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Sample records for acoustic field radiated

  1. Multimodal far-field acoustic radiation pattern: An approximate equation

    NASA Technical Reports Server (NTRS)

    Rice, E. J.

    1977-01-01

    The far-field sound radiation theory for a circular duct was studied for both single mode and multimodal inputs. The investigation was intended to develop a method to determine the acoustic power produced by turbofans as a function of mode cut-off ratio. With reasonable simplifying assumptions the single mode radiation pattern was shown to be reducible to a function of mode cut-off ratio only. With modal cut-off ratio as the dominant variable, multimodal radiation patterns can be reduced to a simple explicit expression. This approximate expression provides excellent agreement with an exact calculation of the sound radiation pattern using equal acoustic power per mode.

  2. 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.

  3. 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.

  4. 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.

  5. Acoustic radiation torque on an irregularly shaped scatterer in an arbitrary sound field.

    PubMed

    Fan, Zongwei; Mei, Deqing; Yang, Keji; Chen, Zichen

    2008-11-01

    To eliminate the limitation of the conventional acoustic radiation torque theory, which is only applicable to a disklike scatterer in a plane sound field, a new theory is established to calculate the radiation torque on any irregularly shaped scatterer in any arbitrary sound field. First, with the aid of the conservation law of angular momentum, the acoustic radiation torque is expressed as the angular momentum flux through a spherical surface with the center at the scatterer's centroid. Second, the velocity potential of the scattered field is derived, taking into account the influences of the translational and rotational movements of the scatterer induced by the first order stress of the incident sound field. Finally, a general calculating formula of the acoustic radiation torque is achieved. For a disklike scatterer in a plane sound filed, results from the above formula are well identical with those conventional formulas. By studying the case of a semicircular cylinder scatterer in a standing-wave sound field, it is found that for an irregularly shaped scatterer its rotation velocity is normally nonzero and the radiation torque changes with the spatial attitude. PMID:19045760

  6. 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

  7. 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

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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. PMID:21802702

  13. Acoustic field modeling for physiotherapy ultrasound applicators by using approximated functions of measured non-uniform radiation distributions.

    PubMed

    Gutiérrez, Mario Ibrahín; Calás, Héctor; Ramos, Antonio; Vera, Arturo; Leija, Lorenzo

    2012-08-01

    The strongest therapeutic effects in ultrasonic physiotherapy are mainly produced at the first centimeters, i.e. close to the applicator surface and, in general, only in the near-field zone. The acoustic field produced in practice by this type of transducers differs from the classical models because the vibration distribution on the real transducer surfaces is non-uniform. However, neither models using uniform distribution, nor those using typical non-uniform distribution patterns for the source accurately represent the radiation of this kind of transducers. Although this therapy is widely used and many efforts have been made in experimentally studying the patterns of ultrasound radiation produced during physiotherapy applications (IEC-61689, 1998), additional modeling researches still would be needed in order to achieve improved models giving field patterns closer to the measured ultrasonic results. In this paper, acoustic patterns produced from two source radiation functions are proposed and evaluated for field modeling of physiotherapy applicators. Both the functions are approximations to the pressure distribution measured close to the emitting surface and they are based on the modulation of the classical simply-supported function using either sinusoidal or Bessel-type distributions. The simply-supported function is accounted for the radiator-fixing condition and the modulation function simulates the complex vibration distribution of this kind of transducer. The modulator Bessel function is based on reports about Bessel-type vibration distributions found in piezoelectric disk resonators. The use of a selected sinusoidal segment represents another analytical option for obtaining an approximated behavior of the measured data in a real applicator. Both the field models are implemented using the finite element method (FEM) to obtain the numerical solution of wave equation at each point in the radiated space. The solution is reached by considering axisymmetric

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Near- to far-field characteristics of acoustic radiation through plug flow jets.

    PubMed

    Gabard, G

    2008-11-01

    This paper reports a theoretical study of the radiation of sound through jet exhausts. It focuses on the transition from near field to far field by considering the features of the near-field solution and how these features translate to the far field. The main focus of this work is the importance in some cases of lateral waves radiating from the jet. While the presence of lateral waves has long been recognized, there has been no systematic investigation of the practical consequences of these waves in the prediction of sound propagation through round jets. The physical mechanisms involved in the generation of these waves are presented as well as the conditions under which they become significant. Another issue is the possibility of "channeled waves" inside the jet associated with strong sound radiation in the forward arc. This paper also discusses the validity of the far-field approximation when lateral waves are present. It is shown that the standard far-field approximation can be improved by adding correction terms that account for the presence of the lateral waves and channeled waves. The challenge posed to computational aeroacoustics by these near-field effects is also discussed. PMID:19045763

  19. 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.

  20. Behavioral consequences of radiation exposure to simulated space radiation in the C57BL/6 mouse: open field, rotorod, and acoustic startle.

    PubMed

    Pecaut, Michael J; Haerich, Paul; Zuccarelli, Cara N; Smith, Anna L; Zendejas, Eric D; Nelson, Gregory A

    2002-12-01

    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. PMID:12641177

  1. Acoustic radiation stress in solids

    NASA Technical Reports Server (NTRS)

    Cantrell, John H.; Yost, William T.

    1986-01-01

    It is shown that the radiation-induced static strains associated with acoustic waves propagating in solids are obtained directly from the virial theorem for an elastic continuum and that the radiation stresses result from combining the virial theorem with the Boltzmann-Ehrenfest principle of adiabatic invariance. The experimental confirmation of critical theoretical predictions in solids is reported. The implications of the results for the fundamental thermal properties of crystals are addressed.

  2. 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.

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

    PubMed

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

    2016-03-01

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

  4. Numerical inverse method predicting acoustic spinning modes radiated by a ducted fan from free-field test data.

    PubMed

    Lewy, Serge

    2008-07-01

    Spinning modes generated by a ducted turbofan at a given frequency determine the acoustic free-field directivity. An inverse method starting from measured directivity patterns is interesting in providing information on the noise sources without requiring tedious spinning-mode experimental analyses. According to a previous article, equations are based on analytical modal splitting inside a cylindrical duct and on a Rayleigh or a Kirchhoff integral on the duct exit cross section to get far-field directivity. Equations are equal in number to free-field measurement locations and the unknowns are the propagating mode amplitudes (there are generally more unknowns than equations). A MATLAB procedure has been implemented by using either the pseudoinverse function or the backslash operator. A constraint comes from the fact that squared modal amplitudes must be positive which involves an iterative least squares fitting. Numerical simulations are discussed along with several examples based on tests performed by Rolls-Royce in the framework of a European project. It is assessed that computation is very fast and it well fits the measured directivities, but the solution depends on the method and is not unique. This means that the initial set of modes should be chosen according to any known physical property of the acoustic sources. PMID:18646973

  5. 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.

  6. Acoustic radiation from lifting airfoils in compressible subsonic flow

    NASA Technical Reports Server (NTRS)

    Atassi, Hafiz M.; Subramaniam, Shankar; Scott, James R.

    1990-01-01

    The far field acoustic radiation from a lifting airfoil in a three-dimensional gust is studied. The acoustic pressure is calculated using the Kirchhoff method, instead of using the classical acoustic analogy approach due to Lighthill. The pressure on the Kirchhoff surface is calculated using an existing numerical solution of the unsteady flow field. The far field acoustic pressure is calculated in terms of these values using Kirchhoff's formula. The method is validated against existing semi-analytical results for a flat plate. The method is then used to study the problem of an airfoil in a harmonic three-dimensional gust, for a wide range of Mach numbers. The effect of variation of the airfoil thickness and angle of attack on the acoustic far field is studied. The changes in the mechanism of sound generation and propagation due to the presence of steady loading and nonuniform mean flow are also studied.

  7. Acoustic radiation from lifting airfoils in compressible subsonic flow

    NASA Technical Reports Server (NTRS)

    Atassi, Hafiz M.; Subramaniam, Shankar; Scott, James R.

    1990-01-01

    The far field acoustic radiation from a lifting airfoil in a three-dimensional gust is studied. The acoustic pressure is calculated using the Kirchhoff method, instead of using the classical acoustic analogy approach due to Lighthill. The pressure on the Kirchhoff surface is calculated using an existing numerical solution of the unsteady flow field. The far field acoustic pressure is calculated in terms of these values using Kirchhoff's formula. The method is validated against existing semi-analytical results for a flat plate. The method is then used to study the problem of an airfoil in a harmonic three-dimensional gust, for a wide range of Mach numbers. The effect of variation of the airfoil thickness and angle of attack on the acoustic far field is studied. The changes in the mechanism of sound generation and propagation due to the presence of steady loading and non-uniform mean flow are also studied.

  8. A study of the acoustical radiation force considering attenuation

    NASA Astrophysics Data System (ADS)

    Wu, RongRong; Liu, XiaoZhou; Gong, XiuFen

    2013-07-01

    Acoustical tweezer is a primary application of the radiation force of a sound field. When an ultrasound focused beam passes through a micro-particle, like a cell or living biological specimens, the particle will be manipulated accurately without physical contact and invasion, due to the three-dimensional acoustical trapping force. Based on the Ray acoustics approach in the Mie regime, this work discusses the effects on the particle caused by Gaussian focused ultrasound, studies the acoustical trapping force of spherical Mie particles by ultrasound in any position, and analyzes the numerical calculation on the two-dimensional acoustical radiation force. This article also analyzes the conditions for the acoustical trapping phenomenon, and discusses the impact of the initial position and size of the particle on the magnitude of the acoustical radiation force. Furthermore, this paper considers the ultrasonic attenuation in a particle in the case of two-dimension, studies the attenuation's effects on the acoustical trapping force, and amends the calculation to the ordinary case with attenuation.

  9. Acoustic field effects on a negative corona discharge

    NASA Astrophysics Data System (ADS)

    Bálek, R.; Červenka, M.; Pekárek, S.

    2014-06-01

    For a negative corona discharge under atmospheric pressure in different regimes, we investigated the effects of an acoustic field both on its electrical parameters and on the change in its visual appearance. We found that the application of an acoustic field on the true corona discharge, for particular currents, decreases the discharge voltage. The application of an acoustic field on the discharge in the filamentary streamer regime substantially extends the range of currents for which the discharge voltage remains more or less constant, i.e. it allows a substantial increase in the power delivered to the discharge. The application of an acoustic field on the discharge causes the discharge to spread within the discharge chamber and consequently, a highly reactive non-equilibrium plasma is created throughout the inter-electrode space. Finally, our experimental apparatus radiates almost no acoustic energy from the discharge chamber.

  10. 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.

  11. Acoustic radiation torque and the conservation of angular momentum (L).

    PubMed

    Zhang, Likun; Marston, Philip L

    2011-04-01

    This note concerns the evaluation of the static acoustic radiation torque exerted by an acoustic field on a scatterer immersed in a nonviscous fluid based on far-field scattering. The radiation torque is expressed as the integral of the time-averaged flux of angular momentum over a spherical surface far removed from the scattering object with its center at the centroid of the object. That result was given previously [G. Maidanik, J. Acoust. Soc. Am. 30, 620-623 (1956)]. Another expression given recently [Z. W. Fan et al., J. Acoust. Soc. Am. 124, 2727-2732 (2008)] is simplified to this formula. Comments are made on obtaining it directly from the general theorem of angular momentum conservation in the integral form. PMID:21476624

  12. The near-field acoustic levitation of high-mass rotors

    SciTech Connect

    Hong, Z. Y.; Lü, P.; Geng, D. L.; Zhai, W.; Yan, N.; Wei, B.

    2014-10-15

    Here we demonstrate that spherical rotors with 40 mm diameter and 0-1 kg mass can be suspended more than tens of micrometers away from an ultrasonically vibrating concave surface by near-field acoustic radiation force. Their rotating speeds exceed 3000 rpm. An acoustic model has been developed to evaluate the near-field acoustic radiation force and the resonant frequencies of levitation system. This technique has potential application in developing acoustic gyroscope.

  13. The near-field acoustic levitation of high-mass rotors

    NASA Astrophysics Data System (ADS)

    Hong, Z. Y.; Lü, P.; Geng, D. L.; Zhai, W.; Yan, N.; Wei, B.

    2014-10-01

    Here we demonstrate that spherical rotors with 40 mm diameter and 0-1 kg mass can be suspended more than tens of micrometers away from an ultrasonically vibrating concave surface by near-field acoustic radiation force. Their rotating speeds exceed 3000 rpm. An acoustic model has been developed to evaluate the near-field acoustic radiation force and the resonant frequencies of levitation system. This technique has potential application in developing acoustic gyroscope.

  14. The near-field acoustic levitation of high-mass rotors.

    PubMed

    Hong, Z Y; Lü, P; Geng, D L; Zhai, W; Yan, N; Wei, B

    2014-10-01

    Here we demonstrate that spherical rotors with 40 mm diameter and 0-1 kg mass can be suspended more than tens of micrometers away from an ultrasonically vibrating concave surface by near-field acoustic radiation force. Their rotating speeds exceed 3000 rpm. An acoustic model has been developed to evaluate the near-field acoustic radiation force and the resonant frequencies of levitation system. This technique has potential application in developing acoustic gyroscope. PMID:25362441

  15. Acoustic emission sensor radiation damage threshold experiment

    SciTech Connect

    Beeson, K.M.; Pepper, C.E.

    1994-09-01

    Determination of the threshold for damage to acoustic emission sensors exposed to radiation is important in their application to leak detection in radioactive waste transport and storage. Proper response to system leaks is necessary to ensure the safe operation of these systems. A radiation impaired sensor could provide ``false negative or false positive`` indication of acoustic signals from leaks within the system. Research was carried out in the Radiochemical Technology Division at Oak Ridge National Laboratory to determine the beta/gamma radiation damage threshold for acoustic emission sensor systems. The individual system consisted of an acoustic sensor mounted with a two part epoxy onto a stainless steel waveguide. The systems were placed in an irradiation fixture and exposed to a Cobalt-60 source. After each irradiation, the sensors were recalibrated by Physical Acoustics Corporation. The results were compared to the initial calibrations performed prior to irradiation and a control group, not exposed to radiation, was used to validate the results. This experiment determines the radiation damage threshold of each acoustic sensor system and verifies its life expectancy, usefulness and reliability for many applications in radioactive environments.

  16. Prediction of the Acoustic Field Associated with Instability Wave Source Model for a Compressible Jet

    NASA Technical Reports Server (NTRS)

    Golubev, Vladimir; Mankbadi, Reda R.; Dahl, Milo D.; Kiraly, L. James (Technical Monitor)

    2002-01-01

    This paper provides preliminary results of the study of the acoustic radiation from the source model representing spatially-growing instability waves in a round jet at high speeds. The source model is briefly discussed first followed by the analysis of the produced acoustic directivity pattern. Two integral surface techniques are discussed and compared for prediction of the jet acoustic radiation field.

  17. 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.

  18. 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.

  19. Material fabrication using acoustic radiation forces

    SciTech Connect

    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.

  20. Reconstruction of transient acoustic radiation from a sphere.

    PubMed

    Wu, Sean F; Lu, Huancai; Bajwa, Manjit S

    2005-04-01

    Transient near-field acoustical holography (NAH) formulation is derived from the Helmholtz equation least squares (HELS) method to reconstruct acoustic radiation from a spherical surface subject to transient excitations in a free field. To facilitate derivations of temporal solutions, we make use of the Laplace transform and expansion in terms of the spherical Hankel functions and spherical harmonics, with their coefficients settled by solving a system of equations obtained by matching an assumed-form solution to the measured acoustic pressure. To derive a general form of solution for a temporal kernel, we replace the spherical Hankel functions and their derivatives by polynomials, recast infinite integrals in the inverse Laplace transform as contour integrals in a complex s-plane, and evaluate it via the residue theorem. The transient acoustic quantities anywhere including the source surface are then obtained by convoluting the temporal kernels with respect to the measured acoustic pressure. Numerical examples of reconstructing transient acoustic fields from explosively expanding, impulsively accelerating, and partially accelerating spheres, and that from a sphere subject to an arbitrarily time-dependent excitation are depicted. To illustrate the effectiveness of HELS-based transient NAH formulations, all input data are collected along an arbitrarily selected line segment and used to reconstruct transient acoustic quantities everywhere. PMID:15898648

  1. Frustrated total internal reflection acoustic field sensor

    DOEpatents

    Kallman, Jeffrey S.

    2000-01-01

    A frustrated total internal reflection acoustic field sensor which allows the acquisition of the acoustic field over an entire plane, all at once. The sensor finds use in acoustic holography and acoustic diffraction tomography. For example, the sensor may be produced by a transparent plate with transparent support members tall enough to support one or more flexible membranes at an appropriate height for frustrated total internal reflection to occur. An acoustic wave causes the membrane to deflect away from its quiescent position and thus changes the amount of light that tunnels through the gap formed by the support members and into the membrane, and so changes the amount of light reflected by the membrane. The sensor(s) is illuminated by a uniform tight field, and the reflection from the sensor yields acoustic wave amplitude and phase information which can be picked up electronically or otherwise.

  2. Numerics of surface acoustic wave (SAW) driven acoustic streaming and radiation force

    NASA Astrophysics Data System (ADS)

    Nama, Nitesh; Barnkob, Rune; Kahler, Christian; Costanzo, Francesco; Jun Huang, Tony

    2015-11-01

    Recently, surface acoustic wave (SAW) based systems have shown great potential for various lab-on-a-chip applications. However, the physical understanding of the precise acoustic fields and associated acoustophoresis is rather limited. In this work, we present a numerical study of the acoustophoretic particle motion inside a SAW-actuated, liquid-filled polydimethylsiloxane (PDMS) microchannel. We utilize a perturbation approach to divide the flow variables into first- and second-order components. The first-order fields result in a time-averaged acoustic radiation force on suspended particles, as well as the time-averaged body force terms that drive the second-order fields. We model the SAW actuation by a displacement function while we utilize impedance boundary conditions to model the PDMS walls. We identify the precise acoustic fields generated inside the microchannel and investigate a range of particle sizes to characterize the transition from streaming-dominated acoustophoresis to radiation-force-dominated acoustophoresis. Lastly, we demonstrate the ability of SAW devices to tune the position of vertical pressure node inside the microchannel by tuning the phase difference between the two incoming surface acoustic waves.

  3. Equilibrium thermodynamics and stochastic nonlinear acoustic fields. [in crystalline lattices

    NASA Technical Reports Server (NTRS)

    Cantrell, J. H.

    1985-01-01

    A crystalline solid is considered to consist of a large number of incoherent nonlinear acoustic radiation sources identified with the vibrating particles of the crystalline lattice. Randomization of the field, together with the assumption of a stochastically independent, fluctuating, radiation field at the absolue zero of temperature, leads to an expression of the temperature-dependent radiation field in terms of the zero-point field. The equation is identified with the Planck distribution formula of quantum mechanics in the linear field limit. The thermodynamic state functions are also obtained in terms of the nonlinear acoustic modal energies per unit mass and reduce to the results of the Debye-Einstein stochastic quantum oscillator model in the linear field limit.

  4. 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

  5. Visualizing underwater acoustic matched-field processing

    NASA Astrophysics Data System (ADS)

    Rosenblum, Lawrence; Kamgar-Parsi, Behzad; Karahalios, Margarida; Heitmeyer, Richard

    1991-06-01

    Matched-field processing is a new technique for processing ocean acoustic data measured by an array of hydrophones. It produces estimates of the location of sources of acoustic energy. This method differs from source localization techniques in other disciplines in that it uses the complex underwater acoustic environment to improve the accuracy of the source localization. An unexplored problem in matched-field processing has been to separate multiple sources within a matched-field ambiguity function. Underwater acoustic processing is one of many disciplines where a synthesis of computer graphics and image processing is producing new insight. The benefits of different volume visualization algorithms for matched-field display are discussed. The authors show how this led to a template matching scheme for identifying a source within the matched-field ambiguity function that can help move toward an automated source localization process.

  6. 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.

  7. 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.

  8. Radiation dominated acoustophoresis driven by surface acoustic waves.

    PubMed

    Guo, Jinhong; Kang, Yuejun; Ai, Ye

    2015-10-01

    Acoustophoresis-based particle manipulation in microfluidics has gained increasing attention in recent years. Despite the fact that experimental studies have been extensively performed to demonstrate this technique for various microfluidic applications, numerical simulation of acoustophoresis driven by surface acoustic waves (SAWs) has still been largely unexplored. In this work, a numerical model taking into account the acoustic-piezoelectric interaction was developed to simulate the generation of a standing surface acoustic wave (SSAW) field and predict the acoustic pressure field in the liquid. Acoustic radiation dominated particle tracing was performed to simulate acoustophoresis of particles with different sizes undergoing a SSAW field. A microfluidic device composed of two interdigital transducers (IDTs) for SAW generation and a microfluidic channel was fabricated for experimental validation. Numerical simulations could well capture the focusing phenomenon of particles to the pressure nodes in the experimental observation. Further comparison of particle trajectories demonstrated considerably quantitative agreement between numerical simulations and experimental results with fitting in the applied voltage. Particle switching was also demonstrated using the fabricated device that could be further developed as an active particle sorting device. PMID:26070191

  9. 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.

  10. Magnetic resonance acoustic radiation force imaging

    PubMed Central

    McDannold, Nathan; Maier, Stephan E.

    2008-01-01

    Acoustic radiation force impulse imaging is an elastography method developed for ultrasound imaging that maps displacements produced by focused ultrasound pulses systematically applied to different locations. The resulting images are “stiffness weighted” and yield information about local mechanical tissue properties. Here, the feasibility of magnetic resonance acoustic radiation force imaging (MR-ARFI) was tested. Quasistatic MR elastography was used to measure focal displacements using a one-dimensional MRI pulse sequence. A 1.63 or 1.5 MHz transducer supplied ultrasound pulses which were triggered by the magnetic resonance imaging hardware to occur before a displacement-encoding gradient. Displacements in and around the focus were mapped in a tissue-mimicking phantom and in an ex vivo bovine kidney. They were readily observed and increased linearly with acoustic power in the phantom (R2=0.99). At higher acoustic power levels, the displacement substantially increased and was associated with irreversible changes in the phantom. At these levels, transverse displacement components could also be detected. Displacements in the kidney were also observed and increased after thermal ablation. While the measurements need validation, the authors have demonstrated the feasibility of detecting small displacements induced by low-power ultrasound pulses using an efficient magnetic resonance imaging pulse sequence that is compatible with tracking of a dynamically steered ultrasound focal spot, and that the displacement increases with acoustic power. MR-ARFI has potential for elastography or to guide ultrasound therapies that use low-power pulsed ultrasound exposures, such as drug delivery. PMID:18777934

  11. Modulation of Radio Frequency Signals by Nonlinearly Generated Acoustic Fields

    NASA Astrophysics Data System (ADS)

    Johnson, Spencer Joseph

    Acousto-electromagnetic scattering is a process in which an acoustic excitation is utilized to induce modulation on an electromagnetic (EM) wave. This phenomenon can be exploited in remote sensing and detection schemes whereby target objects are mechanically excited by high powered acoustic waves resulting in unique object characterizations when interrogated with EM signals. Implementation of acousto-EM sensing schemes, however, are limited by a lack of fundamental understanding of the nonlinear interaction between acoustic and EM waves and inefficient simulation methods in the determination of the radiation patterns of higher order scattered acoustic fields. To address the insufficient simulation issue, a computationally efficient mathematical model describing higher order scattered sound fields, particularly of third-order in which a 40x increase in computation speed is achieved, is derived using a multi-Gaussian beam (MGB) expansion that expresses the sound field of any arbitrary axially symmetric beam as a series of Gaussian base functions. The third-order intermodulation (IM3) frequency components are produced by considering the cascaded nonlinear second-order effects when analyzing the interaction between the first- and second-order frequency components during the nonlinear scattering of sound by sound from two noncollinear ultrasonic baffled piston sources. The theory is extended to the modeling of the sound beams generated by parametric transducer arrays, showing that the MGB model can be efficiently used to calculate both the second- and third-order sound fields of the array. Additionally, a near-to-far-field (NTFF) transformation method is developed to model the far-field characteristics of scattered sound fields, extending Kirchhoff's theorem, typically applied to EM waves, determining the far-field patterns of an acoustic source from amplitude and phase measurements made in the near-field by including the higher order sound fields generated by the

  12. 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

  13. 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.

  14. 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).

  15. 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.

  16. 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.

  17. Experimental Study of Acoustic Radiation Force of an Ultrasound Beam on Absorbing and Scattering Objects

    PubMed Central

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

    2016-01-01

    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. PMID:27147775

  18. 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.

  19. Theoretical and experimental examination of near-field acoustic levitation.

    PubMed

    Nomura, Hideyuki; Kamakura, Tomoo; Matsuda, Kazuhisa

    2002-04-01

    A planar object can be levitated stably close to a piston sound source by making use of acoustic radiation pressure. This phenomenon is called near-field acoustic levitation [Y. Hashimoto et al., J. Acoust. Soc. Am. 100, 2057-2061 (1996)]. In the present article, the levitation distance is predicted theoretically by numerically solving basic equations in a compressible viscous fluid subject to the appropriate initial and boundary conditions. Additionally, experiments are carried out using a 19.5-kHz piston source with a 40-mm aperture and various aluminum disks of different sizes. The measured levitation distance agrees well with the theory, which is different from a conventional theory, and the levitation distance is not inversely proportional to the square root of the surface density of the levitated disk in a strict sense. PMID:12002842

  20. Reconstructing transient acoustic radiation from an arbitrary object with a uniform surface velocity distribution.

    PubMed

    Wu, Sean F

    2014-08-01

    This paper presents the general formulations for reconstructing the transient acoustic field generated by an arbitrary object with a uniformly distributed surface velocity in free space. These formulations are derived from the Kirchhoff-Helmholtz integral theory that correlates the transient acoustic pressure at any field point to those on the source surface. For a class of acoustic radiation problems involving an arbitrarily oscillating object with a uniformly distributed surface velocity, for example, a loudspeaker membrane, the normal surface velocity is frequency dependent but is spatially invariant. Accordingly, the surface acoustic pressure is expressible as the product of the surface velocity and the quantity that can be solved explicitly by using the Kirchhoff-Helmholtz integral equation. This surface acoustic pressure can be correlated to the field acoustic pressure using the Kirchhoff-Helmholtz integral formulation. Consequently, it is possible to use nearfield acoustic holography to reconstruct acoustic quantities in entire three-dimensional space based on a single set of acoustic pressure measurements taken in the near field of the target object. Examples of applying these formulations to reconstructing the transient acoustic pressure fields produced by various arbitrary objects are demonstrated. PMID:25096086

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

    PubMed

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

    2015-09-01

    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. PMID:26239679

  3. Acoustic vector fields in underwater waveguides

    NASA Astrophysics Data System (ADS)

    Rapids, Brian

    2005-09-01

    The ability to compute the sound pressure level as well as the vectors associated with the acoustic particle motion has existed for some time. However, propagation studies and ambient noise investigations have typically focused only upon the sound pressure levels that would be observed by an omnidirectional hydrophone or array of hydrophones. Recent interest in geophones and accelerometers for use as vector and dyadic sensors should encourage the investigation and analysis of the underlying vector fields contributing to the acoustic intensity and energy density fields. The frequency domain properties of the acoustic vector field generated by monopole sources having frequencies <1kHz in a simple iso-velocity waveguide are presented in order to build a fundamental understanding of the related quantities. Subsequently, similar field quantities computed for more realistic environments such as downward refracting profiles and deep-water profiles supporting convergence zone propagation will be discussed. Regions and phenomena associated with perturbations in the energy flux density will be highlighted.

  4. 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.

  5. 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. PMID:27102956

  6. Acoustic radiation force impulse of the liver

    PubMed Central

    D’Onofrio, Mirko; Crosara, Stefano; De Robertis, Riccardo; Canestrini, Stefano; Demozzi, Emanuele; Gallotti, Anna; Pozzi Mucelli, Roberto

    2013-01-01

    Acoustic radiation force impulse (ARFI) imaging is a new and promising ultrasound-based diagnostic technique that, evaluating the wave propagation speed, allows the assessment of the tissue stiffness. ARFI is implemented in the ultrasound scanner. By short-duration acoustic radiation forces (less than 1 ms), localized displacements are generated in a selected region of interest not requiring any external compression so reducing the operator dependency. The generated wave scan provides qualitative or quantitative (wave velocity values) responses. Several non-invasive methods for assessing the staging of fibrosis are used, in order to avoid liver biopsy. Liver function tests and transient elastography are non-invasive, sensitive and accurate tools for the assessment of liver fibrosis and for the discrimination between cirrhotic and non-cirrhotic liver. Many published studies analyse ARFI performance and feasibility in studying diffuse liver diseases and compare them to other diagnostic imaging modalities such as conventional ultrasonography and transient elastography. Solid focal liver lesions, both benign and malignant, are common findings during abdominal examinations. The accurate characterization and differential diagnosis are important aims of all the imaging modalities available today. Only few papers describe the application of ARFI technology in the study of solid focal liver lesions, with different results. In the present study, the existing literature, to the best of our knowledge, about ARFI application on diffuse and focal liver pathology has been evaluated and results and statistical analyses have been compared, bringing to the conclusion that ARFI can be used in the study of the liver with similar accuracy as transient elastography in diagnosing significant fibrosis or cirrhosis and has got some advantages in respect to transient elastography since it does not require separate equipment, better displays anatomical structures and measurements can be

  7. System for Manipulating Drops and Bubbles Using Acoustic Radiation Pressure

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C. (Inventor)

    1999-01-01

    The manipulation and control of drops of liquid and gas bubbles is achieved using high intensity acoustics in the form of and/or acoustic radiation pressure and acoustic streaming. generated by a controlled wave emission from a transducer. Acoustic radiation pressure is used to deploy or dispense drops into a liquid or a gas or bubbles into a liquid at zero or near zero velocity from the discharge end of a needle such as a syringe needle. Acoustic streaming is useful in manipulating the drop or bubble during or after deployment. Deployment and discharge is achieved by focusing the acoustic radiation pressure on the discharge end of the needle, and passing the acoustic waves through the fluid in the needle. through the needle will itself, or coaxially through the fluid medium surrounding the needle. Alternatively, the acoustic waves can be counter-deployed by focusing on the discharge end of the needle from a transducer axially aligned with the needle, but at a position opposite the needle, to prevent premature deployment of the drop or bubble. The acoustic radiation pressure can also be used for detecting the presence or absence of a drop or a bubble at the tip of a needle or for sensing various physical characteristics of the drop or bubble such as size or density.

  8. The directional sensitivity of the acoustic radiation force to particle diameter.

    PubMed

    Ran, W; Saylor, J R

    2015-06-01

    When viscous corrections to the inviscid acoustic radiation force theory are implemented and applied to a standing wave field, the direction of the acoustic radiation force on particles varies from theory to theory. Specifically, some theories predict that the direction of the force depends on the particle diameter, while others reveal that the direction of the force is independent of particle diameter. The present study is an experimental investigation of the direction of the acoustic radiation force which suggests that particle diameter does affect the direction. Experiments were conducted in air using an ultrasonic standing wave field with a nominal frequency of 30 kHz. Smoke particles and fine water droplets having a range of diameters were flowed into the region of a standing wave field. The direction of the acoustic radiation force was determined by observing whether the particles accumulated in the nodes or the anti-nodes of the standing wave. Results show a change in the direction of the acoustic radiation force at a particle diameter of 0.3±0.1 μm, which corresponds to a particle diameter to acoustic-boundary-layer thickness ratio of 0.023±0.008. PMID:26093419

  9. Fourth-order acoustic torque in intense sound fields

    NASA Technical Reports Server (NTRS)

    Wang, T. G.; Kanber, H.; Olli, E. E.

    1978-01-01

    The observation of a fourth-order acoustic torque in intense sound fields is reported. The torque was determined by measuring the acoustically induced angular deflection of a polished cylinder suspended by a torsion fiber. This torque was measured in a sound field of amplitude greater than that in which first-order acoustic torque has been observed.

  10. Acoustic field positioning for containerless processing

    NASA Technical Reports Server (NTRS)

    Whymark, R. R.

    1975-01-01

    The noncontact positioning of materials in a space processing chamber is accomplished using a new type of acoustic levitator. Liquid and solid materials are positioned using a single source of sound. Fine control of position may be obtained by motion of an acoustical reflector. The electrical power required is usually less than 100 watts. The system operates satisfactorily at high and low temperatures and is adaptable as an 'add-on' feature to existing space experiments. Containerless melting and solidification can be performed and a freely suspended liquid can be shaped to the contour of the sound field. Experiments are described in which aluminum, glass and plastic materials are melted and solidified in the containerless state. The system has applications to containerless crystal growth, melting and related processes.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  12. Acoustic radiosity for computation of sound fields in diffuse environments

    NASA Astrophysics Data System (ADS)

    Muehleisen, Ralph T.; Beamer, C. Walter

    2002-05-01

    The use of image and ray tracing methods (and variations thereof) for the computation of sound fields in rooms is relatively well developed. In their regime of validity, both methods work well for prediction in rooms with small amounts of diffraction and mostly specular reflection at the walls. While extensions to the method to include diffuse reflections and diffraction have been made, they are limited at best. In the fields of illumination and computer graphics the ray tracing and image methods are joined by another method called luminous radiative transfer or radiosity. In radiosity, an energy balance between surfaces is computed assuming diffuse reflection at the reflective surfaces. Because the interaction between surfaces is constant, much of the computation required for sound field prediction with multiple or moving source and receiver positions can be reduced. In acoustics the radiosity method has had little attention because of the problems of diffraction and specular reflection. The utility of radiosity in acoustics and an approach to a useful development of the method for acoustics will be presented. The method looks especially useful for sound level prediction in industrial and office environments. [Work supported by NSF.

  13. 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.

  14. Droplet Vaporization In A Levitating Acoustic Field

    NASA Technical Reports Server (NTRS)

    Ruff, G. A.; Liu, S.; Ciobanescu, I.

    2003-01-01

    Combustion experiments using arrays of droplets seek to provide a link between single droplet combustion phenomena and the behavior of complex spray combustion systems. Both single droplet and droplet array studies have been conducted in microgravity to better isolate the droplet interaction phenomena and eliminate or reduce the effects of buoyancy-induced convection. In most experiments involving droplet arrays, the droplets are supported on fibers to keep them stationary and close together before the combustion event. The presence of the fiber, however, disturbs the combustion process by introducing a source of heat transfer and asymmetry into the configuration. As the number of drops in a droplet array increases, supporting the drops on fibers becomes less practical because of the cumulative effect of the fibers on the combustion process. To eliminate the effect of the fiber, several researchers have conducted microgravity experiments using unsupported droplets. Jackson and Avedisian investigated single, unsupported drops while Nomura et al. studied droplet clouds formed by a condensation technique. The overall objective of this research is to extend the study of unsupported drops by investigating the combustion of well-characterized drop clusters in a microgravity environment. Direct experimental observations and measurements of the combustion of droplet clusters would provide unique experimental data for the verification and improvement of spray combustion models. In this work, the formation of drop clusters is precisely controlled using an acoustic levitation system so that dilute, as well as dense clusters can be created and stabilized before combustion in microgravity is begun. While the low-gravity test facility is being completed, tests have been conducted in 1-g to characterize the effect of the acoustic field on the vaporization of single and multiple droplets. This is important because in the combustion experiment, the droplets will be formed and

  15. Strategies for single particle manipulation using acoustic and flow fields.

    PubMed

    Oberti, S; Möller, D; Neild, A; Dual, J; Beyeler, F; Nelson, B J; Gutmann, S

    2010-02-01

    Acoustic radiation forces have often been used for the manipulation of large amounts of micrometer sized suspended particles. The nature of acoustic standing wave fields is such that they are present throughout the whole fluidic volume; this means they are well suited to such operations, with all suspended particles reacting at the same time upon exposure. Here, this simultaneous positioning capability is exploited to pre-align particles along the centerline of channels, so that they can successively be removed by means of an external tool for further analysis. This permits a certain degree of automation in single particle manipulation processes to be achieved as initial identification of particles' location is no longer necessary, rather predetermined. Two research fields in which applications are found have been identified. First, the manipulation of copolymer beads and cells using a microgripper is presented. Then, sample preparation for crystallographic analysis by positioning crystals into a loop using acoustic manipulation and a laminar flow will be presented. PMID:19837446

  16. Acoustic field in unsteady moving media

    NASA Technical Reports Server (NTRS)

    Bauer, F.; Maestrello, L.; Ting, L.

    1995-01-01

    In the interaction of an acoustic field with a moving airframe the authors encounter a canonical initial value problem for an acoustic field induced by an unsteady source distribution, q(t,x) with q equivalent to 0 for t less than or equal to 0, in a medium moving with a uniform unsteady velocity U(t)i in the coordinate system x fixed on the airframe. Signals issued from a source point S in the domain of dependence D of an observation point P at time t will arrive at point P more than once corresponding to different retarded times, Tau in the interval (0, t). The number of arrivals is called the multiplicity of the point S. The multiplicity equals 1 if the velocity U remains subsonic and can be greater when U becomes supersonic. For an unsteady uniform flow U(t)i, rules are formulated for defining the smallest number of I subdomains V(sub i) of D with the union of V(sub i) equal to D. Each subdomain has multiplicity 1 and a formula for the corresponding retarded time. The number of subdomains V(sub i) with nonempty intersection is the multiplicity m of the intersection. The multiplicity is at most I. Examples demonstrating these rules are presented for media at accelerating and/or decelerating supersonic speed.

  17. 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

  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. Eccentricity effects on acoustic radiation from a spherical source suspended within a thermoviscous fluid sphere.

    PubMed

    Hasheminejad, Seyyed M; Azarpeyvand, Mahdi

    2003-11-01

    Acoustic radiation from a spherical source undergoing angularly periodic axisymmetric harmonic surface vibrations while eccentrically suspended within a thermoviscous fluid sphere, which is immersed in a viscous thermally conducting unbounded fluid medium, is analyzed in an exact fashion. The formulation uses the appropriate wave-harmonic field expansions along with the translational addition theorem for spherical wave functions and the relevant boundary conditions to develop a closed-form solution in form of infinite series. The analytical results are illustrated with a numerical example in which the vibrating source is eccentrically positioned within a chemical fluid sphere submerged in water. The modal acoustic radiation impedance load on the source and the radiated far-field pressure are evaluated and discussed for representative values of the parameters characterizing the system. The proposed model can lead to a better understanding of dynamic response of an underwater acoustic lens. It is equally applicable in miniature transducer analysis and design with applications in medical ultrasonics. PMID:14682628

  20. 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.

  1. Near-field acoustical holography of military jet aircraft noise

    NASA Astrophysics Data System (ADS)

    Wall, Alan T.; Gee, Kent L.; Neilsen, Tracianne; Krueger, David W.; Sommerfeldt, Scott D.; James, Michael M.

    2010-10-01

    Noise radiated from high-performance military jet aircraft poses a hearing-loss risk to personnel. Accurate characterization of jet noise can assist in noise prediction and noise reduction techniques. In this work, sound pressure measurements were made in the near field of an F-22 Raptor. With more than 6000 measurement points, this is the most extensive near-field measurement of a high-performance jet to date. A technique called near-field acoustical holography has been used to propagate the complex pressure from a two- dimensional plane to a three-dimensional region in the jet vicinity. Results will be shown and what they reveal about jet noise characteristics will be discussed.

  2. 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.

  3. Imaging of acoustic fields using optical feedback interferometry.

    PubMed

    Bertling, Karl; Perchoux, Julien; Taimre, Thomas; Malkin, Robert; Robert, Daniel; Rakić, Aleksandar D; Bosch, Thierry

    2014-12-01

    This study introduces optical feedback interferometry as a simple and effective technique for the two-dimensional visualisation of acoustic fields. We present imaging results for several pressure distributions including those for progressive waves, standing waves, as well as the diffraction and interference patterns of the acoustic waves. The proposed solution has the distinct advantage of extreme optical simplicity and robustness thus opening the way to a low cost acoustic field imaging system based on mass produced laser diodes. PMID:25606963

  4. 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

  5. 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.

  6. 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.

  7. Polymer coating of glass microballoons levitated in a focused acoustic field

    NASA Technical Reports Server (NTRS)

    Young, A. T.; Lee, M. C.; Feng, I.-A.; Elleman, D. D.; Wang, T. G.

    1982-01-01

    Inertial confinement fusion (ICF) glass microballoons (GMBs) levitated in a focusing radiator acoustic device can be coated with liquid materials by deploying the liquid into the levitation field with a stepped-horn atomizer. The GMB can be forced to the center of the coating liquid with a strong acoustically generated centering force. Water solutions of organic polymers, UV-curable liquid organic monomers, and paraffin waxes have been used to prepare solid coatings on the surface of GMBs using this technique.

  8. 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.

  9. 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.

  10. 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

  11. Impact of Acoustic Standing Waves on Structural Responses: Reverberant Acoustic Testing (RAT) vs. Direct Field Acoustic Testing (DFAT)

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    Loudspeakers have been used for acoustic qualification of spacecraft, reflectors, solar panels, and other acoustically responsive structures for more than a decade. Limited measurements from some of the recent speaker tests used to qualify flight hardware have indicated significant spatial variation of the acoustic field within the test volume. Also structural responses have been reported to differ when similar tests were performed using reverberant chambers. To address the impact of non-uniform acoustic field on structural responses, a series of acoustic tests were performed using a flat panel and a 3-ft cylinder exposed to the field controlled by speakers and repeated in a reverberant chamber. The speaker testing was performed using multi-input-single-output (MISO) and multi-input-multi-output (MIMO) control schemes with and without the test articles. In this paper the spatial variation of the acoustic field due to acoustic standing waves and their impacts on the structural responses in RAT and DFAT (both using MISO and MIMO controls for DFAT) are discussed in some detail.

  12. Acoustic radiation of a submerged cylindrical shell in low frequency.

    PubMed

    Van de Loock, Julien; Décultot, Dominique; Léon, Fernand; Chati, Farid; Maze, Gérard; Rajaona, Dominique Raphael; Klauson, Aleksander

    2013-01-01

    The evaluation of sound pressure levels produced by submerged structures is a part of regulations on underwater noise pollution. The purpose of this work is the study of the underwater acoustic radiation of a stainless steel tube subjected to vibrations generated by a shock obtained by using a hammer. The vibrations of the tube, placed successively in air and in water, are measured by using accelerometers. In water, the acoustic radiation measurements are performed by using a hydrophone. Results are presented as frequency spectra and are confronted with results of the elastic theory. PMID:23298014

  13. Underwater hybrid near-field acoustical holography based on the measurement of vector hydrophone array

    NASA Astrophysics Data System (ADS)

    Hu, Bo; Yang, Desen; Sun, Yu

    2010-06-01

    Hybrid near-field acoustical holography (NAH) is developed for reconstructing acoustic radiation from a cylindrical source in a complex underwater environment. In hybrid NAH, we combine statistically optimized near-field acoustical holography (SONAH) and broadband acoustical holography from intensity measurements (BAHIM) to reconstruct the underwater cylindrical source field. First, the BAHIM is utilized to regenerate as much acoustic pressures on the hologram surface as necessary, and then the acoustic pressures are taken as input to the formulation implemented numerically by SONAH. The main advantages of this technology are that the complex pressure on the hologram surface can be reconstructed without reference signal, and the measurement array can be smaller than the source, thus the practicability and efficiency of this technology are greatly enhanced. Numerical examples of a cylindrical source are demonstrated. Test results show that hybrid NAH can yield a more accurate reconstruction than conventional NAH. Then, an experiment has been carried out with a vector hydrophone array. The experimental results show the advantage of hybrid NAH in the reconstruction of an acoustic field and the feasibility of using a vector hydrophone array in an underwater NAH measurement, as well as the identification and localization of noise sources.

  14. Diversity of acoustic streaming in a rectangular acoustofluidic field.

    PubMed

    Tang, Qiang; Hu, Junhui

    2015-04-01

    Diversity of acoustic streaming field in a 2D rectangular chamber with a traveling wave and using water as the acoustic medium is numerically investigated by the finite element method. It is found that the working frequency, the vibration excitation source length, and the distance and phase difference between two separated symmetric vibration excitation sources can cause the diversity in the acoustic streaming pattern. It is also found that a small object in the acoustic field results in an additional eddy, and affects the eddy size in the acoustic streaming field. In addition, the computation results show that with an increase of the acoustic medium's temperature, the speed of the main acoustic streaming decreases first and then increases, and the angular velocity of the corner eddies increases monotonously, which can be clearly explained by the change of the acoustic dissipation factor and shearing viscosity of the acoustic medium with temperature. Commercialized FEM software COMSOL Multiphysics is used to implement the computation tasks, which makes our method very easy to use. And the computation method is partially verified by an established analytical solution. PMID:25541360

  15. 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.

  16. 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.

  17. Nondestructive acoustic electric field probe apparatus and method

    DOEpatents

    Migliori, Albert

    1982-01-01

    The disclosure relates to a nondestructive acoustic electric field probe and its method of use. A source of acoustic pulses of arbitrary but selected shape is placed in an oil bath along with material to be tested across which a voltage is disposed and means for receiving acoustic pulses after they have passed through the material. The received pulses are compared with voltage changes across the material occurring while acoustic pulses pass through it and analysis is made thereof to determine preselected characteristics of the material.

  18. 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

  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. 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.

  1. Properties of the Acoustic Vector Field in Underwater Waveguides

    NASA Astrophysics Data System (ADS)

    Dall'Osto, David R.

    This thesis focuses on the description and measurement of the underwater acoustic field, based on vector properties of acoustic particle velocity. The specific goal is to interpret vector sensor measurements in underwater waveguides, in particular those measurements made in littoral (shallow) waters. To that end, theoretical models, which include the effects of reflections from the waveguide boundaries, are developed for the acoustic intensity, i.e. the product of acoustic pressure and acoustic particle velocity. Vector properties of acoustic intensity are shown to correspond to a non-dimensional vector property of acoustic particle velocity, its degree of circularity, which describes the trajectory of particle motion. Both experimental measurements and simulations of this non-dimensional vector property are used to analyze characteristics of sound propagation in underwater waveguides. Two measurement techniques are utilized in the experiments described in this thesis. In the first, particle velocity is obtained indirectly by time integration of the measured pressure gradient between two closely spaced (with respect to an acoustic wavelength) conventional pressure sensitive hydrophones. This method was used in ocean experiments conducted with vertical line arrays of hydrophones. In the second technique, particle velocity is measured directly by time integration of the signal generated by an accelerometer. An additional pressure measurement from a co-located hydrophone forms what is known as a "combined sensor" in the Russian literature, which allows for estimation of the vector acoustic intensity. This method was utilized mainly in laboratory experiments.

  2. Field Measurement of the Acoustic Nonlinearity Parameter in Turbine Blades

    NASA Technical Reports Server (NTRS)

    Hinton, Yolanda L.; Na, Jeong K.; Yost, William T.; Kessel, Gregory L.

    2000-01-01

    Nonlinear acoustics techniques were used to measure fatigue in turbine blades in a power generation plant. The measurements were made in the field using a reference based measurement technique, and a reference sample previously measured in the laboratory. The acoustic nonlinearity parameter showed significant increase with fatigue in the blades, as indicated by service age and areas of increased stress. The technique shows promise for effectively measuring fatigue in field applications and predicting subsequent failures.

  3. Non-contact transportation using near-field acoustic levitation

    PubMed

    Ueha; Hashimoto; Koike

    2000-03-01

    Near-field acoustic levitation, where planar objects 10 kg in weight can levitate stably near the vibrating plate, is successfully applied both to non-contact transportation of objects and to a non-contact ultrasonic motor. Transporting apparatuses and an ultrasonic motor have been fabricated and their characteristics measured. The theory of near-field acoustic levitation both for a piston-like sound source and a flexural vibration source is also briefly described. PMID:10829622

  4. 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

  5. A probability density function method for acoustic field uncertainty analysis

    NASA Astrophysics Data System (ADS)

    James, Kevin R.; Dowling, David R.

    2005-11-01

    Acoustic field predictions, whether analytical or computational, rely on knowledge of the environmental, boundary, and initial conditions. When knowledge of these conditions is uncertain, acoustic field predictions will also be uncertain, even if the techniques for field prediction are perfect. Quantifying acoustic field uncertainty is important for applications that require accurate field amplitude and phase predictions, like matched-field techniques for sonar, nondestructive evaluation, bio-medical ultrasound, and atmospheric remote sensing. Drawing on prior turbulence research, this paper describes how an evolution equation for the probability density function (PDF) of the predicted acoustic field can be derived and used to quantify predicted-acoustic-field uncertainties arising from uncertain environmental, boundary, or initial conditions. Example calculations are presented in one and two spatial dimensions for the one-point PDF for the real and imaginary parts of a harmonic field, and show that predicted field uncertainty increases with increasing range and frequency. In particular, at 500 Hz in an ideal 100 m deep underwater sound channel with a 1 m root-mean-square depth uncertainty, the PDF results presented here indicate that at a range of 5 km, all phases and a 10 dB range of amplitudes will have non-negligible probability. Evolution equations for the two-point PDF are also derived.

  6. 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.

  7. Microwave-Field Driven Acoustic Modes in Selected DNA Molecules

    NASA Astrophysics Data System (ADS)

    Edwards, Glenn Steven

    The direct coupling of a microwave field to selected DNA molecules is demonstrated using standard dielectrometry. The absorption is resonant with a typical lifetime of 300 picoseconds. Such a long lifetime is unexpected for DNA in aqueous solution at room temperature and has interesting implications for microscopic considerations in future models of solvent damping. Resonant absorption at fundamental and harmonic frequencies for both supercoiled circular and linear DNA agrees with an acoustic mode model. Our associated acoustic velocities for linear DNA are very close to the acoustic velocity of the longitudinal acoustic mode independently observed on DNA fibers using Brillouin Spectroscopy. The difference in acoustic velocities for supercoiled circular and linear DNA is discussed in terms of a conformation dependent model. *This research has been funded by the Office of Naval Research, the Center for Devices and Radiological Health, and the National Science Foundation.

  8. Experimental investigation of the interference structure in a shallow-water vector acoustic field

    NASA Astrophysics Data System (ADS)

    Lin, Wangsheng; Liang, Guolong; Wang, Yan; Wang, Yilin

    2012-11-01

    The waveguide invariant concept describes the interference striations in the acoustic pressure spectrograms produced with an underwater broadband source. In this paper, the existence of interference structure in the vector acoustic field is examined using sea trial data, and the waveguide invariant is exploited to interpret fringes of the vector field. The experimental data, which recorded a merchant vessel passing on a straight path, were collected by a 2-dimensional vector sensor during an experiment in the South China Sea. The intensity and phase spectra of the energy flux density vector in the acoustic field radiated by the moving vessel are obtained from the magnitude and phase angle of the product of the pressure and the horizontal particle velocity's complex conjugate. Distinct interference patterns appear in the vector intensity and phase spectra. The characteristics of these have been analyzed by comparison with the scaled acoustic field. The equation describing the striations associated with the ship's trajectory is derived from waveguide invariant theory. The Hough transform method is used to extract the waveguide invariant from the data. To improve the quality of the patterns derived from the vector field, a better value of waveguide invariant can be estimated. Good agreement between reconstructed trajectories and real patterns suggests that it is feasible to use the interference structure in an acoustic vector field to determine the waveguide characteristics.

  9. Dynamics of a spherical particle in an acoustic field: A multiscale approach

    SciTech Connect

    Xie, Jin-Han Vanneste, Jacques

    2014-10-15

    A rigid spherical particle in an acoustic wave field oscillates at the wave period but has also a mean motion on a longer time scale. The dynamics of this mean motion is crucial for numerous applications of acoustic microfluidics, including particle manipulation and flow visualisation. It is controlled by four physical effects: acoustic (radiation) pressure, streaming, inertia, and viscous drag. In this paper, we carry out a systematic multiscale analysis of the problem in order to assess the relative importance of these effects depending on the parameters of the system that include wave amplitude, wavelength, sound speed, sphere radius, and viscosity. We identify two distinguished regimes characterised by a balance among three of the four effects, and we derive the equations that govern the mean particle motion in each regime. This recovers and organises classical results by King [“On the acoustic radiation pressure on spheres,” Proc. R. Soc. A 147, 212–240 (1934)], Gor'kov [“On the forces acting on a small particle in an acoustical field in an ideal fluid,” Sov. Phys. 6, 773–775 (1962)], and Doinikov [“Acoustic radiation pressure on a rigid sphere in a viscous fluid,” Proc. R. Soc. London A 447, 447–466 (1994)], clarifies the range of validity of these results, and reveals a new nonlinear dynamical regime. In this regime, the mean motion of the particle remains intimately coupled to that of the surrounding fluid, and while viscosity affects the fluid motion, it plays no part in the acoustic pressure. Simplified equations, valid when only two physical effects control the particle motion, are also derived. They are used to obtain sufficient conditions for the particle to behave as a passive tracer of the Lagrangian-mean fluid motion.

  10. 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).

  11. [Nonionizing radiation and electromagnetic fields].

    PubMed

    Bernhardt, J H

    1991-01-01

    Nonionising radiation comprises all kinds of radiation and fields of the electromagnetic spectrum where biological matter is not ionised, as well as mechanical waves such as infrasound and ultrasound. The electromagnetic spectrum is subdivided into individual sections and includes: Static and low-frequency electric and magnetic fields including technical applications of energy with mains frequency, radio frequency fields, microwaves and optic radiation (infrared, visible light, ultraviolet radiation including laser). The following categories of persons can be affected by emissions by non-ionising radiation: Persons in the environment and in the household, workers, patients undergoing medical diagnosis or treatment. If the radiation is sufficiently intense, or if the fields are of appropriate strength, a multitude of effects can occur (depending on the type of radiation), such as heat and stimulating or irritating action, inflammations of the skin or eyes, changes in the blood picture, burns or in some cases cancer as a late sequel. The ability of radiation to penetrate into the human body, as well as the types of interaction with biological tissue, with organs and organisms, differs significantly for the various kinds of nonionising radiation. The following aspects of nonionising radiation are discussed: protection of humans against excessive sunlight rays when sunbathing and when exposed to UV radiation (e.g. in solaria); health risks of radio and microwaves (safety of microwave cookers and mobile radio units); effects on human health by electric and magnetic fields in everyday life. PMID:1837859

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

    SciTech Connect

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

    2015-10-28

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

  13. Military jet noise source imaging using multisource statistically optimized near-field acoustical holography.

    PubMed

    Wall, Alan T; Gee, Kent L; Neilsen, Tracianne B; McKinley, Richard L; James, Michael M

    2016-04-01

    The identification of acoustic sources is critical to targeted noise reduction efforts for jets on high-performance tactical aircraft. This paper describes the imaging of acoustic sources from a tactical jet using near-field acoustical holography techniques. The measurement consists of a series of scans over the hologram with a dense microphone array. Partial field decomposition methods are performed to generate coherent holograms. Numerical extrapolation of data beyond the measurement aperture mitigates artifacts near the aperture edges. A multisource equivalent wave model is used that includes the effects of the ground reflection on the measurement. Multisource statistically optimized near-field acoustical holography (M-SONAH) is used to reconstruct apparent source distributions between 20 and 1250 Hz at four engine powers. It is shown that M-SONAH produces accurate field reconstructions for both inward and outward propagation in the region spanned by the physical hologram measurement. Reconstructions across the set of engine powers and frequencies suggests that directivity depends mainly on estimated source location; sources farther downstream radiate at a higher angle relative to the inlet axis. At some frequencies and engine powers, reconstructed fields exhibit multiple radiation lobes originating from overlapped source regions, which is a phenomenon relatively recently reported for full-scale jets. PMID:27106340

  14. Nonlinear acoustic fields in acoustic metamaterial based on a cylindrical pipe with periodically arranged side holes.

    PubMed

    Fan, Li; Ge, Huan; Zhang, Shu-yi; Gao, Hai-fei; Liu, Yong-hui; Zhang, Hui

    2013-06-01

    Nonlinear acoustic fields in transmission-line acoustic metamaterials based on a cylindrical pipe with periodically arranged side holes are studied, in which the dispersions and characteristic parameters of the nonlinear acoustic waves are obtained with the Bloch theory, and meanwhile the distributions of the fundamental wave (FW) and second harmonic wave (SHW) in the metamaterial are simulated. Three characteristic frequency bands are defined according to the relations between the frequencies of the FW, SHW, and the low-frequency forbidden band (LFB) in the metamaterial. Especially, when the FW is in the LFB while the SHW is outside the LFB, the SHW can transmit through the metamaterial although the FW is blocked, which exhibits the possibility to extract the information from the SHW instead of the FW. In addition, experiments are carried out to measure the distributions of the acoustic pressures for the FW and SHW along the metamaterial and the experimental results are in agreement with the theory. PMID:23742339

  15. Magnetic resonance imaging of acoustic streaming: absorption coefficient and acoustic field shape estimation.

    PubMed

    Madelin, Guillaume; Grucker, Daniel; Franconi, Jean-Michel; Thiaudiere, Eric

    2006-07-01

    In this study, magnetic resonance imaging (MRI) is used to visualize acoustic streaming in liquids. A single-shot spin echo sequence (HASTE) with a saturation band perpendicular to the acoustic beam permits the acquisition of an instantaneous image of the flow due to the application of ultrasound. An average acoustic streaming velocity can be estimated from the MR images, from which the ultrasonic absorption coefficient and the bulk viscosity of different glycerol-water mixtures can be deduced. In the same way, this MRI method could be used to assess the acoustic field and time-average power of ultrasonic transducers in water (or other liquids with known physical properties), after calibration of a geometrical parameter that is dependent on the experimental setup. PMID:16650447

  16. 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

  17. 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

  18. Gamma radiation field intensity meter

    DOEpatents

    Thacker, L.H.

    1994-08-16

    A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode. 4 figs.

  19. Gamma radiation field intensity meter

    DOEpatents

    Thacker, Louis H.

    1995-01-01

    A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode.

  20. Gamma radiation field intensity meter

    DOEpatents

    Thacker, Louis H.

    1994-01-01

    A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode.

  1. Gamma radiation field intensity meter

    DOEpatents

    Thacker, L.H.

    1995-10-17

    A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode. 4 figs.

  2. On the relationship between acoustic energy density flux near the jet and far field acoustic intensity

    NASA Technical Reports Server (NTRS)

    Maestrello, L.

    1973-01-01

    The relationship between the distribution of the outflow of acoustic energy over the jet boundary and the far-field directivity and intensity distribution is established by measurement and analysis. The numerical and experimental procedures involved have been checked out by using a known source. The results indicate that the acoustic power output per unit length of the jet, in the region from which the sound emanates, peaks at approximately 9 diameters downstream. The acoustic emission for a jet Strouhal number of about 0.3 exceeds the emission for all other Strouhal numbers nearly everywhere along the measurement plane. However, the far-field peak intensity distribution obtained from the contribution of each station was found to depend on the spatial extent of the region where sound emanates from the jet, which, in turn, depends more on the far-field angle than on the Strouhal number. The implications of these results for sound suppression techniques are discussed.

  3. 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

  4. 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.

  5. Schlieren imaging of the standing wave field in an ultrasonic acoustic levitator

    NASA Astrophysics Data System (ADS)

    Rendon, Pablo Luis; Boullosa, Ricardo R.; Echeverria, Carlos; Porta, David

    2015-11-01

    We consider a model of a single axis acoustic levitator consisting of two cylinders immersed in air and directed along the same axis. The first cylinder has a flat termination and functions as a sound emitter, and the second cylinder, which is simply a refector, has the side facing the first cylinder cut out by a spherical surface. By making the first cylinder vibrate at ultrasonic frequencies a standing wave is produced in the air between the cylinders which makes it possible, by means of the acoustic radiation pressure, to levitate one or several small objects of different shapes, such as spheres or disks. We use schlieren imaging to observe the acoustic field resulting from the levitation of one or several objects, and compare these results to previous numerical approximations of the field obtained using a finite element method. The authors acknowledge financial support from DGAPA-UNAM through project PAPIIT IN109214.

  6. Acoustic streaming field structure. Part II. Examples that include boundary-driven flow.

    PubMed

    Bradley, Charles

    2012-01-01

    In this paper three simple acoustic streaming problems are presented and solved. The purpose of the paper is to demonstrate the use of a previously published streaming model by Bradley [J. Acoust. Soc. Am. 100(3), 1399-1408 (1996)] and illustrate, with concrete examples, some of the features of streaming flows that were predicted by the general model. In particular, the problems are intended to demonstrate cases in which the streaming field boundary condition at the face of the radiator has a nontrivial lateral dc velocity component. Such a boundary condition drives a steady solenoidal flow just like a laterally translating boundary drives Couette flow. PMID:22280567

  7. Characterizing the stiffness of Human Prostates using Acoustic Radiation Force

    PubMed Central

    Zhai, Liang; Madden, John; Foo, Wen-Chi; Mouraviev, Vladimir; Polascik, Thomas J.; Palmeri, Mark L.; Nightingale, Kathryn R.

    2012-01-01

    Acoustic Radiation Force Impulse (ARFI) imaging has been previously reported to portray normal anatomic structures and pathologies in ex vivo human prostates with good contrast and resolution. These findings were based on comparison with histological slides and McNeal’s zonal anatomy. In ARFI images, the central zone (CZ) appears darker (smaller displacement) than other anatomic zones, and prostate cancer (PCa) is darker than normal tissue in the peripheral zone (PZ). Since displacement amplitudes in ARFI images are determined by both the underlying tissue stiffness and the amplitude of acoustic radiation force which varies with acoustic attenuation, one question that arises is: how are the relative displacements in prostate ARFI images related to the underlying prostatic tissue stiffness? In linear, isotropic elastic materials and in tissues that are relatively uniform in acoustic attenuation (e.g. liver), relative displacement in ARFI images has been shown to be correlated with underlying tissue stiffness. However, the prostate is known to be heterogeneous. Variations in acoustic attenuation of prostatic structures could confound the interpretation of ARFI images due to the associated variations in the applied acoustic radiation force. Therefore, in this study, co-registered three-dimensional (3D) ARFI datasets and quantitative shear wave elasticity imaging (SWEI) datasets were acquired in freshly excised human prostates to investigate the relationship between displacement amplitudes in ARFI prostate images and the matched reconstructed shear moduli. The lateral time-to-peak (LTTP) algorithm was applied to the SWEI data to compute the shear wave speed and reconstruct the shear moduli. Five types of prostatic tissue (PZ, CZ, transition zone (TZ) and benign prostatic hyperplasia (BPH), PCa, and atrophy) were identified, whose shear moduli were quantified to be 4.1±0.8 kPa, 9.9±0.9 kPa, 4.8±0.6 kPa, 10.0±1.0 kPa and 8.0 kPa, respectively. Linear regression was

  8. 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

  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. Acoustic centering of sources with high-order radiation patterns.

    PubMed

    Shabtai, Noam R; Vorländer, Michael

    2015-04-01

    Surrounding spherical microphone arrays have recently been used in order to model the radiation pattern of acoustic sources that are assumed to be at the center of the array. Source centering algorithms are applied to the measurements in order to reduce the negative effect of acoustic source misalignment with regard to the physical center of the microphone array. Recent works aim to minimize the energy that is contained in the high-order coefficients of the radiation pattern in the spherical harmonics domain, in order to directly address the problem of increased order and spatial aliasing resulted by this misalignment. However, objective functions which directly minimize the norm of these coefficients were shown to be convex only when employed on sources with low-order radiation patterns. This work presents a source centering algorithm that operates on plane sections and aims to achieve a convex objective function on every plane section. The results of the proposed algorithm are shown to be more convex than the previous algorithms for sources with higher-order radiation pattern, usually at higher frequencies. PMID:25920846

  11. On the contribution of circumferential resonance modes in acoustic radiation force experienced by cylindrical shells

    NASA Astrophysics Data System (ADS)

    Rajabi, Majid; Behzad, Mehdi

    2014-10-01

    A body insonified by a constant (time-varying) intensity sound field is known to experience a steady (oscillatory) force that is called the steady-state (dynamic) acoustic radiation force. Using the classical resonance scattering theorem (RST) which suggests the scattered field as a superposition of a resonance field and a background (non-resonance) component, we show that the radiation force acting on a cylindrical shell may be synthesized as a composition of three components: background part, resonance part and their interaction. The background component reveals the pure geometrical reflection effects and illustrates a regular behavior with respect to frequency, while the others demonstrate a singular behavior near the resonance frequencies. The results illustrate that the resonance effects associated to partial waves can be isolated by the subtraction of the background component from the total (steady-state or dynamic) radiation force function (i.e., residue component). In the case of steady-state radiation force, the components are exerted on the body as static forces. For the case of oscillatory amplitude excitation, the components are exerted at the modulation frequency with frequency-dependant phase shifts. The results demonstrate the dominant contribution of the non-resonance component of dynamic radiation force at high frequencies with respect to the residue component, which offers the potential application of ultrasound stimulated vibro-acoustic spectroscopy technique in low frequency resonance spectroscopy purposes. Furthermore, the proposed formulation may be useful essentially due to its intrinsic value in physical acoustics. In addition, it may unveil the contribution of resonance modes in the dynamic radiation force experienced by the cylindrical objects and its underlying physics.

  12. Field-Deployable Acoustic Digital Systems for Noise Measurement

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A.; Wright, Kenneth D.; Lunsford, Charles B.; Smith, Charlie D.

    2000-01-01

    Langley Research Center (LaRC) has for years been a leader in field acoustic array measurement technique. Two field-deployable digital measurement systems have been developed to support acoustic research programs at LaRC. For several years, LaRC has used the Digital Acoustic Measurement System (DAMS) for measuring the acoustic noise levels from rotorcraft and tiltrotor aircraft. Recently, a second system called Remote Acquisition and Storage System (RASS) was developed and deployed for the first time in the field along with DAMS system for the Community Noise Flight Test using the NASA LaRC-757 aircraft during April, 2000. The test was performed at Airborne Airport in Wilmington, OH to validate predicted noise reduction benefits from alternative operational procedures. The test matrix was composed of various combinations of altitude, cutback power, and aircraft weight. The DAMS digitizes the acoustic inputs at the microphone site and can be located up to 2000 feet from the van which houses the acquisition, storage and analysis equipment. Digitized data from up to 10 microphones is recorded on a Jaz disk and is analyzed post-test by microcomputer system. The RASS digitizes and stores acoustic inputs at the microphone site that can be located up to three miles from the base station and can compose a 3 mile by 3 mile array of microphones. 16-bit digitized data from the microphones is stored on removable Jaz disk and is transferred through a high speed array to a very large high speed permanent storage device. Up to 30 microphones can be utilized in the array. System control and monitoring is accomplished via Radio Frequency (RF) link. This paper will present a detailed description of both systems, along with acoustic data analysis from both systems.

  13. 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.

  14. 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.

  15. Acoustic Radiation from a Mach 14 Turbulent Boundary layer

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Duan, Lian; Choudhari, Meelan

    2015-11-01

    Direct numerical simulations (DNS) are used to examine the pressure fluctuations 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 emphasis is on characterizing the acoustic radiation from the turbulent boundary layer and comparing it with previous simulations at Mach 2.5 and Mach 6 to assess the Mach-number dependence of the freestream pressure fluctuations. In particular, the numerical database is used to provide insights into the pressure disturbance spectrum and amplitude scaling with respect to the freestream Mach number as well as to understand the acoustic source mechanisms at very high Mach numbers. Such information is important for characterizing the freestream disturbance environment in conventional (i.e., noisy) hypersonic wind tunnels. Spectral characteristics of pressure fluctuations at the surface are also investigated. Sponsored by Air Force Office of Scientific Research.

  16. 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

  17. Radiation and propagation of short acoustical pulses from underground explosions

    SciTech Connect

    Banister, J.R.

    1982-06-01

    Radiation and propagation of short acoustical pulses from underground nuclear explosions were analyzed. The cone of more intense radiation is defined by the ratio of sound speeds in the ground and air. The pressure history of the radiated pulse is a function of the vertical ground-motion history, the range, the burial depth, and the velocity of longitudinal seismic waves. The analysis of short-pulse propagation employed an N-wave model with and without enegy conservation. Short pulses with initial wave lengths less than 100 m are severely attenuated by the energy loss in shocks and viscous losses in the wave interior. The methods developed in this study should be useful for system analysis.

  18. On noninvasive assessment of acoustic fields acting on the fetus

    NASA Astrophysics Data System (ADS)

    Antonets, V. A.; Kazakov, V. V.

    2014-05-01

    The aim of this study is to verify a noninvasive technique for assessing the characteristics of acoustic fields in the audible range arising in the uterus under the action of maternal voice, external sounds, and vibrations. This problem is very important in view of actively developed methods for delivery of external sounds to the uterus: music, maternal voice recordings, sounds from outside the mother's body, etc., that supposedly support development of the fetus at the prenatal stage psychologically and cognitively. However, the parameters of acoustic signals have been neither measured nor normalized, which may be dangerous for the fetus and hinder actual assessment of their impact on fetal development. The authors show that at frequencies below 1 kHz, acoustic pressure in the uterus may be measured noninvasively using a hydrophone placed in a soft capsule filled with liquid. It was found that the acoustic field at frequencies up to 1 kHz arising in the uterus under the action of an external sound field has amplitude-frequency parameters close to those of the external field; i.e., the external field penetrates the uterus with hardly any difficulty.

  19. Aerodynamic sound generation due to vortex-aerofoil interaction. Part 2: Analysis of the acoustic field

    NASA Technical Reports Server (NTRS)

    Parasarathy, R.; Karamcheti, K.

    1972-01-01

    The Lighthill method was the basic procedure used to analyze the sound field associated with a vortex of modified strength interacting with an airfoil. A free vortex interacting with an airfoil in uniform motion was modeled in order to determine the sound field due to all the acoustic sources, not only on the airfoil surfaces (dipoles), but also the ones distributed on the perturbed flow field (quadrupoles) due to the vortex-airfoil interaction. Because inviscid flow is assumed in the study of the interaction, the quadrupoles considered in the perturbed flow field are entirely due to an unsteady flow field. The effects of airfoil thickness on the second radiation are examined by using a symmetric Joukowski airfoil for the vortex-airfoil interaction. Sound radiation in a plane, far field simplification, and computation of the sound field are discussed.

  20. 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.

  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. 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'.

  3. FIELD TESTING OF PROTOTYPE ACOUSTIC EMISSION SEWER FLOWMETER

    EPA Science Inventory

    This investigation concerns verifying the operating principles of the acoustic emission flowmeter (U.S. Patent 3,958,458) in the natural environment of three different storm sewer field sites in Nassau County, New York. The flowmeter is a novel, passive, nonintrusive method that ...

  4. Material selection for acoustic radiators that are light and stiff.

    PubMed

    Porter, S P; Markley, D C; Van Tol, D J; Meyer, R J

    2011-01-01

    The headmass is a key element in tonpilz transducer design. As an acoustic radiator, a successful headmass must be built from a material that is both light and stiff. To assess the suitability of ceramics for this application, the authors used the mechanical properties of candidate materials to perform a theoretical comparison based on the flexural behavior of square plates. Although not a comprehensive metric for identifying the best headmass materials, the headmass flexure may be usefully employed as a first-level selection criteria. A software routine based on thin plate and thick plate theory was created to evaluate the flexural behavior in candidate materials. PMID:21302996

  5. 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.

  6. Modelling of wind tunnel wall effects on the radiation characteristics of acoustic sources

    NASA Technical Reports Server (NTRS)

    Eversman, W.; Baumeister, K. J.

    1984-01-01

    It is pointed out that the relatively high fuel economy available from propeller-driven aircraft has renewed interest in high speed, highly loaded multiple blade turboprop propulsion systems. Undesirable features related to community noise and the high intensity cabin noise have stimulated new research on the acoustic characteristics of turboprops. The present investigation has the objective to develop a mathematical model of the essential features of the radiation of acoustic disturbances from propellers in a duct and in free space in order to quantify the success with which duct testing can be expected to approximate free field conditions. In connection with the importance of source directionality, a detailed model is considered which consists of a finite element representation of the Gutin propeller theory valid in both the near and far field.

  7. Relationship between acoustic power and acoustic radiation force on absorbing and reflecting targets for spherically focusing radiators.

    PubMed

    Gélat, Pierre; Shaw, Adam

    2015-03-01

    Total acoustic output power is an important parameter required by standards for most ultrasonic medical equipment including high-intensity focused ultrasound (HIFU) systems. Radiation force balances are routinely used; however, radiation force is not strictly dependent on the ultrasound power but, rather, on the wave momentum resolved in one direction. Consequently, measurements based on radiation force become progressively less accurate as the ultrasound wave deviates further from a true plane wave. HIFU transducers can be very strongly focused with F-numbers less than one: under these conditions, the uncertainty associated with use of the radiation force method becomes very significant. International Standards IEC 61161 and IEC 62555 suggest plane-wave correction factors for unfocused transducers radiating onto an ideal absorbing target and focusing corrections for focused transducers radiating onto ideal absorbing targets and onto conical reflecting targets (IEC 61161). Previous models have relied on calculations based on the Rayleigh integral, which is not strictly correct for curved sources. In the work described here, an approach combining finite element methods with a discretization of the Helmholtz equation was developed, making it possible to model the boundary condition at the structure/fluid interface more correctly. This has been used to calculate the relationship between radiation force and total power for both absorbing and conical reflecting targets for transducers ranging from planar to an F-number of 0.5 (hemispherical) and to compare with the recommendations of IEC 61161 and IEC 62555. PMID:25683223

  8. Acoustic spectroscopy: A powerful analytical method for the pharmaceutical field?

    PubMed

    Bonacucina, Giulia; Perinelli, Diego R; Cespi, Marco; Casettari, Luca; Cossi, Riccardo; Blasi, Paolo; Palmieri, Giovanni F

    2016-04-30

    Acoustics is one of the emerging technologies developed to minimize processing, maximize quality and ensure the safety of pharmaceutical, food and chemical products. The operating principle of acoustic spectroscopy is the measurement of the ultrasound pulse intensity and phase after its propagation through a sample. The main goal of this technique is to characterise concentrated colloidal dispersions without dilution, in such a way as to be able to analyse non-transparent and even highly structured systems. This review presents the state of the art of ultrasound-based techniques in pharmaceutical pre-formulation and formulation steps, showing their potential, applicability and limits. It reports in a simplified version the theory behind acoustic spectroscopy, describes the most common equipment on the market, and finally overviews different studies performed on systems and materials used in the pharmaceutical or related fields. PMID:26976503

  9. A field-deployable digital acoustic measurement system

    NASA Technical Reports Server (NTRS)

    Gray, David L.; Wright, Kenneth D., II; Rowland, Wayne D.

    1991-01-01

    A field deployable digital acoustic measurement system was developed to support acoustic research programs at the Langley Research Center. The system digitizes the acoustic inputs at the microphone, which can be located up to 1000 feet from the van which houses the acquisition, storage, and analysis equipment. Digitized data from up to 12 microphones is recorded on high density 8mm tape and is analyzed post-test by a microcomputer system. Synchronous and nonsynchronous sampling is available with maximum sample rates of 12,500 and 40,000 samples per second respectively. The high density tape storage system is capable of storing 5 gigabytes of data at transfer rates up to 1 megabyte per second. System overall dynamic range exceeds 83 dB.

  10. Sound field simulation and acoustic animation in urban squares

    NASA Astrophysics Data System (ADS)

    Kang, Jian; Meng, Yan

    2005-04-01

    Urban squares are important components of cities, and the acoustic environment is important for their usability. While models and formulae for predicting the sound field in urban squares are important for their soundscape design and improvement, acoustic animation tools would be of great importance for designers as well as for public participation process, given that below a certain sound level, the soundscape evaluation depends mainly on the type of sounds rather than the loudness. This paper first briefly introduces acoustic simulation models developed for urban squares, as well as empirical formulae derived from a series of simulation. It then presents an acoustic animation tool currently being developed. In urban squares there are multiple dynamic sound sources, so that the computation time becomes a main concern. Nevertheless, the requirements for acoustic animation in urban squares are relatively low compared to auditoria. As a result, it is important to simplify the simulation process and algorithms. Based on a series of subjective tests in a virtual reality environment with various simulation parameters, a fast simulation method with acceptable accuracy has been explored. [Work supported by the European Commission.

  11. Preliminary study of the effect of the turbulent flow field around complex surfaces on their acoustic characteristics

    NASA Technical Reports Server (NTRS)

    Olsen, W. A.; Boldman, D.

    1978-01-01

    Fairly extensive measurements have been conducted of the turbulent flow around various surfaces as a basis for a study of the acoustic characteristics involved. In the experiments the flow from a nozzle was directed upon various two-dimensional surface configurations such as the three-flap model. A turbulent flow field description is given and an estimate of the acoustic characteristics is provided. The developed equations are based upon fundamental theories for simple configurations having simple flows. Qualitative estimates are obtained regarding the radiation pattern and the velocity power law. The effect of geometry and turbulent flow distribution on the acoustic emission from simple configurations are discussed.

  12. Considerations on the acoustic energy radiated by toothed gears. [model for calculating noise intensity

    NASA Technical Reports Server (NTRS)

    Popinceanu, N. G.; Kremmer, I.

    1974-01-01

    A mechano-acoustic model is reported for calculating acoustic energy radiated by a working gear. According to this model, a gear is an acoustic coublet formed of the two wheels. The wheel teeth generate cylindrical acoustic waves while the front surfaces of the teeth behave like vibrating pistons. Theoretical results are checked experimentally and good agreement is obtained with open gears. The experiments show that the air noise effect is negligible as compared with the structural noise transmitted to the gear box.

  13. 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

  14. 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.

  15. 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.

  16. Acoustic emission and magnification of atomic lines resolution for laser breakdown of salt water in ultrasound field

    NASA Astrophysics Data System (ADS)

    Bulanov, Alexey V.; Nagorny, Ivan G.

    2015-10-01

    Researches of the acoustic effects accompanying optical breakdown in a water, generated by the focused laser radiation with power ultrasound have been carried out. Experiments were performed by using 532 nm pulses from Brilliant B Nd:YAG laser. Acoustic radiation was produced by acoustic focusing systems in the form hemisphere and ring by various resonance frequencies of 10.7 kHz and 60 kHz. The experimental results are obtained, that show the sharply strengthens effects of acoustic emission from a breakdown zone by the joint influence of a laser and ultrasonic irradiation. Essentially various thresholds of breakdown and character of acoustic emission in fresh and sea water are found out. The experimental result is established, testifying that acoustic emission of optical breakdown of sea water at presence and at absence of ultrasound essentially exceeds acoustic emission in fresh water. Atomic lines of some chemical elements like a Sodium, Magnesium and so on were investigated for laser breakdown of water with ultrasound field. The effect of magnification of this lines resolution for salt water in ultrasound field was obtained.

  17. Acoustic emission and magnification of atomic lines resolution for laser breakdown of salt water in ultrasound field

    SciTech Connect

    Bulanov, Alexey V.; Nagorny, Ivan G.

    2015-10-28

    Researches of the acoustic effects accompanying optical breakdown in a water, generated by the focused laser radiation with power ultrasound have been carried out. Experiments were performed by using 532 nm pulses from Brilliant B Nd:YAG laser. Acoustic radiation was produced by acoustic focusing systems in the form hemisphere and ring by various resonance frequencies of 10.7 kHz and 60 kHz. The experimental results are obtained, that show the sharply strengthens effects of acoustic emission from a breakdown zone by the joint influence of a laser and ultrasonic irradiation. Essentially various thresholds of breakdown and character of acoustic emission in fresh and sea water are found out. The experimental result is established, testifying that acoustic emission of optical breakdown of sea water at presence and at absence of ultrasound essentially exceeds acoustic emission in fresh water. Atomic lines of some chemical elements like a Sodium, Magnesium and so on were investigated for laser breakdown of water with ultrasound field. The effect of magnification of this lines resolution for salt water in ultrasound field was obtained.

  18. 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

  19. Identification of vibration excitations from acoustic measurements using near field acoustic holography and the force analysis technique

    NASA Astrophysics Data System (ADS)

    Pézerat, C.; Leclère, Q.; Totaro, N.; Pachebat, M.

    2009-10-01

    This study presents a method of using acoustic holography and the force analysis technique to identify vibration sources from radiated noise measurements. The structure studied is a plate excited by a shaker on which three measurements were performed: the first is a reference measurement of plate velocity obtained by scanning laser vibrometry, the second is based on sound pressure measurements in the near field of the structure, and the third is the measurement of normal acoustic velocities by using a p-U probe recently developed by Microflown Technologies. This was followed by the application of classical NAH, known as pressure-to-velocity holography and velocity-to-velocity holography to predict the plate velocity field from acoustic measurements at distances of 1 and 5 cm. Afterwards, the force analysis technique, also known as the RIFF technique, is applied with these five data sets. The principle is to inject the displacement field of the structure into its equation of motion and extract the resulting force distribution. This technique requires regularization done by a low-pass filter in the wavenumber domain. Apart from pressure-to-velocity holography at 5 cm, the reconstructed force distribution allows localizing the excitation point in the measurement area. FAT regularization is also shown to improve results as its cutoff wavenumber is optimized with the natural wavenumber of the plate. Lastly, quantitative force values are extracted from force distributions at all frequencies of the band 0-4 kHz studied and compared with the force spectrum measured directly by a piezoelectric sensor.

  20. Three-dimensional acoustic radiation force on an arbitrarily located elastic sphere.

    PubMed

    Baresch, Diego; Thomas, Jean-Louis; Marchiano, Régis

    2013-01-01

    This work aims to model the acoustic radiation forces acting on an elastic sphere placed in an inviscid fluid. An expression of the axial and transverse forces exerted on the sphere is derived. The analysis is based on the scattering of an arbitrary acoustic field expanded in the spherical coordinate system centered on the spherical scatterer. The sphere is allowed to be arbitrarily located. The special case of high order Bessel beams, acoustical vortices, are considered. These types of beams have a helicoidal wave front, i.e., a screw-type phase singularity and hence, the beam has a central dark core of zero amplitude surrounded by an intense ring. Depending on the sphere's radius, different radial equilibrium positions may exist and the sphere can be set in rotation around the beam axis by an azimuthal force. This confirms the pseudo-angular moment transfer from the beam to the sphere. Cases where the axial force is directed opposite to the direction of the beam propagation are investigated and the potential use of Bessel beams as tractor beams is demonstrated. Numerical results provide an impetus for further designing acoustical tweezers for potential applications in particle entrapment and remote controlled manipulation. PMID:23297880

  1. 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.

  2. 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

  3. 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

  4. 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

  5. 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.

  6. 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

  7. 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).

  8. Laval nozzle as an acoustic analogue of a massive field

    NASA Astrophysics Data System (ADS)

    Cuyubamba, M. A.

    2013-10-01

    We study a gas flow in the Laval nozzle, which is a convergent-divergent tube that has a sonic point in its throat. We show how to obtain the appropriate form of the tube, so that the acoustic perturbations of the gas flow in it satisfy any given wave-like equation. With the help of the proposed method we find the Laval nozzle, which is an acoustic analogue of the massive scalar field in the background of the Schwarzschild black hole. This gives us a possibility to observe in a laboratory the quasinormal ringing of the massive scalar field, which, for special set of the parameters, can have infinitely long-living oscillations in its spectrum.

  9. Driven acoustic oscillations within a vertical magnetic field

    NASA Technical Reports Server (NTRS)

    Hindman, Bradley W.; Zweibel, Ellen G.; Cally, P. S.

    1995-01-01

    The effects of a vertical magnetic field on p-mode frequencies, line widths, and eigenfunctions, are examined. A solar model, consisting of a neutrally stable polytropic interior matched to an isothermal chromosphere, is applied. The p-modes are produced by a spatially distributed driver. The atmosphere is threaded by a constant vertical magnetic field. The frequency shifts due to the vertical magnetic field are found to be much smaller than the shifts caused by horizontal fields of similar strength. A large vertical field of 2000 G produces shifts of several nHz. It is found that the frequency shifts decrease with increasing frequency and increase with field strength. The coupling of the acoustic fast mode to the escaping slow modes is inefficient. Constant vertical magnetic field models are therefore incapable of explaining the high level of absorption observed in sunspots and plage.

  10. 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

  11. Propagation of acoustic pulses in random gravity wave fields

    NASA Astrophysics Data System (ADS)

    Millet, Christophe; de La Camara, Alvaro; Lott, François

    2015-11-01

    A linear solution modeling the interaction between an incoming acoustic wave and a randomly perturbed atmosphere is developed, using the normal mode method. The wave mode structure is determined by a sound speed profile that is confining. The environmental uncertainty is described by a stochastic field obtained with a multiwave stochastic parameterization of gravity waves (GW). Using the propagating modes of the unperturbed atmosphere, the wave propagation problem is reduced to solving a system of ordinary differential equations. We focus on the asymptotic behavior of the transmitted waves in the weakly heterogeneous regime. In this regime, the coupling between the acoustic pulse and the randomly perturbed waveguides is weak and the propagation distance must be large enough for the wave to experience significant scattering. A general expression for the pressure far-field is derived in terms of saddle-point contributions. The saddle-points are obtained from a WKB approximation of the vertical eigenvalue problem. We present preliminary results that show how statistics of the transmitted signal are related to some eigenvalues and how an ``optimal'' GW field can trigger large deviations in the acoustic signals. The present model is used to explain the variability of infrasound signals.

  12. Material properties from acoustic radiation force step response

    PubMed Central

    Orescanin, Marko; Toohey, Kathleen S.; Insana, Michael F.

    2009-01-01

    An ultrasonic technique for estimating viscoelastic properties of hydrogels, including engineered biological tissues, is being developed. An acoustic radiation force is applied to deform the gel locally while Doppler pulses track the induced movement. The system efficiently couples radiation force to the medium through an embedded scattering sphere. A single-element, spherically-focused, circular piston element transmits a continuous-wave burst to suddenly apply and remove a radiation force to the sphere. Simultaneously, a linear array and spectral Doppler technique are applied to track the position of the sphere over time. The complex shear modulus of the gel was estimated by applying a harmonic oscillator model to measurements of time-varying sphere displacement. Assuming that the stress-strain response of the surrounding gel is linear, this model yields an impulse response function for the gel system that may be used to estimate material properties for other load functions. The method is designed to explore the force-frequency landscape of cell-matrix viscoelasticity. Reported measurements of the shear modulus of gelatin gels at two concentrations are in close agreement with independent rheometer measurements of the same gels. Accurate modulus measurements require that the rate of Doppler-pulse transmission be matched to a priori estimates of gel properties. PMID:19425636

  13. 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

  14. Field tests of acoustic telemetry for a portable coastal observatory

    USGS Publications Warehouse

    Martini, M.; Butman, B.; Ware, J.; Frye, D.

    2006-01-01

    Long-term field tests of a low-cost acoustic telemetry system were carried out at two sites in Massachusetts Bay. At each site, an acoustic Doppler current profiler mounted on a bottom tripod was fitted with an acoustic modem to transmit data to a surface buoy; electronics mounted on the buoy relayed these data to shore via radio modem. The mooring at one site (24 m water depth) was custom-designed for the telemetry application, with a custom designed small buoy, a flexible electro-mechanical buoy to mooring joint using a molded chain connection to the buoy, quick-release electro-mechanical couplings, and dual hydrophones suspended 7 m above the bottom. The surface buoy at the second site (33 m water depth) was a U.S. Coast Guard (USCG) channel buoy fitted with telemetry electronics and clamps to hold the hydrophones. The telemetry was tested in several configurations for a period of about four years. The custom-designed buoy and mooring provided nearly error-free data transmission through the acoustic link under a variety of oceanographic conditions for 261 days at the 24 m site. The electro mechanical joint, cables and couplings required minimal servicing and were very reliable, lasting 862 days deployed before needing repairs. The acoustic communication results from the USCG buoy were poor, apparently due to the hard cobble bottom, noise from the all-steel buoy, and failure of the hydrophone assembly. Access to the USCG buoy at sea required ideal weather. ??2006 IEEE.

  15. Near-Field Acoustical Characterization of Clustered Rocket Engines

    NASA Technical Reports Server (NTRS)

    Kandula, Max; Vu, Bruce T.; Lindsay Halie K.

    2005-01-01

    This paper presents an approach for the prediction and characterization of the near-field acoustic levels from closely-spaced clustered rocket engines. The calculations are based on the method proposed by Eldred, wherein the flowfield from the clustered rockets is divided into two zones. Zone 1 contains the isolated nozzles which produce noise independently, and extends up to a distance where the individual flows completely mix to form an equivalent single nozzle flow. Zone 2 is occupied by the single mixed stream starting from the station where the jets merge. The acoustic fields from the two zones are computed separately on the basis of the NASA-SP method of Eldred developed for a single equivalent nozzle. A summation of the spectra for the two zones yields the total effective sound pressure level for the clustered engines. Under certain conditions of nozzle spacing and flow parameters, the combined sound pressure level spectrum for the clustered nozzles displays a double peak. Test cases are presented here to demonstrate the importance of hydrodynamic interactions responsible for the double peak in the sound spectrum in the case of clustered rocket nozzles, and the role of ground reflections in the case of non-interfering jets. A graphics interface (Rocket Acoustic Prediction Tool) has been developed to take into account the effects of clustered nozzles and ground reflections.

  16. Acoustic source localization in mixed field using spherical microphone arrays

    NASA Astrophysics Data System (ADS)

    Huang, Qinghua; Wang, Tong

    2014-12-01

    Spherical microphone arrays have been used for source localization in three-dimensional space recently. In this paper, a two-stage algorithm is developed to localize mixed far-field and near-field acoustic sources in free-field environment. In the first stage, an array signal model is constructed in the spherical harmonics domain. The recurrent relation of spherical harmonics is independent of far-field and near-field mode strengths. Therefore, it is used to develop spherical estimating signal parameter via rotational invariance technique (ESPRIT)-like approach to estimate directions of arrival (DOAs) for both far-field and near-field sources. In the second stage, based on the estimated DOAs, simple one-dimensional MUSIC spectrum is exploited to distinguish far-field and near-field sources and estimate the ranges of near-field sources. The proposed algorithm can avoid multidimensional search and parameter pairing. Simulation results demonstrate the good performance for localizing far-field sources, or near-field ones, or mixed field sources.

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

    PubMed Central

    Sapozhnikov, Oleg A.; Bailey, Michael R.

    2013-01-01

    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. PMID:23363086

  18. Effects of Horizontal Magnetic Fields on Acoustic Travel Times

    NASA Astrophysics Data System (ADS)

    Jain, Rekha

    2007-02-01

    Local helioseismology techniques seek to probe the subsurface magnetic fields and flows by observing waves that emerge at the solar surface after passing through these inhomogeneities. Active regions on the surface of the Sun are distinguished by their strong magnetic fields, and techniques such as time-distance helioseismology can provide a useful diagnostic for probing these structures. Above the active regions, the fields fan out to create a horizontal magnetic canopy. We investigate the effect of a uniform horizontal magnetic field on the travel time of acoustic waves by considering vertical velocity in a simple plane-parallel adiabatically stratified polytrope. It is shown that such fields can lower the upper turning point of p-modes and hence influence their travel time. It is found that acoustic waves reflected from magnetically active regions have travel times up to a minute less than for waves similarly reflected in quiet regions. It is also found that sound speeds are increased below the active regions. These findings are consistent with time-distance measurements.

  19. Generation of thermo-acoustic waves from pulsed solar/IR radiation

    NASA Astrophysics Data System (ADS)

    Rahman, Aowabin

    Acoustic waves could potentially be used in a wide range of engineering applications; however, the high energy consumption in generating acoustic waves from electrical energy and the cost associated with the process limit the use of acoustic waves in industrial processes. Acoustic waves converted from solar radiation provide a feasible way of obtaining acoustic energy, without relying on conventional nonrenewable energy sources. One of the goals of this thesis project was to experimentally study the conversion of thermal to acoustic energy using pulsed radiation. The experiments were categorized into "indoor" and "outdoor" experiments, each with a separate experimental setup. The indoor experiments used an IR heater to power the thermo-acoustic lasers and were primarily aimed at studying the effect of various experimental parameters on the amplitude of sound waves in the low frequency range (below 130 Hz). The IR radiation was modulated externally using a chopper wheel and then impinged on a porous solid, which was housed inside a thermo-acoustic (TA) converter. A microphone located at a certain distance from the porous solid inside the TA converter detected the acoustic signals. The "outdoor" experiments, which were targeted at TA conversion at comparatively higher frequencies (in 200 Hz-3 kHz range) used solar energy to power the thermo-acoustic laser. The amplitudes (in RMS) of thermo-acoustic signals obtained in experiments using IR heater as radiation source were in the 80-100 dB range. The frequency of acoustic waves corresponded to the frequency of interceptions of the radiation beam by the chopper. The amplitudes of acoustic waves were influenced by several factors, including the chopping frequency, magnitude of radiation flux, type of porous material, length of porous material, external heating of the TA converter housing, location of microphone within the air column, and design of the TA converter. The time-dependent profile of the thermo-acoustic signals

  20. Acoustic and Cavitation Fields of Shock Wave Therapy Devices

    NASA Astrophysics Data System (ADS)

    Chitnis, Parag V.; Cleveland, Robin O.

    2006-05-01

    Extracorporeal shock wave therapy (ESWT) is considered a viable treatment modality for orthopedic ailments. Despite increasing clinical use, the mechanisms by which ESWT devices generate a therapeutic effect are not yet understood. The mechanistic differences in various devices and their efficacies might be dependent on their acoustic and cavitation outputs. We report acoustic and cavitation measurements of a number of different shock wave therapy devices. Two devices were electrohydraulic: one had a large reflector (HMT Ossatron) and the other was a hand-held source (HMT Evotron); the other device was a pneumatically driven device (EMS Swiss DolorClast Vet). Acoustic measurements were made using a fiber-optic probe hydrophone and a PVDF hydrophone. A dual passive cavitation detection system was used to monitor cavitation activity. Qualitative differences between these devices were also highlighted using a high-speed camera. We found that the Ossatron generated focused shock waves with a peak positive pressure around 40 MPa. The Evotron produced peak positive pressure around 20 MPa, however, its acoustic output appeared to be independent of the power setting of the device. The peak positive pressure from the DolorClast was about 5 MPa without a clear shock front. The DolorClast did not generate a focused acoustic field. Shadowgraph images show that the wave propagating from the DolorClast is planar and not focused in the vicinity of the hand-piece. All three devices produced measurable cavitation with a characteristic time (cavitation inception to bubble collapse) that varied between 95 and 209 μs for the Ossatron, between 59 and 283 μs for the Evotron, and between 195 and 431 μs for the DolorClast. The high-speed camera images show that the cavitation activity for the DolorClast is primarily restricted to the contact surface of the hand-piece. These data indicate that the devices studied here vary in acoustic and cavitation output, which may imply that the

  1. Power method for calculating the far acoustic field of the helicopter lift rotor

    NASA Astrophysics Data System (ADS)

    Samokhin, V. F.

    2011-05-01

    A semiempirical method for calculating the far acoustic field of the lift rotor of a helicopter operating in the regime of oblique flow over it is described. The basic parametric relations for the acoustic radiation power of rotor noise components have been obtained on the basis of the Lamb idea that vortex-free motion arises under the action of a periodic force on an infinitely small volume of the medium. All sources of lift rotor noise are subdivided into two groups pertaining, respectively, to the inductive and profile parts of the total power supplied to the rotor. A comparison has been made between the results of calculation of the harmonic components of lift rotor noise made on the basis of the power method and the experimental data for the Mi-28 helicopter.

  2. A hybrid numerical technique for predicting the aerodynamic and acoustic fields of advanced turboprops

    NASA Technical Reports Server (NTRS)

    Homicz, G. F.; Moselle, J. R.

    1985-01-01

    A hybrid numerical procedure is presented for the prediction of the aerodynamic and acoustic performance of advanced turboprops. A hybrid scheme is proposed which in principle leads to a consistent simultaneous prediction of both fields. In the inner flow a finite difference method, the Approximate-Factorization Alternating-Direction-Implicit (ADI) scheme, is used to solve the nonlinear Euler equations. In the outer flow the linearized acoustic equations are solved via a Boundary-Integral Equation (BIE) method. The two solutions are iteratively matched across a fictitious interface in the flow so as to maintain continuity. At convergence the resulting aerodynamic load prediction will automatically satisfy the appropriate free-field boundary conditions at the edge of the finite difference grid, while the acoustic predictions will reflect the back-reaction of the radiated field on the magnitude of the loading source terms, as well as refractive effects in the inner flow. The equations and logic needed to match the two solutions are developed and the computer program implementing the procedure is described. Unfortunately, no converged solutions were obtained, due to unexpectedly large running times. The reasons for this are discussed and several means to alleviate the situation are suggested.

  3. Acoustic experience shapes female mate choice in field crickets

    PubMed Central

    Bailey, Nathan W; Zuk, Marlene

    2008-01-01

    Female choice can drive the evolution of extravagant male traits. In invertebrates, the influence of prior social experience on female choice has only recently been considered. To better understand the evolutionary implications of experience-mediated plasticity in female choice, we investigated the effect of acoustic experience during rearing on female responsiveness to male song in the field cricket Teleogryllus oceanicus. Acoustic experience has unique biological relevance in this species: a morphological mutation has rendered over 90 per cent of males on the Hawaiian island of Kauai silent in fewer than 20 generations, impeding females' abilities to locate potential mates. Females reared in silent conditions mimicking Kauai were less discriminating of male calling song and more responsive to playbacks, compared with females that experienced song during rearing. Our results to our knowledge, are the first demonstration of long-term effects of acoustic experience in an arthropod, and suggest that female T. oceanicus may be able to compensate for the reduced availability of long-range male sexual signals by increasing their responsiveness to the few remaining signallers. Understanding the adaptive significance of experience-mediated plasticity in female choice provides insight into processes that facilitate rapid evolutionary change and shape sexual selection pressure in natural populations. PMID:18700205

  4. Modeling of spray combustion in an acoustic field

    SciTech Connect

    Dubey, R.K.; McQuay, M.Q.; Carvalho, J.A. Jr.

    1998-07-01

    Combustion characteristics of an ethanol flame in a Rijke-tube, pulse combustor was theoretically studied to analyze the effects of injection velocity, burner location, droplet size distribution, surrounding gas velocity, and droplet phase difference on Sauter-mean diameter. The effects of these parameters were studied at first (80 Hz), second (160 Hz), and third (240 Hz) acoustic modes with steady (no oscillations) case as reference. The sound pressure level was kept constant at 150 decibels for all theoretical simulations. The simulation frequencies and sound pressure level was selected to match the actual conditions inside the rector. For all simulations, actual droplet size and velocity distributions, as experimentally measured using a phase-Doppler particle analyzer, at the injector exit were used. Significant effects on spray size distributions were found when the burning droplets were placed at the locations corresponding to the maximum acoustic velocity amplitude. Also, for both simulations and experimental results, the Sauter-mean diameters were higher for oscillating conditions compared to steady value because small droplets burn faster under an acoustic field and therefore, Sauter-mean diameter, which is biased towards larger droplets, increases.

  5. Acoustic experience shapes female mate choice in field crickets.

    PubMed

    Bailey, Nathan W; Zuk, Marlene

    2008-11-22

    Female choice can drive the evolution of extravagant male traits. In invertebrates, the influence of prior social experience on female choice has only recently been considered. To better understand the evolutionary implications of experience-mediated plasticity in female choice, we investigated the effect of acoustic experience during rearing on female responsiveness to male song in the field cricket Teleogryllus oceanicus. Acoustic experience has unique biological relevance in this species: a morphological mutation has rendered over 90 per cent of males on the Hawaiian island of Kauai silent in fewer than 20 generations, impeding females' abilities to locate potential mates. Females reared in silent conditions mimicking Kauai were less discriminating of male calling song and more responsive to playbacks, compared with females that experienced song during rearing. Our results to our knowledge, are the first demonstration of long-term effects of acoustic experience in an arthropod, and suggest that female T. oceanicus may be able to compensate for the reduced availability of long-range male sexual signals by increasing their responsiveness to the few remaining signallers. Understanding the adaptive significance of experience-mediated plasticity in female choice provides insight into processes that facilitate rapid evolutionary change and shape sexual selection pressure in natural populations. PMID:18700205

  6. Fast computation of the acoustic field for ultrasound elements.

    PubMed

    Güven, H Emre; Miller, Eric L; Cleveland, Robin O

    2009-09-01

    A fast method for computing the acoustic field of ultrasound transducers is presented with application to rectangular elements that are cylindrically focused. No closed-form solutions exist for this case but several numerical techniques have been described in the ultrasound imaging literature. Our motivation is the rapid calculation of imaging kernels for physics-based diagnostic imaging for which current methods are too computationally intensive. Here, the surface integral defining the acoustic field from a baffled piston is converted to a 3-D spatial convolution of the element surface and the Green's function. A 3-D version of the overlap-save method from digital signal processing is employed to obtain a fast computational algorithm based on spatial Fourier transforms. Further efficiency is gained by using a separable approximation to the Green's function through singular value decomposition and increasing the effective sampling rate by polyphase filtering. The tradeoff between accuracy and spatial sampling rate is explored to determine appropriate parameters for a specific transducer. Comparisons with standard tools such as Field II are presented, where nearly 2 orders of magnitude improvement in computation speed is observed for similar accuracy. PMID:19811993

  7. Particle trapping and transport achieved via an adjustable acoustic field above a phononic crystal plate

    NASA Astrophysics Data System (ADS)

    Wang, T.; Ke, M.; Qiu, C.; Liu, Z.

    2016-06-01

    We present the design for an acoustic system that can achieve particle trapping and transport using the acoustic force field above a phononic crystal plate. The phononic crystal plate comprised a thin brass plate with periodic slits alternately embedded with two kinds of elastic inclusions. Enhanced acoustic transmission and localized acoustic fields were achieved when the structure was excited by external acoustic waves. Because of the different resonant frequencies of the two elastic inclusions, the acoustic field could be controlled via the working frequency. Particles were transported between adjacent traps under the influence of the adjustable acoustic field. This device provides a new and versatile avenue for particle manipulation that would complement other means of particle manipulation.

  8. Acoustic radiation force on a sphere in standing and quasi-standing zero-order Bessel beam tweezers

    NASA Astrophysics Data System (ADS)

    Mitri, F. G.

    2008-07-01

    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 β of its plane wave components, such that β = 0 represents a plane wave. It is assumed here that the half-cone angle β 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. 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.

  10. Weakly Dissipative Dust Ion-Acoustic Solitons in the Presence of Electromagnetic Radiation

    SciTech Connect

    Golub', A. P.; Izvekova, Y. N.; Losseva, T. V.; Popel, S. I.; Shukla, P. K.

    2011-11-29

    We present the model, which describes nonlinear dust ion-acoustic (DIA) perturbations in complex plasmas with electromagnetic radiation. We study time-evolution of the individual DIA soliton and interaction of two DIA solitons.

  11. Ultrafast strain gauge: Observation of THz radiation coherently generated by acoustic waves

    SciTech Connect

    Armstrong, M; Reed, E; Kim, K; Glownia, J; Howard, W M; Piner, E; Roberts, J

    2008-08-14

    The study of nanoscale, terahertz frequency (THz) acoustic waves has great potential for elucidating material and chemical interactions as well as nanostructure characterization. Here we report the first observation of terahertz radiation coherently generated by an acoustic wave. Such emission is directly related to the time-dependence of the stress as the acoustic wave crosses an interface between materials of differing piezoelectric response. This phenomenon enables a new class of strain wave metrology that is fundamentally distinct from optical approaches, providing passive remote sensing of the dynamics of acoustic waves with ultrafast time resolution. The new mechanism presented here enables nanostructure measurements not possible using existing optical or x-ray approaches.

  12. Angular Spectrum Method for the Focused Acoustic Field of a Linear Transducer

    NASA Astrophysics Data System (ADS)

    Belgroune, D.; de Belleval, J. F.; Djelouah, H.

    Applications involving non-destructive testing or acoustical imaging are more and more sophisticated. In this context, a model based on the angular spectrum approach is tackled in view to calculate the focused impulse field radiated by a linear transducer through a plane fluid-solid interface. It is well known that electronic focusing, based on a cylindrical delay law, like for the classical cases (lenses, curved transducer), leads to an inaccurate focusing in the solid due to geometric aberrations errors affecting refraction. Generally, there is a significant difference between the acoustic focal distance and the geometrical focal due to refraction. In our work, an optimized delay law, based on the Fermat's principle is established, particularly at an oblique incidence where the geometrical considerations, relatively simple in normal incidence, become quickly laborious. Numerical simulations of impulse field are judiciously carried out. Subsequently, the input parameters are optimally selected in order to achieve good computation accuracy and a high focusing. The overall results, involving compression and shear waves, have highlighted the focusing improvement in the solid when compared to the currently available approaches. Indeed, the acoustic focal distance is very close to geometrical focal distance and then, allows better control of the refracted angular beam profile (refraction angle, focusing depth and focal size).

  13. Ultrasonic Measurement of Microdisplacement Induced by Acoustic Radiation Force

    NASA Astrophysics Data System (ADS)

    Nagaoka, Ryo; Izumi, Takuya; Komatsu, Yosuke; Kobayashi, Kazuto; Saijo, Yoshifumi

    2013-07-01

    Quantitative evaluation of human skin aging is achieved by measuring the viscoelasticity of the skin. In the present study, microdisplacement induced by acoustic radiation force (ARF) is quantitatively measured by high-frequency ultrasonography (HFUS) and the result is confirmed by laser-Doppler velocimetry (LDV). Poly(vinyl alcohol) (PVA) with 1% cellulose particles was used as the biological phantom. A concave piezoelectric zirconate titanate (PZT) transducer with a diameter and focal length of 3 cm was used as an applicator to generate ARF. Microdisplacement at each depth of PVA was measured by the phased tracking method at 100 MHz of ultrasound with a repetition rate of 2000 Hz. When 80 tone-burst pulses were applied, the displacement measured by HFUS was 9 µm and the same result was obtained by LDV. As the displacement at each depth of PVA is measurable using ARF and the HFUS system, the system could be applied to measuring the viscoelasticity of the layered structure of the human skin.

  14. 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.

  15. 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

  16. Acoustic tracking of a freely drifting sonobuoy field.

    PubMed

    Dosso, Stan E; Collison, Nicole E B

    2002-05-01

    This paper develops an acoustic inversion algorithm to track a field of freely drifting sonobuoys using travel-time measurements from a series of nonsimultaneous impulsive sources deployed around the field. In this scenario, the time interval between sources can be sufficiently long that significant independent movement of the individual sonobuoys occurs. In addition, the source transmission instants are unknown, and the source positions and initial sonobuoy positions are known only approximately. The formulation developed here solves for the track of each sonobuoy (parametrized by the sonobuoy positions at the time of each source transmission), allowing arbitrary, independent sonobuoy motion between transmissions, as well as for the source positions and transmission instants. This leads to a strongly underdetermined inverse problem. However, regularized inversion provides meaningful solutions by incorporating a priori information consisting of prior estimates (with uncertainties) for the source positions and initial sonobuoy positions, and a physical model for preferred sonobuoy motion. Several models for sonobuoy motion are evaluated, with the best results obtained by minimizing the second spatial derivative of the tracks to obtain the minimum-curvature or smoothest track, subject to fitting the acoustic data to a statistically appropriate level. PMID:12051436

  17. Acoustic tracking of a freely drifting sonobuoy field

    NASA Astrophysics Data System (ADS)

    Dosso, Stan E.; Collison, Nicole E. B.

    2002-05-01

    This paper develops an acoustic inversion algorithm to track a field of freely drifting sonobuoys using travel-time measurements from a series of nonsimultaneous impulsive sources deployed around the field. In this scenario, the time interval between sources can be sufficiently long that significant independent movement of the individual sonobuoys occurs. In addition, the source transmission instants are unknown, and the source positions and initial sonobuoy positions are known only approximately. The formulation developed here solves for the track of each sonobuoy (parametrized by the sonobuoy positions at the time of each source transmission), allowing arbitrary, independent sonobuoy motion between transmissions, as well as for the source positions and transmission instants. This leads to a strongly underdetermined inverse problem. However, regularized inversion provides meaningful solutions by incorporating a priori information consisting of prior estimates (with uncertainties) for the source positions and initial sonobuoy positions, and a physical model for preferred sonobuoy motion. Several models for sonobuoy motion are evaluated, with the best results obtained by minimizing the second spatial derivative of the tracks to obtain the minimum-curvature or smoothest track, subject to fitting the acoustic data to a statistically appropriate level.

  18. Evidence of Longitudinal Acoustic Phonon Generation in Si Doping Superlattices by Ge Prism-Coupled THz Laser Radiation

    NASA Astrophysics Data System (ADS)

    Wilson, T.; Kasper, E.; Oehme, M.; Schulze, J.; Korolev, K.

    2014-11-01

    We report on the direct excitation of 246 GHz longitudinal acoustic phonons in silicon doping superlattices by the resonant absorption of nanosecond-pulsed far-infrared laser radiation of the same frequency. A longitudinally polarized evanescent laser light field is coupled to the superlattice through a germanium prism providing total internal reflection at the superlattice interface. The ballistic phonon signal is detected by a superconducting aluminum bolometer. The sample is immersed in low-temperature liquid helium.

  19. Nonlinear electron acoustic waves in presence of shear magnetic field

    SciTech Connect

    Dutta, Manjistha; Khan, Manoranjan; Ghosh, Samiran; Chakrabarti, Nikhil

    2013-12-15

    Nonlinear electron acoustic waves are studied in a quasineutral plasma in the presence of a variable magnetic field. The fluid model is used to describe the dynamics of two temperature electron species in a stationary positively charged ion background. Linear analysis of the governing equations manifests dispersion relation of electron magneto sonic wave. Whereas, nonlinear wave dynamics is being investigated by introducing Lagrangian variable method in long wavelength limit. It is shown from finite amplitude analysis that the nonlinear wave characteristics are well depicted by KdV equation. The wave dispersion arising in quasineutral plasma is induced by transverse magnetic field component. The results are discussed in the context of plasma of Earth's magnetosphere.

  20. Study of acoustic field modulation in the regenerator by double loudspeakers method.

    PubMed

    Zhou, Lihua; Xie, Xiujuan; Li, Qing

    2011-11-01

    A model to modulate acoustic field in a regenerator of a thermoacoustic system by the double loudspeakers method is presented in this paper. The equations are derived for acoustic field modulation. They represent the relations among acoustic field (complex pressure p(0), complex velocity u(0), and acoustic impedance Z(0)), driving parameters of loudspeakers (voltage amplitude and its phase difference), and operating parameters involved in a matrix H (frequency, temperature of regenerator). The range of acoustic field is adjustable and limited by the maximal driving voltages of loudspeakers according to driving parameters. The range is simulated and analyzed in the amplitude-phase and complex coordinate planes for a given or variable H. The simulated results indicate that the range has its intrinsic characteristics. The expected acoustic field in a regenerator can be obtained feasibly by the modulation. PMID:22087899

  1. Iodine-starch clathrate complexes in low-field acoustic fields

    NASA Astrophysics Data System (ADS)

    Fadeev, G. N.; Boldyrev, V. S.; Ermolaeva, V. I.; Eliseeva, N. M.

    2013-01-01

    Experimental data on the kinetics of formation and decomposition of iodine-starch clathrate complexes (amyloiodine and amylopectoiodine) in low-frequency (5-45 Hz) acoustic fields are reported. The biological activity of these compounds suggests their use as a model of biocatalysts, in which iodine represents the coenzyme active group and starch homopolysaccharides (amylopectin and amylose) represents the apoenzyme.

  2. 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.

  3. 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.

  4. 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.

  5. Some far-field acoustics characteristics of the XV-15 tilt-rotor aircraft

    NASA Technical Reports Server (NTRS)

    Golub, Robert A.; Conner, David A.; Becker, Lawrence E.; Rutledge, C. Kendall; Smith, Rita A.

    1990-01-01

    Far-field acoustics tests have been conducted on an instrumented XV-15 tilt-rotor aircraft. The purpose of these acoustic measurements was to create an encompassing, high confidence (90 percent), and accurate (-1.4/ +1/8 dB theoretical confidence interval) far-field acoustics data base to validate ROTONET and other current rotorcraft noise prediction computer codes. This paper describes the flight techniques used, with emphasis on the care taken to obtain high-quality far-field acoustic data. The quality and extensiveness of the data base collected are shown by presentation of ground acoustic contours for level flyovers for the airplane flight mode and for several forward velocities and nacelle tilts for the transition mode and helicopter flight mode. Acoustic pressure time-histories and fully analyzed ensemble averaged far-field data results (spectra) are shown for each of the ground contour cases.

  6. Acoustic Radiation Force Impulse Measurement in Renal Transplantation

    PubMed Central

    Lee, Juhan; Oh, Young Taik; Joo, Dong Jin; Ma, Bo Gyoung; Lee, A-lan; Lee, Jae Geun; Song, Seung Hwan; Kim, Seung Up; Jung, Dae Chul; Chung, Yong Eun; Kim, Yu Seun

    2015-01-01

    Abstract Interstitial fibrosis and tubular atrophy (IF/TA) is a common cause of kidney allograft loss. Several noninvasive techniques developed to assess tissue fibrosis are widely used to examine the liver. However, relatively few studies have investigated the use of elastographic methods to assess transplanted kidneys. The aim of this study was to explore the clinical implications of the acoustic radiation force impulse (ARFI) technique in renal transplant patients. A total of 91 patients who underwent living donor renal transplantation between September 2010 and January 2013 were included in this prospective study. Shear wave velocity (SWV) was measured by ARFI at baseline and predetermined time points (1 week and 6 and 12 months after transplantation). Protocol biopsies were performed at 12 months. Instead of reflecting IF/TA, SWVs were found to be related to time elapsed after transplantation. Mean SWV increased continuously during the first postoperative year (P < 0.001). In addition, mixed model analysis showed no correlation existed between SWV and serum creatinine (r = −0.2426, P = 0.0771). There was also no evidence of a relationship between IF/TA and serum creatinine (odds ratio [OR] = 1.220, P = 0.7648). Furthermore, SWV temporal patterns were dependent on the kidney weight to body weight ratio (KW/BW). In patients with a KW/BW <3.5 g/kg, mean SWV continuously increased for 12 months, whereas it decreased after 6 months in those with a KW/BW ≥3.5 g/kg. No significant correlation was observed between SWV and IF/TA or renal dysfunction. However, SWV was found to be related to the time after transplantation. Renal hemodynamics influenced by KW/BW might impact SWV values. PMID:26426636

  7. Drop dynamics in space and interference with acoustic field (M-15)

    NASA Technical Reports Server (NTRS)

    Yamanaka, Tatsuo

    1993-01-01

    The objective of the experiment is to study contactless positioning of liquid drops, excitation of capillary waves on the surface of acoustically levitated liquid drops, and deformation of liquid drops by means of acoustic radiation pressure. Contactless positioning technologies are very important in space materials processing because the melt is processed without contacting the wall of a crucible which can easily contaminate the melt specifically for high melting temperatures and chemically reactive materials. Among the contactless positioning technologies, an acoustic technology is especially important for materials unsusceptible to electromagnetic fields such as glasses and ceramics. The shape of a levitated liquid drop in the weightless condition is determined by its surface tension and the internal and external pressure distribution. If the surface temperature is constant and there exist neither internal nor external pressure perturbations, the levitated liquid drop forms a shape of perfect sphere. If temperature gradients on the surface and internal or external pressure perturbations exist, the liquid drop forms various modes of shapes with proper vibrations. A rotating liquid drop was specifically studied not only as a classical problem of theoretical mechanics to describe the shapes of the planets of the solar system, as well as their arrangement, but it is also more a contemporary problem of modern non-linear mechanics. In the experiment, we are expecting to observe various shapes of a liquid drop such as cocoon, tri-lobed, tetropod, multi-lobed, and doughnut.

  8. Modeling and experimental study on near-field acoustic levitation by flexural mode.

    PubMed

    Liu, Pinkuan; Li, Jin; Ding, Han; Cao, Wenwu

    2009-12-01

    Near-field acoustic levitation (NFAL) has been used in noncontact handling and transportation of small objects to avoid contamination. We have performed a theoretical analysis based on nonuniform vibrating surface to quantify the levitation force produced by the air film and also conducted experimental tests to verify our model. Modal analysis was performed using ANSYS on the flexural plate radiator to obtain its natural frequency of desired mode, which is used to design the measurement system. Then, the levitation force was calculated as a function of levitation distance based on squeeze gas film theory using measured amplitude and phase distributions on the vibrator surface. Compared with previous fluid-structural analyses using a uniform piston motion, our model based on the nonuniform radiating surface of the vibrator is more realistic and fits better with experimentally measured levitation force. PMID:20040404

  9. Numerical derivation of forces on particles and agglomerates in a resonant acoustic field

    NASA Astrophysics Data System (ADS)

    Knoop, Claas; Fritsching, Udo

    2013-10-01

    Particles and agglomerates are investigated in gaseous acoustic flow fields. Acoustic fields exert forces on solid objects, which can influence the shape of the exposed bodies, even to the point of breakage of the structures. Motivated by experimentally observed breakage of agglomerates in an acoustic levitator (f = 20 kHz), a numerical study is presented that derives the acoustic forces on a complex model agglomerate from the pressure and velocity fields of a resonant standing ultrasound wave, calculated by computational fluid dynamics (CFD). It is distinguished between the drag and lift/lateral forces on the overall agglomerate and on the different primary particles of the model.

  10. 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. PMID:22087995

  11. 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.

  12. Orbital motions of bubbles in an acoustic field

    NASA Astrophysics Data System (ADS)

    Shirota, Minori; Yamashita, Ko; Inamura, Takao

    2012-09-01

    This experimental study aims to clarify the mechanism of orbital motion of two oscillating bubbles in an acoustic field. Trajectory of the orbital motion on the wall of a spherical levitator was observed using a high-speed video camera. Because of a good repeatability in volume oscillation of bubbles, we were also able to observe the radial motion driven at 24 kHz by stroboscopic like imaging technique. The orbital motions of bubbles raging from 0.13 to 0.18 mm were examined with different forcing amplitude and in different viscous oils. As a result, we found that pairs of bubbles revolve along an elliptic orbit around the center of mass of the bubbles. We also found that the two bubbles perform anti-phase radial oscillation. Although this radial oscillation should result in a repulsive secondary Bjerknes force, the bubbles kept a constant separate distance of about 1 mm, which indicates the existence of centripetal primary Bjerknes force.

  13. Convergent acoustic field of view in echolocating bats.

    PubMed

    Jakobsen, Lasse; Ratcliffe, John M; Surlykke, Annemarie

    2013-01-01

    Most echolocating bats exhibit a strong correlation between body size and the frequency of maximum energy in their echolocation calls (peak frequency), with smaller species using signals of higher frequency than larger ones. Size-signal allometry or acoustic detection constraints imposed on wavelength by preferred prey size have been used to explain this relationship. Here we propose the hypothesis that smaller bats emit higher frequencies to achieve directional sonar beams, and that variable beam width is critical for bats. Shorter wavelengths relative to the size of the emitter translate into more directional sound beams. Therefore, bats that emit their calls through their mouths should show a relationship between mouth size and wavelength, driving smaller bats to signals of higher frequency. We found that in a flight room mimicking a closed habitat, six aerial hawking vespertilionid species (ranging in size from 4 to 21 g, ref. 5) produced sonar beams of extraordinarily similar shape and volume. Each species had a directivity index of 11 ± 1 dB (a half-amplitude angle of approximately 37°) and an on-axis sound level of 108 ± 4 dB sound pressure level referenced to 20 μPa root mean square at 10 cm. Thus all bats adapted their calls to achieve similar acoustic fields of view. We propose that the necessity for high directionality has been a key constraint on the evolution of echolocation, which explains the relationship between bat size and echolocation call frequency. Our results suggest that echolocation is a dynamic system that allows different species, regardless of their body size, to converge on optimal fields of view in response to habitat and task. PMID:23172147

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

    PubMed Central

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

    2015-01-01

    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. 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

  16. Acoustics

    NASA Astrophysics Data System (ADS)

    The acoustics research activities of the DLR fluid-mechanics department (Forschungsbereich Stroemungsmechanik) during 1988 are surveyed and illustrated with extensive diagrams, drawings, graphs, and photographs. Particular attention is given to studies of helicopter rotor noise (high-speed impulsive noise, blade/vortex interaction noise, and main/tail-rotor interaction noise), propeller noise (temperature, angle-of-attack, and nonuniform-flow effects), noise certification, and industrial acoustics (road-vehicle flow noise and airport noise-control installations).

  17. Potential theoretic methods for far field sound radiation calculations

    NASA Technical Reports Server (NTRS)

    Hariharan, S. I.; Stenger, Edward J.; Scott, J. R.

    1995-01-01

    In the area of computational acoustics, procedures which accurately predict the far-field sound radiation are much sought after. A systematic development of such procedures are found in a sequence of papers by Atassi. The method presented here is an alternate approach to predicting far field sound based on simple layer potential theoretic methods. The main advantages of this method are: it requires only a simple free space Green's function, it can accommodate arbitrary shapes of Kirchoff surfaces, and is readily extendable to three-dimensional problems. Moreover, the procedure presented here, though tested for unsteady lifting airfoil problems, can easily be adapted to other areas of interest, such as jet noise radiation problems. Results are presented for lifting airfoil problems and comparisons are made with the results reported by Atassi. Direct comparisons are also made for the flat plate case.

  18. Effect of tidal internal wave fields on shallow water acoustic propagation

    NASA Astrophysics Data System (ADS)

    Lin, Ju; Wang, Huan; Sun, Junping

    2010-09-01

    Internal waves are one of the most pronounced oceanic phenomenons to the oceanographer. During past decades much effort has been made to investigate the effect of internal waves on shallow water acoustic propagation. Even though many field observations, such as SWARM '95, have provided fruitful information about the relation between internal waves and acoustic propagation, it is necessary to conduct more numerical simulations due to their extensive feasibility. In this study, the shallow water internal wave environment is constructed by using a non-hydrostatic ocean model, the open boundary forcing is set by considering single or several internal wave modes at the M2 tidal frequency. In order to show the mode coupling caused by the internal wave field more clearly, the acoustic starting field with different single normal modes is adopted. The acoustic simulation can be used to check whether a specific combination of internal wave modes is related to the mode coupling, and which mode pair will be affected. The combination of internal wave modes can be separated into several groups. Even though the internal wave fields are different among every case in each group, the acoustic field structure and the mode coupling are similar. Different acoustic normal mode coupling occurs due to the different combinations of internal wave mode forcing. When the parameters of internal wave mode are modified gently, the acoustic mode coupling becomes quite different. It is interesting and important to investigate the sensitivity of acoustic fields to the variability of the internal mode combination.

  19. Characterization of Transducer Performance and Narrowband Transient Ultrasonic Fields in Metals by Rayleigh-Sommerfeld Backpropagation of Compression Acoustic Waves Measured with Double-Pulsed Tv Holography

    NASA Astrophysics Data System (ADS)

    Trillo, Cristina; Doval, Ángel F.; Fernández, José L.; Rodríguez-Gómez, Pablo; López-Vázquez, J. Carlos

    2014-10-01

    This article presents a method aimed at the characterization of the narrowband transient acoustic field radiated by an ultrasonic plane transducer into a homogeneous, isotropic and optically opaque prismatic solid, and the assessment of the performance of the acoustic source. The method relies on a previous technique based on the full-field optical measurement of an acoustic wavepacket at the surface of a solid and its subsequent numerical backpropagation within the material. The experimental results show that quantitative transversal and axial profiles of the complex amplitude of the beam can be obtained at any plane between the measurement and excitation surfaces. The reconstruction of the acoustic field at the transducer face, carried out on a defective transducer model, shows that the method could also be suitable for the nondestructive testing of the performance of ultrasonic sources. In all cases, the measurements were performed with the transducer working under realistic loading conditions.

  20. 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.

  1. Theoretical analysis of a cell's oscillations in an acoustic field

    NASA Astrophysics Data System (ADS)

    Allen, John S.; Zinin, Pavel

    2005-09-01

    The analysis and deformation of an individual cell in a high-frequency acoustic field is of fundamental interest for a variety of applications such as ultrasound cell separation and drug delivery. The oscillations of biological cells in a sound field are investigated using a shell model for the cell following an approach developed previously [Zinin, Ultrasonics, 30, 26-34 (1992)]. The model accounts for the three components which comprise the cell's motion: the internal fluid (cytoplasma), the cell membrane, and the surrounding fluid. The cell membrane whose thickness is small compared to the cell radius can be approximated as a thin elastic shell. The elastic properties of this shell together with the viscosities of the internal and external fluids determine the oscillations of the cell. The dipole oscillations of the cell depend on the surface area modulus and the maximum frequency for the relative change in cell area can be determined. Moreover, the higher order oscillations starting with the quadrupole oscillations are governed by the shell's shear modulus. Induced stresses in bacteria cell membranes in the vicinity of an oscillating bubble are investigated and cell rupture with respect to these stresses is analyzed.

  2. 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

  3. 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

  4. Comparison between experimental and computational methods for the acoustic and thermal characterization of therapeutic ultrasound fields.

    PubMed

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

    2015-04-01

    For high intensity therapeutic ultrasound (HITU) devices, pre-clinical testing can include measurement of power, pressure/intensity and temperature distribution, acoustic and thermal simulations, and assessment of targeting accuracy and treatment monitoring. Relevant International Electrotechnical Commission documents recently have been published. However, technical challenges remain because of the often focused, large amplitude pressure fields encountered. Measurement and modeling issues include using hydrophones and radiation force balances at HITU power levels, validation of simulation models, and tissue-mimicking material (TMM) development for temperature measurements. To better understand these issues, a comparison study was undertaken between simulations and measurements of the HITU acoustic field distribution in water and TMM and temperature rise in TMM. For the specific conditions of this study, the following results were obtained. In water, the simulated values for p+ and p- were 3% lower and 10% higher, respectively, than those measured by hydrophone. In TMM, the simulated values for p+ and p- were 2% and 10% higher than those measured by hydrophone, respectively. The simulated spatial-peak temporal-average intensity values in water and TMM were greater than those obtained by hydrophone by 3%. Simulated and measured end-of-sonication temperatures agreed to within their respective uncertainties (coefficients of variation of approximately 20% and 10%, respectively). PMID:25920823

  5. Production of Local Acoustic Radiation Force to Constrain Direction of Microcapsules in Flow

    NASA Astrophysics Data System (ADS)

    Kohji Masuda,; Nobuyuki Watarai,; Ryusuke Nakamoto,; Yusuke Muramatsu,

    2010-07-01

    We have ever reported our attempt to control the direction of microcapsules in flow by acoustic radiation force. However, the diameter of capsules was too large to be applied in vivo. Furthermore, the acoustic radiation force affected only the focal area because focused ultrasound was used. Thus, we have improved our experiment by using microcapsules as small as blood cells and introducing a plane wave of ultrasound. We prepared an artificial blood vessel including a Y-form bifurcation established in two observation areas. Then, we newly defined the induction index to evaluate the difference in capsule density in two downstream paths. As a result, the optimum angle of ultrasound emission to induct to the desired path was derived. The induction index increased in proportion to the central frequency of ultrasound, which is affected by the aggregation of capsules to receive more acoustic radiation force.

  6. Tomographic reconstruction of transient acoustic fields recorded by pulsed TV holography.

    PubMed

    Gren, P; Schedin, S; Li, X

    1998-02-10

    Pulsed TV holography combined with computerized tomography (CT) are used to evaluate the three-dimensional distribution of transient acoustic fields in air. Experiments are performed with an electrical discharge between two electrodes as the sound source. Holograms from several directions of the acoustic field are recorded directly onto a CCD detector by use of a double-pulsed ruby laser as the light source. Phase maps, representing projections of the acoustic field, are evaluated quantitatively from the recorded holograms. The projections are used for the CT reconstruction to evaluate the pressure-field distribution in any cross section of the measured volume of air. PMID:18268660

  7. 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

  8. Development of anticavitation hydrophone using a titanium front plate: Effect of the titanium front plate in high-intensity acoustic field with generation of acoustic cavitation

    NASA Astrophysics Data System (ADS)

    Shiiba, Michihisa; Okada, Nagaya; Kurosawa, Minoru; Takeuchi, Shinichi

    2016-07-01

    Novel anticavitation hydrophones were fabricated by depositing a hydrothermally synthesized lead zirconate titanate polycrystalline film at the back of a titanium front plate. These anticavitation hydrophones were not damaged by the measurement of the acoustic field formed by a high-intensity focused ultrasound (HIFU) device. Their sensitivity was improved by approximately 20 dB over that of the conventional anticavitation hydrophone by modifying their basic structure and materials. The durability of the anticavitation hydrophone that we fabricated was compared by exposing it to a high-intensity acoustic field at the focal point of the HIFU field and in the water tank of an ultrasound cleaner. Therefore, the effect of the surface of the titanium front plate on acoustic cavitation was investigated by exposing such a surface to the high-intensity acoustic field. We found that the fabricated anticavitation hydrophone was robust and was not damaged easily, even in the focused acoustic field where acoustic cavitation occurs.

  9. 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

  10. 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.

  11. 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.

  12. Frequency dependence of the acoustic field generated from a spherical cavity transducer with open ends

    SciTech Connect

    Li, Faqi; Zeng, Deping; He, Min; Wang, Zhibiao E-mail: wangzhibiao@haifu.com.cn; Song, Dan; Lei, Guangrong; Lin, Zhou; Zhang, Dong E-mail: wangzhibiao@haifu.com.cn; Wu, Junru

    2015-12-15

    Resolution of high intensity focused ultrasound (HIFU) focusing is limited by the wave diffraction. We have developed a spherical cavity transducer with two open ends to improve the focusing precision without sacrificing the acoustic intensity (App Phys Lett 2013; 102: 204102). This work aims to theoretically and experimentally investigate the frequency dependence of the acoustic field generated from the spherical cavity transducer with two open ends. The device emits high intensity ultrasound at the frequency ranging from 420 to 470 kHz, and the acoustic field is measured by a fiber optic probe hydrophone. The measured results shows that the spherical cavity transducer provides high acoustic intensity for HIFU treatment only in its resonant modes, and a series of resonant frequencies can be choosen. Furthermore, a finite element model is developed to discuss the frequency dependence of the acoustic field. The numerical simulations coincide well with the measured results.

  13. Frequency dependence of the acoustic field generated from a spherical cavity transducer with open ends

    NASA Astrophysics Data System (ADS)

    Li, Faqi; Song, Dan; Zeng, Deping; Lin, Zhou; He, Min; Lei, Guangrong; Wu, Junru; Zhang, Dong; Wang, Zhibiao

    2015-12-01

    Resolution of high intensity focused ultrasound (HIFU) focusing is limited by the wave diffraction. We have developed a spherical cavity transducer with two open ends to improve the focusing precision without sacrificing the acoustic intensity (App Phys Lett 2013; 102: 204102). This work aims to theoretically and experimentally investigate the frequency dependence of the acoustic field generated from the spherical cavity transducer with two open ends. The device emits high intensity ultrasound at the frequency ranging from 420 to 470 kHz, and the acoustic field is measured by a fiber optic probe hydrophone. The measured results shows that the spherical cavity transducer provides high acoustic intensity for HIFU treatment only in its resonant modes, and a series of resonant frequencies can be choosen. Furthermore, a finite element model is developed to discuss the frequency dependence of the acoustic field. The numerical simulations coincide well with the measured results.

  14. 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

  15. Detection of in-plane displacements of acoustic wave fields using extrinsic Fizeau fiber interferometric sensors

    NASA Technical Reports Server (NTRS)

    Dhawan, R.; Gunther, M. F.; Claus, R. O.

    1991-01-01

    Quantitative measurements of the in-plane particle displacement components of ultrasonic surface acoustic wave fields using extrinsic Fizeau fiber interferometric (EFFI) sensors are reported. Wave propagation in materials and the fiber sensor elements are briefly discussed. Calibrated experimental results obtained for simulated acoustic emission events on homogeneous metal test specimens are reported and compared to previous results obtained using piezoelectric transducers.

  16. Modified ion-acoustic solitary waves in plasmas with field-aligned shear flows

    SciTech Connect

    Saleem, H.; Haque, Q.

    2015-08-15

    The nonlinear dynamics of ion-acoustic waves is investigated in a plasma having field-aligned shear flow. A Korteweg-deVries-type nonlinear equation for a modified ion-acoustic wave is obtained which admits a single pulse soliton solution. The theoretical result has been applied to solar wind plasma at 1 AU for illustration.

  17. Improving Classroom Acoustics (ICA): A Three-Year FM Sound Field Classroom Amplification Study.

    ERIC Educational Resources Information Center

    Rosenberg, Gail Gegg; Blake-Rahter, Patricia; Heavner, Judy; Allen, Linda; Redmond, Beatrice Myers; Phillips, Janet; Stigers, Kathy

    1999-01-01

    The Improving Classroom Acoustics (ICA) special project was designed to determine if students' listening and learning behaviors improved as a result of an acoustical environment enhanced through the use of FM sound field classroom amplification. The 3-year project involved 2,054 students in 94 general education kindergarten, first-, and…

  18. Influence of the outer scales of temperature and dynamic turbulence on the characteristics of transmitted acoustic radiation

    NASA Astrophysics Data System (ADS)

    Shamanaeva, L. G.; Belov, V. V.; Burkatovskaya, Yu. B.; Krasnenko, N. P.

    2015-11-01

    In the present work, the problem of propagation of monochromatic acoustic radiation in the lower 500-meter layer of the plain stratified moving turbulent atmosphere is solved by the Monte Carlo method. The influence of the parameters of models of the outer scales of temperature and dynamic turbulence on the intensity of transmitted acoustic radiation intensity is investigated.

  19. 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

  20. 3D Finite-Difference Modeling of Acoustic Radiation from Seismic Sources

    NASA Astrophysics Data System (ADS)

    Chael, E. P.; Aldridge, D. F.; Jensen, R. P.

    2013-12-01

    Shallow seismic events, earthquakes as well as explosions, often generate acoustic waves in the atmosphere observable at local or even regional distances. Recording both the seismic and acoustic signals can provide additional constraints on source parameters such as epicenter coordinates, depth, origin time, moment, and mechanism. Recent advances in finite-difference (FD) modeling methods enable accurate numerical treatment of wave propagation across the ground surface between the (solid) elastic and (fluid) acoustic domains. Using a fourth-order, staggered-grid, velocity-stress FD algorithm, we are investigating the effects of various source parameters on the acoustic (or infrasound) signals transmitted from the solid earth into the atmosphere. Compressional (P), shear (S), and Rayleigh waves all radiate some acoustic energy into the air at the ground surface. These acoustic wavefronts are typically conical in shape, since their phase velocities along the surface exceed the sound speed in air. Another acoustic arrival with a spherical wavefront can be generated from the vicinity of the epicenter of a shallow event, due to the strong vertical ground motions directly above the buried source. Images of acoustic wavefields just above the surface reveal the radiation patterns and relative amplitudes of the various arrivals. In addition, we compare the relative effectiveness of different seismic source mechanisms for generating acoustic energy. For point sources at a fixed depth, double-couples with almost any orientation produce stronger acoustic signals than isotropic explosions, due to higher-amplitude S and Rayleigh waves. Of course, explosions tend to be shallower than most earthquakes, which can offset the differences due to mechanism. Low-velocity material in the shallow subsurface acts to increase vertical seismic motions there, enhancing the coupling to acoustic waves in air. If either type of source breaks the surface (e.g., an earthquake with surface rupture

  1. Patch nearfield acoustic holography combined with sound field separation technique applied to a non-free field

    NASA Astrophysics Data System (ADS)

    Bi, ChuanXing; Jing, WenQian; Zhang, YongBin; Xu, Liang

    2015-02-01

    The conventional nearfield acoustic holography (NAH) is usually based on the assumption of free-field conditions, and it also requires that the measurement aperture should be larger than the actual source. This paper is to focus on the problem that neither of the above-mentioned requirements can be met, and to examine the feasibility of reconstructing the sound field radiated by partial source, based on double-layer pressure measurements made in a non-free field by using patch NAH combined with sound field separation technique. And also, the sensitivity of the reconstructed result to the measurement error is analyzed in detail. Two experiments involving two speakers in an exterior space and one speaker inside a car cabin are presented. The experimental results demonstrate that the patch NAH based on single-layer pressure measurement cannot obtain a satisfied result due to the influences of disturbing sources and reflections, while the patch NAH based on double-layer pressure measurements can successfully remove these influences and reconstruct the patch sound field effectively.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Radiation Q of dipole-generated fields

    NASA Astrophysics Data System (ADS)

    Grimes, Dale M.; Grimes, Craig A.

    1999-03-01

    The radiation Q of several dipole fields in free space are determined using the time-dependent Poynting theorem. Earlier works on this subject, recently summarized by McLean [1996], are based upon the complex Poynting theorem. It was previously shown [Grimes and Grimes, 1997] that the full complex Poynting theorem is correct only for single-mode radiation fields. The time-dependent theorem shows that three numbers are necessary to completely specify time-varying power, and complex numbers supply but two; the third piece of information, a phase, is discarded when complex notation is formed. Omissions inherent in the complex Poynting theorem affect the calculated value of standing energy about an antenna and hence the calculated value of Q. To avoid such omissions, we develop a method of determining Q based upon the time-dependent Poynting theorem that builds upon and extends our earlier work [Grimes and Grimes, 1997]. The purposes of this paper are to (1) provide a time domain basis for calculating Q in mixed modal radiation fields, (2) determine the Q of electric and magnetic dipoles, alone and in combination, and (3) demonstrate how source structure and relative phasing affect the physics of several combinations of electric and magnetic dipole radiation fields. The primary conclusion of this work is that the minimum possible Q of a radiation source established by Chu [1948] does not extend to properly mixed and phased multimodal radiation fields. A radiation source is presented for which, by our analysis, the radiation Q is zero.

  7. 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.

  8. 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.

  9. 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

  10. 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

  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. Study on Transient Properties of Levitated Object in Near-Field Acoustic Levitation

    NASA Astrophysics Data System (ADS)

    Jia, Bing; Chen, Chao; Zhao, Chun-Sheng

    2011-12-01

    A new approach to the study on the transient properties of the levitated object in near-field acoustic levitation (NFAL) is presented. In this article, the transient response characteristics, including the levitated height of an object with radius of 24 mm and thickness of 5 mm, the radial velocity and pressure difference of gas at the boundary of clearance between the levitated object and radiating surface (squeeze film), is calculated according to several velocity amplitudes of radiating surface. First, the basic equations in fluid areas on Arbitrary Lagrange—Euler (ALE) form are numerically solved by using streamline upwind petrov galerkin (SUPG) finite elements method. Second, the formed algebraic equations and solid control equations are solved by using synchronous alternating method to gain the transient messages of the levitated object and gas in the squeeze film. Through theoretical and numerical analyses, it is found that there is a oscillation time in the transient process and that the response time does not simply increase with the increasing of velocity amplitudes of radiating surface. More investigations in this paper are helpful for the understanding of the transient properties of levitated object in NFAL, which are in favor of enhancing stabilities and responsiveness of levitated object.

  13. 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.

  14. Field observation of low-to-mid-frequency acoustic propagation characteristics of an estuarine salt wedge.

    PubMed

    Reeder, D Benjamin

    2016-01-01

    The estuarine environment often hosts a salt wedge, the stratification of which is a function of the tide's range and speed of advance, river discharge volumetric flow rate, and river mouth morphology. Competing effects of temperature and salinity on sound speed in this stratified environment control the degree of acoustic refraction occurring along an acoustic path. A field experiment was carried out in the Columbia River Estuary to test the hypothesis: the estuarine salt wedge is acoustically observable in terms of low-to-mid-frequency acoustic propagation. Linear frequency-modulated acoustic signals in the 500-2000 Hz band were transmitted during the advance and retreat of the salt wedge during May 27-29, 2013. Results demonstrate that the salt wedge front is the dominant physical mechanism controlling acoustic propagation in this environment: received signal energy is relatively stable before and after the passage of the salt wedge front when the acoustic path consists of a single medium (either entirely fresh water or entirely salt water), and suffers a 10-15 dB loss and increased variability during salt wedge front passage. Physical parameters and acoustic propagation modeling corroborate and inform the acoustic observations. PMID:26827001

  15. Reversible swarming and separation of self-propelled chemically powered nanomotors under acoustic fields.

    PubMed

    Xu, Tailin; Soto, Fernando; Gao, Wei; Dong, Renfeng; Garcia-Gradilla, Victor; Magaña, Ernesto; Zhang, Xueji; Wang, Joseph

    2015-02-18

    The collective behavior of biological systems has inspired efforts toward the controlled assembly of synthetic nanomotors. Here we demonstrate the use of acoustic fields to induce reversible assembly of catalytic nanomotors, controlled swarm movement, and separation of different nanomotors. The swarming mechanism relies on the interaction between individual nanomotors and the acoustic field, which triggers rapid migration and assembly around the nearest pressure node. Such on-demand assembly of catalytic nanomotors is extremely fast and reversible. Controlled movement of the resulting swarm is illustrated by changing the frequency of the acoustic field. Efficient separation of different types of nanomotors, which assemble in distinct swarming regions, is illustrated. The ability of acoustic fields to regulate the collective behavior of catalytic nanomotors holds considerable promise for a wide range of practical applications. PMID:25634724

  16. Influence of Acoustic Field Structure on Polarization Characteristics of Acousto-optic Interaction in Crystals

    NASA Astrophysics Data System (ADS)

    Muromets, A. V.; Trushin, A. S.

    Influence of acoustic field structure on polarization characteristics of acousto-optic interaction is investigated. It is shown that inhomogeneity of acoustic field and mechanism of ultrasound excitation causes changes in values of acousto-optic figure of merit for ordinary and extraordinary light beams in comparison with theoretic values. The theoretic values were derived under assumption that acoustic wave is homogeneous. Experimental analysis was carried out in acousto-optic cell based on lithium niobate crystal where the acoustic wave propagates at the angle 13 degrees to Z axis of the crystal. We used three different methods of ultrasound generation in the crystal: by means of external piezotransducer, by interdigital transducer and by two sets of electrodes placed on top of the crystal surface. In the latter case, the first pair of the electrodes was directed along X crystal axis, while the second pair of the electrodes was directed orthogonally to X crystal axis and the direction of ultrasound. Obtained values for diffraction efficiencies for ordinary and extraordinary polarized optical beams were qualitatively different which may be caused by spatial inhomogeneity of the generated acoustic waves in the crystal. Structure of acoustic field generated by these sets of electrodes was examined by laser probing. We performed the analysis of the acoustic field intensity using acousto-optic method. A relation of diffraction efficiencies for ordinary and extraordinary light waves was measured during each iteration of the laser probing.

  17. Lift-Off Acoustics Prediction of Clustered Rocket Engines in the Near Field

    NASA Technical Reports Server (NTRS)

    Vu, Bruce; Plotkin, Ken

    2010-01-01

    This slide presentation presents a method of predicting acoustics during lift-off of the clustered rocket engines in the near field. Included is a definition of the near field, and the use of deflectors and shielding. There is discussion about the use of PAD, a software system designed to calculate the acoustic levels from the lift of of clustered rocket enginee, including updates to extend the calculation to directivity, water suppression, and clustered nozzles.

  18. Chemical Processes in Astrophysical Radiation Fields

    SciTech Connect

    Stancil, P.C.; Dalgarno, A.

    1997-12-31

    The effects of stimulated photon emission on chemical processes in a radiation field are considered and their influence on the chemistry of the early universe and other astrophysical environments is investigated. Spontaneous and stimulated radiative attachment rate coefficients for H(-), Li(-) and C(-) are presented.

  19. Deformation of biological cells in the acoustic field of an oscillating bubble

    NASA Astrophysics Data System (ADS)

    Zinin, Pavel V.; Allen, John S., III

    2009-02-01

    In this work we develop a theoretical framework of the interaction of microbubbles with bacteria in the ultrasound field using a shell model of the bacteria, following an approach developed previously [P. V. Zinin , Phys. Rev. E 72, 61907 (2005)]. Within the shell model, the motion of the cell in an ultrasonic field is determined by the motion of three components: the internal viscous fluid, a thin elastic shell, and the surrounding viscous fluid. Several conclusions can be drawn from the modeling of sound interaction with a biological cell: (a) the characteristics of a cell’s oscillations in an ultrasonic field are determined both by the elastic properties of the shell the viscosities of all components of the system, (b) for dipole quadrupole oscillations the cell’s shell deforms due to a change in the shell area this oscillation depends on the surface area modulus KA , (c) the relative change in the area has a maximum at frequency fK˜(1)/(2π)KA/(ρa3) , where a is the cell’s radius and ρ is its density. It was predicted that deformation of the cell wall at the frequency fK is high enough to rupture small bacteria such as E . coli in which the quality factor of natural vibrations is less than 1 (Q<1) . For bacteria with high value quality factors (Q>1) , the area deformation has a strong peak near a resonance frequency fK ; however, the value of the deformation near the resonance frequency is not high enough to produce sufficient mechanical effect. The theoretical framework developed in this work can be extended for describing the deformation of a biological cell under any arbitrary, external periodic force including radiation forces unduced by acoustical (acoustical levitation) or optical waves (optical tweezers).

  20. Deformation of biological cells in the acoustic field of an oscillating bubble.

    PubMed

    Zinin, Pavel V; Allen, John S

    2009-02-01

    In this work we develop a theoretical framework of the interaction of microbubbles with bacteria in the ultrasound field using a shell model of the bacteria, following an approach developed previously [P. V. Zinin, Phys. Rev. E 72, 61907 (2005)]. Within the shell model, the motion of the cell in an ultrasonic field is determined by the motion of three components: the internal viscous fluid, a thin elastic shell, and the surrounding viscous fluid. Several conclusions can be drawn from the modeling of sound interaction with a biological cell: (a) the characteristics of a cell's oscillations in an ultrasonic field are determined both by the elastic properties of the shell the viscosities of all components of the system, (b) for dipole quadrupole oscillations the cell's shell deforms due to a change in the shell area this oscillation depends on the surface area modulus K{A} , (c) the relative change in the area has a maximum at frequency f{K} approximately 1/2pi square root[K{A}(rhoa;{3})] , where a is the cell's radius and rho is its density. It was predicted that deformation of the cell wall at the frequency f{K} is high enough to rupture small bacteria such as E . coli in which the quality factor of natural vibrations is less than 1 (Q<1). For bacteria with high value quality factors (Q>1) , the area deformation has a strong peak near a resonance frequency f{K} however, the value of the deformation near the resonance frequency is not high enough to produce sufficient mechanical effect. The theoretical framework developed in this work can be extended for describing the deformation of a biological cell under any arbitrary, external periodic force including radiation forces unduced by acoustical (acoustical levitation) or optical waves (optical tweezers). PMID:19391781

  1. Deformation of biological cells in the acoustic field of an oscillating bubble

    PubMed Central

    Zinin, Pavel V.; Allen, John S.

    2009-01-01

    In this work we develop a theoretical framework of the interaction of microbubbles with bacteria in the ultrasound field using a shell model of the bacteria, following an approach developed previously [P. V. Zinin et al., Phys. Rev. E 72, 61907 (2005)]. Within the shell model, the motion of the cell in an ultrasonic field is determined by the motion of three components: the internal viscous fluid, a thin elastic shell, and the surrounding viscous fluid. Several conclusions can be drawn from the modeling of sound interaction with a biological cell: (a) the characteristics of a cell’s oscillations in an ultrasonic field are determined both by the elastic properties of the shell the viscosities of all components of the system, (b) for dipole quadrupole oscillations the cell’s shell deforms due to a change in the shell area this oscillation depends on the surface area modulus KA, (c) the relative change in the area has a maximum at frequency fK∼12πKA/(ρa3), where a is the cell’s radius and ρ is its density. It was predicted that deformation of the cell wall at the frequency fK is high enough to rupture small bacteria such as E. coli in which the quality factor of natural vibrations is less than 1 (Q < 1). For bacteria with high value quality factors (Q > 1), the area deformation has a strong peak near a resonance frequency fK; however, the value of the deformation near the resonance frequency is not high enough to produce sufficient mechanical effect. The theoretical framework developed in this work can be extended for describing the deformation of a biological cell under any arbitrary, external periodic force including radiation forces unduced by acoustical (acoustical levitation) or optical waves (optical tweezers). PMID:19391781

  2. High Intensity Radiated Fields (HIRF) project plan

    NASA Astrophysics Data System (ADS)

    Glynn, Michael S.; Blair, Jerry T.; Hintze, M. Marx

    1991-09-01

    Addressed here is the Federal Aviation Administration's approach to High Intensity Radiated Fields (HIRF) affecting the aviation community. Near- and far-term tasks are described. Deliverables, program management, scheduling, and cost issues are discussed.

  3. Acoustically Generated Flow and Temperature Fields in a Rectangular Cavity

    NASA Astrophysics Data System (ADS)

    Farouk, Bakhtier; Oran, Elaine

    1998-11-01

    Flows induced by a vibrating transducer in a gas-filled two-dimensional cavity are investigated by solving the two-dimensional compressible Navier-Stokes equations. The transducer (driver) is located along the left vertical wall of the cavity whereas the right rigid wall acts as an acoustic reflector. Both the left and right vertical walls of the cavity are considered to be conducting (isothermal) walls. The top and the bottom walls are insulated. The frequency of the driver was varied between 10 and 500 kHz. The length of the cavity was adjusted such that standing waves are formed within the cavity, which in turn create well defined vortical flows (acoustic streaming. The characteristics of the two-dimensional acoustically generated flows are studied systematically by varying the frequency and amplitude of the motion of the transducer and the aspect ratio of the cavity. The result exhibit organized flow structures within the cavity and the existence of lateral temperature gradients. Such acoustically induced temperature gradients are essential in the operation of thermoacoustic engines and refrigerators. The effect of cooling or heating the reflector wall on the acoustically generated flows are also investigated. Long time solutions of the governing equations exhibit the existence of pseudo-steady oscillatory flow conditions.

  4. 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.

  5. 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.

  6. 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.

  7. Source signature and acoustic field of seismic physical modeling

    NASA Astrophysics Data System (ADS)

    Lin, Q.; Jackson, C.; Tang, G.; Burbach, G.

    2004-12-01

    As an important tool of seismic research and exploration, seismic physical modeling simulates the real world data acquisition by scaling the model, acquisition parameters, and some features of the source generated by a transducer. Unlike the numerical simulation where a point source is easily satisfied, the transducer can't be made small enough for approximating the point source in physical modeling, therefore yield different source signature than the sources applied in the field data acquisition. To better understand the physical modeling data, characterizing the wave field generated by ultrasonic transducers is desirable and helpful. In this study, we explode several aspects of source characterization; including their radiation pattern, directivity, sensitivity and frequency response. We also try to figure out how to improve the acquired data quality, such as minimize ambient noise, use encoded chirp to prevent ringing, apply deterministic deconvolution to enhance data resolution and t-P filtering to remove linear events. We found that the transducer and their wave field, the modeling system performance, as well as material properties of the model and their coupling conditions all play roles in the physical modeling data acquisition.

  8. Acoustically swept rotor. [helicopter noise reduction

    NASA Technical Reports Server (NTRS)

    Schmitz, F. H.; Boxwell, D. A.; Vause, R. (Inventor)

    1979-01-01

    Impulsive noise reduction is provided in a rotor blade by acoustically sweeping the chord line from root to tip so that the acoustic radiation resulting from the summation of potential singularities used to model the flow about the blade tend to cancel for all times at an observation point in the acoustic far field.

  9. On the relationship between acoustic energy density flux near the jet axis and far field acoustic intensity

    NASA Technical Reports Server (NTRS)

    Maestrello, L.

    1973-01-01

    By measurement and analysis, the relationship between the distribution of the outflow of acoustic energy over the jet boundary and the far-field intensity is considered. The physical quantity used is the gradient of the pressure evaluated on a geometrical plane at the smallest possible radial distance from the jet axis, but outside the vortical region, in the area where the homogeneous wave equation is reasonably well satisfied. The numerical and experimental procedures involved have been checked out by using a known source. Results indicate that the acoustic power output per unit length of the jet, in the region from which the sound emanates, peaks at approximately 9 diameters downstream. The acoustic emission for a jet Strouhal number of about 0.3 exceeds the emission for all other Strouhal numbers nearly everywhere along the measurement plane. However, the far-field peak intensity distribution obtained from the contribution of each station was found to depend on the spatial extent of the region where sound emanates from the jet, which, in turn, depends more on the far-field angle than on the Strouhal number.

  10. Backcoupling of acoustic streaming on the temperature field inside high-intensity discharge lamps

    NASA Astrophysics Data System (ADS)

    Schwieger, J.; Baumann, B.; Wolff, M.; Manders, F.; Suijker, J.

    2015-11-01

    Operating high-intensity discharge lamps in the high frequency range (20-300 kHz) provides energy-saving and cost reduction potentials. However, commercially available lamp drivers do not make use of this operating strategy because light intensity fluctuations and even lamp destruction are possible. The reason for the fluctuating discharge arc are acoustic resonances in this frequency range that are excited in the arc tube. The acoustic resonances in turn generate a fluid flow that is caused by the acoustic streaming effect. Here, we present a 3D multiphysics model to determine the influence of acoustic streaming on the temperature field in the vicinity of an acoustic eigenfrequency. In that case a transition from stable to instable behavior occurs. The model is able to predict when light flicker can be expected. The results are in very good accordance with accompanying experiments.

  11. 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.

  12. Radiated fields from an electromagnetic pulse simulator

    NASA Astrophysics Data System (ADS)

    Pelletier, M.; Delisle, G. Y.; Kashyap, S.

    Simulators of electromagnetic pulses allow generation within a limited time of very high-intensity fields such as those produced in a nuclear explosion. These fields can be radiated out of the test zone at a lower but nevertheless significant level; if the intensity of these fields is sufficiently high, damage to humans and electronic equipment can result. An evaluation of the potential danger of these simulator emissions requires knowledge of the amplitude, duration, and the energy of the radiated impulses. A technique is presented for calculating the fields radiated by a parallel-plane electromagnetic pulse simulator. The same method can also be applied to a rhombic type simulator. Sample numerical results are presented along with the calculations of the energy and power density and a discussion of the formation of the field in the frequency domain.

  13. Optical theorem for acoustic non-diffracting beams and application to radiation force and torque

    PubMed Central

    Zhang, Likun; Marston, Philip L.

    2013-01-01

    Acoustical and optical non-diffracting beams are potentially useful for manipulating particles and larger objects. An extended optical theorem for a non-diffracting beam was given recently in the context of acoustics. The theorem relates the extinction by an object to the scattering at the forward direction of the beam’s plane wave components. Here we use this theorem to examine the extinction cross section of a sphere centered on the axis of the beam, with a non-diffracting Bessel beam as an example. The results are applied to recover the axial radiation force and torque on the sphere by the Bessel beam. PMID:24049681

  14. 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

  15. Empirical and quadrature approximation of acoustic field and array response probability density functions.

    PubMed

    Hayward, Thomas J; Oba, Roger M

    2013-07-01

    Numerical methods are presented for approximating the probability density functions (pdf's) of acoustic fields and receiver-array responses induced by a given joint pdf of a set of acoustic environmental parameters. An approximation to the characteristic function of the random acoustic field (the inverse Fourier transform of the field pdf) is first obtained either by construction of the empirical characteristic function (ECF) from a random sample of the acoustic parameters, or by application of generalized Gaussian quadrature to approximate the integral defining the characteristic function. The Fourier transform is then applied to obtain an approximation of the pdf by a continuous function of the field variables. Application of both the ECF and generalized Gaussian quadrature is demonstrated in an example of a shallow-water ocean waveguide with two-dimensional uncertainty of sound speed and attenuation coefficient in the ocean bottom. Both approximations lead to a smoother estimate of the field pdf than that provided by a histogram, with generalized Gaussian quadrature providing a smoother estimate at the tails of the pdf. Potential applications to acoustic system performance quantification and to nonparametric acoustic signal processing are discussed. PMID:23862782

  16. Direct-field acoustic testing of a flight system : logistics, challenges, and results.

    SciTech Connect

    Stasiunas, Eric Carl; Gurule, David Joseph; Babuska, Vit; Skousen, Troy J.

    2010-10-01

    Before a spacecraft can be considered for launch, it must first survive environmental testing that simulates the launch environment. Typically, these simulations include vibration testing performed using an electro-dynamic shaker. For some spacecraft however, acoustic excitation may provide a more severe loading environment than base shaker excitation. Because this was the case for a Sandia Flight System, it was necessary to perform an acoustic test prior to launch in order to verify survival due to an acoustic environment. Typically, acoustic tests are performed in acoustic chambers, but because of scheduling, transportation, and cleanliness concerns, this was not possible. Instead, the test was performed as a direct field acoustic test (DFAT). This type of test consists of surrounding a test article with a wall of speakers and controlling the acoustic input using control microphones placed around the test item, with a closed-loop control system. Obtaining the desired acoustic input environment - proto-flight random noise input with an overall sound pressure level (OASPL) of 146.7 dB-with this technique presented a challenge due to several factors. An acoustic profile with this high OASPL had not knowingly been obtained using the DFAT technique prior to this test. In addition, the test was performed in a high-bay, where floor space and existing equipment constrained the speaker circle diameter. And finally, the Flight System had to be tested without contamination of the unit, which required a contamination bag enclosure of the test unit. This paper describes in detail the logistics, challenges, and results encountered while performing a high-OASPL, direct-field acoustic test on a contamination-sensitive Flight System in a high-bay environment.

  17. Measurements of the force fields within an acoustic standing wave using holographic optical tweezers

    SciTech Connect

    Bassindale, P. G.; Drinkwater, B. W.; Phillips, D. B.; Barnes, A. C.

    2014-04-21

    Direct measurement of the forces experienced by micro-spheres in an acoustic standing wave device have been obtained using calibrated optical traps generated with holographic optical tweezers. A micro-sphere, which is optically trapped in three dimensions, can be moved through the acoustic device to measure forces acting upon it. When the micro-sphere is subjected to acoustic forces, it's equilibrium position is displaced to a position where the acoustic forces and optical forces are balanced. Once the optical trapping stiffness has been calibrated, observation of this displacement enables a direct measurement of the forces acting upon the micro-sphere. The measured forces are separated into a spatially oscillating component, attributed to the acoustic radiation force, and a constant force, attributed to fluid streaming. As the drive conditions of the acoustic device were varied, oscillating forces (>2.5 pN{sub pp}) and streaming forces (<0.2 pN) were measured. A 5 μm silica micro-sphere was used to characterise a 6.8 MHz standing wave, λ = 220 μm, to a spatial resolution limited by the uncertainty in the positioning of the micro-sphere (here to within 2 nm) and with a force resolution on the order of 10 fN. The results have application in the design and testing of acoustic manipulation devices.

  18. Forces acting on a small particle in an acoustical field in a thermoviscous fluid.

    PubMed

    Karlsen, Jonas T; Bruus, Henrik

    2015-10-01

    We present a theoretical analysis of the acoustic radiation force on a single small spherical particle, either a thermoviscous fluid droplet or a thermoelastic solid particle, suspended in a viscous and heat-conducting fluid medium. Within the perturbation assumptions, our analysis places no restrictions on the length scales of the viscous and thermal boundary-layer thicknesses δ(s) and δ(t) relative to the particle radius a, but it assumes the particle to be small in comparison to the acoustic wavelength λ. This is the limit relevant to scattering of ultrasound waves from nanometer- and micrometer-sized particles. For particles of size comparable to or smaller than the boundary layers, the thermoviscous theory leads to profound consequences for the acoustic radiation force. Not only do we predict forces orders of magnitude larger than expected from ideal-fluid theory, but for certain relevant choices of materials, we also 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 acoustic separation of microparticles in gases, as well as to handling of nanoparticles in lab-on-a-chip systems. PMID:26565335

  19. Forces acting on a small particle in an acoustical field in a thermoviscous fluid

    NASA Astrophysics Data System (ADS)

    Karlsen, Jonas T.; Bruus, Henrik

    2015-10-01

    We present a theoretical analysis of the acoustic radiation force on a single small spherical particle, either a thermoviscous fluid droplet or a thermoelastic solid particle, suspended in a viscous and heat-conducting fluid medium. Within the perturbation assumptions, our analysis places no restrictions on the length scales of the viscous and thermal boundary-layer thicknesses δs and δt relative to the particle radius a , but it assumes the particle to be small in comparison to the acoustic wavelength λ . This is the limit relevant to scattering of ultrasound waves from nanometer- and micrometer-sized particles. For particles of size comparable to or smaller than the boundary layers, the thermoviscous theory leads to profound consequences for the acoustic radiation force. Not only do we predict forces orders of magnitude larger than expected from ideal-fluid theory, but for certain relevant choices of materials, we also 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 acoustic separation of microparticles in gases, as well as to handling of nanoparticles in lab-on-a-chip systems.

  20. NATO TG-53: acoustic detection of weapon firing joint field experiment

    NASA Astrophysics Data System (ADS)

    Robertson, Dale N.; Pham, Tien; Scanlon, Michael V.; Srour, Nassy; Reiff, Christian G.; Sim, Leng K.; Solomon, Latasha; Thompson, Dorothea F.

    2006-05-01

    In this paper, we discuss the NATO Task Group 53 (TG-53) acoustic detection of weapon firing field joint experiment at Yuma Proving Ground during 31 October to 4 November 2005. The participating NATO countries include France, the Netherlands, UK and US. The objectives of the joint experiments are: (i) to collect acoustic signatures of direct and indirect firings from weapons such as sniper, mortar, artillery and C4 explosives and (ii) to share signatures among NATO partners from a variety of acoustic sensing platforms on the ground and in the air distributed over a wide area.

  1. Determination of near and far field acoustics for advanced propeller configurations

    NASA Technical Reports Server (NTRS)

    Korkan, K. D.; Jaeger, S. M.; Kim, J. H.

    1989-01-01

    A method has been studied for predicting the acoustic field of the SR-3 transonic propfan using flow data generated by two versions of the NASPROP-E computer code. Since the flow fields calculated by the solvers include the shock-wave system of the propeller, the nonlinear quadrupole noise source term is included along with the monopole and dipole noise sources in the calculation of the acoustic near field. Acoustic time histories in the near field are determined by transforming the azimuthal coordinate in the rotating, blade-fixed coordinate system to the time coordinate in a nonrotating coordinate system. Fourier analysis of the pressure time histories is used to obtain the frequency spectra of the near-field noise.

  2. 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

  3. 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.

  4. Particle Transport across Bi-Fluid Interface Using Acoustic Radiation Force

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Lim, Kian-Meng

    A bi-fluid micro-flow system is proposed for separating particles from its original solvent and re-diluting them into another solvent simultaneously. In this micro-flow system, two different miscible solvents flow parallel to each other through a 2-inlet-2-outlet micro-channel, where an acoustic standing wave is set up. Due to the differences in acoustic properties of these solvents, the pressure node of the acoustic wave is shifted from the middle line of the channel. Under the action of the acoustic radiation force, particles with positive ϕ-factors are extracted from their original solvent and re-suspended into the other solvent, wherein the pressure node resides. Particles suspended in the new solvent are collected at one of the two outlets downstream. Experiments were conducted on a prototype using two aqueous solutions: deionized water and 40% glycerin aqueous solution with polystyrene micro-particles. The results show that under the action of the acoustic standing wave, most of the particles were successfully transported from its original solvent to the other solvent and collected at the outlet.

  5. Experimental validation of a method for the prediction of the acoustic field produced by an acoustic source and the reflected field produced by a solid interface

    NASA Astrophysics Data System (ADS)

    Diaz, Sandra; Chopra, Rajiv; Pichardo, Samuel

    2012-11-01

    In this work we present a model to calculate the acoustic pressure generated by the interaction of forward and reflected waves in the vicinity of a solid interface and compare it to experimental data. An experimental setup was designed to measure the forward and the combined forward-reflected acoustic fields produced by a solid interface. A 0.785mm-needle hydrophone was used to characterize the acoustic field produced by a 7.29MHz-ultrasound transducer focused at 6cm. The hydrophone was positioned perpendicularly to the sound propagation direction and moved between the transducer and a 9mm-thick acrylic sample using a robotic arm. Simulations were carried out using a modified Rayleigh-Sommerfeld integral that calculates the particle displacement over a reflecting surface. This particle displacement at the boundary of the interface is then used as an acoustic source to obtain the reflected particle displacement. The complex sum of the forward and reflected fields was compared to the experimental measurements. The measurements showed an interference pattern that increased the pressure amplitude in average 10.4% with peaks of up to 25.8%. The proposed model is able to represent the interference pattern produced by the reflected wave with an average absolute error of 3.4+/-0.54% and a maximal error of 5.6%. The comparison between the experimental measurements and the simulations indicates that the presented model predicts with good accuracy the acoustic field generated by ultrasound transducers facing a solid interface. This model can be used to foresee the outcome of therapeutic applications where the devices are used in proximity to a bone interface.

  6. 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.

  7. Ocean acoustic field simulations for monitoring large-scale ocean structures

    NASA Astrophysics Data System (ADS)

    Shang, E. C.; Wang, Y. Y.

    1991-04-01

    Substantial numerical simulations of low-frequency acoustic field under different ocean models have been carried out on the CYBER-205 at WPL/NOAA. The purpose of these numerical simulations is to investigate our potential ability to monitor large-scale ocean structures by using modal ocean acoustic tomography (MOAT). For example, the possibility of monitoring El Niño by using MOAT has been illustrated.

  8. Customization of the acoustic field produced by a piezoelectric array through interelement delays

    PubMed Central

    Chitnis, Parag V.; Barbone, Paul E.; Cleveland, Robin O.

    2008-01-01

    A method for producing a prescribed acoustic pressure field from a piezoelectric array was investigated. The array consisted of 170 elements placed on the inner surface of a 15 cm radius spherical cap. Each element was independently driven by using individual pulsers each capable of generating 1.2 kV. Acoustic field customization was achieved by independently controlling the time when each element was excited. The set of time delays necessary to produce a particular acoustic field was determined by using an optimization scheme. The acoustic field at the focal plane was simulated by using the angular spectrum method, and the optimization searched for the time delays that minimized the least squared difference between the magnitudes of the simulated and desired pressure fields. The acoustic field was shaped in two different ways: the −6 dB focal width was increased to different desired widths and the ring-shaped pressure distributions of various prescribed diameters were produced. For both cases, the set of delays resulting from the respective optimization schemes were confirmed to yield the desired pressure distributions by using simulations and measurements. The simulations, however, predicted peak positive pressures roughly half those obtained from the measurements, which was attributed to the exclusion of nonlinearity in the simulations. PMID:18537369

  9. Computing the acoustic radiation force exerted on a sphere using the translational addition theorem.

    PubMed

    Silva, Glauber T; Baggio, André L; Lopes, J Henrique; Mitri, Farid G

    2015-03-01

    In this paper, the translational addition theorem for spherical functions is employed to calculate the acoustic radiation force produced by an arbitrary shaped beam on a sphere arbitrarily suspended in an inviscid fluid. The procedure is also based on the partial-wave expansion method, which depends on the beam-shape and scattering coefficients. Given a set of beam-shape coefficients (BSCs) for an acoustic beam relative to a reference frame, the translational addition theorem can be used to obtain the BSCs relative to the sphere positioned anywhere in the medium. The scattering coefficients are obtained from the acoustic boundary conditions across the sphere's surface. The method based on the addition theorem is particularly useful to avoid quadrature schemes to obtain the BSCs. We use it to compute the acoustic radiation force exerted by a spherically focused beam (in the paraxial approximation) on a silicone-oil droplet (compressible fluid sphere). The analysis is carried out in the Rayleigh (i.e., the particle diameter is much smaller than the wavelength) and Mie (i.e., the particle diameter is of the order of the wavelength or larger) scattering regimes. The obtained results show that the paraxial focused beam can only trap particles in the Rayleigh scattering regime. PMID:25768823

  10. 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.

  11. Numerical Analysis of the Acoustic Field of Tip-Clearance Flow

    NASA Astrophysics Data System (ADS)

    Alavi Moghadam, S. M.; M. Meinke Team; W. Schröder Team

    2015-11-01

    Numerical simulations of the acoustic field generated by a shrouded axial fan are studied by a hybrid fluid-dynamics-acoustics method. In a first step, large-eddy simulations are performed to investigate the dynamics of tip clearance flow for various tip gap sizes and to determine the acoustic sources. The simulations are performed for a single blade out of five blades with periodic boundary conditions in the circumferential direction on a multi-block structured mesh with 1.4 ×108 grid points. The turbulent flow is simulated at a Reynolds number of 9.36 ×105 at undisturbed inflow condition and the results are compared with experimental data. The diameter and strength of the tip vortex increase with the tip gap size, while simultaneously the efficiency of the fan decreases. In a second step, the acoustic field on the near field is determined by solving the acoustic perturbation equations (APE) on a mesh for a single blade consisting of approx. 9.8 ×108 grid points. The overall agreement of the pressure spectrum and its directivity with measurements confirm the correct identification of the sound sources and accurate prediction of the acoustic duct propagation. The results show that the longer the tip gap size the higher the broadband noise level. Senior Scientist, Institute of Aerodynamics, RWTH Aachen University.

  12. The direct and inverse problems of an air-saturated porous cylinder submitted to acoustic radiation

    NASA Astrophysics Data System (ADS)

    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.

  13. The NASA High Intensity Radiated Fields Laboratory

    NASA Technical Reports Server (NTRS)

    Williams, Reuben A.

    1997-01-01

    High Intensity Radiated Fields (HIRF) are the result of a multitude of intentional and nonintentional electromagnetic sources that currently exists in the world. Many of today's digital systems are susceptible to electronic upset if subjected to certain electromagnetic environments (EME). Modern aerospace designers and manufacturers increasingly rely on sophisticated digital electronic systems to provide critical flight control in both military, commercial, and general aviation aircraft. In an effort to understand and emulate the undesired environment that high energy RF provides modern electronics, the Electromagnetics Research Branch (ERB) of the Flight Electronics and Technology Division (FETD) conducts research on RF and microwave measurement methods related to the understanding of HIRF. In the High Intensity Radiated Fields Laboratory, the effects of high energy radiating electromagnetic fields on avionics and electronic systems are tested and studied.

  14. Phase decorrelation, streamwise vortices and acoustic radiation in mixing layers

    NASA Technical Reports Server (NTRS)

    Ho, C. M.; Zohar, Y.; Moser, R. D.; Rogers, M. M.; Lele, S. K.; Buell, J. C.

    1988-01-01

    Several direct numerical simulations were performed and analyzed to study various aspects of the early development of mixing layers. Included are the phase jitter of the large-scale eddies, which was studied using a 2-D spatially-evolving mixing layer simulation; the response of a time developing mixing layer to various spanwise disturbances; and the sound radiation from a 2-D compressible time developing mixing layer.

  15. 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.

  16. Full-Field Imaging of GHz Film Bulk Acoustic Resonator Motion

    SciTech Connect

    Telschow, Kenneth Louis; Deason, Vance Albert; Cottle, David Lynn; Larson III, J. D.

    2003-10-01

    A full-field view laser ultrasonic imaging method has been developed that measures acoustic motion at a surface without scanning. Images are recorded at normal video frame rates by using dynamic holography with photorefractive interferometric detection. By extending the approach to ultra high frequencies, an acoustic microscope has been developed that is capable of operation at gigahertz frequency and micron length scales. Both acoustic amplitude and phase are recorded, allowing full calibration and determination of phases to within a single arbitrary constant. Results are presented of measurements at frequencies of 800-900 MHz, illustrating a multitude of normal mode behavior in electrically driven thin film acoustic resonators. Coupled with microwave electrical impedance measurements, this imaging mode provides an exceptionally fast method for evaluation of electric-to-acoustic coupling of these devices and their performance. Images of 256 /spl times/ 240 pixels are recorded at 18 fps rates synchronized to obtain both in-phase and quadrature detection of the acoustic motion. Simple averaging provides sensitivity to the subnanometer level at each pixel calibrated over the image using interferometry. Identification of specific acoustic modes and their relationship to electrical impedance characteristics show the advantages and overall high speed of the technique.

  17. Helicopter main-rotor speed effects on far-field acoustic levels

    NASA Technical Reports Server (NTRS)

    Mueller, Arnold W.; Childress, Otis S.; Hardesty, Mark

    1987-01-01

    The design of a helicopter is based on an understanding of many parameters and their interactions. For example, in the design stage of a helicopter, the weight, engine, and rotor speed must be considered along with the rotor geometry when considering helicopter operations. However, the relationship between the noise radiated from the helicopter and these parameters is not well understood, with only limited model and full-scale test data to study. In general, these data have shown that reduced rotor speeds result in reduced far-field noise levels. This paper reviews the status of a recent helicopter noise research project designed to provide experimental flight data to be used to better understand helicopter rotor-speed effects on far-field acoustic levels. Preliminary results are presented relative to tests conducted with a McDonnell Douglas model 500E helicopter operating with the rotor speed as the control variable over the range of 103% of the main-rotor speed (NR) to 75% NR, and with the forward speed maintained at a constant value of 80 knots.

  18. Acoustic holography as a metrological tool for characterizing medical ultrasound sources and fields

    PubMed Central

    Sapozhnikov, Oleg A.; Tsysar, Sergey A.; Khokhlova, Vera A.; Kreider, Wayne

    2015-01-01

    Acoustic holography is a powerful technique for characterizing ultrasound sources and the fields they radiate, with the ability to quantify source vibrations and reduce the number of required measurements. These capabilities are increasingly appealing for meeting measurement standards in medical ultrasound; however, associated uncertainties have not been investigated systematically. Here errors associated with holographic representations of a linear, continuous-wave ultrasound field are studied. To facilitate the analysis, error metrics are defined explicitly, and a detailed description of a holography formulation based on the Rayleigh integral is provided. Errors are evaluated both for simulations of a typical therapeutic ultrasound source and for physical experiments with three different ultrasound sources. Simulated experiments explore sampling errors introduced by the use of a finite number of measurements, geometric uncertainties in the actual positions of acquired measurements, and uncertainties in the properties of the propagation medium. Results demonstrate the theoretical feasibility of keeping errors less than about 1%. Typical errors in physical experiments were somewhat larger, on the order of a few percent; comparison with simulations provides specific guidelines for improving the experimental implementation to reduce these errors. Overall, results suggest that holography can be implemented successfully as a metrological tool with small, quantifiable errors. PMID:26428789

  19. Prediction of the acoustic and bubble fields in insonified freeze-drying vials.

    PubMed

    Louisnard, O; Cogné, C; Labouret, S; Montes-Quiroz, W; Peczalski, R; Baillon, F; Espitalier, F

    2015-09-01

    The acoustic field and the location of cavitation bubble are computed in vials used for freeze-drying, insonified from the bottom by a vibrating plate. The calculations rely on a nonlinear model of sound propagation in a cavitating liquid [Louisnard, Ultrason. Sonochem., 19, (2012) 56-65]. Both the vibration amplitude and the liquid level in the vial are parametrically varied. For low liquid levels, a threshold amplitude is required to form a cavitation zone at the bottom of the vial. For increasing vibration amplitudes, the bubble field slightly thickens but remains at the vial bottom, and the acoustic field saturates, which cannot be captured by linear acoustics. On the other hand, increasing the liquid level may promote the formation of a secondary bubble structure near the glass wall, a few centimeters below the free liquid surface. These predictions suggest that rather complex acoustic fields and bubble structures can arise even in such small volumes. As the acoustic and bubble fields govern ice nucleation during the freezing step, the final crystal's size distribution in the frozen product may crucially depend on the liquid level in the vial. PMID:25800984

  20. Analyzing panel acoustic contributions toward the sound field inside the passenger compartment of a full-size automobile.

    PubMed

    Wu, Sean F; Moondra, Manmohan; Beniwal, Ravi

    2015-04-01

    The Helmholtz equation least squares (HELS)-based nearfield acoustical holography (NAH) is utilized to analyze panel acoustic contributions toward the acoustic field inside the interior region of an automobile. Specifically, the acoustic power flows from individual panels are reconstructed, and relative contributions to sound pressure level and spectrum at any point of interest are calculated. Results demonstrate that by correlating the acoustic power flows from individual panels to the field acoustic pressure, one can correctly locate the panel allowing the most acoustic energy transmission into the vehicle interior. The panel on which the surface acoustic pressure amplitude is the highest should not be used as indicative of the panel responsible for the sound field in the vehicle passenger compartment. Another significant advantage of this HELS-based NAH is that measurements of the input data only need to be taken once by using a conformal array of microphones in the near field, and ranking of panel acoustic contributions to any field point can be readily performed. The transfer functions between individual panels of any vibrating structure to the acoustic pressure anywhere in space are calculated not measured, thus significantly reducing the time and effort involved in panel acoustic contributions analyses. PMID:25920860

  1. A mapping relationship based near-field acoustic holography with spherical fundamental solutions for Helmholtz equation

    NASA Astrophysics Data System (ADS)

    Wu, Haijun; Jiang, Weikang; Zhang, Haibin

    2016-07-01

    In the procedure of the near-field acoustic holography (NAH) based on the fundamental solutions for Helmholtz equation (FS), the number of FS and the measurement setup to obtain their coefficients are two crucial issues to the successful reconstruction. The current work is motivated to develop a framework for the NAH which supplies a guideline to the determination of the number of FS as well as an optimized measurement setup. A mapping relationship between modes on surfaces of boundary and hologram is analytically derived by adopting the modes as FS in spherical coordinates. Thus, reconstruction is converted to obtain the coefficients of participant modes on holograms. In addition, an integral identity is firstly to be derived for the modes on convex surfaces, which is useful in determining the inefficient or evanescent modes for acoustic radiation in free space. To determine the number of FS adopted in the mapping relationship based NAH (MRS-based NAH), two approaches are proposed to supply reasonable estimations with criteria of point-wise pressure and energy, respectively. A technique to approximate a specific degree of mode on patches by a set of locally orthogonal patterns is explored for three widely used holograms, such as planar, cylindrical and spherical holograms, which results in an automatic determinations of the number and position of experimental setup for a given tolerance. Numerical examples are set up to validate the theory and techniques in the MRS-based NAH. Reconstructions of a cubic model demonstrate the potential of the proposed method for regular models even with corners and shapers. Worse results for the elongated cylinder with two spherical caps reveal the deficiency of the MRS-based NAH for irregular models which is largely due to the adopted modes are FS in spherical coordinates. The NAH framework pursued in the current work provides a new insight to the reconstruction procedure based on the FS in spherical coordinates.

  2. Mean force on a finite-sized spherical particle due to an acoustic field in a viscous compressible medium

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    An analytical expression to evaluate the second-order mean force (acoustic radiation force) on a finite-sized, rigid, spherical particle due to an acoustic wave is presented. The medium in which the particle is situated is taken to be both viscous and compressible. A far-field derivation approach has been used in determining the force, which is a function of the particle size, acoustic wavelength, and viscous boundary-layer thickness. It is assumed that the viscous length scale is negligibly small compared to the acoustic wavelength. The force expression presented here (i) reduces to the correct inviscid behavior (for both small- and finite-sized particles) and (ii) is identical to recent viscous results [M. Settnes and H. Bruus, Phys. Rev. E 85, 016327 (2012), 10.1103/PhysRevE.85.016327] for small-sized particles. Further, the computed force qualitatively matches the computational fluid dynamics (finite-element) results [D. Foresti, M. Nabavi, and D. Poulikakos, J. Fluid Mech. 709, 581 (2012), 10.1017/jfm.2012.350] for finite-sized particles. Additionally, the mean force is interpreted in terms of a multipole expansion. Subsequently, considering the fact that the force expansion is an infinite series, the number of terms that are required or adequate to capture the force to a specified accuracy is also provided as a function of the particle size to acoustic wavelength ratio. The dependence of the force on particle density, kinematic viscosity, and bulk viscosity of the fluid is also investigated. Here, both traveling and standing waves are considered.

  3. 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.

  4. Radiation Entropy and Near-Field Thermophotovoltaics

    NASA Astrophysics Data System (ADS)

    Zhang, Zhuomin M.

    2008-08-01

    Radiation entropy was key to the original derivation of Planck's law of blackbody radiation, in 1900. This discovery opened the door to quantum mechanical theory and Planck was awarded the Nobel Prize in Physics in 1918. Thermal radiation plays an important role in incandescent lamps, solar energy utilization, temperature measurements, materials processing, remote sensing for astronomy and space exploration, combustion and furnace design, food processing, cryogenic engineering, as well as numerous agricultural, health, and military applications. While Planck's law has been fruitfully applied to a large number of engineering problems for over 100 years, questions have been raised about its limitation in micro/nano systems, especially at subwavelength distances or in the near field. When two objects are located closer than the characteristic wavelength, wave interference and photon tunneling occurs that can result in significant enhancement of the radiative transfer. Recent studies have shown that the near-field effects can realize emerging technologies, such as superlens, sub-wavelength light source, polariton-assisted nanolithography, thermophotovoltaic (TPV) systems, scanning tunneling thermal microscopy, etc. The concept of entropy has also been applied to explain laser cooling of solids as well as the second law efficiency of devices that utilize thermal radiation to produce electricity. However, little is known as regards the nature of entropy in near-field radiation. Some history and recent advances are reviewed in this presentation with a call for research of radiation entropy in the near field, due to the important applications in the optimization of thermophotovoltaic converters and in the design of practical systems that can harvest photon energies efficiently.

  5. Optical acoustic experimental investigation of propagation femtosecond laser radiation in air and biological tissues

    NASA Astrophysics Data System (ADS)

    Bochkarev, N. N.; Kabanov, A. M.; Protasevich, E. S.; Stepanov, A. N.

    2008-01-01

    Using two optical acoustic approaches we experimentally investigated spatial location of filament zone of propagation channel of focused laser radiation. For femtosecond pulses passing in air it was shown that nonlinear focus length had spatial scale of 1/P at initial power P moderate for self-focusing and at optical system focus distance significantly lower than Rayleigh beam length. The results of experimental optical acoustic investigation of femto- and nanosecond pulses attenuation by some biological tissues (muscular tissue, adipose tissue, cutaneous covering, and milk) and optical breakdown thresholds on these one are presented. It was shown that penetration depth of short laser pulse radiation into biological tissues is the same as for longer one. However, amplitude of acoustic response to a process of interaction of femtosecond laser pulse with biological tissue is larger in several times than that to interaction with nanosecond pulses of the same power and spectral distribution. The obtained threshold values can be interesting for tabulation of limit allowable levels of irradiation at work with laser radiation. Such values are unknown for femtosecond laser pulses today.

  6. Sound field diffusivity in NASA Langley Research Center hardwalled acoustic facilities

    NASA Technical Reports Server (NTRS)

    Mcgary, M. C.

    1982-01-01

    Cross correlation measurements were performed to determine the quality of the sound fields in the ANRL reverberation room and the ANRL transmission loss facility. The results indicate the level of sound field diffuseness which may be attained in these hardwalled acoustic facilities.

  7. 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.

  8. Acoustic noise from volcanoes - Theory and experiment

    NASA Technical Reports Server (NTRS)

    Woulff, G.; Mcgetchin, T. R.

    1976-01-01

    The paper discusses some theoretical aspects of acoustic investigation of volcanoes and describes a field experiment involving the recording, analysis, and interpretation of acoustic radiation from energetic fumaroles at Volcan Acatenango, Guatemala, during mid-January 1973. Particular attention is given to deriving information about the flow velocity of the erupting medium from acoustics as a means to study eruption dynamics. Theoretical considerations suggest that acoustic power radiated during gaseous volcanic eruptions may be related to gas exit velocity according to appropriate power laws. Eruption acoustics proves useful as a means of quantitative monitoring of volcanic activity.

  9. Gated photon correlation spectroscopy for acoustical particle velocity measurements in free-field conditions.

    PubMed

    Koukoulas, Triantafillos; Piper, Ben; Theobald, Pete

    2013-03-01

    The measurement of acoustic pressure at a point in space using optical methods has been the subject of extensive research in airborne acoustics over the last four decades. The main driver is to reliably establish the acoustic pascal, thus allowing the calibration of microphones with standard and non-standard dimensions to be realized in an absolute and direct manner. However, the research work so far has mostly been limited to standing wave tubes. This Letter reports on the development of an optical system capable of measuring acoustic particle velocities in free-field conditions; agreement within less than 0.6 dB was obtained with standard microphone measurements during these initial experiments. PMID:23464122

  10. Thermally induced secondary atomization of droplet in an acoustic field

    NASA Astrophysics Data System (ADS)

    Basu, Saptarshi; Saha, Abhishek; Kumar, Ranganathan

    2012-01-01

    We study the thermal effects that lead to instability and break up in acoustically levitated vaporizing fuel droplets. For selective liquids, atomization occurs at the droplet equator under external heating. Short wavelength [Kelvin-Helmholtz (KH)] instability for diesel and bio-diesel droplets triggers this secondary atomization. Vapor pressure, latent heat, and specific heat govern the vaporization rate and temperature history, which affect the surface tension gradient and gas phase density, ultimately dictating the onset of KH instability. We develop a criterion based on Weber number to define a condition for the inception of secondary atomization.

  11. Auralization of concert hall acoustics using finite difference time domain methods and wave field synthesis

    NASA Astrophysics Data System (ADS)

    Hochgraf, Kelsey

    Auralization methods have been used for a long time to simulate the acoustics of a concert hall for different seat positions. The goal of this thesis was to apply the concept of auralization to a larger audience area that the listener could walk through to compare differences in acoustics for a wide range of seat positions. For this purpose, the acoustics of Rensselaer's Experimental Media and Performing Arts Center (EMPAC) Concert Hall were simulated to create signals for a 136 channel wave field synthesis (WFS) system located at Rensselaer's Collaborative Research Augmented Immersive Virtual Environment (CRAIVE) Laboratory. By allowing multiple people to dynamically experience the concert hall's acoustics at the same time, this research gained perspective on what is important for achieving objective accuracy and subjective plausibility in an auralization. A finite difference time domain (FDTD) simulation on a three-dimensional face-centered cubic grid, combined at a crossover frequency of 800 Hz with a CATT-Acoustic(TM) simulation, was found to have a reverberation time, direct to reverberant sound energy ratio, and early reflection pattern that more closely matched measured data from the hall compared to a CATT-Acoustic(TM) simulation and other hybrid simulations. In the CRAIVE lab, nine experienced listeners found all hybrid auralizations (with varying source location, grid resolution, crossover frequency, and number of loudspeakers) to be more perceptually plausible than the CATT-Acoustic(TM) auralization. The FDTD simulation required two days to compute, while the CATT-Acoustic(TM) simulation required three separate TUCT(TM) computations, each taking four hours, to accommodate the large number of receivers. Given the perceptual advantages realized with WFS for auralization of a large, inhomogeneous sound field, it is recommended that hybrid simulations be used in the future to achieve more accurate and plausible auralizations. Predictions are made for a

  12. Flow Field and Acoustic Predictions for Three-Stream Jets

    NASA Technical Reports Server (NTRS)

    Simmons, Shaun Patrick; Henderson, Brenda S.; Khavaran, Abbas

    2014-01-01

    Computational fluid dynamics was used to analyze a three-stream nozzle parametric design space. The study varied bypass-to-core area ratio, tertiary-to-core area ratio and jet operating conditions. The flowfield solutions from the Reynolds-Averaged Navier-Stokes (RANS) code Overflow 2.2e were used to pre-screen experimental models for a future test in the Aero-Acoustic Propulsion Laboratory (AAPL) at the NASA Glenn Research Center (GRC). Flowfield solutions were considered in conjunction with the jet-noise-prediction code JeNo to screen the design concepts. A two-stream versus three-stream computation based on equal mass flow rates showed a reduction in peak turbulent kinetic energy (TKE) for the three-stream jet relative to that for the two-stream jet which resulted in reduced acoustic emission. Additional three-stream solutions were analyzed for salient flowfield features expected to impact farfield noise. As tertiary power settings were increased there was a corresponding near nozzle increase in shear rate that resulted in an increase in high frequency noise and a reduction in peak TKE. As tertiary-to-core area ratio was increased the tertiary potential core elongated and the peak TKE was reduced. The most noticeable change occurred as secondary-to-core area ratio was increased thickening the secondary potential core, elongating the primary potential core and reducing peak TKE. As forward flight Mach number was increased the jet plume region decreased and reduced peak TKE.

  13. 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.

  14. Prediction of sound fields in acoustical cavities using the boundary element method. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Kipp, C. R.; Bernhard, R. J.

    1985-01-01

    A method was developed to predict sound fields in acoustical cavities. The method is based on the indirect boundary element method. An isoparametric quadratic boundary element is incorporated. Pressure, velocity and/or impedance boundary conditions may be applied to a cavity by using this method. The capability to include acoustic point sources within the cavity is implemented. The method is applied to the prediction of sound fields in spherical and rectangular cavities. All three boundary condition types are verified. Cases with a point source within the cavity domain are also studied. Numerically determined cavity pressure distributions and responses are presented. The numerical results correlate well with available analytical results.

  15. Geodesic acoustic modes in tokamak plasmas with a radial equilibrium electric field

    SciTech Connect

    Zhou, Deng

    2015-09-15

    The dispersion relation of geodesic acoustic modes in the tokamak plasma with an equilibrium radial electric field is derived and analyzed. Multiple branches of eigenmodes have been found, similar to the result given by the fluid model with a poloidal mass flow. Frequencies and damping rates of both the geodesic acoustic mode and the sound wave increase with respect to the strength of radial electric field, while the frequency and the damping rate of the lower frequency branch slightly decrease. Possible connection to the experimental observation is discussed.

  16. 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.

  17. Field installation of an acoustic slug-detection system

    SciTech Connect

    Dhulesia, H.; Bernicot, M.; Romanet, T.

    1997-02-01

    A pipeline operating in the slug flow regime creates high fluctuations in gas and liquid flow rates at the outlet. The detection of slugs and the estimation of their length and velocity are necessary to minimize the upsets in the operation of downstream process facilities. A new method based on the acoustic principle has been developed by Total and Syminex with two variants--passive and active. The passive method gives the slug length and velocity, whereas the active method also gives the fluid density. The prototype of this system has been installed permanently on a 20-in. multiphase pipeline in Argentina. As this system detects the slugs and determines their characteristics approximately 2 minutes before they arrive at the first-stage separator, the operators take appropriate action in the case of arrival of an excessively long slug and, thus, avoid possible shutdowns. At a later stage, an automatic adjustment of the process control valves will be realized.

  18. Azimuthal cement evaluation with an acoustic phased-arc array transmitter: numerical simulations and field tests

    NASA Astrophysics Data System (ADS)

    Che, Xiao-Hua; Qiao, Wen-Xiao; Ju, Xiao-Dong; Wang, Rui-Jia

    2016-03-01

    We developed a novel cement evaluation logging tool, named the azimuthally acoustic bond tool (AABT), which uses a phased-arc array transmitter with azimuthal detection capability. We combined numerical simulations and field tests to verify the AABT tool. The numerical simulation results showed that the radiation direction of the subarray corresponding to the maximum amplitude of the first arrival matches the azimuth of the channeling when it is behind the casing. With larger channeling size in the circumferential direction, the amplitude difference of the casing wave at different azimuths becomes more evident. The test results showed that the AABT can accurately locate the casing collars and evaluate the cement bond quality with azimuthal resolution at the casing—cement interface, and can visualize the size, depth, and azimuth of channeling. In the case of good casing—cement bonding, the AABT can further evaluate the cement bond quality at the cement—formation interface with azimuthal resolution by using the amplitude map and the velocity of the formation wave.

  19. 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

  20. 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.

  1. Field support, data analysis and associated research for the acoustic grenade sounding program

    NASA Technical Reports Server (NTRS)

    Barnes, T. G.; Bullard, E. R.

    1976-01-01

    Temperature and horizontal winds in the 30 to 90 km altitude range of the upper atmosphere, were determined by acoustic grenade soundings conducted at Wallops Island, Virginia and Kourou, French Guiana. Field support provided at these locations included deployment of the large area microphone system, supervision, maintenance and operation of sound ranging stations; and coordination of activities. Data analysis efforts included the analysis of field data to determine upper atmospheric meteorological parameters. Profiles for upper atmospheric temperature, wind and density are provided in plots and tables for each of the acoustic grenade soundings conducted during the contract period. Research efforts were directed toward a systematic comparison of temperature data from acoustic grenade with other meteorological sensor probes in the upper atmosphere.

  2. Robust acoustic wave manipulation of bubbly liquids

    NASA Astrophysics Data System (ADS)

    Gumerov, N. A.; Akhatov, I. S.; Ohl, C.-D.; Sametov, S. P.; Khazimullin, M. V.; Gonzalez-Avila, S. R.

    2016-03-01

    Experiments with water-air bubbly liquids when exposed to acoustic fields of frequency ˜100 kHz and intensity below the cavitation threshold demonstrate that bubbles ˜30 μm in diameter can be "pushed" away from acoustic sources by acoustic radiation independently from the direction of gravity. This manifests formation and propagation of acoustically induced transparency waves (waves of the bubble volume fraction). In fact, this is a collective effect of bubbles, which can be described by a mathematical model of bubble self-organization in acoustic fields that matches well with our experiments.

  3. Uncertain Acoustic Field Modeling and Robust Source Localization in Shallow Water

    NASA Astrophysics Data System (ADS)

    Zhao, Hangfang; Gong, Xianyi; Yu, Zibin

    2010-09-01

    Oceanic environmental uncertainty can cause significant performance degradation of the SONAR system. Understanding and modeling the uncertainty propagating from environment to acoustic field and then to steering vector is necessary for SONAR design and operation to mitigate the uncertainty effect and provide robust detection and location of targets. The statistical property of uncertainty can be described by the probability density functions or second-order moments of environmental parameters and acoustic fields. Based on the probability description, a stochastic response surface method is used to propagate the uncertainty from environment to acoustic field by polynomial chaos expansion. Then covariance matrix and associated ellipsoidal neighboring space are used to describe the uncertainty set of acoustic field and steering vector for sonar signal processing. Finally, a robust Minimum Variance (MV) matched-field processing method is derived by extending the constrained optimization of MV from single point to an uncertainty steering vector ellipsoid. We apply sea test data collected by a vertical array in shallow water to source localization.

  4. Acoustic characterization of high intensity focused ultrasound fields generated from a transmitter with a large aperture

    NASA Astrophysics Data System (ADS)

    Chen, Tao; Fan, Tingbo; Zhang, Wei; Qiu, Yuanyuan; Tu, Juan; Guo, Xiasheng; Zhang, Dong

    2014-03-01

    Prediction and measurement of the acoustic field emitted from a high intensity focused ultrasound (HIFU) is essential for the accurate ultrasonic treatment. In this study, the acoustic field generated from a strongly focused HIFU transmitter was characterized by a combined experiment and simulation method. The spheroidal beam equation (SBE) was utilized to describe the nonlinear sound propagation. The curve of the source pressure amplitude versus voltage excitation was determined by fitting the measured ratio of the second harmonic to the fundamental component of the focal waveform to the simulation result; finally, the acoustic pressure field generated by the strongly focused HIFU transmitter was predicted by using the SBE model. A commercial fiber optic probe hydrophone was utilized to measure the acoustic pressure field generated from a 1.1 MHz HIFU transmitter with a large half aperture angle of 30°. The maximum measured peak-to-peak pressure was up to 72 MPa. The validity of this combined approach was confirmed by the comparison between the measured results and the calculated ones. The results indicate that the current approach might be useful to describe the HIFU field. The results also suggest that this method is not valid for low excitations owing to low sensitivity of the second harmonic.

  5. Acoustic characterization of high intensity focused ultrasound fields generated from a transmitter with a large aperture

    SciTech Connect

    Chen, Tao; Fan, Tingbo; Zhang, Wei; Qiu, Yuanyuan; Tu, Juan E-mail: dzhang@nju.edu.cn; Guo, Xiasheng; Zhang, Dong E-mail: dzhang@nju.edu.cn

    2014-03-21

    Prediction and measurement of the acoustic field emitted from a high intensity focused ultrasound (HIFU) is essential for the accurate ultrasonic treatment. In this study, the acoustic field generated from a strongly focused HIFU transmitter was characterized by a combined experiment and simulation method. The spheroidal beam equation (SBE) was utilized to describe the nonlinear sound propagation. The curve of the source pressure amplitude versus voltage excitation was determined by fitting the measured ratio of the second harmonic to the fundamental component of the focal waveform to the simulation result; finally, the acoustic pressure field generated by the strongly focused HIFU transmitter was predicted by using the SBE model. A commercial fiber optic probe hydrophone was utilized to measure the acoustic pressure field generated from a 1.1 MHz HIFU transmitter with a large half aperture angle of 30°. The maximum measured peak-to-peak pressure was up to 72 MPa. The validity of this combined approach was confirmed by the comparison between the measured results and the calculated ones. The results indicate that the current approach might be useful to describe the HIFU field. The results also suggest that this method is not valid for low excitations owing to low sensitivity of the second harmonic.

  6. Acoustic propagation through anisotropic internal wave fields: transmission loss, cross-range coherence, and horizontal refraction.

    PubMed

    Oba, Roger; Finette, Steven

    2002-02-01

    Results of a computer simulation study are presented for acoustic propagation in a shallow water, anisotropic ocean environment. The water column is characterized by random volume fluctuations in the sound speed field that are induced by internal gravity waves, and this variability is superimposed on a dominant summer thermocline. Both the internal wave field and resulting sound speed perturbations are represented in three-dimensional (3D) space and evolve in time. The isopycnal displacements consist of two components: a spatially diffuse, horizontally isotropic component and a spatially localized contribution from an undular bore (i.e., a solitary wave packet or solibore) that exhibits horizontal (azimuthal) anisotropy. An acoustic field is propagated through this waveguide using a 3D parabolic equation code based on differential operators representing wide-angle coverage in elevation and narrow-angle coverage in azimuth. Transmission loss is evaluated both for fixed time snapshots of the environment and as a function of time over an ordered set of snapshots which represent the time-evolving sound speed distribution. Horizontal acoustic coherence, also known as transverse or cross-range coherence, is estimated for horizontally separated points in the direction normal to the source-receiver orientation. Both transmission loss and spatial coherence are computed at acoustic frequencies 200 and 400 Hz for ranges extending to 10 km, a cross-range of 1 km, and a water depth of 68 m. Azimuthal filtering of the propagated field occurs for this environment, with the strongest variations appearing when propagation is parallel to the solitary wave depressions of the thermocline. A large anisotropic degradation in horizontal coherence occurs under the same conditions. Horizontal refraction of the acoustic wave front is responsible for the degradation, as demonstrated by an energy gradient analysis of in-plane and out-of-plane energy transfer. The solitary wave packet is

  7. Acoustic propagation through anisotropic internal wave fields: Transmission loss, cross-range coherence, and horizontal refraction

    NASA Astrophysics Data System (ADS)

    Oba, Roger; Finette, Steven

    2002-02-01

    Results of a computer simulation study are presented for acoustic propagation in a shallow water, anisotropic ocean environment. The water column is characterized by random volume fluctuations in the sound speed field that are induced by internal gravity waves, and this variability is superimposed on a dominant summer thermocline. Both the internal wave field and resulting sound speed perturbations are represented in three-dimensional (3D) space and evolve in time. The isopycnal displacements consist of two components: a spatially diffuse, horizontally isotropic component and a spatially localized contribution from an undular bore (i.e., a solitary wave packet or solibore) that exhibits horizontal (azimuthal) anisotropy. An acoustic field is propagated through this waveguide using a 3D parabolic equation code based on differential operators representing wide-angle coverage in elevation and narrow-angle coverage in azimuth. Transmission loss is evaluated both for fixed time snapshots of the environment and as a function of time over an ordered set of snapshots which represent the time-evolving sound speed distribution. Horizontal acoustic coherence, also known as transverse or cross-range coherence, is estimated for horizontally separated points in the direction normal to the source-receiver orientation. Both transmission loss and spatial coherence are computed at acoustic frequencies 200 and 400 Hz for ranges extending to 10 km, a cross-range of 1 km, and a water depth of 68 m. Azimuthal filtering of the propagated field occurs for this environment, with the strongest variations appearing when propagation is parallel to the solitary wave depressions of the thermocline. A large anisotropic degradation in horizontal coherence occurs under the same conditions. Horizontal refraction of the acoustic wave front is responsible for the degradation, as demonstrated by an energy gradient analysis of in-plane and out-of-plane energy transfer. The solitary wave packet is

  8. Effect of Existence of Red Blood Cells in Trapping Performance of Microbubbles by Acoustic Radiation Force

    NASA Astrophysics Data System (ADS)

    Masuda, Kohji; Nakamoto, Ryusuke; Watarai, Nobuyuki; Koda, Ren; Taguchi, Yuto; Kozuka, Teruyuki; Miyamoto, Yoshitaka; Kakimoto, Takashi; Enosawa, Shin; Chiba, Toshio

    2011-07-01

    We have proposed a method to control microbubbles by making use of acoustic radiation force, which is generated with acoustic propagation, to correspond to therapeutic applications of ultrasound. By preventing bubbles from passing through the desired target area, the local concentration of bubbles can be enhanced. However, we have never experimentally confirmed this phenomenon under in vivo conditions or close to those. Thus, we carried out an experiment to evaluate the trapping performance of bubbles using a suspension of red blood cells (RBCs) and an artificial blood vessel. By defining the trapping index to evaluate the amount of trapped microbubbles, we have confirmed that the trapping performance was enhanced according to the concentration of RBCs and the sound pressure, but not according to the central frequency of ultrasound. The results indicate that the existence of RBCs near microbubbles contributed to the increase in the size of aggregations propelled against the vessel wall.

  9. Temporal coherence of the acoustic field forward propagated through a continental shelf with random internal waves.

    PubMed

    Gong, Zheng; Chen, Tianrun; Ratilal, Purnima; Makris, Nicholas C

    2013-11-01

    An analytical model derived from normal mode theory for the accumulated effects of range-dependent multiple forward scattering is applied to estimate the temporal coherence of the acoustic field forward propagated through a continental-shelf waveguide containing random three-dimensional internal waves. The modeled coherence time scale of narrow band low-frequency acoustic field fluctuations after propagating through a continental-shelf waveguide is shown to decay with a power-law of range to the -1/2 beyond roughly 1 km, decrease with increasing internal wave energy, to be consistent with measured acoustic coherence time scales. The model should provide a useful prediction of the acoustic coherence time scale as a function of internal wave energy in continental-shelf environments. The acoustic coherence time scale is an important parameter in remote sensing applications because it determines (i) the time window within which standard coherent processing such as matched filtering may be conducted, and (ii) the number of statistically independent fluctuations in a given measurement period that determines the variance reduction possible by stationary averaging. PMID:24180758

  10. Radiation Effects on Current Field Programmable Technologies

    NASA Technical Reports Server (NTRS)

    Katz, R.; LaBel, K.; Wang, J. J.; Cronquist, B.; Koga, R.; Penzin, S.; Swift, G.

    1997-01-01

    Manufacturers of field programmable gate arrays (FPGAS) take different technological and architectural approaches that directly affect radiation performance. Similar y technological and architectural features are used in related technologies such as programmable substrates and quick-turn application specific integrated circuits (ASICs). After analyzing current technologies and architectures and their radiation-effects implications, this paper includes extensive test data quantifying various devices total dose and single event susceptibilities, including performance degradation effects and temporary or permanent re-configuration faults. Test results will concentrate on recent technologies being used in space flight electronic systems and those being developed for use in the near term. This paper will provide the first extensive study of various configuration memories used in programmable devices. Radiation performance limits and their impacts will be discussed for each design. In addition, the interplay between device scaling, process, bias voltage, design, and architecture will be explored. Lastly, areas of ongoing research will be discussed.

  11. 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.

  12. Field performance of an acoustic scour-depth monitoring system

    USGS Publications Warehouse

    Mason, Jr., Robert R.; Sheppard, D. Max

    1994-01-01

    The Herbert C. Bonner Bridge over Oregon Inlet serves as the only land link between Bodie and Hatteras Islands, part of the Outer Banks of North Carolina. Periodic soundings over the past 30 years have documented channel migration, local scour, and deposition at several pilings that support the bridge. In September 1992, a data-collection system was installed to permit the off-site monitoring of scour at 16 bridge pilings. The system records channel-bed elevations at 15-minute intervals and transmits the data to a satellite receiver. A cellular phone connection also permits downloading and reviewing of the data as they are being collected. A digitally recording, acoustic fathometer is the main component of the system. In November 1993, current velocity, water-surface elevation, wave characteristics, and water temperature measuring instruments were also deployed at the site. Several performance problems relating to the equipment and to the harsh marine environment have not been resolved, but the system has collected and transmitted reliable scour-depth and water-level data.

  13. Radiative reactions in halo effective field theory

    NASA Astrophysics Data System (ADS)

    Rupak, Gautam

    2016-03-01

    In this article we review the recent progress in radiative reaction calculations in halo effective field theory. We look at radiative capture and breakup processes that involve a halo nucleus with a single valence neutron or proton. Looking at 7Li(n,γ) 8Li,14C(n,γ)15C and related reactions, the dominant source of theoretical uncertainty in s- and p-wave halo nuclei reaction calculations is quantified in a model-independent framework. The analysis for neutron halos is extended to proton halo systems. The effective field theory results quantify which observable parameters of the strong interaction at low energy need to be determined more precisely for accurate cross-section calculations.

  14. Radiative instabilities in sheared magnetic field

    NASA Technical Reports Server (NTRS)

    Drake, J. F.; Sparks, L.; Van Hoven, G.

    1988-01-01

    The structure and growth rate of the radiative instability in a sheared magnetic field B have been calculated analytically using the Braginskii fluid equations. In a shear layer, temperature and density perturbations are linked by the propagation of sound waves parallel to the local magnetic field. As a consequence, density clumping or condensation plays an important role in driving the instability. Parallel thermal conduction localizes the mode to a narrow layer where K(parallel) is small and stabilizes short wavelengths k larger-than(c) where k(c) depends on the local radiation and conduction rates. Thermal coupling to ions also limits the width of the unstable spectrum. It is shown that a broad spectrum of modes is typically unstable in tokamak edge plasmas and it is argued that this instability is sufficiently robust to drive the large-amplitude density fluctuations often measured there.

  15. Hydrophone arrays for instantaneous measurement of high-pressure acoustic fields

    NASA Astrophysics Data System (ADS)

    Ketterling, Jeffrey A.; Kracht, Jonathan M.; Cleveland, Robin O.

    2010-03-01

    Electrohydraulic lithotripter acoustic fields are measured with single-element hydrophones even though the acoustic fields are not highly repeatable. The ability to obtain an instantaneous "snapshot" of the sound field would have broad implications for advancing the understanding of how lithotripters fragment stones and damage kidney tissue. To better characterize the acoustic field of lithotripters, linear hydrophone arrays were fabricated by bonding a 9 μm piezopolymer film to a copper-clad polyimide which had an array pattern etched on the copper layer. After bonding, the devices were backed with an epoxy plug in order to provide structural support. The array elements were each 0.5 by 0.5 mm, spaced 1.25 mm center to center, and there were 20 elements. The relative sensitivity of each hydrophone element was measured at 5.25 MHz for an acoustic pressure of 4.5 kPa and the elements were found to vary by ≈ 6%. The arrays were then placed in the focus of a piezoelectric lithotripter and were found to maintain their sensitivity for roughly 500 shock waves before gradually losing sensitivity.

  16. Plasma wake field XUV radiation source

    DOEpatents

    Prono, Daniel S.; Jones, Michael E.

    1997-01-01

    A XUV radiation source uses an interaction of electron beam pulses with a gas to create a plasma radiator. A flowing gas system (10) defines a circulation loop (12) with a device (14), such as a high pressure pump or the like, for circulating the gas. A nozzle or jet (16) produces a sonic atmospheric pressure flow and increases the density of the gas for interacting with an electron beam. An electron beam is formed by a conventional radio frequency (rf) accelerator (26) and electron pulses are conventionally formed by a beam buncher (28). The rf energy is thus converted to electron beam energy, the beam energy is used to create and then thermalize an atmospheric density flowing gas to a fully ionized plasma by interaction of beam pulses with the plasma wake field, and the energetic plasma then loses energy by line radiation at XUV wavelengths Collection and focusing optics (18) are used to collect XUV radiation emitted as line radiation when the high energy density plasma loses energy that was transferred from the electron beam pulses to the plasma.

  17. Haemopoietic cell renewal in radiation fields.

    PubMed

    Fliedner, T M; Nothdurft, W; Tibken, B; Hofer, E; Weiss, M; Kindler, H

    1994-10-01

    Space flight activities are inevitably associated with a chronic exposure of astronauts to a complex mixture of ionising radiation. Although no acute radiation consequences are to be expected as a rule, the possibility of Solar Particle Events (SPE) associated with relatively high doses of radiation (1 or more Gray) cannot be excluded. It is the responsibility of physicians in charge of the health of astronauts to evaluate before, during and after space flight activities the functional status of haemopoietic cell renewal. Chronic low level exposure of dogs indicate that daily gamma-exposure doses below about 2 cGy are tolerated for several years as far as blood cell concentrations are concerned. However, the stem cell pool may be severely affected. The maintenance of sufficient blood cell counts is possible only through increased cell production to compensate for the radiation inflicted excess cell loss. This behaviour of haemopoietic cell renewal during chronic low level exposure can be simulated by bioengineering models of granulocytopoiesis. It is possible to define a "turbulence region" for cell loss rates, below which an prolonged adaptation to increased radiation fields can be expected to be tolerated. On the basis of these experimental results, it is recommended to develop new biological indicators to monitor haemopoietic cell renewal at the level of the stem cell pool using blood stem cells in addition to the determination of cytokine concentrations in the serum (and other novel approaches). To prepare for unexpected haemopoietic effects during prolonged space missions, research should be increased to modify the radiation sensitivity of haemopoietic stem cells (for instance by the application of certain regulatory molecules). In addition, a "blood stem cell bank" might be established for the autologous storage of stem cells and for use in space activities keeping them in a radiation protected container. PMID:11539991

  18. Haemopoietic cell renewal in radiation fields

    NASA Astrophysics Data System (ADS)

    Fliedner, T. M.; Nothdurft, W.; Tibken, B.; Hofer, E.; Weiss, M.; Kindler, H.

    1994-10-01

    Space flight activities are inevitably associated with a chronic exposure of astronauts to a complex mixture of ionising radiation. Although no acute radiation consequences are to be expected as a rule, the possibility of Solar Particle Events (SPE) associated with relatively high doses of radiation (1 or more Gray) cannot be excluded. It is the responsibility of physicians in charge of the health of astronauts to evaluate before, during and after space flight activities the functional status of haemopoietic cell renewal. Chronic low level exposure of dogs indicate that daily gamma-exposure doses below about 2 cGy are tolerated for several years as far as blood cell concentrations are concerned. However, the stem cell pool may be severely affected. The maintenance of sufficient blood cell counts is possible only through increased cell production to compensate for the radiation inflicted excess cell loss. This behaviour of haemopoietic cell renewal during chronic low level exposure can be simulated by bioengineering models of granulocytopoiesis. It is possible to define a ``turbulence region'' for cell loss rates, below which an prolonged adaptation to increased radiation fields can be expected to be tolerated. On the basis of these experimental results, it is recommended to develop new biological indicators to monitor haemopoietic cell renewal at the level of the stem cell pool using blood stem cells in addition to the determination of cytokine concentrations in the serum (and other novel approaches). To prepare for unexpected haemopoietic effects during prolonged space missions, research should be increased to modify the radiation sensitivity of haemopoietic stem cells (for instance by the application of certain regulatory molecules). In addition, a ``blood stem cell bank'' might be established for the autologous storage of stem cells and for use in space activities keeping them in a radiation protected container.

  19. Bioacoustic Field Research: A Primer to Acoustic Analyses and Playback Experiments With Primates

    PubMed Central

    FISCHER, JULIA; NOSER, RAHEL; HAMMERSCHMIDT, KURT

    2013-01-01

    Acoustic analyses of primate vocalizations as well as playback experiments are staple methods in primatology. Acoustic analyses have been used to investigate the influence of factors such as individuality, context, sex, age, and size on variation in calls. More recent studies have expanded our knowledge on the effects of phylogenetic relatedness and the structure of primate vocal repertoires in general. Complementary playback experiments allow direct testing of hypotheses regarding the attribution of meaning to calls, the cognitive mechanisms underpinning responses, and/or the adaptive value of primate behavior. After briefly touching on the historical background of this field of research, we first provide an introduction to recording primate vocalizations and discuss different approaches to describe primate calls in terms of their temporal and spectral properties. Second, we present a tutorial regarding the preparation, execution, and interpretation of field playback experiments, including a review of studies that have used such approaches to investigate the responses to acoustic variation in calls including the integration of contextual and acoustic information, recognition of kin and social relationships, and social knowledge. Based on the review of the literature and our own experience, we make a number of recommendations regarding the most common problems and pitfalls. The power of acoustic analyses typically hinges on the quality of the recordings and the number of individuals represented in the sample. Playback experiments require profound knowledge of the natural behavior of the animals for solid interpretation; experiments should be conducted sparingly, to avoid habituation of the subjects to the occurrence of the calls; experimenter-blind designs chosen whenever possible; and researchers should brace themselves for long periods of waiting times until the appropriate moments to do the experiment arise. If all these aspects are considered, acoustic analyses

  20. Generation and development of small-amplitude disturbances in a laminar boundary layer in the presence of an acoustic field

    NASA Technical Reports Server (NTRS)

    Kachanov, Y. S.; Kozlov, V. V.; Levchenko, V. Y.

    1985-01-01

    A low-turbulence subsonic wind tunnel was used to study the influence of acoustic disturbances on the development of small sinusoidal oscillations (Tollmien-Schlichting waves) which constitute the initial phase of turbulent transition. It is found that acoustic waves propagating opposite to the flow generate vibrations of the model (plate) in the flow. Neither the plate vibrations nor the acoustic field itself have any appreciable influence on the stability of the laminar boundary layer. The influence of an acoustic field on laminar boundary layer disturbances is limited to the generation of Tollmien-Schlichting waves at the leading-edge of the plate.

  1. Adaptive Plasticity in Wild Field Cricket’s Acoustic Signaling

    PubMed Central

    Bertram, Susan M.; Harrison, Sarah J.; Thomson, Ian R.; Fitzsimmons, Lauren P.

    2013-01-01

    Phenotypic plasticity can be adaptive when phenotypes are closely matched to changes in the environment. In crickets, rhythmic fluctuations in the biotic and abiotic environment regularly result in diel rhythms in density of sexually active individuals. Given that density strongly influences the intensity of sexual selection, we asked whether crickets exhibit plasticity in signaling behavior that aligns with these rhythmic fluctuations in the socio-sexual environment. We quantified the acoustic mate signaling behavior of wild-caught males of two cricket species, Gryllus veletis and G. pennsylvanicus. Crickets exhibited phenotypically plastic mate signaling behavior, with most males signaling more often and more attractively during the times of day when mating activity is highest in the wild. Most male G. pennsylvanicus chirped more often and louder, with shorter interpulse durations, pulse periods, chirp durations, and interchirp durations, and at slightly higher carrier frequencies during the time of the day that mating activity is highest in the wild. Similarly, most male G. veletis chirped more often, with more pulses per chirp, longer interpulse durations, pulse periods, and chirp durations, shorter interchirp durations, and at lower carrier frequencies during the time of peak mating activity in the wild. Among-male variation in signaling plasticity was high, with some males signaling in an apparently maladaptive manner. Body size explained some of the among-male variation in G. pennsylvanicus plasticity but not G. veletis plasticity. Overall, our findings suggest that crickets exhibit phenotypically plastic mate attraction signals that closely match the fluctuating socio-sexual context they experience. PMID:23935965

  2. Imaging of transient surface acoustic waves by full-field photorefractive interferometry

    SciTech Connect

    Xiong, Jichuan; Xu, Xiaodong E-mail: christ.glorieux@fys.kuleuven.be; Glorieux, Christ E-mail: christ.glorieux@fys.kuleuven.be; Matsuda, Osamu; Cheng, Liping

    2015-05-15

    A stroboscopic full-field imaging technique based on photorefractive interferometry for the visualization of rapidly changing surface displacement fields by using of a standard charge-coupled device (CCD) camera is presented. The photorefractive buildup of the space charge field during and after probe laser pulses is simulated numerically. The resulting anisotropic diffraction upon the refractive index grating and the interference between the polarization-rotated diffracted reference beam and the transmitted signal beam are modeled theoretically. The method is experimentally demonstrated by full-field imaging of the propagation of photoacoustically generated surface acoustic waves with a temporal resolution of nanoseconds. The surface acoustic wave propagation in a 23 mm × 17 mm area on an aluminum plate was visualized with 520 × 696 pixels of the CCD sensor, yielding a spatial resolution of 33 μm. The short pulse duration (8 ns) of the probe laser yields the capability of imaging SAWs with frequencies up to 60 MHz.

  3. Characterization of the Acoustic Field in Marine Environments with Anthropogenic Noise

    NASA Astrophysics Data System (ADS)

    Guan, Shane

    Most animals inhabit the aquatic environment are acoustical-oriented, due to the physical characteristics of water that favors sound transmission. Many aquatic animals depend on underwater sound to navigate, communicate, find prey, and avoid predators. The degradation of underwater acoustic environment due to human activities is expected to affected these animals' well-being and survival at the population level. This dissertation presents three original studies on the characteristics and behavior of underwater sound fields in three unique marine environments with anthropogenic noises. The first study examines the soundscape of the Chinese white dolphin habitat in Taiwan. Acoustic recordings were made at two coastal shallow water locations, Yunlin and Waisanding, in 2012. Results show that croaker choruses are dominant sound sources in the 1.2--2.4 kHz frequency band for both locations at night, and noises from container ships in the 150--300 Hz frequency band define the relative higher broadband sound levels at Yunlin. Results also illustrate interrelationships among different biotic, abiotic, and anthropogenic elements that shape the fine-scale soundscape in a coastal environment. The second study investigates the inter-pulse sound field during an open-water seismic survey in coastal shallow waters of the Arctic. The research uses continuous acoustic recordings collected from one bottom-mounted hydrophone deployed in the Beaufort Sea in summer 2012. Two quantitative methods were developed to examine the inter-pulse sound field characteristics and its dependence on source distances. Results show that inter-pulse sound field could raise the ambient noise floor by as much as 9 dB, depending on ambient condition and source distance. The third study examines the inter-ping sound field of simulated mid-frequency active sonar in deep waters off southern California in 2013 and 2014. The study used drifting acoustic recorder buoys to collect acoustic data during sonar

  4. Influence of an oscillating circuit on the radiation of transient acoustic waves by an electroelastic cylinder.

    PubMed

    Babaev, A E; Babaev, A A; Yanchevskiy, I V

    2010-04-01

    The problem of nonstationary wave radiation in an infinitely long thick-wall piezoelectric cylinder in fluid medium is considered. The influence of an oscillating circuit with lumped parameters on characteristics of transient process is taken into consideration. Problem formulation is executed within the forced electrostatic theory, acoustic approximations, and quasistatic theory for electric circuit. The solution method is based on the integral Laplace transform in time. This allows analytically reducing the problem to solving a system of Volterra integral equations with retarded arguments. The numerical results of calculations are presented and analyzed. PMID:20370009

  5. 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.

  6. Experimental Study of the Acoustic Navigation of a Helicopter by Its Noise Radiation

    NASA Astrophysics Data System (ADS)

    Antonov, V. P.; Kuz'menko, A. K.; Svet, V. D.; Spitsyn, E. I.

    2000-11-01

    Results of experimental measurements of the coordinates and trajectories of an MI-8 helicopter flight are presented for various types of maneuvers and the landing approach. The current coordinates are measured in real time by acoustic differential navigation methods using the noise radiation of a helicopter. It is shown that, when a measuring base with a microphone spacing of 2 m or less is used, the spatial correlation coefficient for the signals in the frequency band from 200 to 5000 Hz approaches unity. This makes it possible to estimate the position of the helicopter with rms errors less than 0.4 m at all stages of flight and at the landing approach.

  7. 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

  8. Scattered acoustic field above a grating of non-parallel rectangular cavities

    NASA Astrophysics Data System (ADS)

    Khanfir, A.; Faiz, A.; Ducourneau, J.; Chatillon, J.; Lami, S. Skali

    2016-01-01

    Geometric or acoustical irregularities induces acoustic scattering. In this paper, a generalization of the model proposed by Khanfir et al. [8] (Journal of Sound and Vibration 332 (4) (2013)) to determine the scattered acoustic field above gratings of parallel rectangular cavities is developed, addressing the case of gratings of non-parallel rectangular cavities. The results provided by the model were compared both to numerical results, obtained with the finite element method, and to experimental ones. The observed agreement between the analytical predictions and the numerical and experimental results supports the validity of the proposed model. The coupling between the different cavities was investigated, in order to attain an explanation for its dependence on frequency and on the spacing between cavities.

  9. Field evaluation of boat-mounted acoustic Doppler instruments used to measure streamflow

    USGS Publications Warehouse

    Mueller, D.S.

    2003-01-01

    The use of instruments based on the Doppler principle for measuring water velocity and computing discharge is common within the U.S. Geological Survey (USGS). The instruments and software have changed appreciably during the last 5 years; therefore, the USGS has begun field validation of the instruments used to make discharge measurements from a moving boat. Instruments manufactured by SonTek/YSI and RD Instruments, Inc. were used to collect discharge data at five different sites. One or more traditional discharge measurements were made using a Price AA current meter and standard USGS procedures concurrent with the acoustic instruments at each site. Discharges measured with the acoustic instruments were compared with discharges measured with Price AA current meters and the USGS stage-discharge rating for each site. The mean discharges measured by each acoustic instrument were within 5 percent of the Price AA-based measurement and (or) discharge from the stage-discharge rating.

  10. Range-dependent flexibility in the acoustic field of view of echolocating porpoises (Phocoena phocoena).

    PubMed

    Wisniewska, Danuta M; Ratcliffe, John M; Beedholm, Kristian; Christensen, Christian B; Johnson, Mark; Koblitz, Jens C; Wahlberg, Magnus; Madsen, Peter T

    2015-01-01

    Toothed whales use sonar to detect, locate, and track prey. They adjust emitted sound intensity, auditory sensitivity and click rate to target range, and terminate prey pursuits with high-repetition-rate, low-intensity buzzes. However, their narrow acoustic field of view (FOV) is considered stable throughout target approach, which could facilitate prey escape at close-range. Here, we show that, like some bats, harbour porpoises can broaden their biosonar beam during the terminal phase of attack but, unlike bats, maintain the ability to change beamwidth within this phase. Based on video, MRI, and acoustic-tag recordings, we propose this flexibility is modulated by the melon and implemented to accommodate dynamic spatial relationships with prey and acoustic complexity of surroundings. Despite independent evolution and different means of sound generation and transmission, whales and bats adaptively change their FOV, suggesting that beamwidth flexibility has been an important driver in the evolution of echolocation for prey tracking. PMID:25793440

  11. Single-shot measurements of the acoustic field of an electrohydraulic lithotripter using a hydrophone array

    PubMed Central

    Alibakhshi, Mohammad A.; Kracht, Jonathan M.; Cleveland, Robin O.; Filoux, Erwan; Ketterling, Jeffrey A.

    2013-01-01

    Piezopolymer-based hydrophone arrays consisting of 20 elements were fabricated and tested for use in measuring the acoustic field from a shock-wave lithotripter. The arrays were fabricated from piezopolymer films and were mounted in a housing to allow submersion into water. The motivation was to use the array to determine how the shot-to-shot variability of the spark discharge in an electrohydraulic lithotripter affects the resulting focused acoustic field. It was found that the dominant effect of shot-to-shot variability was to laterally shift the location of the focus by up to 5 mm from the nominal acoustic axis of the lithotripter. The effect was more pronounced when the spark discharge was initiated with higher voltages. The lateral beamwidth of individual, instantaneous shock waves were observed to range from 1.5 mm to 24 mm. Due to the spatial variation of the acoustic field, the average of instantaneous beamwidths were observed to be 1 to 2 mm narrower than beamwidths determined from traditional single-point measurements that average the pressure measured at each location before computing beamwidth. PMID:23654419

  12. Integrating Acoustic Imaging of Flow Regimes With Bathymetry: A Case Study, Main Endeavor Field

    NASA Astrophysics Data System (ADS)

    Bemis, K. G.; Rona, P. A.; Jackson, D. R.; Jones, C. D.

    2003-12-01

    A unified view of the seafloor and the hydrothermal flow regimes (plumes and diffuse flow) is constructed for three major vent clusters in the Main Endeavour Field (e.g., Grotto, S&M, and Salut) of the Endeavour Segment, Juan de Fuca Ridge. The Main Endeavour Field is one of RIDGE 2000's Integrated Study Sites. A variety of visualization techniques are used to reconstruct the plumes (3D) and the diffuse flow field (2D) based on our acoustic imaging data set (July 2000 cruise). Plumes are identified as volumes of high backscatter intensity (indicating high particulate content or sharp density contrasts due to temperature variations) that remained high intensity when successive acoustic pings were subtracted (indicating that the acoustic targets producing the backscatter were in motion). Areas of diffuse flow are detected using our acoustic scintillation technique (AST). For the Grotto vent region (where a new Doppler technique was used to estimate vertical velocities in the plume), we estimate the areal partitioning between black smoker and diffuse flow in terms of volume fluxes. The volumetric and areal regions, where plume and diffuse flow were imaged, are registered over the bathymetry and compared to geologic maps of each region. The resulting images provide a unified view of the seafloor by integrating hydrothermal flow with geology.

  13. Acoustic field interaction with a boiling system under terrestrial gravity and microgravity.

    PubMed

    Sitter, J S; Snyder, T J; Chung, J N; Marston, P L

    1998-11-01

    Pool boiling experiments from a platinum wire heater in FC-72 liquid were conducted under terrestrial and microgravity conditions, both with and without the presence of a high-intensity acoustic standing wave within the fluid. The purpose of this research was to study the interaction between an acoustic field and a pool boiling system in normal gravity and microgravity. The absence of buoyancy in microgravity complicates the process of boiling. The acoustic force on a vapor bubble generated from a heated wire in a standing wave was shown to be able to play the role of buoyancy in microgravity. The microgravity environment was achieved with 0.6 and 2.1-s drop towers. The sound was transmitted through the fluid medium by means of a half wavelength sonic transducer driven at 10.18 kHz. At high enough acoustic pressure amplitudes cavitation and streaming began playing an important role in vapor bubble dynamics and heat transfer. Several different fixed heat fluxes were chosen for the microgravity experiment and the effects of acoustics on the surface temperature of the heater were recorded and the vapor bubble movement was filmed. Video images of the pool boiling processes and heat transfer data are presented. PMID:9821335

  14. A finite difference analysis of the field present behind an acoustically impenetrable two-layer barrier.

    PubMed

    Hurrell, Andrew M

    2008-06-01

    The interaction of an incident sound wave with an acoustically impenetrable two-layer barrier is considered. Of particular interest is the presence of several acoustic wave components in the shadow region of this barrier. A finite difference model capable of simulating this geometry is validated by comparison to the analytical solution for an idealized, hard-soft barrier. A panel comprising a high air-content closed cell foam backed with an elastic (metal) back plate is then examined. The insertion loss of this panel was found to exceed the dynamic range of the measurement system and was thus acoustically impenetrable. Experimental results from such a panel are shown to contain artifacts not present in the diffraction solution, when acoustic waves are incident upon the soft surface. A finite difference analysis of this experimental configuration replicates the presence of the additional field components. Furthermore, the simulated results allow the additional components to be identified as arising from the S(0) and A(0) Lamb modes traveling in the elastic plate. These Lamb mode artifacts are not found to be present in the shadow region when the acoustic waves are incident upon the elastic surface. PMID:18537372

  15. A gearbox fault diagnosis scheme based on near-field acoustic holography and spatial distribution features of sound field

    NASA Astrophysics Data System (ADS)

    Lu, Wenbo; Jiang, Weikang; Yuan, Guoqing; Yan, Li

    2013-05-01

    Vibration signal analysis is the main technique in machine condition monitoring or fault diagnosis, whereas in some cases vibration-based diagnosis is restrained because of its contact measurement. Acoustic-based diagnosis (ABD) with non-contact measurement has received little attention, although sound field may contain abundant information related to fault pattern. A new scheme of ABD for gearbox based on near-field acoustic holography (NAH) and spatial distribution features of sound field is presented in this paper. It focuses on applying distribution information of sound field to gearbox fault diagnosis. A two-stage industrial helical gearbox is experimentally studied in a semi-anechoic chamber and a lab workshop, respectively. Firstly, multi-class faults (mild pitting, moderate pitting, severe pitting and tooth breakage) are simulated, respectively. Secondly, sound fields and corresponding acoustic images in different gearbox running conditions are obtained by fast Fourier transform (FFT) based NAH. Thirdly, by introducing texture analysis to fault diagnosis, spatial distribution features are extracted from acoustic images for capturing fault patterns underlying the sound field. Finally, the features are fed into multi-class support vector machine for fault pattern identification. The feasibility and effectiveness of our proposed scheme is demonstrated on the good experimental results and the comparison with traditional ABD method. Even with strong noise interference, spatial distribution features of sound field can reliably reveal the fault patterns of gearbox, and thus the satisfactory accuracy can be obtained. The combination of histogram features and gray level gradient co-occurrence matrix features is suggested for good diagnosis accuracy and low time cost.

  16. 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.

  17. 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.

  18. 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

  19. The optimization of acoustic fields for ablative therapies of tumours in the upper abdomen

    NASA Astrophysics Data System (ADS)

    Gélat, P.; ter Haar, G.; Saffari, N.

    2012-12-01

    High intensity focused ultrasound (HIFU) enables highly localized, non-invasive tissue ablation and its efficacy has been demonstrated in the treatment of a range of cancers, including those of the kidney, prostate and breast. HIFU offers the ability to treat deep-seated tumours locally, and potentially bears fewer side effects than more invasive treatment modalities such as resection, chemotherapy and ionizing radiation. There remains however a number of significant challenges which currently hinder its widespread clinical application. One of these challenges is the need to transmit sufficient energy through the ribcage to ablate tissue at the required foci whilst minimizing the formation of side lobes and sparing healthy tissue. Ribs both absorb and reflect ultrasound strongly. This sometimes results in overheating of bone and overlying tissue during treatment, leading to skin burns. Successful treatment of a patient with tumours in the upper abdomen therefore requires a thorough understanding of the way acoustic and thermal energy is deposited. Previously, a boundary element approach based on a Generalized Minimal Residual (GMRES) implementation of the Burton-Miller formulation was developed to predict the field of a multi-element HIFU array scattered by human ribs, the topology of which was obtained from CT scan data (Gélat et al 2011 Phys. Med. Biol. 56 5553-81). The present paper describes the reformulation of the boundary element equations as a least-squares minimization problem with nonlinear constraints. The methodology has subsequently been tested at an excitation frequency of 1 MHz on a spherical multi-element array in the presence of ribs. A single array-rib geometry was investigated on which a 50% reduction in the maximum acoustic pressure magnitude on the surface of the ribs was achieved with only a 4% reduction in the peak focal pressure compared to the spherical focusing case. This method was then compared with a binarized apodization approach

  20. The optimization of acoustic fields for ablative therapies of tumours in the upper abdomen.

    PubMed

    Gélat, P; Ter Haar, G; Saffari, N

    2012-12-21

    High intensity focused ultrasound (HIFU) enables highly localized, non-invasive tissue ablation and its efficacy has been demonstrated in the treatment of a range of cancers, including those of the kidney, prostate and breast. HIFU offers the ability to treat deep-seated tumours locally, and potentially bears fewer side effects than more invasive treatment modalities such as resection, chemotherapy and ionizing radiation. There remains however a number of significant challenges which currently hinder its widespread clinical application. One of these challenges is the need to transmit sufficient energy through the ribcage to ablate tissue at the required foci whilst minimizing the formation of side lobes and sparing healthy tissue. Ribs both absorb and reflect ultrasound strongly. This sometimes results in overheating of bone and overlying tissue during treatment, leading to skin burns. Successful treatment of a patient with tumours in the upper abdomen therefore requires a thorough understanding of the way acoustic and thermal energy is deposited. Previously, a boundary element approach based on a Generalized Minimal Residual (GMRES) implementation of the Burton-Miller formulation was developed to predict the field of a multi-element HIFU array scattered by human ribs, the topology of which was obtained from CT scan data (Gélat et al 2011 Phys. Med. Biol. 56 5553-81). The present paper describes the reformulation of the boundary element equations as a least-squares minimization problem with nonlinear constraints. The methodology has subsequently been tested at an excitation frequency of 1 MHz on a spherical multi-element array in the presence of ribs. A single array-rib geometry was investigated on which a 50% reduction in the maximum acoustic pressure magnitude on the surface of the ribs was achieved with only a 4% reduction in the peak focal pressure compared to the spherical focusing case. This method was then compared with a binarized apodization approach

  1. Antifade sonar employs acoustic field diversity to recover signals from multipath fading

    SciTech Connect

    Lubman, D.

    1996-04-01

    Co-located pressure and particle motion (PM) hydrophones together with four-channel diversity combiners may be used to recover signals from multipath fading. Multipath fading is important in both shallow and deep water propagation and can be an important source of signal loss. The acoustic field diversity concept arises from the notion of conservation of signal energy and the observation that in rooms at least, the total acoustic energy density is the sum of potential energy (scalar field-sound pressure) and kinetic energy (vector field-sound PM) portions. One pressure hydrophone determines acoustic potential energy density at a point. In principle, three PM sensors (displacement, velocity, or acceleration) directed along orthogonal axes describe the kinetic energy density at a point. For a single plane wave, the time-averaged potential and kinetic field energies are identical everywhere. In multipath interference, however, potential and kinetic field energies at a point are partitioned unequally, depending mainly on relative signal phases. Thus, when pressure signals are in deep fade, abundant kinetic field signal energy may be available at that location. Performance benefits require a degree of uncorrelated fading between channels. The expectation of nearly uncorrelated fading is motivated from room theory. Performance benefits for sonar limited by independent Rayleigh fading are suggested by analogy to antifade radio. Average SNR can be improved by several decibels, holding time on target is multiplied manifold, and the bit error rate for data communication is reduced substantially. {copyright} {ital 1996 American Institute of Physics.}

  2. Antifade sonar employs acoustic field diversity to recover signals from multipath fading

    NASA Astrophysics Data System (ADS)

    Lubman, David

    1996-04-01

    Co-located pressure and particle motion (PM) hydrophones together with four-channel diversity combiners may be used to recover signals from multipath fading. Multipath fading is important in both shallow and deep water propagation and can be an important source of signal loss. The acoustic field diversity concept arises from the notion of conservation of signal energy and the observation that in rooms at least, the total acoustic energy density is the sum of potential energy (scalar field-sound pressure) and kinetic energy (vector field-sound PM) portions. One pressure hydrophone determines acoustic potential energy density at a point. In principle, three PM sensors (displacement, velocity, or acceleration) directed along orthogonal axes describe the kinetic energy density at a point. For a single plane wave, the time-averaged potential and kinetic field energies are identical everywhere. In multipath interference, however, potential and kinetic field energies at a point are partitioned unequally, depending mainly on relative signal phases. Thus, when pressure signals are in deep fade, abundant kinetic field signal energy may be available at that location. Performance benefits require a degree of uncorrelated fading between channels. The expectation of nearly uncorrelated fading is motivated from room theory. Performance benefits for sonar limited by independent Rayleigh fading are suggested by analogy to antifade radio. Average SNR can be improved by several decibels, holding time on target is multiplied manifold, and the bit error rate for data communication is reduced substantially.

  3. Limited-field radiation for bifocal germinoma

    SciTech Connect

    Lafay-Cousin, Lucie . E-mail: lucie.lafay-cousin@sickkids.ca; Millar, Barbara-Ann; Mabbott, Donald; Spiegler, Brenda; Drake, Jim; Bartels, Ute; Huang, Annie; Bouffet, Eric

    2006-06-01

    Purpose: To report the incidence, characteristics, treatment, and outcomes of bifocal germinomas treated with chemotherapy followed by focal radiation. Methods and Materials: This was a retrospective review. Inclusion criteria included radiologic diagnosis of bifocal germinoma involving the pineal and neurohypophyseal region, no evidence of dissemination on spinal MRI, negative results from cerebrospinal fluid cytologic evaluation, and negative tumor markers. Results: Between 1995 and 2004, 6 patients (5 male, 1 female; median age, 12.8 years) fulfilled the inclusion criteria. All had symptoms of diabetes insipidus at presentation. On MRI, 4 patients had a pineal and suprasellar mass, and 2 had a pineal mass associated with abnormal neurohypophyseal enhancement. All patients received chemotherapy followed by limited-field radiation and achieved complete remission after chemotherapy. The radiation field involved the whole ventricular system (range, 2,400-4,000 cGy) with or without a boost to the primary lesions. All patients remain in complete remission at a median follow-up of 48.1 months (range, 9-73.4 months). Conclusions: This experience suggests that bifocal germinoma can be considered a locoregional rather than a metastatic disease. Chemotherapy and focal radiotherapy might be sufficient to provide excellent outcomes. Staging refinement with new diagnostic tools will likely increase the incidence of the entity.

  4. Radiative processes in external gravitational fields

    SciTech Connect

    Papini, Giorgio

    2010-07-15

    Kinematically forbidden processes may be allowed in the presence of external gravitational fields. These can be taken into account by introducing generalized particle momenta. The corresponding transition probabilities can then be calculated to all orders in the metric deviation from the field-free expressions by simply replacing the particle momenta with their generalized counterparts. The procedure applies to particles of any spin and to any gravitational fields. Transition probabilities, emission power, and spectra are, to leading order, linear in the metric deviation. It is also shown how a small dissipation term in the particle wave equations can trigger a strong backreaction that introduces resonances in the radiative process and deeply affects the resulting gravitational background.

  5. Underwater patch near-field acoustical holography based on particle velocity and vector hydrophone array

    NASA Astrophysics Data System (ADS)

    Hu, Bo; Yang, DeSen; Li, SiChun; Sun, Yu; Mo, ShiQi; Shi, ShengGuo

    2012-11-01

    One-step patch near-field acoustical holography (PNAH) is a powerful tool for identifying noise sources from the partially known sound pressure field. The acoustical property to be reconstructed on the surface of interest is related to the partially measured pressure on the hologram surface in terms of sampling and bandlimiting matrices, which cost more in computation. A one-step procedure based on measuring of the normal component of the particle velocity is described, including the mathematical formulation. The numerical simulation shows that one-step PNAH based on particle velocity can obtain more accurately reconstructed results and it is also less sensitive to noise than the method based on pressure. These findings are confirmed by an underwater near-field acoustical holography experiment conducted with a vector hydrophone array. The experimental results have illustrated the high performance of one-step PNAH based on particle velocity in the reconstruction of sound field and the advantages of a vector hydrophone array in an underwater near-field measurement.

  6. 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.

  7. 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.

  8. Acoustic radiation pressure: A 'phase contrast' agent for x-ray phase contrast imaging

    SciTech Connect

    Bailat, Claude J.; Hamilton, Theron J.; Rose-Petruck, Christoph; Diebold, Gerald J.

    2004-11-08

    We show that the radiation pressure exerted by a beam of ultrasound can be used for contrast enhancement in high-resolution x-ray imaging of tissue and soft materials. Interfacial features of objects are highlighted as a result of both the displacement introduced by the ultrasound and the inherent sensitivity of x-ray phase contrast imaging to density variations. The potential of the method is demonstrated by imaging microscopic tumor phantoms embedded into tissue with a thickness typically presented in mammography. The detection limit of micrometer size masses exceeds the resolution of currently available mammography imaging systems. The directionality of the acoustic radiation force and its localization in space permits the imaging of ultrasound-selected tissue volumes. The results presented here suggest that the method may permit the detection of tumors in soft tissue in their early stage of development.

  9. Determination of the Accommodation Coefficient Using Vapor/gas Bubble Dynamics in an Acoustic Field

    NASA Technical Reports Server (NTRS)

    Gumerov, Nail A.; Hsiao, Chao-Tsung; Goumilevski, Alexei G.; Allen, Jeff (Technical Monitor)

    2001-01-01

    Nonequilibrium liquid/vapor phase transformations can occur in superheated or subcooled liquids in fast processes such as in evaporation in a vacuum. The rate at which such a phase transformation occurs depends on the "condensation" or "accommodation" coefficient, Beta, which is a property of the interface. Existing measurement techniques for Beta are complex and expensive. The development of a relatively inexpensive and reliable technique for measurement of Beta for a wide range of substances and temperatures is of great practical importance. The dynamics of a bubble in an acoustic field strongly depends on the value of Beta. It is known that near the saturation temperature, small vapor bubbles grow under the action of an acoustic field due to "rectified heat transfer." This finding can be used as the basis for an effective measurement technique of Beta. We developed a theory of vapor bubble behavior in an isotropic acoustic wave and in a plane standing acoustic wave. A numerical code was developed which enables simulation of a variety of experimental situations and accurately takes into account slowly evolving temperature. A parametric study showed that the measurement of Beta can be made over a broad range of frequencies and bubble sizes. We found several interesting regimes and conditions which can be efficiently used for measurements of Beta. Measurements of Beta can be performed in both reduced and normal gravity environments.

  10. Virtual radiation fields for ALARA determination

    SciTech Connect

    Knight, T.W.

    1995-12-31

    As computing power has increased, so too has the ability to model and simulate complex systems and processes. In addition, virtual reality technology has made it possible to visualize and understand many complex scientific and engineering problems. For this reason, a virtual dosimetry program called Virtual Radiation Fields (VRF) is developed to model radiation dose rate and cumulative dose to a receptor operating in a virtual radiation environment. With the design and testing of many facilities and products taking place in the virtual world, this program facilitates the concurrent consideration of radiological concerns during the design process. Three-dimensional (3D) graphical presentation of the radiation environment is made possible through the use of IGRIP, a graphical modeling program developed by Deneb Robotics, Inc. The VRF simulation program was designed to model and display a virtual dosimeter. As a demonstration of the program`s capability, the Hanford tank, C-106, was modeled to predict radiation doses to robotic equipment used to remove radioactive waste from the tank. To validate VRF dose predictions, comparison was made with reported values for tank C-106, which showed agreement to within 0.5%. Graphical information is presented regarding the 3D dose rate variation inside the tank. Cumulative dose predictions were made for the cleanup operations of tank C-106. A four-dimensional dose rate map generated by VRF was used to model the dose rate not only in 3D space but also as a function of the amount of waste remaining in the tank. This allowed VRF to predict dose rate at any stage in the waste removal process for an accurate simulation of the radiological conditions throughout the tank cleanup procedure.

  11. The development and potential of acoustic radiation force impulse (ARFI) imaging for carotid artery plaque characterization.

    PubMed

    Allen, Jason D; Ham, Katherine L; Dumont, Douglas M; Sileshi, Bantayehu; Trahey, Gregg E; Dahl, Jeremy J

    2011-08-01

    Stroke is the third leading cause of death and long-term disability in the USA. Currently, surgical intervention decisions in asymptomatic patients are based upon the degree of carotid artery stenosis. While there is a clear benefit of endarterectomy for patients with severe (> 70%) stenosis, in those with high/moderate (50-69%) stenosis the evidence is less clear. Evidence suggests ischemic stroke is associated less with calcified and fibrous plaques than with those containing softer tissue, especially when accompanied by a thin fibrous cap. A reliable mechanism for the identification of individuals with atherosclerotic plaques which confer the highest risk for stroke is fundamental to the selection of patients for vascular interventions. Acoustic radiation force impulse (ARFI) imaging is a new ultrasonic-based imaging method that characterizes the mechanical properties of tissue by measuring displacement resulting from the application of acoustic radiation force. These displacements provide information about the local stiffness of tissue and can differentiate between soft and hard areas. Because arterial walls, soft tissue, atheromas, and calcifications have a wide range in their stiffness properties, they represent excellent candidates for ARFI imaging. We present information from early phantom experiments and excised human limb studies to in vivo carotid artery scans and provide evidence for the ability of ARFI to provide high-quality images which highlight mechanical differences in tissue stiffness not readily apparent in matched B-mode images. This allows ARFI to identify soft from hard plaques and differentiate characteristics associated with plaque vulnerability or stability. PMID:21447606

  12. Applications of whole field interferometry in mechanics and acoustics

    NASA Astrophysics Data System (ADS)

    Molin, Nils-Erik

    1999-07-01

    A description is given of fringe formation in holographic interferometry, in electronic speckle pattern interferometry, in electro-optic or TV holography and for a newly developed system for pulsed TV-holography. A numerical example, which simulates the equations describing the different techniques, is included. A strain measuring system using defocused digital speckle photography is described. Experiments showing mode shapes of musical instruments, transient bending wave propagation in beams and plates as well as sound pressure fields in air are included.

  13. Production and Validation of Acoustic Field to Enhance Trapping Efficiency of Microbubbles by Using a Matrix Array Transducer

    NASA Astrophysics Data System (ADS)

    Hosaka, Naoto; Koda, Ren; Onogi, Shinya; Mochizuki, Takashi; Masuda, Kohji

    2013-07-01

    We have developed a new matrix array transducer for controlling the behavior of microbubbles, which is different from that for high-intensity focused ultrasound (HIFU) therapy, in order to emit continuous wave by designing an acoustic field including multiple focal points. In the experiment using a thin-channel model, a wider acoustic field has an advantage for trapping microbubbles. In the experiment using a straight-path model, we have confirmed that a higher concentration of acoustic energy does not result in more aggregates. The dispersion of acoustic energy is important because the trapping performance is affected by the relationship between the shape of the acoustic field and the concentration of the suspension.

  14. Radiation forces and torque on a rigid elliptical cylinder in acoustical plane progressive and (quasi)standing waves with arbitrary incidence

    NASA Astrophysics Data System (ADS)

    Mitri, F. G.

    2016-07-01

    This paper presents two key contributions; the first concerns the development of analytical expressions for the axial and transverse acoustic radiation forces exerted on a 2D rigid elliptical cylinder placed in the field of plane progressive, quasi-standing, or standing waves with arbitrary incidence. The second emphasis is on the acoustic radiation torque per length. The rigid elliptical cylinder case is important to be considered as a first-order approximation of the behavior of a cylindrical fluid column trapped in air because of the significant acoustic impedance mismatch at the particle boundary. Based on the rigorous partial-wave series expansion method in cylindrical coordinates, non-dimensional acoustic radiation force and torque functions are derived and defined in terms of the scattering coefficients of the elliptic cylinder. A coupled system of linear equations is obtained after applying the Neumann boundary condition for an immovable surface in a non-viscous fluid and solved numerically by matrix inversion after performing a single numerical integration procedure. Computational results for the non-dimensional force components and torque, showing the transition from the progressive to the (equi-amplitude) standing wave behavior, are performed with particular emphasis on the aspect ratio a/b, where a and b are the semi-axes of the ellipse, the dimensionless size parameter, as well as the angle of incidence ranging from end-on to broadside incidence. The results show that the elliptical geometry has a direct influence on the radiation force and torque, so that the standard theory for circular cylinders (at normal incidence) leads to significant miscalculations when the cylinder cross section becomes non-circular. Moreover, the elliptical cylinder experiences, in addition to the acoustic radiation force, a radiation torque that vanishes for the circular cylinder case. The application of the formalism presented here may be extended to other 2D surfaces of

  15. Underwater Acoustic Matched Field Imaging Based on Compressed Sensing

    PubMed Central

    Yan, Huichen; Xu, Jia; Long, Teng; Zhang, Xudong

    2015-01-01

    Matched field processing (MFP) is an effective method for underwater target imaging and localizing, but its performance is not guaranteed due to the nonuniqueness and instability problems caused by the underdetermined essence of MFP. By exploiting the sparsity of the targets in an imaging area, this paper proposes a compressive sensing MFP (CS-MFP) model from wave propagation theory by using randomly deployed sensors. In addition, the model’s recovery performance is investigated by exploring the lower bounds of the coherence parameter of the CS dictionary. Furthermore, this paper analyzes the robustness of CS-MFP with respect to the displacement of the sensors. Subsequently, a coherence-excluding coherence optimized orthogonal matching pursuit (CCOOMP) algorithm is proposed to overcome the high coherent dictionary problem in special cases. Finally, some numerical experiments are provided to demonstrate the effectiveness of the proposed CS-MFP method. PMID:26457708

  16. Underwater Acoustic Matched Field Imaging Based on Compressed Sensing.

    PubMed

    Yan, Huichen; Xu, Jia; Long, Teng; Zhang, Xudong

    2015-01-01

    Matched field processing (MFP) is an effective method for underwater target imaging and localizing, but its performance is not guaranteed due to the nonuniqueness and instability problems caused by the underdetermined essence of MFP. By exploiting the sparsity of the targets in an imaging area, this paper proposes a compressive sensing MFP (CS-MFP) model from wave propagation theory by using randomly deployed sensors. In addition, the model's recovery performance is investigated by exploring the lower bounds of the coherence parameter of the CS dictionary. Furthermore, this paper analyzes the robustness of CS-MFP with respect to the displacement of the sensors. Subsequently, a coherence-excluding coherence optimized orthogonal matching pursuit (CCOOMP) algorithm is proposed to overcome the high coherent dictionary problem in special cases. Finally, some numerical experiments are provided to demonstrate the effectiveness of the proposed CS-MFP method. PMID:26457708

  17. Field theory for zero sound and ion acoustic wave in astrophysical matter

    NASA Astrophysics Data System (ADS)

    Gabadadze, Gregory; Rosen, Rachel A.

    2016-02-01

    We set up a field theory model to describe the longitudinal low-energy modes in high density matter present in white dwarf stars. At the relevant scales, ions—the nuclei of oxygen, carbon, and helium—are treated as heavy pointlike spin-0 charged particles in an effective field theory approach, while the electron dynamics is described by the Dirac Lagrangian at the one-loop level. We show that there always exists a longitudinal gapless mode in the system irrespective of whether the ions are in a plasma, crystal, or quantum liquid state. For certain values of the parameters, the gapless mode can be interpreted as a zero sound mode and, for other values, as an ion acoustic wave; we show that the zero sound and ion acoustic wave are complementary to each other. We discuss possible physical consequences of these modes for properties of white dwarfs.

  18. Varying the agglomeration position of particles in a micro-channel using Acoustic Radiation Force beyond the resonance condition.

    PubMed

    Dron, Olivier; Aider, Jean-Luc

    2013-09-01

    It is well-known that particles can be focused at mid-height of a micro-channel using Acoustic Radiation Force (ARF) tuned at the resonance frequency (h=λ/2). The resonance condition is a strong limitation to the use of acoustophoresis (particles manipulation using acoustic force) in many applications. In this study we show that it is possible to focus the particles anywhere along the height of a micro-channel just by varying the acoustic frequency, in contradiction with the resonance condition. This result has been thoroughly checked experimentally. The different physical properties as well as wall materials have been changed. The wall materials is finally the only critical parameters. One of the specificity of the micro-channel is the thickness of the carrier and reflector layer. A preliminary analysis of the experimental results suggests that the acoustic focusing beyond the classic resonance condition can be explained in the framework of the multilayered resonator proposed by Hill [1]. Nevertheless, further numerical studies are needed in order to confirm and fully understand how the acoustic pressure node can be moved over the entire height of the micro channel by varying the acoustic frequency. Despite some uncertainties about the origin of the phenomenon, it is robust and can be used for improved acoustic sorting or manipulation of particles or biological cells in confined set-ups. PMID:23628114

  19. Detection and processing of electromagnetic and near-field acoustic signals in elasmobranch fishes.

    PubMed Central

    Kalmijn, A D

    2000-01-01

    The acoustic near field of quietly moving underwater objects and the bio-electric field of aquatic animals exhibit great similarity, as both are predominantly governed by Laplace's equation. The acoustic and electrical sensory modalities thus may, in directing fishes to their prey, employ analogous processing algorithms, suggesting a common evolutionary design, founded on the salient physical features shared by the respective stimulus fields. Sharks and rays are capable of orientating to the earth's magnetic field and, hence, have a magnetic sense. The electromagnetic theory of orientation offers strong arguments for the animals using the electric fields induced by ocean currents and by their own motions in the earth's magnetic field. In the animal's frame of reference, in which the sense organs are at rest, the classical concept of motional electricity must be interpreted in relativistic terms. In the ampullae of Lorenzini, weak electric fields cause the ciliated apical receptor-cell membranes to produce graded, negative receptor currents opposite in direction to the fields applied. The observed currents form part of a positive-feedback mechanism, supporting the generation of receptor potentials much larger than the input signal. Acting across the basal cell membranes, the receptor potentials control the process of synaptic transmission. PMID:11079385

  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. 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

  2. A method for characterizing photon radiation fields

    SciTech Connect

    Whicker, J.J.; Hsu, H.H.; Hsieh, F.H.; Borak, T.B.

    1999-04-01

    Uncertainty in dosimetric and exposure rate measurements can increase in areas where multi-directional and low-energy photons (< 100 keV) exist because of variations in energy and angular measurement response. Also, accurate measurement of external exposures in spatially non-uniform fields may require multiple dosimetry. Therefore, knowledge of the photon fields in the workplace is required for full understanding of the accuracy of dosimeters and instruments, and for determining the need for multiple dosimeters. This project was designed to develop methods to characterize photon radiation fields in the workplace, and to test the methods in a plutonium facility. The photon field at selected work locations was characterized using TLDs and a collimated NaI(Tl) detector from which spatial variations in photon energy distributions were calculated from measured spectra. Laboratory results showed the accuracy and utility of the method. Field measurement results combined with observed work patterns suggested the following: (1) workers are exposed from all directions, but not isotropically, (2) photon energy distributions were directionally dependent, (3) stuffing nearby gloves into the glovebox reduced exposure rates significantly, (4) dosimeter placement on the front of the chest provided for a reasonable estimate of the average dose equivalent to workers` torsos, (5) justifiable conclusions regarding the need for multiple dosimetry can be made using this quantitative method, and (6) measurements of the exposure rates with ionization chambers pointed with open beta windows toward the glovebox provided the highest measured rates, although absolute accuracy of the field measurements still needs to be assessed.

  3. 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.

  4. Possible variations of E-layer electromagnetic fields by acoustic waves above earthquake preparation regions

    NASA Astrophysics Data System (ADS)

    Meister, C.-V.; Mayer, B.; Hoffmann, D. H. H.

    2012-04-01

    The many-fluid magnetohydrodynamic theory is applied to describe the modification of the electromagnetic field of the ionospheric E-layer by acoustic-type waves. These waves originate from lower altitudes and may be caused by earthquake preparation processes. In comparison to former works, the different stratification of the positively and negatively charged ionospheric particles and of the neutral constituents is taken into account. There also the influence of the mean electric field on the different hight scales of the plasma parameters is discussed. Besides, the hight scales of the electric and magnetic wave fields are modeled. It is shown that at E-layer altitudes the acoustic waves may be converted into Alfvén waves. The dependence of these waves on the height scales of the plasma parameters of the particles and on the momentum transport between the charged and neutral particles is analysed. First estimates of the temperature variations within the E-layer because of the assumed acoustic-type waves of seismic origin are made.

  5. Generalized acoustic energy density based active noise control in single frequency diffuse sound fields.

    PubMed

    Xu, Buye; Sommerfeldt, Scott D

    2014-09-01

    In a diffuse sound field, prior research has established that a secondary source can theoretically achieve perfect cancellation at an error microphone in the far field of the secondary source. However, the sound pressure level is generally only reduced in a small zone around the error sensor, and at a distance half of a wavelength away from the error sensor, the averaged sound pressure level will be increased by more than 10 dB. Recently an acoustic energy quantity, referred to as the generalized acoustic energy density (GED), has been introduced. The GED is obtained by using a weighting factor in the formulation of total acoustic energy density. Different values of the weighting factor can be chosen for different applications. When minimizing the GED at the error sensor, one can adjust the weighting factor to increase the spatial extent of the "quiet zone" and to achieve a desired balance between the degree of attenuation in the quiet zone and the total energy added into the sound field. PMID:25190386

  6. Coupled acoustic-gravity field for dynamic evaluation of ion exchange with a single resin bead.

    PubMed

    Kanazaki, Takahiro; Hirawa, Shungo; Harada, Makoto; Okada, Tetsuo

    2010-06-01

    A coupled acoustic-gravity field is efficient for entrapping a particle at the position determined by its acoustic properties rather than its size. This field has been applied to the dynamic observation of ion-exchange reactions occurring in a single resin bead. The replacement of counterions in an ion-exchange resin induces changes in its acoustic properties, such as density and compressibility. Therefore, we can visually trace the advancement of an ion-exchange reaction as a time change in the levitation position of a resin bead entrapped in the field. Cation-exchange reactions occurring in resin beads with diameters of 40-120 microm are typically completed within 100-200 s. Ion-exchange equilibrium or kinetics is often evaluated with off-line chemical analyses, which require a batch amount of ion exchangers. Measurements with a single resin particle allow us to evaluate ion-exchange dynamics and kinetics of ions including those that are difficult to measure by usual off-line analyses. The diffusion properties of ions in resins have been successfully evaluated from the time change in the levitation positions of resin beads. PMID:20462180

  7. On the slow dynamics of near-field acoustically levitated objects under High excitation frequencies

    NASA Astrophysics Data System (ADS)

    Ilssar, Dotan; Bucher, Izhak

    2015-10-01

    This paper introduces a simplified analytical model describing the governing dynamics of near-field acoustically levitated objects. The simplification converts the equation of motion coupled with the partial differential equation of a compressible fluid, into a compact, second order ordinary differential equation, where the local stiffness and damping are transparent. The simplified model allows one to more easily analyse and design near-field acoustic levitation based systems, and it also helps to devise closed-loop controller algorithms for such systems. Near-field acoustic levitation employs fast ultrasonic vibrations of a driving surface and exploits the viscosity and the compressibility of a gaseous medium to achieve average, load carrying pressure. It is demonstrated that the slow dynamics dominates the transient behaviour, while the time-scale associated with the fast, ultrasonic excitation has a small presence in the oscillations of the levitated object. Indeed, the present paper formulates the slow dynamics under an ultrasonic excitation without the need to explicitly consider the latter. The simplified model is compared with a numerical scheme based on Reynolds equation and with experiments, both showing reasonably good results.

  8. Acoustic backscattering enhancements for circular elastic plates and acrylic targets, the application of acoustic holography to the study of scattering from planar elastic objects, and other research on the radiation of sound

    NASA Astrophysics Data System (ADS)

    Hefner, Brian Todd

    2000-08-01

    Backscattering enhancements on both circular elastic plates and acrylic targets are investigated as well as several techniques for the study of the radiation of sound. For sound scattered from a circular plate, two backscattering enhancements associated with the extensional wave are observed. The first of these enhancements involves extensional wave excitation along the diameter of the plate. When the extensional wave strikes the plate edge, reflection occurs which produces radiation into the backscattering direction. For those portions of the leaky wave which strike the edge at oblique incidence, there is mode conversion into a trapped shear wave. For certain angles of incidence on the plate edge, this wave can undergo multiple reflections and convert back into a leaky wave directed in the backscattering direction. Each of these enhancements are modeled using quantitative ray methods. Acoustic holography is also used to image the surface motion of the plate to identify the causes of these enhancements and to assess the validity of the ray model. Backscattering enhancements associated with antisymmetric Lamb wave excitation are also investigated. Scattering at the first-order antisymmetric wave coupling angle is studied using acoustic holography. Significant mode- conversion between the zeroth and first-order antisymmetric waves is observed which plays a significant role in the scattering processes. Quantitative ray models were also used to examine the backscattering from acrylic targets. Polymer solids typically have shear and Rayleigh wave phase velocities which are less than the speed of sound in water. For solid acrylic spheres, low frequency resonances are observed both experimentally and in the exact backscattering form functions which are due to coupling between the incident field and the subsonic Rayleigh wave on the sphere. The effects of material absorption, which is generally high in polymers, is examined in both the exact solutions and the quantitative

  9. 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

  10. Features of Propagation of the Acoustic-Gravity Waves Generated by High-Power Periodic Radiation

    NASA Astrophysics Data System (ADS)

    Chernogor, L. F.; Frolov, V. L.

    2013-09-01

    We present the results of the bandpass filtering of temporal variations of the Doppler frequency shift of radio signals from a vertical-sounding Doppler radar located near the city of Kharkov when the ionosphere was heated by high-power periodic (with 10 and 15-min periods) radiation from the Sura facility. The filtering was done in the ranges of periods that are close to the acoustic cutoff period and the Brunt—Väisälä period (4-6, 8-12, and 13-17 min). Oscillations with periods of 4-6 min and amplitudes of 50-100 mHz were not recorded in fact. Oscillations with periods of 8-12 and 13-17 min and amplitudes of 60-100 mHz were detected in almost all the sessions. In the former and the latter oscillations, the time of delay with respect to the heater switch-on was close to 100 min and about 40-50 min, respectively. These values correspond to group propagation velocities of about 160 and 320-400 m/s. The Doppler shift oscillations were caused by the acoustic-gravity waves which led to periodic variations in the electron number density with a relative amplitude of about 0.1-1.0%. It was demonstrated that the acoustic-gravity waves were not recorded when the effective power of the Sura facility was equal to 50 MW and they were confidently observed when the effective power was increased up to 130 MW. It is shown that the period of the wave processes was determined by the period of the heating-pause cycles, and the duration of the wave trains did not depend on the duration of the series of heating-pause cycles. The data suggest that the generation mechanism of recorded wave disturbances is different from the mechanism proposed in 1970-1990.

  11. Applications of velocity potential function to acoustic duct propagation and radiation from inlets using finite element theory

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Majjigi, R. K.

    1979-01-01

    A finite element velocity potential program was developed to study acoustic wave propagation in complex geometries. For irrotational flows, relatively low sound frequencies, and plane wave input, the finite element solutions showed significant effects of inlet curvature and flow gradients on the attenuation of a given acoustic liner in a realistic variable area turbofan inlet. The velocity potential approach can not be used to estimate the effects of rotational flow on acoustic propagation, since the potential acoustic disturbances propagate at the speed of the media in sheared flow. Approaches are discussed that are being considered for extending the finite element solution to include the far field, as well as the internal portion of the duct. A new matrix partitioning approach is presented that can be incorporated in previously developed programs to allow the finite element calculation to be marched into the far field. The partitioning approach provided a large reduction in computer storage and running times.

  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. Measurement and modeling of the acoustic field near an underwater vehicle and implications for acoustic source localization.

    PubMed

    Lepper, Paul A; D'Spain, Gerald L

    2007-08-01

    The performance of traditional techniques of passive localization in ocean acoustics such as time-of-arrival (phase differences) and amplitude ratios measured by multiple receivers may be degraded when the receivers are placed on an underwater vehicle due to effects of scattering. However, knowledge of the interference pattern caused by scattering provides a potential enhancement to traditional source localization techniques. Results based on a study using data from a multi-element receiving array mounted on the inner shroud of an autonomous underwater vehicle show that scattering causes the localization ambiguities (side lobes) to decrease in overall level and to move closer to the true source location, thereby improving localization performance, for signals in the frequency band 2-8 kHz. These measurements are compared with numerical modeling results from a two-dimensional time domain finite difference scheme for scattering from two fluid-loaded cylindrical shells. Measured and numerically modeled results are presented for multiple source aspect angles and frequencies. Matched field processing techniques quantify the source localization capabilities for both measurements and numerical modeling output. PMID:17672639

  14. Application of acoustic tomography to reconstruct the horizontal flow velocity field in a shallow river

    NASA Astrophysics Data System (ADS)

    Razaz, Mahdi; Kawanisi, Kiyosi; Kaneko, Arata; Nistor, Ioan

    2015-12-01

    A novel acoustic tomographic measurement system capable of resolving sound travel time in extremely shallow rivers is introduced and the results of an extensive field measurements campaign are presented and further discussed. Acoustic pulses were transmitted over a wide frequency band of 20-35 kHz between eight transducers for about a week in a meandering reach of theBāsen River, Hiroshima, Japan. The purpose of the field experiment was validating the concept of acoustic tomography in rivers for visualizing current fields. The particular novelty of the experiment resides in its unusual tomographic features: subbasin scale (100 m × 270 m) and shallowness (0.5-3.0 m) of the physical domain, frequency of the transmitted acoustic signals (central frequency of 30 kHz), and the use of small sampling intervals (105 s). Inverse techniques with no a priori statistical information were used to estimate the depth-average current velocity components from differential travel times. Zeroth-order Tikhonov regularization, in conjunction with L-curve method deployed to stabilize the solution and to determine the weighting factor appearing in the inverse analysis. Concurrent direct environmental measurements were provided in the form of ADCP readings close to the right and left bank. Very good agreement found between along-channel velocities larger than 0.2 m/s obtained from the two techniques. Inverted quantities were, however, underestimated, perhaps due to vicinity of the ADCPs to the banks and strong effect of river geometry on the readings. In general, comparing the visualized currents with direct nodal measurements illustrate the plausibility of the tomographically reconstructed flow structures.

  15. 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 ...

  16. Distributed Acoustic Sensing Technology in a Magmatic Geothermal Field - First Results From a Survey in Iceland

    NASA Astrophysics Data System (ADS)

    Reinsch, Thomas; Jousset, Philippe; Henninges, Jan; Blanck, Hanna

    2016-04-01

    Seismic methods are particularly suited for investigating the Earth's subsurface. Compared to surface-measurements , wellbore measurements can be used to acquire more detailed information about rock properties and possible fluid pathways within a geothermal reservoir. For high temperature geothermal wells, however, ambient temperatures are often far above the operating temperature range of conventional geophones. One way to overcome this limitation is the application of fiber optic sensor systems, where only the passive optical fiber is subjected to downhole conditions. Their applicability is thus determined by the operating temperature range of the optical fiber. Choosing appropriate fibers, such sensor systems can be operated at temperatures far above 200°C. Along an optical fiber, the distributed acoustic sensing technology (DAS) can be used to acquire acoustic signals with a high spatial and temporal resolution. Previous experiments have shown that the DAS technology is well suited for active seismic measurements. Within the framework of the EC funded project IMAGE, a fiber optic cable was deployed in a newly drilled geothermal well (RN-34) within the Reykjanes geothermal field, Iceland. Additionally, a >15 km fiber optic cable, already available at the surface, was connected to a DAS read-out unit. Acoustic data was acquired continuously for 9 days. Hammer shots were performed at the wellhead as well as along the surface cable in order to locate individual acoustic traces and calibrate the spatial distribution of the acoustic information. During the monitoring period both signals from on- and offshore explosive sources and natural seismic events could be recorded. We compare the fiber optic data to conventional seismic records from a dense seismic network deployed on the Reykjanes in the course of the IMAGE project. Here, first results from the seismic survey will be presented.

  17. Lamb Wave-Based Acoustic Radiation Force-Driven Particle Ring Formation Inside a Sessile Droplet.

    PubMed

    Destgeer, Ghulam; Ha, Byunghang; Park, Jinsoo; Sung, Hyung Jin

    2016-04-01

    We demonstrate an acoustofluidic device using Lamb waves (LWs) to manipulate polystyrene (PS) microparticles suspended in a sessile droplet of water. The LW-based acoustofluidic platform used in this study is advantageous in that the device is actuated over a range of frequencies without changing the device structure or electrode pattern. In addition, the device is simple to operate and cheap to fabricate. The LWs, produced on a piezoelectric substrate, attenuate inside the fluid and create acoustic streaming flow (ASF) in the form of a poloidal flow with toroidal vortices. The PS particles experience direct acoustic radiation force (ARF) in addition to being influenced by the ASF, which drive the concentration of particles to form a ring. This phenomenon was previously attributed to the ASF alone, but the present experimental results confirm that the ARF plays an important role in forming the particle ring, which would not be possible in the presence of only the ASF. We used a range of actuation frequencies (45-280 MHz), PS particle diameters (1-10 μm), and droplet volumes (5, 7.5, and 10 μL) to experimentally demonstrate this phenomenon. PMID:26937678

  18. Near-field/far-field array manifold of an acoustic vector-sensor near a reflecting boundary.

    PubMed

    Wu, Yue Ivan; Lau, Siu-Kit; Wong, Kainam Thomas

    2016-06-01

    The acoustic vector-sensor (a.k.a. the vector hydrophone) is a practical and versatile sound-measurement device, with applications in-room, open-air, or underwater. It consists of three identical uni-axial velocity-sensors in orthogonal orientations, plus a pressure-sensor-all in spatial collocation. Its far-field array manifold [Nehorai and Paldi (1994). IEEE Trans. Signal Process. 42, 2481-2491; Hawkes and Nehorai (2000). IEEE Trans. Signal Process. 48, 2981-2993] has been introduced into the technical field of signal processing about 2 decades ago, and many direction-finding algorithms have since been developed for this acoustic vector-sensor. The above array manifold is subsequently generalized for outside the far field in Wu, Wong, and Lau [(2010). IEEE Trans. Signal Process. 58, 3946-3951], but only if no reflection-boundary is to lie near the acoustic vector-sensor. As for the near-boundary array manifold for the general case of an emitter in the geometric near field, the far field, or anywhere in between-this paper derives and presents that array manifold in terms of signal-processing mathematics. Also derived here is the corresponding Cramér-Rao bound for azimuth-elevation-distance localization of an incident emitter, with the reflected wave shown to play a critical role on account of its constructive or destructive summation with the line-of-sight wave. The implications on source localization are explored, especially with respect to measurement model mismatch in maximum-likelihood direction finding and with regard to the spatial resolution between coexisting emitters. PMID:27369140

  19. Acoustic-radiation-force-induced shear wave propagation in cardiac tissue

    NASA Astrophysics Data System (ADS)

    Bouchard, Richard R.; Wolf, Patrick D.; Hsu, Stephen J.; Dumont, Douglas M.; Trahey, Gregg E.

    2009-02-01

    Shear wave elasticity imaging (SWEI) was employed to track acoustic radiation force (ARF)-induced shear waves in the myocardium of a beating heart. Shear waves were generated in and tracked through the myocardium of the left ventricular free wall (LVFW) in an in vivo heart that was exposed through a thoracotomy; matched studies were also preformed on an ex vivo myocardial specimen. Average shear wave velocities ranged from 2.22 to 2.53 m/s for the ex vivo specimen and 1.5 to 2.9 m/s (1.5-2.09 m/s during diastole; 2.9 m/s during systole) for in vivo specimens. Despite the known rotation of myocardial fiber orientation with tissue depth, there was no statistically significant shear wave velocity depth dependence observed in any of the experimental trials.

  20. Loss tangent and complex modulus estimated by acoustic radiation force creep and shear wave dispersion

    NASA Astrophysics Data System (ADS)

    Amador, Carolina; Urban, Matthew W.; Chen, Shigao; Greenleaf, James F.

    2012-03-01

    Elasticity imaging methods have been used to study tissue mechanical properties and have demonstrated that tissue elasticity changes with disease state. In current shear wave elasticity imaging methods typically only shear wave speed is measured and rheological models, e.g. Kelvin-Voigt, Maxwell and Standard Linear Solid, are used to solve for tissue mechanical properties such as the shear viscoelastic complex modulus. This paper presents a method to quantify viscoelastic material properties in a model-independent way by estimating the complex shear elastic modulus over a wide frequency range using time-dependent creep response induced by acoustic radiation force. This radiation force induced creep method uses a conversion formula that is the analytic solution of a constitutive equation. The proposed method in combination with shearwave dispersion ultrasound vibrometry is used to measure the complex modulus so that knowledge of the applied radiation force magnitude is not necessary. The conversion formula is shown to be sensitive to sampling frequency and the first reliable measure in time according to numerical simulations using the Kelvin-Voigt model creep strain and compliance. Representative model-free shear complex moduli from homogeneous tissue mimicking phantoms and one excised swine kidney were obtained. This work proposes a novel model-free ultrasound-based elasticity method that does not require a rheological model with associated fitting requirements.

  1. Loss tangent and complex modulus estimated by acoustic radiation force creep and shear wave dispersion.

    PubMed

    Amador, Carolina; Urban, Matthew W; Chen, Shigao; Greenleaf, James F

    2012-03-01

    Elasticity imaging methods have been used to study tissue mechanical properties and have demonstrated that tissue elasticity changes with disease state. In current shear wave elasticity imaging methods typically only shear wave speed is measured and rheological models, e.g. Kelvin-Voigt, Maxwell and Standard Linear Solid, are used to solve for tissue mechanical properties such as the shear viscoelastic complex modulus. This paper presents a method to quantify viscoelastic material properties in a model-independent way by estimating the complex shear elastic modulus over a wide frequency range using time-dependent creep response induced by acoustic radiation force. This radiation force induced creep method uses a conversion formula that is the analytic solution of a constitutive equation. The proposed method in combination with shearwave dispersion ultrasound vibrometry is used to measure the complex modulus so that knowledge of the applied radiation force magnitude is not necessary. The conversion formula is shown to be sensitive to sampling frequency and the first reliable measure in time according to numerical simulations using the Kelvin-Voigt model creep strain and compliance. Representative model-free shear complex moduli from homogeneous tissue mimicking phantoms and one excised swine kidney were obtained. This work proposes a novel model-free ultrasound-based elasticity method that does not require a rheological model with associated fitting requirements. PMID:22345425

  2. Loss tangent and complex modulus estimated by acoustic radiation force creep and shear wave dispersion

    PubMed Central

    Amador, Carolina; Urban, Matthew W; Chen, Shigao; Greenleaf, James F

    2012-01-01

    Elasticity imaging methods have been used to study tissue mechanical properties and have demonstrated that tissue elasticity changes with disease state. In current shear wave elasticity imaging methods typically only shear wave speed is measured and rheological models, e.g., Kelvin-Voigt, Maxwell and Standard Linear Solid, are used to solve for tissue mechanical properties such as the shear viscoelastic complex modulus. This paper presents a method to quantify viscoelastic material properties in a model-independent way by estimating the complex shear elastic modulus over a wide frequency range using time-dependent creep response induced by acoustic radiation force. This radiation force induced creep (RFIC) method uses a conversion formula that is the analytic solution of a constitutive equation. The proposed method in combination with Shearwave Dispersion Ultrasound Vibrometry (SDUV) is used to measure the complex modulus so that knowledge of the applied radiation force magnitude is not necessary. The conversion formula is shown to be sensitive to sampling frequency and the first reliable measure in time according to numerical simulations using the Kelvin-Voigt model creep strain and compliance. Representative model-free shear complex moduli from homogeneous tissue mimicking phantoms and one excised swine kidney were obtained. This work proposes a novel model-free ultrasound-based elasticity method that does not require a rheological model with associated fitting requirements. PMID:22345425

  3. Image quality, tissue heating, and frame rate trade-offs in acoustic radiation force impulse imaging.

    PubMed

    Bouchard, Richard R; Dahl, Jeremy J; Hsu, Stephen J; Palmeri, Mark L; Trahey, Gregg E

    2009-01-01

    The real-time application of acoustic radiation force impulse (ARFI) imaging requires both short acquisition times for a single ARFI image and repeated acquisition of these frames. Due to the high energy of pulses required to generate appreciable radiation force, however, repeated acquisitions could result in substantial transducer face and tissue heating. We describe and evaluate several novel beam sequencing schemes which, along with parallel-receive acquisition, are designed to reduce acquisition time and heating. These techniques reduce the total number of radiation force impulses needed to generate an image and minimize the time between successive impulses. We present qualitative and quantitative analyses of the trade-offs in image quality resulting from the acquisition schemes. Results indicate that these techniques yield a significant improvement in frame rate with only moderate decreases in image quality. Tissue and transducer face heating resulting from these schemes is assessed through finite element method modeling and thermocouple measurements. Results indicate that heating issues can be mitigated by employing ARFI acquisition sequences that utilize the highest track-to-excitation ratio possible. PMID:19213633

  4. Classification of underwater targets from autonomous underwater vehicle sampled bistatic acoustic scattered fields.

    PubMed

    Fischell, Erin M; Schmidt, Henrik

    2015-12-01

    One of the long term goals of autonomous underwater vehicle (AUV) minehunting is to have multiple inexpensive AUVs in a harbor autonomously classify hazards. Existing acoustic methods for target classification using AUV-based sensing, such as sidescan and synthetic aperture sonar, require an expensive payload on each outfitted vehicle and post-processing and/or image interpretation. A vehicle payload and machine learning classification methodology using bistatic angle dependence of target scattering amplitudes between a fixed acoustic source and target has been developed for onboard, fully autonomous classification with lower cost-per-vehicle. To achieve the high-quality, densely sampled three-dimensional (3D) bistatic scattering data required by this research, vehicle sampling behaviors and an acoustic payload for precision timed data acquisition with a 16 element nose array were demonstrated. 3D bistatic scattered field data were collected by an AUV around spherical and cylindrical targets insonified by a 7-9 kHz fixed source. The collected data were compared to simulated scattering models. Classification and confidence estimation were shown for the sphere versus cylinder case on the resulting real and simulated bistatic amplitude data. The final models were used for classification of simulated targets in real time in the LAMSS MOOS-IvP simulation package [M. Benjamin, H. Schmidt, P. Newman, and J. Leonard, J. Field Rob. 27, 834-875 (2010)]. PMID:26723332

  5. Two Years of Industrial Experience in the Use of a Small, Direct Field Acoustic Chamber

    NASA Astrophysics Data System (ADS)

    Saggini, Nicola; Di Pietro, Vincenzo; Poulain, Nicolas; Herzog, Philippe

    2012-07-01

    Within Thales Alenia Space - Italy small satellite Assembly Integration and Test (AIT) plant, the need to develop a suitable facility for spacecraft acoustic noise test has arisen, with additional constraints posed by the necessity of a low impact on the existing building layout, low cost of procurement and operations, while maintaining a high reliability of the system for a theoretical maximum throughput of one test per week over an extended period of time, e.g. six months. The needs have been answered by developing a small (~40 m3 test volume), direct field (DF A T) acoustic test chamber, christened “Alpha Cabin”, where noise generation is achieved by means of commercial audio drivers equipped with custom enclosures. The paper starts with a brief presentation of the main characteristics of the system, but then concentrates on the lessons learnt and return of experience from the tests conducted in more than two years of continuous use. Starting from test article structural responses and their comparison with reverberant chambers, properties of the acoustic field and their implications on the former are analyzed.

  6. Investigation on the reproduction performance versus acoustic contrast control in sound field synthesis.

    PubMed

    Bai, Mingsian R; Wen, Jheng-Ciang; Hsu, Hoshen; Hua, Yi-Hsin; Hsieh, Yu-Hao

    2014-10-01

    A sound reconstruction system is proposed for audio reproduction with extended sweet spot and reduced reflections. An equivalent source method (ESM)-based sound field synthesis (SFS) approach, with the aid of dark zone minimization is adopted in the study. Conventional SFS that is based on the free-field assumption suffers from synthesis error due to boundary reflections. To tackle the problem, the proposed system utilizes convex optimization in designing array filters with both reproduction performance and acoustic contrast taken into consideration. Control points are deployed in the dark zone to minimize the reflections from the walls. Two approaches are employed to constrain the pressure and velocity in the dark zone. Pressure matching error (PME) and acoustic contrast (AC) are used as performance measures in simulations and experiments for a rectangular loudspeaker array. Perceptual Evaluation of Audio Quality (PEAQ) is also used to assess the audio reproduction quality. The results show that the pressure-constrained (PC) method yields better acoustic contrast, but poorer reproduction performance than the pressure-velocity constrained (PVC) method. A subjective listening test also indicates that the PVC method is the preferred method in a live room. PMID:25324063

  7. Helicopter far-field acoustic levels as a function of reduced main-rotor advancing blade-tip Mach number

    NASA Astrophysics Data System (ADS)

    Mueller, Arnold W.; Smith, Charles D.; Lemasurier, Philip

    1990-07-01

    During the design of a helicopter, the weight, engine, rotor speed, and rotor geometry are given significant attention when considering the specific operations for which the helicopter will be used. However, the noise radiated from the helicopter and its relationship to the design variables is currently not well modeled with only a limited set of full-scale field test data to study. In general, limited field data have shown that reduced main-rotor advancing blade-tip Mach numbers result in reduced far-field noise levels. The status of a recent helicopter noise research project is reviewed. It is designed to provide flight experimental data which may be used to further understand helicopter main-rotor advancing blade-tip Mach number effects on far-field acoustic levels. Preliminary results are presented relative to tests conducted with a Sikorsky S-76A helicopter operating with both the rotor speed and the flight speed as the control variable. The rotor speed was operated within the range of 107 to 90 percent NR at nominal forward speeds of 35, 100, and 155 knots.

  8. Helicopter far-field acoustic levels as a function of reduced main-rotor advancing blade-tip Mach number

    NASA Technical Reports Server (NTRS)

    Mueller, Arnold W.; Smith, Charles D.; Lemasurier, Philip

    1990-01-01

    During the design of a helicopter, the weight, engine, rotor speed, and rotor geometry are given significant attention when considering the specific operations for which the helicopter will be used. However, the noise radiated from the helicopter and its relationship to the design variables is currently not well modeled with only a limited set of full-scale field test data to study. In general, limited field data have shown that reduced main-rotor advancing blade-tip Mach numbers result in reduced far-field noise levels. The status of a recent helicopter noise research project is reviewed. It is designed to provide flight experimental data which may be used to further understand helicopter main-rotor advancing blade-tip Mach number effects on far-field acoustic levels. Preliminary results are presented relative to tests conducted with a Sikorsky S-76A helicopter operating with both the rotor speed and the flight speed as the control variable. The rotor speed was operated within the range of 107 to 90 percent NR at nominal forward speeds of 35, 100, and 155 knots.

  9. On the applicability of the spherical wave expansion with a single origin for near-field acoustical holography.

    PubMed

    Gomes, Jesper; Hald, Jorgen; Juhl, Peter; Jacobsen, Finn

    2009-03-01

    The spherical wave expansion with a single origin is sometimes used in connection with near-field acoustical holography to determine the sound field on the surface of a source. The radiated field is approximated by a truncated expansion, and the expansion coefficients are determined by matching the sound field model to the measured pressure close to the source. This problem is ill posed, and therefore regularization is required. The present paper investigates the consequence of using only the expansion truncation as regularization approach and compares it with results obtained when additional regularization (the truncated singular value decomposition) is introduced. Important differences between applying the method when using a microphone array surrounding the source completely and an array covering only a part of the source are described. Another relevant issue is the scaling of the wave functions. It is shown that it is important for the additional regularization to work properly that the wave functions are scaled in such a way that their magnitude on the measurement surface decreases with the order. Finally, the method is applied on nonspherical sources using a vibrating plate in both simulations and an experiment, and the performance is compared with the equivalent source method. PMID:19275311

  10. On an acoustic field generated by subsonic jet at low Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Yamamoto, K.; Arndt, R. E. A.

    1978-01-01

    An acoustic field generated by subsonic jets at low Reynolds numbers was investigated. This work is motivated by the need to increase the fundamental understanding of the jet noise generation mechanism which is essential to the development of further advanced techniques of noise suppression. The scope of this study consists of two major investigation. One is a study of large scale coherent structure in the jet turbulence, and the other is a study of the Reynolds number dependence of jet noise. With this in mind, extensive flow and acoustic measurements in low Reynolds number turbulent jets (8,930 less than or equal to M less than or equal to 220,000) were undertaken using miniature nozzles of the same configuration but different diameters at various exist Mach numbers (0.2 less than or equal to M less than or equal to 0.9).

  11. Dynamics of a Coagulating Polydisperse Gas Suspension in the Nonlinear Wave Field of an Acoustic Resonator

    NASA Astrophysics Data System (ADS)

    Tukmakov, A. L.

    2015-01-01

    A model of a multivelocity multitemperature polydisperse gas suspension has been constructed with account taken of coagulation. Calculations of the dynamics of an aerosol of a polydisperse composition in an acoustic resonator have been done and the derived regularities have been described. A system of Navier-Stokes equations for a compressible heat-conducting gas was used to describe the motion of a carrier medium. The dynamics of dispersed fractions is described by a system of equations including continuity, momentum, and internal-energy equations. The equations of motion of the carrier medium and dispersed fractions have been written with account of the interphase exchange of momentum and energy. The Lagrangian model has been used to describe the process of coagulation. The change in the dispersity of the gas suspension in the nonlinear field of an acoustic resonator has been analyzed.

  12. Quasi-plane shear wave propagation induced by acoustic radiation force with a focal line region: a simulation study.

    PubMed

    Guo, Min; Abbott, Derek; Lu, Minhua; Liu, Huafeng

    2016-03-01

    Shear wave propagation speed has been regarded as an attractive indicator for quantitatively measuring the intrinsic mechanical properties of soft tissues. While most existing techniques use acoustic radiation force (ARF) excitation with focal spot region based on linear array transducers, we try to employ a special ARF with a focal line region and apply it to viscoelastic materials to create shear waves. First, a two-dimensional capacitive micromachined ultrasonic transducer with 64 × 128 fully controllable elements is realised and simulated to generate this special ARF. Then three-dimensional finite element models are developed to simulate the resulting shear wave propagation through tissue phantom materials. Three different phantoms are explored in our simulation study using: (a) an isotropic viscoelastic medium, (b) within a cylindrical inclusion, and (c) a transverse isotropic viscoelastic medium. For each phantom, the ARF creates a quasi-plane shear wave which has a preferential propagation direction perpendicular to the focal line excitation. The propagation of the quasi-plane shear wave is investigated and then used to reconstruct shear moduli sequentially after the estimation of shear wave speed. In the phantom with a transverse isotropic viscoelastic medium, the anisotropy results in maximum speed parallel to the fiber direction and minimum speed perpendicular to the fiber direction. The simulation results show that the line excitation extends the displacement field to obtain a large imaging field in comparison with spot excitation, and demonstrate its potential usage in measuring the mechanical properties of anisotropic tissues. PMID:26768475

  13. 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

  14. Prediction of acoustic radiation from axisymmetric surfaces with arbitrary boundary conditions using the boundary element method on a distributed computing system.

    PubMed

    Wright, Louise; Robinson, Stephen P; Humphrey, Victor F

    2009-03-01

    This paper presents a computational technique using the boundary element method for prediction of radiated acoustic waves from axisymmetric surfaces with nonaxisymmetric boundary conditions. The aim is to predict the far-field behavior of underwater acoustic transducers based on their measured behavior in the near-field. The technique is valid for all wavenumbers and uses a volume integral method to calculate the singular integrals required by the boundary element formulation. The technique has been implemented on a distributed computing system to take advantage of its parallel nature, which has led to significant reductions in the time required to generate results. Measurement data generated by a pair of free-flooding underwater acoustic transducers encapsulated in a polyurethane polymer have been used to validate the technique against experiment. The dimensions of the outer surface of the transducers (including the polymer coating) were an outer diameter of 98 mm with an 18 mm wall thickness and a length of 92 mm. The transducers were mounted coaxially, giving an overall length of 185 mm. The cylinders had resonance frequencies at 13.9 and 27.5 kHz, and the data were gathered at these frequencies. PMID:19275294

  15. Transition from near-field thermal radiation to phonon heat conduction at sub-nanometre gaps.

    PubMed

    Chiloyan, Vazrik; Garg, Jivtesh; Esfarjani, Keivan; Chen, Gang

    2015-01-01

    When the separation of two surfaces approaches sub-nanometre scale, the boundary between the two most fundamental heat transfer modes, heat conduction by phonons and radiation by photons, is blurred. Here we develop an atomistic framework based on microscopic Maxwell's equations and lattice dynamics to describe the convergence of these heat transfer modes and the transition from one to the other. For gaps >1 nm, the predicted conductance values are in excellent agreement with the continuum theory of fluctuating electrodynamics. However, for sub-nanometre gaps we find the conductance is enhanced up to four times compared with the continuum approach, while avoiding its prediction of divergent conductance at contact. Furthermore, low-frequency acoustic phonons tunnel through the vacuum gap by coupling to evanescent electric fields, providing additional channels for energy transfer and leading to the observed enhancement. When the two surfaces are in or near contact, acoustic phonons become dominant heat carriers. PMID:25849305

  16. Experimental research of the Multi-frequency Acoustic Backscatter System using the field sediment

    NASA Astrophysics Data System (ADS)

    Zhang, wenxiang

    2014-05-01

    The measurements of suspended sediment concentration and particle size profiles are very important to the engineering and environmental applications, especially in the estuarine and coastal areas. In recent years acoustic method has obtained increasing acceptance by many researchers. The theory of this method for measuring them is based on the acoustic backscattering and attenuation properties of the sediment in suspension. The Multi-frequency Acoustic Backscatter System (MABS), which has four acoustic sensors with different frequencies, can be measuring the profiles in the shallow water environment (no more than 10 meters). The experiments were conducted for AQUAscat1000 (MABS) (Made in UK) by the 'test tower' (φ600mm by 1500mm) in Laboratory. The frequency of the acoustic transducer is 0.5MHz, 1MHz, 2MHz and 4MHz, respectively. Two different places sediment were obtained from the Yangtze estuary. The average particle size is about 15μm and 115μm, respectively. Suspended sediment concentration in the 'test tower' was relatively constant during each phase of the sampling. The experimental procedures were as follows: (1) obtaining the background value of the instrument system; (2) add the field sediment to the tower according to the weight and allowing the mixture to homogenize; (3) obtaining water samples in different depths from the 'test tower'; (4) analyzing the water samples. These preliminary results show that (1) the MABS sensors are estimated from a complex function, depending on the receiving information (Voltage), measured at range, the speed of sound in water and the attenuation of sound by water, the sediment density and radius, and backscattering property of the sediment; (2) the appropriate calibration and regression approaches should be selected so as to obtain the reliable results of suspended sediment concentration(**R2 >0.7) and particle size(**R2 >0.5) measurements; (3) the MABS could be applied in the relative fine sediment condition, and

  17. Broadband control of plate radiation using a piezoelectric, double-amplifier active-skin and structural acoustic sensing

    PubMed

    Johnson; Fuller

    2000-02-01

    The potential of a piezoelectric, double-amplifier active-skin with structural acoustic sensing (SAS) is demonstrated for the reduction of broadband acoustic radiation from a clamped, aluminum plate. The active-skin is a continuous covering of the vibrating portions of the plate with active, independently controllable piezoelectric, double-amplifier elements and is designed to affect control by altering the continuous structural radiation impedance rather than structural vibration. In simulation, acoustic models are sought for the primary and secondary sources that incorporate finite element methods. Simulation indicates that a total radiated power attenuation in excess of 10 dB may be achieved between 250 and 750 Hz with microphone error sensing, while under SAS the radiated power is reduced by nearly 8 dB in the same frequency range. In experiment, the adaptive feed forward filtered-x LMS (least mean square) algorithm, implemented on a Texas Instruments C40 DSP, was used in conjunction with the 6I6O control system. With microphone error sensing, 11.8-dB attenuation was achieved in the overall radiated power between 175 and 600 Hz, while inclusion of SAS resulted in a 7.3-dB overall power reduction in this frequency band. PMID:10687697

  18. Imaging of transient surface acoustic waves by full-field photorefractive interferometry.

    PubMed

    Xiong, Jichuan; Xu, Xiaodong; Glorieux, Christ; Matsuda, Osamu; Cheng, Liping

    2015-05-01

    A stroboscopic full-field imaging technique based on photorefractive interferometry for the visualization of rapidly changing surface displacement fields by using of a standard charge-coupled device (CCD) camera is presented. The photorefractive buildup of the space charge field during and after probe laser pulses is simulated numerically. The resulting anisotropic diffraction upon the refractive index grating and the interference between the polarization-rotated diffracted reference beam and the transmitted signal beam are modeled theoretically. The method is experimentally demonstrated by full-field imaging of the propagation of photoacoustically generated surface acoustic waves with a temporal resolution of nanoseconds. The surface acoustic wave propagation in a 23 mm × 17 mm area on an aluminum plate was visualized with 520 × 696 pixels of the CCD sensor, yielding a spatial resolution of 33 μm. The short pulse duration (8 ns) of the probe laser yields the capability of imaging SAWs with frequencies up to 60 MHz. PMID:26026514

  19. 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

  20. Range-dependent flexibility in the acoustic field of view of echolocating porpoises (Phocoena phocoena)

    PubMed Central

    Wisniewska, Danuta M; Ratcliffe, John M; Beedholm, Kristian; Christensen, Christian B; Johnson, Mark; Koblitz, Jens C; Wahlberg, Magnus; Madsen, Peter T

    2015-01-01

    Toothed whales use sonar to detect, locate, and track prey. They adjust emitted sound intensity, auditory sensitivity and click rate to target range, and terminate prey pursuits with high-repetition-rate, low-intensity buzzes. However, their narrow acoustic field of view (FOV) is considered stable throughout target approach, which could facilitate prey escape at close-range. Here, we show that, like some bats, harbour porpoises can broaden their biosonar beam during the terminal phase of attack but, unlike bats, maintain the ability to change beamwidth within this phase. Based on video, MRI, and acoustic-tag recordings, we propose this flexibility is modulated by the melon and implemented to accommodate dynamic spatial relationships with prey and acoustic complexity of surroundings. Despite independent evolution and different means of sound generation and transmission, whales and bats adaptively change their FOV, suggesting that beamwidth flexibility has been an important driver in the evolution of echolocation for prey tracking. DOI: http://dx.doi.org/10.7554/eLife.05651.001 PMID:25793440

  1. 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

  2. Inverse method predicting spinning modes radiated by a ducted fan from free-field measurements.

    PubMed

    Lewy, Serge

    2005-02-01

    In the study the inverse problem of deducing the modal structure of the acoustic field generated by a ducted turbofan is addressed using conventional farfield directivity measurements. The final objective is to make input data available for predicting noise radiation in other configurations that would not have been tested. The present paper is devoted to the analytical part of that study. The proposed method is based on the equations governing ducted sound propagation and free-field radiation. It leads to fast computations checked on Rolls-Royce tests made in the framework of previous European projects. Results seem to be reliable although the system of equations to be solved is generally underdetermined (more propagating modes than acoustic measurements). A limited number of modes are thus selected according to any a priori knowledge of the sources. A first guess of the source amplitudes is obtained by adjusting the calculated maximum of radiation of each mode to the measured sound pressure level at the same angle. A least squares fitting gives the final solution. A simple correction can be made to take account of the mean flow velocity inside the nacelle which shifts the directivity patterns. It consists of modifying the actual frequency to keep the cut-off ratios unchanged. PMID:15759694

  3. Inverse method predicting spinning modes radiated by a ducted fan from free-field measurements

    NASA Astrophysics Data System (ADS)

    Lewy, Serge

    2005-02-01

    In the study the inverse problem of deducing the modal structure of the acoustic field generated by a ducted turbofan is addressed using conventional farfield directivity measurements. The final objective is to make input data available for predicting noise radiation in other configurations that would not have been tested. The present paper is devoted to the analytical part of that study. The proposed method is based on the equations governing ducted sound propagation and free-field radiation. It leads to fast computations checked on Rolls-Royce tests made in the framework of previous European projects. Results seem to be reliable although the system of equations to be solved is generally underdetermined (more propagating modes than acoustic measurements). A limited number of modes are thus selected according to any a priori knowledge of the sources. A first guess of the source amplitudes is obtained by adjusting the calculated maximum of radiation of each mode to the measured sound pressure level at the same angle. A least squares fitting gives the final solution. A simple correction can be made to take account of the mean flow velocity inside the nacelle which shifts the directivity patterns. It consists of modifying the actual frequency to keep the cut-off ratios unchanged. .

  4. Transmitted sound field due to an impulsive line acoustic source bounded by a plate followed by a vortex sheet

    NASA Technical Reports Server (NTRS)

    Miura, T.; Chao, C. C.

    1980-01-01

    The propagation of sound due to a line acoustic source in the moving stream across a semiinfinite vortex sheet which trails from a rigid plate is examined in a linear theory for the subsonic case. A solution for the transmitted sound field is obtained with the aid of multiple integral transforms and the Wiener-Hopf technique for both the steady state (time harmonic) and initial value (impulsive source) situations. The contour of inverse transform and hence the decomposition of the functions are determined through causality and radiation conditions. The solution obtained satisfies causality and the full Kutta conditions. The transmitted sound field is composed of two waves in both the stady state and initial value problems. One is the wave scattered from the edge of the plate which is associated with the bow wave and the instability wave. These waves exist in the downstream sectors. The other is the wave transmitted through the vortex sheet which is also associated with the instability wave. Regional divisions of the transmitted sound field are identified.

  5. 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.

  6. 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.

  7. Radiation burst from a single γ-photon field

    NASA Astrophysics Data System (ADS)

    Shakhmuratov, R. N.; Vagizov, F.; Kocharovskaya, O.

    2011-10-01

    The radiation burst from a single γ-photon field interacting with a dense resonant absorber is studied theoretically and experimentally. This effect was discovered for the fist time by P. Helisto [Phys. Rev. Lett. PRLTAO0031-900710.1103/PhysRevLett.66.203766, 2037 (1991)] and it was named the “gamma echo.” The echo is generated by a 180∘ phase shift of the incident radiation field, attained by an abrupt change of the position of the absorber with respect to the radiation source during the coherence time of the photon wave packet. Three distinguishing cases of the gamma echo are considered; i.e., the photon is in exact resonance with the absorber, close to resonance (on the slope of the absorption line), and far from resonance (on the far wings of the resonance line). In resonance the amplitude of the radiation burst is two times larger than the amplitude of the input radiation field just before its phase shift. This burst was explained by Helisto as a result of constructive interference of the coherently scattered field with the phase-shifted input field, both having almost the same amplitude. We found that out of resonance the scattered radiation field acquires an additional component with almost the same amplitude as the amplitude of the incident radiation field. The phase of the additional field depends on the optical thickness of the absorber and resonant detuning. Far from resonance this field interferes destructively with the phase-shifted incident radiation field and radiation quenching is observed. Close to resonance the three fields interfere constructively and the amplitude of the radiation burst is three times larger than the amplitude of the input radiation field.

  8. Radiation burst from a single {gamma}-photon field

    SciTech Connect

    Shakhmuratov, R. N.; Vagizov, F.; Kocharovskaya, O.

    2011-10-15

    The radiation burst from a single {gamma}-photon field interacting with a dense resonant absorber is studied theoretically and experimentally. This effect was discovered for the fist time by P. Helisto et al.[Phys. Rev. Lett. 66, 2037 (1991)] and it was named the ''gamma echo''. The echo is generated by a 180 Degree-Sign phase shift of the incident radiation field, attained by an abrupt change of the position of the absorber with respect to the radiation source during the coherence time of the photon wave packet. Three distinguishing cases of the gamma echo are considered; i.e., the photon is in exact resonance with the absorber, close to resonance (on the slope of the absorption line), and far from resonance (on the far wings of the resonance line). In resonance the amplitude of the radiation burst is two times larger than the amplitude of the input radiation field just before its phase shift. This burst was explained by Helisto et al. as a result of constructive interference of the coherently scattered field with the phase-shifted input field, both having almost the same amplitude. We found that out of resonance the scattered radiation field acquires an additional component with almost the same amplitude as the amplitude of the incident radiation field. The phase of the additional field depends on the optical thickness of the absorber and resonant detuning. Far from resonance this field interferes destructively with the phase-shifted incident radiation field and radiation quenching is observed. Close to resonance the three fields interfere constructively and the amplitude of the radiation burst is three times larger than the amplitude of the input radiation field.

  9. 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)

  10. 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

  11. Acoustic field in a thermoacoustic Stirling engine having a looped tube and resonator

    NASA Astrophysics Data System (ADS)

    Ueda, Yuki; Biwa, Tetsushi; Mizutani, Uichiro; Yazaki, Taichi

    2002-12-01

    S. Backhaus and G. W. Swift [Nature 399, 335(1999)] have built a prototype thermoacoustic Stirling engine based on traveling wave energy conversions, and demonstrated that its efficiency reached above 40% of the Carnot efficiency. We experimentally investigate an acoustic field in the engine through simultaneous measurements of velocity U and pressure P. By focusing on the phase lead Φ of U relative to P in its regenerator, we find that the engine can achieve such a high efficiency by the negative Φ about -20° rather than a traveling wave phase (Φ=0).

  12. Far-field hover acoustic characteristics of the XV-15 tiltrotor aircraft with Advanced Technology Blades

    NASA Astrophysics Data System (ADS)

    Conner, David A.; Wellman, Brent

    1991-05-01

    An experimental investigation has been conducted with the XV-15 tilt-rotor VTOL aircraft in order to ascertain the noise-reduction efficacy of Advanced Technology Blades (ATBs). Attention is given to acoustic directivity characteristics in the lower hemisphere of the sound field. Modest overall sound pressure levels (OASPLs) were measured near the in-plane position, showing that thickness noise is not significant in hover when ATBs are used; rotor tip-speed reductions reduced the average OASPL by nearly 8 dB in-plane and by nearly 5 dB at 12.6 deg below the rotor plane.

  13. Acoustic field characterization of the Duolith: measurements and modeling of a clinical shock wave therapy device.

    PubMed

    Perez, Camilo; Chen, Hong; Matula, Thomas J; Karzova, Maria; Khokhlova, Vera A

    2013-08-01

    Extracorporeal shock wave therapy (ESWT) uses acoustic pulses to treat certain musculoskeletal disorders. In this paper the acoustic field of a clinical portable ESWT device (Duolith SD1) was characterized. Field mapping was performed in water for two different standoffs of the electromagnetic head (15 or 30 mm) using a fiber optic probe hydrophone. Peak positive pressures at the focus ranged from 2 to 45 MPa, while peak negative pressures ranged from -2 to -11 MPa. Pulse rise times ranged from 8 to 500 ns; shock formation did not occur for any machine settings. The maximum standard deviation in peak pressure at the focus was 1.2%, indicating that the Duolith SD1 generates stable pulses. The results compare qualitatively, but not quantitatively with manufacturer specifications. Simulations were carried out for the short standoff by matching a Khokhlov-Zabolotskaya-Kuznetzov equation to the measured field at a plane near the source, and then propagating the wave outward. The results of modeling agree well with experimental data. The model was used to analyze the spatial structure of the peak pressures. Predictions from the model suggest that a true shock wave could be obtained in water if the initial pressure output of the device were doubled. PMID:23927207

  14. Acoustic field characterization of the Duolith: Measurements and modeling of a clinical shock wave therapy device

    PubMed Central

    Perez, Camilo; Chen, Hong; Matula, Thomas J.; Karzova, Maria; Khokhlova, Vera A.

    2013-01-01

    Extracorporeal shock wave therapy (ESWT) uses acoustic pulses to treat certain musculoskeletal disorders. In this paper the acoustic field of a clinical portable ESWT device (Duolith SD1) was characterized. Field mapping was performed in water for two different standoffs of the electromagnetic head (15 or 30 mm) using a fiber optic probe hydrophone. Peak positive pressures at the focus ranged from 2 to 45 MPa, while peak negative pressures ranged from −2 to −11 MPa. Pulse rise times ranged from 8 to 500 ns; shock formation did not occur for any machine settings. The maximum standard deviation in peak pressure at the focus was 1.2%, indicating that the Duolith SD1 generates stable pulses. The results compare qualitatively, but not quantitatively with manufacturer specifications. Simulations were carried out for the short standoff by matching a Khokhlov-Zabolotskaya-Kuznetzov equation to the measured field at a plane near the source, and then propagating the wave outward. The results of modeling agree well with experimental data. The model was used to analyze the spatial structure of the peak pressures. Predictions from the model suggest that a true shock wave could be obtained in water if the initial pressure output of the device were doubled. PMID:23927207

  15. Far-Field Acoustic Characteristics of Multiple Blade-Vane Configurations for a High Tip Speed Fan, Supplement

    NASA Technical Reports Server (NTRS)

    Woodward, Richard P.

    2004-01-01

    The contents of this CD-ROM include: 1) Aero Data; 2) Data Documents (Daily Acoustic Data Logs, Test Documentation, Test Photos); 3) EPNL Data (All Core Tones Removed, All Core Tones Removed and Various Bypass Tones, Core BPF Tone Removed, Core Tones Present); 4) Far-Field Acoustic Data, 5) High Speed Fan Reports; 6) Sound Power Levels (As-Measured PWL, Lossless PWL).

  16. Acoustic and electromagnetic waves

    NASA Astrophysics Data System (ADS)

    Jones, Douglas Samuel

    Theoretical models of EM and acoustic wave propagation are presented in an introductory text intended for intermediate-level science and engineering students. Chapters are devoted to the mathematical representation of acoustic and EM fields, the special theory of relativity, radiation, resonators, waveguide theory, refraction, surface waves, scattering by smooth objects, diffraction by edges, and transient waves. The mathematical tools required for the analysis (Bessel, Legendre, Mathieu, parabolic-cylinder, and spheroidal functions; tensor calculus; and the asymptotic evaluation of integrals) are covered in appendices.

  17. Structural Acoustics and Vibrations

    NASA Astrophysics Data System (ADS)

    Chaigne, Antoine

    This chapter is devoted to vibrations of structures and to their coupling with the acoustic field. Depending on the context, the radiated sound can be judged as desirable, as is mostly the case for musical instruments, or undesirable, like noise generated by machinery. In architectural acoustics, one main goal is to limit the transmission of sound through walls. In the automobile industry, the engineers have to control the noise generated inside and outside the passenger compartment. This can be achieved by means of passive or active damping. In general, there is a strong need for quieter products and better sound quality generated by the structures in our daily environment.

  18. Near-field sound radiation of fan tones from an installed turbofan aero-engine.

    PubMed

    McAlpine, Alan; Gaffney, James; Kingan, Michael J

    2015-09-01

    The development of a distributed source model to predict fan tone noise levels of an installed turbofan aero-engine is reported. The key objective is to examine a canonical problem: how to predict the pressure field due to a distributed source located near an infinite, rigid cylinder. This canonical problem is a simple representation of an installed turbofan, where the distributed source is based on the pressure pattern generated by a spinning duct mode, and the rigid cylinder represents an aircraft fuselage. The radiation of fan tones can be modelled in terms of spinning modes. In this analysis, based on duct modes, theoretical expressions for the near-field acoustic pressures on the cylinder, or at the same locations without the cylinder, have been formulated. Simulations of the near-field acoustic pressures are compared against measurements obtained from a fan rig test. Also, the installation effect is quantified by calculating the difference in the sound pressure levels with and without the adjacent cylindrical fuselage. Results are shown for the blade passing frequency fan tone radiated at a supersonic fan operating condition. PMID:26428770

  19. Heart sounds as a result of acoustic dipole radiation of heart valves

    NASA Astrophysics Data System (ADS)

    Kasoev, S. G.

    2005-11-01

    Heart sounds are associated with impulses of force acting on heart valves at the moment they close under the action of blood-pressure difference. A unified model for all the valves represents this impulse as an acoustic dipole. The near pressure field of this dipole creates a distribution of the normal velocity on the breast surface with features typical of auscultation practice: a pronounced localization of heart sound audibility areas, an individual area for each of the valves, and a noncoincidence of these areas with the projections of the valves onto the breast surface. In the framework of the dipole theory, the optimum size of the stethoscope’s bell is found and the spectrum of the heart sounds is estimated. The estimates are compared with the measured spectrum.

  20. Convergence of intense aerial acoustic waves radiated by a rectangular transverse vibrating plate

    NASA Astrophysics Data System (ADS)

    Nakai, Tomoki; Asami, Takuya; Miura, Hikaru

    2016-07-01

    A stripe-mode rectangular transverse vibrating plate can be used as a sound source that emits intense ultrasonic waves in air by placing a jut driving point outside the vibrating plate. The aim of this research was to use this vibrating plate to focus sound waves in the direction perpendicular to the nodal lines of the vibrating plate, which differs from the conventional direction. In this study, we investigated new methods for focusing the emitted sound waves by arranging reflective plates around the vibrating plate, using a design equation for each node between nodes in the vibrating plate, and placing additional reflective plates at an outer position beyond the convergence point, and found that a powerful acoustic field can be formed at an arbitrary position.

  1. Dust acoustic shock wave in electronegative dusty plasma: Roles of weak magnetic field

    SciTech Connect

    Ghosh, Samiran; Ehsan, Z.; Murtaza, G.

    2008-02-15

    The effects of nonsteady dust charge variations and weak magnetic field on small but finite amplitude nonlinear dust acoustic wave in electronegative dusty plasma are investigated. The dynamics of the nonlinear wave are governed by a Korteweg-de Vries Burger equation that possesses dispersive shock wave. The weak magnetic field is responsible for the dispersive term, whereas nonsteady dust charge variation is responsible for dissipative term, i.e., the Burger term. The coefficient of dissipative term depends only on the obliqueness of the magnetic field. It is found that for parallel propagation the dynamics of the nonlinear wave are governed by the Burger equation that possesses monotonic shock wave. The relevances of the findings to cometary dusty plasma, e.g., Comet Halley are briefly discussed.

  2. Renal elasticity quantification by acoustic radiation force impulse applied to the evaluation of kidney diseases: a review.

    PubMed

    Zaffanello, Marco; Piacentini, Giorgio; Bruno, Costanza; Brugnara, Milena; Fanos, Vassilios

    2015-04-01

    For centuries, clinicians have used palpation to evaluate abdominal organs. After exploring almost all the different methods of interaction between x-rays, ultrasound, and magnetic fields on tissues, recent interest has focused on the evaluation of their mechanical properties.Acoustic radiation force impulse (ARFI) is a recent, established ultrasound-based diagnostic technique that allows physicians to obtain a measure of the elastic properties of an organ. Shear wave velocity, obtained by the ARFI technique, depends on the elasticity of tissues.To date, there are studies on the ARFI technique applied to normal kidneys, chronic kidney diseases, and kidney transplants. Mechanical properties of the kidney, such as stiffness and deformity, depend on various conditions that alter its histology, in particular the amount of fibrosis in the renal parenchyma; urinary pressure and renal blood perfusion may be other important contributing factors. Unfortunately, the ARFI technique applied to native renal pathologies is still limited, and not all studies are comparable because they used different methods. Therefore, the results reported in recent literature encourage further improvement of this method and the drawing up of standardized guidelines of investigation. PMID:25738649

  3. Miniature probe for mechanical properties of vascular lesions using acoustic radiation force optical coherence elastography (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Qu, Yueqiao; Ma, Teng; He, Youmin; Yu, Mingyue; Li, Rui; Zhu, Jiang; Dai, Cuixia; Piao, Zhonglie; Shung, K. Kirk; Zhou, Qifa; Chen, Zhongping

    2016-03-01

    Changes in tissue biomechanical properties often signify the onset and progression of diseases, such as in determining the vulnerability of atherosclerotic plaques. Acoustic radiation force optical coherence elastography (ARF-OCE) has been used in the detection of tissue elasticity to obtain high-resolution elasticity maps. We have developed a probe-based ARF-OCE technology that utilizes a miniature 10 MHz ring ultrasonic transducer for excitation and Doppler optical coherence tomography (OCT) for detection. The transducer has a small hole in the center for the OCT light to propagate through. This allows for a confocal stress field and light detection within a small region for high sensitivity and localized excitation. This device is a front-facing probe that is only 3.5 mm in diameter and it is the smallest ARF-OCE catheter to the best of our knowledge. We have tested the feasibility of the probe by measuring the point displacement of an agarose tissue-mimicking phantom using different ARF excitation voltages. Small displacement values ranging from 30 nm to 90 nm have been detected and are shown to be directly proportional to the excitation voltage as expected. We are currently working on obtaining 2D images using a scanning mechanism. We will be testing to capture 2D elastograms of phantoms to further verify feasibility, and eventually characterize the mechanical properties of cardiovascular tissue. With its high portability and sensitivity, this novel technology can be applied to the diagnosis and characterization of vulnerable atherosclerotic plaques.

  4. 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

  5. Light-Cone Effect of Radiation Fields in Cosmological Radiative Transfer Simulations

    NASA Astrophysics Data System (ADS)

    Ahn, Kyungjin

    2015-02-01

    We present a novel method to implement time-delayed propagation of radiation fields in cosmo-logical radiative transfer simulations. Time-delayed propagation of radiation fields requires construction of retarded-time fields by tracking the location and lifetime of radiation sources along the corresponding light-cones. Cosmological radiative transfer simulations have, until now, ignored this "light-cone effect" or implemented ray-tracing methods that are computationally demanding. We show that radiative trans-fer calculation of the time-delayed fields can be easily achieved in numerical simulations when periodic boundary conditions are used, by calculating the time-discretized retarded-time Green's function using the Fast Fourier Transform (FFT) method and convolving it with the source distribution. We also present a direct application of this method to the long-range radiation field of Lyman-Werner band photons, which is important in the high-redshift astrophysics with first stars.

  6. Chromospheric heating by acoustic shock waves

    NASA Technical Reports Server (NTRS)

    Jordan, Stuart D.

    1993-01-01

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

  7. 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.

  8. Magnetic fields and nonthermal electromagnetic radiation of stars

    NASA Astrophysics Data System (ADS)

    Kryvdyk, Volodymyr

    2016-07-01

    The results of the astrophysical observations of the magnetic fields and the nonthermal electromagnetic radiation of stars and the mechanisms generation of the nonthermal electromagnetic radiation from the magnetized stars of different spectral classes on the different stages their evolution are present. Results of observations allow to calculate the plasma parameters and the magnetic fields in areas around magnetized stars where is generated given radiation and their change during stellar evolution.

  9. 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.

  10. The acoustic field of singing humpback whales in the vertical plane

    NASA Astrophysics Data System (ADS)

    Au, Whitlow W. L.; Pack, Adam A.; Lammers, Marc O.; Herman, Louis; Andrews, Kimberly; Deakos, Mark

    2003-04-01

    A vertical array of five hydrophones was used to measure the acoustic field of singing humpback whales. Once a singer was located, two swimmers with snorkel gear were deployed to determine the orientation of the whale and to position the boat so that the array could be deployed in front of the whale at a minimum standoff distance of 10 m. The spacing of the hydrophones was 7 m with the deepest hydrophone deployed at depth of 35 m. An 8-channel TASCAM recorder having a bandwidth of 24 kHz was used to record the hydrophone signals. The location of the singer was determined by computing the time of arrival differences between the hydrophone signals. The maximum source level varied between individual units in a song, with values between 180 and 190 dB. The acoustic field determined by considering the relative intensity of higher frequency harmonics in the signals indicate that the sounds are projected in the horizontal direction with the singer's head canted downward 45 to 60°. High-frequency harmonics extended beyond 24 kHz, suggesting that humpback whales may have an upper frequency limit of hearing as high as 24 kHz.

  11. Translational motion of two interacting bubbles in a strong acoustic field.

    PubMed

    Doinikov, A A

    2001-08-01

    Using the Lagrangian formalism, equations of radial and translational motions of two coupled spherical gas bubbles have been derived up to terms of third order in the inverse distance between the bubbles. The equations of radial pulsations were then modified, for the purpose of allowing for effects of liquid compressibility, using Keller-Miksis' approach, and the equations of translation were added by viscous forces in the form of the Levich drag. This model was then used in a numerical investigation of the translational motion of two small, driven well below resonance, bubbles in strong acoustic fields with pressure amplitudes exceeding 1 bar. It has been found that, if the forcing is strong enough, the bubbles form a bound pair with a steady spacing rather than collide and coalesce, as classical Bjerknes theory predicts. Moreover, the viscous forces cause skewness in the system, which results in self-propulsion of the bubble pair. The latter travels as a unit along the center line in a direction that is determined by the ratio of the initial bubble radii. The results obtained are of immediate interest for understanding and modeling collective bubble phenomena in strong fields, such as acoustic cavitation streamers. PMID:11497693

  12. 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.

  13. Computer and laboratory modeling of radiation-acoustic detector for charged particles pulse beams and plasma parameters measuring

    SciTech Connect

    Kresnin, Yu.A.; Stervoedov, N.G.

    1996-12-31

    Model investigations and laboratory tests of detectors for charged particles pulse beams and plasma parameters measuring are presented. Detector represents combination of classic Faraday cup with electrical way of signal getting and radiation-acoustic meter of pulse beams parameters. Radiation-acoustic meter consists of two parts--thin detector, transparent for beams of high energy particles, and thick detector with full absorption. Ultrasonic oscillations, which arise during interaction of charged particles pulse beams or plasma with detector material, are transformed by piezoelectric detector into electric signals, whose amplitude-frequency and time characteristics functionally depended on beams parameters. All the signals come into microcontroller device Intel MSC51. This device produces calculations of following beam parameters: average energy, pulse charge, pulse currents, density, beam size and pulse time. Calculated characteristics of meter well coincide with experimental measurements, carried out at accelerators in particles energy range from 1 to 100 Mev.

  14. Towards field and laboratory experiments with ocean acoustic-gravity waves

    NASA Astrophysics Data System (ADS)

    Oliveira, Tiago; Kadri, Usama; Lin, Ying-Tsong; Morozov, Andrey

    2016-04-01

    Acoustic-gravity waves (AGWs) can be generated in the ocean by mechanical energy transfer from the Earth's crust (e.g. earthquakes or volcanoes) and by energy transfer occurring at the water surface (e.g. interaction of opposing gravity waves, ice-quakes or localized pressure changes). Recent theoretical studies shed light on the underlying physics of the generation and propagation of AGWs in the ocean. However, these theories are yet to be verified further with very challenging field experiments due to the associated low frequency signals required, and ambient disturbances involved. Here, we present a unique setup of field experiments and large scale laboratory tests to verify the main physical properties of AGWs in ocean generated by different types of sources. We also present a novel methodology to generate and measure AGWs in the ocean.

  15. Flow and acoustic field due to an inclined plate with a downstream splitter

    NASA Technical Reports Server (NTRS)

    Kim, C. M.; Conlisk, A. T.

    1993-01-01

    In the present work, the high Reynolds number flow past an inclined plate with a splitter plate placed in its wake is considered numerically. A numerical conformal mapping technique is employed to transform the two-plate system into the same number of cylinders: the flow field is assumed to be two-dimensional. The vortex shedding from the inclined plate is modelled using the discrete vortex method. It is shown that the splitter plate has a profound effect on the development of the flow over a range of values of a suitably defined offset parameter and for a range of positions of the leading edge of the splitter plate. The acoustic field is also calculated and the spectrum reflects the flow results.

  16. Helicopter far-field acoustic levels as a function of reduced rotor speeds

    NASA Technical Reports Server (NTRS)

    Mueller, Arnold W.; Lemasurier, Philip; Smith, Charles D.

    1990-01-01

    This paper will present far-field measured noise levels relative to tests conducted with a model S-76A helicopter. The project was designed to provide supplemental experimental flight data which may be used to further study reduced helicopter rotor speeds (and thus, advancing blade-tip Mach number) effects on far-field acoustic levels. The aircraft was flown in straight and level flight while operating with both the rotor speed and flight speed as test variables. The rotor speed was varied over the range of 107 percent of the main-rotor speed (NR) to 90 percent NR and with the forward flight speed varied over the range of 155 to 35 knots indicated air speed. These conditions produced a wide range of advancing blade-tip Mach numbers to which the noise data are related.

  17. Acoustic radiation force impulse elastography for hepatocellular carcinoma-associated radiofrequency ablation

    PubMed Central

    Kwon, Hee-Jin; Kang, Myong-Jin; Cho, Jin-Han; Oh, Jong-Young; Nam, Kyung-Jin; Han, Sang-Yeong; Lee, Sung Wook

    2011-01-01

    AIM: To evaluate the potential usefulness of acoustic radiation force impulse (ARFI) images for evaluation of hepatocellular carcinomas (HCC)-associated radiofrequency ablation. METHODS: From January 2010 to June 2010, a total of 38 patients with HCC including recurred HCCs after RFA underwent ARFI elastography. The brightness of tumor was checked and the shear wave velocity was measured for the quantification of stiffness. According to the brightness, the tumors were classified as brighter, same color and darker compared with adjacent parenchyma. Using the same methods, 8 patients with recurred HCCs after RFA state were evaluated about the brightness compared with adjacent RFA ablation area. RESULTS: In the 38 patients with HCCs, 20 (52.6%) were brighter than surrounding cirrhotic parenchyma. Another 13 (34.2%) were darker. The others (5 cases, 13.2%) were seen as the same color as the adjacent liver parenchyma. Post-RFA lesions were darker than previous tumor and surrounding parenchyma in all 38 cases. However, recurred HCCs were brighter than the treated site in all 8 cases. CONCLUSION: Using ARFI technique is helpful for differential diagnosis in order to detect recurred HCCs more easily in patients with confusing status. PMID:21528062

  18. 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

  19. Acoustic radiation force impulse (ARFI) imaging of zebrafish embryo by high-frequency coded excitation sequence.

    PubMed

    Park, Jinhyoung; Lee, Jungwoo; Lau, Sien Ting; Lee, Changyang; Huang, Ying; Lien, Ching-Ling; Kirk Shung, K

    2012-04-01

    Acoustic radiation force impulse (ARFI) imaging has been developed as a non-invasive method for quantitative illustration of tissue stiffness or displacement. Conventional ARFI imaging (2-10 MHz) has been implemented in commercial scanners for illustrating elastic properties of several organs. The image resolution, however, is too coarse to study mechanical properties of micro-sized objects such as cells. This article thus presents a high-frequency coded excitation ARFI technique, with the ultimate goal of displaying elastic characteristics of cellular structures. Tissue mimicking phantoms and zebrafish embryos are imaged with a 100-MHz lithium niobate (LiNbO₃) transducer, by cross-correlating tracked RF echoes with the reference. The phantom results show that the contrast of ARFI image (14 dB) with coded excitation is better than that of the conventional ARFI image (9 dB). The depths of penetration are 2.6 and 2.2 mm, respectively. The stiffness data of the zebrafish demonstrate that the envelope is harder than the embryo region. The temporal displacement change at the embryo and the chorion is as large as 36 and 3.6 μm. Consequently, this high-frequency ARFI approach may serve as a remote palpation imaging tool that reveals viscoelastic properties of small biological samples. PMID:22101757

  20. 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.

  1. Viscoelastic characterization of thin tissues using acoustic radiation force and model-based inversion

    NASA Astrophysics Data System (ADS)

    Guzina, Bojan B.; Tuleubekov, Kairat; Liu, Dalong; Ebbini, Emad S.

    2009-07-01

    By means of the viscoelastodynamic model for a two-layer solid-fluid system and a detailed account of the locally induced acoustic radiation force, a rational analytical and computational framework is established for the viscoelastic characterization of thin tissues from high-frequency ultrasound (HFUS) measurements. For practical applications, the back-analysis is set up to interpret the frequency response function, signifying the tissue's axial displacement (captured by the imaging transducer) per squared voltage driving the 'pushing' transducer, as experimental input. On parametrizing the tissue's viscoelastic behavior in terms of the standard linear model, the proposed methodology is applied to a set of measurements performed on tissue-mimicking phantom constructs with thicknesses ranging from 0.5 to 4 mm. The results demonstrate that the model-based inversion, which carefully mimics the local boundary conditions and applied ultrasound excitation, yields viscoelastic properties for the phantom that are virtually invariant over the range of specimen thicknesses tested. Beyond its immediate application to in vitro viscoelastic characterization of thin excised tissues and tissue constructs, the proposed methodology may also find use in the characterization of skin or skin lesions over bone in vivo.

  2. In Vivo Cardiac, Acoustic-Radiation-Force-Driven, Shear Wave Velocimetry

    PubMed Central

    Hsu, Stephen J.; Wolf, Patrick D.; Trahey, Gregg E.

    2009-01-01

    Shear wave elasticity imaging (SWEI) was employed to track acoustic radiation force impulse (ARFI) -induced shear waves in the mid-myocardium of the left ventricular free wall (LVFW) of a beating canine heart. Shear waves were generated and tracked with a linear ultrasound transducer that was placed directly on the exposed epicardium. Acquinsition was ECG-gated arid coincided with the mid-diastolic portion of the cardiac cycle. Axial displacement profiles consistent with shear wave propagation were clearly evident in all SWEI acquisitions (i.e., those including an ARFI excitation); displacement data from control cases (i.e., sequences lacking an ARFI excitation) offered no evidence of shear wave propagation and yielded a peak absolute mean displacement below 0.31 μm after motion filtering. Shear wave velocity estimates ranged from 0.82 to 2.65 m/s and were stable across multiple heartbeats for the same interrogation region, with coefficients of variation less than 19% for all matched acquisitions. Variations in velocity estimates suggest a spatial dependence of shear wave velocity through the mid-myocardium of the LVFW, with velocity estimates changing, in limited cases, through depth and lateral position. PMID:19771962

  3. 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.

  4. The 'sixth sense' of ultrasound: probing nonlinear elasticity with acoustic radiation force.

    PubMed

    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. PMID:25905553

  5. 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. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26255624

  6. 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

  7. Radiation field associated with Hiroshima and Nagasaki

    SciTech Connect

    Loewe, W.E.

    1984-08-01

    Accuracy of dosimetric estimates can determine the value of the atomic bomb survivor experience in establishing radiation risks. The status of a major revision of this dosimetry, initiated in 1980, is assessed. 3 references, 6 figures.

  8. Comments on “The boundary point method for the calculation of exterior acoustic radiation problem” [S.Y. Zhang, X.Z. Chen, Journal of Sound and Vibration 228(4) (1999) 761 772

    NASA Astrophysics Data System (ADS)

    Chen, J. T.; Chen, I. L.; Lee, Y. T.

    2008-03-01

    Zhang and Chen [The boundary point method for the calculation of exterior acoustic radiation problem, Journal of Sound and Vibration 228 (1999) 761-772] proposed a boundary point method (BPM) for exterior acoustic problems. The idea is similar to the CHUNKY CHIEF by Wu [A weighted residual formulation for the CHIEF method in acoustic, Journal of Acoustical Society of America 90 (1991) 1608-1614], but Chunky CHIEF provides constraints using null-field equations while the BPM used the CHUNKY BLOCK singularity outside the domain. The mathematical structure is similar to Trefftz method and method of fundamental solutions [J.T. Chen et al., On the equivalence of the Trefftz method and method of fundamental solutions for Laplace and biharmonic equations, Computers & Mathematics with Applications 53 (2007) 851-879], since the interpolation function satisfies the governing equation. Later, Wu commented twice [Sean F. Wu, Comments on "The boundary point method for the calculation of exterior acoustic radiation" (by S.Y. Zhang, X.Z. Chen, Journal of Sound and Vibration 228(4) (1999) 761-772), Journal of Sound and Vibration, 298 (2006) 1173]; Sean F. Wu, Comments on "Reply to the comments on 'The boundary point method for the calculation of exterior acoustic radiation' (by S.Y. Zhang, X.Z. Chen, Journal of Sound and Vibration 228(4) (1999) 761-772)", Journal of Sound and Vibration, 298 (2006) 1176-1177] that the formulation of BPM is wrong and the authors replied also twice [X.Z. Chen, C.X. Bi, Reply to the comments on "The boundary point method for the calculation of exterior acoustic radiation" (by S.Y. Zhang, X.Z. Chen, Journal of Sound and Vibration 228(4) (1999) 761-772), Journal of Sound and Vibration, 298 (2006) 1174-1175; [X.Z. Chen, C.X. Bi, Reply to the comments on "Reply to the comments on 'The boundary point method for the calculation of exterior acoustic radiation' (by S.Y. Zhang, X.Z. Chen, Journal of Sound and Vibration 228(4) (1999) 761-772)", Journal of Sound

  9. On the Inverse Problems of Nonlinear Acoustics and Acoustic Turbulence

    NASA Astrophysics Data System (ADS)

    Gurbatov, S. N.; Rudenko, O. V.

    2015-12-01

    We consider the problem of retrieval of the radiated acoustic signal parameters from the measured wave field in some cross section of the nonlinear medium. The possibilities of solving regular and statistical inverse problems are discussed on the basis of the solution of the Burgers equation for zero and infinitesimal viscosities.

  10. 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

  11. A theoretical study of the feasibility of acoustical tweezers: Ray acoustics approach

    NASA Astrophysics Data System (ADS)

    Lee, Jungwoo; Ha, Kanglyeol; Shung, K. Kirk

    2005-05-01

    The optical tweezer has been found to have many biomedical applications in trapping macromolecules and cells. For the trapping mechanism, there has to be a sharp spatial change in axial optical intensity and the particle size must be much greater than the wavelength. Similar phenomenon may exist in acoustics. This work was undertaken to demonstrate theoretically that it is possible to acoustically trap particles near the focal point where most of the acoustic energy is concentrated if certain conditions are met. Acoustic force exerted on a fluid particle in ultrasonic fields is analyzed in a ray acoustics regime where the wavelength of acoustic beam is much smaller than the size of the particle. In order to apply the acoustical tweezer to manipulating macromolecules and cells whose size is in the order of a few microns or less, a prerequisite is that the ultrasound wavelength has to be much smaller than a few microns. In this paper, the analysis is therefore based on the field pattern produced by a strongly focused 100 MHz ultrasonic transducer with Gaussian intensity distribution. For the realization of acoustic trapping, negative axial radiation force has to be generated to pull a particle towards a focus. The fat particle considered for acoustic trapping in this paper has an acoustic impedance of 1.4 MRayls. The magnitude of the acoustic axial radiation force that has been calculated as the size of the fat particle is varied from 8λ to 14λ. In addition, both Fresnel coefficients at various positions are also calculated to assess the interaction of reflection and refraction and their relative contribution to the effect of the acoustical tweezer. The simulation results show that the feasibility of the acoustical tweezer depends on both the degree of acoustic impedance mismatch and the degree of focusing relative to the particle size. .

  12. Permeability, electrical impedance, and acoustic velocities on reservoir rocks from the Geysers geothermal field

    SciTech Connect

    Boitnott, G.N.; Boyd, P.J.

    1996-01-24

    Previous measurements of acoustic velocities on NEGU- 17 cores indicate that saturation effects are significant enough to cause Vp/Vs anomalies observed in the field. In this study we report on the results of new measurements on core recently recovered from SB-15-D along with some additional measurements on the NEGU-17 cores. The measurements indicate correlations between mechanical, transport, and water storage properties of the matrix which may prove useful for reservoir assessment and management. The SB-15-D material is found to be similar to the NEGU-17 material in terms of acoustic velocities, being characterized by a notably weak pressure dependence on the velocities and a modest Vp/Vs signature of saturation. The effect of saturation on Vp/Vs appears to result in part from a chemo-mechanical weakening of the shear modulus due to the presence of water. Electrical properties of SB-15-D material are qualitatively similar to those of the NEGU-17 cores, although resistivities of SB-15-D cores are notably lower and dielectric permittivities higher than in their NEGU- 17 counterparts. While some limited correlations of measured properties with depth are noted, no clear change in character is observed within SB-15-D cores which can be associated with the proposed cap-rock/reservoir boundary.

  13. Acoustic experience shapes alternative mating tactics and reproductive investment in male field crickets.

    PubMed

    Bailey, Nathan W; Gray, Brian; Zuk, Marlene

    2010-05-11

    Developmental plasticity allows juvenile animals to assess environmental cues and adaptively shape behavioral and morphological traits to maximize fitness in their adult environment. Sexual signals are particularly conspicuous cues, making them likely candidates for mediating such responses. Plasticity in male reproductive traits is a common phenomenon, but empirical evidence for signal-mediated plasticity in males is lacking. We tested whether experience of acoustic sexual signals during juvenile stages influences the development of three adult traits in the continuously breeding field cricket Teleogryllus oceanicus: male mating tactics, reproductive investment, and condition. All three traits were affected by juvenile acoustic experience. Males of this species produce a long-range calling song to attract receptive females, but they can also behave as satellites by parasitizing other males' calls. Males reared in an environment mimicking a population with many calling males were less likely to exhibit satellite behavior, invested more in reproductive tissues, and attained higher condition than males reared in a silent environment. These results contrast with other studies and demonstrate how the effects of juvenile social experience on adult male morphology, reproductive investment, and behavior may subsequently influence sexual selection and phenotypic evolution. PMID:20417103

  14. Near-field acoustic microbead trapping as remote anchor for single particle manipulation

    SciTech Connect

    Hwang, Jae Youn; Cheon, Dong Young; Shin, Hyunjune; Kim, Hyun Bin; Lee, Jungwoo

    2015-05-04

    We recently proposed an analytical model of a two-dimensional acoustic trapping of polystyrene beads in the ray acoustics regime, where a bead diameter is larger than the wavelength used. As its experimental validation, this paper demonstrates the transverse (or lateral) trapping of individual polystyrene beads in the near field of focused ultrasound. A 100 μm bead is immobilized on the central beam axis by a focused sound beam from a 30 MHz single element lithium niobate transducer, after being laterally displaced through hundreds of micrometers. Maximum displacement, a longest lateral distance at which a trapped bead can be directed towards the central axis, is thus measured over a discrete frequency range from 24 MHz to 36 MHz. The displacement data are found to be between 323.7 μm and 470.2 μm, depending on the transducer's driving frequency and input voltage amplitude. The experimental results are compared with their corresponding model values, and their relative errors lie between 0.9% and 3.9%. The results suggest that this remote maneuvering technique may be employed to manipulate individual cells through solid microbeads, provoking certain cellular reactions to localized mechanical disturbance without direct contact.

  15. Efficient modeling of flat and homogeneous acoustic treatments for vibroacoustic finite element analysis. Direct field formulations

    NASA Astrophysics Data System (ADS)

    Alimonti, L.; Atalla, N.

    2016-04-01

    This paper is concerned with the development of a simplified model for noise control treatments to speed up finite element analysis in vibroacoustic applications. The methodology relies on the assumption that the acoustic treatment is flat and homogeneous. Moreover, its finite lateral extent is neglected. This hypothesis is justified by short wavelength and large dissipation, which suggest that the reflected field emanating from the acoustic treatment lateral boundaries does not substantially affect its dynamic response. Under these circumstances, the response of the noise control treatment can be formally obtained by means of convolution integrals involving simple analytical kernels (i.e. Green functions). Such fundamental solutions can be computed efficiently by the transfer matrix method. However, some arbitrariness arises in the formulation of the mathematical model, resulting in different baffling conditions at the two ends of the treatment to be considered. Thus, the paper investigates the possibility of different formulations (i.e. baffling conditions) within the same hybrid finite element-transfer matrix framework, seeking for the best strategy in terms of tradeoff between efficiency and accuracy. Numerical examples are provided to show strengths and limitations of the proposed methodology.

  16. LCLS Far-Field Spontaneous Radiation

    2004-04-16

    This application (FarFieldDisplay) is a tool for displaying and analyzing far-field spontaneous spectral flux data for the Linac Coherent Light Source (LCLS) Calculated by Roman Tatchyn (Stanford University). This tool allows the user to view sliced spatial and energy distributions of the fat-field photons selected for specific energies or positions transverse to the beam axis,

  17. Detection of alpha radiation in a beta radiation field

    DOEpatents

    Mohagheghi, Amir H.; Reese, Robert P.

    2001-01-01

    An apparatus and method for detecting alpha particles in the presence of high activities of beta particles utilizing an alpha spectrometer. The apparatus of the present invention utilizes a magnetic field applied around the sample in an alpha spectrometer to deflect the beta particles from the sample prior to reaching the detector, thus permitting detection of low concentrations of alpha particles. In the method of the invention, the strength of magnetic field required to adequately deflect the beta particles and permit alpha particle detection is given by an algorithm that controls the field strength as a function of sample beta energy and the distance of the sample to the detector.

  18. Near-field radiative thermal transport: From theory to experiment

    SciTech Connect

    Song, Bai Fiorino, Anthony; Meyhofer, Edgar; Reddy, Pramod

    2015-05-15

    Radiative thermal transport via the fluctuating electromagnetic near-field has recently attracted increasing attention due to its fundamental importance and its impact on a range of applications from data storage to thermal management and energy conversion. After a brief historical account of radiative thermal transport, we summarize the basics of fluctuational electrodynamics, a theoretical framework for the study of radiative heat transfer in terms of thermally excited propagating and evanescent electromagnetic waves. Various approaches to modeling near-field thermal transport are briefly discussed, together with key results and proposals for manipulation and utilization of radiative heat flow. Subsequently, we review the experimental advances in the characterization of both near-field heat flow and energy density. We conclude with remarks on the opportunities and challenges for future explorations of radiative heat transfer at the nanoscale.

  19. Scalar field radiation from dilatonic black holes

    NASA Astrophysics Data System (ADS)

    Gohar, H.; Saifullah, K.

    2012-12-01

    We study radiation of scalar particles from charged dilaton black holes. The Hamilton-Jacobi method has been used to work out the tunneling probability of outgoing particles from the event horizon of dilaton black holes. For this purpose we use WKB approximation to solve the charged Klein-Gordon equation. The procedure gives Hawking temperature for these black holes as well.

  20. Resonant coupling of ionization waves and acoustic gravity waves in the presence of a magnetic field

    NASA Technical Reports Server (NTRS)

    Eun, H.; Gross, S. H.

    1976-01-01

    The nature of the two resonant directions that occur for a single frequency in the presence of a magnetic field is demonstrated, along with the manner in which the resonances change with the dip angle and the angle of propagation from the meridian plane. The conditions under which acoustic branch resonances may occur are outlined. It is found that the calculated frequencies and directions for resonance are in the range of observed values for TID's obtained from ground and satellite measurements. This result is indicative of a possible connection between TID's and the resonance phenomenon. It is shown that a strong resonance type of response may be possible in the F region at a particular frequency from a region that can be as great as 100 km in altitude.

  1. Novel Transfer Method Using Near-Field Acoustic Levitation and Its Application

    NASA Astrophysics Data System (ADS)

    Yano, Ryuto; Aoyagi, Manabu; Tamura, Hideki; Takano, Takehiro

    2011-07-01

    The holding of a levitated object above stator vibrators by utilizing the holding force, which is generated by near-field acoustic levitation, is possible. The holding force yields at the edge of a vibration plate and nodes of a bending vibration mode, and it is in proportion to the vibration amplitude of the vibration plate. In this paper, we describe methods of transfer and positioning of a levitated object above many aligned stator vibrators, some experimental results, and the proposition of the application as a noncontact-stepping ultrasonic motor (NCS-USM). Linear-type and rotary-type NCS-USMs can be flexibly constructed. The NCS-USM has a possibility of high torque performance compared with an ordinary noncontact USM using a traveling wave.

  2. Visualized measurement of the acoustic levitation field based on digital holography with phase multiplication

    NASA Astrophysics Data System (ADS)

    Zheng, Puchao; Li, Enpu; Zhao, Jianlin; Di, Jianglei; Zhou, Wangmin; Wang, Hao; Zhang, Ruifeng

    2009-11-01

    By using digital holographic interferometory with phase multiplication, the visualized measurement of the acoustic levitation field (ALF) with single axis is carried out. The digital holograms of the ALF under different conditions are recorded by use of CCD. The corresponding digital holographic interferograms reflecting the sound pressure distribution and the interference phase distribution are obtained by numerical reconstruction and phase subtraction, which are consistent with the theoretical results. It indicates that the proposed digital holographic interferometory with phase multiplication can successfully double the fringe number of the interference phase patterns of the ALF and improve the measurement precision. Compared with the conventional optical holographic interferometory, digital holographic interferometory has the merits of quasi real-time, more exactitude and convenient operation, and it provides an effective way for studying the sound pressure distribution of the ALF.

  3. The acoustic field in the ionosphere caused by an underground nuclear explosion

    NASA Astrophysics Data System (ADS)

    Krasnov, V. M.; Drobzheva, Ya. V.

    2005-07-01

    The problem of describing the generation and propagation of an infrasonic wave emitted by a finite extended source in the inhomogeneous absorbing atmosphere is the focus of this paper. It is of interest since the role of infrasonic waves in the energy balance of the upper atmosphere remains largely unknown. We present an algorithm, which allows adaptation of a point source model for calculating the infrasonic field from an underground nuclear explosion at ionospheric altitudes. Our calculations appear to agree remarkably well with HF Doppler sounding data measured for underground nuclear explosions at the Semipalatinsk Test Site. We show that the temperature and ionospheric electron density perturbation caused by an acoustic wave from underground nuclear explosion can reach 10% of background levels.

  4. On the horizontal wobbling of an object levitated by near-field acoustic levitation.

    PubMed

    Kim, Cheol-Ho; Ih, Jeong-Guon

    2007-11-01

    A circular planar object can be levitated with several hundreds of microns by ultrasonic near-field acoustic levitation (NFAL). However, when both the sound source and the levitated object are circularly shaped and the center of the levitated object does not coincide with the source center, instability problem often occurs. When this happens, it becomes difficult to pick up or transport the object for the next process. In this study, when the center of the levitated object was offset from the source center, the moving direction of the levitated object was predicted by using the time averaged potential around the levitated object. The wobbling frequency of the levitated object was calculated by analyzing the nonlinear wobbling motion of the object. It was shown that the predicted wobbling frequencies agreed with measured ones well. Finally, a safe zone was suggested to avoid the unstable movement of an object. PMID:17590402

  5. Applications of velocity potential function to acoustic duct propagation and radiation from inlets using finite element theory

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Majjigi, R. K.

    1979-01-01

    A finite element velocity potential program has been developed to study acoustic wave propagation in complex geometries. For irrotational flows, relatively low sound frequencies, and plane wave input, the finite element solutions show significant effects of inlet curvature and flow gradients on the attenuation of a given acoustic liner in a realistic variable area turbofan inlet. In addition, as shown in the paper, the velocity potential approach can not be used to estimate the effects of rotational flow on acoustic propagation since the potential acoustic disturbances propagate at the speed of the media in sheared flow. Approaches are discussed that are being considered for extending the finite element solution to include the far field as well as the internal portion of the duct. A new matrix partitioning approach is presented that can be incorporated in previously developed programs to allow the finite element calculation to be marched into the far field. The partitioning approach provides a large reduction in computer storage and running times.

  6. The Electromagnetic Dipole Radiation Field through the Hamiltonian Approach

    ERIC Educational Resources Information Center

    Likar, A.; Razpet, N.

    2009-01-01

    The dipole radiation from an oscillating charge is treated using the Hamiltonian approach to electrodynamics where the concept of cavity modes plays a central role. We show that the calculation of the radiation field can be obtained in a closed form within this approach by emphasizing the role of coherence between the cavity modes, which is…

  7. Radiation tolerant silicon nitride insulated gate field effect transistors

    NASA Technical Reports Server (NTRS)

    Newman, P. A.

    1969-01-01

    Metal-Insulated-Semiconductor Field Effect Transistor /MISFET/ device uses a silicon nitride passivation layer over a thin silicon oxide layer to enhance the radiation tolerance. It is useful in electronic systems exposed to space radiation environment or the effects of nuclear weapons.

  8. Radiative heat transfer in the extreme near field.

    PubMed

    Kim, Kyeongtae; Song, Bai; Fernández-Hurtado, Víctor; Lee, Woochul; Jeong, Wonho; Cui, Longji; Thompson, Dakotah; Feist, Johannes; Reid, M T Homer; García-Vidal, Francisco J; Cuevas, Juan Carlos; Meyhofer, Edgar; Reddy, Pramod

    2015-12-17

    Radiative transfer of energy at the nanometre length scale is of great importance to a variety of technologies including heat-assisted magnetic recording, near-field thermophotovoltaics and lithography. Although experimental advances have enabled elucidation of near-field radiative heat transfer in gaps as small as 20-30 nanometres (refs 4-6), quantitative analysis in the extreme near field (less than 10 nanometres) has been greatly limited by experimental challenges. Moreover, the results of pioneering measurements differed from theoretical predictions by orders of magnitude. Here we use custom-fabricated scanning probes with embedded thermocouples, in conjunction with new microdevices capable of periodic temperature modulation, to measure radiative heat transfer down to gaps as small as two nanometres. For our experiments we deposited suitably chosen metal or dielectric layers on the scanning probes and microdevices, enabling direct study of extreme near-field radiation between silica-silica, silicon nitride-silicon nitride and gold-gold surfaces to reveal marked, gap-size-dependent enhancements of radiative heat transfer. Furthermore, our state-of-the-art calculations of radiative heat transfer, performed within the theoretical framework of fluctuational electrodynamics, are in excellent agreement with our experimental results, providing unambiguous evidence that confirms the validity of this theory for modelling radiative heat transfer in gaps as small as a few nanometres. This work lays the foundations required for the rational design of novel technologies that leverage nanoscale radiative heat transfer. PMID:26641312

  9. School Facilities and Electric and Magnetic Field Radiation.

    ERIC Educational Resources Information Center

    Carr, Richard L.

    1990-01-01

    The possibility that electric and magnetic field radiation poses a health hazard should be recognized during the planning and designing of a school. A preconstruction assessment of possible exposure should be evaluated before the start of construction. (MLF)

  10. The utility of acoustic radiation force impulse imaging in diagnosing acute appendicitis and staging its severity

    PubMed Central

    Göya, Cemil; Hamidi, Cihad; Okur, Mehmet Hanifi; İçer, Mustafa; Oğuz, Abdullah; Hattapoğlu, Salih; Çetinçakmak, Mehmet Güli; Teke, Memik

    2014-01-01

    PURPOSE The aim of this study was to investigate the feasibility of using acoustic radiation force impulse (ARFI) imaging to diagnose acute appendicitis. METHODS Abdominal ultrasonography (US) and ARFI imaging were performed in 53 patients that presented with right lower quadrant pain, and the results were compared with those obtained in 52 healthy subjects. Qualitative evaluation of the patients was conducted by Virtual Touch™ tissue imaging (VTI), while quantitative evaluation was performed by Virtual Touch™ tissue quantification (VTQ) measuring the shear wave velocity (SWV). The severity of appendix inflammation was observed and rated using ARFI imaging in patients diagnosed with acute appendicitis. Alvarado scores were determined for all patients presenting with right lower quadrant pain. All patients diagnosed with appendicitis received appendectomies. The sensitivity and specificity of ARFI imaging relative to US was determined upon confirming the diagnosis of acute appendicitis via histopathological analysis. RESULTS The Alvarado score had a sensitivity and specificity of 70.8% and 20%, respectively, in detecting acute appendicitis. Abdominal US had 83.3% sensitivity and 80% specificity, while ARFI imaging had 100% sensitivity and 98% specificity, in diagnosing acute appendicitis. The median SWV value was 1.11 m/s (range, 0.6–1.56 m/s) for healthy appendix and 3.07 m/s (range, 1.37–4.78 m/s) for acute appendicitis. CONCLUSION ARFI imaging may be useful in guiding the clinical management of acute appendicitis, by helping its diagnosis and determining the severity of appendix inflammation. PMID:25323836

  11. 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

  12. In vivo study of transverse carpal ligament stiffness using acoustic radiation force impulse (ARFI) imaging.

    PubMed

    Shen, Zhilei Liu; Vince, D Geoffrey; Li, Zong-Ming

    2013-01-01

    The transverse carpal ligament (TCL) forms the volar boundary of the carpal tunnel and may provide mechanical constraint to the median nerve, leading to carpal tunnel syndrome. Therefore, the mechanical properties of the TCL are essential to better understand the etiology of carpal tunnel syndrome. The purpose of this study was to investigate the in vivo TCL stiffness using acoustic radiation force impulse (ARFI) imaging. The shear wave velocity (SWV) of the TCL was measured using Virtual Touch IQ(TM) software in 15 healthy, male subjects. The skin and the thenar muscles were also examined as reference tissues. In addition, the effects of measurement location and ultrasound transducer compression on the SWV were studied. The SWV of the TCL was dependent on the tissue location, with greater SWV values within the muscle-attached region than those outside of the muscle-attached region. The SWV of the TCL was significantly smaller without compression (5.21 ± 1.08 m/s) than with compression (6.62 ± 1.18 m/s). The SWV measurements of the skin and the thenar muscles were also affected by transducer compression, but to different extents than the SWV of the TCL. Therefore to standardize the ARFI imaging procedure, it is recommended that a layer of ultrasound gel be maintained to minimize the effects of tissue compression. This study demonstrated the feasibility of ARFI imaging for assessing the stiffness characteristics of the TCL in vivo, which has the potential to identify pathomechanical changes of the tissue. PMID:23861919

  13. Acoustic Radiation Force Impulse Elastography for Focal Hepatic Tumors: Usefulness for Differentiating Hemangiomas from Malignant Tumors

    PubMed Central

    Kim, Ji Eun; Bae, Kyung Soo; Han, Joon Koo; Choi, Byung Ihn

    2013-01-01

    Objective The purpose of this study is to investigate whether acoustic radiation force impulse (ARFI) elastography with ARFI quantification and ARFI 2-dimensional (2D) imaging is useful for differentiating hepatic hemangiomas from malignant hepatic tumors. Materials and Methods One-hundred-and-one tumors in 74 patients were included in this study: 28 hemangiomas, 26 hepatocellular carcinomas (HCCs), three cholangiocarcinomas (CCCs), 20 colon cancer metastases and 24 other metastases. B-mode ultrasound, ARFI 2D imaging, and ARFI quantification were performed in all tumors. Shear wave velocities (SWVs) of the tumors and the adjacent liver and their SWV differences were compared among the tumor groups. The ARFI 2D images were compared with B-mode images regarding the stiffness, conspicuity and size of the tumors. Results The mean SWV of the hemangiomas was significantly lower than the malignant hepatic tumor groups: hemangiomas, 1.80 ± 0.57 m/sec; HCCs, 2.66 ± 0.94 m/sec; CCCs, 3.27 ± 0.64 m/sec; colon cancer metastases, 3.70 ± 0.61 m/sec; and other metastases, 2.82 ± 0.96 m/sec (p < 0.05). The area under the receiver operating characteristics curve of SWV for differentiating hemangiomas from malignant tumors was 0.86, with a sensitivity of 96.4% and a specificity of 65.8% at a cut-off value of 2.73 m/sec (p < 0.05). In the ARFI 2D images, the malignant tumors except HCCs were stiffer and more conspicuous as compared with the hemangiomas (p < 0.05). Conclusion ARFI elastography with ARFI quantification and ARFI 2D imaging may be useful for differentiating hepatic hemangiomas from malignant hepatic tumors. PMID:24043967

  14. Acoustic Radiation Force Impulse Measurement in Renal Transplantation: A Prospective, Longitudinal Study With Protocol Biopsies.

    PubMed

    Lee, Juhan; Oh, Young Taik; Joo, Dong Jin; Ma, Bo Gyoung; Lee, A-lan; Lee, Jae Geun; Song, Seung Hwan; Kim, Seung Up; Jung, Dae Chul; Chung, Yong Eun; Kim, Yu Seun

    2015-09-01

    Interstitial fibrosis and tubular atrophy (IF/TA) is a common cause of kidney allograft loss. Several noninvasive techniques developed to assess tissue fibrosis are widely used to examine the liver. However, relatively few studies have investigated the use of elastographic methods to assess transplanted kidneys. The aim of this study was to explore the clinical implications of the acoustic radiation force impulse (ARFI) technique in renal transplant patients. A total of 91 patients who underwent living donor renal transplantation between September 2010 and January 2013 were included in this prospective study. Shear wave velocity (SWV) was measured by ARFI at baseline and predetermined time points (1 week and 6 and 12 months after transplantation). Protocol biopsies were performed at 12 months. Instead of reflecting IF/TA, SWVs were found to be related to time elapsed after transplantation. Mean SWV increased continuously during the first postoperative year (P < 0.001). In addition, mixed model analysis showed no correlation existed between SWV and serum creatinine (r = -0.2426, P = 0.0771). There was also no evidence of a relationship between IF/TA and serum creatinine (odds ratio [OR] = 1.220, P = 0.7648). Furthermore, SWV temporal patterns were dependent on the kidney weight to body weight ratio (KW/BW). In patients with a KW/BW < 3.5 g/kg, mean SWV continuously increased for 12 months, whereas it decreased after 6 months in those with a KW/BW ≥ 3.5 g/kg.No significant correlation was observed between SWV and IF/TA or renal dysfunction. However, SWV was found to be related to the time after transplantation. Renal hemodynamics influenced by KW/BW might impact SWV values. PMID:26426636

  15. Acoustic Radiation Force Impulse Elastography in the Diagnosis of Thyroid Nodules: Useful or Not Useful?

    PubMed

    Zhang, Yi-Feng; Xu, Hui-Xiong; Xu, Jun-Mei; Liu, Chang; Guo, Le-Hang; Liu, Lin-Na; Zhang, Jing; Xu, Xiao-Hong; Qu, Shen; Xing, Mingzhao

    2015-10-01

    The goal of this study is to evaluate the diagnostic performance of acoustic radiation force impulse (ARFI) elastography for differentiating benign from malignant thyroid nodules. One hundred and seventy-four pathologically proven thyroid nodules (139 benign, 35 malignant) in 154 patients (mean age: 49.2 ± 12.1 y; range: 16-72 y) were included in this study. Conventional ultrasound (US) and ARFI elastography using virtual touch tissue imaging (VTI) and virtual touch tissue quantification (VTQ) were performed to examine the thyroid nodules. Two blinded readers with different amounts of experience independently scored the likelihood of malignancy on the basis of a five-point scale in three different image-reading sets. The diagnostic performances among different image-reading sets and between the two readers were compared. The diagnostic specificity of both readers improved significantly after reading the VTI images or both VTI and VTQ images (all p < 0.05). After review of the results of both VTI and VTQ, the numbers of correctly diagnosed nodules increased in nodules <1.0 cm for both readers and in both nodular goiter and papillary thyroid carcinoma for the junior reader (p < 0.05). The nodules with definite diagnoses (i.e., confidence levels including definite benign and definite malignant cases) increased after review of VTI and VTQ images versus conventional US for the senior reader (p < 0.05). In conclusion, adding ARFI elastography improves the specificity in diagnosing malignant thyroid nodules compared with conventional US on its own. ARFI elastography particularly facilitates the specific diagnosis for thyroid nodules smaller than 1.0 cm. ARFI elastography is also able to increase the diagnostic confidence of the readers. PMID:26119458

  16. Breast Lesions Evaluated by Color-Coded Acoustic Radiation Force Impulse (ARFI) Imaging.

    PubMed

    Zhou, JianQiao; Yang, ZhiFang; Zhan, WeiWei; Zhang, JingWen; Hu, Na; Dong, YiJie; Wang, YingYing

    2016-07-01

    The goal of our study was to investigate the value of color-coded Virtual Touch tissue imaging (VTI) using acoustic radiation force impulse (ARFI) technology in the characterization of breast lesions and to compare it with conventional ultrasound (US). Conventional US and color-coded VTI were performed in 196 solid breast lesions in 196 consecutive women (age range 17-91 y; mean 48.17 ± 14.46 y). A four-point scale VTI score was assigned for each lesion according to the color pattern both in the lesion and in the surrounding breast tissue. The mean VTI score was significantly higher for malignant lesions (3.80 ± 0.66, range 1-4) than for benign ones (2.02 ± 1.20, range 1-4) (p < 0.001), and the optimal cut-off value was between score 3 and score 4. The area under the receiver operating characteristic (ROC) curve for combined conventional US and VTI (0.945) was significantly higher than that for conventional US (0.902) and for VTI (0.871) (p = 0.0021 and p < 0.001, respectively). It was concluded that color-coded VTI with the proposed four-point scale score system combined with conventional US might have the potential to aid in the characterization of benign and malignant breast lesions. PMID:27131841

  17. Mapping viscoelastic properties by multi-line (ML) acoustic radiation force

    NASA Astrophysics Data System (ADS)

    Gomyo, Mikako; Kondo, Kengo; Yamakawa, Makoto; Shiina, Tsuyoshi

    2015-03-01

    In these days ultrasound studies of non-invasive diagnostic methods using the elastic property of tissue have showed very promising results. Biological soft tissues are viscoelastic in nature; therefore several recent studies have shown the feasibility of shear wave dispersion in order to express viscosity which is considered to be valid for early diagnoses. Shear wave Dispersion Ultrasound Vibrometry (SDUV) has been conducted under ex vivo and in vivo conditions, which could estimate the value of shear elasticity and viscosity from a 40 x 40 mm2 area. In this study, our proposed Multi-line (ML) acoustic radiation force method could map shear elasticity and viscosity at 0.2 x 0.2 mm2 pixel in 25.6 mm width and 29.6 mm depth area. ML uses seven focus points in depth to create much planar shear wave than ever, and twenty pushing line to obtain data such a broader area than ever. These sequences contribute to express precise values of shear elasticity and viscosity at each pixel. A 10% gelatin phantom with a 10% gelatin and 1% xanthan gum mixture inclusion was prepared for ML experiment, and one homogenous phantom made of the same concentrations as the background of ML experiments was for ML and SDUV experiments three times to validate. The ML measurement resulted μ1 = 1.129±0.118 kPa, μ2 = 0.893±0.090 Pa・s in the 10% gelatin background; their corresponding SDUV measurement were μ1 = 1.250±0.129 kPa, μ2 = 0.833±0.098 Pa・s in 10% gelatin phantom. Though further evaluations such as frequency and rheological model are required, the results could show the effectiveness of this proposed method in mapping viscoelasticity and the feasibility of in vivo and ex vivo experiments.

  18. The performance of acoustic radiation force impulse imaging in predicting liver fibrosis in chronic liver diseases.

    PubMed

    Lin, Yi-Hung; Yeh, Ming-Lun; Huang, Ching-I; Yang, Jeng-Fu; Liang, Po-Cheng; Huang, Chung-Feng; Dai, Chia-Yen; Lin, Zu-Yau; Chen, Shinn-Cherng; Huang, Jee-Fu; Yu, Ming-Lung; Chuang, Wan-Long

    2016-07-01

    Sonography-based noninvasive liver fibrosis assessment is promising in the prediction of treatment efficacy and prognosis in chronic liver disease (CLD) patients. Acoustic radiation force impulse imaging (ARFI) is a newly-developed transient elastography (TE) method integrated into a conventional ultrasound machine. The study aimed to assess the performance of ARFI imaging in the diagnosis of liver fibrosis in Taiwanese CLD patients. We also aimed to search for the optimal cut-off values in different fibrosis stages. A total of 60 CLD patients (40 males; mean age, 51.8±11 years) were consecutively included. They received standard ARFI measurement within 2 weeks at the time of liver biopsy. There were eight patients with Metavir fibrosis stage 0 (F0), 16 patients with F1, 20 patients with F2, eight patients with F3, and eight patients with F4, respectively. The mean values among patient with F0, F1, F2, F3, and F4 were 1.17±0.13, 1.30±0.17, 1.31±0.24, 2.01±0.45, and 2.69±0.91, respectively (p<0.001). The optimal cut-off ARFI value for significant fibrosis (F≥2) was 1.53 with the accuracy of 0.733, while it was 1.66 for advanced fibrosis (F≥3) with the accuracy of 0.957. Our study demonstrated that ARFI imaging is competent for fibrosis diagnosis, particularly in CLD patients with advanced fibrosis. PMID:27450025

  19. Reconstruction of radiating sound fields using minimum energy method.

    PubMed

    Bader, Rolf

    2010-01-01

    A method for reconstructing a pressure field at the surface of a radiating body or source is presented using recording data of a microphone array. The radiation is assumed to consist of many spherical radiators, as microphone positions are present in the array. These monopoles are weighted using a parameter alpha, which broadens or narrows the overall radiation directivity as an effective and highly intuitive parameter of the radiation characteristics. A radiation matrix is built out of these weighted monopole radiators, and for different assumed values of alpha, a linear equation solver reconstructs the pressure field at the body's surface. It appears that from these many arbitrary reconstructions, the correct one minimizes the reconstruction energy. The method is tested, localizing the radiation points of a Balinese suling flute, reconstructing complex radiation from a duff frame drum, and determining the radiation directivity for the first seven modes of an Usbek tambourine. Stability in terms of measurement noise is demonstrated for the plain method, and additional highly effective algorithm is added for a noise level up to 0 dB. The stability of alpha in terms of minimal reconstruction energy is shown over the whole range of possible values for alpha. Additionally, the treatment of unwanted room reflections is discussed, still leading to satisfactory results in many cases. PMID:20058977

  20. Methods And Systems For Using Reference Images In Acoustic Image Processing

    DOEpatents

    Moore, Thomas L.; Barter, Robert Henry

    2005-01-04

    A method and system of examining tissue are provided in which a field, including at least a portion of the tissue and one or more registration fiducials, is insonified. Scattered acoustic information, including both transmitted and reflected waves, is received from the field. A representation of the field, including both the tissue and the registration fiducials, is then derived from the received acoustic radiation.