fronts in porous media is composed of numerous rapid pore-scale interfacial jumps and pressure bursts that involve intense interfacial energy release in the form of acoustic emissions. The characteristics of these pore scale events affect residual phase entrapment and transport properties behind the front. We present experimental studies using acoustic emission technique (AE), rapid imaging, and liquid pressure measurements to characterize these processes during drainage and imbibition in simple porous media. Imbibition and drainage produce different AE signatures (AE amplitudes obey a power law). For rapid drainage, AE signals persist long after cessation of front motion reflecting fluid redistribution and interfacial relaxation. Imaging revealed that the velocity of interfacial jumps often exceeds front velocity by more than 50 fold and is highly inertial component (Re>1000). Pore invasion volumes reduced deduced from pressure fluctuations waiting times (for constant withdrawal rates) show remarkable agreement with geometrically-deduced pore volumes. Discrepancies between invaded volumes and geometrical pores increase with increasing capillary numbers due to constraints on evacuation opportunity times and simultaneous invasion events. A mechanistic model for interfacial motions in a pore-throat network was developed to investigate interfacial dynamics focusing on the role of inertia. Results suggest that while pore scale dynamics were sensitive to variations in pore geometry and boundary conditions, inertia exerted only a minor effect on phase entrapment. The study on pore scale invasion events paints a complex picture of rapid and inertial motions and provides new insights on mechanisms at displacement fronts that are essential for improved macroscopic description of multiphase flows in porous media.

  19. Solar radiation and water vapor pressure to forecast chickenpox epidemics.

    PubMed

    Hervás, D; Hervás-Masip, J; Nicolau, A; Reina, J; Hervás, J A

    2015-03-01

    The clear seasonality of varicella infections in temperate regions suggests the influence of meteorologic conditions. However, there are very few data on this association. The aim of this study was to determine the seasonal pattern of varicella infections on the Mediterranean island of Mallorca (Spain), and its association with meteorologic conditions and schooling. Data on the number of cases of varicella were obtained from the Network of Epidemiologic Surveillance, which is composed of primary care physicians who notify varicella cases on a compulsory basis. From 1995 to 2012, varicella cases were correlated to temperature, humidity, rainfall, water vapor pressure, atmospheric pressure, wind speed, and solar radiation using regression and time-series models. The influence of schooling was also analyzed. A total of 68,379 cases of varicella were notified during the study period. Cases occurred all year round, with a peak incidence in June. Varicella cases increased with the decrease in water vapor pressure and/or the increase of solar radiation, 3 and 4 weeks prior to reporting, respectively. An inverse association was also observed between varicella cases and school holidays. Using these variables, the best fitting autoregressive moving average with exogenous variables (ARMAX) model could predict 95 % of varicella cases. In conclusion, varicella in our region had a clear seasonality, which was mainly determined by solar radiation and water vapor pressure.

  20. Solar radiation and water vapor pressure to forecast chickenpox epidemics.

    PubMed

    Hervás, D; Hervás-Masip, J; Nicolau, A; Reina, J; Hervás, J A

    2015-03-01

    The clear seasonality of varicella infections in temperate regions suggests the influence of meteorologic conditions. However, there are very few data on this association. The aim of this study was to determine the seasonal pattern of varicella infections on the Mediterranean island of Mallorca (Spain), and its association with meteorologic conditions and schooling. Data on the number of cases of varicella were obtained from the Network of Epidemiologic Surveillance, which is composed of primary care physicians who notify varicella cases on a compulsory basis. From 1995 to 2012, varicella cases were correlated to temperature, humidity, rainfall, water vapor pressure, atmospheric pressure, wind speed, and solar radiation using regression and time-series models. The influence of schooling was also analyzed. A total of 68,379 cases of varicella were notified during the study period. Cases occurred all year round, with a peak incidence in June. Varicella cases increased with the decrease in water vapor pressure and/or the increase of solar radiation, 3 and 4 weeks prior to reporting, respectively. An inverse association was also observed between varicella cases and school holidays. Using these variables, the best fitting autoregressive moving average with exogenous variables (ARMAX) model could predict 95 % of varicella cases. In conclusion, varicella in our region had a clear seasonality, which was mainly determined by solar radiation and water vapor pressure. PMID:25265908

  1. The Role of Radiation Pressure in Assembling Super Star Clusters

    NASA Astrophysics Data System (ADS)

    Tsz-Ho Tsang, Benny; Milosavljevic, Milos

    2016-06-01

    Super star clusters are the most extreme star-forming regions of the Universe - they occupy the most massive end of the Kennicutt-Schmidt relation, forming stars at exceptionally high rates and gas surface densities. The radiation feedback from the dense population of massive stars is expected to play a dynamic role during the assembly of the clusters, and represents a potential mechanism for launching large-scale galactic outflows. Observationally, large distances and dust obscuration have been withholding clues about the early stages of massive cluster formation; theoretically, the lack of accurate and efficient radiation transfer schemes in multi-dimensional hydrodynamic simulations has been deterring our understanding of radiative feedback. By extending the adaptive mesh refinement code FLASH with a closure-free, Monte Carlo radiation transport scheme, we perform 3D radiation hydrodynamical simulations of super star cluster formation from the collapse of turbulent molecular clouds. Our simulations probe the star formation in densities typical for starbursts, with both non-ionizing UV and dust-reprocessed IR radiation treated self-consistently. We aim to determine the role of radiation pressure in regulating star formation, and its capacity in driving intense outflows.

  2. The Action of Pressure-Radiation Forces on Pulsating Vapor Bubbles

    NASA Technical Reports Server (NTRS)

    Hao, Y.; Oguz, N.; Prosperetti, A.

    2001-01-01

    The action of pressure-radiation (or Bjerknes) forces on gas bubbles is well understood. This paper studies the analogous phenomenon for vapor bubbles, about which much less is known. A possible practical application is the removal of boiling bubbles from the neighborhood of a heated surface in the case of a downward facing surface or in the absence of gravity. For this reason, the case of a bubble near a plane rigid surface is considered in detail. It is shown that, when the acoustic wave fronts are parallel to the surface, the bubble remains trapped due to secondary Bjerknes force caused by an "image bubble." When the wave fronts are perpendicular to the surface, on the other hand, the bubble can be made to slide laterally.

  3. Measurement of radiation-pressure-induced optomechanical dynamics in a suspended Fabry-Perot cavity

    SciTech Connect

    Corbitt, Thomas; Ottaway, David; Innerhofer, Edith; Pelc, Jason; Mavalvala, Nergis

    2006-08-15

    We report on experimental observation of radiation-pressure induced effects in a high-power optical cavity. These effects play an important role in next-generation gravitational wave detectors, as well as in quantum nondemolition interferometers. We measure the properties of an optical spring, created by coupling of an intense laser field to the pendulum mode of a suspended mirror, and also the parametric instability (PI) that arises from the coupling between acoustic modes of the cavity mirrors and the cavity optical mode. We measure an unprecedented optical rigidity of K=(3.08{+-}0.09)x10{sup 4} N/m, corresponding to an optical rigidity that is 6000 times stiffer than the mechanical stiffness, and PI strength R{approx_equal}3. We measure the unstable nature of the optical spring resonance, and demonstrate that the PI can be stabilized by feedback to the frequency of the laser source.

  4. 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.

  5. Solar radiation pressure effects on the Helios spacecraft

    NASA Technical Reports Server (NTRS)

    Georgevic, R. M.

    1976-01-01

    A mathematical model of the solar radiation force and torques, developed for the Mariner 10 Venus/Mercury spacecraft mission, was used for a detailed analysis of the effects of solar light pressure on the Helios spacecraft. Due to the fact that the main body of the Helios spacecraft is a surface of enclosure, inside of which most of the reradiated thermal energy is lost, expressions for the portion of the solar radiation force, produced by the thermal reradiation, had to be given a different form. Hence the need for the derivation of a somewhat different theoretical model for the force acting on the main body of the spacecraft.

  6. Generation of terahertz radiation via an electromagnetically induced transparency at ion acoustic frequency region in laser-produced dense plasmas.

    PubMed

    Nakagawa, Makoto; Kodama, Ryosuke; Higashiguchi, Takeshi; Yugami, Noboru

    2009-08-01

    Electromagnetically induced transparency is a well-known quantum phenomena that electromagnetic wave controls the refractive index of medium. It enables us to create a passband for low-frequency electromagnetic wave in a dense plasma even if the plasma is opaque for the electromagnetic wave. This technique can be used to prove the ion acoustic wave because the ion acoustic frequency is lower than the plasma frequency. We have investigated a feasibility of electromagnetic radiation at THz region corresponding to the ion acoustic frequency from a dense plasma. We confirmed that the passband is created at about 7.5 THz corresponding to the ion acoustic frequency in the electron plasma density of 10(21) cm(-3) with a Ti:Sapphire laser with the wavelength of 800 nm and the laser intensity of 10(17) W/cm(2). The estimated radiation power is around 1 MW, which is expected to be useful for nonlinear THz science and applications.

  7. Acoustophoresis of disk-shaped microparticles: A numerical and experimental study of acoustic radiation forces and torques.

    PubMed

    Garbin, Alexander; Leibacher, Ivo; Hahn, Philipp; Le Ferrand, Hortense; Studart, André; Dual, Jürg

    2015-11-01

    Disk-shaped microparticles experience an acoustic radiation force and torque in an ultrasonic standing wave. Hence, they are translated by the acoustic field, an effect called acoustophoresis, and rotated. The torque effect is also known from the "Rayleigh disk" which is described in literature for sound intensity measurements. In this paper, inviscid numerical simulations of acoustic radiation forces and torques for disks with radius ≪ wavelength in water are developed in good agreement with former analytical solutions, and the dependence on disk geometry, density, and orientation is discussed. Experiments with alumina disks (diameter 7.5 μm), suspended in an aqueous liquid in a silicon microchannel, confirm the theoretical results qualitatively at the microscale and ultrasonic frequencies around 2 MHz. These results can potentially be applied for the synthesis of disk-reinforced composite materials. The insights are also relevant for the acoustic handling of various disk-shaped particles, such as red blood cells. PMID:26627752

  8. Detection scheme for acoustic quantum radiation in Bose-Einstein condensates.

    PubMed

    Schützhold, Ralf

    2006-11-10

    Based on doubly detuned Raman transitions between (meta)stable atomic or molecular states and recently developed atom counting techniques, a detection scheme for sound waves in dilute Bose-Einstein condensates is proposed whose accuracy might reach down to the level of a few or even single phonons. This scheme could open up a new range of applications including the experimental observation of quantum radiation phenomena such as the Hawking effect in sonic black-hole analogues or the acoustic analogue of cosmological particle creation. PMID:17155600

  9. Estimation of mechanical properties of gelatin using a microbubble under acoustic radiation force

    NASA Astrophysics Data System (ADS)

    Shirota, Eriko; Ando, Keita

    2015-12-01

    This paper is concerned with observations of the translation of a microbubble (80 μm or 137 μm in radius) in a viscoelastic medium (3 w% gelatin), which is induced by acoustic radiation force originating from 1 MHz focused ultrasound. An optical system using a high-speed camera was designed to visualize the bubble translation and deformation. If the bubble remains its spherical shape under the sonication, the bubble translation we observed can be described by theory based on the Voigt model for linear viscoelastic solids; mechanical properties of the gelatin are calculated from measurements of the terminal displacement under the sonication.

  10. A Fabry-Perot fiber-optic ultrasonic hydrophone for the simultaneous measurement of temperature and acoustic pressure.

    PubMed

    Morris, Paul; Hurrell, Andrew; Shaw, Adam; Zhang, Edward; Beard, Paul

    2009-06-01

    A dual sensing fiber-optic hydrophone that can make simultaneous measurements of acoustic pressure and temperature at the same location has been developed for characterizing ultrasound fields and ultrasound-induced heating. The transduction mechanism is based on the detection of acoustically- and thermally-induced thickness changes in a polymer film Fabry-Perot interferometer deposited at the tip of a single mode optical fiber. The sensor provides a peak noise-equivalent pressure of 15 kPa (at 5 MHz, over a 20 MHz measurement bandwidth), an acoustic bandwidth of 50 MHz, and an optically defined element size of 10 microm. As well as measuring acoustic pressure, temperature changes up to 70 degrees C can be measured, with a resolution of 0.34 degrees C. To evaluate the thermal measurement capability of the sensor, measurements were made at the focus of a high-intensity focused ultrasound (HIFU) field in a tissue mimicking phantom. These showed that the sensor is not susceptible to viscous heating, is able to withstand high intensity fields, and can simultaneously acquire acoustic waveforms while monitoring induced temperature rises. These attributes, along with flexibility, small physical size (OD approximately 150 microm), immunity to Electro-Magnetic Interference (EMI), and low sensor cost, suggest that this type of hydrophone may provide a practical alternative to piezoelectric based hydrophones. PMID:19507943

  11. Imaging the position-dependent 3D force on microbeads subjected to acoustic radiation forces and streaming.

    PubMed

    Lamprecht, Andreas; Lakämper, Stefan; Baasch, Thierry; Schaap, Iwan A T; Dual, Jurg

    2016-07-01

    Acoustic particle manipulation in microfluidic channels is becoming a powerful tool in microfluidics to control micrometer sized objects in medical, chemical and biological applications. By creating a standing acoustic wave in the channel, the resulting pressure field can be employed to trap or sort particles. To design efficient and reproducible devices, it is important to characterize the pressure field throughout the volume of the microfluidic device. Here, we used an optically trapped particle as probe to measure the forces in all three dimensions. By moving the probe through the volume of the channel, we imaged spatial variations in the pressure field. In the direction of the standing wave this revealed a periodic energy landscape for 2 μm beads, resulting in an effective stiffness of 2.6 nN m(-1) for the acoustic trap. We found that multiple fabricated devices showed consistent pressure fields. Surprisingly, forces perpendicular to the direction of the standing wave reached values of up to 20% of the main-axis-values. To separate the direct acoustic force from secondary effects, we performed experiments with different bead sizes, which attributed some of the perpendicular forces to acoustic streaming. This method to image acoustically generated forces in 3D can be used to either minimize perpendicular forces or to employ them for specific applications in novel acoustofluidic designs. PMID:27302661

  12. Imaging the position-dependent 3D force on microbeads subjected to acoustic radiation forces and streaming.

    PubMed

    Lamprecht, Andreas; Lakämper, Stefan; Baasch, Thierry; Schaap, Iwan A T; Dual, Jurg

    2016-07-01

    Acoustic particle manipulation in microfluidic channels is becoming a powerful tool in microfluidics to control micrometer sized objects in medical, chemical and biological applications. By creating a standing acoustic wave in the channel, the resulting pressure field can be employed to trap or sort particles. To design efficient and reproducible devices, it is important to characterize the pressure field throughout the volume of the microfluidic device. Here, we used an optically trapped particle as probe to measure the forces in all three dimensions. By moving the probe through the volume of the channel, we imaged spatial variations in the pressure field. In the direction of the standing wave this revealed a periodic energy landscape for 2 μm beads, resulting in an effective stiffness of 2.6 nN m(-1) for the acoustic trap. We found that multiple fabricated devices showed consistent pressure fields. Surprisingly, forces perpendicular to the direction of the standing wave reached values of up to 20% of the main-axis-values. To separate the direct acoustic force from secondary effects, we performed experiments with different bead sizes, which attributed some of the perpendicular forces to acoustic streaming. This method to image acoustically generated forces in 3D can be used to either minimize perpendicular forces or to employ them for specific applications in novel acoustofluidic designs.

  13. Risk of a second cancer from scattered radiation in acoustic neuroma treatment

    NASA Astrophysics Data System (ADS)

    Yoon, Myonggeun; Lee, Hyunho; Sung, Jiwon; Shin, Dongoh; Park, Sungho; Chung, Weon Kuu; Jahng, Geon-Ho; Kim, Dong Wook

    2014-06-01

    The present study aimed to compare the risk of a secondary cancer from scattered and leakage doses in patients receiving intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), and stereotactic radiosurgery (SRS). Four acoustic neuroma patients were treated with IMRT, VMAT, or SRS. Their excess relative risk (ERR), excess absolute risk (EAR), and lifetime attributable risk (LAR) of a secondary cancer were estimated using the corresponding secondary doses measured at various organs by using radio-photoluminescence glass dosimeters (RPLGD) placed inside a humanoid phantom. When a prescription dose was delivered in the planning target volume of the 4 patients, the average organ equivalent doses (OED) at the thyroid, lung, liver, bowel, bladder, prostate (or ovary), and rectum were 14.6, 1.7, 0.9, 0.8, 0.6, 0.6, and 0.6 cGy, respectively, for IMRT whereas they were 19.1, 1.8, 2.0, 0.6, 0.4, 0.4, and 0.4 cGy, respectively, for VMAT, and 22.8, 4.6, 1.4, 0.7, 0.5, 0.5, and 0.5 cGy, respectively, for SRS. The OED decreased as the distance from the primary beam increased. The thyroid received the highest OED compared to other organs. A lifetime attributable risk evaluation estimated that more than 0.03% of acoustic neuroma (AN) patients would get radiation-induced cancer within 20 years of receiving radiation therapy. The organ with the highest radiation-induced cancer risk after radiation treatment for AN was the thyroid. We found that the LAR could be increased by the transmitted dose from the primary beam. No modality-specific difference in radiation-induced cancer risk was observed in our study.

  14. Sound propagation in and radiation from acoustically lined flow ducts: A comparison of experiment and theory

    NASA Technical Reports Server (NTRS)

    Plumblee, H. E., Jr.; Dean, P. D.; Wynne, G. A.; Burrin, R. H.

    1973-01-01

    The results of an experimental and theoretical study of many of the fundamental details of sound propagation in hard wall and soft wall annular flow ducts are reported. The theory of sound propagation along such ducts and the theory for determining the complex radiation impedance of higher order modes of an annulus are outlined, and methods for generating acoustic duct modes are developed. The results of a detailed measurement program on propagation in rigid wall annular ducts with and without airflow through the duct are presented. Techniques are described for measuring cut-on frequencies, modal phase speed, and radial and annular mode shapes. The effects of flow velocity on cut-on frequencies and phase speed are measured. Comparisons are made with theoretical predictions for all of the effects studies. The two microphone method of impedance is used to measure the effects of flow on acoustic liners. A numerical study of sound propagation in annular ducts with one or both walls acoustically lined is presented.

  15. Laser-Induced Acoustic Desorption Atmospheric Pressure Photoionization via VUV-Generating Microplasmas

    NASA Astrophysics Data System (ADS)

    Benham, Kevin; Hodyss, Robert; Fernández, Facundo M.; Orlando, Thomas M.

    2016-11-01

    We demonstrate the first application of laser-induced acoustic desorption (LIAD) and atmospheric pressure photoionization (APPI) as a mass spectrometric method for detecting low-polarity organics. This was accomplished using a Lyman-α (10.2 eV) photon generating microhollow cathode discharge (MHCD) microplasma photon source in conjunction with the addition of a gas-phase molecular dopant. This combination provided a soft desorption and a relatively soft ionization technique. Selected compounds analyzed include α-tocopherol, perylene, cholesterol, phenanthrene, phylloquinone, and squalene. Detectable surface concentrations as low as a few pmol per spot sampled were achievable using test molecules. The combination of LIAD and APPI provided a soft desorption and ionization technique that can allow detection of labile, low-polarity, structurally complex molecules over a wide mass range with minimal fragmentation.

  16. Laser-Induced Acoustic Desorption Atmospheric Pressure Photoionization via VUV-Generating Microplasmas

    NASA Astrophysics Data System (ADS)

    Benham, Kevin; Hodyss, Robert; Fernández, Facundo M.; Orlando, Thomas M.

    2016-09-01

    We demonstrate the first application of laser-induced acoustic desorption (LIAD) and atmospheric pressure photoionization (APPI) as a mass spectrometric method for detecting low-polarity organics. This was accomplished using a Lyman-α (10.2 eV) photon generating microhollow cathode discharge (MHCD) microplasma photon source in conjunction with the addition of a gas-phase molecular dopant. This combination provided a soft desorption and a relatively soft ionization technique. Selected compounds analyzed include α-tocopherol, perylene, cholesterol, phenanthrene, phylloquinone, and squalene. Detectable surface concentrations as low as a few pmol per spot sampled were achievable using test molecules. The combination of LIAD and APPI provided a soft desorption and ionization technique that can allow detection of labile, low-polarity, structurally complex molecules over a wide mass range with minimal fragmentation.

  17. Multi-dimensional effects in radiation pressure acceleration of ions

    SciTech Connect

    Tripathi, V. K.

    2015-07-31

    A laser carries momentum. On reflection from an ultra-thin overdense plasma foil, it deposits recoil momentum on the foil, i.e. exerts radiation pressure on the foil electrons and pushes them to the rear. The space charge field thus created takes the ions along, accelerating the electron-ion double layer as a single unit. When the foil has surface ripple, of wavelength comparable to laser wavelength, the radiation pressure acts non-uniformly on the foil and the perturbation grows as Reyleigh-Taylor (RT) instability as the foil moves. The finite spot size of the laser causes foil to bend. These effects limit the quasi-mono energy acceleration of ions. Multi-ion foils, e.g., diamond like carbon foil embedded with protons offer the possibility of suppressing RT instability.

  18. Quantitative measurement of ultrasound pressure field by optical phase contrast method and acoustic holography

    NASA Astrophysics Data System (ADS)

    Oyama, Seiji; Yasuda, Jun; Hanayama, Hiroki; Yoshizawa, Shin; Umemura, Shin-ichiro

    2016-07-01

    A fast and accurate measurement of an ultrasound field with various exposure sequences is necessary to ensure the efficacy and safety of various ultrasound applications in medicine. The most common method used to measure an ultrasound pressure field, that is, hydrophone scanning, requires a long scanning time and potentially disturbs the field. This may limit the efficiency of developing applications of ultrasound. In this study, an optical phase contrast method enabling fast and noninterfering measurements is proposed. In this method, the modulated phase of light caused by the focused ultrasound pressure field is measured. Then, a computed tomography (CT) algorithm used to quantitatively reconstruct a three-dimensional (3D) pressure field is applied. For a high-intensity focused ultrasound field, a new approach that combines the optical phase contrast method and acoustic holography was attempted. First, the optical measurement of focused ultrasound was rapidly performed over the field near a transducer. Second, the nonlinear propagation of the measured ultrasound was simulated. The result of the new approach agreed well with that of the measurement using a hydrophone and was improved from that of the phase contrast method alone with phase unwrapping.

  19. Pressure transfer function of a JT15D nozzle due to acoustic and convected entropy fluctuations

    NASA Astrophysics Data System (ADS)

    Miles, J. H.

    An acoustic transmission matrix analysis of sound propagation in a variable area duct with and without flow is extended to include convected entropy fluctuations. The boundary conditions used in the analysis are a transfer function relating entropy and pressure at the nozzle inlet and the nozzle exit impedance. The nozzle pressure transfer function calculated is compared with JT15D turbofan engine nozzle data. The one dimensional theory for sound propagation in a variable area nozzle with flow but without convected entropy is good at the low engine speeds where the nozzle exit Mach number is low (M=0.2) and the duct exit impedance model is good. The effect of convected entropy appears to be so negligible that it is obscured by the inaccuracy of the nozzle exit impedance model, the lack of information on the magnitude of the convected entropy and its phase relationship with the pressure, and the scatter in the data. An improved duct exit impedance model is required at the higher engine speeds where the nozzle exit Mach number is high (M=0.56) and at low frequencies (below 120 Hz).

  20. Extension of the angular spectrum method to calculate pressure from a spherically curved acoustic source.

    PubMed

    Vyas, Urvi; Christensen, Douglas A

    2011-11-01

    The angular spectrum method is an accurate and computationally efficient method for modeling acoustic wave propagation. The use of the typical 2D fast Fourier transform algorithm makes this a fast technique but it requires that the source pressure (or velocity) be specified on a plane. Here the angular spectrum method is extended to calculate pressure from a spherical transducer-as used extensively in applications such as magnetic resonance-guided focused ultrasound surgery-to a plane. The approach, called the Ring-Bessel technique, decomposes the curved source into circular rings of increasing radii, each ring a different distance from the intermediate plane, and calculates the angular spectrum of each ring using a Fourier series. Each angular spectrum is then propagated to the intermediate plane where all the propagated angular spectra are summed to obtain the pressure on the plane; subsequent plane-to-plane propagation can be achieved using the traditional angular spectrum method. Since the Ring-Bessel calculations are carried out in the frequency domain, it reduces calculation times by a factor of approximately 24 compared to the Rayleigh-Sommerfeld method and about 82 compared to the Field II technique, while maintaining accuracies of better than 96% as judged by those methods for cases of both solid and phased-array transducers.

  1. Acoustic scattering by circular cylinders of various aspect ratios. [pressure gradient microphones

    NASA Technical Reports Server (NTRS)

    Maciulaitis, A.

    1979-01-01

    The effects of acoustic scattering on the useful frequency range of pressure gradient microphones were investigated experimentally between ka values of 0.407 and 4.232 using two circular cylindrical models (L/D = 0.5 and 0.25) having a 25 cm outside diameter. Small condenser microphones, attached to preamplifiers by flexible connectors, were installed from inside the cylindrical bodies, and flush mounted on the exterior surface of the cylinders. A 38 cm diameter woofer in a large speaker enclosure was used as the sound source. Surface pressure augmentation and phase differences were computed from measured data for various sound wave incidence angles. Results are graphically compared with theoretical predictions supplied by NASA for ka = 0.407, 2.288, and 4.232. All other results are tabulated in the appendices. With minor exceptions, the experimentally determined pressure augmentations agreed within 0.75 dB with theoretical predictions. The agreement for relative phase angles was within 5 percent without any exceptions. Scattering parameter variations with ka and L/D ratio, as computed from experimental data, are also presented.

  2. Pressure transfer function of a JT15D nozzle due to acoustic and convected entropy fluctuations

    NASA Technical Reports Server (NTRS)

    Miles, J. H.

    1982-01-01

    An acoustic transmission matrix analysis of sound propagation in a variable area duct with and without flow is extended to include convected entropy fluctuations. The boundary conditions used in the analysis are a transfer function relating entropy and pressure at the nozzle inlet and the nozzle exit impedance. The nozzle pressure transfer function calculated is compared with JT15D turbofan engine nozzle data. The one dimensional theory for sound propagation in a variable area nozzle with flow but without convected entropy is good at the low engine speeds where the nozzle exit Mach number is low (M=0.2) and the duct exit impedance model is good. The effect of convected entropy appears to be so negligible that it is obscured by the inaccuracy of the nozzle exit impedance model, the lack of information on the magnitude of the convected entropy and its phase relationship with the pressure, and the scatter in the data. An improved duct exit impedance model is required at the higher engine speeds where the nozzle exit Mach number is high (M=0.56) and at low frequencies (below 120 Hz).

  3. Experimental feasibility of investigating acoustic waves in Couette flow with entropy and pressure gradients

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Zorumski, William E.; Rawls, John W., Jr.

    1990-01-01

    The feasibility is discussed for an experimental program for studying the behavior of acoustic wave propagation in the presence of strong gradients of pressure, temperature, and flow. Theory suggests that gradients effects can be experimentally observed as resonant frequency shifts and mode shape changes in a waveguide. A convenient experimental geometry for such experiments is the annular region between two co-rotating cylinders. Radial temperature gradients in a spinning annulus can be generated by differentially heating the two cylinders via electromagnetic induction. Radial pressure gradients can be controlled by varying the cylinder spin rates. Present technology appears adequate to construct an apparatus to allow independent control of temperature and pressure gradients. A complicating feature of a more advanced experiment, involving flow gradients, is the requirement for independently controlled cylinder spin rates. Also, the boundary condition at annulus terminations must be such that flow gradients are minimally disturbed. The design and construction of an advanced apparatus to include flow gradients will require additional technology development.

  4. Ambient pressure laser desorption and laser-induced acoustic desorption ion mobility spectrometry detection of explosives.

    PubMed

    Ehlert, Sven; Walte, Andreas; Zimmermann, Ralf

    2013-11-19

    The development of fast, mobile, and sensitive detection systems for security-relevant substances is of enormous importance. Because of the low vapor pressures of explosives and improvised explosive devices, adequate sampling procedures are crucial. Ion mobility spectrometers (IMSs) are fast and sensitive instruments that are used as detection systems for explosives. Ambient pressure laser desorption (APLD) and ambient pressure laser-induced acoustic desorption (AP-LIAD) are new tools suitable to evaporate explosives in order to detect them in the vapor phase. Indeed, the most important advantage of APLD or AP-LIAD is the capability to sample directly from the surface of interest without any transfer of the analyte to other surfaces such as wipe pads. A much more gentle desorption, compared to classical thermal-based desorption, is possible with laser-based desorption using very short laser pulses. With this approach the analyte molecules are evaporated in a very fast process, comparable to a shock wave. The thermal intake is reduced considerably. The functionality of APLD and AP-LIAD techniques combined with a hand-held IMS system is shown for a wide range of common explosives such as EGDN (ethylene glycol dinitrate), urea nitrate, PETN (pentaerythritol tetranitrate), HMTD (hexamethylene triperoxide diamine), RDX (hexogen), tetryl (2,4,6-trinitrophenylmethylnitramine), and TNT (trinitrotoluene). Detection limits down to the low nanogram range are obtained. The successful combination of IMS detection and APLD/AP-LIAD sampling is shown.

  5. Pressure probe and hot-film probe rsponses to acoustic excitation in mean flow

    NASA Technical Reports Server (NTRS)

    Parrott, T. L.; Jones, M. G.

    1986-01-01

    An experiment was conducted to compare the relative responses of a hot-film probe and a pressure probe positioned in a flow duct carrying mean flow and progressive acoustic waves. The response of each probe was compared with that of a condenser-type microphone flush mounted in the duct wall for flow Mach numbers up to about 0.5. The response of the pressure probe was less than that of the flush-mounted microphone by not more than about 2.1 dB at the highest centerline Mach number. This decreased response of the probe can likely be attributed to flow-induced impedance changes at the probe sensor orifices. The response of the hot-film probe, expressed in terms of fluctuating pressure, was greater than that of the flush-mounted microphone by as much as 6.0 dB at the two higher centerline Mach numbers. Removal of the contribution from fluctuating temperature in the hot-film analytical model greatly improved the agreement between the two transducer responses.

  6. Radiation-pressure-driven dust waves inside bursting interstellar bubbles

    NASA Astrophysics Data System (ADS)

    Ochsendorf, B. B.; Verdolini, S.; Cox, N. L. J.; Berné, O.; Kaper, L.; Tielens, A. G. G. M.

    2014-06-01

    Massive stars drive the evolution of the interstellar medium through their radiative and mechanical energy input. After their birth, they form "bubbles" of hot gas surrounded by a dense shell. Traditionally, the formation of bubbles is explained through the input of a powerful stellar wind, even though direct evidence supporting this scenario is lacking. Here we explore the possibility that interstellar bubbles seen by the Spitzer- and Herschel space telescopes, blown by stars with log (L/L⊙) ≲ 5.2, form and expand because of the thermal pressure that accompanies the ionization of the surrounding gas. We show that density gradients in the natal cloud or a puncture in the swept-up shell lead to an ionized gas flow through the bubble into the general interstellar medium, which is traced by a dust wave near the star, which demonstrates the importance of radiation pressure during this phase. Dust waves provide a natural explanation for the presence of dust inside H II bubbles, offer a novel method to study dust in H II regions and provide direct evidence that bubbles are relieving their pressure into the interstellar medium through a champagne flow, acting as a probe of the radiative interaction of a massive star with its surroundings. We explore a parameter space connecting the ambient density, the ionizing source luminosity, and the position of the dust wave, while using the well studied H II bubbles RCW 120 and RCW 82 as benchmarks of our model. Finally, we briefly examine the implications of our study for the environments of super star clusters formed in ultraluminous infrared galaxies, merging galaxies, and the early Universe, which occur in very luminous and dense environments and where radiation pressure is expected to dominate the dynamical evolution.

  7. Shear wave elastography using amplitude-modulated acoustic radiation force and phase-sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Nguyen, Thu-Mai; Arnal, Bastien; Song, Shaozhen; Huang, Zhihong; Wang, Ruikang K.; O'Donnell, Matthew

    2015-01-01

    Investigating the elasticity of ocular tissue (cornea and intraocular lens) could help the understanding and management of pathologies related to biomechanical deficiency. In previous studies, we introduced a setup based on optical coherence tomography for shear wave elastography (SWE) with high resolution and high sensitivity. SWE determines tissue stiffness from the propagation speed of shear waves launched within tissue. We proposed acoustic radiation force to remotely induce shear waves by focusing an ultrasound (US) beam in tissue, similar to several elastography techniques. Minimizing the maximum US pressure is essential in ophthalmology for safety reasons. For this purpose, we propose a pulse compression approach. It utilizes coded US emissions to generate shear waves where the energy is spread over a long emission, and then numerically compressed into a short, localized, and high-energy pulse. We used a 7.5-MHz single-element focused transducer driven by coded excitations where the amplitude is modulated by a linear frequency-swept square wave (1 to 7 kHz). An inverse filter approach was used for compression. We demonstrate the feasibility of performing shear wave elastography measurements in tissue-mimicking phantoms at low US pressures (mechanical index <0.6).

  8. Shear wave elastography using amplitude-modulated acoustic radiation force and phase-sensitive optical coherence tomography

    PubMed Central

    Nguyen, Thu-Mai; Arnal, Bastien; Song, Shaozhen; Huang, Zhihong; Wang, Ruikang K.; O’Donnell, Matthew

    2015-01-01

    Abstract. Investigating the elasticity of ocular tissue (cornea and intraocular lens) could help the understanding and management of pathologies related to biomechanical deficiency. In previous studies, we introduced a setup based on optical coherence tomography for shear wave elastography (SWE) with high resolution and high sensitivity. SWE determines tissue stiffness from the propagation speed of shear waves launched within tissue. We proposed acoustic radiation force to remotely induce shear waves by focusing an ultrasound (US) beam in tissue, similar to several elastography techniques. Minimizing the maximum US pressure is essential in ophthalmology for safety reasons. For this purpose, we propose a pulse compression approach. It utilizes coded US emissions to generate shear waves where the energy is spread over a long emission, and then numerically compressed into a short, localized, and high-energy pulse. We used a 7.5-MHz single-element focused transducer driven by coded excitations where the amplitude is modulated by a linear frequency-swept square wave (1 to 7 kHz). An inverse filter approach was used for compression. We demonstrate the feasibility of performing shear wave elastography measurements in tissue-mimicking phantoms at low US pressures (mechanical index <0.6). PMID:25554970

  9. Self-organization of cosmic radiation pressure instability

    NASA Technical Reports Server (NTRS)

    Hogan, Craig J.

    1991-01-01

    Under some circumstances the absorption of radiation momentum by an absorbing medium opens the possibility of a dynamical instability, sometimes called 'mock gravity'. Here, a simplified abstract model is studied in which the radiation source is assumed to remain spatially uniform, there is no reabsorption or reradiated light, and no forces other than radiative pressure act on the absorbing medium. It is shown that this model displays the unique feature of being not only unstable, but also self-organizing. The structure approaches a statistical dynamical steady state which is almost independent of initial conditions. In this saturated state the absorbers are concentrated in thin walls around empty bubbles; as the instability develops the big bubbles get bigger and the small ones get crushed and disappear. A linear analysis shows that to first order the thin walls are indeed stable structures. It is speculated that this instability may play a role in forming cosmic large-scale structure.

  10. On the acoustic radiation modes of compact regular polyhedral arrays of independent loudspeakers.

    PubMed

    Pasqual, Alexander Mattioli; Martin, Vincent

    2011-09-01

    Compact spherical loudspeaker arrays can be used to provide control over their directivity pattern. Usually, this is made by adjusting the gains of preprogrammed spatial filters corresponding to a finite set of spherical harmonics, or to the acoustic radiation modes of the loudspeaker array. Unlike the former, the latter are closely related to the radiation efficiency of the source and span the subspace of the directivities it can produce. However, the radiation modes depend on frequency for arbitrary distributions of transducers on the sphere, which yields complex directivity filters. This work focuses on the most common loudspeaker array configurations, those following the regular shape of the Platonic solids. It is shown that the radiation modes of these sources are frequency independent, and simple algebraic expressions are derived for their radiation efficiencies. In addition, since such modes are vibration patterns driven by electrical signals, the transduction mechanism of compact multichannel sources is also investigated, which is an important issue, especially if the transducers interact inside a shared cabinet. For Platonic solid loudspeakers, it is shown that the common enclosure does not lead to directivity filters that depend on frequency.

  11. Inhomogeneous Radiation Boundary Conditions Simulating Incoming Acoustic Waves for Computational Aeroacoustics

    NASA Technical Reports Server (NTRS)

    Tam, Christopher K. W.; Fang, Jun; Kurbatskii, Konstantin A.

    1996-01-01

    A set of nonhomogeneous radiation and outflow conditions which automatically generate prescribed incoming acoustic or vorticity waves and, at the same time, are transparent to outgoing sound waves produced internally in a finite computation domain is proposed. This type of boundary condition is needed for the numerical solution of many exterior aeroacoustics problems. In computational aeroacoustics, the computation scheme must be as nondispersive ans nondissipative as possible. It must also support waves with wave speeds which are nearly the same as those of the original linearized Euler equations. To meet these requirements, a high-order/large-stencil scheme is necessary The proposed nonhomogeneous radiation and outflow boundary conditions are designed primarily for use in conjunction with such high-order/large-stencil finite difference schemes.

  12. Laser-Doppler acoustic probing of granular media with in-depth property gradient and varying pore pressures

    SciTech Connect

    Bodet, L.; Dhemaied, A.; Mourgues, R.; Tournat, V.; Rejiba, F.

    2012-05-24

    Non-contacting ultrasonic techniques recently proved to be efficient in the physical modeling of seismic-wave propagation at various application scales, as for instance in the context of geological analogue and seismic modeling. An innovative experimental set-up is proposed here to perform laser-Doppler acoustic probing of unconsolidated granular media with varying pore pressures. The preliminary experiments presented here provide reproducible results and exploitable data, thus validating both the proposed medium preparation and pressure gradient generation procedure.

  13. Thermal safety simulations of transient temperature rise during acoustic radiation force-based ultrasound elastography.

    PubMed

    Liu, Yunbo; Herman, Bruce A; Soneson, Joshua E; Harris, Gerald R

    2014-05-01

    Ultrasound transient elastography is a new diagnostic imaging technique that uses acoustic radiation force to produce motion in solid tissue via a high-intensity, long-duration "push" beam. In our previous work, we developed analytical models for calculating transient temperature rise, both in soft tissue and at a bone/soft tissue interface, during a single acoustic radiation force impulse (ARFI) imaging frame. The present study expands on these temperature rise calculations, providing applicable range assessment and error analysis for a single ARFI frame. Furthermore, a "virtual source" approach is described for temperature and thermal dose calculation under multiple ARFI frames. By use of this method, the effect of inter-frame cooling duration on temperature prediction is analyzed, and a thermal buildup phenomenon is revealed. Thermal safety assessment indicates that the thermal dose values, especially at the absorptive bone/soft tissue interface, could approach recommended dose thresholds if the cooling interval of multiple-frame ARFI elastography is too short.

  14. Acoustic techniques in nuclear safeguards

    SciTech Connect

    Olinger, C.T.; Sinha, D.N.

    1995-07-01

    Acoustic techniques can be employed to address many questions relevant to current nuclear technology needs. These include establishing and monitoring intrinsic tags and seals, locating holdup in areas where conventional radiation-based measurements have limited capability, process monitoring, monitoring containers for corrosion or changes in pressure, and facility design verification. These acoustics applications are in their infancy with respect to safeguards and nuclear material management, but proof-of-principle has been demonstrated in many of the areas listed.

  15. Acoustically-driven microfluidic systems

    SciTech Connect

    Wang, A W; Benett, W J; Tarte, L R

    2000-06-23

    We have demonstrated a non-contact method of concentrating and mixing particles in a plastic microfluidic chamber employing acoustic radiation pressure. A flaw cell package has also been designed that integrates liquid sample interconnects, electrical contacts and a removable sample chamber. Experiments were performed on 1, 3, 6, and 10 {micro}m polystyrene beads. Increased antibody binding to a solid-phase substrate was observed in the presence of acoustic mixing due to improve mass transport.

  16. 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.

  17. Solar Radiation Pressure and Attitude Modeling of GNSS Satellites

    NASA Astrophysics Data System (ADS)

    Rodriguez-Solano, C.; Hugentobler, U.; Steigenberger, P.

    2011-12-01

    The main non-gravitational orbit perturbation acting on GNSS satellites is the solar radiation pressure. There are two main approaches to model this force: 1) adjusting empirical parameters that fit best the GNSS tracking data, and 2) computing the a priori force from analytical models based on the detailed satellite structure and information available on ground. The first approach is not based on the physical interaction between solar radiation and the satellite, while the second one cannot be easily adjusted to the real on-orbit behaviour of the satellites, e.g., changes due to aging of optical properties or deviations from nominal attitude. We use here an intermediate approach, an analytical box-wing model based on the physical interaction between the solar radiation and a satellite consisting of a bus (box shape) and solar panels. Furthermore, some of the parameters of the box-wing model can be adjusted to fit the GNSS tracking data, namely the optical properties of the satellite surfaces. It was found that a pure box-wing model interacting with solar radiation is not sufficient for precise orbit determination. In particular a rotation lag angle of the solar panels was identified. This deviation of the solar panels from nominal attitude is a key factor to obtain precise GNSS orbits. Moreover, the yaw attitude of GNSS satellites during eclipse seasons deviates from nominal attitude due to maneuvers performed by the satellites. As mentioned in other studies, the phase measurements are degraded if these maneuvers are not taken into account since the modelled position of the navigation antenna may differ from the true position. In this study we focus on the impact of the yaw attitude on the solar radiation pressure parameters and the benefits for precise orbit determination and prediction.

  18. Acoustic receptivity due to weak surface inhomogeneities in adverse pressure gradient boundary layers

    NASA Technical Reports Server (NTRS)

    Choudhari, Meelan; Ng, Lian; Streett, Craig

    1995-01-01

    The boundary layer receptivity to free-stream acoustic waves in the presence of localized surface disturbances is studied for the case of incompressible Falkner-Skan flows with adverse pressure gradients. These boundary layers are unstable to both viscous and inviscid (i.e., inflectional) modes, and the finite Reynolds number extension of the Goldstein-Ruban theory provides a convenient method to compare the efficiency of the localized receptivity processes in these two cases. The value of the efficiency function related to the receptivity caused by localized distortions in surface geometry is relatively insensitive to the type of instability mechanism, provided that the same reference length scale is used to normalize the efficiency function for each type of instability. In contrast, when the receptivity is induced by variations in wall suction velocity or in wall admittance distribution, the magnitudes of the related efficiency functions, as well as the resulting coupling coefficients, are smaller for inflectional (i.e., Rayleigh) modes than for the viscous Tollmien-Schlichting waves. The reduced levels of receptivity can be attributed mainly to the shorter wavelengths and higher frequencies of the inflectional modes. Because the most critical band of frequencies shifts toward higher values, the overall efficiency of the wall suction- and the wall admittance-induced receptivity decreases with an increase in the adverse pressure gradient.

  19. Radiation force of an arbitrary acoustic beam on an elastic sphere in a fluid.

    PubMed

    Sapozhnikov, Oleg A; Bailey, Michael R

    2013-02-01

    A theoretical approach is developed to calculate the radiation force of an arbitrary acoustic beam on an elastic sphere in a liquid or gas medium. First, the incident beam is described as a sum of plane waves by employing conventional angular spectrum decomposition. Then, the classical solution for the scattering of a plane wave from an elastic sphere is applied for each plane-wave component of the incident field. The net scattered field is expressed as a superposition of the scattered fields from all angular spectrum components of the incident beam. With this formulation, the incident and scattered waves are superposed in the far field to derive expressions for components of the radiation stress tensor. These expressions are then integrated over a spherical surface to analytically describe the radiation force on an elastic sphere. Limiting cases for particular types of incident beams are presented and are shown to agree with known results. Finally, the analytical expressions are used to calculate radiation forces associated with two specific focusing transducers.

  20. SU-E-T-208: Incidence Cancer Risk From the Radiation Treatment for Acoustic Neuroma Patient

    SciTech Connect

    Kim, D; Chung, W; Shin, D; Yoon, M

    2014-06-01

    Purpose: The present study aimed to compare the incidence risk of a secondary cancer from therapeutic doses in patients receiving intensitymodulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), and stereotactic radiosurgery (SRS). Methods: Four acoustic neuroma patients were treated with IMRT, VMAT, or SRS. Their incidnece excess relative risk (ERR), excess absolute risk (EAR), and lifetime attributable risk (LAR) were estimated using the corresponding therapeutic doses measured at various organs by radio-photoluminescence glass dosimeters (RPLGD) placed inside a humanoid phantom. Results: When a prescription dose was delivered in the planning target volume of the 4 patients, the average organ equivalent doses (OED) at the thyroid, lung, normal liver, colon, bladder, prostate (or ovary), and rectum were measured. The OED decreased as the distance from the primary beam increased. The thyroid received the highest OED compared to other organs. A LAR were estimated that more than 0.03% of AN patients would get radiation-induced cancer. Conclusion: The tyroid was highest radiation-induced cancer risk after radiation treatment for AN. We found that LAR can be increased by the transmitted dose from the primary beam. No modality-specific difference in radiation-induced cancer risk was observed in our study.

  1. Towards a reference cavitating vessel Part III—design and acoustic pressure characterization of a multi-frequency sonoreactor

    NASA Astrophysics Data System (ADS)

    Wang, Lian; Memoli, Gianluca; Hodnett, Mark; Butterworth, Ian; Sarno, Dan; Zeqiri, Bajram

    2015-08-01

    A multi-frequency cavitation vessel (RV-multi) has been commissioned at the National Physical Laboratory (NPL, UK), with the aim of establishing a standard source of acoustic cavitation in water, with reference to which details of the cavitation process can be studied and cavitation measurement techniques evaluated. The vessel is a cylindrical cavity with a maximum capacity up to 17 L, and is designed to work at six frequency ranges, from 21 kHz to 136 kHz, under controlled temperature conditions. This paper discusses the design of RV-multi and reports experiments carried out to establish the reproducibility of the acoustic pressure field established within the vessel and its operating envelope, including sensitivity to aspects such as water depth and temperature. The acoustic field distribution was determined along the radial and depth directions within the vessel using a miniature hydrophone, for two input voltage levels under low power transducer excitation conditions (e.g. below the cavitation threshold). Particular care was taken in determining peak acoustic pressure locations, as these are critical for accompanying cavitation studies. Perturbations of the vessel by the measuring hydrophone were also monitored with a bottom-mounted pressure sensor.

  2. Ultrasound and microbubble mediated drug delivery: acoustic pressure as determinant for uptake via membrane pores or endocytosis.

    PubMed

    De Cock, Ine; Zagato, Elisa; Braeckmans, Kevin; Luan, Ying; de Jong, Nico; De Smedt, Stefaan C; Lentacker, Ine

    2015-01-10

    Although promising results are achieved in ultrasound mediated drug delivery, its underlying biophysical mechanisms remain to be elucidated. Pore formation as well as endocytosis has been reported during ultrasound application. Due to the plethora of ultrasound settings used in literature, it is extremely difficult to draw conclusions on which mechanism is actually involved. To our knowledge, we are the first to show that acoustic pressure influences which route of drug uptake is addressed, by inducing different microbubble-cell interactions. To investigate this, FITC-dextrans were used as model drugs and their uptake was analyzed by flow cytometry. In fluorescence intensity plots, two subpopulations arose in cells with FITC-dextran uptake after ultrasound application, corresponding to cells having either low or high uptake. Following separation of the subpopulations by FACS sorting, confocal images indicated that the low uptake population showed endocytic uptake. The high uptake population represented uptake via pores. Moreover, the distribution of the subpopulations shifted to the high uptake population with increasing acoustic pressure. Real-time confocal recordings during ultrasound revealed that membrane deformation by microbubbles may be the trigger for endocytosis via mechanostimulation of the cytoskeleton. Pore formation was shown to be caused by microbubbles propelled towards the cell. These results provide a better insight in the role of acoustic pressure in microbubble-cell interactions and the possible consequences for drug uptake. In addition, it pinpoints the need for a more rational, microbubble behavior based choice of acoustic parameters in ultrasound mediated drug delivery experiments.

  3. Quasi-Sun-Pointing of Spacecraft Using Radiation Pressure

    NASA Technical Reports Server (NTRS)

    Spilker, Thomas

    2003-01-01

    A report proposes a method of utilizing solar-radiation pressure to keep the axis of rotation of a small spin-stabilized spacecraft pointed approximately (typically, within an angle of 10 deg to 20 deg) toward the Sun. Axisymmetry is not required. Simple tilted planar vanes would be attached to the outer surface of the body, so that the resulting spacecraft would vaguely resemble a rotary fan, windmill, or propeller. The vanes would be painted black for absorption of Solar radiation. A theoretical analysis based on principles of geometric optics and mechanics has shown that torques produced by Solar-radiation pressure would cause the axis of rotation to precess toward Sun-pointing. The required vane size would be a function of the angular momentum of the spacecraft and the maximum acceptable angular deviation from Sun-pointing. The analysis also shows that the torques produced by the vanes would slowly despin the spacecraft -- an effect that could be counteracted by adding specularly reflecting "spin-up" vanes.

  4. A Advanced Boundary Element Formulation for Acoustic Radiation and Scattering in Three Dimensions.

    NASA Astrophysics Data System (ADS)

    Soenarko, Benjamin

    A computational method is presented for determining acoustic fields produced by arbitrary shaped three-dimensional bodies. The formulation includes both radiation and scattering problems. In particular an isoparametric element formulation is introduced in which both the surface geometry and the acoustic variables on the surface of the body are represented by second order shape functions within the local coordinate system. A general result for the surface velocity potential and the exterior field is derived. This result is applicable to non-smooth bodies, i.e. it includes the case where the surface may have a non-unique normal (e.g. at the edge of a cube). Test cases are shown involving spherical, cylindrical and cubical geometry for both radiation and scattering problems. The present formulation is also extended to include half-space problems in which the effect of the reflected wave from an infinite plane is taken into account. By selecting an appropriate Green's function, the surface integral over the plane is nullified; thus all the computational efforts can be performed only on the radiating or scattering body at issue and thereby greatly simplify the solution. A special formulation involving axisymmetric bodies and boundary conditions is also presented. For this special case, the surface integrals are reduced to line integrals and an integral over the angle of revolution. The integration over the angle is performed partly analytically in terms of elliptic integrals and partly numerically using simple Gaussian quadrature formula. Since the rest of the integrals involve only line integrals along the generator of the body, any discretization scheme can be easily obtained to achieve a desired degree of accuracy in evaluating these integrals.

  5. ACOUSTIC RADIATION FORCE-DRIVEN ASSESSMENT OF MYOCARDIAL ELASTICITY USING THE DISPLACEMENT RATIO RATE (DRR) METHOD

    PubMed Central

    Bouchard, Richard R.; Hsu, Stephen J.; Palmeri, Mark L.; Rouze, Ned C.; Nightingale, Kathryn R.; Trahey, Gregg E.

    2011-01-01

    A noninvasive method of characterizing myocardial stiffness could have significant implications in diagnosing cardiac disease. Acoustic radiation force (ARF)–driven techniques have demonstrated their ability to discern elastic properties of soft tissue. For the purpose of myocardial elasticity imaging, a novel ARF-based imaging technique, the displacement ratio rate (DRR) method, was developed to rank the relative stiffnesses of dynamically varying tissue. The basis and performance of this technique was demonstrated through numerical and phantom imaging results. This new method requires a relatively small temporal (<1 ms) and spatial (tenths of mm2) sampling window and appears to be independent of applied ARF magnitude. The DRR method was implemented in two in vivo canine studies, during which data were acquired through the full cardiac cycle by imaging directly on the exposed epicardium. These data were then compared with results obtained by acoustic radiation force impulse (ARFI) imaging and shear wave velocimetry, with the latter being used as the gold standard. Through the cardiac cycle, velocimetry results portray a range of shear wave velocities from 0.76–1.97 m/s, with the highest velocities observed during systole and the lowest observed during diastole. If a basic shear wave elasticity model is assumed, such a velocity result would suggest a period of increased stiffness during systole (when compared with diastole). Despite drawbacks of the DRR method (i.e., sensitivity to noise and limited stiffness range), its results predicted a similar cyclic stiffness variation to that offered by velocimetry while being insensitive to variations in applied radiation force. PMID:21645966

  6. Collisional and radiative processes in high-pressure discharge plasmas

    NASA Astrophysics Data System (ADS)

    Becker, Kurt H.; Kurunczi, Peter F.; Schoenbach, Karl H.

    2002-05-01

    Discharge plasmas at high pressures (up to and exceeding atmospheric pressure), where single collision conditions no longer prevail, provide a fertile environment for the experimental study of collisions and radiative processes dominated by (i) step-wise processes, i.e., the excitation of an already excited atomic/molecular state and by (ii) three-body collisions leading, for instance, to the formation of excimers. The dominance of collisional and radiative processes beyond binary collisions involving ground-state atoms and molecules in such environments allows for many interesting applications of high-pressure plasmas such as high power lasers, opening switches, novel plasma processing applications and sputtering, absorbers and reflectors for electromagnetic waves, remediation of pollutants and waste streams, and excimer lamps and other noncoherent vacuum-ultraviolet light sources. Here recent progress is summarized in the use of hollow cathode discharge devices with hole dimensions in the range 0.1-0.5 mm for the generation of vacuum-ultraviolet light.

  7. The acoustic radiation force on a small thermoviscous or thermoelastic particle suspended in a viscous and heat-conducting fluid

    NASA Astrophysics Data System (ADS)

    Karlsen, Jonas; Bruus, Henrik

    2015-11-01

    We present a theoretical analysis (arxiv.org/abs/1507.01043) of the acoustic radiation force on a single small particle, either a thermoviscous fluid droplet or a thermoelastic solid particle, suspended in a viscous and heat-conducting fluid. Our analysis places no restrictions on the viscous and thermal boundary layer thicknesses relative to the particle radius, but it assumes the particle to be small in comparison to the acoustic wavelength. This is the limit relevant to scattering of ultrasound waves from sub-micrometer particles. For particle sizes smaller than the boundary layer widths, our theory leads to profound consequences for the acoustic radiation force. For example, for liquid droplets and solid particles suspended in gasses we predict forces orders of magnitude larger than expected from ideal-fluid theory. Moreover, for certain relevant choices of materials, we find a sign change in the acoustic radiation force on different-sized but otherwise identical particles. These findings lead to the concept of a particle-size-dependent acoustophoretic contrast factor, highly relevant to applications in acoustic levitation or separation of micro-particles in gases, as well as to handling of μm- and nm-sized particles such as bacteria and vira in lab-on-a-chip systems.

  8. Finite series expansion of a Gaussian beam for the acoustic radiation force calculation of cylindrical particles in water.

    PubMed

    Zhang, Xiaofeng; Song, Zhiguang; Chen, Dongmei; Zhang, Guangbin; Cao, Hui

    2015-04-01

    This paper focuses on studying the interaction between an acoustical Gaussian beam and cylindrical particles. Based on the finite series method, the Gaussian beam is expanded as cylindrical functions and the beam coefficient of a Gaussian beam is obtained. An expression for the acoustic radiation force function that is the radiation force per unit energy density and unit cross-sectional surface area for a cylinder in a Gaussian beam is presented. Numerical results for the radiation force function of a Gaussian beam are presented for rigid cylinders, liquid cylinders, elastic cylinders, and viscoelastic cylinders to illustrate the theory. The radiation force function versus the dimensionless frequency ka (where k is the wave number and a is the radius of the cylinder) are discussed for different beam waists. The simulation results show the differences from those of a plane wave when the beam waist w0≤5λ (where λ is the wave length). The beam waist has no effects on the radiation force function when ka<1, while the beam waist has greater effects when ka>1. The radiation force function reaches the plane wave limit when w0>5λ. The acoustic radiation force function is also determined by the parameters of the particles.

  9. JET FORMATION FROM MASSIVE YOUNG STARS: MAGNETOHYDRODYNAMICS VERSUS RADIATION PRESSURE

    SciTech Connect

    Vaidya, Bhargav; Porth, Oliver; Fendt, Christian; Beuther, Henrik E-mail: fendt@mpia.de

    2011-11-20

    Observations indicate that outflows from massive young stars are more collimated during their early evolution compared to later stages. Our paper investigates various physical processes that impact the outflow dynamics, i.e., its acceleration and collimation. We perform axisymmetric magnetohydrodynamic (MHD) simulations particularly considering the radiation pressure exerted by the star and the disk. We have modified the PLUTO code to include radiative forces in the line-driving approximation. We launch the outflow from the innermost disk region (r < 50 AU) by magnetocentrifugal acceleration. In order to disentangle MHD effects from radiative forces, we start the simulation in pure MHD and later switch on the radiation force. We perform a parameter study considering different stellar masses (thus luminosity), magnetic flux, and line-force strength. For our reference simulation-assuming a 30 M{sub Sun} star-we find substantial de-collimation of 35% due to radiation forces. The opening angle increases from 20 Degree-Sign to 32 Degree-Sign for stellar masses from 20 M{sub Sun} to 60 M{sub Sun }. A small change in the line-force parameter {alpha} from 0.60 to 0.55 changes the opening angle by {approx}8 Degree-Sign . We find that it is mainly the stellar radiation that affects the jet dynamics. Unless the disk extends very close to the star, its force is too small to have much impact. Essentially, our parameter runs with different stellar masses can be understood as a proxy for the time evolution of the star-outflow system. Thus, we have shown that when the stellar mass (thus luminosity) increases with age, the outflows become less collimated.

  10. Solar Radiation Pressure Binning for the Geosynchronous Orbit

    NASA Technical Reports Server (NTRS)

    Hejduk, M. D.; Ghrist, R. W.

    2011-01-01

    Orbital maintenance parameters for individual satellites or groups of satellites have traditionally been set by examining orbital parameters alone, such as through apogee and perigee height binning; this approach ignored the other factors that governed an individual satellite's susceptibility to non-conservative forces. In the atmospheric drag regime, this problem has been addressed by the introduction of the "energy dissipation rate," a quantity that represents the amount of energy being removed from the orbit; such an approach is able to consider both atmospheric density and satellite frontal area characteristics and thus serve as a mechanism for binning satellites of similar behavior. The geo-synchronous orbit (of broader definition than the geostationary orbit -- here taken to be from 1300 to 1800 minutes in orbital period) is not affected by drag; rather, its principal non-conservative force is that of solar radiation pressure -- the momentum imparted to the satellite by solar radiometric energy. While this perturbation is solved for as part of the orbit determination update, no binning or division scheme, analogous to the drag regime, has been developed for the geo-synchronous orbit. The present analysis has begun such an effort by examining the behavior of geosynchronous rocket bodies and non-stabilized payloads as a function of solar radiation pressure susceptibility. A preliminary examination of binning techniques used in the drag regime gives initial guidance regarding the criteria for useful bin divisions. Applying these criteria to the object type, solar radiation pressure, and resultant state vector accuracy for the analyzed dataset, a single division of "large" satellites into two bins for the purposes of setting related sensor tasking and orbit determination (OD) controls is suggested. When an accompanying analysis of high area-to-mass objects is complete, a full set of binning recommendations for the geosynchronous orbit will be available.

  11. Sitnikov restricted four-body problem with radiation pressure

    NASA Astrophysics Data System (ADS)

    Suraj, Md Sanam; Hassan, M. R.

    2014-02-01

    An analytical study of the elliptic Sitnikov restricted four-body problem when all the primaries as source of same radiation pressure is presented. We find a solution, which is valid for small bounded oscillations in case of moderate eccentricity of the primary. We have linearized the equation of motion to obtain the Hill's type equation. Using the Courant and Snyder transformation, Hill's equation transformed into harmonic oscillator type equation. We have used the Lindstedt-Poincare perturbation method and again we have applied the Courant and Snyder transformation to obtain the final result.

  12. 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.

  13. Applications of finite and wave envelope element approximations to acoustic radiation from turbofan engine inlets in flight

    NASA Astrophysics Data System (ADS)

    Parrett, A. V.

    1984-12-01

    The problem of acoustic radiation from turbofan engine inlets in flow has not lent itself fully to analysis by numerical means because of the large domains and high frequencies involved. The use of finite elements and wave envelope elements, elements which simulate decay and wavelike behavior in their interpolation functions were extended from the no-flow case in which they were proven, to cases incorporating mean flow. By employing an irrotational mean flow assumption, the acoustics problem was posed in axisymmetric formulation in terms of acoustic velocity potential, thus minimizing computer solution storage requirements. The results obtained from the numerical procedures agree well with known analytical solutions and static jet engine inflow experimental data. Some discrepancy with flight test data exists but the combined finite element-wave envelope element solution radiation directivity trends are in good agreement with analytical predictions.

  14. A simulation technique for 3D MR-guided acoustic radiation force imaging

    SciTech Connect

    Payne, Allison; Bever, Josh de; Farrer, Alexis; Coats, Brittany; Parker, Dennis L.; Christensen, Douglas A.

    2015-02-15

    Purpose: In magnetic resonance-guided focused ultrasound (MRgFUS) therapies, the in situ characterization of the focal spot location and quality is critical. MR acoustic radiation force imaging (MR-ARFI) is a technique that measures the tissue displacement caused by the radiation force exerted by the ultrasound beam. This work presents a new technique to model the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model. Methods: When a steady-state point-source force acts internally in an infinite homogeneous medium, the displacement of the material in all directions is given by the Somigliana elastostatic tensor. The radiation force field, which is caused by absorption and reflection of the incident ultrasound intensity pattern, will be spatially distributed, and the tensor formulation takes the form of a convolution of a 3D Green’s function with the force field. The dynamic accumulation of MR phase during the ultrasound pulse can be theoretically accounted for through a time-of-arrival weighting of the Green’s function. This theoretical model was evaluated experimentally in gelatin phantoms of varied stiffness (125-, 175-, and 250-bloom). The acoustic and mechanical properties of the phantoms used as parameters of the model were measured using independent techniques. Displacements at focal depths of 30- and 45-mm in the phantoms were measured by a 3D spin echo MR-ARFI segmented-EPI sequence. Results: The simulated displacements agreed with the MR-ARFI measured displacements for all bloom values and focal depths with a normalized RMS difference of 0.055 (range 0.028–0.12). The displacement magnitude decreased and the displacement pattern broadened with increased bloom value for both focal depths, as predicted by the theory. Conclusions: A new technique that models the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model theory has been rigorously validated through comparison

  15. Electrochemical Processes Enhanced by Acoustic Liquid Manipulation

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C.

    2004-01-01

    Acoustic liquid manipulation is a family of techniques that employ the nonlinear acoustic effects of acoustic radiation pressure and acoustic streaming to manipulate the behavior of liquids. Researchers at the NASA Glenn Research Center are exploring new methods of manipulating liquids for a variety of space applications, and we have found that acoustic techniques may also be used in the normal Earth gravity environment to enhance the performance of existing fluid processes. Working in concert with the NASA Commercial Technology Office, the Great Lakes Industrial Technology Center, and Alchemitron Corporation (Elgin, IL), researchers at Glenn have applied nonlinear acoustic principles to industrial applications. Collaborating with Alchemitron Corporation, we have adapted the devices to create acoustic streaming in a conventional electroplating process.

  16. Applications of acoustic radiation force impulse quantification in chronic kidney disease: a review.

    PubMed

    Wang, Liang

    2016-10-01

    Acoustic radiation force impulse (ARFI) imaging is an emerging technique with great promise in the field of elastography. Previous studies have validated ARFI quantification as a method of estimating fibrosis in chronic liver disease. Similarly, fibrosis is the principal process underlying the progression of chronic kidney disease, which is the major cause of renal failure. However, the quantification of tissue stiffness using ARFI imaging is more complex in the kidney than in the liver. Moreover, not all previous studies are comparable because they employed different procedures. Therefore, subsequent studies are warranted, both in animal models and in clinical patients, in order to better understand the histopathological mechanisms associated with renal elasticity and to further improve this imaging method by developing a standardized guidelines for its implementation.

  17. Applications of acoustic radiation force impulse quantification in chronic kidney disease: a review.

    PubMed

    Wang, Liang

    2016-10-01

    Acoustic radiation force impulse (ARFI) imaging is an emerging technique with great promise in the field of elastography. Previous studies have validated ARFI quantification as a method of estimating fibrosis in chronic liver disease. Similarly, fibrosis is the principal process underlying the progression of chronic kidney disease, which is the major cause of renal failure. However, the quantification of tissue stiffness using ARFI imaging is more complex in the kidney than in the liver. Moreover, not all previous studies are comparable because they employed different procedures. Therefore, subsequent studies are warranted, both in animal models and in clinical patients, in order to better understand the histopathological mechanisms associated with renal elasticity and to further improve this imaging method by developing a standardized guidelines for its implementation. PMID:27599890

  18. Output of acoustical sources. [effects of structural elements and background flow on immobile multipolar point radiation

    NASA Technical Reports Server (NTRS)

    Levine, H.

    1980-01-01

    Acoustic radiation from a source, here viewed as an immobile point singularity with periodic strength and a given multipolar nature, is affected by the presence of nearly structural elements (e.g., rigid or impedance surfaces) as well as that of a background flow in the medium. An alternative to the conventional manner of calculating the net source output by integrating the energy flux over a distant control surface is described; this involves a direct evaluation of the secondary wavefunction at the position of the primary source and obviates the need for a (prospectively difficult) flux integration. Various full and half-planar surface configurations with an adjacent source are analyzed in detail, and the explicit results obtained, in particular, for the power factor of a dipole brings out a substantial rise in its output as the source nears the sharp edge of a half-plane.

  19. Jitter reduction technique for acoustic radiation force impulse microscopy via photoacoustic detection

    PubMed Central

    Kang, Bong Jin; Yoon, Changhan; Man Park, Jin; Hwang, Jae Youn; Shung, K. Kirk

    2015-01-01

    We demonstrate a jitter noise reduction technique for acoustic radiation force impulse microscopy via photoacoustic detection (PA-ARFI), which promises to be capable of measuring cell mechanics. To reduce the jitter noise induced by Q-switched pulsed laser operated at high repetition frequency, photoacoustic signals from the surface of an ultrasound transducer are aligned by cross-correlation and peak-to-peak detection, respectively. Each method is then employed to measure the displacements of a target sample in an agar phantom and a breast cancer cell due to ARFI application, followed by the quantitative comparison between their performances. The suggested methods for PA-ARFI significantly reduce jitter noises, thus allowing us to measure displacements of a target cell due to ARFI application by less than 3 μm. PMID:26367579

  20. Applications of acoustic radiation force impulse quantification in chronic kidney disease: a review

    PubMed Central

    2016-01-01

    Acoustic radiation force impulse (ARFI) imaging is an emerging technique with great promise in the field of elastography. Previous studies have validated ARFI quantification as a method of estimating fibrosis in chronic liver disease. Similarly, fibrosis is the principal process underlying the progression of chronic kidney disease, which is the major cause of renal failure. However, the quantification of tissue stiffness using ARFI imaging is more complex in the kidney than in the liver. Moreover, not all previous studies are comparable because they employed different procedures. Therefore, subsequent studies are warranted, both in animal models and in clinical patients, in order to better understand the histopathological mechanisms associated with renal elasticity and to further improve this imaging method by developing a standardized guidelines for its implementation. PMID:27599890

  1. Concurrent Visualization of Acoustic Radiation Force Displacement and Shear Wave Propagation with 7T MRI

    PubMed Central

    Liu, Yu; Fite, Brett Z.; Mahakian, Lisa M.; Johnson, Sarah M.; Larrat, Benoit; Dumont, Erik; Ferrara, Katherine W.

    2015-01-01

    Manual palpation is a common and very informative diagnostic tool based on estimation of changes in the stiffness of tissues that result from pathology. In the case of a small lesion or a lesion that is located deep within the body, it is difficult for changes in mechanical properties of tissue to be detected or evaluated via palpation. Furthermore, palpation is non-quantitative and cannot be used to localize the lesion. Magnetic Resonance-guided Focused Ultrasound (MRgFUS) can also be used to evaluate the properties of biological tissues non-invasively. In this study, an MRgFUS system combines high field (7T) MR and 3 MHz focused ultrasound to provide high resolution MR imaging and a small ultrasonic interrogation region (~0.5 x 0.5 x 2 mm), as compared with current clinical systems. MR-Acoustic Radiation Force Imaging (MR-ARFI) provides a reliable and efficient method for beam localization by detecting micron-scale displacements induced by ultrasound mechanical forces. The first aim of this study is to develop a sequence that can concurrently quantify acoustic radiation force displacements and image the resulting transient shear wave. Our motivation in combining these two measurements is to develop a technique that can rapidly provide both ARFI and shear wave velocity estimation data, making it suitable for use in interventional radiology. Secondly, we validate this sequence in vivo by estimating the displacement before and after high intensity focused ultrasound (HIFU) ablation, and we validate the shear wave velocity in vitro using tissue-mimicking gelatin and tofu phantoms. Such rapid acquisitions are especially useful in interventional radiology applications where minimizing scan time is highly desirable. PMID:26439259

  2. High pressure x-ray diffraction techniques with synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Jing, Liu

    2016-07-01

    This article summarizes the developments of experimental techniques for high pressure x-ray diffraction (XRD) in diamond anvil cells (DACs) using synchrotron radiation. Basic principles and experimental methods for various diffraction geometry are described, including powder diffraction, single crystal diffraction, radial diffraction, as well as coupling with laser heating system. Resolution in d-spacing of different diffraction modes is discussed. More recent progress, such as extended application of single crystal diffraction for measurements of multigrain and electron density distribution, time-resolved diffraction with dynamic DAC and development of modulated heating techniques are briefly introduced. The current status of the high pressure beamline at BSRF (Beijing Synchrotron Radiation Facility) and some results are also presented. Project supported by the National Natural Science Foundation of China (Grant Nos. 10875142, 11079040, and 11075175). The 4W2 beamline of BSRF was supported by the Chinese Academy of Sciences (Grant Nos. KJCX2-SW-N20, KJCX2-SW-N03, and SYGNS04).

  3. Abnormal acoustic wave velocities in basaltic and (Fe,Al)-bearing silicate glasses at high pressures

    NASA Astrophysics Data System (ADS)

    Liu, Jin; Lin, Jung-Fu

    2014-12-01

    We have measured acoustic VP and VS velocities of (Fe,Al)-bearing MgSiO3 silicate glasses and an Icelandic basalt glass up to 25 GPa. The velocity profiles of the (Fe,Al)-bearing and basaltic silicate glasses display decreased VP and VS with minima at approximately 5 and 2 GPa, respectively, which could be explained by the mode softening in the aluminosilicate networks. Our results represent the first observation of such velocity softening extending into the chemically complex basaltic glass at a relatively low transition pressure, which is likely due to its degree of polymerization, while the Fe and Al substitutions reduce sound velocities in MgSiO3 glass. If the velocity softening in the basaltic and silicate glasses can be used as analogs for understanding melts in Earth's interior, these observations suggest that the melt fraction needed to account for the velocity reduction in the upper mantle low-velocity zone may be smaller than previously thought.

  4. Laser-Induced Acoustic Desorption/Atmospheric Pressure Chemical Ionization Mass Spectrometry

    PubMed Central

    Gao, Jinshan; Borton, David J.; Owen, Benjamin C.; Jin, Zhicheng; Hurt, Matt; Amundson, Lucas M.; Madden, Jeremy T.; Qian, Kuangnan; Kenttämaa, Hilkka I.

    2010-01-01

    Laser-induced acoustic desorption (LIAD) was successfully coupled to a conventional atmospheric pressure chemical ionization (APCI) source in a linear quadrupole ion trap mass spectrometer (LQIT). Model compounds representing a wide variety of different types, including basic nitrogen and oxygen compounds, aromatic and aliphatic compounds, as well as unsaturated and saturated hydrocarbons, were tested separately and as a mixture. These model compounds were successfully evaporated into the gas phase by using LIAD and then ionized by using APCI with different reagents. Four APCI reagent systems were tested: the traditionally used mixture of methanol and water, neat benzene, neat carbon disulfide, and nitrogen gas (no liquid reagent). The mixture of methanol and water produced primarily protonated molecules, as expected. However, only the most basic compounds yielded ions under these conditions. In sharp contrast, using APCI with either neat benzene or neat carbon disulfide as the reagent resulted in the ionization of all the analytes studied to predominantly yield stable molecular ions. Benzene yielded a larger fraction of protonated molecules than carbon disulfide, which is a disadvantage. A similar amount of fragmentation was observed for these reagents. When the experiment was performed without a liquid reagent(nitrogen gas was the reagent), more fragmentation was observed. Analysis of a known mixture as well as a petroleum cut was also carried out. In summary, the new experiment presented here allows the evaporation of thermally labile compounds, both polar and nonpolar, without dissociation or aggregation, and their ionization to form stable molecular ions. PMID:21472571

  5. Estimation of broadband acoustic power due to rib forces on a reinforced panel under turbulent boundary layer-like pressure excitation. II. Applicability and validation.

    PubMed

    Rumerman, M L

    2001-02-01

    The previous paper showed that, when the attachment forces on a rib-reinforced panel subjected to turbulent boundary layer excitation can be considered to radiate independently, the rib-related acoustic power in a broad (e.g., one-third octave) frequency band can be estimated as the product of the average mean squared force, the real part of the radiation admittance of an attachment force, and the number of ribs. This paper shows that the radiation condition is always approximated when the acoustic wavelength is less than twice the rib spacing of a periodically reinforced panel, and generally applies at lower frequencies where the acoustic wavelength is less than four times the rib spacing. The procedure is used to estimate the broadband acoustic power radiated per rib of an infinite periodically reinforced membrane and plate in water, and the results are shown to agree with those of "exact" calculations.

  6. Vibroacoustics of the piano soundboard: Reduced models, mobility synthesis, and acoustical radiation regime

    NASA Astrophysics Data System (ADS)

    Boutillon, Xavier; Ege, Kerem

    2013-09-01

    In string musical instruments, the sound is radiated by the soundboard, subject to the strings excitation. This vibration of this rather complex structure is described here with models which need only a small number of parameters. Predictions of the models are compared with the results of experiments that have been presented in Ege et al. [Vibroacoustics of the piano soundboard: (non)linearity and modal properties in the low- and mid-frequency ranges, Journal of Sound and Vibration 332 (5) (2013) 1288-1305]. The apparent modal density of the soundboard of an upright piano in playing condition, as seen from various points of the structure, exhibits two well-separated regimes, below and above a frequency flim that is determined by the wood characteristics and by the distance between ribs. Above flim, most modes appear to be localised, presumably due to the irregularity of the spacing and height of the ribs. The low-frequency regime is predicted by a model which consists of coupled sub-structures: the two ribbed areas split by the main bridge and, in most cases, one or two so-called cut-off corners. In order to assess the dynamical properties of each of the subplates (considered here as homogeneous plates), we propose a derivation of the (low-frequency) modal density of an orthotropic homogeneous plate which accounts for the boundary conditions on an arbitrary geometry. Above flim, the soundboard, as seen from a given excitation point, is modelled as a set of three structural wave-guides, namely the three inter-rib spacings surrounding the excitation point. Based on these low- and high-frequency models, computations of the point-mobility and of the apparent modal densities seen at several excitation points match published measurements. The dispersion curve of the wave-guide model displays an acoustical radiation scheme which differs significantly from that of a thin homogeneous plate. It appears that piano dimensioning is such that the subsonic regime of acoustical

  7. Highly physical penumbra solar radiation pressure modeling with atmospheric effects

    NASA Astrophysics Data System (ADS)

    Robertson, Robert; Flury, Jakob; Bandikova, Tamara; Schilling, Manuel

    2015-10-01

    We present a new method for highly physical solar radiation pressure (SRP) modeling in Earth's penumbra. The fundamental geometry and approach mirrors past work, where the solar radiation field is modeled using a number of light rays, rather than treating the Sun as a single point source. However, we aim to clarify this approach, simplify its implementation, and model previously overlooked factors. The complex geometries involved in modeling penumbra solar radiation fields are described in a more intuitive and complete way to simplify implementation. Atmospheric effects are tabulated to significantly reduce computational cost. We present new, more efficient and accurate approaches to modeling atmospheric effects which allow us to consider the high spatial and temporal variability in lower atmospheric conditions. Modeled penumbra SRP accelerations for the Gravity Recovery and Climate Experiment (GRACE) satellites are compared to the sub-nm/s2 precision GRACE accelerometer data. Comparisons to accelerometer data and a traditional penumbra SRP model illustrate the improved accuracy which our methods provide. Sensitivity analyses illustrate the significance of various atmospheric parameters and modeled effects on penumbra SRP. While this model is more complex than a traditional penumbra SRP model, we demonstrate its utility and propose that a highly physical model which considers atmospheric effects should be the basis for any simplified approach to penumbra SRP modeling.

  8. Acoustic radiation force on a sphere in standing and quasi-standing zero-order Bessel beam tweezers

    SciTech Connect

    Mitri, F.G.

    2008-07-15

    Starting from the exact acoustic scattering from a sphere immersed in an ideal fluid and centered along the propagation axis of a standing or quasi-standing zero-order Bessel beam, explicit partial-wave representations for the radiation force are derived. A standing or a quasi-standing acoustic field is the result of propagating two equal or unequal amplitude zero-order Bessel beams, respectively, along the same axis but in opposite sense. The Bessel beam is characterized by the half-cone angle {beta} of its plane wave components, such that {beta} = 0 represents a plane wave. It is assumed here that the half-cone angle {beta} for each of the counter-propagating acoustic Bessel beams is equal. Fluid, elastic and viscoelastic spheres immersed in water are treated as examples. Results indicate the capability of manipulating spherical targets based on their mechanical and acoustical properties. This condition provides an impetus for further designing acoustic tweezers operating with standing or quasi-standing Bessel acoustic waves. Potential applications include particle manipulation in micro-fluidic lab-on-chips as well as in reduced gravity environments.

  9. Symptoms of Acoustic Neuroma

    MedlinePlus

    ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ...

  10. Acoustic Neuroma Educational Video

    MedlinePlus

    ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ... Watch and Wait Radiation Microsurgery Acoustic Neuroma Decision Tree Questions for Your Physician Questions to Ask Yourself ...

  11. Quantitative measurement of radiation pressure on a microcantilever in ambient environment

    SciTech Connect

    Ma, Dakang; Munday, Jeremy N.; Garrett, Joseph L.

    2015-03-02

    Light reflected off a material or absorbed within it exerts radiation pressure through the transfer of momentum. Micro/nano-mechanical transducers have become sensitive enough that radiation pressure can influence these systems. However, photothermal effects often accompany and overwhelm the radiation pressure, complicating its measurement. In this letter, we investigate the radiation force on an uncoated silicon nitride microcantilever in ambient conditions. We identify and separate the radiation pressure and photothermal forces through an analysis of the cantilever's frequency response. Further, by working in a regime where radiation pressure is dominant, we are able to accurately measure the radiation pressure. Experimental results are compared to theory and found to agree within the measured and calculated uncertainties.

  12. An Acoustic Emission and Acousto-Ultrasonic Analysis of Impact Damaged Composite Pressure Vessels

    NASA Technical Reports Server (NTRS)

    Walker, James L.; Workman, Gary L.; Workman, Gary L.

    1996-01-01

    The research presented herein summarizes the development of acoustic emission (AE) and acousto-ultrasonic (AU) techniques for the nondestructive evaluation of filament wound composite pressure vessels. Vessels fabricated from both graphite and kevlar fibers with an epoxy matrix were examined prior to hydroburst using AU and during hydroburst using AE. A dead weight drop apparatus featuring both blunt and sharp impactor tips was utilized to produce a single known energy 'damage' level in each of the vessels so that the degree to which the effects of impact damage could be measured. The damage levels ranged from barely visible to obvious fiber breakage and delamination. Independent neural network burst pressure prediction models were developed from a sample of each fiber/resin material system. Here, the cumulative AE amplitude distribution data collected from low level proof test (25% of the expected burst for undamaged vessels) were used to measure the effects of the impact on the residual burst pressure of the vessels. The results of the AE/neural network model for the inert propellant filled graphite/epoxy vessels 'IM7/3501-6, IM7/977-2 and IM7/8553-45' demonstrated that burst pressures can be predicted from low level AE proof test data, yielding an average error of 5.0%. The trained network for the IM7/977-2 class vessels was also able to predict the expected burst pressure of taller vessels (three times longer hoop region length) constructed of the same material and using the same manufacturing technique, with an average error of 4.9%. To a lesser extent, the burst pressure prediction models could also measure the effects of impact damage to the kevlar/epoxy 'Kevlar 49/ DPL862' vessels. Here though, due to the higher attenuation of the material, an insufficient amount of AE amplitude information was collected to generate robust network models. Although, the worst case trial errors were less than 6%, when additional blind predictions were attempted, errors as

  13. Acoustic radiation force due to a diverging wave: Demonstration and theory

    NASA Astrophysics Data System (ADS)

    Denardo, Bruce C.; Freemyers, Stanley G.; Schock, Michael P.; Sundem, Scott T.

    2014-02-01

    A radiation force is the time-averaged force exerted by any kind of wave on a body. In the case of a divergent traveling acoustic wave, it is known that a relatively small rigid body can experience a radiation force that is directed toward the source. We show that this effect can be readily demonstrated with a styrofoam sphere pendulum near a horizontally directed loudspeaker that is emitting sound of sufficiently high amplitude and low frequency. The attraction is surprising because repulsive forces are exerted by a traveling plane wave and by an outward jetting or "wind" from the loudspeaker. We argue that the attractive force near a source that is small compared to the wavelength can be roughly understood and calculated as a time-averaged Bernoulli effect, if scattering is ignored. The result is within a factor of two of rigorous published results based on scattering calculations, when these results are specialized to the case of a rigid body whose average density is much greater than the density of the fluid. However, repulsion occurs when the average density of the body is less than the density of the fluid, in which case our Bernoulli result completely fails.

  14. On the Feasibility of Quantifying Fibrous Cap Thickness With Acoustic Radiation Force Impulse (ARFI) Ultrasound.

    PubMed

    Czernuszewicz, Tomasz J; Gallippi, Caterina M

    2016-09-01

    Acute cerebrovascular accidents are associated with the rupture of vulnerable atherosclerotic plaques in the carotid arteries. Fibrous cap (FC) thickness has been shown to be an important predictor of plaque rupture but has been challenging to measure accurately with clinical noninvasive imaging modalities. The goals of this investigation were first, to evaluate the feasibility of using transcutaneous acoustic radiation force impulse (ARFI) ultrasound to quantify FC thickness and second, to optimize both imaging and motion-tracking parameters to support such measurements. FCs with varying thickness (0.1-1.0 mm) were simulated using a simple-layered geometry, and their mechanical response to an impulse of radiation force was solved using finite-element method (FEM) modeling. Ultrasound tracking of FEM displacements was performed in Field II utilizing three center frequencies (6, 9, and 12 MHz) and eight motion-tracking kernel lengths ( 0.5λ-4λ). Additionally, FC thickness in two carotid plaques imaged in vivo was measured with ARFI and compared to matched histology. The results of this study demonstrate that 1) tracking pulse frequencies around 12 MHz are necessary to resolve caps around 0.2 mm; 2) large motion-tracking kernel sizes introduce bias into thickness measurements and overestimate the true cap thickness; and 3) color saturation settings on ARFI peak displacement images can impact thickness measurement accuracy substantially. PMID:26955026

  15. Acoustic tractor beam.

    PubMed

    Démoré, Christine E M; Dahl, Patrick M; Yang, Zhengyi; Glynne-Jones, Peter; Melzer, Andreas; Cochran, Sandy; MacDonald, Michael P; Spalding, Gabriel C

    2014-05-01

    Negative radiation forces act opposite to the direction of propagation, or net momentum, of a beam but have previously been challenging to definitively demonstrate. We report an experimental acoustic tractor beam generated by an ultrasonic array operating on macroscopic targets (>1 cm) to demonstrate the negative radiation forces and to map out regimes over which they dominate, which we compare to simulations. The result and the geometrically simple configuration show that the effect is due to nonconservative forces, produced by redirection of a momentum flux from the angled sides of a target and not by conservative forces from a potential energy gradient. Use of a simple acoustic setup provides an easily understood illustration of the negative radiation pressure concept for tractor beams and demonstrates continuous attraction towards the source, against a net momentum flux in the system. PMID:24836252

  16. Acoustic Tractor Beam

    NASA Astrophysics Data System (ADS)

    Démoré, Christine E. M.; Dahl, Patrick M.; Yang, Zhengyi; Glynne-Jones, Peter; Melzer, Andreas; Cochran, Sandy; MacDonald, Michael P.; Spalding, Gabriel C.

    2014-05-01

    Negative radiation forces act opposite to the direction of propagation, or net momentum, of a beam but have previously been challenging to definitively demonstrate. We report an experimental acoustic tractor beam generated by an ultrasonic array operating on macroscopic targets (>1 cm) to demonstrate the negative radiation forces and to map out regimes over which they dominate, which we compare to simulations. The result and the geometrically simple configuration show that the effect is due to nonconservative forces, produced by redirection of a momentum flux from the angled sides of a target and not by conservative forces from a potential energy gradient. Use of a simple acoustic setup provides an easily understood illustration of the negative radiation pressure concept for tractor beams and demonstrates continuous attraction towards the source, against a net momentum flux in the system.

  17. Dependence of the Radiation Pressure on the Background Refractive Index

    NASA Astrophysics Data System (ADS)

    Webb, Kevin J.

    2013-07-01

    The 1978 experiments by Jones and Leslie showing that the radiation pressure on a mirror depends on the background medium refractive index have yet to be adequately explained using a force model and have provided a leading challenge to the Abraham form of the electromagnetic momentum. Those experimental results are predicted for the first time using a force representation that incorporates the Abraham momentum by utilizing the power calibration method employed in the Jones and Leslie experiments. With an extension of the same procedure, the polarization and angle independence of the experimental data are also explained by this model. Prospects are good for this general form of the electromagnetic force density to be effective in predicting other experiments with macroscopic materials. Furthermore, the rigorous representation of material dispersion makes the representation important for metamaterials that operate in the vicinity of homogenized material resonances.

  18. Nonlinear Radiation Pressure Dynamics in an Optomechanical Crystal.

    PubMed

    Krause, Alex G; Hill, Jeff T; Ludwig, Max; Safavi-Naeini, Amir H; Chan, Jasper; Marquardt, Florian; Painter, Oskar

    2015-12-01

    Utilizing a silicon nanobeam optomechanical crystal, we investigate the attractor diagram arising from the radiation pressure interaction between a localized optical cavity at λ_{c}=1542  nm and a mechanical resonance at ω_{m}/2π=3.72  GHz. At a temperature of T_{b}≈10  K, highly nonlinear driving of mechanical motion is observed via continuous wave optical pumping. Introduction of a time-dependent (modulated) optical pump is used to steer the system towards an otherwise inaccessible dynamically stable attractor in which mechanical self-oscillation occurs for an optical pump red detuned from the cavity resonance. An analytical model incorporating thermo-optic effects due to optical absorption heating is developed and found to accurately predict the measured device behavior.

  19. RADIATION PRESSURE DETECTION AND DENSITY ESTIMATE FOR 2011 MD

    SciTech Connect

    Micheli, Marco; Tholen, David J.; Elliott, Garrett T. E-mail: tholen@ifa.hawaii.edu

    2014-06-10

    We present our astrometric observations of the small near-Earth object 2011 MD (H ∼ 28.0), obtained after its very close fly-by to Earth in 2011 June. Our set of observations extends the observational arc to 73 days, and, together with the published astrometry obtained around the Earth fly-by, allows a direct detection of the effect of radiation pressure on the object, with a confidence of 5σ. The detection can be used to put constraints on the density of the object, pointing to either an unexpectedly low value of ρ=(640±330)kg m{sup −3} (68% confidence interval) if we assume a typical probability distribution for the unknown albedo, or to an unusually high reflectivity of its surface. This result may have important implications both in terms of impact hazard from small objects and in light of a possible retrieval of this target.

  20. Radiation pressure induced difference-sideband generation beyond linearized description

    NASA Astrophysics Data System (ADS)

    Xiong, Hao; Fan, Yu-Wan; Yang, Xiaoxue; Wu, Ying

    2016-08-01

    We investigate radiation-pressure induced generation of the frequency components at the difference-sideband in an optomechanical system, which beyond the conventional linearized description of optomechanical interactions between cavity fields and the mechanical oscillation. We analytically calculate amplitudes of these signals, and identify a simple square-root law for both the upper and lower difference-sideband generation which can describe the dependence of the intensities of these signals on the pump power. Further calculation shows that difference-sideband generation can be greatly enhanced via achieving the matching conditions. The effect of difference-sideband generation, which may have potential application for manipulation of light, is especially suited for on-chip optomechanical devices, where nonlinear optomechanical interaction in the weak coupling regime is within current experimental reach.

  1. A gas-dynamical approach to radiation pressure acceleration

    NASA Astrophysics Data System (ADS)

    Schmidt, Peter; Boine-Frankenheim, Oliver

    2016-06-01

    The study of high intensity ion beams driven by high power pulsed lasers is an active field of research. Of particular interest is the radiation pressure acceleration, for which simulations predict narrow band ion energies up to GeV. We derive a laser-piston model by applying techniques for non-relativistic gas-dynamics. The model reveals a laser intensity limit, below which sufficient laser-piston acceleration is impossible. The relation between target thickness and piston velocity as a function of the laser pulse length yields an approximation for the permissible target thickness. We performed one-dimensional Particle-In-Cell simulations to confirm the predictions of the analytical model. These simulations also reveal the importance of electromagnetic energy transport. We find that this energy transport limits the achievable compression and rarefies the plasma.

  2. Angular trapping of a mirror using radiation pressure

    NASA Astrophysics Data System (ADS)

    Kelley, David B.

    Alignment control in gravitational-wave detectors has consistently proven to be a difficult problem due to the stringent noise contamination requirement for the gravitational wave readout and the radiation-pressure induced angular instability in Fabry-Perot cavities (Sidles-Sigg instability). In this thesis, I present optical springs as a tool to damp the motion of a mirror. I discuss the design and implementation of a single degree-of-freedom optical spring system and the importance of the photothermal effect in properly predicting optical spring behavior. I also present the development and implementation of an angular control scheme, attempting to damp two degrees of freedom with two optical cavities. I then extend this understanding into a plausible concept for implementing optical-spring-based angular control in the Advanced LIGO detectors.

  3. Radiation pressure efficiency measurements of nanoparticle coated microspheres

    SciTech Connect

    Kim, Soo Y.; Taylor, Joseph D.; Ladouceur, Harold D.; Hart, Sean J.; Terray, Alex

    2013-12-02

    Experimental measurements of the radiation pressure efficiency (Q{sub pr}) for several microparticles have been compared to theoretical calculations extrapolated from the Bohren-Huffman code for Mie scattering of coated particles. An increased shift of the Q{sub pr} parameter was observed for 2 μm SiO{sub 2} core particles coated with nanoparticles of higher refractive indices. Coatings of 14 nm melamine particles were found to increase the Q{sub pr} parameter 135 times over similar coatings using SiO{sub 2} particles of the same size. While a coating of 100 nm polystyrene particles also showed a significant increase, they did not agree well with theoretical values. It is hypothesized that other factors such as increased scatter, drag, and finite coating coverage are no longer negligible for coatings using nanoparticles in this size regime.

  4. A Correlated Study of the Response of a Satellite to Acoustic Radiation Using Statistical Energy Analysis and Acoustic Test Data

    SciTech Connect

    CAP,JEROME S.; TRACEY,BRIAN

    1999-11-15

    Aerospace payloads, such as satellites, are subjected to vibroacoustic excitation during launch. Sandia's MTI satellite has recently been certified to this environment using a combination of base input random vibration and reverberant acoustic noise. The initial choices for the acoustic and random vibration test specifications were obtained from the launch vehicle Interface Control Document (ICD). In order to tailor the random vibration levels for the laboratory certification testing, it was necessary to determine whether vibration energy was flowing across the launch vehicle interface from the satellite to the launch vehicle or the other direction. For frequencies below 120 Hz this issue was addressed using response limiting techniques based on results from the Coupled Loads Analysis (CLA). However, since the CLA Finite Element Analysis FEA model was only correlated for frequencies below 120 Hz, Statistical Energy Analysis (SEA) was considered to be a better choice for predicting the direction of the energy flow for frequencies above 120 Hz. The existing SEA model of the launch vehicle had been developed using the VibroAcoustic Payload Environment Prediction System (VAPEPS) computer code [1]. Therefore, the satellite would have to be modeled using VAPEPS as well. As is the case for any computational model, the confidence in its predictive capability increases if one can correlate a sample prediction against experimental data. Fortunately, Sandia had the ideal data set for correlating an SEA model of the MTI satellite--the measured response of a realistic assembly to a reverberant acoustic test that was performed during MTI's qualification test series. The first part of this paper will briefly describe the VAPEPS modeling effort and present the results of the correlation study for the VAPEPS model. The second part of this paper will present the results from a study that used a commercial SEA software package [2] to study the effects of in-plane modes and to

  5. Laplace plane modifications arising from solar radiation pressure

    SciTech Connect

    Rosengren, Aaron J.; Scheeres, Daniel J.

    2014-05-01

    The dynamical effects of solar radiation pressure (SRP) in the solar system have been rigorously studied since the early 1900s. This non-gravitational perturbation plays a significant role in the evolution of dust particles in circumplanetary orbits, as well as in the orbital motion about asteroids and comets. For gravitationally dominated orbits, SRP is negligible and the resulting motion is largely governed by the oblateness of the primary and the attraction of the Sun. The interplay between these gravitational perturbations gives rise to three mutually perpendicular planes of equilibrium for circular satellite orbits. The classical Laplace plane lies between the equatorial and orbital planes of the primary, and is the mean reference plane about whose axis the pole of a satellite's orbit precesses. From a previously derived solution for the secular motion of an orbiter about a small body in a SRP dominated environment, we find that SRP acting alone will cause an initially circular orbit to precess around the pole of the primary's heliocentric orbital plane. When the gravitational and non-gravitational perturbations act in concert, the resulting equilibrium planes turn out to be qualitatively different, in some cases, from those obtained without considering the radiation pressure. The warping of the surfaces swept out by the modified equilibria as the semi-major axis varies depends critically on the cross-sectional area of the body exposed. These results, together with an adiabatic invariance argument on Poynting-Robertson drag, provide a natural qualitative explanation for the initial albedo dichotomy of Saturn's moon, Iapetus.

  6. The effect of temperature dependent tissue parameters on acoustic radiation force induced displacements

    NASA Astrophysics Data System (ADS)

    Suomi, Visa; Han, Yang; Konofagou, Elisa; Cleveland, Robin O.

    2016-10-01

    Multiple ultrasound elastography techniques rely on acoustic radiation force (ARF) in monitoring high-intensity focused ultrasound (HIFU) therapy. However, ARF is dependent on tissue attenuation and sound speed, both of which are also known to change with temperature making the therapy monitoring more challenging. Furthermore, the viscoelastic properties of tissue are also temperature dependent, which affects the displacements induced by ARF. The aim of this study is to quantify the temperature dependent changes in the acoustic and viscoelastic properties of liver and investigate their effect on ARF induced displacements by using both experimental methods and simulations. Furthermore, the temperature dependent viscoelastic properties of liver are experimentally measured over a frequency range of 0.1–200 Hz at temperatures reaching 80 °C, and both conventional and fractional Zener models are used to fit the data. The fractional Zener model was found to fit better with the experimental viscoelasticity data with respect to the conventional model with up to two orders of magnitude lower sum of squared errors (SSE). The characteristics of experimental displacement data were also seen in the simulations due to the changes in attenuation coefficient and lesion development. At low temperatures before thermal ablation, attenuation was found to affect the displacement amplitude. At higher temperature, the decrease in displacement amplitude occurs approximately at 60–70 °C due to the combined effect of viscoelasticity changes and lesion growth overpowering the effect of attenuation. The results suggest that it is necessary to monitor displacement continuously during HIFU therapy in order to ascertain when ablation occurs.

  7. Direct opto-acoustic in vitro measurement of the spatial distribution of laser radiation in biological media

    SciTech Connect

    Pelivanov, Ivan M; Belov, Sergej A; Solomatin, Vladimir S; Khokhlova, Tanya D; Karabutov, Aleksander A

    2006-12-31

    The problem of opto-acoustic (AO) diagnostics of light scattering and absorption in biological media is considered. The objects under study were milk, bovine and porcine liver, and bovine muscle tissue. The forward and backward schemes for recording acoustic signals were used in experiments. The spatial distribution of the light intensity was measured for each biological medium from the temporal profile of the excited OA pulse and the absorption coefficient and reduced scattering coefficient were determined. Opto-acoustic signals were excited by a 1064-nm pulsed Nd:YAG laser and a tunable Ti:sapphire laser at 779 nm. It is shown that the proposed method can be used for obtaining a priori information on a biological medium in problems of optical and AO tomography. (special issue devoted to multiple radiation scattering in random media)

  8. Comparison of Different Measurement Technologies for the In-Flight Assessment of Radiated Acoustic Intensity

    NASA Technical Reports Server (NTRS)

    Klos, Jacob; Palumbo, Daniel L.; Buehrle, Ralph D.; Williams, Earl G.; Valdivia, Nicolas; Herdic, Peter C.; Sklanka, Bernard

    2005-01-01

    A series of tests was planned and conducted in the Interior Noise Test Facility at Boeing Field, on the NASA Aries 757 flight research aircraft, and in the Structural Acoustic Loads and Transmission Facility at NASA Langley Research Center. These tests were designed to answer several questions concerning the use of array methods in flight. One focus of the tests was determining whether and to what extent array methods could be used to identify the effects of an acoustical treatment applied to a limited portion of an aircraft fuselage. Another focus of the tests was to verify that the arrays could be used to localize and quantify a known source purposely placed in front of the arrays. Thus the issues related to backside sources and flanking paths present in the complicated sound field were addressed during these tests. These issues were addressed through the use of reference transducers, both accelerometers mounted to the fuselage and microphones in the cabin, that were used to correlate the pressure holograms. measured by the microphone arrays using either SVD methods or partial coherence methods. This correlation analysis accepts only energy that is coherent with the sources sensed by the reference transducers, allowing a noise control engineer to only identify and study those vibratory sources of interest. The remainder of this paper will present a detailed description of the test setups that were used in this test sequence and typical results of the NAH/IBEM analysis used to reconstruct the sound fields. Also, a comparison of data obtained in the laboratory environments and during flights of the 757 aircraft will be made.

  9. Evaluating the intensity of the acoustic radiation force impulse (ARFI) in intravascular ultrasound (IVUS) imaging: Preliminary in vitro results.

    PubMed

    Shih, Cho-Chiang; Lai, Ting-Yu; Huang, Chih-Chung

    2016-08-01

    The ability to measure the elastic properties of plaques and vessels is significant in clinical diagnosis, particularly for detecting a vulnerable plaque. A novel concept of combining intravascular ultrasound (IVUS) imaging and acoustic radiation force impulse (ARFI) imaging has recently been proposed. This method has potential in elastography for distinguishing between the stiffness of plaques and arterial vessel walls. However, the intensity of the acoustic radiation force requires calibration as a standard for the further development of an ARFI-IVUS imaging device that could be used in clinical applications. In this study, a dual-frequency transducer with 11MHz and 48MHz was used to measure the association between the biological tissue displacement and the applied acoustic radiation force. The output intensity of the acoustic radiation force generated by the pushing element ranged from 1.8 to 57.9mW/cm(2), as measured using a calibrated hydrophone. The results reveal that all of the acoustic intensities produced by the transducer in the experiments were within the limits specified by FDA regulations and could still displace the biological tissues. Furthermore, blood clots with different hematocrits, which have elastic properties similar to the lipid pool of plaques, with stiffness ranging from 0.5 to 1.9kPa could be displaced from 1 to 4μm, whereas the porcine arteries with stiffness ranging from 120 to 291kPa were displaced from 0.4 to 1.3μm when an acoustic intensity of 57.9mW/cm(2) was used. The in vitro ARFI images of the artery with a blood clot and artificial arteriosclerosis showed a clear distinction of the stiffness distributions of the vessel wall. All the results reveal that ARFI-IVUS imaging has the potential to distinguish the elastic properties of plaques and vessels. Moreover, the acoustic intensity used in ARFI imaging has been experimentally quantified. Although the size of this two-element transducer is unsuitable for IVUS imaging, the

  10. Iterative solution of multiple radiation and scattering problems in structural acoustics using the BL-QMR algorithm

    SciTech Connect

    Malhotra, M.

    1996-12-31

    Finite-element discretizations of time-harmonic acoustic wave problems in exterior domains result in large sparse systems of linear equations with complex symmetric coefficient matrices. In many situations, these matrix problems need to be solved repeatedly for different right-hand sides, but with the same coefficient matrix. For instance, multiple right-hand sides arise in radiation problems due to multiple load cases, and also in scattering problems when multiple angles of incidence of an incoming plane wave need to be considered. In this talk, we discuss the iterative solution of multiple linear systems arising in radiation and scattering problems in structural acoustics by means of a complex symmetric variant of the BL-QMR method. First, we summarize the governing partial differential equations for time-harmonic structural acoustics, the finite-element discretization of these equations, and the resulting complex symmetric matrix problem. Next, we sketch the special version of BL-QMR method that exploits complex symmetry, and we describe the preconditioners we have used in conjunction with BL-QMR. Finally, we report some typical results of our extensive numerical tests to illustrate the typical convergence behavior of BL-QMR method for multiple radiation and scattering problems in structural acoustics, to identify appropriate preconditioners for these problems, and to demonstrate the importance of deflation in block Krylov-subspace methods. Our numerical results show that the multiple systems arising in structural acoustics can be solved very efficiently with the preconditioned BL-QMR method. In fact, for multiple systems with up to 40 and more different right-hand sides we get consistent and significant speed-ups over solving the systems individually.

  11. Acoustic performance of low pressure axial fan rotors with different blade chord length and radial load distribution

    NASA Astrophysics Data System (ADS)

    Carolus, Thomas

    The paper examines the acoustic and aerodynamic performance of low-pressure axial fan rotors with a hub/tip ratio of 0.45. Six rotors were designed for the same working point by means of the well-known airfoil theory. The condition of an equilibrium between the static pressure gradient and the centrifugal forces is maintained. All rotors have unequally spaced blades to diminish tonal noise. The rotors are tested in a short cylindrical housing without guide vanes. All rotors show very similar flux-pressure difference characteristics. The peak efficiency and the noise performance is considerably influenced by the chosen blade design. The aerodynamically and acoustically optimal rotor is the one with the reduced load at the hub and increased load in the tip region under satisfied equilibrium conditions. It runs at the highest aerodynamic efficiency, and its noise spectrum is fairly smooth. The overall sound pressure level of this rotor is up to 8 dB (A) lower compared to the other rotors under consideration.

  12. The Role of Radiation Pressure in the Narrow Line Regions of Seyfert Host Galaxies

    NASA Astrophysics Data System (ADS)

    Davies, Rebecca L.; Dopita, Michael A.; Kewley, Lisa; Groves, Brent; Sutherland, Ralph; Hampton, Elise J.; Shastri, Prajval; Kharb, Preeti; Bhatt, Harish; Scharwächter, Julia; Jin, Chichuan; Banfield, Julie; Zaw, Ingyin; James, Bethan; Juneau, Stéphanie; Srivastava, Shweta

    2016-06-01

    We investigate the relative significance of radiation pressure and gas pressure in the extended narrow line regions (ENLRs) of four Seyfert galaxies from the integral field Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7). We demonstrate that there exist two distinct types of starburst-active galactic nucleus (AGN) mixing curves on standard emission line diagnostic diagrams, which reflect the balance between gas pressure and radiation pressure in the ENLR. In two of the galaxies the ENLR is radiation pressure dominated throughout and the ionization parameter remains constant (log U ˜ 0). In the other two galaxies radiation pressure is initially important, but gas pressure becomes dominant as the ionization parameter in the ENLR decreases from log U ˜ 0 to ‑3.2 ≲ log U ≲ ‑3.4. Where radiation pressure is dominant, the AGN regulates the density of the interstellar medium on kiloparsec scales and may therefore have a direct impact on star formation activity and/or the incidence of outflows in the host galaxy to scales far beyond the zone of influence of the black hole. We find that both radiation pressure dominated and gas pressure dominated ENLRs are dynamically active with evidence for outflows, indicating that radiation pressure may be an important source of AGN feedback even when it is not dominant over the entire ENLR.

  13. Cyclones and attractive streaming generated by acoustical vortices.

    PubMed

    Riaud, Antoine; Baudoin, Michael; Thomas, Jean-Louis; Bou Matar, Olivier

    2014-07-01

    Acoustical and optical vortices have attracted great interest due to their ability to capture and manipulate particles with the use of radiation pressure. Here we show that acoustical vortices can also induce axial vortical flow reminiscent of cyclones, whose topology can be controlled by adjusting the properties of the acoustical beam. In confined geometry, the phase singularity enables generating "attractive streaming" with the flow directed toward the transducer. This opens perspectives for contactless vortical flow control.

  14. Inverse problem of nonlinear acoustics: Synthesizing intense signals to intensify the thermal and radiation action of ultrasound

    NASA Astrophysics Data System (ADS)

    Rudenko, O. V.; Gurbatov, S. N.

    2016-07-01

    Inverse problems of nonlinear acoustics have important applied significance. On the one hand, they are necessary for nonlinear diagnostics of media, materials, manufactured articles, building units, and biological and geological structures. On the other hand, they are needed for creating devices that ensure optimal action of acoustic radiation on a target. However, despite the many promising applications, this direction remains underdeveloped, especially for strongly distorted high-intensity waves containing shock fronts. An example of such an inverse problem is synthesis of the spatiotemporal structure of a field in a radiating system that ensures the highest possible energy density in the focal region. This problem is also related to the urgent problems of localizing wave energy and the theory of strongly nonlinear waves. Below we analyze some quite general and simple inverse nonlinear problems.

  15. Acoustic radiation force impulse and supersonic shear imaging versus transient elastography for liver fibrosis assessment.

    PubMed

    Sporea, Ioan; Bota, Simona; Jurchis, Ana; Sirli, Roxana; Grădinaru-Tascău, Oana; Popescu, Alina; Ratiu, Iulia; Szilaski, Milana

    2013-11-01

    Our study compared three elastographic methods--transient elastography (TE), acoustic radiation force impulse (ARFI) imaging and supersonic shear imaging (SSI)--with respect to the feasibility of their use in liver fibrosis evaluation. We also compared the performance of ARFI imaging and SSI, with TE as the reference method. The study included 332 patients, with or without hepatopathies, in which liver stiffness was evaluated using TE, ARFI and SSI. Reliable measurements were defined as a median value of 10 (TE, ARFI imaging) or 5 (SSI) liver stiffness measurements with a success rate ≥60% and an interquartile range interval <30%. A significantly higher percentage of reliable measurements were obtained using ARFI than by using TE and SSI: 92.1% versus 72.2% (p < 0.0001) and 92.1% versus 71.3% (p < 0.0001). Higher body mass index and older age were significantly associated with inability to obtain reliable measurements of liver stiffness using TE and SSI. In 55.4% of patients, reliable liver stiffness measurements were obtained using all three elastographic methods, and ARFI imaging and TE were similarly accurate in diagnosing significant fibrosis and cirrhosis, with TE as the reference method.

  16. Assessment of Placental Stiffness Using Acoustic Radiation Force Impulse Elastography in Pregnant Women with Fetal Anomalies

    PubMed Central

    Göya, Cemil; Tunç, Senem; Teke, Memik; Hattapoğlu, Salih

    2016-01-01

    Objective We aimed to evaluate placental stiffness measured by acoustic radiation force impulse (ARFI) elastography in pregnant women in the second trimester with a normal fetus versus those with structural anomalies and non-structural findings. Materials and Methods Forty pregnant women carrying a fetus with structural anomalies diagnosed sonographically at 18–28 weeks of gestation comprised the study group. The control group consisted of 34 healthy pregnant women with a sonographically normal fetus at a similar gestational age. Placental shear wave velocity (SWV) was measured by ARFI elastography and compared between the two groups. Structural anomalies and non-structural findings were scored based on sonographic markers. Placental stiffness measurements were compared among fetus anomaly categories. Doppler parameters of umbilical and uterine arteries were compared with placental SWV measurements. Results All placental SWV measurements, including minimum SWV, maximum SWV, and mean SWV were significantly higher in the study group than the control group ([0.86 ± 0.2, 0.74 ± 0.1; p < 0.001], [1.89 ± 0.7, 1.59 ± 0.5; p = 0.04], and [1.26 ± 0.4, 1.09 ± 0.2; p = 0.01]), respectively. Conclusion Placental stiffness evaluated by ARFI elastography during the second trimester in pregnant women with fetuses with congenital structural anomalies is higher than that of pregnant women with normal fetuses. PMID:26957906

  17. Burton-Miller-type singular boundary method for acoustic radiation and scattering

    NASA Astrophysics Data System (ADS)

    Fu, Zhuo-Jia; Chen, Wen; Gu, Yan

    2014-08-01

    This paper proposes the singular boundary method (SBM) in conjunction with Burton and Miller's formulation for acoustic radiation and scattering. The SBM is a strong-form collocation boundary discretization technique using the singular fundamental solutions, which is mathematically simple, easy-to-program, meshless and introduces the concept of source intensity factors (SIFs) to eliminate the singularities of the fundamental solutions. Therefore, it avoids singular numerical integrals in the boundary element method (BEM) and circumvents the troublesome placement of the fictitious boundary in the method of fundamental solutions (MFS). In the present method, we derive the SIFs of exterior Helmholtz equation by means of the SIFs of exterior Laplace equation owing to the same order of singularities between the Laplace and Helmholtz fundamental solutions. In conjunction with the Burton-Miller formulation, the SBM enhances the quality of the solution, particularly in the vicinity of the corresponding interior eigenfrequencies. Numerical illustrations demonstrate efficiency and accuracy of the present scheme on some benchmark examples under 2D and 3D unbounded domains in comparison with the analytical solutions, the boundary element solutions and Dirichlet-to-Neumann finite element solutions.

  18. A Bayesian approach for characterization of soft tissue viscoelasticity in acoustic radiation force imaging.

    PubMed

    Zhao, Xiaodong; Pelegri, Assimina A

    2016-04-01

    Biomechanical imaging techniques based on acoustic radiation force (ARF) have been developed to characterize the viscoelasticity of soft tissue by measuring the motion excited by ARF non-invasively. The unknown stress distribution in the region of excitation limits an accurate inverse characterization of soft tissue viscoelasticity, and single degree-of-freedom simplified models have been applied to solve the inverse problem approximately. In this study, the ARF-induced creep imaging is employed to estimate the time constant of a Voigt viscoelastic tissue model, and an inverse finite element (FE) characterization procedure based on a Bayesian formulation is presented. The Bayesian approach aims to estimate a reasonable quantification of the probability distributions of soft tissue mechanical properties in the presence of measurement noise and model parameter uncertainty. Gaussian process metamodeling is applied to provide a fast statistical approximation based on a small number of computationally expensive FE model runs. Numerical simulation results demonstrate that the Bayesian approach provides an efficient and practical estimation of the probability distributions of time constant in the ARF-induced creep imaging. In a comparison study with the single degree of freedom models, the Bayesian approach with FE models improves the estimation results even in the presence of large uncertainty levels of the model parameters.

  19. Study on the radial vibration and acoustic field of an isotropic circular ring radiator.

    PubMed

    Lin, Shuyu; Xu, Long

    2012-01-01

    Based on the exact analytical theory, the radial vibration of an isotropic circular ring is studied and its electro-mechanical equivalent circuit is obtained. By means of the equivalent circuit model, the resonance frequency equation is derived; the relationship between the radial resonance frequency, the radial displacement amplitude magnification and the geometrical dimensions, the material property is analyzed. For comparison, numerical method is used to simulate the radial vibration of isotropic circular rings. The resonance frequency and the radial vibrational displacement distribution are obtained, and the radial radiation acoustic field of the circular ring in radial vibration is simulated. It is illustrated that the radial resonance frequencies from the analytical method and the numerical method are in good agreement when the height is much less than the radius. When the height becomes large relative to the radius, the frequency deviation from the two methods becomes large. The reason is that the exact analytical theory is limited to thin circular ring whose height must be much less than its radius.

  20. Generation and Radiation of Acoustic Waves from a 2D Shear Layer

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.

    2000-01-01

    A thin free shear layer containing an inflection point in the mean velocity profile is inherently unstable. Disturbances in the flow field can excite the unstable behavior of a shear layer, if the appropriate combination of frequencies and shear layer thicknesses exists, causing instability waves to grow. For other combinations of frequencies and thicknesses, these instability waves remain neutral in amplitude or decay in the downstream direction. A growing instability wave radiates noise when its phase velocity becomes supersonic relative to the ambient speed of sound. This occurs primarily when the mean jet flow velocity is supersonic. Thus, the small disturbances in the flow, which themselves may generate noise, have generated an additional noise source. It is the purpose of this problem to test the ability of CAA to compute this additional source of noise. The problem is idealized such that the exciting disturbance is a fixed known acoustic source pulsating at a single frequency. The source is placed inside of a 2D jet with parallel flow; hence, the shear layer thickness is constant. With the source amplitude small enough, the problem is governed by the following set of linear equations given in dimensional form.

  1. The ‘sixth sense’ of ultrasound: probing nonlinear elasticity with acoustic radiation force

    NASA Astrophysics Data System (ADS)

    Guzina, Bojan B.; Dontsov, Egor V.; Urban, Matthew W.; Fatemi, Mostafa

    2015-05-01

    Prompted by a recent finding that the magnitude of the acoustic radiation force (ARF) in isotropic tissue-like solids depends linearly on a particular third-order modulus of elasticity—hereon denoted by C, this study investigates the possibility of estimating C from the amplitude of the ARF-generated shear waves. The featured coefficient of nonlinear elasticity, which captures the incipient nonlinear interaction between the volumetric and deviatoric modes of deformation, has so far received only a limited attention in the context of soft tissues due to the fact that the latter are often approximated as (i) fluid-like when considering ultrasound waves, and (ii) incompressible under static deformations. On establishing the analytical and computational platform for the proposed sensing methodology, the study proceeds with applying the prototype technique toward estimating via ARF the third-order modulus C in a series of tissue-mimicking phantoms. To help validate the concept and its implementation, the germane third-order modulus is independently estimated in each phantom via an established technique known as acoustoelasticity. The C-estimates obtained respectively via acoustoelasticity and the new theory of ARF show a significant degree of consistency. The key features of the new sensing methodology are that: (a) it requires no external deformation of a material other than that produced by the ARF, and (b) it estimates the nonlinear C-modulus locally, over the focal region of an ultrasound beam—where the shear waves are being generated.

  2. A Bayesian approach for characterization of soft tissue viscoelasticity in acoustic radiation force imaging.

    PubMed

    Zhao, Xiaodong; Pelegri, Assimina A

    2016-04-01

    Biomechanical imaging techniques based on acoustic radiation force (ARF) have been developed to characterize the viscoelasticity of soft tissue by measuring the motion excited by ARF non-invasively. The unknown stress distribution in the region of excitation limits an accurate inverse characterization of soft tissue viscoelasticity, and single degree-of-freedom simplified models have been applied to solve the inverse problem approximately. In this study, the ARF-induced creep imaging is employed to estimate the time constant of a Voigt viscoelastic tissue model, and an inverse finite element (FE) characterization procedure based on a Bayesian formulation is presented. The Bayesian approach aims to estimate a reasonable quantification of the probability distributions of soft tissue mechanical properties in the presence of measurement noise and model parameter uncertainty. Gaussian process metamodeling is applied to provide a fast statistical approximation based on a small number of computationally expensive FE model runs. Numerical simulation results demonstrate that the Bayesian approach provides an efficient and practical estimation of the probability distributions of time constant in the ARF-induced creep imaging. In a comparison study with the single degree of freedom models, the Bayesian approach with FE models improves the estimation results even in the presence of large uncertainty levels of the model parameters. PMID:26255624

  3. Testicular microlithiasis and preliminary experience of acoustic radiation force impulse imaging

    PubMed Central

    Osther, Palle Jørn Sloth; Rafaelsen, Søren Rafael

    2016-01-01

    Background Elastography of the testis can be used as a part of multiparametric examination of the scrotum. Purpose To determine the testicular stiffness using acoustic radiation force impulse imaging (ARFI) technique in men with testicular microlithiasis (TML). Material and Methods In 2013, 12 patients with diagnosed testicular microlithiasis in 2008 (mean age, 51 years; age range, 25–76 years) underwent a 5-year follow-up B-mode ultrasonography with three ARFI elastography measurements of each testis. We used a Siemens Acuson S3000 machine. Results No malignancy was found at the 5-year follow-up B-mode and elastography in 2013. However, we found an increase in TML; in the previous ultrasonography in 2008, eight men had bilateral TML, whereas in 2013, 10 men were diagnosed with bilateral TML. The mean elasticity of testicles with TML was 0.82 m/s (interquartile range [IQR], 0.72–0.88 m/s; range, 65–1.08 m/s). Conclusion Elastography velocity of testis with TML seems to be in the same velocity range as in men with normal testis tissue. PMID:27504193

  4. Optical tracking of acoustic radiation force impulse-induced dynamics in a tissue-mimicking phantom

    PubMed Central

    Bouchard, Richard R.; Palmeri, Mark L.; Pinton, Gianmarco F.; Trahey, Gregg E.; Streeter, Jason E.; Dayton, Paul A.

    2009-01-01

    Optical tracking was utilized to investigate the acoustic radiation force impulse (ARFI)-induced response, generated by a 5-MHz piston transducer, in a translucent tissue-mimicking phantom. Suspended 10-μm microspheres were tracked axially and laterally at multiple locations throughout the field of view of an optical microscope with 0.5-μm displacement resolution, in both dimensions, and at frame rates of up to 36 kHz. Induced dynamics were successfully captured before, during, and after the ARFI excitation at depths of up to 4.8 mm from the phantom’s proximal boundary. Results are presented for tracked axial and lateral displacements resulting from on-axis and off-axis (i.e., shear wave) acquisitions; these results are compared to matched finite element method modeling and independent ultrasonically based empirical results and yielded reasonable agreement in most cases. A shear wave reflection, generated by the proximal boundary, consistently produced an artifact in tracked displacement data later in time (i.e., after the initial ARFI-induced displacement peak). This tracking method provides high-frame-rate, two-dimensional tracking data and thus could prove useful in the investigation of complex ARFI-induced dynamics in controlled experimental settings. PMID:19894849

  5. Scanning Acoustic Microscopy-A Novel Noninvasive Method to Determine Tumor Interstitial Fluid Pressure in a Xenograft Tumor Model.

    PubMed

    Hofmann, Matthias; Pflanzer, Ralph; Habib, Anowarul; Shelke, Amit; Bereiter-Hahn, Jürgen; Bernd, August; Kaufmann, Roland; Sader, Robert; Kippenberger, Stefan

    2016-06-01

    Elevated tumor interstitial fluid pressure (TIFP) is a prominent feature of solid tumors and hampers the transmigration of therapeutic macromolecules, for example, large monoclonal antibodies, from tumor-supplying vessels into the tumor interstitium. TIFP values of up to 40 mm Hg have been measured in experimental solid tumors using two conventional invasive techniques: the wick-in-needle and the micropuncture technique. We propose a novel noninvasive method of determining TIFP via ultrasonic investigation with scanning acoustic microscopy at 30-MHz frequency. In our experimental setup, we observed for the impedance fluctuations in the outer tumor hull of A431-vulva carcinoma-derived tumor xenograft mice. The gain dependence of signal strength was quantified, and the relaxation of tissue was calibrated with simultaneous hydrostatic pressure measurements. Signal patterns from the acoustical images were translated into TIFP curves, and a putative saturation effect was found for tumor pressures larger than 3 mm Hg. This is the first noninvasive approach to determine TIFP values in tumors. This technique can provide a potentially promising noninvasive assessment of TIFP and, therefore, can be used to determine the TIFP before treatment approach as well to measure therapeutic efficacy highlighted by lowered TFP values. PMID:27267834

  6. Exploring Rotations Due to Radiation Pressure: 2-D to 3-D Transition Is Interesting!

    ERIC Educational Resources Information Center

    Waxman, Michael A.

    2010-01-01

    Radiation pressure is an important topic within a standard physics course (see, in particular, Refs. 1 and 2). The physics of radiation pressure is described, the magnitude of it is derived, both for the case of a perfectly absorbing surface and of a perfect reflector, and various applications of this interesting effect are discussed, such as…

  7. Rayleigh-Taylor modes in constant-density incompressible fluids accelerated by radiation pressure. [astrophysical models

    NASA Technical Reports Server (NTRS)

    Krolik, J. H.

    1977-01-01

    The paper examines the behavior of linear perturbations in an incompressible fluid undergoing acceleration by radiation pressure, with reference to processes occurring in quasars, supernovae, and planetary nebulae. It is shown that, contrary to prior expectation, fluids accelerated by radiation pressure, are not always unstable to Rayleigh-Taylor modes. Some are, in fact, unstable, but the nature of the instability is qualitatively different.

  8. Neural network burst pressure prediction in impact damaged Kevlar/epoxy bottles from acoustic emission amplitude data

    SciTech Connect

    Walker, J.L.; Workman, G.L.; Russell, S.S.

    1994-12-31

    Acoustic emission (AE) signal analysis has been used to measure the effect of impact damage on the burst pressure of 5.75 inch diameter filament wound Kevlar/epoxy pressure vessels. A calibrated dead weight drop fixture, featuring both sharp and blunt hemispherical impact tups, generated impact damages with energies up to twenty ft-lb{sub f} in the mid hoop region of each vessel. Burst pressures were obtained by hydrostatically testing twenty-seven damaged and undamaged bottles, eleven of which were filled with inert propellant to simulate a rocket motor. Burst pressure prediction models were developed by correlating the differential AE amplitude distributions, Generated during the first pressure ramp to 25% of the expected burst pressure for the undamaged vessels, to known burst pressures using back propagation neural networks. Independent networks were created for the inert propellant filled vessels and the unfilled vessels using a small subset of each during the training phases. The remaining bottles served as the test sets. The eleven filled vessels had an average prediction error of 5.6%, while the unfilled bottles averaged 5.4%. Both of these results were within the 95% prediction interval, but a portion of the vessel burst pressure errors were greater than the {+-}5% worst case error obtained in previous work. in conclusion, the AE amplitude distribution data collected at low proof loads provided a suitable input for neural network burst pressure prediction in damaged and undamaged Kevlar/epoxy bottles. This included pressure vessels both with and without propellant backing. Work is ongoing to decrease the magnitude of the prediction error through network restructuring.

  9. Variable ultrasound trigger delay for improved magnetic resonance acoustic radiation force imaging

    NASA Astrophysics Data System (ADS)

    Mougenot, Charles; Waspe, Adam; Looi, Thomas; Drake, James M.

    2016-01-01

    Magnetic resonance acoustic radiation force imaging (MR-ARFI) allows the quantification of microscopic displacements induced by ultrasound pulses, which are proportional to the local acoustic intensity. This study describes a new method to acquire MR-ARFI maps, which reduces the measurement noise in the quantification of displacement as well as improving its robustness in the presence of motion. Two MR-ARFI sequences were compared in this study. The first sequence ‘variable MSG’ involves switching the polarity of the motion sensitive gradient (MSG) between odd and even image frames. The second sequence named ‘static MSG’ involves a variable ultrasound trigger delay to sonicate during the first or second MSG for odd and even image frames, respectively. As previously published, the data acquired with a variable MSG required the use of reference data acquired prior to any sonication to process displacement maps. In contrary, data acquired with a static MSG were converted to displacement maps without using reference data acquired prior to the sonication. Displacement maps acquired with both sequences were compared by performing sonications for three different conditions: in a polyacrylamide phantom, in the leg muscle of a freely breathing pig and in the leg muscle of pig under apnea. The comparison of images acquired at even image frames and odd image frames indicates that the sequence with a static MSG provides a significantly better steady state (p  <  0.001 based on a Student’s t-test) than the images acquired with a variable MSG. In addition no reference data prior to sonication were required to process displacement maps for data acquired with a static MSG. The absence of reference data prior to sonication provided a 41% reduction of the spatial distribution of noise (p  <  0.001 based on a Student’s t-test) and reduced the sensitivity to motion for displacements acquired with a static MSG. No significant differences were expected and

  10. Theory of radiation pressure on magneto-dielectric materials

    NASA Astrophysics Data System (ADS)

    Barnett, Stephen M.; Loudon, Rodney

    2015-06-01

    We present a classical linear response theory for a magneto-dielectric material and determine the polariton dispersion relations. The electromagnetic field fluctuation spectra are obtained and polariton sum rules for their optical parameters are presented. The electromagnetic field for systems with multiple polariton branches is quantized in three dimensions and field operators are converted to 1-dimensional forms appropriate for parallel light beams. We show that the field-operator commutation relations agree with previous calculations that ignored polariton effects. The Abraham (kinetic) and Minkowski (canonical) momentum operators are introduced and their corresponding single-photon momenta are identified. The commutation relations of these and of their angular analogues support the identification, in particular, of the Minkowski momentum with the canonical momentum of the light. We exploit the Heaviside-Larmor symmetry of Maxwell’s equations to obtain, very directly, the Einsetin-Laub force density for action on a magneto-dielectric. The surface and bulk contributions to the radiation pressure are calculated for the passage of an optical pulse into a semi-infinite sample.

  11. 1D problems of radiation pressure on elastic solids

    NASA Astrophysics Data System (ADS)

    Požar, Tomaž; Možina, Janez

    2015-08-01

    We treat the light-matter interaction due to radiation pressure in one dimension using the fundamental, nonrelativistic conservation principles of energy and momentum. Additionally, we assume that the center of mass-energy maintains the same uniform motion if the interaction takes place or not. Since we handle solids as elastic objects, the results are consistent with the principle of causality and agree with recent experimental observations. We analyze the problem of reflection of a light pulse from a fully-reflective mirror and show that its reflection gives rise to an elastic wave with a measurable amplitude and a correct Doppler shift of the reflected pulse. We also analyze the problem of light pulse transmission into an anti-reflection coated, non-dispersive and lossless dielectric, where an elastic wave may as well be accompanied by a mechanical wave escorting the light pulse. We show that the Balazs rigid box thought experiment can be also realized in elastic dielectrics where some of the energy of the incident light is transferred to the wave motion. It follows from our approach that the electromagnetic momentum of the light pulse in the dielectric acquires Abraham's form only when a single type of the mechanical waves accompanies the interaction.

  12. Satellite de-orbiting via controlled solar radiation pressure

    NASA Astrophysics Data System (ADS)

    Deienno, Rogerio; Sanchez, Diogo Merguizo; de Almeida Prado, Antonio Fernando Bertachini; Smirnov, Georgi

    2016-06-01

    The goal of the present research was to study the use of solar radiation pressure to place a satellite in an orbit that makes it to re-enter the atmosphere of the Earth. This phase of the mission is usual, since the orbital space around the Earth is crowded and all satellites have to be discarded after the end of their lifetimes. The technique proposed here is based on a device that can increase and decrease the area-to-mass ratio of the satellite when it is intended to reduce its altitude until a re-entry point is reached. Equations that predict the evolution of the eccentricity and semi-major axis of the orbit of the satellite are derived and can be used to allow the evaluation of the time required for the decay of the satellite. Numerical simulations are made, and they show the time required for the decay as a function of the area-to-mass ratio and the evolution of the most important orbital elements. The results show maps that indicate regions of fast decays as a function of the area-to-mass ratio and the initial inclination of the orbit of the satellite. They also confirmed the applicability of the equations derived here. The numerical results showed the role played by the evection and the Sun-synchronous resonances in the de-orbiting time.

  13. Enhanced solar radiation pressure modeling for Galileo satellites

    NASA Astrophysics Data System (ADS)

    Montenbruck, O.; Steigenberger, P.; Hugentobler, U.

    2015-03-01

    This paper introduces a new approach for modeling solar radiation pressure (SRP) effects on Global Navigation Satellite Systems (GNSSs). It focuses on the Galileo In-Orbit Validation (IOV) satellites, for which obvious SRP modeling deficits can be identified in presently available precise orbit products. To overcome these problems, the estimation of empirical accelerations in the Sun direction (D), solar panel axis (Y) and the orthogonal (B) axis is complemented by an a priori model accounting for the contribution of the rectangular spacecraft body. Other than the GPS satellites, which comprise an almost cubic body, the Galileo IOV satellites exhibit a notably rectangular shape with a ratio of about 2:1 for the main body axes. Use of the a priori box model allows to properly model the varying cross section exposed to the Sun during yaw-steering attitude mode and helps to remove systematic once-per-revolution orbit errors that have so far affected the Galileo orbit determination. Parameters of a simple a priori cuboid model suitable for the IOV satellites are established from the analysis of a long-term set of GNSS observations collected with the global network of the Multi-GNSS Experiment of the International GNSS Service. The model is finally demonstrated to reduce the peak magnitude of radial orbit errors from presently 20 cm down to 5 cm outside eclipse phases.

  14. 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.

  15. Relativistic drag and emission radiation pressures in an isotropic photonic gas

    NASA Astrophysics Data System (ADS)

    Lee, Jeffrey S.; Cleaver, Gerald B.

    2016-06-01

    By invoking the relativistic spectral radiance, as derived by Lee and Cleaver,1 the drag radiation pressure of a relativistic planar surface moving through an isotropic radiation field, with which it is in thermal equilibrium, is determined in inertial and non-inertial frames. The forward- and backward-directed emission radiation pressures are also derived and compared. A fleeting (inertial frames) or ongoing (some non-inertial frames) Carnot cycle is shown to exist as a result of an intra-surfaces temperature gradient. The drag radiation pressure on an object with an arbitrary frontal geometry is also described.

  16. Characterization of intense ion beam energy density and beam induced pressure on the target with acoustic diagnostics

    SciTech Connect

    Pushkarev, A. I.; Isakova, Yu. I.; Khailov, I. P.; Yu, Xiao

    2013-08-15

    We have developed the acoustic diagnostics based on a piezoelectric transducer for characterization of high-intensity pulsed ion beams. The diagnostics was tested using the TEMP-4M accelerator (150 ns, 250–300 kV). The beam is composed of C{sup +} ions (85%) and protons, the beam energy density is 0.5–5 J/cm{sup 2} (depending on diode geometry). A calibration dependence of the signal from a piezoelectric transducer on the ion beam energy density is obtained using thermal imaging diagnostics. It is shown that the acoustic diagnostics allows for measurement of the beam energy density in the range of 0.1–2 J/cm{sup 2}. The dependence of the beam generated pressure on the input energy density is also determined and compared with the data from literature. The developed acoustic diagnostics do not require sophisticated equipment and can be used for operational control of pulsed ion beam parameters with a repetition rate of 10{sup 3} pulses/s.

  17. Characterization of intense ion beam energy density and beam induced pressure on the target with acoustic diagnostics.

    PubMed

    Pushkarev, A I; Isakova, Yu I; Yu, Xiao; Khailov, I P

    2013-08-01

    We have developed the acoustic diagnostics based on a piezoelectric transducer for characterization of high-intensity pulsed ion beams. The diagnostics was tested using the TEMP-4M accelerator (150 ns, 250-300 kV). The beam is composed of C(+) ions (85%) and protons, the beam energy density is 0.5-5 J∕cm(2) (depending on diode geometry). A calibration dependence of the signal from a piezoelectric transducer on the ion beam energy density is obtained using thermal imaging diagnostics. It is shown that the acoustic diagnostics allows for measurement of the beam energy density in the range of 0.1-2 J∕cm(2). The dependence of the beam generated pressure on the input energy density is also determined and compared with the data from literature. The developed acoustic diagnostics do not require sophisticated equipment and can be used for operational control of pulsed ion beam parameters with a repetition rate of 10(3) pulses∕s.

  18. Effects of Lingual Effort on Swallow Pressures Following Radiation Treatment

    ERIC Educational Resources Information Center

    Lenius, Kerry; Stierwalt, Julie; LaPointe, Leonard L.; Bourgeois, Michelle; Carnaby, Giselle; Crary, Michael

    2015-01-01

    Purpose: This article investigated the effects of increased oral lingual pressure on pharyngeal pressures during swallowing in patients who have undergone radiotherapy for head and neck cancer. It was hypothesized that increased oral lingual pressure would result in increased pharyngeal pressures. Method: A within-subject experimental design was…

  19. [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.

  20. Technical aspects of acoustic myography (AMG) of human skeletal muscle: contact pressure and force/AMG relationships.

    PubMed

    Smith, T G; Stokes, M J

    1993-04-01

    The effect of contact pressure on acoustic myographic (AMG) recordings was examined during voluntary isometric contractions of the human quadriceps muscle in 20 normal males. A piezoelectric disk for recording muscle sounds was placed over rectus femoris at approximately mid-thigh and secured with a rubber electromyography (EMG) strap. Contact pressure was monitored by a load cell placed between the AMG device and the strap. With the subject seated, force at different percentage levels of maximum voluntary contraction (MVC) were held for 5 s each. Both AMG and EMG recordings were full-wave rectified and integrated (IAMG and IEMG) and expressed as a percentage of activity at MVC. Two contraction series were performed with 2 different contact pressures. Pressure 1 (P1), of 180 Pa was applied in all subjects. A higher pressure of either 790 Pa (P2; in 5 subjects) or 1200 Pa (P3; in 15 subjects) was also applied. No significant changes in IAMG activity (P > 0.1) occurred between P1 and P2 but P3 produced increases in IAMG at all force levels (P < 0.05 at 10, 50 and 75% MVC). Both linear and non-linear relationships between force and IAMG were observed in different subjects but the relationship also varied with the 2 contact pressures within some subjects. The force/IEMG relationship was linear in all cases. These results provide quantitative evidence that contact pressure can influence the degree of IAMG activity if the pressure is high enough. The change in the force/IAMG relationship with pressure in some subjects suggests that the different relationships observed are not determined by physiological differences between subjects but rather by technical factors.

  1. A NEW MECHANISM FOR MASS ACCRETION UNDER RADIATION PRESSURE IN MASSIVE STAR FORMATION

    SciTech Connect

    Tanaka, Kei E. I.; Nakamoto, Taishi

    2010-05-01

    During the formation of a massive star, strong radiation pressure from the central star acts on the dust sublimation front and tends to halt the accretion flow. To overcome this strong radiation pressure, it has been considered that a strong ram pressure produced by a high-mass accretion rate of 10{sup -3} M{sub sun} yr{sup -1} or more is needed. We reinvestigated the necessary condition to overcome the radiation pressure and found a new mechanism for overcoming it. Accumulated mass in a stagnant flow near the dust sublimation front helps the mass accretion by its weight. This mechanism relaxes the condition for the massive star formation. We call this mechanism the 'OMOSHI effect', where OMOSHI is an acronym for 'One Mechanism for Overcoming Stellar High radiation pressure by weIght'. Additionally, in Japanese, OMOSHI is a noun meaning a weight that is put on something to prevent it from moving. We investigate the generation of the OMOSHI effect using local one-dimensional radiation hydrodynamics simulations. The radiation pressure and the gravitational force are connected through the gas pressure, and to sum up, the radiation pressure is balanced or overcome by the gravitational force. We also discuss the global structure and temporal variation of the accretion flow.

  2. Cavitation mapping by sonochemiluminescence with less bubble displacement induced by acoustic radiation force in a 1.2 MHz HIFU.

    PubMed

    Yin, Hui; Qiao, Yangzi; Cao, Hua; Li, Zhaopeng; Wan, Mingxi

    2014-03-01

    An acoustic radiation force counterbalanced appliance was employed to map the cavitation distribution in water. The appliance was made up of a focused ultrasound transducer and an aluminum alloy reflector with the exactly same shape. They were centrosymmetry around the focus of the source transducer. Spatial-temporal dynamics of cavitation bubble clouds in the 1.2 MHz ultrasonic field within this appliance were observed in water. And they were mapped by sonochemiluminescence (SCL) recordings and high-speed photography. There were significant differences in spatial distribution and temporal evolution between normal group and counterbalanced group. The reflector could avoid bubble directional displacement induced by acoustic radiation force under certain electric power (≤50 W). As a result, the SCL intensity in the pre-focal region was larger than that of normal group. In event of high electric power (≥70 W), most of the bubbles were moving in acoustic streaming. When electric power decreased, bubbles kept stable and showed stripe structure in SCL images. Both stationary bubbles and moving bubbles have been captured, and exhibited analytical potential with respect to bubbles in therapeutic ultrasound.

  3. Anisotropic Properties of Breast Tissue Measured by Acoustic Radiation Force Impulse Quantification.

    PubMed

    Zhou, JianQiao; Yang, ZhiFang; Zhan, WeiWei; Dong, YiJie; Zhou, Chun

    2016-10-01

    The goal of our study was to investigate the anisotropy of normal breast glandular and fatty tissue with acoustic radiation force impulse (ARFI) quantification. A total of 137 breasts in 137 women were enrolled. These breasts were divided into the duct-apparent group and the duct-inapparent group, divided into the ligament-apparent group and the ligament-inapparent group. Shear wave velocity (SWV) in the radial (SWV(r)) and anti-radial (SWV(a-r)) directions was measured. The elastic anisotropy of glandular tissue and fatty tissue was evaluated as the ratio between SWV(r) and SWV(a-r). The SWV ratio was 1.30 ± 0.45 for glandular tissue and 1.27 ± 0.53 for fatty tissue in the total group. In glandular tissue, the SWV ratio of the duct-apparent group was higher than that of the duct-inapparent group (p = 0.011). In both glandular and fatty tissue, the SWV ratio was higher in the ligament-apparent group than in the ligament-inapparent group (p < 0.05 for both). SWV(r) was higher than SWV(a-r) in both glandular tissue and fatty tissue in all groups (p < 0.05 for all) except in breast fatty tissue in the ligament-inapparent group (p = 0.913). It is concluded that both breast glandular tissue and fatty tissue exhibited anisotropy of elastic behavior. To improve the diagnostic power of elastography in breast lesions, the elastic anisotropy of glandular tissue and fatty tissue should be taken into account in calculating strain ratio or elasticity ratio.

  4. Anisotropic Properties of Breast Tissue Measured by Acoustic Radiation Force Impulse Quantification.

    PubMed

    Zhou, JianQiao; Yang, ZhiFang; Zhan, WeiWei; Dong, YiJie; Zhou, Chun

    2016-10-01

    The goal of our study was to investigate the anisotropy of normal breast glandular and fatty tissue with acoustic radiation force impulse (ARFI) quantification. A total of 137 breasts in 137 women were enrolled. These breasts were divided into the duct-apparent group and the duct-inapparent group, divided into the ligament-apparent group and the ligament-inapparent group. Shear wave velocity (SWV) in the radial (SWV(r)) and anti-radial (SWV(a-r)) directions was measured. The elastic anisotropy of glandular tissue and fatty tissue was evaluated as the ratio between SWV(r) and SWV(a-r). The SWV ratio was 1.30 ± 0.45 for glandular tissue and 1.27 ± 0.53 for fatty tissue in the total group. In glandular tissue, the SWV ratio of the duct-apparent group was higher than that of the duct-inapparent group (p = 0.011). In both glandular and fatty tissue, the SWV ratio was higher in the ligament-apparent group than in the ligament-inapparent group (p < 0.05 for both). SWV(r) was higher than SWV(a-r) in both glandular tissue and fatty tissue in all groups (p < 0.05 for all) except in breast fatty tissue in the ligament-inapparent group (p = 0.913). It is concluded that both breast glandular tissue and fatty tissue exhibited anisotropy of elastic behavior. To improve the diagnostic power of elastography in breast lesions, the elastic anisotropy of glandular tissue and fatty tissue should be taken into account in calculating strain ratio or elasticity ratio. PMID:27471118

  5. Tissue elasticity quantification by acoustic radiation force impulse for the assessment of renal allograft function.

    PubMed

    He, Wan-Yuan; Jin, Yun-Jie; Wang, Wen-Ping; Li, Chao-Lun; Ji, Zheng-Biao; Yang, Cheng

    2014-02-01

    Acoustic radiation force impulse (ARFI) quantification, a novel ultrasound-based elastography method, has been used to measure liver fibrosis. However, few studies have been performed on the use of ARFI quantification in kidney examinations. We evaluated renal allograft stiffness using ARFI quantification in patients with stable renal function (n = 52) and those with biopsy-proven allograft dysfunction (n = 50). ARFI quantification, given as shear wave velocity (SWV), was performed. The resistance index (RI) was calculated by pulsed-wave Doppler ultrasound, and clinical and laboratory data were collected. Morphologic changes in transplanted kidneys were diagnosed by an independent pathologist. Mean SWV was more significantly negatively correlated with estimated glomerular filtration rate (eGFR) (r = -0.657, p < 0.0001) than was RI (r = -0.429, p = 0.0004) in transplanted kidneys. Receiver operating characteristic curve analysis revealed that the sensitivity and specificity of quantitative ultrasound in the diagnosis of renal allograft dysfunction were 72.0% and 86.5% (cutoff value = 2.625), respectively. The latter values were better than those of RI, which were 62.0% and 69.2% (cutoff value = 0.625), respectively. The coefficient of variation for repeat SWV measurements of the middle part of transplanted kidney was 8.64%, and inter-observer agreement on SWV was good (Bland-Altman method, ICC = 0.890). In conclusion, tissue elasticity quantification by ARFI is more accurate than the RI in diagnosing renal allograft function.

  6. Acoustic radiation force impulse imaging for assessing liver fibrosis in alcoholic liver disease

    PubMed Central

    Kiani, Anita; Brun, Vanessa; Lainé, Fabrice; Turlin, Bruno; Morcet, Jeff; Michalak, Sophie; Le Gruyer, Antonia; Legros, Ludivine; Bardou-Jacquet, Edouard; Gandon, Yves; Moirand, Romain

    2016-01-01

    AIM: To evaluate the performance of elastography by ultrasound with acoustic radiation force impulse (ARFI) in determining fibrosis stage in patients with alcoholic liver disease (ALD) undergoing alcoholic detoxification in relation to biopsy. METHODS: Eighty-three patients with ALD undergoing detoxification were prospectively enrolled. Each patient underwent ARFI imaging and a liver biopsy on the same day. Fibrosis was staged according to the METAVIR scoring system. The median of 10 valid ARFI measurements was calculated for each patient. RESULTS: Sixty-nine males and thirteen females (one patient excluded due to insufficient biopsy size) were assessed with a mean alcohol consumption of 132.4 ± 128.8 standard drinks per week and mean cumulative year duration of 17.6 ± 9.5 years. Sensitivity and specificity were respectively 82.4% (0.70-0.95) and 83.3% (0.73-0.94) (AUROC = 0.87) for F ≥ 2 with a cut-off value of 1.63m/s; 82.4% (0.64-1.00) and 78.5% (0.69-0.89) (AUROC = 0.86) for F ≥ 3 with a cut-off value of 1.84m/s; and 92.3% (0.78-1.00] and 81.6% (0.72-0.90) (AUROC = 0.89) for F = 4 with a cut-off value of 1.94 m/s. CONCLUSION: ARFI is an accurate, non-invasive and easy method for assessing liver fibrosis in patients with ALD undergoing alcoholic detoxification. PMID:27239119

  7. Intracardiac Acoustic Radiation Force Impulse (ARFI) and Shear Wave Imaging in Pigs with Focal Infarctions

    PubMed Central

    Hollender, Peter; Bradway, David; Wolf, Patrick; Goswami, Robi; Trahey, Gregg

    2013-01-01

    Four pigs, three with focal infarctions in the apical intraventricular septum (IVS) and/or left ventricular free wall (LVFW), were imaged with an intracardiac echocardiography (ICE) transducer. Custom beam sequences were used to excite the myocardium with focused acoustic radiation force (ARF) impulses and image the subsequent tissue response. Tissue displacement in response to the ARF excitation was calculated with a phase-based estimator, and transverse wave magnitude and velocity were each estimated at every depth. The excitation sequence was repeated rapidly, either in the same location to generate 40 Hz M-Modes at a single steering angle, or with a modulated steering angle to synthesize 2-D displacement magnitude and shear wave velocity images at 17 points in the cardiac cycle. Both types of images were acquired from various views in the right and left ventricles, in and out of infarcted regions. In all animals, ARFI and SWEI estimates indicated diastolic relaxation and systolic contraction in non-infarcted tissues. The M-Mode sequences showed high beat-to-beat spatio-temporal repeatability of the measurements for each imaging plane. In views of noninfarcted tissue in the diseased animals, no significant elastic remodeling was indicated when compared to the control. Where available, views of infarcted tissue were compared to similar views from the control animal. In views of the LVFW, the infarcted tissue presented as stiff and non-contractile compared to the control. In a view of the IVS, no significant difference was seen between infarcted and healthy tissue, while in another view, a heterogeneous infarction was seen presenting itself as non-contractile in systole. PMID:25004538

  8. Optical pressure/acoustic sensor with precise Fabry-Perot cavity length control using angle polished fiber.

    PubMed

    Wang, Wenhui; Wu, Nan; Tian, Ye; Wang, Xingwei; Niezrecki, Christopher; Chen, Julie

    2009-09-14

    This paper presents a novel Fabry-Perot (FP) optical fiber pressure/acoustic sensor. It consists of two V-shaped grooves having different sized widths, a diaphragm on the surface of the larger V-groove, and a 45 degrees angle-polished fiber. The precision of FP cavity length is determined by the fabrication process of photolithography and anisotropic etching of a silicon crystal. Therefore, the cavity length can be controlled on the order of ten nm. Sensors were fabricated and tested. Test results indicate that the sensors' cavity lengths have been controlled precisely. The packaged sensor has demonstrated very good static and dynamic responses compared to a commercially available pressure sensor and a microphone. PMID:19770876

  9. Effect of anisotropic dust pressure and superthermal electrons on propagation and stability of dust acoustic solitary waves

    SciTech Connect

    Bashir, M. F.; Behery, E. E.; El-Taibany, W. F.

    2015-06-15

    Employing the reductive perturbation technique, Zakharov–Kuznetzov (ZK) equation is derived for dust acoustic (DA) solitary waves in a magnetized plasma which consists the effects of dust anisotropic pressure, arbitrary charged dust particles, Boltzmann distributed ions, and Kappa distributed superthermal electrons. The ZK solitary wave solution is obtained. Using the small-k expansion method, the stability analysis for DA solitary waves is also discussed. The effects of the dust pressure anisotropy and the electron superthermality on the basic characteristics of DA waves as well as on the three-dimensional instability criterion are highlighted. It is found that the DA solitary wave is rarefactive (compressive) for negative (positive) dust. In addition, the growth rate of instability increases rapidly as the superthermal spectral index of electrons increases with either positive or negative dust grains. A brief discussion for possible applications is included.

  10. A study of solar radiation pressure acting on GPS satellites

    NASA Astrophysics Data System (ADS)

    Froideval, Laurent Olivier

    An increasing number of GPS applications require a high level of accuracy. To reduce the error contributed by the GPS ephemerides, an accurate modeling of the forces acting on GPS satellites is necessary. These forces can be categorized into gravitational and non-gravitational forces. The non-gravitational forces are a significant contribution to the total force on a GPS satellite but they are still not fully understood whereas the gravitational forces are well modeled. This study focuses on two non-gravitational forces: Solar Radiation Pressure (SRP) and the y-bias force. Different SRP models are available in the University of Texas Multi-Satellite Orbit Determination Program (MSODP). The recently developed University College London model was implemented for the purpose of this study. Several techniques to compute parameters associated with SRP models and the y-bias force during an orbit prediction were examined. Using the International GNSS Service (IGS) precise ephemerides as a reference, five different models were compared in the study. Satellite Laser Ranging (SLR) residuals were also studied to validate the approach. Results showed that the analytical UCL model performed as well as a purely empirical model such as the Extended CODE model. This is important since analytical models attempt to represent the physical phenomena and thus might be better suited to separate SRP from other forces. The y-bias force was then shown to have a once per revolution effect. The time evolution of the y-bias was found to be dependent on the SRP model used, the satellite Block type, the orbital plane, and the attitude of the satellite which suggests that estimates of y-bias contain errors from other sources, particularly the SRP models. The dependency of the y-bias evolution on the orbital plane suggests that the orientation of the plane towards the Sun is important.

  11. Procedures for ambient-pressure and tympanometric tests of aural acoustic reflectance and admittance in human infants and adults.

    PubMed

    Keefe, Douglas H; Hunter, Lisa L; Feeney, M Patrick; Fitzpatrick, Denis F

    2015-12-01

    Procedures are described to measure acoustic reflectance and admittance in human adult and infant ears at frequencies from 0.2 to 8 kHz. Transfer functions were measured at ambient pressure in the ear canal, and as down- or up-swept tympanograms. Acoustically estimated ear-canal area was used to calculate ear reflectance, which was parameterized by absorbance and group delay over all frequencies (and pressures), with substantial data reduction for tympanograms. Admittance measured at the probe tip in adults was transformed into an equivalent admittance at the eardrum using a transmission-line model for an ear canal with specified area and ear-canal length. Ear-canal length was estimated from group delay around the frequency above 2 kHz of minimum absorbance. Illustrative measurements in ears with normal function are described for an adult, and two infants at 1 month of age with normal hearing and a conductive hearing loss. The sensitivity of this equivalent eardrum admittance was calculated for varying estimates of area and length. Infant-ear patterns of absorbance peaks aligned in frequency with dips in group delay were explained by a model of resonant canal-wall mobility. Procedures will be applied in a large study of wideband clinical diagnosis and monitoring of middle-ear and cochlear function.

  12. Acoustic forcing of a liquid drop

    NASA Technical Reports Server (NTRS)

    Lyell, M. J.

    1992-01-01

    The development of systems such as acoustic levitation chambers will allow for the positioning and manipulation of material samples (drops) in a microgravity environment. This provides the capability for fundamental studies in droplet dynamics as well as containerless processing work. Such systems use acoustic radiation pressure forces to position or to further manipulate (e.g., oscillate) the sample. The primary objective was to determine the effect of a viscous acoustic field/tangential radiation pressure forcing on drop oscillations. To this end, the viscous acoustic field is determined. Modified (forced) hydrodynamic field equations which result from a consistent perturbation expansion scheme are solved. This is done in the separate cases of an unmodulated and a modulated acoustic field. The effect of the tangential radiation stress on the hydrodynamic field (drop oscillations) is found to manifest as a correction to the velocity field in a sublayer region near the drop/host interface. Moreover, the forcing due to the radiation pressure vector at the interface is modified by inclusion of tangential stresses.

  13. Directional Electrostatic Accretion Process Employing Acoustic Droplet Formation

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard (Inventor)

    1998-01-01

    The present invention is directed to an apparatus for manufacturing a free standing solid metal part. In the present invention, metal droplets are ejected in a nozzleless fashion from a free surface pool of molten metal by applying focused acoustic radiation pressure. The acoustic radiation pressure is produced by high intensity acoustic tone bursts emitted from an acoustic source positioned at the bottom of the pool which directs the acoustic energy at the pool surface. The metal droplets are electrostatically charged so their trajectory can be controlled by electric fields that guide the droplets to predetermined points on a target. The droplets impinge upon the target and solidify with the target material. The accretion of the electrostatically directed solidified droplets forms the free standing metal part.

  14. OUTWARD MOTION OF POROUS DUST AGGREGATES BY STELLAR RADIATION PRESSURE IN PROTOPLANETARY DISKS

    SciTech Connect

    Tazaki, Ryo; Nomura, Hideko

    2015-02-01

    We study the dust motion at the surface layer of protoplanetary disks. Dust grains in the surface layer migrate outward owing to angular momentum transport via gas-drag force induced by the stellar radiation pressure. In this study we calculate the mass flux of the outward motion of compact grains and porous dust aggregates by the radiation pressure. The radiation pressure force for porous dust aggregates is calculated using the T-Matrix Method for the Clusters of Spheres. First, we confirm that porous dust aggregates are forced by strong radiation pressure even if they grow to be larger aggregates, in contrast to homogeneous and spherical compact grains, for which radiation pressure efficiency becomes lower when their sizes increase. In addition, we find that the outward mass flux of porous dust aggregates with monomer size of 0.1 μm is larger than that of compact grains by an order of magnitude at the disk radius of 1 AU, when their sizes are several microns. This implies that large compact grains like calcium-aluminum-rich inclusions are hardly transported to the outer region by stellar radiation pressure, whereas porous dust aggregates like chondritic-porous interplanetary dust particles are efficiently transported to the comet formation region. Crystalline silicates are possibly transported in porous dust aggregates by stellar radiation pressure from the inner hot region to the outer cold cometary region in the protosolar nebula.

  15. An acoustic emission and acousto-ultrasonic analysis of impact damaged composite pressure vessels

    NASA Technical Reports Server (NTRS)

    Workman, Gary L. (Principal Investigator); Walker, James L.

    1996-01-01

    The use of acoustic emission to characterize impact damage in composite structures is being performed on composite bottles wrapped with graphite epoxy and kevlar bottles. Further development of the acoustic emission methodology will include neural net analysis and/or other multivariate techniques to enhance the capability of the technique to identify dominant failure mechanisms during fracture. The acousto-ultrasonics technique will also continue to be investigated to determine its ability to predict regions prone to failure prior to the burst tests. Characterization of the stress wave factor before, and after impact damage will be useful for inspection purposes in manufacturing processes. The combination of the two methods will also allow for simple nondestructive tests capable of predicting the performance of a composite structure prior to its being placed in service and during service.

  16. Generation of ion-acoustic waves in an inductively coupled, low-pressure discharge lamp

    SciTech Connect

    Camparo, J. C.; Klimcak, C. M.

    2006-04-15

    For a number of years it has been known that the alkali rf-discharge lamps used in atomic clocks can exhibit large amplitude intensity oscillations. These oscillations arise from ion-acoustic plasma waves and have typically been associated with erratic clock behavior. Though large amplitude ion-acoustic plasma waves are clearly deleterious for atomic clock operation, it does not follow that small amplitude oscillations have no utility. Here, we demonstrate two easily implemented methods for generating small amplitude ion-acoustic plasma waves in alkali rf-discharge lamps. Furthermore, we demonstrate that the frequency of these waves is proportional to the square root of the rf power driving the lamp and therefore that their examination can provide an easily accessible parameter for monitoring and controlling the lamp's plasma conditions. This has important consequences for precise timekeeping, since the atomic ground-state hyperfine transition, which is the heart of the atomic clock signal, can be significantly perturbed by changes in the lamp's output via the ac-Stark shift.

  17. Acoustic telemetry.

    SciTech Connect

    Drumheller, Douglas Schaeffer; Kuszmaul, Scott S.

    2003-08-01

    Broadcasting messages through the earth is a daunting task. Indeed, broadcasting a normal telephone conversion through the earth by wireless means is impossible with todays technology. Most of us don't care, but some do. Industries that drill into the earth need wireless communication to broadcast navigation parameters. This allows them to steer their drill bits. They also need information about the natural formation that they are drilling. Measurements of parameters such as pressure, temperature, and gamma radiation levels can tell them if they have found a valuable resource such as a geothermal reservoir or a stratum bearing natural gas. Wireless communication methods are available to the drilling industry. Information is broadcast via either pressure waves in the drilling fluid or electromagnetic waves in the earth and well tubing. Data transmission can only travel one way at rates around a few baud. Given that normal Internet telephone modems operate near 20,000 baud, these data rates are truly very slow. Moreover, communication is often interrupted or permanently blocked by drilling conditions or natural formation properties. Here we describe a tool that communicates with stress waves traveling through the steel drill pipe and production tubing in the well. It's based on an old idea called Acoustic Telemetry. But what we present here is more than an idea. This tool exists, it's drilled several wells, and it works. Currently, it's the first and only acoustic telemetry tool that can withstand the drilling environment. It broadcasts one way over a limited range at much faster rates than existing methods, but we also know how build a system that can communicate both up and down wells of indefinite length.

  18. First images of thunder: Acoustic imaging of triggered lightning

    NASA Astrophysics Data System (ADS)

    Dayeh, M. A.; Evans, N. D.; Fuselier, S. A.; Trevino, J.; Ramaekers, J.; Dwyer, J. R.; Lucia, R.; Rassoul, H. K.; Kotovsky, D. A.; Jordan, D. M.; Uman, M. A.

    2015-07-01

    An acoustic camera comprising a linear microphone array is used to image the thunder signature of triggered lightning. Measurements were taken at the International Center for Lightning Research and Testing in Camp Blanding, FL, during the summer of 2014. The array was positioned in an end-fire orientation thus enabling the peak acoustic reception pattern to be steered vertically with a frequency-dependent spatial resolution. On 14 July 2014, a lightning event with nine return strokes was successfully triggered. We present the first acoustic images of individual return strokes at high frequencies (>1 kHz) and compare the acoustically inferred profile with optical images. We find (i) a strong correlation between the return stroke peak current and the radiated acoustic pressure and (ii) an acoustic signature from an M component current pulse with an unusual fast rise time. These results show that acoustic imaging enables clear identification and quantification of thunder sources as a function of lightning channel altitude.

  19. ON RADIATION PRESSURE IN STATIC, DUSTY H II REGIONS

    SciTech Connect

    Draine, B. T.

    2011-05-10

    Radiation pressure acting on gas and dust causes H II regions to have central densities that are lower than the density near the ionized boundary. H II regions in static equilibrium comprise a family of similarity solutions with three parameters: {beta}, {gamma}, and the product Q{sub 0} n{sub rms}; {beta} characterizes the stellar spectrum, {gamma} characterizes the dust/gas ratio, Q{sub 0} is the stellar ionizing output (photons/s), and n{sub rms} is the rms density within the ionized region. Adopting standard values for {beta} and {gamma}, varying Q{sub 0} n{sub rms} generates a one-parameter family of density profiles, ranging from nearly uniform density (small Q{sub 0} n{sub rms}) to shell-like (large Q{sub 0} n{sub rms}). When Q{sub 0} n{sub rms} {approx}> 10{sup 52} cm{sup -3} s{sup -1}, dusty H II regions have conspicuous central cavities, even if no stellar wind is present. For given {beta}, {gamma}, and Q{sub 0} n{sub rms}, a fourth quantity, which can be Q{sub 0}, determines the overall size and density of the H II region. Examples of density and emissivity profiles are given. We show how quantities of interest-such as the peak-to-central emission measure ratio, the rms-to-mean density ratio, the edge-to-rms density ratio, and the fraction of the ionizing photons absorbed by the gas-depend on {beta}, {gamma}, and Q{sub 0} n{sub rms}. For dusty H II regions, compression of the gas and dust into an ionized shell results in a substantial increase in the fraction of the stellar photons that actually ionize H (relative to a uniform-density H II region with the same dust/gas ratio and density n = n{sub rms}). We discuss the extent to which radial drift of dust grains in H II regions can alter the dust-to-gas ratio. The applicability of these solutions to real H II regions is discussed.

  20. CODE's new solar radiation pressure model for GNSS orbit determination

    NASA Astrophysics Data System (ADS)

    Arnold, D.; Meindl, M.; Beutler, G.; Dach, R.; Schaer, S.; Lutz, S.; Prange, L.; Sośnica, K.; Mervart, L.; Jäggi, A.

    2015-08-01

    The Empirical CODE Orbit Model (ECOM) of the Center for Orbit Determination in Europe (CODE), which was developed in the early 1990s, is widely used in the International GNSS Service (IGS) community. For a rather long time, spurious spectral lines are known to exist in geophysical parameters, in particular in the Earth Rotation Parameters (ERPs) and in the estimated geocenter coordinates, which could recently be attributed to the ECOM. These effects grew creepingly with the increasing influence of the GLONASS system in recent years in the CODE analysis, which is based on a rigorous combination of GPS and GLONASS since May 2003. In a first step we show that the problems associated with the ECOM are to the largest extent caused by the GLONASS, which was reaching full deployment by the end of 2011. GPS-only, GLONASS-only, and combined GPS/GLONASS solutions using the observations in the years 2009-2011 of a global network of 92 combined GPS/GLONASS receivers were analyzed for this purpose. In a second step we review direct solar radiation pressure (SRP) models for GNSS satellites. We demonstrate that only even-order short-period harmonic perturbations acting along the direction Sun-satellite occur for GPS and GLONASS satellites, and only odd-order perturbations acting along the direction perpendicular to both, the vector Sun-satellite and the spacecraft's solar panel axis. Based on this insight we assess in the third step the performance of four candidate orbit models for the future ECOM. The geocenter coordinates, the ERP differences w. r. t. the IERS 08 C04 series of ERPs, the misclosures for the midnight epochs of the daily orbital arcs, and scale parameters of Helmert transformations for station coordinates serve as quality criteria. The old and updated ECOM are validated in addition with satellite laser ranging (SLR) observations and by comparing the orbits to those of the IGS and other analysis centers. Based on all tests, we present a new extended ECOM which

  1. Mechanobiological Modulation of Cytoskeleton and Calcium Influx in Osteoblastic Cells by Short-Term Focused Acoustic Radiation Force

    PubMed Central

    Zhang, Shu; Cheng, Jiqi; Qin, Yi-Xian

    2012-01-01

    Mechanotransduction has demonstrated potential for regulating tissue adaptation in vivo and cellular activities in vitro. It is well documented that ultrasound can produce a wide variety of biological effects in biological systems. For example, pulsed ultrasound can be used to noninvasively accelerate the rate of bone fracture healing. Although a wide range of studies has been performed, mechanism for this therapeutic effect on bone healing is currently unknown. To elucidate the mechanism of cellular response to mechanical stimuli induced by pulsed ultrasound radiation, we developed a method to apply focused acoustic radiation force (ARF) (duration, one minute) on osteoblastic MC3T3-E1 cells and observed cellular responses to ARF using a spinning disk confocal microscope. This study demonstrates that the focused ARF induced F-actin cytoskeletal rearrangement in MC3T3-E1 cells. In addition, these cells showed an increase in intracellular calcium concentration following the application of focused ARF. Furthermore, passive bending movement was noted in primary cilium that were treated with focused ARF. Cell viability was not affected. Application of pulsed ultrasound radiation generated only a minimal temperature rise of 0.1°C, and induced a streaming resulting fluid shear stress of 0.186 dyne/cm2, suggesting that hyperthermia and acoustic streaming might not be the main causes of the observed cell responses. In conclusion, these data provide more insight in the interactions between acoustic mechanical stress and osteoblastic cells. This experimental system could serve as basis for further exploration of the mechanosensing mechanism of osteoblasts triggered by ultrasound. PMID:22701628

  2. Highly Localized Acoustic Streaming and Size-Selective Submicrometer Particle Concentration Using High Frequency Microscale Focused Acoustic Fields.

    PubMed

    Collins, David J; Ma, Zhichao; Ai, Ye

    2016-05-17

    Concentration and separation of particles and biological specimens are fundamental functions of micro/nanofluidic systems. Acoustic streaming is an effective and biocompatible way to create rapid microscale fluid motion and induce particle capture, though the >100 MHz frequencies required to directly generate acoustic body forces on the microscale have traditionally been difficult to generate and localize in a way that is amenable to efficient generation of streaming. Moreover, acoustic, hydrodynamic, and electrical forces as typically applied have difficulty manipulating specimens in the submicrometer regime. In this work, we introduce highly focused traveling surface acoustic waves (SAW) at high frequencies between 193 and 636 MHz for efficient and highly localized production of acoustic streaming vortices on microfluidic length scales. Concentration occurs via a novel mechanism, whereby the combined acoustic radiation and streaming field results in size-selective aggregation in fluid streamlines in the vicinity of a high-amplitude acoustic beam, as opposed to previous acoustic radiation induced particle concentration where objects typically migrate toward minimum pressure locations. Though the acoustic streaming is induced by a traveling wave, we are able to manipulate particles an order of magnitude smaller than possible using the traveling wave force alone. We experimentally and theoretically examine the range of particle sizes that can be captured in fluid streamlines using this technique, with rapid particle concentration demonstrated down to 300 nm diameters. We also demonstrate that locations of trapping and concentration are size-dependent, which is attributed to the combined effects of the acoustic streaming and acoustic forces.

  3. A rapid magnetic resonance acoustic radiation force imaging sequence for ultrasonic refocusing

    NASA Astrophysics Data System (ADS)

    Mougenot, Charles; Pichardo, Samuel; Engler, Steven; Waspe, Adam; Constanciel Colas, Elodie; Drake, James M.

    2016-08-01

    Magnetic resonance guided acoustic radiation force imaging (MR-ARFI) is being used to correct for aberrations induced by tissue heterogeneities when using high intensity focusing ultrasound (HIFU). A compromise between published MR-ARFI adaptive solutions is proposed to achieve efficient refocusing of the ultrasound beam in under 10 min. In addition, an ARFI sequence based on an EPI gradient echo sequence was used to simultaneously monitor displacement and temperature with a large SNR and low distortion. This study was conducted inside an Achieva 3T clinical MRI using a Philips Sonalleve MR-HIFU system to emit a 1 ms pulsed sonication with duty cycle of 2.3% at 300 Wac inside a polymer phantom. Virtual elements defined by a Hadamard array with sonication patterns composed of 6 phase steps were used to characterize 64 groups of 4 elements to find the optimal phase of the 256 elements of the transducer. The 384 sonication patterns were acquired in 580 s to identify the set of phases that maximize the displacement at the focal point. Three aberrators (neonatal skull, 8 year old skull and a checkered pattern) were added to each sonication pattern to evaluate the performance of this refocusing algorithm (n  =  4). These aberrators reduced the relative intensities to 95.3%, 69.6% and 25.5% for the neonatal skull, 8 year old skull, and checkered pattern virtual aberrators respectively. Using a 10 min refocusing algorithm, relative intensities of 101.6%, 91.3% and 93.3% were obtained. Better relative intensities of 103.9%, 94.3% and 101% were achieved using a 25 min refocusing algorithm. An average temperature increase of 4.2 °C per refocusing test was induced for the 10 min refocusing algorithm, resulting in a negligible thermal dose of 2 EM. A rapid refocusing of the beam can be achieved while keeping thermal effects to a minimum.

  4. A rapid magnetic resonance acoustic radiation force imaging sequence for ultrasonic refocusing.

    PubMed

    Mougenot, Charles; Pichardo, Samuel; Engler, Steven; Waspe, Adam; Colas, Elodie Constanciel; Drake, James M

    2016-08-01

    Magnetic resonance guided acoustic radiation force imaging (MR-ARFI) is being used to correct for aberrations induced by tissue heterogeneities when using high intensity focusing ultrasound (HIFU). A compromise between published MR-ARFI adaptive solutions is proposed to achieve efficient refocusing of the ultrasound beam in under 10 min. In addition, an ARFI sequence based on an EPI gradient echo sequence was used to simultaneously monitor displacement and temperature with a large SNR and low distortion. This study was conducted inside an Achieva 3T clinical MRI using a Philips Sonalleve MR-HIFU system to emit a 1 ms pulsed sonication with duty cycle of 2.3% at 300 Wac inside a polymer phantom. Virtual elements defined by a Hadamard array with sonication patterns composed of 6 phase steps were used to characterize 64 groups of 4 elements to find the optimal phase of the 256 elements of the transducer. The 384 sonication patterns were acquired in 580 s to identify the set of phases that maximize the displacement at the focal point. Three aberrators (neonatal skull, 8 year old skull and a checkered pattern) were added to each sonication pattern to evaluate the performance of this refocusing algorithm (n  =  4). These aberrators reduced the relative intensities to 95.3%, 69.6% and 25.5% for the neonatal skull, 8 year old skull, and checkered pattern virtual aberrators respectively. Using a 10 min refocusing algorithm, relative intensities of 101.6%, 91.3% and 93.3% were obtained. Better relative intensities of 103.9%, 94.3% and 101% were achieved using a 25 min refocusing algorithm. An average temperature increase of 4.2 °C per refocusing test was induced for the 10 min refocusing algorithm, resulting in a negligible thermal dose of 2 EM. A rapid refocusing of the beam can be achieved while keeping thermal effects to a minimum. PMID:27401452

  5. Primary biliary cirrhosis degree assessment by acoustic radiation force impulse imaging and hepatic fibrosis indicators

    PubMed Central

    Zhang, Hai-Chun; Hu, Rong-Fei; Zhu, Ting; Tong, Ling; Zhang, Qiu-Qin

    2016-01-01

    AIM: To evaluate the assessment of primary biliary cirrhosis degree by acoustic radiation force impulse imaging (ARFI) and hepatic fibrosis indicators. METHODS: One hundred and twenty patients who developed liver cirrhosis secondary to primary biliary cirrhosis were selected as the observation group, with the degree of patient liver cirrhosis graded by Child-Pugh (CP) score. Sixty healthy individuals were selected as the control group. The four indicators of hepatic fibrosis were detected in all research objects, including hyaluronic acid (HA), laminin (LN), type III collagen (PC III), and type IV collagen (IV-C). The liver parenchyma hardness value (LS) was then measured by ARFI technique. LS and the four indicators of liver fibrosis (HA, LN, PC III, and IV-C) were observed in different grade CP scores. The diagnostic value of LS and the four indicators of liver fibrosis in determining liver cirrhosis degree with PBC, whether used alone or in combination, were analyzed by receiver operating characteristic (ROC) curve. RESULTS: LS and the four indicators of liver fibrosis within the three classes (A, B, and C) of CP scores in the observation group were higher than in the control group, with C class > B class > A class; the differences were statistically significant (P < 0.01). Although AUC values of LS within the three classes of CP scores were higher than in the four indicators of liver fibrosis, sensitivity and specificity were unstable. The ROC curves of LS combined with the four indicators of liver fibrosis revealed that: AUC and sensitivity in all indicators combined in the A class of CP score were higher than in LS alone, albeit with slightly decreased specificity; AUC and specificity in all indicators combined in the B class of CP score were higher than in LS alone, with unchanged sensitivity; AUC values (0.967), sensitivity (97.4%), and specificity (90%) of all indicators combined in the C class of CP score were higher than in LS alone (0.936, 92.1%, 83

  6. Preclinical evaluation of acoustic radiation force impulse measurements in regions of heterogeneous elasticity

    PubMed Central

    Gaßmann, Bernhard; Wagenpfeil, Stefan; Moog, Philipp; Vo-Cong, Minh-Truc; Heemann, Uwe; Stock, Konrad Friedrich

    2016-01-01

    Purpose The purpose of this study was to compare the reliability of ultrasound-based shear wave elastography in regions of homogeneous versus heterogeneous elasticity by using two different probes. Methods Using acoustic radiation force impulse (ARFI) elastography, we measured the shear wave velocity (SWV) in different lesions of an elastography phantom with the convex 4C1 probe and the linear 9L4 probe. The region of interest (ROI) was positioned in such a way that it was partly filled by one of the lesions (0%, 25%, 50%, 75%, and 100%) and partly by the background of the phantom (100%, 75%, 50%, 25%, and 0%, respectively). Results The success rate was 98.5%. The measured value and the reference value of SWV correlated significantly (r=0.89, P<0.001). Further, a comparison of the two probes revealed that there was no statistical difference in either the mean or the variance values. However, the deviation of SWV from the reference was higher in the case of the 9L4 probe than in the case of the 4C1 probe, both overall and in measurements in which the ROI contained structures of different elasticity (P=0.021 and P=0.002). Taking into account all data, for both probes, we found that there was a greater spread and deviation of the SWV from the reference value when the ROI was positioned in structures having different elastic properties (standard deviation, 0.02±0.01 m/sec vs. 0.04±0.04 m/sec; P=0.010; deviation from the reference value, 0.21±0.12 m/sec vs. 0.38±0.27 m/sec; P=0.050). Conclusion Quantitative ARFI elastography was achievable in structures of different elasticity; however, the validity and the reliability of the SWV measurements decreased in comparison to those of the measurements performed in structures of homogeneous elasticity. Therefore, a convex probe is preferred for examining heterogeneous structures. PMID:27599889

  7. Acoustic Radiation Force Impulse Imaging for Noninvasive Evaluation of Renal Parenchyma Elasticity: Preliminary Findings

    PubMed Central

    Xu, Hui-Xiong; Peng, Ai; Zhang, Yi-Feng; Liu, Lin-Na

    2013-01-01

    Objective To evaluate the diagnostic value of acoustic radiation force impulse (ARFI) to test the elasticity of renal parenchyma by measuring the shear wave velocity (SWV) which might be used to detect chronic kidney disease (CKD). Methods 327 healthy volunteers and 64 CKD patients were enrolled in the study. The potential influencing factors and measurement reproducibility were evaluated in the healthy volunteers. Correlations between SWV and laboratory tests were analyzed in CKD patients.?Receiver-operating characteristic curve (ROC) analyses were performed to assess the diagnostic performance of ARFI. Results The SWV of healthy volunteers correlated significantly to age (r = −0.22, P<0.001, n = 327) and differed significantly between men and women (2.06±0.48 m/s vs. 2.2±0.52 m/s, P = 0.018, n = 327). However, it did not correlate significantly to height, weight, body mass index, waistline, kidney dimension and the depth for SWV measurement (n = 30). Inter- and intraobserver agreement expressed as intraclass coefficient correlation were 0.64 (95% CI: 0.13 to 0.82, P = 0.011) and 0.6 (95% CI: 0.31 to 0.81, P = 0.001) (n = 40). The mean SWV in healthy volunteers was 2.15±0.51 m/s, while was 1.81±0.43 m/s, 1.79±0.29 m/s, 1.81±0.44 m/s, 1.64±0.55 m/s, and 1.36±0.17 m/s for stage 1, 2, 3, 4 and 5 in CKD patients respectively. The SWV was significantly higher for healthy volunteers compared with each stage in CKD patients. ARFI could not predict the different stages of CKD except stage 5. In CKD patients, SWV correlated to e-GFR (r = 0.3, P = 0.018), to urea nitrogen (r =  −0.3, P = 0.016), and to creatinine (r =  −0.41, P = 0.001). ROC analyses indicated that the area under the ROC curve was 0.752 (95% CI: 0.704 to 0.797) (P<0.001). The cut-off value for predicting CKD was 1.88 m/s (sensitivity 71.87% and specificity 69.69%). Conclusion ARFI may be a potentially useful tool in detecting CKD. PMID

  8. Phenomenological Description of Acoustic Emission Processes Occurring During High-Pressure Sand Compaction

    NASA Astrophysics Data System (ADS)

    Delgado-Martín, Jordi; Muñoz-Ibáñez, Andrea; Grande-García, Elisa; Rodríguez-Cedrún, Borja

    2016-04-01

    Compaction, pore collapse and grain crushing have a significant impact over the hydrodynamic properties of sand formations. The assessment of the crushing stress threshold constitutes valuable information in order to assess the behavior of these formations provided that it can be conveniently identified. Because of the inherent complexities of the direct observation of sand crushing, different authors have developed several indirect methods, being acoustic emission a promising one. However, previous researches have evidenced that there are different processes triggering acoustic emissions which need to be carefully accounted. Worth mentioning among them are grain bearing, grain to container friction, intergranular friction and crushing. The work presented here addresses this purpose. A broadband acoustic emission sensor (PA MicroHF200) connected to a high-speed data acquisition system and control software (AeWIN for PCI1 2.10) has been attached to a steel ram and used to monitor the different processes occurring during the oedometric compaction of uniform quartz sand up to an axial load of about 110 MPa and constant temperature. Load was stepwise applied using a servocontrolled hydraulic press acting at a constant load rate. Axial strain was simultaneously measured with the aid of a LDT device. Counts, energy, event duration, rise time and amplitude were recorded along each experiment and after completion selected waveforms were transformed from the time to the frequency domain via FFT transform. Additional simplified tests were performed in order to isolate the frequency characteristics of the dominant processes occurring during sand compaction. Our results show that, from simple tests, it is possible to determine process-dependent frequency components. When considering more complex experiments, many of the studied processes overlap but it is still possible to identify when a particular one dominates as well as the likely onset of crushing.

  9. Apparatus and method for non-contact, acoustic resonance determination of intraocular pressure

    DOEpatents

    Sinha, Dipen N.; Wray, William O.

    1994-01-01

    Apparatus and method for measuring intraocular pressure changes in an eye under investigation by detection of vibrational resonances therein. An ultrasonic transducer operating at its resonant frequency is amplitude modulated and swept over a range of audio frequencies in which human eyes will resonate. The output therefrom is focused onto the eye under investigation, and the resonant vibrations of the eye observed using a fiber-optic reflection vibration sensor. Since the resonant frequency of the eye is dependent on the pressure therein, changes in intraocular pressure may readily be determined after a baseline pressure is established.

  10. Apparatus and method for non-contact, acoustic resonance determination of intraocular pressure

    DOEpatents

    Sinha, D.N.; Wray, W.O.

    1994-12-27

    The apparatus and method for measuring intraocular pressure changes in an eye under investigation by detection of vibrational resonances therein. An ultrasonic transducer operating at its resonant frequency is amplitude modulated and swept over a range of audio frequencies in which human eyes will resonate. The output therefrom is focused onto the eye under investigation, and the resonant vibrations of the eye observed using a fiber-optic reflection vibration sensor. Since the resonant frequency of the eye is dependent on the pressure therein, changes in intraocular pressure may readily be determined after a baseline pressure is established. 3 figures.

  11. Acoustic behaviour and equation of state of amorphous ethylene-vinyl acetate copolymer studied by means of high-pressure Brillouin scattering spectroscopy

    NASA Astrophysics Data System (ADS)

    Ko, Jae-Hyeon; Ko, Young Ho; Kim, Kwang Joo

    2014-06-01

    The determination of the equation of state (EOS) of amorphous materials is very important for fundamental understanding of the glass transition and applications as well. Simultaneous observation of both longitudinal and transverse acoustic modes by Brillouin scattering spectroscopy has been one of the major methods to obtain EOS of amorphous materials. However, the transverse acoustic mode is hardly seen from some of the amorphous polymers, which makes it difficult to derive EOS. The temperature and pressure dependences of the acoustic properties of amorphous ethylene-vinyl acetate (EVA) copolymer were measured by using high-pressure Brillouin scattering spectroscopy. The temperature variation induced large changes in the frequency shift and linewidth of the longitudinal acoustic mode due to strong coupling between the structural relaxation process and the propagating density fluctuations. The residual linewidth in the glassy state was attributed to the remnant intramolecular motions of EVA, the activation energy of which was estimated to be ∼3.30 ± 0.27 kcal/mol. The pressure-density relationship of EVA could be obtained for the first time by measuring the refractive index and using the Lorentz-Lorenz equation. The density and the refractive index exhibited monotonic increase up to approximately 12 GPa. The strong reduction of the acoustic damping at low pressures below ∼3 GPa was attributed to the collapsing free volume in EVA. The present study clearly shows that measuring the refractive index by high-pressure Brillouin spectroscopy may be an alternative method to get the EOS of polymeric materials whose transverse acoustic mode is too weak to be observed.

  12. A theoretical study of inertial cavitation from acoustic radiation force impulse (ARFI) imaging and implications for the mechanical index

    PubMed Central

    Church, Charles C.; Labuda, Cecille; Nightingale, Kathryn

    2014-01-01

    The mechanical index (MI) attempts to quantify the likelihood that exposure to diagnostic ultrasound will produce an adverse biological effect by a nonthermal mechanism. The current formulation of the MI implicitly assumes that the acoustic field is generated using the short pulse durations appropriate to B-mode imaging. However, acoustic radiation force impulse (ARFI) imaging employs high-intensity pulses up to several hundred acoustic periods long. The effect of increased pulse durations on the thresholds for inertial cavitation was studied computationally in water, urine, blood, cardiac and skeletal muscle, brain, kidney, liver and skin. The results show that while the effect of pulse duration on cavitation thresholds in the three liquids can be considerable, reducing them by, e.g., 6% – 24% at 1 MHz, the effect in tissue is minor. More importantly, the frequency dependence of the MI appears to be unnecessarily conservative, i.e., that the magnitude of the exponent on frequency could be increased to 0.75. Comparison of these theoretical results with experimental measurements suggests that some tissues do not contain the pre-existing, optimally sized bubbles assumed for the MI. This means that in these tissues the MI is not necessarily a strong predictor of the probability for an adverse biological effect. PMID:25592457

  13. Axial and transverse acoustic radiation forces on a fluid sphere placed arbitrarily in Bessel beam standing wave tweezers

    SciTech Connect

    Mitri, F.G.

    2014-03-15

    The axial and transverse radiation forces on a fluid sphere placed arbitrarily in the acoustical field of Bessel beams of standing waves are evaluated. The three-dimensional components of the time-averaged force are expressed in terms of the beam-shape coefficients of the incident field and the scattering coefficients of the fluid sphere using a partial-wave expansion (PWE) method. Examples are chosen for which the standing wave field is composed of either a zero-order (non-vortex) Bessel beam, or a first-order Bessel vortex beam. It is shown here, that both transverse and axial forces can push or pull the fluid sphere to an equilibrium position depending on the chosen size parameter ka (where k is the wave-number and a the sphere’s radius). The corresponding results are of particular importance in biophysical applications for the design of lab-on-chip devices operating with Bessel beams standing wave tweezers. Moreover, potential investigations in acoustic levitation and related applications in particle rotation in a vortex beam may benefit from the results of this study. -- Highlights: •The axial and transverse forces on a fluid sphere in acoustical Bessel beams tweezers are evaluated. •The attraction or repulsion to an equilibrium position in the standing wave field is examined. •Potential applications are in particle manipulation using standing waves.

  14. Contributions of John Henry Poynting to the understanding of radiation pressure

    PubMed Central

    Loudon, R.; Baxter, C.

    2012-01-01

    The name of Poynting is universally recognized for his development of the well-known expression for the flow of electromagnetic energy. Not so well known is Poynting's series of papers on radiation pressure, with 2011 marking the centenary of the last of his 15 publications on this topic. This paper reviews and assesses his radiation-pressure work, with a level of coverage aimed at the reader familiar with the Maxwell electromagnetic theory and interested in the current understanding of radiation pressure. We begin with brief details of Poynting's life, followed by accounts of the relevant publications by others before and during his period of activity in the field from 1903 to 1911. His contributions to the understanding of radiation-pressure effects in the solar system, and the linear and angular momenta of light are discussed, with evaluations from a modern perspective. PMID:22792039

  15. Acoustic study of the elastic and inelastic properties of high-pressure polyethylene samples with different irradiation histories

    NASA Astrophysics Data System (ADS)

    Kardashev, B. K.; Nikanorov, S. P.; Kravchenko, V. S.; Malinov, V. I.; Punin, V. T.

    2007-11-01

    The influence of vibrational deformation amplitude ɛ on the dynamic elasticity modulus (Young’s modulus E) and internal friction (logarithmic decrement δ) of high-pressure polyethylene samples with different histories is studied. Acoustic measurements are made by a resonance method using the longitudinal vibrations of a composite piezoelectric vibrator at a frequency of ≈ 100 kHz. The dependences E(ɛ) and δ(ɛ) are taken at room temperature. From the acoustic data, the elasticity and microplasticity of the samples are estimated. It is found that the microplasticity remains almost unaffected upon irradiation and aging, while the elasticity modulus and breaking elongation per unit length considerably depend on the history and clearly correlated with each other. The observed effects are explained by the fact that atom-atom interaction and defects inside polymer macromolecules substantially influence the elastic modulus and breaking strength, while the inelastic microplastic strain is most likely associated with molecule-molecule interaction, which is affected by irradiation insignificantly.

  16. The direct and inverse problems of an air-saturated porous cylinder submitted to acoustic radiation.

    PubMed

    Ogam, Erick; Depollier, Claude; Fellah, Z E A

    2010-09-01

    Gas-saturated porous skeleton materials such as geomaterials, polymeric and metallic foams, or biomaterials are fundamental in a diverse range of applications, from structural materials to energy technologies. Most polymeric foams are used for noise control applications and knowledge of the manner in which the energy of sound waves is dissipated with respect to the intrinsic acoustic properties is important for the design of sound packages. Foams are often employed in the audible, low frequency range where modeling and measurement techniques for the recovery of physical parameters responsible for energy loss are still few. Accurate acoustic methods of characterization of porous media are based on the measurement of the transmitted and/or reflected acoustic waves by platelike specimens at ultrasonic frequencies. In this study we develop an acoustic method for the recovery of the material parameters of a rigid-frame, air-saturated polymeric foam cylinder. A dispersion relation for sound wave propagation in the porous medium is derived from the propagation equations and a model solution is sought based on plane-wave decomposition using orthogonal cylindrical functions. The explicit analytical solution equation of the scattered field shows that it is also dependent on the intrinsic acoustic parameters of the porous cylinder, namely, porosity, tortuosity, and flow resistivity (permeability). The inverse problem of the recovery of the flow resistivity and porosity is solved by seeking the minima of the objective functions consisting of the sum of squared residuals of the differences between the experimental and theoretical scattered field data. PMID:20887001

  17. Non-invasive estimation of static and pulsatile intracranial pressure from transcranial acoustic signals.

    PubMed

    Levinsky, Alexandra; Papyan, Surik; Weinberg, Guy; Stadheim, Trond; Eide, Per Kristian

    2016-05-01

    The aim of the present study was to examine whether a method for estimation of non-invasive ICP (nICP) from transcranial acoustic (TCA) signals mixed with head-generated sounds estimate the static and pulsatile invasive ICP (iICP). For that purpose, simultaneous iICP and mixed TCA signals were obtained from patients undergoing continuous iICP monitoring as part of clinical management. The ear probe placed in the right outer ear channel sent a TCA signal with fixed frequency (621 Hz) that was picked up by the left ear probe along with acoustic signals generated by the intracranial compartment. Based on a mathematical model of the association between mixed TCA and iICP, the static and pulsatile nICP values were determined. Total 39 patients were included in the study; the total number of observations for prediction of static and pulsatile iICP were 5789 and 6791, respectively. The results demonstrated a good agreement between iICP/nICP observations, with mean difference of 0.39 mmHg and 0.53 mmHg for static and pulsatile ICP, respectively. In summary, in this cohort of patients, mixed TCA signals estimated the static and pulsatile iICP with rather good accuracy. Further studies are required to validate whether mixed TCA signals may become useful for measurement of nICP. PMID:26997563

  18. Observations of x-ray radiation pressure force on individual gold nanocrystals

    SciTech Connect

    Sasaki, Yuji C.; Okumura, Yasuaki; Miyazaki, Takuya; Higurashi, Takashi; Oishi, Noboru

    2006-07-31

    We report observations of x-ray radiation pressure force on individual single nanocrystals using an x-ray single molecular methodology. The observed gold nanocrystals are linked to the adsorbed protein molecules. We observed the directed Brownian motion of individual linked nanocrystals. The observed force is estimated at about 0.13-0.63 aN. We will be able to control and measure dynamics of micro- or nanocrystalline materials using x-ray radiation pressure force.

  19. Laser Imaging of Airborne Acoustic Emission by Nonlinear Defects

    NASA Astrophysics Data System (ADS)

    Solodov, Igor; Döring, Daniel; Busse, Gerd

    2008-06-01

    Strongly nonlinear vibrations of near-surface fractured defects driven by an elastic wave radiate acoustic energy into adjacent air in a wide frequency range. The variations of pressure in the emitted airborne waves change the refractive index of air thus providing an acoustooptic interaction with a collimated laser beam. Such an air-coupled vibrometry (ACV) is proposed for detecting and imaging of acoustic radiation of nonlinear spectral components by cracked defects. The photoelastic relation in air is used to derive induced phase modulation of laser light in the heterodyne interferometer setup. The sensitivity of the scanning ACV to different spatial components of the acoustic radiation is analyzed. The animated airborne emission patterns are visualized for the higher harmonic and frequency mixing fields radiated by planar defects. The results confirm a high localization of the nonlinear acoustic emission around the defects and complicated directivity patterns appreciably different from those observed for fundamental frequencies.

  20. External and middle ear sound pressure distribution and acoustic coupling to the tympanic membrane

    PubMed Central

    Bergevin, Christopher; Olson, Elizabeth S.

    2014-01-01

    Sound energy is conveyed to the inner ear by the diaphanous, cone-shaped tympanic membrane (TM). The TM moves in a complex manner and transmits sound signals to the inner ear with high fidelity, pressure gain, and a short delay. Miniaturized sensors allowing high spatial resolution in small spaces and sensitivity to high frequencies were used to explore how pressure drives the TM. Salient findings are: (1) A substantial pressure drop exists across the TM, and varies in frequency from ∼10 to 30 dB. It thus appears reasonable to approximate the drive to the TM as being defined solely by the pressure in the ear canal (EC) close to the TM. (2) Within the middle ear cavity (MEC), spatial variations in sound pressure could vary by more than 20 dB, and the MEC pressure at certain locations/frequencies was as large as in the EC. (3) Spatial variations in pressure along the TM surface on the EC-side were typically less than 5 dB up to 50 kHz. Larger surface variations were observed on the MEC-side. PMID:24606269

  1. External and middle ear sound pressure distribution and acoustic coupling to the tympanic membrane.

    PubMed

    Bergevin, Christopher; Olson, Elizabeth S

    2014-03-01

    Sound energy is conveyed to the inner ear by the diaphanous, cone-shaped tympanic membrane (TM). The TM moves in a complex manner and transmits sound signals to the inner ear with high fidelity, pressure gain, and a short delay. Miniaturized sensors allowing high spatial resolution in small spaces and sensitivity to high frequencies were used to explore how pressure drives the TM. Salient findings are: (1) A substantial pressure drop exists across the TM, and varies in frequency from ∼10 to 30 dB. It thus appears reasonable to approximate the drive to the TM as being defined solely by the pressure in the ear canal (EC) close to the TM. (2) Within the middle ear cavity (MEC), spatial variations in sound pressure could vary by more than 20 dB, and the MEC pressure at certain locations/frequencies was as large as in the EC. (3) Spatial variations in pressure along the TM surface on the EC-side were typically less than 5 dB up to 50 kHz. Larger surface variations were observed on the MEC-side.

  2. Elaborate visual and acoustic signals evolve independently in a large, phenotypically diverse radiation of songbirds

    PubMed Central

    Mason, Nicholas A.; Shultz, Allison J.; Burns, Kevin J.

    2014-01-01

    The concept of a macroevolutionary trade-off among sexual signals has a storied history in evolutionary biology. Theory predicts that if multiple sexual signals are costly for males to produce or maintain and females prefer a single, sexually selected trait, then an inverse correlation between sexual signal elaborations is expected among species. However, empirical evidence for what has been termed the ‘transfer hypothesis’ is mixed, which may reflect different selective pressures among lineages, evolutionary covariates or methodological differences among studies. Here, we examine interspecific correlations between song and plumage elaboration in a phenotypically diverse, widespread radiation of songbirds, the tanagers. The tanagers (Thraupidae) are the largest family of songbirds, representing nearly 10% of all songbirds. We assess variation in song and plumage elaboration across 301 species, representing the largest scale comparative study of multimodal sexual signalling to date. We consider whether evolutionary covariates, including habitat, structural and carotenoid-based coloration, and subfamily groupings influence the relationship between song and plumage elaboration. We find that song and plumage elaboration are uncorrelated when considering all tanagers, although the relationship between song and plumage complexity varies among subfamilies. Taken together, we find that elaborate visual and vocal sexual signals evolve independently among tanagers. PMID:24943371

  3. Use of large-scale acoustic monitoring to assess anthropogenic pressures on Orthoptera communities.

    PubMed

    Penone, Caterina; Le Viol, Isabelle; Pellissier, Vincent; Julien, Jean-François; Bas, Yves; Kerbiriou, Christian

    2013-10-01

    Biodiversity monitoring at large spatial and temporal scales is greatly needed in the context of global changes. Although insects are a species-rich group and are important for ecosystem functioning, they have been largely neglected in conservation studies and policies, mainly due to technical and methodological constraints. Sound detection, a nondestructive method, is easily applied within a citizen-science framework and could be an interesting solution for insect monitoring. However, it has not yet been tested at a large scale. We assessed the value of a citizen-science program in which Orthoptera species (Tettigoniidae) were monitored acoustically along roads. We used Bayesian model-averaging analyses to test whether we could detect widely known patterns of anthropogenic effects on insects, such as the negative effects of urbanization or intensive agriculture on Orthoptera populations and communities. We also examined site-abundance correlations between years and estimated the biases in species detection to evaluate and improve the protocol. Urbanization and intensive agricultural landscapes negatively affected Orthoptera species richness, diversity, and abundance. This finding is consistent with results of previous studies of Orthoptera, vertebrates, carabids, and butterflies. The average mass of communities decreased as urbanization increased. The dispersal ability of communities increased as the percentage of agricultural land and, to a lesser extent, urban area increased. Despite changes in abundances over time, we found significant correlations between yearly abundances. We identified biases linked to the protocol (e.g., car speed or temperature) that can be accounted for ease in analyses. We argue that acoustic monitoring of Orthoptera along roads offers several advantages for assessing Orthoptera biodiversity at large spatial and temporal extents, particularly in a citizen science framework.

  4. Use of large-scale acoustic monitoring to assess anthropogenic pressures on Orthoptera communities.

    PubMed

    Penone, Caterina; Le Viol, Isabelle; Pellissier, Vincent; Julien, Jean-François; Bas, Yves; Kerbiriou, Christian

    2013-10-01

    Biodiversity monitoring at large spatial and temporal scales is greatly needed in the context of global changes. Although insects are a species-rich group and are important for ecosystem functioning, they have been largely neglected in conservation studies and policies, mainly due to technical and methodological constraints. Sound detection, a nondestructive method, is easily applied within a citizen-science framework and could be an interesting solution for insect monitoring. However, it has not yet been tested at a large scale. We assessed the value of a citizen-science program in which Orthoptera species (Tettigoniidae) were monitored acoustically along roads. We used Bayesian model-averaging analyses to test whether we could detect widely known patterns of anthropogenic effects on insects, such as the negative effects of urbanization or intensive agriculture on Orthoptera populations and communities. We also examined site-abundance correlations between years and estimated the biases in species detection to evaluate and improve the protocol. Urbanization and intensive agricultural landscapes negatively affected Orthoptera species richness, diversity, and abundance. This finding is consistent with results of previous studies of Orthoptera, vertebrates, carabids, and butterflies. The average mass of communities decreased as urbanization increased. The dispersal ability of communities increased as the percentage of agricultural land and, to a lesser extent, urban area increased. Despite changes in abundances over time, we found significant correlations between yearly abundances. We identified biases linked to the protocol (e.g., car speed or temperature) that can be accounted for ease in analyses. We argue that acoustic monitoring of Orthoptera along roads offers several advantages for assessing Orthoptera biodiversity at large spatial and temporal extents, particularly in a citizen science framework. PMID:23692213

  5. Wind turbine acoustics

    NASA Technical Reports Server (NTRS)

    Hubbard, Harvey H.; Shepherd, Kevin P.

    1990-01-01

    Available information on the physical characteristics of the noise generated by wind turbines is summarized, with example sound pressure time histories, narrow- and broadband frequency spectra, and noise radiation patterns. Reviewed are noise measurement standards, analysis technology, and a method of characterizing wind turbine noise. Prediction methods are given for both low-frequency rotational harmonics and broadband noise components. Also included are atmospheric propagation data showing the effects of distance and refraction by wind shear. Human perception thresholds, based on laboratory and field tests, are given. Building vibration analysis methods are summarized. The bibliography of this report lists technical publications on all aspects of wind turbine acoustics.

  6. Electrostatic charging of acoustically suspended dust grains by ultraviolet radiation and by plasma

    SciTech Connect

    Dyer, T.W.

    1992-01-01

    An experimental apparatus was developed for the study of dust grain charging by photoemission and by immersion in plasma. The technique used to do this involved acoustically suspending the dust grains against gravity while they are exposed to the charging influences. The apparatus consisted of a terminated acoustic plane-wave tube coupled to an assembly of microwave equipment for use in the plasma charging studies. The origin of the acoustic force used to levitate the dust grains is a nonlinear dependence of fluid drag on an object with the flow velocity past the object. The effectiveness of the resulting force for the levitation of dust grains against gravity was inversely proportional to both grain radius and grain density. Grains of various materials including metals and silica with diameters ranging from 5 to 90[mu]m were readily levitated in krypton gas at 100 torr. These dust grain parameters and background gas conditions were standard for all of the grain charging. The interaction between a high intensity traveling acoustic wave with a highly collisional microwave producted plasma was investigated. The dominant effect of the acoustic wave on the plasma occurred in the plasma production rate. The resulting audio frequency plasma density fluctuations then propagated away from the production region in both directions as the plasma diffused out from this region against the background gas. In the dust grain charging studies, the steady state charge acquired by the grains was set by a condition on the electrostatic potential of the grains. This was true in both the photoemission charging experiments and the plasma charging studies. All of the grain charge measurements were made by observing the electrophoresis of the grains through the background gas in an externally applied electric field. The mobility of spherical grains varies proportionally with the ratio q/r. The mobility was independent of radius observed in the experiments.

  7. Toward a reference ultrasonic cavitation vessel: Part 2--investigating the spatial variation and acoustic pressure threshold of inertial cavitation in a 25 kHz ultrasound field.

    PubMed

    Hodnett, Mark; Zeqiri, Bajram

    2008-08-01

    As part of an ongoing project to establish a reference facility for acoustic cavitation at the National Physical Laboratory (NPL), carefully controlled studies on a 25 kHz, 1.8 kW cylindrical vessel are described. Using a patented high-frequency acoustic emission detection method and a sonar hydrophone, results are presented of the spatial variation of inertial acoustic cavitation with increasing peak-negative pressure. Results show that at low operating levels, inertial acoustic cavitation is restricted to, and is strongly localized on, the vessel axis. At intermediate power settings, inertial acoustic cavitation also occurs close to the vessel walls, and at higher settings, a complex spatial variation is seen that is not apparent in measurements of the 25 kHz driving field alone. At selected vessel locations, a systematic investigation of the inertial cavitation threshold is described. This was carried out by making simultaneous measurements of the peak-negative pressures leading to inertial cavitation and the resultant MHz-frequency emissions, and indicates an inertial cavitation threshold of 101 kPa +/- 14% (estimated expanded uncertainty). However, an intermediate threshold at 84 kPa +/- 14% (estimated expanded uncertainty) is also seen. The results are discussed alongside theoretical predictions and recent experimental findings.

  8. Opto-acoustic cell permeation

    SciTech Connect

    Visuri, S R; Heredia, N

    2000-03-09

    Optically generated acoustic waves have been used to temporarily permeate biological cells. This technique may be useful for enhancing transfection of DNA into cells or enhancing the absorption of locally delivered drugs. A diode-pumped frequency-doubled Nd:YAG laser operating at kHz repetition rates was used to produce a series of acoustic pulses. An acoustic wave was formed via thermoelastic expansion by depositing laser radiation into an absorbing dye. Generated pressures were measured with a PVDF hydrophone. The acoustic waves were transmitted to cultured and plated cells. The cell media contained a selection of normally- impermeable fluorescent-labeled dextran dyes. Following treatment with the opto-acoustic technique, cellular incorporation of dyes, up to 40,000 Molecular Weight, was noted. Control cells that did not receive opto-acoustic treatment had unremarkable dye incorporation. Uptake of dye was quantified via fluorescent microscopic analysis. Trypan Blue membrane exclusion assays and fluorescent labeling assays confirmed the vitality of cells following treatment. This method of enhanced drug delivery has the potential to dramatically reduce required drug dosages and associated side effects and enable revolutionary therapies.

  9. Acoustic anisotropy of hcp metals at high pressure: the example of cobalt

    NASA Astrophysics Data System (ADS)

    Antonangeli, D.; Occelli, F.; Aracne, C.; Farber, D.; Guyot, F.; Requardt, H.; Fiquet, G.; Krisch, M.

    2003-04-01

    Beyond studies of the bulk properties of the Earth's core, seismological studies show that the inner core is elastically anisotropic (e.g. Woodhouse et al., Geophys. Res. Lett. 13, 1549, 1986). with an axial symmetry and an amplitude of about 3%, with the fast direction oriented parallel to the Earth's rotation axis. Several hypotheses have been proposed to explain this feature, however the anisotropy of hcp iron at very high pressure is not quantitatively known. Indeed, theoretical results predict a rather low intrinsic anisotropy, almost requiring a perfect alignment of iron hcp crystals in order to account for the observed seismic anisotropy (Stixrude and Cohen, Science, 267, 1972, 1995). On the other hand, texture x-ray diffraction measurements of iron at very high-pressure (Mao et al., Nature 399, 280, 1999; Wenk et al., Nature 405, 1044, 2000) indicate a large compressional-wave anisotropy which relieves the "perfect alignment" textural constraint. The anisotropy proposed by texture measurements, when compared to calculations, is not only different in magnitude, but as well in direction. In order to settle these discrepancies among the various indirect experimental techniques and theory, a direct experimental determination of the elastic constants of hcp iron and their evolution with pressure and temperature is needed. However, obtaining single crystals of hcp-Fe at high pressure is currently not possible. To address the issue of elastic anisotropy, we present results obtained on cobalt. Unlike iron, hcp cobalt is stable at room temperature and ambient pressure to at least 79 GPa (Fujihisa and Takemura, Phys. Rev. B 54, 5, 1996). Cobalt is located next to iron in the 3d transition metals classification and exhibits similar thermo-elastic behaviour in its highly compact hcp-structure, which should make of cobalt a good proxy for iron at high-pressure. The five independent elastic constants (C11, C33, C44, C12, C13) and their pressure dependence have been

  10. Effects of an acoustic diode on the pressure waveform and cavitation bubble dynamics produced by a piezoelectric shock wave generator

    NASA Astrophysics Data System (ADS)

    Zhu, Songlin; Zhong, Pei

    2003-10-01

    High-speed schlieren imaging, combined with fiber optical probe hydrophone (FOPH) and passive cavitation detection (PCD) were used to access the effects of an acoustic diode (AD) on the pressure waveform and associated cavitation activities produced by a piezoelectric shock wave (PSW) generator. Without the AD, a typical pressure waveform at the focus of the PSW generator consists of a leading shock wave, followed by a tensile wave and several oscillation waves (OWs) of gradually reduced amplitudes. When the AD was placed 30 mm in front of the focus, the amplitude of the tensile wave was reduced and the subsequent OWs were removed. The pulse intensity integral of the tensile wave was reduced by 58%, and subsequently, PSW-induced bubble dynamics were altered significantly. Based on PCD data, the collapse time of cavitation bubble(s) was reduced by about 11%. Although intensive collapse of microbubbles was observed in about 10 μs following the shock front of the original PSW, the forced collapse of microbubbles was not observed when the AD was used, presumably due to the removal of the OWs. Theoretical calculation based on the Gilmore model confirmed these experimental observations. [Work supported by the Whitaker Foundation and NIH.

  11. Optically selective, acoustically resonant gas detecting transducer

    NASA Technical Reports Server (NTRS)

    Dimeff, J. (Inventor)

    1977-01-01

    A gas analyzer is disclosed which responds to the resonant absorption or emission spectrum of a specific gas by producing an acoustic resonance in a chamber containing a sample of that gas, and which measures the amount of that emission or absorption by measuring the strength of that acoustic resonance, e.g., the maximum periodic pressure, velocity or density achieved. In the preferred embodiment, a light beam is modulated periodically at the acoustical resonance frequency of a closed chamber which contains an optically dense sample of the gas of interest. Periodic heating of the absorbing gas by the light beam causes a cyclic expansion, movement, and pressure within the gas. An amplitude is reached where the increased losses were the cyclic radiation energy received. A transducing system is inclined for converting the pressure variations of the resonant gas into electronic readout signals.

  12. EFFECTS OF LASER RADIATION ON MATTER: Influence of the ambient air pressure on short-wavelength radiation from a laser plasma

    NASA Astrophysics Data System (ADS)

    Golovin, A. F.; Zemtsov, S. S.; Fedyushin, B. T.

    1991-12-01

    A detailed experimental investigation was made of the radiation from a plasma created on an aluminum target by a pulsed CO2 laser at different ambient gas pressures. Measurements were made of the energy and angular distribution of the radiation and of the efficiency of conversion of laser energy into reemitted plasma radiation. The intensity of this radiation was found to exhibit pressure-dependent pulsations. The maximum reflection of the laser radiation from the plasma was recorded at a pressure of ~ 40 Torr. An interpretation is given of the experimental data.

  13. How Significant is Radiation Pressure in the Dynamics of the Gas around Young Stellar Clusters?

    NASA Astrophysics Data System (ADS)

    Silich, Sergiy; Tenorio-Tagle, Guillermo

    2013-03-01

    The impact of radiation pressure on the dynamics of the gas in the vicinity of young stellar clusters is thoroughly discussed. The radiation over the thermal/ram pressure ratio time evolution is calculated explicitly and the crucial roles of the cluster mechanical power, the strong time evolution of the ionizing photon flux, and the bolometric luminosity of the exciting cluster are stressed. It is shown that radiation has only a narrow window of opportunity to dominate the wind-driven shell dynamics. This may occur only at early stages of the bubble evolution and if the shell expands into a dusty and/or a very dense proto-cluster medium. The impact of radiation pressure on the wind-driven shell always becomes negligible after about 3 Myr. Finally, the wind-driven model results allow one to compare the model predictions with the distribution of thermal pressure derived from X-ray observations. The shape of the thermal pressure profile then allows us to distinguish between the energy and the momentum-dominated regimes of expansion and thus conclude whether radiative losses of energy or the leakage of hot gas from the bubble interior have been significant during bubble evolution.

  14. HOW SIGNIFICANT IS RADIATION PRESSURE IN THE DYNAMICS OF THE GAS AROUND YOUNG STELLAR CLUSTERS?

    SciTech Connect

    Silich, Sergiy; Tenorio-Tagle, Guillermo

    2013-03-01

    The impact of radiation pressure on the dynamics of the gas in the vicinity of young stellar clusters is thoroughly discussed. The radiation over the thermal/ram pressure ratio time evolution is calculated explicitly and the crucial roles of the cluster mechanical power, the strong time evolution of the ionizing photon flux, and the bolometric luminosity of the exciting cluster are stressed. It is shown that radiation has only a narrow window of opportunity to dominate the wind-driven shell dynamics. This may occur only at early stages of the bubble evolution and if the shell expands into a dusty and/or a very dense proto-cluster medium. The impact of radiation pressure on the wind-driven shell always becomes negligible after about 3 Myr. Finally, the wind-driven model results allow one to compare the model predictions with the distribution of thermal pressure derived from X-ray observations. The shape of the thermal pressure profile then allows us to distinguish between the energy and the momentum-dominated regimes of expansion and thus conclude whether radiative losses of energy or the leakage of hot gas from the bubble interior have been significant during bubble evolution.

  15. Acoustic radiation force on an air bubble and soft fluid spheres in ideal liquids: Example of a high-order Bessel beam of quasi-standing waves

    NASA Astrophysics Data System (ADS)

    Mitri, F. G.

    2009-04-01

    The partial wave series for the scattering of a high-order Bessel beam (HOBB) of acoustic quasi-standing waves by an air bubble and fluid spheres immersed in water and centered on the axis of the beam is applied to the calculation of the acoustic radiation force. A HOBB refers to a type of beam having an axial amplitude null and an azimuthal phase gradient. Radiation force examples obtained through numerical evaluation of the radiation force function are computed for an air bubble, a hexane, a red blood and mercury fluid spheres in water. The examples were selected to illustrate conditions having progressive, standing and quasi-standing waves with appropriate selection of the waves’ amplitude ratio. An especially noteworthy result is the lack of a specific vibrational mode contribution to the radiation force determined by appropriate selection of the HOBB parameters.

  16. A dynamic pressure view cell for acoustic stimulation of fluids—Micro-bubble generation and fluid movement in porous media

    NASA Astrophysics Data System (ADS)

    Stewart, Robert A.; Shaw, J. M.

    2015-09-01

    The development and baseline operation of an acoustic view cell for observing fluids, and fluid-fluid and fluid-solid interfaces in porous media over the frequency range of 10-5000 Hz is described. This range includes the industrially relevant frequency range 500-5000 Hz that is not covered by existing devices. Pressure waveforms of arbitrary shape are generated in a 17.46 mm ID by 200 mm and 690.5 mm long glass tubes at flow rates up to 200 ml/min using a syringe pump. Peak-to-peak amplitudes exceeding 80 kPa are readily realized at frequencies from 10 to 5000 Hz in bubble free fluids when actuated with 20 Vpp as exemplified using castor oil. At resonant frequencies, peak-to-peak pressure amplitudes exceeding 500 kPa were obtained (castor oil at 2100 Hz when actuated with 20 Vpp). Impacts of vibration on macroscopic liquid-liquid and liquid-vapour interfaces and interface movement are illustrated. Pressure wave transmission and attenuation in a fluid saturated porous medium, randomly packed 250-330 μm spherical silica beads, is also demonstrated. Attenuation differences and frequency shifts in resonant peaks are used to detect the presence and generation of dispersed micro-bubbles (<180 μm diameter), and bubbles within porous media that are not readily visualized. Envisioned applications include assessment of the impacts of vibration on reaction, mass transfer, and flow/flow pattern outcomes. This knowledge will inform laboratory and pilot scale process studies, where nuisance vibrations may affect the interpretation of process outcomes, and large scale or in situ processes in aquifers or hydrocarbon reservoirs where imposed vibration may be deployed to improve aspects of process performance. Future work will include miscible interface observation and quantitative measurements in the bulk and in porous media where the roles of micro-bubbles comprise subjects of special interest.

  17. A dynamic pressure view cell for acoustic stimulation of fluids--Micro-bubble generation and fluid movement in porous media.

    PubMed

    Stewart, Robert A; Shaw, J M

    2015-09-01

    The development and baseline operation of an acoustic view cell for observing fluids, and fluid-fluid and fluid-solid interfaces in porous media over the frequency range of 10-5000 Hz is described. This range includes the industrially relevant frequency range 500-5000 Hz that is not covered by existing devices. Pressure waveforms of arbitrary shape are generated in a 17.46 mm ID by 200 mm and 690.5 mm long glass tubes at flow rates up to 200 ml/min using a syringe pump. Peak-to-peak amplitudes exceeding 80 kPa are readily realized at frequencies from 10 to 5000 Hz in bubble free fluids when actuated with 20 Vpp as exemplified using castor oil. At resonant frequencies, peak-to-peak pressure amplitudes exceeding 500 kPa were obtained (castor oil at 2100 Hz when actuated with 20 Vpp). Impacts of vibration on macroscopic liquid-liquid and liquid-vapour interfaces and interface movement are illustrated. Pressure wave transmission and attenuation in a fluid saturated porous medium, randomly packed 250-330 μm spherical silica beads, is also demonstrated. Attenuation differences and frequency shifts in resonant peaks are used to detect the presence and generation of dispersed micro-bubbles (<180 μm diameter), and bubbles within porous media that are not readily visualized. Envisioned applications include assessment of the impacts of vibration on reaction, mass transfer, and flow/flow pattern outcomes. This knowledge will inform laboratory and pilot scale process studies, where nuisance vibrations may affect the interpretation of process outcomes, and large scale or in situ processes in aquifers or hydrocarbon reservoirs where imposed vibration may be deployed to improve aspects of process performance. Future work will include miscible interface observation and quantitative measurements in the bulk and in porous media where the roles of micro-bubbles comprise subjects of special interest.

  18. Axial and transverse acoustic radiation forces on a fluid sphere placed arbitrarily in Bessel beam standing wave tweezers

    NASA Astrophysics Data System (ADS)

    Mitri, F. G.

    2014-03-01

    The axial and transverse radiation forces on a fluid sphere placed arbitrarily in the acoustical field of Bessel beams of standing waves are evaluated. The three-dimensional components of the time-averaged force are expressed in terms of the beam-shape coefficients of the incident field and the scattering coefficients of the fluid sphere using a partial-wave expansion (PWE) method. Examples are chosen for which the standing wave field is composed of either a zero-order (non-vortex) Bessel beam, or a first-order Bessel vortex beam. It is shown here, that both transverse and axial forces can push or pull the fluid sphere to an equilibrium position depending on the chosen size parameter ka (where k is the wave-number and a the sphere's radius). The corresponding results are of particular importance in biophysical applications for the design of lab-on-chip devices operating with Bessel beams standing wave tweezers. Moreover, potential investigations in acoustic levitation and related applications in particle rotation in a vortex beam may benefit from the results of this study.

  19. Computation of instantaneous and time-averaged active acoustic intensity field around rotating source

    NASA Astrophysics Data System (ADS)

    Mao, Yijun; Xu, Chen; Qi, Datong

    2015-02-01

    A vector aeroacoustics method is developed to analyze the acoustic energy flow path from the rotating source. In this method, the instantaneous and time-averaged active acoustic intensity vectors are evaluated from the time-domain and frequency-domain acoustic pressure and acoustic velocity formulations, respectively. With the above method, the acoustic intensity vectors and the acoustic energy streamlines are visualized to investigate the propagation feature of the noise radiated from the monopole and dipole point sources and the rotor in subsonic rotation. The result reveals that a portion of the acoustic energy spirals many circles before moving towards the far field, and another portion of the acoustic energy firstly flows inward along the radial direction and then propagates along the axial direction. Further, an acoustic black hole exists in the plane of source rotation, from which the acoustic energy cannot escape once the acoustic energy flows into it. Moreover, by visualizing the acoustic intensity field around the rotating sources, the acoustic-absorption performance of the acoustic liner built in the casing and centerbody is discussed.

  20. Acoustic and aerodynamic performance of a 1.83 meter (6 foot) diameter 1.2 pressure ratio fan (QF-6). [for short takeoff aircraft

    NASA Technical Reports Server (NTRS)

    Woodward, R. P.; Lucas, J. G.; Stakolich, E. G.

    1974-01-01

    A 1.2-pressure-ratio, 1.83-meter-(6-ft-) diameter experimental fan stage with characteristics suitable for use in STOL aircraft engines was tested for acoustic and aerodynamic performance. The design incorporated features for low noise, including absence of inlet guide vanes, low rotor-blade-tip speed, low aerodynamic blade loading, and long axial spacing between the rotor and stator rows. The stage was run with four nozzles of different area. The perceived noise along a 152.4 meter (500-ft) sideline was rear-quadrant dominated with a maximum design-point level of 103.9 PNdb. The acoustic 1/3-octave results were analytically separated into broadband and pure-tone components. It was found that the stage noise levels generally increase with a decrease in nozzle area, with this increase observed primarily in the broadband noise component. A stall condition was documented acoustically with a 90-percent-of-design-area nozzle.

  1. Acousto-optic Bragg diffraction in paratellurite by the sidelobes of the spatial radiation spectrum of an acoustic transducer

    NASA Astrophysics Data System (ADS)

    Kotov, V. M.

    2016-09-01

    Acousto-optic Bragg diffraction in paratellurite is investigated within the two first diffraction orders for the case of diffraction by the sidelobes of the spatial radiation spectrum of an acoustic transducer. One of the diffraction orders is due to anisotropic diffraction, and the other, to isotropic diffraction. Such a diffraction regime is achieved when the diffraction plane is inclined toward the optical axis of the crystal. For light with a wavelength of 0.63 × 10-4 cm diffracted by a "slow" sound wave with a frequency of 26 MHz, the effect manifests itself when the angle between the acousto-optic diffraction plane and the optical axis of paratellurite is ~3°. The effect is experimentally verified. The diffraction efficiency is 20% for each of the diffraction orders for a microwave signal of 8 V at the transducer.

  2. Behavioral consequences of radiation exposure to simulated space radiation in the C57BL/6 mouse: open field, rotorod, and acoustic startle

    NASA Technical Reports Server (NTRS)

    Pecaut, Michael J.; Haerich, Paul; Zuccarelli, Cara N.; Smith, Anna L.; Zendejas, Eric D.; Nelson, Gregory A.

    2002-01-01

    Two experiments were carried out to investigate the consequences of exposure to proton radiation, such as might occur for astronauts during space flight. C57BL/6 mice were exposed, either with or without 15-g/cm2 aluminum shielding, to 0-, 3-, or 4-Gy proton irradiation mimicking features of a solar particle event. Irradiation produced transient direct deficits in open-field exploratory behavior and acoustic startle habituation. Rotorod performance at 18 rpm was impaired by exposure to proton radiation and was impaired at 26 rpm, but only for mice irradiated with shielding and at the 4-Gy dose. Long-term (>2 weeks) indirect deficits in open-field activity appeared as a result of impaired experiential encoding immediately following exposure. A 2-week recovery prior to testing decreased most of the direct effects of exposure, with only rotorod performance at 26 rpm being impaired. These results suggest that the performance deficits may have been mediated by radiation damage to hippocampal, cerebellar, and possibly, forebrain dopaminergic function.

  3. Quantum optomechanical correlations induced by radiation pressure between light and mirrors

    NASA Astrophysics Data System (ADS)

    Briant, T.; Verlot, P.; Tavernarakis, A.; Cohadon, P.-F.; Heidmann, A.

    2009-02-01

    Radiation pressure exerted by light in interferometric measurements is responsible for displacements of mirrors which appear as an additional back-action noise and limit the sensitivity of the measurement. We experimentally study these effects by monitoring in a very high-finesse optical cavity the displacements of a mirror with a sensitivity at the 10-20m/√Hz level. This unique sensitivity is a step towards the first observation of the fundamental quantum effects of radiation pressure and the resulting standard quantum limit in interferometric measurements. Our experiment may become a powerful facility to test quantum noise reduction schemes, and we already have demonstrated radiation-pressure induced correlations between two optical beams sent into the same moving mirror cavity. Our scheme can be extended down to the quantum level and has applications both in high-sensitivity measurements and in quantum optics.

  4. Observation of radiation-pressure effects and back-action cancellation in interferometric measurements

    NASA Astrophysics Data System (ADS)

    Heidmann, A.; Caniard, T.; Verlot, P.; Briant, T.; Cohadon, P.-F.

    2008-02-01

    Radiation pressure exerted by light in interferometric measurements is responsible for displacements of mirrors which appear as an additional back-action noise and limit the sensitivity of the measurement. We experimentally study these effects by monitoring in a very highfinesse optical cavity the displacements of a mirror with a sensitivity at the 10 -20 m/√Hz level. This unique sensitivity is a step towards the first observation of the fundamental quantum effects of radiation pressure and the resulting standard quantum limit in interferometric measurements. Our experiment may become a powerful facility to test quantum noise reduction schemes, and we already report the first experimental demonstration of a back-action noise cancellation. Using a classical radiation-pressure noise to mimic the quantum noise of light, we have observed a drastic improvement of sensitivity both in position and force measurements.

  5. Radiation pressure acceleration of protons to 93 MeV with circularly polarized petawatt laser pulses

    NASA Astrophysics Data System (ADS)

    Kim, I. Jong; Pae, Ki Hong; Choi, Il Woo; Lee, Chang-Lyoul; Kim, Hyung Taek; Singhal, Himanshu; Sung, Jae Hee; Lee, Seong Ku; Lee, Hwang Woon; Nickles, Peter V.; Jeong, Tae Moon; Kim, Chul Min; Nam, Chang Hee

    2016-07-01

    The radiation pressure acceleration (RPA) of charged particles has been a challenging task in laser-driven proton/ion acceleration due to its stringent requirements in laser and target conditions. The realization of radiation-pressure-driven proton acceleration requires irradiating ultrathin targets with an ultrahigh contrast and ultraintense laser pulses. We report the generation of 93-MeV proton beams achieved by applying 800-nm 30-fs circularly polarized laser pulses with an intensity of 6.1 × 10 20 W / cm 2 to 15-nm-thick polymer targets. The radiation pressure acceleration was confirmed from the obtained optimal target thickness, quadratic energy scaling, polarization dependence, and three-dimensional particle-in-cell simulations. We expect this clear demonstration of RPA to facilitate the realization of laser-driven proton/ion sources delivering energetic and short-pulse particle beams for novel applications.

  6. The effects of pulse duration on ablation pressure driven by laser radiation

    SciTech Connect

    Zhou, Lei; Li, Xiao-Ya Zhu, Wen-Jun; Wang, Jia-Xiang; Tang, Chang-Jian

    2015-03-28

    The effects of laser pulse duration on the ablation pressure induced by laser radiation are investigated using Al target. Numerical simulation results using one dimensional radiation hydro code for laser intensities from 5×10{sup 12}W/cm{sup 2} to 5×10{sup 13}W/cm{sup 2} and pulse durations from 0.5 ns to 20 ns are presented. These results suggest that the laser intensity scaling law of ablation pressure differs for different pulse durations. And the theoretical analysis shows that the effects of laser pulse duration on ablation pressure are mainly caused by two regimes: the unsteady-state flow and the radiative energy loss to vacuum.

  7. Constraining the minute amount of audible energy radiated from binary collisions of light plastic spheres in conditions of incomplete angular coverage of the measured pressure.

    PubMed

    Petculescu, Andi; Riner, Joshua

    2010-10-01

    Usually, the energy released as air-coupled sound following a collision is dismissed as negligible. The goal of this Letter is to quantify the value of this small but measurable quantity, since it can be useful to impact studies. Measurements of sound radiation from binary collisions of polypropylene balls were performed in order to constrain the fraction of incident energy radiated as sound in air. In the experiments, one ball is released from rest, directly above a stationary target ball. The transient acoustic waveforms are detected by a microphone rotated about the impact point at a radius of 10 cm. The sound pressure was measured as a function of the polar angle θ (the azimuthal symmetry of the problem was verified by rotating the microphone in the horizontal plane). The angular pattern has two main lobes that are asymmetric with respect to the impact plane. This asymmetry is ascribable to interference and/or scattering effects. Gaps in the acoustic measurements at the "poles" (i.e., around 0° and 180°) pose a challenge similar to that of extrapolating the cosmic microwave background in the galactic "cut." The data was continued in the gaps by polynomial interpolation rather than least-squares fitting, a choice dictated by the accuracy of the reconstructed pattern. The acoustic energy radiated during the impact, estimated by multiplying the collision time by the sound intensity integrated over a spherical surface centered at the impact point, is calculated as four orders of magnitude smaller than the incident energy (0.23 μJ versus 1.6 mJ).

  8. Radiation pressure force from optical cycling on a polyatomic molecule

    NASA Astrophysics Data System (ADS)

    Kozyryev, Ivan; Baum, Louis; Matsuda, Kyle; Hemmerling, Boerge; Doyle, John M.

    2016-07-01

    We demonstrate multiple photon cycling and radiative force deflection on the triatomic free radical strontium monohydroxide (SrOH). Optical cycling is achieved on SrOH in a cryogenic buffer-gas beam by employing the rotationally closed P(N\\prime\\prime =1) branch of the vibronic transition {\\tilde{X}}2{{{Σ }}}+(000)≤ftrightarrow {\\tilde{A}}2{{{\\Pi }}}1/2(000). A single repumping laser excites the Sr-O stretching vibrational mode, and photon cycling of the molecule deflects the SrOH beam by an angle of 0.2^\\circ via scattering of ˜100 photons per molecule. This approach can be used for direct laser cooling of SrOH and more complex, isoelectronic species.

  9. The effects of pressure sensor acoustics on airdata derived from a High-angle-of-attack Flush Airdata Sensing (HI-FADS) system

    NASA Technical Reports Server (NTRS)

    Whitmore, Stephen A.; Moes, Timothy R.

    1991-01-01

    The accuracy of a nonintrusive high angle-of-attack flush airdata sensing (HI-FADS) system was verified for quasi-steady flight conditions up to 55 deg angle of attack during the F-18 High Alpha Research Vehicle (HARV) Program. The system is a matrix of nine pressure ports arranged in annular rings on the aircraft nose. The complete airdata set is estimated using nonlinear regression. Satisfactory frequency response was verified to the system Nyquist frequency (12.5 Hz). The effects of acoustical distortions within the individual pressure sensors of the nonintrusive pressure matrix on overall system performance are addressed. To quantify these effects, a frequency-response model describing the dynamics of acoustical distortion is developed and simple design criteria are derived. The model adjusts measured HI-FADS pressure data for the acoustical distortion and quantifies the effects of internal sensor geometries on system performance. Analysis results indicate that sensor frequency response characteristics very greatly with altitude, thus it is difficult to select satisfactory sensor geometry for all altitudes. The solution used presample filtering to eliminate resonance effects, and short pneumatic tubing sections to reduce lag effects. Without presample signal conditioning the system designer must use the pneumatic transmission line to attenuate the resonances and accept the resulting altitude variability.

  10. Study of noise sources in a subsonic fan using measured blade pressures and acoustic theory

    NASA Technical Reports Server (NTRS)

    Hanson, D. B.

    1975-01-01

    Sources of noise in a 1.4 m (4.6 ft) diameter subsonic tip speed propulsive fan running statically outdoors are studied using a combination of techniques. Signals measured with pressure transducers on a rotor blade are plotted in a format showing the space-time history of inlet distortion. Study of these plots visually and with statistical correlation analysis confirms that the inlet flow contains long, thin eddies of turbulence. Turbulence generated in the boundary layer of the shroud upstream of the rotor tips was not found to be an important noise source. Fan noise is diagnosed by computing narrowband spectra of rotor and stator sound power and comparing these with measured sound power spectra. Rotor noise is computed from spectra of the measured blade pressures and stator noise is computed using the author's stator noise theory. It is concluded that the rotor and stator sources contribute about equally at frequencies in the vicinity of the first three harmonics of blade passing frequency. At higher frequencies, the stator contribution diminishes rapidly and the rotor/inlet turbulence mechanism dominates. Two parametric studies are performed by using the rotor noise calculation procedure which was correlated with test. In the first study, the effects on noise spectrum and directivity are calculated for changes in turbulence properties, rotational Mach number, number of blades, and stagger angle. In the second study the influences of design tip speed and blade number on noise are evaluated.

  11. Control of tetrahedron satellite formation flying in the geosynchronous orbit using solar radiation pressure

    NASA Astrophysics Data System (ADS)

    Hou, Yong-Gang; Zhang, Ming-Jiang; Zhao, Chang-Yin; Sun, Rong-Yu

    2016-04-01

    In this paper, the control of tetrahedron satellite formation flying in the geosynchronous orbit (GEO) using solar radiation pressure is investigated. The long term disturbing effect of the main zonal and tesseral harmonics J2 and J_{22} of the geopotential are eliminated by adjusting the initial orbital elements, and a tetrahedron satellite formation flying in the GEO is designed. Then a control system using solar radiation pressure is further proposed to maintain the tetrahedron satellite formation, in which a sliding mode control (SMC) is developed to determine the control force. The control force is acquired from the solar sails equipped on the satellites, and the final control law and strategy using solar radiation pressure are presented. Moreover, three kinds of numerical simulations are especially given to verify the validity of the control system using solar radiation. It shows that Laplace precession of the GEO satellite can be avoided effectively, and the in-plane and out-of-plane errors of the formation can be eliminated easily. And hence the control of tetrahedron satellite formation flying in the GEO using solar radiation pressure is proved to be feasible.

  12. Particle sizes in Comet Bennett /1970 II/. [radiation pressure models for coma and tail

    NASA Technical Reports Server (NTRS)

    O'Dell, C. R.

    1974-01-01

    The particle size distribution in the coma and tail of Comet Bennett has been determined by several methods, each sensitive to a particular size range. It is confirmed that a minimum value of the particle density, size, and radiation pressure efficiency function exists at about .00003 to .00010 g/sq cm. The existence of such a cutoff is probably due to the decreasing radiation pressure efficiency for particles smaller than the wavelength of the light being scattered. An exact determination of this cutoff may allow identification of the particle type.

  13. Surface deformation effects induced by radiation pressure and electrostriction forces in dielectric solids

    NASA Astrophysics Data System (ADS)

    Astrath, N. G. C.; Lukasievicz, G. V. B.; Malacarne, L. C.; Bialkowski, S. E.

    2013-06-01

    The surface displacement produced by radiation pressure and electrostriction forces is investigated considering the commonly accepted theories proposed by Minkowski and Abraham for the energy-momentum tensor. The contributions are modeled considering each effect separately assuming non-absorbing and absorbing solids and the thermoelastic deformation equations are solved numerically. We show that the surface deformation profiles as calculated by the Minkowski or Abraham momenta give different surface curvature, which could in principle be detected by measuring the surface displacement. Finally, an all-optical pump-probe photothermal method to detect the radiation pressure and electrostriction forces in transparent dielectric solids is proposed.

  14. Exospheric perturbations by radiation pressure. 2: Solution for orbits in the ecliptic plane

    NASA Technical Reports Server (NTRS)

    Chamberlain, J. W.

    1980-01-01

    The instantaneous rates of change for the orbital elements eccentricity, longitude of perigee from the Sun, and longitude from the Sun of the ascending node are integrated simultaneously for the case of the inclination i = 0. The results confirm the validity of using mean rates when the orbits are tightly bound to the planet and serve as examples to be reproduced by the complicated numerical solutions required for arbitrary inclination. Strongly bound hydrogen atoms escaping from Earth due to radiation pressure do not seem a likely cause of the geotail extending in the anti-sun direction. Instead, radiation pressure will cause those particles' orbits to deteriorate into the Earth's atmosphere.

  15. Radiation pressure and gas drag forces on a melamine-formaldehyde microsphere in a dusty plasma

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Goree, J.; Nosenko, V.; Boufendi, L.

    2003-01-01

    Measurements are reported for the radiation pressure and gas drag forces acting on a single melamine-formaldehyde microsphere. The radiation pressure force coefficient q, which would be unity if all incident photons were absorbed, has the value q=0.94±0.11. For argon, the Epstein gas drag force coefficient δ, which would be unity if impinging molecules underwent specular reflection, has the value δ=1.26±0.13 as measured with our single-particle laser acceleration method, or δ=1.44±0.19 as measured using the vertical resonance method.

  16. Temporal Behavior of Radiation-Pressure-Induced Vibrations of an Optical Microcavity Phonon Mode

    NASA Astrophysics Data System (ADS)

    Carmon, Tal; Rokhsari, Hossein; Yang, Lan; Kippenberg, Tobias J.; Vahala, Kerry J.

    2005-06-01

    We analyze experimentally and theoretically mechanical oscillation within an optical cavity stimulated by the pressure of circulating optical radiation. The resulting radio frequency cavity vibrations (phonon mode) cause modulation of the incident, continuous-wave (cw) input pump beam. Furthermore, with increasing cw pump power, an evolution from sinusoidal modulation to random oscillations is observed in the pump power coupled from the resonator. The temporal evolution with pump power is studied, and agreement was found with theory. In addition to applications in quantum optomechanics, the present work suggests that radiation-pressure-induced effects can establish a practical limit for the miniaturization of optical silica microcavities.

  17. Effect of electromagnetic pulse transverse inhomogeneity on ion acceleration by radiation pressure

    SciTech Connect

    Lezhnin, K. V.; Kamenets, F. F.; Beskin, V. S.; Kando, M.; Esirkepov, T. Zh.; Bulanov, S. V.

    2015-03-15

    During ion acceleration by radiation pressure, a transverse inhomogeneity of an electromagnetic pulse leads to an off-axis displacement of the irradiated target, limiting the achievable ion energy. This effect is analytically described within the framework of a thin foil target model and with particle-in-cell simulations showing that the maximum energy of the accelerated ions decreases as the displacement from the axis of the target's initial position increases. The results obtained can be applied to the optimization of ion acceleration by the laser radiation pressure with mass-limited targets.

  18. Acoustic method for levitation of small living animals

    NASA Astrophysics Data System (ADS)

    Xie, W. J.; Cao, C. D.; Lü, Y. J.; Hong, Z. Y.; Wei, B.

    2006-11-01

    Ultrasonic levitation of some small living animals such as ant, ladybug, and young fish has been achieved with a single-axis acoustic levitator. The vitality of ant and ladybug is not evidently influenced during the acoustic levitation, whereas that of the young fish is reduced because of the inadequacy of water supply. Numerical analysis shows that the sound pressures on the ladybug's surface almost reach the incident pressure amplitude p0 due to sound scattering. It is estimated that 99.98% of the acoustic energy is reflected away from the ladybug. The acoustic radiation pressure pa on the ladybug's surface is only 1%-3% of p0, which plays a compression role on the central region and a suction role on the peripheral region.

  19. Acoustic detection of cracks in the anvil of a large-volume cubic high-pressure apparatus

    NASA Astrophysics Data System (ADS)

    Yan, Zhaoli; Chen, Bin; Tian, Hao; Cheng, Xiaobin; Yang, Jun

    2015-12-01

    A large-volume cubic high-pressure apparatus with three pairs of tungsten carbide anvils is the most popular device for synthetic diamond production. Currently, the consumption of anvils is one of the important costs for the diamond production industry. If one of the anvils is fractured during the production process, the other five anvils in the apparatus may be endangered as a result of a sudden loss of pressure. It is of critical importance to detect and replace cracked anvils before they fracture for reduction of the cost of diamond production and safety. An acoustic detection method is studied in this paper. Two new features, nested power spectrum centroid and modified power spectrum variance, are proposed and combined with linear prediction coefficients to construct a feature vector. A support vector machine model is trained for classification. A sliding time window is proposed for decision-level information fusion. The experiments and analysis show that the recognition rate of anvil cracks is 95%, while the false-alarm rate is as low as 5.8 × 10-4 during a time window; this false-alarm rate indicates that at most one false alarm occurs every 2 months at a confidence level of 90%. An instrument to monitor anvil cracking was designed based on a digital signal processor and has been running for more than eight months in a diamond production field. In this time, two anvil-crack incidents occurred and were detected by the instrument correctly. In addition, no false alarms occurred.

  20. Acoustic detection of cracks in the anvil of a large-volume cubic high-pressure apparatus

    SciTech Connect

    Yan, Zhaoli Tian, Hao; Cheng, Xiaobin; Yang, Jun; Chen, Bin

    2015-12-15

    A large-volume cubic high-pressure apparatus with three pairs of tungsten carbide anvils is the most popular device for synthetic diamond production. Currently, the consumption of anvils is one of the important costs for the diamond production industry. If one of the anvils is fractured during the production process, the other five anvils in the apparatus may be endangered as a result of a sudden loss of pressure. It is of critical importance to detect and replace cracked anvils before they fracture for reduction of the cost of diamond production and safety. An acoustic detection method is studied in this paper. Two new features, nested power spectrum centroid and modified power spectrum variance, are proposed and combined with linear prediction coefficients to construct a feature vector. A support vector machine model is trained for classification. A sliding time window is proposed for decision-level information fusion. The experiments and analysis show that the recognition rate of anvil cracks is 95%, while the false-alarm rate is as low as 5.8 × 10{sup −4} during a time window; this false-alarm rate indicates that at most one false alarm occurs every 2 months at a confidence level of 90%. An instrument to monitor anvil cracking was designed based on a digital signal processor and has been running for more than eight months in a diamond production field. In this time, two anvil-crack incidents occurred and were detected by the instrument correctly. In addition, no false alarms occurred.