WorldWideScience

Sample records for acoustic radiation force

  1. Liquid lens using acoustic radiation force.

    Science.gov (United States)

    Koyama, Daisuke; Isago, Ryoichi; Nakamura, Kentaro

    2011-03-01

    A liquid lens is proposed that uses acoustic radiation force with no mechanical moving parts. It consists of a cylindrical acrylic cell filled with two immiscible liquids (degassed water and silicone oil) and a concave ultrasound transducer. The focal point of the transducer is located on the oil-water interface, which functions as a lens. The acoustic radiation force is generated when there is a difference in the acoustic energy densities of different media. An acoustic standing wave was generated in the axial direction of the lens and the variation of the shape of the oil-water interface was observed by optical coherence tomography (OCT). The lens profile can be rapidly changed by varying the acoustic radiation force from the transducer. The kinematic viscosity of silicone oil was optimized to minimize the response times of the lens. Response times of 40 and 80 ms when switching ultrasonic radiation on and off were obtained with a kinematic viscosity of 200 cSt. The path of a laser beam transmitted through the lens was calculated by ray-tracing simulations based on the experimental results obtained by OCT. The transmitted laser beam could be focused by applying an input voltage. The liquid lens could be operated as a variable-focus lens by varying the input voltage.

  2. Material fabrication using acoustic radiation forces

    Science.gov (United States)

    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.

  3. Magnetic resonance acoustic radiation force imaging.

    Science.gov (United States)

    McDannold, Nathan; Maier, Stephan E

    2008-08-01

    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.

  4. Transthoracic Cardiac Acoustic Radiation Force Impulse Imaging

    Science.gov (United States)

    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. A study of the acoustical radiation force considering attenuation

    Science.gov (United States)

    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.

  6. Acoustic radiation force analysis using finite difference time domain method.

    Science.gov (United States)

    Grinenko, A; Wilcox, P D; Courtney, C R P; Drinkwater, B W

    2012-05-01

    Acoustic radiation force exerted by standing waves on particles is analyzed using a finite difference time domain Lagrangian method. This method allows the acoustic radiation force to be obtained directly from the solution of nonlinear fluid equations, without any assumptions on size or geometry of the particles, boundary conditions, or acoustic field amplitude. The model converges to analytical results in the limit of small particle radii and low field amplitudes, where assumptions within the analytical models apply. Good agreement with analytical and numerical models based on solutions of linear scattering problems is observed for compressible particles, whereas some disagreement is detected when the compressibility of the particles decreases.

  7. Acoustic radiation force and torque on an absorbing particle

    CERN Document Server

    Silva, Glauber T

    2013-01-01

    Exact formulas of the radiation force and torque exerted on an absorbing particle in the Rayleigh scattering limit caused by an arbitrary harmonic acoustic wave are presented. They are used to analyze the trapping conditions by a single-beam acoustical tweezer based on a spherically focused ultrasound beam. Results reveal that particle's absorption has a pivotal role in single-beam trapping. Furthermore, we obtain the radiation torque induced by a Bessel beam in an on-axis particle.

  8. Image reconstruction with acoustic radiation force induced shear waves

    Science.gov (United States)

    McAleavey, Stephen A.; Nightingale, Kathryn R.; Stutz, Deborah L.; Hsu, Stephen J.; Trahey, Gregg E.

    2003-05-01

    Acoustic radiation force may be used to induce localized displacements within tissue. This phenomenon is used in Acoustic Radiation Force Impulse Imaging (ARFI), where short bursts of ultrasound deliver an impulsive force to a small region. The application of this transient force launches shear waves which propagate normally to the ultrasound beam axis. Measurements of the displacements induced by the propagating shear wave allow reconstruction of the local shear modulus, by wave tracking and inversion techniques. Here we present in vitro, ex vivo and in vivo measurements and images of shear modulus. Data were obtained with a single transducer, a conventional ultrasound scanner and specialized pulse sequences. Young's modulus values of 4 kPa, 13 kPa and 14 kPa were observed for fat, breast fibroadenoma, and skin. Shear modulus anisotropy in beef muscle was observed.

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

    Science.gov (United States)

    Rajabi, Majid; Mojahed, Alireza

    2016-11-01

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

  10. Characterizing stiffness of human prostates using acoustic radiation force.

    Science.gov (United States)

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

    2010-10-01

    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 that varies with acoustic attenuation, one question that arises is how the relative displacements in prostate ARFI images are 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

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

    Science.gov (United States)

    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

  12. Identifying Vulnerable Plaques with Acoustic Radiation Force Impulse Imaging

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Nikolaeva, Anastasiia V., E-mail: niko200707@mail.ru; Kryzhanovsky, Maxim A.; Tsysar, Sergey A. [Department of Acoustics, Physics Faculty, Moscow State University, Leninskie Gory, Moscow 119991 (Russian Federation); Kreider, Wayne [Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th St. Seattle WA 98105 (United States); Sapozhnikov, Oleg A. [Department of Acoustics, Physics Faculty, Moscow State University, Leninskie Gory, Moscow 119991 (Russian Federation); Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th St. Seattle WA 98105 (United States)

    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.

  15. Investigation into the Effect of Acoustic Radiation Force and Acoustic Streaming on Particle Patterning in Acoustic Standing Wave Fields

    Directory of Open Access Journals (Sweden)

    Shilei Liu

    2017-07-01

    Full Text Available Acoustic standing waves have been widely used in trapping, patterning, and manipulating particles, whereas one barrier remains: the lack of understanding of force conditions on particles which mainly include acoustic radiation force (ARF and acoustic streaming (AS. In this paper, force conditions on micrometer size polystyrene microspheres in acoustic standing wave fields were investigated. The COMSOL® Mutiphysics particle tracing module was used to numerically simulate force conditions on various particles as a function of time. The velocity of particle movement was experimentally measured using particle imaging velocimetry (PIV. Through experimental and numerical simulation, the functions of ARF and AS in trapping and patterning were analyzed. It is shown that ARF is dominant in trapping and patterning large particles while the impact of AS increases rapidly with decreasing particle size. The combination of using both ARF and AS for medium size particles can obtain different patterns with only using ARF. Findings of the present study will aid the design of acoustic-driven microfluidic devices to increase the diversity of particle patterning.

  16. Harmonic tracking of acoustic radiation force-induced displacements.

    Science.gov (United States)

    Doherty, Joshua R; Dahl, Jeremy J; Trahey, Gregg E

    2013-11-01

    Ultrasound-based elasticity imaging methods rely upon accurate estimates of tissue deformation to characterize the mechanical properties of soft tissues. These methods are corrupted by clutter, which can bias and/or increase variance in displacement estimates. Harmonic imaging methods are routinely used for clutter suppression and improved image quality in conventional B-mode ultrasound, but have not been utilized in ultrasound-based elasticity imaging methods. We introduce a novel, fully-sampled pulse-inversion harmonic method for tracking tissue displacements that corrects the loss in temporal sampling frequency associated with conventional pulse-inversion techniques. The method is implemented with acoustic radiation force impulse (ARFI) imaging to monitor the displacements induced by an impulsive acoustic radiation force excitation. Custom pulse sequences were implemented on a diagnostic ultrasound scanner to collect spatially-matched fundamental and harmonic information within a single acquisition. B-mode and ARFI images created from fundamental data collected at 4 MHz and 8 MHz are compared with 8-MHz harmonic images created using a band-pass filter approach and the fully sampled pulse-inversion method. In homogeneous, tissue-mimicking phantoms, where no visible clutter was observed, there was little difference in the axial displacements, estimated jitter, and normalized cross-correlation among the fundamental and harmonic tracking methods. The similarity of the lower- and higher-frequency methods suggests that any improvement resulting from the increased frequency of the harmonic components is negligible. The harmonic tracking methods demonstrated a marked improvement in B-mode and ARFI image quality of in vivo carotid arteries. Improved feature detection and decreased variance in estimated displacements were observed in the arterial walls of harmonic ARFI images, especially in the pulse-inversion harmonic ARFI images. Within the lumen, the harmonic tracking

  17. Harmonic Tracking of Acoustic Radiation Force Induced Displacements

    Science.gov (United States)

    Doherty, Joshua R.; Dahl, Jeremy J.; Trahey, Gregg E.

    2014-01-01

    Ultrasound-based elasticity imaging methods rely upon accurate estimates of tissue deformation to characterize the mechanical properties of soft tissues. These methods are corrupted by clutter, which can bias and/or increase variance in displacement estimates. Harmonic imaging methods are routinely used for clutter suppression and improved image quality in conventional B-mode ultrasound, but have not been utilized in ultrasound-based elasticity imaging methods. We introduce a novel, fully-sampled pulse inversion harmonic method for tracking tissue displacements that corrects the loss in temporal sampling frequency associated with conventional pulse inversion techniques. The method is implemented with Acoustic Radiation Force Impulse (ARFI) imaging to monitor the displacements induced by an impulsive acoustic radiation force excitation. Custom pulse sequences were implemented on a diagnostic ultrasound scanner to collect spatially-matched fundamental and harmonic information within a single acquisition. B-mode and ARFI images created from fundamental data collected at 4 MHz and 8 MHz are compared with 8 MHz harmonic images created using a bandpass filter approach and the fully sampled pulse inversion method. In homogeneous, tissue-mimicking phantoms, where no visible clutter was observed, there was little difference in the axial displacements, estimated jitter, and normalized cross-correlation among the fundamental and harmonic tracking methods. The similarity of the lower and higher frequency methods suggests that any improvement due to the increased frequency of the harmonic components is negligible. The harmonic tracking methods demonstrated a marked improvement in B-mode and ARFI image quality of in vivo carotid arteries. Improved feature detection and decreased variance in estimated displacements were observed in the arterial walls of harmonic ARFI images, especially in the pulse inversion harmonic ARFI images. Within the lumen, the harmonic tracking methods

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

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Rongrong; Cheng, Kaixuan; Liu, Jiehui; Mao, Yiwei; Gong, Xiufen [Key Laboratory of Modern Acoustics, Institute of Acoustics, Nanjing University, Nanjing 210093 (China); Liu, Xiaozhou, E-mail: xzliu@nju.edu.cn [Key Laboratory of Modern Acoustics, Institute of Acoustics, Nanjing University, Nanjing 210093 (China); State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190 (China)

    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.

  19. Radiation acoustics

    CERN Document Server

    Lyamshev, Leonid M

    2004-01-01

    Radiation acoustics is a developing field lying at the intersection of acoustics, high-energy physics, nuclear physics, and condensed matter physics. Radiation Acoustics is among the first books to address this promising field of study, and the first to collect all of the most significant results achieved since research in this area began in earnest in the 1970s.The book begins by reviewing the data on elementary particles, absorption of penetrating radiation in a substance, and the mechanisms of acoustic radiation excitation. The next seven chapters present a theoretical treatment of thermoradiation sound generation in condensed media under the action of modulated penetrating radiation and radiation pulses. The author explores particular features of the acoustic fields of moving thermoradiation sound sources, sound excitation by single high-energy particles, and the efficiency and optimal conditions of thermoradiation sound generation. Experimental results follow the theoretical discussions, and these clearl...

  20. Acoustic radiation force of high-order Bessel beam standing wave tweezers on a rigid sphere.

    Science.gov (United States)

    Mitri, F G

    2009-12-01

    Particle manipulation using the acoustic radiation force of Bessel beams is an active field of research. In a previous investigation, [F.G. Mitri, Acoustic radiation force on a sphere in standing and quasi-standing zero-order Bessel beam tweezers, Annals of Physics 323 (2008) 1604-1620] an expression for the radiation force of a zero-order Bessel beam standing wave experienced by a sphere was derived. The present work extends the analysis of the radiation force to the case of a high-order Bessel beam (HOBB) of positive order m having an angular dependence on the phase phi. The derivation for the general expression of the force is based on the formulation for the total acoustic scattering field of a HOBB by a sphere [F.G. Mitri, Acoustic scattering of a high-order Bessel beam by an elastic sphere, Annals of Physics 323 (2008) 2840-2850; F.G. Mitri, Equivalence of expressions for the acoustic scattering of a progressive high order Bessel beam by an elastic sphere, IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 56 (2009) 1100-1103] to derive the general expression for the radiation force function YJm,st(ka,beta,m)Bessel beam standing wave incident upon a rigid sphere immersed in non-viscous water are computed. The rigid sphere calculations for YJm,st(ka,beta,m)Bessel beam standing wave (m=0). The proposed theory is of particular interest essentially due to its inherent value as a canonical problem in particle manipulation using the acoustic radiation force of a HOBB standing wave on a sphere. It may also serve as the benchmark for comparison to other solutions obtained by strictly numerical or asymptotic approaches.

  1. A numerical study of microparticle acoustophoresis driven by acoustic radiation forces and streaming-induced drag forces

    DEFF Research Database (Denmark)

    Muller, Peter Barkholt; Barnkob, Rune; Jensen, Mads Jakob Herring;

    2012-01-01

    We present a numerical study of the transient acoustophoretic motion of microparticles suspended in a liquid-filled microchannel and driven by the acoustic forces arising from an imposed standing ultrasound wave: the acoustic radiation force from the scattering of sound waves on the particles...... parameters using a numerical particle-tracking scheme. The model shows the transition in the acoustophoretic particle motion from being dominated by streaming-induced drag to being dominated by radiation forces as a function of particle size, channel geometry, and material properties....

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

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Wenjuan [Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road East, Irvine, California 92612 (United States); Department of Chemical Engineering and Materials Science, University of California, Irvine, Irvine, California 92697 (United States); Li, Rui [Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road East, Irvine, California 92612 (United States); Ma, Teng; Kirk Shung, K.; Zhou, Qifa [Department of Biomedical Engineering, NIH Ultrasonic Transducer Resource Center, University of Southern California, Los Angeles, California 90089 (United States); Chen, Zhongping, E-mail: z2chen@uci.edu [Beckman Laser Institute, University of California, Irvine, 1002 Health Sciences Road East, Irvine, California 92612 (United States); Department of Chemical Engineering and Materials Science, University of California, Irvine, Irvine, California 92697 (United States); Department of Biomedical Engineering, University of California, Irvine, Irvine, California 92697 (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Koyama, Daisuke, E-mail: dkoyama@mail.doshisha.ac.jp; Kashihara, Yuta; Matsukawa, Mami [Faculty of Science and Engineering, Doshisha University, 1-3 Tataramiyakodani, Kyotanabe 610-0321 (Japan); Wave Electronics Research Center, Doshisha University, 1-3 Tataramiyakodani, Kyotanabe 610-0321 (Japan); Hatanaka, Megumi [Faculty of Life and Medical Sciences, Doshisha University, 1-3 Tataramiyakodani, Kyotanabe 610-0321 (Japan); Wave Electronics Research Center, Doshisha University, 1-3 Tataramiyakodani, Kyotanabe 610-0321 (Japan); Nakamura, Kentaro [Precision and Intelligence Laboratory, Tokyo Institute of Technology, 4259-R2-26, Nagatsutacho, Midoriku, Yokohama 226-8503 (Japan)

    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.

  4. Measurement of the acoustic radiation force on a sphere embedded in a soft solid

    CERN Document Server

    Lidon, Pierre; Taberlet, Nicolas; Manneville, Sébastien

    2016-01-01

    The acoustic radiation force exerted on a small sphere located at the focus of an ultrasonic beam is measured in a soft gel. It is proved to evolve quadratically with the local amplitude of the acoustic field. Strong oscillations of the local pressure are observed and attributed to an acoustic Fabry-P{\\'e}rot effect between the ultrasonic emitter and the sphere. Taking this effect into account with a simple model, a quantitative link between the radiation force and the acoustic pressure is proposed and compared to theoretical predictions in the absence of dissipation. The discrepancy between experiment and theory suggests that dissipative effects should be taken into account for fully modeling the observations.

  5. Analytical and numerical calculations of optimum design frequency for focused ultrasound therapy and acoustic radiation force.

    Science.gov (United States)

    Ergün, A Sanlı

    2011-10-01

    Focused ultrasound therapy relies on acoustic power absorption by tissue. The stronger the absorption the higher the temperature increase is. However, strong acoustic absorption also means faster attenuation and limited penetration depth. Hence, there is a trade-off between heat generation efficacy and penetration depth. In this paper, we formulated the acoustic power absorption as a function of frequency and attenuation coefficient, and defined two figures of merit to measure the power absorption: spatial peak of the acoustic power absorption density, and the acoustic power absorbed within the focal area. Then, we derived "rule of thumb" expressions for the optimum frequencies that maximized these figures of merit given the target depth and homogeneous tissue type. We also formulated a method to calculate the optimum frequency for inhomogeneous tissue given the tissue composition for situations where the tissue structure can be assumed to be made of parallel layers of homogeneous tissue. We checked the validity of the rules using linear acoustic field simulations. For a one-dimensional array of 4cm acoustic aperture, and for a two-dimensional array of 4×4cm(2) acoustic aperture, we found that the power absorbed within the focal area is maximized at 0.86MHz, and 0.79MHz, respectively, when the target depth is 4cm in muscle tissue. The rules on the other hand predicted the optimum frequencies for acoustic power absorption as 0.9MHz and 0.86MHz, respectively for the 1D and 2D array case, which are within 6% and 9% of the field simulation results. Because radiation force generated by an acoustic wave in a lossy propagation medium is approximately proportional to the acoustic power absorption, these rules can be used to maximize acoustic radiation force generated in tissue as well.

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

    Science.gov (United States)

    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.

  7. Optical observations of acoustical radiation force effects on individual air bubbles

    NARCIS (Netherlands)

    Palanchon, Peggy; Tortoli, Piero; Bouakaz, Ayache; Versluis, Andreas Michel; de Jong, N.

    2005-01-01

    Previous studies dealing with contrast agent microbubbles have demonstrated that ultrasound (US) can significantly influence the movement of microbubbles. In this paper, we investigated the influence of the acoustic radiation force on individual air bubbles using high-speed photography. We emphasize

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

    Science.gov (United States)

    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.

  9. Numerical study of acoustic streaming and radiation forces on micro particles

    DEFF Research Database (Denmark)

    Jensen, Mads Jakob Herring; Muller, Peter Barkholt; Barnkob, Rune;

    2012-01-01

    , and 2) Stokes drag from the induced acoustic streaming flow. Both effects are second order and require the solution of the full linearized Navier-Stokes equation in order to be captured correctly. The model shows the transition from streaming drag to radiation force dominated regimes. The transition...

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

    Science.gov (United States)

    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.

  11. An exploration in acoustic radiation force experienced by cylindrical shells via resonance scattering theory.

    Science.gov (United States)

    Rajabi, Majid; Behzad, Mehdi

    2014-04-01

    In nonlinear acoustic regime, a body insonified by a sound field is known to experience a steady force that is called the acoustic radiation force (RF). This force is a second-order quantity of the velocity potential function of the ambient medium. Exploiting the sufficiency of linear solution representation of potential function in RF formulation, and following the classical resonance scattering theorem (RST) which suggests the scattered field as a superposition of the resonant field and a background (non-resonant) component, we will show that the radiation force is a composition of three components: background part, resonant part and their interaction. Due to the nonlinearity effects, each part contains the contribution of pure partial waves in addition to their mutual interaction. The numerical results propose the residue component (i.e., subtraction of the background component from the RF) as a good indicator of the contribution of circumferential surface waves in RF. Defining the modal series of radiation force function and its components, it will be shown that within each partial wave, the resonance contribution can be synthesized as the Breit-Wigner form for adequately none-close resonant frequencies. The proposed formulation may be helpful essentially due to its inherent value as a canonical subject in physical acoustics. Furthermore, it may make a tunnel through the circumferential resonance reducing effects on radiation forces.

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

    Energy Technology Data Exchange (ETDEWEB)

    Mitri, F. G., E-mail: F.G.Mitri@ieee.org [Chevron, Area 52 Technology–ETC, Santa Fe, New Mexico 87508 (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Treweek, Benjamin C., E-mail: btreweek@utexas.edu; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F. [Applied Research Laboratories, The University of Texas at Austin, P.O. Box 8029, Austin, TX 78713-8029 (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Rajabi, Majid, E-mail: majid_rajabi@iust.ac.ir; Mojahed, Alireza

    2016-09-15

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

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

    Science.gov (United States)

    Rajabi, Majid; Mojahed, Alireza

    2016-09-01

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

  16. Computations of radiation force using the translational addition theorem: Applications to acoustical tweezers

    CERN Document Server

    Baggio, André L; Silva, Glauber T

    2012-01-01

    This work proposes a method to compute both axial and transverse radiation forces produced by an ultrasound beam of arbitrary wavefront based on the partial-wave expansion (PWE) and the translational addition theorem for spherical wave functions. The major advantage of using the addition theorem is the computation of acoustic radiation force for a wide variety of beams which satisfy the Helmholtz equation without the need of numerical quadrature schemes. The PWE method is applied to calculate the radiation force exerted on a silicone-oil droplet suspended in water. The force is produced by a single-beam acoustical tweezer composed by a spherically focused transducer with driving frequency of 3.1 MHz and F-number of 1.6. The droplet can be positioned anywhere in the host medium. The radiation force is analyzed in the Rayleigh and resonant scattering regimes. The obtained results in the Rayleigh scattering regime are compared to those calculated with Gor'kov's radiation force theory. It turns out to be that bot...

  17. Off-axial acoustic radiation force of pressor and tractor Bessel beams on a sphere

    CERN Document Server

    Silva, Glauber T; Lobo, Tiago P; Mitri, Farid G

    2012-01-01

    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 "pressor" and "tractor" behaviors. The pressor 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 3D 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...

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Lipkens, Bart, E-mail: blipkens@wne.edu [Mechanical Engineering, Western New England University, Springfield, Massachusetts, 01119 (United States); Ilinskii, Yurii A., E-mail: ilinskii@gmail.com; Zabolotskaya, Evgenia A., E-mail: zheniazabolotskaya@gmail.com [Applied Research Laboratories, The University of Texas at Austin, Austin, Texas 78713–8029 (United States)

    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

  20. Influences of the geometry and acoustic parameter on acoustic radiation forces on three-layered nucleate cells

    Science.gov (United States)

    Wang, Yuan-Yuan; Yao, Jie; Wu, Xue-Wei; Wu, Da-Jian; Liu, Xiao-Jun

    2017-09-01

    Acoustic radiation forces (ARFs) on three-layered micro-shells (TLSs) are investigated using Mie scattering theory. The TLS is proposed to simulate a nucleate cell with nucleus, cytoplasm, and membrane. It is found that the existence of the inner core or outer shell greatly influences ARFs on nucleate cells. We focus on the influences of the geometry, acoustic parameters, and the surrounding medium on ARFs on TLSs. With increasing inner core radius or outer shell thickness, the ARF on the TLS shows a distinct increase. We find that the impedance of each layer of the TLS plays a dominant role with regard to the ARF, while the density and the sound velocity separately provide distinct modulations. In addition, it is found that the higher impedance of the surrounding medium induces larger ARF on the TLS. Our work may be beneficial for the acoustic manipulation of nucleate cells.

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

    Science.gov (United States)

    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.

  2. Computation of the acoustic radiation force using the finite-difference time-domain method.

    Science.gov (United States)

    Cai, Feiyan; Meng, Long; Jiang, Chunxiang; Pan, Yu; Zheng, Hairong

    2010-10-01

    The computational details related to calculating the acoustic radiation force on an object using a 2-D grid finite-difference time-domain method (FDTD) are presented. The method is based on propagating the stress and velocity fields through the grid and determining the energy flow with and without the object. The axial and radial acoustic radiation forces predicted by FDTD method are in excellent agreement with the results obtained by analytical evaluation of the scattering method. In particular, the results indicate that it is possible to trap the steel cylinder in the radial direction by optimizing the width of Gaussian source and the operation frequency. As the sizes of the relating objects are smaller than or comparable to wavelength, the algorithm presented here can be easily extended to 3-D and include torque computation algorithms, thus providing a highly flexible and universally usable computation engine.

  3. Acoustic radiation force impulse imaging for evaluation of renal parenchyma elasticity in diabetic nephropathy.

    Science.gov (United States)

    Goya, Cemil; Kilinc, Faruk; Hamidi, Cihad; Yavuz, Alpaslan; Yildirim, Yasar; Cetincakmak, Mehmet Guli; Hattapoglu, Salih

    2015-02-01

    OBJECTIVE. The goal of this study is to evaluate the changes in the elasticity of the renal parenchyma in diabetic nephropathy using acoustic radiation force impulse imaging. SUBJECTS AND METHODS. The study included 281 healthy volunteers and 114 patients with diabetic nephropathy. In healthy volunteers, the kidney elasticity was assessed quantitatively by measuring the shear-wave velocity using acoustic radiation force impulse imaging based on age, body mass index, and sex. The changes in the renal elasticity were compared between the different stages of diabetic nephropathy and the healthy control group. RESULTS. In healthy volunteers, there was a statistically significant correlation between the shear-wave velocity values and age and sex. The shear-wave velocity values for the kidneys were 2.87, 3.14, 2.95, 2.68, and 2.55 m/s in patients with stage 1, 2, 3, 4, and 5 diabetic nephropathy, respectively, compared with 2.35 m/s for healthy control subjects. Acoustic radiation force impulse imaging was able to distinguish between the different diabetic nephropathy stages (except for stage 5) in the kidneys. The threshold value for predicting diabetic nephropathy was 2.43 m/s (sensitivity, 84.1%; specificity, 67.3%; positive predictive value, 93.1%; negative predictive value 50.8%; accuracy, 72.1%; positive likelihood ratio, 2.5; and negative likelihood ratio, 0.23). CONCLUSION. Acoustic radiation force impulse imaging could be used for the evaluation of the renal elasticity changes that are due to secondary structural and functional changes in diabetic nephropathy.

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

    Science.gov (United States)

    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.

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

    CERN Document Server

    Leao-Neto, J P

    2015-01-01

    We provide a detailed analysis on the acoustic radiation force and torque exerted on a homogeneous viscoelastic particle in the long-wave limit (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 considering the low- and high-frequency approximation in the viscoelastic model. The developed theory is used to describe the interaction of acoustic waves (traveling and standing plane waves, and zero- and first-order Bessel beams) with a low- and high-density polyethylene particle chosen as examples. Negative axial radiation force and torque are predicted when the ratio of the longitudinal to shear relaxation times is smaller than a constant that depends on the speed of sound in the particle. In addition, a full 3D tractor Bessel vortex beam acting on the high-density polyethylene is depic...

  6. Building an open-source simulation platform of acoustic radiation force-based breast elastography.

    Science.gov (United States)

    Wang, Yu; Peng, Bo; Jiang, Jingfeng

    2017-03-07

    Ultrasound-based elastography including strain elastography, acoustic radiation force impulse (ARFI) imaging, point shear wave elastography and supersonic shear imaging (SSI) have been used to differentiate breast tumors among other clinical applications. The objective of this study is to extend a previously published virtual simulation platform built for ultrasound quasi-static breast elastography toward acoustic radiation force-based breast elastography. Consequently, the extended virtual breast elastography simulation platform can be used to validate image pixels with known underlying soft tissue properties (i.e. 'ground truth') in complex, heterogeneous media, enhancing confidence in elastographic image interpretations. The proposed virtual breast elastography system inherited four key components from the previously published virtual simulation platform: an ultrasound simulator (Field II), a mesh generator (Tetgen), a finite element solver (FEBio) and a visualization and data processing package (VTK). Using a simple message passing mechanism, functionalities have now been extended to acoustic radiation force-based elastography simulations. Examples involving three different numerical breast models with increasing complexity-one uniform model, one simple inclusion model and one virtual complex breast model derived from magnetic resonance imaging data, were used to demonstrate capabilities of this extended virtual platform. Overall, simulation results were compared with the published results. In the uniform model, the estimated shear wave speed (SWS) values were within 4% compared to the predetermined SWS values. In the simple inclusion and the complex breast models, SWS values of all hard inclusions in soft backgrounds were slightly underestimated, similar to what has been reported. The elastic contrast values and visual observation show that ARFI images have higher spatial resolution, while SSI images can provide higher inclusion-to-background contrast. In

  7. Building an open-source simulation platform of acoustic radiation force-based breast elastography

    Science.gov (United States)

    Wang, Yu; Peng, Bo; Jiang, Jingfeng

    2017-03-01

    Ultrasound-based elastography including strain elastography, acoustic radiation force impulse (ARFI) imaging, point shear wave elastography and supersonic shear imaging (SSI) have been used to differentiate breast tumors among other clinical applications. The objective of this study is to extend a previously published virtual simulation platform built for ultrasound quasi-static breast elastography toward acoustic radiation force-based breast elastography. Consequently, the extended virtual breast elastography simulation platform can be used to validate image pixels with known underlying soft tissue properties (i.e. ‘ground truth’) in complex, heterogeneous media, enhancing confidence in elastographic image interpretations. The proposed virtual breast elastography system inherited four key components from the previously published virtual simulation platform: an ultrasound simulator (Field II), a mesh generator (Tetgen), a finite element solver (FEBio) and a visualization and data processing package (VTK). Using a simple message passing mechanism, functionalities have now been extended to acoustic radiation force-based elastography simulations. Examples involving three different numerical breast models with increasing complexity—one uniform model, one simple inclusion model and one virtual complex breast model derived from magnetic resonance imaging data, were used to demonstrate capabilities of this extended virtual platform. Overall, simulation results were compared with the published results. In the uniform model, the estimated shear wave speed (SWS) values were within 4% compared to the predetermined SWS values. In the simple inclusion and the complex breast models, SWS values of all hard inclusions in soft backgrounds were slightly underestimated, similar to what has been reported. The elastic contrast values and visual observation show that ARFI images have higher spatial resolution, while SSI images can provide higher inclusion-to-background contrast

  8. Acoustic radiation force impulse (ARFI) imaging: Characterizing the mechanical properties of tissues using their transient response to localized force

    Science.gov (United States)

    Nightingale, Kathryn R.; Palmeri, Mark L.; Congdon, Amy N.; Frinkely, Kristin D.; Trahey, Gregg E.

    2004-05-01

    Acoustic radiation force impulse (ARFI) imaging utilizes brief, high energy, focused acoustic pulses to generate radiation force in tissue, and conventional diagnostic ultrasound methods to detect the resulting tissue displacements in order to image the relative mechanical properties of tissue. The magnitude and spatial extent of the applied force is dependent upon the transmit beam parameters and the tissue attenuation. Forcing volumes are on the order of 5 mm3, pulse durations are less than 1 ms, and tissue displacements are typically several microns. Images of tissue displacement reflect local tissue stiffness, with softer tissues (e.g., fat) displacing farther than stiffer tissues (e.g., muscle). Parametric images of maximum displacement, time to peak displacement, and recovery time provide information about tissue material properties and structure. In both in vivo and ex vivo data, structures shown in matched B-mode images are in good agreement with those shown in ARFI images, with comparable resolution. Potential clinical applications under investigation include soft tissue lesion characterization, assessment of focal atherosclerosis, and imaging of thermal lesion formation during tissue ablation procedures. Results from ongoing studies will be presented. [Work supported by NIH Grant R01 EB002132-03, and the Whitaker Foundation. System support from Siemens Medical Solutions USA, Inc.

  9. The effect of temperature dependent tissue parameters on acoustic radiation force induced displacements

    CERN Document Server

    Suomi, Visa; Konofagou, Elisa; Cleveland, Robin

    2016-01-01

    Multiple ultrasound elastography techniques rely on acoustic radiation force (ARF) in monitoring high-intensity focused ultrasound (HIFU) therapy. However, ARF is dependent on tissue attenuation and sound speed, both of which are also known to change with temperature making the therapy monitoring more challenging. Furthermore, the viscoelastic properties of tissue are also temperature dependent, which affects the displacements induced by ARF. The aim of this study is to quantify the temperature dependent changes in the acoustic and viscoelastic properties of liver and investigate their effect on ARF induced displacements by using both experimental methods and simulations. Furthermore, the temperature dependent viscoelastic properties of liver are experimentally measured over a frequency range of 0.1-200 Hz at temperatures reaching 80 C, and both conventional and fractional Zener models are used to fit the data. The fractional Zener model was found to fit better with the experimental viscoelasticity data with ...

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

    Energy Technology Data Exchange (ETDEWEB)

    Payne, Allison, E-mail: apayne@ucair.med.utah.edu [Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah 84112 (United States); Bever, Josh de [Department of Computer Science, University of Utah, Salt Lake City, Utah 84112 (United States); Farrer, Alexis [Department of Bioengineering, University of Utah, Salt Lake City, Utah 84112 (United States); Coats, Brittany [Department of Mechanical Engineering, University of Utah, Salt Lake City, Utah 84112 (United States); Parker, Dennis L. [Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah 84108 (United States); Christensen, Douglas A. [Department of Bioengineering, University of Utah, Salt Lake City, Utah 84112 and Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah 84112 (United States)

    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

  11. First-principle simulation of the acoustic radiation force on microparticles in ultrasonic standing waves

    DEFF Research Database (Denmark)

    Jensen, Mads Jakob Herring; Bruus, Henrik

    2013-01-01

    The recent development in the field of microparticle acoutophoresis in microsystems has led to an increased need for more accurate theoretical predections for the acoustic radiation force on a single microparticle in an ultrasonic standing wave. Increasingly detailed analytical solutions of this ......The recent development in the field of microparticle acoutophoresis in microsystems has led to an increased need for more accurate theoretical predections for the acoustic radiation force on a single microparticle in an ultrasonic standing wave. Increasingly detailed analytical solutions...... of this specific problem can be found in the literature [Settnes ans Bruus, Phys. Rev. E 85, 016327 (2012), and references therein], but none have included the complete contribution from thermoviscous effects. Here, we solve this problem numerically by applying a finite-element method to solve directly the mass...... (continuity), momentum (Navier-Stokes), and energy conservation equations using perturbation theory to second order in the imposed time-harmonic ultrasound field. In a two-stage calculation, we first solve the first-order equations resolving the thermoviscous boundary layer surrounding the microparticle...

  12. Acoustic radiation force in tissue-like solids due to modulated sound field

    Science.gov (United States)

    Dontsov, Egor V.; Guzina, Bojan B.

    2012-10-01

    The focus of this study is the sustained body force (the so-called acoustic radiation force) in homogeneous tissue-like solids generated by an elevated-intensity, focused ultrasound field (Mach number=O(10-3)) in situations when the latter is modulated by a low-frequency signal. This intermediate-asymptotics problem, which bears relevance to a number of emerging biomedical applications, is characterized by a number of small (but non-vanishing) parameters including the Mach number, the ratio between the modulation and ultrasound frequency, the ratio of the shear to bulk modulus, and the dimensionless attenuation coefficient. On approximating the response of soft tissues as that of a nonlinear viscoelastic solid with heat conduction, the featured second-order problem is tackled via a scaling paradigm wherein the transverse coordinates are scaled by the width of the focal region, while the axial and temporal coordinate are each split into a "fast" and "slow" component with the twin aim of: (i) canceling the linear terms from the field equations governing the propagation of elevated-intensity ultrasound, and (ii) accounting for the effect of ultrasound modulation. In the context of the focused ultrasound analyses, the key feature of the proposed study revolves around the dual-time-scale treatment of the temporal variable, which allows one to parse out the contribution of ultrasound and its modulation in the nonlinear solution. In this way the acoustic radiation force (ARF), giving rise to the mean tissue motion, is exacted by computing the "fast" time average of the germane field equations. A comparison with the existing theory reveals a number of key features that are brought to light by the new formulation, including the contributions to the ARF of ultrasound modulation and thermal expansion, as well as the precise role of constitutive nonlinearities in generating the sustained body force in tissue-like solids by a focused ultrasound beam.

  13. Concurrent Visualization of Acoustic Radiation Force Displacement and Shear Wave Propagation with 7T MRI.

    Directory of Open Access Journals (Sweden)

    Yu Liu

    Full Text Available 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.

  14. Differentiation of benign from malignant liver masses with Acoustic Radiation Force Impulse technique.

    Science.gov (United States)

    Yu, Hojun; Wilson, Stephanie R

    2011-12-01

    The objective of the study was to determine the performance of Acoustic Radiation Force Impulse (ARFI) imaging to differentiate benign from malignant liver masses, both of hepatocellular origin and metastases, by quantification of their stiffness. This study has institutional review board approval and informed consent. Eighty-nine patients (42 female and 47 male patients) with 105 liver masses had ARFI evaluation on ultrasound, S2000 (Siemens, Mountain View, Calif). Mean age of the patients was 53.67 years (range, 27-83 years). Mean diameter of the masses was 2.77 cm (range, 1.0-13.0 cm). Final diagnoses, confirmed by imaging on contrast-enhanced computed tomography, magnetic resonance, or ultrasound or biopsy, include hepatocellular carcinoma (n = 28), metastasis (n = 13), hemangioma (n = 35), focal nodular hyperplasia (n = 15), focal fat sparing (n = 8), focal fat deposit (n = 4), and adenoma (n = 2). Receiver operating characteristic analysis was performed to evaluate the diagnostic accuracy of the ARFI measurement and to extract the optimal cutoff values in the differentiation of benign from malignant disease. Acoustic Radiation Force Impulse values showed a statistically significant difference between benign (1.73 [SD, 0.8] m/sec) and malignant masses (2.57 [SD, 1.01] m/sec) (P fair accuracy. For differentiation of malignant from benign masses, the sensitivity, specificity, positive predictive value, and negative predictive value were 68% (28/41), 69% (44/64), 58% (28/48), and 77% (44/57), respectively, when 1.9 m/sec was chosen as a cutoff value, reflective of a wide variation of ARFI values in each diagnosis. For differentiation of metastasis from benign masses, sensitivity, specificity, positive predictive value, and NPV were 69% (9/13), 89% (57/64), 56% (9/16), and 93% (57/61), respectively, when 2.72 m/sec was chosen as a cutoff value. Acoustic Radiation Force Impulse measurement may be helpful to differentiate benign masses from metastases, in particular

  15. Optical quantification of harmonic acoustic radiation force excitation in a tissue-mimicking phantom

    CERN Document Server

    Suomi, Visa; Cleveland, Robin

    2016-01-01

    Optical tracking was used to characterize acoustic radiation force (ARF) induced displacements in a tissue-mimicking phantom. Amplitude modulated (AM) 3.3 MHz ultrasound was used to induce ARF in the phantom which was embedded with 10 {\\mu}m microspheres that were tracked using a microscope objective and high speed camera. For sine and square AM the harmonic components of the fundamental and second and third harmonic frequencies were measured. The displacement amplitudes were found to increase linearly with ARF up to 10 {\\mu}m with sine modulation having 19.5% lower peak-to-peak amplitude values than square modulation. Square modulation produced almost no second harmonic but energy was present in the third harmonic. For the sine modulation energy was present in the second harmonic and low energy in the third harmonic. A finite element model was used to simulate the deformation and was both qualitatively and quantitatively in agreement with the measurements.

  16. Measurement of Elastic Properties of Tissue by Shear Wave Propagation Generated by Acoustic Radiation Force

    Science.gov (United States)

    Tabaru, Marie; Azuma, Takashi; Hashiba, Kunio

    2010-07-01

    Acoustic radiation force (ARF) imaging has been developed as a novel elastography technology to diagnose hepatic disease and breast cancer. The accuracy of shear wave speed estimation, which is one of the applications of ARF elastography, is studied. The Young's moduli of pig liver and foie gras samples estimated from the shear wave speed were compared with those measured the static Young's modulus measurement. The difference in the two methods was 8%. Distance attenuation characteristics of the shear wave were also studied using finite element method (FEM) analysis. We found that the differences in the axial and lateral beam widths in pressure and ARF are 16 and 9% at F-number=0.9. We studied the relationship between two branch points in distance attenuation characteristics and the shape of ARF. We found that the maximum measurable length to estimate shear wave speed for one ARF excitation was 8 mm.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Liang [Dept. of Ultrasound, Chinese Academy of Medical Sciences and Peking Union Medical College Hospital, Beijing (China)

    2016-08-15

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

  18. Acoustic radiation force on a sphere in a progressive and standing zero-order quasi-Bessel-Gauss beam.

    Science.gov (United States)

    Jiang, Chen; Liu, Xiaozhou; Liu, Jiehui; Mao, Yiwei; Marston, Philip L

    2017-04-01

    By means of series expansion theory, the incident quasi-Bessel-Gauss beam is expanded using spherical harmonic functions, and the beam coefficients of the quasi-Bessel-Gauss beam are calculated. According to the theory, the acoustic radiation force function, which is the radiation force per unit energy on a unit cross-sectional surface on a sphere made of diverse materials and immersed in an ideal fluid along the propagation axis of zero-order quasi-Bessel-Gauss progressive and standing beams, is investigated. The acoustic radiation force function is calculated as a function of the spherical radius parameter ka and the half-cone angle β with different beam widths in a progressive and standing zero-order Bessel-Gauss beam. Simulation results indicate that the acoustic radiation forces with different waist radii demonstrate remarkably different features from those found in previous studies. The results are expected to be useful in potential applications such as acoustic tweezers. Copyright © 2016 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

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

    2016-04-05

    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.

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

    Science.gov (United States)

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

    2016-02-01

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

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

    Science.gov (United States)

    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.

  2. The effect of temperature dependent tissue parameters on acoustic radiation force induced displacements

    Science.gov (United States)

    Suomi, Visa; Han, Yang; Konofagou, Elisa; Cleveland, Robin O.

    2016-10-01

    Multiple ultrasound elastography techniques rely on acoustic radiation force (ARF) in monitoring high-intensity focused ultrasound (HIFU) therapy. However, ARF is dependent on tissue attenuation and sound speed, both of which are also known to change with temperature making the therapy monitoring more challenging. Furthermore, the viscoelastic properties of tissue are also temperature dependent, which affects the displacements induced by ARF. The aim of this study is to quantify the temperature dependent changes in the acoustic and viscoelastic properties of liver and investigate their effect on ARF induced displacements by using both experimental methods and simulations. Furthermore, the temperature dependent viscoelastic properties of liver are experimentally measured over a frequency range of 0.1-200 Hz at temperatures reaching 80 °C, and both conventional and fractional Zener models are used to fit the data. The fractional Zener model was found to fit better with the experimental viscoelasticity data with respect to the conventional model with up to two orders of magnitude lower sum of squared errors (SSE). The characteristics of experimental displacement data were also seen in the simulations due to the changes in attenuation coefficient and lesion development. At low temperatures before thermal ablation, attenuation was found to affect the displacement amplitude. At higher temperature, the decrease in displacement amplitude occurs approximately at 60-70 °C due to the combined effect of viscoelasticity changes and lesion growth overpowering the effect of attenuation. The results suggest that it is necessary to monitor displacement continuously during HIFU therapy in order to ascertain when ablation occurs.

  3. Role of Acoustic Radiation Force Impulse (ARFI) Elastography in Determination of Severity of Benign Prostate Hyperplasia

    Science.gov (United States)

    Alan, Bircan; Utangaç, Mazhar; Göya, Cemil; Dağgülli, Mansur

    2016-01-01

    Background The aim of this study was to investigate the potential contribution of acoustic radiation force impulse (ARFI) elastography to the determination of the severity of benign prostate hypertrophy (BPH) by performing shear wave velocity (SWV) measurements of the prostate using ARFI technology. Material/Methods Sixty BPH patients and 40 healthy volunteers were included in this study. SWV measurements of the prostate were performed by transabdominal ultrasonography (US), both in the BPH patients and control subjects. The BPH patients also underwent uroflowmetry measurements. Using the International Prostate Symptom Score (IPSS), the BPH patients were divided into two subgroups, a mild-to-moderate BPH group and a severe BPH group, to compare SWV values. Results The BPH patients had higher SWV values for the central area of the prostate compared to the control subjects (2.52±0.59 m/s and 1.47±0.42 m/s, pprostate were higher in the severe BPH group compared to the mild-to-moderate BPH group (2.62±0.58 and 2.25±0.55, p=0.02). Conclusions Our ARFI elastography results indicated that the central prostate SWV values of BPH patients were significantly higher relative to those of a healthy control group. The central prostate SWV values increased in proportion to the increased severity of BPH. Measurement of SWV by ARFI technology constitutes a non-invasive alternative to other methods for the determination of BPH severity. PMID:27876713

  4. Acoustic radiation force imaging sonoelastography for noninvasive staging of liver fibrosis

    Institute of Scientific and Technical Information of China (English)

    Carmen Fierbinteanu-Braticevici; Dan Andronescu; Radu Usvat; Dragos Cretoiu; Cristian Baicus; Gabriela Marinoschi

    2009-01-01

    AIM: To investigate the diagnostic accuracy of acoustic radiation force impulse (ARFI) imaging as a noninvasive method for the assessment of liver fibrosis in chronic hepatitis C (CHC) patients.METHODS: We performed a prospective blind comparison of ARFI elastography, APRI index and FibroMax in a consecutive series of patients who underwent liver biopsy for CHC in University Hospital Bucharest. Histopathological staging of liver fibrosis according to the METAVIR scoring system served as the reference. A total of 74 patients underwent ARFI elastography, APRI index, FibroMax and successful liver biopsy.RESULTS: The noninvasive tests had a good correlation with the liver biopsy results. The most powerful test in predicting fibrosis was ARFI elastography. The diagnostic accuracy of ARFI elastography, expressed as area under receiver operating characteristic curve (AUROC) had a validity of 90.2% (95% CI AUROC =0.831-0.972, P < 0.001) for the diagnosis of significant fibrosis (F ≥ 2). ARFI sonoelastography predicted even better F3 or F4 fibrosis (AUROC = 0.993, 95% CI =0.979-1).CONCLUSION: ARFI elastography had very good accuracy for the assessment of liver fibrosis and was superior to other noninvasive methods (APRI Index,FibroMax) for staging liver fibrosis.

  5. Assessment of placental stiffness using acoustic radiation force impulse elastography in pregnant women with fetal anomalies

    Energy Technology Data Exchange (ETDEWEB)

    Alan, Bircan; Goya, Cemil; Tunc, Senem; Teke, Memik; Hattapoglu, Salih [Dicle University Medical Faculty, Diyarbakir (Turkmenistan)

    2016-04-15

    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. 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. 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. 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.

  6. Shear wave velocity of the healthy thyroid gland in children with acoustic radiation force impulse elastography.

    Science.gov (United States)

    Ceyhan Bilgici, Meltem; Sağlam, Dilek; Delibalta, Semra; Yücel, Serap; Tomak, Leman; Elmalı, Muzaffer

    2017-04-19

    Acoustic radiation force impulse imaging is a kind of shear wave elastography that can be used in children for differentiating thyroid pathologies. Possible changes in the healthy thyroid gland in children may create difficulties in the use of shear wave velocities (SWV) in thyroid pathologies. The aim of this study was to define the normal values of SWV for the healthy thyroid gland in children, elucidate the correlation of the SWV values with potential influencing factors, and evaluate intra-operator reproducibility of the SWV. Between January 2015 and December 2015, a total of 145 healthy children (81 girls, 64 boys; mean age, 10.5 ± 3.14 years; range 6-17 years) were enrolled in the study. The SWV and volume of the thyroid gland were determined. The mean shear wave velocity of the thyroid gland was 1.22 ± 0.20 m/s. There was no correlation between age and the mean SWV of the thyroid gland (Spearman Rho = 0.049, p = 0.556). There was also no correlation between the thyroid gland volume or BSA and the mean SWV. The only correlation detected was between BSA and total thyroid gland volume (p thyroid gland in children was determined. There was no correlation between the SWV of the thyroid gland and age, BSA, or thyroid gland volume.

  7. Assessment of liver steatosis in chicken by using acoustic radiation force impulse imaging: preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Guzman Aroca, Florentina; Serrano, Laura; Berna-Serna, Juan D.; Reus, Manuel [Virgen de la Arrixaca University Hospital, Department of Radiology, El Palmar, Murcia (Spain); Ayala, Ignacio [University of Murcia, Department of Animal Medicine and Surgery, Murcia (Spain); Castell, Maria T. [University of Murcia, Department of Cell Biology, Murcia (Spain); Garcia-Perez, Bartolome [Virgen de la Arrixaca University Hospital, Internal Medicine Service, El Palmar, Murcia (Spain)

    2010-10-15

    To evaluate acoustic radiation force impulse (ARFI) imaging as a non-invasive tool for quantification of the grades of liver steatosis in chickens. We used two different diets: a standard diet (SD group) and a hyperlipidaemic diet (HD group). The ARFI technique was performed in all the animals in the right hepatic lobe and shear wave velocity (SWV) was measured and expressed in metres per second (m/s). Plasma lipid levels were analysed. Steatosis was quantified by using semiquantitative analysis. Statistical analysis was used and Pearson's correlation coefficient was calculated. Mean SWV was 0.94 {+-} 0.16 m/s (range 0.8-1.3 m/s) in the SD group and 1.91 {+-} 0.25 m/s (range 1.3-2.2 m/s) in the HD group (p < 0.001). The lowest SWVs ({<=}1.3 m/s) corresponded to the chickens in the SD group, with 100% of the animals returning a score of 0, whereas the range of SWV in the HD group chickens was between 1.6 and 2.2 m/s. A substantial correlation was observed between SWVs with histological semiquantitative analysis of steatosis (r = 0.85, p < 0.001). ARFI imaging is a non-invasive diagnostic tool that allows discrimination between the grades of liver steatosis in chickens. (orig.)

  8. A Bayesian approach for characterization of soft tissue viscoelasticity in acoustic radiation force imaging.

    Science.gov (United States)

    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.

  9. Renal elasticity quantification by acoustic radiation force impulse in children born preterm: preliminary results

    Directory of Open Access Journals (Sweden)

    Marco Zaffanello

    2015-02-01

    Full Text Available An emerging hypothesis from the recent literature describes how specific adverse factors related to growth retardation and low birth weight might influence renal development during fetal life and the insurgence of relevant pathologies in adulthood. Preterm births and related perinatal events can affect the mechanical proprieties of kidneys in childhood. We retrieved the laboratory medical records of 3 children born preterm, all in good condition, and investigated the elastic properties of their kidneys using the acoustic radiation force impulse (ARFI technique. Shear wave velocity (SWV obtained by the ARFI technique depends on the elasticity of a parenchymatous tissue.Medical records of case patient 1 showed a shorter right kidney (5th percentile, a greater protein/creatinine ratio and higher α1-microglobulin in the urine spot if compared with controls. Patients 2 and 3 had unremarkable laboratory results. Moreover, compared with the same results of healthy full-term normal children obtained from a previous study of ours, we observed higher SWV values (m/s for the left kidney in patients 1 and 3; patient 2 had lower SWV values in both kidneys. The altered SWV values, measured in these children born preterm, may be correlated with a possible underlying renal pathology (for instance, disruption of the renal histology. Altered SWV values are generally observed also in 2 out of 3 children with a history of normal laboratory markers of renal function. Further studies are needed on larger cohorts of patients.

  10. Testicular microlithiasis and preliminary experience of acoustic radiation force impulse imaging

    Science.gov (United States)

    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

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

    Science.gov (United States)

    Guzina, Bojan B; Dontsov, Egor V; Urban, Matthew W; Fatemi, Mostafa

    2015-05-07

    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.

  12. The ‘sixth sense’ of ultrasound: probing nonlinear elasticity with acoustic radiation force

    Science.gov (United States)

    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.

  13. Dynamic simulation of viscoelastic soft tissue in acoustic radiation force creep imaging.

    Science.gov (United States)

    Zhao, Xiaodong; Pelegri, Assimina A

    2014-09-01

    Acoustic radiation force (ARF) creep imaging applies step ARF excitation to induce creep displacement of soft tissue, and the corresponding time-dependent responses are used to estimate soft tissue viscoelasticity or its contrast. Single degree of freedom (SDF) and homogeneous analytical models have been used to characterize soft tissue viscoelasticity in ARF creep imaging. The purpose of this study is to investigate the fundamental limitations of the commonly used SDF and homogeneous assumptions in ARF creep imaging. In this paper, finite element (FE) models are developed to simulate the dynamic behavior of viscoelastic soft tissue subjected to step ARF. Both homogeneous and heterogeneous models are studied with different soft tissue viscoelasticity and ARF configurations. The results indicate that the SDF model can provide good estimations for homogeneous soft tissue with high viscosity, but exhibits poor performance for low viscosity soft tissue. In addition, a smaller focal region of the ARF is desirable to reduce the estimation error with the SDF models. For heterogeneous media, the responses of the focal region are highly affected by the local heterogeneity, which results in deterioration of the effectiveness of the SDF and homogeneous simplifications.

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

    Science.gov (United States)

    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.

  15. Role of Acoustic Radiation Force Impulse (ARFI) Elastography in Determination of Severity of Benign Prostate Hyperplasia.

    Science.gov (United States)

    Alan, Bircan; Utangaç, Mazhar; Göya, Cemil; Dağgülli, Mansur

    2016-11-23

    BACKGROUND The aim of this study was to investigate the potential contribution of acoustic radiation force impulse (ARFI) elastography to the determination of the severity of benign prostate hypertrophy (BPH) by performing shear wave velocity (SWV) measurements of the prostate using ARFI technology. MATERIAL AND METHODS Sixty BPH patients and 40 healthy volunteers were included in this study. SWV measurements of the prostate were performed by transabdominal ultrasonography (US), both in the BPH patients and control subjects. The BPH patients also underwent uroflowmetry measurements. Using the International Prostate Symptom Score (IPSS), the BPH patients were divided into two subgroups, a mild-to-moderate BPH group and a severe BPH group, to compare SWV values. RESULTS The BPH patients had higher SWV values for the central area of the prostate compared to the control subjects (2.52±0.59 m/s and 1.47±0.42 m/s, pprostate were higher in the severe BPH group compared to the mild-to-moderate BPH group (2.62±0.58 and 2.25±0.55, p=0.02). CONCLUSIONS Our ARFI elastography results indicated that the central prostate SWV values of BPH patients were significantly higher relative to those of a healthy control group. The central prostate SWV values increased in proportion to the increased severity of BPH. Measurement of SWV by ARFI technology constitutes a non-invasive alternative to other methods for the determination of BPH severity.

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

    Institute of Scientific and Technical Information of China (English)

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

    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 measure-d for the quantification of stiffness.According to the b-rightness, 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.

  17. Tissue elasticity quantification by acoustic radiation force impulse for the assessment of renal allograft function.

    Science.gov (United States)

    He, Wan-Yuan; Jin, Yun-Jie; Wang, Wen-Ping; Li, Chao-Lun; Ji, Zheng-Biao; Yang, Cheng

    2014-02-01

    Acoustic radiation force impulse (ARFI) quantification, a novel ultrasound-based elastography method, has been used to measure liver fibrosis. However, few studies have been performed on the use of ARFI quantification in kidney examinations. We evaluated renal allograft stiffness using ARFI quantification in patients with stable renal function (n = 52) and those with biopsy-proven allograft dysfunction (n = 50). ARFI quantification, given as shear wave velocity (SWV), was performed. The resistance index (RI) was calculated by pulsed-wave Doppler ultrasound, and clinical and laboratory data were collected. Morphologic changes in transplanted kidneys were diagnosed by an independent pathologist. Mean SWV was more significantly negatively correlated with estimated glomerular filtration rate (eGFR) (r = -0.657, p renal allograft dysfunction were 72.0% and 86.5% (cutoff value = 2.625), respectively. The latter values were better than those of RI, which were 62.0% and 69.2% (cutoff value = 0.625), respectively. The coefficient of variation for repeat SWV measurements of the middle part of transplanted kidney was 8.64%, and inter-observer agreement on SWV was good (Bland-Altman method, ICC = 0.890). In conclusion, tissue elasticity quantification by ARFI is more accurate than the RI in diagnosing renal allograft function.

  18. Evaluating the intensity of the acoustic radiation force impulse (ARFI) in intravascular ultrasound (IVUS) imaging: Preliminary in vitro results.

    Science.gov (United States)

    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

  19. Acoustic radiation force impulse imaging of human prostates: initial in vivo demonstration.

    Science.gov (United States)

    Zhai, Liang; Polascik, Thomas J; Foo, Wen-Chi; Rosenzweig, Stephen; Palmeri, Mark L; Madden, John; Nightingale, Kathryn R

    2012-01-01

    Reliably detecting prostate cancer (PCa) has been a challenge for current imaging modalities. Acoustic radiation force impulse (ARFI) imaging is an elasticity imaging method that uses remotely generated, focused acoustic beams to probe tissue stiffness. A previous study on excised human prostates demonstrated ARFI images portray various prostatic structures and has the potential to guide prostate needle biopsy with improved sampling accuracy. The goal of this study is to demonstrate the feasibility of ARFI imaging to portray internal structures and PCa in the human prostate in vivo. Custom ARFI imaging sequences were designed and implemented using a modified Siemens Antares™ scanner with a three-dimensional (3-D) wobbler, end-firing, trans-cavity transducer, EV9F4. Nineteen patients were consented and imaged immediately preceding surgical prostatectomy. Pathologies and anatomic structures were identified in histologic slides by a pathologist blinded to ARFI data and were then registered with structures found in ARFI images. The results demonstrated that when PCa is visible, it generally appears as bilaterally asymmetric stiff structures; benign prostatic hyperplasia (BPH) appears heterogeneous with a nodular texture; the verumontanum and ejaculatory ducts appears softer compared with surrounding tissue, which form a unique 'V' shape; and the boundary of the transitional zone (TZ) forms a stiff rim separating the TZ from the peripheral zone (PZ). These characteristic appearances of prostatic structures are consistent with those found in our previous study of prostate ARFI imaging on excised human prostates. Compared with the matched B-mode images, ARFI images, in general, portray prostate structures with higher contrast. With the end-firing transducer used for this study, ARFI depth penetration was limited to 22 mm. Image contrast and resolution were decreased as compared with the previous ex vivo study due to the small transducer aperture. Even with these

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

    Science.gov (United States)

    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

  1. A rapid magnetic resonance acoustic radiation force imaging sequence for ultrasonic refocusing

    Science.gov (United States)

    Mougenot, Charles; Pichardo, Samuel; Engler, Steven; Waspe, Adam; Constanciel Colas, Elodie; Drake, James M.

    2016-08-01

    Magnetic resonance guided acoustic radiation force imaging (MR-ARFI) is being used to correct for aberrations induced by tissue heterogeneities when using high intensity focusing ultrasound (HIFU). A compromise between published MR-ARFI adaptive solutions is proposed to achieve efficient refocusing of the ultrasound beam in under 10 min. In addition, an ARFI sequence based on an EPI gradient echo sequence was used to simultaneously monitor displacement and temperature with a large SNR and low distortion. This study was conducted inside an Achieva 3T clinical MRI using a Philips Sonalleve MR-HIFU system to emit a 1 ms pulsed sonication with duty cycle of 2.3% at 300 Wac inside a polymer phantom. Virtual elements defined by a Hadamard array with sonication patterns composed of 6 phase steps were used to characterize 64 groups of 4 elements to find the optimal phase of the 256 elements of the transducer. The 384 sonication patterns were acquired in 580 s to identify the set of phases that maximize the displacement at the focal point. Three aberrators (neonatal skull, 8 year old skull and a checkered pattern) were added to each sonication pattern to evaluate the performance of this refocusing algorithm (n  =  4). These aberrators reduced the relative intensities to 95.3%, 69.6% and 25.5% for the neonatal skull, 8 year old skull, and checkered pattern virtual aberrators respectively. Using a 10 min refocusing algorithm, relative intensities of 101.6%, 91.3% and 93.3% were obtained. Better relative intensities of 103.9%, 94.3% and 101% were achieved using a 25 min refocusing algorithm. An average temperature increase of 4.2 °C per refocusing test was induced for the 10 min refocusing algorithm, resulting in a negligible thermal dose of 2 EM. A rapid refocusing of the beam can be achieved while keeping thermal effects to a minimum.

  2. Preclinical evaluation of acoustic radiation force impulse measurements in regions of heterogeneous elasticity

    Energy Technology Data Exchange (ETDEWEB)

    Hollerieth, Katharina; Moog, Philipp; Vo-Cong, Minh-Truc; Heemann, Uwe [Nephrology Department, Klinikum Rechts der Isar of the Technical University of Munich, Munich (Germany); Gassmann, Bernhard [Meso International GmbH, Berlin (Germany); Wagenpfeil, Stefan [Institute for Medical Biometry, Epidemiology and Medical Informatics, Saarland University, Campus Homburg (Saar), Homburg (Germany)

    2016-08-15

    The purpose of this study was to compare the reliability of ultrasound-based shear wave elastography in regions of homogeneous versus heterogeneous elasticity by using two different probes. Using acoustic radiation force impulse (ARFI) elastography, we measured the shear wave velocity (SWV) in different lesions of an elastography phantom with the convex {sub 4}C{sub 1} probe and the linear {sub 9}L{sub 4} probe. The region of interest (ROI) was positioned in such a way that it was partly filled by one of the lesions (0%, 25%, 50%, 75%, and 100%) and partly by the background of the phantom (100%, 75%, 50%, 25%, and 0%, respectively). The success rate was 98.5%. The measured value and the reference value of SWV correlated significantly (r=0.89, P<0.001). Further, a comparison of the two probes revealed that there was no statistical difference in either the mean or the variance values. However, the deviation of SWV from the reference was higher in the case of the {sub 9}L{sub 4} probe than in the case of the {sub 4}C{sub 1} probe, both overall and in measurements in which the ROI contained structures of different elasticity (P=0.021 and P=0.002). Taking into account all data, for both probes, we found that there was a greater spread and deviation of the SWV from the reference value when the ROI was positioned in structures having different elastic properties (standard deviation, 0.02±0.01 m/sec vs. 0.04±0.04 m/sec; P=0.010; deviation from the reference value, 0.21±0.12 m/sec vs. 0.38±0.27 m/sec; P=0.050). Quantitative ARFI elastography was achievable in structures of different elasticity; however, the validity and the reliability of the SWV measurements decreased in comparison to those of the measurements performed in structures of homogeneous elasticity. Therefore, a convex probe is preferred for examining heterogeneous structures.

  3. Effects of acoustic radiation force and shear waves for absorption and stiffness sensing in ultrasound modulated optical tomography.

    Science.gov (United States)

    Li, Rui; Elson, Daniel S; Dunsby, Chris; Eckersley, Robert; Tang, Meng-Xing

    2011-04-11

    Ultrasound-modulated optical tomography (UOT) combines optical contrast with ultrasound spatial resolution and has great potential for soft tissue functional imaging. One current problem with this technique is the weak optical modulation signal, primarily due to strong optical scattering in diffuse media and minimal acoustically induced modulation. The acoustic radiation force (ARF) can create large particle displacements in tissue and has been shown to be able to improve optical modulation signals. However, shear wave propagation induced by the ARF can be a significant source of nonlocal optical modulation which may reduce UOT spatial resolution and contrast. In this paper, the time evolution of shear waves was examined on tissue mimicking-phantoms exposed to 5 MHz ultrasound and 532 nm optical radiation and measured with a CCD camera. It has been demonstrated that by generating an ARF with an acoustic burst and adjusting both the timing and the exposure time of the CCD measurement, optical contrast and spatial resolution can be improved by ~110% and ~40% respectively when using the ARF rather than 5 MHz ultrasound alone. Furthermore, it has been demonstrated that this technique simultaneously detects both optical and mechanical contrast in the medium and the optical and mechanical contrast can be distinguished by adjusting the CCD exposure time.

  4. Imaging and characterizing shear wave and shear modulus under orthogonal acoustic radiation force excitation using OCT Doppler variance method.

    Science.gov (United States)

    Zhu, Jiang; Qu, Yueqiao; Ma, Teng; Li, Rui; Du, Yongzhao; Huang, Shenghai; Shung, K Kirk; Zhou, Qifa; Chen, Zhongping

    2015-05-01

    We report on a novel acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE) technique for imaging shear wave and quantifying shear modulus under orthogonal acoustic radiation force (ARF) excitation using the optical coherence tomography (OCT) Doppler variance method. The ARF perpendicular to the OCT beam is produced by a remote ultrasonic transducer. A shear wave induced by ARF excitation propagates parallel to the OCT beam. The OCT Doppler variance method, which is sensitive to the transverse vibration, is used to measure the ARF-induced vibration. For analysis of the shear modulus, the Doppler variance method is utilized to visualize shear wave propagation instead of Doppler OCT method, and the propagation velocity of the shear wave is measured at different depths of one location with the M scan. In order to quantify shear modulus beyond the OCT imaging depth, we move ARF to a deeper layer at a known step and measure the time delay of the shear wave propagating to the same OCT imaging depth. We also quantitatively map the shear modulus of a cross-section in a tissue-equivalent phantom after employing the B scan.

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

    CERN Document Server

    Mitri, F G

    2016-01-01

    Analytical expressions for the axial and transverse acoustic radiation forces as well as the radiation torque per length are derived for a rigid elliptical cylinder placed arbitrarily in the field of in plane progressive, quasi-standing or standing waves. The rigid elliptical cylinder case is important to be considered as a first-order approximation of the behavior of a fluid particle suspended in air, because of the significant acoustic impedance mismatch at the particle's boundary. Based on the 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 compone...

  6. Air-coupled acoustic radiation force source for non-contact measurement of soft media elasticity (Conference Presentation)

    Science.gov (United States)

    Ambroziński, Lukasz; Pelivanov, Ivan; Song, Shaozhen; Yoon, Soon Joon; Li, David S.; Gao, Liang; Shen, Tueng T.; Wang, Ruikang K.; O'Donnell, Matthew

    2017-04-01

    Acoustic radiation force (ARF) is commonly used in ultrasound (US)-based elastography to generate shear waves deep within soft tissue. These waves can be detected with different methods, e.g. contact conventional ultrasound imaging probes or contact free magnetic resonance or optical coherence tomography (OCT). For many clinical applications, however, for instance the eye, a totally non-contact system for generation/detection of mechanical waves is needed. Here, we present a method for efficient non-contact excitation of broadband transverse mechanical waves in soft media. The approach is based on pushing the medium under study with a 1 MHz chirped US wave focused to its surface from air. The US beam reflected from the air/medium interface provides the ARF force to the medium surface launching a transient mechanical wave in the transverse (lateral) direction. The design and performance of the air-coupled transducer is discussed. The focal zone, peak pressure and acoustic intensity are measured for transducers with different numerical apertures. Time and frequency characteristics of the propagating mechanical waves, generated in soft tissue, are tracked with a phase-sensitive ultra-fast frame rate OCT imaging system. Application of the proposed method for non-contact, non-invasive, sub-mm resolution elasticity measurement in soft tissue is proposed.

  7. Propagation of Shear Waves Generated by Acoustic Radiation Force in Nondissipative Inhomogeneous Media

    Institute of Scientific and Technical Information of China (English)

    LU Ming-Zhu; LIU Xue-Jin; SHI Yu; KANG Yan-Ni; GUAN Yu-Bo; WAN Ming-Xi

    2012-01-01

    We concentrate on the nondissipative mechanism induced shear wave in inhomogenous tissue.The shear wave equation of radiation force in inhomogeneous media is solved numerically with a finite-difference time-domain method.A rarely studied nondissipative mechanism of shear displacement due to a smooth medium inhomogeneity is evaluated.It is noted that unlike the dissipative effect,the nondissipative action on a localized inhomogeneity with its hardness parameter changing smoothly along the beam axis,compresses or stretches the focus area.The shear waves in nondissipative inhomogeneous media remain the property of sharp turn with 100% peak positive displacement and 64% peak negative displacement.This action is useful in discerning the water-like lesion.%We concentrate on the nondissipative mechanism induced shear wave in inhomogenous tissue. The shear wave equation of radiation force in inhomogeneous media is solved numerically with a finite-difference time-domain method. A rarely studied nondissipative mechanism of shear displacement due to a smooth medium inhomogeneity is evaluated. It is noted that unlike the dissipative effect, the nondissipative action on a localized inhomogeneity with its hardness parameter changing smoothly along the beam axis, compresses or stretches the focus area. The shear waves in nondissipative inhomogeneous media remain the property of sharp turn with 100% peak positive displacement and 64% peak negative displacement. This action is useful in discerning the water-like lesion.

  8. Tissue elasticity estimated by acoustic radiation force impulse quantification depends on the applied transducer force: an experimental study in kidney transplant patients

    Energy Technology Data Exchange (ETDEWEB)

    Syversveen, Trygve; Berstad, Audun E.; Brabrand, Knut; Abildgaard, Andreas [Oslo University Hospital, Department of Radiology and Nuclear Medicine, Rikshospitalet, Oslo (Norway); Midtvedt, Karsten [Oslo University Hospital, Medical Department, Section of Nephrology, Rikshospitalet, Oslo (Norway); Stroem, Erik H. [Oslo University Hospital, Department of Pathology, Rikshospitalet, Oslo (Norway)

    2012-10-15

    Acoustic radiation force impulse (ARFI) quantification estimates tissue elasticity by measuring shear-wave velocity (SWV) and has been applied to various organs. We evaluated the impact of variations in the transducer force applied to the skin on the SWV ultrasound measurements in kidney transplant cortex and ARFI's ability to detect fibrosis in kidney transplants. SWV measurements were performed in the cortex of 31 patients with kidney allografts referred for surveillance biopsies. A mechanical device held the transducer and applied forces were equal to a compression weight of 22, 275, 490, 975, 2,040 and 2,990 g. SWV group means were significantly different by repeat measures ANOVA [F(2.85,85.91) = 84.75, P < 0.0005 for 22, 275, 490, 975 and 2,040 g compression weight] and also by pairwise comparisons. Biopsy specimens were sufficient for histological evaluation in 29 of 31 patients. Twelve had grade 0, 11 grade 1, five grade 2 and one grade 3 fibrosis. One-way ANOVA showed no difference in SWV performed with any of the applied transducer forces between grafts with various degrees of fibrosis. SWV measurements in kidney transplants are dependent on the applied transducer force and do not differ in grafts with different grades of fibrosis. (orig.)

  9. Preliminary results of acoustic radiation force impulses (ARFI) ultrasound imaging of solid suspicious breast lesions

    Institute of Scientific and Technical Information of China (English)

    Lei Ye; Liping Wang; Yuan Huang; Youbin Deng

    2013-01-01

    Objective: The aim of our study was to make the qualitative and quantitative analysis to breast lesions usingacoustic radiation force impulses (ARFI), and assess the diagnostic value of ARFI for differentiation between benign andmalignant solid breast masses, meanwhile evaluate the influences of ARFI with breast imaging reporting and data system(BI-RADS) of suspicious masses. Methods: Seventy-five women with 86 breast lesions underwent conventional breast ultrasoundexamination. Then B-mode BI-RADS features and assessments were recorded and standard breast US supplementedby ARFI elastographic examination were repeated. The data were recorded and analyzed as following: area ratio of breastlesion, the shear-wave velocity, the ratio of the shear-wave velocity between lesions and surrounding normal tissues, andaccording to the elastographic data reconsidered the BI-RADS category, all the results have been correlated with pathologicalresults and make statistical evaluations of ARFI for differentiation between benign and malignant solid breast masses.Meantime our study has correlated the adjusted BI-RADS category of suspicious breast lesions with the pathological resultsand made assessment. Results: Thirty-eight patients were malignant breast carcinoma (31 invasive ductal carcinoma, 5intraductal carcinoma in situ, 2 medullary carcinoma, 2 invasive lobular carcinoma), 48 patients were benign breast lesions(23 fibroadenoma, 12 benign nodular hyperplasia, 5 phyllodes tumor, 6 adenosis, 2 intraductal papilloma). Underwent conventionalbreast ultrasound exam, 42 cases were BI-RADS category 3, 23 cases were BI-RADS category 4. When addingelastographic data, 46 cases were BI-RADS category 3 and 20 cases were BI-RADS category 4. Compared with pathologicalresults showed for both the specificity of BIRADS features and the area under ROC curve has risen. Virtual touch tissue imaging(VTI) and virtual touch tissue quantification (VTQ) data showed the area ratio (AR) between

  10. Effects of acoustic radiation force on the binding efficiency of BR55, a VEGFR2-specific ultrasound contrast agent.

    Science.gov (United States)

    Frinking, Peter J A; Tardy, Isabelle; Théraulaz, Martine; Arditi, Marcel; Powers, Jeffry; Pochon, Sibylle; Tranquart, François

    2012-08-01

    This work describes an in vivo study analyzing the effect of acoustic radiation force (ARF) on the binding of BR55 VEGFR2-specific contrast-agent microbubbles in a model of prostatic adenocarcinoma in rat. A commercial ultrasound system was modified by implementing high duty-cycle 3.5-MHz center frequency ARF bursts in a scanning configuration. This enabled comparing the effects of ARF on binding in tumor and healthy tissue effectively in the same field of view. Bubble binding was established by measuring late-phase enhancement in amplitude modulation (AM) contrast-specific imaging mode (4 MHz, 150 kPa) 10 min after agent injection when the unbound bubbles were cleared from the circulation. Optimal experimental conditions, such as agent concentration (0.4 × 10(8)-1.6 × 10(8) bubbles/kg), acoustic pressure amplitude (26-51 kPa) and duty-cycle (20%-95%) of the ARF bursts, were evaluated in their ability to enhance binding in tumor without significantly increasing binding in healthy tissue. Using the optimal conditions (38 kPa peak-negative pressure, 95% duty cycle), ARF-assisted binding of BR55 improved significantly in tumor (by a factor of 7) at a lower agent dose compared with binding without ARF, and it had an insignificant effect on binding in healthy tissue. Thus, the high binding specificity of BR55 microbubbles for targeting VEGFR2 present at sites of active angiogenesis was confirmed by this study. Therefore, it is believed that based on the results obtained in this work, ultrasound molecular imaging using target-specific contrast-agent microbubbles should preferably be performed in combination with ARF. Copyright © 2012 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  11. The texture quantitative analysis of the normal mammary parenchyma and in breast lesions: acoustic radiation force impulse (ARFI) technology.

    Science.gov (United States)

    Li, Y; Liu, C; Geng, J; Zheng, X; Chen, B; Lu, Z; Wang, X

    2014-01-01

    The purpose of this work is to investigate the feasibility of acoustic radiation force impulse (ARFI) technology in the normal mammary parenchyma and in breast lesions. The virtual touch tissue quantification (VTQ) value was measured on a total of 150 cases in the normal mammary parenchyma and a total of 69 cases in breast lesions (19 cases of nodules, 28 cases of fibroadenoma, and 22 cases of cancer). Then the statistic analysis was carried out on the VTQ value combined with mammographic density, ages, menstrual stages, and pathological result. The VTQ value of mammary parenchyma rose with the increase of the mammographic density, and the value of VTQ had statistical differences in the comparison of group C with group B and in the comparison of group D with group C. The comparison of the VTQ value of the mammary parenchyma in patients with breast cancer and the nodule had statistical difference. The comparison of the VTQ value of the mammary parenchyma in patients with breast cancer, and the fibroadenoma had statistical difference. The value ofVTQ in masses gradually increased in the groups of nodule, fibroadenoma, and breast cancer. There was significant difference in the comparison of VTQ value of the nodule group and the fibroadenoma group with breast cancer group respectively. ARFI-VTQ technology has some reference value in assessing mammographic density. ARFI-VTQ can be used as the quantitative indicater for differentially diagnosing the breast lesions.

  12. Acoustic radiation force impulse imaging (ARFI) for differentiation of benign and malignant thyroid nodules--A meta-analysis.

    Science.gov (United States)

    Zhan, Jia; Jin, Jia-Mei; Diao, Xue-Hong; Chen, Yue

    2015-11-01

    Work-up of thyroid nodules remains challenging. Acoustic radiation force impulse imaging (ARFI)-generated shear wave elastography, which can measure quantitatively tissue stiffness (virtual touch tissue quantification) is used as a complement to conventional sonography for improving the diagnosis of thyroid nodules. This meta-analysis was performed to expand on a previous meta-analysis to assess the diagnostic power of ARFI in differentiating benign and malignant thyroid nodules. The MEDLINE, PubMed, SpringerLink databases up to December 31, 2014, were searched. The pooled sensitivity, specificity, and summary receiver operating characteristic curve were obtained from individual studies with a random effects model. Sixteen studies that included a total of 2436 nodules in 2147 patients for ARFI studies were analyzed. The overall mean sensitivity and specificity of ARFI for differentiation of thyroid nodules were 0.80 (95% confidence interval [CI], 0.73-0.87) and 0.85 (95% CI, 0.80-0.90), respectively. A significant heterogeneity was found for both sensitivity and specificity of the different studies (P<0.001). The area under the curve for the ARFI was 0.91. ARFI has high sensitivity and specificity for identification of thyroid. This technique might be useful to select patients with thyroid nodules for surgery. Copyright © 2015. Published by Elsevier Ireland Ltd.

  13. Assessing hepatic fibrosis: comparing the intravoxel incoherent motion in MRI with acoustic radiation force impulse imaging in US

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Chih-Horng; Liang, Po-Chin; Shih, Tiffany Ting-Fang [National Taiwan University Hospital, Department of Medical Imaging, Taipei (China); National Taiwan University College of Medicine, Department of Radiology, Taipei (China); Ho, Ming-Chih; Hu, Rey-Heng; Lai, Hong-Shiee [National Taiwan University Hospital and College of Medicine, Department of Surgery, Taipei (China); Jeng, Yung-Ming [National Taiwan University Hospital and College of Medicine, Department of Pathology, Taipei (China)

    2015-12-15

    This study compared the diagnostic performance of intravoxel incoherent motion (IVIM) in magnetic resonance imaging (MRI) and acoustic radiation force impulse imaging (ARFI) in ultrasound (US) for liver fibrosis (LF) evaluation. A total of 49 patients scheduled for liver surgery were recruited. LF in the non-tumorous liver parenchyma at the right lobe was estimated using a slow diffusion coefficient, fast diffusion coefficient (D{sub fast}), perfusion fraction (f) of the IVIM parameters, the total apparent diffusion coefficient of conventional diffusion-weighted imaging and the shear wave velocity (Vs) of ARFI. LF was graded using the Metavir scoring system on histological examination. The Spearman rank correlation coefficient for correlation and analysis of variance was used for determining difference. The diagnostic performance was compared using receiver operating characteristic curve analysis. LF exhibited significant correlation with the three parameters D{sub fast}, f, and Vs (r = -0.528, -0.337, and 0.481, respectively, P < 0.05). The D{sub fast} values in the F4 group were significantly lower than those in the F0, F1 and F2 groups. D{sub fast} exhibited a non-inferior performance for diagnosing all fibrosis grades compared with that of Vs. Both IVIM and ARFI provide reliable estimations for the noninvasive assessment of LF. (orig.)

  14. Virtual touch tissue quantification of acoustic radiation force impulse: a new ultrasound elastic imaging in the diagnosis of thyroid nodules.

    Directory of Open Access Journals (Sweden)

    Yi-Feng Zhang

    Full Text Available OBJECTIVE: Virtual touch tissue quantification (VTQ of acoustic radiation force impulse (ARFI is a new quantitative technique to measure tissue stiffness. The study was aimed to assess the usefulness of VTQ in the diagnosis of thyroid nodules. METHODS: 173 pathologically proven thyroid nodules in 142 patients were included and all were examined by conventional ultrasound (US, conventional elasticity imaging (EI and VTQ of ARFI. The tissue stiffness for VTQ was expressed as shear wave velocity (SWV (m/s. Receiver-operating characteristic curve (ROC analyses were performed to assess the diagnostic performance. Intra- and inter-observer reproducibility of VTQ measurement was assessed. RESULTS: The SWVs of benign and malignant thyroid nodules were 2.34±1.17 m/s (range: 0.61-9.00 m/s and 4.82±2.53 m/s (range: 2.32-9.00 m/s respectively (P20 mm and lowest for those ≤10 mm. The correlation coefficients were 0.904 for intraobserver measurement and 0.864 for interobserver measurement. CONCLUSIONS: VTQ of ARFI provides quantitative and reproducible information about the tissue stiffness, which is useful for the differentiation between benign and malignant thyroid nodules. The diagnostic performance of VTQ is higher than that of conventional EI.

  15. Solid hypo-echoic thyroid nodules on ultrasound: the diagnostic value of acoustic radiation force impulse elastography.

    Science.gov (United States)

    Xu, Jun-Mei; Xu, Hui-Xiong; Xu, Xiao-Hong; Liu, Chang; Zhang, Yi-Feng; Guo, Le-Hang; Liu, Lin-Na; Zhang, Jin

    2014-09-01

    The aim of the study described here was to evaluate the diagnostic performance of acoustic radiation force impulse (ARFI) elastography in the differential diagnosis between benign and malignant solid hypo-echoic thyroid nodules (SHTNs) on ultrasound. In this retrospective study, 183 histologically proven SHTNs in 159 patients were enrolled. Conventional US, as well as Virtual Touch tissue imaging (VTI) and Virtual Touch tissue quantification (VTQ) of ARFI elastography, was performed on each nodule. The VTI features of SHTNs were divided into six grades, where higher grades represent harder tissue. VTQ was expressed as shear wave velocity, where higher shear wave velocity values indicate stiffer tissue. The sensitivity, specificity, accuracy, positive predictive value, negative predictive value and Youden index for ultrasound and ARFI were assessed. The 183 pathologically proven SHTNs included 117 benign and 66 malignant lesions. Nodules classified as VTI grades IV to VI were more frequently malignant (49/66, 74.2%) than benign (10/117, 8.5%) (p ultrasound; 68.2%, 76.9%, 73.8%, 62.5%, 81.1% and 0.451 for VTQ; and 74.2%, 91.5%, 85.2%, 83.1%, 86.3% and 0.657 for VTI, respectively. ARFI elastography performed at a superior level, compared with conventional ultrasound, in the differential diagnosis between malignant and benign SHTNs. The diagnostic performance of VTI is higher than that of VTQ.

  16. Hepatic and Splenic Acoustic Radiation Force Impulse Shear Wave Velocity Elastography in Children with Liver Disease Associated with Cystic Fibrosis

    Directory of Open Access Journals (Sweden)

    Teresa Cañas

    2015-01-01

    Full Text Available Background. Liver disease associated with cystic fibrosis (CFLD is the second cause of mortality in these patients. The diagnosis is difficult because none of the available tests are specific enough. Noninvasive elastographic techniques have been proven to be useful to diagnose hepatic fibrosis. Acoustic radiation force impulse (ARFI imaging is an elastography imaging system. The purpose of the work was to study the utility of liver and spleen ARFI Imaging in the detection of CFLD. Method. 72 patients with cystic fibrosis (CF were studied and received ARFI imaging in the liver and in the spleen. SWV values were compared with the values of 60 healthy controls. Results. Comparing the SWV values of CFLD with the control healthy group, values in the right lobe were higher in patients with CFLD. We found a SWV RHL cut-off value to detect CFLD of 1.27 m/s with a sensitivity of 56.5% and a specificity of 90.5%. CF patients were found to have higher SWC spleen values than the control group. Conclusions. ARFI shear wave elastography in the right hepatic lobe is a noninvasive technique useful to detect CFLD in our sample of patients. Splenic SWV values are higher in CF patients, without any clinical consequence.

  17. Clinical utility of acoustic radiation force impulse imaging for identification of malignant liver lesions: a meta-analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ying, Li; Lin, Xiao; Xie, Zuo-Liu; Tang, Fei-Yun; Hu, Yuan-Ping [First Affiliated Hospital of Wenzhou Medical College, Department of Ultrasonography, Wenzhou (China); Shi, Ke-Qing [First Affiliated Hospital of Wenzhou Medical College, Department of Infection and Liver Diseases, Institution of Hepatology, Wenzhou (China)

    2012-12-15

    To assess the performance of acoustic radiation force impulse (ARFI) imaging for identification of malignant liver lesions using meta-analysis. PubMed, the Cochrane Library, the ISI Web of Knowledge and the China National Knowledge Infrastructure were searched. The studies published in English or Chinese relating to evaluation accuracy of ARFI imaging for identification of malignant liver lesions were collected. A hierarchical summary receiver operating characteristic (HSROC) curve was used to examine the ARFI imaging accuracy. Clinical utility of ARFI imaging for identification of malignant liver lesions was evaluated by Fagan plot analysis. A total of eight studies which included 590 liver lesions were analysed. The summary sensitivity and specificity for identification of malignant liver lesions were 0.86 (95 % confidence interval (CI) 0.74-0.93) and 0.89 (95 % CI 0.81-0.94), respectively. The HSROC was 0.94 (95 % CI 0.91-0.96). After ARFI imaging results over the cut-off value for malignant liver lesions (''positive'' result), the corresponding post-test probability for the presence (if pre-test probability was 50 %) was 89 %; in ''negative'' measurement, the post-test probability was 13 %. ARFI imaging has a high accuracy in the classification of liver lesions. (orig.)

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

    Science.gov (United States)

    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

  19. Usefulness of acoustic radiation force impulse elastography in the differential diagnosis of benign and malignant solid pancreatic lesions

    Energy Technology Data Exchange (ETDEWEB)

    Park, Min Kyoung; Jo, Jeong Hyun; Kwon, Hee Jin; Cho, Jin Han; Oh, Jong Young; Noh, Myung Hwan; Nam, Kyung Jin [Dong-A University College of Medicine, Busan (Korea, Republic of)

    2014-03-15

    The aim of this study was to evaluate the tissue stiffness of solid pancreatic lesions by using acoustic radiation force impulse (ARFI) elastography to differentiate benign from malignant pancreatic lesions. ARFI elastography was performed in 26 patients who had 27 focal solid pancreatic lesions, including 8 benign lesions (mass-forming pancreatitis, 5; autoimmune pancreatitis, 3) and 19 malignant lesions (pancreatic adenocarcinoma, 16; metastasis from colorectal cancer, 2; malignant neuroendocrine tumor, 1). On the elastographic images of virtual touch tissue imaging (VTI), the echogenicity of the mass was categorized on a 5-grade scale. On the elastographic image of virtual touch tissue quantification (VTQ), the shear wave velocities (SWVs) of the lesion and surrounding parenchyma were measured. On the VTI images, the mean echogenicity score of the malignant lesions (3.7±1.0) was higher than that of the benign lesions (3.1±0.4; P=0.023). On the VTQ images, there were no statistical differences in the mean SWV between the benign (2.4±1.1 m/sec) and malignant (3.3±1.0 m/sec) lesions (P=0.101). However, the mean SWV difference values between the lesion and background parenchyma of the malignant lesions (1.5±0.8 m/sec) were higher than those of the benign lesions (0.4±0.3 m/sec; P=0.011). ARFI elastography can determine the relative stiffness between a lesion and the background pancreatic parenchyma using VTI and VTQ, which is helpful in the differentiation between benign and malignant solid pancreatic lesions.

  20. Acoustic radiation force impulse imaging for non-invasive assessment of renal histopathology in chronic kidney disease.

    Directory of Open Access Journals (Sweden)

    Qiao Hu

    Full Text Available OBJECTIVE: To investigate the stiffness values obtained by acoustic radiation force impulse (ARFI quantification in assessing renal histological fibrosis of chronic kidney disease (CKD. METHODS: 163 patients with CKD and 32 healthy volunteers were enrolled between June 2013 and April 2014. ARFI quantification, given as shear wave velocity (SWV, was performed to measure renal parenchyma stiffness. Diagnostic performance of ARFI imaging and conventional ultrasound (US were compared with histologic scores at renal biopsy. Intra- and inter-observer reliability of SWV measurement was analyzed. RESULTS: In CKD patients, SWV measurements correlated significantly with pathological parameters (r = -0.422--0.511, P<0.001, serum creatinine (r = -0.503, P<0.001, and glomerular filtration rate (r = 0.587, P<0.001. The mean SWV in kidneys with severely impaired (histologic score: ≥19 points was significant lower than that mildly impaired (histologic score: ≤9 points, moderately impaired (histologic score: 10-18 points, and control groups (all P<0.001. Receiver operating characteristic (ROC curves analyses indicated that the area under the ROC curve for the diagnosis of renal histological fibrosis using ARFI imaging was superior to these conventional US parameters. Using the optimal cut-off value of 2.65 m/s for the diagnosis of mildly impaired kidneys, 2.50 m/s for moderately impaired kidneys, and 2.33 m/s for severely impaired kidneys, the corresponding area under the ROC curves were 0.735, 0.744, and 0.895, respectively. Intra- and intre-observer agreement of SWV measurements were 0.709 (95% CI: 0.390-0.859, P<0.001 and 0.627 (95% CI: 0.233-0.818, P = 0.004, respectively. CONCLUSIONS: ARFI may be an effective tool for evaluating renal histological fibrosis in CKD patients.

  1. Acoustic Radiation Force Impulse Elastography for fibrosis evaluation in patients with chronic hepatitis C: An international multicenter study

    Energy Technology Data Exchange (ETDEWEB)

    Sporea, Ioan, E-mail: isporea@umft.ro [Department of Gastroenterology and Hepatology, University of Medicine and Pharmacy Timisoara (Romania); Bota, Simona, E-mail: bota_simona1982@yahoo.com [Department of Gastroenterology and Hepatology, University of Medicine and Pharmacy Timisoara (Romania); Peck-Radosavljevic, Markus, E-mail: markus.peck@meduniwien.ac.at [Internal Medicine III, Division of Gastroenterology and Hepatology, Medical University of Vienna (Austria); Sirli, Roxana, E-mail: roxanasirli@gmail.com [Department of Gastroenterology and Hepatology, University of Medicine and Pharmacy Timisoara (Romania); Tanaka, Hironori, E-mail: hironori@hyo-med.ac.jp [Department of Internal Medicine, Hyogo College of Medicine, Nishinomiya (Japan); Iijima, Hiroko, E-mail: hiroko.iijima@nifty.com [Department of Internal Medicine, Hyogo College of Medicine, Nishinomiya (Japan); Badea, Radu, E-mail: rbadea2003@yahoo.com [3rd Medical Clinic, University of Medicine, Cluj Napoca (Romania); Lupsor, Monica, E-mail: monica.lupsor@umfcluj.ro [3rd Medical Clinic, University of Medicine, Cluj Napoca (Romania); Fierbinteanu-Braticevici, Carmen, E-mail: cfierbinteanu@yahoo.com [2nd Medical Clinic and Gastroenterology, University Hospital, Bucharest (Romania); Petrisor, Ana, E-mail: ana1petrisor@yahoo.com [2nd Medical Clinic and Gastroenterology, University Hospital, Bucharest (Romania); Saito, Hidetsugu, E-mail: hidetsugusaito@gmail.com [Department of Internal Medicine, School of Medicine, Keio University, Tokyo (Japan); Ebinuma, Hirotoshi, E-mail: ebinuma@a5.keio.jp [Department of Internal Medicine, School of Medicine, Keio University, Tokyo (Japan); Friedrich-Rust, Mireen, E-mail: Mireen.Friedrich-Rust@kgu.de [Department of Internal Medicine, J.W. Goethe University, Frankfurt/Main (Germany); Sarrazin, Christoph, E-mail: sarrazin@em.uni-frankfurt.de [Department of Internal Medicine, J.W. Goethe University, Frankfurt/Main (Germany); and others

    2012-12-15

    Aim: The aim of this international multicenter study was to evaluate the reliability of Acoustic Radiation Force Impulse (ARFI) elastography for predicting fibrosis severity, in patients with chronic hepatitis C. Patients and methods: We compared ARFI to liver biopsy (LB) in 914 patients (10 centers, 5 countries) with chronic hepatitis C. In each patient LB (evaluated according to the METAVIR score) and ARFI measurements were performed (median of 5–10 valid measurements, expressed in meters/second – m/s). In 400 from the 914 patients, transient elastography (TE) was also performed (median of 6–10 valid measurements, expressed in kiloPascals – kPa). Results: Valid ARFI measurements were obtained in 911 (99.6%) of 914 cases. On LB 61 cases (6.7%) had F0, 241 (26.4%) had F1, 202 (22.1%) had F2, 187 (20.4%) had F3, and 223 (24.4%) had F4 fibrosis. A highly significant correlation (r = 0.654) was found between ARFI measurements and fibrosis (p < 0.0001). The predictive values of ARFI for various stages of fibrosis were: F ≥ 1 – cut-off > 1.19 m/s (AUROC = 0.779), F ≥ 2 – cut-off > 1.33 m/s (AUROC = 0.792), F ≥ 3 – cut-off > 1.43 m/s (AUROC = 0.829), F = 4 – cut-off > 1.55 m/s (AUROC = 0.842). The correlation with histological fibrosis was not significantly different for TE in comparison with ARFI elastography: r = 0.728 vs. 0.689, p = 0.28. TE was better than ARFI for predicting the presence of liver cirrhosis (p = 0.01) and fibrosis (F ≥ 1, METAVIR) (p = 0.01). Conclusion: ARFI elastography is a reliable method for predicting fibrosis severity in chronic hepatitis C patients.

  2. Quantitative shear wave optical coherence elastography (SW-OCE) with acoustic radiation force impulses (ARFI) induced by phase array transducer

    Science.gov (United States)

    Song, Shaozhen; Le, Nhan Minh; Wang, Ruikang K.; Huang, Zhihong

    2015-03-01

    Shear Wave Optical Coherence Elastography (SW-OCE) uses the speed of propagating shear waves to provide a quantitative measurement of localized shear modulus, making it a valuable technique for the elasticity characterization of tissues such as skin and ocular tissue. One of the main challenges in shear wave elastography is to induce a reliable source of shear wave; most of nowadays techniques use external vibrators which have several drawbacks such as limited wave propagation range and/or difficulties in non-invasive scans requiring precisions, accuracy. Thus, we propose linear phase array ultrasound transducer as a remote wave source, combined with the high-speed, 47,000-frame-per-second Shear-wave visualization provided by phase-sensitive OCT. In this study, we observed for the first time shear waves induced by a 128 element linear array ultrasound imaging transducer, while the ultrasound and OCT images (within the OCE detection range) were triggered simultaneously. Acoustic radiation force impulses are induced by emitting 10 MHz tone-bursts of sub-millisecond durations (between 50 μm - 100 μm). Ultrasound beam steering is achieved by programming appropriate phase delay, covering a lateral range of 10 mm and full OCT axial (depth) range in the imaging sample. Tissue-mimicking phantoms with agarose concentration of 0.5% and 1% was used in the SW-OCE measurements as the only imaging samples. The results show extensive improvements over the range of SW-OCE elasticity map; such improvements can also be seen over shear wave velocities in softer and stiffer phantoms, as well as determining the boundary of multiple inclusions with different stiffness. This approach opens up the feasibility to combine medical ultrasound imaging and SW-OCE for high-resolution localized quantitative measurement of tissue biomechanical property.

  3. Acoustic Force Density Acting on Inhomogeneous Fluids in Acoustic Fields

    DEFF Research Database (Denmark)

    Karlsen, Jonas Tobias; Augustsson, Per; Bruus, Henrik

    2016-01-01

    We present a theory for the acoustic force density acting on inhomogeneous fluids in acoustic fields on time scales that are slow compared to the acoustic oscillation period. The acoustic force density depends on gradients in the density and compressibility of the fluid. For microfluidic systems...

  4. Acoustic interaction forces between small particles in an ideal fluid

    CERN Document Server

    Silva, Glauber T

    2014-01-01

    We present a theoretical expression for the acoustic interaction force between small spherical particles suspended in an ideal fluid exposed to an external acoustic wave. The acoustic interaction force is the part of the acoustic radiation force on one given particle involving the scattered waves from the other particles. The particles, either compressible liquid droplets or elastic microspheres, are considered to be much smaller than the acoustic wavelength. In this so-called Rayleigh limit, the acoustic interaction forces between the particles are well approximated by gradients of pair-interaction potentials with no restriction on the inter-particle distance. The theory is applied to studies of the acoustic interaction force on a particle suspension in either standing or traveling plane waves. The results show aggregation regions along the wave propagation direction, while particles may attract or repel each other in the transverse direction. In addition, a mean-field approximation is developed to describe ...

  5. Acoustical and optical radiation pressure and the development of single beam acoustical tweezers

    Science.gov (United States)

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

    2017-07-01

    Studies on radiation pressure in acoustics and optics have enriched one another and have a long common history. Acoustic radiation pressure is used for metrology, levitation, particle trapping and actuation. However, the dexterity and selectivity of single-beam optical tweezers are still to be matched with acoustical devices. Optical tweezers can trap, move and position micron size particles, biological samples or even atoms with subnanometer accuracy in three dimensions. One limitation of optical tweezers is the weak force that can be applied without thermal damage due to optical absorption. Acoustical tweezers overcome this limitation since the radiation pressure scales as the field intensity divided by the speed of propagation of the wave. However, the feasibility of single beam acoustical tweezers was demonstrated only recently. In this paper, we propose a historical review of the strong similarities but also the specificities of acoustical and optical radiation pressures, from the expression of the force to the development of single-beam acoustical tweezers.

  6. Axial acoustic radiation force on rigid oblate and prolate spheroids in Bessel vortex beams of progressive, standing and quasi-standing waves.

    Science.gov (United States)

    Mitri, F G

    2017-02-01

    The analysis using the partial-wave series expansion (PWSE) method in spherical coordinates is extended to evaluate the acoustic radiation force experienced by rigid oblate and prolate spheroids centered on the axis of wave propagation of high-order Bessel vortex beams composed of progressive, standing and quasi-standing waves, respectively. A coupled system of linear equations is derived 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. The system of linear equations depends on the partial-wave index n and the order of the Bessel vortex beam m using truncated but converging PWSEs in the least-squares sense. Numerical results for the radiation force function, which is the radiation force per unit energy density and unit cross-sectional surface, are computed with particular emphasis on the amplitude ratio describing the transition from the progressive to the pure standing waves cases, the aspect ratio (i.e., the ratio of the major axis over the minor axis of the spheroid), the half-cone angle and order of the Bessel vortex beam, as well as the dimensionless size parameter. A generalized expression for the radiation force function is derived for cases encompassing the progressive, standing and quasi-standing waves of Bessel vortex beams. This expression can be reduced to other types of beams/waves such as the zeroth-order Bessel non-vortex beam or the infinite plane wave case by appropriate selection of the beam parameters. The results for progressive waves reveal a tractor beam behavior, characterized by the emergence of an attractive pulling force acting in opposite direction of wave propagation. Moreover, the transition to the quasi-standing and pure standing wave cases shows the acoustical tweezers behavior in dual-beam Bessel vortex beams. Applications in acoustic levitation, particle manipulation and acousto

  7. Axial acoustic radiation force on rigid oblate and prolate spheroids in Bessel vortex beams of progressive, standing and quasi-standing waves

    CERN Document Server

    Mitri, F G

    2016-01-01

    The analysis using the partial-wave series expansion (PWSE) method in spherical coordinates is extended to evaluate the acoustic radiation force experienced by rigid oblate and prolate spheroids centered on the axis of wave propagation of high-order Bessel vortex beams composed of progressive, standing and quasi-standing waves, respectively. A coupled system of linear equations is derived 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. The system of linear equations depends on the partial-wave index n and the order of the Bessel vortex beam m using truncated but converging PWSEs in the least-squares sense. Numerical results for the radiation force function, which is the radiation force per unit energy density and unit cross-sectional surface, are computed with particular emphasis on the amplitude ratio describing the transition from the progressive to the pure st...

  8. In vivo feasibility case study for evaluating abdominal aortic aneurysm tissue properties and rupture potential using acoustic radiation force impulse imaging.

    Science.gov (United States)

    Tierney, Aine P; Callanan, Anthony; McGloughlin, Timothy M

    2011-04-01

    An abdominal aortic aneurysm (AAA) is defined as a permanent and irreversible localized dilatation of the abdominal aorta. A reliable, non-invasive method to assess the wall mechanics of an aneurysm may provide additional information regarding their susceptibility to rupture. Acoustic radiation force impulse (ARFI) imaging is a phenomenon associated with the propagation of acoustic waves in attenuating media. This study was a preliminary evaluation to explore the feasibility of using ARFI imaging to examine an AAA in vivo. A previously diagnosed in vivo aneurysm case study was imaged to demonstrate the viability of excitation of the abdominal aorta using ARFI imaging. Ex vivo experiments were used to assess an artificially induced aneurysm to establish its development and whether ARFI was able to capture the mechanical changes during artificial aneurysm formation. A combination of in vivo and ex vivo results demonstrated a proposed hypothesis of estimation of the tissue's stiffness properties. The study details a method for non-invasive rupture potential prediction of AAAs using patient-specific moduli to generate a physiological stiffness rupture potential index (PSRPI) of the AAA. Clinical feasibility of ARFI imaging as an additional surgical tool to interrogate AAAs was verified and methods to utilize this data as a diagnostic tool was demonstrated with the PSRPI.

  9. Radiation-force-based estimation of acoustic attenuation using harmonic motion imaging (HMI) in phantoms and in vitro livers before and after HIFU ablation.

    Science.gov (United States)

    Chen, Jiangang; Hou, Gary Y; Marquet, Fabrice; Han, Yang; Camarena, Francisco; Konofagou, Elisa

    2015-10-07

    Acoustic attenuation represents the energy loss of the propagating wave through biological tissues and plays a significant role in both therapeutic and diagnostic ultrasound applications. Estimation of acoustic attenuation remains challenging but critical for tissue characterization. In this study, an attenuation estimation approach was developed using the radiation-force-based method of harmonic motion imaging (HMI). 2D tissue displacement maps were acquired by moving the transducer in a raster-scan format. A linear regression model was applied on the logarithm of the HMI displacements at different depths in order to estimate the acoustic attenuation. Commercially available phantoms with known attenuations (n = 5) and in vitro canine livers (n = 3) were tested, as well as HIFU lesions in in vitro canine livers (n = 5). Results demonstrated that attenuations obtained from the phantoms showed a good correlation (R² = 0.976) with the independently obtained values reported by the manufacturer with an estimation error (compared to the values independently measured) varying within the range of 15-35%. The estimated attenuation in the in vitro canine livers was equal to 0.32   ±   0.03 dB cm(-1) MHz(-1), which is in good agreement with the existing literature. The attenuation in HIFU lesions was found to be higher (0.58   ±   0.06 dB cm(-1) MHz(-1)) than that in normal tissues, also in agreement with the results from previous publications. Future potential applications of the proposed method include estimation of attenuation in pathological tissues before and after thermal ablation.

  10. Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

    Science.gov (United States)

    Ambroziński, Łukasz; Pelivanov, Ivan; Song, Shaozhen; Yoon, Soon Joon; Li, David; Gao, Liang; Shen, Tueng T.; Wang, Ruikang K.; O'Donnell, Matthew

    2016-07-01

    A non-contact method for efficient, non-invasive excitation of mechanical waves in soft media is proposed, in which we focus an ultrasound (US) signal through air onto the surface of a medium under study. The US wave reflected from the air/medium interface provides radiation force to the medium surface that launches a transient mechanical wave in the transverse (lateral) direction. The type of mechanical wave is determined by boundary conditions. To prove this concept, a home-made 1 MHz piezo-ceramic transducer with a matching layer to air sends a chirped US signal centered at 1 MHz to a 1.6 mm thick gelatin phantom mimicking soft biological tissue. A phase-sensitive (PhS)-optical coherence tomography system is used to track/image the mechanical wave. The reconstructed transient displacement of the mechanical wave in space and time demonstrates highly efficient generation, thus offering great promise for non-contact, non-invasive characterization of soft media, in general, and for elasticity measurements in delicate soft tissues and organs in bio-medicine, in particular.

  11. Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

    Energy Technology Data Exchange (ETDEWEB)

    Ambroziński, Łukasz [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); AGH University of Science and Technology, Krakow 30059 (Poland); Pelivanov, Ivan, E-mail: ivanp3@uw.edu [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Faculty of Physics, Moscow State University, Moscow 119991 (Russian Federation); Song, Shaozhen; Yoon, Soon Joon; Gao, Liang; O' Donnell, Matthew [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Li, David [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Department of Chemical Engineering, University of Washington Seattle, Washington 98195 (United States); Shen, Tueng T.; Wang, Ruikang K. [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Department of Ophthalmology, University of Washington, Seattle, Washington 98104 (United States)

    2016-07-25

    A non-contact method for efficient, non-invasive excitation of mechanical waves in soft media is proposed, in which we focus an ultrasound (US) signal through air onto the surface of a medium under study. The US wave reflected from the air/medium interface provides radiation force to the medium surface that launches a transient mechanical wave in the transverse (lateral) direction. The type of mechanical wave is determined by boundary conditions. To prove this concept, a home-made 1 MHz piezo-ceramic transducer with a matching layer to air sends a chirped US signal centered at 1 MHz to a 1.6 mm thick gelatin phantom mimicking soft biological tissue. A phase-sensitive (PhS)-optical coherence tomography system is used to track/image the mechanical wave. The reconstructed transient displacement of the mechanical wave in space and time demonstrates highly efficient generation, thus offering great promise for non-contact, non-invasive characterization of soft media, in general, and for elasticity measurements in delicate soft tissues and organs in bio-medicine, in particular.

  12. Photoacoustic radiation force on a microbubble

    Science.gov (United States)

    Erkol, Hakan; Aytac-Kipergil, Esra; Unlu, Mehmet Burcin

    2014-08-01

    We investigate the radiation force on a microbubble due to the photoacoustic wave which is generated by using a pulsed laser. In particular, we focus on the dependence of pulsed laser parameters on the radiation force. In order to do so, we first obtain a new and comprehensive analytical solution to the photoacoustic wave equation based on the Fourier transform for various absorption profiles. Then, we write an expression of the radiation force containing explicit laser parameters, pulse duration, and beamwidth of the laser. Furthermore, we calculate the primary radiation force acting on a microbubble. We show that laser parameters and the position of the microbubble relative to a photoacoustic source have a considerable effect on the primary radiation force. By means of recent developments in laser technologies that render tunability of pulse duration and repetition frequency possible, an adjustable radiation force can be applied to microbubbles. High spatial control of applied force is ensured on account of smaller focal spots achievable by focused optics. In this context, conventional piezoelectric acoustic source applications could be surpassed. In addition, it is possible to increase the radiation force by making source wavelength with the absorption peak of absorber concurrent. The application of photoacoustic radiation force can open a cache of opportunities such as manipulation of microbubbles used as contrast agents and as carrier vehicles for drugs and genes with a desired force along with in vivo applications.

  13. Force Measurements in Vibration and Acoustic Tests

    Science.gov (United States)

    Scharton, T. D.

    1996-01-01

    The advent of triaxial, piezoelectric force gages and the associated signal processing is a precursor to several dynamics testing innovations. This new technology is applicable to spacecraft programs that JPL manages. An application of force measurement is force limiting (when testing spacecraft in random vibration tests). Base-drive and acoustic modal testing is a potential application.

  14. Detection of non-alcoholic steatohepatitis in patients with morbid obesity before bariatric surgery: preliminary evaluation with acoustic radiation force impulse imaging

    Energy Technology Data Exchange (ETDEWEB)

    Guzman-Aroca, F.; Reus, M.; Dios Berna-Serna, Juan de [Virgen de la Arrixaca University Hospital, Department of of Radiology, El Palmar, Murcia (Spain); Frutos-Bernal, M.D.; Lujan-Mompean, J.A.; Parrilla, P. [Virgen de la Arrixaca University Hospital, Department of Surgery, El Palmar, Murcia (Spain); Bas, A. [Virgen de la Arrixaca University Hospital, Department of Pathology, El Palmar, Murcia (Spain)

    2012-11-15

    To investigate the utility of acoustic radiation force impulse (ARFI) imaging, with the determination of shear wave velocity (SWV), to differentiate non-alcoholic fatty liver disease (NAFLD) from non-alcoholic steatohepatitis (NASH) in patients with morbid obesity before bariatric surgery. Thirty-two patients with morbid obesity were evaluated with ARFI and conventional ultrasound before bariatric surgery. The ARFI and ultrasound results were compared with liver biopsy findings, which is the reference standard. The patients were classed according to their histological findings into three groups: group A, simple steatosis; group B, inflammation; and group C, fibrosis. The median SWV was 1.57 {+-} 0.79 m/s. Hepatic alterations were observed in the histopathological findings for all the patients in the study (100 %), with the results of the laboratory tests proving normal. Differences in SWV were also observed between groups A, B and C: 1.34 {+-} 0.90 m/s, 1.55 {+-} 0.79 m/s and 1.86 {+-} 0.75 m/s (P < 0.001), respectively. The Az for differentiating NAFLD from NASH or fibrosis was 0.899 (optimal cut-off value 1.3 m/s; sensitivity 85 %; specificity 83.3 %). The ARFI technique is a useful diagnostic tool for differentiating NAFLD from NASH in asymptomatic patients with morbid obesity. (orig.)

  15. A pilot study of the characterization of hepatic tissue strain in children with cystic-fibrosis-associated liver disease (CFLD) by acoustic radiation force impulse imaging

    Energy Technology Data Exchange (ETDEWEB)

    Behrens, Christopher B.; Langholz, Juliane H.; Eiler, Jessika; Jenewein, Raphael; Fuchs, Konstantin; Alzen, Gerhard F.P. [University Hospital Giessen, Department of Pediatric Radiology, Giessen (Germany); Naehrlich, Lutz [University Hospital Giessen, Department of Pediatrics, Giessen (Germany); Harth, Sebastian; Krombach, Gabriele A. [University Hospital Giessen, Department of Radiology, Giessen (Germany)

    2013-03-15

    Progressive fibrotic alterations of liver tissue represent a major complication in children with cystic fibrosis. Correct assessment of cystic-fibrosis-associated liver disease (CFLD) in clinical routine is a challenging issue. Sonographic elastography based on acoustic radiation force impulse imaging (ARFI) is a new noninvasive approach for quantitatively assessing in vivo elasticity of biological tissues in many organs. To characterize ARFI elastography as a diagnostic tool to assess alteration of liver tissue elasticity related to cystic fibrosis in children. ARFI elastography and B-mode US imaging were performed in 36 children with cystic fibrosis. The children's clinical history and laboratory parameters were documented. According to the findings on conventional US, children were assigned to distinct groups indicating severity of hepatic tissue alterations. The relationship between US findings and respective elastography values was assessed. Additionally, differences between ARFI elastography values of each US group were statistically tested. Children with sonomorphologic characteristics of fibrotic tissue remodeling presented significantly increased values for tissue elasticity. Children with normal B-mode US or discrete signs of hepatic tissue alterations showed a tendency toward increased tissue stiffness indicating early tissue remodeling. Assessment of children with CFLD by means of ARFI elastography yields adequate results when compared to conventional US. For detection of early stages of liver disease with mild fibrotic reactions of hepatic tissue, ARFI elastography might offer diagnostic advantages over conventional US. Thus, liver stiffness measured by means of elastography might represent a valuable biological parameter for evaluation and follow-up of CFLD. (orig.)

  16. The diagnostic performance of acoustic radiation force impulse elasticity imaging to differentiate malignant from benign thyroid nodules: Comparison with conventional B- mode sonographic findings

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Won Sang; An, Yeong Yi; Ihn, Yon Kwon; Park, Young Ha [Dept. of Radiology, St. Vincent' s Hospital, The Catholic University of Korea, Suwon (Korea, Republic of)

    2016-02-15

    The purpose of this study was to evaluate the diagnostic performance of acoustic radiation force impulse (ARFI) elasticity imaging. One hundred and twenty-seven thyroid nodules were examined by both ARFI elastography and B-mode sonography. Virtual Touch tissue quantification (VTQ) values of the thyroid nodules were measured. Scoring of B-mode sonographic findings of each thyroid nodules was performed. The sums of these VTQ and the B-mode scores were determined. The comparative diagnostic performances of the VTQ value, the B-mode score, and the combined score were analyzed. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of each scoring mode were: B-mode score, 84%, 85%, 66%, 94%, and 85%; VTQ, 75%, 91%, 73%, 92%, and 86%; and combined score, 88%, 87%, 70%, 95%, and 88%. The areas under the curves for B-mode, VTQ, and combined score were 0.895, 0.837, and 0.912, respectively. Pairwise comparisons of receiver-operating characteristic curves showed no statistical differences between B-mode and VTQ, and B-mode and combined score. Combined score showed better diagnostic performance than VTQ value (p = 0.0023). ARFI VTQ value is a good diagnostic modality for differentiating malignant thyroid nodules from benign nodules. However, ARFI evaluation is not superior to B-mode sonographic evaluation, but only has a better diagnostic performance when combined with B-mode sonographic findings.

  17. A high pulse repetition frequency ultrasound system for the ex vivo measurement of mechanical properties of crystalline lenses with laser-induced microbubbles interrogated by acoustic radiation force.

    Science.gov (United States)

    Yoon, Sangpil; Aglyamov, Salavat; Karpiouk, Andrei; Emelianov, Stanislav

    2012-08-07

    A high pulse repetition frequency ultrasound system for an ex vivo measurement of mechanical properties of an animal crystalline lens was developed and validated. We measured the bulk displacement of laser-induced microbubbles created at different positions within the lens using nanosecond laser pulses. An impulsive acoustic radiation force was applied to the microbubble, and spatio-temporal measurements of the microbubble displacement were assessed using a custom-made high pulse repetition frequency ultrasound system consisting of two 25 MHz focused ultrasound transducers. One of these transducers was used to emit a train of ultrasound pulses and another transducer was used to receive the ultrasound echoes reflected from the microbubble. The developed system was operating at 1 MHz pulse repetition frequency. Based on the measured motion of the microbubble, Young's moduli of surrounding tissue were reconstructed and the values were compared with those measured using the indentation test. Measured values of Young's moduli of four bovine lenses ranged from 2.6 ± 0.1 to 26 ± 1.4 kPa, and there was good agreement between the two methods. Therefore, our studies, utilizing the high pulse repetition frequency ultrasound system, suggest that the developed approach can be used to assess the mechanical properties of ex vivo crystalline lenses. Furthermore, the potential of the presented approach for in vivo measurements is discussed.

  18. Combined acoustic radiation force impulse, aminotransferase to platelet ratio index and Forns index assessment for hepatic fibrosis grading in hepatitis B

    Institute of Scientific and Technical Information of China (English)

    Chang-Feng; Dong; Jia; Xiao; Ling-Bo; Shan; Han-Ying; Li; Yong-Jia; Xiong; Gui-Lin; Yang; Jing; Liu; Si-Min; Yao; Sha-Xi; Li; Xiao-Hua; Le; Jing; Yuan; Bo-Ping; Zhou; George; L; Tipoe; Ying-Xia; Liu

    2016-01-01

    AIM: To investigate the combined diagnostic accuracy of acoustic radiation force impulse(ARFI), aspartate aminotransferase to platelet ratio index(APRI) and Forns index for a non-invasive assessment of liver fibrosis in patients with chronic hepatitis B(CHB). METHODS: In this prospective study, 206 patients had CHB with liver fibrosis stages F0-F4 classified by METAVIR and 40 were healthy volunteers were measured by ARFI, APRI and Forns index separately or combined as indicated. RESULTS: ARFI, APRI or Forns index demonstrated a significant correlation with the histological stage(all P < 0.001). According to the AUROC of ARFI and APRI for evaluating fibrotic stages more than F2, ARFI showed an enhanced diagnostic accuracy than APRI(P < 0.05). The combined measurement of ARFI and APRI exhibited better accuracy than ARFI alone when evaluating ≥ F2 fibrotic stage(Z = 2.77, P = 0.006). Combination of ARFI, APRI and Forns index did not obviously improve the diagnostic accuracy compared to the combination of ARFI and APRI(Z = 0.958, P = 0.338). CONCLUSION: ARFI + APRI showed enhanced diagnostic accuracy than ARFI or APRI alone for significant liver fibrosis and ARFI + APRI + Forns index shows the same effect with ARFI + APRI.

  19. Kidney shear wave speed values in subjects with and without renal pathology and inter-operator reproducibility of acoustic radiation force impulse elastography (ARFI--preliminary results.

    Directory of Open Access Journals (Sweden)

    Flaviu Bob

    Full Text Available to assess the inter-operator reproducibility of kidney shear wave speed, evaluated by means of Acoustic Radiation Force Impulse (ARFI elastography, and the factors which influence it.Our prospective pilot study included 107 subjects with or without kidney pathology in which kidney shear wave speed was evaluated by means of ARFI elastography. Intraclass correlation coefficient (ICC was used to assess ARFI elastography reproducibility.A strong agreement was obtained between kidney shear wave speed measurements obtained by the two operators: ICC = 0.71 (right kidney and 0.69 (left kidney. Smaller ICCs were obtained in "healthy subjects", as compared to patients with kidney diseases (0.68 vs. 0.75, in women as compared with men (0.59 vs. 0.78, in subjects younger than 50 years as compared with those aged at least 50 years (0.63 vs. 0.71, in obese as compared with normal weight and overweight subjects (0.36 vs. 0.66 and 0.78 and in case of measurements depth 6 cm as compared with those performed at a depth of 4-6 cm from the skin (0.32 and 0.60 vs. 0.81.ARFI elastography is a reproducible method for kidney shear wave speed assessment.

  20. Comparison of ultrasound B-mode, strain imaging, acoustic radiation force impulse displacement and shear wave velocity imaging using real time clinical breast images

    Science.gov (United States)

    Manickam, Kavitha; Machireddy, Ramasubba Reddy; Raghavan, Bagyam

    2016-04-01

    It has been observed that many pathological process increase the elastic modulus of soft tissue compared to normal. In order to image tissue stiffness using ultrasound, a mechanical compression is applied to tissues of interest and local tissue deformation is measured. Based on the mechanical excitation, ultrasound stiffness imaging methods are classified as compression or strain imaging which is based on external compression and Acoustic Radiation Force Impulse (ARFI) imaging which is based on force generated by focused ultrasound. When ultrasound is focused on tissue, shear wave is generated in lateral direction and shear wave velocity is proportional to stiffness of tissues. The work presented in this paper investigates strain elastography and ARFI imaging in clinical cancer diagnostics using real time patient data. Ultrasound B-mode imaging, strain imaging, ARFI displacement and ARFI shear wave velocity imaging were conducted on 50 patients (31 Benign and 23 malignant categories) using Siemens S2000 machine. True modulus contrast values were calculated from the measured shear wave velocities. For ultrasound B-mode, ARFI displacement imaging and strain imaging, observed image contrast and Contrast to Noise Ratio were calculated for benign and malignant cancers. Observed contrast values were compared based on the true modulus contrast values calculated from shear wave velocity imaging. In addition to that, student unpaired t-test was conducted for all the four techniques and box plots are presented. Results show that, strain imaging is better for malignant cancers whereas ARFI imaging is superior than strain imaging and B-mode for benign lesions representations.

  1. Coupling between plate vibration and acoustic radiation

    Science.gov (United States)

    Frendi, Abdelkader; Maestrello, Lucio; Bayliss, Alvin

    1993-01-01

    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.

  2. Factors associated with the impossibility to obtain reliable liver stiffness measurements by means of Acoustic Radiation Force Impulse (ARFI) elastography—Analysis of a cohort of 1031 subjects

    Energy Technology Data Exchange (ETDEWEB)

    Bota, Simona, E-mail: bota_simona1982@yahoo.com; Sporea, Ioan, E-mail: isporea@umft.ro; Sirli, Roxana, E-mail: roxanasirli@gmail.com; Popescu, Alina, E-mail: alinamircea.popescu@gmail.com; Danila, Mirela, E-mail: mireladanila@gmail.com; Jurchis, Ana, E-mail: ana.jurchis@yahoo.com; Gradinaru-Tascau, Oana, E-mail: bluonmyown@yahoo.com

    2014-02-15

    Introduction: Acoustic Radiation Force Impulse (ARFI) elastography is a non-invasive technique for liver fibrosis assessment. Aim: To assess the feasibility of ARFI elastography in a large cohort of subjects and to identify factors associated with impossibility to obtain reliable liver stiffness (LS) measurements by means of this technique. Methods: Our retrospective study included 1031 adult subjects with or without chronic liver disease. In each subject LS was assessed by means of ARFI elastography. Failure of ARFI measurements was defined if no valid measurement was obtained after at least 10 shots and unreliable in the following situations: fewer than 10 valid shots; or median value of 10 valid measurements with a success rate (SR) < 60% and/or an interquartile range interval (IQR) ≥ 30%. Results: Failure of LS measurements by means of ARFI was observed in 4 subjects (0.3%), unreliable measurements in 66 subjects (6.4%), so reliable measurements were obtained in 961 subjects (93.3%). In univariant analysis, the following risk factors were associated with failed and unreliable measurements: age over 58 years (OR = 0.49; 95% CI 0.30–0.80, p = 0.005), male gender (OR = 0.58; 95% CI 0.34–0.94, p = 0.04), BMI > 27.7 kg/m{sup 2} (OR = 0.23, 95% CI 0.13–0.41, p < 0.0001). In multivariate analysis all the factors mentioned above were independently associated with the risk of failed and unreliable measurements. Conclusions: Reliable LS measurements by means of ARFI elastography were obtained in 93.3% of cases. Older age, higher BMI and male gender were associated with the risk of failed and unreliable measurements, but their influence is limited as compared with Transient Elastography.

  3. Relationship between the estimated glomerular filtration rate and kidney shear wave speed values assessed by acoustic radiation force impulse elastography: a pilot study.

    Science.gov (United States)

    Bob, Flaviu; Bota, Simona; Sporea, Ioan; Sirli, Roxana; Popescu, Alina; Schiller, Adalbert

    2015-04-01

    The aim of the study was to establish the relationship between the estimated glomerular filtration rate (GFR) and kidney shear wave speed values assessed by acoustic radiation force impulse (ARFI) elastography. Our study included 104 patients with or without chronic kidney disease in which the kidney shear wave speed was evaluated by ARFI elastography and correlated with the estimated GFR. Five ARFI measurements were performed in the parenchyma of each kidney. A median value expressed as meters per second was calculated. Five valid ARFI elastographic measurements were obtained in the right kidney in all patients and in the left kidney in 97.1% of patients. The mean kidney shear wave speed values ± SD in the right and left kidneys were similar: 2.17 ± 0.81 versus 2.06 ± 0.75 m/s (P = .30). The mean kidney shear wave speed decreased with the decrease in the estimated GFR. Statistically significant differences were obtained only when kidney shear wave speed values obtained in patients with an estimated GFR of greater than 90 mL/min/1.73 m(2) were compared to values in patients with stage 4 (estimated GFR, 15-29 mL/min/1.73 m(2)) and stage 5 (estimated GFR, wave speed had 86.7% sensitivity, 48.3% specificity, a 22.1% positive predictive value, and a 95.6% negative predictive value (area under the receiver operating characteristic curve, 0.692; P = .008) for predicting the presence of an estimated GFR of less than 30 mL/min/1.73 m(2). Kidney shear wave speed values obtained by ARFI elastography decrease with the decrease in the estimated GFR. © 2015 by the American Institute of Ultrasound in Medicine.

  4. Research on modal analysis of structural acoustic radiation using structural vibration modes and acoustic radiation modes

    Institute of Scientific and Technical Information of China (English)

    LI Sheng; ZHAO Deyou

    2004-01-01

    Modal analysis of structural acoustic radiation from a vibrating structure is discussed using structural vibration modes and acoustic radiation modes based on the quadratic form of acoustic power. The finite element method is employed for discretisizing the structure.The boundary element method and Rayleigh integral are used for modeling the acoustic fluid.It is shown that the power radiated by a single vibration mode is to increase the radiated power and the effect of modal interaction can lead to an increase or a decrease or no change in the radiated power, moreover, control of vibration modes is a good way to reduce both vibration and radiated sound as long as the influence of interaction of vibration modes on sound radiation is insignificant. Stiffeners may change mode shapes of a plate and thus change radiation efficiency of the plate's modes. The CHIEF method is adopted to obtain an acoustic radiation mode formulation without the nonuniqueness difficulty at critical frequencies for three-dimensional structures by using Moore-Penrose inverse. A pulsating cube is involved to verify the formulation. Good agreement is obtained between the numerical and analytical solutions. The shapes and radiation efficiencies of acoustic radiation modes of the cube are discussed. The structural acoustic control using structural vibration modes and acoustic radiation modes are compared and studied.

  5. Generalized Faxén's theorem: Evaluating first-order (hydrodynamic drag) and second-order (acoustic radiation) forces on finite-sized rigid particles, bubbles and droplets in arbitrary complex flows

    Science.gov (United States)

    Annamalai, Subramanian; Balachandar, S.

    2016-11-01

    In recent times, study of complex disperse multiphase problems involving several million particles (e.g. volcanic eruptions, spray control etc.) is garnering momentum. The objective of this work is to present an accurate model (termed generalized Faxén's theorem) to predict the hydrodynamic forces on such inclusions (particles/bubbles/droplets) without having to solve for the details of flow around them. The model is developed using acoustic theory and the force obtained as a summation of infinite series (monopole, dipole and higher sources). The first-order force is the time-dependent hydrodynamic drag force arising from the dipole component due to interaction between the gas and the inclusion at the microscale level. The second-order force however is a time-averaged differential force (contributions arise both from monopole and dipole), also known as the acoustic radiation force primarily used to levitate particles. In this work, the monopole and dipole strengths are represented in terms of particle surface and volume averages of the incoming flow properties and therefore applicable to particle sizes of the order of fluid length scale and subjected to any arbitrary flow. Moreover, this model can also be used to account for inter-particle coupling due to neighboring particles. U.S. DoE, NNSA, Advanced Simulation and Computing Program, Cooperative Agreement under PSAAP-II, Contract No. DE-NA0002378.

  6. Vibration and Acoustic Radiation from Submerged Spherical Double-Shell

    Institute of Scientific and Technical Information of China (English)

    陈军明; 黄玉盈; 陈应波

    2003-01-01

    Based on the motion differential equations of vibration and acoustic coupling system for a thin elastic spherical double-shell with several elastic plates attached to the shells, in which Dirac-δ functions are employed to introduce the forces and moments applied by the attachments, and by means of expanding field quantities as the Legendre series, a semi-analytic solution is derived for the solution to the vibration and acoustic radiation from a submerged spherical double-shell. This solution has a satisfying computational effectiveness and precision for arbitrary frequency range excitation. It is concluded that the internal plates attached to shells can change significantly the mechanical and acoustical characteristics of shells, and make the coupling system have a very rich resonance frequency spectrum. Moreover, the present method can be used to study the acoustic radiation mechanism of the type of structure.

  7. Influence of different frequencies and insertion depths on the diagnostic accuracy of liver elastography by acoustic radiation force impulse imaging (ARFI)

    Energy Technology Data Exchange (ETDEWEB)

    Potthoff, Andrej, E-mail: potthoff.andrej@mh-hannover.de [Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover (Germany); Attia, Dina; Pischke, Sven; Kirschner, Janina; Mederacke, Ingmar; Wedemeyer, Heiner; Manns, Michael P.; Gebel, Michael J.; Rifai, Kinan [Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover (Germany)

    2013-08-15

    Background: Acoustic Radiation Force Impulse Imaging (ARFI) is an innovative elastography for staging of liver fibrosis. We evaluated the diagnostic accuracy of different probes to perform ARFI at different insertion depths. Methods: In a prospective study, 89 chronic HCV infected patients underwent ARFI elastography using both available probes (c-ARFI: C4-1-MHz; l-ARFI: L9-4 MHz) in comparison to Fibroscan{sup ®}. Variability of ARFI elastography at different insertion depths was systematically evaluated in 39 patients (44%). According to Fibroscan{sup ®} elastography, 32 patients (36%) presented with liver cirrhosis, 23 patients (26%) had significant fibrosis and 34 patients (38%) had no significant fibrosis. Results: Mean propagation velocity with c-ARFI was 1.70 ± 0.67 m/s and 1.91 ± 0.87 m/s with l-ARFI. Results of both probes were correlated to each other (p < 0.001; r = 0.70) and to Fibroscan{sup ®} (p < 0.001, r = 0.82 and 0.84, respectively). In patients with significant fibrosis or with cirrhosis, mean values by l-ARFI were significantly higher than by c-ARFI (p < 0.001). For detection of liver cirrhosis, AUROC was 0.97 for c-ARFI (cut-off level 1.72 m/s) and 0.90 for l-ARFI (cut-off 2.04 m/s). Correlation coefficients of c-ARFI with Fibroscan{sup ®} were highest at an insertion depth of 5–6 cm (r = 0.882 and 0.864, respectively, p < 0.001) and at 3–4 cm for l-ARFI (r = 0.850 and 0.838, respectively, p < 0.001). Conclusions: ARFI elastography with the linear and with the convex probes showed comparable validity and accuracy in the estimation of liver stiffness. The linear probe gave higher ARFI values. The most accurate insertion depth was 5–6 cm for c-ARFI and 3–4 cm for l-ARFI indicating that measurements should not be performed close to the liver capsule.

  8. B-mode and acoustic radiation force impulse (ARFI) imaging of prostate zonal anatomy: comparison with 3T T2-weighted MR imaging.

    Science.gov (United States)

    Palmeri, Mark L; Miller, Zachary A; Glass, Tyler J; Garcia-Reyes, Kirema; Gupta, Rajan T; Rosenzweig, Stephen J; Kauffman, Christopher; Polascik, Thomas J; Buck, Andrew; Kulbacki, Evan; Madden, John; Lipman, Samantha L; Rouze, Ned C; Nightingale, Kathryn R

    2015-01-01

    Prostate cancer (PCa) is the most common non-cutaneous malignancy among men in the United States and the second leading cause of cancer-related death. Multi-parametric magnetic resonance imaging (mpMRI) has gained recent popularity to characterize PCa. Acoustic Radiation Force Impulse (ARFI) imaging has the potential to aid PCa diagnosis and management by using tissue stiffness to evaluate prostate zonal anatomy and lesions. MR and B-mode/ARFI in vivo imaging datasets were compared with one another and with gross pathology measurements made immediately after radical prostatectomy. Images were manually segmented in 3D Slicer to delineate the central gland (CG) and prostate capsule, and 3D models were rendered to evaluate zonal anatomy dimensions and volumes. Both imaging modalities showed good correlation between estimated organ volume and gross pathologic weights. Ultrasound and MR total prostate volumes were well correlated (R(2) = 0.77), but B-mode images yielded prostate volumes that were larger (16.82% ± 22.45%) than MR images, due to overestimation of the lateral dimension (18.4% ± 13.9%), with less significant differences in the other dimensions (7.4% ± 17.6%, anterior-to-posterior, and -10.8% ± 13.9%, apex-to-base). ARFI and MR CG volumes were also well correlated (R(2) = 0.85). CG volume differences were attributed to ARFI underestimation of the apex-to-base axis (-28.8% ± 9.4%) and ARFI overestimation of the lateral dimension (21.5% ± 14.3%). B-mode/ARFI imaging yielded prostate volumes and dimensions that were well correlated with MR T2-weighted image (T2WI) estimates, with biases in the lateral dimension due to poor contrast caused by extraprostatic fat. B-mode combined with ARFI imaging is a promising low-cost, portable, real-time modality that can complement mpMRI for PCa diagnosis, treatment planning, and management. © The Author(s) 2014.

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

    DEFF Research Database (Denmark)

    Karlsen, Jonas Tobias; Bruus, Henrik

    2015-01-01

    -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...

  10. Acoustofluidics: Theory and simulation of streaming and radiation forces at ultrasound resonances in microfluidic devices

    DEFF Research Database (Denmark)

    Bruus, Henrik

    2009-01-01

    fields, which are directly related to the acoustic radiation force on single particles and to the acoustic streaming of the liquid. For the radiation pressure effects, there is good agreement between theory and simulation, while the numeric results for the acoustic streaming effects are more problematic...

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

    Energy Technology Data Exchange (ETDEWEB)

    Bassindale, P. G.; Drinkwater, B. W. [Faculty of Engineering, Queens building, University of Bristol, Bristol BS8 1TR (United Kingdom); Phillips, D. B. [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Barnes, A. C. [Department of Physics, H.H.Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom)

    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.

  12. Radiation-Force Assisted Targeting Facilitates Ultrasonic Molecular Imaging

    Directory of Open Access Journals (Sweden)

    Shukui Zhao

    2004-07-01

    Full Text Available Ultrasonic molecular imaging employs contrast agents, such as microbubbles, nanoparticles, or liposomes, coated with ligands specific for receptors expressed on cells at sites of angiogenesis, inflammation, or thrombus. Concentration of these highly echogenic contrast agents at a target site enhances the ultrasound signal received from that site, promoting ultrasonic detection and analysis of disease states. In this article, we show that acoustic radiation force can be used to displace targeted contrast agents to a vessel wall, greatly increasing the number of agents binding to available surface receptors. We provide a theoretical evaluation of the magnitude of acoustic radiation force and show that it is possible to displace micron-sized agents physiologically relevant distances. Following this, we show in a series of experiments that acoustic radiation force can enhance the binding of targeted agents: The number of biotinylated microbubbles adherent to a synthetic vessel coated with avidin increases as much as 20-fold when acoustic radiation force is applied; the adhesion of contrast agents targeted to αvβ3 expressed on human umbilical vein endothelial cells increases 27-fold within a mimetic vessel when radiation force is applied; and finally, the image signal-to-noise ratio in a phantom vessel increases up to 25 dB using a combination of radiation force and a targeted contrast agent, over use of a targeted contrast agent alone.

  13. Force approach to radiation reaction

    Energy Technology Data Exchange (ETDEWEB)

    López, Gustavo V., E-mail: gulopez@udgserv.cencar.udg.mx

    2016-02-15

    The difficulty of the usual approach to deal with the radiation reaction is pointed out, and under the condition that the radiation force must be a function of the external force and is zero whenever the external force be zero, a new and straightforward approach to radiation reaction force and damping is proposed. Starting from the Larmor formula for the power radiated by an accelerated charged particle, written in terms of the applied force instead of the acceleration, an expression for the radiation force is established in general, and applied to the examples for the linear and circular motion of a charged particle. This expression is quadratic in the magnitude of the applied force, inversely proportional to the speed of the charged particle, and directed opposite to the velocity vector. This force approach may contribute to the solution of the very old problem of incorporating the radiation reaction to the motion of the charged particles, and future experiments may tell us whether or not this approach point is in the right direction.

  14. Force approach to radiation reaction

    Science.gov (United States)

    López, Gustavo V.

    2016-02-01

    The difficulty of the usual approach to deal with the radiation reaction is pointed out, and under the condition that the radiation force must be a function of the external force and is zero whenever the external force be zero, a new and straightforward approach to radiation reaction force and damping is proposed. Starting from the Larmor formula for the power radiated by an accelerated charged particle, written in terms of the applied force instead of the acceleration, an expression for the radiation force is established in general, and applied to the examples for the linear and circular motion of a charged particle. This expression is quadratic in the magnitude of the applied force, inversely proportional to the speed of the charged particle, and directed opposite to the velocity vector. This force approach may contribute to the solution of the very old problem of incorporating the radiation reaction to the motion of the charged particles, and future experiments may tell us whether or not this approach point is in the right direction.

  15. Radiation directivity rotation by acoustic metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Xue; Liang, Bin, E-mail: liangbin@nju.edu.cn, E-mail: jccheng@nju.edu.cn; Zou, Xin-ye; Cheng, Jian-chun, E-mail: liangbin@nju.edu.cn, E-mail: jccheng@nju.edu.cn [Key Laboratory of Modern Acoustics, MOE, Department of Physics, Institute of Acoustics, Nanjing University, Nanjing 210093 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Zhang, Likun [Department of Physics and Center for Nonlinear Dynamics, University of Texas at Austin, Austin, Texas 78712 (United States)

    2015-08-31

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

  16. Acoustic Radiation Force Impulse Imaging in Diagnosing Nonalcoholic Fatty Liver Analysis%声辐射力脉冲成像技术对非酒精性单纯性脂肪肝的诊断价值分析

    Institute of Scientific and Technical Information of China (English)

    李玉丹

    2015-01-01

    目的 对声辐射力脉冲成像技术在非酒精性单纯性脂肪肝中的诊断价值进行研究. 方法 随机选取2013年11月-2014年11月该院诊治的100例非酒精性单纯性脂肪肝患者和30例健康体检者, 采用声辐射力脉冲成像技术对两组进行VTQ值检测. 结果 对照组VTQ测量值为(1.05±0.14)m/s,轻度患者为(1.02±0.06)m/s,中度患者为(1.56±0.67)m/s,重度患者为(0.82±0.06)m/s,肝脏剪切传播速度与ALT、AST具有较大相关性. 结论 声辐射力脉冲成像技术与传统超声相结合,能够定量评估非酒精性单纯性脂肪肝的分度,诊断价值较大.%Objective Diagnostic value of acoustic radiation force impulse imaging in nonalcoholic fatty liver were studied. Meth-ods Select November 2013-November 2014 100 cases nonalcoholic fatty liver patients and 30 healthy subjects, using acoustic ra-diation force impulse imaging technology to detect two groups VTQ value. Results In control group VTQ measured value (1.05 ± 0.14) m/s, mild patients (1.02 ± 0.06) m/s, moderate patients (1.56±0.67) m/s, with severe patients (0.82±0.06) m/s, the propagation velocity and shear liver ALT, AST have greater relevance. Conclusion The acoustic radiation force impulse imaging technology combined with traditional ultrasound, can be quantitatively evaluate indexing nonalcoholic fatty liver disease, diagnostics great value.

  17. A Treatise on Acoustic Radiation. Volume 1.

    Science.gov (United States)

    1981-01-01

    8217po ,,.a .- - - _~ ~ .~ ~ a* W W;, V~ ~v ~ ,d-vw ~ .- .. * . - " ,.• ,% A Treatise on Acoustic Radiation REFERENCES I. P. M. Morse, K. U. Ingard ...34Methods of Theoretical Physics", McGraw-Hill, 1953, p. 837. 5. L. L. Foldy, H. Primakoff, JASA. 17, 109-120 (1945). 6. P. M. Morse, K. V. Ingard ...Ref. (24), p. 17. 26. P. M. Morse, K. U. Ingard , "Theoretical Acoustics", McGraw-Hill (1969) p. 315. 27. L. D. Landau, E. M. Lifshitz, "Fluid

  18. 声辐射力脉冲成像鉴别诊断肾肿瘤%Acoustic radiation force impulse imaging in differential diagnosis of renal tumors

    Institute of Scientific and Technical Information of China (English)

    傅宁华; 杨斌; 魏淑萍; 雷丽; 朱世杰

    2013-01-01

    Objective To explore the value of acoustic radiation force impulse imaging (ARFI) in differential diagnosis of benign and malignant renal tumors, and to explore the correlation between the elasticity of tumors obtained with ARFI and blood perfusion obtained with CEUS. Methods Thirty-five patients with renal tumors confirmed with surgical operation or pathology underwent ARFI and CEUS. Shear wave velocity (SWV) of tumors were measured with virtual touch tissue quantification (VTQ), the cut-off point for SWV was obtained with ROC curve analysis, and the elasticity of tumors obtained with ARFI was compared with the blood perfusion obtained with CEUS. Results SWV of benign and malignant renal tumors was (2. 25±0. 33)m/s and (2. 72±0. 46)m/s (P<0. 05) , respectively. Taking the cut-off point of 2. 355 m/s for SWV in differential diagnosis of benign and malignant renal tumors, the sensitivity and specificity was 83. 30% and 72. 70% , respectively. SWV of renal tumors were higher than that of renal cortex in 22 (22/35, 62. 86%) patients, among which 19 tumors appeared hyper-enhancement and 3 appeared hypo-enhancement. SWV of renal tumors were lower than that of renal cortex in 13 (13/35, 37. 14%) patients, among which 5 tumors appeared hyper-enhancement and 8 appeared hypo-enhancement. Tumors with different elasticity had different enhancement, stiff tumors tended to appeared hyper-enhancement, and soft tumors tended to appeared hypo-enhancement (P<0. 05). Conclusion ARFI is helpful to the differential diagnosis of benign and malignant renal tumors. There is correlation between elasticity obtained with ARFI and blood perfusion obtained with CEUS in renal tumors.%目的 探讨声辐射力脉冲成像(ARFI)鉴别诊断肾良恶性肿瘤的价值,以及ARFI所示肿瘤硬度与CEUS反映的肿瘤灌注之间的关系.方法 对经手术或穿刺病理证实的35例肾肿瘤患者依次行ARFI及CEUS检查,运用声触诊组织量化(VTQ)技术测量肿瘤组织的剪切

  19. Acoustic interaction forces and torques acting on suspended spheres in an ideal fluid

    CERN Document Server

    Lopes, J Henrique; Silva, G T

    2014-01-01

    In this paper, the acoustic interaction forces and torques exerted by an arbitrary time-harmonic wave on a set of N spheres suspended in an inviscid fluid are theoretically analyzed. In so doing, we utilize the partial-wave expansion method to solve the related multiple scattering problem. The acoustic interaction force and torque are computed for a sphere using the farfield radiation force and torque formulas. To exemplify the method, we calculate the interaction forces exerted by an external traveling and standing plane wave on an arrangement of two and three olive-oil droplets in water. The droplets radii are comparable to the wavelength (i.e. Mie scattering regime). The results show that the radiation force may considerably deviates from that exerted solely by the external incident wave. In addition, we find that acoustic interaction torques arise on the droplets when a nonsymmetric effective incident wave interacts with the droplets.

  20. Acoustically Forced Coaxial Hydrogen / Liquid Oxygen Jet Flames

    Science.gov (United States)

    2016-05-15

    visualized for both reacting and nonreacting cases. The jet flame was studied unforced, without acoustics , and forced, with transverse acoustic waves in...liquid rocket injector flames react to acoustic waves . In this study, a representative coaxial gaseous hydrogen / liquid oxygen (LOX) jet flame is...hydrogen / liquid oxygen (LOX) jet flame is visualized for both reacting and nonreacting cases. The jet flame was studied unforced, without acoustics , and

  1. EVALUATION OF ACOUSTIC FORCES ON A PARTICLE IN AEROSOL MEDIUM

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S; Richard Dimenna, R

    2007-09-27

    The acoustic force exerted on a solid particle was evaluated to develop a fundamental understanding of the critical physical parameters or constraints affecting particle motion and capture in a collecting device. The application of an acoustic force to the collection of a range of submicron-to-micron particles in a highly turbulent airflow stream laden with solid particles was evaluated in the presence of other assisting and competing forces. This scoping estimate was based on the primary acoustic force acting directly on particles in a dilute aerosol system, neglecting secondary interparticle effects such as agglomeration of the sub-micron particles. A simplified analysis assuming a stable acoustic equilibrium with an infinite sound speed in the solid shows that for a solid-laden air flow in the presence of a standing wave, particles will move toward the nearest node. The results also show that the turbulent drag force on a 1-{micro}m particle resulting from eddy motion is dominant when compared with the electrostatic force or the ultrasonic acoustic force. At least 180 dB acoustic pressure level at 1 MHz is required for the acoustic force to be comparable to the electrostatic or turbulent drag forces in a high-speed air stream. It is noted that particle size and pressure amplitude are dominant parameters for the acoustic force. When acoustic pressure level becomes very large, the acoustic energy will heat up the surrounding air medium, which may cause air to expand. With an acoustic power of about 600 watts applied to a 2000-lpm air flow, the air temperature can increase by as much as 15 C at the exit of the collector.

  2. Aerosol absorption and radiative forcing

    Directory of Open Access Journals (Sweden)

    P. Stier

    2007-05-01

    Full Text Available We present a comprehensive examination of aerosol absorption with a focus on evaluating the sensitivity of the global distribution of aerosol absorption to key uncertainties in the process representation. For this purpose we extended the comprehensive aerosol-climate model ECHAM5-HAM by effective medium approximations for the calculation of aerosol effective refractive indices, updated black carbon refractive indices, new cloud radiative properties considering the effect of aerosol inclusions, as well as by modules for the calculation of long-wave aerosol radiative properties and instantaneous aerosol forcing. The evaluation of the simulated aerosol absorption optical depth with the AERONET sun-photometer network shows a good agreement in the large scale global patterns. On a regional basis it becomes evident that the update of the BC refractive indices to Bond and Bergstrom (2006 significantly improves the previous underestimation of the aerosol absorption optical depth. In the global annual-mean, absorption acts to reduce the short-wave anthropogenic aerosol top-of-atmosphere (TOA radiative forcing clear-sky from –0.79 to –0.53 W m−2 (33% and all-sky from –0.47 to –0.13 W m−2 (72%. Our results confirm that basic assumptions about the BC refractive index play a key role for aerosol absorption and radiative forcing. The effect of the usage of more accurate effective medium approximations is comparably small. We demonstrate that the diversity in the AeroCom land-surface albedo fields contributes to the uncertainty in the simulated anthropogenic aerosol radiative forcings: the usage of an upper versus lower bound of the AeroCom land albedos introduces a global annual-mean TOA forcing range of 0.19 W m−2 (36% clear-sky and of 0.12 W m−2 (92% all-sky. The consideration of black carbon inclusions on cloud radiative properties results in a small global annual-mean all-sky absorption of 0.05 W

  3. Acoustic Radiation from Transducer in Semi-infinite Fluid Medium

    Science.gov (United States)

    2016-06-07

    IIIII v 841087 121CilN ACOUSTIC RADIATION F~ TRANSDUCER IN SFMI-INFINITE FLUID MEDIUM Date: June 19, 1984 Prepared by: Jay ant S. Patel...1. REPORT DATE 19 JUN 1984 2. REPORT TYPE Technical Memo 3. DATES COVERED 19-06-1984 to 19-06-1984 4. TITLE AND SUBTITLE Acoustic Radiation ...Technical Menorandum TM No. 841087 ACOUSTIC RADIATION FROM TRANSOOCER IN SEMI-INFINITE FliJID MEDIUM Date: June 19, 1984 Prepared by: Jayant s. Patel

  4. Acoustofluidics: theory and simulation of radiation forces at ultrasound resonances in microfluidic devices

    DEFF Research Database (Denmark)

    Barnkob, Rune; Bruus, Henrik

    2009-01-01

    Theoretical analysis is combined with numerical simulations to optimize designs and functionalities of acoustofluidic devices, i.e. microfluidic devices in which ultrasound waves are used to anipulate biological particles. The resonance frequencies and corresponding modes of the acoustic fields...... the largest possible acoustic powers are obtained in the microfluidic system, the time-averaged acoustic radiation force on single particles is determined. Schemes for in situ calibration of this force are presented and discussed....

  5. Analysis of acoustic radiation mode in time domain

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The acoustic radiation mode of plane, whose radiating operator is constructed by Rayleigh integral, is investigated in the time domain and its physical meaning is given. The relationship between the acoustic radiation modes of time domain and frequency domain is discussed. It is verified that the acoustic radiation modes are the natural property of the radiator and they can be obtained by different methods. These time domain radiation modes, whose shapes are only dependent on the geometry size and shape of the radiator, can radiate sound power independently. Especially, the first time domain radiation mode accounts for most of the sound radiation. All these simplify the calculation and control of the structure-borne sound power. Based on these observations, the sound power radiated from the vibrating plate is estimated by the time domain radiation mode for verifying the proposed method. The influence factors on the estimating accuracy in different conditions are discussed.

  6. The acoustic force density acting on inhomogeneous fluids in acoustic fields

    CERN Document Server

    Karlsen, Jonas T; Bruus, Henrik

    2016-01-01

    We present a theory for the acoustic force density acting on inhomogeneous fluids in acoustic fields on time scales that are slow compared to the acoustic oscillation period. The acoustic force density depends on gradients in the density and compressibility of the fluid. For microfluidic systems, the theory predicts a relocation of the inhomogeneities into stable field-dependent configurations, which are qualitatively different from the horizontally layered configurations due to gravity. Experimental validation is obtained by confocal imaging of aqueous solutions in a glass-silicon microchip.

  7. Frequency adaptation for enhanced radiation force amplitude in dynamic elastography.

    Science.gov (United States)

    Ouared, Abderrahmane; Montagnon, Emmanuel; Kazemirad, Siavash; Gaboury, Louis; Robidoux, André; Cloutier, Guy

    2015-08-01

    In remote dynamic elastography, the amplitude of the generated displacement field is directly related to the amplitude of the radiation force. Therefore, displacement improvement for better tissue characterization requires the optimization of the radiation force amplitude by increasing the push duration and/or the excitation amplitude applied on the transducer. The main problem of these approaches is that the Food and Drug Administration (FDA) thresholds for medical applications and transducer limitations may be easily exceeded. In the present study, the effect of the frequency used for the generation of the radiation force on the amplitude of the displacement field was investigated. We found that amplitudes of displacements generated by adapted radiation force sequences were greater than those generated by standard nonadapted ones (i.e., single push acoustic radiation force impulse and supersonic shear imaging). Gains in magnitude were between 20 to 158% for in vitro measurements on agar-gelatin phantoms, and 170 to 336% for ex vivo measurements on a human breast sample, depending on focus depths and attenuations of tested samples. The signal-to-noise ratio was also improved more than 4-fold with adapted sequences. We conclude that frequency adaptation is a complementary technique that is efficient for the optimization of displacement amplitudes. This technique can be used safely to optimize the deposited local acoustic energy without increasing the risk of damaging tissues and transducer elements.

  8. Acoustic interaction forces between small particles in an ideal fluid

    DEFF Research Database (Denmark)

    Silva, Glauber T.; Bruus, Henrik

    2014-01-01

    from the other particles. The particles, either compressible liquid droplets or elastic microspheres, are considered to be much smaller than the acoustic wavelength. In this so-called Rayleigh limit, the acoustic interaction forces between the particles are well approximated by gradients of pair...

  9. MODAL ACOUSTIC IMPEDANCE FORCE ON A SPHERICAL SOURCE NEAR A RIGID INTERFACE

    Institute of Scientific and Technical Information of China (English)

    Seyyed M. HASHEMINEJAD

    2003-01-01

    The modal acoustic radiation load on a spherical surface undergoing angularly periodic axisymmetric harmonic vibrations while immersed in an acoustic halfspace with a rigid (infinite impedance) planar boundary is analyzed in an exact fashion using the classical technique of separation of variables. The formulation utilizes the appropriate wave field expansions, the classical method of images and the appropriate translational addition theorem to simulate the relevant boundary conditions for the given configuration. The associated acoustic field quantities such as the modal impedance matrix and the modal acoustic radiation force acting on the spherical surface are determined. The analytical results are illustrated with a numerical example in which the spherical surface, excited in vibrational modes of various orders, is immersed near an impervious rigid wall. The presented solution could eventually be used to validate those obtained by numerical approximation techniques.

  10. Factors Affecting Aerosol Radiative Forcing

    Science.gov (United States)

    Wang, Jingxu; Lin, Jintai; Ni, Ruijing

    2016-04-01

    Rapid industrial and economic growth has meant a large amount of aerosols in the atmosphere with strong radiative forcing (RF) upon the climate system. Over parts of the globe, the negative forcing of aerosols has overcompensated for the positive forcing of greenhouse gases. Aerosol RF is determined by emissions and various chemical-transport-radiative processes in the atmosphere, a multi-factor problem whose individual contributors have not been well quantified. In this study, we analyze the major factors affecting RF of secondary inorganic aerosols (SIOAs, including sulfate, nitrate and ammonium), primary organic aerosol (POA), and black carbon (BC). We analyze the RF of aerosols produced by 11 major regions across the globe, including but not limited to East Asia, Southeast Asia, South Asia, North America, and Western Europe. Factors analyzed include population size, per capita gross domestic production (GDP), emission intensity (i.e., emissions per unit GDP), chemical efficiency (i.e., mass per unit emissions) and radiative efficiency (i.e., RF per unit mass). We find that among the 11 regions, East Asia produces the largest emissions and aerosol RF, due to relatively high emission intensity and a tremendous population size. South Asia produce the second largest RF of SIOA and BC and the highest RF of POA, in part due to its highest chemical efficiency among all regions. Although Southeast Asia also has large emissions, its aerosol RF is alleviated by its lowest chemical efficiency. The chemical efficiency and radiative efficiency of BC produced by the Middle East-North Africa are the highest across the regions, whereas its RF is lowered by a small per capita GDP. Both North America and Western Europe have low emission intensity, compensating for the effects on RF of large population sizes and per capita GDP. There has been a momentum to transfer industries to Southeast Asia and South Asia, and such transition is expected to continue in the coming years. The

  11. Factors Affecting Aerosol Radiative Forcing

    Science.gov (United States)

    Wang, J.; Lin, J.; Ni, R.

    2016-12-01

    Rapid industrial and economic growth has meant large amount of aerosols in the atmosphere with strong radiative forcing (RF) upon the climate system. Over parts of the globe, the negative forcing of aerosols has overcompensated for the positive forcing of greenhouse gases. Aerosol RF is determined by emissions and various chemical-transport-radiative processes in the atmosphere, a multi-factor problem whose individual contributors have not been well quantified. In this study, we analyze the major factors affecting RF of secondary inorganic aerosols (SIOAs, including sulfate, nitrate and ammonium), primary organic aerosol (POA), and black carbon (BC). We analyze the RFof aerosols produced by 11 major regions across the globe, including but not limited to East Asia, Southeast Asia, South Asia, North America, and Western Europe. Factors analyzed include population size, per capita gross domestic production (GDP), emission intensity (i.e., emissionsper unit GDP), chemical efficiency (i.e., mass per unit emissions) and radiative efficiency (i.e., RF per unit mass). We find that among the 11 regions, East Asia produces the largest emissions and aerosol RF, due to relatively high emission intensity and a tremendous population size.South Asia produce the second largest RF of SIOA and BC and the highest RF of POA, in part due to its highest chemical efficiency among all regions. Although Southeast Asia also has large emissions,its aerosol RF is alleviated by its lowest chemical efficiency.The chemical efficiency and radiative efficiency of BC produced by the Middle East-North Africa are the highest across the regions, whereas its RF is loweredbyasmall per capita GDP.Both North America and Western Europe have low emission intensity, compensating for the effects on RF of large population sizes and per capita GDP. There has been a momentum to transfer industries to Southeast Asia and South Asia, and such transition is expected to continue in the coming years. The resulting

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

    CERN Document Server

    Karlsen, Jonas Tobias

    2015-01-01

    We present a theoretical analysis 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 medium. Our analysis places no restrictions on the length scales of the viscous and thermal boundary layer thicknesses $\\delta_\\mathrm{s}$ and $\\delta_\\mathrm{t}$ relative to the particle radius $a$, but it assumes the particle to be small in comparison to the acoustic wavelength $\\lambda$. This is the limit relevant to scattering of sound and ultrasound waves from 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 parti...

  13. Pattern-formation under acoustic driving forces

    Science.gov (United States)

    Valverde, Jose Manuel

    2015-07-01

    Chemical and metallurgical processes enhanced by high intensity acoustic waves, thermoacoustic engines and refrigerators, fuel rods in nuclear reactors, heat exchanger tubes, offshore and vibrating structures, solar thermal collectors, acoustic levitators, microfluidic devices, cycling, musical acoustics, blood flow through veins/arteries, hearing in the mammalian ear, carbon nanotube loudspeakers, etc. The evolution of a myriad of processes involving the oscillation of viscous fluids in the presence of solid boundaries is up to a certain extent influenced by acoustic streaming. In addition to the sound field, viscous energy dissipation at the fluid-solid boundary causes a time-independent fluid circulation, which can lead to a significant enhancement of heat, mass and momentum transfer at large oscillation amplitudes. A particularly relevant phenomenon that can be notably affected by acoustic streaming is the promotion of sound waves by temperature gradients or viceversa (thermoacoustics), which is at the basis of potentially efficient and environmental friendly engines and refrigerators that have attracted a renewed interest in the last years. In the present manuscript, historical developments and the underlying basic physics behind acoustic streaming and thermoacoustics are reviewed from an unifying perspective.

  14. Giant Magnetostrictive Material Loudspeaker System Acoustic Radiation Simulation

    Institute of Scientific and Technical Information of China (English)

    WANG Rui; ZHANG Yong-fa

    2008-01-01

    An infinite panel model of giant magnetostrictive material loudspeaker system (GMMLS) is proposed by making use of finite element method(FEM). Bending wave eigenfunction is introduced to describe the acoustic radiation condition of the panel. Far-field response in different conditions is calculated by changing the mass surface density. Conclusion is obtained by analyzing the curves simulated, that panel which has larger mass surface density can hardly generate far-field acoustic radiation for lower frequency, while the panel has smaller mass surface density generates far-field acoustic radiation for lower frequency evenly and stronger.

  15. Radiation and reflection acoustical fields of an annular phased array

    Institute of Scientific and Technical Information of China (English)

    LAI Puxiang; ZHANG Bixing; WANG Chenghao

    2007-01-01

    The characteristics of the radiation and reflection acoustical fields of an annular phased array are investigated. The effects of the element number, element radius, interelement spacing, centre frequency, focus position, and other parameters on the radiation acoustical field of the annular phased array is theoretically studied. In experiment, an annular transducer with 8 equal-area elements is designed and fabricated, and a series of experimental measurements are conducted. The radiation acoustical field and its reflection on a liquid-solid interface are theoretically and experimentally studied. The experimental result is in good agreement with the theoretical one.

  16. Radiation force on absorbing targets and power measurements of a high intensity focused ultrasound (HIFU) source

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Based on the analytic expressions for the radiated field of a circular concave piston given by Hasegawa et al.,an integral for calculation of the radiation force on a plane absorbing target in a spherically focused field is derived.A general relation between acoustic power P and normal radiation force Fn is obtained under the condition of kr 1.Numerical computation is carried out by using the symbolic computation program for practically focused sources and absorbing circular targets.The results show that,for a given source,there is a range of target positions where the radiation force is independent of the target’s position under the assumption that the contribution of the acoustic field behind the target to the radiation force can be neglected.The experiments are carried out and confirm that there is a range of target positions where the measured radiation force is basically independent of the target’s position even at high acoustic power (up to 700 W).It is believed that when the radiation force method is used to measure the acoustic power radiated from a focused source,the size of the target must be selected in such a way that no observable sound can be found in the region behind the target.

  17. The Radiation Magnetic Force (FmR)

    Science.gov (United States)

    Yousif, Mahmoud

    2017-01-01

    The detection of Circular Magnetic Field (CMF), associated with electrons movement, not incorporated in theoretical works; is introduced as elements of attraction and repulsion for magnetic force between two conductors carrying electric currents; it also created magnetic force between charged particles and magnetic field, or Lorentz force; CMF contain energy of Electromagnetic Radiation (EM-R); a relationship has been established between the magnetic part of the EM-R, and radiation force, showing the magnetic force as a frequency controlled entity, in which a Radiation Magnetic Force formula is derived, the force embedded EM-Wave, similar to Electromagnetic Radiation Energy given by Planck's formula; the force is accountable for electron removal from atom in the Photoelectric Effects, stabilizing orbital atoms, excitation and ionization atoms, initiating production of secondary EM-R in Compton Effect mechanism; the paper aimed at reviving the wave nature of EM-R, which could reflects in a better understanding of the microscopic-world.

  18. A New Sampling Method for Spleen Stiffness Measurement Based on Quantitative Acoustic Radiation Force Impulse Elastography for Noninvasive Assessment of Esophageal Varices in Newly Diagnosed HCV-Related Cirrhosis

    Directory of Open Access Journals (Sweden)

    Leonardo Rizzo

    2014-01-01

    Full Text Available In our study, we evaluated the feasibility of a new sampling method for splenic stiffness (SS measurement by Quantitative Acoustic Radiation Force Impulse Elastography (Virtual Touch Tissue Quantification (VTTQ.We measured SS in 54 patients with HCV-related cirrhosis of whom 28 with esophageal varices (EV, 27 with Chronic Hepatitis C (CHC F1–F3, and 63 healthy controls. VTTQ-SS was significantly higher among cirrhotic patients with EV (3.37 m/s in comparison with controls (2.19 m/s, P<0.001, CHC patients (2.37 m/s, P<0.001, and cirrhotic patients without EV (2.7 m/s, P<0.001. Moreover, VTTQ-SS was significantly higher among cirrhotic patients without EV in comparison with both controls (P<0.001 and CHC patients (P<0.01. The optimal VTTQ-SS cut-off value for predicting EV was 3.1 m/s (AUROC = 0.96, sensitivity 96.4%, specificity 88.5%, positive predictive value 90%, negative predictive value 96%, positive likelihood ratio 8.36, and negative likelihood ratio 0.04. In conclusion, VTTQ-SS is a promising noninvasive and reliable diagnostic tool to screen cirrhotic patients for EV and reduce the need for upper gastrointestinal endoscopy. By using our cut-off value of 3.1 m/s, we would avoid endoscopy in around 45% of cirrhotic subjects, with significant time and cost savings.

  19. Radiation Forces and Torques without Stress (Tensors)

    Science.gov (United States)

    Bohren, Craig F.

    2011-01-01

    To understand radiation forces and torques or to calculate them does not require invoking photon or electromagnetic field momentum transfer or stress tensors. According to continuum electromagnetic theory, forces and torques exerted by radiation are a consequence of electric and magnetic fields acting on charges and currents that the fields induce…

  20. Radiation Forces and Torques without Stress (Tensors)

    Science.gov (United States)

    Bohren, Craig F.

    2011-01-01

    To understand radiation forces and torques or to calculate them does not require invoking photon or electromagnetic field momentum transfer or stress tensors. According to continuum electromagnetic theory, forces and torques exerted by radiation are a consequence of electric and magnetic fields acting on charges and currents that the fields induce…

  1. Acoustic Interaction Forces and Torques Acting on Suspended Spheres in an Ideal Fluid.

    Science.gov (United States)

    Lopes, J Henrique; Azarpeyvand, Mahdi; Silva, Glauber T

    2016-01-01

    In this paper, the acoustic interaction forces and torques exerted by an arbitrary time-harmonic wave on a set of N objects suspended in an inviscid fluid are theoretically analyzed. We utilize the partial-wave expansion method with translational addition theorem and re-expansion of multipole series to solve the related multiple scattering problem. We show that the acoustic interaction force and torque can be obtained using the farfield radiation force and torque formulas. To exemplify the method, we calculate the interaction forces exerted by an external traveling and standing plane wave on an arrangement of two and three olive-oil droplets in water. The droplets' radii are comparable to the wavelength (i.e., Mie scattering regime). The results show that the acoustic interaction forces present an oscillatory spatial distribution which follows the pattern formed by interference between the external and rescattered waves. In addition, acoustic interaction torques arise on the absorbing droplets whenever a nonsymmetric wavefront is formed by the external and rescattered waves' interference.

  2. Acoustics forces on a solid sphere in focused sound fields and their use for acoustical traps

    DEFF Research Database (Denmark)

    Cutanda Henriquez, Vicente; Juhl, Peter Møller; Kristensen, Søren H.

    2009-01-01

    It is known that stationary sound fields can be used to levitate small objects in air; this phenomenon has potential applications in containerless processing of materials. Recently the use of acoustic forces have been considered for the manipulation of small samples, which offers several advantages...... as the medium for the propagation of the acoustic waves. The objective of the work to be presented has been to study the extent to which it is possible to use focused sound fields for the manipulation of a rigid sphere in air. The possibility of developing acoustical tweezers has been the main motivation...... of the work. A theoretical investigation based on the boundary element method (BEM) is first described, where the acoustical forces on a rigid sphere are analyzed. It is assumed that the focused sound field is generated by means of a piezoelectric transducer with a shape of a section of a sphere, which...

  3. Observation of a single-beam gradient force acoustical trap for elastic particles: acoustical tweezers

    CERN Document Server

    Baresch, Diego; Marchiano, Régis

    2016-01-01

    The ability to manipulate matter precisely is critical for the study and development of a large variety of systems. Optical tweezers are excellent tools to handle particles ranging in size from a few micrometers to hundreds of nanometers but become inefficient and damaging on larger objects. We demonstrate for the first reported time the trapping of elastic particles by the large gradient force of a single acoustical beam in three dimensions. We show that at equal power, acoustical forces overtake by 8 orders of magnitude that of optical ones on macroscopic objects. Acoustical tweezers can push, pull and accurately control both the position of the particle and the forces exerted under damage-free conditions. The large spectrum of frequencies covered by coherent ultrasonic sources will provide a wide variety of manipulation possibilities from macro- to microscopic length scales. We believe our observations improve the prospects for wider use of non-contact manipulation in biology, biophysics, microfluidics and...

  4. Analysis of acoustic radiation mode in time domain

    Institute of Scientific and Technical Information of China (English)

    WU WeiGuo

    2009-01-01

    The acoustic radiation mode of plane,whose radiating operator is constructed by Rayleigh integral,is Investigated in the time domain and its physical meaning is given.The relationship between the acoustic radiation modes of time domain end frequency domain is discussed.It is verified that the acoustic radiation modes are the natural property of the radiator and they can be obtained by different methods.These time domain radiation modes,whose shapes are only dependent on the geometry size and shape of the radiator,can radiate sound power independently.Especially,the first time domain radiation mode accounts for most of the sound radiation.All these simplify the calculation and control of the structure-borne sound power.Based on these observations,the sound power radiated from the vibrating plate is estimated by the time domain radiation mode for verifying the proposed method.The influence factors on the estimating accuracy in different conditions are discussed.

  5. Circuit Design of Surface Acoustic Wave Based Micro Force Sensor

    Directory of Open Access Journals (Sweden)

    Yuanyuan Li

    2014-01-01

    Full Text Available Pressure sensors are commonly used in industrial production and mechanical system. However, resistance strain, piezoresistive sensor, and ceramic capacitive pressure sensors possess limitations, especially in micro force measurement. A surface acoustic wave (SAW based micro force sensor is designed in this paper, which is based on the theories of wavelet transform, SAW detection, and pierce oscillator circuits. Using lithium niobate as the basal material, a mathematical model is established to analyze the frequency, and a peripheral circuit is designed to measure the micro force. The SAW based micro force sensor is tested to show the reasonable design of detection circuit and the stability of frequency and amplitude.

  6. Droplet actuation by surface acoustic waves: an interplay between acoustic streaming and radiation pressure

    Science.gov (United States)

    Brunet, Philippe; Baudoin, Michael; Matar, Olivier Bou; Zoueshtiagh, Farzam

    2010-11-01

    Surface acoustic waves (SAW) are known to be a versatile technique for the actuation of sessile drops. Droplet displacement, internal mixing or drop splitting, are amongst the elementary operations that SAW can achieve, which are useful on lab-on-chip microfluidics benches. On the purpose to understand the underlying physical mechanisms involved during these operations, we study experimentally the droplet dynamics varying different physical parameters. Here in particular, the influence of liquid viscosity and acoustic frequency is investigated: it is indeed predicted that both quantities should play a role in the acoustic-hydrodynamic coupling involved in the dynamics. The key point is to compare the relative magnitude of the attenuation length, i.e. the scale within which the acoustic wave decays in the fluid, and the size of the drop. This relative magnitude governs the relative importance of acoustic streaming and acoustic radiation pressure, which are both involved in the droplet dynamics.

  7. Changes in a coflowing jet structure caused by acoustic forcing

    Energy Technology Data Exchange (ETDEWEB)

    Cerecedo, Luis M.; Aisa, Luis; Garcia, Juan A.; Santolaya, Jose L. [Fluid Mechanics Department, University of Zaragoza, Zaragoza (Spain)

    2004-06-01

    In the present work, the changes in the basic turbulence field of an axisymmetric jet in a coflow when acoustic forcing is applied are investigated. The main objective is to discriminate between changes produced by the acoustic forcing and those produced by the presence of solid particles in a two-phase flow. Power spectra of the axial velocities, u(t), are analyzed to reinforce the idea of the existence of a natural frequency. Time-averaged data are used to characterize the basic flow. This basic flow is compared with the flow altered by the acoustic forcing. By smoothing the phase-averaged rms data (mean statistical curve), the general behavior of the instantaneous fluctuations are unveiled and compared with that of the natural (unforced) jet. In this way, it can be seen that rms values in the forced cases are higher than in the unforced ones, due to the contribution of the external forcing. However, once the coherent structures are extinguished, both forced and unforced jets show a similar trend. (orig.)

  8. Acoustic myography, electromyography and bite force in the masseter muscle.

    Science.gov (United States)

    Tortopidis, D; Lyons, M F; Baxendale, R H

    1998-12-01

    Acoustic myography (AMG) offers some advantages over electromyography (EMG) in certain circumstances, but the use of AMG on the jaw-closing muscles has not been fully tested. The purpose of this study was to examine the relationship between AMG, EMG and force in the masseter muscles of nine healthy male subjects. The AMG was recorded using a piezoelectric crystal microphone and the EMG was recorded simultaneously with surface electrodes. Force was recorded between the anterior teeth with a strain-gauge transducer. Analysis showed that Pearson's correlation coefficient was 0.913 for force/AMG and 0.973 for force/EMG in all subjects, indicating a linear relationship between force, AMG and EMG at the four different force levels tested (25-75% of maximum). It is apparent that AMG may be used as an accurate monitor of masseter muscle force production, although some care is required in the technique.

  9. Radiation damping forces and radiation from charged particles

    Science.gov (United States)

    Klepikov, N. P.

    1985-06-01

    In the present evaluation of reported results on the radiation reaction force to which a charged particle is subject, the expression obtained for this force by Lorentz (1909), Abraham (1904), and Dirac (1938) is noted to be in physically reasonable agreement with the radiation of energy, momentum and angular momentum; it has, moreover, been successfully used in investigations of the motion of particles in a field. A theory is presented for the losses of energy, momentum, and angular momentum by a system of charged particles as they move together, taking the external field, the radiation damping forces, and the retarded Lienard-Wiechert forces into account. Formulas are given for the spectral and angular distribution of the radiation from a system of particles, and a system of equations is constructed for finding the angular momenta of EM waves radiated by particles of the system.

  10. Prediction and Measurement of the Vibration and Acoustic Radiation of Panels Subjected to Acoustic Loading

    Science.gov (United States)

    Turner, Travis L.; Rizzi, Stephen A.

    1995-01-01

    Interior noise and sonic fatigue are important issues in the development and design of advanced subsonic and supersonic aircraft. Conventional aircraft typically employ passive treatments, such as constrained layer damping and acoustic absorption materials, to reduce the structural response and resulting acoustic levels in the aircraft interior. These techniques require significant addition of mass and only attenuate relatively high frequency noise transmitted through the fuselage. Although structural acoustic coupling is in general very important in the study of aircraft fuselage interior noise, analysis of noise transmission through a panel supported in an infinite rigid baffle (separating two semi-infinite acoustic domains) can be useful in evaluating the effects of active/adaptive materials, complex loading, etc. Recent work has been aimed at developing adaptive and/or active methods of controlling the structural acoustic response of panels to reduce the transmitted noise1. A finite element formulation was recently developed to study the dynamic response of shape memory alloy (SMA) hybrid composite panels (conventional composite panel with embedded SMA fibers) subject to combined acoustic and thermal loads2. Further analysis has been performed to predict the far-field acoustic radiation using the finite element dynamic panel response prediction3. The purpose of the present work is to validate the panel vibration and acoustic radiation prediction methods with baseline experimental results obtained from an isotropic panel, without the effect of SMA.

  11. Radiative screening of fifth forces

    CERN Document Server

    Burrage, Clare; Millington, Peter

    2016-01-01

    We describe a symmetron model in which the screening of fifth forces arises at the one-loop level through the Coleman-Weinberg mechanism of spontaneous symmetry breaking. We show that such a theory can avoid current constraints on the existence of fifth forces, but still has the potential to give rise to observable deviations from general relativity.

  12. Researches on active structural acoustic control by radiation modes

    Institute of Scientific and Technical Information of China (English)

    MAO Qibo; JIANG Zhe

    2001-01-01

    Based on the radiation modes, an active control strategy is presented for sound radiation from elastic structures with an example of simply supported rectangular panel. The physical characteristics and mathematical meaning of the radiation modes are analyzed. The radiation efficiency of radiation mode falls off very rapidly with the increase of modes order at low frequency. A new control strategy is developed in which by canceling the adjoint coefficient of the first k radiation modes, the sound powers of the first k radiation modes is zero theoretically. The numerical calculation is made by using point force actuators as control forces.

  13. METHODOLOGICAL NOTES: Radiation damping forces and radiation from charged particles

    Science.gov (United States)

    Klepikov, N. P.

    1985-06-01

    A review of the literature on the radiation reaction force on a charged particle shows that the expression given for this force obtained by Lorentz, Abraham, and Dirac is in physically reasonable agreement with the radiation of energy, momentum, and angular momentum, and is successfully used in investigating the motion of particles in a field. A selection of physical solutions by the methods presented herein guarantees that the conservation laws are satisfied. In the first approximation, which is the only one utilized in the majority of physical situations, radiation damping does not depend on assumptions concerning the structure of the charge of the particle. A theory is presented of the losses of energy, momentum and angular momentum by a system of charged particles in the course of their moving together taking into account the external field, the radiation damping forces, and the retarded Lienard-Wiechert forces. Formulas are given for the spectral and angular distribution of the radiation from a system of particles. The concept of a center of a system of events with relativistic particles is utilized in constructing a system of equations for finding the angular momenta of the electromagnetic waves radiated by particles of the system. The angular distribution and the total intensity of the radiation from a system of particles at an arbitrary instant of time is obtained. Using the example of the joint synchrotron radiation from two particles the consistency of all three approaches to the radiation from a system of particles is demonstrated.

  14. Introduction of acoustical diffraction in the radiative transfer method

    Science.gov (United States)

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

    2004-07-01

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

  15. An approximate method to acoustic radiation problems: element radiation superposition method

    Institute of Scientific and Technical Information of China (English)

    wANG Bin; TANG weilin; FAN Jun

    2008-01-01

    An approximate method is brought forward to predict the acoustic pressure based on the surface velocity.It is named Element Radiation Superposition Method(ERSM).The study finds that each element in Acoustic Transfer Vector(ATV)equals the acoustic pressure radiated by the corresponding surface element vibrating in unit velocity and other surface elements keep still.that is the acoustic pressure radiated by the corresponding baffled pistonvibrating in unit velocity.So,it utilizes the acoustic pressure radiated by a baffled piston to establish the transfer relationship between the surfaEe velocity and the acoustic pressure.The total acoustic pressure is obtained through summing up the products of the surface velocity and the transfer quantity.It adopts the regular baffle to fit the actual baffle in order to calculate the acoustic pressure radiated by the baffled piston.This approximate method has larger advantage in calculating speed and memory space than Boundary Element Method.Numerical simulations show that this approximate method is reasonable and feasible.

  16. Chromospheric heating by acoustic waves compared to radiative cooling

    CERN Document Server

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

    2016-01-01

    Acoustic and magnetoacoustic waves are among the possible candidate mechanisms that heat the upper layers of solar atmosphere. A weak chromospheric plage near a large solar pore NOAA 11005 was observed on October 15, 2008 in the lines Fe I 617.3 nm and Ca II 853.2 nm with the Interferometric Bidimemsional Spectrometer (IBIS) attached to the Dunn Solar Telescope. Analyzing the Ca II observations with spatial and temporal resolutions of 0.4" and 52 s, the energy deposited by acoustic waves is compared with that released by radiative losses. The deposited acoustic flux is estimated from power spectra of Doppler oscillations measured in the Ca II line core. The radiative losses are calculated using a grid of seven 1D hydrostatic semi-empirical model atmospheres. The comparison shows that the spatial correlation of maps of radiative losses and acoustic flux is 72 %. In quiet chromosphere, the contribution of acoustic energy flux to radiative losses is small, only of about 15 %. In active areas with photospheric ma...

  17. About Radiation Reaction with Force Approach

    CERN Document Server

    Velazquez, Gustavo Lopez

    2015-01-01

    The difficulty of usual approach to radiation reaction is pointed out , and a possible approach based on the force acting to the charged particle which produces the acceleration itself, is presented. This approach brings about an expression such that acceleration is zero whenever the external force is zero.

  18. VIBRATION AND ACOUSTIC RADIATION FROM SUBMERGED STIFFENED SPHERICAL SHELL WITH DECK-TYPE INTERNAL PLATE

    Institute of Scientific and Technical Information of China (English)

    ChenJnnming; HuangYuying

    2003-01-01

    Based on the motion differential equations of vibration and acoustic coupling system for thin elastic spherical shell with an elastic plate attached to its internal surface, in which Dirac-δ functions are employed to introduce the moments and forces applied by the attachment on the surface of shell, by means of expanding field quantities as Legendre series, a semi-analytic solution is derived for the vibration and acoustic radiation from a submerged stiffened spherical shell with a deck-type internal plate, which has a satisfactory computational effectiveness and precision for an arbitrary frequency range. It is easy to analyze the effect of the internal plate on the acoustic radiation field by using the formulas obtained by the method proposed. It is concluded that the internal plate can significantly change the mechanical and acoustic characteristics of shell, and give the coupling system a very rich resonance frequency spectrum. Moreover, the method can be used to study the acoustic radiation mechanism in similar structures as the one studied here.

  19. Radiation Reaction Force on a Particle

    OpenAIRE

    Fearn, H.; Bengtsson, J.

    2012-01-01

    The Abrahamn Lorentz radiation reaction force term, with da/dt, derived in text books is shown to be incomplete. We show that, with the addition of a term, the classical radiation reaction force can be generalized to the relativistic force expression. This addition is the Poynting Robertson term, seen mostly in astrophysics and usually missing from texts in electromagnetism. With this term added, it takes into account the rate of change of mass dm/dt of the particle and makes the generalizati...

  20. A modal analysis for the acoustic radiation problems,II.Examples

    Institute of Scientific and Technical Information of China (English)

    JIANG Zhe

    2004-01-01

    The acoustic radiation modes and the field distribution modes describe the radiation patterns of a complex vibrating surface and the field distribution patterns respectively.The physical meanings of the acoustic radiation modes and the field distribution modes are revealed by numerical method. For a sphere body, a spinning body and a rectangular body, the geometrical patterns of the acoustic radiation modes and the field distribution modes are given.The radiation mode 1 represents the radiation behavior of a monopole radiator, the radiation modes 2 through 4 represent the radiation behavior of dipole radiators respectively, and the radiation modes 5 through 9 represent the radiation behavior of quadrapole radiators respectively. The acoustic radiation modes and the field distribution modes introduce the multi-pole decomposition method into discussion of the acoustic radiation problems.

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

    Science.gov (United States)

    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.

  2. Radiation force and balance of electromagnetic momentum

    Science.gov (United States)

    Campos, I.; Jiménez, J. L.; Roa-Neri, J. A. E.

    2016-07-01

    Some force densities can be expressed as a divergence of a stress tensor, as is the case with the electromagnetic force density. We have shown elsewhere that from the Maxwell equations several balance equations of electromagnetic momentum can be derived, depending on the form these equations are expressed in terms of fields E, D, B, H, and polarisations P and M. These balance equations imply different force densities and different stress tensors, providing a great flexibility to solve particular problems. Among these force densities we have found some proposed in the past with plausibility arguments, like the Einstein-Laub force density, while other proposed force densities appear as particular or limit cases of these general force densities, like the Helmholtz force density. We calculate the radiation force of an electromagnetic wave incident on a semi-infinite negligibly absorbing material using these balance equations, corroborating in this way that the surface integration of the stress tensor gives the same result that the calculation made through a volume integration of the force density, as done by Bohren. As is usual in applications of Gauss’s theorem, the surface on which the surface integral is to be performed must be chosen judiciously, and due care of discontinuities on the boundary conditions must be taken. Advanced undergraduates and graduate students will find a different approach to new aspects of the interaction of radiation with matter.

  3. Low dose ionizing radiation induced acoustic neuroma: A putative link?

    Directory of Open Access Journals (Sweden)

    Sachin A Borkar

    2012-01-01

    Full Text Available Although exposure to high dose ionizing radiation (following therapeutic radiotherapy has been incriminated in the pathogenesis of many brain tumors, exposure to chronic low dose ionizing radiation has not yet been shown to be associated with tumorigenesis. The authors report a case of a 50-year-old atomic reactor scientist who received a cumulative dose of 78.9 mSv over a 10-year period and was detected to have an acoustic neuroma another 15 years later. Although there is no proof that exposure to ionizing radiation was the cause for the development of the acoustic neuroma, this case highlights the need for extended follow-up periods following exposure to low dose ionizing radiation.

  4. Receptivity and Forced Response to Acoustic Disturbances in High-Speed Boundary Layers

    Science.gov (United States)

    Balakumar, P.; King, Rudolph A.; Chou, Amanda; Owens, Lewis R.; Kegerise, Michael A.

    2016-01-01

    Supersonic boundary-layer receptivity to freestream acoustic disturbances is investigated by solving the Navier-Stokes equations for Mach 3.5 flow over a sharp flat plate and a 7-deg half-angle cone. The freestream disturbances are generated from a wavy wall placed at the nozzle wall. The freestream acoustic disturbances radiated by the wavy wall are obtained by solving the linearized Euler equations. The results for the flat plate show that instability modes are generated at all the incident angles ranging from zero to highly oblique. However, the receptivity coefficient decreases by about 20 times when the incident angle increases from zero to a highly oblique angle of 68 degrees. The results for the cone show that no instability modes are generated when the acoustic disturbances impinge the cone obliquely. The results show that the perturbations generated inside the boundary layer by the acoustic disturbances are the response of the boundary layer to the external forcing. The amplitude of the forced disturbances inside the boundary layer are about 2.5 times larger than the incoming field for zero azimuthal wavenumber and they are about 1.5 times for large azimuthal wavenumbers.

  5. Acoustic radiation- and streaming-induced microparticle velocities determined by micro-PIV in an ultrasound symmetry plane

    CERN Document Server

    Barnkob, Rune; Laurell, Thomas; Bruus, Henrik

    2012-01-01

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

  6. Anomaly Analysis of Hawking Radiation from Acoustic Black Hole

    CERN Document Server

    Kim, Wontae

    2007-01-01

    The Hawking radiation from the three dimensional rotating acoustic black hole is considered from the viewpoint of anomaly cancellation method initiated by Robinson and Wilczek. Quantum field near the horizon is effectively described by two dimensional charged field with a charge identified as the angular momentum m. The fluxes of charge and energy are obtained from the anomaly cancellation condition and regularity at the horizon, and are shown to match with those of the two dimensional black body radiation at the Hawking temperature.

  7. Tunable acoustic radiation pattern assisted by effective impedance boundary

    Science.gov (United States)

    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.

  8. Comparison of Acoustic Radiation Force Impulse (ARFI) Elastography Measurements with the 4C1 Transducer to the 6C1HD Transducer: A Phantom and Patient Study.

    Science.gov (United States)

    Pfeifer, L; Goertz, R S; Neurath, M F; Strobel, D; Wildner, D

    2016-10-01

    Purpose: The aim of this study was to evaluate whether acoustic radiation force impulse (ARFI) elastography done with the 4C1 probe yields comparable results to the recently introduced 6C1HD probe. Materials and Methods: Measurements with the 4C1 and 6C1HD probes (Acuson S2000) were performed and compared in four different inclusions of an elasticity phantom model (QA049 CIRS) as well as in the liver of healthy individuals and patients with liver cirrhosis. Results: Measurements with the 6C1HD probe were slightly higher in all phantom inclusions (8, 14, 45, 80kPA) with a mean of 1.48 m/s (95 %-CI; 1.47 - 1.49), 2.18 m/s (95 %-CI; 2.17 - 2.19), 3.61 m/s (95 %-CI; 3.57 - 3.64) and 4.34 m/s (95 %-CI; 4.29 - 4.39) compared to the 4C1 transducer with 1.46 m/s (95 %-CI; 1.45 - 1.47), 2.15 m/s (95 %-CI; 2.14 - 2.16), 3.39 m/s (95 %-CI; 3.37 - 3.41) and 3.98 m/s (95 %-CI; 3.75 - 4.21), respectively (p = 0.04, p transducer compared to 2.81 m/s (95 %-CI; 2.64 - 2.99) with the 4C1 transducer (p = 0.03). Healthy individuals (n = 20) had a mean shear wave speed of 1.12 m/s (95 %-CI; 1.06 - 1.17) with the 6C1HD probe and 1.12 m/s (95 %-CI; 1.05 - 1.19) with the 4C1 probe (p = 0.96). Conclusion: ARFI values assessed with a 6C1HD transducer are slightly higher than measurements with a 4C1 transducer in an ARFI phantom and in patients with liver cirrhosis. As the difference is small, current cut-off values keep their usefulness but should be interpreted with caution if measurements are close to the cut-off. © Georg Thieme Verlag KG Stuttgart · New York.

  9. Collective effects in the radiation pressure force

    CERN Document Server

    Bachelard, R; Guerin, W; Kaiser, R

    2016-01-01

    We discuss the role of diffuse, Mie and cooperative scattering on the radiation pressure force acting on the center of mass of a cloud of cold atoms. Even though a mean-field Ansatz (the `timed Dicke state'), previously derived from a cooperative scattering approach, has been shown to agree satisfactorily with experiments, diffuse scattering also describes very well most features of the radiation pressure force on large atomic clouds. We compare in detail an incoherent, random walk model for photons and a diffraction approach to the more complete description based on coherently coupled dipoles. We show that a cooperative scattering approach, although it provides a quite complete description of the scattering process, is not necessary to explain the previous experiments on the radiation pressure force.

  10. Structural and acoustic responses of a submarine hull due to propeller forces

    Science.gov (United States)

    Merz, Sascha; Kinns, Roger; Kessissoglou, Nicole

    2009-08-01

    The low frequency structural and acoustic responses of a simplified axisymmetric submarine model to fluctuating propeller forces along the submarine axis are investigated. The forces arise from a hydrodynamic mechanism and are transmitted from the propeller to the submarine hull through both the shaft and the fluid. Numerical models have been developed to simulate the strongly coupled structure-fluid interaction of a submerged vessel in the frequency domain. The structure is modelled using the finite element method, so that more complex features such as ring-stiffeners, bulkheads and the propulsion system can be taken into account. A simple, passive vibration attenuation system known as a resonance changer is included in the model of the propeller/shafting system. The surrounding fluid is modelled using the boundary element method. The influence and importance of model parameters such as structural stiffness and fluid loading effects are investigated. Due to the fluctuating propeller forces, the hull is excited by axial structural forces transmitted through the propeller/shafting system as well as by acoustic dipoles, where the dipoles are correlated to the structural forces in strength and direction. The acoustic dipole at the propeller also radiates sound directly to the far field of the surrounding fluid. It is demonstrated that the performance of the RC is negatively influenced at frequencies above the fundamental axial resonance of the hull by the effect of forces transmitted through the fluid. Another problem arises due to increased axial movement of the propeller, when the RC is optimised to minimise excitation of the hull via the propeller shaft. This results in an additional sound field that excites the submarine hull in a similar manner to the fluid forces that arise directly from the hydrodynamic mechanism.

  11. Modulation of synchrotron radiation by acoustic oscillations

    CERN Document Server

    Mkrtchyan, A R; Kocharyan, L A; Mirzoyan, V K

    1986-01-01

    By means of a quartz single crystal excited by piezoelectric oscillations, the modulation of synchrotron radiation reflected from the quartz planes (1011) is realized for frequencies ranging from 1 Hz to 15 kHz when the Bragg condition is satisfied. The wavelength of synchrotron radiation ranged from 0.3 to 12A. The patterns of modulated beams taken from oscillograph and analyzer screens are shown.

  12. Physics of Acoustic Radiation from Jet Engine Inlets

    Science.gov (United States)

    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.

  13. Applications of Lorentz force in medical acoustics: Lorentz force hydrophone, Lorentz Force Electrical Impedance Tomography, Imaging of shear waves induced by Lorentz force

    CERN Document Server

    Grasland-Mongrain, Pol

    2014-01-01

    The ability of the Lorentz force to link a mechanical displacement to an electrical current presents a strong interest for medical acoustics, and three applications were studied in this thesis. In the first part of this work, a hydrophone was developed for mapping the particle velocity of an acoustic field. This hydrophone was constructed using a thin copper wire and an external magnetic field. A model was elaborated to determine the relationship between the acoustic pressure and the measured electrical current, which is induced by Lorentz force when the wire vibrates in the acoustic field of an ultrasound transducer. The built prototype was characterized and its spatial resolution, frequency response, sensitivity, robustness and directivity response were investigated. An imaging method called Lorentz Force Electrical Impedance Tomography was also studied. In this method, a biological tissue is vibrated by ultrasound in a magnetic field, which induces an electrical current by Lorentz force. The electrical imp...

  14. Interferometric correlator for acoustic radiation and underlying structural vibration

    Science.gov (United States)

    Apostol, Adela; Kilpatrick, James; Markov, Vladimir; Bendiksen, Oddvar O.

    2016-12-01

    In this paper we discuss the background and principles of an optical non-contact sensor fusion concept, the Interferometric Correlator for Acoustic Radiation and Underlying Structural Vibration (ICARUSV) and give practical example of its capabilities, focusing on its ability to simultaneously capture, visualize and quantitatively characterize full-field non-stationary structural dynamics and unsteady radiated sound fields or transient flow fields around the structure of interest. The ICARUSV's multi-sensor design is based on a parallel architecture and therefore the data capture is fast and inherently support a wide variety of spatio-temporal or spatio-spectral analysis methods which characterize the structural or acoustic/flow field dynamics as it occurs in real time, including short-lived transient events. No other technology available today offers this level of multi-parameter multi-dimensional data1.

  15. GUP assisted Hawking radiation of rotating acoustic black holes

    Science.gov (United States)

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

    2016-10-01

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

  16. GUP Assisted Hawking Radiation of Rotating Acoustic Black Holes

    CERN Document Server

    Sakalli, I; Jusufi, K

    2016-01-01

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

  17. 螺旋桨激振力传递模式下的艇体振动和声辐射分析%Analysis of vibration and acoustic radiation of submarines under transfer modes of propeller excitation force

    Institute of Scientific and Technical Information of China (English)

    武星宇; 纪刚; 周其斗; 黄振卫

    2016-01-01

    潜艇的艇体结构是潜艇螺旋桨激振力向外辐射噪声的重要通道,而轴系是螺旋桨激振力传递到艇体的必经之路,因此有必要研究潜艇轴系向艇体传递的激振力对潜艇艇体振动和辐射声功率的影响。为此,分别针对螺旋桨轴向激振力、螺旋桨侧向激振力和螺旋桨垂向激振力工况,使用模式分析的方法,将轴系对艇体的作用力分解为互不相关的力传递模式的叠加。建立潜艇结构有限元模型,采用结构有限元耦合流体边界元的附加质量附加阻尼算法,分析单阶力传递模式作用于艇体时艇体的振动和声辐射特性。所做的研究可为分析螺旋桨激振力作用下的艇体振动和声辐射提供一种新的方法。%The hull system is an important path for radiating propeller noise. Propeller excitation must be transmitted by the thrust to the hull system. As such,the study of the relations between force transmission and the vibration and sound power of submarines is very important. To this end,this paper aims at propel⁃ler excitation force,lateral excitation force and vertical excitation force. The transmission modes of the force loaded by the thrust system are analyzed,and the combined fluid-structure interaction,vibration and sound power of the finite element model of the submarine are analyzed. This provides a new method for analyzing the vibration and radiation of submarines under propeller excitation force.

  18. Diagnostic value of acoustic radiation force impulse imaging in breast tumor%声脉冲辐射力成像对乳腺肿瘤的诊断价值

    Institute of Scientific and Technical Information of China (English)

    张杰; 隋秀芳; 王磊; 叶磊; 崔亚云

    2016-01-01

    目的:评价声脉冲辐射力成像(ARFI)技术对乳腺良恶性病变的鉴别诊断价值。方法选取84例患者共87个肿块进行常规超声、声触诊组织成像(VTI)及声触诊组织量化(VTQ)检查,得出剪切波速度值,并运用image J软件对VTI图像进行后处理得出肿块的平均光密度值,以病理结果为金标准,绘制受试者工作特征(ROC)曲线,评价ARFI的意义。结果经手术病理证实,87个乳腺肿块中良性病灶56个、恶性病灶31个。恶性病灶V T Q≥3.49 m/s (临界值)的病灶数为21个,<3.49 m/s为10个。良性病灶V T Q≥3.49 m/s病灶数为3个,<3.49 m/s为53个。恶性病灶平均光密度值大于或等于202.25(临界值)的病灶数为28个,<202.25为3个。良性病变平均光密度值大于或等于202.25的病灶数6个,<202.25为50个。乳腺良恶性病灶VTQ剪切波速度及VTI平均光密度值比较,差异均有统计学意义(P=0.000)。关于乳腺肿瘤的诊断灵敏度、特异度、阳性预测值、阴性预测值、准确率及约登指数,常规超声分别为96.8%、67.8%、62.5%、97.4%、78.2%、0.645;ARFI分别为93.5%、98.2%、96.7%、96.5%、96.6%、0.917。结论 ARFI成像对乳腺肿瘤诊断的特异度、准确率优于常规超声。%Objective To evaluate the differentiation diagnostic value of acoustic radiation force impulse imaging (ARFI) technique to the benign and malignant breast lesions .Methods A total of 87 breast masses in 84 patients were selected and per‐formed the routine ultrasound ,virtual touch imaging(VTI) and virtual touch quantification(VTQ) examination .The shear wave ve‐locity was obtained .The average optical density of the tumor was obtained by processing the VTI images by using the image J soft‐ware .The pathological results served as the gold standard and the ROC curve was drawn .Finally

  19. Acoustic Radiation Force Impulse Imaging for the Assessment of Renal Histopathology in Chronic Glomerulonephritis%声脉冲辐射力弹性成像评价慢性肾小球肾炎的病理特征

    Institute of Scientific and Technical Information of China (English)

    胡巧; 王小燕; 康利克; 韦海明; 贺红光; 贺琰

    2015-01-01

    Purpose To observe the change of renal parenchyma elasticity in patients with chronic glomerulonephritis (CGN), and to explore the value of acoustic radiation force impulse (ARFI) in the assessment of renal histological damages in CGN. Materials and Methods 123 patients with CGN and 27 healthy volunteers were enrolled, CGN patients were divided into three groups according to renal histologic scores: mildly, moderately, and severely impaired. Shear wave velocities (SWV) of the renal parenchyma were measured and compared in different groups, the correlation between the SWV measurements and renal fibrosis Katafuchi scores, serum creatinine (Scr) and estimated glomerular filtration rate (e-GFR) was accessed, and receiver operating characteristic (ROC) curves analyses were also performed to assess the value of ARFI for the diagnosis of pathology impairment degree in CGN. Results There were statistically significant differences in SWV measurements between each CGN patient group and the control group (F=16.592, P<0.01); the mean SWV in patients with severe kidney impairment was significant lower than that of mildly impaired, moderately impaired, and the control groups (P<0.001). SWV measurements correlated significantly with renal fibrosis Katafuchi scores (r=-0.481, P<0.01), Scr (r=-0.441, P<0.01), and e-GFR (r=0.546, P<0.01); ROC analyses indicated that the sensitivity was 63.4%, 71.4%, 93.8%, specificity was 77.8%, 71.3%, 79.9%, and the area under the curve was 0.730, 0.738 and 0.870, when using the optimal cut-off value of 2.65 m/s for the diagnosis of mildly impaired kidneys, 2.50 m/s for moderately impaired kidneys, and 2.34 m/s for severely impaired kidneys, respectively. Conclusion ARFI is expected to become an effective tool for non-invasive evaluating of renal histological fibrosis in CGN patients.%目的:应用声脉冲辐射弹性成像(ARFI)观察慢性肾小球肾炎(CGN)患者肾实质弹性变化,探讨 ARFI 评价 CGN 病理损

  20. Acoustic design sensitivity analysis of structural sound radiation

    Institute of Scientific and Technical Information of China (English)

    许智生

    2009-01-01

    This paper presents an acoustic design sensitivity(ADS)analysis on sound radiation of structures by using the boundary element method(BEM).We calculated the velocity distribution of the thin plate by analytical method and the surface sound pressure by Rayleigh integral,and expressed the sound radiation power of the structure in a positive definite quadratic form of the Hermitian with an impedance matrix.The ADS analysis of the plate was thus translated into the analysis of structure dynamic sensitivity and ...

  1. Radiation force on a spherical object in the field of a focused cylindrical transducer.

    Science.gov (United States)

    Chen, X; Apfel, R E

    1997-05-01

    An exact solution of the radiation force on a spherical object, when positioned on the acoustic axis of a cylindrical transducer, is provided. The solution is valid for any type of sphere of any size. The radiation force function allows the calibration of high-frequency focused ultrasound fields from radiation force measurements and expands the utility of the elastic sphere radiometer developed by Dunn et al. [Acustica 38, 58-61 (1977)]. Numeral results reveal an oscillatory behavior of the radiation force function for small spheres near the transducer surface and this behavior may present an opportunity for particle sorting based on the mechanical properties of the particle and other types of manipulation.

  2. Response to acoustic forcing of laminar coflow jet diffusion flames

    KAUST Repository

    Chrystie, Robin

    2014-04-23

    Toward the goal of understanding and controlling instability in combustion systems, we present a fundamental characterization of the interaction of the buoyancy-induced instability in flickering flames with forced excitation of fuel supply. Laminar coflow diffusion flames were acoustically forced, whose frequency responses were recorded as a function of excitation frequency and amplitude. The evolving structure of such flames was also examined through the use of video analysis and particle imaging velocimetry (PIV). For specific combinations of excitation frequency and amplitude, the frequency response of the flames was found to couple to that of the forcing, where the contribution of natural puffing frequency disappears. Such instances of coupling exhibited many harmonics of the excitation frequency, related indirectly to the natural puffing frequency. We showed how such harmonics form, through application of PIV, and furthermore unveiled insight into the physics of how the flame couples to the forcing under certain conditions. Our frequency response characterization provides quantitative results, which are of utility for both modeling studies and active-control strategies. Copyright © Taylor & Francis Group, LLC.

  3. A theoretical approach to room acoustic simulations based on a radiative transfer model

    DEFF Research Database (Denmark)

    Ruiz-Navarro, Juan-Miguel; Jacobsen, Finn; Escolano, José

    2010-01-01

    A theoretical approach to room acoustic simulations based on a radiative transfer model is developed by adapting the classical radiative transfer theory from optics to acoustics. The proposed acoustic radiative transfer model expands classical geometrical room acoustic modeling algorithms...... by incorporating a propagation medium that absorbs and scatters radiation, handling both diffuse and non-diffuse reflections on boundaries and objects in the room. The main scope of this model is to provide a proper foundation for a wide number of room acoustic simulation models, in order to establish and unify...... their principles. It is shown that this room acoustic modeling technique establishes the basis of two recently proposed algorithms, the acoustic diffusion equation and the room acoustic rendering equation. Both methods are derived in detail using an analytical approximation and a simplified integral equation...

  4. A novel prediction method of vibration and acoustic radiation for rectangular plate with particle dampers

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Dongqiang; Wu, Chengjun [Xi' an Jiaotong University, Xi' an (China)

    2016-03-15

    Particle damping technology is widely used in mechanical and structural systems or civil engineering to reduce vibration and suppress noise as a result of its high efficiency, simplicity and easy implementation, low cost, and energy-saving characteristic without the need for any auxiliary power equipment. Research on particle damping theory has focused on the vibration response of the particle damping structure, but the acoustic radiation of the particle damping structure is rarely investigated. Therefore, a feasible modeling method to predict the vibration response and acoustic radiation of the particle damping structure is desirable to satisfy the actual requirements in industrial practice. In this paper, a novel simulation method based on multiphase flow theory of gas particle by COMSOL multiphysics is developed to study the vibration and acoustic radiation characteristics of a cantilever rectangular plate with Particle dampers (PDs). The frequency response functions and scattered far-field sound pressure level of the plate without and with PDs under forced vibration are predicted, and the predictions agree well with the experimental results. Results demonstrate that the added PDs have a significant effect on vibration damping and noise reduction for the primary structure. The presented work in this paper shows that the theoretical work is valid, which can provide important theoretical guidance for low-noise optimization design of particle damping structure. This model also has an important reference value for the noise control of this kind of structure.

  5. The relationship between acoustic radiation modes and structural modes and its applications

    Institute of Scientific and Technical Information of China (English)

    LI Shuang; CHEN Ke'an

    2007-01-01

    Both acoustic radiation modes and structural modes play an important role in the field of structure-borne sound, however, little work has been done for inherent relations between these two kinds of modes. This paper is focused on the relationship between the radiation modes and structural modes and its physical mechanisms. First, a governing equation for relating the radiation mode and structural mode is given based on the characteristics of the modes. Then, using the symmetric or anti-symmetric properties of two kinds of modes, the corresponding relations are presented. And then, numerical examples are given to verify the theoretical investigations, and it has been shown that, for a simply supported rectangular panel vibrating at low frequencies, the first radiation mode is dominant corresponding to (odd, odd)structural modes; the following radiation modes are respectively dominant corresponding to (even, odd), (odd, even), and (even, even) structural modes. Finally, such relations are applied to active acoustic structural control and provide a direct help for the design of active control strategy and arrangement of the secondary forces.

  6. Acoustic Imaging Frequency Dynamics of Ferroelectric Domains by Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    ZHAO Kun-Yu; Shunji Takekawa; Kenji Kitamura; ZENG Hua-Rong; SONG Hong-Zhang; HUI Sen-Xing; LI Guo-Rong; YIN Qing-Rui; Kiyoshi Shimamura; Chinna Venkadasamy Kannan; Encarnacion Antonia Garcia Villora

    2008-01-01

    We report the acoustic imaging frequency dynamics of ferroelectric domains by low-frequency acoustic probe microscopy based on the commercial atomic force microscopy. It is found that ferroelectric domain could be firstly visualized at lower frequency down to 0.h kHz by AFM-based acoustic microscopy. The frequency-dependent acoustic signal revealed a strong acoustic response in the frequency range from 7 kHz to lO kHz, and reached maximum at 8.1 kHz. The acoustic contrast mechanism can be ascribed to the different elastic response of ferroelectric microstructures to local elastic stress fields, which is induced by the acoustic wave transmitting in the sample when the piezoelectric transducer is vibrating and exciting acoustic wave under ac electric fields due to normal piezoelectric effects.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  9. Acoustic radiation field of the truncated parametric source generated by a piston radiator model and experiment

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xiaoliang; ZHU Zhemin; DU Gonghuan; TANG Haiqing; LI Shui; MIAO Rongxing

    2001-01-01

    A theoretical model is presented to describe the parametric acoustic field generated by a piston radiator. In the model, the high-frequency primary wave interaction region that is truncated by a low-pass acoustic filter can be viewed as a cylindrical source within the Rayleigh distance of the piston. When the radius of the piston is much smaller than the length of the parametric region, this model is reduced to the Berketey's End-Fire Line Array model. Comparison between numerical calculations and experimental measurement show that the generated parametric sound field (especially near the axis) agrees well with the experiment results.

  10. Actuation of atomic force microscopy microcantilevers using contact acoustic nonlinearities

    Energy Technology Data Exchange (ETDEWEB)

    Torello, D.; Degertekin, F. Levent, E-mail: levent.degertekin@me.gatech.edu [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

    2013-11-15

    A new method of actuating atomic force microscopy (AFM) cantilevers is proposed in which a high frequency (>5 MHz) wave modulated by a lower frequency (∼300 kHz) wave passes through a contact acoustic nonlinearity at the contact interface between the actuator and the cantilever chip. The nonlinearity converts the high frequency, modulated signal to a low frequency drive signal suitable for actuation of tapping-mode AFM probes. The higher harmonic content of this signal is filtered out mechanically by the cantilever transfer function, providing for clean output. A custom probe holder was designed and constructed using rapid prototyping technologies and off-the-shelf components and was interfaced with an Asylum Research MFP-3D AFM, which was then used to evaluate the performance characteristics with respect to standard hardware and linear actuation techniques. Using a carrier frequency of 14.19 MHz, it was observed that the cantilever output was cleaner with this actuation technique and added no significant noise to the system. This setup, without any optimization, was determined to have an actuation bandwidth on the order of 10 MHz, suitable for high speed imaging applications. Using this method, an image was taken that demonstrates the viability of the technique and is compared favorably to images taken with a standard AFM setup.

  11. Sensitivity of aerosol radiative forcing calculations to spectral resolution

    Energy Technology Data Exchange (ETDEWEB)

    Grant, K.E.

    1996-10-01

    Potential impacts of aerosol radiative forcing on climate have generated considerable recent interest. An important consideration in estimating the forcing from various aerosol components is the spectral resolution used for the solar radiative transfer calculations. This paper examines the spectral resolution required from the viewpoint of overlapping spectrally varying aerosol properties with other cross sections. A diagnostic is developed for comparing different band choices, and the impact of these choices on the radiative forcing calculated for typical sulfate and biomass aerosols was investigated.

  12. Minimizing the acoustic power radiated by a fluid-loaded curved panel excited by turbulent boundary layer flow.

    Science.gov (United States)

    Shepherd, Micah R; Hambric, Stephen A

    2014-11-01

    In order to address noise control problems in the design stage, structural-acoustic optimization procedures can be used to find the optimal design for reduced noise or vibration. However, most structural-acoustic optimization procedures are not general enough to include both heavy fluid loading and complex forcing functions. Additionally, it can be difficult to determine and assess trade-offs between weight and sound radiation. A structural-acoustic optimization approach is presented for minimizing the radiated power of structures with heavy fluid loading excited by complex forcing functions. The procedure is demonstrated on a curved underwater panel excited by a point drive and by turbulent boundary layer flow. To facilitate more efficient analysis, an uncorrelated pressure assumption is made for the turbulent boundary layer forcing function. The thicknesses of groups of elements were used as the design variables with an adaptive covariance matrix evolutionary strategy as the search algorithm. The objective function was a weighted sum of total sound power and panel mass and the Pareto front was computed to show the optimum trade-off between the two objectives. The optimal designs are presented which illustrate the best methods for reducing radiated sound and mass simultaneously.

  13. Strong enhancement of dispersion forces from microwave radiation

    Science.gov (United States)

    Sernelius, B. E.

    2002-11-01

    We have studied non-thermal effects of microwave radiation on the forces between objects. This is the first step in a study of possible effects of microwave radiation from cellular phones on biological tissue. We have used a simplified model for human blood cells in blood. We find for the normal radiation level of cellular phones an enhancement of the attractive force with ten orders of magnitude as compared to the corresponding effect at thermal radiation.

  14. Structural acoustics model of the violin radiativity profile.

    Science.gov (United States)

    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.

  15. Analysis of spherical thermo-acoustic radiation in gas

    Directory of Open Access Journals (Sweden)

    Hanping Hu

    2012-09-01

    Full Text Available A general solution of the spherical thermo-acoustic (TA radiation from any solid in gas is derived by using a fully thermally-mechanically coupled TA model. Therefore, the characteristics and regularities of spherical TA emission can be studied more completely. It is shown that flat amplitude-frequency response, the most important feature for planar TA emission from technical standpoint, still exists for spherical TA emission, and changes with the radius of a sphere, thickness of TA sample, and the distance from surface. This expression agrees well with experimental and theoretical results of planer TA emission for much larger sphere and lays the foundation to calculate complex TA emission problems.

  16. Acoustic dose and acoustic dose-rate.

    Science.gov (United States)

    Duck, Francis

    2009-10-01

    Acoustic dose is defined as the energy deposited by absorption of an acoustic wave per unit mass of the medium supporting the wave. Expressions for acoustic dose and acoustic dose-rate are given for plane-wave conditions, including temporal and frequency dependencies of energy deposition. The relationship between the acoustic dose-rate and the resulting temperature increase is explored, as is the relationship between acoustic dose-rate and radiation force. Energy transfer from the wave to the medium by means of acoustic cavitation is considered, and an approach is proposed in principle that could allow cavitation to be included within the proposed definitions of acoustic dose and acoustic dose-rate.

  17. Analyzing excitation forces acting on a plate based on measured acoustic pressure.

    Science.gov (United States)

    Wu, Sean F; Zhou, Pan

    2016-07-01

    This paper presents a theoretical study on "seeing" through an elastic structure to uncover the root cause of sound and vibration by using nearfield acoustical holography (NAH) and normal modes expansion. This approach is of generality because vibro-acoustic responses on the surface of a vibrating structure can always be reconstructed, exactly or approximately. With these vibro-acoustic responses, excitation forces acting on the structure can always be determined, analytically or numerically, given any set of boundary conditions. As an example, the explicit formulations for reconstructing time-harmonic excitation forces, including point, line and surface forces, and their arbitrary combinations acting on a rectangular thin plate in vacuum mounted on an infinite baffle are presented. The reason for choosing this example is that the analytic solutions to vibro-acoustic responses are available, and in-depth analyses of results are possible. Results demonstrate that this approach allows one to identify excitation forces based on measured acoustic pressures and reveal their characteristics such as locations, types and amplitudes, as if one could "see" excitation forces acting behind the plate based on acoustic pressure measured on the opposite side. This approach is extendable to general elastic structures, except that in such circumstance numerical results must be sought.

  18. Force-Depending Radiation Reaction study in an undulator devise

    CERN Document Server

    López, Gustavo V

    2016-01-01

    The effect of force-depending radiation reaction on charge motion traveling inside an undulator is studied using the new force approach for radiation reaction. The effect on the dynamics of a charged particle is determined with the hope that this one can be measured experimentally and can be determined whether or not this approach points on the right direction to understand the nature of radiation reaction.

  19. A modal analysis for the acoustic radiation problems,I.Theory

    Institute of Scientific and Technical Information of China (English)

    JIANG Zhe

    2004-01-01

    For the acoustic radiation problems from a complex vibrating body surface, a modal analysis approach is put forward. All the normal vibration velocities on a vibrating surface form the Hilbert space. In the Hilbert space, an operator is defined, which includes the radiation property of the vibrating surface and is linear, self-adjoint and positive. Using the operator, a set of basis functions in the Hilbert space are obtained, which describe the radiation patterns and are called the radiation modes. Based on the radiation modes, a set of basis functions of the radiation field are obtained by the Helmholtz simple layer potentials,which describe the distribution patterns of the radiation field and are called the field distribution modes. The radiation behavior can be expressed by expansions of the radiation modes and the field distribution modes. The modal analysis approach is introduced into the acoustic radiation problems.

  20. Vibration and Acoustic Radiation from Orthogonally Stiffened Infinite Circular Cylindrical Shells in Water

    Institute of Scientific and Technical Information of China (English)

    陈军明; 黄玉盈; 曾革委

    2002-01-01

    Based on the motion differential equations of vibration and acoustic coupling system for thin elastic shells with ribs,by means of the Fourier integral transformation and the Fourier inverse transformation, as well as the stationary phasemethod, an analytic solution, which has satisfying computational effectiveness and precision, is derived for the solution tothe vibration and acoustic radiation from a submerged stiffened infinite circular cylinder with both ring and axial ribs. It iseasy to analyze the effect of stiffening supports in the acoustic radiation field by use of the formulas obtainod by the pre-sented method and corresponding numerical computation. It is shown that the axial-stiffeners can improve the mechanicaland acoustical characteristics. Moreover, the present method can be used to study the acoustic radiation mechanism of thetype of structure.

  1. Total aerosol effect: forcing or radiative flux perturbation?

    Energy Technology Data Exchange (ETDEWEB)

    Lohmann, Ulrike; Storelvmo, Trude; Jones, Andy; Rotstayn, Leon; Menon, Surabi; Quaas, Johannes; Ekman, Annica; Koch, Dorothy; Ruedy, Reto

    2009-09-25

    Uncertainties in aerosol forcings, especially those associated with clouds, contribute to a large extent to uncertainties in the total anthropogenic forcing. The interaction of aerosols with clouds and radiation introduces feedbacks which can affect the rate of rain formation. Traditionally these feedbacks were not included in estimates of total aerosol forcing. Here we argue that they should be included because these feedbacks act quickly compared with the time scale of global warming. We show that for different forcing agents (aerosols and greenhouse gases) the radiative forcings as traditionally defined agree rather well with estimates from a method, here referred to as radiative flux perturbations (RFP), that takes these fast feedbacks and interactions into account. Thus we propose replacing the direct and indirect aerosol forcing in the IPCC forcing chart with RFP estimates. This implies that it is better to evaluate the total anthropogenic aerosol effect as a whole.

  2. ACOUSTIC RADIATION ENERGY AT A VARIATION OF THE COMPOSITE MECHANICAL DESTRUCTION AREA

    Directory of Open Access Journals (Sweden)

    Sergii Filonenko

    2016-06-01

    Full Text Available Purpose: The technological parameters of composite materials machining and also cutting tool state determine deforming and destruction of their surface layers conditions. Change of this conditions results to appearance of miscellaneous defects, loss of quality and produced items reliability. Therefore, optimization, control, diagnosis and monitoring of composite materials machining technological parameters are directed on obtaining the items given quality. For the solution of these problems tasks carry out researches of technological processes with usage of different methods. One of such methods is the acoustic emission method. Methods: The simulation and analysis of acoustic radiation energy parameters is carried out at change of composite material machining depth for prevailing mechanical destruction its surface layer. Results: We showed that to composite material machining the acoustic radiation energy has continuous nature. The ascending of composite material machining depth results to increase of acoustic emission statistical energy parameters. The regularity of acoustic emission energy parameters change are obtained and described. Is showed, that acoustic radiation most sensing parameter is the acoustic emission signals energy average level dispersion. Discussion: The outcomes researches demonstrate regularity influencing of composite material machining depth on acoustic emission energy parameters. Thus the analysis of acoustic emission signals energy average level dispersion can be used at mining methods of diagnostic, monitoring and control of composite materials machining technological parameters.

  3. Experimental validation of a boundary element solver for exterior acoustic radiation problems

    OpenAIRE

    Visser, Rene; Nilsson, A; Boden, H.

    2003-01-01

    The relation between harmonic structural vibrations and the corresponding acoustic radiation is given by the Helmholtz integral equation (HIE). To solve this integral equation a new solver (BEMSYS) based on the boundary element method (BEM) has been implemented. This numerical tool can be used for both sound radiation and nearfield acoustic source localization purposes. After validation of the solver with analytic solutions of simple test problems, a well-defined experimental setup has been d...

  4. Acoustic Radiation by 3D Vortex Rings in Air

    Directory of Open Access Journals (Sweden)

    Fedor V. Shugaev

    2015-11-01

    Full Text Available Acoustic radiation emitted by three-dimensional (3D vortex rings in air has been investigated on the basis of the unsteady Navier–Stokes equations. Power series expansions of the unknown functions with respect to the initial vorticity which is supposed to be small are used. In such a manner the system of the Navier–Stokes equations is reduced to a parabolic system with constant coefficients at high derivatives. The initial value problem is as follows. The vorticity is defined inside a toroid at t = 0. Other gas parameters are assumed to be constant throughout the whole space at t = 0. The solution is expressed by multiple integrals which are evaluated with the aid of the Korobov grids. Density oscillations are analyzed. The results show that the frequency band depends on the initial size of the vortex ring and its helicity. The presented data may be applied to the study of a flow in a wake region behind an aerodynamic body.

  5. Response of cloud supersaturation to radiative forcing

    Science.gov (United States)

    Davies, R.

    1985-01-01

    Time-dependent solutions are obtained for droplet temperatures and supersaturation, in a study of the diffusional growth or evaporation of cloud droplets due to net emission or absorption of radiation, taking into account the partitioning of the net radiation budget between the droplets and the ambient air. Radiative perturbations are noted to result in very high rates of change in droplet temperatures. As the droplets evaporate or grow due to radiative effects, the saturation ratio of the ambient air adjusts in keeping with changes in the water vapor density and temperature of the air.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  7. Effect of secondary radiation force on aggregation between encapsulated microbubbles

    Institute of Scientific and Technical Information of China (English)

    Zhang Yan-Li; Zheng Hai-Rng; Tang Meng-Xing; Zhang Dong

    2011-01-01

    Secondary radiation force can be an attractive force causing aggregates of encapsulated microbubbles in ultrasonic molecular imaging. The influence of the secondary radiation force on aggregation between two coated bubbles is investigated in this study. Numerical calculations are performed based on four simultaneous differential equations of radial and translational motions.Results show that the secondary force can change from attraction to repulsion during approach,and stable microbubble pairs can be formed in the vicinity of resonant regions; the possibility of microbubble aggregations can be reduced by using low exciting amplitude,ultrasonic frequencies deviating from the resonant frequencies or microbubbles with small compressibility.

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

    Science.gov (United States)

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

    2016-07-01

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

  9. Generalization of the Force Approach to Radiation Reaction

    CERN Document Server

    Lopez, Gustavo V

    2016-01-01

    A generalization of the force approach to radiation reaction is given, taken into consideration an arbitrary motion of the charged particle . The expression obtained brings about the expression already given for the linear an the circular acceleration cases.

  10. The effect of acoustic forcing on trailing edge separation and near wake development of an airfoil

    Science.gov (United States)

    Huang, L. S.; Bryant, T. D.; Maestrello, L.

    1988-01-01

    An experimental study was conducted to investigate the effect of acoustic forcing on flow fields near the trailing edge of a symmetric airfoil at zero angle of attack. At low chord Reynolds numbers, the boundary layers separate from the surfaces in the rear part of the airfoil and create recirculation regions near the trailing edge. It is shown that with the introduction of acoustic forcing through a slot in the vicinity of the separation point, periodic large-scale structures are generated in the trailing edge region. Significant reduction of trailing edge separation is achieved. It is also found that the most effective forcing frequency to control trailing edge separation is the wake vortex shedding frequency. As a result of forcing, applied only on the upper surface, the upper boundary layer is accelerated and the flow over the lower surface decelerated. Consequently, an asymmetric wake is formed. The results presented indicate that the development of the near wake varies with forcing conditions.

  11. Unsteady hydrodynamics of blade forces and acoustic responses of a model scaled submarine excited by propeller's thrust and side-forces

    Science.gov (United States)

    Wei, Yingsan; Wang, Yongsheng

    2013-04-01

    This study presents the unsteady hydrodynamics of the excitations from a 5-bladed propeller at two rotating speeds running in the wake of a small-scaled submarine and the behavior of the submarine's structure and acoustic responses under the propeller excitations. Firstly, the propeller flow and submarine flows are independently validated. The propulsion of the hull-propeller is simulated using computational fluid dynamics (CFD), so as to obtain the transient responses of the propeller excitations. Finally, the structure and acoustic responses of the submarine under propeller excitations are predicted using a finite element/boundary element model in the frequency domain. Results show that (1) the propeller excitations are tonal at the propeller harmonics, and the propeller transversal force is bigger than vertical force. (2) The structure and acoustic responses of the submarine hull is tonal mainly at the propeller harmonics and the resonant mode frequencies of the hull, and the breathing mode in axial direction as well as the bending modes in vertical and transversal directions of the hull can generate strong structure vibration and underwater noise. (3) The maximum sound pressure of the field points increases with the increasing propeller rotating speed at structure resonances and propeller harmonics, and the rudders resonant mode also contributes a lot to the sound radiation. Lastly, the critical rotating speeds of the submarine propeller are determined, which should be carefully taken into consideration when match the propeller with prime mover in the propulsion system. This work shows the importance of the propeller's tonal excitation and the breathing mode plus the bending modes in evaluating submarine's noise radiation.

  12. Black carbon radiative forcing at TOA decreased during aging

    Science.gov (United States)

    Wu, Yu; Cheng, Tianhai; Zheng, Lijuan; Chen, Hao

    2016-12-01

    During aging processing, black carbon (also called soot) particles may tend to be mixed with other aerosols, and highly influence their radiative forcing. In this study, freshly emitted soot particles were simulated as fractal aggregates composed of small spherical primary monomers. After aging in the atmosphere, soot monomers were coated by a thinly layer of sulfate as thinly coated soot particles. These soot particles were entirely embedded into large sulfate particle by further aging, and becoming heavily coated soot particles. In clear-sky conditions, black carbon radiative forcing with different aging states were investigated for the bottom and top of atmosphere (BOA and TOA). The simulations showed that black carbon radiative forcing increased at BOA and decreased at TOA after their aging processes. Thinly and heavily coated states increased up to ~12% and ~35% black carbon radiative forcing at BOA, and black carbon radiative forcing at TOA can reach to ~20% and ~100% smaller for thinly and heavily coated states than those of freshly emitted states, respectively. The effect of aging states of black carbon radiative forcing was varied with surface albedo, aerosol optical depth and solar zenith angles. These findings would be helpful for the assessments of climate change.

  13. Acoustic Radiation and Diffraction from Convex and Concave Domes

    Science.gov (United States)

    1981-03-21

    U. Ingard , Theoretical Acoustics, pp. 332-356, McGraw-Hill, New York (1968). [4] J. A. Stratton, P. M. Morse,-L. J. Chu, J. D. C. Little, and F. J...Springer-Verlag, New York (1971). [34] P. M. Morse and K. U. Ingard , Theoretical Acoustics, pp. 352-353, McGraw-Hill, New York (1968). [35] I. S

  14. Acoustics forces on a solid sphere in focused sound fields and their use for acoustical traps

    DEFF Research Database (Denmark)

    Cutanda Henriquez, Vicente; Juhl, Peter Møller; Kristensen, Søren H.

    2009-01-01

    in the cases of hazardous substances, processing of materials under pure conditions, handling of fragile or sticky objects, for instance. Several theoretical investigations on the use of focused Gaussian and Bessel acoustic beams have been reported in literature. In those papers, water has been assumed...

  15. Evaluation of experimental methods for assessing safety for ultrasound radiation force elastography.

    Science.gov (United States)

    Skurczynski, M J; Duck, F A; Shipley, J A; Bamber, J C; Melodelima, D

    2009-08-01

    Standard test tools have been evaluated for the assessment of safety associated with a prototype transducer intended for a novel radiation force elastographic imaging system. In particular, safety has been evaluated by direct measurement of temperature rise, using a standard thermal test object, and detection of inertial cavitation from acoustic emission. These direct measurements have been compared with values of the thermal index and mechanical index, calculated from acoustic measurements in water using standard formulae. It is concluded that measurements using a thermal test object can be an effective alternative to the calculation of thermal index for evaluating thermal hazard. Measurement of the threshold for cavitation was subject to considerable variability, and it is concluded that the mechanical index still remains the preferred standard means for assessing cavitation hazard.

  16. THE IMPACT OF RELATIVE HUMIDITY ON THE RADIATIVE PROPERTY AND RADIATIVE FORCING OF SULFATE AEROSOL

    Institute of Scientific and Technical Information of China (English)

    张立盛; 石广玉

    2001-01-01

    With the data of complex refractive index of sulfate aerosol, the radiative properties of the aerosol under 8 relative humidity conditions are calculated in this paper. By using the concentration distribution from two CTM models and LASG GOALS/AGCM, the radiative forcing due to hygroscopic sulfate aerosol is simulated. The results show that: (1) With the increase of relative humidity, the mass extinction coefficiency factor decreases in the shortwave spectrum: single scattering albedo keeps unchanged except for a little increase in longwave spectrum, and asymmetry factor increases in whole spectrum. (2) Larger differences occur in radiative forcing simulated by using two CTM data, and the global mean forcing is -0. 268 and -0. 816 W/m2,respectively. (3) When the impact of relative humidity on radiative property is taken into account,the distribution pattern of radiative forcing due to the wet particles is very similar to that of dry sulfate, but the forcing value decreases by 6%.

  17. Simulated 2050 aviation radiative forcing from contrails and aerosols

    Science.gov (United States)

    Chen, Chih-Chieh; Gettelman, Andrew

    2016-06-01

    The radiative forcing from aviation-induced cloudiness is investigated by using the Community Atmosphere Model Version 5 (CAM5) in the present (2006) and the future (through 2050). Global flight distance is projected to increase by a factor of 4 between 2006 and 2050. However, simulated contrail cirrus radiative forcing in 2050 can reach 87 mW m-2, an increase by a factor of 7 from 2006, and thus does not scale linearly with fuel emission mass. This is due to non-uniform regional increase in air traffic and different sensitivities for contrail radiative forcing in different regions. CAM5 simulations indicate that negative radiative forcing induced by the indirect effect of aviation sulfate aerosols on liquid clouds in 2050 can be as large as -160 mW m-2, an increase by a factor of 4 from 2006. As a result, the net 2050 radiative forcing of contrail cirrus and aviation aerosols may have a cooling effect on the planet. Aviation sulfate aerosols emitted at cruise altitude can be transported down to the lower troposphere, increasing the aerosol concentration, thus increasing the cloud drop number concentration and persistence of low-level clouds. Aviation black carbon aerosols produce a negligible net forcing globally in 2006 and 2050 in this model study. Uncertainties in the methodology and the modeling are significant and discussed in detail. Nevertheless, the projected percentage increase in contrail radiative forcing is important for future aviation impacts. In addition, the role of aviation aerosols in the cloud nucleation processes can greatly influence on the simulated radiative forcing from aircraft-induced cloudiness and even change its sign. Future research to confirm these results is necessary.

  18. Surface energy budget responses to radiative forcing at Summit, Greenland

    Science.gov (United States)

    Miller, Nathaniel B.; Shupe, Matthew D.; Cox, Christopher J.; Noone, David; Persson, P. Ola G.; Steffen, Konrad

    2017-02-01

    Greenland Ice Sheet surface temperatures are controlled by an exchange of energy at the surface, which includes radiative, turbulent, and ground heat fluxes. Data collected by multiple projects are leveraged to calculate all surface energy budget (SEB) terms at Summit, Greenland, for the full annual cycle from July 2013 to June 2014 and extend to longer periods for the radiative and turbulent SEB terms. Radiative fluxes are measured directly by a suite of broadband radiometers. Turbulent sensible heat flux is estimated via the bulk aerodynamic and eddy correlation methods, and the turbulent latent heat flux is calculated via a two-level approach using measurements at 10 and 2 m. The subsurface heat flux is calculated using a string of thermistors buried in the snow pack. Extensive quality-control data processing produced a data set in which all terms of the SEB are present 75 % of the full annual cycle, despite the harsh conditions. By including a storage term for a near-surface layer, the SEB is balanced in this data set to within the aggregated uncertainties for the individual terms. November and August case studies illustrate that surface radiative forcing is driven by synoptically forced cloud characteristics, especially by low-level, liquid-bearing clouds. The annual cycle and seasonal diurnal cycles of all SEB components indicate that the non-radiative terms are anticorrelated to changes in the total radiative flux and are hence responding to cloud radiative forcing. Generally, the non-radiative SEB terms and the upwelling longwave radiation component compensate for changes in downwelling radiation, although exact partitioning of energy in the response terms varies with season and near-surface characteristics such as stability and moisture availability. Substantial surface warming from low-level clouds typically leads to a change from a very stable to a weakly stable near-surface regime with no solar radiation or from a weakly stable to neutral

  19. Resonant vibrations and acoustic radiation of rotating spherical structures.

    CSIR Research Space (South Africa)

    Shatalov, M

    2006-07-01

    Full Text Available and the second – equality of radial displacements of the sphere and the medium at r a= . mn − component of pressure in the acoustic medium is ( ( ) ( ) ( ) ( )2n n nh kr j kr i y kr= − ⋅ - Hankel spherical function, ( )mc - speed of sound in the acoustical... loaded surface for 2, 2; 3, 2; 3, 3n m n m n m= = = = = = . Parameters of the acoustic medium are: sound speed - ( ) 1500m mc s = and mass density - ( ) 31000m kg m ρ = . Corresponding values of the Bryan’s factors of the spheroidal modes are also...

  20. Unbinding of targeted ultrasound contrast agent microbubbles by secondary acoustic forces

    NARCIS (Netherlands)

    V. Garbin (Valeria); M. Overvelde (Marlies); B. Dollet (Benjamin); N. de Jong (Nico); D. Lohse (Detlef); M. Versluis (Michel)

    2011-01-01

    textabstractTargeted molecular imaging with ultrasound contrast agent microbubbles is achieved by incorporating targeting ligands on the bubble coating and allows for specific imaging of tissues affected by diseases. Improved understanding of the interplay between the acoustic forces acting on the b

  1. Acoustic black holes horizons, ergospheres, and Hawking radiation

    CERN Document Server

    Visser, M

    1998-01-01

    It is a deceptively simple question to ask how acoustic disturbances propagate in a non-homogeneous flowing fluid. This question can be answered by invoking the language of Lorentzian differential geometry: If the fluid is barotropic and inviscid, and the flow is irrotational (though possibly time dependent), then the equation of motion for the velocity potential describing a sound wave is identical to that for a minimally coupled massless scalar field propagating in a (3+1)-dimensional Lorentzian geometry. The acoustic metric governing the propagation of sound depends algebraically on the density, flow velocity, and local speed of sound. This rather simple physical system is the basis underlying a deep and fruitful analogy between the black holes of Einstein gravity and supersonic fluid flows. Many results and definitions can be carried over directly from one system to another. For example, I will show how to define the ergosphere, trapped regions, acoustic apparent horizon, and acoustic event horizon for a ...

  2. Megacity Radiative Forcing: A Mexico City Case Study

    Science.gov (United States)

    Dubey, M.; Olsen, S.; Mazzoleni, C.; Chylek, P.; Zhang, Y.; Randerson, J. T.; Horowitz, L.

    2007-05-01

    We assess the radiative forcing of the largest megacity in North America, Mexico City. While particular aspects of the regional environmental impacts of cities on their surroundings have been thoroughly investigated, e.g., air quality and acid rain, relatively little effort has been focused on the net radiative impact of a megacity on global climate. The range of radiative impacts from a megacity covers many spatial and temporal scales from short-term regional-scale effects due to aerosols and relatively short-lived gases (ozone) to long-term global-scale impacts due to longer-lived trace gases (e.g., carbon dioxide, methane). In this study we combine chemistry-transport model simulations from the Model for Ozone And Related Chemical Tracers (MOZART-2) with in situ and satellite observations from the Aerosol Robotic Network (AERONET) and the Moderate Resolution Imaging Spectroradiometer (MODIS) to calculate the global radiative forcing of megacity emissions. We also explore the radiative impact of various emission control strategies that focus on improving regional air quality. Our results suggest that the warming by greenhouse gases like carbon dioxide and ozone can be moderated or exacerbated by aerosols depending on their optical properties. As the size and number of megacities increase and clean air regulations are implemented, metrics such as the net radiative forcing may become increasingly important in comparing the impact of urban centers and assessing the trade-offs between improving local air quality and minimizing global radiative impacts.

  3. IMPROVING DISPLACEMENT SIGNAL-TO-NOISE RATIO FOR LOW-SIGNAL RADIATION FORCE ELASTICITY IMAGING USING BAYESIAN TECHNIQUES

    Science.gov (United States)

    Dumont, Douglas M.; Walsh, Kristy M.; Byram, Brett C.

    2017-01-01

    Radiation force-based elasticity imaging is currently being investigated as a possible diagnostic modality for a number of clinical tasks, including liver fibrosis staging and the characterization of cardiovascular tissue. In this study, we evaluate the relationship between peak displacement magnitude and image quality and propose using a Bayesian estimator to overcome the challenge of obtaining viable data in low displacement signal environments. Displacement data quality were quantified for two common radiation force-based applications, acoustic radiation force impulse imaging, which measures the displacement within the region of excitation, and shear wave elasticity imaging, which measures displacements outside the region of excitation. Performance as a function of peak displacement magnitude for acoustic radiation force impulse imaging was assessed in simulations and lesion phantoms by quantifying signal-to-noise ratio (SNR) and contrast-to-noise ratio for varying peak displacement magnitudes. Overall performance for shear wave elasticity imaging was assessed in ex vivo chicken breast samples by measuring the displacement SNR as a function of distance from the excitation source. The results show that for any given displacement magnitude level, the Bayesian estimator can increase the SNR by approximately 9 dB over normalized cross-correlation and the contrast-to-noise ratio by a factor of two. We conclude from the results that a Bayesian estimator may be useful for increasing data quality in SNR-limited imaging environments. PMID:27157861

  4. Radiative forcings for 28 potential Archean greenhouse gases

    Directory of Open Access Journals (Sweden)

    B. Byrne

    2014-05-01

    Full Text Available Despite reduced insolation in the late Archean, evidence suggests a warm climate which was likely sustained by a stronger greenhouse effect, the so-called Faint Young Sun Problem (FYSP. CO2 and CH4 are generally thought to be the mainstays of this enhanced greenhouse, though many other gases have been proposed. We present high accuracy radiative forcings for CO2, CH4 and 26 other gases, performing the radiative transfer calculations at line-by-line resolution and using HITRAN 2012 line data for background pressures of 0.5, 1, and 2 bar. For CO2 to resolve the FYSP alone, 0.21 bar is needed with 0.5 bar of atmospheric pressure, 0.13 bar with 1 bar of atmospheric pressures, or 0.07 bar with 2 bar of atmospheric pressure. For CH4, we find that near-infrared absorption is much stronger than previously thought, arising from updates to the HITRAN database. CH4 radiative forcing peaks at 10.3, 9, or 8.3 W m−2 for background pressures of 0.5, 1 or 2 bar, likely limiting the utility of CH4 for warming the Archean. For the other 26 HITRAN gases, radiative forcings of up to a few to 10 W m−2 are obtained from concentrations of 0.1–1 ppmv for many gases. We further calculate the reduction of radiative forcing due to gas overlap for the 20 strongest gases. We recommend the forcings provided here be used both as a first reference for which gases are likely good greenhouse gases, and as a standard set of calculations for validation of radiative forcing calculations for the Archean.

  5. Competition between radiative and strong force decay

    Science.gov (United States)

    Tabor, Samuel

    2017-01-01

    For nuclear states unbound to neutron decay, radiative emission is often assumed to not dominate over neutron decay mediated by the far stronger strong interaction, except for very low neutron energies and high angular momentum barriers. Recent experimental investigations of 19O and 27 Mg populated in heavy-ion fusion-evaporation reactions have revealed predominantly gamma decays from a number of states unbound to neutron decay by up to 2 MeV. In most cases the angular momentum barrier is not sufficient to inhibit neutron decay enough to allow E-M decay with widths of up to an eV or so to win. Other inhibitions to particle decay, including low spectroscopic factors, will be discussed. Supported in part by NSF Grant No. 1401574.

  6. Generation of a reference radiation pattern of string instruments using automatic excitation and acoustic centering.

    Science.gov (United States)

    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.

  7. Effect of the free surface and the rigid plane on structural vibration and acoustic radiation

    Institute of Scientific and Technical Information of China (English)

    ZOU Yuanjie; ZHAO Deyou; LI Sheng

    2004-01-01

    The coupled fluid-structure interaction equation is established for bodies in the haft-space fluid domain, especially sitting on the infinite plane, based on the BEM (Boundary Element Method) theory. Then, the natural frequencies, vibration responses and the acoustic radiation for a box are calculated, and the effect of the free surface and the rigid plane is discussed. Finally, several relative factors including the plate thickness, the structure damping and the distance between the body and the infinite plane are studied. The results show that the effect of the free surface and the rigid plane on the structural natural frequencies, vibration responses and the acoustic radiation cannot be ignored.

  8. Manipulating particles with light: radiation and gradient forces

    Science.gov (United States)

    Bradshaw, David S.; Andrews, David L.

    2017-05-01

    The manipulation of matter with electromagnetic radiation is a capacity that has been known for over a century. However, the prominence of such optical effects only grew rapidly following the invention of optical tweezers in the 1980s. While both the original theory and the early trapping techniques are based on the radiation force, optical tweezing uses the gradient force. This paper aims to differentiate between these two clearly distinct types of optical forces, which are sometimes confused in the literature. We also discuss three completely separate forms of optical torque that can be applied to a particle, also due to an electromagnetic field. These involve the transfer of either spin or orbital angular momentum from the beam to the particle, depending on the character of the light, or the often overlooked alignment effect that can act on a cylindrical particle due to a gradient force.

  9. A NOVEL SEMI-ANALYTICAL METHOD FOR SOLVING ACOUSTIC RADIATION FROM LONGITUDINALLY STIFFENED INFINITE ONO-CIRCULAR CYLINDRICAL SHELLS IN WATER

    Institute of Scientific and Technical Information of China (English)

    Xiang Yu; Huang Yuying

    2005-01-01

    Based on the extended homogeneous capacity hihg precision integration method and the spetrum method of virtual boundary with a complex radius vector, a novel semi-analyticalmethod,which has satisfactory computation effectiveness and precision,is presented for solving the acoustic radiation from a submerged infinte non-circular cylindrical shell stiffened by longitudinalribs by means of the Fourier integral transformation and stationary phase method.In this work,besides the normal interacting force, which is commonly adopted by some researchers,the otherinteracting forces and moments between the longitudinal ribs and the non-circular cylindrical shell are considered at the same time.The effects of the number adn the size of the cross-section of longitudinlal ribs on the characteristics of acoustic radiation are investigated.Numerical results show that the method proposed is more efficient than the eisting mixed FE-BE method.

  10. Acoustic-wave generation in the process of CO2-TEA-laser-radiation interaction with metal targets in air

    Science.gov (United States)

    Apostol, Ileana; Teodorescu, G.; Serbanescu-Oasa, Anca; Dragulinescu, Dumitru; Chis, Ioan; Stoian, Razvan

    1995-03-01

    Laser radiation interaction with materials is a complex process in which creation of acoustic waves or stress waves is a part of it. As a function of the laser radiation energy and intensity incident on steel target surface ultrasound signals were registered and studied. Thermoelastic, ablation and breakdown mechanisms of generation of acoustic waves were analyzed.

  11. Radiative decay of the one-dimensional large acoustic polaron

    Energy Technology Data Exchange (ETDEWEB)

    Ivic, Zoran; Zekovic, Slobodan; Przulj, Zeljko

    2002-12-30

    Finite temperature dynamics and stability of the adiabatic large acoustic polaron in one-dimensional systems have been examined by means of the perturbation method based upon the inverse scattering transform. Polaron life-time was estimated in dependence of temperature and electron (exciton)-phonon coupling constant.

  12. Nearfield Acoustic Radiation from a Point-Excited Cylindrical Shell

    Science.gov (United States)

    1988-05-26

    8217 . .>- . U.,U. U . :’.’, f. * ’.*., *\\,, _ -, .’- - .,-.- *"U* * v, . ,’ P -. , *’ ’ ., 9.. : ;<’ .. ;.-: 84 solution [e.g. Morse and Ingard (1968...New York). Morse, P. M., and Ingard , K. U. (1968). Theoretical Acoustics (McGraw-Hill, New York), pp. 3S6-66. Muller, D. E. (1956). "A method for

  13. [Comparision of forced expiratory time, recorded by two spirometers with flow sensors of various types, and acoustic duration of tracheal forced expiratory noises].

    Science.gov (United States)

    Malaeva, V V; Pochekutova, I A; Korenbaum, V I

    2015-01-01

    In the sample of 44 volunteers forced expiratory time values obtained in spirometers, equipped with flow sensor of Lilly type and turbine flow sensor, and acoustic duration of tracheal forced expiratory noises are compared. It is shown that spirometric forced expiratory time is dependent on flow sensor type. Therefore it can't be used in diagnostic aims.

  14. Numerical study on scanning radiation acoustic field in formations generated from a borehole

    Institute of Scientific and Technical Information of China (English)

    CHE Xiaohua; ZHANG Hailan; QIAO Wenxiao; JU Xiaodong

    2005-01-01

    Numerical study on scanning radiation acoustic field in formations generated by linear phased array transmitters in a fluid-filled borehole is carried out using a real axis integration (RAI) method. The main lobe width of the acoustic beams and the incident angle on the borehole wall can be controlled by means of adjusting parameters, such as the element number and the delay time between the neighboring array elements of linear phased array transmitter. The steered angle of longitudinal waves generated in the formation satisfies the Snell's law for plane waves when the incident angle on the borehole wall is less than the first critical angle. When the lobe width of the acoustic beams is narrow and the steered angle is less than the first critical angle, the acoustic field in the formation can be approximately calculated given that the linear phased array is put in the formation without borehole. The technique of scanning radiation acoustic field can be applied to enhancing investigation resolution and signal-to-noise ratio in crosswell seismic survey and borehole acoustic reflection imaging.

  15. Comparison of the electron-spin force and radiation reaction force

    Science.gov (United States)

    Mahajan, Swadesh M.; Asenjo, Felipe A.; Hazeltine, Richard D.

    2015-02-01

    It is shown that the forces that originate from the electron-spin interacting with the electromagnetic field can play, along with the Lorentz force, a fundamentally important role in determining the electron motion in a high energy density plasma embedded in strong high-frequency radiation, a situation that pertains to both laser-produced and astrophysical systems. These forces, for instance, dominate the standard radiation reaction force as long as there is a `sufficiently' strong ambient magnetic field for affecting spin alignment. The inclusion of spin forces in any advanced modelling of electron dynamics pertaining to high energy density systems (for instance in particle-in-cell codes), therefore, is a must.

  16. Design of a phased array for the generation of adaptive radiation force along a path surrounding a breast lesion for dynamic ultrasound elastography imaging.

    Science.gov (United States)

    Ekeom, Didace; Hadj Henni, Anis; Cloutier, Guy

    2013-03-01

    This work demonstrates, with numerical simulations, the potential of an octagonal probe for the generation of radiation forces in a set of points following a path surrounding a breast lesion in the context of dynamic ultrasound elastography imaging. Because of the in-going wave adaptive focusing strategy, the proposed method is adapted to induce shear wave fronts to interact optimally with complex lesions. Transducer elements were based on 1-3 piezocomposite material. Three-dimensional simulations combining the finite element method and boundary element method with periodic boundary conditions in the elevation direction were used to predict acoustic wave radiation in a targeted region of interest. The coupling factor of the piezocomposite material and the radiated power of the transducer were optimized. The transducer's electrical impedance was targeted to 50 Ω. The probe was simulated by assembling the designed transducer elements to build an octagonal phased-array with 256 elements on each edge (for a total of 2048 elements). The central frequency is 4.54 MHz; simulated transducer elements are able to deliver enough power and can generate the radiation force with a relatively low level of voltage excitation. Using dynamic transmitter beamforming techniques, the radiation force along a path and resulting acoustic pattern in the breast were simulated assuming a linear isotropic medium. Magnitude and orientation of the acoustic intensity (radiation force) at any point of a generation path could be controlled for the case of an example representing a heterogeneous medium with an embedded soft mechanical inclusion.

  17. Radiation torque on an absorptive spherical drop centered on an acoustic helicoidal Bessel beam

    Science.gov (United States)

    Zhang, Likun; Marston, Philip L.

    2009-11-01

    Circularly polarized electromagnetic waves carry axial angular momentum and analysis shows that the axial radiation torque on an illuminated sphere is proportional to the power absorbed by the sphere [1]. Helicoidal acoustic beams also carry axial angular momentum and absorption of such a beam should also produce an axial radiation torque [2]. In the present work the acoustic radiation torque on solid spheres and spherical drops centered on acoustic helicoidal Bessel beams is examined. The torque is predicted to be proportional to the ratio of the absorbed power to the acoustic frequency. Depending on the beam helicity, the torque is parallel or anti-parallel to the beam axis. The analysis uses a relation between the scattering and the partial wave coefficients for a sphere in a helicoidal Bessel beam. Calculations suggest that beams with a low topological charge are more efficient for generating torques on solid spheres.[4pt] [1] P. L. Marston and J. H. Crichton, Phys. Rev. A. 30, 2508-2516 (1984).[0pt] [2] B. T. Hefner and P. L. Marston, J. Acoust. Soc. Am. 106, 3313-3316 (1999).

  18. Measurement of acoustic field radiated by low frequency power ultrasonic transducer with laser-interferometer

    Institute of Scientific and Technical Information of China (English)

    QIAN Menglu; GAO Wen; HU Wenxiang

    2000-01-01

    Based on the piezo-optic effect of medium, the refractive index of medium is the function of its density, and so it's also the function of acoustic pressure. Therefore, acoustic pressure in the optical path everywhere can be determined absolutely by laser-interferometric technique and relative distribution of pressure in the middle and far acoustic field, which can be obtained from theory or experiment respectively. Theory and experiment of measurement of pressure in acoustic field with laser-interferometer are introduced. Distribution of pressure radiated by a power ultrasonic transducer is determined by laser interferometric technique.The theoretical and experimental results are in good agreement. The receiving sensitivity of a PVDF (Polyvinylidene fluoride) transducer in free field is also calibrated absolutely due to above results and its sensitivity is -118.5 dB.

  19. Forced acoustical response of an open cavity coupled with a semi-infinite space

    CERN Document Server

    Tong, Yuhui; Pan, Jie

    2016-01-01

    This paper presents a study of the forced acoustical response of an open cavity from the perspective of modal expansion. Based on the coupled mode theory, it is shown that the sound pressure distribution of an open cavity excited by a point source placed within the cavity can be expanded by a set of frequency-dependent eigenmodes, which are derived from the coupling between the cavity and a semi-infinite space. The calculation of the acoustical responses for baffled and unbaffled open cavities indicates that the proposed modal expansion converges with only a few frequency-dependent eigenmodes in the frequency range of interest. The results of this study eliminate the ambiguity involving the selection of appropriate basis functions, in modal expansion for the forced response problem in open cavities.

  20. Local-linear-prediction analysis for underwater acoustic target radiated noise

    Institute of Scientific and Technical Information of China (English)

    LIANG Juan; LU Jiren

    2002-01-01

    Local-linear-prediction in phase space is performed for the underwater acoustic target radiated noise. Relation curve of average prediction error versus neighboring points' number is calculated. The result is used in judging the nonlinearity of radiated noise time series, and obtaining the appropriate form and coefficients of predicting model. The line and continuous spectral component are predicted respectively. Choice of some model parameters minimizing the prediction error is also discussed.

  1. Radiative Forcing and Climate Response: From Paleoclimate to Future Climate

    Science.gov (United States)

    Caldeira, K.; Cao, L.

    2011-12-01

    The concept of radiative forcing was introduced to allow comparison of climate effects of different greenhouse gases. In the classic view, radiative forcing is applied to the climate system and the climate responds to this forcing, approaching some equilibrium temperature change that is the product of the radiative forcing times the 'climate sensitivity' to radiative forcing. However, this classic view is oversimplified in several respects. Climate forcing and response often cannot be clearly separated. When carbon dioxide is added to the atmosphere, within days, the increased absorption of longwave radiation begins to warm the interior of the troposphere, affecting various tropospheric properties. Especially in the case of aerosols, it has been found that considering rapid tropospheric adjustment gives a better predictor of "equilibrium" climate change than does the classic definition of radiative forcing. Biogeochemistry also provides additional feedbacks on the climate system. It is generally thought that biogeochemistry helps diminish climate sensitivity to a carbon dioxide emission, since carbon dioxide tends to stimulate carbon dioxide uptake by land plants and the ocean. However, there is potential to destabilize carbon locked up in permafrost and at least some possibility to destabilize methane in continental shelf sediments. Furthermore, wetlands may provide a significant methane feedback. These and other possible biogeochemical feedbacks have the potential to greatly increase the sensitivity of the climate system to carbon dioxide emissions. As time scales extend out to millennia, the large ice sheets can begin to play an important role. In addition to affecting atmospheric flows by their sheer bulk, ice sheets tend to reflect a lot of energy to space. If carbon dioxide remains in the atmosphere long enough, there is potential to melt back the large ice sheets, which would add additional warming to the climate system. It is likely that these millennial

  2. 声辐射力脉冲成像技术评价肝脏纤维化及早期肝硬化的初步研究%Acoustic radiation force impulse for evaluation of hepatic fibrosis and early stage cirrhosis

    Institute of Scientific and Technical Information of China (English)

    董常峰; 刘映霞; 杨桂林; 李汉英; 黄婷; 王耀

    2012-01-01

    目的 探讨运用声辐射力脉冲成像技术( ARFI)评价肝脏纤维化及早期肝硬化的价值.方法 选取66例经肝穿活检证实的病毒性肝炎患者与33例健康者正常对照组(S0),应用声辐射力脉冲成像技术测量受检者肝脏s5、s6、s7、s8段及肝包膜的剪切波速度,同时常规测量所有受检者的肝、脾大小及门静脉内径.结果 66例病毒性肝炎患者按照肝穿活检病理结果分为S1组、肝脏纤维化组(S2-S3)、早期肝硬化组(S4).早期肝硬化组(S4)的肝脏各段剪切波速度与S0组、S1组、肝脏纤维化组(S2-S3)间的相应肝段剪切波速度均存在统计学差异(P<0.05),肝脏纤维化组(S2-S3)与S0组、S1组间的相应肝段剪切波速度也均存在统计学差异(P<0.05),而S1组与S0组间的各肝段剪切波速度无统计学差异(P>0.05),各组间肝包膜剪切波速度无统计学差异(P>0.05).早期肝硬化组的脾脏厚度及门静脉内径较其他组有增加,并具统计学差异(P<0.05).结论 声辐射力脉冲成像技术可无创评价病毒性肝炎患者肝脏纤维化及早期肝硬化程度,方法可行,适合于临床推广应用.%Objective To investigate the value of acoustic radiation force impulse (ARFI) in evaluating the stage of hepatic fibrosis and early stage cirrhosis.Methods Sixty-six patients with viral hepatitis underwent liver biopsy and 33 normal subjects (S0) were selected to accept ARFI,the shear wave velocity of hepatic segments s5,s6,s7,s8 and size of liver were measured.The results of liver and spleen size and portal vein's diameter were also measured.Results The 66 patients were divided into 3 groups:S1,S2-S3,S4.ARFI for 66 patients and 33 normal subjects showed good image quality.There were statistically significant differences between S4 group and S0 group,S1 group,S2-S3 group for the shear wave velocity of hepatic segments s5,s6,s7,s8 ( P < 0.05 ).Between S2-S3 group and S0 group S1 group,the shear wave

  3. Dosimetric comparison of different radiation treatment modalities for acoustic neuromas

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong Wook; Chung, Weon Kuu [Kyung Hee University Hospital at Gangdong, Seoul (Korea, Republic of); Shin, Dong Oh [Kyung Hee Medical Center, Seoul (Korea, Republic of); Shin, Dongho [National Cancer Center, Goyang (Korea, Republic of)

    2014-11-15

    The dosimetric differences for intensity-modulatedradiotherapy (IMRT), volumetric modulated arc therapy (VMAT), proton therapy(PROTON) and stereotactic radiosurgery (SRS) in patient with acoustic neuroma (AN) were compared by using the dose-volume histogram (DVH). In the present study, we estimated the dosimetric differences for patient with AN who received different treatment modalities. In this study, we found proton therapy is relatively effective treatment techniques than the other.

  4. Cryogenic Impinging Jets Subjected to High Frequency Transverse Acoustic Forcing in a High Pressure Environment

    Science.gov (United States)

    2016-07-27

    Forcing in a High Pressure Environment 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Mario Roa, S. Alex Schumaker...disclose the work. PA Clearance Number: 16308 Clearance Date: 6/17/2016 13. SUPPLEMENTARY NOTES For presentation at AIAA Propulsion and Energy; Salt...the coupling between the impact waves created by impinging jets and high frequency acoustic pressure perturbations. High speed, backlit imaging was

  5. Cryogenic Impinging Jets Subjected to High Frequency Transverse Acoustic Forcing in a High Pressure Environment

    Science.gov (United States)

    2016-07-27

    other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a ...Transverse Acoustic Forcing in a High Pressure Environment 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Mario...Briefing Charts 15. SUBJECT TERMS N/ A 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE

  6. Pull-in voltage of microswitch rough plates in the presence of electromagnetic and acoustic Casimir forces

    NARCIS (Netherlands)

    Palasantzas, George

    2007-01-01

    In this work, we investigate the combined influence of electromagnetic and acoustic Casimir forces on the pull-in voltage of microswitches with self-affine rough plates. It is shown that for plate separations within the micron range the acoustic term arising from pressure fluctuations can influence

  7. Pull-in voltage of microswitch rough plates in the presence of electromagnetic and acoustic Casimir forces

    NARCIS (Netherlands)

    Palasantzas, George

    2007-01-01

    In this work, we investigate the combined influence of electromagnetic and acoustic Casimir forces on the pull-in voltage of microswitches with self-affine rough plates. It is shown that for plate separations within the micron range the acoustic term arising from pressure fluctuations can influence

  8. Experimental validation of a boundary element solver for exterior acoustic radiation problems

    NARCIS (Netherlands)

    Visser, Rene; Nilsson, A.; Boden, H.

    2003-01-01

    The relation between harmonic structural vibrations and the corresponding acoustic radiation is given by the Helmholtz integral equation (HIE). To solve this integral equation a new solver (BEMSYS) based on the boundary element method (BEM) has been implemented. This numerical tool can be used for b

  9. Imaging and analyzing the elasticity of vascular smooth muscle cells by atomic force acoustic microscope.

    Science.gov (United States)

    Zhang, Bo; Cheng, Qian; Chen, Ming; Yao, Wengang; Qian, Menglu; Hu, Bing

    2012-08-01

    Vascular smooth muscle cells (VSMCs) play an important role in the good performance of the vasculature. To study the surface, intracellular structure and elasticity of VSMCs, atomic force acoustic microscope (AFAM) was used for imaging VSMCs from A7r5 rat aorta arteries. The topography images of VSMCs were obtained in contact mode and the acoustic images were obtained by AFAM in sample vibration mode. Then, the force curve measurement derived using Young's modulus of the interested areas was used for evaluating elasticity properties. The acoustic images were found in higher resolution with more information than the topography images. The force curves showed the difference in Young's modulus of the different parts of VSMC. These findings demonstrate that AFAM is useful for displaying the surface, structure and elasticity property of VSMCs clearly, with short scanning time, negligible harm or damage to cell and nanometer-level resolution. Copyright © 2012 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  10. Highly asymmetric interaction forces induced by acoustic waves in coupled plate structures

    CERN Document Server

    Fan, Xiying; Zhang, Shenwei; Ke, Manzhu; Liu, Zhengyou

    2015-01-01

    Mutual forces can be induced between coupled structures when illuminated by external acoustic waves. In this Letter, we propose a concept of asymmetric interaction between two coupled plate-like structures, which is generated by oppositely incident plane waves. Besides the striking contrast in magnitude, the mutual force induced by one of the incidences can be tuned extremely strong due to the resonant excitation of the flexural plate modes. The highly asymmetric interaction with enhanced strength in single side should be potentially useful, such as in designing ultrasound instruments and sensors.

  11. Nonlinear dust acoustic waves with polarization force effects in Kappa distribution plasma

    Science.gov (United States)

    Chen, Hui; Zhou, Suyun; Luo, Rongxiang; Liu, Sanqiu

    2017-01-01

    The propagation characteristics of dust acoustic solitary waves (DASWs) in dusty plasmas with the effects of polarization force and superthermal ions are studied. First, the polarization force induced by superthermal ions is obtained. It is shown that the superthermality of background ions affect the Debye screening of dust grains as well as the polarization force significantly. Then for small amplitude solitary waves, the KdV equation is obtained by applying the reductive perturbation technique. And for the arbitrary amplitude solitary waves, the Sagdeev potential method is employed and the Sagdeev potential is analyzed. In both case, the effects of the polarization force associated the ions’ superthermality on the characteristic of the DASWs are analyzed.

  12. Acoustic levitation of a large solid sphere

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, Marco A. B., E-mail: marcobrizzotti@gmail.com [Institute of Physics, University of São Paulo, São Paulo 05508-090 (Brazil); Bernassau, Anne L. [School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Adamowski, Julio C. [Department of Mechatronics and Mechanical Systems Engineering, Escola Politécnica, University of São Paulo, São Paulo 05508-030 (Brazil)

    2016-07-25

    We demonstrate that acoustic levitation can levitate spherical objects much larger than the acoustic wavelength in air. The acoustic levitation of an expanded polystyrene sphere of 50 mm in diameter, corresponding to 3.6 times the wavelength, is achieved by using three 25 kHz ultrasonic transducers arranged in a tripod fashion. In this configuration, a standing wave is created between the transducers and the sphere. The axial acoustic radiation force generated by each transducer on the sphere was modeled numerically as a function of the distance between the sphere and the transducer. The theoretical acoustic radiation force was verified experimentally in a setup consisting of an electronic scale and an ultrasonic transducer mounted on a motorized linear stage. The comparison between the numerical and experimental acoustic radiation forces presents a good agreement.

  13. Acoustic levitation of a large solid sphere

    Science.gov (United States)

    Andrade, Marco A. B.; Bernassau, Anne L.; Adamowski, Julio C.

    2016-07-01

    We demonstrate that acoustic levitation can levitate spherical objects much larger than the acoustic wavelength in air. The acoustic levitation of an expanded polystyrene sphere of 50 mm in diameter, corresponding to 3.6 times the wavelength, is achieved by using three 25 kHz ultrasonic transducers arranged in a tripod fashion. In this configuration, a standing wave is created between the transducers and the sphere. The axial acoustic radiation force generated by each transducer on the sphere was modeled numerically as a function of the distance between the sphere and the transducer. The theoretical acoustic radiation force was verified experimentally in a setup consisting of an electronic scale and an ultrasonic transducer mounted on a motorized linear stage. The comparison between the numerical and experimental acoustic radiation forces presents a good agreement.

  14. Net radiative forcing from widespread deployment of photovoltaics.

    Science.gov (United States)

    Nemet, Gregory F

    2009-03-15

    If photovoltaics (PV) are to contribute significantly to stabilizing the climate, they will need to be deployed on the scale of multiple terawatts. Installation of that much PV would cover substantial portions of the Earth's surface with dark-colored, sunlight-absorbing panels, reducing the Earth's albedo. How much radiative forcing would result from this change in land use? How does this amount compare to the radiative forcing avoided by substituting PV for fossil fuels? This analysis uses a series of simple equations to compare the two effects and finds that substitution dominates; the avoided radiative forcing due to substitution of PV for fossil fuels is approximately 30 times largerthan the forcing due to albedo modification. Sensitivity analysis, including discounting of future costs and benefits, identifies unfavorable yet plausible configurations in which the albedo effect substantially reduces the climatic benefits of PV. The value of PV as a climate mitigation option depends on how it is deployed, not just how much it is deployed--efficiency of PV systems and the carbon intensity of the substituted energy are particularly important

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

    Science.gov (United States)

    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.

  16. Extraction and application of the low dimensional dynamical component from underwater acoustic target radiating noise

    Institute of Scientific and Technical Information of China (English)

    LIANG Juan; LU Jiren

    2001-01-01

    Signal processing in phase space based on nonlinear dynamics theory is a new method for underwater acoustic signal processing. One key problem when analyzing actual acoustic signal in phase space is how to reduce the noise and lower the embedding dimension. In this paper, local-geometric-projection method is applied to obtain low dimensional element from various target radiating noise and the derived phase portraits show obviously low dimensional attractors. Furthermore, attractor dimension and cross prediction error are used for classification. It concludes that combining these features representing the geometric and dynamical properties respectively shows effects in target classification.

  17. Resolution of Forces and Strain Measurements from an Acoustic Ground Test

    Science.gov (United States)

    Smith, Andrew M.; LaVerde, Bruce T.; Hunt, Ronald; Waldon, James M.

    2013-01-01

    The Conservatism in Typical Vibration Tests was Demonstrated: Vibration test at component level produced conservative force reactions by approximately a factor of 4 (approx.12 dB) as compared to the integrated acoustic test in 2 out of 3 axes. Reaction Forces Estimated at the Base of Equipment Using a Finite Element Based Method were Validated: FEM based estimate of interface forces may be adequate to guide development of vibration test criteria with less conservatism. Element Forces Estimated in Secondary Structure Struts were Validated: Finite element approach provided best estimate of axial strut forces in frequency range below 200 Hz where a rigid lumped mass assumption for the entire electronics box was valid. Models with enough fidelity to represent diminishing apparent mass of equipment are better suited for estimating force reactions across the frequency range. Forward Work: Demonstrate the reduction in conservatism provided by; Current force limited approach and an FEM guided approach. Validate proposed CMS approach to estimate coupled response from uncoupled system characteristics for vibroacoustics.

  18. Halogen chemistry reduces tropospheric O3 radiative forcing

    Science.gov (United States)

    Sherwen, Tomás; Evans, Mat J.; Carpenter, Lucy J.; Schmidt, Johan A.; Mickley, Loretta J.

    2017-01-01

    Tropospheric ozone (O3) is a global warming gas, but the lack of a firm observational record since the preindustrial period means that estimates of its radiative forcing (RFTO3) rely on model calculations. Recent observational evidence shows that halogens are pervasive in the troposphere and need to be represented in chemistry-transport models for an accurate simulation of present-day O3. Using the GEOS-Chem model we show that tropospheric halogen chemistry is likely more active in the present day than in the preindustrial. This is due to increased oceanic iodine emissions driven by increased surface O3, higher anthropogenic emissions of bromo-carbons, and an increased flux of bromine from the stratosphere. We calculate preindustrial to present-day increases in the tropospheric O3 burden of 113 Tg without halogens but only 90 Tg with, leading to a reduction in RFTO3 from 0.43 to 0.35 Wm-2. We attribute ˜ 50 % of this reduction to increased bromine flux from the stratosphere, ˜ 35 % to the ocean-atmosphere iodine feedback, and ˜ 15 % to increased tropospheric sources of anthropogenic halogens. This reduction of tropospheric O3 radiative forcing due to halogens (0.087 Wm-2) is greater than that from the radiative forcing of stratospheric O3 (˜ 0.05 Wm-2). Estimates of RFTO3 that fail to consider halogen chemistry are likely overestimates (˜ 25 %).

  19. Progressive Shear Failure in Granular Materials: Linking Force Fluctuations With Acoustic Emissions

    Science.gov (United States)

    Michlmayr, G. K.; Cohen, D. O.; Or, D.

    2011-12-01

    Natural hazards associated with rapid mass movements such as shallow landslides, rock falls or debris flows are notoriously difficult to predict even though precursor events associated with small internal failures are known to occur. In this study we focus on grain scale processes preceding the formation of a shear plane in granular materials such as frictional sliding of grain contacts, accommodation of contact networks and fracturing of grain bonds (in cohesive materials) - all of which are discrete micro-mechanical failure events that emit characteristic acoustic emissions that could be used to study internal failure and potentially provide early warning (albeit short). Experiments involving direct shear tests using glass beads and sand were combined with acoustic emission (AE) measurements using piezoelectric sensors with sensitivities to frequencies in the range of 20kHz - 200kHz and accelerometers (0.2kHz - 20kHz) buried within the sheared sample. We obtained good correlations between shear deformation and associated grain-scale mechanical behavior with key characteristics of measured AE (frequency content, signal energy). Fluctuations of shear force occurring during strain controlled deformation are assumed to represent micro-structural rearrangements of the material. We obtained exponential distributions of force fluctuation magnitudes and low frequency AE event statistics. The number of AE events increased with confining stress as well as with particle roughness and were inversely related to grain size. These results were linked with conceptual models of failure accumulation such as the fiber-bundle model. The statistics of AE event occurrence, particularly magnitude-frequency distributions may provide prediction of imminent mechanical collapse. The strong attenuation of acoustic signals within most earth materials present a major challenge to field applications requiring innovative deployment strategies such as the use of acoustic waveguides.

  20. Cooperative scattering and radiation pressure force in dense atomic clouds

    CERN Document Server

    Bachelard, Romain; Courteille, Philippe

    2011-01-01

    We consider the collective scattering by a cloud of $N$ two-level atoms driven by an uniform radiation field. Dense atomic clouds can be described by a continuous density and the problem reduces to deriving the spectrum of the atom-atom coupling operator. For clouds much larger than the optical wavelength, the spectrum is treated as a continuum, and analytical expressions for several macroscopic quantities, such as scattered radiation intensity and radiation pressure force, are derived. The analytical results are then compared to the exact $N$-body solution and with those obtained assuming a symmetric timed Dicke state. In contrast with the symmetric timed Dicke state, our calculations takes account of the back action of the atoms on the driving field leading to phase shifts due to the finite refraction of the cloud.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Z. Y.; Lü, P.; Geng, D. L.; Zhai, W.; Yan, N.; Wei, B., E-mail: bbwei@nwpu.edu.cn [Department of Applied Physics, Northwestern Polytechnical University, Xi' an 710072 (China)

    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.

  3. Anthropogenic Aerosols in Asia, Radiative Forcing, and Climate Change

    Science.gov (United States)

    Ramaswamy, V.; Bollasina, M. A.; Ming, Y.; Ocko, I.; Persad, G.

    2014-12-01

    Aerosols arising as a result of human-induced emissions in Asia form a key 'driver' in causing pollution and in the forcing of anthropogenic climate change. The manner of the forced climate change is sensitive to the scattering and absorption properties of the aerosols and the aerosol-cloud microphysical interactions. Using the NOAA/ GFDL global climate models and observations from multiple platforms, we investigate the radiative perturbations due to the 20th Century sulfate and carbonaceous aerosol emissions and the resultant impacts on surface temperature, tropical precipitation, Indian monsoon, hemispheric circulation, and atmospheric and oceanic heat transports. The influence of the aerosol species has many contrasts with that due to the anthropogenic well-mixed greenhouse gas emissions e.g., the asymmetry in the hemispheric climate response, but is subject to larger uncertainties. The aerosol forcing expected in the future indicates a significant control on the 21st Century anthropogenic climate change in Asia.

  4. A diffraction correction for storage and loss moduli imaging using radiation force based elastography

    Science.gov (United States)

    Budelli, Eliana; Brum, Javier; Bernal, Miguel; Deffieux, Thomas; Tanter, Mickaël; Lema, Patricia; Negreira, Carlos; Gennisson, Jean-Luc

    2017-01-01

    Noninvasive evaluation of the rheological behavior of soft tissues may provide an important diagnosis tool. Nowadays, available commercial ultrasound systems only provide shear elasticity estimation by shear wave speed assessment under the hypothesis of a purely elastic model. However, to fully characterize the rheological behavior of tissues, given by its storage (G‧) and loss (G″) moduli, it is necessary to estimate both: shear wave speed and shear wave attenuation. Most elastography techniques use the acoustic radiation force to generate shear waves. For this type of source the shear waves are not plane and a diffraction correction is needed to properly estimate the shear wave attenuation. The use of a cylindrical wave approximation to evaluate diffraction has been proposed by other authors before. Here the validity of such approximation is numerically and experimentally revisited. Then, it is used to generate images of G‧ and G″ in heterogeneous viscoelastic mediums. A simulation algorithm based on the anisotropic and viscoelastic Green’s function was used to establish the validity of the cylindrical approximation. Moreover, two experiments were carried out: a transient elastography experiment where plane shear waves were generated using a vibrating plate and a SSI experiment that uses the acoustic radiation force to generate shear waves. For both experiments the shear wave propagation was followed with an ultrafast ultrasound scanner. Then, the shear wave velocity and shear wave attenuation were recovered from the phase and amplitude decay versus distance respectively. In the SSI experiment the cylindrical approximation was applied to correct attenuation due to diffraction effects. The numerical and experimental results validate the use of a cylindrical correction to assess shear wave attenuation. Finally, by applying the cylindrical correction G‧ and G″ images were generated in heterogeneous phantoms and a preliminary in vivo feasibility study

  5. Effective radiative forcing from historical land use change

    Science.gov (United States)

    Andrews, Timothy; Betts, Richard A.; Booth, Ben B. B.; Jones, Chris D.; Jones, Gareth S.

    2017-06-01

    The effective radiative forcing (ERF) from the biogeophysical effects of historical land use change is quantified using the atmospheric component of the Met Office Hadley Centre Earth System model HadGEM2-ES. The global ERF at 2005 relative to 1860 (1700) is -0.4 (-0.5) Wm-2, making it the fourth most important anthropogenic driver of climate change over the historical period (1860-2005) in this model and larger than most other published values. The land use ERF is found to be dominated by increases in the land surface albedo, particularly in North America and Eurasia, and occurs most strongly in the northern hemisphere winter and spring when the effect of unmasking underlying snow, as well as increasing the amount of snow, is at its largest. Increased bare soil fraction enhances the seasonal cycle of atmospheric dust and further enhances the ERF. Clouds are shown to substantially mask the radiative effect of changes in the underlying surface albedo. Coupled atmosphere-ocean simulations forced only with time-varying historical land use change shows substantial global cooling (d T = -0.35 K by 2005) and the climate resistance (ERF/d T = 1.2 Wm-2 K-1) is consistent with the response of the model to increases in CO2 alone. The regional variation in land surface temperature change, in both fixed-SST and coupled atmosphere-ocean simulations, is found to be well correlated with the spatial pattern of the forced change in surface albedo. The forcing-response concept is found to work well for historical land use forcing—at least in our model and when the forcing is quantified by ERF. Our results suggest that land-use changes over the past century may represent a more important driver of historical climate change then previously recognised and an underappreciated source of uncertainty in global forcings and temperature trends over the historical period.

  6. Assessing estimates of radiative forcing for solar geoengineering starts with accurate aerosol radiative properties

    Science.gov (United States)

    Dykema, J. A.; Keith, D.; Keutsch, F. N.

    2016-12-01

    The deliberate modification of Earth's albedo as a complement to mitigation in order to slow climate change brings with it a range of risks. A range of different approaches have been studied, including the injection of aerosol particles into the stratosphere to decrease solar energy input into the climate system. Key side effects from this approach include ozone loss and radiative heating. Both of these side effects may produce dynamical changes with further consequences for stratospheric and tropospheric climate. Studies of past volcanic eruptions suggest that sulfate aerosol injection may be capable of achieving a compensating radiative forcing of -1 W m-2 or more. It is also expected that such injection of sulfate aerosols will result in loss of stratospheric ozone and of significant infrared heating. The problems resulting from sulfate aerosols intended have motivated the investigation of alternative materials, including high refractive index solid materials. High refractive index materials have the potential to scatter more efficiently per unit mass, leading to a reduction in surface area for heterogeneous chemistry, and, depending on details of absorption, less radiative heating. Fundamentally, assessing these trade-offs requires accurate knowledge of the complex refractive index of materials being considered over the full range of wavelengths relevant to atmospheric radiative transfer, that is, from ultraviolet to far-infrared. Our survey of the relevant literature finds that such measurements are not available for all materials of interest at all wavelengths. We utilize a method developed in astrophysics to fill in spectral gaps, and find that some materials may heat the stratosphere substantially more than was found in previous work. Stratospheric heating can warm the tropical tropopause layer, increasing the flux of water vapor into the stratosphere, with further consequences for atmospheric composition and radiative forcing. We analyze this consequence

  7. Double modulation of X radiation diffracted in a quartz single crystal by high and low frequency acoustic waves

    CERN Document Server

    Kocharyan, L A; Bornazyan, H S

    1986-01-01

    The time dependence of X radiation diffracted in a quartz single crystal is experimentally investigated when surface acoustic waves modulated by low frequency oscillations of different frequencies and forms are excited in the crystal.

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

    Science.gov (United States)

    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.

  9. The statistical distributed source boundary point method to calculate the acoustic radiation from the random vibrating body

    Institute of Scientific and Technical Information of China (English)

    WANGXiufeng; CHENXinzhao; LIUZhao

    2003-01-01

    The statistical distributed source boundary point method (SDSBPM) put forward is applied to calculate the acoustic radiation from the random vibrating body. A detailed description of this method is presented. A test for the SDSBPM is carried out through the random vibrating sphere and the random vibrating cuboid. An experiment on the exterior acoustic radiation of a random vibrating simulation axial box of the lathe tool is performed in a semi-anechoic chamber.

  10. Radiative forcings for 28 potential Archean greenhouse gases

    CERN Document Server

    Byrne, Brendan

    2014-01-01

    Despite reduced insolation in the late Archean, evidence suggests a warm climate which was likely sustained by a stronger greenhouse effect, the so-called Faint Young Sun Problem (FYSP). CO2 and CH4 are generally thought to be the mainstays of this enhanced greenhouse, though many other gases have been proposed. We present high accuracy radiative forcings for CO2, CH4 and 26 other gases, performing the radiative transfer calculations at line-by-line resolution and using HITRAN 2012 line data for background pressures of 0.5, 1, and 2 bar of atmospheric N2. For CO2 to resolve the FYSP alone at 2.8 Gyr BP (80% of present solar luminosity), 0.32 bar is needed with 0.5 bar of atmospheric N2, 0.20 bar with 1 bar of atmospheric N2, or 0.11 bar with 2 bar of atmospheric N2. For CH4, we find that near-infrared absorption is much stronger than previously thought, arising from updates to the HITRAN database. CH4 radiative forcing peaks at 10.3, 9, or 8.3 Wm-2 for background pressures of 0.5, 1 or 2 bar, likely limiting ...

  11. Endothelial Adhesion of Targeted Microbubbles in Both Small and Great Vessels Using Ultrasound Radiation Force

    Directory of Open Access Journals (Sweden)

    Jia Liu

    2012-01-01

    Full Text Available The effectiveness of microbubble-mediated ultrasound molecular imaging and drug delivery has been significantly affected by the axial laminar flow of vessels which prevents ultrasound contrast agents (UCAs from targeting vascular endothelium. Studies show that acoustic manipulation could increase targeted UCA adhesion in microcirculation and some small vessels. In this study we demonstrate that ultrasound radiation force (USRF can also significantly enhance the targeted adhesion of microbubbles in both small and great vessels. Our results indicate that the UCA adhesion targeted to ICAM-1 expressed on mouse cremaster microvascular endothelial cells increase about 9-fold when USRF is applied at 1 MHz and 73.9 kPa. The adhesion of anti-CD34 microbubbles to the endothelia of rat abdominal aorta was visually analyzed using scanning electron microscopy for the first time and thousands of microbubbles were found attached to the aortic endothelia after USRF application at the same acoustic parameters. Our data illustrate that targeted adhesion of anti-CD34 microbubbles is possible in normal abdominal aorta and we demonstrate the potential of using USRF in molecular imaging of a vascular target.

  12. Partially Acoustic Dark Matter, Interacting Dark Radiation, and Large Scale Structure

    CERN Document Server

    Chacko, Zackaria; Hong, Sungwoo; Okui, Takemichi; Tsai, Yuhsin

    2016-01-01

    The standard paradigm of collisionless cold dark matter is in tension with measurements on large scales. In particular, the best fit values of the Hubble rate $H_0$ and the matter density perturbation $\\sigma_8$ inferred from the cosmic microwave background seem inconsistent with the results from direct measurements. We show that both problems can be solved in a framework in which dark matter consists of two distinct components, a dominant component and a subdominant component. The primary component is cold and collisionless. The secondary component is also cold, but interacts strongly with dark radiation, which itself forms a tightly coupled fluid. The growth of density perturbations in the subdominant component is inhibited by dark acoustic oscillations due to its coupling to the dark radiation, solving the $\\sigma_8$ problem, while the presence of tightly coupled dark radiation ameliorates the $H_0$ problem. The subdominant component of dark matter and dark radiation continue to remain in thermal equilibri...

  13. An accurate quantification of the flow structure along the acoustic signal cycle in a forced two-phase jet

    Directory of Open Access Journals (Sweden)

    Calvo Bernad Esteban

    2014-03-01

    Full Text Available This paper provides an experimental study of an acoustically forced two-phase air jet generated by a convergent nozzle. The used particles are transparent glass spheres with diameters between 2 and 50 μm (which gives Stokes number of order 1 and the selected forcing frequency (f=400 Hz induces a powerful nearly periodic flow pattern. Measurements were done by a two-colour Phase-Doppler Anemometer. The experimental setup is computer-controlled to provide an accurate control with a high long-term stability. Measurements cover the whole forcing signal cycle. Raw measurements were carefully post-processed to avoid bias induced by the forcing and the instrument setup, as well as obtain right mean values of the dispersed flow. The effect of the forcing and the particle load allows authors to establish the effect of the acoustic forcing and the particle load on the jet.

  14. Visualization of Coherent Structures in Acoustically Forced,Gas-Particle Turbulent Round Jet

    Institute of Scientific and Technical Information of China (English)

    容易; 张会强; 王希麟; 陈昌麒

    2004-01-01

    To show the effects of the particles and forced disturbances on the instantaneous large-scale vortex structures in a gas-particle round jet, coherent structures in gas-particle turbulent round jets were investigated experimentally by flow visualization. The 45-μm and 350-μm diameter glass beads were used as the particles in the experiments. An acoustic speaker was used to introduce velocity perturbations at the jet exit. The Strouhal number based on the nozzle diameter, exit velocity, and forcing frequency was varied from 0.1 to 0.9. The Reynolds number was 9400. The coherent structures were visualized in unforced and forced single-phase jet flows and unforced and forced particle-laden jet flows with different diameter glass beads. The experimental results show that the particles have significant effects on the gas phase coherent structures. The coherent structures are controlled by the large 350-μm diameter particles, while the structures are mainly dominated by the forced disturbances in the flows with 45-μm diameter particles.

  15. Black Carbon Vertical Profiles Strongly Affect Its Radiative Forcing Uncertainty

    Science.gov (United States)

    Samset, B. H.; Myhre, G.; Schulz, M.; Balkanski, Y.; Bauer, S.; Berntsen, T. K.; Bian, H.; Bellouin, N.; Diehl, T.; Easter, R. C.; Ghan, S. J.; Iversen, T.; Kinne, S.; Kirkevag, A.; Lamarque, J.-F.; Lin, G.; Liu, X.; Penner, J. E.; Seland, O.; Skeie, R. B.; Stier, P.; Takemura, T.; Tsigaridis, K.; Zhang, K.

    2013-01-01

    The impact of black carbon (BC) aerosols on the global radiation balance is not well constrained. Here twelve global aerosol models are used to show that at least 20% of the present uncertainty in modeled BC direct radiative forcing (RF) is due to diversity in the simulated vertical profile of BC mass. Results are from phases 1 and 2 of the global aerosol model intercomparison project (AeroCom). Additionally, a significant fraction of the variability is shown to come from high altitudes, as, globally, more than 40% of the total BC RF is exerted above 5 km. BC emission regions and areas with transported BC are found to have differing characteristics. These insights into the importance of the vertical profile of BC lead us to suggest that observational studies are needed to better characterize the global distribution of BC, including in the upper troposphere.

  16. Gravitational self-force from radiation-gauge metric perturbations

    CERN Document Server

    Pound, Adam; Barack, Leor

    2014-01-01

    Calculations of the gravitational self-force (GSF) in curved spacetime require as input the metric perturbation in a sufficiently regular gauge. A basic challenge in the program to compute the GSF for orbits around a Kerr black hole is that the standard procedure for reconstructing the perturbation is formulated in a class of radiation gauges, in which the particle singularity is non-isotropic and extends away from the particle's location. Here we present two practical schemes for calculating the GSF using a radiation-gauge reconstructed metric as input. The schemes are based on a detailed analysis of the local structure of the particle singularity in the radiation gauges. We identify 3 types of radiation gauges: two containing a radial string-like singularity emanating from the particle, either in one direction ("half-string" gauges) or both directions ("full-string" gauges); and a third type containing no strings but with a jump discontinuity across a surface intersecting the particle. Based on a flat-space...

  17. Climate Response of Direct Radiative Forcing of Anthropogenic Black Carbon

    Science.gov (United States)

    Chung, Serena H.; Seinfeld,John H.

    2008-01-01

    The equilibrium climate effect of direct radiative forcing of anthropogenic black carbon (BC) is examined by 100-year simulations in the Goddard Institute for Space Studies General Circulation Model II-prime coupled to a mixed-layer ocean model. Anthropogenic BC is predicted to raise globally and annually averaged equilibrium surface air temperature by 0.20 K if BC is assumed to be externally mixed. The predicted increase is significantly greater in the Northern Hemisphere (0.29 K) than in the Southern Hemisphere (0.11 K). If BC is assumed to be internally mixed with the present day level of sulfate aerosol, the predicted annual mean surface temperature increase rises to 0.37 K globally, 0.54 K for the Northern Hemisphere, and 0.20 K for the Southern Hemisphere. The climate sensitivity of BC direct radiative forcing is calculated to be 0.6 K W (sup -1) square meters, which is about 70% of that of CO2, independent of the assumption of BC mixing state. The largest surface temperature response occurs over the northern high latitudes during winter and early spring. In the tropics and midlatitudes, the largest temperature increase is predicted to occur in the upper troposphere. Direct radiative forcing of anthropogenic BC is also predicted to lead to a change of precipitation patterns in the tropics; precipitation is predicted to increase between 0 and 20 N and decrease between 0 and 20 S, shifting the intertropical convergence zone northward. If BC is assumed to be internally mixed with sulfate instead of externally mixed, the change in precipitation pattern is enhanced. The change in precipitation pattern is not predicted to alter the global burden of BC significantly because the change occurs predominantly in regions removed from BC sources.

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

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, Rodrigo; Socrates, Aristotle [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States)

    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.

  19. Do Diurnal Aerosol Changes Affect Daily Average Radiative Forcing?

    Energy Technology Data Exchange (ETDEWEB)

    Kassianov, Evgueni I.; Barnard, James C.; Pekour, Mikhail S.; Berg, Larry K.; Michalsky, Joseph J.; Lantz, K.; Hodges, G. B.

    2013-06-17

    Strong diurnal variability of aerosol has been observed frequently for many urban/industrial regions. How this variability may alter the direct aerosol radiative forcing (DARF), however, is largely unknown. To quantify changes in the time-averaged DARF, we perform an assessment of 29 days of high temporal resolution ground-based data collected during the Two-Column Aerosol Project (TCAP) on Cape Cod, which is downwind of metropolitan areas. We demonstrate that strong diurnal changes of aerosol loading (about 20% on average) have a negligible impact on the 24-h average DARF, when daily averaged optical properties are used to find this quantity. However, when there is a sparse temporal sampling of aerosol properties, which may preclude the calculation of daily averaged optical properties, large errors (up to 100%) in the computed DARF may occur. We describe a simple way of reducing these errors, which suggests the minimal temporal sampling needed to accurately find the forcing.

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

    Science.gov (United States)

    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.

  1. Contrasting regional versus global radiative forcing by megacity pollution emissions

    Science.gov (United States)

    Dang, H.; Unger, N.

    2015-10-01

    We assess the regional and global integrated radiative forcing on 20- and 100-year time horizons caused by a one-year pulse of present day pollution emissions from 10 megacity areas: Los Angeles, Mexico City, New York City, Sao Paulo, Lagos, Cairo, New Delhi, Beijing, Shanghai and Manila. The assessment includes well-mixed greenhouse gases: carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4); and short-lived climate forcers: tropospheric ozone (O3) and fine mode aerosol particles (sulfate, nitrate, black carbon, primary and secondary organic aerosol). All megacities contribute net global warming on both time horizons. Most of the 10 megacity areas exert a net negative effect on their own regional radiation budget that is 10-100 times larger in magnitude than their global radiative effects. Of the cities examined, Beijing, New Delhi, Shanghai and New York contribute most to global warming with values ranging from +0.03 to 0.05 Wm-2yr on short timescales and +0.07-0.10 Wm-2yr on long timescales. Regional net 20-year radiative effects are largest for Mexico City (-0.84 Wm-2yr) and Beijing (-0.78 Wm-2yr). Megacity reduction of non-CH4 O3 precursors to improve air quality offers zero co-benefits to global climate. Megacity reduction of aerosols to improve air quality offers co-benefits to the regional radiative budget but minimal or no co-benefits to global climate with the exception of black carbon reductions in a few cities, especially Beijing and New Delhi. Results suggest that air pollution and global climate change mitigation can be treated as separate environmental issues in policy at the megacity level with the exception of CH4 action. Individual megacity reduction of CO2 and CH4 emissions can mitigate global warming and therefore offers climate safety improvements to the entire planet.

  2. Effects of autologous peripheral stem cell transplantation on acoustic radiation force impulse in patients with HBV-related decompensated cirrhosis%自体外周血干细胞移植对乙型肝炎肝硬化失代偿期患者肝脏声脉冲辐射力成像的影响

    Institute of Scientific and Technical Information of China (English)

    邓勤智; 蔡挺; 张顺; 胡爱荣; 张行芬; 黄建荣

    2015-01-01

    目的 观察自体外周血干细胞(APBSC)移植对乙型肝炎肝硬化失代偿期患者肝脏声脉冲辐射力成像值(ARFI)的影响. 方法 采用前瞻性随机对照的方法,将68例入组患者随机分组,33例为治疗组,综合内科治疗基础上接受APBSC移植治疗,35例为对照组,单纯内科综合治疗.观察患者移植后12周、24周、36周、48周血总胆红素、凝血酶原时间(PT)、白蛋白(Alb)水平和脾脏大小、肝脏ARFI等改变,并与移植治疗前及同期对照组比较.据资料不同分别用t检验、非参数检验或x2检验.结果 治疗组患者治疗后24周、36周、48周Alb、PT改善,36周、48周脾脏大小、肝脏ARFI指数与治疗前及对照组比较改善.移植后36周、48周脾脏长度分别为(140.09±23.05)mm、(139.55±24.12)mm,与移植前[(149.36±24.56)mm]差异有统计学意义(t值分别为3.43、-2.21,P<0.05),与同期对照组[(150.26±18.27) mm、(151.66±19.76) mm]比较,差异有统计学意义(t值分别为-2.02、-2,27,P<0.05).移植后36周、48周ARFI分别为(2.21±0.43)m/s、(2.19±0.43)m/s,与移植前[(2.49±0.31) m/s]差异有统计学意义(t=3.00,P=0.005;t=3.21,P=0.003),与同期对照组比较差异有统计学意义(P<0.05).结论 APBSC移植治疗能够改善乙型肝炎肝硬化失代偿期患者的肝功能,肝脏ARFI指数及肝脏纤维化程度.%Objective To perform a prospective study the effects of autologous peripheral blood stem cell (APBSC) transplantation on acoustic radiation force impulse (ARFI) in patients with hepatitis B virus (HBV)-related decompensated cirrhosis.Methods A total of 68 hospitalized patients with HBV-related decompensated cirrhosis undergoing conventional treatment were included in the study.Thirty-three of these patients also received APBSC transplantation therapy (treatment group) and 35 did not (control group).The treatment group was observed for postoperative adverse reaction, and changes (pre-vs.post-treatment) in total

  3. The Pilot Study of Acoustic Radiation Force Impulse Technology in the Differential Diagnosis of Breast Iesions%声辐射力脉冲成像技术对乳腺肿块鉴别诊断价值的初步研究

    Institute of Scientific and Technical Information of China (English)

    栾艳艳; 王燕; 曾敏霞; 李艺; 胡兵

    2012-01-01

    目的 利用声辐射力脉冲成像技术(ARFI)测量剪切波速度(SWV)的方法定量评价正常乳腺组织及乳腺肿块的硬度,分析其对乳腺良、恶性肿块鉴别诊断的临床价值.方法 利用常规超声和ARFI技术对101例患者的正常乳腺组织及146枚肿块进行检查,测量正常乳腺组织及乳腺肿块的SWV值.对结果进行对比分析,鉴别诊断肿块良、恶性.结果 正常乳腺腺体组织的SWV值为(1.63±0.47) m/s,乳腺良性肿块的SWV值为(2.38±0.55) m/s,恶性肿块的SWV值为(7.34±1.76) m/s.正常乳腺组织、乳腺良性肿块及恶性肿块SWV值之间的差异有统计学意义(P<0.05).以实性肿块中央部位SWV值为xxx m/s为诊断乳腺恶性肿瘤的标准,ARFI诊断乳腺恶性肿瘤的敏感性、特异性、准确度及阳性预测值分别为90.0%、100%、97.9%、100%.该标准结合BIRADS分类,诊断乳腺恶性肿瘤的敏感性、特异性、准确度及阳性预测值分别为100%、97.4%、98.6%、90.9%.结论 ARFI技术可定量评价组织硬度,结合常规超声检查可提高乳腺恶性肿瘤诊断的敏感度和准确度.%Objective The shear wave velocity (SWV) detected by acoustic radiation force impulse (ARFI) technology is a quantitative assessment of the tissue stiffness property. SWV of normal mammary gland parenchyma and breast lesions was investigated using ARFI technology. The present study was conducted to investigate the value of SWV in the differential diagnosis of breast tumor of benign and malignancy. Methods The examination of the normal mammary gland parenchyma and the 146 lesions in 101 patients started with conventional ultrasound followed by ARFI technology. The results were compared and analysised to distinguish the benign and malignant tumors of breast. Results The mean shear wave velocity in the normal mammary gland parenchyma was (1. 63 ± 0. 47) m/s. The mean shear wave velocity of the benign lesions and the malignant lesions were

  4. The radiative forcing potential of different climate geoengineering options

    Directory of Open Access Journals (Sweden)

    T. M. Lenton

    2009-01-01

    Full Text Available Climate geoengineering proposals seek to rectify the Earth's current radiative imbalance, either by reducing the absorption of incoming solar (shortwave radiation, or by removing CO2 from the atmosphere and transferring it to long-lived reservoirs, thus increasing outgoing longwave radiation. A fundamental criterion for evaluating geoengineering options is their climate cooling effectiveness, which we quantify here in terms of radiative forcing potential. We use a simple analytical approach, based on the global energy balance and pulse response functions for the decay of CO2 perturbations. This aids transparency compared to calculations with complex numerical models, but is not intended to be definitive. Already it reveals some significant errors in existing calculations, and it allows us to compare the relative effectiveness of a range of proposals. By 2050, only stratospheric aerosol injections or sunshades in space have the potential to cool the climate back toward its pre-industrial state, but some land carbon cycle geoengineering options are of comparable magnitude to mitigation "wedges". Strong mitigation, i.e. large reductions in CO2 emissions, combined with global-scale air capture and storage, afforestation, and bio-char production, i.e. enhanced CO2 sinks, might be able to bring CO2 back to its pre-industrial level by 2100, thus removing the need for other geoengineering. Alternatively, strong mitigation stabilising CO2 at 500 ppm, combined with geoengineered increases in the albedo of marine stratiform clouds, grasslands, croplands and human settlements might achieve a patchy cancellation of radiative forcing. Ocean fertilisation options are only worthwhile if sustained on a millennial timescale and phosphorus addition probably has greater long-term potential than iron or nitrogen fertilisation. Enhancing ocean upwelling or downwelling have trivial effects on any

  5. The radiative forcing potential of different climate geoengineering options

    Directory of Open Access Journals (Sweden)

    T. M. Lenton

    2009-08-01

    Full Text Available Climate geoengineering proposals seek to rectify the Earth's current and potential future radiative imbalance, either by reducing the absorption of incoming solar (shortwave radiation, or by removing CO2 from the atmosphere and transferring it to long-lived reservoirs, thus increasing outgoing longwave radiation. A fundamental criterion for evaluating geoengineering options is their climate cooling effectiveness, which we quantify here in terms of radiative forcing potential. We use a simple analytical approach, based on energy balance considerations and pulse response functions for the decay of CO2 perturbations. This aids transparency compared to calculations with complex numerical models, but is not intended to be definitive. It allows us to compare the relative effectiveness of a range of proposals. We consider geoengineering options as additional to large reductions in CO2 emissions. By 2050, some land carbon cycle geoengineering options could be of comparable magnitude to mitigation "wedges", but only stratospheric aerosol injections, albedo enhancement of marine stratocumulus clouds, or sunshades in space have the potential to cool the climate back toward its pre-industrial state. Strong mitigation, combined with global-scale air capture and storage, afforestation, and bio-char production, i.e. enhanced CO2 sinks, might be able to bring CO2 back to its pre-industrial level by 2100, thus removing the need for other geoengineering. Alternatively, strong mitigation stabilising CO2 at 500 ppm, combined with geoengineered increases in the albedo of marine stratiform clouds, grasslands, croplands and human settlements might achieve a patchy cancellation of radiative forcing. Ocean fertilisation options are only worthwhile if sustained on a millennial timescale and phosphorus addition may have greater long-term potential than iron or nitrogen fertilisation. Enhancing ocean

  6. Radiative forcing in the ACCMIP historical and future climate simulations

    Energy Technology Data Exchange (ETDEWEB)

    Shindell, D. T.; Lamarque, J. -F.; Schulz, M.; Flanner, M.; Jiao, C.; Chin, M.; Young, P. J.; Lee, Y. H.; Rotstayn, L.; Mahowald, N.; Milly, G.; Faluvegi, G.; Balkanski, Y.; Collins, W. J.; Conley, A. J.; Dalsoren, S.; Easter, R.; Ghan, S.; Horowitz, L.; Liu, X.; Myhre, G.; Nagashima, T.; Naik, V.; Rumbold, S. T.; Skeie, R.; Sudo, K.; Szopa, S.; Takemura, T.; Voulgarakis, A.; Yoon, J. -H.; Lo, F.

    2013-01-01

    The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) examined the short-lived drivers of climate change in current climate models. Here we evaluate the 10 ACCMIP models that included aerosols, 8 of which also participated in the Coupled Model Intercomparison Project phase 5 (CMIP5). The models reproduce present-day total aerosol optical depth (AOD) relatively well, though many are biased low. Contributions from individual aerosol components are quite different, however, and most models underestimate east Asian AOD. The models capture most 1980-2000 AOD trends well, but underpredict increases over the Yellow/Eastern Sea. They strongly underestimate absorbing AOD in many regions. We examine both the direct radiative forcing (RF) and the forcing including rapid adjustments (effective radiative forcing; ERF, including direct and indirect effects). The models’ all-sky 1850 to 2000 global mean annual average total aerosol RF is (mean; range) -0.26Wm-2-2. Screening based on model skill in capturing observed AOD yields a best estimate of -0.42Wm-2-2-2-2forcing than direct RF. Despite this, the multi-model spread relative to the mean is typically the same for ERF as it is for RF, or even smaller, over areas with substantial forcing. The largest 1850 to 2000 negative aerosol RF and ERF values are over and near Europe, south and east Asia and North America. ERF, however, is positive over the Sahara, the Karakoram, high Southern latitudes and especially the Arctic. Global

  7. Radiative forcing in the ACCMIP historical and future climate simulations

    Directory of Open Access Journals (Sweden)

    D. T. Shindell

    2013-03-01

    Full Text Available The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP examined the short-lived drivers of climate change in current climate models. Here we evaluate the 10 ACCMIP models that included aerosols, 8 of which also participated in the Coupled Model Intercomparison Project phase 5 (CMIP5. The models reproduce present-day total aerosol optical depth (AOD relatively well, though many are biased low. Contributions from individual aerosol components are quite different, however, and most models underestimate east Asian AOD. The models capture most 1980–2000 AOD trends well, but underpredict increases over the Yellow/Eastern Sea. They strongly underestimate absorbing AOD in many regions. We examine both the direct radiative forcing (RF and the forcing including rapid adjustments (effective radiative forcing; ERF, including direct and indirect effects. The models' all-sky 1850 to 2000 global mean annual average total aerosol RF is (mean; range −0.26 W m−2; −0.06 to −0.49 W m−2. Screening based on model skill in capturing observed AOD yields a best estimate of −0.42 W m−2; −0.33 to −0.50 W m−2, including adjustment for missing aerosol components in some models. Many ACCMIP and CMIP5 models appear to produce substantially smaller aerosol RF than this best estimate. Climate feedbacks contribute substantially (35 to −58% to modeled historical aerosol RF. The 1850 to 2000 aerosol ERF is −1.17 W m−2; −0.71 to −1.44 W m−2. Thus adjustments, including clouds, typically cause greater forcing than direct RF. Despite this, the multi-model spread relative to the mean is typically the same for ERF as it is for RF, or even smaller, over areas with substantial forcing. The largest 1850 to 2000 negative aerosol RF and ERF values are over and near Europe, south and east Asia and North America. ERF, however, is positive over the Sahara, the Karakoram, high Southern latitudes and especially the Arctic. Global aerosol RF

  8. Calculation of radiation acoustical fields from phased arrays with nonparaxial multi-Gaussian beam model

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xinyu; GANG Tie; ZHANG Bixing

    2009-01-01

    A nonparaxial multi-Gaussian beam model based on the rectangular aperture is proposed in order to overcome the hmitation of paraxial Gaussian beam model which losing accuracy in off-axis beam fields. With the method, acoustical field generated by an ultra-sonic linear phased array transducer is calculated and compared with the corresponding field obtained by Rayleigh-Sommerfeld integral, paraxial multi-Gaussian beam model, and Fraunhof-fer approximation method. Simulation examples show that nonparaxial multi-Gaussian beam model is not limited by the paraxial approximation condition and can predict efficiently and accurately the acoustical field radiated by a linear phased array transducer over a wide range of steering angles.

  9. Radiative Forcing in the ACCMIP Historical and Future Climate Simulations

    Science.gov (United States)

    Shindell, Drew Todd; Lamarque, J.-F.; Schulz, M.; Flanner, M.; Jiao, C.; Chin, M.; Young, P. J.; Lee, Y. H.; Rotstayn, L.; Mahowald, N.; hide

    2013-01-01

    A primary goal of the Atmospheric Chemistry and Climate Model IntercomparisonProject (ACCMIP) was to characterize the short-lived drivers of preindustrial to 2100climate change in the current generation of climate models. Here we evaluate historicaland 5 future radiative forcing in the 10 ACCMIP models that included aerosols, 8 of whichalso participated in the Coupled Model Intercomparison Project phase 5 (CMIP5).The models generally reproduce present-day climatological total aerosol opticaldepth (AOD) relatively well. components to this total, however, and most appear to underestimate AOD over East10 Asia. The models generally capture 1980-2000 AOD trends fairly well, though theyunderpredict AOD increases over the YellowEastern Sea. They appear to strongly underestimate absorbing AOD, especially in East Asia, South and Southeast Asia, SouthAmerica and Southern Hemisphere Africa.We examined both the conventional direct radiative forcing at the tropopause (RF) and the forcing including rapid adjustments (adjusted forcing AF, including direct andindirect effects). The models calculated all aerosol all-sky 1850 to 2000 global meanannual average RF ranges from 0.06 to 0.49 W m(sup -2), with a mean of 0.26 W m(sup -2) and a median of 0.27 W m(sup -2. Adjusting for missing aerosol components in some modelsbrings the range to 0.12 to 0.62W m(sup -2), with a mean of 0.39W m(sup -2). Screen20ing the models based on their ability to capture spatial patterns and magnitudes ofAOD and AOD trends yields a quality-controlled mean of 0.42W m(sup -2) and range of0.33 to 0.50 W m(sup -2) (accounting for missing components). The CMIP5 subset of ACCMIPmodels spans 0.06 to 0.49W m(sup -2), suggesting some CMIP5 simulations likelyhave too little aerosol RF. A substantial, but not well quantified, contribution to histori25cal aerosol RF may come from climate feedbacks (35 to 58). The mean aerosol AF during this period is 1.12W m(sup -2) (median value 1.16W m(sup -2), range 0.72 to1.44W m

  10. Measurement of Acoustic Intensity Distribution and Radiation Power of Flat-Plate Phased-Array Sound Source

    Science.gov (United States)

    Yokoyama, Tomoki; Takahashi, Kumiko; Seki, Daizaburou; Hasegawa, Akio

    2002-05-01

    The acoustic intensity distribution and radiation power of a flat-plate phased-array sound source consisting of Tonpilz-type transducers were measured. This study shows that the active acoustic intensity is skewed in the direction of wave propagation. In addition, it clarifies that if the measurement is carried out in the immediate vicinity of the sound source, the reactive acoustic intensity distribution is effective for identifying the positions of the individual sound source elements. Experimental values of active radiation power agree well with theoretical values. Conversely, experimental values of reactive radiation power do not agree with theoretical values; it is clear that they fluctuate significantly with distance from the radiating surface. The reason for this is explained in the case of a point sound source.

  11. Effect of Fuel Composition on the Response of an Acoustically Forced Flat Flame

    Science.gov (United States)

    Gorski, Jan

    Interest in alternative fuels for power generation is growing, yet these fuels bring new challenges to gas turbine design and operation. Among these challenges are combustor operability issues, highlighted by problems with combustion instabilities. For this thesis, a fundamental study of the effects of fuel composition on combustion dynamics was undertaken. An acoustically forced flat flame burner was constructed, allowing measurement of the flame transfer function (FTF) relating acoustic perturbations to heat release rate fluctuations in the flame. Tests were done using methane, along with simulated syngas and biogas fuel mixtures over a variety of operating conditions. Large variations in methane concentration had a significant impact on the FTF, while variations in the hydrogen to carbon monoxide ratio did not impact the FTF in fuel mixtures of equal parts methane and syngas. The Strouhal number was found to be an important parameter in predicting phase response independent of the fuel type. Flame liftoff distance and fuel composition were the key parameters determining the peak FTF magnitude. A hypothesis on the role of the non-adiabatic nature of the flat flame and thermal-diffusive effects on the trends in peak FTF magnitude is presented and discussed.

  12. Nonlinear Evolution of the Radiation-Driven Magneto-Acoustic Instability (RMI)

    CERN Document Server

    Fernández, Rodrigo

    2012-01-01

    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-MHD 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 (2003) in that the RMI operates even in gas pressure-dominated environments that a...

  13. Anthropogenic influence on SOA and the resulting radiative forcing

    Directory of Open Access Journals (Sweden)

    C. R. Hoyle

    2009-04-01

    Full Text Available The effect of chemical changes in the atmosphere since the pre-industrial period on the distributions and burdens of Secondary Organic Aerosol (SOA has been calculated using the off-line aerosol chemistry transport model Oslo CTM2. The production of SOA was found to have increased from about 35 Tg yr−1 to 53 Tg yr−1 since pre-industrial times, leading to an increase in the global annual mean SOA burden from 0.33 Tg to 0.50 Tg, or about 51%. The effect of allowing semi-volatile species to partition to sulphate aerosol was also tested, leading to an increase in SOA production from about 43 Tg yr−1 to 69 Tg yr−1 since pre-industrial times, while the annual mean SOA burden increased from 0.44 Tg to 0.70 Tg, or about 59%. The increases were greatest over industrialised areas, especially when partitioning to sulphate aerosol was allowed, as well as over regions with high biogenic precursor emissions. The contribution of emissions from different sources to the larger SOA burdens has been calculated. The results suggest that the majority of the increase was caused by emissions of primary organic aerosols (POA, from fossil fuel and bio fuel combustion. As yet, very few radiative forcing estimates of SOA exist, and no such estimates were provided in the latest IPCC report. In this study, we found that the change in SOA burden caused a radiative forcing (defined here as the difference between the pre-industrial and the present day run of −0.09 W m−2, when SOA was allowed to partition to both organic and sulphate aerosols, and −0.06 W m−2 when only partitioning to organic aerosols was assumed. Therefore, the radiative forcing of SOA was found to be stronger than the best estimate for POA in the latest IPCC assessment.

  14. Re-radiation of acoustic waves from the A0 wave on a submerged elastic shell.

    Science.gov (United States)

    Ahyi, A C; Cao, Hui; Raju, P K; Uberall, Herbert

    2005-07-01

    We consider evacuated thin semi-infinite shells immersed in a fluid, which may be either of cylindrical shape with a hemispherical shell endcap, or formed two-dimensionally by semi-infinite parallel plates joined together by a semi-cylinder. The connected shell portions are joined in a manner to satisfy continuity but with a discontinuous radius of curvature. Acoustic waves are considered incident along the axis of symmetry (say the z axis) onto the curved portion of the shell, where they, at the critical angle of coincidence, generate Lamb and Stoneley-type waves in the shell. Computations were carried out using a code developed by Cao et al. [Chinese J. Acoust. 14, 317 (1995)] and was used in order to computationally visualize the waves in the fluid that have been re-radiated by the shell waves a the critical angle. The frequency range was below that of the lowest Lamb wave, and only the A0 wave (and partly the S0 wave) was observed to re-radiate into the fluid under our assumptions. The results will be compared to experimental results in which the re-radiated waves are optically visualized by the Schardin-Cranz schlieren method.

  15. Numerical evaluation of acoustic power radiation and radiation efficiencies of baffled plates

    NARCIS (Netherlands)

    Lemmen, R.L.C.; Panuszka, R.J.

    1996-01-01

    In this paper expressions are given for the numerical evaluation of radiation efficiencies and power radiation of baffled plates. The expressions can be used as a postprocessing tool in the Finite Element Method. Numerical results for simply supported plates are presented and compared with results o

  16. Indirect radiative forcing by ion-mediated nucleation of aerosol

    Directory of Open Access Journals (Sweden)

    F. Yu

    2012-12-01

    Full Text Available A clear understanding of particle formation mechanisms is critical for assessing aerosol indirect radiative forcing and associated climate feedback processes. Recent studies reveal the importance of ion-mediated nucleation (IMN in generating new particles and cloud condensation nuclei (CCN in the atmosphere. Here we implement the IMN scheme into the Community Atmosphere Model version 5 (CAM5. Our simulations show that, compared to globally averaged results based on H2SO4-H2O binary homogeneous nucleation (BHN, the presence of ionization (i.e., IMN halves H2SO4 column burden, but increases the column integrated nucleation rate by around one order of magnitude, total particle number burden by a factor of ~3, CCN burden by ~10% (at 0.2% supersaturation to 65% (at 1.0% supersaturation, and cloud droplet number burden by ~18%. Compared to BHN, IMN increases cloud liquid water path by 7.5%, decreases precipitation by 1.1%, and increases total cloud cover by 1.9%. This leads to an increase of total shortwave cloud radiative forcing (SWCF by 3.67 W m−2 (more negative and longwave cloud forcing by 1.78 W m−2 (more positive, with large spatial variations. The effect of ionization on SWCF derived from this study (3.67 W m−2 is a factor of ~3 higher that of a previous study (1.15 W m−2 based on a different ion nucleation scheme and climate model. Based on the present CAM5 simulation, the 5-yr mean impacts of solar cycle induced changes in ionization rates on CCN and cloud forcing are small (~−0.02 W m−2 but have larger inter-annual (from −0.18 to 0.17 W m−2 and spatial variations.

  17. Radiative forcing in the ACCMIP historical and future climate simulations

    Directory of Open Access Journals (Sweden)

    D. T. Shindell

    2012-08-01

    Full Text Available A primary goal of the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP was to characterize the short-lived drivers of preindustrial to 2100 climate change in the current generation of climate models. Here we evaluate historical and future radiative forcing in the 10 ACCMIP models that included aerosols, 8 of which also participated in the Coupled Model Intercomparison Project phase 5 (CMIP5.

    The models generally reproduce present-day climatological total aerosol optical depth (AOD relatively well. They have quite different contributions from various aerosol components to this total, however, and most appear to underestimate AOD over East Asia. The models generally capture 1980–2000 AOD trends fairly well, though they underpredict AOD increases over the Yellow/Eastern Sea. They appear to strongly underestimate absorbing AOD, especially in East Asia, South and Southeast Asia, South America and Southern Hemisphere Africa.

    We examined both the conventional direct radiative forcing at the tropopause (RF and the forcing including rapid adjustments (adjusted forcing; AF, including direct and indirect effects. The models' calculated all aerosol all-sky 1850 to 2000 global mean annual average RF ranges from −0.06 to −0.49 W m−2, with a mean of −0.26 W m−2 and a median of −0.27 W m−2. Adjusting for missing aerosol components in some models brings the range to −0.12 to −0.62 W m−2, with a mean of −0.39 W m−2. Screening the models based on their ability to capture spatial patterns and magnitudes of AOD and AOD trends yields a quality-controlled mean of −0.42 W m−2 and range of −0.33 to −0.50 W m−2 (accounting for missing components. The CMIP5 subset of ACCMIP models spans −0.06 to −0.49 W m−2, suggesting some CMIP5 simulations likely have too little aerosol RF. A substantial, but not

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

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Myonggeun; Lee, Hyunho; Sung, Jiwon [Korea University, Seoul (Korea, Republic of); Shin, Dongoh [Kyung Hee University Medical Center, Seoul (Korea, Republic of); Park, Sungho [Ulsan University Hospital, Ulsan (Korea, Republic of); Chung, Weonkuu; Jahng, Geonho; Kim, Dongwook [Kyung Hee University Hospital at Gangdong, Seoul (Korea, Republic of)

    2014-06-15

    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.

  19. AIRFORCE. Aircraft emissions and radiative forcing from emissions

    Energy Technology Data Exchange (ETDEWEB)

    Meijer, E.W.; Kelder, H.; Velthoven, P.F.J. van; Wauben, W.M.F. [Royal Netherlands Meteorological Inst., De Bilt (Netherlands); Beck, J.P.; Velders, G.J.M. [National Inst. of Public Health and the Environment, Bilthoven (Netherlands); Lelieveld, J.; Scheeren, B.A. [Institute of Marine and Atmospheric Research Utrecht (Netherlands)

    1997-12-31

    The Dutch AIRFORCE project focuses on the effects of subsonic aircraft emissions on the chemical composition of the atmosphere and subsequent radiative forcing. It includes measurements in the tropopause region and the modelling of exhaust plumes and large-scale effects. An aircraft exhaust plume model has been developed to study plume processes. The results of the plume model are used in the global transport chemistry model CTMK to determine large-scale effects of plume processes. Due to the efficient conversion of NO{sub x} into HNO{sub 3} inside aircraft exhaust plumes, a decrease of about 25% of the O{sub 3} perturbation was found in the NAFC at 200 hPa in July. Measurements of hydrocarbons revealed a dominant role of the anthropogenic continental emissions of light hydrocarbons in the tropopause region. (author) 20 refs.

  20. Radiation Pressure Force from Optical Cycling on a Polyatomic Molecule

    CERN Document Server

    Kozyryev, Ivan; Matsuda, Kyle; Hemmerling, Boerge; Doyle, John M

    2016-01-01

    We demonstrate multiple photon cycling and radiative force deflection on the triatomic free radical strontium monohydroxide (SrOH). Optical cycling is achieved on SrOH in a cryogenic buffer-gas beam by employing the rotationally closed $P\\left(N''=1\\right)$ branch of the vibronic transition $\\tilde{X}^{2}\\Sigma^{+}\\left(000\\right)\\leftrightarrow\\tilde{A}^{2}\\Pi_{1/2}\\left(000\\right)$. A single repumping laser excites the Sr-O stretching vibrational mode, and photon cycling of the molecule deflects the SrOH beam by an angle of $0.2^{\\circ}$ via scattering of $\\sim100$ photons per molecule. This approach can be used for direct laser cooling of SrOH and more complex, isoelectronic species.

  1. Cooperative scattering and radiation pressure force in dense atomic clouds

    Energy Technology Data Exchange (ETDEWEB)

    Bachelard, R. [University of Nova Gorica, School of Applied Sciences, Vipavska 11c SI-5270 Ajdovscina (Slovenia); Piovella, N. [Dipartimento di Fisica, Universita Degli Studi di Milano, Via Celoria 16, I-20133 Milano (Italy); Courteille, Ph. W. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, 13560-970 Sao Carlos, SP (Brazil)

    2011-07-15

    Atomic clouds prepared in ''timed Dicke'' states, i.e. states where the phase of the oscillating atomic dipole moments linearly varies along one direction of space, are efficient sources of superradiant light emission [Scully et al., Phys. Rev. Lett. 96, 010501 (2006)]. Here, we show that, in contrast to previous assertions, timed Dicke states are not the states automatically generated by incident laser light. In reality, the atoms act back on the driving field because of the finite refraction of the cloud. This leads to nonuniform phase shifts, which, at higher optical densities, dramatically alter the cooperative scattering properties, as we show by explicit calculation of macroscopic observables, such as the radiation pressure force.

  2. Interplay between radiation pressure force and scattered light intensity in the cooperative scattering by cold atoms

    CERN Document Server

    Bienaime, Tom; Chabe, Julien; Rouabah, Mohamed-Taha; Bellando, Louis; Courteille, Philippe W; Piovella, Nicola; Kaiser, Robin

    2013-01-01

    The interplay between the superradiant emission of a cloud of cold two-level atoms and the radiation pressure force is discussed. Using a microscopic model of coupled atomic dipoles driven by an external laser, the radiation field and the average radiation pressure force are derived. A relation between the far-field scattered intensity and the force is derived, using the optical theorem. Finally, the scaling of the sample scattering cross section with the parameters of the system is studied.

  3. 声脉冲辐射力弹性成像在伴有钙化的甲状腺结节良恶性鉴别诊断中的应用价值%Value of acoustic radiation force impulse imaging in the differential diagnosis between benign and malignant thyroid nodules with calcifications

    Institute of Scientific and Technical Information of China (English)

    邢春燕; 徐辉雄; 章晶; 张一峰; 孙丽萍; 刘畅; 刘琳娜

    2013-01-01

    应用可提高甲状腺结节的诊断水平。%Objective To investigate the value of acoustic radiation force impulse (ARFI) elastography in the differential diagnosis between benign and malignant thyroid nodules with calcifications at ultrasound. Methods The ARFI elastography characteristics and conventional ultrasound(US)features of 54 histologically proven thyroid nodules with calcifications in 52 patients were reviewed. With the pathological diagnosis as the gold standard, the sensitivity, specificity, accuracy of US, virtual touch tissue quantification(VTQ) and virtual touch tissue imaging(VTI)in diagnosis of thyroid nodules were evaluated. Results 54 nodules included 34 malignant lesions and 20 benign lesions. 27 of 34 malignant nodules had 3 or more malignant features (include hypoechogenicity, an irregular or microlobulated margin, microcalcifications, intranodular bloodflow and a shape that was taller than wide), and the remaining 7 malignant nodules had less than 3 of these features. The SWV(shear wave velocity)values of 23 malignant nodules were greater than or equal to 2.87 m/s, and 11 other malignant nodules less than 2.87 m/s. 32 of 34 malignant nodules had VTI scores greater than or equal to Ⅳ and 2 malignant nodules with VTI score less than Ⅳ The sensitivity, specificity, accuracy of US were79.4%, 75%, 77.7%, respectively;of VTQ were 67.6%, 70%, 68.5%, respectively;of VTI were 94.1%, 35%, 72.2%, respectively; and of US+VTI+VTQ were 97.0%, 75%, 88.8%, respectively.Conclusion ARFI alone is not superior to US in predicting malignancy in thyroid nodules but conventional ultrasound in combination with ARFI improves the diagnostic level.

  4. Placement and efficiency effects on radiative forcing of solar installations

    Energy Technology Data Exchange (ETDEWEB)

    Burg, Brian R.; Ruch, Patrick; Paredes, Stephan; Michel, Bruno, E-mail: bmi@zurich.ibm.com [IBM Research - Zurich, Säumerstrasse 4, CH-8803 Rüschlikon (Switzerland)

    2015-09-28

    The promise for harnessing solar energy being hampered by cost, triggered efforts to reduce them. As a consequence low-efficiency, low-cost photovoltaics (PV) panels prevail. Conversely, in the traditional energy sector efficiency is extremely important due to the direct costs associated to fuels. This also affects solar energy due to the radiative forcing caused by the dark solar panels. In this paper we extend the concept of energy payback time by including the effect of albedo change, which gives a better assessment of the system sustainability. We present an analysis on the short and medium term climate forcing effects of different solar collectors in Riyadh, Saudi Arabia and demonstrate that efficiency is important to reduce the collector area and cost. This also influences the embodied energy and the global warming potential. We show that a placement of a high concentration photovoltaic thermal solar power station outside of the city using a district cooling system has a double beneficial effect since it improves the solar conversion efficiency and reduces the energy demand for cooling in the city. We also explain the mechanisms of the current economic development of solar technologies and anticipate changes.

  5. Placement and efficiency effects on radiative forcing of solar installations

    Science.gov (United States)

    Burg, Brian R.; Ruch, Patrick; Paredes, Stephan; Michel, Bruno

    2015-09-01

    The promise for harnessing solar energy being hampered by cost, triggered efforts to reduce them. As a consequence low-efficiency, low-cost photovoltaics (PV) panels prevail. Conversely, in the traditional energy sector efficiency is extremely important due to the direct costs associated to fuels. This also affects solar energy due to the radiative forcing caused by the dark solar panels. In this paper we extend the concept of energy payback time by including the effect of albedo change, which gives a better assessment of the system sustainability. We present an analysis on the short and medium term climate forcing effects of different solar collectors in Riyadh, Saudi Arabia and demonstrate that efficiency is important to reduce the collector area and cost. This also influences the embodied energy and the global warming potential. We show that a placement of a high concentration photovoltaic thermal solar power station outside of the city using a district cooling system has a double beneficial effect since it improves the solar conversion efficiency and reduces the energy demand for cooling in the city. We also explain the mechanisms of the current economic development of solar technologies and anticipate changes.

  6. Role of the radiation-reaction force in the optical response of two-dimensional crystals

    CERN Document Server

    Merano, Michele

    2016-01-01

    A classical theory of a radiating two-dimensional crystal is proposed and an expression for the radiative-reaction force is derived. It is shown how this force, acting on the dipoles forming the material, induces a flow of energy away from the dipole vibrations into radiative electromagnetic energy. As conservation of energy requires, the time-average work per unit time and unit area done by the radiation-reaction force is negative and equal in absolute value to the time-average intensity radiated by the crystal.

  7. Non-Kyoto radiative forcing in long-run greenhouse gas emissions and climate change scenarios

    NARCIS (Netherlands)

    Rose, S.K.; Kriegler, E.; Bibas, R.; Calvin, K.; Popp, A.; van Vuuren, D.P.; Weyant, J.

    2014-01-01

    Climate policies must consider radiative forcing from Kyoto greenhouse gases, as well as other forcing constituents, such as aerosols and tropospheric ozone that result from air pollutants. Non-Kyoto forcing constituents contribute negative, as well as positive forcing, and overall increases in tota

  8. Non-Kyoto radiative forcing in long-run greenhouse gas emissions and climate change scenarios

    NARCIS (Netherlands)

    Rose, S.K.; Kriegler, E.; Bibas, R.; Calvin, K.; Popp, A.; van Vuuren, D.P.; Weyant, J.

    2014-01-01

    Climate policies must consider radiative forcing from Kyoto greenhouse gases, as well as other forcing constituents, such as aerosols and tropospheric ozone that result from air pollutants. Non-Kyoto forcing constituents contribute negative, as well as positive forcing, and overall increases in

  9. Modeling of an omni-directional electromagnetic acoustic transducer driven by the Lorentz force mechanism

    Science.gov (United States)

    Wang, Shen; Huang, Songling; Zhang, Yu; Zhao, Wei

    2016-12-01

    The electromagnetic acoustic transducers (EMATs) are gaining much attention in recent years due to their non-contact operation in ultrasonic wave generation and reception in NDT field. Quite often the transduction efficiency of EMATs is low, so efforts are always necessary to gain a better understanding of their complex and multi-physics transduction mechanism. In this work, we focused on modeling of an omni-directional Lorentz force-based EMAT operating on an aluminum disk and containing a rounded meander coil to generate a pure Lamb wave mode. We introduced an approach to solve the underlying eddy current equations in cylindrical coordinates directly, and applied this approach to a multi-conductor electromagnetic model to investigate the skin and proximity effects. These effects existed both for the complete and incomplete equations. Then we built the omni-directional EMAT model composed of three sub-models and two geometries. The two-geometry structure made it possible to reduce the total number of elements. Time varying spatial distribution of the Lorentz force vector was plotted. Propagation velocity of the simulated wave packet was compared with the group velocity of desired S0 mode Lamb waves. Interaction of the waves with a slot defect with a depth of 50% thickness was studied. The response to high current excitation and dynamic magnetic field was also investigated.

  10. Gravitational self-force from radiation-gauge metric perturbations

    Science.gov (United States)

    Pound, Adam; Merlin, Cesar; Barack, Leor

    2014-01-01

    Calculations of the gravitational self-force (GSF) on a point mass in curved spacetime require as input the metric perturbation in a sufficiently regular gauge. A basic challenge in the program to compute the GSF for orbits around a Kerr black hole is that the standard procedure for reconstructing the metric perturbation is formulated in a class of “radiation” gauges, in which the particle singularity is nonisotropic and extends away from the particle’s location. Here we present two practical schemes for calculating the GSF using a radiation-gauge reconstructed metric as input. The schemes are based on a detailed analysis of the local structure of the particle singularity in the radiation gauges. We show that three types of radiation gauge exist: two containing a radial stringlike singularity emanating from the particle, either in one direction (“half-string” gauges) or both directions (“full-string” gauges); and a third type containing no strings but with a jump discontinuity (and possibly a delta function) across a surface intersecting the particle. Based on a flat-space example, we argue that the standard mode-by-mode reconstruction procedure yields the “regular half” of a half-string solution, or (equivalently) either of the regular halves of a no-string solution. For the half-string case, we formulate the GSF in a locally deformed radiation gauge that removes the string singularity near the particle. We derive a mode-sum formula for the GSF in this gauge, which is analogous to the standard Lorenz-gauge formula but requires a correction to the values of the regularization parameters. For the no-string case, we formulate the GSF directly, without a local deformation, and we derive a mode-sum formula that requires no correction to the regularization parameters but involves a certain averaging procedure. We explain the consistency of our results with Gralla’s invariance theorem for the regularization parameters, and we discuss the

  11. Analytical Model of the Nonlinear Dynamics of Cantilever Tip-Sample Surface Interactions for Various Acoustic-Atomic Force Microscopies

    Science.gov (United States)

    Cantrell, John H., Jr.; Cantrell, Sean A.

    2008-01-01

    A comprehensive analytical model of the interaction of the cantilever tip of the atomic force microscope (AFM) with the sample surface is developed that accounts for the nonlinearity of the tip-surface interaction force. The interaction is modeled as a nonlinear spring coupled at opposite ends to linear springs representing cantilever and sample surface oscillators. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a standard iteration procedure. Solutions are obtained for the phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) techniques including force modulation microscopy, atomic force acoustic microscopy, ultrasonic force microscopy, heterodyne force microscopy, resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), and the commonly used intermittent contact mode (TappingMode) generally available on AFMs. The solutions are used to obtain a quantitative measure of image contrast resulting from variations in the Young modulus of the sample for the amplitude and phase images generated by the A-AFM techniques. Application of the model to RDF-AFUM and intermittent soft contact phase images of LaRC-cp2 polyimide polymer is discussed. The model predicts variations in the Young modulus of the material of 24 percent from the RDF-AFUM image and 18 percent from the intermittent soft contact image. Both predictions are in good agreement with the literature value of 21 percent obtained from independent, macroscopic measurements of sheet polymer material.

  12. Partially acoustic dark matter, interacting dark radiation, and large scale structure

    Science.gov (United States)

    Chacko, Zackaria; Cui, Yanou; Hong, Sungwoo; Okui, Takemichi; Tsai, Yuhsinz

    2016-12-01

    The standard paradigm of collisionless cold dark matter is in tension with measurements on large scales. In particular, the best fit values of the Hubble rate H 0 and the matter density perturbation σ 8 inferred from the cosmic microwave background seem inconsistent with the results from direct measurements. We show that both problems can be solved in a framework in which dark matter consists of two distinct components, a dominant component and a subdominant component. The primary component is cold and collisionless. The secondary component is also cold, but interacts strongly with dark radiation, which itself forms a tightly coupled fluid. The growth of density perturbations in the subdominant component is inhibited by dark acoustic oscillations due to its coupling to the dark radiation, solving the σ 8 problem, while the presence of tightly coupled dark radiation ameliorates the H 0 problem. The subdominant component of dark matter and dark radiation continue to remain in thermal equilibrium until late times, inhibiting the formation of a dark disk. We present an example of a simple model that naturally realizes this scenario in which both constituents of dark matter are thermal WIMPs. Our scenario can be tested by future stage-IV experiments designed to probe the CMB and large scale structure.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D [Kyung Hee University International Med. Serv., Seoul (Korea, Republic of); Chung, W [Kyung Hee University Hospital at Gangdong, Seoul, Seoul (Korea, Republic of); Shin, D [Kyung Hee University Hospital, Seoul, Seoul (Korea, Republic of); Yoon, M [Korea University, Seoul (Korea, Republic of)

    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.

  14. Radiation closure and diurnal cycle of the clear-sky dust instantaneous direct radiative forcing over Arabian Peninsula

    KAUST Repository

    Osipov, Sergey

    2015-04-01

    To better quantify radiative effects of dust over the Arabian Peninsula we have developed a standalone column radiation transport model coupled with the Mie calculations and driven by reanalysis meteorological fields and atmospheric composition. Numerical experiments are carried out for a wide range of aerosol optical depths, including extreme values developed during the dust storm on 18-20 March 2012. Comprehensive ground-based observations and satellite retrievals are used to estimate aerosol optical properties, validate calculations and carry out radiation closure. The broadband surface albedo, fluxes at the bottom and top of the atmosphere as well as instantaneous dust radiative forcing are estimated both from the model and from observations. Diurnal cycle of the the shortwave instantaneous dust direct radiative forcing is studied for a range of aerosol and surface characteristics representative for the Arabian Peninsula. Mechanisms and parameters responsible for diurnal variability of the radiative forcing are evaluated. We found that intrinsic variability of the surface albedo and its dependence on atmospheric conditions along with anisotropic aerosol scattering are mostly responsible for diurnal effects. We also discuss estimates of the climatological dust instantaneous direct radiative forcing over land and the Red Sea using two approaches. The first approach is based on the probability density function of the aerosol optical depth, and the second is based on the climatologically average Spinning Enhanced Visible and Infrared Imager (SEVIRI) aerosol optical depth. Results are compared with Geostationary Earth Radiation Budget (GERB) derived top of the atmosphere climatological forcing over the Red Sea.

  15. Radiative forcing from particle emissions by future supersonic aircraft

    Directory of Open Access Journals (Sweden)

    G. Pitari

    2008-07-01

    Full Text Available In this work we focus on the direct radiative forcing (RF of black carbon (BC and sulphuric acid particles emitted by future supersonic aircraft, as well as on the ozone RF due to changes produced by emissions of both gas species (NOx, H2O and aerosol particles capable of affecting stratospheric ozone chemistry. Heterogeneous chemical reactions on the surface of sulphuric acid stratospheric particles (SSA-SAD are the main link between ozone chemistry and supersonic aircraft emissions of sulphur precursors (SO2 and particles (H2O–H2SO4. Photochemical O3 changes are compared from four independent 3-D atmosphere-chemistry models (ACMs, using as input the perturbation of SSA-SAD calculated in the University of L'Aquila model, which includes on-line a microphysics code for aerosol formation and growth. The ACMs in this study use aircraft emission scenarios for the year 2050 developed by AIRBUS as a part of the EU project SCENIC, assessing options for fleet size, engine technology (NOx emission index, Mach number, range and cruising altitude. From our baseline modeling simulation, the impact of supersonic aircraft on sulphuric acid aerosol and BC mass burdens is 53 and 1.5 μg/m2, respectively, with a direct RF of −11.4 and 4.6 mW/m2 (net RF=−6.8 mW/m2. This paper discusses the similarities and differences amongst the participating models in terms of changes to O3 precursors due to aircraft emissions (NOx, HOx,Clx,Brx and the stratospheric ozone sensitivity to them. In the baseline case, the calculated global ozone change is −0.4 ±0.3 DU, with a net radiative forcing (IR+UV of −2.5± 2 mW/m2. The fraction of this O3-RF attributable to SSA-SAD changes is, however, highly variable among the models, depending on the NOx removal

  16. Value of acoustic radiation force impulse imaging in the differential diagnosis between benign and malignant solitary solid thyroid nodules%声辐射力脉冲弹性成像在甲状腺单发实性结节良恶性鉴别诊断中的应用价值

    Institute of Scientific and Technical Information of China (English)

    章晶; 徐辉雄; 张一峰; 徐军妹; 刘畅; 郭乐杭; 刘琳娜

    2013-01-01

    级≥Ⅳ级的结节19个,包括良性结节8个,恶性结节11个;VTI分级<Ⅳ级的结节23个,包括良性结节22个,恶性结节1个;VTI诊断甲状腺恶性单发实性结节的敏感度、特异度、阳性预测值、阴性预测值分别为91.7%(11/12)、73.3%(22/30)、57.8%(11/19)、95.7%(22/23)。常规超声+VTI诊断甲状腺恶性单发实性结节的敏感度、特异度、阳性预测值、阴性预测值分别为91.7%(11/12)、80.0%(24/30)、64.7%(11/17)、96.0%(24/25)。而常规超声+VTQ诊断甲状腺恶性单发实性结节的敏感度、特异度、阳性预测值、阴性预测值分别为91.7%(11/12)、83.3%(25/30)、68.8%(11/16)、96.2%(25/26)。结论单独的ARFI技术诊断甲状腺单发实性结节良恶性的能力并不优于常规超声,但是两者联合应用可提高甲状腺单发实性结节良恶性鉴别诊断水平。%Objective To explore the value of virtual touch tissue imaging (VTI) and virtual touch tissue quantification ( VTQ) of acoustic radiation force impulse ( ARFI) elastography in the differential diagnosis between benign and malignant solitary solid thyroid nodules in ultrasound .Methods The ARFI elastography characteristics and ultrasound (US) features of 42 histologically proven solid or predominantly solid thyroid nodules in 42 patients with a solitary nodule were reviewed .The pathological diagnosis was the gold standard and the sensitivity ,specificity,positive predictive value (PPV) and negative predictive value (NPV) of US, VTQ and VTI in diagnosis of malignant solitary solid thyroid nodules were caculated. Results Forty-two nodules included 30 benign lesions(16 nodular goiters,13 adenomatous goiters and one subacute thyroiditis)and 12 malignant lesions(papillary carcinomas).The sonographic features that suggested malignancy include hypoechogenicity , irregular or microlobulated margin

  17. Force Limiting Vibration Tests Evaluated from both Ground Acoustic Tests and FEM Simulations of a Flight Like Vehicle System Assembly

    Science.gov (United States)

    Smith, Andrew; LaVerde, Bruce; Waldon, James; Hunt, Ron

    2014-01-01

    Marshall Space Flight Center has conducted a series of ground acoustic tests with the dual goals of informing analytical judgment, and validating analytical methods when estimating vibroacoustic responses of launch vehicle subsystems. The process of repeatedly correlating finite element-simulated responses with test-measured responses has assisted in the development of best practices for modeling and post-processing. In recent work, force transducers were integrated to measure interface forces at the base of avionics box equipment. Other force data was indirectly measured using strain gauges. The combination of these direct and indirect force measurements has been used to support and illustrate the advantages of implementing the Force Limiting approach for equipment qualification tests. The comparison of force response from integrated system level tests to measurements at the same locations during component level vibration tests provides an excellent illustration. A second comparison of the measured response cases from the system level acoustic tests to finite element simulations has also produced some principles for assessing the suitability of Finite Element Models (FEMs) for making vibroacoustics estimates. The results indicate that when FEM models are employed to guide force limiting choices, they should include sufficient detail to represent the apparent mass of the system in the frequency range of interest.

  18. Regional and seasonal radiative forcing by perturbations to aerosol and ozone precursor emissions

    Science.gov (United States)

    Bellouin, Nicolas; Baker, Laura; Hodnebrog, Øivind; Olivié, Dirk; Cherian, Ribu; Macintosh, Claire; Samset, Bjørn; Esteve, Anna; Aamaas, Borgar; Quaas, Johannes; Myhre, Gunnar

    2016-11-01

    Predictions of temperature and precipitation responses to changes in the anthropogenic emissions of climate forcers require the quantification of the radiative forcing exerted by those changes. This task is particularly difficult for near-term climate forcers like aerosols, methane, and ozone precursors because their short atmospheric lifetimes cause regionally and temporally inhomogeneous radiative forcings. This study quantifies specific radiative forcing, defined as the radiative forcing per unit change in mass emitted, for eight near-term climate forcers as a function of their source regions and the season of emission by using dedicated simulations by four general circulation and chemistry-transport models. Although differences in the representation of atmospheric chemistry and radiative processes in different models impede the creation of a uniform dataset, four distinct findings can be highlighted. Firstly, specific radiative forcing for sulfur dioxide and organic carbon are stronger when aerosol-cloud interactions are taken into account. Secondly, there is a lack of agreement on the sign of the specific radiative forcing of volatile organic compound perturbations, suggesting they are better avoided in climate mitigation strategies. Thirdly, the strong seasonalities of the specific radiative forcing of most forcers allow strategies to minimise positive radiative forcing based on the timing of emissions. Finally, European and shipping emissions exert stronger aerosol specific radiative forcings compared to East Asia where the baseline is more polluted. This study can therefore form the basis for further refining climate mitigation options based on regional and seasonal controls on emissions. For example, reducing summertime emissions of black carbon and wintertime emissions of sulfur dioxide in the more polluted regions is a possible way to improve air quality without weakening the negative radiative forcing of aerosols.

  19. Aerosol Direct Radiative Forcing and Forcing Efficiencies at Surface from the shortwave Irradiance Measurements in Abu Dhabi, UAE

    Science.gov (United States)

    Beegum S, N.; Ben Romdhane, H.; Ghedira, H.

    2013-12-01

    Atmospheric aerosols are known to affect the radiation balance of the Earth-Atmospheric system directly by scattering and absorbing the solar and terrestrial radiation, and indirectly by affecting the lifetime and albedo of the clouds. Continuous and simultaneous measurements of short wave global irradiance in combination with synchronous spectral aerosol optical depth (AOD) measurements (from 340 nm to 1640 nm in 8 channels), for a period of 1 year from June 2012 to May 2013, were used for the determination of the surface direct aerosol radiative forcing and forcing efficiencies under cloud free conditions in Abu Dhabi (24.42°N, 54.61o E, 7m MSL), a coastal location in United Arab Emirates (UAE) in the Arabian Peninsula. The Rotating Shadow band Pyranometer (RSP, LI-COR) was used for the irradiance measurements (in the spectral region 400-1100 nm), whereas the AOD measurements were carried out using CIMEL Sunphotometer (CE 318-2, under AERONET program). The differential method, which is neither sensitive to calibration uncertainties nor model assumptions, has been employed for estimating forcing efficiencies from the changes in the measured fluxes. The forcing efficiency, which quantifies the net change in irradiance per unit change in AOD, is an appropriate parameter for the characterization of the aerosol radiative effects even if the microphysical and optical properties of the aerosols are not completely understood. The corresponding forcing values were estimated from the forcing efficiencies. The estimated radiative forcing and forcing efficiencies exhibited strong monthly variations. The forcing efficiencies (absolute magnitudes) were highest during March, and showed continuous decrease thereafter to reach the lowest value during September. In contrast, the forcing followed a slightly different pattern of variability, with the highest solar dimming during April ( -60 W m-2) and the minimum during February ( -20 W m-2). The results indicate that the aerosol

  20. Uncertainities in carbon dioxide radiative forcing in atmospheric general circulation models

    Energy Technology Data Exchange (ETDEWEB)

    Cess, R.D.; Zhang, M.H. (State Univ. of New York, Stony Brook, NY (United States)); Potter, G.L.; Gates, W.L.; Taylor, K.E. (Lawrence Livermore National Laboratory, CA (United States)); Colman, R.A.; Fraser, J.R.; McAvaney, B.J. (Bureau of Meterorology Research Centre, Victoria (Australia)); Dazlich, D.A.; Randall, D.A. (Colorado State Univ., Fort Collins, CO (United States)); Del Genio, A.D.; Lacis, A.A. (Goddard Institute for Space Studies, New York, NY (United States)); Esch, M.; Roeckner, E. (Max Planck Institute for Meteorology, Hamburg (Germany)); Galin, V. (Russian Academy of Sciences, Moscow (Russian Federation)); Hack, J.J.; Kiehl, J.T. (National Center for Atmospheric Research, Boulder, CO (United States)); Ingram, W.J. (Hadley Centre for Climate Prediction and Research, Berkshire (United Kingdom)); Le Treut, H.; Lli, Z.X. (Laboratoire de Meteorologie Dynamique, Paris (France)); Liang, X.Z.; Wang, W.C. (State Univ. of New York, Albany, NY (United States)); Mahfouf,

    1993-11-19

    Global warming, caused by an increase in the concentrations of greenhouse gases, is the direct result of greenhouse gas-induced radiative forcing. When a doubling of atmospheric carbon dioxide is considered, this forcing differed substantially among 15 atmospheric general circulation models. Although there are several potential causes, the largest contributor was the carbon dioxide radiation parameterizations of the models.

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

    Science.gov (United States)

    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.

  2. Dictums for problem solving and approximation in mathematical acoustics: examples involving low-frequency vibration and radiation.

    Science.gov (United States)

    Pierce, Allan D; Thiam, Amadou G

    2012-03-01

    A sequence of dictums for mathematical acoustics is given representing opinions intended to be regarded as authoritative, but not necessarily universally agreed upon. The dictums are presented in the context of the detailed solution for a class of problems involving the forced vibration of a long cylinder protruding half-way into a half-space bounded by a compliant surface (impedance boundary) characterized by a spring constant. One limiting case corresponds to a cylinder vibrating within an infinite rigid baffle, and another limiting case corresponds to a vibrating cylinder on the compliant surface of an incompressible fluid. The second limiting case is identified as analogous to that of a floating half-submerged cylinder whose vibrations cause water waves to propagate over the surface. Attention is focused on vibrations at very low frequencies. Difficulties with insuring a causal solution are pointed out and dictums are given as to how one overcomes such difficulties. Various approximation techniques are described. The derivations involve application of the theory of complex variables and the method of matched asymptotic expansions, and the results include the apparent entrained mass in the near field of the cylinder and the radiation resistance per unit length experienced by the vibrating cylinder.

  3. Acoustoelectric effects in reflection of leaky-wave-radiated bulk acoustic waves from piezoelectric crystal-conductive liquid interface.

    Science.gov (United States)

    Rimeika, Romualdas; Čiplys, Daumantas; Jonkus, Vytautas; Shur, Michael

    2016-01-01

    The leaky surface acoustic wave (SAW) propagating along X-axis of Y-cut lithium tantalate crystal strongly radiates energy in the form of an obliquely propagating narrow bulk acoustic wave (BAW) beam. The reflection of this beam from the crystal-liquid interface has been investigated. The test liquids were solutions of potassium nitrate in distilled water and of lithium chloride in isopropyl alcohol with the conductivity varied by changing the solution concentration. The strong dependences of the reflected wave amplitude and phase on the liquid conductivity were observed and explained by the acoustoelectric interaction in the wave reflection region. The novel configuration of an acoustic sensor for liquid media featuring important advantages of separate measuring and sensing surfaces and rigid structure has been proposed. The application of leaky-SAW radiated bulk waves for identification of different brands of mineral water has been demonstrated.

  4. Elastic stiffness and damping measurements in titanium alloys using atomic force acoustic microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kalyan Phani, M. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 Tamil Nadu (India); Kumar, Anish, E-mail: anish@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102 Tamil Nadu (India); Arnold, W. [Department of Materials and Materials Technology, Saarland University, Campus D 2.2, D-66123 Saarbrücken (Germany); 1. Physikalisches Institut, Georg-August-Universität, Friedrich Hund Platz 1, D-37077 Göttingen (Germany); Samwer, K. [1. Physikalisches Institut, Georg-August-Universität, Friedrich Hund Platz 1, D-37077 Göttingen (Germany)

    2016-08-15

    Atomic force acoustic microscopy (AFAM) has been used to study the distribution of elastic stiffness and damping properties across different phases, such as α &β phases in a β titanium alloy (Ti−10V−4.5Fe−1.5Al) and α, β and α′ phases in an α + β alloy (Ti−6Al−4V). Contact-resonance spectra were obtained with a 100 nm spatial resolution in various specimens of the two titanium alloys heat-treated at different temperatures. The study indicates that the metastable β phase has the minimum modulus and maximum damping followed by α′ and α-phases. Employing the rule of mixtures, the average modulus measured by AFAM was then compared with the modulus obtained by ultrasonic velocity measurements. The error in the average modulus values obtained by both techniques is discussed. - Highlights: • Mapping of elastic stiffness and damping across various phases in titanium alloys. • Influence of alloy chemistry and crystal orientation on the results are discussed. • β phase has the minimum modulus and maximum damping followed by α′ and α-phases. • Average modulus of sample calculated from AFAM measurements on individual phases.

  5. Temperature response of an acoustically forced turbulent lean premixed flame: A quantitative experimental determination

    KAUST Repository

    Chrystie, Robin

    2013-01-02

    Temperature measurements have been taken on an acoustically forced lean premixed turbulent bluff-body stabilized flame. The burner used in this study is a test-bed to investigate thermoacoustic instability in gas-turbine engines at the University of Cambridge. Numerous experiments have been performed on the burner, one of which used two-line OH planar laser induced fluorescence to measure temperature. Here, we employ vibrational coherent anti-Stokes Raman scattering (CARS) of nitrogen as an alternative to measure temperature, circumventing the limitations of the former method. The use of nitrogen CARS avoids the problem of probing regions of the flame with low OH concentrations that resulted in erroneous temperature. Such an application of CARS showed that the results from previous efforts were systematically biased up to 47% close to the bluff-body. We also critically review the limitations of CARS used in our experiments, pertaining to spatial resolution and associated biasing further downstream from the bluff-body. Using the more accurate results from this work, more up-to-date computational fluid dynamical (CFD) models of the burner can be validated, with the aim of improved understanding and prediction of thermoacoustic instability in gas turbines. © 2013 Copyright Taylor and Francis Group, LLC.

  6. Quantifying immediate radiative forcing by black carbon and organic matter with the Specific Forcing Pulse

    Directory of Open Access Journals (Sweden)

    T. C. Bond

    2011-02-01

    12 additional models. We outline a framework for combining a large number of simple models with a smaller number of enhanced models that have greater complexity. Adjustments for black carbon internal mixing and for regional variability are discussed. Emitting regions with more deep convection have greater model diversity. Our best estimate of global-mean SFP is +1.03 ± 0.52 GJ g−1 for direct atmosphere forcing of black carbon, +1.15 ± 0.53 GJ g−1 for black carbon including direct and cryosphere forcing, and −0.064 (−0.02, −0.13 GJ g−1 for organic matter. These values depend on the region and timing of emission. The lowest OM:BC mass ratio required to produce a neutral effect on top-of-atmosphere direct forcing is 15:1 for any region. Any lower ratio results in positive direct forcing. However, important processes, particularly cloud changes that tend toward cooling, have not been included here.

    Global-average SFP for energy-related emissions can be converted to a 100-year GWP of about 740 ± 370 for BC without snow forcing, and 830 ± 440 with snow forcing. 100-year GWP for OM is −46 (−18, −92. Best estimates of atmospheric radiative impact (without snow forcing by black and organic matter are +0.47 ± 0.26 W m−2 and −0.17 (−0.07, −0.35 W m−2 for BC and OM, respectively, assuming total emission rates of 7.4 and 45 Tg yr−1. Anthropogenic forcing is +0.40 ± 0.18 W m−2 and −0.13 (−0.05, −0.25 W m−2 for BC and OM, respectively, assuming anthropogenic emission rates of 6.3 and 32.6 Tg yr−1. Black carbon forcing is only 18% higher than that given by the Intergovernmental Panel on Climate Change (IPCC, although the value presented here includes enhanced absorption due to internal mixing.

  7. Radiative transfer of acoustic waves in continuous complex media: Beyond the Helmholtz equation

    CERN Document Server

    Baydoun, Ibrahim; Pierrat, Romain; Derode, Arnaud

    2016-01-01

    Heterogeneity can be accounted for by a random potential in the wave equation. For acoustic waves in a fluid with fluctuations of both density and compressibility (as well as for electromagnetic waves in a medium with fluctuation of both permittivity and permeability) the random potential entails a scalar and an operator contribution. For simplicity, the latter is usually overlooked in multiple scattering theory: whatever the type of waves, this simplification amounts to considering the Helmholtz equation with a sound speed $c$ depending on position $\\mathbf{r}$. In this work, a radiative transfer equation is derived from the wave equation, in order to study energy transport through a multiple scattering medium. In particular, the influence of the operator term on various transport parameters is studied, based on the diagrammatic approach of multiple scattering. Analytical results are obtained for fundamental quantities of transport theory such as the transport mean-free path $\\ell^*$, scattering phase functi...

  8. The enhanced volume source boundary point method for the calculation of acoustic radiation problem

    Institute of Scientific and Technical Information of China (English)

    WANG Xiufeng; CHEN Xinzhao; WANG Youcheng

    2003-01-01

    The Volume Source Boundary Point Method (VSBPM) is greatly improved so that it will speed up the VSBPM's solution of the acoustic radiation problem caused by the vibrating body. The fundamental solution provided by Helmholtz equation is enforced in a weighted residual sense over a tetrahedron located on the normal line of the boundary node to replace the coefficient matrices of the system equation. Through the enhanced volume source boundary point analysis of various examples and the sound field of a vibrating rectangular box in a semi-anechoic chamber, it has revealed that the calculating speed of the EVSBPM is more than 10 times faster than that of the VSBPM while it works on the aspects of its calculating precision and stability, adaptation to geometric shape of vibrating body as well as its ability to overcome the non-uniqueness problem.

  9. Nonlinear vibration and radiation from a panel with transition to chaos induced by acoustic waves

    Science.gov (United States)

    Maestrello, Lucio; Frendi, Abdelkader; Brown, Donald E.

    1992-01-01

    The dynamic response of an aircraft panel forced at resonance and off-resonance by plane acoustic waves at normal incidence is investigated experimentally and numerically. Linear, nonlinear (period doubling) and chaotic responses are obtained by increasing the sound pressure level of the excitation. The response time history is sensitive to the input level and to the frequency of excitation. The change in response behavior is due to a change in input conditions, triggered either naturally or by modulation of the bandwidth of the incident waves. Off-resonance, bifurcation is diffused and difficult to maintain, thus the panel response drifts into a linear behavior. The acoustic pressure emanated by the panel is either linear or nonlinear as is the vibration response. The nonlinear effects accumulate during the propagation with distance. Results are also obtained on the control of the panel response using damping tape on aluminum panel and using a graphite epoxy panel having the same size and weight. Good agreement is obtained between the experimental and numerical results.

  10. Aerosol types and radiative forcing estimates over East Asia

    Science.gov (United States)

    Bhawar, Rohini L.; Lee, Woo-Seop; Rahul, P. R. C.

    2016-09-01

    Using the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) and MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data sets along with the CSIRO-MK 3.6.0 model simulations, we analyzed the aerosol optical depth (AOD) variability during March-May (MAM), June-August (JJA) along with their annual mean variability over East Asia for the period 2006-2012. The CALIPSO measurements correlated well with the MODIS measurements and the CSIRO-MK 3.6.0 model simulations over the spatial distribution patterns of the aerosols, but CALIPSO underestimated the magnitudes of the AOD. Maximum smoke aerosol loading is observed to occur during JJA, as a result of wind transport from Southern China while dust loading dominated during MAM via the transport from desert region. The vertical distribution profiles revealed that there is uniform distribution of smoke aerosols during both MAM and JJA, only differing at the altitude at which they peak; while the dust aerosols during MAM showed a significant distribution from the surface to 10 km altitude and JJA was marked with lower dust loading at the same altitudes. Both dust and smoke aerosols warm the atmosphere in MAM but due to the absorbing nature of smoke aerosols, they cause considerable cooling at the surface which is double when compared to the dust aerosols. The top of the atmosphere aerosol radiative forcing (ARF) due to smoke and dust aerosols is positive in MAM which indicates warming over East Asia. During MAM a consistent declining trend of the surface ARF due to smoke aerosols persisted over the last three decades as conspicuously evidenced from model analysis; the decline is ∼10 W/m2 from 1980 to 2012.

  11. Acoustic Neuroma Educational Video

    Medline Plus

    Full Text Available ... Back Learn about acoustic neuroma AN Facts What is acoustic neuroma? Diagnosing Symptoms Side Effects Keywords Questions ... kit Treatment Options Overview Observation Radiation Surgery What is acoustic neuroma Diagnosing Symptoms Side effects Question To ...

  12. Highly Localized Acoustic Streaming and Size-Selective Submicrometer Particle Concentration Using High Frequency Microscale Focused Acoustic Fields.

    Science.gov (United States)

    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.

  13. Vibroacoustics of the piano soundboard: Reduced models, mobility synthesis, and acoustical radiation regime

    Science.gov (United States)

    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. Thermal convection driven by acoustic field under microgravity

    OpenAIRE

    Tanabe, Mitsuaki; 田辺 光昭

    2007-01-01

    Natural convection is suppressed in space environment due to the weightlessness. Only centrifugal force is utilized currently to drive gas-phase thermal convection in space. This paper presents an alternative way to drive thermal convection. From the investigation of combustion oscillation in rocket motors, a new thermal convection had been found in stationary acoustic fields. Analyzing the phenomena, acoustic radiation force is found to be the candidate driving force. With a simplified syste...

  15. The Effect of Non-Lambertian Surface Reflectance on Aerosol Radiative Forcing

    Energy Technology Data Exchange (ETDEWEB)

    Ricchiazzi, P.; O' Hirok, W.; Gautier, C.

    2005-03-18

    Surface reflectance is an important factor in determining the strength of aerosol radiative forcing. Previous studies of radiative forcing assumed that the reflected surface radiance is isotropic and does not depend on incident illumination angle. This Lambertian reflection model is not a very good descriptor of reflectance from real land and ocean surfaces. In this study we present computational results for the seasonal average of short and long wave aerosol radiative forcing at the top of the atmosphere and at the surface. The effect of the Lambertian assumption is found through comparison with calculations using a more detailed bi-direction reflectance distribution function (BRDF).

  16. Acoustics of finite-aperture vortex beams

    CERN Document Server

    Mitri, F G

    2014-01-01

    A method based on the Rayleigh-Sommerfeld surface integral is provided, which makes it feasible to rigorously model, evaluate and compute the acoustic scattering and other mechanical effects of finite-aperture vortex beams such as the acoustic radiation force and torque on a viscoelastic sphere in various applications in acoustic tweezers and microfluidics, particle entrapment, manipulation and rotation. Partial-wave series expansions are derived for the incident field of acoustic spiraling (vortex) beams, comprising high-order Bessel and Bessel-Gauss beams.

  17. Mapping of elasticity and damping in an α + β titanium alloy through atomic force acoustic microscopy

    Directory of Open Access Journals (Sweden)

    M. Kalyan Phani

    2015-03-01

    Full Text Available The distribution of elastic stiffness and damping of individual phases in an α + β titanium alloy (Ti-6Al-4V measured by using atomic force acoustic microscopy (AFAM is reported in the present study. The real and imaginary parts of the contact stiffness k* are obtained from the contact-resonance spectra and by using these two quantities, the maps of local elastic stiffness and the damping factor are derived. The evaluation of the data is based on the mass distribution of the cantilever with damped flexural modes. The cantilever dynamics model considering damping, which was proposed recently, has been used for mapping of indentation modulus and damping of different phases in a metallic structural material. The study indicated that in a Ti-6Al-4V alloy the metastable β phase has the minimum modulus and the maximum damping followed by α′- and α-phases. Volume fractions of the individual phases were determined by using a commercial material property evaluation software and were validated by using X-ray diffraction (XRD and electron back-scatter diffraction (EBSD studies on one of the heat-treated samples. The volume fractions of the phases and the modulus measured through AFAM are used to derive average modulus of the bulk sample which is correlated with the bulk elastic properties obtained by ultrasonic velocity measurements. The average modulus of the specimens estimated by AFAM technique is found to be within 5% of that obtained by ultrasonic velocity measurements. The effect of heat treatments on the ultrasonic attenuation in the bulk sample could also be understood based on the damping measurements on individual phases using AFAM.

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

    Science.gov (United States)

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

    2016-09-01

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

  19. The Impacts of Optical Properties on Radiative Forcing Due to Dust Aerosol

    Institute of Scientific and Technical Information of China (English)

    WANG Hong; SHI Guangyu; LI Shuyan; LI Wei; WANG Biao; HUANG Yanbin

    2006-01-01

    There are large uncertainties in the quantitative assessment of radiative effects due to atmospheric dust aerosol. The optical properties contribute much to those uncertainties. The authors perform several sensitivity experiments to estimate the impacts of optical characteristics on regional radiative forcing in this paper. The experiments involve in refractive indices, single scattering albedo, asymmetry factor and optical depth. An updated dataset of refractive indices representing East Asian dust and the one recommended by the World Meteorology Organization (WMO) are contrastively analyzed and used. A radiative transfer code for solar and thermal infrared radiation with detailed aerosol parameterization is employed. The strongest emphasis is on the refractive indices since other optical parameters strongly depend on it, and the authors found a strong sensitivity of radiative forcing on refractive indices. Studies show stronger scattering, weaker absorption and forward scattering of the East Asian dust particles at solar wavelengths, which leads to higher negative forcing, lower positive forcing and bigger net forcing at the top of the atmosphere (TOA) than that of the WMO dust model. It is also found that the TOA forcings resulting from these two dust models have opposite signs in certain regions, which implies the importance of accurate measurements of optical properties in the quantitative estimation of radiative forcing.

  20. Simulation of the spatial distribution of mineral dust and its direct radiative forcing over Australia

    Directory of Open Access Journals (Sweden)

    Omid Alizadeh Choobari

    2013-05-01

    Full Text Available Direct radiative forcing by mineral dust is important as it significantly affects the climate system by scattering and absorbing short-wave and long-wave radiation. The multi-angle imaging spectro radiometer (MISR and cloud–aerosol lidar with orthogonal polarisation (CALIOP aerosol data are used to observe mineral dust distribution over Australia. In addition, the weather research and forecasting with chemistry (WRF/Chem model is used to estimate direct radiative forcing by dust. At the surface, the model domain clear-sky short-wave and long-wave direct radiative forcing by dust averaged for a 6-month period (austral spring and summer was estimated to be −0.67 W m−2 and 0.13 W m−2, respectively. The long-wave warming effect of dust therefore offsets 19.4% of its short-wave cooling effect. However, over Lake Eyre Basin where coarse particles are more abundant, the long-wave warming effect of dust offsets 60.9% of the short-wave cooling effect. At the top of the atmosphere (TOA, clear-sky short-wave and long-wave direct radiative forcing was estimated to be −0.26 W m−2 and −0.01 W m−2, respectively. This leads to a net negative direct radiative forcing of dust at the TOA, indicating cooling of the atmosphere by an increase in outgoing radiation. Short-wave and long-wave direct radiative forcing by dust is shown to have a diurnal variation due to changes in solar zenith angle and in the intensity of infrared radiation. Atmospheric heating due to absorption of short-wave radiation was simulated, while the interaction of dust with long-wave radiation was associated with atmospheric cooling. The net effect was cooling of the atmosphere near the surface (below 0.2 km, with warming of the atmosphere at higher altitudes.

  1. The Potential Radiative Forcing of Global Land Use and Land Cover Change Activities

    Science.gov (United States)

    Ward, D. S.; Mahowald, N. M.; Kloster, S.

    2014-12-01

    Given the expected increase in pressure on land resources over the next century, there is a need to understand the total impacts of activities associated with land use and land cover change (LULCC). Here we quantify these impacts using the radiative forcing metric, including forcings from changes in long-lived greenhouse gases, tropospheric ozone, aerosol effects, and land surface albedo. We estimate radiative forcings from the different agents for historical LULCC and for six future projections using simulations from the National Center for Atmospheric Research Community Land Model and Community Atmosphere Models and additional offline analyses. When all forcing agents are considered together we show that 45% (+30%, -20%) of the present-day (2010) anthropogenic radiative forcing can be attributed to LULCC. Changes in the emission of non-CO2 greenhouse gases and aerosols from LULCC enhance the total LULCC radiative forcing by a factor of 2 to 3 with respect to the forcing from CO2 alone. In contrast, the non-CO2 forcings from fossil fuel burning are roughly neutral, due largely to the negative (cooling) impact of aerosols from these sources. We partition the global LULCC radiative forcing into three major sources: direct modification of land cover (e.g. deforestation), agricultural activities, and fire regime changes. Contributions from deforestation and agriculture are roughly equal in the present day, while changes to wildfire activity impose a small negative forcing globally. In 2100, deforestation activities comprise the majority of the LULCC radiative forcing for all projections except one (Representative Concentration Pathway (RCP) 4.5). This suggests that realistic scenarios of future forest area change are essential for projecting the contribution of LULCC to climate change. However, the commonly used RCP land cover change projections all include decreases in global deforestation rates over the next 85 years. To place an upper bound on the potential

  2. Dust vertical profile impact on global radiative forcing estimation using a coupled chemical-transport–radiative-transfer model

    Directory of Open Access Journals (Sweden)

    L. Zhang

    2013-07-01

    Full Text Available Atmospheric mineral dust particles exert significant direct radiative forcings and are important drivers of climate and climate change. We used the GEOS-Chem global three-dimensional chemical transport model (CTM coupled with the Fu-Liou-Gu (FLG radiative transfer model (RTM to investigate the dust radiative forcing and heating rate based on different vertical profiles for April 2006. We attempt to actually quantify the sensitivities of radiative forcing to dust vertical profiles, especially the discrepancies between using realistic and climatological vertical profiles. In these calculations, dust emissions were constrained by observations of aerosol optical depth (AOD. The coupled calculations utilizing a more realistic dust vertical profile simulated by GEOS-Chem minimize the physical inconsistencies between 3-D CTM aerosol fields and the RTM. The use of GEOS-Chem simulated vertical profile of dust extinction, as opposed to the FLG prescribed vertical profile, leads to greater and more spatially heterogeneous changes in the estimated radiative forcing and heating rate produced by dust. Both changes can be attributed to a different vertical structure between dust and non-dust source regions. Values of the dust vertically resolved AOD per grid level (VRAOD are much larger in the middle troposphere, though smaller at the surface when the GEOS-Chem simulated vertical profile is used, which leads to a much stronger heating rate in the middle troposphere. Compared to the FLG vertical profile, the use of GEOS-Chem vertical profile reduces the solar radiative forcing at the top of atmosphere (TOA by approximately 0.2–0.25 W m−2 over the African and Asian dust source regions. While the Infrared (IR radiative forcing decreases 0.2 W m−2 over African dust belt, it increases 0.06 W m−2 over the Asian dust belt when the GEOS-Chem vertical profile is used. Differences in the solar radiative forcing at the surface between the use of the GEOS-Chem and

  3. The anomalous radiation force of light on a left-handed material

    Institute of Scientific and Technical Information of China (English)

    Yi Xu-Nong; Liu Jin-Song; Chen Huan; Du Qiu-Jiao

    2010-01-01

    This paper derives the force of the electromagnetic radiation on left-handed materials(LHMs)by a direct applica-tion of the Lorentz law of classical electrodynamics.The expressions of radiation force are given for TE-polarised and TM-polarised fields.The numerical results demonstrate that electromagnetic waves exert an inverse lateral radiation force on each edge of the beams,that is,the lateral pressure is expansive for TE-polarised beams and compressive for TM-polarised beams.The investigation of the radiation force will provide insights into the fundamental properties of LHMs and will provide to better understanding of the interaction of light with LHMs.

  4. Iterative solution of multiple radiation and scattering problems in structural acoustics using the BL-QMR algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Malhotra, M. [Stanford Univ., CA (United States)

    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.

  5. Direct Radiative Forcing of Anthropogenic Aerosols over Oceans from Satellite Observations

    Institute of Scientific and Technical Information of China (English)

    CHEN Lin; SHI Guangyu; QIN Shiguang; YANG Su; ZHANG Peng

    2011-01-01

    Anthropogenic aerosols play an important role in the atmospheric energy balance. Anthropogenic aerosol optical depth (AOD) and its accompanying shortwave radiative forcing (RF) are usually simulated by numerical models. Recently, with the development of space-borne instruments and sophisticated retrieval algorithms, it has become possible to estimate aerosol radiative forcing based on satellite observations. In this study, we have estimated shortwave direct radiative forcing due to anthropogenic aerosols over oceans in all-sky conditions by combining clouds and the Single Scanner Footprint data of the Clouds and Earth's Radiant Energy System (CERES/SSF) experiment, which provide measurements of upward shortwave fluxes at the top of atmosphere, with Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol and cloud products. We found that globally averaged aerosol radiative forcing over oceans in the clear-sky conditions and all-sky conditions were -1.03±0.48 W m-2 and -0.34 ±0.16 W m-2, respectively. Direct radiative forcing by anthropogenic aerosols shows large regional and seasonal variations. In some regions and in particular seasons, the magnitude of direct forcing by anthropogenic aerosols can be comparable to the forcing of greenhouse gases. However, it shows that aerosols caused the cooling effect, rather than warming effect from global scale, which is different from greenhouse gases.

  6. Cloud forming properties of ambient aerosol in the Netherlands and resultant shortwave radiative forcing of climate

    NARCIS (Netherlands)

    Khlystov, A.

    1998-01-01

    This thesis discusses properties of ambient aerosols in the Netherlands which are controlling the magnitude of the local aerosol radiative forcing. Anthropogenic aerosols influence climate by changing the radiative transfer through the atmosphere via two effects, one is direct and a second

  7. Aerosol properties and radiative forcing for three air masses transported in Summer 2011 to Sopot, Poland

    Science.gov (United States)

    Rozwadowska, Anna; Stachlewska, Iwona S.; Makuch, P.; Markowicz, K. M.; Petelski, T.; Strzałkowska, A.; Zieliński, T.

    2013-05-01

    Properties of atmospheric aerosols and solar radiation reaching the Earth's surface were measured during Summer 2011 in Sopot, Poland. Three cloudless days, characterized by different directions of incoming air-flows, which are typical transport pathways to Sopot, were used to estimate a radiative forcing due to aerosols present in each air mass.

  8. Cloud forming properties of ambient aerosol in the Netherlands and resultant shortwave radiative forcing of climate.

    NARCIS (Netherlands)

    Khlystov, A.

    1998-01-01

    This thesis discusses properties of ambient aerosols in the Netherlands which are controlling the magnitude of the local aerosol radiative forcing. Anthropogenic aerosols influence climate by changing the radiative transfer through the atmosphere via two effects, one is direct and a second is indire

  9. A Matlab Toolbox for Parametric Identification of Radiation-Force Models of Ships and Offshore Structures

    Directory of Open Access Journals (Sweden)

    Tristan Perez

    2009-01-01

    Full Text Available This article describes a Matlab toolbox for parametric identification of fluid-memory models associated with the radiation forces ships and offshore structures. Radiation forces are a key component of force-to- motion models used in simulators, motion control designs, and also for initial performance evaluation of wave-energy converters. The software described provides tools for preparing non-parmatric data and for identification with automatic model-order detection. The identification problem is considered in the frequency domain.

  10. Radiation pressure forces on individual micron-size dust particles: a new experimental approach

    Energy Technology Data Exchange (ETDEWEB)

    Krauss, Oliver [Institute for Planetology, University of Muenster, Wilhelm-Klemm-Str. 10, D-48149 Muenster (Germany)]. E-mail: okrauss@uni-muenster.de; Wurm, Gerhard [Institute for Planetology, University of Muenster, Wilhelm-Klemm-Str. 10, D-48149 Muenster (Germany)

    2004-12-15

    We present a newly developed experimental setup for the measurement of radiation pressure forces on individual dust particles. The principle of measurement is to observe the momentum transfer from a high-power laser pulse to a particle that is levitated in a quadrupole trap. Microscopic observation of the particle motion provides information on the forces that act on the particle in the directions parallel and perpendicular to the incident laser beam. First measurements with micron-size graphite grains that serve as analog particles for carbonaceous dust grains in various astrophysical environments reveal that such highly irregularly shaped particles show very high ratios of transversal to radial radiation pressure forces.

  11. Use of acoustic vortices in acoustic levitation

    DEFF Research Database (Denmark)

    Cutanda Henriquez, Vicente; Santillan, Arturo Orozco; Juhl, Peter Møller

    2009-01-01

    Acoustic fields are known to exert forces on the surfaces of objects. These forces are noticeable if the sound pressure is sufficiently high. Two phenomena where acoustic forces are relevant are: i) acoustic levitation, where strong standing waves can hold small objects at certain positions...... of acoustical vortices uses an efficient numerical implementation based on the superposition of two orthogonal sound fields with a delay of 90° between them. It is shown that acoustic levitation and the use of acoustic vortices can be combined to manipulate objects in an efficient and controlled manner without...

  12. Modeling Study of the Global Distribution of Radiative Forcing by Dust Aerosol

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hua; MA Jinghui; ZHENG Youfei

    2010-01-01

    To quantitatively understand the dust aerosol effects on climate change, we calculated the global dis-tribution of direct radiative forcing due to dust aerosol under clear and cloudy skies in both winter and summer, by using an improved radiative transfer model and the global distribution of dust mass concentra-tion given by GADS (Global Aerosol Data Set). The results show that the global means of the solar forcing due to dust aerosol at the tropopause for winter and summer are -0.48 and -0.50 W m-2, respectively; the corresponding values for the longwave forcing due to dust are 0.11 and 0.09 W m-2, respectively. At the surface, the global means of the solar forcing clue to dust are -1.36 W m-2 for winter and -1.56 W m-2 for summer, whereas the corresponding values for the longwave forcing are 0.27 and 0.23 W m-2, respectively. This work points out that the absolute values of the solar forcing due to dust aerosol at both the tropopause and surface increase linearly with the cosine of solar zenith angle and surface albedo. The solar zenith angle influences both the strength and distribution of the solar forcing greatly. Clouds exert great effects on the direct radiative forcing of dust, depending on many factors including cloud cover, cloud height, cloud water path, surface albedo, solar zenith angle, etc. The effects of low clouds and middle clouds are larger than those of high clouds. The existence of clouds reduces the longwave radiative forcing at the tropopause, where the influences of low clouds are the most obvious. Therefore, the impacts of clouds should not be ignored when estimating the direct radiative forcing due to dust aerosol.

  13. Study of Radiative Forcing of Dust Aerosols and its impact on Climate Characteristics

    KAUST Repository

    Qureshi, Fawwad H

    2012-12-01

    The purpose of following project is to study the effect of dust aerosols on the radiative forcing which is directly related to the surface temperature. A single column radiative convective model is used for simulation purpose. A series of simulations have been performed by varying the amount of dust aerosols present in the atmosphere to study the trends in ground temperature, heating rate and radiative forcing for both its longwave and shortwave components. A case study for dust storm is also performed as dust storms are common in Arabian Peninsula. A sensitivity analyses is also performed to study the relationship of surface temperature minimum and maximum against aerosol concentration, single scattering albedo and asymmetry factor. These analyses are performed to get more insight into the role of dust aerosols on radiative forcing.

  14. The Lorentz Force and the Radiation Pressure of Light

    CERN Document Server

    Rothman, Tony

    2008-01-01

    In order to make plausible the idea that light exerts a pressure on matter, some introductory physics texts consider the force exerted by an electromagnetic wave on an electron. The argument as presented is both mathematically incorrect and has several serious conceptual difficulties without obvious resolution at the classical, yet alone introductory, level. We discuss these difficulties and propose an alternate demonstration.

  15. Particle manipulation with acoustic vortex beam induced by a brass plate with spiral shape structure

    Science.gov (United States)

    Wang, Tian; Ke, Manzhu; Li, Weiping; Yang, Qian; Qiu, Chunyin; Liu, Zhengyou

    2016-09-01

    In this work, we give direct demonstration of acoustic radiation force and acoustic torque on particles exerted by an acoustic vortex beam, which is realized by an acoustic artificial structure plate instead of traditional transducer arrays. First, the first order acoustic vortex beam, which has the distinctive features of a linear and continuous phase variation from -π to π around its propagation axis and a magnitude null at its core, is obtained through one single acoustic source incident upon a structured brass plate with Archimedean spiral grating engraved on the back surface. Second, annular self-patterning of polystyrene particles with a radius of 90 μm is realized in the gradient field of this acoustic vortex beam. In addition, we further exhibit acoustic angular momentum transfer to an acoustic absorptive matter, which is verified by a millimeter-sized polylactic acid disk self-rotating in water in the acoustic field of the generated vortex beam.

  16. Visualization of subsurface nanoparticles in a polymer matrix using resonance tracking atomic force acoustic microscopy and contact resonance spectroscopy

    Science.gov (United States)

    Kimura, Kuniko; Kobayashi, Kei; Yao, Atsushi; Yamada, Hirofumi

    2016-10-01

    A visualization technique of subsurface features with a nanometer-scale spatial resolution is strongly demanded. Some research groups have demonstrated the visualization of subsurface features using various techniques based on atomic force microscopy. However, the imaging mechanisms have not yet been fully understood. In this study, we demonstrated the visualization of subsurface Au nanoparticles buried in a polymer matrix 900 nm from the surface using two techniques; i.e., resonance tracking atomic force acoustic microscopy and contact resonance spectroscopy. It was clarified that the subsurface features were visualized by the two techniques as the area with a higher contact resonance frequency and a higher Q-factor than those in the surrounding area, which suggests that the visualization is realized by the variation of the contact stiffness and damping of the polymer matrix due to the existence of the buried nanoparticles.

  17. Airy acoustical-sheet spinner tweezers

    Science.gov (United States)

    Mitri, F. G.

    2016-09-01

    The Airy acoustical beam exhibits parabolic propagation and spatial acceleration, meaning that the propagation bending angle continuously increases before the beam trajectory reaches a critical angle where it decays after a propagation distance, without applying any external bending force. As such, it is of particular importance to investigate its properties from the standpoint of acoustical radiation force, spin torque, and particle dynamics theories, in the development of novel particle sorting techniques and acoustically mediated clearing systems. This work investigates these effects on a two-dimensional (2D) circular absorptive structure placed in the field of a nonparaxial Airy "acoustical-sheet" (i.e., finite beam in 2D), for potential applications in surface acoustic waves and acousto-fluidics. Based on the characteristics of the acoustic field, the beam is capable of manipulating the circular cylindrical fluid cross-section and guides it along a transverse or parabolic trajectory. This feature of Airy acoustical beams could lead to a unique characteristic in single-beam acoustical tweezers related to acoustical sieving, filtering, and removal of particles and cells from a section of a small channel. The analysis developed here is based on the description of the nonparaxial Airy beam using the angular spectrum decomposition of plane waves in close association with the partial-wave series expansion method in cylindrical coordinates. The numerical results demonstrate the ability of the nonparaxial Airy acoustical-sheet beam to pull, propel, or accelerate a particle along a parabolic trajectory, in addition to particle confinement in the transverse direction of wave propagation. Negative or positive radiation force and spin torque causing rotation in the clockwise or the anticlockwise direction can occur depending on the nondimensional parameter ka (where k is the wavenumber and a is the radius) and the location of the cylinder in the beam. Applications in

  18. Rates of change in natural and anthropogenic radiative forcing over the past 20,000 years.

    Science.gov (United States)

    Joos, Fortunat; Spahni, Renato

    2008-02-05

    The rate of change of climate codetermines the global warming impacts on natural and socioeconomic systems and their capabilities to adapt. Establishing past rates of climate change from temperature proxy data remains difficult given their limited spatiotemporal resolution. In contrast, past greenhouse gas radiative forcing, causing climate to change, is well known from ice cores. We compare rates of change of anthropogenic forcing with rates of natural greenhouse gas forcing since the Last Glacial Maximum and of solar and volcanic forcing of the last millennium. The smoothing of atmospheric variations by the enclosure process of air into ice is computed with a firn diffusion and enclosure model. The 20th century increase in CO(2) and its radiative forcing occurred more than an order of magnitude faster than any sustained change during the past 22,000 years. The average rate of increase in the radiative forcing not just from CO(2) but from the combination of CO(2), CH(4), and N(2)O is larger during the Industrial Era than during any comparable period of at least the past 16,000 years. In addition, the decadal-to-century scale rate of change in anthropogenic forcing is unusually high in the context of the natural forcing variations (solar and volcanoes) of the past millennium. Our analysis implies that global climate change, which is anthropogenic in origin, is progressing at a speed that is unprecedented at least during the last 22,000 years.

  19. Classical tunneling as a consequence of radiation reaction forces

    Science.gov (United States)

    Denef, Frederik; Raeymaekers, Joris; Studer, Urban M.; Troost, Walter

    1997-09-01

    We show that the classical equation of motion of a radiating charged point particle (the Lorentz-Dirac equation) has ``tunneling'' solutions. For a given initial position and velocity we find that, contrary to common belief, several different physically acceptable solutions exist for a range of initial data. Both features are demonstrated for a rectangular barrier. To check that these phenomena are not dependent on the discontinuities of the potential, we also study in detail the solutions for a smoothened (single) potential step.

  20. Aerosol Radiative Forcing and Weather Forecasts in the ECMWF Model

    Science.gov (United States)

    Bozzo, A.; Benedetti, A.; Rodwell, M. J.; Bechtold, P.; Remy, S.

    2015-12-01

    Aerosols play an important role in the energy balance of the Earth system via direct scattering and absorpiton of short-wave and long-wave radiation and indirect interaction with clouds. Diabatic heating or cooling by aerosols can also modify the vertical stability of the atmosphere and influence weather pattern with potential impact on the skill of global weather prediction models. The Copernicus Atmosphere Monitoring Service (CAMS) provides operational daily analysis and forecast of aerosol optical depth (AOD) for five aerosol species using a prognostic model which is part of the Integrated Forecasting System of the European Centre for Medium-Range Weather Forecasts (ECMWF-IFS). The aerosol component was developed during the research project Monitoring Atmospheric Composition and Climate (MACC). Aerosols can have a large impact on the weather forecasts in case of large aerosol concentrations as found during dust storms or strong pollution events. However, due to its computational burden, prognostic aerosols are not yet feasible in the ECMWF operational weather forecasts, and monthly-mean climatological fields are used instead. We revised the aerosol climatology used in the operational ECMWF IFS with one derived from the MACC reanalysis. We analyse the impact of changes in the aerosol radiative effect on the mean model climate and in medium-range weather forecasts, also in comparison with prognostic aerosol fields. The new climatology differs from the previous one by Tegen et al 1997, both in the spatial distribution of the total AOD and the optical properties of each aerosol species. The radiative impact of these changes affects the model mean bias at various spatial and temporal scales. On one hand we report small impacts on measures of large-scale forecast skill but on the other hand details of the regional distribution of aerosol concentration have a large local impact. This is the case for the northern Indian Ocean where the radiative impact of the mineral

  1. Net radiative forcing due to changes in regional emissions of tropospheric ozone precursors

    Science.gov (United States)

    Naik, Vaishali; Mauzerall, Denise; Horowitz, Larry; Schwarzkopf, M. Daniel; Ramaswamy, V.; Oppenheimer, Michael

    2005-12-01

    The global distribution of tropospheric ozone (O3) depends on the emission of precursors, chemistry, and transport. For small perturbations to emissions, the global radiative forcing resulting from changes in O3 can be expressed as a sum of forcings from emission changes in different regions. Tropospheric O3 is considered in present climate policies only through the inclusion of indirect effect of CH4 on radiative forcing through its impact on O3 concentrations. The short-lived O3 precursors (NOx, CO, and NMHCs) are not directly included in the Kyoto Protocol or any similar climate mitigation agreement. In this study, we quantify the global radiative forcing resulting from a marginal reduction (10%) in anthropogenic emissions of NOx alone from nine geographic regions and a combined marginal reduction in NOx, CO, and NMHCs emissions from three regions. We simulate, using the global chemistry transport model MOZART-2, the change in the distribution of global O3 resulting from these emission reductions. In addition to the short-term reduction in O3, these emission reductions also increase CH4 concentrations (by decreasing OH); this increase in CH4 in turn counteracts part of the initial reduction in O3 concentrations. We calculate the global radiative forcing resulting from the regional emission reductions, accounting for changes in both O3 and CH4. Our results show that changes in O3 production and resulting distribution depend strongly on the geographical location of the reduction in precursor emissions. We find that the global O3 distribution and radiative forcing are most sensitive to changes in precursor emissions from tropical regions and least sensitive to changes from midlatitude and high-latitude regions. Changes in CH4 and O3 concentrations resulting from NOx emission reductions alone produce offsetting changes in radiative forcing, leaving a small positive residual forcing (warming) for all regions. In contrast, for combined reductions of anthropogenic

  2. Role of radiatively forced temperature changes in enhanced semi-arid warming over East Asia

    Directory of Open Access Journals (Sweden)

    X. Guan

    2015-08-01

    Full Text Available As the climate change occurred over East Asia since 1950s, intense interest and debate have arisen concerning the contribution of human activities to the warming observed in previous decades. In this study, we investigate surface temperature change using a recently developed methodology that can successfully identify and separate the dynamically induced temperature (DIT and radiatively forced temperature (RFT changes in raw surface air temperature (SAT data. For regional averages, DIT and RFT make 43.7 and 56.3 % contributions to the SAT over East Asia, respectively. The DIT changes dominate the SAT decadal variability and are mainly determined by internal climate variability, such as the North Atlantic Oscillation (NAO, Pacific Decadal Oscillation (PDO, and Atlantic Multi-decadal Oscillation (AMO. The radiatively forced SAT changes made major contribution to the global-scale warming trend and the regional-scale enhanced semi-arid warming (ESAW. Such enhanced warming is also found in radiatively forced daily maximum and minimum SAT. The long-term global-mean SAT warming trend is mainly related to radiative forcing produced by global well-mixed greenhouse gases. The regional anthropogenic radiative forcing, however, caused the enhanced warming in the semi-arid region, which may be closely associated with local human activities. Finally, the relationship between global warming hiatus and regional enhanced warming is discussed.

  3. Global analysis of radiative forcing from fire-induced shortwave albedo change

    Directory of Open Access Journals (Sweden)

    G. López-Saldaña

    2014-05-01

    Full Text Available Land surface albedo, a key parameter to derive Earth's surface energy balance, is used in the parameterization of numerical weather prediction, climate monitoring and climate change impact assessments. Changes in albedo due to fire have not been fully investigated at continental and global scale. The main goal of this study therefore, is to quantify the changes in albedo produced by biomass burning activities and their associated shortwave radiative forcing. The study relies on the Moderate Resolution Imaging Spectroradiometer (MODIS MCD64A1 burned area product to create an annual composite of areas affected by fire and the MCD43C2 BRDF-Albedo snow-free product to compute a bihemispherical reflectance time series. The approximate day of burn is used to calculate the instantaneous change in shortwave Albedo. Using the corresponding National Centers for Environmental Prediction (NCEP monthly mean downward solar radiation flux at the surface, the global radiative forcing associated to fire was computed. The analysis reveals a mean decrease in shortwave albedo of −0.023 (1σ = 0.018 causing a mean positive radiative forcing of 6.31 W m–2 (1σ = 5.04 over the 2002–2012 time period in areas affected by fire. The greatest drop in mean shortwave albedo change occurs in 2002, which corresponds to the highest total area burnt (3.66 Mha observed in the same year and produces the highest mean radiative forcing (6.75 W m–2. Africa is the main contributor in terms of burned area but forests globally are giving the highest radiative forcing per unit area, thus give detectable changes in shortwave albedo. The global mean radiative forcing for the whole studied period ~ 0.04 W m–2 shows that the contribution of fires into the Earth system is not insignificant.

  4. The impact of diurnal variations of air traffic on contrail radiative forcing

    Directory of Open Access Journals (Sweden)

    N. Stuber

    2007-06-01

    Full Text Available We combined high resolution aircraft flight data from the EU Fifth Framework Programme project AERO2k with analysis data from the ECMWF's integrated forecast system to calculate diurnally resolved 3-D contrail cover. We scaled the contrail cover in order to match observational data for the Bakan area (eastern-Atlantic/western-Europe.

    We found that less than 40% of the global distance travelled by aircraft is due to flights during local night time. Yet, due to the cancellation of shortwave and longwave effects during daytime, night time flights contribute a disproportional 60% to the global annual mean forcing. Under clear sky conditions the night flights contribute even more disproportionally at 76%. There are pronounced regional variations in night flying and the associated radiative forcing. Over parts of the North Atlantic flight corridor 75% of air traffic and 84% of the forcing occurs during local night, whereas only 35% of flights are during local night in South-East Asia, yet these contribute 68% of the radiative forcing. In general, regions with a significant local contrail radiative forcing are also regions for which night time flights amount to less than half of the daily total of flights. Therefore, neglecting diurnal variations in air traffic/contrail cover by assuming a diurnal mean contrail cover can over-estimate the global mean radiative forcing by up to 30%.

  5. Ozone precursors have regionally variable effect on radiative forcing

    Science.gov (United States)

    Schultz, Colin

    2013-02-01

    When released near the surface, carbon monoxide, assorted nitrogen oxides (NOx ), and nonmethane hydrocarbons (NMHC) contribute to the production of ozone, a key component of photochemical smog, which is known to have serious deleterious effects on human health. However, when ozone gets lifted into the troposphere, it is a greenhouse gas. That these ozone precursors have such a dual-pronged effect—affecting both human health and the global radiation budget—suggests that mitigating their emissions could be a potential method to both improve air quality and dampen the rate of anthropogenic climate change.

  6. Acoustic radiation from out-of-plane modes of an annular disk using thin and thick plate theories

    Science.gov (United States)

    Lee, Hyeongill; Singh, Rajendra

    2005-04-01

    Out-of-plane (flexural) vibration is a major source of sound radiation from many mechanical or structural components having annular or circular disk shape. The typical thickness of practical components is often beyond the thin plate theory limit and it may have considerable effect on sound radiation. But, traditionally, thin annular disk models have been employed for such structures neglecting the thickness effect. In this article, structural eigensolutions for the out-of-plane modes and sound radiation from the modal vibration of a thick annular disk with free-free boundaries have been calculated using both thick and thin plate theories. A new analytical formulation is proposed for the sound radiation problem. In addition, the same problem has been solved by a semi-analytical procedure in which the disk surface velocity is numerically defined by a finite-element model and sound radiation is then analytically obtained using a modified circular radiator model. Also, the effects of radii and thickness ratios on the structural and acoustic radiation characteristics are investigated using the analytical procedure. Finally, the effect of boundary conditions is briefly examined.

  7. Crustal Seismic Attenuation in Germany Measured with Acoustic Radiative Transfer Theory

    Science.gov (United States)

    Gaebler, Peter J.; Eulenfeld, Tom; Wegler, Ulrich

    2017-04-01

    This work is carried out in the context of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). As part of this treaty a verification regime was introduced to detect, locate and characterize nuclear explosion testings. The study of seismology can provide essential information in the form of broadband waveform recordings for the identification and verification of these critical events. A profound knowledge of the Earth's subsurface between source and receiver is required for a detailed description of the seismic wave field. In addition to underground parameters such as seismic velocity or anisotropy, information about seismic attenuation values of the medium are required. Goal of this study is the creation of a comprehensive model of crustal seismic attenuation in Germany and adjacent areas. Over 20 years of earthquake data from the German Central Seismological Observatory data archive is used to estimate the spatial dependent distribution of seismic intrinsic and scattering attenuation of S-waves for frequencies between 0.5 and 20 Hz. The attenuation models are estimated by fitting synthetic seismogram envelopes calculated with acoustic radiative transfer theory to observed seismogram envelopes. This theory describes the propagation of seismic S-energy under the assumption of multiple isotropic scattering, the crustal structure of the scattering medium is hereby represented by a half-space model. We present preliminary results of the spatial distribution of intrinsic attenuation represented by the absorption path length, as well as of scattering attenuation in terms of the mean free path and compare the outcomes to results from previous studies. Furthermore catalog magnitudes are compared to moment magnitudes estimated during the inversion process. Additionally site amplification factors of the stations are presented.

  8. Radiative transfer of acoustic waves in continuous complex media: Beyond the Helmholtz equation

    Science.gov (United States)

    Baydoun, Ibrahim; Baresch, Diego; Pierrat, Romain; Derode, Arnaud

    2016-11-01

    Heterogeneity can be accounted for by a random potential in the wave equation. For acoustic waves in a fluid with fluctuations of both density and compressibility (as well as for electromagnetic waves in a medium with fluctuation of both permittivity and permeability) the random potential entails a scalar and an operator contribution. For simplicity, the latter is usually overlooked in multiple scattering theory: whatever the type of waves, this simplification amounts to considering the Helmholtz equation with a sound speed c depending on position r . In this work, a radiative transfer equation is derived from the wave equation, in order to study energy transport through a multiple scattering medium. In particular, the influence of the operator term on various transport parameters is studied, based on the diagrammatic approach of multiple scattering. Analytical results are obtained for fundamental quantities of transport theory such as the transport mean-free path ℓ*, scattering phase function f , and anisotropy factor g . Discarding the operator term in the wave equation is shown to have a significant impact on f and g , yet limited to the low-frequency regime, i.e., when the correlation length of the disorder ℓc is smaller than or comparable to the wavelength λ . More surprisingly, discarding the operator part has a significant impact on the transport mean-free path ℓ* whatever the frequency regime. When the scalar and operator terms have identical amplitudes, the discrepancy on the transport mean-free path is around 300 % in the low-frequency regime, and still above 30 % for ℓc/λ =103 no matter how weak fluctuations of the disorder are. Analytical results are supported by numerical simulations of the wave equation and Monte Carlo simulations.

  9. Radiative transfer of acoustic waves in continuous complex media: Beyond the Helmholtz equation.

    Science.gov (United States)

    Baydoun, Ibrahim; Baresch, Diego; Pierrat, Romain; Derode, Arnaud

    2016-11-01

    Heterogeneity can be accounted for by a random potential in the wave equation. For acoustic waves in a fluid with fluctuations of both density and compressibility (as well as for electromagnetic waves in a medium with fluctuation of both permittivity and permeability) the random potential entails a scalar and an operator contribution. For simplicity, the latter is usually overlooked in multiple scattering theory: whatever the type of waves, this simplification amounts to considering the Helmholtz equation with a sound speed c depending on position r. In this work, a radiative transfer equation is derived from the wave equation, in order to study energy transport through a multiple scattering medium. In particular, the influence of the operator term on various transport parameters is studied, based on the diagrammatic approach of multiple scattering. Analytical results are obtained for fundamental quantities of transport theory such as the transport mean-free path ℓ^{*}, scattering phase function f, and anisotropy factor g. Discarding the operator term in the wave equation is shown to have a significant impact on f and g, yet limited to the low-frequency regime, i.e., when the correlation length of the disorder ℓ_{c} is smaller than or comparable to the wavelength λ. More surprisingly, discarding the operator part has a significant impact on the transport mean-free path ℓ^{*} whatever the frequency regime. When the scalar and operator terms have identical amplitudes, the discrepancy on the transport mean-free path is around 300% in the low-frequency regime, and still above 30% for ℓ_{c}/λ=10^{3} no matter how weak fluctuations of the disorder are. Analytical results are supported by numerical simulations of the wave equation and Monte Carlo simulations.

  10. Resonance-Radiation Force Exerted by a Circularly Polarized Light on an Atomic Wave Packet

    Institute of Scientific and Technical Information of China (English)

    YE Yong-Hua; ZENG Gao-Jian; LI Jin-Hui

    2006-01-01

    We study the behaviour of an atomic wave packet in a circularly polarized light, and especially give the calculation of the radiative force exerted by the circularly polarized light on the atomic wave packet under the resonance condition. A general method of the calculation is presented and the result is interesting. For example, under the condition that the wave packet is very narrow or/and the interaction is very strong, no matter whether the atom is initially in its ground state or excited state, as time approaches to infinity, the resonance-radiation force exerted by the light on the atom approaches to zero. If the atom is initially in its ground state and excited state with the probability 1/2 respectively, and if the momentum density is a even function, then the resonance-radiation force exerted by the light on the atom is equal to zero.

  11. Implications of multiple scattering on the assessment of black carbon aerosol radiative forcing

    Science.gov (United States)

    Nair, Vijayakumar S.; Suresh Babu, S.; Krishna Moorthy, K.; Satheesh, S. K.

    2014-11-01

    The effects of radiative coupling between scattering and absorbing aerosols, in an external mixture, on the aerosol radiative forcing (ARF) due to black carbon (BC), its sensitivity to the composite aerosol loading and composition, and surface reflectance are investigated using radiative transfer model simulations. The ARF due to BC is found to depend significantly on the optical properties of the ‘neighboring’ (non-BC) aerosol species. The scattering due to these species significantly increases the top of the atmospheric warming due to black carbon aerosols, and significant changes in the radiative forcing efficiency of BC. This is especially significant over dark surfaces (such as oceans), despite the ARF due to BC being higher over snow and land-surfaces. The spatial heterogeneity of this effect (coupling or multiple scattering by neighboring aerosol species) imposes large uncertainty in the estimation ARF due to BC aerosols, especially over the oceans.

  12. A global modeling study on carbonaceous aerosol microphysical characteristics and radiative forcing

    Directory of Open Access Journals (Sweden)

    S. E. Bauer

    2010-02-01

    Full Text Available Recently, attention has been drawn towards black carbon aerosols as a short-term climate warming mitigation candidate. However the global and regional impacts of the direct, cloud-indirect and semi-direct forcing effects are highly uncertain, due to the complex nature of aerosol evolution and the way that mixed, aged aerosols interact with clouds and radiation. A detailed aerosol microphysical scheme, MATRIX, embedded within the GISS climate model is used in this study to present a quantitative assessment of the impact of microphysical processes involving black carbon, such as emission size distributions and optical properties on aerosol cloud activation and radiative forcing.

    Our best estimate for net direct and indirect aerosol radiative forcing between 1750 and 2000 is −0.56 W/m2. However, the direct and indirect aerosol effects are quite sensitive to the black and organic carbon size distribution and consequential mixing state. The net radiative forcing can vary between −0.32 to −0.75 W/m2 depending on these carbonaceous particle properties at emission. Assuming that sulfates, nitrates and secondary organics form a coating around a black carbon core, rather than forming a uniformly mixed particle, changes the overall net aerosol radiative forcing from negative to positive. Taking into account internally mixed black carbon particles let us simulate correct aerosol absorption. Black carbon absorption is amplified by sulfate and nitrate coatings, but even more strongly by organic coatings. Black carbon mitigation scenarios generally showed reduced radiative forcing when sources with a large proportion of black carbon, such as diesel, are reduced; however reducing sources with a larger organic carbon component as well, such as bio-fuels, does not necessarily lead to climate benefits.

  13. Radiation Reaction as a Non-conservative Force

    CERN Document Server

    Aashish, Sandeep

    2016-01-01

    We study a system of a finite-size charged particle and electromagnetic field by exploiting the Hamilton's principle for classical non-conservative systems introduced recently by Galley[1] and obtain the equation of motion of the charged particle which turns out to be the same as obtained by Jackson[2]. We show that radiation reaction stems from the non-conservative potential of the effective Lagrangian. We derive the Abraham-Lorentz equation using the effective non-conservative Lagrangian for a point charge. We establish a correspondence between a charge interacting with its own electromagnetic field and that of a particle interacting with infinite bath oscillators which in turn affords a way to justify the non-conservative nature of the former system.

  14. Observational determination of surface radiative forcing by CO2 from 2000 to 2010

    Energy Technology Data Exchange (ETDEWEB)

    Feldman, Daniel R.; Collins, William D.; Gero, P. Johnathan; Torn, Margaret S.; Mlawer, Eli J.; Shippert, Timothy R.

    2015-02-25

    The climatic impact of CO2 and other greenhouse gases is usually quantified in terms of radiative forcing1, calculated as the difference between estimates of the Earth’s radiation field from pre-industrial and present-day concentrations of these gases. Radiative transfer models calculate that the increase in CO2 since 1750 corresponds to a global annual-mean radiative forcing at the tropopause of 1.82 ± 0.19 W m-2 (ref. 2). However, despite widespread scientific discussion and modelling of the climate impacts of well-mixed greenhouse gases, there is little direct observational evidence of the radiative impact of increasing atmospheric CO2. Here we present observationally based evidence of clear-sky CO2 surface radiative forcing that is directly attributable to the increase, between 2000 and 2010, of 22 parts per million atmospheric CO2. The time series of this forcing at the two locations—the Southern Great Plains and the North Slope of Alaska—are derived from Atmospheric Emitted Radiance Interferometer spectra3 together with ancillary measurements and thoroughly corroborated radiative transfer calculations4. The time series both show statistically significant trends of 0.2 W m-2 per decade (with respective uncertainties of ±0.06 W m-2 per decade and ±0.07 W m-2 per decade) and have seasonal ranges of 0.1–0.2 W m-2. This is approximately ten per cent of the trend in downwelling longwave radiation5, 6, 7. These results confirm theoretical predictions of the atmospheric greenhouse effect due to anthropogenic emissions, and provide empirical evidence of how rising CO2 levels, mediated by temporal variations due to photosynthesis and respiration, are affecting the surface energy balance.

  15. Influence of future air pollution mitigation strategies on total aerosol radiative forcing

    Directory of Open Access Journals (Sweden)

    S. Kloster

    2008-11-01

    Full Text Available We apply different aerosol and aerosol precursor emission scenarios reflecting possible future control strategies for air pollution in the ECHAM5-HAM model, and simulate the resulting effect on the Earth's radiation budget. We use two opposing future mitigation strategies for the year 2030: one in which emission reduction legislation decided in countries throughout the world are effectively implemented (current legislation; CLE 2030 and one in which all technical options for emission reductions are being implemented independent of their cost (maximum feasible reduction; MFR 2030.

    We consider the direct, semi-direct and indirect radiative effects of aerosols. The total anthropogenic aerosol radiative forcing defined as the difference in the top-of-the-atmosphere radiation between 2000 and pre-industrial times amounts to −2.00 W/m2. In the future this negative global annual mean aerosol radiative forcing will only slightly change (+0.02 W/m2 under the "current legislation" scenario. Regionally, the effects are much larger: e.g. over Eastern Europe radiative forcing would increase by +1.50 W/m2 because of successful aerosol reduction policies, whereas over South Asia it would decrease by −1.10 W/m2 because of further growth of emissions. A "maximum feasible reduction" of aerosols and their precursors would lead to an increase of the global annual mean aerosol radiative forcing by +1.13 W/m2. Hence, in the latter case, the present day negative anthropogenic aerosol forcing could be more than halved by 2030 because of aerosol reduction policies and climate change thereafter will be to a larger extent be controlled by greenhouse gas emissions.

    We combined these two opposing future mitigation strategies for a number of experiments focusing on different sectors and regions. In addition, we performed sensitivity studies to estimate the importance of future changes in

  16. Influence of future air pollution mitigation strategies on total aerosol radiative forcing

    Directory of Open Access Journals (Sweden)

    S. Kloster

    2008-03-01

    Full Text Available We apply different aerosol and aerosol precursor emission scenarios reflecting possible future control strategies for air pollution in the ECHAM5-HAM model, and simulate the resulting effect on the Earth's radiation budget. We use two opposing future mitigation strategies for the year 2030: one in which emission reduction legislation decided in countries throughout the world are effectively implemented (current legislation; CLE 2030 and one in which all technical options for emission reductions are being implemented independent of their cost (maximum feasible reduction; MFR 2030.

    We consider the direct, semi-direct and indirect radiative effects of aerosols. The total anthropogenic aerosol radiative forcing defined as the difference in the top-of-the-atmosphere radiation between 2000 and pre-industrial times amounts to −2.05 W/m2. In the future this negative global annual mean aerosol radiative forcing will only slightly change (+0.02 W/m2 under the "current legislation" scenario. Regionally, the effects are much larger: e.g. over Eastern Europe radiative forcing would increase by +1.50 W/m2 because of successful aerosol reduction policies, whereas over South Asia it would decrease by −1.10 W/m2 because of further growth of emissions. A "maximum feasible reduction" of aerosols and their precursors would lead to an increase of the global annual mean aerosol radiative forcing by +1.13 W/m2. Hence, in the latter case, the present day negative anthropogenic aerosol forcing cloud be more than halved by 2030 because of aerosol reduction policies and climate change thereafter will be to a larger extend be controlled by greenhouse gas emissions.

    We combined these two opposing future mitigation strategies for a number of experiments focusing on different sectors and regions. In addition, we performed sensitivity studies to estimate the importance of future changes in

  17. Experimental Demonstration of a Synthetic Lorentz Force by Using Radiation Pressure

    Science.gov (United States)

    Šantić, N.; Dubček, T.; Aumiler, D.; Buljan, H.; Ban, T.

    2015-09-01

    Synthetic magnetism in cold atomic gases opened the doors to many exciting novel physical systems and phenomena. Ubiquitous are the methods used for the creation of synthetic magnetic fields. They include rapidly rotating Bose-Einstein condensates employing the analogy between the Coriolis and the Lorentz force, and laser-atom interactions employing the analogy between the Berry phase and the Aharonov-Bohm phase. Interestingly, radiation pressure - being one of the most common forces induced by light - has not yet been used for synthetic magnetism. We experimentally demonstrate a synthetic Lorentz force, based on the radiation pressure and the Doppler effect, by observing the centre-of-mass motion of a cold atomic cloud. The force is perpendicular to the velocity of the cold atomic cloud, and zero for the cloud at rest. Our novel concept is straightforward to implement in a large volume, for a broad range of velocities, and can be extended to different geometries.

  18. Capacitive Sensors for the Long-wave Acoustic Radiation by Directed Waves

    Directory of Open Access Journals (Sweden)

    L.V. Zaitseva

    2016-06-01

    Full Text Available Consider from the common position present-day state, prospects and the possibility of non-destructive testing capacitive method using. Developed mathematical model of the process of acoustic wave’s excitation (longitudinal and surface with a capacitor allow carrying out the output signal calculation for the subsequent choice of methods and devices for receiving the acoustic oscillations data. A device layout has been developed for realization of capacitive method. The possibility of excitation and reception of acoustic vibrations by capacitive transducers it has been established.

  19. Diurnal cycle of the dust instantaneous direct radiative forcing over the Arabian Peninsula

    KAUST Repository

    Osipov, S.

    2015-08-27

    In this study we attempted to better quantify radiative effects of dust over the Arabian Peninsula and their dependence on input parameters. For this purpose we have developed a stand-alone column radiation transport model coupled with the Mie, T-matrix and geometric optics calculations and driven by reanalysis meteorological fields and atmospheric composition. Numerical experiments were carried out for a wide range of aerosol optical depths, including extreme values developed during the dust storm on 18–20 March 2012. Comprehensive ground-based observations and satellite retrievals were used to estimate aerosol optical properties, validate calculations and carry out radiation closure. The broadband surface albedo, fluxes at the bottom and top of the atmosphere as well as instantaneous dust radiative forcing were estimated both from the model and observations. Diurnal cycle of the shortwave instantaneous dust direct radiative forcing was studied for a range of aerosol and surface characteristics representative of the Arabian Peninsula. Mechanisms and parameters responsible for diurnal variability of the radiative forcing were evaluated. We found that intrinsic variability of the surface albedo and its dependence on atmospheric conditions, along with anisotropic aerosol scattering, are mostly responsible for diurnal effects.

  20. Quantifying the effects of aviation on radiative forcing and temperature with a climate response model

    OpenAIRE

    Lim, L; Lee, D. S.; Sausen, R.; Ponater, M.

    2007-01-01

    Simplified climate models can be used to calculate and to compare temperature response contributions from small forcings without the need for considerable computer resources. A linear climate response model using Green’s functions has been formulated to calculate radiative forcing (RF) and the global mean temperature response from aviation. The model, LinClim, can calculate aviation RF for CO2, O3, CH4, water vapour, contrails, sulphate and black carbon aerosols. From these RFs, temperatur...

  1. Synthetic Lorentz force in classical atomic gases via Doppler effect and radiation pressure

    CERN Document Server

    Dubček, T; Jukić, D; Aumiler, D; Ban, T; Buljan, H

    2014-01-01

    We theoretically predict a novel type of synthetic Lorentz force for classical (cold) atomic gases, which is based on the Doppler effect and radiation pressure. A fairly uniform and strong force can be constructed for gases in macroscopic volumes of several cubic millimeters and more. This opens the possibility to mimic classical charged gases in magnetic fields, such as those in a tokamak, in cold atom experiments.

  2. Magnitude and pattern of Arctic warming governed by the seasonality of radiative forcing

    Science.gov (United States)

    Bintanja, Richard; Krikken, Folmer

    2015-04-01

    Observed and projected climate warming is strongest in the Arctic regions, and maximum in autumn/winter. Attempts to explain this feature have focused primarily on identifying the associated climate feedbacks, particularly the ice-albedo and lapse-rate feedbacks. However, the impact of seasonally varying climate forcing has not been identified and quantified. Here we use a state-of-the-art global climate model in idealized seasonal forcing simulations to show that Arctic warming is very sensitive to the season in which the radiative forcing occurs. More specifically, Arctic warming and sea ice decline (especially in winter) are particularly sensitive to forcing in spring, during which the energy is effectively 'absorbed' by the ocean (through sea ice melt and ocean warming, amplified by the ice-albedo feedback) and consequently released to the lower atmosphere in autumn and winter, mainly along the sea ice periphery. In contrast, wintertime radiative forcing yields a more evenly distributed winter warming, which, surprisingly, in certain regions is even smaller than that due to spring forcing. The dependence of the magnitude and pattern of Arctic warming on the seasonality of the climate forcing has important implications in terms of projected increases in anthropogenic forcing. For instance, shipping-induced emissions such as those of black carbon are projected to peak in the ice-free summer and will thereby exert a comparatively strong impact on Arctic warming.

  3. Dusty cloud radiative forcing derived from satellite data for middle latitude regions of East Asia

    Institute of Scientific and Technical Information of China (English)

    HUANG Jianping; WANG Yujie; WANG Tianhe; YI Yuhong

    2006-01-01

    The dusty cloud radiative forcing over the middle latitude regions of East Asia was estimated by using the 2-year (July 2002-June 2004) data of collocated clouds and the Earth's radiant energy system (CERES) scanner and moderate resolution imaging spectroradiometer (MOD1S) from Aqua Edition 1B SSF (single scanner footprint). The dusty cloud is defined as the cloud in dust storm environment or dust contaminated clouds. For clouds growing in the presence of dust, the instantaneous short-wave (SW) forcing at the top of the atmosphere (TOA) is about - 275.7 W/m2 for cloud over dust (COD) region. The clouds developing in no-dust cloud (CLD) regions yield the most negative short-wave (SW) forcing ( - 311.0 W/m2), which is about 12.8 % stronger than those in COD regions.For long-wave (LW) radiative forcing, the no-dust cloud (CLD) is around 102.8 W/m2, which is 20% less than the LW forcing from COD regions. The instantaneous TOA net radiative forcing for the CLD region is about - 208.2 W/m2, which is 42.1% larger than the values of COD regions. The existence of dust aerosols under clouds significantly reduces the cooling effect of clouds.

  4. Ground-based measurements of aerosol optical properties and radiative forcing in North China

    Institute of Scientific and Technical Information of China (English)

    Hongbin Chen; Xiangao Xia; Pucai Wang; Wenxing Zhang

    2007-01-01

    In order to gain an insight into the aerosol properties and their climatic effect over the continental source regions of China, it is of significance to carry out long-term ground-based measurements of aerosol optical properties and radiative forcing. A couple of temporary and permanent Aerosol Robotic Network (AERONET) sites and three comprehensive radiative sites were established in China as a result of international cooperation in recent years. Heavy aerosol loading and significant temporal and spatial variation over North China are revealed by the AERONET data.Aerosol-induced reductions in surface radiation budget are examined on the basis of collocated observations by sun photometers and pyranometers.

  5. Note: Measurement system for the radiative forcing of greenhouse gases in a laboratory scale.

    Science.gov (United States)

    Kawamura, Yoshiyuki

    2016-01-01

    The radiative forcing of the greenhouse gases has been studied being based on computational simulations or the observation of the real atmosphere meteorologically. In order to know the greenhouse effect more deeply and to study it from various viewpoints, the study on it in a laboratory scale is important. We have developed a direct measurement system for the infrared back radiation from the carbon dioxide (CO2) gas. The system configuration is similar with that of the practical earth-atmosphere-space system. Using this system, the back radiation from the CO2 gas was directly measured in a laboratory scale, which roughly coincides with meteorologically predicted value.

  6. Note: Measurement system for the radiative forcing of greenhouse gases in a laboratory scale

    Energy Technology Data Exchange (ETDEWEB)

    Kawamura, Yoshiyuki [Department of Intelligent Mechanical Engineering, Fukuoka Institute of Technology, 3-30-1 Wajirohigashi, Higashiku, Fukuoka 811-0295 (Japan)

    2016-01-15

    The radiative forcing of the greenhouse gases has been studied being based on computational simulations or the observation of the real atmosphere meteorologically. In order to know the greenhouse effect more deeply and to study it from various viewpoints, the study on it in a laboratory scale is important. We have developed a direct measurement system for the infrared back radiation from the carbon dioxide (CO{sub 2}) gas. The system configuration is similar with that of the practical earth-atmosphere-space system. Using this system, the back radiation from the CO{sub 2} gas was directly measured in a laboratory scale, which roughly coincides with meteorologically predicted value.

  7. Aerosol direct radiative forcing in desert and semi-desert regions of northwestern China

    Science.gov (United States)

    Xin, Jinyuan; Gong, Chongshui; Wang, Shigong; Wang, Yuesi

    2016-05-01

    The optical properties of dust aerosols were measured using narrow-band data from a portable sun photometer at four desert and semi-desert stations in northwestern China from 2004 to 2007. Ground-based and satellite observations indicated absorbing dust aerosol loading over the region surrounded by eight large-scale deserts. Radiation forcing was identified by using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model. The ranges of annual mean aerosol optical depth (AOD), Angström exponents, and single-scattering albedo (SSA) were from 0.25 to 0.35, from - 0.73 to 1.18, and from 0.77 to 0.86, respectively. The ranges of annual mean aerosol direct radiative forcing values at the top of the atmosphere (TOA), mid-atmosphere, and on the surface were from 3.9 to 12.0, from 50.0 to 53.1, and from - 39.1 to - 48.1 W/m2, respectively. The aerosols' optical properties and radiative characteristics showed strong seasonal variations in both the desert and semi-desert regions. Strong winds and relatively low humidity will lead dust aerosols in the atmosphere to an increase, which played greatly affected these optical properties during spring and winter in northwestern China. Based on long-term observations and retrieved data, aerosol direct radiative forcing was confirmed to heat the atmosphere (50-53 W/m2) and cool the surface (- 39 to - 48 W/m2) above the analyzed desert. Radiative forcing in the atmosphere in spring and winter was 18 to 21 W/m2 higher than other two seasons. Based on the dust sources around the sites, the greater the AOD, the more negative the forcing. The annual averaged heating rates for aerosols close to the ground (1 km) were approximately 0.80-0.85 K/day.

  8. Parameterization of sea-salt optical properties and physics of the associated radiative forcing

    Science.gov (United States)

    Li, J.; Ma, X.; von Salzen, K.; Dobbie, S.

    2008-08-01

    The optical properties of sea-salt aerosol have been parameterized at shortwave and longwave wavelengths. The optical properties were parameterized in a simple functional form in terms of the ambient relative humidity based on Mie optical property calculations. The proposed parameterization is tested relative to Mie calculations and is found to be accurate to within a few percent. In the parameterization, the effects of the size distribution on the optical properties are accounted for in terms of effective radius of the sea-salt size distribution. This parameterization differs from previous works by being formulated directly with the wet sea-salt size distribution and, to our knowledge, this is the first published sea-salt parameterization to provide a parameterization for both shortwave and longwave wavelengths. We have used this parameterization in a set of idealized 1-D radiative transfer calculations to investigate the sensitivity of various attributes of sea-salt forcing, including the dependency on sea-salt column loading, effective variance, solar angle, and surface albedo. From these sensitivity tests, it is found that sea-salt forcings for both shortwave and longwave spectra are linearly related to the sea-salt loading for realistic values of loadings. The radiative forcing results illustrate that the shortwave forcing is an order of magnitude greater than the longwave forcing results and opposite in sign, for various loadings. Forcing sensitivity studies show that the influence of effective variance for sea-salt is minor; therefore, only one value of effective variance is used in the parameterization. The dependence of sea-salt forcing with solar zenith angle illustrates an interesting result that sea-salt can generate a positive top-of-the-atmosphere result (i.e. warming) when the solar zenith angle is relatively small (i.e. <30°). Finally, it is found that the surface albedo significantly affects the shortwave radiative forcing, with the forcing

  9. Hydrological and ecological implications of radiative forcing by dust in snow

    Science.gov (United States)

    Painter, T.; Bryant, A. C.; Deems, J. S.; Skiles, M.

    2012-12-01

    The runoff from the Colorado River supplies water to over 30 million people in seven US states and Mexico. Climate change projections suggest that this runoff will decrease in the next 50 years by 7-20% due to increases in evapotranspiration and decreases in the ratio of snowfall to rain. Such scenarios challenge the sustainability of the freshwater supply to the southwest US. Recent research however has shown that radiative forcing by dust in snow has been shortening snow cover duration by several weeks due to a 5-7-fold increase in dust loading relative to prior to the European-settlement of the western US in the mid-1800s. In the mountains of the Upper Colorado River, the absolute dust radiative forcing across the period ranges from 30 to 75 W m-2, in turn shortening snow cover duration by 21 to 51 days. Extended to the scale of the Upper Colorado River Basin, this impact has brought peak normalized runoff at Lee's Ferry, AZ (Lake Powell) more than three weeks earlier and reduced the total annual runoff by an average of ~5%. In this region, earlier snowmelt forced by dust radiative forcing impacts alpine vegetation by increasing synchronicity in phenology across the alpine landscape with increasingly earlier snowmelt. Whereas reduced dust load results in topographically-sensitive melt and loss of snow cover, the more spatially-uniform snowmelt from dust radiative forcing leads to synchronized growth and flowering across the landscape. Water managers in the Upper Colorado basin now seek detailed real-time knowledge of dust presence, radiative forcing, and its potential to accelerate snowmelt, as well as understanding its implications for water supply under current conditions and in a changed climate. Likewise, water stakeholder groups, water conservation districts, and state and federal agencies are discussing efforts to restabilize soil surfaces in the dust-emitting regions to mitigate impacts of dust on snowmelt and runoff. However, as these policy

  10. Tropospheric Radiative Forcing from EL Chichon and MT. Pinatubo: Theory and Observations

    Science.gov (United States)

    Dutton, Ellsworth George

    1995-01-01

    The possibility of volcanic effects on global and regional climate variables has had a long history of speculation, correlative study, and proposed physical mechanisms. The potential for widespread surface cooling following the extensive spreading of long-lived stratospheric aerosols following major volcanic eruptions is based on the partial blocking of solar radiation incident at the top of the troposphere. Relatively simple physical mechanisms oppose this potential for cooling: dominant forward solar scattering and absorption of outgoing infrared radiation by the aerosols. More complex considerations are the spatial and temporal variations of the distributed aerosol and its optical and physical properties; potential for water/ice cloud modification by the volcanic particles; surface albedo, water vapor, and cloud feedbacks to a temperature change; the role of the oceans in a large-scale radiatively forced temperature variation; possible circulation modifications; and other forced and random variations in climate. In the current work, rigorous radiative transfer calculations relative to a subset of the above considerations are carried out and compared to observational data to examine deterministic volcanic effects on climate. Specifically, zonally resolved volcanic radiative forcing at the tropopause, and other levels, is computed from the best available information on the spatial and temporal distribution of volcanic aerosols from two recent eruptions, El Chichon (Mexico, 1982) and Mt. Pinatubo (Philippines, 1991). Accuracy of the radiative calculations is partially verified with surface- and satellite -based irradiance observations. Maximum global seasonal -mean radiative forcings of -4.5 and -2.2 W m^{-2} are calculated following the Mt. Pinatubo and El Chichon eruptions, respectively. Within hemisphere irradiance gradient anomalies of up to 16% at the tropopause are calculated for the second N. Hemisphere summer following the eruptions. The computed radiative

  11. Airborne spectral radiation measurements to derive solar radiative forcing of Saharan dust mixed with biomass burning smoke particles

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, S.; Bierwirth, E.; Wendisch, M. (Leipzig Inst. for Meteorology (LIM), Univ. of Leipzig, Leipzig (Germany)), e-mail: s.bauer@uni-leipzig.de; Esselborn, M.; Petzold, A.; Trautmann, T. (Deutsches Zentrum fur Luft- und Raumfahrt (DLR), Oberpfaffenhofen (Germany)); Macke, A. (Leibniz Inst. for Tropospheric Research (IfT) (Germany))

    2011-09-15

    Airborne measurements of upward solar spectral irradiances were performed during the second Saharan Mineral dUst experiMent (SAMUM-2) campaign based on the Cape Verde Islands. Additionally, airborne high resolution lidar measurements of vertical profiles of particle extinction coefficients were collected in parallel to the radiation data. Aerosol layers of Saharan dust, partly mixed with biomass-burning smoke, were probed. With corresponding radiative transfer simulations the single scattering albedo and the asymmetry parameter of the aerosol particles were derived although with high uncertainty. The broad-band aerosol solar radiative forcing at the top of atmosphere was calculated and examined as a function of the aerosol types. However, due to uncertainties in both the measurements and the calculations the chemical composition cannot be identified. In addition, a mostly measurement-based method to derive the broad-band aerosol solar radiative forcing was used. This approach revealed clear differences of broad-band net irradiances as a function of the aerosol optical depth. The data were used to identify different aerosol types from different origins. Higher portions of biomass-burning smoke lead to larger broad-band net irradiances

  12. Accounting for radiative forcing from albedo change in future global land-use scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Andrew D. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Calvin, Katherine V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Collins, William D. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Edmonds, James A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-08-01

    We demonstrate the effectiveness of a new method for quantifying radiative forcing from land use and land cover change (LULCC) within an integrated assessment model, the Global Change Assessment Model (GCAM). The method relies on geographically differentiated estimates of radiative forcing from albedo change associated with major land cover transitions derived from the Community Earth System Model. We find that conversion of 1 km² of woody vegetation (forest and shrublands) to non-woody vegetation (crops and grassland) yields between 0 and –0.71 nW/m² of globally averaged radiative forcing determined by the vegetation characteristics, snow dynamics, and atmospheric radiation environment characteristic within each of 151 regions we consider globally. Across a set of scenarios designed to span a range of potential future LULCC, we find LULCC forcing ranging from –0.06 to –0.29 W/m² by 2070 depending on assumptions regarding future crop yield growth and whether climate policy favors afforestation or bioenergy crops. Inclusion of this previously uncounted forcing in the policy targets driving future climate mitigation efforts leads to changes in fossil fuel emissions on the order of 1.5 PgC/yr by 2070 for a climate forcing limit of 4.5 Wm–2, corresponding to a 12–67 % change in fossil fuel emissions depending on the scenario. Scenarios with significant afforestation must compensate for albedo-induced warming through additional emissions reductions, and scenarios with significant deforestation need not mitigate as aggressively due to albedo-induced cooling. In all scenarios considered, inclusion of albedo forcing in policy targets increases forest and shrub cover globally.

  13. Radiative Forcing Due to Major Aerosol Emitting Sectors in China and India

    Science.gov (United States)

    Streets, David G.; Shindell, Drew Todd; Lu, Zifeng; Faluvegi, Greg

    2013-01-01

    Understanding the radiative forcing caused by anthropogenic aerosol sources is essential for making effective emission control decisions to mitigate climate change. We examined the net direct plus indirect radiative forcing caused by carbonaceous aerosol and sulfur emissions in key sectors of China and India using the GISS-E2 chemistry-climate model. Diesel trucks and buses (67 mW/ sq. m) and residential biofuel combustion (52 mW/ sq. m) in India have the largest global mean, annual average forcings due mainly to the direct and indirect effects of BC. Emissions from these two sectors in China have near-zero net global forcings. Coal-fired power plants in both countries exert a negative forcing of about -30 mW/ sq. m from production of sulfate. Aerosol forcings are largest locally, with direct forcings due to residential biofuel combustion of 580 mW/ sq. m over India and 416 mW/ sq. m over China, but they extend as far as North America, Europe, and the Arctic

  14. Halogen chemistry reduces tropospheric O3 radiative forcing

    DEFF Research Database (Denmark)

    Sherwen, Tomás; Evans, Mat J.; Carpenter, Lucy J.

    2017-01-01

    Tropospheric ozone (O3) is a global warming gas, but the lack of a firm observational record since the preindustrial period means that estimates of its radiative forcing (RFTO3) rely on model calculations. Recent observational evidence shows that halogens are pervasive in the troposphere and need...

  15. Heat transfer in a gray tube with forced convection, internal radiation and axial wall conduction

    Science.gov (United States)

    Chung, B. T. F.; Thompson, J. E.

    1983-01-01

    A method of successive approximations is employed to solve the problem of heat transfer to a transparent gas flowing through a radiating-conducting tube with turbulent forced convection between the tube wall and the gas, and with energy generation in the wall. Emphasis is given to the effect of emissivity of the wall to the tube and gas temperature profiles.

  16. Effect of cruise altitude and alternative aviation fuels on radiative forcing

    NARCIS (Netherlands)

    Snijders, T.A.; Melkert, J.A.

    2011-01-01

    The radiative forcing caused by the emissions of jet aircraft is calculated using data from an aircraft performance model. Data from the performance model is needed to calculate the emissions of the aircraft. The sensitivity function and lifetime of the emitted gasses and particles are used to calcu

  17. An overview of black carbon deposition and its radiative forcing over the Arctic

    Directory of Open Access Journals (Sweden)

    Ting-Feng Dou

    2016-09-01

    Full Text Available This paper gives an overview of the current understanding of the observations of black carbon (BC in snow and ice, and the estimates of BC deposition and its radiative forcing over the Arctic. Both of the observations and model results show that, in spring, the average BC concentration and the resulting radiative forcing in Russian Arctic > Canadian and Alaskan Arctic > Arctic Ocean and Greenland. The observed BC concentration presented a significant decrease trend from the Arctic coastal regions to the center of Arctic Ocean. In summer, due to the combined effects of BC accumulation and enlarged snow grain size, the averaged radiative forcing per unit area over the Arctic Ocean is larger than that over each sector of the Arctic in spring. However, because summer sea ice is always covered by a large fraction of melt ponds, the role of BC in sea ice albedo evolution during this period is secondary. Multi-model mean results indicate that the annual mean radiative forcing from all sources of BC in snow and ice over the Arctic was ∼0.17 W m−2. Wet deposition is the dominant removal mechanism in the Arctic, which accounts for more than 90% of the total deposition. In the last part, we discuss the uncertainties in present modeling studies, and suggest potential approaches to reduce the uncertainties.

  18. Transverse (lateral) instantaneous force of an acoustical first-order Bessel vortex beam centered on a rigid sphere.

    Science.gov (United States)

    Mitri, F G; Fellah, Z E A

    2012-01-01

    In a recent report [F.G. Mitri, Z.E.A. Fellah, Ultrasonics 51 (2011) 719-724], it has been found that the instantaneous axial force (i.e. acting along the axis of wave propagation) of a Bessel acoustic beam centered on a sphere is only determined for the fundamental order (i.e. m=0) but vanishes when the beam is of vortex type (i.e. m>0, where m is the order (or helicity) of the beam). It has also been recognized that for circularly symmetric beams (such as Bessel beams of integer order), the transverse (lateral) instantaneous force should vanish as required by symmetry. Nevertheless, in this commentary, the present analysis unexpectedly reveals the existence of a transverse instantaneous force on a rigid sphere centered on the axis of a Bessel vortex beam of unit magnitude order (i.e. |m|=1) not reported in [F.G. Mitri, Z.E.A. Fellah, Ultrasonics 51 (2011) 719-724]. The presence of the transverse instantaneous force components of a first-order Bessel vortex beam results from mathematical anti-symmetry in the surface integrals, but vanishes for the fundamental (m=0) and higher-order Bessel (vortex) beams (i.e. |m|>1). Here, closed-form solutions for the instantaneous force components are obtained and examples for the transverse components for progressive waves are computed for a fixed and a movable rigid sphere. The results show that only the dipole (n=1) mode in the scattering contributes to the instantaneous force components, as well as how the transverse instantaneous force per unit cross-sectional surface varies versus the dimensionless frequency ka (k is the wave number in the fluid medium and a is the sphere's radius), and the half-cone angle β of the beam. Moreover, the velocity of the movable sphere is evaluated based on the concept of mechanical impedance. The proposed analysis may be of interest in the analysis of transverse instantaneous forces on spherical particles for particle manipulation and rotation in drug delivery and other biomedical or

  19. Evapo-transpiration, role of aerosol radiative forcing: a study over a dense canopy

    Science.gov (United States)

    Bhanage, VInayak; Latha, R.; Murthy, B. S.

    2016-05-01

    Current study uses Satellite and Reanalysis data to quantify the effect of aerosol on ET at various space and time scales. All the data are obtained for the period June 2008 to May 2009 over Dibrugarh district, Assam, Indi a where NDVI has limited change of through the year. Monthly Evapo-Transpiration (ET, cumulative), Normalized Difference Vegetation Index (NDVI) and Aerosol Optical Depth (AOD) are retrieved from satellite images of Terra-MODIS. The AOD data are evaluated against in-situ observations. Maximum values of AOD are observed in the pre-monsoon season while minimum AOD values are perceived in October and November. Aerosol Radiative Forcing (ARF) is calculated by using the MERRA data sets of `clean-clear radiation' and `clear-radiation' at surface over the study area. Maximum aerosol radiative forcing is observed during the pre-monsoon season; this is in tune with ground observations. Strong positive correlation (r=0.75) between ET and NDVI is observed and it is found that the dense vegetative surfaces exhibit higher rate of evapo-transpiration. A strong positive correlation (r= -0.85) between ARF at surface and AOD is observed with radiative forcing efficiency of 35 W/m2. A statistical regression equation of ET a s a function of NDVI and AOD i.e. ET = 0.25 + (-84.27) * AOD + (131.51) * NDVI, is obtained that shows a correlation of 0.824.

  20. Investigating the relationship between pressure force and acoustic waveform in footstep sounds

    DEFF Research Database (Denmark)

    Grani, Francesco; Serafin, Stefania; Götzen, Amalia De;

    2013-01-01

    In this paper we present an inquiry into of the relationships between audio waveforms and ground reaction force in recorded footstep sounds. In an anechoic room, we recorded several footstep sounds produced while walking on creaking wood and gravel. The recordings were performed by using a pair...... of sandals embedded with six pressure sensors each. Investigations of the relationships between recorded force and footstep sounds is presented, together with several possible applications of the system....

  1. Direct and semi-direct radiative forcing of smoke aerosols over clouds

    Science.gov (United States)

    Wilcox, E. M.

    2012-01-01

    Observations from Earth observing satellites indicate that dark carbonaceous aerosols that absorb solar radiation are widespread in the tropics and subtropics. When these aerosols mix with clouds, there is generally a reduction of cloudiness owing to absorption of solar energy in the aerosol layer. Over the subtropical South Atlantic Ocean, where smoke from savannah burning in southern Africa resides above a persistent deck of marine stratocumulus clouds, radiative heating of the smoke layer leads to a thickening of the cloud layer. Here, satellite observations of the albedo of overcast scenes of 25 km2 size or larger are combined with additional satellite observations of clouds and aerosols to estimate the top-of-atmosphere direct radiative forcing attributable to presence of dark aerosol above bright cloud, and the negative semi-direct forcing attributable to the thickening of the cloud layer. The average positive direct radiative forcing by smoke over an overcast scene is 9.2±6.6 W m-2 for cases with an unambiguous signal of absorbing aerosol over cloud in passive ultraviolet remote sensing observations. However, cloud liquid water path is enhanced by 16.3±7.7 g m-2 across the range of values for sea surface temperature for cases of smoke over cloud. The negative radiative forcing associated with this semi-direct effect of smoke over clouds is estimated to be -5.9±3.5 W m-2. Therefore, the cooling associated with the semi-direct cloud thickening effect compensates for greater than 60 % of the direct radiative effect. Accounting for the frequency of occurrence of significant absorbing aerosol above overcast scenes leads to an estimate of the average direct forcing of 1.0±0.7 W m-2 contributed by these scenes averaged over the subtropical southeast Atlantic Ocean during austral winter. The regional average of the negative semi-direct forcing is -0.7±0.4 W m-2. Therefore, smoke aerosols overlaying the decks of overcast marine stratocumulus clouds considered

  2. Regularity of acoustic radiation at ascending load on a pair of friction from a composite material

    Directory of Open Access Journals (Sweden)

    С. Ф. Філоненко

    2013-07-01

    Full Text Available In this article the simulation the results of acoustic emission signals formed by friction surfaces with composite materials at load increasing were showed. The results showed that at increase of axial load increases the amplitude of the resulting parameters of acoustic emission signals, such as the average amplitude, its standard deviation and variance. Thus were obtained the basic changes of amplitude parameters generated signals. Was determined that the variation of the percentage increase in the average amplitude, its standard deviation and variance were  the same type of character, with well approximate by linear functions. The results showed that with growing of axial load the percent increase in average amplitude of the resulting acoustic emission signals. Also, an analysis of the energy parameters of acoustic emission with increasing axial load on the friction pair with composite materials was conducted. The simulation results showed that the percentage increase in the average level of energy and its standard deviation are approximate by linear functions. At the same time the greatest percentage increase with increasing axial load on the friction pair is observed in the dispersion of the average energy of the resulting acoustic emission signals. The results showed that at experimental study of the acoustic emission signals with increasing axial load on the friction pair with composite materials greatest growth is expected in the average amplitude of the resulting AE signals. The growth of its standard deviation and variance will be not significant. At the same time, the greatest growth is expected in the dispersion of the average energy of acoustic emission signals

  3. Use of acoustic vortices in acoustic levitation

    DEFF Research Database (Denmark)

    Cutanda Henriquez, Vicente; Santillan, Arturo Orozco; Juhl, Peter Møller

    2009-01-01

    Acoustic fields are known to exert forces on the surfaces of objects. These forces are noticeable if the sound pressure is sufficiently high. Two phenomena where acoustic forces are relevant are: i) acoustic levitation, where strong standing waves can hold small objects at certain positions......, counterbalancing their weight, and ii) acoustic vortices, spinning sound fields that can impinge angular momentum and cause rotation of objects. In this contribution, both force-creating sound fields are studied by means of numerical simulations. The Boundary Element Method is employed to this end. The simulation...... of acoustical vortices uses an efficient numerical implementation based on the superposition of two orthogonal sound fields with a delay of 90° between them. It is shown that acoustic levitation and the use of acoustic vortices can be combined to manipulate objects in an efficient and controlled manner without...

  4. A Comparison of Pre-monsoonal and Monsoonal Radiative Forcing by Anthropogenic Aerosols over South Asia

    Science.gov (United States)

    Lee, S.; Cohen, J. B.; Wang, C.

    2012-12-01

    Radiative forcing by anthropogenic aerosols after monsoon onset is often considered unimportant compared to forcing during the pre-monsoonal period, due to precipitation scavenging. We tested this assumption for the South Asian monsoon using three model runs with forcing prescribed during the pre-monsoonal period (March-May), monsoon period (June-September) and both periods. The forcing represents the direct radiative effects of sulfate, organic carbon and black carbon. It was derived from a set of Kalman filter-optimised black carbon emissions from a modelling system based on the CAM3 GCM, a two-moment multi-scheme aerosol and radiation model, and a coupled urban scale processing package; we expect it to be reliable within its given error bounds. The monthly climatological forcing values were prescribed over South Asia every year for 100 years to CESM 1.0.4, a coupled atmosphere-ocean model. We shall compare the three resultant climatologies with climatologies from a no aerosol model and a full aerosol model.

  5. Radiative forcing and temperature response to changes in urban albedos and associated CO2 offsets

    Energy Technology Data Exchange (ETDEWEB)

    Menon, Surabi; Akbari, Hashem; Mahanama, Sarith; Sednev, Igor; Levinson, Ronnen

    2010-02-12

    The two main forcings that can counteract to some extent the positive forcings from greenhouse gases from pre-industrial times to present-day are the aerosol and related aerosol-cloud forcings, and the radiative response to changes in surface albedo. Here, we quantify the change in radiative forcing and land surface temperature that may be obtained by increasing the albedos of roofs and pavements in urban areas in temperate and tropical regions of the globe by 0.1. Using the catchment land surface model (the land model coupled to the GEOS-5 Atmospheric General Circulation Model), we quantify the change in the total outgoing (outgoing shortwave+longwave) radiation and land surface temperature to a 0.1 increase in urban albedos for all global land areas. The global average increase in the total outgoing radiation was 0.5 Wm{sup -2}, and temperature decreased by {approx}0.008 K for an average 0.003 increase in surface albedo. These averages represent all global land areas where data were available from the land surface model used and are for the boreal summer (June-July-August). For the continental U.S. the total outgoing radiation increased by 2.3 Wm{sup -2}, and land surface temperature decreased by {approx}0.03 K for an average 0.01 increase in surface albedo. Based on these forcings, the expected emitted CO{sub 2} offset for a plausible 0.25 and 0.15 increase in albedos of roofs and pavements, respectively, for all global urban areas, was found to be {approx} 57 Gt CO{sub 2}. A more meaningful evaluation of the impacts of urban albedo increases on global climate and the expected CO{sub 2} offsets would require simulations which better characterizes urban surfaces and represents the full annual cycle.

  6. On the radiative forcing of volcanic plumes: modelling the impact of Mount Etna in the Mediterranean

    Directory of Open Access Journals (Sweden)

    Pasquale Sellitto

    2015-12-01

    Full Text Available The impact of small to moderate volcanic eruptions on the regional to global radiative forcing and climate is still largely unknown and thought to be presently underestimated. In this work, daily average shortwave radiative forcing efficiencies at the surface (RFEdSurf, at top of the atmosphere (RFEdTOA and their ratio (f, for upper tropospheric volcanic plumes with different optical characterization, are derived using the radiative transfer model UVSPEC and the LibRadtran suite. The optical parameters of the simulated aerosol layer, i.e., the Ångströem coefficient (alpha, the single scattering albedo (SSA and the asymmetry factor (g, have been varied to mimic volcanic ash (bigger and more absorbing particles, sulphate aerosols (smaller and more reflective particles and intermediate/mixed conditions. The characterization of the plume and its vertical distribution have been set-up to simulate Mount Etna, basing on previous studies. The radiative forcing and in particular the f ratio is strongly affected by the SSA and g, and to a smaller extent by alpha, especially for sulphates-dominated plumes. The impact of the altitude and thickness of the plume on the radiative forcing, for a fixed optical characterization of the aerosol layer, has been found negligible (less than 1% for RFEdSurf, RFEdTOA and f. The simultaneous presence of boundary layer/lower tropospheric marine or dust aerosols, like expected in the Mediterranean area, modulates only slightly (up to 12 and 14% for RFEdSurf and RFEdTOA, and 3 to 4% of the f ratio the radiative effects of the upper tropospheric volcanic layer.

  7. Importance of tropospheric volcanic aerosol for indirect radiative forcing of climate

    Directory of Open Access Journals (Sweden)

    A. Schmidt

    2012-03-01

    Full Text Available Observations and models have shown that continuously degassing volcanoes have a potentially large effect on the natural background aerosol loading and the radiative state of the atmosphere. Here, we use a global aerosol microphysics model to quantify the impact of these volcanic emissions on the cloud albedo radiative forcing under pre-industrial (PI and present-day (PD conditions. We find that volcanic degassing increases global annual mean cloud droplet number concentrations by 40% under PI conditions, but by only 10% under PD conditions. Consequently, volcanic degassing causes a global annual mean cloud albedo effect of −1.06 W m−2 in the PI era but only −0.56 W m−2 in the PD era. This non-equal effect is explained partly by the lower background aerosol concentrations in the PI era, but also because more aerosol particles are produced per unit of volcanic sulphur emission in the PI atmosphere. The higher sensitivity of the PI atmosphere to volcanic emissions has an important consequence for the anthropogenic cloud radiative forcing because the large uncertainty in volcanic emissions translates into an uncertainty in the PI baseline cloud radiative state. Assuming a −50/+100% uncertainty range in the volcanic sulphur flux, we estimate the annual mean anthropogenic cloud albedo forcing to lie between −1.16 W m−2 and −0.86 W m−2. Therefore, the volcanically induced uncertainty in the PI baseline cloud radiative state substantially adds to the already large uncertainty in the magnitude of the indirect radiative forcing of climate.

  8. Unexpectedly Large Surface Gravities for Acoustic Horizons?

    CERN Document Server

    Liberati, S; Visser, M; Liberati, Stefano; Sonego, Sebastiano; Visser, Matt

    2000-01-01

    Acoustic black holes are fluid dynamic analogs of general relativistic black holes, wherein the behaviour of sound waves in a moving fluid acts as an analog for scalar fields propagating in a gravitational background. Acoustic horizons possess many of the properties more normally associated with the event horizons of general relativity, up to and including Hawking radiation. They have received much attention because it would seem to be much easier to experimentally create an acoustic horizon than to create an event horizon. We wish to point out some potential difficulties (and opportunities) in actually setting up an experiment that possesses an acoustic horizon. We show that in zero-viscosity, stationary fluid flow with generic boundary conditions, the creation of an acoustic horizon is accompanied by a formally infinite ``surface gravity'', and a formally infinite Hawking flux. Only by applying a suitable non-constant external body force, and for very specific boundary conditions on the flow, can these quan...

  9. Capillary forces in the acoustics of patchy-saturated porous media.

    Science.gov (United States)

    Tserkovnyak, Yaroslav; Johnson, David Linton

    2003-11-01

    A linearized theory of the acoustics of porous elastic formations, such as rocks, saturated with two different viscous fluids is generalized to take into account a pressure discontinuity across the fluid boundaries. The latter can arise due to the surface tension of the membrane separating the fluids. We show that the frequency-dependent bulk modulus K(omega) for wavelengths longer than the characteristic structural dimensions of the fluid patches has a similar analytic behavior to the case of a vanishing membrane stiffness and depends on the same parameters of the fluid-distribution topology. The effect of the capillary stiffness can be accounted for by renormalizing the coefficients of the leading terms in the low-frequency limit of K(omega).

  10. The Helmholtz equation least squares method for reconstructing and predicting acoustic radiation

    CERN Document Server

    Wu, Sean F

    2015-01-01

    This book gives a comprehensive introduction to the Helmholtz Equation Least Squares (HELS) method and its use in diagnosing noise and vibration problems. In contrast to the traditional NAH technologies, the HELS method does not seek an exact solution to the acoustic field produced by an arbitrarily shaped structure. Rather, it attempts to obtain the best approximation of an acoustic field through the expansion of certain basis functions. Therefore, it significantly simplifies the complexities of the reconstruction process, yet still enables one to acquire an understanding of the root causes of different noise and vibration problems that involve arbitrarily shaped surfaces in non-free space using far fewer measurement points than either Fourier acoustics or BEM based NAH. The examples given in this book illustrate that the HELS method may potentially become a practical and versatile tool for engineers to tackle a variety of complex noise and vibration issues in engineering applications.

  11. Radiative Forcing of SO2 and Nox: A Case Study in Beijing

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A case study was performed in Beijing in 2000 to observe concentrations of SO2 and NOx in the atmosphere and to evaluate their radiative impact. It was found that the concentrations of these gases are usually high in the morning due to a temperature inversion in the boundary layer. The average concentrations obtained from the observations are much higher than those used in the McClatchey reference atmosphere. The radiative impacts of these gases are calculated using a line-by-line radiative transfer model. The results show that the radiative forcing at the surface due to SO2 is 0.0576 W m-2 and that due to NOx is 0.0032 W m-2. These figures are almost compatible with that due to CFC11.

  12. Forces acting on a small particle in an acoustical field in a viscous fluid

    DEFF Research Database (Denmark)

    Settnes, Mikkel; Bruus, Henrik

    2012-01-01

    force, which is valid for any particle radius and boundary-layer thickness provided that both of these length scales are much smaller than the wavelength of the ultrasound wave (millimeters in water at megahertz frequencies). The acoustophoretic response of suspended microparticles is predicted...

  13. Direct Radiative Forcing and Climatic Effects of Aerosols over East Asia by RegCM3

    Institute of Scientific and Technical Information of China (English)

    JU Li-Xia; HAN Zhi-Wei

    2011-01-01

    The authors used a high-resolution regional climate model (RegCM3) coupled with a chemistry/ aerosol module to simulate East Asian climate in 2006 and to test the climatic impacts of aerosols on regional- scale climate. The direct radiative forcing and climatic effects of aerosols (dust, sulfate, black carbon, and organic carbon) were discussed. The results indicated that aerosols generally produced negative radiative forcing at the top-of-the-atmosphere (TOA) over most areas of East Asia. The radiative forcing induced by aerosols exhibited significant seasonal and regional variations, with the strongest forcing occurring in summer. The aerosol feed- backs on surface air temperature and precipitation were clear. Surface cooling dominated features over the East Asian continental areas, which varied in the approximate range of-0.5 to -2℃ with the maximum up to -3℃ in summer over the deserts of West China. The aerosols induced complicated variations of precipitation. Except in summer, the rainfall generally varied in the range of-1 to 1 mm d^-1 over most areas of China.

  14. Modelling the effect of the radiation reaction force on the acceleration of ultra-thin foils

    Science.gov (United States)

    Duff, M. J.; Capdessus, R.; King, M.; Del Sorbo, D.; Ridgers, C. P.; McKenna, P.

    2017-05-01

    An investigation of the effects of the radiation reaction force on radiation pressure acceleration is presented. Through 1D(3V) PIC code simulations, it is found that radiation reaction causes a decrease in the target velocity during the interaction of an ultra-intense laser pulse with a solid density thin foil of varying thickness. This change in the target velocity can be related to the loss of backwards-directed electrons due to cooling and reflection in the laser field. The loss of this electron population changes the distribution of the emitted synchrotron radiation. We demonstrate that it is the emission of radiation which leads to the observed decrease in target velocity. Through a modification to the light sail equation of motion (which is used to describe radiation pressure acceleration in thin foils), which accounts for the conversion of laser energy to synchrotron radiation, we can describe this change in target velocity. This model can be tested in future experiments with ultra-high intensity lasers, and will lead to a better understanding of the process of relativistically induced transparency in the new intensity regime.

  15. Origin and radiative forcing of black carbon transported to the Himalayas and Tibetan Plateau

    Science.gov (United States)

    Kopacz, M.; Mauzerall, D. L.; Wang, J.; Leibensperger, E. M.; Henze, D. K.; Singh, K.

    2011-03-01

    The remote and high elevation regions of central Asia are influenced by black carbon (BC) emissions from a variety of locations. BC deposition contributes to melting of glaciers and questions exist, of both scientific and policy interest, as to the origin of the BC reaching the glaciers. We use the adjoint of the GEOS-Chem model to identify the location from which BC arriving at a variety of locations in the Himalayas and Tibetan Plateau originates. We then calculate its direct and snow-albedo radiative forcing. We analyze the seasonal variation in the origin of BC using an adjoint sensitivity analysis, which provides a detailed map of the location of emissions that directly contribute to black carbon concentrations at receptor locations. We find that emissions from northern India and central China contribute the majority of BC to the Himalayas, although the precise location varies with season. The Tibetan Plateau receives most BC from western and central China, as well as from India, Nepal, the Middle East, Pakistan and other countries. The magnitude of contribution from each region varies with season and receptor location. We find that sources as varied as African biomass burning and Middle Eastern fossil fuel combustion can significantly contribute to the BC reaching the Himalayas and Tibetan Plateau. We compute radiative forcing in the snow-covered regions and find the forcing due to the BC induced snow-albedo effect to vary from 5-15 W m-2 within the region, an order of magnitude larger than radiative forcing due to the direct effect, and with significant seasonal variation in the northern Tibetan Plateau. Radiative forcing from reduced snow albedo likely accelerates glacier melting. Our analysis may help inform mitigation efforts to slow the rate of glacial melt by identifying regions that make the largest contributions to BC deposition in the Himalayas and Tibetan Plateau.

  16. Origin and radiative forcing of black carbon transported to the Himalayas and Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    M. Kopacz

    2011-03-01

    Full Text Available The remote and high elevation regions of central Asia are influenced by black carbon (BC emissions from a variety of locations. BC deposition contributes to melting of glaciers and questions exist, of both scientific and policy interest, as to the origin of the BC reaching the glaciers. We use the adjoint of the GEOS-Chem model to identify the location from which BC arriving at a variety of locations in the Himalayas and Tibetan Plateau originates. We then calculate its direct and snow-albedo radiative forcing. We analyze the seasonal variation in the origin of BC using an adjoint sensitivity analysis, which provides a detailed map of the location of emissions that directly contribute to black carbon concentrations at receptor locations. We find that emissions from northern India and central China contribute the majority of BC to the Himalayas, although the precise location varies with season. The Tibetan Plateau receives most BC from western and central China, as well as from India, Nepal, the Middle East, Pakistan and other countries. The magnitude of contribution from each region varies with season and receptor location. We find that sources as varied as African biomass burning and Middle Eastern fossil fuel combustion can significantly contribute to the BC reaching the Himalayas and Tibetan Plateau. We compute radiative forcing in the snow-covered regions and find the forcing due to the BC induced snow-albedo effect to vary from 5–15 W m−2 within the region, an order of magnitude larger than radiative forcing due to the direct effect, and with significant seasonal variation in the northern Tibetan Plateau. Radiative forcing from reduced snow albedo likely accelerates glacier melting. Our analysis may help inform mitigation efforts to slow the rate of glacial melt by identifying regions that make the largest contributions to BC deposition in the Himalayas and Tibetan Plateau.

  17. Origin and radiative forcing of black carbon transported to the Himalayas and Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    M. Kopacz

    2010-09-01

    Full Text Available The remote and high elevation regions of central Asia are influenced by black carbon (BC emissions from a variety of locations. BC deposition contributes to melting of glaciers and questions exist, of both scientific and policy interest, as to the origin of the BC reaching the glaciers. We use the adjoint of the GEOS-Chem model to identify the location from which BC arriving at a variety of locations in the Himalayas and Tibetan Plateau originates. We then calculate its direct and snow-albedo radiative forcing. We analyze the seasonal variation in the origin of BC using an adjoint sensitivity analysis, which provides a detailed map of the location of emissions that directly contribute to black carbon concentrations at receptor locations. We find that emissions from northern India and central China contribute the majority of BC to the Himalayas, although the precise location varies with season. The Tibetan Plateau receives most BC from western and central China, as well as from India, Nepal, the Middle East, Pakistan and other countries. The magnitude of contribution from each region varies with season and receptor location. We find that sources as varied as African biomass burning and Middle Eastern fossil fuel combustion can significantly contribute to the BC reaching the Himalayas and Tibetan Plateau. We compute radiative forcing in the snow-covered regions and estimate the forcing due to the BC induced snow-albedo effect at about 5–15 W m−2 within the region, an order of magnitude larger than radiative forcing due to the direct effect, and with significant seasonal variation in the northern Tibetan Plateau. Radiative forcing from reduced snow albedo accelerates glacier melting. Our analysis can help inform mitigation efforts to slow the rate of glacial melt by identifying regions that make the largest contributions to BC deposition in the Himalayas and Tibetan Plateau.

  18. Nonlinear Acoustics in a Dispersive Continuum: Random Waves, Radiation Pressure, and Quantum Noise.

    Science.gov (United States)

    1983-03-01

    Karpman , Nonlinear Waves in Dispersive Media, Pergamon Press, New York, 1975, p. 76. 26. R. Beyers, Nonlinear Acoustics, U.S. Government Printing...20301 U. S. Army Research nffice 2 copies Box 12211 Research Triangle Park tlorth Carolina 27709 Defense Technical Information Center 12 copies Cameron

  19. Direct Radiative Forcing from Saharan Mineral Dust Layers from In-situ Measurements and Satellite Retrievals

    Science.gov (United States)

    Sauer, D. N.; Vázquez-Navarro, M.; Gasteiger, J.; Chouza, F.; Weinzierl, B.

    2016-12-01

    Mineral dust is the major species of airborne particulate matter by mass in the atmosphere. Each year an estimated 200-3000 Tg of dust are emitted from the North African desert and arid regions alone. A large fraction of the dust is lifted into the free troposphere and gets transported in extended dust layers westward over the Atlantic Ocean into the Caribbean Sea. Especially over the dark surface of the ocean, those dust layers exert a significant effect on the atmospheric radiative balance though aerosol-radiation interactions. During the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in summer 2013 airborne in-situ aerosol measurements on both sides of the Atlantic Ocean, near the African coast and the Caribbean were performed. In this study we use data about aerosol microphysical properties acquired between Cabo Verde and Senegal to derive the aerosol optical properties and the resulting radiative forcing using the radiative transfer package libRadtran. We compare the results to values retrieved from MSG/SEVIRI data using the RRUMS algorithm. The RRUMS algorithm can derive shortwave and longwave top-of-atmosphere outgoing fluxes using only information issued from the narrow-band MSG/SEVIRI channels. A specific calibration based on collocated Terra/CERES measurements ensures a correct retrieval of the upwelling flux from the dust covered pixels. The comparison of radiative forcings based on in-situ data to satellite-retrieved values enables us to extend the radiative forcing estimates from small-scale in-situ measurements to large scale satellite coverage over the Atlantic Ocean.

  20. Top-of-atmosphere radiative forcing affected by brown carbon in the upper troposphere

    Science.gov (United States)

    Zhang, Yuzhong; Forrister, Haviland; Liu, Jiumeng; Dibb, Jack; Anderson, Bruce; Schwarz, Joshua P.; Perring, Anne E.; Jimenez, Jose L.; Campuzano-Jost, Pedro; Wang, Yuhang; Nenes, Athanasios; Weber, Rodney J.

    2017-07-01

    Carbonaceous aerosols affect the global radiative balance by absorbing and scattering radiation, which leads to warming or cooling of the atmosphere, respectively. Black carbon is the main light-absorbing component. A portion of the organic aerosol known as brown carbon also absorbs light. The climate sensitivity to absorbing aerosols rapidly increases with altitude, but brown carbon measurements are limited in the upper troposphere. Here we present aircraft observations of vertical aerosol distributions over the continental United States in May and June 2012 to show that light-absorbing brown carbon is prevalent in the troposphere, and absorbs more short-wavelength radiation than black carbon at altitudes between 5 and 12 km. We find that brown carbon is transported to these altitudes by deep convection, and that in-cloud heterogeneous processing may produce brown carbon. Radiative transfer calculations suggest that brown carbon accounts for about 24% of combined black and brown carbon warming effect at the tropopause. Roughly two-thirds of the estimated brown carbon forcing occurs above 5 km, although most brown carbon is found below 5 km. The highest radiative absorption occurred during an event that ingested a wildfire plume. We conclude that high-altitude brown carbon from biomass burning is an unappreciated component of climate forcing.

  1. Large Aerosol Radiative Forcing due to the 1997 Indonesian Forest Fire

    Science.gov (United States)

    Podgorny, I. A.; Li, F.; Ramanathan, V.

    2003-01-01

    During the last decade, the feedback between El Niño and biomass burning caused the Indonesia's forest fire aerosols to be the second most significant source of anthropogenic aerosol over the tropical Indian Ocean after the South Asian Haze. In this paper, the estimates of the radiative forcing during the 1997 Indonesia's forest fire have been obtained by integrating satellite derived aerosol optical depths and cloud cover with in-situ observations of single scattering albedo and a Monte-Carlo Aerosol-Cloud radiation model. The haze reduced the seasonal average solar radiation absorbed by the equatorial Indian ocean by as much as 30 to 60 W m-2 during September to November 1997, and increased the atmospheric solar heating by as much as 50% to 100% within the first 3 kilometers. The radiative forcing at the top of the atmosphere (TOA) was in the range of 5 to 15 W m-2 under cloudy skies. The significance of such large radiative flux changes to the tropical ocean-atmosphere heat budget and climate needs to be examined with climate models.

  2. Effect of dust ion collision on dust ion acoustic waves in the framework of damped Zakharov-Kuznetsov equation in presence of external periodic force

    Science.gov (United States)

    Kanti Das, Tushar; Ali, Rustam; Chatterjee, Prasanta

    2017-10-01

    The dynamics of dust ion acoustic waves (DIAWs) is investigated in a magnetized dusty plasma whose constituents are cold ions, superthermal electrons, and dust particles in the framework of a damped Zakharov-Kuznetsov (dZK) equation in the presence of externally applied periodic force. The dZK equation is derived employing the standard reductive perturbation technique. The effect of dust ion collision on the quasiperiodic and chaotic motion of dust ion acoustic waves is discussed. It is observed that the collision frequency νid 0 plays the role of a switching parameter from the quasiperiodic route to chaos for the DIAWs.

  3. Seasonal absolute acoustic intensity, atmospheric forcing and currents in a tropical coral reef system

    Science.gov (United States)

    de Jesús Salas Pérez, José; Salas-Monreal, David; Monreal-Gómez, María Adela; Riveron-Enzastiga, Mayra Lorena; Llasat, Carme

    2012-03-01

    The seasonal patterns of marine circulation and biovolume were obtained from time-series measurements carried out in the "Parque Nacional Sistema Arrecifal Veracruzano" (PNSAV), located in the western continental shelf of the Gulf of Mexico, from June 2008 to September 2009. Two mechanisms were depicted as the responsible for the current pattern observed in the PNSAV and not only one as suggested in large-scale studies. The first mechanism is the wind generated currents. This mechanism by itself is responsible for up to 78% of total variation of the seasonal circulation in the PNSAV as estimated with the first mode of the EOF's (Empirical Orthogonal Functions), which was correlated (Normalized Lagged Correlation) with the north-south wind component. Therefore, the wind and the first mode were highly correlated for most of the year (r > 0.7). The second mode was attributed to the low frequency current, associated to the meso-scale circulation of the Gulf of Mexico, owing to the cyclonic eddy of the Campeche Bay. Both mechanisms were mostly observed throughout the year. Nevertheless, the cyclonic eddy of the Campeche Bay (meso-scale) was the first responsible for the current fluctuations observed during the summer of 2008 and 2009. The absolute acoustic intensity (plankton biovolumes) was highly correlated to currents, showing high spatial variability, attributed to advection produced by the meso-scale circulation and to river discharges, but also by eddy diffusion produced by atmospheric and coastal water fronts.

  4. Influence Of Changing the Flow Rate In The Acoustic Response And Saturation During Forced Imbibition In A Limestone

    Science.gov (United States)

    Lopes, S.; Lebedev, M.; Muller, T. M.

    2012-12-01

    Forced imbibition was performed in a Limestone Savonnieres by injecting water into a dry sample. The injection was monitored with X-ray Computed Tomography (CT) and active ultrasonic measurements so that the time-space distribution of the invading fluid could be simultaneously observed in CT images and quantified through measuring P-wave velocities and water saturation. The CT scans allowed us to observe a water front advancing away from the area of injection and estimate saturation. Through the evolution of P-wave velocities, we observed that the approaching of the water front to the monitored position decreased P-wave velocities while the saturation increased continuously. Decreasing injection rate decreased P-wave velocities and saturation. Increasing injection rate, increased P-wave velocities and saturation, sharply and for a short period of time followed by a slight decrease for P-wave velocities and a continuous increase. Our experimental data confirms how sensitive acoustic waves are to the presence of water and that changing injection rates promote considerable fluid distribution that is drastically reflected in the acoustic velocities. Furthermore, the same patterns have been observed in our previous work with sandstones.; Waveforms for the P-waves picked during this experiment: before injection (blue line) and after injecting 8.4 mL of volume of water (orange line). Note the decrease of wave-amplitude and increase of wavelength. ; P-wave velocities with volume of water injected. Dashed lines represent the moments when we decreased injection rate, at 7.9 mL of volume of water injected, and when we increased injection rate at 10.7 mL. Note the immediate decrease and increase of P-wave velocity when we decrease and increase the injection rate, respectively.

  5. Radiative Forcing and Climate Response Due to Black Carbon in Snow and Ice

    Institute of Scientific and Technical Information of China (English)

    WANG Zhili; ZHANG Hua; SHEN Xueshun

    2011-01-01

    The radiative forcing and climate response due to black carbon (BC) in snow and/or ice were investigated by integrating observed effects of BC on snow/ice albedo into an atmospheric general circulation model (BCC_AGCM2.0.1) developed by the National Climate Center (NCC) of the China Meteorological Administration (CMA).The results show that the global annual mean surface radiative forcing due to BC in snow/ice is +0.042 W m-2,with maximum forcing found over the Tibetan Plateau and regional mean forcing exceeding +2.8 W m-2.The global annual mean surface temperature increased 0.071℃ due to BC in snow/ice.Positive surface radiative forcing was clearly shown in winter and spring and increased the surface temperature of snow/ice in the Northern Hemisphere.The surface temperatures of snow-covered areas of Eurasia and North America in winter (spring) increased by 0.83℃ (0.6℃) and 0.83℃ (0.46℃),respectively.Snowmelt rates also increased greatly,leading to earlier snowmelt and peak runoff times.With the rise of surface temperatures in the Arctic,more water vapor could be released into the atmosphere,allowing easier cloud formation,which could lead to higher thermal emittance in the Arctic. However,the total cloud forcing could decrease due to increasing cloud cover,which will offset some of the positive feedback mechanism of the clouds.

  6. Vibration and acoustic radiation of a finite cylindrical shell submerged at finite depth from the free surface

    Science.gov (United States)

    Guo, Wenjie; Li, Tianyun; Zhu, Xiang; Miao, Yuyue; Zhang, Guanjun

    2017-04-01

    The far-field acoustic radiation of a cylindrical shell with finite length submerged at finite depth from the water surface is studied. Two steps are utilized to solve the problem. The first step is to determine the vibration response of the submerged cylindrical shell by using an analytical method and the second one is to determine the far field sound radiation with the boundary element method. To address the vibration responses of the shell analytically, the cylindrical shell and surrounding fluid are described by the Flügge shell equations and Laplace equation in the cylindrical coordinate system respectively. The free surface effect is taken into consideration by using the image method and the Graf's addition theorem. The reliability and efficiency of the present method are validated by comparison with the finite element method. Then, based on the vibration responses of the shell obtained from the first step, the far-field sound pressure is computed by using the boundary element method. It is found that the vibration of the cylindrical shell submerged at finite depth from the free surface tends to be the same as that in infinite fluid when the submerged depth exceeds a certain value. The frequency and the submerged depth have crucial effects on the fluctuation of the far-field sound pressure, while for the curve of sound pressure level versus immersion depth, the ratio of the distance between the adjacent peak points of sound pressure to the wavelength is independent of the frequency. Moreover, the petal number of the directivity of the far-field sound pressure increases with the increase of the frequency and the submerged depth. The work provides more understanding on the vibration and acoustic radiation behavior of a finite cylindrical shell submerged at finite depth.

  7. Letter to the Editor Aerosol radiative forcing over land: effect of surface and cloud reflection

    Directory of Open Access Journals (Sweden)

    S. K. Satheesh

    Full Text Available It is now clearly understood that atmospheric aerosols have a significant impact on climate due to their important role in modifying the incoming solar and outgoing infrared radiation. The question of whether aerosol cools (negative forcing or warms (positive forcing the planet depends on the relative dominance of absorbing aerosols. Recent investigations over the tropical Indian Ocean have shown that, irrespective of the comparatively small percentage contribution in optical depth ( ~ 11%, soot has an important role in the overall radiative forcing. However, when the amount of absorbing aerosols such as soot are significant, aerosol optical depth and chemical composition are not the only determinants of aerosol climate effects, but the altitude of the aerosol layer and the altitude and type of clouds are also important. In this paper, the aerosol forcing in the presence of clouds and the effect of different surface types (ocean, soil, vegetation, and different combinations of soil and vegetation are examined based on model simulations, demonstrating that aerosol forcing changes sign from negative (cooling to positive (warming when reflection from below (either due to land or clouds is high.Key words. Atmospheric composition and structure (aerosols and particles History of Geophysics (atmospheric sciences Hydrology (anthropogenic effects

  8. Tailored long range forces on polarizable particles by collective scattering of broadband radiation

    Science.gov (United States)

    Holzmann, D.; Ritsch, H.

    2016-10-01

    Collective coherent light scattering by polarizable particles creates surprisingly strong, long range inter-particle forces originating from interference of the light scattered by different particles. While for monochromatic laser beams this interaction decays with the inverse distance, we show here that in general the effective interaction range and geometry can be controlled by the illumination bandwidth and geometry. As generic example we study the modifications inter-particle forces within a 1D chain of atoms trapped in the field of a confined optical nanofiber mode. For two particles we find short range attraction as well as optical binding at multiple distances. The range of stable distances shrinks with increasing light bandwidth and for a very large bandwidth field as e.g. blackbody radiation. We find a strongly attractive potential up to a critical distance beyond which the force gets repulsive. Including multiple scattering can even lead to the appearance of a stable configuration at a large distance. Such broadband scattering forces should be observable contributions in ultra-cold atom interferometers or atomic clocks setups. They could be studied in detail in 1D geometries with ultra-cold atoms trapped along or within an optical nanofiber. Broadband radiation force interactions might also contribute in astrophysical scenarios as illuminated cold dust clouds.

  9. Identification of impact force acting on composite laminated plates using the radiated sound measured with microphones

    Science.gov (United States)

    Atobe, Satoshi; Nonami, Shunsuke; Hu, Ning; Fukunaga, Hisao

    2017-09-01

    Foreign object impact events are serious threats to composite laminates because impact damage leads to significant degradation of the mechanical properties of the structure. Identification of the location and force history of the impact that was applied to the structure can provide useful information for assessing the structural integrity. This study proposes a method for identifying impact forces acting on CFRP (carbon fiber reinforced plastic) laminated plates on the basis of the sound radiated from the impacted structure. Identification of the impact location and force history is performed using the sound pressure measured with microphones. To devise a method for identifying the impact location from the difference in the arrival times of the sound wave detected with the microphones, the propagation path of the sound wave from the impacted point to the sensor is examined. For the identification of the force history, an experimentally constructed transfer matrix is employed to relate the force history to the corresponding sound pressure. To verify the validity of the proposed method, impact tests are conducted by using a CFRP cross-ply laminate as the specimen, and an impulse hammer as the impactor. The experimental results confirm the validity of the present method for identifying the impact location from the arrival time of the sound wave detected with the microphones. Moreover, the results of force history identification show the feasibility of identifying the force history accurately from the measured sound pressure using the experimental transfer matrix.

  10. Characterization of material properties of soft solid thin layers with acoustic radiation force and wave propagation.

    Science.gov (United States)

    Urban, Matthew W; Nenadic, Ivan Z; Qiang, Bo; Bernal, Miguel; Chen, Shigao; Greenleaf, James F

    2015-10-01

    Evaluation of tissue engineering constructs is performed by a series of different tests. In many cases it is important to match the mechanical properties of these constructs to those of native tissues. However, many mechanical testing methods are destructive in nature which increases cost for evaluation because of the need for additional samples reserved for these assessments. A wave propagation method is proposed for characterizing the shear elasticity of thin layers bounded by a rigid substrate and fluid-loading, similar to the configuration for many tissue engineering applications. An analytic wave propagation model was derived for this configuration and compared against finite element model simulations and numerical solutions from the software package Disperse. The results from the different models found very good agreement. Experiments were performed in tissue-mimicking gelatin phantoms with thicknesses of 1 and 4 mm and found that the wave propagation method could resolve the shear modulus with very good accuracy, no more than 4.10% error. This method could be used in tissue engineering applications to monitor tissue engineering construct maturation with a nondestructive wave propagation method to evaluate the shear modulus of a material.

  11. Acoustic radiation force impulse (ARFI) ultrasound imaging of pancreatic cystic lesions

    Energy Technology Data Exchange (ETDEWEB)

    D' Onofrio, M., E-mail: mirko.donofrio@univr.it [Department of Radiology, University Hospital G.B. Rossi, Piazzale L.A. Scuro 10, University of Verona, 37134 Verona (Italy); Gallotti, A. [Department of Radiology, University Hospital G.B. Rossi, Piazzale L.A. Scuro 10, University of Verona, 37134 Verona (Italy); Salvia, R. [Department of Surgery, University Hospital G.B. Rossi, Piazzale L.A. Scuro 10, University of Verona, 37134 Verona (Italy); Capelli, P. [Department of Pathology, University Hospital G.B. Rossi, Piazzale L.A. Scuro 10, University of Verona, 37134 Verona (Italy); Mucelli, R. Pozzi [Department of Radiology, University Hospital G.B. Rossi, Piazzale L.A. Scuro 10, University of Verona, 37134 Verona (Italy)

    2011-11-15

    Purpose: To evaluate the ARFI ultrasound imaging with Virtual Touch tissue quantification in studying pancreatic cystic lesions, compared with phantom fluid models. Materials and methods: Different phantom fluids at different viscosity or density (water, iodinate contrast agent, and oil) were evaluated by two independent operators. From September to December 2008, 23 pancreatic cystic lesions were prospectively studied. All lesions were pathologically confirmed. Results: Non-numerical values on water and numerical values on other phantoms were obtained. Inter-observer evaluation revealed a perfect correlation (rs = 1.00; p < 0.0001) between all measurements achieved by both operators per each balloon and fluid. Among the pancreatic cystic lesions, 14 mucinous cystadenomas, 4 pseudocysts, 3 intraductal papillary-mucinous neoplasms and 2 serous cystadenomas were studied. The values obtained ranged from XXXX/0-4,85 m/s in mucinous cystadenomas, from XXXX/0-3,11 m/s in pseudocysts, from XXXX/0-4,57 m/s in intraductal papillary-mucinous neoplasms. In serous cystadenomas all values measured were XXXX/0 m/s. Diagnostic accuracy in benign and non-benign differentiation of pancreatic cystic lesions was 78%. Conclusions: Virtual Touch tissue quantification can be applied in the analysis of fluids and is potentially able to differentiate more complex (mucinous) from simple (serous) content in studying pancreatic cystic lesions.

  12. Acoustic Radiation Force Impulse Imaging: A New Tool for the Diagnosis of Papillary Thyroid Microcarcinoma

    Directory of Open Access Journals (Sweden)

    Yi-Feng Zhang

    2014-01-01

    Full Text Available Purpose. To evaluate the diagnostic performance of ARFI imaging in differentiating between benign and malignant thyroid nodules 3.10 m/s had been found to be independent risk factors for predicting PTMC. Conclusion. ARFI elastography can provide elasticity information of PTMC quantitatively (VTQ and directly reflects the overall elastic properties (VTI. Gender, hypoechogenicity, taller than wide, VTI elastography score ≥ 4, and SWV > 3.10 m/s are independent risk factors for predicting PTMC. ARFI elastography seems to be a new tool for the diagnosis of PTMC.

  13. Influence of radiation reaction force on ultraintense laser-driven ion acceleration.

    Science.gov (United States)

    Capdessus, R; McKenna, P

    2015-05-01

    The role of the radiation reaction force in ultraintense laser-driven ion acceleration is investigated. For laser intensities ∼10(23)W/cm(2), the action of this force on electrons is demonstrated in relativistic particle-in-cell simulations to significantly enhance the energy transfer to ions in relativistically transparent targets, but strongly reduce the ion energy in dense plasma targets. An expression is derived for the revised piston velocity, and hence ion energy, taking account of energy loses to synchrotron radiation generated by electrons accelerated in the laser field. Ion mass is demonstrated to be important by comparing results obtained with proton and deuteron plasma. The results can be verified in experiments with cryogenic hydrogen and deuterium targets.

  14. Laboratory for Structural Acoustics

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Supports experimental research where acoustic radiation, scattering, and surface vibration measurements of fluid-loaded and non-fluid-loaded structures are...

  15. Monsoon sensitivity to aerosol direct radiative forcing in the community atmosphere model

    Science.gov (United States)

    Sajani, S.; Krishna Moorthy, K.; Rajendran, K.; Nanjundiah, Ravi S.

    2012-08-01

    Aerosol forcing remains a dominant uncertainty in climate studies. The impact of aerosol direct radiative forcing on Indian monsoon is extremely complex and is strongly dependent on the model, aerosol distribution and characteristics specified in the model, modelling strategy employed as well as on spatial and temporal scales. The present study investigates (i) the aerosol direct radiative forcing impact on mean Indian summer monsoon when a combination of quasi-realistic mean annual cycles of scattering and absorbing aerosols derived from an aerosol transport model constrained with satellite observed Aerosol Optical Depth (AOD) is prescribed, (ii) the dominant feedback mechanism behind the simulated impact of all-aerosol direct radiative forcing on monsoon and (iii) the relative impacts of absorbing and scattering aerosols on mean Indian summer monsoon. We have used CAM3, an atmospheric GCM (AGCM) that has a comprehensive treatment of the aerosol-radiation interaction. This AGCM has been used to perform climate simulations with three different representations of aerosol direct radiative forcing due to the total, scattering aerosols and black carbon aerosols. We have also conducted experiments without any aerosol forcing. Aerosol direct impact due to scattering aerosols causes significant reduction in summer monsoon precipitation over India with a tendency for southward shift of Tropical Convergence Zones (TCZs) over the Indian region. Aerosol forcing reduces surface solar absorption over the primary rainbelt region of India and reduces the surface and lower tropospheric temperatures. Concurrent warming of the lower atmosphere over the warm oceanic region in the south reduces the land-ocean temperature contrast and weakens the monsoon overturning circulation and the advection of moisture into the landmass. This increases atmospheric convective stability, and decreases convection, clouds, precipitation and associated latent heat release. Our analysis reveals a

  16. Parameterization of sea-salt optical properties and physics of the associated radiative forcing

    Directory of Open Access Journals (Sweden)

    J. Li

    2008-03-01

    Full Text Available The optical properties of sea-salt aerosol have been parameterized at solar and longwave wavelengths. The optical properties were parameterized in a simple functional form in terms of the ambient relative humidity based on Mie optical property calculations. The proposed parameterization is tested relative to Mie calculations and is found to be accurate to within a few percent. In the parameterization, the effects of the size distribution on the optical properties are accounted for in terms of effective radius of the sea-salt size distribution. This parameterization differs from previous works by being formulated directly with the wet sea-salt size distribution (and compared to AERONET results and, to our knowledge, this is the first published sea-salt parameterization to provide a parameterization for both solar and longwave wavelengths. We have used this parameterization in a set of idealized 1-D radiative transfer calculations to investigate the sensitivity of various attributes of sea-salt forcing, such as dependence with sea-salt column loading, effective variance, solar angle, and surface albedo. From these sensitivity tests, it is found that sea-salt forcings for both solar and longwave spectra are linearly related to the sea-salt loading for realistic values of loadings. The radiative forcing results illustrate that the shortwave forcing is an order of magnitude greater than the longwave forcing results and opposite in sign, for various loadings. Studies of the sensitivity of forcing results to variations in effective variance show there to be minimal variation; therefore, only one value of effective variance is used in the parameterization. The dependence of sea-salt forcing with solar angle illustrates an interesting result that sea-salt can generate a positive top-of-the-atmosphere result (i.ewarming when the solar zenith angle is relatively small 30° Finally, it is found that the surface albedo significantly affects the solar

  17. Classical Radiation Reaction Off-Shell Corrections to the Covariant Lorentz Force

    OpenAIRE

    Oron, O.; Horwitz, L. P.

    2000-01-01

    It has been shown by Gupta and Padmanabhan that the radiation reaction force of the Abraham-Lorentz-Dirac equation can be obtained by a coordinate transformation from the inertial frame of an accelerating charged particle to that of the laboratory. We show that the problem may be formulated in a flat space of five dimensions, with five corresponding gauge fields in the framework of the classical version of a fully gauge covariant form of the Stueckelberg- Feynman-Schwinger covariant mechanics...

  18. Plasma acceleration and cooling by strong laser field due to the action of radiation reaction force.

    Science.gov (United States)

    Berezhiani, V I; Mahajan, S M; Yoshida, Z

    2008-12-01

    It is shown that for super intense laser pulses propagating in a hot plasma, the action of the radiation reaction force (appropriately incorporated into the equations of motion) causes strong bulk plasma motion with the kinetic energy raised even to relativistic values; the increase in bulk energy is accompanied by a corresponding cooling (intense cooling) of the plasma. The effects are demonstrated through explicit analytical calculations.

  19. The Impact of Desert Dust Aerosol Radiative Forcing on Global and West African Precipitation

    Science.gov (United States)

    Jordan, A.; Zaitchik, B. F.; Gnanadesikan, A.; Dezfuli, A. K.

    2015-12-01

    Desert dust aerosols exert a radiative forcing on the atmosphere, influencing atmospheric temperature structure and modifying radiative fluxes at the top of the atmosphere (TOA) and surface. As dust aerosols perturb radiative fluxes, the atmosphere responds by altering both energy and moisture dynamics, with potentially significant impacts on regional and global precipitation. Global Climate Model (GCM) experiments designed to characterize these processes have yielded a wide range of results, owing to both the complex nature of the system and diverse differences across models. Most model results show a general decrease in global precipitation, but regional results vary. Here, we compare simulations from GFDL's CM2Mc GCM with multiple other model experiments from the literature in order to investigate mechanisms of radiative impact and reasons for GCM differences on a global and regional scale. We focus on West Africa, a region of high interannual rainfall variability that is a source of dust and that neighbors major Sahara Desert dust sources. As such, changes in West African climate due to radiative forcing of desert dust aerosol have serious implications for desertification feedbacks. Our CM2Mc results show net cooling of the planet at TOA and surface, net warming of the atmosphere, and significant increases in precipitation over West Africa during the summer rainy season. These results differ from some previous GCM studies, prompting comparative analysis of desert dust parameters across models. This presentation will offer quantitative analysis of differences in dust aerosol parameters, aerosol optical properties, and overall particle burden across GCMs, and will characterize the contribution of model differences to the uncertainty of forcing and climate response affecting West Africa.

  20. Variability of aerosol optical depth and aerosol radiative forcing over Northwest Himalayan region

    Science.gov (United States)

    Saheb, Shaik Darga; Kant, Yogesh; Mitra, D.

    2016-05-01

    In recent years, the aerosol loading in India is increasing that has significant impact on the weather/climatic conditions. The present study discusses the analysis of temporal (monthly and seasonal) variation of aerosol optical depth(AOD) by the ground based observations from sun photometer and estimate the aerosol radiative forcing and heating rate over selected station Dehradun in North western Himalayas, India during 2015. The in-situ measurements data illustrate that the maximum seasonal average AOD observed during summer season AOD at 500nm ≍ 0.59+/-0.27 with an average angstrom exponent, α ≍0.86 while minimum during winter season AOD at 500nm ≍ 0.33+/-0.10 with angstrom exponent, α ≍1.18. The MODIS and MISR derived AOD was also compared with the ground measured values and are good to be in good agreement. Analysis of air mass back trajectories using HYSPLIT model reveal that the transportation of desert dust during summer months. The Optical Properties of Aerosols and clouds (OPAC) model was used to compute the aerosol optical properties like single scattering albedo (SSA), Angstrom coefficient (α) and Asymmetry(g) parameter for each day of measurement and they are incorporated in a Discrete Ordinate Radiative Transfer model, i.e Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) to estimate the direct short-wave (0.25 to 4 μm) Aerosol Radiative forcing at the Surface (SUR), the top-of-atmosphere (TOA) and Atmosphere (ATM). The maximum Aerosol Radiative Forcing (ARF) was observed during summer months at SUR ≍ -56.42 w/m2, at TOA ≍-21.62 w/m2 whereas in ATM ≍+34.79 w/m2 with corresponding to heating rate 1.24°C/day with in lower atmosphere.

  1. Surface aerosol radiative forcing derived from collocated ground-based radiometric observations during PRIDE, SAFARI, and ACE-Asia.

    Science.gov (United States)

    Hansell, Richard A; Tsay, Si-Chee; Ji, Qiang; Liou, K N; Ou, Szu-Cheng

    2003-09-20

    An approach is presented to estimate the surface aerosol radiative forcing by use of collocated cloud-screened narrowband spectral and thermal-offset-corrected radiometric observations during the Puerto Rico Dust Experiment 2000, South African Fire Atmosphere Research Initiative (SAFARI) 2000, and Aerosol Characterization Experiment-Asia 2001. We show that aerosol optical depths from the Multiple-Filter Rotating Shadowband Radiometer data match closely with those from the Cimel sunphotometer data for two SAFARI-2000 dates. The observed aerosol radiative forcings were interpreted on the basis of results from the Fu-Liou radiative transfer model, and, in some cases, cross checked with satellite-derived forcing parameters. Values of the aerosol radiative forcing and forcing efficiency, which quantifies the sensitivity of the surface fluxes to the aerosol optical depth, were generated on the basis of a differential technique for all three campaigns, and their scientific significance is discussed.

  2. Radiation Acoustic Field of a Linear Phased Array on a Cylindrical Surface

    Institute of Scientific and Technical Information of China (English)

    DENG Fang-Qing; ZHANG Bi-Xing; WANG Dong; SONG Gong-Pu

    2006-01-01

    A new linear ultrasonic phased array fixed on a cylindrical surface is designed. This kind of the cylindrical phased array can meet the specific requirements of the application in testing pipe quality inside pipes. Using the transducer, we can not only avoid mechanical rotating but also test the quality of any point in a pipe by ultrasonic phase array technology. The focused acoustic field distributions in the axial, radial and tangential directions of the transducer are investigated theoretically by numerical simulation. The energy flux density, the width of the main lobe, the imaging resolution, the grating lobe elimination and other characteristics are analysed. The effect of the focal distance, effective aperture, transducer radius, number of total element, and steering angle on the acoustic field distribution is also studied.thoroughly. Many important results are obtained.

  3. Implications of Representative Concentration Pathway 4.5 Methane Emissions to Stabilize Radiative Forcing

    Energy Technology Data Exchange (ETDEWEB)

    Emanuel, William R.; Janetos, Anthony C.

    2013-02-01

    Increases in the abundance of methane (CH4) in the Earth’s atmosphere are responsible for significant radiative forcing of climate change (Forster et al., 2007; Wuebbles and Hayhoe, 2002). Since 1750, a 2.5 fold increase in atmospheric CH4 contributed 0.5 W/m2 to direct radiative forcing and an additional 0.2 W/m2 indirectly through changes in atmospheric chemistry. Next to water and carbon dioxide (CO2), methane is the most abundant greenhouse gas in the troposphere. Additionally, CH4 is significantly more effective as a greenhouse gas on a per molecule basis than is CO2, and increasing atmospheric CH4 has been second only to CO2 in radiative forcing (Forster et al., 2007). The chemical reactivity of CH4 is important to both tropospheric and stratospheric chemistry. Along with carbon monoxide, methane helps control the amount of the hydroxyl radical (OH) in the troposphere where oxidation of CH4 by OH leads to the formation of formaldehyde, carbon monoxide, and ozone.

  4. Magnitude and pattern of Arctic warming governed by the seasonality of radiative forcing

    Science.gov (United States)

    Bintanja, R.; Krikken, F.

    2016-12-01

    Observed and projected climate warming is strongest in the Arctic regions, peaking in autumn/winter. Attempts to explain this feature have focused primarily on identifying the associated climate feedbacks, particularly the ice-albedo and lapse-rate feedbacks. Here we use a state-of-the-art global climate model in idealized seasonal forcing simulations to show that Arctic warming (especially in winter) and sea ice decline are particularly sensitive to radiative forcing in spring, during which the energy is effectively ‘absorbed’ by the ocean (through sea ice melt and ocean warming, amplified by the ice-albedo feedback) and consequently released to the lower atmosphere in autumn and winter, mainly along the sea ice periphery. In contrast, winter radiative forcing causes a more uniform response centered over the Arctic Ocean. This finding suggests that intermodel differences in simulated Arctic (winter) warming can to a considerable degree be attributed to model uncertainties in Arctic radiative fluxes, which peak in summer.

  5. Indirect Radiative Forcing and Climatic Effect of the Anthropogenic Nitrate Aerosol on Regional Climate of China

    Institute of Scientific and Technical Information of China (English)

    LI Shu; WANG Wijian; ZHUANG Bingliang; HAN Yong

    2009-01-01

    The regional climate model (RegCM3) and a tropospheric atmosphere chemistry model (TACM) were couplcd, thus a regional climate chemistry modeling system (RegCCMS) was constructed, which was applied to investigate the spatial distribution of anthropogenic nitrate aerosols, indirect radiative forcing, as well as its climatic effect over China. TACM includes the thermodynamic equilibrium model ISORROPIA and a condensed gas-phase chemistry model. Investigations show that the concentration of nitrate aerosols is relatively high over North and East China with a maximum of 29μg m-3 in January and 8 μg m-3 in July.Due to the influence of air temperature on thermodynamic equilibrium, wet scavenging of precipitation and the monsoon climate, there are obvious seasonal differences in nitrate concentrations. The average indirect radiative forcing at the tropopause due to nitrate aerosols is -1.63 W m-2 in January and -2.65 W m-2 in July, respectively. In some areas, indirect radiative forcing reaches -10 W m-2. Sensitivity tests show that nitrate aerosols make the surface air temperature drop and the precipitation reduce on the national level. The mean changes in surface air temperature and precipitation are -0.13 K and -0.01 mm d-1 in January and -0.09 K and -0.11 mm d-1 in July, respectively, showing significant differences in different regions.

  6. Radiation pressure force emission line profiles and black hole mass in active galactic nuclei

    CERN Document Server

    Netzer, H

    2010-01-01

    We present a new analysis of the motion of broad line region (BLR) clouds in active galactic nuclei (AGNs) taking into account the combined influence of gravity and radiation pressure force. We calculate cloud orbits under a large range of conditions and include the effect of a changing column density as a function of location. The dependence of radiation pressure force on the level of ionization and the column density are accurately computed. The main results are: a. The mean cloud location r(BLR) and the line widths (FWHMs) are combined in such a way that the simple virial mass estimate, r{BLR} FWHM^2/G, gives a reasonable approximation to the black hole mass M even when radiation pressure force is important. The reason is that L/M rather than L is the main parameter affecting the planar cloud motion. b. Reproducing the observed mean radius, FWHM and intensity of H-beta and CIV 1549 requires at least two different populations of clouds. c. The cloud location is a function of both L^{1/2} and L/M. Given this...

  7. Toric focusing for radiation force applications using a toric lens coupled to a spherically focused transducer.

    Science.gov (United States)

    Arnal, Bastien; Nguyen, Thu-Mai; O'Donnell, Matthew

    2014-12-01

    Dynamic elastography using radiation force requires that an ultrasound field be focused during hundreds of microseconds at a pressure of several megapascals. Here, we address the importance of the focal geometry. Although there is usually no control of the elevational focal width in generating a tissue mechanical response, we propose a tunable approach to adapt the focus geometry that can significantly improve radiation force efficiency. Several thin, in-house-made polydimethylsiloxane lenses were designed to modify the focal spot of a spherical transducer. They exhibited low absorption and the focal spot widths were extended up to 8-fold in the elevation direction. Radiation force experiments demonstrated an 8-fold increase in tissue displacements using the same pressure level in a tissue-mimicking phantom with a similar shear wave spectrum, meaning it does not affect elastography resolution. Our results demonstrate that larger tissue responses can be obtained for a given pressure level, or that similar response can be reached at a much lower mechanical index (MI). We envision that this work will impact 3-D elastography using 2-D phased arrays, where such shaping can be achieved electronically with the potential for adaptive optimization.

  8. Aerosol Optical Properties and Its Radiative Forcing over Yulin, China in 2001 and 2002

    Institute of Scientific and Technical Information of China (English)

    CHE Huizheng; ZHANG Xiaoye; Stephane ALFRARO; Bernadette CHATENET; Laurent GOMES; ZHAO Jianqi

    2009-01-01

    The aerosol optical properties and direct radiative forcing over the Mu Us desert of northern China, acquired through a CE318 sunphotometer of the ground-bascd Aerosol Robotic Network (AERONET), are analyzed. The seasonal variations in the aerosol optical properties are examined. The effect of meteorological elements (pressure, temperature, water vapor pressure, relative humidity and wind speed) on the aerosol optical properties is also studied. Then, the sources and optical properties under two different cases, a dust event and a pollution event, are compared. The results show that the high aerosol optical depth (AOD) found in Yulin was mostly attributed to the occurrence of dust events in spring from the Mu Us desert and deserts of West China and Mongolia, as well as the impacts of anthropogenic pollutant particles from the middle part of China in the other seasons. The seasonal variation and the probability distribution of the radiative forcing and the radiative forcing efficiency at the surface and the top of the atmosphere are analyzed and regressed using the linear and Gaussian regression methods.

  9. Jeans instability in collisional strongly coupled dusty plasma with radiative condensation and polarization force

    Energy Technology Data Exchange (ETDEWEB)

    Prajapati, R. P., E-mail: prajapati-iter@yahoo.co.in; Bhakta, S. [Department of Pure and Applied Physics, Guru Ghasidas Central University, Bilaspur-495009 (C.G.) (India); Chhajlani, R. K. [Retired from School of Studies in Physics, Vikram University, Ujjain-456010 (M.P.) (India)

    2016-05-15

    The influence of dust-neutral collisions, polarization force, and electron radiative condensation is analysed on the Jeans (gravitational) instability of partially ionized strongly coupled dusty plasma (SCDP) using linear perturbation (normal mode) analysis. The Boltzmann distributed ions, dynamics of inertialess electrons, charged dust and neutral particles are considered. Using the plane wave solutions, a general dispersion relation is derived which is modified due to the presence of dust-neutral collisions, strong coupling effect, polarization force, electron radiative condensation, and Jeans dust/neutral frequencies. In the long wavelength perturbations, the Jeans instability criterion depends upon strong coupling effect, polarization interaction parameter, and thermal loss, but it is independent of dust-neutral collision frequency. The stability of the considered configuration is analysed using the Routh–Hurwitz criterion. The growth rates of Jeans instability are illustrated, and stabilizing influence of viscoelasticity and dust-neutral collision frequency while destabilizing effect of electron radiative condensation, polarization force, and Jeans dust-neutral frequency ratio is observed. This work is applied to understand the gravitational collapse of SCDP with dust-neutral collisions.

  10. Dynamic Nonlinear Focal Shift in Amplitude Modulated Moderately Focused Acoustic Beams

    CERN Document Server

    Jiménez, Noé; González-Salido, Nuria

    2016-01-01

    The phenomenon of the displacement of the position of the pressure, intensity and acoustic radiation force maxima along the axis of focused acoustic beams under increasing driving amplitudes (nonlinear focal shift) is studied for the case of a moderately focused beam excited with continuous and 25 kHz amplitude modulated signals, both in water and tissue. We prove that in amplitude modulated beams the linear and nonlinear propagation effects coexist in a semi-period of modulation, giving place to a complex dynamic behaviour, where the singular points of the beam (peak pressure, rarefaction, intensity and acoustic radiation force) locate at different points on axis as a function of time. These entire phenomena are explained in terms of harmonic generation and absorption during the propagation in a lossy nonlinear medium both, for a continuous and an amplitude modulated beam. One of the possible applications of the acoustic radiation force displacement is the generation of shear waves at different locations by ...

  11. Adaptation of the Neural Network Recognition System of the Helicopter on Its Acoustic Radiation to the Flight Speed

    Directory of Open Access Journals (Sweden)

    V. K. Hohlov

    2015-01-01

    Full Text Available The article concerns the adaptation of a neural tract that recognizes a helicopter from the aerodynamic and ground objects by its acoustic radiation to the helicopter flight speed. It uses non-centered informative signs-indications of estimating signal spectra, which correspond to the local extremes (maximums and minimums of the power spectrum of input signal and have the greatest information when differentiating the helicopter signals from those of tracked vehicles. The article gives justification to the principle of the neural network (NN adaptation and adaptation block structure, which solves problems of blade passage frequency estimation when capturing the object and track it when tracking a target, as well as forming a signal to control the resonant filter parameters of the selection block of informative signs. To create the discriminatory characteristics of the discriminator are used autoregressive statistical characteristics of the quadrature components of signal, obtained through the discrete Hilbert Converter (DGC that perforMathematical modeling of the tracking meter using the helicopter signals obtained in real conditions is performed. The article gives estimates of the tracking parameter when using a tracking meter with DGC by sequential records of realized acoustic noise of the helicopter. It also shows a block-diagram of the adaptive NN. The scientific novelty of the work is that providing the invariance of used informative sign, the counts of local extremes of power spectral density (PSD to changes in the helicopter flight speed is reached due to adding the NN structure and adaptation block, which is implemented as a meter to track the apparent passage frequency of the helicopter rotor blades using its relationship with a function of the autoregressive acoustic signal of the helicopter.Specialized literature proposes solutions based on the use of training classifiers with different parametric methods of spectral representations

  12. Low Energy Gamma Radiation Induced Effects on Ultrasonic Velocity and Acoustic Parameters in Polyvinylidene Fluoride Solution

    Directory of Open Access Journals (Sweden)

    S. S. Kulkarni

    2016-01-01

    Full Text Available The modification of polyvinylidene fluoride (PVDF polymer properties with irradiation is of interest as it possesses unique piezo-, pyro-, and ferroelectric properties. In this paper, we report the results of acoustic parameters of irradiated PVDF mixed with dimethylacetamide (DMAC solution with low energy γ-source (Cs-137. The polymer solution covered with mica film assures only γ-ray passage and the duration was increased from 18 to 50 hours to achieve the higher dose rate. The dose rate was estimated using the strength of the radioactive source and the duration of the exposure. The ultrasonic velocity (v, density (ρ, and viscosity (η of 0.2 wt% and 0.5 wt% PVDF dissolved in pure DMAC solution, irradiated with different dose rate were measured using ultrasonic interferometer (Mittal make, Pyknometer, and Oswald’s viscometer, respectively. It is observed that the values of v, ρ, and η change with dose rate. The acoustic parameters such as adiabatic compressibility (β, intermolecular free path length (Lf, acoustic impedance (Z, relative association (RA, ultrasonic attenuation (α/f2, and relaxation time (τ are calculated using the experimental data. These results are interpreted in terms of the solute-solvent interaction in a polymer solution and scissoring chain damage.

  13. Constructing a Mass-Current Radiation-Reaction Force For Numerical Simulations

    CERN Document Server

    Rezzolla, L; Asada, H; Baumgarte, T W; Shapiro, S L

    1999-01-01

    We present a new set of 3.5 Post-Newtonian equations in which Newtonian hydrodynamics is coupled to the nonconservative effects of gravitational radiation emission. Our formalism differs in two significant ways from a similar 3.5 Post-Newtonian approach proposed by Blanchet (1993, 1997). Firstly we concentrate only on the radiation-reaction effects produced by a time-varying mass-current quadrupole $S_{ij}$. Secondly, we adopt a gauge in which the radiation-reaction force densities depend on the fourth time derivative of $S_{ij}$, rather than on the fifth, as in Blanchet's approach. This difference makes our formalism particularly well-suited to numerical implementation and could prove useful in performing fully numerical simulations of the recently discovered $r$-mode instability for rotating neutron stars subject to axial perturbations.

  14. Analytic solutions in the acoustic black hole analogue of the conical Kerr metric: massless scalar fields and Hawking-Unruh radiation

    CERN Document Server

    Vieira, H S

    2016-01-01

    We study the sound perturbation of the rotating acoustic black hole in the presence of a disclination. The radial part of the massless Klein-Gordon equation is written into a Heun form, and its analytical solution is obtained. These solutions have an explicit dependence on the parameter of the disclination. We obtain the exact Hawking-Unruh radiation spectrum.

  15. Mechanisms for Induction of Pulmonary Capillary Hemorrhage by Diagnostic Ultrasound: Review and Consideration of Acoustical Radiation Surface Pressure.

    Science.gov (United States)

    Miller, Douglas L

    2016-12-01

    Diagnostic ultrasound can induce pulmonary capillary hemorrhage (PCH) in rats and other mammals. This phenomenon represents the only clearly demonstrated biological effect of (non-contrast enhanced) diagnostic ultrasound and thus presents a uniquely important safety issue. However, the physical mechanism responsible for PCH remains uncertain more than 25 y after its discovery. Experimental research has indicated that neither heating nor acoustic cavitation, the predominant mechanisms for bioeffects of ultrasound, is responsible for PCH. Furthermore, proposed theoretical mechanisms based on gas-body activation, on alveolar resonance and on impulsive generation of liquid droplets all appear unlikely to be responsible for PCH, owing to unrealistic model assumptions. Here, a simple model based on the acoustical radiation surface pressure (ARSP) at a tissue-air interface is hypothesized as the mechanism for PCH. The ARSP model seems to explain some features of PCH, including the approximate frequency independence of PCH thresholds and the dependence of thresholds on biological factors. However, ARSP evaluated for experimental threshold conditions appear to be too weak to fully account for stress failure of pulmonary capillaries, gauging by known stresses for injurious physiologic conditions. Furthermore, consideration of bulk properties of lung tissue suggests substantial transmission of ultrasound through the pleura, with reduced ARSP and potential involvement of additional mechanisms within the pulmonary interior. Although these recent findings advance our knowledge, only a full understanding of PCH mechan