The normative study of acoustic parameters in normal Egyptian ...

African Journals Online (AJOL)

Yehia A. Abo-Ras

2013-03-21

Mar 21, 2013 ... all children were subjected to computerized acoustic analysis using Multidimensional voice program ... cal quality is important for social relations to happen effectively. ... lish comparative parameters with the normal values of the acoustic ... from lower age ranges in the normative studies since the child's.

Varying acoustic-phonemic ambiguity reveals that talker normalization is obligatory in speech processing.

Science.gov (United States)

Choi, Ja Young; Hu, Elly R; Perrachione, Tyler K

2018-04-01

The nondeterministic relationship between speech acoustics and abstract phonemic representations imposes a challenge for listeners to maintain perceptual constancy despite the highly variable acoustic realization of speech. Talker normalization facilitates speech processing by reducing the degrees of freedom for mapping between encountered speech and phonemic representations. While this process has been proposed to facilitate the perception of ambiguous speech sounds, it is currently unknown whether talker normalization is affected by the degree of potential ambiguity in acoustic-phonemic mapping. We explored the effects of talker normalization on speech processing in a series of speeded classification paradigms, parametrically manipulating the potential for inconsistent acoustic-phonemic relationships across talkers for both consonants and vowels. Listeners identified words with varying potential acoustic-phonemic ambiguity across talkers (e.g., beet/boat vs. boot/boat) spoken by single or mixed talkers. Auditory categorization of words was always slower when listening to mixed talkers compared to a single talker, even when there was no potential acoustic ambiguity between target sounds. Moreover, the processing cost imposed by mixed talkers was greatest when words had the most potential acoustic-phonemic overlap across talkers. Models of acoustic dissimilarity between target speech sounds did not account for the pattern of results. These results suggest (a) that talker normalization incurs the greatest processing cost when disambiguating highly confusable sounds and (b) that talker normalization appears to be an obligatory component of speech perception, taking place even when the acoustic-phonemic relationships across sounds are unambiguous.

Nonlinear generation of non-acoustic modes by low-frequency sound in a vibrationally relaxing gas

International Nuclear Information System (INIS)

Perelomova, A.

2010-01-01

Two dynamic equations referring to a weakly nonlinear and weakly dispersive flow of a gas in which molecular vibrational relaxation takes place, are derived. The first one governs an excess temperature associated with the thermal mode, and the second one describes variations in vibrational energy. Both quantities refer to non-wave types of gas motion. These variations are caused by the nonlinear transfer of acoustic energy into thermal mode and internal vibrational degrees of freedom of a relaxing gas. The final dynamic equations are instantaneous; they include a quadratic nonlinear acoustic source, reflecting the nonlinear character of interaction of low-frequency acoustic and non-acoustic motions of the fluid. All types of sound, periodic or aperiodic, may serve as an acoustic source of both phenomena. The low-frequency sound is considered in this study. Some conclusions about temporal behavior of non-acoustic modes caused by periodic and aperiodic sound are made. Under certain conditions, acoustic cooling takes place instead of heating. (author)

Electron/electron acoustic instability

International Nuclear Information System (INIS)

Gary, S.P.

1987-01-01

The electron acoustic wave becomes a normal mode of an unmagnetized collisionless plasma in the presence of two electron components with similar densities, but strongly disparate temperatures. The characteristic frequency of this mode is the plasma frequency of the cooler electron component. If these two electron components have a relative drift speed several times the thermal speed of the cooler component, the electron/electron acoustic instability may arise. This paper describes the parametric dependences of the threshold drift speed and maximum growth rate of this instability, and compares these with the same properties of the electron/ion acoustic instability. Under the condition of zero current, the electron/ion acoustic instability typically has the lower threshold drift speed, so that observation of the electron/electron acoustic instability is a strong indication of the presence of an electrical current in the plasma

Predications and Observations of Global Beta-induced Alfven-acoustic Modes in JET and NSTX

International Nuclear Information System (INIS)

Gorelenkov, N.N.

2008-01-01

In this paper we report on observations and interpretations of a new class of global MHD eigenmode solutions arising in gaps in the low frequency Alfven-acoustic continuum below the geodesic acoustic mode frequency. These modes have been just reported (Gorelenkov et al 2007 Phys. Lett. 370 70-7) where preliminary comparisons indicate qualitative agreement between theory and experiment. Here we show a more quantitative comparison emphasizing recent NSTX experiments on the observations of the global eigenmodes, referred to as beta-induced Alfven-acoustic eigenmodes (BAAEs), which exist near the extrema of the Alfven-acoustic continuum. In accordance to the linear dispersion relations, the frequency of these modes may shift as the safety factor, q, profile relaxes. We show that BAAEs can be responsible for observations in JET plasmas at relatively low beta 20%. In NSTX plasma observed magnetic activity has the same properties as predicted by theory for the mode structure and the frequency. Found numerically in NOVA simulations BAAEs are used to explain the observed properties of relatively low frequency experimental signals seen in NSTX and JET tokamaks

Normal modes of weak colloidal gels

Science.gov (United States)

Varga, Zsigmond; Swan, James W.

2018-01-01

The normal modes and relaxation rates of weak colloidal gels are investigated in calculations using different models of the hydrodynamic interactions between suspended particles. The relaxation spectrum is computed for freely draining, Rotne-Prager-Yamakawa, and accelerated Stokesian dynamics approximations of the hydrodynamic mobility in a normal mode analysis of a harmonic network representing several colloidal gels. We find that the density of states and spatial structure of the normal modes are fundamentally altered by long-ranged hydrodynamic coupling among the particles. Short-ranged coupling due to hydrodynamic lubrication affects only the relaxation rates of short-wavelength modes. Hydrodynamic models accounting for long-ranged coupling exhibit a microscopic relaxation rate for each normal mode, λ that scales as l-2, where l is the spatial correlation length of the normal mode. For the freely draining approximation, which neglects long-ranged coupling, the microscopic relaxation rate scales as l-γ, where γ varies between three and two with increasing particle volume fraction. A simple phenomenological model of the internal elastic response to normal mode fluctuations is developed, which shows that long-ranged hydrodynamic interactions play a central role in the viscoelasticity of the gel network. Dynamic simulations of hard spheres that gel in response to short-ranged depletion attractions are used to test the applicability of the density of states predictions. For particle concentrations up to 30% by volume, the power law decay of the relaxation modulus in simulations accounting for long-ranged hydrodynamic interactions agrees with predictions generated by the density of states of the corresponding harmonic networks as well as experimental measurements. For higher volume fractions, excluded volume interactions dominate the stress response, and the prediction from the harmonic network density of states fails. Analogous to the Zimm model in polymer

Normal mode analysis and applications in biological physics.

Science.gov (United States)

Dykeman, Eric C; Sankey, Otto F

2010-10-27

Normal mode analysis has become a popular and often used theoretical tool in the study of functional motions in enzymes, viruses, and large protein assemblies. The use of normal modes in the study of these motions is often extremely fruitful since many of the functional motions of large proteins can be described using just a few normal modes which are intimately related to the overall structure of the protein. In this review, we present a broad overview of several popular methods used in the study of normal modes in biological physics including continuum elastic theory, the elastic network model, and a new all-atom method, recently developed, which is capable of computing a subset of the low frequency vibrational modes exactly. After a review of the various methods, we present several examples of applications of normal modes in the study of functional motions, with an emphasis on viral capsids.

Investigation of energetic particle induced geodesic acoustic mode

Science.gov (United States)

Schneller, Mirjam; Fu, Guoyong; Chavdarovski, Ilija; Wang, Weixing; Lauber, Philipp; Lu, Zhixin

2017-10-01

Energetic particles are ubiquitous in present and future tokamaks due to heating systems and fusion reactions. Anisotropy in the distribution function of the energetic particle population is able to excite oscillations from the continuous spectrum of geodesic acoustic modes (GAMs), which cannot be driven by plasma pressure gradients due to their toroidally and nearly poloidally symmetric structures. These oscillations are known as energetic particle-induced geodesic acoustic modes (EGAMs) [G.Y. Fu'08] and have been observed in recent experiments [R. Nazikian'08]. EGAMs are particularly attractive in the framework of turbulence regulation, since they lead to an oscillatory radial electric shear which can potentially saturate the turbulence. For the presented work, the nonlinear gyrokinetic, electrostatic, particle-in-cell code GTS [W.X. Wang'06] has been extended to include an energetic particle population following either bump-on-tail Maxwellian or slowing-down [Stix'76] distribution function. With this new tool, we study growth rate, frequency and mode structure of the EGAM in an ASDEX Upgrade-like scenario. A detailed understanding of EGAM excitation reveals essential for future studies of EGAM interaction with micro-turbulence. Funded by the Max Planck Princeton Research Center. Computational resources of MPCDF and NERSC are greatefully acknowledged.

Geodesic acoustic modes in noncircular cross section tokamaks

Energy Technology Data Exchange (ETDEWEB)

Sorokina, E. A., E-mail: sorokina.ekaterina@gmail.com; Lakhin, V. P. [National Research Center “Kurchatov Institute,” (Russian Federation); Konovaltseva, L. V. [People’s Friendship University of Russia (Russian Federation); Ilgisonis, V. I. [National Research Center “Kurchatov Institute,” (Russian Federation)

2017-03-15

The influence of the shape of the plasma cross section on the continuous spectrum of geodesic acoustic modes (GAMs) in a tokamak is analyzed in the framework of the MHD model. An expression for the frequency of a local GAM for a model noncircular cross section plasma equilibrium is derived. Amendments to the oscillation frequency due to the plasma elongation and triangularity and finite tokamak aspect ratio are calculated. It is shown that the main factor affecting the GAM spectrum is the plasma elongation, resulting in a significant decrease in the mode frequency.

Acoustic properties of naturally produced clear speech at normal speaking rates

Science.gov (United States)

Krause, Jean C.; Braida, Louis D.

2004-01-01

Sentences spoken ``clearly'' are significantly more intelligible than those spoken ``conversationally'' for hearing-impaired listeners in a variety of backgrounds [Picheny et al., J. Speech Hear. Res. 28, 96-103 (1985); Uchanski et al., ibid. 39, 494-509 (1996); Payton et al., J. Acoust. Soc. Am. 95, 1581-1592 (1994)]. While producing clear speech, however, talkers often reduce their speaking rate significantly [Picheny et al., J. Speech Hear. Res. 29, 434-446 (1986); Uchanski et al., ibid. 39, 494-509 (1996)]. Yet speaking slowly is not solely responsible for the intelligibility benefit of clear speech (over conversational speech), since a recent study [Krause and Braida, J. Acoust. Soc. Am. 112, 2165-2172 (2002)] showed that talkers can produce clear speech at normal rates with training. This finding suggests that clear speech has inherent acoustic properties, independent of rate, that contribute to improved intelligibility. Identifying these acoustic properties could lead to improved signal processing schemes for hearing aids. To gain insight into these acoustical properties, conversational and clear speech produced at normal speaking rates were analyzed at three levels of detail (global, phonological, and phonetic). Although results suggest that talkers may have employed different strategies to achieve clear speech at normal rates, two global-level properties were identified that appear likely to be linked to the improvements in intelligibility provided by clear/normal speech: increased energy in the 1000-3000-Hz range of long-term spectra and increased modulation depth of low frequency modulations of the intensity envelope. Other phonological and phonetic differences associated with clear/normal speech include changes in (1) frequency of stop burst releases, (2) VOT of word-initial voiceless stop consonants, and (3) short-term vowel spectra.

Predictions and observations of global beta-induced Alfven-acoustic modes in JET and NSTX

Energy Technology Data Exchange (ETDEWEB)

Gorelenkov, N N [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Berk, H L [Institute for Fusion Studies, University of Texas, Austin, TX 78712 (United States); Crocker, N A [Institute of Plasma and Fusion Research, University of California, Los Angeles, CA 90095-1354 (United States); Fredrickson, E D [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Kaye, S [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Kubota, S [Institute of Plasma and Fusion Research, University of California, Los Angeles, CA 90095-1354 (United States); Park, H [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Peebles, W [Institute of Plasma and Fusion Research, University of California, Los Angeles, CA 90095-1354 (United States); Sabbagh, S A [Department of Applied Physics, Columbia University, New York, NY 10027-6902 (United States); Sharapov, S E [Euroatom/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Stutmat, D [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Tritz, K [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Levinton, F M [Nova Photonics, One Oak Place, Princeton, NJ 08540 (United States); Yuh, H [Nova Photonics, One Oak Place, Princeton, NJ 08540 (United States)

2007-12-15

In this paper we report on observations and interpretations of a new class of global MHD eigenmode solutions arising in gaps in the low frequency Alfven-acoustic continuum below the geodesic acoustic mode frequency. These modes have been just reported (Gorelenkov et al 2007 Phys. Lett. 370 70-7) where preliminary comparisons indicate qualitative agreement between theory and experiment. Here we show a more quantitative comparison emphasizing recent NSTX experiments on the observations of the global eigenmodes, referred to as beta-induced Alfven-acoustic eigenmodes (BAAEs), which exist near the extrema of the Alfven-acoustic continuum. In accordance to the linear dispersion relations, the frequency of these modes may shift as the safety factor, q, profile relaxes. We show that BAAEs can be responsible for observations in JET plasmas at relatively low beta <2% as well as in NSTX plasmas at relatively high beta >20%. In NSTX plasma observed magnetic activity has the same properties as predicted by theory for the mode structure and the frequency. Found numerically in NOVA simulations BAAEs are used to explain the observed properties of relatively low frequency experimental signals seen in NSTX and JET tokamaks.

D33 mode piezoelectric diaphragm based acoustic transducer with high sensitivity

KAUST Repository

Shen, Zhiyuan; Lu, Jingyu; Tan, Cheewee; Miao, Jianmin; Wang, Zhihong

2013-01-01

This paper presents the design, fabrication, and characterization of an acoustic transducer using a piezoelectric freestanding bulk diaphragm as the sensing element. The diaphragm bearing the spiral electrode operates in d 33 mode, which allows the in-plane deformation of the diaphragm to be converted to the out-of-plane deformation and generates an acoustic wave in the same direction. A finite element code is developed to reorient the material polarization distribution according to the poling field calculated. The first four resonance modes have been simulated and verified by impedance and velocity spectra. The sensitivity and the sound pressure level of the transducer were characterized. The realized sensitivity of 126.21 μV/Pa at 1 kHz is nearly twenty times of the sensitivity of a sandwich d31 mode transducer. © 2012 Elsevier B.V.

Customized shaping of vibration modes by acoustic metamaterial synthesis

Science.gov (United States)

Xu, Jiawen; Li, Shilong; Tang, J.

2018-04-01

Acoustic metamaterials have attractive potential in elastic wave guiding and attenuation over specific frequency ranges. The vast majority of related investigations are on transient waves. In this research we focus on stationary wave manipulation, i.e., shaping of vibration modes. Periodically arranged piezoelectric transducers shunted with inductive circuits are integrated to a beam structure to form a finite-length metamaterial beam. We demonstrate for the first time that, under a given operating frequency of interest, we can facilitate a metamaterial design such that this frequency becomes a natural frequency of the integrated system. Moreover, the vibration mode corresponding to this natural frequency can be customized and shaped to realize tailored/localized response distribution. This is fundamentally different from previous practices of utilizing geometry modification and/or feedback control to achieve mode tailoring. The metamaterial design is built upon the combinatorial effects of the bandgap feature and the effective resonant cavity feature, both attributed to the dynamic characteristics of the metamaterial beam. Analytical investigations based on unit-cell dynamics and modal analysis of the metamaterial beam are presented to reveal the underlying mechanism. Case illustrations are validated by finite element analyses. Owing to the online tunability of circuitry integrated, the proposed mode shaping technique can be online adjusted to fit specific requirements. The customized shaping of vibration modes by acoustic metamaterial synthesis has potential applications in vibration suppression, sensing enhancement and energy harvesting.

Neural underpinnings of background acoustic noise in normal aging and mild cognitive impairment.

Science.gov (United States)

Sinanaj, Indrit; Montandon, Marie-Louise; Rodriguez, Cristelle; Herrmann, François; Santini, Francesco; Haller, Sven; Giannakopoulos, Panteleimon

2015-12-03

Previous contributions in younger cohorts have revealed that reallocation of cerebral resources, a crucial mechanism for working memory (WM), may be disrupted by parallel demands of background acoustic noise suppression. To date, no study has explored the impact of such disruption on brain activation in elderly individuals with or without subtle cognitive deficits. We performed a functional Magnetic Resonance Imaging (fMRI) study in 23 cases (mean age=75.7 y.o., 16 men) with mild cognitive impairment (MCI) and 16 elderly healthy controls (HC, mean age=70.1 y.o., three men) using a 2-back WM task, under two distinct MRI background acoustic noise conditions (louder vs. lower noise echo-planar imaging). General linear models were used to assess brain activation as a function of group and noise. In both groups, lower background noise is associated with increased activation of the working memory network (WMN). A decrease of the normally observed deactivation of the default mode network (DMN) is found under louder noise in both groups. Unlike HC, MCI cases also show decreased deactivation of the DMN under both louder and lower background noise. Under louder noise, this decrease is observed in anterior parts of the DMN in HC, and in the posterior cingulate cortex in MCI cases. Our results suggest that background acoustic noise has a differential impact on WMN activation in normal aging as a function of the cognitive status. Only louder noise has a disruptive effect on the usually observed DMN deactivation during WM task performance in HC. In contrast, MCI cases show altered DMN reactivity even in the presence of lower noise. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

Helicon normal modes in Proto-MPEX

Science.gov (United States)

Piotrowicz, P. A.; Caneses, J. F.; Green, D. L.; Goulding, R. H.; Lau, C.; Caughman, J. B. O.; Rapp, J.; Ruzic, D. N.

2018-05-01

The Proto-MPEX helicon source has been operating in a high electron density ‘helicon-mode’. Establishing plasma densities and magnetic field strengths under the antenna that allow for the formation of normal modes of the fast-wave are believed to be responsible for the ‘helicon-mode’. A 2D finite-element full-wave model of the helicon antenna on Proto-MPEX is used to identify the fast-wave normal modes responsible for the steady-state electron density profile produced by the source. We also show through the simulation that in the regions of operation in which core power deposition is maximum the slow-wave does not deposit significant power besides directly under the antenna. In the case of a simulation where a normal mode is not excited significant edge power is deposited in the mirror region. ).

Impact of acoustic airflow on intrasinus drug deposition: New insights into the vibrating mode and the optimal acoustic frequency to enhance the delivery of nebulized antibiotic.

Science.gov (United States)

Leclerc, Lara; Merhie, Amira El; Navarro, Laurent; Prévôt, Nathalie; Durand, Marc; Pourchez, Jérémie

2015-10-15

We investigated the impact of vibrating acoustic airflow, the high frequency (f≥100 Hz) and the low frequency (f≤45 Hz) sound waves, on the enhancement of intrasinus drug deposition. (81m)Kr-gas ventilation study was performed in a plastinated human cast with and without the addition of vibrating acoustic airflow. Similarly, intrasinus drug deposition in a nasal replica using gentamicin as a marker was studied with and without the superposition of different modes of acoustic airflow. Ventilation experiments demonstrate that no sinus ventilation was observed without acoustic airflow although sinus ventilation occurred whatever the modes of acoustic airflow applied. Intrasinus drug deposition experiments showed that the high frequency acoustic airflow led to 4-fold increase in gentamicin deposition into the left maxillary sinus and to 2-fold deposition increase into the right maxillary sinus. Besides, the low frequency acoustic airflow demonstrated a significant increase of 4-fold and 2-fold in the right and left maxillary sinuses, respectively. We demonstrated the benefit of different modes of vibrating acoustic airflow for maxillary sinus ventilation and intrasinus drug deposition. The degree of gentamicin deposition varies as a function of frequency of the vibrating acoustic airflow and the geometry of the ostia. Copyright © 2015 Elsevier B.V. All rights reserved.

On normal modes and dispersive properties of plasma systems

International Nuclear Information System (INIS)

Weiland, J.

1976-01-01

The description of nonlinear wave phenomena in terms of normal modes contra that of electric fields is discussed. The possibility of defining higher order normal modes is pointed out and the field energy is expressed in terms of the normal mode and the electric field. (Auth.)

Normal modes of Bardeen discs

International Nuclear Information System (INIS)

Verdaguer, E.

1983-01-01

The short wavelength normal modes of self-gravitating rotating polytropic discs in the Bardeen approximation are studied. The discs' oscillations can be seen in terms of two types of modes: the p-modes whose driving forces are pressure forces and the r-modes driven by Coriolis forces. As a consequence of differential rotation coupling between the two takes place and some mixed modes appear, their properties can be studied under the assumption of weak coupling and it is seen that they avoid the crossing of the p- and r-modes. The short wavelength analysis provides a basis for the classification of the modes, which can be made by using the properties of their phase diagrams. The classification is applied to the large wavelength modes of differentially rotating discs with strong coupling and to a uniformly rotating sequence with no coupling, which have been calculated in previous papers. Many of the physical properties and qualitative features of these modes are revealed by the analysis. (author)

Compensating for evanescent modes and estimating characteristic impedance in waveguide acoustic impedance measurements

DEFF Research Database (Denmark)

Nørgaard, Kren Rahbek; Fernandez Grande, Efren

2017-01-01

The ear-canal acoustic impedance and reflectance are useful for assessing conductive hearing disorders and calibrating stimulus levels in situ. However, such probe-based measurements are affected by errors due to the presence of evanescent modes and incorrect estimates or assumptions regarding...... characteristic impedance. This paper proposes a method to compensate for evanescent modes in measurements of acoustic impedance, reflectance, and sound pressure in waveguides, as well as estimating the characteristic impedance immediately in front of the probe. This is achieved by adjusting the characteristic...... impedance and subtracting an acoustic inertance from the measured impedance such that the non-causality in the reflectance is minimized in the frequency domain using the Hilbert transform. The method is thus capable of estimating plane-wave quantities of the sought-for parameters by supplying only...

Propagation of dust electro-acoustic modes in dusty plasma

International Nuclear Information System (INIS)

Avinash, K.

2001-01-01

The propagation of the dust electro-acoustic (DEA) mode in dusty plasma with different electron and ion temperatures T e and T i and different ion species is studied. The critical ratio of the dust space charge to the ion space charge ε for the excitation of DEA mode is found to decrease with increasing T e /T i and increase with m i /m e (m i and m e are the ion and electron masses). Thus experiments with hydrogen plasma where electrons are sufficiently hotter than ions and where the reduction in the dust charge with ε is more than 50% are essential for the observation of self-shielding and the DEA mode

Analysis of shallow water experimental acoustic data including normal mode model comparisons

NARCIS (Netherlands)

McHugh, R.; Simons, D.G.

2000-01-01

Ss part of a propagation model validation exercise experimental acoustic and oceanographic data was collected from a shallow-water, long-range channel, off the west coast of Scotland. Temporal variability effects in this channel were assessed through visual inspection of stacked plots, each of which

A numerical study on acoustic behavior in gas turbine combustor with acoustic resonator

International Nuclear Information System (INIS)

Park, I Sun; Sohn, Chae Hoon

2005-01-01

Acoustic behavior in gas turbine combustor with acoustic resonator is investigated numerically by adopting linear acoustic analysis. Helmholtz-type resonator is employed as acoustic resonator to suppress acoustic instability passively. The tuning frequency of acoustic resonator is adjusted by varying its length. Through harmonic analysis, acoustic-pressure responses of chamber to acoustic excitation are obtained and the resonant acoustic modes are identified. Acoustic damping effect of acoustic resonator is quantified by damping factor. As the tuning frequency of acoustic resonator approaches the target frequency of the resonant mode to be suppressed, mode split from the original resonant mode to lower and upper modes appears and thereby complex patterns of acoustic responses show up. Considering mode split and damping effect as a function of tuning frequency, it is desirable to make acoustic resonator tuned to broad-band frequencies near the maximum frequency of those of the possible upper modes

Normal mode-guided transition pathway generation in proteins.

Directory of Open Access Journals (Sweden)

Byung Ho Lee

Full Text Available The biological function of proteins is closely related to its structural motion. For instance, structurally misfolded proteins do not function properly. Although we are able to experimentally obtain structural information on proteins, it is still challenging to capture their dynamics, such as transition processes. Therefore, we need a simulation method to predict the transition pathways of a protein in order to understand and study large functional deformations. Here, we present a new simulation method called normal mode-guided elastic network interpolation (NGENI that performs normal modes analysis iteratively to predict transition pathways of proteins. To be more specific, NGENI obtains displacement vectors that determine intermediate structures by interpolating the distance between two end-point conformations, similar to a morphing method called elastic network interpolation. However, the displacement vector is regarded as a linear combination of the normal mode vectors of each intermediate structure, in order to enhance the physical sense of the proposed pathways. As a result, we can generate more reasonable transition pathways geometrically and thermodynamically. By using not only all normal modes, but also in part using only the lowest normal modes, NGENI can still generate reasonable pathways for large deformations in proteins. This study shows that global protein transitions are dominated by collective motion, which means that a few lowest normal modes play an important role in this process. NGENI has considerable merit in terms of computational cost because it is possible to generate transition pathways by partial degrees of freedom, while conventional methods are not capable of this.

Graphical analysis of electron inertia induced acoustic instability

International Nuclear Information System (INIS)

Karmakar, P.K.; Deka, U.; Dwivedi, C.B.

2005-01-01

Recently, the practical significance of the asymptotic limit of m e /m i →0 for electron density distribution has been judged in a two-component plasma system with drifting ions. It is reported that in the presence of drifting ions with drift speed exceeding the ion acoustic wave speed, the electron inertial delay effect facilitates the resonance coupling of the usual fluid ion acoustic mode with the ion-beam mode. In this contribution the same instability is analyzed by graphical and numerical methods. This is to note that the obtained dispersion relation differs from those of the other known normal modes of low frequency ion plasma oscillations and waves. This is due to consideration of electron inertial delay in derivation of the dispersion relation of the ion acoustic wave fluctuations. Numerical calculations of the dispersion relation and wave energy are carried out to depict the graphical appearance of poles and positive-negative energy modes. It is found that the electron inertia induced ion acoustic wave instability arises out of linear resonance coupling between the negative and positive energy modes. Characterization of the resonance nature of the instability in Mach number space for different wave numbers of the ion acoustic mode is presented

Acoustic Levitator With Furnace And Laser Heating

Science.gov (United States)

Barmatz, Martin B.; Stoneburner, James D.

1991-01-01

Acoustic-levitation apparatus incorporates electrical-resistance furnace for uniform heating up to temperature of about 1,000 degrees C. Additional local heating by pair of laser beams raise temperature of sample to more than 1,500 degrees C. High temperature single-mode acoustic levitator generates cylindrical-mode accoustic resonance levitating sample. Levitation chamber enclosed in electrical-resistance furnace. Infrared beams from Nd:YAG laser provide additional local heating of sample. Designed for use in containerless processing of materials in microgravity or in normal Earth gravity.

On normal modes of gas sheets and discs

International Nuclear Information System (INIS)

Drury, L.O'C.

1980-01-01

A method is described for calculating the reflection and transmission coefficients characterizing normal modes of the Goldreich-Lynden-Bell gas sheet. Two families of gas discs without self-gravity for which the normal modes can be found analytically are given and used to illustrate the validity of the sheet approximation. (author)

The dust-acoustic mode in two-temperature electron plasmas with ...

Indian Academy of Sciences (India)

... charging fluctuations, the dispersion peculiarities of dust-acoustic waves are studied based on dust fluid dynamics. The present results show that the effect will introduce a dissipation on the mode, and the dispersion and the dissipation depend on the temperature ratio and number density ratio of hot and cold electrons.

A Bloch mode expansion approach for analyzing quasi-normal modes in open nanophotonic structures

DEFF Research Database (Denmark)

de Lasson, Jakob Rosenkrantz; Kristensen, Philip Trøst; Mørk, Jesper

2014-01-01

We present a new method for determining quasi-normal modes in open nanophotonic structures using a modal ex- pansion technique. The outgoing wave boundary condition of the quasi-normal modes is satisfied automatically without absorbing boundaries, representing a significant advantage compared...

Theoretical analysis of leaky surface acoustic waves of point-focused acoustic lens and some experiments

International Nuclear Information System (INIS)

Ishikawa, Isao; Suzuki, Yoshiaki; Ogura, Yukio; Katakura, Kageyoshi

1997-01-01

When a point-focused acoustic lens in the scanning acoustic microscope (SAM) is faced to test specimen and defocused to some extent, two effective echoes can be obtained. One is the echo of longitudinal wave, which is normally incident upon the specimen of an on-axis beam in the central region of the lens and is reflected normal to the lens surface, hence detected by the transducer. The other is of leaky surface acoustic waves(LSAW), which are mode converted front a narrow beam of off-axis longitudinal wave, then propagate across the surface of the specimen and reradiate at angles normal to the lens surface, thus detected by the transducer. These two echoes are either interfered or separated with each other depending ell the defocused distance. It turned out theoretically that the LSAW have a narrow focal spot in the central region of the point-focused acoustic lens, whose size is approximately 40% of the LSAW wavelength. On top of that, a wavelength of LSAW is about 50% short as that of longitudinal wave. So, It is expected that high resolution images can be obtained provided LSAW are used in the scanning acoustic microscope.

Vertical discretizations for compressible Euler equation atmospheric models giving optimal representation of normal modes

International Nuclear Information System (INIS)

Thuburn, J.; Woollings, T.J.

2005-01-01

Accurate representation of different kinds of wave motion is essential for numerical models of the atmosphere, but is sensitive to details of the discretization. In this paper, numerical dispersion relations are computed for different vertical discretizations of the compressible Euler equations and compared with the analytical dispersion relation. A height coordinate, an isentropic coordinate, and a terrain-following mass-based coordinate are considered, and, for each of these, different choices of prognostic variables and grid staggerings are considered. The discretizations are categorized according to whether their dispersion relations are optimal, are near optimal, have a single zero-frequency computational mode, or are problematic in other ways. Some general understanding of the factors that affect the numerical dispersion properties is obtained: heuristic arguments concerning the normal mode structures, and the amount of averaging and coarse differencing in the finite difference scheme, are shown to be useful guides to which configurations will be optimal; the number of degrees of freedom in the discretization is shown to be an accurate guide to the existence of computational modes; there is only minor sensitivity to whether the equations for thermodynamic variables are discretized in advective form or flux form; and an accurate representation of acoustic modes is found to be a prerequisite for accurate representation of inertia-gravity modes, which, in turn, is found to be a prerequisite for accurate representation of Rossby modes

Contactless transport of matter in the first five resonance modes of a line-focused acoustic manipulator.

Science.gov (United States)

Foresti, Daniele; Nabavi, Majid; Poulikakos, Dimos

2012-02-01

The first five resonance modes for transport of matter in a line-focused acoustic levitation system are investigated. Contactless transport was achieved by varying the height between the radiating plate and the reflector. Transport and levitation of droplets in particular involve two limits of the acoustic forces. The lower limit corresponds to the minimum force required to overcome the gravitational force. The upper limit corresponds to the maximum acoustic pressure beyond which atomization of the droplet occurs. As the droplet size increases, the lower limit increases and the upper limit decreases. Therefore to have large droplets levitated, relatively flat radiation pressure amplitude during the translation is needed. In this study, using a finite element model, the Gor'kov potential was calculated for different heights between the reflector and the radiating plate. The application of the Gor'kov potential was extended to study the range of droplet sizes for which the droplets can be levitated and transported without atomization. It was found that the third resonant mode (H(3)-mode) represents the best compromise between high levitation force and smooth pattern transition, and water droplets of millimeter radius can be levitated and transported. The H(3)-mode also allows for three translation lines in parallel. © 2012 Acoustical Society of America

Full-angle Negative Reflection with An Ultrathin Acoustic Gradient Metasurface: Floquet-Bloch Modes Perspective and Experimental Verification

KAUST Repository

Liu, Bingyi

2017-07-01

Metasurface with gradient phase response offers new alternative for steering the propagation of waves. Conventional Snell\\'s law has been revised by taking the contribution of local phase gradient into account. However, the requirement of momentum matching along the metasurface sets its nontrivial beam manipulation functionality within a limited-angle incidence. In this work, we theoretically and experimentally demonstrate that the acoustic gradient metasurface supports the negative reflection for full-angle incidence. The mode expansion theory is developed to help understand how the gradient metasurface tailors the incident beams, and the full-angle negative reflection occurs when the first negative order Floquet-Bloch mode dominates. The coiling-up space structures are utilized to build desired acoustic gradient metasurface and the full-angle negative reflections have been perfectly verified by experimental measurements. Our work offers the Floquet-Bloch modes perspective for qualitatively understanding the reflection behaviors of the acoustic gradient metasurface and enables a new degree of the acoustic wave manipulating.

Confined longitudinal acoustic phonon modes in free-standing Si membranes coherently excited by femtosecond laser pulses

OpenAIRE

Hudert, Florian; Bruchhausen, Axel; Issenmann, Daniel; Schecker, Olivier; Waitz, Reimar; Erbe, Artur; Scheer, Elke; Dekorsy, Thomas; Mlayah, Adnen; Huntzinger, Jean-Roch

2009-01-01

In this Rapid Communication we report the first time-resolved measurements of confined acoustic phonon modes in free-standing Si membranes excited by fs laser pulses. Pump-probe experiments using asynchronous optical sampling reveal the impulsive excitation of discrete acoustic modes up to the 19th harmonic order for membranes of two different thicknesses. The modulation of the membrane thickness is measured with fm resolution. The experimental results are compared with a theoretical model in...

Acoustic multipath arrivals in the horizontal plane due to approaching nonlinear internal waves.

Science.gov (United States)

Badiey, Mohsen; Katsnelson, Boris G; Lin, Ying-Tsong; Lynch, James F

2011-04-01

Simultaneous measurements of acoustic wave transmissions and a nonlinear internal wave packet approaching an along-shelf acoustic path during the Shallow Water 2006 experiment are reported. The incoming internal wave packet acts as a moving frontal layer reflecting (or refracting) sound in the horizontal plane. Received acoustic signals are filtered into acoustic normal mode arrivals. It is shown that a horizontal multipath interference is produced. This has previously been called a horizontal Lloyd's mirror. The interference between the direct path and the refracted path depends on the mode number and frequency of the acoustic signal. A mechanism for the multipath interference is shown. Preliminary modeling results of this dynamic interaction using vertical modes and horizontal parabolic equation models are in good agreement with the observed data.

On the influence of drag effect on acoustic modes in two-condensate relativistic superfluid systems

International Nuclear Information System (INIS)

Vil'chinskij, S.I.

1999-01-01

Equations of velocities of acoustic excitations in a relativistic two-condensate superfluid system are derived with due account of reciprocal drag of superfluid motion (drag effect). The influence of the drag effect on acoustic modes in the system is considered. It is shown that the effect does not influence the nature of acoustic excitation oscillations but produces changes in the velocities of the second, third and fourth sounds

Sphalerons, deformed sphalerons and normal modes

International Nuclear Information System (INIS)

Brihaye, Y.; Kunz, J.; Oldenburg Univ.

1992-01-01

Topological arguments suggest that tha Weinberg-Salam model posses unstable solutions, sphalerons, representing the top of energy barriers between inequivalent vacua of the gauge theory. In the limit of vanishing Weinberg angle, such unstable solutions are known: the sphaleron of Klinkhamer and Manton and at large values of the Higgs mass in addition the deformed sphalerons. Here a systematic study of the discrete normal modes about these sphalerons for the full range Higgs mass is presented. The emergence of deformed sphalerons at critical values of the Higgs mass is seem to be related to the crossing of zero of the eigenvalue of the particular normal modes about the sphaleron. 6 figs., 1 tab., 19 refs. (author)

Acoustic-gravity waves in atmospheric and oceanic waveguides.

Science.gov (United States)

Godin, Oleg A

2012-08-01

A theory of guided propagation of sound in layered, moving fluids is extended to include acoustic-gravity waves (AGWs) in waveguides with piecewise continuous parameters. The orthogonality of AGW normal modes is established in moving and motionless media. A perturbation theory is developed to quantify the relative significance of the gravity and fluid compressibility as well as sensitivity of the normal modes to variations in sound speed, flow velocity, and density profiles and in boundary conditions. Phase and group speeds of the normal modes are found to have certain universal properties which are valid for waveguides with arbitrary stratification. The Lamb wave is shown to be the only AGW normal mode that can propagate without dispersion in a layered medium.

Emergence of acoustic waves from vorticity fluctuations: impact of non-normality.

Science.gov (United States)

George, Joseph; Sujith, R I

2009-10-01

Chagelishvili et al. [Phys. Rev. Lett. 79, 3178 (1997)] discovered a linear mechanism of acoustic wave emergence from vorticity fluctuations in shear flows. This paper illustrates how this "nonresonant" phenomenon is related to the non-normality of the operator governing the linear dynamics of disturbances in shear flows. The non-self-adjoint nature of the governing operator causes the emergent acoustic wave to interact strongly with the vorticity disturbance. Analytical expressions are obtained for the nondivergent vorticity perturbation. A discontinuity in the x component of the velocity field corresponding to the vorticity disturbance was originally identified to be the cause of acoustic wave emergence. However, a different mechanism is proposed in this paper. The correct "acoustic source" is identified and the reason for the abrupt nature of wave emergence is explained. The impact of viscous damping is also discussed.

The energy spectrum of electromagnetic normal modes in dissipative media: modes between two metal half spaces

International Nuclear Information System (INIS)

Sernelius, Bo E

2008-01-01

The energy spectrum of electromagnetic normal modes plays a central role in the theory of the van der Waals and Casimir interaction. Here we study the modes in connection with the van der Waals interaction between two metal half spaces. Neglecting dissipation leads to distinct normal modes with real-valued frequencies. Including dissipation seems to have the effect that these distinct modes move away from the real axis into the complex frequency plane. The summation of the zero-point energies of these modes render a complex-valued result. Using the contour integration, resulting from the use of the generalized argument principle, gives a real-valued and different result. We resolve this contradiction and show that the spectrum of true normal modes forms a continuum with real frequencies

Quasi-Normal Modes of Stars and Black Holes

Directory of Open Access Journals (Sweden)

Kokkotas Kostas

1999-01-01

Full Text Available Perturbations of stars and black holes have been one of the main topics of relativistic astrophysics for the last few decades. They are of particular importance today, because of their relevance to gravitational wave astronomy. In this review we present the theory of quasi-normal modes of compact objects from both the mathematical and astrophysical points of view. The discussion includes perturbations of black holes (Schwarzschild, Reissner-Nordström, Kerr and Kerr-Newman and relativistic stars (non-rotating and slowly-rotating. The properties of the various families of quasi-normal modes are described, and numerical techniques for calculating quasi-normal modes reviewed. The successes, as well as the limits, of perturbation theory are presented, and its role in the emerging era of numerical relativity and supercomputers is discussed.

Geodesic acoustic modes excited by finite beta drift waves

DEFF Research Database (Denmark)

Chakrabarti, Nikhil Kumar; Guzdar, P.N.; Kleva, R.G.

2008-01-01

Presented in this paper is a mode-coupling analysis for the nonlinear excitation of the geodesic acoustic modes (GAMs) in tokamak plasmas by finite beta drift waves. The finite beta effects give rise to a strong stabilizing influence on the parametric excitation process. The dominant finite beta...... effect is the combination of the Maxwell stress, which has a tendency to cancel the primary drive from the Reynolds stress, and the finite beta modification of the drift waves. The zonal magnetic field is also excited at the GAM frequency. However, it does not contribute to the overall stability...... of the three-wave process for parameters of relevance to the edge region of tokamaks....

Nonlinear excitation of geodesic acoustic modes by drift waves

International Nuclear Information System (INIS)

Chakrabarti, N.; Singh, R.; Kaw, P. K.; Guzdar, P. N.

2007-01-01

In this paper, two mode-coupling analyses for the nonlinear excitation of the geodesic acoustic modes (GAMs) in tokamak plasmas by drift waves are presented. The first approach is a coherent parametric process, which leads to a three-wave resonant interaction. This investigation allows for the drift waves and the GAMs to have comparable scales. The second approach uses the wave-kinetic equations for the drift waves, which then couples to the GAMs. This requires that the GAM scale length be large compared to the wave packet associated with the drift waves. The resonance conditions for these two cases lead to specific predictions of the radial wave number of the excited GAMs

On normal modes in classical Hamiltonian systems

NARCIS (Netherlands)

van Groesen, Embrecht W.C.

1983-01-01

Normal modes of Hamittonian systems that are even and of classical type are characterized as the critical points of a normalized kinetic energy functional on level sets of the potential energy functional. With the aid of this constrained variational formulation the existence of at least one family

Ion acoustic solitons/double layers in two-ion plasma revisited

International Nuclear Information System (INIS)

Lakhina, G. S.; Singh, S. V.; Kakad, A. P.

2014-01-01

Ion acoustic solitons and double layers are studied in a collisionless plasma consisting of cold heavier ion species, a warm lighter ion species, and hot electrons having Boltzmann distributions by Sagdeev pseudo-potential technique. In contrast to the previous results, no double layers and super-solitons are found when both the heavy and lighter ion species are treated as cold. Only the positive potential solitons are found in this case. When the thermal effects of the lighter ion species are included, in addition to the usual ion-acoustic solitons occurring at M > 1 (where the Mach number, M, is defined as the ratio of the speed of the solitary wave and the ion-acoustic speed considering temperature of hot electrons and mass of the heavier ion species), slow ion-acoustic solitons/double layers are found to occur at low Mach number (M < 1). The slow ion-acoustic mode is actually a new ion-ion hybrid acoustic mode which disappears when the normalized number density of lighter ion species tends to 1 (i.e., no heavier species). An interesting property of the new slow ion-acoustic mode is that at low number density of the lighter ion species, only negative potential solitons/double layers are found whereas for increasing densities there is a transition first to positive solitons/double layers, and then only positive solitons. The model can be easily applicable to the dusty plasmas having positively charged dust grains by replacing the heavier ion species by the dust mass and doing a simple normalization to take account of the dust charge

Normal mode approach to modelling of feedback stabilization of the resistive wall mode

International Nuclear Information System (INIS)

Chu, M.S.; Chance, M.S.; Okabayashi, M.; Glasser, A.H.

2003-01-01

Feedback stabilization of the resistive wall mode (RWM) of a plasma in a general feedback configuration is formulated in terms of the normal modes of the plasma-resistive wall system. The growth/damping rates and the eigenfunctions of the normal modes are determined by an extended energy principle for the plasma during its open (feedback) loop operation. A set of equations are derived for the time evolution of these normal modes with currents in the feedback coils. The dynamics of the feedback system is completed by the prescription of the feedback logic. The feasibility of the feedback is evaluated by using the Nyquist diagram method or by solving the characteristic equations. The elements of the characteristic equations are formed from the growth and damping rates of the normal modes, the sensor matrix of the perturbation fluxes detected by the sensor loops, the excitation matrix of the energy input to the normal modes by the external feedback coils, and the feedback logic. (The RWM is also predicted to be excited by an external error field to a large amplitude when it is close to marginal stability.) This formulation has been implemented numerically and applied to the DIII-D tokamak. It is found that feedback with poloidal sensors is much more effective than feedback with radial sensors. Using radial sensors, increasing the number of feedback coils from a central band on the outboard side to include an upper and a lower band can substantially increase the effectiveness of the feedback system. The strength of the RWM that can be stabilized is increased from γτ w = 1 to 30 (γ is the growth rate of the RWM in the absence of feedback and τ w is the resistive wall time constant) Using poloidal sensors, just one central band of feedback coils is sufficient for the stabilization of the RWM with γτ w = 30. (author)

WEBnm@: a web application for normal mode analyses of proteins

Directory of Open Access Journals (Sweden)

Reuter Nathalie

2005-03-01

Full Text Available Abstract Background Normal mode analysis (NMA has become the method of choice to investigate the slowest motions in macromolecular systems. NMA is especially useful for large biomolecular assemblies, such as transmembrane channels or virus capsids. NMA relies on the hypothesis that the vibrational normal modes having the lowest frequencies (also named soft modes describe the largest movements in a protein and are the ones that are functionally relevant. Results We developed a web-based server to perform normal modes calculations and different types of analyses. Starting from a structure file provided by the user in the PDB format, the server calculates the normal modes and subsequently offers the user a series of automated calculations; normalized squared atomic displacements, vector field representation and animation of the first six vibrational modes. Each analysis is performed independently from the others and results can be visualized using only a web browser. No additional plug-in or software is required. For users who would like to analyze the results with their favorite software, raw results can also be downloaded. The application is available on http://www.bioinfo.no/tools/normalmodes. We present here the underlying theory, the application architecture and an illustration of its features using a large transmembrane protein as an example. Conclusion We built an efficient and modular web application for normal mode analysis of proteins. Non specialists can easily and rapidly evaluate the degree of flexibility of multi-domain protein assemblies and characterize the large amplitude movements of their domains.

Resonant transmission and mode modulation of acoustic waves in H-shaped metallic gratings

International Nuclear Information System (INIS)

Deng, Yu-Qiang; Fan, Ren-Hao; Zhang, Kun; Peng, Ru-Wen; Qi, Dong-Xiang

2015-01-01

In this work, we demonstrate that resonant full transmission of acoustic waves exists in subwavelength H-shaped metallic gratings, and transmission peaks can be efficiently tuned by adjusting the grating geometry. We investigate this phenomenon through both numerical simulations and theoretical calculations based on rigorous-coupled wave analysis. The transmission peaks are originated from Fabry-Perot resonances together with the couplings between the diffractive wave on the surface and the multiple guided modes in the slits. Moreover, the transmission modes can be efficiently tuned by adjusting the cavity geometry, without changing the grating thickness. The mechanism is analyzed based on an equivalent circuit model and verified by both the theoretical calculations and the numerical simulations. This research has potential application in acoustic-device miniaturization over a wide range of wavelengths

Acoustic lenses

International Nuclear Information System (INIS)

Kittmer, C.A.

1983-03-01

Acoustic lenses focus ultrasound to produce pencil-like beams with reduced near fields. When fitted to conventional (flat-faced) transducers, such lenses greatly improve the ability to detect and size defects. This paper describes a program developed to design acoustic lenses for use in immersion or contact inspection, using normal or angle beam mode with flat or curved targets. Lens surfaces are circular in geometry to facilitate machining. For normal beam inspection of flat plate, spherical or cylindrical lenses are used. For angle beam or curved surface inspections, a compound lens is required to correct for the extra induced aberration. Such a lens is aspherical with one radius of curvature in the plane of incidence, and a different radius of curvature in the plane perpendicular to the incident plane. The resultant beam profile (i.e., location of the acoustic focus, beam diameter, 6 dB working range) depends on the degree of focusing and the transducer used. The operating frequency and bandwidth can be affected by the instrumentation used. Theoretical and measured beam profiles are in good agreement. Various applications, from zone focusing used for defect sizing in thick plate, to line focusing for pipe weld inspection, are discussed

New vibrational mode of the acoustic type in Nd(Pr)2 Cu O4 single crystals

International Nuclear Information System (INIS)

Fil', D.V.; Kolobov, I.G.; Fil', V.D.; Barilo, S.N.; Zhigunov, D.I.

1995-01-01

Sound velocities along main symmetry directions as well as their angle dependences in (100),(110)-type planes are measured in Nd(Pr) 2 Cu O 4 . Anomalies in the angle dependences are found, which are interpreted as a result of the interaction of elastic vibrations with an additional plane mode of the acoustic type. According to the proposed interpretation, the bare spectrum of the additional mode is two-dimensional, and the origin of the mode is connected with the electron degrees of freedom in the Cu O 2 -planes. A phenomenological model for description of acoustic mode spectra in the investigated systems is proposed. On the basis of the anion model of HTSC, a possible microscopic scenario of the appearance of the additional mode is analyzed. In the framework of the phenomenological model, the Debye temperatures are computed, which are in agreement with the specific heat data. The values of the components of the elastic moduli tensor are given

Nonlocal analysis of the excitation of the geodesic acoustic mode by drift waves

DEFF Research Database (Denmark)

Guzdar, P.N.; Kleva, R.G.; Chakrabarti, N.

2009-01-01

The geodesic acoustic modes (GAMs) are typically observed in the edge region of toroidal plasmas. Drift waves have been identified as a possible cause of excitation of GAMs by a resonant three wave parametric process. A nonlocal theory of excitation of these modes in inhomogeneous plasmas typical...... of the edge region of tokamaks is presented in this paper. The continuum GAM modes with coupling to the drift waves can create discrete "global" unstable eigenmodes localized in the edge "pedestal" region of the plasma. Multiple resonantly driven unstable radial eigenmodes can coexist on the edge pedestal....

Quasi-normal modes from non-commutative matrix dynamics

Science.gov (United States)

Aprile, Francesco; Sanfilippo, Francesco

2017-09-01

We explore similarities between the process of relaxation in the BMN matrix model and the physics of black holes in AdS/CFT. Focusing on Dyson-fluid solutions of the matrix model, we perform numerical simulations of the real time dynamics of the system. By quenching the equilibrium distribution we study quasi-normal oscillations of scalar single trace observables, we isolate the lowest quasi-normal mode, and we determine its frequencies as function of the energy. Considering the BMN matrix model as a truncation of N=4 SYM, we also compute the frequencies of the quasi-normal modes of the dual scalar fields in the AdS5-Schwarzschild background. We compare the results, and we finda surprising similarity.

Mean E×B shear effect on geodesic acoustic modes in Tokamaks

International Nuclear Information System (INIS)

Singh, Rameswar; Gurcan, Ozgur D.

2015-01-01

E × B shearing effect on geodesic acoustic mode (GAM) is investigated for the first time both as an initial value problem in the shearing frame and as an eigenvalue value problem in the lab frame. The nontrivial effects are that E × B shearing couples the standard GAM perturbations to their complimentary poloidal parities. The resulting GAM acquires an effective inertia increasing in time leading to GAM damping. Eigenmode analysis shows that GAMs are radially localized by E × B shearing with the mode width being inversely proportional and radial wave number directly proportional to the shearing rate for weak shear. (author)

On matrix superpotential and three-component normal modes

Energy Technology Data Exchange (ETDEWEB)

Rodrigues, R. de Lima [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Lima, A.F. de [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Dept. de Fisica; Mello, E.R. Bezerra de; Bezerra, V.B. [Universidade Federal da Paraiba (UFPB), Joao Pessoa, PB (Brazil). Dept. de Fisica]. E-mails: rafael@df.ufcg.edu.br; aerlima@df.ufcg.edu.br; emello@fisica.ufpb.br; valdir@fisica.ufpb.br

2007-07-01

We consider the supersymmetric quantum mechanics(SUSY QM) with three-component normal modes for the Bogomol'nyi-Prasad-Sommerfield (BPS) states. An explicit form of the SUSY QM matrix superpotential is presented and the corresponding three-component bosonic zero-mode eigenfunction is investigated. (author)

A numerical model for ocean ultra-low frequency noise: wave-generated acoustic-gravity and Rayleigh modes.

Science.gov (United States)

Ardhuin, Fabrice; Lavanant, Thibaut; Obrebski, Mathias; Marié, Louis; Royer, Jean-Yves; d'Eu, Jean-François; Howe, Bruce M; Lukas, Roger; Aucan, Jerome

2013-10-01

The generation of ultra-low frequency acoustic noise (0.1 to 1 Hz) by the nonlinear interaction of ocean surface gravity waves is well established. More controversial are the quantitative theories that attempt to predict the recorded noise levels and their variability. Here a single theoretical framework is used to predict the noise level associated with propagating pseudo-Rayleigh modes and evanescent acoustic-gravity modes. The latter are dominant only within 200 m from the sea surface, in shallow or deep water. At depths larger than 500 m, the comparison of a numerical noise model with hydrophone records from two open-ocean sites near Hawaii and the Kerguelen islands reveal: (a) Deep ocean acoustic noise at frequencies 0.1 to 1 Hz is consistent with the Rayleigh wave theory, in which the presence of the ocean bottom amplifies the noise by 10 to 20 dB; (b) in agreement with previous results, the local maxima in the noise spectrum support the theoretical prediction for the vertical structure of acoustic modes; and (c) noise level and variability are well predicted for frequencies up to 0.4 Hz. Above 0.6 Hz, the model results are less accurate, probably due to the poor estimation of the directional properties of wind-waves with frequencies higher than 0.3 Hz.

Electrical modulation and switching of transverse acoustic phonons

Science.gov (United States)

Jeong, H.; Jho, Y. D.; Rhim, S. H.; Yee, K. J.; Yoon, S. Y.; Shim, J. P.; Lee, D. S.; Ju, J. W.; Baek, J. H.; Stanton, C. J.

2016-07-01

We report on the electrical manipulation of coherent acoustic phonon waves in GaN-based nanoscale piezoelectric heterostructures which are strained both from the pseudomorphic growth at the interfaces as well as through external electric fields. In such structures, transverse symmetry within the c plane hinders both the generation and detection of the transverse acoustic (TA) modes, and usually only longitudinal acoustic phonons are generated by ultrafast displacive screening of potential gradients. We show that even for c -GaN, the combined application of lateral and vertical electric fields can not only switch on the normally forbidden TA mode, but they can also modulate the amplitudes and frequencies of both modes. By comparing the transient differential reflectivity spectra in structures with and without an asymmetric potential distribution, the role of the electrical controllability of phonons was demonstrated as changes to the propagation velocities, the optical birefringence, the electrically polarized TA waves, and the geometrically varying optical sensitivities of phonons.

Acoustic emission measurement on large scale coils at JAERI

International Nuclear Information System (INIS)

Yoshida, K.; Hattori, Y.; Nishi, M.F.; Shimamoto, S.; Tsuji, H.

1986-01-01

The objective of acoustic emission measurement at Japan Atomic Energy Research Institute (JAERI) is an establishment of a general diagnostic method for superconducting magnet systems. Output of strain and displacement gages can not cover a whole system in monitoring premonitory phenomena of a magnet system s failure, because these sensors are mounted on points and therefore localized. Acoustic emissions can be transmitted to sensors through structural materials without electrical noise. Monitoring of acoustic emission will be one of the methods to predict a serious failure of magnet systems in a vacuum vessel. For this purpose, several sensors were installed on the Japanese LCT coil and the Test Module Coil (TMC). Some of acoustic activity was similar as seen in these coils. The correlation between voltage spikes and acoustic events is excellent during single coil charging mode, but poorer during out of plane force mode. There are no indicative acoustical phenomena before a magnet quench or during normal zone generation. The conditioning of acoustic events and voltage spikes can be seen after any cooling down. The localization of electrical insulation damage with the acoustic emission technique is one of its most useful applications

Optical and acoustic phonon modes in strained InGaAs/GaAs rolled up tubes

Science.gov (United States)

Angelova, T.; Shtinkov, N.; Ivanov, Ts.; Donchev, V.; Cantarero, A.; Deneke, Ch.; Schmidt, O. G.; Cros, A.

2012-05-01

Rolled-up semiconductor tubes of various diameters made of alternating In0.215Ga0.785As/GaAs layers have been investigated by means of Raman scattering. The optical and acoustic phonon modes of individual tubes have been studied and compared with the characteristics of the surrounding material. After tube formation, the frequency of the phonon modes shifts with respect to the as-grown material and disorder activated modes are observed. The frequency shifts are related to the residual strain in the tubes through the deformation potential approximation. Good agreement with atomistic valence force field simulations and x-ray micro-diffraction measurements is found. By comparison with x-ray data, a Raman strain constant K = 0.65 is proposed for In0.215Ga0.785As. In the low frequency range, acoustic mode doublets are observed on the tubes that are absent in the surrounding material. They show clear evidence of the formation of periodic superlattices after the rolling-up process, and give insight into the quality of their interfaces.

From explicit to implicit normal mode initialization of a limited-area model

Energy Technology Data Exchange (ETDEWEB)

Bijlsma, S.J.

2013-02-15

In this note the implicit normal mode initialization of a limited-area model is discussed from a different point of view. To that end it is shown that the equations describing the explicit normal mode initialization applied to the shallow water equations in differentiated form on the sphere can readily be derived in normal mode space if the model equations are separable, but only in the case of stationary Rossby modes can be transformed into the implicit equations in physical space. This is a consequence of the simple relations between the components of the different modes in that case. In addition a simple eigenvalue problem is given for the frequencies of the gravity waves. (orig.)

New method for computing ideal MHD normal modes in axisymmetric toroidal geometry

International Nuclear Information System (INIS)

Wysocki, F.; Grimm, R.C.

1984-11-01

Analytic elimination of the two magnetic surface components of the displacement vector permits the normal mode ideal MHD equations to be reduced to a scalar form. A Galerkin procedure, similar to that used in the PEST codes, is implemented to determine the normal modes computationally. The method retains the efficient stability capabilities of the PEST 2 energy principle code, while allowing computation of the normal mode frequencies and eigenfunctions, if desired. The procedure is illustrated by comparison with earlier various of PEST and by application to tilting modes in spheromaks, and to stable discrete Alfven waves in tokamak geometry

Comparative Study of Various Normal Mode Analysis Techniques Based on Partial Hessians

OpenAIRE

GHYSELS, AN; VAN SPEYBROECK, VERONIQUE; PAUWELS, EWALD; CATAK, SARON; BROOKS, BERNARD R.; VAN NECK, DIMITRI; WAROQUIER, MICHEL

2010-01-01

Standard normal mode analysis becomes problematic for complex molecular systems, as a result of both the high computational cost and the excessive amount of information when the full Hessian matrix is used. Several partial Hessian methods have been proposed in the literature, yielding approximate normal modes. These methods aim at reducing the computational load and/or calculating only the relevant normal modes of interest in a specific application. Each method has its own (dis)advantages and...

Characteristics of fundamental acoustic wave modes in thin piezoelectric plates.

Science.gov (United States)

Joshi, S G; Zaitsev, B D; Kuznetsova, I E; Teplykh, A A; Pasachhe, A

2006-12-22

The characteristics of the three lowest order plate waves (A(0), S(0), and SH(0)) propagating in piezoelectric plates whose thickness h is much less than the acoustic wavelength lambda are theoretically analyzed. It is found that these waves can provide much higher values of electromechanical coupling coefficient K(2) and lower values of temperature coefficient of delay (TCD) than is possible with surface acoustic waves (SAWs). For example, in 30Y-X lithium niobate, the SH(0) mode has K(2)=0.46 and TCD=55 ppm/degrees C. The corresponding values for SAW in the widely used, strong coupling material of 128Y-X lithium niobate are K(2)=0.053 and TCD=75 ppm/degrees C. Another important advantage of plate waves is that, unlike the case of SAWs, they can operate satisfactorily in contact with a liquid medium, thus making possible their use in liquid phase sensors.

Normal-Mode Splitting in a Weakly Coupled Optomechanical System

Science.gov (United States)

Rossi, Massimiliano; Kralj, Nenad; Zippilli, Stefano; Natali, Riccardo; Borrielli, Antonio; Pandraud, Gregory; Serra, Enrico; Di Giuseppe, Giovanni; Vitali, David

2018-02-01

Normal-mode splitting is the most evident signature of strong coupling between two interacting subsystems. It occurs when two subsystems exchange energy between themselves faster than they dissipate it to the environment. Here we experimentally show that a weakly coupled optomechanical system at room temperature can manifest normal-mode splitting when the pump field fluctuations are antisquashed by a phase-sensitive feedback loop operating close to its instability threshold. Under these conditions the optical cavity exhibits an effectively reduced decay rate, so that the system is effectively promoted to the strong coupling regime.

On Mode Correlation of Solar Acoustic Oscillations

Directory of Open Access Journals (Sweden)

Heon-Young Chang

2009-09-01

Full Text Available In helioseismology it is normally assumed that p-mode oscillations are excited in a statistically independent fashion. Unfortunately, however, this issue is not clearly settled down in that two experiments exist, which apparently look in discrepancy. That is, Appourchaux et al.~(2000 looked at bin-to-bin correlation and found no evidence that the assumption is invalid. On the other hand, Roth (2001 reported that p-mode pairs with nearby frequencies tend to be anti-correlated, possibly by a mode-coupling effect. This work is motivated by an idea that one may test if there exists an excess of anticorrelated power variations of pairs of solar p-modes. We have analyzed a 72-day MDI spherical-harmonic time series to examine temporal variations of p-mode power and their correlation. The power variation is computed by a running-window method after the previous study by Roth (2001, and then distribution function of power correlation between mode pairs is produced. We have confirmed Roth's result that there is an excess of anti-correlated p-mode pairs with nearby frequencies. On the other hand, the amount of excess was somewhat smaller than the previous study. Moreover, the distribution function does not exhibit significant change when we paired modes with non-nearby frequencies, implying that the excess is not due to mode coupling. We conclude that the origin of this excess of anticorrelations may not be a solar physical process, by pointing out the possibility of statistical bias playing the central role in producing the excess.

Normal modes and continuous spectra

International Nuclear Information System (INIS)

Balmforth, N.J.; Morrison, P.J.

1994-12-01

The authors consider stability problems arising in fluids, plasmas and stellar systems that contain singularities resulting from wave-mean flow or wave-particle resonances. Such resonances lead to singularities in the differential equations determining the normal modes at the so-called critical points or layers. The locations of the singularities are determined by the eigenvalue of the problem, and as a result, the spectrum of eigenvalues forms a continuum. They outline a method to construct the singular eigenfunctions comprising the continuum for a variety of problems

Towards an Intelligent Acoustic Front End for Automatic Speech Recognition: Built-in Speaker Normalization

Directory of Open Access Journals (Sweden)

Umit H. Yapanel

2008-08-01

Full Text Available A proven method for achieving effective automatic speech recognition (ASR due to speaker differences is to perform acoustic feature speaker normalization. More effective speaker normalization methods are needed which require limited computing resources for real-time performance. The most popular speaker normalization technique is vocal-tract length normalization (VTLN, despite the fact that it is computationally expensive. In this study, we propose a novel online VTLN algorithm entitled built-in speaker normalization (BISN, where normalization is performed on-the-fly within a newly proposed PMVDR acoustic front end. The novel algorithm aspect is that in conventional frontend processing with PMVDR and VTLN, two separating warping phases are needed; while in the proposed BISN method only one single speaker dependent warp is used to achieve both the PMVDR perceptual warp and VTLN warp simultaneously. This improved integration unifies the nonlinear warping performed in the front end and reduces simultaneously. This improved integration unifies the nonlinear warping performed in the front end and reduces computational requirements, thereby offering advantages for real-time ASR systems. Evaluations are performed for (i an in-car extended digit recognition task, where an on-the-fly BISN implementation reduces the relative word error rate (WER by 24%, and (ii for a diverse noisy speech task (SPINE 2, where the relative WER improvement was 9%, both relative to the baseline speaker normalization method.

Towards an Intelligent Acoustic Front End for Automatic Speech Recognition: Built-in Speaker Normalization

Directory of Open Access Journals (Sweden)

Yapanel UmitH

2008-01-01

Full Text Available A proven method for achieving effective automatic speech recognition (ASR due to speaker differences is to perform acoustic feature speaker normalization. More effective speaker normalization methods are needed which require limited computing resources for real-time performance. The most popular speaker normalization technique is vocal-tract length normalization (VTLN, despite the fact that it is computationally expensive. In this study, we propose a novel online VTLN algorithm entitled built-in speaker normalization (BISN, where normalization is performed on-the-fly within a newly proposed PMVDR acoustic front end. The novel algorithm aspect is that in conventional frontend processing with PMVDR and VTLN, two separating warping phases are needed; while in the proposed BISN method only one single speaker dependent warp is used to achieve both the PMVDR perceptual warp and VTLN warp simultaneously. This improved integration unifies the nonlinear warping performed in the front end and reduces simultaneously. This improved integration unifies the nonlinear warping performed in the front end and reduces computational requirements, thereby offering advantages for real-time ASR systems. Evaluations are performed for (i an in-car extended digit recognition task, where an on-the-fly BISN implementation reduces the relative word error rate (WER by 24%, and (ii for a diverse noisy speech task (SPINE 2, where the relative WER improvement was 9%, both relative to the baseline speaker normalization method.

Drift effects on electromagnetic geodesic acoustic modes

Energy Technology Data Exchange (ETDEWEB)

Sgalla, R. J. F., E-mail: reneesgalla@gmail.com [Institute of Physics, University of São Paulo, São Paulo 05508-900 (Brazil)

2015-02-15

A two fluid model with parallel viscosity is employed to derive the dispersion relation for electromagnetic geodesic acoustic modes (GAMs) in the presence of drift (diamagnetic) effects. Concerning the influence of the electron dynamics on the high frequency GAM, it is shown that the frequency of the electromagnetic GAM is independent of the equilibrium parallel current but, in contrast with purely electrostatic GAMs, significantly depends on the electron temperature gradient. The electromagnetic GAM may explain the discrepancy between the f ∼ 40 kHz oscillation observed in tokamak TCABR [Yu. K. Kuznetsov et al., Nucl. Fusion 52, 063044 (2012)] and the former prediction for the electrostatic GAM frequency. The radial wave length associated with this oscillation, estimated presently from this analytical model, is λ{sub r} ∼ 25 cm, i.e., an order of magnitude higher than the usual value for zonal flows (ZFs)

Neutron scattering investigation of the acoustic-mode Grüneisen parameters in RbBr

DEFF Research Database (Denmark)

Ernst, G.; Krexner, G.; Quittner, G.

1984-01-01

The microscopic Grüneisen parameters in RbBr have been determined for 44 acoustic modes in the main symmetry directions Δ, Σ, and Λ by inelastic neutron scattering under hydrostatic pressure. The experimental data are well described within the framework of a breathing-shell model, which includes...

Evaluating acoustic speaker normalization algorithms: evidence from longitudinal child data.

Science.gov (United States)

Kohn, Mary Elizabeth; Farrington, Charlie

2012-03-01

Speaker vowel formant normalization, a technique that controls for variation introduced by physical differences between speakers, is necessary in variationist studies to compare speakers of different ages, genders, and physiological makeup in order to understand non-physiological variation patterns within populations. Many algorithms have been established to reduce variation introduced into vocalic data from physiological sources. The lack of real-time studies tracking the effectiveness of these normalization algorithms from childhood through adolescence inhibits exploration of child participation in vowel shifts. This analysis compares normalization techniques applied to data collected from ten African American children across five time points. Linear regressions compare the reduction in variation attributable to age and gender for each speaker for the vowels BEET, BAT, BOT, BUT, and BOAR. A normalization technique is successful if it maintains variation attributable to a reference sociolinguistic variable, while reducing variation attributable to age. Results indicate that normalization techniques which rely on both a measure of central tendency and range of the vowel space perform best at reducing variation attributable to age, although some variation attributable to age persists after normalization for some sections of the vowel space. © 2012 Acoustical Society of America

Normal modes of vibration in nickel

Energy Technology Data Exchange (ETDEWEB)

Birgeneau, R J [Yale Univ., New Haven, Connecticut (United States); Cordes, J [Cambridge Univ., Cambridge (United Kingdom); Dolling, G; Woods, A D B

1964-07-01

The frequency-wave-vector dispersion relation, {nu}(q), for the normal vibrations of a nickel single crystal at 296{sup o}K has been measured for the [{zeta}00], [{zeta}00], [{zeta}{zeta}{zeta}], and [0{zeta}1] symmetric directions using inelastic neutron scattering. The results can be described in terms of the Born-von Karman theory of lattice dynamics with interactions out to fourth-nearest neighbors. The shapes of the dispersion curves are very similar to those of copper, the normal mode frequencies in nickel being about 1.24 times the corresponding frequencies in copper. The fourth-neighbor model was used to calculate the frequency distribution function g({nu}) and related thermodynamic properties. (author)

SwarmDock and the Use of Normal Modes in Protein-Protein Docking

Directory of Open Access Journals (Sweden)

Paul A. Bates

2010-09-01

Full Text Available Here is presented an investigation of the use of normal modes in protein-protein docking, both in theory and in practice. Upper limits of the ability of normal modes to capture the unbound to bound conformational change are calculated on a large test set, with particular focus on the binding interface, the subset of residues from which the binding energy is calculated. Further, the SwarmDock algorithm is presented, to demonstrate that the modelling of conformational change as a linear combination of normal modes is an effective method of modelling flexibility in protein-protein docking.

Speech intelligibility for normal hearing and hearing-impaired listeners in simulated room acoustic conditions

DEFF Research Database (Denmark)

Arweiler, Iris; Dau, Torsten; Poulsen, Torben

Speech intelligibility depends on many factors such as room acoustics, the acoustical properties and location of the signal and the interferers, and the ability of the (normal and impaired) auditory system to process monaural and binaural sounds. In the present study, the effect of reverberation...... on spatial release from masking was investigated in normal hearing and hearing impaired listeners using three types of interferers: speech shaped noise, an interfering female talker and speech-modulated noise. Speech reception thresholds (SRT) were obtained in three simulated environments: a listening room......, a classroom and a church. The data from the study provide constraints for existing models of speech intelligibility prediction (based on the speech intelligibility index, SII, or the speech transmission index, STI) which have shortcomings when reverberation and/or fluctuating noise affect speech...

Method of determination of thermo-acoustic coolant instability boundaries in reactor core at NPPs with WWER

International Nuclear Information System (INIS)

Skalozubov, Volodymyr; Kolykhanov, Viktor; Kovryzhkin, Yuriy

2007-01-01

The regulatory body of Ukraine, the National Atomic Energy Company and the Scientific and Production Centre have led team-works concerned with previously unstudied factors or phenomena affecting reactor safety. As a result it is determined that the thermo-acoustic coolant instability conditions can appear in the core at definite operating WWER regimes. Considerable cyclic dynamic loads affect fuel claddings over thermo-acoustic pressure oscillations. These loads can result in inadmissible cassette design damage and containment damage. Taking into account calculation and experimental research authors submit a method of on-line assessment of WWER core state concerning thermo-acoustic coolant instability. According to this method, the thermo-acoustic coolant instability appearance conditions can be estimated using normal registered parameters (pressure, temperature, heat demand etc.). At operative modes, a WWER-1000 core is stable to tracheotomies oscillations, but reduction of coolant discharge through the core for some times can result in thermo-acoustic coolant instability. Thermo-acoustic instability appears at separate transitional modes concerned with reactor scram and unloading/loading at all power units. When thermo-acoustic instability begins in transitional modes, core elements are under influence of high-frequency coolant pressure pulsations for a long time (tens of hours)

NEAR- AND FAR-FIELD RESPONSE TO COMPACT ACOUSTIC SOURCES IN STRATIFIED CONVECTION ZONES

International Nuclear Information System (INIS)

Cally, Paul S.

2013-01-01

The role of the acoustic continuum associated with compact sources in the Sun's interior wave field is explored for a simple polytropic model. The continuum produces a near-field acoustic structure—the so-called acoustic jacket—that cannot be represented by a superposition of discrete normal modes. Particular attention is paid to monochromatic point sources of various frequency and depth, and to the surface velocity power that results, both in the discrete f- and p-mode spectrum and in the continuum. It is shown that a major effect of the continuum is to heal the surface wave field produced by compact sources, and therefore to hide them from view. It is found that the continuous spectrum is not a significant contributor to observable inter-ridge seismic power.

A design of a mode converter for electron cyclotron heating by the method of normal mode expansion

International Nuclear Information System (INIS)

Hoshino, Katsumichi; Kawashima, Hisato; Hata, Kenichiro; Yamamoto, Takumi

1983-09-01

Mode conversion of electromagnetic wave propagating in the over-size circular waveguide is attained by giving a periodical perturbation in the guide wall. Mode coupling equation is expressed by ''generalized telegraphist's equations'' which are derived from the Maxwell's equations using a normal mode expansion. A computer code to solve the coupling equations is developed and mode amplitude, conversion efficiency, etc. of a particular type of mode converter for the 60 GHz electron cyclotron heating are obtained. (author)

Wormhole potentials and throats from quasi-normal modes

Science.gov (United States)

Völkel, Sebastian H.; Kokkotas, Kostas D.

2018-05-01

Exotic compact objects refer to a wide class of black hole alternatives or effective models to describe phenomenologically quantum gravitational effects on the horizon scale. In this work we show how the knowledge of the quasi-normal mode spectrum of non-rotating wormhole models can be used to reconstruct the effective potential that appears in perturbation equations. From this it is further possible to obtain the parameters that characterize the specific wormhole model, which in this paper was chosen to be the one by Damour and Solodukhin. We also address the question whether one can distinguish such type of wormholes from ultra compact stars, if only the quasi-normal mode spectrum is known. We have proven that this is not possible by using the trapped modes only, but requires additional information. The inverse method presented here is an extension of work that has previously been developed and applied to the oscillation spectra of ultra compact stars and gravastars. However, it is not limited to the study of exotic compact objects, but applicable to symmetric double barrier potentials that appear in one-dimensional wave equations. Therefore we think it can be of interest for other fields too.

Extremely high Q-factor mechanical modes in quartz bulk acoustic wave resonators at millikelvin temperature

Energy Technology Data Exchange (ETDEWEB)

Goryachev, M.; Creedon, D. L.; Ivanov, E. N.; Tobar, M. E. [ARC Centre of Excellence for Engineered Quantum Systems, University of Western Australia, 35 Stirling Highway, Crawley WA 6009 (Australia); Galliou, S.; Bourquin, R. [Department of Time and Frequency, FEMTO-ST Institute, ENSMM, 26 Chemin de l' Épitaphe, 25000, Besançon (France)

2014-12-04

We demonstrate that Bulk Acoustic Wave (BAW) quartz resonator cooled down to millikelvin temperatures are excellent building blocks for hybrid quantum systems with extremely long coherence times. Two overtones of the longitudinal mode at frequencies of 15.6 and 65.4 MHz demonstrate a maximum f.Q product of 7.8×10{sup 16} Hz. With this result, the Q-factor in such devices near the quantum ground state can be four orders of magnitude better than previously attained in other mechanical systems. Tested quartz resonators possess the ultra low acoustic losses crucial for electromagnetic cooling to the phonon ground state.

Relation between Protein Intrinsic Normal Mode Weights and Pre-Existing Conformer Populations.

Science.gov (United States)

Ozgur, Beytullah; Ozdemir, E Sila; Gursoy, Attila; Keskin, Ozlem

2017-04-20

Intrinsic fluctuations of a protein enable it to sample a large repertoire of conformers including the open and closed forms. These distinct forms of the protein called conformational substates pre-exist together in equilibrium as an ensemble independent from its ligands. The role of ligand might be simply to alter the equilibrium toward the most appropriate form for binding. Normal mode analysis is proved to be useful in identifying the directions of conformational changes between substates. In this study, we demonstrate that the ratios of normalized weights of a few normal modes driving the protein between its substates can give insights about the ratios of kinetic conversion rates of the substates, although a direct relation between the eigenvalues and kinetic conversion rates or populations of each substate could not be observed. The correlation between the normalized mode weight ratios and the kinetic rate ratios is around 83% on a set of 11 non-enzyme proteins and around 59% on a set of 17 enzymes. The results are suggestive that mode motions carry intrinsic relations with thermodynamics and kinetics of the proteins.

2-D modeling of dual-mode acoustic phonon excitation of a triangular nanoplate

International Nuclear Information System (INIS)

Tai, Po-Tse; Yu, Pyng; Tang, Jau

2010-01-01

Graphical abstract: Modeling the lattice dynamics of a triangular plate with the arrows indicating the direction of impulsive thermal stress. We investigated ultrafast structural dynamics of triangular nanoplates based on 2-D Fermi-Pasta-Ulam model to explain coherent acoustic phonon excitation in nanoprisms. - Abstract: In this theoretical work, we investigated coherent phonon excitation of a triangular nanoplate based on 2-D Fermi-Pasta-Ulam lattice model. Based on the two-temperature model commonly used in description of laser heating of metals, we considered two kinds of forces related to electronic and lattice stresses. Based on extensive simulation and analysis, we identified two major planar phonon modes, namely, a standing wave mode related to the triangle bisector and another mode corresponding to half of the side length. This work elucidates the roles of laser-induced electronic stress and lattice stress in controlling the initial phase and the amplitude ratio between these two phonon modes.

Energy trapping of thickness-extensional modes in thin film bulk acoustic wave filters

Directory of Open Access Journals (Sweden)

Zinan Zhao

2016-01-01

Full Text Available This paper presents the thickness-extensional vibration of a rectangular piezoelectric thin film bulk acoustic wave filter with two pairs of electrodes symmetrically deposited on the center of the zinc oxide film. The two-dimensional scalar differential equations which were first derived to describe in-plane vibration distribution by Tiersten and Stevens are employed. The Ritz method with trigonometric functions as basis functions is used based on a variational formulation developed in our previous paper. Free vibration resonant frequencies and corresponding modes are obtained. The modes may separate into symmetric and antisymmetric ones for such a structurally symmetric filter. Trapped modes with vibrations mainly under the driving electrodes are exhibited. The six corner-type regions of the filter neglected by Tiersten and Stevens for an approximation are taken into account in our analysis. Results show that their approximation can lead to an inaccuracy on the order of dozens of ppm for the fundamental mode, which is quite significant in filter operation and application.

Extended Majorana zero modes in a topological superconducting-normal T-junction

Science.gov (United States)

Spånslätt, Christian; Ardonne, Eddy

2017-03-01

We investigate the sub gap properties of a three terminal Josephson T-junction composed of topologically superconducting wires connected by a normal metal region. This system naturally hosts zero energy Andreev bound states which are of self-conjugate Majorana nature and we show that they are, in contrast to ordinary Majorana zero modes, spatially extended in the normal metal region. If the T-junction respects time-reversal symmetry, we show that a zero mode is distributed only in two out of three arms in the junction and tuning the superconducting phases allows for transfer of the mode between the junction arms. We further provide tunneling conductance calculations showing that these features can be detected in experiments. Our findings suggest an experimental platform for studying the nature of spatially extended Majorana zero modes.

Modal analysis of inter-area oscillations using the theory of normal modes

Energy Technology Data Exchange (ETDEWEB)

Betancourt, R.J. [School of Electromechanical Engineering, University of Colima, Manzanillo, Col. 28860 (Mexico); Barocio, E. [CUCEI, University of Guadalajara, Guadalajara, Jal. 44480 (Mexico); Messina, A.R. [Graduate Program in Electrical Engineering, Cinvestav, Guadalajara, Jal. 45015 (Mexico); Martinez, I. [State Autonomous University of Mexico, Toluca, Edo. Mex. 50110 (Mexico)

2009-04-15

Based on the notion of normal modes in mechanical systems, a method is proposed for the analysis and characterization of oscillatory processes in power systems. The method is based on the property of invariance of modal subspaces and can be used to represent complex power system modal behavior by a set of decoupled, two-degree-of-freedom nonlinear oscillator equations. Using techniques from nonlinear mechanics, a new approach is outlined, for determining the normal modes (NMs) of motion of a general n-degree-of-freedom nonlinear system. Equations relating the normal modes and the physical velocities and displacements are developed from the linearized system model and numerical issues associated with the application of the technique are discussed. In addition to qualitative insight, this method can be utilized in the study of nonlinear behavior and bifurcation analyses. The application of these procedures is illustrated on a planning model of the Mexican interconnected system using a quadratic nonlinear model. Specifically, the use of normal mode analysis as a basis for identifying modal parameters, including natural frequencies and damping ratios of general, linear systems with n degrees of freedom is discussed. Comparisons to conventional linear analysis techniques demonstrate the ability of the proposed technique to extract the different oscillation modes embedded in the oscillation. (author)

Comparative study of various normal mode analysis techniques based on partial Hessians.

Science.gov (United States)

Ghysels, An; Van Speybroeck, Veronique; Pauwels, Ewald; Catak, Saron; Brooks, Bernard R; Van Neck, Dimitri; Waroquier, Michel

2010-04-15

Standard normal mode analysis becomes problematic for complex molecular systems, as a result of both the high computational cost and the excessive amount of information when the full Hessian matrix is used. Several partial Hessian methods have been proposed in the literature, yielding approximate normal modes. These methods aim at reducing the computational load and/or calculating only the relevant normal modes of interest in a specific application. Each method has its own (dis)advantages and application field but guidelines for the most suitable choice are lacking. We have investigated several partial Hessian methods, including the Partial Hessian Vibrational Analysis (PHVA), the Mobile Block Hessian (MBH), and the Vibrational Subsystem Analysis (VSA). In this article, we focus on the benefits and drawbacks of these methods, in terms of the reproduction of localized modes, collective modes, and the performance in partially optimized structures. We find that the PHVA is suitable for describing localized modes, that the MBH not only reproduces localized and global modes but also serves as an analysis tool of the spectrum, and that the VSA is mostly useful for the reproduction of the low frequency spectrum. These guidelines are illustrated with the reproduction of the localized amine-stretch, the spectrum of quinine and a bis-cinchona derivative, and the low frequency modes of the LAO binding protein. 2009 Wiley Periodicals, Inc.

Electromagnetic characteristics of geodesic acoustic mode in the COMPASS tokamak

Czech Academy of Sciences Publication Activity Database

Seidl, Jakub; Krbec, Jaroslav; Hron, Martin; Adámek, Jiří; Hidalgo, C.; Markovič, Tomáš; Melnikov, A.V.; Stöckel, Jan; Weinzettl, Vladimír; Aftanas, Milan; Bílková, Petra; Bogár, Ondrej; Böhm, Petr; Eliseev, L.G.; Háček, Pavel; Havlíček, Josef; Horáček, Jan; Imríšek, Martin; Kovařík, Karel; Mitošinková, Klára; Pánek, Radomír; Tomeš, Matěj; Vondráček, Petr

2017-01-01

Roč. 57, č. 12 (2017), č. článku 126048. ISSN 0029-5515 R&D Projects: GA ČR(CZ) GA16-25074S; GA ČR(CZ) GA14-35260S; GA AV ČR(CZ) GA16-24724S; GA ČR(CZ) GA15-10723S; GA MŠk(CZ) 8D15001; GA MŠk(CZ) LM2015045 EU Projects: European Commission(XE) 633053 - EUROfusion Institutional support: RVO:61389021 Keywords : geodesic acoustic mode * tokamak * turbulence * COMPASS Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 3.307, year: 2016

CASTOR: Normal-mode analysis of resistive MHD plasmas

NARCIS (Netherlands)

Kerner, W.; Goedbloed, J. P.; Huysmans, G. T. A.; Poedts, S.; Schwarz, E.

1998-01-01

The CASTOR (complex Alfven spectrum of toroidal plasmas) code computes the entire spectrum of normal-modes in resistive MHD for general tokamak configurations. The applied Galerkin method, in conjunction with a Fourier finite-element discretisation, leads to a large scale eigenvalue problem A (x)

NEAR- AND FAR-FIELD RESPONSE TO COMPACT ACOUSTIC SOURCES IN STRATIFIED CONVECTION ZONES

Energy Technology Data Exchange (ETDEWEB)

Cally, Paul S., E-mail: paul.cally@monash.edu [Monash Centre for Astrophysics and School of Mathematical Sciences, Monash University, Clayton, Victoria 3800 (Australia)

2013-05-01

The role of the acoustic continuum associated with compact sources in the Sun's interior wave field is explored for a simple polytropic model. The continuum produces a near-field acoustic structure-the so-called acoustic jacket-that cannot be represented by a superposition of discrete normal modes. Particular attention is paid to monochromatic point sources of various frequency and depth, and to the surface velocity power that results, both in the discrete f- and p-mode spectrum and in the continuum. It is shown that a major effect of the continuum is to heal the surface wave field produced by compact sources, and therefore to hide them from view. It is found that the continuous spectrum is not a significant contributor to observable inter-ridge seismic power.

Matching Impedances and Modes in Acoustic Levitation

Science.gov (United States)

Barmatz, M. B.

1985-01-01

Temperature differences accommodated with tunable coupler. Report discusses schemes for coupling sound efficiently from cool outside atmosphere into hot acoustic-levitation chamber. Theoretical studies have practical implications for material-processing systems that employ acoustic levitation.

Acoustic and Thermal Vibrational Behavior of Rare Earth Glasses

International Nuclear Information System (INIS)

Senin, H. B.; Kancono, W.; Sidek, H. A. A.

2007-01-01

The ultrasonic wave velocity and the thermal expansion of the rare earth glasses have been measured as functions of temperature and pressure to test predictions of the soft potential model for the acoustic and thermal properties. The longitudinal ultrasonic wave velocities increase under pressure. The hydrostatic pressure derivative of the bulk modulus is positive: these glasses show a normal elastic response as compressed. However, the pressure derivative of the shear modulus is negative and small, indicating weak softening of shear modes under pressure. The results found are used to determine the Gruneisen parameters. This is to obtain the acoustic mode contribution to thermal expansion. After subtraction of the relaxation and anharmonic contributions, the temperature dependence of the shear wave ultrasound velocity follows a linear law as predicted by the Soft Potential Model

Comparative Investigation of Normal Modes and Molecular Dynamics of Hepatitis C NS5B Protein

International Nuclear Information System (INIS)

Asafi, M S; Tekpinar, M; Yildirim, A

2016-01-01

Understanding dynamics of proteins has many practical implications in terms of finding a cure for many protein related diseases. Normal mode analysis and molecular dynamics methods are widely used physics-based computational methods for investigating dynamics of proteins. In this work, we studied dynamics of Hepatitis C NS5B protein with molecular dynamics and normal mode analysis. Principal components obtained from a 100 nanoseconds molecular dynamics simulation show good overlaps with normal modes calculated with a coarse-grained elastic network model. Coarse-grained normal mode analysis takes at least an order of magnitude shorter time. Encouraged by this good overlaps and short computation times, we analyzed further low frequency normal modes of Hepatitis C NS5B. Motion directions and average spatial fluctuations have been analyzed in detail. Finally, biological implications of these motions in drug design efforts against Hepatitis C infections have been elaborated. (paper)

Mode Transition and Intermittency in an Acoustically Uncoupled Lean Premixed Swirl-Stabilized Combustor

KAUST Repository

LaBry, Zachary A.; Taamallah, Soufien; Kewlani, Gaurav; Shanbhogue, Santosh J.; Ghoniem, Ahmed F.

2014-01-01

The prediction of dynamic instability remains an open and important issue in the development of gas turbine systems, particularly those constrained by emissions limitations. The existence and characteristics of dynamic instability are known to be functions of combustor geometry, flow conditions, and combustion parameters, but the form of dependence is not well understood. By modifying the acoustic boundary conditions, changes in flame and flow structure due to inlet parameters can be studied independent of the acoustic modes with which they couple. This paper examines the effect of equivalence ratio on the flame macrostructure — the relationship between the turbulent flame brush and the dominant flow structures — in an acoustically uncoupled environment. The flame brush is measured using CH* chemiluminescence, and the flow is interrogated using two-dimensional particle image velocimetry. We examine a range of equivalence ratios spanning three distinct macrostructures. The first macrostructure (ϕ = 0.550) is characterized by a diffuse flame brush confined to the interior of the inner recirculation zone. We observe a conical flame in the inner shear layer, continuing along the wall shear layer in the second macrostructure (ϕ = 0.600). The third macrostructure exhibits the same flame brush as the second, with an additional flame brush in the outer shear layer (ϕ = 0.650). Between the second and third macrostructures, we observe a regime in which the flame brush transitions intermittently between the two structures. We use dynamic mode decomposition on the PIV data to show that this transition event, which we call flickering, is linked to vorticity generated by the intermittent expansion of the outer recirculation zone as the flame jumps in and out of the outer shear layer. In a companion paper, we show how the macrostructures described in this paper are linked with dynamic instability [1].

Mode Transition and Intermittency in an Acoustically Uncoupled Lean Premixed Swirl-Stabilized Combustor

KAUST Repository

LaBry, Zachary A.

2014-06-16

The prediction of dynamic instability remains an open and important issue in the development of gas turbine systems, particularly those constrained by emissions limitations. The existence and characteristics of dynamic instability are known to be functions of combustor geometry, flow conditions, and combustion parameters, but the form of dependence is not well understood. By modifying the acoustic boundary conditions, changes in flame and flow structure due to inlet parameters can be studied independent of the acoustic modes with which they couple. This paper examines the effect of equivalence ratio on the flame macrostructure — the relationship between the turbulent flame brush and the dominant flow structures — in an acoustically uncoupled environment. The flame brush is measured using CH* chemiluminescence, and the flow is interrogated using two-dimensional particle image velocimetry. We examine a range of equivalence ratios spanning three distinct macrostructures. The first macrostructure (ϕ = 0.550) is characterized by a diffuse flame brush confined to the interior of the inner recirculation zone. We observe a conical flame in the inner shear layer, continuing along the wall shear layer in the second macrostructure (ϕ = 0.600). The third macrostructure exhibits the same flame brush as the second, with an additional flame brush in the outer shear layer (ϕ = 0.650). Between the second and third macrostructures, we observe a regime in which the flame brush transitions intermittently between the two structures. We use dynamic mode decomposition on the PIV data to show that this transition event, which we call flickering, is linked to vorticity generated by the intermittent expansion of the outer recirculation zone as the flame jumps in and out of the outer shear layer. In a companion paper, we show how the macrostructures described in this paper are linked with dynamic instability [1].

Off-Resonance Acoustic Levitation Without Rotation

Science.gov (United States)

Barmatz, M. B.; Allen, J. L.

1984-01-01

Orthogonal acoustic-levitation modes excited at slightly different frequencies to control rotation. Rotation of object in square cross-section acoustic-levitation chamber stopped by detuning two orthogonal (x and y) excitation drivers in plane of square cross section. Detuning done using fundamental degenerate modes or odd harmonic modes.

Frequency Response of the Sample Vibration Mode in Scanning Probe Acoustic Microscope

International Nuclear Information System (INIS)

Ya-Jun, Zhao; Qian, Cheng; Meng-Lu, Qian

2010-01-01

Based on the interaction mechanism between tip and sample in the contact mode of a scanning probe acoustic microscope (SPAM), an active mass of the sample is introduced in the mass-spring model. The tip motion and frequency response of the sample vibration mode in the SPAM are calculated by the Lagrange equation with dissipation function. For the silicon tip and glass assemblage in the SPAM the frequency response is simulated and it is in agreement with the experimental result. The living myoblast cells on the glass slide are imaged at resonance frequencies of the SPAM system, which are 20kHz, 30kHz and 120kHz. It is shown that good contrast of SPAM images could be obtained when the system is operated at the resonance frequencies of the system in high and low-frequency regions

Acoustic Levitation With Less Equipment

Science.gov (United States)

Barmatz, M. B.; Jacobi, N.

1983-01-01

Certain chamber shapes require fewer than three acoustic drivers. Levitation at center of spherical chamber attained using only one acoustic driver. Exitation of lowest spherical mode produces asymmetric acoustic potential well.

Acoustically Induced Vibration of Structures: Reverberant Vs. Direct Acoustic Testing

Science.gov (United States)

Kolaini, Ali R.; O'Connell, Michael R.; Tsoi, Wan B.

2009-01-01

Large reverberant chambers have been used for several decades in the aerospace industry to test larger structures such as solar arrays and reflectors to qualify and to detect faults in the design and fabrication of spacecraft and satellites. In the past decade some companies have begun using direct near field acoustic testing, employing speakers, for qualifying larger structures. A limited test data set obtained from recent acoustic tests of the same hardware exposed to both direct and reverberant acoustic field testing has indicated some differences in the resulting structural responses. In reverberant acoustic testing, higher vibration responses were observed at lower frequencies when compared with the direct acoustic testing. In the case of direct near field acoustic testing higher vibration responses appeared to occur at higher frequencies as well. In reverberant chamber testing and direct acoustic testing, standing acoustic modes of the reverberant chamber or the speakers and spacecraft parallel surfaces can strongly couple with the fundamental structural modes of the test hardware. In this paper data from recent acoustic testing of flight hardware, that yielded evidence of acoustic standing wave coupling with structural responses, are discussed in some detail. Convincing evidence of the acoustic standing wave/structural coupling phenomenon will be discussed, citing observations from acoustic testing of a simple aluminum plate. The implications of such acoustic coupling to testing of sensitive flight hardware will be discussed. The results discussed in this paper reveal issues with over or under testing of flight hardware that could pose unanticipated structural and flight qualification issues. Therefore, it is of paramount importance to understand the structural modal coupling with standing acoustic waves that has been observed in both methods of acoustic testing. This study will assist the community to choose an appropriate testing method and test setup in

Fast Eigensolver for Computing 3D Earth's Normal Modes

Science.gov (United States)

Shi, J.; De Hoop, M. V.; Li, R.; Xi, Y.; Saad, Y.

2017-12-01

We present a novel parallel computational approach to compute Earth's normal modes. We discretize Earth via an unstructured tetrahedral mesh and apply the continuous Galerkin finite element method to the elasto-gravitational system. To resolve the eigenvalue pollution issue, following the analysis separating the seismic point spectrum, we utilize explicitly a representation of the displacement for describing the oscillations of the non-seismic modes in the fluid outer core. Effectively, we separate out the essential spectrum which is naturally related to the Brunt-Väisälä frequency. We introduce two Lanczos approaches with polynomial and rational filtering for solving this generalized eigenvalue problem in prescribed intervals. The polynomial filtering technique only accesses the matrix pair through matrix-vector products and is an ideal candidate for solving three-dimensional large-scale eigenvalue problems. The matrix-free scheme allows us to deal with fluid separation and self-gravitation in an efficient way, while the standard shift-and-invert method typically needs an explicit shifted matrix and its factorization. The rational filtering method converges much faster than the standard shift-and-invert procedure when computing all the eigenvalues inside an interval. Both two Lanczos approaches solve for the internal eigenvalues extremely accurately, comparing with the standard eigensolver. In our computational experiments, we compare our results with the radial earth model benchmark, and visualize the normal modes using vector plots to illustrate the properties of the displacements in different modes.

Acoustic dew point and bubble point detector for gas condensates and reservoir fluids

Energy Technology Data Exchange (ETDEWEB)

Sivaraman, A.; Hu, Y.; Thomas, F. B.; Bennion, D. B.; Jamaluddin, A. K. M. [Hycal Energy Research Labs. Ltd., Calgary, AB (Canada)

1997-08-01

Detailed knowledge of bubblepoint and dewpoint pressures at reservoir temperature are crucial for natural gas processing, transportation, metering and utilization. This paper introduces a new acoustic dewpoint and bubblepoint detector that can be applied to a broad range of phase transitions, including very lean gas systems and opaque heavy oils. The system uses two acoustic transducers, one to stimulate and the other to detect normal mode vibrations of reservoir fluids in a small cylindrical resonator. The acoustic spectra are recorded at close intervals throughout the phase envelope, along with temperature, pressure and volume measurements, and the data is processed to obtain the specific condition of phase transition. Results of two systems, a binary mixture and live reservoir fluid, are presented. The detector system is claimed to be capable of operation in an isothermal mode with variable volume, and in a constant volume mode with variable temperatures. Interpretation of results is free of operator subjectivity; they show excellent agreement with results obtained by visual methods and equations of state calculations. 4 refs., 2 tabs., 4 figs.

Normal mode analysis for linear resistive magnetohydrodynamics

International Nuclear Information System (INIS)

Kerner, W.; Lerbinger, K.; Gruber, R.; Tsunematsu, T.

1984-10-01

The compressible, resistive MHD equations are linearized around an equilibrium with cylindrical symmetry and solved numerically as a complex eigenvalue problem. This normal mode code allows to solve for very small resistivity eta proportional 10 -10 . The scaling of growthrates and layer width agrees very well with analytical theory. Especially, both the influence of current and pressure on the instabilities is studied in detail; the effect of resistivity on the ideally unstable internal kink is analyzed. (orig.)

Seismic transmission operator reciprocity - II: impedance-operator symmetry via elastic lateral modes

Science.gov (United States)

Thomson, C. J.

2015-08-01

The properties of the overburden transmission response are of particular interest for the analysis of reflectivity illumination or blurring in seismic depth imaging. The first step to showing a transmission-operator reciprocity property is to identify the symmetry of the so-called displacement-to-traction operators. The latter are analogous to Dirichlet-to-Neumann operators and they may also be called impedance operators. Their symmetry is deduced here after development of a formal spectral or modal theory of lateral wavefunctions in a laterally heterogeneous generally anisotropic elastic medium. The elastic lateral modes are displacement-traction 6-vectors and they are built from two auxiliary 3-vector lateral-mode bases. These auxiliary modes arise from Hermitian and anti-Hermitian operators, so they have familiar properties such as orthogonality. There is no assumption of down/up symmetry of the elasticity tensor, but basic assumptions are made about the existence and completeness of the elastic modes. A point-symmetry property appears and plays a central role. The 6-vector elastic modes have a symplectic orthogonality property, which facilitates the development of modal expansions for 6-vector functions of the lateral coordinates when completeness is assumed. While the elastic modal theory is consistent with the laterally homogeneous case, numerical work would provide confidence that it is correct in general. An appendix contains an introductory overview of acoustic lateral modes that were studied by other authors, given from the perspective of this new work. A distinction is drawn between unit normalization of scalar auxiliary modes and a separate energy-flux normalization of 2-vector acoustic modes. Neither is crucial to the form of acoustic pressure-to-velocity or impedance operators. This statement carries over to the elastic case for the 3-vector auxiliary- and 6-vector elastic-mode normalizations. The modal theory is used to construct the kernel of the

Vocal fold contact patterns based on normal modes of vibration.

Science.gov (United States)

Smith, Simeon L; Titze, Ingo R

2018-05-17

The fluid-structure interaction and energy transfer from respiratory airflow to self-sustained vocal fold oscillation continues to be a topic of interest in vocal fold research. Vocal fold vibration is driven by pressures on the vocal fold surface, which are determined by the shape of the glottis and the contact between vocal folds. Characterization of three-dimensional glottal shapes and contact patterns can lead to increased understanding of normal and abnormal physiology of the voice, as well as to development of improved vocal fold models, but a large inventory of shapes has not been directly studied previously. This study aimed to take an initial step toward characterizing vocal fold contact patterns systematically. Vocal fold motion and contact was modeled based on normal mode vibration, as it has been shown that vocal fold vibration can be almost entirely described by only the few lowest order vibrational modes. Symmetric and asymmetric combinations of the four lowest normal modes of vibration were superimposed on left and right vocal fold medial surfaces, for each of three prephonatory glottal configurations, according to a surface wave approach. Contact patterns were generated from the interaction of modal shapes at 16 normalized phases during the vibratory cycle. Eight major contact patterns were identified and characterized by the shape of the flow channel, with the following descriptors assigned: convergent, divergent, convergent-divergent, uniform, split, merged, island, and multichannel. Each of the contact patterns and its variation are described, and future work and applications are discussed. Copyright © 2018 Elsevier Ltd. All rights reserved.

Acoustic-wave sensor apparatus for analyzing a petroleum-based composition and sensing solidification of constituents therein

Science.gov (United States)

Spates, J.J.; Martin, S.J.; Mansure, A.J.

1997-08-26

An acoustic-wave sensor apparatus and method are disclosed. The apparatus for analyzing a normally liquid petroleum-based composition includes at least one acoustic-wave device in contact with the petroleum-based composition for sensing or detecting the presence of constituents (e.g. paraffins or petroleum waxes) therein which solidify upon cooling of the petroleum-based composition below a cloud-point temperature. The acoustic-wave device can be a thickness-shear-mode device (also termed a quartz crystal microbalance), a surface-acoustic-wave device, an acoustic-plate-mode device or a flexural plate-wave device. Embodiments of the present invention can be used for measuring a cloud point, a pour point and/or a freeze point of the petroleum-based composition, and for determining a temperature characteristic of each point. Furthermore, measurements with the acoustic-wave sensor apparatus can be made off-line by using a sample having a particular petroleum-based composition; or in-situ with the petroleum-based composition contained within a pipeline or storage tank. The acoustic-wave sensor apparatus has uses in many different petroleum technology areas, including the recovery, transport, storage, refining and use of petroleum and petroleum-based products. 7 figs.

Levitation With a Single Acoustic Driver

Science.gov (United States)

Barmatz, M. B.; Gaspar, M. S.; Allen, J. L.

1986-01-01

Pair of reports describes acoustic-levitation systems in which only one acoustic resonance mode excited, and only one driver needed. Systems employ levitation chambers of rectangular and cylindrical geometries. Reports first describe single mode concept and indicate which modes used to levitate sample without rotation. Reports then describe systems in which controlled rotation of sample introduced.

Confinement of acoustical modes due to the electron-phonon interaction within 2D-electron gas

International Nuclear Information System (INIS)

Kochelap, V.A.; Gulseren, O.

1992-09-01

We study the confinement of acoustical modes within 2DEG due only to the electron-phonon interaction. The confined modes split out from the bulk phonons even at uniform lattice parameters, when the 2DEG is created by means of modulation doping. The effect is more pronounced when the wave vector q of the modes increases and is maximum at q = 2 k F (k F is the Fermi wave vector). In the case of several electron sheets the additional features of the confinement effect appear. In the limit of the strong electron-phonon coupling and high surface concentration of the electrons the considered system can suffer Peierls-type phase transition. In this case periodical deformation of the lattice and charge density wave are confined within the electron sheet. (author). 18 refs, 2 figs

Flow-excited acoustic resonance excitation mechanism, design guidelines, and counter measures

International Nuclear Information System (INIS)

Ziada, Samir; Lafon, Philippe

2014-01-01

The excitation mechanism of acoustic resonances has long been recognized, but the industry continues to be plagued by its undesirable consequences, manifested in severe vibration and noise problems in a wide range of industrial applications. This paper focuses on the nature of the excitation mechanism of acoustic resonances in piping systems containing impinging shear flows, such as flow over shallow and deep cavities. Since this feedback mechanism is caused by the coupling between acoustic resonators and shear flow instabilities, attention is focused first on the nature of various types of acoustic resonance modes and then on the aero-acoustic sound sources, which result from the interaction of the inherently unstable shear flow with the sound field generated by the resonant acoustic modes. Various flow-sound interaction patterns are discussed, in which the resonant sound field can be predominantly parallel or normal to the mean flow direction and the acoustic wavelength can be an order of magnitude longer than the length scale of the separated shear flow or as short as the cavity length scale. Since the state of knowledge in this field has been recently reviewed by Tonon et al. (2011, 'Aero-acoustics of Pipe Systems With Closed Branches', Int. J. Aeroacoust., 10(2), pp. 201-276), this article focuses on the more practical aspects of the phenomenon, including various flow sound interaction patterns and the resulting aero-acoustic sources, which are relevant to industrial applications. A general design guide proposal and practical means to alleviate the excitation mechanism are also presented. These are demonstrated by two examples of recent industrial case histories dealing with acoustic fatigue failure of the steam dryer in a boiling water reactor (BWR) due to acoustic resonance in the main steam piping and acoustic resonances in the roll posts of the Short Take-Off and Vertical Lift Joint Strike Fighter (JSF). (authors)

Acoustic modes of the phonon dispersion relation of NbD/sub x/ alloys

International Nuclear Information System (INIS)

Rowe, J.M.; Vagelatos, N.; Rush, J.J.; Flotow, H.E.

1975-01-01

The acoustic modes of the phonon dispersion relation in Nb, NbD 0 . 15 , and NbD 0 . 45 were measured at 473 0 K for phonons with wave vectors along the [100], [110], and [111] axes by coherent neutron scattering. The observed neutron groups for both alloys were well defined, with little or no apparent broadening. Results are compared to similar data for Nb--Mo alloys and with previous lattice-dynamics results for PdD 0 . 63 . This comparison shows that despite differences in detail, the general features of the dispersion relations of NbD/sub x/ and Nb--Mo are similar after allowing for the differences in lattice parameters for the two alloys. The measured dispersion curves and derived phonon frequency distributions for the Nb--D alloys are quite different from the analogous results for PdD 0 . 63 in that the average acoustic phonon frequencies increase with increasing deuterium concentration and lattice parameter

Panel acoustic contribution analysis.

Science.gov (United States)

Wu, Sean F; Natarajan, Logesh Kumar

2013-02-01

Formulations are derived to analyze the relative panel acoustic contributions of a vibrating structure. The essence of this analysis is to correlate the acoustic power flow from each panel to the radiated acoustic pressure at any field point. The acoustic power is obtained by integrating the normal component of the surface acoustic intensity, which is the product of the surface acoustic pressure and normal surface velocity reconstructed by using the Helmholtz equation least squares based nearfield acoustical holography, over each panel. The significance of this methodology is that it enables one to analyze and rank relative acoustic contributions of individual panels of a complex vibrating structure to acoustic radiation anywhere in the field based on a single set of the acoustic pressures measured in the near field. Moreover, this approach is valid for both interior and exterior regions. Examples of using this method to analyze and rank the relative acoustic contributions of a scaled vehicle cabin are demonstrated.

Acoustic mode coupling induced by shallow water nonlinear internal waves: sensitivity to environmental conditions and space-time scales of internal waves.

Science.gov (United States)

Colosi, John A

2008-09-01

While many results have been intuited from numerical simulation studies, the precise connections between shallow-water acoustic variability and the space-time scales of nonlinear internal waves (NLIWs) as well as the background environmental conditions have not been clearly established analytically. Two-dimensional coupled mode propagation through NLIWs is examined using a perturbation series solution in which each order n is associated with nth-order multiple scattering. Importantly, the perturbation solution gives resonance conditions that pick out specific NLIW scales that cause coupling, and seabed attenuation is demonstrated to broaden these resonances, fundamentally changing the coupling behavior at low frequency. Sound-speed inhomogeneities caused by internal solitary waves (ISWs) are primarily considered and the dependence of mode coupling on ISW amplitude, range width, depth structure, location relative to the source, and packet characteristics are delineated as a function of acoustic frequency. In addition, it is seen that significant energy transfer to modes with initially low or zero energy involves at least a second order scattering process. Under moderate scattering conditions, comparisons of first order, single scattering theoretical predictions to direct numerical simulation demonstrate the accuracy of the approach for acoustic frequencies upto 400 Hz and for single as well as multiple ISW wave packets.

Passive Mode Carbon Nanotube Underwater Acoustic Transducer

Science.gov (United States)

2016-09-20

Acoustical transducer arrays can reflect a sound signal in reverse to the sender which can be used for echo location devices. [0008] In Jiang...States Patent No. 8,494,187) a sound wave generator is disclosed which includes a carbon nanotube structure and an insulating reinforcement structure... acoustic device that includes an electrode layer and a sound wave generator. The sound wave generator is disposed on a surface of the electrode

High transmission acoustic focusing by impedance-matched acoustic meta-surfaces

KAUST Repository

Al Jahdali, Rasha

2016-01-19

Impedance is an important issue in the design of acoustic lenses because mismatched impedance is detrimental to real focusing applications. Here, we report two designs of acoustic lenses that focus acoustic waves in water and air, respectively. They are tailored by acoustic meta-surfaces, which are rigid thin plates decorated with periodically distributed sub-wavelength slits. Their respective building blocks are constructed from the coiling-up spaces in water and the layered structures in air. Analytic analysis based on coupled-mode theory and transfer matrix reveals that the impedances of the lenses are matched to those of the background media. With these impedance-matched acoustic lenses, we demonstrate the acoustic focusing effect by finite-element simulations.

High transmission acoustic focusing by impedance-matched acoustic meta-surfaces

KAUST Repository

Al Jahdali, Rasha; Wu, Ying

2016-01-01

Impedance is an important issue in the design of acoustic lenses because mismatched impedance is detrimental to real focusing applications. Here, we report two designs of acoustic lenses that focus acoustic waves in water and air, respectively. They are tailored by acoustic meta-surfaces, which are rigid thin plates decorated with periodically distributed sub-wavelength slits. Their respective building blocks are constructed from the coiling-up spaces in water and the layered structures in air. Analytic analysis based on coupled-mode theory and transfer matrix reveals that the impedances of the lenses are matched to those of the background media. With these impedance-matched acoustic lenses, we demonstrate the acoustic focusing effect by finite-element simulations.

Acoustic Levitation With One Transducer

Science.gov (United States)

Barmatz, Martin B.

1987-01-01

Higher resonator modes enables simplification of equipment. Experimental acoustic levitator for high-temperature containerless processing has round cylindrical levitation chamber and only one acoustic transducer. Stable levitation of solid particle or liquid drop achieved by exciting sound in chamber to higher-order resonant mode that makes potential well for levitated particle or drop at some point within chamber.

Sound radiation modes of cylindrical surfaces and their application to vibro-acoustics analysis of cylindrical shells

Science.gov (United States)

Sun, Yao; Yang, Tiejun; Chen, Yuehua

2018-06-01

In this paper, sound radiation modes of baffled cylinders have been derived by constructing the radiation resistance matrix analytically. By examining the characteristics of sound radiation modes, it is found that radiation coefficient of each radiation mode increases gradually with the increase of frequency while modal shapes of sound radiation modes of cylindrical shells show a weak dependence upon frequency. Based on understandings on sound radiation modes, vibro-acoustics behaviors of cylindrical shells have been analyzed. The vibration responses of cylindrical shells are described by modified Fourier series expansions and solved by Rayleigh-Ritz method involving Flügge shell theory. Then radiation efficiency of a resonance has been determined by examining whether the vibration pattern is in correspondence with a sound radiation mode possessing great radiation efficiency. Furthermore, effects of thickness and boundary conditions on sound radiation of cylindrical shells have been investigated. It is found that radiation efficiency of thicker shells is greater than thinner shells while shells with a clamped boundary constraint radiate sound more efficiently than simply supported shells under thin shell assumption.

Normal force of magnetorheological fluids with foam metal under oscillatory shear modes

Energy Technology Data Exchange (ETDEWEB)

Yao, Xingyan, E-mail: yaoxingyan-jsj@163.com [Research Center of System Health Maintenance, Chongqing Technology and Business University, Chongqing 400067 (China); Chongqing Engineering Laboratory for Detection Control and Integrated System, Chongqing 400067 (China); Liu, Chuanwen; Liang, Huang; Qin, Huafeng [Chongqing Engineering Laboratory for Detection Control and Integrated System, Chongqing 400067 (China); Yu, Qibing; Li, Chuan [Research Center of System Health Maintenance, Chongqing Technology and Business University, Chongqing 400067 (China); Chongqing Engineering Laboratory for Detection Control and Integrated System, Chongqing 400067 (China)

2016-04-01

The normal force of magnetorheological (MR) fluids in porous foam metal was investigated in this paper. The dynamic repulsive normal force was studied using an advanced commercial rheometer under oscillatory shear modes. In the presence of magnetic fields, the influences of time, strain amplitude, frequency and shear rate on the normal force of MR fluids drawn from the porous foam metal were systematically analysed. The experimental results indicated that the magnetic field had the greatest effect on the normal force, and the effect increased incrementally with the magnetic field. Increasing the magnetic field produced a step-wise increase in the shear gap. However, other factors in the presence of a constant magnetic field only had weak effects on the normal force. This behaviour can be regarded as a magnetic field-enhanced normal force, as increases in the magnetic field resulted in more MR fluids being released from the porous foam metal, and the chain-like magnetic particles in the MR fluids becoming more elongated with aggregates spanning the gap between the shear plates. - Highlights: • Normal force of MR fluids with metal foam under oscillatory shear modes was studied. • The shear gap was step-wise increased with magnetic fields. • The magnetic field has a greater impact on the normal force.

Normal force of magnetorheological fluids with foam metal under oscillatory shear modes

International Nuclear Information System (INIS)

Yao, Xingyan; Liu, Chuanwen; Liang, Huang; Qin, Huafeng; Yu, Qibing; Li, Chuan

2016-01-01

The normal force of magnetorheological (MR) fluids in porous foam metal was investigated in this paper. The dynamic repulsive normal force was studied using an advanced commercial rheometer under oscillatory shear modes. In the presence of magnetic fields, the influences of time, strain amplitude, frequency and shear rate on the normal force of MR fluids drawn from the porous foam metal were systematically analysed. The experimental results indicated that the magnetic field had the greatest effect on the normal force, and the effect increased incrementally with the magnetic field. Increasing the magnetic field produced a step-wise increase in the shear gap. However, other factors in the presence of a constant magnetic field only had weak effects on the normal force. This behaviour can be regarded as a magnetic field-enhanced normal force, as increases in the magnetic field resulted in more MR fluids being released from the porous foam metal, and the chain-like magnetic particles in the MR fluids becoming more elongated with aggregates spanning the gap between the shear plates. - Highlights: • Normal force of MR fluids with metal foam under oscillatory shear modes was studied. • The shear gap was step-wise increased with magnetic fields. • The magnetic field has a greater impact on the normal force.

NOLB: Nonlinear Rigid Block Normal Mode Analysis Method

OpenAIRE

Hoffmann , Alexandre; Grudinin , Sergei

2017-01-01

International audience; We present a new conceptually simple and computationally efficient method for nonlinear normal mode analysis called NOLB. It relies on the rotations-translations of blocks (RTB) theoretical basis developed by Y.-H. Sanejouand and colleagues. We demonstrate how to physically interpret the eigenvalues computed in the RTB basis in terms of angular and linear velocities applied to the rigid blocks and how to construct a nonlinear extrapolation of motion out of these veloci...

Density-near-zero using the acoustically induced transparency of a Fano acoustic resonator

KAUST Repository

Elayouch, A.; Addouche, M.; Farhat, Mohamed; El-Amin, Mohamed; Bagci, Hakan; Khelif, A.

2017-01-01

We report experimental results of near-zero mass density involving an acoustic metamaterial supporting Fano resonance. For this, we designed and fabricated an acoustic resonator with two closely coupled modes and measured its transmission properties

Acoustic beam steering by light refraction: illustration with directivity patterns of a tilted volume photoacoustic source.

Science.gov (United States)

Raetz, Samuel; Dehoux, Thomas; Perton, Mathieu; Audoin, Bertrand

2013-12-01

The symmetry of a thermoelastic source resulting from laser absorption can be broken when the direction of light propagation in an elastic half-space is inclined relatively to the surface. This leads to an asymmetry of the directivity patterns of both compressional and shear acoustic waves. In contrast to classical surface acoustic sources, the tunable volume source allows one to take advantage of the mode conversion at the surface to control the directivity of specific modes. Physical interpretations of the evolution of the directivity patterns with the increasing light angle of incidence and of the relations between the preferential directions of compressional- and shear-wave emission are proposed. In order to compare calculated directivity patterns with measurements of normal displacement amplitudes performed on plates, a procedure is proposed to transform the directivity patterns into pseudo-directivity patterns representative of the experimental conditions. The comparison of the theoretical with measured pseudo-directivity patterns demonstrates the ability to enhance bulk-wave amplitudes and to steer specific bulk acoustic modes by adequately tuning light refraction.

Investigation on flow oscillation modes and aero-acoustics generation mechanism in cavity

Science.gov (United States)

Yang, Dang-Guo; Lu, Bo; Cai, Jin-Sheng; Wu, Jun-Qiang; Qu, Kun; Liu, Jun

2018-05-01

Unsteady flow and multi-scale vortex transformation inside a cavity of L/D = 6 (ratio of length to depth) at Ma = 0.9 and 1.5 were studied using the numerical simulation method of modified delayed detached eddy simulation (DDES) in this paper. Aero-acoustic characteristics for the cavity at same flow conditions were obtained by the numerical method and 0.6 m by 0.6 m transonic and supersonic wind-tunnel experiments. The analysis on the computational and experimental results indicates that some vortex generates from flow separation in shear-layer over the cavity, and the vortex moves from forward to downward of the cavity at some velocity, and impingement of the vortex and the rear-wall of the cavity occurs. Some sound waves spread abroad to the cavity fore-wall, which induces some new vortex generation, and the vortex sheds, moves and impinges on the cavity rear-wall. New sound waves occur. The research results indicate that sound wave feedback created by the impingement of the shedding-vortices and rear cavity face leads to flow oscillations and noise generation inside the cavity. Analysis on aero-acoustic characteristics inside the cavity is feasible. The simulated self-sustained flow-oscillation modes and peak sound pressure on typical frequencies inside the cavity agree well with Rossiter’s and Heller’s predicated results. Moreover, the peak sound pressure occurs in the first and second flow-oscillation modes and most of sound energy focuses on the low-frequency region. Compared with subsonic speed (Ma = 0.9), aerodynamic noise is more intense at Ma = 1.5, which is induced by compression wave or shock wave in near region of fore and rear cavity face.

Reciprocity principle in duct acoustics

Science.gov (United States)

Cho, Y.-C.

1979-01-01

Various reciprocity relations in duct acoustics have been derived on the basis of the spatial reciprocity principle implied in Green's functions for linear waves. The derivation includes the reciprocity relations between mode conversion coefficients for reflection and transmission in nonuniform ducts, and the relation between the radiation of a mode from an arbitrarily terminated duct and the absorption of an externally incident plane wave by the duct. Such relations are well defined as long as the systems remain linear, regardless of acoustic properties of duct nonuniformities which cause the mode conversions.

Surface acoustic waves voltage controlled directional coupler

Science.gov (United States)

Golan, G.; Griffel, G.; Yanilov, E.; Ruschin, S.; Seidman, A.; Croitoru, N.

1988-10-01

An important condition for the development of surface wave integrated-acoustic devices is the ability to guide and control the propagation of the acoustic energy. This can be implemented by deposition of metallic "loading" channels on an anisotropic piezoelectric substrate. Deposition of such two parallel channels causes an effective coupling of acoustic energy from one channel to the other. A basic requirement for this coupling effect is the existence of the two basic modes: a symmetrical and a nonsymmetrical one. A mode map that shows the number of sustained modes as a function of the device parameters (i.e., channel width; distance between channels; material velocity; and acoustical exciting frequency) is presented. This kind of map can help significantly in the design process of such a device. In this paper we devise an advanced acoustical "Y" coupler with the ability to control its effective coupling by an externally applied voltage, thereby causing modulation of the output intensities of the signals.

A Numerical Theory for Impedance Education in Three-Dimensional Normal Incidence Tubes

Science.gov (United States)

Watson, Willie R.; Jones, Michael G.

2016-01-01

A method for educing the locally-reacting acoustic impedance of a test sample mounted in a 3-D normal incidence impedance tube is presented and validated. The unique feature of the method is that the excitation frequency (or duct geometry) may be such that high-order duct modes may exist. The method educes the impedance, iteratively, by minimizing an objective function consisting of the difference between the measured and numerically computed acoustic pressure at preselected measurement points in the duct. The method is validated on planar and high-order mode sources with data synthesized from exact mode theory. These data are then subjected to random jitter to simulate the effects of measurement uncertainties on the educed impedance spectrum. The primary conclusions of the study are 1) Without random jitter the method is in excellent agreement with that for known impedance samples, and 2) Random jitter that is compatible to that found in a typical experiment has minimal impact on the accuracy of the educed impedance.

[An improved case of bedridden mental impairment with normal pressure hydrocephalus associated with acoustic neurinoma after tumor resection].

Science.gov (United States)

Sugimoto, Seiichiro; Sugimoto, Akiko; Saita, Kazuko; Kishi, Masahiko; Shioya, Keiichi; Higa, Toshinobu

2008-08-01

A 67-year-old woman developed gait disturbance, dysarthria, cognitive impairment and incontinence at age 65, and became bedridden. She showed mutism, stupor and lower limb spasticity. Cranial CT and MRI revealed marked ventricular enlargement and a cerebellopontine angle tumor. CSF study showed normal pressure (125 mmH2O) and elevated protein (143 mg/dl). Radionuclide cisternography showed redistribution of radionuclide to the ventricles and intraventricular residual radionuclide after 72 hours, which allowed a diagnosis of normal pressure hydrocephalus. After removal of the tumor, ventricle size and CSF protein decreased, and the symptoms of cognitive impairment and motor dysfunction resolved. Histological examination showed acoustic neurinoma. Over the half of hydrocephalus following acoustic neurinoma shows a tendency to improve by surgical resection of the tumor. Neurologists who see cognitively impaired spastic bedridden patients should not overlook this pathology.

The reduction of structural acoustic coupling in car bodies

OpenAIRE

Richards, T. L.

1982-01-01

The nature of sound in cars is discussed in the light of previous experimental and theoretical work, and the major contributions to interior noise are identified. The acoustic field inside a vibrating structure is analysed theoretically in terms of the acoustic cavity modes and the structural modes, and it is shown that'reduction of structural-acoustic coupling could reduce the response for a wide variety of force inputs. Finite element analyses of prismatic acoustic cavi...

Perturbations and quasi-normal modes of black holes in Einstein-Aether theory

International Nuclear Information System (INIS)

Konoplya, R.A.; Zhidenko, A.

2007-01-01

We develop a new method for calculation of quasi-normal modes of black holes, when the effective potential, which governs black hole perturbations, is known only numerically in some region near the black hole. This method can be applied to perturbations of a wide class of numerical black hole solutions. We apply it to the black holes in the Einstein-Aether theory, a theory where general relativity is coupled to a unit time-like vector field, in order to observe local Lorentz symmetry violation. We found that in the non-reduced Einstein-Aether theory, real oscillation frequency and damping rate of quasi-normal modes are larger than those of Schwarzschild black holes in the Einstein theory

Modulation of photonic structures by surface acoustic waves

International Nuclear Information System (INIS)

Mauricio M de Lima Jr; Santos, Paulo V

2005-01-01

This paper reviews the interaction between coherently stimulated acoustic phonons in the form of surface acoustic waves with light beams in semiconductor based photonic structures. We address the generation of surface acoustic wave modes in these structures as well as the technological aspects related to control of the propagation and spatial distribution of the acoustic fields. The microscopic mechanisms responsible for the interaction between light and surface acoustic modes in different structures are then reviewed. Particular emphasis is given to the acousto-optical interaction in semiconductor microcavities and its application in photon control. These structures exhibit high optical modulation levels under acoustic excitation and are compatible with integrated light sources and detectors

Quasi-normal modes of extremal BTZ black holes in TMG

Science.gov (United States)

Afshar, Hamid R.; Alishahiha, Mohsen; Mosaffa, Amir E.

2010-08-01

We study the spectrum of tensor perturbations on extremal BTZ black holes in topologically massive gravity for arbitrary values of the coefficient of the Chern-Simons term, μ. Imposing proper boundary conditions at the boundary of the space and at the horizon, we find that the spectrum contains quasi-normal modes.

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

Science.gov (United States)

Lin, Po-Cheng; I, Lin

2016-02-01

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

A net normal dispersion all-fiber laser using a hybrid mode-locking mechanism

International Nuclear Information System (INIS)

Xu, Bo; Martinez, Amos; Yamashita, Shinji; Set, Sze Yun; Goh, Chee Seong

2014-01-01

We propose and demonstrate an all-fiber, dispersion-mapped, erbium-doped fiber laser with net normal dispersion generating dissipative solitons. The laser is mode-locked by a hybrid mode-locking mechanism consisting of a nonlinear amplifying loop mirror and a carbon nanotube saturable absorber. We achieve self-starting, mode-locked operation generating 2.75 nJ pulses at a fundamental repetition rate of 10.22 MHz with remarkable long term stability. (letter)

Earth's Outer Core Properties Estimated Using Bayesian Inversion of Normal Mode Eigenfrequencies

Science.gov (United States)

Irving, J. C. E.; Cottaar, S.; Lekic, V.

2016-12-01

The outer core is arguably Earth's most dynamic region, and consists of an iron-nickel liquid with an unknown combination of lighter alloying elements. Frequencies of Earth's normal modes provide the strongest constraints on the radial profiles of compressional wavespeed, VΦ, and density, ρ, in the outer core. Recent great earthquakes have yielded new normal mode measurements; however, mineral physics experiments and calculations are often compared to the Preliminary reference Earth model (PREM), which is 35 years old and does not provide uncertainties. Here we investigate the thermo-elastic properties of the outer core using Earth's free oscillations and a Bayesian framework. To estimate radial structure of the outer core and its uncertainties, we choose to exploit recent datasets of normal mode centre frequencies. Under the self-coupling approximation, centre frequencies are unaffected by lateral heterogeneities in the Earth, for example in the mantle. Normal modes are sensitive to both VΦ and ρ in the outer core, with each mode's specific sensitivity depending on its eigenfunctions. We include a priori bounds on outer core models that ensure compatibility with measurements of mass and moment of inertia. We use Bayesian Monte Carlo Markov Chain techniques to explore different choices in parameterizing the outer core, each of which represents different a priori constraints. We test how results vary (1) assuming a smooth polynomial parametrization, (2) allowing for structure close to the outer core's boundaries, (3) assuming an Equation-of-State and adiabaticity and inverting directly for thermo-elastic parameters. In the second approach we recognize that the outer core may have distinct regions close to the core-mantle and inner core boundaries and investigate models which parameterize the well mixed outer core separately from these two layers. In the last approach we seek to map the uncertainties directly into thermo-elastic parameters including the bulk

Bifurcations of the normal modes of the Ne...Br{sub 2} complex

Energy Technology Data Exchange (ETDEWEB)

Blesa, Fernando [Departamento de Fisica Aplicada, Universidad de Zaragoza, Zaragoza (Spain); Mahecha, Jorge [Instituto de Fisica, Universidad de Antioquia, Medellin (Colombia); Salas, J. Pablo [Area de Fisica Aplicada, Universidad de La Rioja, Logrono (Spain); Inarrea, Manuel, E-mail: manuel.inarrea@unirioja.e [Area de Fisica Aplicada, Universidad de La Rioja, Logrono (Spain)

2009-12-28

We study the classical dynamics of the rare gas-dihalogen Ne...Br{sub 2} complex in its ground electronic state. By considering the dihalogen bond frozen at its equilibrium distance, the system has two degrees of freedom and its potential energy surface presents linear and T-shape isomers. We find the nonlinear normal modes of both isomers that determine the phase space structure of the system. By means of surfaces of section and applying the numerical continuation of families of periodic orbits, we detect and identify the different bifurcations suffered by the normal modes as a function of the system energy. Finally, using the Orthogonal Fast Lyapunov Indicator (OFLI), we study the evolution of the fraction of the phase space volume occupied by regular motions.

Experimental Studies of Acoustics in a Spherical Couette Flow

Science.gov (United States)

Gowen, Savannah; Adams, Matthew; Stone, Douglas; Lathrop, Daniel

2016-11-01

The Earth, like many other astrophysical bodies, contains turbulent flows of conducting fluid which are able to sustain magnetic field. To investigate the hydromagnetic flow in the Earth's outer core, we have created an experiment which generates flows in liquid sodium. However, measuring these flows remains a challenge because liquid sodium is opaque. One possible solution is the use of acoustic waves. Our group has previously used acoustic wave measurements in air to infer azimuthal velocity profiles, but measurements attempted in liquid sodium remain challenging. In the current experiments we measure acoustic modes and their mode splittings in both air and water in a spherical Couette device. The device is comprised of a hollow 30-cm outer sphere which contains a smaller 10-cm rotating inner sphere to drive flow in the fluid in between. We use water because it has material properties that are similar to those of sodium, but is more convenient and less hazardous. Modes are excited and measured using a speaker and microphones. Measured acoustic modes and their mode splittings correspond well with the predicted frequencies in air. However, water modes are more challenging. Further investigation is needed to understand acoustic measurements in the higher density media.

Separation of acoustic waves in isentropic flow perturbations

International Nuclear Information System (INIS)

Henke, Christian

2015-01-01

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

Normal Modes of Magnetized Finite Two-Dimensional Yukawa Crystals

Science.gov (United States)

Marleau, Gabriel-Dominique; Kaehlert, Hanno; Bonitz, Michael

2009-11-01

The normal modes of a finite two-dimensional dusty plasma in an isotropic parabolic confinement, including the simultaneous effects of friction and an external magnetic field, are studied. The ground states are found from molecular dynamics simulations with simulated annealing, and the influence of screening, friction, and magnetic field on the mode frequencies is investigated in detail. The two-particle problem is solved analytically and the limiting cases of weak and strong magnetic fields are discussed.[4pt] [1] C. Henning, H. K"ahlert, P. Ludwig, A. Melzer, and M.Bonitz. J. Phys. A 42, 214023 (2009)[2] B. Farokhi, M. Shahmansouri, and P. K. Shukla. Phys.Plasmas 16, 063703 (2009)[3] L. Cândido, J.-P. Rino, N. Studart, and F. M. Peeters. J. Phys.: Condens. Matter 10, 11627--11644 (1998)

Ion acoustic waves in one- and two-negative ion species plasmas

International Nuclear Information System (INIS)

Ichiki, Ryuta; Shindo, Masako; Yoshimura, Shinji; Watanabe, Tsuguhiro; Kawai, Yoshinobu

2001-01-01

Ion acoustic waves in multi-ion plasmas including two negative ion species are investigated both numerically and experimentally. Numerically, the kinetic dispersion relation in two-negative ion plasmas is investigated. There are three modes of the ion acoustic waves in two-negative ion plasmas. In an Ar + -F - -SF 6 - plasma, only one of the three modes is dominant, regardless of the values of the electron and the ion temperatures. In a Xe + -F - -SF 6 - plasma, on the other hand, two modes can be important for a certain range of the electron-ion temperature ratio. The results also imply the possibility of the coexistence of the fast mode and the slow mode in one-negative ion plasmas. Experimentally, ion acoustic waves are observed in an Ar + -F - -SF 6 - plasma and are found to show a mode transition that agrees with the theoretical prediction for one of the three ion acoustic modes

An acoustic analysis of laughter produced by congenitally deaf and normally hearing college students1

Science.gov (United States)

Makagon, Maja M.; Funayama, E. Sumie; Owren, Michael J.

2008-01-01

Relatively few empirical data are available concerning the role of auditory experience in nonverbal human vocal behavior, such as laughter production. This study compared the acoustic properties of laughter in 19 congenitally, bilaterally, and profoundly deaf college students and in 23 normally hearing control participants. Analyses focused on degree of voicing, mouth position, air-flow direction, temporal features, relative amplitude, fundamental frequency, and formant frequencies. Results showed that laughter produced by the deaf participants was fundamentally similar to that produced by the normally hearing individuals, which in turn was consistent with previously reported findings. Finding comparable acoustic properties in the sounds produced by deaf and hearing vocalizers confirms the presumption that laughter is importantly grounded in human biology, and that auditory experience with this vocalization is not necessary for it to emerge in species-typical form. Some differences were found between the laughter of deaf and hearing groups; the most important being that the deaf participants produced lower-amplitude and longer-duration laughs. These discrepancies are likely due to a combination of the physiological and social factors that routinely affect profoundly deaf individuals, including low overall rates of vocal fold use and pressure from the hearing world to suppress spontaneous vocalizations. PMID:18646991

Plantar fascia softening in plantar fasciitis with normal B-mode sonography.

Science.gov (United States)

Wu, Chueh-Hung; Chen, Wen-Shiang; Wang, Tyng-Guey

2015-11-01

To investigate plantar fascia elasticity in patients with typical clinical manifestations of plantar fasciitis but normal plantar fascia morphology on B-mode sonography. Twenty patients with plantar fasciitis (10 unilateral and 10 bilateral) and 30 healthy volunteers, all with normal plantar fascia morphology on B-mode sonography, were included in the study. Plantar fascia elasticity was evaluated by sonoelastographic examination. All sonoelastograms were quantitatively analyzed, and less red pixel intensity was representative of softer tissue. Pixel intensity was compared among unilateral plantar fasciitis patients, bilateral plantar fasciitis patients, and healthy volunteers by one-way ANOVA. A post hoc Scheffé's test was used to identify where the differences occurred. Compared to healthy participants (red pixel intensity: 146.9 ± 9.1), there was significantly less red pixel intensity in the asymptomatic sides of unilateral plantar fasciitis (140.4 ± 7.3, p = 0.01), symptomatic sides of unilateral plantar fasciitis (127.1 ± 7.4, p plantar fasciitis (129.4 ± 7.5, p plantar fascia thickness or green or blue pixel intensity among these groups. Sonoelastography revealed that the plantar fascia is softer in patients with typical clinical manifestations of plantar fasciitis, even if they exhibit no abnormalities on B-mode sonography.

Acoustic trapping in bubble-bounded micro-cavities

Science.gov (United States)

O'Mahoney, P.; McDougall, C.; Glynne-Jones, P.; MacDonald, M. P.

2016-12-01

We present a method for controllably producing longitudinal acoustic trapping sites inside microfluidic channels. Air bubbles are injected into a micro-capillary to create bubble-bounded `micro-cavities'. A cavity mode is formed that shows controlled longitudinal acoustic trapping between the two air/water interfaces along with the levitation to the centre of the channel that one would expect from a lower order lateral mode. 7 μm and 10 μm microspheres are trapped at the discrete acoustic trapping sites in these micro-cavities.We show this for several lengths of micro-cavity.

Receptivity of Hypersonic Boundary Layers to Distributed Roughness and Acoustic Disturbances

Science.gov (United States)

Balakumar, P.

2013-01-01

Boundary-layer receptivity and stability of Mach 6 flows over smooth and rough seven-degree half-angle sharp-tipped cones are numerically investigated. The receptivity of the boundary layer to slow acoustic disturbances, fast acoustic disturbances, and vortical disturbances is considered. The effects of three-dimensional isolated roughness on the receptivity and stability are also simulated. The results for the smooth cone show that the instability waves are generated in the leading edge region and that the boundary layer is much more receptive to slow acoustic waves than to the fast acoustic waves. Vortical disturbances also generate unstable second modes, however the receptivity coefficients are smaller than that of the slow acoustic wave. Distributed roughness elements located near the nose region decreased the receptivity of the second mode generated by the slow acoustic wave by a small amount. Roughness elements distributed across the continuous spectrum increased the receptivity of the second mode generated by the slow and fast acoustic waves and the vorticity wave. The largest increase occurred for the vorticity wave. Roughness elements distributed across the synchronization point did not change the receptivity of the second modes generated by the acoustic waves. The receptivity of the second mode generated by the vorticity wave increased in this case, but the increase is lower than that occurred with the roughness elements located across the continuous spectrum. The simulations with an isolated roughness element showed that the second mode waves generated by the acoustic disturbances are not influenced by the small roughness element. Due to the interaction, a three-dimensional wave is generated. However, the amplitude is orders of magnitude smaller than the two-dimensional wave.

Transverse acoustic forcing of a round hydrodynamically self-excited jet

Science.gov (United States)

Kushwaha, Abhijit Kumar; Mazur, Marek; Worth, Nicholas; Dawson, James; Li, Larry K. B.

2017-11-01

Hydrodynamically self-excited jets can readily synchronize with longitudinal acoustic forcing, but their response to transverse acoustic forcing is less clear. In this experimental study, we apply transverse acoustic forcing to an axisymmetric low-density jet at frequencies around its natural global frequency. We place the jet in a rectangular box containing two loudspeakers, one at each end, producing nominally one-dimensional standing pressure waves. By traversing the jet across this box, we subject it to a range of acoustic modes, from purely longitudinal (streamwise) modes at the pressure anti-node to purely transverse (cross-stream) modes at the pressure node. Using time-resolved Background-Oriented Schlieren (BOS) imaging and hot-wire anemometry, we characterize the jet response for different forcing frequencies, amplitudes and mode shapes, providing new insight into the way transverse acoustic oscillations interact with axisymmetric hydrodynamic oscillations. This work was supported by the Research Grants Council of Hong Kong (Project No. 16235716 and 26202815).

Coupled Acoustic-Mechanical Bandgaps

DEFF Research Database (Denmark)

Jensen, Jakob Søndergaard; Kook, Junghwan

2016-01-01

medium and the presence of acoustic resonances. It is demonstrated that corrugation of the plate structure can introduce bending wave bandgaps and bandgaps in the acoustic domain in overlapping and audible frequency ranges. This effect is preserved also when taking the physical coupling between the two...... domains into account. Additionally, the coupling is shown to introduce extra gaps in the band structure due to modal interaction and the appearance of a cut-on frequency for the fundamental acoustic mode....

Acoustic Wave in a Dusty Plasma with Frequent Grain Charging Collisions

International Nuclear Information System (INIS)

Lee, Hee J.; Cho, Sang-Hoon

2003-01-01

The sink terms in the electron and ion continuity equations and the frictional terms in the momentum equations of a dusty plasma are obtained by taking moments of a kinetic equation which takes into account the grain charging collisions by electrons and ions. We show that an acoustic wave can propagate as a normal mode in the parameter regime where the frequencies of charging collisions are much greater than the wave frequency

Transmission mode acoustic time-reversal imaging for nondestructive evaluation

Science.gov (United States)

Lehman, Sean K.; Devaney, Anthony J.

2002-11-01

In previous ASA meetings and JASA papers, the extended and formalized theory of transmission mode time reversal in which the transceivers are noncoincident was presented. When combined with the subspace concepts of a generalized MUltiple SIgnal Classification (MUSIC) algorithm, this theory is used to form super-resolution images of scatterers buried in a medium. These techniques are now applied to ultrasonic nondestructive evaluation (NDE) of parts, and shallow subsurface seismic imaging. Results are presented of NDE experiments on metal and epoxy blocks using data collected from an adaptive ultrasonic array, that is, a ''time-reversal machine,'' at Lawrence Livermore National Laboratory. Also presented are the results of seismo-acoustic subsurface probing of buried hazardous waste pits at the Idaho National Engineering and Environmental Laboratory. [Work performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.] [Work supported in part by CenSSIS, the Center for Subsurface Sensing and Imaging Systems, under the Engineering Research Centers Program of the NSF (award number EEC-9986821) as well as from Air Force Contracts No. F41624-99-D6002 and No. F49620-99-C0013.

Free and forced Rossby normal modes in a rectangular gulf of arbitrary orientation

Science.gov (United States)

Graef, Federico

2016-09-01

A free Rossby normal mode in a rectangular gulf of arbitrary orientation is constructed by considering the reflection of a Rossby mode in a channel at the head of the gulf. Therefore, it is the superposition of four Rossby waves in an otherwise unbounded ocean with the same frequency and wavenumbers perpendicular to the gulf axis whose difference is equal to 2mπ/W, where m is a positive integer and W the gulf's width. The lower (or higher) modes with small m (or large m) are oscillatory (evanescent) in the coordinate along the gulf; these are elucidated geometrically. However for oceanographically realistic parameter values, most of the modes are evanescent. When the gulf is forced at the mouth with a single Fourier component, the response is in general an infinite sum of modes that are needed to match the value of the streamfunction at the gulf's entrance. The dominant mode of the response is the resonant one, which corresponds to forcing with a frequency ω and wavenumber normal to the gulf axis η appropriate to a gulf mode: η =- β sin α/(2ω) ± Mπ/W, where α is the angle between the gulf's axis and the eastern direction (+ve clockwise) and M the resonant's mode number. For zonal gulfs ω drops out of the resonance condition. For the special cases η = 0 in which the free surface goes up and down at the mouth with no flow through it, or a flow with a sinusoidal profile, resonant modes can get excited for very specific frequencies (only for non-zonal gulfs in the η = 0 case). The resonant mode is around the annual frequency for a wide range of gulf orientations α ∈ [40°, 130°] or α ∈ [220°, 310°] and gulf widths between 150 and 200 km; these include the Gulf of California and the Adriatic Sea. If η is imaginary, i.e. a flow with an exponential profile, there is no resonance. In general less modes get excited if the gulf is zonally oriented.

Effect of cobratoxin binding on the normal mode vibration within acetylcholine binding protein.

Science.gov (United States)

Bertaccini, Edward J; Lindahl, Erik; Sixma, Titia; Trudell, James R

2008-04-01

Recent crystal structures of the acetylcholine binding protein (AChBP) have revealed surprisingly small structural alterations upon ligand binding. Here we investigate the extent to which ligand binding may affect receptor dynamics. AChBP is a homologue of the extracellular component of ligand-gated ion channels (LGICs). We have previously used an elastic network normal-mode analysis to propose a gating mechanism for the LGICs and to suggest the effects of various ligands on such motions. However, the difficulties with elastic network methods lie in their inability to account for the modest effects of a small ligand or mutation on ion channel motion. Here, we report the successful application of an elastic network normal mode technique to measure the effects of large ligand binding on receptor dynamics. The present calculations demonstrate a clear alteration in the native symmetric motions of a protein due to the presence of large protein cobratoxin ligands. In particular, normal-mode analysis revealed that cobratoxin binding to this protein significantly dampened the axially symmetric motion of the AChBP that may be associated with channel gating in the full nAChR. The results suggest that alterations in receptor dynamics could be a general feature of ligand binding.

A normal mode treatment of semi-diurnal body tides on an aspherical, rotating and anelastic Earth

Science.gov (United States)

Lau, Harriet C. P.; Yang, Hsin-Ying; Tromp, Jeroen; Mitrovica, Jerry X.; Latychev, Konstantin; Al-Attar, David

2015-08-01

Normal mode treatments of the Earth's body tide response were developed in the 1980s to account for the effects of Earth rotation, ellipticity, anelasticity and resonant excitation within the diurnal band. Recent space-geodetic measurements of the Earth's crustal displacement in response to luni-solar tidal forcings have revealed geographical variations that are indicative of aspherical deep mantle structure, thus providing a novel data set for constraining deep mantle elastic and density structure. In light of this, we make use of advances in seismic free oscillation literature to develop a new, generalized normal mode theory for the tidal response within the semi-diurnal and long-period tidal band. Our theory involves a perturbation method that permits an efficient calculation of the impact of aspherical structure on the tidal response. In addition, we introduce a normal mode treatment of anelasticity that is distinct from both earlier work in body tides and the approach adopted in free oscillation seismology. We present several simple numerical applications of the new theory. First, we compute the tidal response of a spherically symmetric, non-rotating, elastic and isotropic Earth model and demonstrate that our predictions match those based on standard Love number theory. Second, we compute perturbations to this response associated with mantle anelasticity and demonstrate that the usual set of seismic modes adopted for this purpose must be augmented by a family of relaxation modes to accurately capture the full effect of anelasticity on the body tide response. Finally, we explore aspherical effects including rotation and we benchmark results from several illustrative case studies of aspherical Earth structure against independent finite-volume numerical calculations of the semi-diurnal body tide response. These tests confirm the accuracy of the normal mode methodology to at least the level of numerical error in the finite-volume predictions. They also demonstrate

A Study of Relationship between the Acoustic Sensitivity of Vestibular System and the Ability to Trigger Sound-Evoked Muscle Reflex of the Middle Ear in Adults with Normal Hearing

Directory of Open Access Journals (Sweden)

S.F. Emami

2014-07-01

Full Text Available Introduction & Objective: The vestibular system is sound sensitive and the sensitivity is related to the saccule. The vestibular afferents are projected to the middle ear muscles (such as the stapedius. The goal of this research was studying the relationship between the vestibular hearing and the sound-evoked muscle reflex of the middle ear to 500 HZ. Materials & Methods: This study was a cross sectional-comparison done in audiology department of Sheikholreis C‍‍linic (Hamadan, Iran. The study groups consisted of thirty healthy people and thirty patients with benign paroxysmal positional vertigo. Inclusion criteria of the present study were to have normal hearing on pure tone audiometry, acoustic reflex, and speech discrimination scores. Based on ipsilateral acoustic reflex test at 500HZ, they were divided to normal and abnormal groups. Then they were evaluated by cervical vestibular evoked myogenic potentials (cVEMPs and finally classified in three groups (N Normal ear , (CVUA Contra lateral vertiginous ear with unaffected saccular sensitivity to sound,(IVA Ipsilateral vertiginous ear with affected saccular sensitivity to sound. Results: Thirty affected ears (IVA with decreased vestibular excitability as detected by ab-normal cVEMPs, revealed abnormal findings of acoustic reflex at 500HZ. Whereas, both un-affected (CVUA and normal ears (N had normal results. Multiple comparisons of mean values of cVEMPs (p13,n23 and acoustic reflex at500HZ among the three groups were sig-nificant. The correlation between acoustic reflex at 500HZ and p13 latencies was significant. The n23 latencies showed significant correlation with acoustic reflex at 500HZ. Conclusion: The vestibular sensitivity to sound retains the ability to trigger sound-evoked re-flex of the middle ear at 500 HZ. (Sci J Hamadan Univ Med Sci 2014; 21 (2:99-104

Calculation of normal modes of the closed waveguides in general vector case

Science.gov (United States)

Malykh, M. D.; Sevastianov, L. A.; Tiutiunnik, A. A.

2018-04-01

The article is devoted to the calculation of normal modes of the closed waveguides with an arbitrary filling ɛ, μ in the system of computer algebra Sage. Maxwell equations in the cylinder are reduced to the system of two bounded Helmholtz equations, the notion of weak solution of this system is given and then this system is investigated as a system of ordinary differential equations. The normal modes of this system are an eigenvectors of a matrix pencil. We suggest to calculate the matrix elements approximately and to truncate the matrix by usual way but further to solve the truncated eigenvalue problem exactly in the field of algebraic numbers. This approach allows to keep the symmetry of the initial problem and in particular the multiplicity of the eigenvalues. In the work would be presented some results of calculations.

Density-near-zero using the acoustically induced transparency of a Fano acoustic resonator

KAUST Repository

Elayouch, A.

2017-01-05

We report experimental results of near-zero mass density involving an acoustic metamaterial supporting Fano resonance. For this, we designed and fabricated an acoustic resonator with two closely coupled modes and measured its transmission properties. Our study reveals that the phenomenon of acoustically induced transparency is accompanied by an effect of near-zero density. Indeed, the dynamic effective parameters obtained from experimental data show the presence of a frequency band where the effective mass density is close to zero, with high transmission levels reaching 0.7. Furthermore, we demonstrate that such effective parameters lead to wave guiding in a 90-degrees-bent channel. This kind of acoustic metamaterial can, therefore, give rise to acoustic functions like controlling the wavefront, which may lead to very promising applications in acoustic cloacking or imaging.

Tunable coupled surface acoustic cavities

Science.gov (United States)

de Lima, M. M.; Santos, P. V.; Kosevich, Yu. A.; Cantarero, A.

2012-06-01

We demonstrate the electric tuning of the acoustic field in acoustic microcavities (MCs) defined by a periodic arrangement of metal stripes within a surface acoustic delay line on LiNbO3 substrate. Interferometric measurements show the enhancement of the acoustic field distribution within a single MC, the presence of a "bonding" and "anti-bonding" modes for two strongly coupled MCs, as well as the positive dispersion of the "mini-bands" formed by five coupled MCs. The frequency and amplitude of the resonances can be controlled by the potential applied to the metal stripes.

Basic mode of nonlinear spin-wave resonance in normally magnetized ferrite films

International Nuclear Information System (INIS)

Gulyaev, Yu.V.; Zil'berman, P.E.; Timiryazev, A.G.; Tikhomirova, M.P.

2000-01-01

Modes of nonlinear and spin-wave resonance (SWR) in the normally magnetized ferrite films were studied both theoretically and experimentally. The particular emphasis was placed on the basic mode of SWR. One showed theoretically that with the growth of the precession amplitude the profile of the basic mode changed. The nonlinear shift of the resonance field depends on the parameters of fixing of the surface spins. Films of ferroyttrium garnet (FYG) with strong gradient of the single-axis anisotropy field along the film thickness, as well as, FYG films of the submicron thickness where investigated experimentally. With the intensification of Uhf-power one observed the sublinear shift of the basic mode resonance field following by the superlinear growth of the absorbed power. That kind of behaviour is explained by variation of the profile of the varying magnetization space distribution [ru

Acoustic Levitation With One Driver

Science.gov (United States)

Wang, T. G.; Rudnick, I.; Elleman, D. D.; Stoneburner, J. D.

1985-01-01

Report discusses acoustic levitation in rectangular chamber using one driver mounted at corner. Placement of driver at corner enables it to couple effectively to acoustic modes along all three axes. Use of single driver reduces cost, complexity and weight of levitation system below those of three driver system.

Quasi-normal frequencies: Semi-analytic results for highly damped modes

International Nuclear Information System (INIS)

Skakala, Jozef; Visser, Matt

2011-01-01

Black hole highly-damped quasi-normal frequencies (QNFs) are very often of the form ω n = (offset) + in (gap). We have investigated the genericity of this phenomenon for the Schwarzschild-deSitter (SdS) black hole by considering a model potential that is piecewise Eckart (piecewise Poschl-Teller), and developing an analytic 'quantization condition' for the highly-damped quasi-normal frequencies. We find that the ω n = (offset) + in (gap) behaviour is common but not universal, with the controlling feature being whether or not the ratio of the surface gravities is a rational number. We furthermore observed that the relation between rational ratios of surface gravities and periodicity of QNFs is very generic, and also occurs within different analytic approaches applied to various types of black hole spacetimes. These observations are of direct relevance to any physical situation where highly-damped quasi-normal modes are important.

Polaritonic normal-mode splitting and light localization in a one-dimensional nanoguide

NARCIS (Netherlands)

Haakh, Harald R.; Faez, Sanli; Sandoghdar, Vahid

2016-01-01

We theoretically investigate the interaction of light and a collection of emitters in a subwavelength one-dimensional medium (nanoguide), where enhanced emitter-photon coupling leads to efficient multiple scattering of photons. We show that the spectrum of the transmitted light undergoes normal-mode

Acoustic Green's function extraction in the ocean

Science.gov (United States)

Zang, Xiaoqin

data were collected in a 100-meter deep coastal ocean environment and a 600-meter deep ocean environment. In the coastal ocean environment, the collected noise data were processed by coherently stacking five days of cross-correlation functions between pairs of hydrophones separated by 5 km, 10 km and 15 km, respectively. NCF waveforms were modeled using the KRAKEN normal mode model, with the difference between the NCFs and the acoustic GFs quantified by a weighting function. Through waveform inversion of NCFs, an optimal geoacoustic model was obtained by minimizing the two-norm misfit between the simulation and the measurement. Using a simulated time-reversal mirror, the extracted GF was back propagated from the receiver location to the virtual source, and a strong focus was found in the vicinity of the source, which provides additional support for the optimality of the aforementioned geoacoustic model. With the extracted GF, dispersion in experimental shallow water environment was visualized in the time-frequency representation. Normal modes of GFs were separated using the time-warping transformation. By separating the modes in the frequency domain of the time-warped signal, we isolated modal arrivals and reconstructed the NCF by summing up the isolated modes, thereby significantly improving the signal-to-noise ratio of NCFs. Finally, these reconstructed NCFs were employed to estimate the depth-averaged current speed in the Florida Straits, based on an effective sound speed approximation. In the mid-deep ocean environment, the noise data were processed using the same noise interferometry method, but the obtained NCFs were not as good as those in the coastal ocean environment. Several highly possible reasons of the difference in the noise interferometry performance were investigated and discussed. The first one is the noise source composition, which is different in the spectrograms of noise records in two environments. The second is strong ocean current variability

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

Science.gov (United States)

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

2009-12-01

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

Normal modes and time evolution of a holographic superconductor after a quantum quench

International Nuclear Information System (INIS)

Gao, Xin; García-García, Antonio M.; Zeng, Hua Bi; Zhang, Hai-Qing

2014-01-01

We employ holographic techniques to investigate the dynamics of the order parameter of a strongly coupled superconductor after a perturbation that drives the system out of equilibrium. The gravity dual that we employ is the AdS_5 Soliton background at zero temperature. We first analyze the normal modes associated to the superconducting order parameter which are purely real since the background has no horizon. We then study the full time evolution of the order parameter after a quench. For sufficiently a weak and slow perturbation we show that the order parameter undergoes simple undamped oscillations in time with a frequency that agrees with the lowest normal model computed previously. This is expected as the soliton background has no horizon and therefore, at least in the probe and large N limits considered, the system will never return to equilibrium. For stronger and more abrupt perturbations higher normal modes are excited and the pattern of oscillations becomes increasingly intricate. We identify a range of parameters for which the time evolution of the order parameter become quasi chaotic. The details of the chaotic evolution depend on the type of perturbation used. Therefore it is plausible to expect that it is possible to engineer a perturbation that leads to the almost complete destruction of the oscillating pattern and consequently to quasi equilibration induced by superposition of modes with different frequencies

A consideration on physical tuning for acoustical coloration in recording studio

Science.gov (United States)

Shimizu, Yasushi

2003-04-01

Coloration due to particular architectural shapes and dimension or less surface absorption has been mentioned as an acoustical defect in recording studio. Generally interference among early reflected sounds arriving within 10 ms in delay after the direct sound produces coloration by comb filter effect over mid- and high-frequency sounds. In addition, less absorbed room resonance modes also have been well known as a major component for coloration in low-frequency sounds. Small size in dimension with recording studio, however, creates difficulty in characterization associated with wave acoustics behavior, that make acoustical optimization more difficult than that of concert hall acoustics. There still remains difficulty in evaluating amount of coloration as well as predicting its acoustical characteristics in acoustical modeling and in other words acoustical tuning technique during construction is regarded as important to optimize acoustics appropriately to the function of recording studio. This paper presents a example of coloration by comb filtering effect and less damped room modes in typical post-processing recording studio. And acoustical design and measurement technique will be presented for adjusting timbre due to coloration based on psycho-acoustical performance with binaural hearing and room resonance control with line array resonator adjusted to the particular room modes considered.

Thermo-acoustic instabilities in lean premixed swirl-stabilized combustion and their link to acoustically coupled and decoupled flame macrostructures

KAUST Repository

Taamallah, Soufien

2015-01-01

© 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved. We investigate the onset of thermo-acoustic instabilities and their link to the mean flame configurations - or macrostructures - under acoustically coupled and decoupled conditions. Methane-hydrogen mixtures are used to explore the role of the fuel in changing the flame macrostructure, as determined by chemilumi-nescence, as the equivalence ratio (φ) varies. We observe four different configurations: a columnar flame (I); a bubble-columnar flame (II); a single conical flame (III); and a double conical flame (IV). We also observe different thermo-acoustic modes in the lean regime investigated, φ ∈ [0.5-0.75], that correspond to different flame configurations. By changing the combustor length without affecting the underlying flow, the resonant modes of the combustor are shifted to higher frequencies allowing for the decoupling of heat release fluctuations and the acoustic field over a range of equivalence ratio. We find that the same flame macrostructures observed in the long, acoustically coupled combustor arise in the short, acoustically decoupled combustor and transition at similar equivalence ratios in both combustors. The onset of the first fully unstable mode in the long combustor occurs at similar equivalence ratio as the flame transition from configuration III to IV. In the acoustically decoupled case, this transition occurs gradually starting with the intermittent appearance of a flame in the outer recirculation zone (ORZ). Spectral analysis of this phenomenon, referred to as "ORZ flame flickering" shows the existence of an unsteady event occurring over a narrow frequency band centered around 28 Hz along with a weaker broadband region at lower frequency in the range [1-10] Hz. The tone at 28 Hz is shown to be associated with the azimuthal advection of the flame by the outer recirculation zone flow. Changes in the fuel composition, by adding hydrogen (up to 20%), do not

Controlling the acoustic streaming by pulsed ultrasounds.

Science.gov (United States)

Hoyos, Mauricio; Castro, Angélica

2013-01-01

We propose a technique based on pulsed ultrasounds for controlling, reducing to a minimum observable value the acoustic streaming in closed ultrasonic standing wave fluidic resonators. By modifying the number of pulses and the repetition time it is possible to reduce the velocity of the acoustic streaming with respect to the velocity generated by the continuous ultrasound mode of operation. The acoustic streaming is observed at the nodal plane where a suspension of 800nm latex particles was focused by primary radiation force. A mixture of 800nm and 15μm latex particles has been also used for showing that the acoustic streaming is hardly reduced while primary and secondary forces continue to operate. The parameter we call "pulse mode factor" i.e. the time of applied ultrasound divided by the duty cycle, is found to be the adequate parameter that controls the acoustic streaming. We demonstrate that pulsed ultrasound is more efficient for controlling the acoustic streaming than the variation of the amplitude of the standing waves. Copyright © 2012 Elsevier B.V. All rights reserved.

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

Science.gov (United States)

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

1990-01-01

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

Time-dependent local-to-normal mode transition in triatomic molecules

Science.gov (United States)

Cruz, Hans; Bermúdez-Montaña, Marisol; Lemus, Renato

2018-01-01

Time-evolution of the vibrational states of two interacting harmonic oscillators in the local mode scheme is presented. A local-to-normal mode transition (LNT) is identified and studied from temporal perspective through time-dependent frequencies of the oscillators. The LNT is established as a polyad-breaking phenomenon from the local standpoint for the stretching degrees of freedom in a triatomic molecule. This study is carried out in the algebraic representation of bosonic operators. The dynamics of the states are determined via the solutions of the corresponding nonlinear Ermakov equation and a local time-dependent polyad is obtained as a tool to identify the LNT. Applications of this formalism to H2O, CO2, O3 and NO2 molecules in the adiabatic, sudden and linear regime are considered.

The acoustic environment in large HTGR's

International Nuclear Information System (INIS)

Burton, T.E.

1979-01-01

Well-known techniques for estimating acoustic vibration of structures have been applied to a General Atomic high-temperature gas-cooled reactor (HTGR) design. It is shown that one must evaluate internal loss factors for both fluid and structure modes, as well as radiation loss factors, to avoid large errors in estimated structural response. At any frequency above 1350 rad/s there are generally at least 20 acoustic modes contributing to acoustic pressure, so statistical energy analysis may be employed. But because the gas circuit consists mainly of high-aspect-ratio cavities, reverberant fields are nowhere isotropic below 7500 rad/s, and in some regions are not isotropic below 60 000 rad/s. In comparison with isotropic reverberant fields, these anistropic fields enhance the radiation efficiencies of some structural modes at low frequencies, but have surprisingly little effect at most frequencies. The efficiency of a dipole sound source depends upon its orientation. (Auth.)

A dual-mode hemispherical sparse array for 3D passive acoustic mapping and skull localization within a clinical MRI guided focused ultrasound device

Science.gov (United States)

Crake, Calum; Brinker, Spencer T.; Coviello, Christian M.; Livingstone, Margaret S.; McDannold, Nathan J.

2018-03-01

Previous work has demonstrated that passive acoustic imaging may be used alongside MRI for monitoring of focused ultrasound therapy. However, past implementations have generally made use of either linear arrays originally designed for diagnostic imaging or custom narrowband arrays specific to in-house therapeutic transducer designs, neither of which is fully compatible with clinical MR-guided focused ultrasound (MRgFUS) devices. Here we have designed an array which is suitable for use within an FDA-approved MR-guided transcranial focused ultrasound device, within the bore of a 3 Tesla clinical MRI scanner. The array is constructed from 5  ×  0.4 mm piezoceramic disc elements arranged in pseudorandom fashion on a low-profile laser-cut acrylic frame designed to fit between the therapeutic elements of a 230 kHz InSightec ExAblate 4000 transducer. By exploiting thickness and radial resonance modes of the piezo discs the array is capable of both B-mode imaging at 5 MHz for skull localization, as well as passive reception at the second harmonic of the therapy array for detection of cavitation and 3D passive acoustic imaging. In active mode, the array was able to perform B-mode imaging of a human skull, showing the outer skull surface with good qualitative agreement with MR imaging. Extension to 3D showed the array was able to locate the skull within  ±2 mm/2° of reference points derived from MRI, which could potentially allow registration of a patient to the therapy system without the expense of real-time MRI. In passive mode, the array was able to resolve a point source in 3D within a  ±10 mm region about each axis from the focus, detect cavitation (SNR ~ 12 dB) at burst lengths from 10 cycles to continuous wave, and produce 3D acoustic maps in a flow phantom. Finally, the array was used to detect and map cavitation associated with microbubble activity in the brain in nonhuman primates.

A phylogenetic analysis of normal modes evolution in enzymes and its relationship to enzyme function.

Science.gov (United States)

Lai, Jason; Jin, Jing; Kubelka, Jan; Liberles, David A

2012-09-21

Since the dynamic nature of protein structures is essential for enzymatic function, it is expected that functional evolution can be inferred from the changes in protein dynamics. However, dynamics can also diverge neutrally with sequence substitution between enzymes without changes of function. In this study, a phylogenetic approach is implemented to explore the relationship between enzyme dynamics and function through evolutionary history. Protein dynamics are described by normal mode analysis based on a simplified harmonic potential force field applied to the reduced C(α) representation of the protein structure while enzymatic function is described by Enzyme Commission numbers. Similarity of the binding pocket dynamics at each branch of the protein family's phylogeny was analyzed in two ways: (1) explicitly by quantifying the normal mode overlap calculated for the reconstructed ancestral proteins at each end and (2) implicitly using a diffusion model to obtain the reconstructed lineage-specific changes in the normal modes. Both explicit and implicit ancestral reconstruction identified generally faster rates of change in dynamics compared with the expected change from neutral evolution at the branches of potential functional divergences for the α-amylase, D-isomer-specific 2-hydroxyacid dehydrogenase, and copper-containing amine oxidase protein families. Normal mode analysis added additional information over just comparing the RMSD of static structures. However, the branch-specific changes were not statistically significant compared to background function-independent neutral rates of change of dynamic properties and blind application of the analysis would not enable prediction of changes in enzyme specificity. Copyright © 2012 Elsevier Ltd. All rights reserved.

Predicting word-recognition performance in noise by young listeners with normal hearing using acoustic, phonetic, and lexical variables.

Science.gov (United States)

McArdle, Rachel; Wilson, Richard H

2008-06-01

To analyze the 50% correct recognition data that were from the Wilson et al (this issue) study and that were obtained from 24 listeners with normal hearing; also to examine whether acoustic, phonetic, or lexical variables can predict recognition performance for monosyllabic words presented in speech-spectrum noise. The specific variables are as follows: (a) acoustic variables (i.e., effective root-mean-square sound pressure level, duration), (b) phonetic variables (i.e., consonant features such as manner, place, and voicing for initial and final phonemes; vowel phonemes), and (c) lexical variables (i.e., word frequency, word familiarity, neighborhood density, neighborhood frequency). The descriptive, correlational study will examine the influence of acoustic, phonetic, and lexical variables on speech recognition in noise performance. Regression analysis demonstrated that 45% of the variance in the 50% point was accounted for by acoustic and phonetic variables whereas only 3% of the variance was accounted for by lexical variables. These findings suggest that monosyllabic word-recognition-in-noise is more dependent on bottom-up processing than on top-down processing. The results suggest that when speech-in-noise testing is used in a pre- and post-hearing-aid-fitting format, the use of monosyllabic words may be sensitive to changes in audibility resulting from amplification.

Scalar-gravitational perturbations and quasi normal modes in the five dimensional Schwarzschild black hole

International Nuclear Information System (INIS)

Cardoso, Vitor; Lemos, Jose P.S.; Yoshida, Shijun

2003-01-01

We calculate the quasi normal modes (QNMs) for gravitational perturbations of the Schwarzschild black hole in the five dimensional (5D) spacetime with a continued fraction method. For all the types of perturbations (scalar-gravitational, vector-gravitational, and tensor-gravitational perturbations), the QNMs associated with l = 2, l 3, and l = 4 are calculated. Our numerical results are summarized as follows: (i) The three types of gravitational perturbations associated with the same angular quantum number l have a different set of the quasi normal (QN) frequencies; (ii) There is no purely imaginary frequency mode; (iii) The three types of gravitational perturbations have the same asymptotic behavior of the QNMs in the limit of the large imaginary frequencies, which are given by ωT H -1 → log 3+ 2πi(n+1/2) as n → ∞, where ω, T H , and n are the oscillation frequency, the Hawking temperature of the black hole, and the mode number, respectively. (author)

Acoustic scaling: A re-evaluation of the acoustic model of Manchester Studio 7

Science.gov (United States)

Walker, R.

1984-12-01

The reasons for the reconstruction and re-evaluation of the acoustic scale mode of a large music studio are discussed. The design and construction of the model using mechanical and structural considerations rather than purely acoustic absorption criteria is described and the results obtained are given. The results confirm that structural elements within the studio gave rise to unexpected and unwanted low-frequency acoustic absorption. The results also show that at least for the relatively well understood mechanisms of sound energy absorption physical modelling of the structural and internal components gives an acoustically accurate scale model, within the usual tolerances of acoustic design. The poor reliability of measurements of acoustic absorption coefficients, is well illustrated. The conclusion is reached that such acoustic scale modelling is a valid and, for large scale projects, financially justifiable technique for predicting fundamental acoustic effects. It is not appropriate for the prediction of fine details because such small details are unlikely to be reproduced exactly at a different size without extensive measurements of the material's performance at both scales.

Evaluation of diaphragmatic motion in normal and diaphragmatic paralyzed dogs using M-mode ultrasonography.

Science.gov (United States)

Choi, Mihyun; Lee, Namsoon; Kim, Ahyoung; Keh, Seoyeon; Lee, Jinsoo; Kim, Hyunwook; Choi, Mincheol

2014-01-01

Diagnosis of unilateral diaphragmatic paralysis in dogs is currently based on fluoroscopic detection of unequal movement between the crura. Bilateral paralysis may be more difficult to confirm with fluoroscopy because diaphragmatic movement is sometimes produced by compensatory abdominal muscle contractions. The purpose of this study was to develop a new method to evaluate diaphragmatic movement using M-mode ultrasonography and to describe findings for normal and diaphragmatic paralyzed dogs. Fifty-five clinically normal dogs and two dogs with diaphragmatic paralysis were recruited. Thoracic radiographs were acquired for all dogs and fluoroscopy studies were also acquired for clinically affected dogs. Two observers independently measured diaphragmatic direction of motion and amplitude of excursion using M-mode ultrasonography for dogs meeting study inclusion criteria. Eight of the clinically normal dogs were excluded due to abnormal thoracic radiographic findings. For the remaining normal dogs, the lower limit values of diaphragmatic excursion were 2.85-2.98 mm during normal breathing. One dog with bilateral diaphragmatic paralysis showed paradoxical movement of both crura at the end of inspiration. One dog with unilateral diaphragmatic paralysis had diaphragmatic excursion values of 2.00 ± 0.42 mm on the left side and 4.05 ± 1.48 mm on the right side. The difference between left and right diaphragmatic excursion values was 55%. Findings indicated that M-mode ultrasonography is a relatively simple and objective method for measuring diaphragmatic movement in dogs. Future studies are needed in a larger number of dogs with diaphragmatic paralysis to determine the diagnostic sensitivity of this promising new technique. © 2013 American College of Veterinary Radiology.

Metamaterial based embedded acoustic filters for structural applications

Directory of Open Access Journals (Sweden)

Hongfei Zhu

2013-09-01

Full Text Available We investigate the use of acoustic metamaterials to design structural materials with frequency selective characteristics. By exploiting the properties of acoustic metamaterials, we tailor the propagation characteristics of the host structure to effectively filter the constitutive harmonics of an incoming broadband excitation. The design approach exploits the characteristics of acoustic waveguides coupled by cavity modes. By properly designing the cavity we can tune the corresponding resonant mode and, therefore, coupling the waveguide at a prescribed frequency. This structural design can open new directions to develop broadband passive vibrations and noise control systems fully integrated in structural components.

Acoustically induced transparency using Fano resonant periodic arrays

KAUST Repository

El-Amin, Mohamed

2015-10-22

A three-dimensional acoustic device, which supports Fano resonance and induced transparency in its response to an incident sound wave, is designed and fabricated. These effects are generated from the destructive interference of closely coupled one broad- and one narrow-band acoustic modes. The proposed design ensures excitation and interference of two spectrally close modes by locating a small pipe inside a wider and longer one. Indeed, numerical simulations and experiments demonstrate that this simple-to-fabricate structure can be used to generate Fano resonance as well as acoustically induced transparency with promising applications in sensing, cloaking, and imaging.

Acoustically induced transparency using Fano resonant periodic arrays

KAUST Repository

El-Amin, Mohamed; Elayouch, A.; Farhat, Mohamed; Addouche, M.; Khelif, A.; Bagci, Hakan

2015-01-01

A three-dimensional acoustic device, which supports Fano resonance and induced transparency in its response to an incident sound wave, is designed and fabricated. These effects are generated from the destructive interference of closely coupled one broad- and one narrow-band acoustic modes. The proposed design ensures excitation and interference of two spectrally close modes by locating a small pipe inside a wider and longer one. Indeed, numerical simulations and experiments demonstrate that this simple-to-fabricate structure can be used to generate Fano resonance as well as acoustically induced transparency with promising applications in sensing, cloaking, and imaging.

Tailoring light-sound interactions in a single mode fiber for the high-power transmission or sensing applications

Science.gov (United States)

Gulistan, Aamir; Rahman, M. M.; Ghosh, Souvik; Rahman, B. M. A.

2018-03-01

A full-vectorial numerically efficient Finite Element Method (FEM) based computer code is developed to study complex light-sound interactions in a single mode fiber (SMF). The SBS gain or SBS threshold in a fiber is highly related to the overlap between the optical and acoustic modes. For a typical SMF the acoustic-optic overlap strongly depends on the optical and acoustic mode profiles and it is observed that the acoustic mode is more confined in the core than the optical mode and reported overlap is around 94 % between these fundamental optical and acoustic modes. However, it is shown here that selective co-doping of Aluminum and Germanium in core reduces the acoustic index while keeping the optical index of the same value and thus results in increased acoustic- optic overlap of 99.7%. On the other hand, a design of acoustic anti-guide fiber for high-power transmission systems is also proposed, where the overlap between acoustic and optical modes is reduced. Here, we show that by keeping the optical properties same as a standard SMF and introducing a Boron doped 2nd layer in the cladding, a very low value of 2.7% overlap is achieved. Boron doping in cladding 2nd layer results in a high acoustic index and acoustic modes shifts in the cladding from the core, allowing much high power delivery through this SMF.

NOMAD-Ref: visualization, deformation and refinement of macromolecular structures based on all-atom normal mode analysis.

Science.gov (United States)

Lindahl, Erik; Azuara, Cyril; Koehl, Patrice; Delarue, Marc

2006-07-01

Normal mode analysis (NMA) is an efficient way to study collective motions in biomolecules that bypasses the computational costs and many limitations associated with full dynamics simulations. The NOMAD-Ref web server presented here provides tools for online calculation of the normal modes of large molecules (up to 100,000 atoms) maintaining a full all-atom representation of their structures, as well as access to a number of programs that utilize these collective motions for deformation and refinement of biomolecular structures. Applications include the generation of sets of decoys with correct stereochemistry but arbitrary large amplitude movements, the quantification of the overlap between alternative conformations of a molecule, refinement of structures against experimental data, such as X-ray diffraction structure factors or Cryo-EM maps and optimization of docked complexes by modeling receptor/ligand flexibility through normal mode motions. The server can be accessed at the URL http://lorentz.immstr.pasteur.fr/nomad-ref.php.

Design of the Acoustic Signal Receiving Unit of Acoustic Telemetry While Drilling

Directory of Open Access Journals (Sweden)

Li Zhigang

2016-01-01

Full Text Available Signal receiving unit is one of the core units of the acoustic telemetry system. A new type of acoustic signal receiving unit is designed to solve problems of the existing devices. The unit is a short joint in whole. It not only can receive all the acoustic signals transmitted along the drill string, without losing any signal, but will not bring additional vibration and interference. In addition, the structure of the amplitude transformer is designed, which can amplify the signal amplitude and improve the receiving efficiency. The design of the wireless communication module makes the whole device can be used in normal drilling process when the drill string is rotating. So, it does not interfere with the normal drilling operation.

Digital PIV Measurements of Acoustic Particle Displacements in a Normal Incidence Impedance Tube

Science.gov (United States)

Humphreys, William M., Jr.; Bartram, Scott M.; Parrott, Tony L.; Jones, Michael G.

1998-01-01

Acoustic particle displacements and velocities inside a normal incidence impedance tube have been successfully measured for a variety of pure tone sound fields using Digital Particle Image Velocimetry (DPIV). The DPIV system utilized two 600-mj Nd:YAG lasers to generate a double-pulsed light sheet synchronized with the sound field and used to illuminate a portion of the oscillatory flow inside the tube. A high resolution (1320 x 1035 pixel), 8-bit camera was used to capture double-exposed images of 2.7-micron hollow silicon dioxide tracer particles inside the tube. Classical spatial autocorrelation analysis techniques were used to ascertain the acoustic particle displacements and associated velocities for various sound field intensities and frequencies. The results show that particle displacements spanning a range of 1-60 microns can be measured for incident sound pressure levels of 100-130 dB and for frequencies spanning 500-1000 Hz. The ability to resolve 1 micron particle displacements at sound pressure levels in the 100 dB range allows the use of DPIV systems for measurement of sound fields at much lower sound pressure levels than had been previously possible. Representative impedance tube data as well as an uncertainty analysis for the measurements are presented.

Acoustic levitation in the presence of gravity

Science.gov (United States)

Collas, P.; Barmatz, M.; Shipley, C.

1989-01-01

The method of Gor'kov (1961) has been applied to derive general expressions for the total potential and force on a small spherical object in a resonant chamber in the presence of both acoustic and gravitational force fields. The levitation position is also determined in rectangular resonators for the simultaneous excitation of up to three acoustic modes, and the results are applied to the triple-axis acoustic levitator. The analysis is applied to rectangular, spherical, and cylindrical single-mode levitators that are arbitrarily oriented relative to the gravitational force field. Criteria are determined for isotropic force fields in rectangular and cylindrical resonators. It is demonstrated that an object will be situated within a volume of possible levitation positions at a point determined by the relative strength of the acoustic and gravitational fields and the orientation of the chamber relative to gravity.

Effects of plasma current on nonlinear interactions of ITG turbulence, zonal flows and geodesic acoustic modes

International Nuclear Information System (INIS)

Angelino, P; Bottino, A; Hatzky, R; Jolliet, S; Sauter, O; Tran, T M; Villard, L

2006-01-01

The mutual interactions of ion temperature gradient (ITG) driven modes, zonal flows and geodesic acoustic modes (GAM) in tokamak plasmas are investigated using a global nonlinear gyrokinetic formulation with totally unconstrained evolution of temperature gradient and profile. A series of numerical simulations with the same initial temperature and density profile specifications is performed using a sequence of ideal MHD equilibria differing only in the value of the total plasma current, in particular with identical magnetic shear profiles and shapes of magnetic surfaces. On top of a bursty or quasi-steady state behaviour the zonal flows oscillate at the GAM frequency. The amplitude of these oscillations increases with the value of the safety factor q, resulting in a less effective suppression of ITG turbulence by zonal flows at a lower plasma current. The turbulence-driven volume-averaged radial heat transport is found to scale inversely with the total plasma current

Non-leaky modes and bandgaps of surface acoustic waves in wrinkled stiff-film/compliant-substrate bilayers

Science.gov (United States)

Li, Guo-Yang; Xu, Guoqiang; Zheng, Yang; Cao, Yanping

2018-03-01

Surface acoustic wave (SAW) devices have found a wide variety of technical applications, including SAW filters, SAW resonators, microfluidic actuators, biosensors, flow measurement devices, and seismic wave shields. Stretchable/flexible electronic devices, such as sensory skins for robotics, structural health monitors, and wearable communication devices, have received considerable attention across different disciplines. Flexible SAW devices are essential building blocks for these applications, wherein piezoelectric films may need to be integrated with the compliant substrates. When piezoelectric films are much stiffer than soft substrates, SAWs are usually leaky and the devices incorporating them suffer from acoustic losses. In this study, the propagation of SAWs in a wrinkled bilayer system is investigated, and our analysis shows that non-leaky modes can be achieved by engineering stress patterns through surface wrinkles in the system. Our analysis also uncovers intriguing bandgaps (BGs) related to the SAWs in a wrinkled bilayer system; these are caused by periodic deformation patterns, which indicate that diverse wrinkling patterns could be used as metasurfaces for controlling the propagation of SAWs.

Masking release with changing fundamental frequency: Electric acoustic stimulation resembles normal hearing subjects.

Science.gov (United States)

Auinger, Alice Barbara; Riss, Dominik; Liepins, Rudolfs; Rader, Tobias; Keck, Tilman; Keintzel, Thomas; Kaider, Alexandra; Baumgartner, Wolf-Dieter; Gstoettner, Wolfgang; Arnoldner, Christoph

2017-07-01

It has been shown that patients with electric acoustic stimulation (EAS) perform better in noisy environments than patients with a cochlear implant (CI). One reason for this could be the preserved access to acoustic low-frequency cues including the fundamental frequency (F0). Therefore, our primary aim was to investigate whether users of EAS experience a release from masking with increasing F0 difference between target talker and masking talker. The study comprised 29 patients and consisted of three groups of subjects: EAS users, CI users and normal-hearing listeners (NH). All CI and EAS users were implanted with a MED-EL cochlear implant and had at least 12 months of experience with the implant. Speech perception was assessed with the Oldenburg sentence test (OlSa) using one sentence from the test corpus as speech masker. The F0 in this masking sentence was shifted upwards by 4, 8, or 12 semitones. For each of these masker conditions the speech reception threshold (SRT) was assessed by adaptively varying the masker level while presenting the target sentences at a fixed level. A statistically significant improvement in speech perception was found for increasing difference in F0 between target sentence and masker sentence in EAS users (p = 0.038) and in NH listeners (p = 0.003). In CI users (classic CI or EAS users with electrical stimulation only) speech perception was independent from differences in F0 between target and masker. A release from masking with increasing difference in F0 between target and masking speech was only observed in listeners and configurations in which the low-frequency region was presented acoustically. Thus, the speech information contained in the low frequencies seems to be crucial for allowing listeners to separate multiple sources. By combining acoustic and electric information, EAS users even manage tasks as complicated as segregating the audio streams from multiple talkers. Preserving the natural code, like fine-structure cues in

Guided acoustic wave inspection system

Science.gov (United States)

Chinn, Diane J.

2004-10-05

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

On Kinetic Slow Modes, Fluid Slow Modes, and Pressure-balanced Structures in the Solar Wind

Energy Technology Data Exchange (ETDEWEB)

Verscharen, Daniel [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States); Chen, Christopher H. K. [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Wicks, Robert T., E-mail: daniel.verscharen@unh.edu, E-mail: christopher.chen@imperial.ac.uk, E-mail: r.wicks@ucl.ac.uk [Mullard Space Science Laboratory, University College London, London WC1E 6BT (United Kingdom)

2017-05-10

Observations in the solar wind suggest that the compressive component of inertial-range solar-wind turbulence is dominated by slow modes. The low collisionality of the solar wind allows for nonthermal features to survive, which suggests the requirement of a kinetic plasma description. The least-damped kinetic slow mode is associated with the ion-acoustic (IA) wave and a nonpropagating (NP) mode. We derive analytical expressions for the IA-wave dispersion relation in an anisotropic plasma in the framework of gyrokinetics and then compare them to fully kinetic numerical calculations, results from two-fluid theory, and magnetohydrodynamics (MHD). This comparison shows major discrepancies in the predicted wave phase speeds from MHD and kinetic theory at moderate to high β . MHD and kinetic theory also dictate that all plasma normal modes exhibit a unique signature in terms of their polarization. We quantify the relative amplitude of fluctuations in the three lowest particle velocity moments associated with IA and NP modes in the gyrokinetic limit and compare these predictions with MHD results and in situ observations of the solar-wind turbulence. The agreement between the observations of the wave polarization and our MHD predictions is better than the kinetic predictions, which suggests that the plasma behaves more like a fluid in the solar wind than expected.

On Kinetic Slow Modes, Fluid Slow Modes, and Pressure-balanced Structures in the Solar Wind

International Nuclear Information System (INIS)

Verscharen, Daniel; Chen, Christopher H. K.; Wicks, Robert T.

2017-01-01

Observations in the solar wind suggest that the compressive component of inertial-range solar-wind turbulence is dominated by slow modes. The low collisionality of the solar wind allows for nonthermal features to survive, which suggests the requirement of a kinetic plasma description. The least-damped kinetic slow mode is associated with the ion-acoustic (IA) wave and a nonpropagating (NP) mode. We derive analytical expressions for the IA-wave dispersion relation in an anisotropic plasma in the framework of gyrokinetics and then compare them to fully kinetic numerical calculations, results from two-fluid theory, and magnetohydrodynamics (MHD). This comparison shows major discrepancies in the predicted wave phase speeds from MHD and kinetic theory at moderate to high β . MHD and kinetic theory also dictate that all plasma normal modes exhibit a unique signature in terms of their polarization. We quantify the relative amplitude of fluctuations in the three lowest particle velocity moments associated with IA and NP modes in the gyrokinetic limit and compare these predictions with MHD results and in situ observations of the solar-wind turbulence. The agreement between the observations of the wave polarization and our MHD predictions is better than the kinetic predictions, which suggests that the plasma behaves more like a fluid in the solar wind than expected.

Electrostatic ion acoustic waves

International Nuclear Information System (INIS)

Hasegawa, A.

1983-01-01

In this paper, certain aspects of plasma physics are illustrated through a study of electrostatic ion acoustic waves. The paper consists of three Sections. Section II deals with linear properties of the ion acoustic wave including derivation of the dispersions relation with the effect of Landau damping and of an ambient magnetic field. The section also introduces the excitation processes of the ion acoustic wave due to an electron drift or to a stimulated Brillouin scattering. The nonlinear properties are introduced in Section III and IV. In Section III, incoherent nonlinear effects such as quasilinear and mode-coupling saturations of the instability are discussed. The coherent nonlinear effects such as the generation of ion acoustic solitons, shocks and weak double layers are presented in Section IV. (Auth.)

A New Normal Form for Multidimensional Mode Conversion

International Nuclear Information System (INIS)

Tracy, E. R.; Richardson, A. S.; Kaufman, A. N.; Zobin, N.

2007-01-01

Linear conversion occurs when two wave types, with distinct polarization and dispersion characteristics, are locally resonant in a nonuniform plasma [1]. In recent work, we have shown how to incorporate a ray-based (WKB) approach to mode conversion in numerical algorithms [2,3]. The method uses the ray geometry in the conversion region to guide the reduction of the full NxN-system of wave equations to a 2x2 coupled pair which can be solved and matched to the incoming and outgoing WKB solutions. The algorithm in [2] assumes the ray geometry is hyperbolic and that, in ray phase space, there is an 'avoided crossing', which is the most common type of conversion. Here, we present a new formulation that can deal with more general types of conversion [4]. This formalism is based upon the fact (first proved in [5]) that it is always possible to put the 2x2 wave equation into a 'normal' form, such that the diagonal elements of the dispersion matrix Poisson-commute with the off-diagonals (at leading order). Therefore, if we use the diagonals (rather than the eigenvalues or the determinant) of the dispersion matrix as ray Hamiltonians, the off-diagonals will be conserved quantities. When cast into normal form, the 2x2 dispersion matrix has a very natural physical interpretation: the diagonals are the uncoupled ray hamiltonians and the off-diagonals are the coupling. We discuss how to incorporate the normal form into ray tracing algorithms

Coherent scattering of CO2 light from ion-acoustic waves

International Nuclear Information System (INIS)

Peratt, A.L.; Watterson, R.L.; Derfler, H.

1977-01-01

Scattering of laser radiation from ion-acoustic waves in a plasma is investigated analytically and experimentally. The formulation predicts a coherent component of the scattered power on a largely incoherent background spectrum when the acoustic analog of Bragg's law and Doppler shift conditions are satisfied. The experiment consists of a hybrid CO 2 laser system capable of either low power continuous wave or high power pulsed mode operation. A heterodyne light mixing scheme is used to detect the scattered power. The proportionality predicted by the theory is verified by scattering from externally excited acoustic and ion-acoustic waves; continuous wave and pulsed modes in each case. Measurement of the ion-acoustic dispersion relation by continuous wave scattering is also presented

Modal analysis and cut-off conditions of multichannel surface-acoustic-waveguide structures.

Science.gov (United States)

Griffel, G; Golan, G; Ruschin, S; Seidman, A; Croitoru, N

1988-01-01

Multichannel guides for surface acoustic waves can improve the efficiency of SAW (surface acoustic-wave) devices significantly. Focusing, steering, and modulating the propagating acoustical modes can be achieved similarly to optical waveguided devices. A general formulation is presented for the analysis of the lateral waveguiding properties of Rayleigh modes in surfaces loaded with deposited strips of different materials. General expressions are obtained for the number of modes and cutoff conditions in these structures. As examples of applications, a simple directional coupler and an electrically controlled coupler are proposed.

Extraordinary acoustic transmission through annuluses in air and its applications in acoustic beam splitter and concentrator

International Nuclear Information System (INIS)

Ge, Yong; Liu, Shu-sen; Yuan, Shou-qi; Xia, Jian-ping; Guan, Yi-jun; Sun, Hong-xiang; Zhang, Shu-yi

2016-01-01

We report an extraordinary acoustic transmission through two layer annuluses made of metal cylinders in air both numerically and experimentally. The effect arises from the enhancement and reconstruction of the incident source induced by different Mie-resonance modes of the annuluses. The proposed system takes advantages of the consistency in the waveform between the input and output waves, the high amplitude amplification of output waves, and the easy adjustment of structure. More interestingly, we investigate the applications of the extraordinary acoustic transmission in the acoustic beam splitter and acoustic concentrator. Our finding should have an impact on ultrasonic applications.

Identification of surface species by vibrational normal mode analysis. A DFT study

Science.gov (United States)

Zhao, Zhi-Jian; Genest, Alexander; Rösch, Notker

2017-10-01

Infrared spectroscopy is an important experimental tool for identifying molecular species adsorbed on a metal surface that can be used in situ. Often vibrational modes in such IR spectra of surface species are assigned and identified by comparison with vibrational spectra of related (molecular) compounds of known structure, e. g., an organometallic cluster analogue. To check the validity of this strategy, we carried out a computational study where we compared the normal modes of three C2Hx species (x = 3, 4) in two types of systems, as adsorbates on the Pt(111) surface and as ligands in an organometallic cluster compound. The results of our DFT calculations reproduce the experimental observed frequencies with deviations of at most 50 cm-1. However, the frequencies of the C2Hx species in both types of systems have to be interpreted with due caution if the coordination mode is unknown. The comparative identification strategy works satisfactorily when the coordination mode of the molecular species (ethylidyne) is similar on the surface and in the metal cluster. However, large shifts are encountered when the molecular species (vinyl) exhibits different coordination modes on both types of substrates.

Mechanical Seal Opening Condition Monitoring Based on Acoustic Emission Technology

Directory of Open Access Journals (Sweden)

Erqing Zhang

2014-06-01

Full Text Available Since the measurement of mechanical sealing film thickness and just-lift-off time is very difficult, the sealing film condition monitoring method based on acoustic emission signal is proposed. The mechanical seal acoustic emission signal present obvious characteristics of time-varying nonlinear and pulsating. In this paper, the acoustic emission signal is used to monitor the seal end faces just-lift-off time and friction condition. The acoustic emission signal is decomposed by empirical mode decomposition into a series of intrinsic mode function with independent characteristics of different time scales and different frequency band. The acoustic emission signal only generated by end faces friction is obtained by eliminating the false intrinsic mode function components. The correlation coefficient of acoustic emission signal and Multi-scale Laplace Wavelet is calculated. It is proved that the maximum frequency (8000 Hz of the correlation coefficient is appeared at the spindle speed of 300 rpm. And at this time (300 rpm the end faces have just lifted off. By a set of mechanical oil seal running test, it is demonstrated that this method could accurately identify mechanical seal end faces just-lift-off time and friction condition.

Parametric and Wavelet Analyses of Acoustic Emission Signals for the Identification of Failure Modes in CFRP Composites Using PZT and PVDF Sensors

Energy Technology Data Exchange (ETDEWEB)

Prasopchaichana, Kritsada; Kwon, Oh Yang [Inha University, Incheon (Korea, Republic of)

2007-12-15

Combination of the parametric and the wavelet analyses of acoustic emission (AE) signals was applied to identify the failure modes in carbon fiber reinforced plastic (CFRP) composite laminates during tensile testing. AE signals detected by surface mounted lead-zirconate-titanate (PZT) and polyvinylidene fluoride (PVDF) sensors were analyzed by parametric analysis based on the time of occurrence which classifies AE signals corresponding to failure modes. The frequency band level-energy analysis can distinguish the dominant frequency band for each failure mode. It was observed that the same type of failure mechanism produced signals with different characteristics depending on the stacking sequences and the type of sensors. This indicates that the proposed method can identify the failure modes of the signals if the stacking sequences and the sensors used are known

VLP seismicity from resonant modes of acoustic-gravity waves in a conduit-crack system filled with multiphase magma

Science.gov (United States)

Liang, C.; Prochnow, B. N.; OReilly, O. J.; Dunham, E. M.; Karlstrom, L.

2016-12-01

Oscillation of magma in volcanic conduits connected to cracks (dikes and sills) has been suggested as an explanation for very long period (VLP) seismic signals recorded at active basaltic volcanoes such as. Kilauea, Hawaii, and Erebus, Antarctica. We investigate the VLP seismicity using a linearized model for waves in and associated eigenmodes of a coupled conduit-crack system filled with multiphase magma, an extension of the Karlstrom and Dunham (2016) model for acoustic-gravity waves in volcanic conduits. We find that the long period surface displacement (as recorded on broadband seismometers) is dominated by opening/closing of the crack rather than the deformation of the conduit conduit walls. While the fundamental eigenmode is sensitive to the fluid properties and the geometry of the magma plumbing system, a closer scrutiny of various resonant modes reveals that the surface displacement is often more sensitive to higher modes. Here we present a systematic analysis of various long period acoustic-gravity wave resonant modes of a coupled conduit-crack system that the surface displacement is most sensitive to. We extend our previous work on a quasi-one-dimensional conduit model with inviscid magma to a more general axisymmetric conduit model that properly accounts for viscous boundary layers near the conduit walls, based on the numerical method developed by Prochnow et al. (submitted to Computers and Fluids, 2016). The surface displacement is dominated by either the fundamental or higher eigenmodes, depending on magma properties and the geometry of conduit and crack. An examination of the energetics of these modes reveals the complex interplay of different restoring forces (magma compressibility in the conduit, gravity, and elasticity of the crack) driving the VLP oscillations. Both nonequilibrium bubble growth and resorption and viscosity contribute to the damping of VLP signals. Our models thus provide a means to infer properties of open-vent basaltic volcanoes

Root finding in the complex plane for seismo-acoustic propagation scenarios with Green's function solutions.

Science.gov (United States)

McCollom, Brittany A; Collis, Jon M

2014-09-01

A normal mode solution to the ocean acoustic problem of the Pekeris waveguide with an elastic bottom using a Green's function formulation for a compressional wave point source is considered. Analytic solutions to these types of waveguide propagation problems are strongly dependent on the eigenvalues of the problem; these eigenvalues represent horizontal wavenumbers, corresponding to propagating modes of energy. The eigenvalues arise as singularities in the inverse Hankel transform integral and are specified by roots to a characteristic equation. These roots manifest themselves as poles in the inverse transform integral and can be both subtle and difficult to determine. Following methods previously developed [S. Ivansson et al., J. Sound Vib. 161 (1993)], a root finding routine has been implemented using the argument principle. Using the roots to the characteristic equation in the Green's function formulation, full-field solutions are calculated for scenarios where an acoustic source lies in either the water column or elastic half space. Solutions are benchmarked against laboratory data and existing numerical solutions.

Rabi splitting in an acoustic cavity embedded plate

International Nuclear Information System (INIS)

Ni, Xu; Liu, Xiao-Ping; Chen, Ze-Guo; Zheng, Li-Yang; Xu, Ye-Long; Lu, Ming-Hui; Chen, Yan-Feng

2014-01-01

We design a structure to realize Rabi splitting and Rabi oscillation in acoustics. We develop rigorous analytical models to analyze the splitting effect from the aspect of phase matching, and from the aspect of mode coupling using a coupled mode model. In this model, we discover that the splitting effect is caused by the coupling of the Fabry–Perot fundamental mode with the resonant mode of an artificial acoustic ‘atom’. We then extract the coupling strength and analyze the impact of structural parameters on it. In addition, we demonstrate Rabi oscillation in the time domain. Such quantum phenomena in the classical regime may have potential applications in the design of novel ultrasonic devices.

Acoustic heating produced in the thermoviscous flow of a Bingham plastic

Science.gov (United States)

Perelomova, Anna

2011-02-01

This study is devoted to the instantaneous acoustic heating of a Bingham plastic. The model of the Bingham plastic's viscous stress tensor includes the yield stress along with the shear viscosity, which differentiates a Bingham plastic from a viscous Newtonian fluid. A special linear combination of the conservation equations in differential form makes it possible to reduce all acoustic terms in the linear part of of the final equation governing acoustic heating, and to retain those belonging to the thermal mode. The nonlinear terms of the final equation are a result of interaction between sounds and the thermal mode. In the field of intense sound, the resulting nonlinear acoustic terms form a driving force for the heating. The final governing dynamic equation of the thermal mode is valid in a weakly nonlinear flow. It is instantaneous, and does not imply that sounds be periodic. The equations governing the dynamics of both sounds and the thermal mode depend on sign of the shear rate. An example of the propagation of a bipolar initially acoustic pulse and the evolution of the heating induced by it is illustrated and discussed.

Geodesic acoustic mode driven by energetic particles with bump-on-tail distribution

Science.gov (United States)

Ren, Haijun; Wang, Hao

2018-04-01

Energetic-particle-driven geodesic acoustic mode (EGAM) is analytically investigated by adopting the bump-on-tail distribution for energetic particles (EPs), which is created by the fact that the charge exchange time (τcx ) is sufficiently shorter than the slowing down time (τsl ). The dispersion relation is derived in the use of gyro-kinetic equations. Due to the finite ratio of the critical energy and the initial energy of EPs, defined as τc , the dispersion relation is numerically evaluated and the effect of finite τc is examined. Following relative simulation and experimental work, we specifically considered two cases: τsl/τcx = 3.4 and τsl/τcx = 20.4 . The pitch angle is shown to significantly enhance the growth rate and meanwhile, the real frequency is dramatically decreased with increasing pitch angle. The excitation of high-frequency EGAM is found, and this is consistent with both the experiment and the simulation. The number density effect of energetic particles, represented by \

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

Science.gov (United States)

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

2013-11-01

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

Acoustic-wave sensor for ambient monitoring of a photoresist-stripping agent

Science.gov (United States)

Pfeifer, K.B.; Hoyt, A.E.; Frye, G.C.

1998-08-18

The acoustic-wave sensor is disclosed. The acoustic-wave sensor is designed for ambient or vapor-phase monitoring of a photoresist-stripping agent such as N-methylpyrrolidinone (NMP), ethoxyethylpropionate (EEP) or the like. The acoustic-wave sensor comprises an acoustic-wave device such as a surface-acoustic-wave (SAW) device, a flexural-plate-wave (FPW) device, an acoustic-plate-mode (APM) device, or a thickness-shear-mode (TSM) device (also termed a quartz crystal microbalance or QCM) having a sensing region on a surface thereof. The sensing region includes a sensing film for sorbing a quantity of the photoresist-stripping agent, thereby altering or shifting a frequency of oscillation of an acoustic wave propagating through the sensing region for indicating an ambient concentration of the agent. According to preferred embodiments of the invention, the acoustic-wave device is a SAW device; and the sensing film comprises poly(vinylacetate), poly(N-vinylpyrrolidinone), or poly(vinylphenol). 3 figs.

Acoustic-hydrodynamic-flame coupling—A new perspective for zero and low Mach number flows

Science.gov (United States)

Pulikkottil, V. V.; Sujith, R. I.

2017-04-01

A combustion chamber has a hydrodynamic field that convects the incoming fuel and oxidizer into the chamber, thereby causing the mixture to react and produce heat energy. This heat energy can, in turn, modify the hydrodynamic and acoustic fields by acting as a source and thereby, establish a positive feedback loop. Subsequent growth in the amplitude of the acoustic field variables and their eventual saturation to a limit cycle is generally known as thermo-acoustic instability. Mathematical representation of these phenomena, by a set of equations, is the subject of this paper. In contrast to the ad hoc models, an explanation of the flame-acoustic-hydrodynamic coupling, based on fundamental laws of conservation of mass, momentum, and energy, is presented in this paper. In this paper, we use a convection reaction diffusion equation, which, in turn, is derived from the fundamental laws of conservation to explain the flame-acoustic coupling. The advantage of this approach is that the physical variables such as hydrodynamic velocity and heat release rate are coupled based on the conservation of energy and not based on an ad hoc model. Our approach shows that the acoustic-hydrodynamic interaction arises from the convection of acoustic velocity fluctuations by the hydrodynamic field and vice versa. This is a linear mechanism, mathematically represented as a convection operator. This mechanism resembles the non-normal mechanism studied in hydrodynamic theory. We propose that this mechanism could relate the instability mechanisms of hydrodynamic and thermo-acoustic systems. Furthermore, the acoustic-hydrodynamic interaction is shown to be responsible for the convection of entropy disturbances from the inlet of the chamber. The theory proposed in this paper also unifies the observations in the fields of low Mach number flows and zero Mach number flows. In contrast to the previous findings, where compressibility is shown to be causing different physics for zero and low Mach

Novel types of surface acoustic wave microreflectors - Performance analysis and simulations

Science.gov (United States)

Golan, G.; Griffel, G.; Seidman, A.; Croitoru, N.

1990-06-01

Surface acoustic waves for micrograting reflectors have been characterized. Based on the perturbation theory, eight different types of structures on an acoustic waveguide were analyzed. Results of simulations of all eight types of corrugation structures were evaluated in order to find the least leaky waveguide, the most efficient reflector (with minimum necessary perturbations), and the optimal mode shape for improved performances. General design curves are presented in order to illustrate the behavior of the incident and reflected waves under a variety of structural conditions. Analytic expressions for the calculations of the mode amplitude and mode shape, and for general acoustic corrugations are derived and then the simulations results are presented.

Acoustic reflex measurements and the loudness function in sensorineural hearing loss

Directory of Open Access Journals (Sweden)

Sheila Uliel

1980-11-01

Full Text Available The suprathreshold acoustic reflex responses of forty two ears affected by sensorineural hearing loss of cochlear origin and fifty-eight ears demonstrating normal hearing, were recorded by means of an electro-acoustic impedance meter and attached X-Y recorder. The recordings were done in ascending and descending fashion,  at successively increasing and decreasing 5dB intensity levels from 90-120-90 dB HL respectively, for the individual pure-tone frequencies of 500, 1 000, 2 000 and 4 000 Hz. The contralateral mode of measurement was employed. Analysis of  these recordings indicated that the acoustic reflex  responses could be differentiated into five  characteristic patterns of  growth, which could be depicted upon a continuum of peaked, peaked-rounded, rounded, rounded-flat,  and flat  shapes. The peaked and peaked-rounded patterns were found  to predominate at all four pure-tone frequencies  in the normal ears, while the rounded-fiat  and flat  patterns were found  to predominate only at the higher pure-tone frequencies of 2 000 and 4 000 Hz in the ears affected  by sensorineural hearing loss. This latter relationship was also able to be applied to two disorders of  the loudness functio— loudness recruitment and hyperacusis. It was concluded that the flattened  acoustic reflex  patterns at the higher pure-tone frequencies  constituted a potential diagnostic cue related to the differential  diagnosis of sensorineural hearing loss, and to disorders of  the loudness function.

Hemispherical breathing mode speaker using a dielectric elastomer actuator.

Science.gov (United States)

Hosoya, Naoki; Baba, Shun; Maeda, Shingo

2015-10-01

Although indoor acoustic characteristics should ideally be assessed by measuring the reverberation time using a point sound source, a regular polyhedron loudspeaker, which has multiple loudspeakers on a chassis, is typically used. However, such a configuration is not a point sound source if the size of the loudspeaker is large relative to the target sound field. This study investigates a small lightweight loudspeaker using a dielectric elastomer actuator vibrating in the breathing mode (the pulsating mode such as the expansion and contraction of a balloon). Acoustic testing with regard to repeatability, sound pressure, vibration mode profiles, and acoustic radiation patterns indicate that dielectric elastomer loudspeakers may be feasible.

Simulation and Optimization of Surface Acoustic Wave Devises

DEFF Research Database (Denmark)

Dühring, Maria Bayard

2007-01-01

In this paper a method to model the interaction of the mechanical field from a surface acoustic wave and the optical field in the waveguides of a Mach-Zehnder interferometer is presented. The surface acoustic waves are generated by interdigital transducers using a plane strain model...... in effective refractive index introduced in the Mach-Zehnder interferometer arms by the stresses from the surface acoustic wave is calculated. It is shown that the effective refractive index of the fundamental optical mode increases at a surface acoustic wave crest and decreases at a trough. The height...... of a piezoelectric, inhomogeneous material and reflections from the boundaries are avoided by applying perfectly matched layers. The optical modes in the waveguides are modeled by the time-harmonic wave equation for the magnetic field. The two models are coupled using the stress-optical relation and the change...

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

Science.gov (United States)

Rajabi, Majid; Behzad, Mehdi

2014-10-01

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

Twist–radial normal mode analysis in double-stranded DNA chains

International Nuclear Information System (INIS)

Torrellas, Germán; Maciá, Enrique

2012-01-01

We study the normal modes of a duplex DNA chain at low temperatures. We consider the coupling between the hydrogen-bond radial oscillations and the twisting motion of each base pair within the Peyrard–Bishop–Dauxois model. The coupling is mediated by the stacking interaction between adjacent base pairs along the helix. We explicitly consider different mass values for different nucleotides, extending previous works. We disclose several resonance conditions of interest, determined by the fine-tuning of certain model parameters. The role of these dynamical effects on the DNA chain charge transport properties is discussed.

Membrane-constrained acoustic metamaterials for low frequency sound insulation

Science.gov (United States)

Wang, Xiaole; Zhao, Hui; Luo, Xudong; Huang, Zhenyu

2016-01-01

We present a constrained membrane-type acoustic metamaterial (CMAM) that employs constraint sticks to add out-of-plane dimensions in the design space of MAM. A CMAM sample, which adopts constraint sticks to suppress vibrations at the membrane center, was fabricated to achieve a sound transmission loss (STL) peak of 26 dB at 140 Hz, with the static areal density of 6.0 kg/m2. The working mechanism of the CMAM as an acoustic metamaterial is elucidated by calculating the averaged normal displacement, the equivalent areal density, and the effective dynamic mass of a unit cell through finite element simulations. Furthermore, the vibration modes of the CMAM indicate that the eigenmodes related to STL dips are shifted into high frequencies, thus broadening its effective bandwidth significantly. Three samples possessing the same geometry and material but different constraint areas were fabricated to illustrate the tunability of STL peaks at low frequencies.

Numerical evaluation of acoustic characteristics and their damping of a thrust chamber using a constant-volume bomb model

Directory of Open Access Journals (Sweden)

Jianxiu QIN

2018-03-01

Full Text Available In order to numerically evaluate the acoustic characteristics of liquid rocket engine thrust chambers by means of a computational fluid dynamics method, a mathematical model of an artificial constant-volume bomb is proposed in this paper. A localized pressure pulse with a very high amplitude can be imposed on specified regions in a combustion chamber, the numerical procedure of which is described. Pressure oscillations actuated by the released constant-volume bomb can then be analyzed via Fast Fourier Transformation (FFT, and their modes can be identified according to the theoretical acoustic eigenfrequencies of the thrust chamber. The damping performances of the corresponding acoustic modes are evaluated by the half-power bandwidth method. The predicted acoustic characteristics and their damping for a special engine combustor agree well with the experimental data, validating the mathematical model and its numerical procedures. A small-thrust liquid rocket engine chamber is then analyzed by the present model. The First Longitudinal (1L acoustic mode can be excited easily and is hard to be damped. The axial position of the central constant-volume bomb has little influence on the amplitude and damping capacity of the First Radial (1R and 1L acoustic modes. Tangential acoustic modes can only be triggered by an off-centered constant-volume bomb, among which the First Tangential (1T mode is the strongest and regarded as the most harmful one. The amplitude of the 1L acoustic mode is smaller, but its damping factor is larger, as a constant-volume bomb is imposed approaching the injector face. These results are contributed to evaluate the acoustic characteristics and their damping of the combustion chamber. Keywords: Acoustic mode, Constant-volume bomb, Damping characteristics, Damping factor, Half-power bandwidth, Pressure oscillation

Model-free methods of analyzing domain motions in proteins from simulation : A comparison of normal mode analysis and molecular dynamics simulation of lysozyme

NARCIS (Netherlands)

Hayward, S.; Kitao, A.; Berendsen, H.J.C.

Model-free methods are introduced to determine quantities pertaining to protein domain motions from normal mode analyses and molecular dynamics simulations, For the normal mode analysis, the methods are based on the assumption that in low frequency modes, domain motions can be well approximated by

Surface acoustic load sensing using a face-shear PIN-PMN-PT single-crystal resonator.

Science.gov (United States)

Kim, Kyungrim; Zhang, Shujun; Jiang, Xiaoning

2012-11-01

Pb(In(0.5)Nb(0.5))O(3)-Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PIN-PMN-PT) resonators for surface acoustic load sensing are presented in this paper. Different acoustic loads are applied to thickness mode, thickness-shear mode, and face-shear mode resonators, and the electrical impedances at resonance and anti-resonance frequencies are recorded. More than one order of magnitude higher sensitivity (ratio of electrical impedance change to surface acoustic impedance change) at the resonance is achieved for the face-shear-mode resonator compared with other resonators with the same dimensions. The Krimholtz, Leedom, and Matthaei (KLM) model is used to verify the surface acoustic loading effect on the electrical impedance spectrum of face-shear PIN-PMN-PT single-crystal resonators. The demonstrated high sensitivity of face-shear mode resonators to surface loads is promising for a broad range of applications, including artificial skin, biological and chemical sensors, touch screens, and other touch-based sensors.

[Raman, FTIR spectra and normal mode analysis of acetanilide].

Science.gov (United States)

Liang, Hui-Qin; Tao, Ya-Ping; Han, Li-Gang; Han, Yun-Xia; Mo, Yu-Jun

2012-10-01

The Raman and FTIR spectra of acetanilide (ACN) were measured experimentally in the regions of 3 500-50 and 3 500-600 cm(-1) respectively. The equilibrium geometry and vibration frequencies of ACN were calculated based on density functional theory (DFT) method (B3LYP/6-311G(d, p)). The results showed that the theoretical calculation of molecular structure parameters are in good agreement with previous report and better than the ones calculated based on 6-31G(d), and the calculated frequencies agree well with the experimental ones. Potential energy distribution of each frequency was worked out by normal mode analysis, and based on this, a detailed and accurate vibration frequency assignment of ACN was obtained.

The acoustic features of human laughter

Science.gov (United States)

Bachorowski, Jo-Anne; Owren, Michael J.

2002-05-01

Remarkably little is known about the acoustic features of laughter, despite laughter's ubiquitous role in human vocal communication. Outcomes are described for 1024 naturally produced laugh bouts recorded from 97 young adults. Acoustic analysis focused on temporal characteristics, production modes, source- and filter-related effects, and indexical cues to laugher sex and individual identity. The results indicate that laughter is a remarkably complex vocal signal, with evident diversity in both production modes and fundamental frequency characteristics. Also of interest was finding a consistent lack of articulation effects in supralaryngeal filtering. Outcomes are compared to previously advanced hypotheses and conjectures about this species-typical vocal signal.

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.

Soliton rains in a graphene-oxide passively mode-locked ytterbium-doped fiber laser with all-normal dispersion

International Nuclear Information System (INIS)

Huang, S S; Yan, P G; Zhang, G L; Zhao, J Q; Li, H Q; Lin, R Y; Wang, Y G

2014-01-01

We experimentally investigated soliton rains in an ytterbium-doped fiber (YDF) laser with a net normal dispersion cavity using a graphene-oxide (GO) saturable absorber (SA). The 195 m-long-cavity, the fiber birefringence filter and the inserted 2.5 nm narrow bandwidth filter play important roles in the formation of the soliton rains. The soliton rain states can be changed by the effective gain bandwidth of the laser. The experimental results can be conducive to an understanding of dissipative soliton features and mode-locking dynamics in all-normal dispersion fiber lasers with GOSAs. To the best of our knowledge, this is the first demonstration of soliton rains in a GOSA passively mode-locked YDF laser with a net normal dispersion cavity. (letter)

A new mode of acoustic NDT via resonant air-coupled emission

Science.gov (United States)

Solodov, Igor; Dillenz, Alexander; Kreutzbruck, Marc

2017-06-01

Resonant modes of non-destructive testing (NDT) which make use of local damage resonance (LDR) have been developed recently and demonstrated a significant increase in efficiency and sensitivity of hybrid inspection techniques by laser vibrometry, ultrasonic thermography, and shearography. In this paper, a new fully acoustic version of resonant NDT is demonstrated for defects in composite materials relevant to automotive and aviation applications. This technique is based on an efficient activation of defect vibrations by using a sonic/ultrasonic wave matched to a fundamental LDR frequency of the defect. On this condition, all points of the faulty area get involved in synchronous out-of-plane vibrations which produce a similar in-phase wave motion in ambient air. This effect of resonant air-coupled emission results in airborne waves emanating from the defect area, which can be received by a commercial microphone (low LDR frequency) or an air-coupled ultrasonic transducer (high frequency LDR). A series of experiments confirm the feasibility of both contact and non-contact versions of the technique for NDT and imaging of simulated and realistic defects (impacts, delaminations, and disbonds) in composites.

Low frequency acoustic waves from explosive sources in the atmosphere

Science.gov (United States)

Millet, Christophe; Robinet, Jean-Christophe; Roblin, Camille; Gloerfelt, Xavier

2006-11-01

In this study, a perturbative formulation of non linear euler equations is used to compute the pressure variation for low frequency acoustic waves from explosive sources in real atmospheres. Based on a Dispersion-Relation-Preserving (DRP) finite difference scheme, the discretization provides good properties for both sound generation and long range sound propagation over a variety of spatial atmospheric scales. It also assures that there is no wave mode coupling in the numerical simulation The background flow is obtained by matching the comprehensive empirical global model of horizontal winds HWM-93 (and MSISE-90 for the temperature profile) with meteorological reanalysis of the lower atmosphere. Benchmark calculations representing cases where there is downward and upward refraction (including shadow zones), ducted propagation, and generation of acoustic waves from low speed shear layers are considered for validation. For all cases, results show a very good agreement with analytical solutions, when available, and with other standard approaches, such as the ray tracing and the normal mode technique. Comparison of calculations and experimental data from the high explosive ``Misty Picture'' test that provided the scaled equivalent airblast of an 8 kt nuclear device (on May 14, 1987), is also considered. It is found that instability waves develop less than one hour after the wavefront generated by the detonation passes.

Nonlinear normal vibration modes in the dynamics of nonlinear elastic systems

International Nuclear Information System (INIS)

Mikhlin, Yu V; Perepelkin, N V; Klimenko, A A; Harutyunyan, E

2012-01-01

Nonlinear normal modes (NNMs) are a generalization of the linear normal vibrations. By the Kauderer-Rosenberg concept in the regime of the NNM all position coordinates are single-values functions of some selected position coordinate. By the Shaw-Pierre concept, the NNM is such a regime when all generalized coordinates and velocities are univalent functions of a couple of dominant (active) phase variables. The NNMs approach is used in some applied problems. In particular, the Kauderer-Rosenberg NNMs are analyzed in the dynamics of some pendulum systems. The NNMs of forced vibrations are investigated in a rotor system with an isotropic-elastic shaft. A combination of the Shaw-Pierre NNMs and the Rauscher method is used to construct the forced NNMs and the frequency responses in the rotor dynamics.

Possibility of observation of polaron normal modes at the far-infrared spectrum of acetanilide and related organics

Science.gov (United States)

Kalosakas, G.; Aubry, S.; Tsironis, G. P.

1998-10-01

We use a stationary and normal mode analysis of the semiclassical Holstein model in order to connect the low-frequency linear polaron modes to low-lying far-infrared lines of the acetanilide spectrum and through parameter fitting we comment on the validity of the polaron results in this system.

Normal Mode Derived Models of the Physical Properties of Earth's Outer Core

Science.gov (United States)

Irving, J. C. E.; Cottaar, S.; Lekic, V.; Wu, W.

2017-12-01

Earth's outer core, the largest reservoir of metal in our planet, is comprised of an iron alloy of an uncertain composition. Its dynamical behaviour is responsible for the generation of Earth's magnetic field, with convection driven both by thermal and chemical buoyancy fluxes. Existing models of the seismic velocity and density of the outer core exhibit some variation, and there are only a small number of models which aim to represent the outer core's density.It is therefore important that we develop a better understanding of the physical properties of the outer core. Though most of the outer core is likely to be well mixed, it is possible that the uppermost outer core is stably stratified: it may be enriched in light elements released during the growth of the solid, iron enriched, inner core; by elements dissolved from the mantle into the outer core; or by exsolution of compounds previously dissolved in the liquid metal which will eventually be swept into the mantle. The stratified layer may host MAC or Rossby waves and it could impede communication between the chemically differentiated mantle and outer core, including screening out some of the geodynamo's signal. We use normal mode center frequencies to estimate the physical properties of the outer core in a Bayesian framework. We estimate the mineral physical parameters needed to best produce velocity and density models of the outer core which are consistent with the normal mode observations. We require that our models satisfy realistic physical constraints. We create models of the outer core with and without a distinct uppermost layer and assess the importance of this region.Our normal mode-derived models are compared with observations of body waves which travel through the outer core. In particular, we consider SmKS waves which are especially sensitive to the uppermost outer core and are therefore an important way to understand the robustness of our models.

A finite element propagation model for extracting normal incidence impedance in nonprogressive acoustic wave fields

Science.gov (United States)

Watson, Willie R.; Jones, Michael G.; Tanner, Sharon E.; Parrott, Tony L.

1995-01-01

A propagation model method for extracting the normal incidence impedance of an acoustic material installed as a finite length segment in a wall of a duct carrying a nonprogressive wave field is presented. The method recasts the determination of the unknown impedance as the minimization of the normalized wall pressure error function. A finite element propagation model is combined with a coarse/fine grid impedance plane search technique to extract the impedance of the material. Results are presented for three different materials for which the impedance is known. For each material, the input data required for the prediction scheme was computed from modal theory and then contaminated by random error. The finite element method reproduces the known impedance of each material almost exactly for random errors typical of those found in many measurement environments. Thus, the method developed here provides a means for determining the impedance of materials in a nonprogressirve wave environment such as that usually encountered in a commercial aircraft engine and most laboratory settings.

Study of the influence of semiconductor material parameters on acoustic wave propagation modes in GaSb/AlSb bi-layered structures by Legendre polynomial method

Energy Technology Data Exchange (ETDEWEB)

Othmani, Cherif, E-mail: othmanicheriffss@gmail.com; Takali, Farid; Njeh, Anouar; Ben Ghozlen, Mohamed Hédi

2016-09-01

The propagation of Rayleigh–Lamb waves in bi-layered structures is studied. For this purpose, an extension of the Legendre polynomial (LP) method is proposed to formulate the acoustic wave equation in the bi-layered structures induced by thin film Gallium Antimonide (GaSb) and with Aluminum Antimonide (AlSb) substrate in moderate thickness. Acoustic modes propagating along a bi-layer plate are shown to be quite different than classical Lamb modes, contrary to most of the multilayered structures. The validation of the LP method is illustrated by a comparison between the associated numerical results and those obtained using the ordinary differential equation (ODE) method. The convergency of the LP method is discussed through a numerical example. Moreover, the influences of thin film GaSb parameters on the characteristics Rayleigh–Lamb waves propagation has been studied in detail. Finally, the advantages of the Legendre polynomial (LP) method to analyze the multilayered structures are described. All the developments performed in this work were implemented in Matlab software.

Study of the influence of semiconductor material parameters on acoustic wave propagation modes in GaSb/AlSb bi-layered structures by Legendre polynomial method

International Nuclear Information System (INIS)

Othmani, Cherif; Takali, Farid; Njeh, Anouar; Ben Ghozlen, Mohamed Hédi

2016-01-01

The propagation of Rayleigh–Lamb waves in bi-layered structures is studied. For this purpose, an extension of the Legendre polynomial (LP) method is proposed to formulate the acoustic wave equation in the bi-layered structures induced by thin film Gallium Antimonide (GaSb) and with Aluminum Antimonide (AlSb) substrate in moderate thickness. Acoustic modes propagating along a bi-layer plate are shown to be quite different than classical Lamb modes, contrary to most of the multilayered structures. The validation of the LP method is illustrated by a comparison between the associated numerical results and those obtained using the ordinary differential equation (ODE) method. The convergency of the LP method is discussed through a numerical example. Moreover, the influences of thin film GaSb parameters on the characteristics Rayleigh–Lamb waves propagation has been studied in detail. Finally, the advantages of the Legendre polynomial (LP) method to analyze the multilayered structures are described. All the developments performed in this work were implemented in Matlab software.

Acoustic streaming in simplified liquid rocket engines with transverse mode oscillations

Science.gov (United States)

Fischbach, Sean R.; Flandro, Gary A.; Majdalani, Joseph

2010-06-01

This study considers a simplified model of a liquid rocket engine in which uniform injection is imposed at the faceplate. The corresponding cylindrical chamber has a small length-to-diameter ratio with respect to solid and hybrid rockets. Given their low chamber aspect ratios, liquid thrust engines are known to experience severe tangential and radial oscillation modes more often than longitudinal ones. In order to model this behavior, tangential and radial waves are superimposed onto a basic mean-flow model that consists of a steady, uniform axial velocity throughout the chamber. Using perturbation tools, both potential and viscous flow equations are then linearized in the pressure wave amplitude and solved to the second order. The effects of the headwall Mach number are leveraged as well. While the potential flow analysis does not predict any acoustic streaming effects, the viscous solution carried out to the second order gives rise to steady secondary flow patterns near the headwall. These axisymmetric, steady contributions to the tangential and radial traveling waves are induced by the convective flow motion through interactions with inertial and viscous forces. We find that suppressing either the convective terms or viscosity at the headwall leads to spurious solutions that are free from streaming. In our problem, streaming is initiated at the headwall, within the boundary layer, and then extends throughout the chamber. We find that nonlinear streaming effects of tangential and radial waves act to alter the outer solution inside a cylinder with headwall injection. As a result of streaming, the radial wave velocities are intensified in one-half of the domain and reduced in the opposite half at any instant of time. Similarly, the tangential waves are either enhanced or weakened in two opposing sectors that are at 90° angle to the radial velocity counterparts. The second-order viscous solution that we obtain clearly displays both an oscillating and a steady flow

Normal vibrations in gallium arsenide

International Nuclear Information System (INIS)

Dolling, G.; Waugh, J.L.T.

1964-01-01

The triple axis crystal spectrometer at Chalk River has been used to observe coherent slow neutron scattering from a single crystal of pure gallium arsenide at 296 o K. The frequencies of normal modes of vibration propagating in the [ζ00], (ζζζ], and (0ζζ] crystal directions have been determined with a precision of between 1 and 2·5 per cent. A limited number of normal modes have also been studied at 95 and 184 o K. Considerable difficulty was experienced in obtaining welt resolved neutron peaks corresponding to the two non-degenerate optic modes for very small wave-vector, particularly at 296 o K. However, from a comparison of results obtained under various experimental conditions at several different points in reciprocal space, frequencies (units 10 12 c/s) for these modes (at 296 o K) have been assigned: T 8·02±0·08 and L 8·55±02. Other specific normal modes, with their measured frequencies are (a) (1,0,0): TO 7·56 ± 008, TA 2·36 ± 0·015, LO 7·22 ± 0·15, LA 6·80 ± 0·06; (b) (0·5, 0·5, 0·5): TO 7·84 ± 0·12, TA 1·86 ± 0·02, LO 7·15 ± 0·07, LA 6·26 ± 0·10; (c) (0, 0·65, 0·65): optic 8·08 ±0·13, 7·54 ± 0·12 and 6·57 ± 0·11, acoustic 5·58 ± 0·08, 3·42 · 0·06 and 2·36 ± 004. These results are generally slightly lower than the corresponding frequencies for germanium. An analysis in terms of various modifications of the dipole approximation model has been carried out. A feature of this analysis is that the charge on the gallium atom appears to be very small, about +0·04 e. The frequency distribution function has been derived from one of the force models. (author)

Propagation of acoustic-gravity waves in arctic zones with elastic ice-sheets

Science.gov (United States)

Kadri, Usama; Abdolali, Ali; Kirby, James T.

2017-04-01

We present an analytical solution of the boundary value problem of propagating acoustic-gravity waves generated in the ocean by earthquakes or ice-quakes in arctic zones. At the surface, we assume elastic ice-sheets of a variable thickness, and show that the propagating acoustic-gravity modes have different mode shape than originally derived by Ref. [1] for a rigid ice-sheet settings. Computationally, we couple the ice-sheet problem with the free surface model by Ref. [2] representing shrinking ice blocks in realistic sea state, where the randomly oriented ice-sheets cause inter modal transition at the edges and multidirectional reflections. We then derive a depth-integrated equation valid for spatially slowly varying thickness of ice-sheet and water depth. Surprisingly, and unlike the free-surface setting, here it is found that the higher acoustic-gravity modes exhibit a larger contribution. These modes travel at the speed of sound in water carrying information on their source, e.g. ice-sheet motion or submarine earthquake, providing various implications for ocean monitoring and detection of quakes. In addition, we found that the propagating acoustic-gravity modes can result in orbital displacements of fluid parcels sufficiently high that may contribute to deep ocean currents and circulation, as postulated by Refs. [1, 3]. References [1] U. Kadri, 2016. Generation of Hydroacoustic Waves by an Oscillating Ice Block in Arctic Zones. Advances in Acoustics and Vibration, 2016, Article ID 8076108, 7 pages http://dx.doi.org/10.1155/2016/8076108 [2] A. Abdolali, J. T. Kirby and G. Bellotti, 2015, Depth-integrated equation for hydro-acoustic waves with bottom damping, J. Fluid Mech., 766, R1 doi:10.1017/jfm.2015.37 [3] U. Kadri, 2014. Deep ocean water transportation by acoustic?gravity waves. J. Geophys. Res. Oceans, 119, doi:10.1002/ 2014JC010234

Acoustic biosensors.

Science.gov (United States)

Fogel, Ronen; Limson, Janice; Seshia, Ashwin A

2016-06-30

Resonant and acoustic wave devices have been researched for several decades for application in the gravimetric sensing of a variety of biological and chemical analytes. These devices operate by coupling the measurand (e.g. analyte adsorption) as a modulation in the physical properties of the acoustic wave (e.g. resonant frequency, acoustic velocity, dissipation) that can then be correlated with the amount of adsorbed analyte. These devices can also be miniaturized with advantages in terms of cost, size and scalability, as well as potential additional features including integration with microfluidics and electronics, scaled sensitivities associated with smaller dimensions and higher operational frequencies, the ability to multiplex detection across arrays of hundreds of devices embedded in a single chip, increased throughput and the ability to interrogate a wider range of modes including within the same device. Additionally, device fabrication is often compatible with semiconductor volume batch manufacturing techniques enabling cost scalability and a high degree of precision and reproducibility in the manufacturing process. Integration with microfluidics handling also enables suitable sample pre-processing/separation/purification/amplification steps that could improve selectivity and the overall signal-to-noise ratio. Three device types are reviewed here: (i) bulk acoustic wave sensors, (ii) surface acoustic wave sensors, and (iii) micro/nano-electromechanical system (MEMS/NEMS) sensors. © 2016 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

Acoustical-Levitation Chamber for Metallurgy

Science.gov (United States)

Barmatz, M. B.; Trinh, E.; Wang, T. G.; Elleman, D. D.; Jacobi, N.

1983-01-01

Sample moved to different positions for heating and quenching. Acoustical levitation chamber selectively excited in fundamental and second-harmonic longitudinal modes to hold sample at one of three stable postions: A, B, or C. Levitated object quickly moved from one of these positions to another by changing modes. Object rapidly quenched at A or C after heating in furnace region at B.

Curbing - The Metallic Mode In-Between

DEFF Research Database (Denmark)

Aaen, Mathias; McGlashan, Julian; Sadolin, Cathrine

2017-01-01

recording of EGG and acoustic signals using Speech Studio. Images were analyzed based on consensus agreement. Statistical analysis of acoustic, LTAS, and EGG parameters was undertaken using Student paired t tests. Results The reduced metallic singing mode Curbing has an identifiable laryngeal gesture....... Curbing has a more open setting than Overdrive and Edge, with high visibility of the vocal folds, and the false folds giving a rectangular appearance. LTAS showed statistically significant differences between Curbing and the full metallic modes, with less energy across all spectra, yielding a high second...

Monolithic acoustic graphene transistors based on lithium niobate thin film

Science.gov (United States)

Liang, J.; Liu, B.-H.; Zhang, H.-X.; Zhang, H.; Zhang, M.-L.; Zhang, D.-H.; Pang, W.

2018-05-01

This paper introduces an on-chip acoustic graphene transistor based on lithium niobate thin film. The graphene transistor is embedded in a microelectromechanical systems (MEMS) acoustic wave device, and surface acoustic waves generated by the resonator induce a macroscopic current in the graphene due to the acousto-electric (AE) effect. The acoustic resonator and the graphene share the lithium niobate film, and a gate voltage is applied through the back side of the silicon substrate. The AE current induced by the Rayleigh and Sezawa modes was investigated, and the transistor outputs a larger current in the Rayleigh mode because of a larger coupling to velocity ratio. The output current increases linearly with the input radiofrequency power and can be effectively modulated by the gate voltage. The acoustic graphene transistor realized a five-fold enhancement in the output current at an optimum gate voltage, outperforming its counterpart with a DC input. The acoustic graphene transistor demonstrates a paradigm for more-than-Moore technology. By combining the benefits of MEMS and graphene circuits, it opens an avenue for various system-on-chip applications.

Cylindrical acoustic levitator/concentrator having non-circular cross-section

Science.gov (United States)

Kaduchak, Gregory; Sinha, Dipen N.

2003-11-11

A low-power, inexpensive acoustic apparatus for levitation and/or concentration of aerosols and small liquid/solid samples having particulates up to several millimeters in diameter in air or other fluids is described. It is constructed from a commercially available, hollow piezoelectric crystal which has been formed with a cylindrical cross-section to tune the resonance frequency of the breathing mode resonance of the crystal to that of the interior cavity of the cylinder. When the resonance frequency of the interior cylindrical cavity is matched to the breathing mode resonance of the cylindrical piezoelectric transducer, the acoustic efficiency for establishing a standing wave pattern in the cavity is high. By deforming the circular cross-section of the transducer, the acoustic force is concentrated along axial regions parallel to the axis of the transducer. The cylinder does not require accurate alignment of a resonant cavity. The concentrated regions of acoustic force cause particles in the fluid to concentrate within the regions of acoustic force for separation from the fluid.

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

Science.gov (United States)

Tsai, Ya-Yi; I, Lin

2014-07-01

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

An experimental randomized study of six different ventilatory modes in a piglet model with normal lungs

DEFF Research Database (Denmark)

Nielsen, J B; Sjöstrand, U H; Henneberg, S W

1991-01-01

A randomized study of 6 ventilatory modes was made in 7 piglets with normal lungs. Using a Servo HFV 970 (prototype system) and a Servo ventilator 900 C the ventilatory modes examined were as follows: SV-20V, i.e. volume-controlled intermittent positive-pressure ventilation (IPPV); SV-20VIosc, i...... ventilatory modes. Also the mean airway pressures were lower with the HFV modes 8-9 cm H2O compared to 11-14 cm H2O for the other modes. The gas distribution was evaluated by N2 wash-out and a modified lung clearance index. All modes showed N2 wash-out according to a two-compartment model. The SV-20P mode had.......e. volume-controlled ventilation (IPPV) with superimposed inspiratory oscillations; and SV-20VEf, i.e. volume-controlled ventilation (IPPV) with expiratory flush of fresh gas; HFV-60 denotes low-compressive high-frequency positive-pressure ventilation (HFPPV) and HVF-20 denotes low-compressive volume...

Modal analysis and acoustic transmission through offset-core honeycomb sandwich panels

Science.gov (United States)

Mathias, Adam Dustin

The work presented in this thesis is motivated by an earlier research that showed that double, offset-core honeycomb sandwich panels increased thermal resistance and, hence, decreased heat transfer through the panels. This result lead to the hypothesis that these panels could be used for acoustic insulation. Using commercial finite element modeling software, COMSOL Multiphysics, the acoustical properties, specifically the transmission loss across a variety of offset-core honeycomb sandwich panels, is studied for the case of a plane acoustic wave impacting the panel at normal incidence. The transmission loss results are compared with those of single-core honeycomb panels with the same cell sizes. The fundamental frequencies of the panels are also computed in an attempt to better understand the vibrational modes of these particular sandwich-structured panels. To ensure that the finite element analysis software is adequate for the task at hand, two relevant benchmark problems are solved and compared with theory. Results from these benchmark results compared well to those obtained from theory. Transmission loss results from the offset-core honeycomb sandwich panels show increased transmission loss, especially for large cell honeycombs when compared to single-core honeycomb panels.

Acoustic parametric pumping of spin waves

Science.gov (United States)

Keshtgar, Hedyeh; Zareyan, Malek; Bauer, Gerrit E. W.

2014-11-01

Recent experiments demonstrated generation of spin currents by ultrasound. We can understand this acoustically induced spin pumping in terms of the coupling between magnetization and lattice waves. Here we study the parametric excitation of magnetization by longitudinal acoustic waves and calculate the acoustic threshold power. The induced magnetization dynamics can be detected by the spin pumping into an adjacent normal metal that displays the inverse spin Hall effect.

Acoustic parametric pumping of spin waves

OpenAIRE

Keshtgar, Hedyeh; Zareyan, Malek; Bauer, Gerrit E. W.

2013-01-01

Recent experiments demonstrated generation of spin currents by ultrasound. We can understand this acoustically induced spin pumping in terms of the coupling between magnetization and lattice waves. Here we study the parametric excitation of magnetization by longitudinal acoustic waves and calculate the acoustic threshold power. The induced magnetization dynamics can be detected by the spin pumping into an adjacent normal metal that displays the inverse spin Hall effect.

Quasinormal modes and classical wave propagation in analogue black holes

International Nuclear Information System (INIS)

Berti, Emanuele; Cardoso, Vitor; Lemos, Jose P.S.

2004-01-01

Many properties of black holes can be studied using acoustic analogues in the laboratory through the propagation of sound waves. We investigate in detail sound wave propagation in a rotating acoustic (2+1)-dimensional black hole, which corresponds to the 'draining bathtub' fluid flow. We compute the quasinormal mode frequencies of this system and discuss late-time power-law tails. Because of the presence of an ergoregion, waves in a rotating acoustic black hole can be superradiantly amplified. We also compute superradiant reflection coefficients and instability time scales for the acoustic black hole bomb, the equivalent of the Press-Teukolsky black hole bomb. Finally we discuss quasinormal modes and late-time tails in a nonrotating canonical acoustic black hole, corresponding to an incompressible, spherically symmetric (3+1)-dimensional fluid flow

Cylindrical acoustic levitator/concentrator

Science.gov (United States)

Kaduchak, Gregory; Sinha, Dipen N.

2002-01-01

A low-power, inexpensive acoustic apparatus for levitation and/or concentration of aerosols and small liquid/solid samples having particulates up to several millimeters in diameter in air or other fluids is described. It is constructed from a commercially available, hollow cylindrical piezoelectric crystal which has been modified to tune the resonance frequency of the breathing mode resonance of the crystal to that of the interior cavity of the cylinder. When the resonance frequency of the interior cylindrical cavity is matched to the breathing mode resonance of the cylindrical piezoelectric transducer, the acoustic efficiency for establishing a standing wave pattern in the cavity is high. The cylinder does not require accurate alignment of a resonant cavity. Water droplets having diameters greater than 1 mm have been levitated against the force of gravity using; less than 1 W of input electrical power. Concentration of aerosol particles in air is also demonstrated.

Normal Mode Analysis to a Poroelastic Half-Space Problem under Generalized Thermoelasticity

Directory of Open Access Journals (Sweden)

Chunbao Xiong

Full Text Available Abstract The thermo-hydro-mechanical problems associated with a poroelastic half-space soil medium with variable properties under generalized thermoelasticity theory were investigated in this study. By remaining faithful to Biot’s theory of dynamic poroelasticity, we idealized the foundation material as a uniform, fully saturated, poroelastic half-space medium. We first subjected this medium to time harmonic loads consisting of normal or thermal loads, then investigated the differences between the coupled thermohydro-mechanical dynamic models and the thermo-elastic dynamic models. We used normal mode analysis to solve the resulting non-dimensional coupled equations, then investigated the effects that non-dimensional vertical displacement, excess pore water pressure, vertical stress, and temperature distribution exerted on the poroelastic half-space medium and represented them graphically.

Quasi-Linear Polarized Modes in Y-Rotated Piezoelectric GaPO4 Plates

Directory of Open Access Journals (Sweden)

Cinzia Caliendo

2014-07-01

Full Text Available The propagation of both surface and flexural acoustic plate modes along y-rotated x-propagation GaPO4 piezoelectric substrates was studied for several y-cut angles: the phase velocity and coupling coefficient dispersion curves were theoretically calculated for two different electroacoustic coupling configurations. The investigation of the acoustic field profile across the plate thickness revealed the presence of thin plate modes having polarization predominantly oriented along the propagation direction, and hence suitable for operation in liquid environment. These modes include the linearly polarized Anisimkin Jr. and the quasi longitudinal plate modes, AMs and QLs, showing a phase velocity close to that of the longitudinal bulk acoustic wave propagating in the same direction. The temperature coefficient of delay (TCD of these longitudinal modes was investigated in the −20 to 420 °C temperature range, in order to identify thermally stable or low TCD cuts. The power flow angle, i.e., the angle between the phase and group velocity vectors, was also estimated to evaluate the substrate anisotropy effect on the acoustic wave propagation. The GaPO4 intrinsic properties, such as its resistance to high temperature and its chemical inertness, make it especially attractive for the development of acoustic waves-based sensors for applications in harsh liquid environment.

Optimization of hardening/softening behavior of plane frame structures using nonlinear normal modes

DEFF Research Database (Denmark)

Dou, Suguang; Jensen, Jakob Søndergaard

2016-01-01

Devices that exploit essential nonlinear behavior such as hardening/softening and inter-modal coupling effects are increasingly used in engineering and fundamental studies. Based on nonlinear normal modes, we present a gradient-based structural optimization method for tailoring the hardening...... involving plane frame structures where the hardening/softening behavior is qualitatively and quantitatively tuned by simple changes in the geometry of the structures....

OBSERVATIONS OF SAUSAGE MODES IN MAGNETIC PORES

International Nuclear Information System (INIS)

Morton, R. J.; Erdelyi, R.; Jess, D. B.; Mathioudakis, M.

2011-01-01

We present here evidence for the observation of the magnetohydrodynamic (MHD) sausage modes in magnetic pores in the solar photosphere. Further evidence for the omnipresent nature of acoustic global modes is also found. The empirical decomposition method of wave analysis is used to identify the oscillations detected through a 4170 A 'blue continuum' filter observed with the Rapid Oscillations in the Solar Atmosphere (ROSA) instrument. Out of phase, periodic behavior in pore size and intensity is used as an indicator of the presence of magnetoacoustic sausage oscillations. Multiple signatures of the magnetoacoustic sausage mode are found in a number of pores. The periods range from as short as 30 s up to 450 s. A number of the magnetoacoustic sausage mode oscillations found have periods of 3 and 5 minutes, similar to the acoustic global modes of the solar interior. It is proposed that these global oscillations could be the driver of the sausage-type magnetoacoustic MHD wave modes in pores.

Mode coupling of electron plasma waves

International Nuclear Information System (INIS)

Harte, J.A.

1975-01-01

The driven coupled mode equations are derived for a two fluid, unequal temperature (T/sub e/ much greater than T/sub i/) plasma in the one-dimensional, electrostatic model and applied to the coupling of electron plasma waves. It is assumed that the electron to ion mass ratio identical with m/sub e/M/sub i// much less than 1 and eta 2 /sub ko/k lambda/sub De/ less than 1 where eta 2 /sub ko/ is the pump wave's power normalized to the plasma thermal energy, k the mode wave number and lambda/sub De/ the electron Debye length. Terms up to quadratic in pump power are retained. The equations describe the linear plasma modes oscillating at the wave number k and at ω/sub ek/, the Bohn Gross frequency, and at Ω/sub k/, the ion acoustic frequency, subject to the damping rates ν/sub ek/ and ν/sub ik/ for electrons and ions and their interactions due to intense high frequency waves E/sub k//sup l/. n/sub o/ is the background density, n/sub ik/ the fluctuating ion density, ω/sub pe/ the plasma frequency

Generation of the vorticity mode by sound in a Bingham plastic

Science.gov (United States)

Perelomova, Anna; Wojda, Pawel

2011-10-01

This study investigates interaction between acoustic and non-acoustic modes, such as vorticity mode, in some class of a non-newtonian fluid called Bingham plastic. The instantaneous equations describing interaction between different modes are derived. The attention is paid to the nonlinear effects in the field of intense sound. The resulting equations which describe dynamics of both sound and the vorticity mode apply to both periodic and aperiodic sound of any waveform. They use only instantaneous quantities and do not imply averaging over the sound period. The theory is illustrated by an example of acoustic force of vorticity induced in the field of a Gaussian sound beam. Some unusual peculiarities in both sound and the vorticity induced in its field as compared to a newtonian fluid, are discovered.

Acoustic agglomeration methods and apparatus

Science.gov (United States)

Barmatz, M. B. (Inventor)

1984-01-01

Methods are described for using acoustic energy to agglomerate fine particles on the order of one micron diameter that are suspended in gas, to provide agglomerates large enough for efficient removal by other techniques. The gas with suspended particles, is passed through the length of a chamber while acoustic energy at a resonant chamber mode is applied to set up one or more acoustic standing wave patterns that vibrate the suspended particles to bring them together so they agglomerate. Several widely different frequencies can be applied to efficiently vibrate particles of widely differing sizes. The standing wave pattern can be applied along directions transversed to the flow of the gas. The particles can be made to move in circles by applying acoustic energy in perpendicular directions with the energy in both directions being of the same wavelength but 90 deg out of phase.

Conjugate gradient filtering of instantaneous normal modes, saddles on the energy landscape, and diffusion in liquids.

Science.gov (United States)

Chowdhary, J; Keyes, T

2002-02-01

Instantaneous normal modes (INM's) are calculated during a conjugate-gradient (CG) descent of the potential energy landscape, starting from an equilibrium configuration of a liquid or crystal. A small number (approximately equal to 4) of CG steps removes all the Im-omega modes in the crystal and leaves the liquid with diffusive Im-omega which accurately represent the self-diffusion constant D. Conjugate gradient filtering appears to be a promising method, applicable to any system, of obtaining diffusive modes and facilitating INM theory of D. The relation of the CG-step dependent INM quantities to the landscape and its saddles is discussed.

Dynamics of acoustic-convective drying of sunflower cake

Science.gov (United States)

Zhilin, A. A.

2017-10-01

The dynamics of drying sunflower cake by a new acoustic-convective method has been studied. Unlike the conventional (thermal-convective) method, the proposed method allows moisture to be extracted from porous materials without applying heat to the sample to be dried. Kinetic curves of drying by the thermal-convective and acoustic-convective methods were obtained and analyzed. The advantages of the acoustic-convective extraction of moisture over the thermal-convective method are discussed. The relaxation times of drying were determined for both drying methods. An intermittent drying mode which improves the efficiency of acoustic-convective extraction of moisture is considered.

The signal of mantle anisotropy in the coupling of normal modes

Science.gov (United States)

Beghein, Caroline; Resovsky, Joseph; van der Hilst, Robert D.

2008-12-01

We investigate whether the coupling of normal mode (NM) multiplets can help us constrain mantle anisotropy. We first derive explicit expressions of the generalized structure coefficients of coupled modes in terms of elastic coefficients, including the Love parameters describing radial anisotropy and the parameters describing azimuthal anisotropy (Jc, Js, Kc, Ks, Mc, Ms, Bc, Bs, Gc, Gs, Ec, Es, Hc, Hs, Dc and Ds). We detail the selection rules that describe which modes can couple together and which elastic parameters govern their coupling. We then focus on modes of type 0Sl - 0Tl+1 and determine whether they can be used to constrain mantle anisotropy. We show that they are sensitive to six elastic parameters describing azimuthal anisotropy, in addition to the two shear-wave elastic parameters L and N (i.e. VSV and VSH). We find that neither isotropic nor radially anisotropic mantle models can fully explain the observed degree two signal. We show that the NM signal that remains after correction for the effect of the crust and mantle radial anisotropy can be explained by the presence of azimuthal anisotropy in the upper mantle. Although the data favour locating azimuthal anisotropy below 400km, its depth extent and distribution is still not well constrained by the data. Consideration of NM coupling can thus help constrain azimuthal anisotropy in the mantle, but joint analyses with surface-wave phase velocities is needed to reduce the parameter trade-offs and improve our constraints on the individual elastic parameters and the depth location of the azimuthal anisotropy.

The acoustic field of a point source in a uniform boundary layer over an impedance plane

Science.gov (United States)

Zorumski, W. E.; Willshire, W. L., Jr.

1986-01-01

The acoustic field of a point source in a boundary layer above an impedance plane is investigated anatytically using Obukhov quasi-potential functions, extending the normal-mode theory of Chunchuzov (1984) to account for the effects of finite ground-plane impedance and source height. The solution is found to be asymptotic to the surface-wave term studies by Wenzel (1974) in the limit of vanishing wind speed, suggesting that normal-mode theory can be used to model the effects of an atmospheric boundary layer on infrasonic sound radiation. Model predictions are derived for noise-generation data obtained by Willshire (1985) at the Medicine Bow wind-turbine facility. Long-range downwind propagation is found to behave as a cylindrical wave, with attention proportional to the wind speed, the boundary-layer displacement thickness, the real part of the ground admittance, and the square of the frequency.

Comparative Study of Bio-implantable Acoustic Generator Architectures

International Nuclear Information System (INIS)

Christensen, D; Roundy, S

2013-01-01

This paper is a comparative study of the design spaces of two bio-implantable acoustically excited generator architectures: the thickness-stretch-mode circular piezoelectric plate and the bending-mode unimorph piezoelectric diaphragm. The generators are part of an acoustic power transfer system for implanted sensors and medical devices such as glucose monitors, metabolic monitors, drug delivery systems, etc. Our studies indicate that at small sizes the diaphragm architecture outperforms the plate architecture. This paper will present the results of simulation studies and initial experiments that explore the characteristics of the two architectures and compare their performance

Resonant and kinematical enhancement of He scattering from LiF(001) surface and pseudosurface vibrational normal modes

International Nuclear Information System (INIS)

Nichols, W.L.; Weare, J.H.

1986-01-01

One-phonon cross sections calculated from sagittally polarized vibrational normal modes account for most salient inelastic-scattering intensities seen in He-LiF(001) and measurements published by Brusdeylins, Doak, and Toennies. We have found that most inelastic intensities which cannot be attributed to potential resonances can be explained as kinematically enhanced scattering from both surface and pseudosurface bulk modes

Single-Phase Full-Wave Rectifier as an Effective Example to Teach Normalization, Conduction Modes, and Circuit Analysis Methods

Directory of Open Access Journals (Sweden)

Predrag Pejovic

2013-12-01

Full Text Available Application of a single phase rectifier as an example in teaching circuit modeling, normalization, operating modes of nonlinear circuits, and circuit analysis methods is proposed.The rectifier supplied from a voltage source by an inductive impedance is analyzed in the discontinuous as well as in the continuous conduction mode. Completely analytical solution for the continuous conduction mode is derived. Appropriate numerical methods are proposed to obtain the circuit waveforms in both of the operating modes, and to compute the performance parameters. Source code of the program that performs such computation is provided.

Multi reflection of Lamb wave emission in an acoustic waveguide sensor.

Science.gov (United States)

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

2013-02-27

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

Cross-code gyrokinetic verification and benchmark on the linear collisionless dynamics of the geodesic acoustic mode

Science.gov (United States)

Biancalani, A.; Bottino, A.; Ehrlacher, C.; Grandgirard, V.; Merlo, G.; Novikau, I.; Qiu, Z.; Sonnendrücker, E.; Garbet, X.; Görler, T.; Leerink, S.; Palermo, F.; Zarzoso, D.

2017-06-01

The linear properties of the geodesic acoustic modes (GAMs) in tokamaks are investigated by means of the comparison of analytical theory and gyrokinetic numerical simulations. The dependence on the value of the safety factor, finite-orbit-width of the ions in relation to the radial mode width, magnetic-flux-surface shaping, and electron/ion mass ratio are considered. Nonuniformities in the plasma profiles (such as density, temperature, and safety factor), electro-magnetic effects, collisions, and the presence of minority species are neglected. Also, only linear simulations are considered, focusing on the local dynamics. We use three different gyrokinetic codes: the Lagrangian (particle-in-cell) code ORB5, the Eulerian code GENE, and semi-Lagrangian code GYSELA. One of the main aims of this paper is to provide a detailed comparison of the numerical results and analytical theory, in the regimes where this is possible. This helps understanding better the behavior of the linear GAM dynamics in these different regimes, the behavior of the codes, which is crucial in the view of a future work where more physics is present, and the regimes of validity of each specific analytical dispersion relation.

Experimental study of acoustic damping induced by gas-liquid scheme injectors in a combustion chamber

International Nuclear Information System (INIS)

Kim, Hak Soon; Sohn, Chae Hoon

2007-01-01

In a liquid rocket engine, acoustic damping induced by gas-liquid scheme injectors is studied experimentally for combustion stability by adopting linear acoustic test. In the previous work, it has been found that gas-liquid scheme injector can play a significant role in acoustic damping or absorption when it is tuned finely. Based on this finding, acoustic-damping characteristics of multi-injectors are intensively investigated. From the experimental data, it is found that acoustic oscillations are almost damped out by multi-injectors when they have the tuning length proposed in the previous study. The length corresponds to a half wavelength of the first longitudinal overtone mode traveling inside the injector with the acoustic frequency intended for damping in the chamber. But, new injector-coupled acoustic modes show up in the chamber with the injectors of the tuning length although the target mode is nearly damped out. And, appreciable frequency shift is always observed except for the case of the worst tuned injector. Accordingly, it is proposed that the tuning length is adjusted to have the shorter length than a half wavelength when these phenomena are considered

Pillar-type acoustic metasurface

DEFF Research Database (Denmark)

Jin, Yabin; Bonello, Bernard; Moiseyenko, Rayisa

2017-01-01

We theoretically investigate acoustic metasurfaces consisting of either a single pillar or a line of identical pillars on a thin plate, and we report on the dependence on the geometrical parameters of both the monopolar compressional and dipolar bending modes. We show that for specific dimensions...

[Acoustic Levitation Methods and Apparatus

Science.gov (United States)

Barmatz, M. B.; Jacobi, N. (Inventor)

1982-01-01

Methods are described for acoustically levitating objects within chambers of spherical and cylindrical shape. The wavelengths for chambers of particular dimensions are given, for generating standing wave patterns of any of a variety of modes within the chambers. For a spherical chamber the lowest resonant mode is excited by applying a wavelength of 3.02R, where R is the chamber radius. The two lowest pure radial modes for that chamber, are excited by applying wavelengths of 1.40R and 0.814R. For a cylindrical chamber of radius R, the lowest mode is at a wavelength of 3.41R, and the lowest pure radial modes are at wavelengths of 1.64R and 0.896R.

Low-frequency electrostatic dust-modes in a nonuniform magnetized dusty plasma

International Nuclear Information System (INIS)

Paul, S.K.; Duha, S.S.; Mamun, A.A.

2004-07-01

A self-consistent and general description of obliquely propagating low frequency electrostatic dust-modes in a inhomogeneous, magnetized dusty plasma system has been presented. A number of different situations, which correspond to different low-frequency electrostatic dust-modes, namely, dust-acoustic mode, dust-drift mode, dust-cyclotron mode, dust-lower-hybrid mode, and other associated modes (such as, accelerated and retarded dust-acoustic modes, accelerated and retarded dust-lower-hybrid modes, etc.), have also been investigated. It has been shown that the effects of obliqueness and inhomogeneities in plasma particle number densities introduce new electrostatic dust modes as well as significantly modify the dispersion properties of the other low-frequency electrostatic dust-modes. The implications of these results to some space and astrophysical dusty plasma systems, especially to planetary ring-systems and cometary tails, are briefly mentioned. (author)

An acoustic prion assay

Directory of Open Access Journals (Sweden)

Gordon Hayward

2016-12-01

Full Text Available An acoustic prion assay has been demonstrated for sheep brain samples. Only five false positives and no false negatives were observed in a test of 45 positive and 45 negative samples. The acoustic prion sensor was constructed using a thickness shear mode quartz resonator coated with a covalently bound recombinant prion protein. The characteristic indicator of a scrapie infected sheep brain sample was an observed shoulder in the frequency decrease in response to a sample.The response of the sensor aligns with a conformational shift in the surface protein and with the propagation mechanism of the disease. This alignment is evident in the response timing and shape, dependence on concentration, cross species behaviour and impact of blood plasma. This alignment is far from sufficient to prove the mechanism of the sensor but it does offer the possibility of a rapid and inexpensive additional tool to explore prion disease. Keywords: Prions, Thickness shear mode quartz sensor

Deformation pathways and breakup modes in acoustically levitated bicomponent droplets under external heating

Science.gov (United States)

Pathak, Binita; Basu, Saptarshi

2016-03-01

Controlled breakup of droplets using heat or acoustics is pivotal in applications such as pharmaceutics, nanoparticle production, and combustion. In the current work we have identified distinct thermal acoustics-induced deformation regimes (ligaments and bubbles) and breakup dynamics in externally heated acoustically levitated bicomponent (benzene-dodecane) droplets with a wide variation in volatility of the two components (benzene is significantly more volatile than dodecane). We showcase the physical mechanism and universal behavior of droplet surface caving in leading to the inception and growth of ligaments. The caving of the top surface is governed by a balance between the acoustic pressure field and the restrictive surface tension of the droplet. The universal collapse of caving profiles for different benzene concentration (70 % by volume). The findings are portable to any similar bicomponent systems with differential volatility.

Acoustic-gravity nonlinear structures

Directory of Open Access Journals (Sweden)

D. Jovanović

2002-01-01

Full Text Available A catalogue of nonlinear vortex structures associated with acoustic-gravity perturbations in the Earth's atmosphere is presented. Besides the previously known Kelvin-Stewart cat's eyes, dipolar and tripolar structures, new solutions having the form of a row of counter-rotating vortices, and several weakly two-dimensional vortex chains are given. The existence conditions for these nonlinear structures are discussed with respect to the presence of inhomogeneities of the shear flows. The mode-coupling mechanism for the nonlinear generation of shear flows in the presence of linearly unstable acoustic-gravity waves, possibly also leading to intermittency and chaos, is presented.

Time-resolved measurement of global synchronization in the dust acoustic wave

Science.gov (United States)

Williams, J. D.

2014-10-01

A spatially and temporally resolved measurement of the synchronization of the naturally occurring dust acoustic wave to an external drive and the relaxation from the driven wave mode back to the naturally occuring wave mode is presented. This measurement provides a time-resolved measurement of the synchronization of the self-excited dust acoustic wave with an external drive and the return to the self-excited mode. It is observed that the wave synchronizes to the external drive in a distinct time-dependent fashion, while there is an immediate loss of synchronization when the external modulation is discontinued.

Measurement of the electron beam mode in earth's foreshock

Science.gov (United States)

Onsager, T. G.; Holzworth, R. H.

1990-01-01

High frequency electric field measurements from the AMPTE IRM plasma wave receiver are used to identify three simultaneously excited electrostatic wave modes in the earth's foreshock region: the electron beam mode, the Langmuir mode, and the ion acoustic mode. A technique is developed which allows the rest frame frequecy and wave number of the electron beam waves to be determined. It is shown that the experimentally determined rest frame frequency and wave number agree well with the most unstable frequency and wave number predicted by linear homogeneous Vlasov theory for a plasma with Maxwellian background electrons and a Lorentzian electron beam. From a comparison of the experimentally determined and theoretical values, approximate limits are put on the electron foreshock beam temperatures. A possible generation mechanism for ion acoustic waves involving mode coupling between the electron beam and Langmuir modes is also discussed.

A Pictorial Visualization of Normal Mode Vibrations of the Fullerene (C[subscript 60]) Molecule in Terms of Vibrations of a Hollow Sphere

Science.gov (United States)

Dunn, Janette L.

2010-01-01

Understanding the normal mode vibrations of a molecule is important in the analysis of vibrational spectra. However, the complicated 3D motion of large molecules can be difficult to interpret. We show how images of normal modes of the fullerene molecule C[subscript 60] can be made easier to understand by superimposing them on images of the normal…

Helioseismology in a bottle: modal acoustic velocimetry

International Nuclear Information System (INIS)

Triana, Santiago Andrés; Zimmerman, Daniel S; Lathrop, Daniel P; Nataf, Henri-Claude; Thorette, Aurélien; Lekic, Vedran

2014-01-01

Measurement of the differential rotation of the Sun's interior is one of the great achievements of helioseismology, providing important constraints for stellar physics. The technique relies on observing and analyzing rotationally-induced splittings of p-modes in the star. Here, we demonstrate the first use of the technique in a laboratory setting. We apply it in a spherical cavity with a spinning central core (spherical-Couette flow) to determine the mean azimuthal velocity of the air filling the cavity. We excite a number of acoustic resonances (analogous to p-modes in the Sun) using a speaker and record the response with an array of small microphones on the outer sphere. Many observed acoustic modes show rotationally-induced splittings, which allow us to perform an inversion to determine the air's azimuthal velocity as a function of both radius and latitude. We validate the method by comparing the velocity field obtained through inversion against the velocity profile measured with a calibrated hot film anemometer. This modal acoustic velocimetry technique has great potential for laboratory setups involving rotating fluids in axisymmetric cavities. It will be useful especially in liquid metals where direct optical methods are unsuitable and ultrasonic techniques very challenging at best. (paper)

Investigating Equations Used to Design a Very Small Normal-Mode Helical Antenna in Free Space

Directory of Open Access Journals (Sweden)

Dang Tien Dung

2018-01-01

Full Text Available A normal-mode helical antenna (NMHA has been applied in some small devices such as tire pressure monitoring systems (TPMS and radio frequency identification (RFID tags. Previously, electrical characteristics of NMHA were obtained through electromagnetic simulations. In practical design of NMHA, equational expressions for the main electrical characteristics are more convenient. Electrical performances of NMHA can be expressed by a combination of a short dipole and small loops. Applicability of equations for a short dipole and a small loop to very small normal-mode helical antennas such as antennas around 1/100 wavelengths was not clear. In this paper, accuracies of equations for input resistances, antenna efficiency, and axial ratios are verified by comparisons with electromagnetic simulation results by FEKO software at 402 MHz. In addition, the structure of the antenna equal to 0.021 λ is fabricated, and measurements are performed to confirm the design accuracy.

Topological Acoustic Delay Line

Science.gov (United States)

Zhang, Zhiwang; Tian, Ye; Cheng, Ying; Wei, Qi; Liu, Xiaojun; Christensen, Johan

2018-03-01

Topological protected wave engineering in artificially structured media is at the frontier of ongoing metamaterials research that is inspired by quantum mechanics. Acoustic analogues of electronic topological insulators have recently led to a wealth of new opportunities in manipulating sound propagation with strikingly unconventional acoustic edge modes immune to backscattering. Earlier fabrications of topological insulators are characterized by an unreconfigurable geometry and a very narrow frequency response, which severely hinders the exploration and design of useful devices. Here we establish topologically protected sound in reconfigurable phononic crystals that can be switched on and off simply by rotating its three-legged "atoms" without altering the lattice structure. In particular, we engineer robust phase delay defects that take advantage of the ultrabroadband reflection-free sound propagation. Such topological delay lines serve as a paradigm in compact acoustic devices, interconnects, and electroacoustic integrated circuits.

Low frequency electrostatic modes in a magnetized dusty plasma

International Nuclear Information System (INIS)

Salimullah, M.; Hassan, M.H.A.

1991-09-01

The dispersion properties of low frequency electrostatic modes in a dusty plasma in the presence of a static homogeneous magnetic field are examined. It is found that the presence of the dust particles and the static magnetic field have significant effects on the dispersion relations. For the parallel propagation the electrostatic mode is slightly modified by the magnetic field for the ion acoustic branch. A new longitudinal mode arises at the extreme low frequency limit, which is unaffected by the magnetic field for the parallel propagation. For the transverse propagation the ion acoustic mode is not affected by the magnetic field. However, the undamped extreme low frequency mode is significantly modified by the presence of the magnetic field for the propagation transverse to the direction of the magnetic field. (author). 23 refs

Normal vibrations in gallium arsenide

Energy Technology Data Exchange (ETDEWEB)

Dolling, G; Waugh, J L T

1964-07-01

The triple axis crystal spectrometer at Chalk River has been used to observe coherent slow neutron scattering from a single crystal of pure gallium arsenide at 296{sup o}K. The frequencies of normal modes of vibration propagating in the [{zeta}00], ({zeta}{zeta}{zeta}], and (0{zeta}{zeta}] crystal directions have been determined with a precision of between 1 and 2{center_dot}5 per cent. A limited number of normal modes have also been studied at 95 and 184{sup o}K. Considerable difficulty was experienced in obtaining welt resolved neutron peaks corresponding to the two non-degenerate optic modes for very small wave-vector, particularly at 296{sup o}K. However, from a comparison of results obtained under various experimental conditions at several different points in reciprocal space, frequencies (units 10{sup 12} c/s) for these modes (at 296{sup o}K) have been assigned: T 8{center_dot}02{+-}0{center_dot}08 and L 8{center_dot}55{+-}02. Other specific normal modes, with their measured frequencies are (a) (1,0,0): TO 7{center_dot}56 {+-} 008, TA 2{center_dot}36 {+-} 0{center_dot}015, LO 7{center_dot}22 {+-} 0{center_dot}15, LA 6{center_dot}80 {+-} 0{center_dot}06; (b) (0{center_dot}5, 0{center_dot}5, 0{center_dot}5): TO 7{center_dot}84 {+-} 0{center_dot}12, TA 1{center_dot}86 {+-} 0{center_dot}02, LO 7{center_dot}15 {+-} 0{center_dot}07, LA 6{center_dot}26 {+-} 0{center_dot}10; (c) (0, 0{center_dot}65, 0{center_dot}65): optic 8{center_dot}08 {+-}0{center_dot}13, 7{center_dot}54 {+-} 0{center_dot}12 and 6{center_dot}57 {+-} 0{center_dot}11, acoustic 5{center_dot}58 {+-} 0{center_dot}08, 3{center_dot}42 {center_dot} 0{center_dot}06 and 2{center_dot}36 {+-} 004. These results are generally slightly lower than the corresponding frequencies for germanium. An analysis in terms of various modifications of the dipole approximation model has been carried out. A feature of this analysis is that the charge on the gallium atom appears to be very small, about +0{center_dot}04 e. The

Model for a Torsional-Mode Ultrasonic Transducer for an Acousto-Optic In-Fiber Isolator

Directory of Open Access Journals (Sweden)

Gerald T. Moore

2010-01-01

torsional modes in a cylindrical fiber. This model predicts that almost all of the power applied to the transducer is radiated into the desired mode. The paper also discusses effects produced by acoustic absorption and the dependence of the acoustic velocity on temperature.

Anomalous acoustic dispersion in architected microlattice metamaterials

Science.gov (United States)

KröDel, Sebastian; Palermo, Antonio; Daraio, Chiara

The ability to control dispersion in acoustic metamaterials is crucial to realize acoustic filtering and rectification devices as well as perfect imaging using negative refractive index materials. Architected microlattice metamaterials immersed in fluid constitute a versatile platform for achieving such control. We investigate architected microlattice materials able to exploit locally resonant modes of their fundamental building blocks that couple with propagating acoustic waves. Using analytical, numerical and experimental methods we find that such lattice materials show a hybrid dispersion behavior governed by Biot's theory for long wavelengths and multiple scattering theory when wave frequency is close to the resonances of the building block. We identify the relevant geometric parameters to alter and control the group and phase velocities in this class of acoustic metamaterials. Furthermore, we fabricate small-scale acoustic metamaterial samples using high precision SLA additive manufacturing and test the resulting materials experimentally using a customized ultrasonic setup. This work paves the way for new acoustic devices based on microlattice metamaterials.

Nonreciprocal acoustics and dynamics in the in-plane oscillations of a geometrically nonlinear lattice.

Science.gov (United States)

Zhang, Zhen; Koroleva, I; Manevitch, L I; Bergman, L A; Vakakis, A F

2016-09-01

We study the dynamics and acoustics of a nonlinear lattice with fixed boundary conditions composed of a finite number of particles coupled by linear springs, undergoing in-plane oscillations. The source of the strongly nonlinearity of this lattice is geometric effects generated by the in-plane stretching of the coupling linear springs. It has been shown that in the limit of low energy the lattice gives rise to a strongly nonlinear acoustic vacuum, which is a medium with zero speed of sound as defined in classical acoustics. The acoustic vacuum possesses strongly nonlocal coupling effects and an orthogonal set of nonlinear standing waves [or nonlinear normal modes (NNMs)] with mode shapes identical to those of the corresponding linear lattice; in contrast to the linear case, however, all NNMs except the one with the highest wavelength are unstable. In addition, the lattice supports two types of waves, namely, nearly linear sound waves (termed "L waves") corresponding to predominantly axial oscillations of the particles and strongly nonlinear localized propagating pulses (termed "NL pulses") corresponding to predominantly transverse oscillating wave packets of the particles with localized envelopes. We show the existence of nonlinear nonreciprocity phenomena in the dynamics and acoustics of the lattice. Two opposite cases are examined in the limit of low energy. The first gives rise to nonreciprocal dynamics and corresponds to collective, spatially extended transverse loading of the lattice leading to the excitation of individual, predominantly transverse NNMs, whereas the second case gives rise to nonreciprocal acoutics by considering the response of the lattice to spatially localized, transverse impulse or displacement excitations. We demonstrate intense and recurring energy exchanges between a directly excited NNM and other NNMs with higher wave numbers, so that nonreciprocal energy exchanges from small-to-large wave numbers are established. Moreover, we show the

Design and simulation of a microfluidic device for acoustic cell separation.

Science.gov (United States)

Shamloo, Amir; Boodaghi, Miad

2018-03-01

Experimental acoustic cell separation methods have been widely used to perform separation for different types of blood cells. However, numerical simulation of acoustic cell separation has not gained enough attention and needs further investigation since by using numerical methods, it is possible to optimize different parameters involved in the design of an acoustic device and calculate particle trajectories in a simple and low cost manner before spending time and effort for fabricating these devices. In this study, we present a comprehensive finite element-based simulation of acoustic separation of platelets, red blood cells and white blood cells, using standing surface acoustic waves (SSAWs). A microfluidic channel with three inlets, including the middle inlet for sheath flow and two symmetrical tilted angle inlets for the cells were used to drive the cells through the channel. Two interdigital transducers were also considered in this device and by implementing an alternating voltage to the transducers, an acoustic field was created which can exert the acoustic radiation force to the cells. Since this force is dependent to the size of the cells, the cells are pushed towards the midline of the channel with different path lines. Particle trajectories for different cells were obtained and compared with a theoretical equation. Two types of separations were observed as a result of varying the amplitude of the acoustic field. In the first mode of separation, white blood cells were sorted out through the middle outlet and in the second mode of separation, platelets were sorted out through the side outlets. Depending on the clinical needs and by using the studied microfluidic device, each of these modes can be applied to separate the desired cells. Copyright © 2017 Elsevier B.V. All rights reserved.

A Parametric Study of the Acoustic Mechanism for Core-collapse Supernovae

International Nuclear Information System (INIS)

Harada, A.; Nagakura, H.; Iwakami, W.; Yamada, S.

2017-01-01

We investigate the criterion for the acoustic mechanism to work successfully in core-collapse supernovae. The acoustic mechanism is an alternative to the neutrino-heating mechanism. It was proposed by Burrows et al., who claimed that acoustic waves emitted by g -mode oscillations in proto-neutron stars (PNS) energize a stalled shock wave and eventually induce an explosion. Previous works mainly studied to which extent the g -modes are excited in the PNS. In this paper, on the other hand, we investigate how strong the acoustic wave needs to be if it were to revive a stalled shock wave. By adding the acoustic power as a new axis, we draw a critical surface, which is an extension of the critical curve commonly employed in the context of neutrino heating. We perform both 1D and 2D parametrized simulations, in which we inject acoustic waves from the inner boundary. In order to quantify the power of acoustic waves, we use the extended Myers theory to take neutrino reactions into proper account. We find for the 1D simulations that rather large acoustic powers are required to relaunch the shock wave, since the additional heating provided by the secondary shocks developed from acoustic waves is partially canceled by the neutrino cooling that is also enhanced. In 2D, the required acoustic powers are consistent with those of Burrows et al. Our results seem to imply, however, that it is the sum of neutrino heating and acoustic powers that matters for shock revival.

A Parametric Study of the Acoustic Mechanism for Core-collapse Supernovae

Energy Technology Data Exchange (ETDEWEB)

Harada, A. [Physics Department, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Nagakura, H. [TAPIR, Walter Burke Institue for Theoretical Physics, Mailcode 350-17, California Institute of Technology, Pasadena, CA 91125 (United States); Iwakami, W.; Yamada, S., E-mail: harada@utap.phys.s.u-tokyo.ac.jp [Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan)

2017-04-10

We investigate the criterion for the acoustic mechanism to work successfully in core-collapse supernovae. The acoustic mechanism is an alternative to the neutrino-heating mechanism. It was proposed by Burrows et al., who claimed that acoustic waves emitted by g -mode oscillations in proto-neutron stars (PNS) energize a stalled shock wave and eventually induce an explosion. Previous works mainly studied to which extent the g -modes are excited in the PNS. In this paper, on the other hand, we investigate how strong the acoustic wave needs to be if it were to revive a stalled shock wave. By adding the acoustic power as a new axis, we draw a critical surface, which is an extension of the critical curve commonly employed in the context of neutrino heating. We perform both 1D and 2D parametrized simulations, in which we inject acoustic waves from the inner boundary. In order to quantify the power of acoustic waves, we use the extended Myers theory to take neutrino reactions into proper account. We find for the 1D simulations that rather large acoustic powers are required to relaunch the shock wave, since the additional heating provided by the secondary shocks developed from acoustic waves is partially canceled by the neutrino cooling that is also enhanced. In 2D, the required acoustic powers are consistent with those of Burrows et al. Our results seem to imply, however, that it is the sum of neutrino heating and acoustic powers that matters for shock revival.

Improved acoustic levitation apparatus

Science.gov (United States)

Berge, L. H.; Johnson, J. L.; Oran, W. A.; Reiss, D. A.

1980-01-01

Concave driver and reflector enhance and shape levitation forces in acoustic resonance system. Single-mode standing-wave pattern is focused by ring element situated between driver and reflector. Concave surfaces increase levitating forces up to factor of 6 as opposed to conventional flat surfaces, making it possible to suspend heavier objects.

Spin Start Line Effects on the J2X Gas Generator Chamber Acoustics

Science.gov (United States)

Kenny, R. Jeremy

2011-01-01

The J2X Gas Generator engine design has a spin start line connected near to the turbine inlet vanes. This line provides helium during engine startup to begin turbomachinery operation. The spin start line also acts as an acoustic side branch which alters the chamber's acoustic modes. The side branch effectively creates 'split modes' in the chamber longitudinal modes, in particular below the first longitudinal mode and within the frequency range associated with the injection-coupled response of the Gas Generator. Interaction between the spin start-modified chamber acoustics and the injection-driven response can create a higher system response than without the spin start attached to the chamber. This work reviews the acoustic effects of the spin start line as seen throughout the workhorse gas generator test program. A simple impedance model of the spin start line is reviewed. Tests were run with no initial spin start gas existing in the line, as well as being initially filled with nitrogen gas. Tests were also run with varying spin start line lengths from 0" to 40". Acoustic impedance changes due to different spin start gas constituents and line lengths are shown. Collected thermocouple and static pressure data in the spin start line was used to help estimate the fluid properties along the line length. The side branch impedance model was coupled to a chamber impedance model to show the effects on the overall chamber response. Predictions of the spin start acoustic behavior for helium operation are shown and compared against available data.

Enhancement and suppression of opto-acoustic parametric interactions using optical feedback

International Nuclear Information System (INIS)

Zhang Zhongyang; Zhao Chunnong; Ju, L.; Blair, D. G.

2010-01-01

A three mode opto-acoustic parametric amplifier (OAPA) is created when two orthogonal optical modes in a high finesse optical cavity are coupled via an acoustic mode of the cavity mirror. Such interactions are predicted to occur in advanced long baseline gravitational wave detectors. They can have high positive gain, which leads to strong parametric instability. Here we show that an optical feedback scheme can enhance or suppress the parametric gain of an OAPA, allowing exploration of three-mode parametric interactions, especially in cavity systems that have insufficient optical power to achieve spontaneous instability. We derive analytical equations and show that optical feedback is capable of controlling predicted instabilities in advanced gravitational wave detectors within a time scale of 13∼10 s.

Multiharmonic Frequency-Chirped Transducers for Surface-Acoustic-Wave Optomechanics

Science.gov (United States)

Weiß, Matthias; Hörner, Andreas L.; Zallo, Eugenio; Atkinson, Paola; Rastelli, Armando; Schmidt, Oliver G.; Wixforth, Achim; Krenner, Hubert J.

2018-01-01

Wide-passband interdigital transducers are employed to establish a stable phase lock between a train of laser pulses emitted by a mode-locked laser and a surface acoustic wave generated electrically by the transducer. The transducer design is based on a multiharmonic split-finger architecture for the excitation of a fundamental surface acoustic wave and a discrete number of its overtones. Simply by introducing a variation of the transducer's periodicity p , a frequency chirp is added. This combination results in wide frequency bands for each harmonic. The transducer's conversion efficiency from the electrical to the acoustic domain is characterized optomechanically using single quantum dots acting as nanoscale pressure sensors. The ability to generate surface acoustic waves over a wide band of frequencies enables advanced acousto-optic spectroscopy using mode-locked lasers with fixed repetition rate. Stable phase locking between the electrically generated acoustic wave and the train of laser pulses is confirmed by performing stroboscopic spectroscopy on a single quantum dot at a frequency of 320 MHz. Finally, the dynamic spectral modulation of the quantum dot is directly monitored in the time domain combining stable phase-locked optical excitation and time-correlated single-photon counting. The demonstrated scheme will be particularly useful for the experimental implementation of surface-acoustic-wave-driven quantum gates of optically addressable qubits or collective quantum states or for multicomponent Fourier synthesis of tailored nanomechanical waveforms.

Experience Changes How Emotion in Music Is Judged: Evidence from Children Listening with Bilateral Cochlear Implants, Bimodal Devices, and Normal Hearing.

Directory of Open Access Journals (Sweden)

Sara Giannantonio

Full Text Available Children using unilateral cochlear implants abnormally rely on tempo rather than mode cues to distinguish whether a musical piece is happy or sad. This led us to question how this judgment is affected by the type of experience in early auditory development. We hypothesized that judgments of the emotional content of music would vary by the type and duration of access to sound in early life due to deafness, altered perception of musical cues through new ways of using auditory prostheses bilaterally, and formal music training during childhood. Seventy-five participants completed the Montreal Emotion Identification Test. Thirty-three had normal hearing (aged 6.6 to 40.0 years and 42 children had hearing loss and used bilateral auditory prostheses (31 bilaterally implanted and 11 unilaterally implanted with contralateral hearing aid use. Reaction time and accuracy were measured. Accurate judgment of emotion in music was achieved across ages and musical experience. Musical training accentuated the reliance on mode cues which developed with age in the normal hearing group. Degrading pitch cues through cochlear implant-mediated hearing induced greater reliance on tempo cues, but mode cues grew in salience when at least partial acoustic information was available through some residual hearing in the contralateral ear. Finally, when pitch cues were experimentally distorted to represent cochlear implant hearing, individuals with normal hearing (including those with musical training switched to an abnormal dependence on tempo cues. The data indicate that, in a western culture, access to acoustic hearing in early life promotes a preference for mode rather than tempo cues which is enhanced by musical training. The challenge to these preferred strategies during cochlear implant hearing (simulated and real, regardless of musical training, suggests that access to pitch cues for children with hearing loss must be improved by preservation of residual hearing and

Experience Changes How Emotion in Music Is Judged: Evidence from Children Listening with Bilateral Cochlear Implants, Bimodal Devices, and Normal Hearing

Science.gov (United States)

Papsin, Blake C.; Paludetti, Gaetano; Gordon, Karen A.

2015-01-01

Children using unilateral cochlear implants abnormally rely on tempo rather than mode cues to distinguish whether a musical piece is happy or sad. This led us to question how this judgment is affected by the type of experience in early auditory development. We hypothesized that judgments of the emotional content of music would vary by the type and duration of access to sound in early life due to deafness, altered perception of musical cues through new ways of using auditory prostheses bilaterally, and formal music training during childhood. Seventy-five participants completed the Montreal Emotion Identification Test. Thirty-three had normal hearing (aged 6.6 to 40.0 years) and 42 children had hearing loss and used bilateral auditory prostheses (31 bilaterally implanted and 11 unilaterally implanted with contralateral hearing aid use). Reaction time and accuracy were measured. Accurate judgment of emotion in music was achieved across ages and musical experience. Musical training accentuated the reliance on mode cues which developed with age in the normal hearing group. Degrading pitch cues through cochlear implant-mediated hearing induced greater reliance on tempo cues, but mode cues grew in salience when at least partial acoustic information was available through some residual hearing in the contralateral ear. Finally, when pitch cues were experimentally distorted to represent cochlear implant hearing, individuals with normal hearing (including those with musical training) switched to an abnormal dependence on tempo cues. The data indicate that, in a western culture, access to acoustic hearing in early life promotes a preference for mode rather than tempo cues which is enhanced by musical training. The challenge to these preferred strategies during cochlear implant hearing (simulated and real), regardless of musical training, suggests that access to pitch cues for children with hearing loss must be improved by preservation of residual hearing and improvements in

Electron-beam-induced acoustic-wave enhancement of gaseous combustion

International Nuclear Information System (INIS)

Bidwell, S.W.; Bosch, R.A.; Gilgenbach, R.M.

1989-01-01

The combustion rate of premixed gases in a closed vessel was increased by injecting a high-current electron beam into the gas mixture within about 20 ms of spark ignition. This effect was observed with the fuels ethylene, methane, ethane, propane, and n-butane. Experimental results provide strong evidence that e-beam excitation of the fundamental longitudinal-acoustic mode of the cylindrical chamber is the mechanism of combustion enhancement. An observable combustion enhancement required that the amplitude of the fluid velocity oscillation in this acoustic mode be greater than or approximately equal to the flame propagation speed and was associated with a wrinkled or cellular flame structure with dimensions on the order of 1/2 cm. These results are in good agreement with values for the threshold acoustic velocity amplitude and dimension of cellular structure predicted for a periodically accelerated flame

On Computations of Duct Acoustics with Near Cut-Off Frequency

Science.gov (United States)

Dong, Thomas Z.; Povinelli, Louis A.

1997-01-01

The cut-off is a unique feature associated with duct acoustics due to the presence of duct walls. A study of this cut-off effect on the computations of duct acoustics is performed in the present work. The results show that the computation of duct acoustic modes near cut-off requires higher numerical resolutions than others to avoid being numerically cut off. Duct acoustic problems in Category 2 are solved by the DRP finite difference scheme with the selective artificial damping method and results are presented and compared to reference solutions.

SEARCH FOR GLOBAL f-MODES AND p-MODES IN THE {sup 8}B NEUTRINO FLUX

Energy Technology Data Exchange (ETDEWEB)

Lopes, Ilídio, E-mail: ilidio.lopes@ist.utl.pt, E-mail: ilopes@uevora.pt [Centro Multidisciplinar de Astrofísica, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Departamento de Física, Escola de Ciências e Tecnologia, Universidade de Évora, Colégio Luis António Verney, 7002-554 Évora (Portugal)

2013-11-01

The impact of global acoustic modes on the {sup 8}B neutrino flux time series is computed for the first time. It is shown that the time fluctuations of the {sup 8}B neutrino flux depend on the amplitude of acoustic eigenfunctions in the region where the {sup 8}B neutrino flux is produced: modes with low n (or order) that have eigenfunctions with a relatively large amplitude in the Sun's core strongly affect the neutrino flux; conversely, modes with high n that have eigenfunctions with a minimal amplitude in the Sun's core have a very small impact on the neutrino flux. It was found that the global modes with a larger impact on the {sup 8}B neutrino flux have a frequency of oscillation in the interval 250 μHz to 500 μHz (or a period in the interval 30 minutes to 70 minutes), such as the f-modes (n = 0) for the low degrees, radial modes of order n ≤ 3, and the dipole mode of order n = 1. Their corresponding neutrino eigenfunctions are very sensitive to the solar inner core and are unaffected by the variability of the external layers of the solar surface. If time variability of neutrinos is observed for these modes, it will lead to new ways of improving the sound speed profile inversion in the central region of the Sun.

Neutrino induced vorticity, Alfven waves and the normal modes

Energy Technology Data Exchange (ETDEWEB)

Bhatt, Jitesh R. [Theory Division, Physical Research Laboratory, Ahmedabad (India); George, Manu [Theory Division, Physical Research Laboratory, Ahmedabad (India); Indian Institute of Technology, Department of Physics, Ahmedabad (India)

2017-08-15

We consider a plasma consisting of electrons and ions in the presence of a background neutrino gas and develop the magnetohydrodynamic equations for the system. We show that the electron neutrino interaction can induce vorticity in the plasma even in the absence of any electromagnetic perturbations if the background neutrino density is left-right asymmetric. This induced vorticity supports a new kind of Alfven wave whose velocity depends on both the external magnetic field and on the neutrino asymmetry. The normal mode analysis show that in the presence of neutrino background the Alfven waves can have different velocities. We also discuss our results in the context of dense astrophysical plasma such as magnetars and show that the difference in the Alfven velocities can be used to explain the observed pulsar kick. We discuss also the relativistic generalisation of the electron fluid in presence of an asymmetric neutrino background. (orig.)

Acoustic Gravity Waves Generated by an Oscillating Ice Sheet in Arctic Zone

Science.gov (United States)

Abdolali, A.; Kadri, U.; Kirby, J. T., Jr.

2016-12-01

We investigate the formation of acoustic-gravity waves due to oscillations of large ice blocks, possibly triggered by atmospheric and ocean currents, ice block shrinkage or storms and ice-quakes.For the idealized case of a homogeneous weakly compressible water bounded at the surface by ice sheet and a rigid bed, the description of the infinite family of acoustic modes is characterized by the water depth h and angular frequency of oscillating ice sheet ω ; The acoustic wave field is governed by the leading mode given by: Nmax=\\floor {(ω h)/(π c)} where c is the sound speed in water and the special brackets represent the floor function (Fig1). Unlike the free-surface setting, the higher acoustic modes might exhibit a larger contribution and therefore all progressive acoustic modes have to be considered.This study focuses on the characteristics of acoustic-gravity waves generated by an oscillating elastic ice sheet in a weakly compressible fluid coupled with a free surface model [Abdolali et al. 2015] representing shrinking ice blocks in realistic sea state, where the randomly oriented ice sheets cause inter modal transition and multidirectional reflections. A theoretical solution and a 3D numerical model have been developed for the study purposes. The model is first validated against the theoretical solution [Kadri, 2016]. To overcome the computational difficulties of 3D models, we derive a depth-integrated equation valid for spatially varying ice sheet thickness and water depth. We show that the generated acoustic-gravity waves contribute significantly to deep ocean currents compared to other mechanisms. In addition, these waves travel at the sound speed in water carrying information on ice sheet motion, providing various implications for ocean monitoring and detection of ice-quakes. Fig1:Snapshots of dynamic pressure given by an oscillating ice sheet; h=4500m, c=1500m/s, semi-length b=10km, ζ =1m, omega=π rad/s. Abdolali, A., Kirby, J. T. and Bellotti, G

Laser Generated Leaky Acoustic Waves for Needle Visualization.

Science.gov (United States)

Wu, Kai-Wen; Wang, Yi-An; Li, Pai-Chi

2018-04-01

Ultrasound (US)-guided needle operation is usually used to visualize both tissue and needle position such as tissue biopsy and localized drug delivery. However, the transducer-needle orientation is limited due to reflection of the acoustic waves. We proposed a leaky acoustic wave method to visualize the needle position and orientation. Laser pulses are emitted on top of the needle to generate acoustic waves; then, these acoustic waves propagate along the needle surface. Leaky wave signals are detected by the US array transducer. The needle position can be calculated by phase velocities of two different wave modes and their corresponding emission angles. In our experiments, a series of needles was inserted into a tissue mimicking phantom and porcine tissue to evaluate the accuracy of the proposed method. The results show that the detection depth is up to 51 mm and the insertion angle is up to 40° with needles of different diameters. It is demonstrated that the proposed approach outperforms the conventional B-mode US-guided needle operation in terms of the detection range while achieving similar accuracy. The proposed method reveals the potentials for further clinical applications.

Acoustic Wake-Up Receivers for Home Automation Control Applications

Directory of Open Access Journals (Sweden)

Amir Bannoura

2016-01-01

Full Text Available Automated home applications are to ease the use of technology and devices around the house. Most of the electronic devices, like shutters or entertainment products (Hifi, TV and even WiFi, are constantly in a standby mode, where they consume a considerable amount of energy. The standby mode is necessary to react to commands triggered by the user, but the time the device spends in a standby mode is considered long. In our work, we present a receiver that is attached to home appliances that allows the devices to be activated while they are completely turned off in order to reduce the energy consumed in the standby mode. The receiver contains a low power wake-up module that reacts to an addressable acoustic 20-kHz sound signal that controls home devices that are connected to it. The acoustic wake-up signal can be sent by any kind of speaker that is available in commercial smartphones. The smartphones will operate as transmitters to the signals. Our wake-up receiver consists of two parts: a low power passive circuit connected to a wake-up chip microcontroller and an active micro-electromechanical system (MEMS microphone that receives the acoustic signal. A duty cycle is required to reduce the power consumption of the receiver, because the signal reception occurs when the microphone is active. The current consumption was measured to be 15 μA in sleep mode and 140 μA in active mode. An average wake-up range of 10 m using a smartphone as a sender was achieved.

A numerically efficient damping model for acoustic resonances in microfluidic cavities

Energy Technology Data Exchange (ETDEWEB)

Hahn, P., E-mail: hahnp@ethz.ch; Dual, J. [Institute of Mechanical Systems (IMES), Department of Mechanical and Process Engineering, ETH Zurich, Tannenstrasse 3, CH-8092 Zurich (Switzerland)

2015-06-15

Bulk acoustic wave devices are typically operated in a resonant state to achieve enhanced acoustic amplitudes and high acoustofluidic forces for the manipulation of microparticles. Among other loss mechanisms related to the structural parts of acoustofluidic devices, damping in the fluidic cavity is a crucial factor that limits the attainable acoustic amplitudes. In the analytical part of this study, we quantify all relevant loss mechanisms related to the fluid inside acoustofluidic micro-devices. Subsequently, a numerical analysis of the time-harmonic visco-acoustic and thermo-visco-acoustic equations is carried out to verify the analytical results for 2D and 3D examples. The damping results are fitted into the framework of classical linear acoustics to set up a numerically efficient device model. For this purpose, all damping effects are combined into an acoustofluidic loss factor. Since some components of the acoustofluidic loss factor depend on the acoustic mode shape in the fluid cavity, we propose a two-step simulation procedure. In the first step, the loss factors are deduced from the simulated mode shape. Subsequently, a second simulation is invoked, taking all losses into account. Owing to its computational efficiency, the presented numerical device model is of great relevance for the simulation of acoustofluidic particle manipulation by means of acoustic radiation forces or acoustic streaming. For the first time, accurate 3D simulations of realistic micro-devices for the quantitative prediction of pressure amplitudes and the related acoustofluidic forces become feasible.

Structural improvement of unliganded simian immunodeficiency virus gp120 core by normal-mode-based X-ray crystallographic refinement

International Nuclear Information System (INIS)

Chen, Xiaorui; Lu, Mingyang; Poon, Billy K.; Wang, Qinghua; Ma, Jianpeng

2009-01-01

The structural model of the unliganded and fully glycosylated simian immunodeficiency virus gp120 core determined to 4.0 Å resolution was substantially improved using a recently developed normal-mode-based anisotropic B-factor refinement method. The envelope protein gp120/gp41 of simian and human immunodeficiency viruses plays a critical role in viral entry into host cells. However, the extraordinarily high structural flexibility and heavy glycosylation of the protein have presented enormous difficulties in the pursuit of high-resolution structural investigation of some of its conformational states. An unliganded and fully glycosylated gp120 core structure was recently determined to 4.0 Å resolution. The rather low data-to-parameter ratio limited refinement efforts in the original structure determination. In this work, refinement of this gp120 core structure was carried out using a normal-mode-based refinement method that has been shown in previous studies to be effective in improving models of a supramolecular complex at 3.42 Å resolution and of a membrane protein at 3.2 Å resolution. By using only the first four nonzero lowest-frequency normal modes to construct the anisotropic thermal parameters, combined with manual adjustments and standard positional refinement using REFMAC5, the structural model of the gp120 core was significantly improved in many aspects, including substantial decreases in R factors, better fitting of several flexible regions in electron-density maps, the addition of five new sugar rings at four glycan chains and an excellent correlation of the B-factor distribution with known structural flexibility. These results further underscore the effectiveness of this normal-mode-based method in improving models of protein and nonprotein components in low-resolution X-ray structures

Stable And Oscillating Acoustic Levitation

Science.gov (United States)

Barmatz, Martin B.; Garrett, Steven L.

1988-01-01

Sample stability or instability determined by levitating frequency. Degree of oscillation of acoustically levitated object along axis of levitation chamber controlled by varying frequency of acoustic driver for axis above or below frequency of corresponding chamber resonance. Stabilization/oscillation technique applied in normal Earth gravity, or in absence of gravity to bring object quickly to rest at nominal levitation position or make object oscillate in desired range about that position.

MHD-model for low-frequency waves in a tokamak with toroidal plasma rotation and problem of existence of global geodesic acoustic modes

Energy Technology Data Exchange (ETDEWEB)

Lakhin, V. P.; Sorokina, E. A., E-mail: sorokina.ekaterina@gmail.com, E-mail: vilkiae@gmail.com; Ilgisonis, V. I. [National Research Centre Kurchatov Institute (Russian Federation); Konovaltseva, L. V. [Peoples’ Friendship University of Russia (Russian Federation)

2015-12-15

A set of reduced linear equations for the description of low-frequency perturbations in toroidally rotating plasma in axisymmetric tokamak is derived in the framework of ideal magnetohydrodynamics. The model suitable for the study of global geodesic acoustic modes (GGAMs) is designed. An example of the use of the developed model for derivation of the integral conditions for GGAM existence and of the corresponding dispersion relation is presented. The paper is dedicated to the memory of academician V.D. Shafranov.

Dual-Mode Gas Sensor Composed of a Silicon Nanoribbon Field Effect Transistor and a Bulk Acoustic Wave Resonator: A Case Study in Freons

Directory of Open Access Journals (Sweden)

Ye Chang

2018-01-01

Full Text Available In this paper, we develop a novel dual-mode gas sensor system which comprises a silicon nanoribbon field effect transistor (Si-NR FET and a film bulk acoustic resonator (FBAR. We investigate their sensing characteristics using polar and nonpolar organic compounds, and demonstrate that polarity has a significant effect on the response of the Si-NR FET sensor, and only a minor effect on the FBAR sensor. In this dual-mode system, qualitative discrimination can be achieved by analyzing polarity with the Si-NR FET and quantitative concentration information can be obtained using a polymer-coated FBAR with a detection limit at the ppm level. The complementary performance of the sensing elements provides higher analytical efficiency. Additionally, a dual mixture of two types of freons (CFC-113 and HCFC-141b is further analyzed with the dual-mode gas sensor. Owing to the small size and complementary metal-oxide semiconductor (CMOS-compatibility of the system, the dual-mode gas sensor shows potential as a portable integrated sensing system for the analysis of gas mixtures in the future.

Low-frequency electrostatic dust-modes in a non-uniform

Indian Academy of Sciences (India)

A self-consistent and general description of obliquely propagating low-frequency electrostatic dust-modes in a non-uniform magnetized dusty plasma system has been presented. A number of different situations, which correspond to different low-frequency electrostatic dust-modes, namely, dust-acoustic mode, dust-drift ...

Acoustic plane waves normally incident on a clamped panel in a rectangular duct. [to explain noise reduction curves for reducing interior noise in aircraft

Science.gov (United States)

Unz, H.; Roskam, J.

1979-01-01

The theory of acoustic plane wave normally incident on a clamped panel in a rectangular duct is developed. The coupling theory between the elastic vibrations of the panel (plate) and the acoustic wave propagation in infinite space and in the rectangular duct is considered. The partial differential equation which governs the vibration of the panel (plate) is modified by adding to its stiffness (spring) forces and damping forces, and the fundamental resonance frequency and the attenuation factor are discussed. The noise reduction expression based on the theory is found to agree well with the corresponding experimental data of a sample aluminum panel in the mass controlled region, the damping controlled region, and the stiffness controlled region. All the frequency positions of the upward and downward resonance spikes in the sample experimental data are identified theoretically as resulting from four cross interacting major resonance phenomena: the cavity resonance, the acoustic resonance, the plate resonance, and the wooden back panel resonance.

Geological formation characterisation by acoustic waves

International Nuclear Information System (INIS)

Mari, J.L.; Gaudiani, P.; Delay, J.

2010-01-01

Document available in extended abstract form only. For many years, the transmission of a sonic wave through formations has been used for drilling measurements. The tools used are of monopole or dipole type. Monopole-type tools are the most commonly used. Sources and receivers are multidirectional. In the fluid, sources generate a compression wave which creates in the formation a compression wave (P wave) and a shear wave (S wave) at the refraction limit angles. In a vertical well, such tools permit the recording of five propagation modes: the refracted compression wave, the refracted shear wave (only in fast formations), the fluid wave, two dispersive guided modes which are the pseudo Rayleigh waves (only in fast formations) and the Stoneley waves. Full waveform acoustic measurements are represented as constant-offset sections or as common source point gathers, similar to those used in seismic operations. For the different modes, the acoustic parameters which are usually measured are: picked time, amplitude and frequency. The acoustic parameters allow one to determine the propagation velocities of the various modes and some petro-physical parameters and to obtain lithologic and mechanical information if the shear velocity of the formation has been measured. Usually the picking of the refracted S wave is difficult due to the interferences of different wave trains such as leaky modes associated with the refracted P waves and the pseudo Rayleigh. To compute a continuous log of shear velocity, we propose an hybrid method based on the local measurement of the shear velocity (picking of the arrival time of the refracted S wave) and on the analysis of the dispersion curve of the Stoneley modes ( Biot 1956, White 1965). We also show the benefit of using a shape index parameter named Ic, computed from the amplitudes (A1, A2 and A3) of the first refracted P wave to detect acoustic anomalies specially in fractured formation. The Ic parameter is independent of the energy of

Acoustic multimode interference and self-imaging phenomena realized in multimodal phononic crystal waveguides

International Nuclear Information System (INIS)

Zou, Qiushun; Yu, Tianbao; Liu, Jiangtao; Wang, Tongbiao; Liao, Qinghua; Liu, Nianhua

2015-01-01

We report an acoustic multimode interference effect and self-imaging phenomena in an acoustic multimode waveguide system which consists of M parallel phononic crystal waveguides (M-PnCWs). Results show that the self-imaging principle remains applicable for acoustic waveguides just as it does for optical multimode waveguides. To achieve the dispersions and replicas of the input acoustic waves produced along the propagation direction, we performed the finite element method on M-PnCWs, which support M guided modes within the target frequency range. The simulation results show that single images (including direct and mirrored images) and N-fold images (N is an integer) are identified along the propagation direction with asymmetric and symmetric incidence discussed separately. The simulated positions of the replicas agree well with the calculated values that are theoretically decided by self-imaging conditions based on the guided mode propagation analysis. Moreover, the potential applications based on this self-imaging effect for acoustic wavelength de-multiplexing and beam splitting in the acoustic field are also presented. (paper)

Signal analysis of acoustic and flow-induced vibrations of BWR main steam line

Energy Technology Data Exchange (ETDEWEB)

Espinosa-Paredes, G., E-mail: gepe@xanum.uam.mx [División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana-Iztapalapa, México, D.F. 09340 (Mexico); Prieto-Guerrero, A. [División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana-Iztapalapa, México, D.F. 09340 (Mexico); Núñez-Carrera, A. [Comisión Nacional de Seguridad Nuclear y Salvaguardias, Doctor Barragán 779, Col. Narvarte, México, D.F. 03020 (Mexico); Vázquez-Rodríguez, A. [División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana-Iztapalapa, México, D.F. 09340 (Mexico); Centeno-Pérez, J. [Instituto Politécnico Nacional, Escuela Superior de Física y Matemáticas Unidad Profesional “Adolfo López Mateos”, Av. IPN, s/n, México, D.F. 07738 (Mexico); Espinosa-Martínez, E.-G. [Departamento de Sistemas Energéticos, Universidad Nacional Autónoma de México, México, D.F. 04510 (Mexico); and others

2016-05-15

Highlights: • Acoustic and flow-induced vibrations of BWR are analyzed. • BWR performance after extended power uprate is considered. • Effect of acoustic side branches (ASB) is analyzed. • The ASB represents a reduction in the acoustic loads to the steam dryer. • Methodology developed for simultaneous analyzing the signals in the MSL. - Abstract: The aim of this work is the signal analysis of acoustic waves due to phenomenon known as singing in Safety Relief Valves (SRV) of the main steam lines (MSL) in a typical BWR5. The acoustic resonance in SRV standpipes and fluctuating pressure is propagated from SRV to the dryer through the MSL. The signals are analyzed with a novel method based on the Multivariate Empirical Mode Decomposition (M-EMD). The M-EMD algorithm has the potential to find common oscillatory modes (IMF) within multivariate data. Based on this fact, we implement the M-EMD technique to find the oscillatory mode in BWR considering the measurements obtained collected by the strain gauges located around the MSL. These IMF, analyzed simultaneously in time, allow obtaining an estimation of the effects of the multiple-SRV in the MSL. Two scenarios are analyzed: the first is the signal obtained before the installation of the acoustic dampers (ASB), and the second, the signal obtained after installation. The results show the effectiveness of the ASB to damp the strong resonances when the steam flow increases, which represents an important reduction in the acoustic loads to the steam dryer.

Signal analysis of acoustic and flow-induced vibrations of BWR main steam line

International Nuclear Information System (INIS)

Espinosa-Paredes, G.; Prieto-Guerrero, A.; Núñez-Carrera, A.; Vázquez-Rodríguez, A.; Centeno-Pérez, J.; Espinosa-Martínez, E.-G.

2016-01-01

Highlights: • Acoustic and flow-induced vibrations of BWR are analyzed. • BWR performance after extended power uprate is considered. • Effect of acoustic side branches (ASB) is analyzed. • The ASB represents a reduction in the acoustic loads to the steam dryer. • Methodology developed for simultaneous analyzing the signals in the MSL. - Abstract: The aim of this work is the signal analysis of acoustic waves due to phenomenon known as singing in Safety Relief Valves (SRV) of the main steam lines (MSL) in a typical BWR5. The acoustic resonance in SRV standpipes and fluctuating pressure is propagated from SRV to the dryer through the MSL. The signals are analyzed with a novel method based on the Multivariate Empirical Mode Decomposition (M-EMD). The M-EMD algorithm has the potential to find common oscillatory modes (IMF) within multivariate data. Based on this fact, we implement the M-EMD technique to find the oscillatory mode in BWR considering the measurements obtained collected by the strain gauges located around the MSL. These IMF, analyzed simultaneously in time, allow obtaining an estimation of the effects of the multiple-SRV in the MSL. Two scenarios are analyzed: the first is the signal obtained before the installation of the acoustic dampers (ASB), and the second, the signal obtained after installation. The results show the effectiveness of the ASB to damp the strong resonances when the steam flow increases, which represents an important reduction in the acoustic loads to the steam dryer.

Enhancement of acousto-optical coupling in two-dimensional air-slot phoxonic crystal cavities by utilizing surface acoustic waves

Energy Technology Data Exchange (ETDEWEB)

Ma, Tian-Xue [Institute of Engineering Mechanics, Beijing Jiaotong University, Beijing 100044 (China); Wang, Yue-Sheng, E-mail: yswang@bjtu.edu.cn [Institute of Engineering Mechanics, Beijing Jiaotong University, Beijing 100044 (China); Zhang, Chuanzeng [Department of Civil Engineering, University of Siegen, D-57068 Siegen (Germany)

2017-01-30

A phoxonic crystal is a periodically patterned material that can simultaneously localize optical and acoustic modes. The acousto-optical coupling in two-dimensional air-slot phoxonic crystal cavities is investigated numerically. The photons can be well confined in the slot owing to the large electric field discontinuity at the air/dielectric interfaces. Besides, the surface acoustic modes lead to the localization of the phonons near the air-slot. The high overlap of the photonic and phononic cavity modes near the slot results in a significant enhancement of the moving interface effect, and thus strengthens the total acousto-optical interaction. The results of two cavities with different slot widths show that the coupling strength is dependent on the slot width. It is expected to achieve a strong acousto-optical/optomechanical coupling in air-slot phoxonic crystal structures by utilizing surface acoustic modes. - Highlights: • Two-dimensional air-slot phoxonic crystal cavities which can confine simultaneously optical and acoustic waves are proposed. • The acoustic and optical waves are highly confined near/in the air-slot. • The high overlap of the photonic and phononic cavity modes significantly enhances the moving interface effect. • Different factors which affect the acousto-optical coupling are discussed.

Treatment of near-skull brain tissue with a focused device using shear-mode conversion: a numerical study

International Nuclear Information System (INIS)

Pichardo, Samuel; Hynynen, Kullervo

2007-01-01

Shear mode transmission through the skull has been previously proposed as a new trans-skull propagation technique for noninvasive therapeutic ultrasound (Clement 2004 J. Acoust. Soc. Am. 115 1356-64). The main advantage of choosing shear over longitudinal mode resides on the fact that there is less wavefront distortion with the former. In the present study, the regions of the brain suitable for shear-mode transmission were established for a simple focused ultrasound device. The device consists of a spherically curved transducer that has a focal length of 10 cm, an aperture between 30 0 and 60 0 and operates at 0.74 MHz. The regions suitable for shear-mode transmission were determined by the shear wave acoustic windows that matched the shape of the device acoustic field. The acoustic windows were calculated using segmentation and triangulation of outer and inner faces of skull from 3D-MRI head datasets. Nine heads of healthy adults were analyzed. The surface considered for the calculations was the head region found above the supra-orbital margin. For every inspected point in the brain volume, the axis of the device was determined by the vector between this inspection point and a point located in the center of the brain. Numerical predictions of the acoustic field, where shear-mode conversion through the skull was considered, were obtained and compared to the case of water-only conditions. The brain tissue that is close to the skull showed suitable acoustic windows for shear waves. The central region of the brain seems to be unreachable using shear-mode. Analysis of the acoustic fields showed a proportional relation between the acoustic window for shear mode and the effective degree of focusing. However, this relation showed significant differences among specimens. In general, highly focused fields were obtained when the acoustic window for shear waves (A SW ) intersected more than 67% of the entering acoustic window (A TX ) of the device. The average depth from the

Comparative analysis of guide mode of government - oriented industry guidance funds under china’s new normal of economic growth

Science.gov (United States)

Sun, Chunling; Cheng, Xuemei

2017-11-01

The government-oriented industry guidance Funds solve the problem of financing difficulty and high innovation under the background of China’s new normal. Through the provinces and cities of the policies and regulations of the collation and comparative analysis, it will be divided into three modes. And then compare among three modes and analyze applicability to guide the construction of provinces and cities.

Mechanical detection and mode shape imaging of vibrational modes of micro and nanomechanical resonators by dynamic force microscopy

International Nuclear Information System (INIS)

Paulo, A S; GarcIa-Sanchez, D; Perez-Murano, F; Bachtold, A; Black, J; Bokor, J; Esplandiu, M J; Aguasca, A

2008-01-01

We describe a method based on the use of higher order bending modes of the cantilever of a dynamic force microscope to characterize vibrations of micro and nanomechanical resonators at arbitrarily large resonance frequencies. Our method consists on using a particular cantilever eigenmode for standard feedback control in amplitude modulation operation while another mode is used for detecting and imaging the resonator vibration. In addition, the resonating sample device is driven at or near its resonance frequency with a signal modulated in amplitude at a frequency that matches the resonance of the cantilever eigenmode used for vibration detection. In consequence, this cantilever mode is excited with an amplitude proportional to the resonator vibration, which is detected with an external lock-in amplifier. We show two different application examples of this method. In the first one, acoustic wave vibrations of a film bulk acoustic resonator around 1.6 GHz are imaged. In the second example, bending modes of carbon nanotube resonators up to 3.1 GHz are characterized. In both cases, the method provides subnanometer-scale sensitivity and the capability of providing otherwise inaccessible information about mechanical resonance frequencies, vibration amplitude values and mode shapes

An Optimisation Approach for Room Acoustics Design

DEFF Research Database (Denmark)

Holm-Jørgensen, Kristian; Kirkegaard, Poul Henning; Andersen, Lars

2005-01-01

This paper discuss on a conceptual level the value of optimisation techniques in architectural acoustics room design from a practical point of view. It is chosen to optimise one objective room acoustics design criterium estimated from the sound field inside the room. The sound field is modeled...... using the boundary element method where absorption is incorporated. An example is given where the geometry of a room is defined by four design modes. The room geometry is optimised to get a uniform sound pressure....

The Effects of Internal Waves on Acoustic Normal Modes.

Science.gov (United States)

1984-12-01

thatp HTp HTv + CvS(!!)(..)(25 The hydrodynamic equations appropriate to an ocean are Du p b + p(fxuL) + Vp - = V-A + F (2.6a) Do + pv.u 0(2.6b) pT Ln+ V...Payne, "User’s Manual for NEMESIS and PLMODE," Applied Research Laboratories Technical Memorandum No. 80-6 . (ARL-TM-80-6), Applied Research Laboratories...1, 6th edition, Reference Manual , 1979. 56. 3. Turner, Buoyancy Effects in Fluids (Cambridqe University Press, Cambridge, London, 1972) Chap. 8. 57. W

Influence of superthermal electrons on obliquely propagating ion-acoustic solitons in magnetized plasmas

International Nuclear Information System (INIS)

Kadijani, M Nouri; Abbasi, H; Pajouh, H Hakimi

2011-01-01

The effect of superthermal electrons, modeled by a Lorentzian velocity distribution function, on the oblique propagation characteristics of linear and nonlinear ion-acoustic waves in an electron-ion plasma in the presence of a uniform external magnetic field is investigated. First, the linear dispersion relations of the fast and slow modes are obtained. It is shown that the superthermal electrons make both modes propagate with smaller phase velocities. Then, the Korteweg-de Vries equation describing the propagation of nonlinear slow and fast ion-acoustic waves is derived. It is shown that the presence of superthermal electrons has a significant influence on the nature of magnetized ion-acoustic solitons. That is, for a larger population of the superthermal electrons, the soliton velocity of both modes in the laboratory frame significantly decreases and the soliton are slimmer, and on approaching the Maxwellian limit, the width becomes maximum.

Nonlinear optical observation of coherent acoustic Dirac plasmons in thin-film topological insulators

Science.gov (United States)

Glinka, Yuri D.; Babakiray, Sercan; Johnson, Trent A.; Holcomb, Mikel B.; Lederman, David

2016-09-01

Low-energy collective electronic excitations exhibiting sound-like linear dispersion have been intensively studied both experimentally and theoretically for a long time. However, coherent acoustic plasmon modes appearing in time-domain measurements are rarely observed due to Landau damping by the single-particle continua. Here we report on the observation of coherent acoustic Dirac plasmon (CADP) modes excited in indirectly (electrostatically) opposite-surface coupled films of the topological insulator Bi2Se3. Using transient second-harmonic generation, a technique capable of independently monitoring the in-plane and out-of-plane electron dynamics in the films, the GHz-range oscillations were observed without corresponding oscillations in the transient reflectivity. These oscillations were assigned to the transverse magnetic and transverse electric guided CADP modes induced by the evanescent guided Lamb acoustic waves and remained Landau undamped due to fermion tunnelling between the opposite-surface Dirac states.

Normal-Mode Analysis of Circular DNA at the Base-Pair Level. 2. Large-Scale Configurational Transformation of a Naturally Curved Molecule.

Science.gov (United States)

Matsumoto, Atsushi; Tobias, Irwin; Olson, Wilma K

2005-01-01

Fine structural and energetic details embedded in the DNA base sequence, such as intrinsic curvature, are important to the packaging and processing of the genetic material. Here we investigate the internal dynamics of a 200 bp closed circular molecule with natural curvature using a newly developed normal-mode treatment of DNA in terms of neighboring base-pair "step" parameters. The intrinsic curvature of the DNA is described by a 10 bp repeating pattern of bending distortions at successive base-pair steps. We vary the degree of intrinsic curvature and the superhelical stress on the molecule and consider the normal-mode fluctuations of both the circle and the stable figure-8 configuration under conditions where the energies of the two states are similar. To extract the properties due solely to curvature, we ignore other important features of the double helix, such as the extensibility of the chain, the anisotropy of local bending, and the coupling of step parameters. We compare the computed normal modes of the curved DNA model with the corresponding dynamical features of a covalently closed duplex of the same chain length constructed from naturally straight DNA and with the theoretically predicted dynamical properties of a naturally circular, inextensible elastic rod, i.e., an O-ring. The cyclic molecules with intrinsic curvature are found to be more deformable under superhelical stress than rings formed from naturally straight DNA. As superhelical stress is accumulated in the DNA, the frequency, i.e., energy, of the dominant bending mode decreases in value, and if the imposed stress is sufficiently large, a global configurational rearrangement of the circle to the figure-8 form takes place. We combine energy minimization with normal-mode calculations of the two states to decipher the configurational pathway between the two states. We also describe and make use of a general analytical treatment of the thermal fluctuations of an elastic rod to characterize the

Time-Frequency Analysis of the Dispersion of Lamb Modes

Science.gov (United States)

Prosser, W. H.; Seale, Michael D.; Smith, Barry T.

1999-01-01

Accurate knowledge of the velocity dispersion of Lamb modes is important for ultrasonic nondestructive evaluation methods used in detecting and locating flaws in thin plates and in determining their elastic stiffness coefficients. Lamb mode dispersion is also important in the acoustic emission technique for accurately triangulating the location of emissions in thin plates. In this research, the ability to characterize Lamb mode dispersion through a time-frequency analysis (the pseudo Wigner-Ville distribution) was demonstrated. A major advantage of time-frequency methods is the ability to analyze acoustic signals containing multiple propagation modes, which overlap and superimpose in the time domain signal. By combining time-frequency analysis with a broadband acoustic excitation source, the dispersion of multiple Lamb modes over a wide frequency range can be determined from as little as a single measurement. In addition, the technique provides a direct measurement of the group velocity dispersion. The technique was first demonstrated in the analysis of a simulated waveform in an aluminum plate in which the Lamb mode dispersion was well known. Portions of the dispersion curves of the A(sub 0), A(sub 1), S(sub 0), and S(sub 2)Lamb modes were obtained from this one waveform. The technique was also applied for the analysis of experimental waveforms from a unidirectional graphite/epoxy composite plate. Measurements were made both along, and perpendicular to the fiber direction. In this case, the signals contained only the lowest order symmetric and antisymmetric modes. A least squares fit of the results from several source to detector distances was used. Theoretical dispersion curves were calculated and are shown to be in good agreement with experimental results.

Acoustic observations of internal tides and tidal currents in shallow water.

Science.gov (United States)

Turgut, Altan; Mignerey, Peter C; Goldstein, David J; Schindall, Jeffrey A

2013-04-01

Significant acoustic travel-time variability and frequency shifts of acoustic intensity level curves in broadband signal spectrograms were measured in the East China Sea during the summer of 2008. The broadband pulses (270-330 Hz) were transmitted from a fixed source and received at a bottomed horizontal array, located at the 33 km range. The acoustic intensity level curves of the received signals indicate regular frequency shifts that are well correlated with the measured internal tides. Similarly, regular travel-time shifts of the acoustic mode arrivals correlate well with the barotropic tides and can be explained by tidal currents along the acoustic propagation track. These observations indicate the potential of monitoring internal tides and tidal currents using low-frequency acoustic signals propagating at long ranges.

Search for Long Period Solar Normal Modes in Ambient Seismic Noise

Science.gov (United States)

Caton, R.; Pavlis, G. L.

2016-12-01

We search for evidence of solar free oscillations (normal modes) in long period seismic data through multitaper spectral analysis of array stacks. This analysis is similar to that of Thomson & Vernon (2015), who used data from the most quiet single stations of the global seismic network. Our approach is to use stacks of large arrays of noisier stations to reduce noise. Arrays have the added advantage of permitting the use of nonparametic statistics (jackknife errors) to provide objective error estimates. We used data from the Transportable Array, the broadband borehole array at Pinyon Flat, and the 3D broadband array in Homestake Mine in Lead, SD. The Homestake Mine array has 15 STS-2 sensors deployed in the mine that are extremely quiet at long periods due to stable temperatures and stable piers anchored to hard rock. The length of time series used ranged from 50 days to 85 days. We processed the data by low-pass filtering with a corner frequency of 10 mHz, followed by an autoregressive prewhitening filter and median stack. We elected to use the median instead of the mean in order to get a more robust stack. We then used G. Prieto's mtspec library to compute multitaper spectrum estimates on the data. We produce delete-one jackknife error estimates of the uncertainty at each frequency by computing median stacks of all data with one station removed. The results from the TA data show tentative evidence for several lines between 290 μHz and 400 μHz, including a recurring line near 379 μHz. This 379 μHz line is near the Earth mode 0T2 and the solar mode 5g5, suggesting that 5g5 could be coupling into the Earth mode. Current results suggest more statistically significant lines may be present in Pinyon Flat data, but additional processing of the data is underway to confirm this observation.

Passive acoustic radiation control for a vibrating panel with piezoelectric shunt damping circuit using particle swarm optimization algorithm

International Nuclear Information System (INIS)

Jeon, Jin Young

2009-01-01

This paper presents a new acoustic radiation optimization method for a vibrating panel-like structure with a passive piezoelectric shunt damping system in order to minimize well-radiating modes generated from the panel. The optimization method is based on an idea of using the p-version finite element method(p-version FEM), the boundary element method(BEM), and the particle swarm optimization algorithm(PSOA). Optimum embossment design for the vibrating panel using the PSOA is first investigated in order to minimize noise radiation over a frequency range of interest. The optimum embossment design works as a kind of stiffener so that well-radiating natural modes are shifted up with some degrees. The optimized panel, however, may still require additional damping for attenuating the peak acoustic amplitudes. A passive shunt damping system is thus employed to additionally damp the well-radiating modes from the optimized panel. To numerically evaluate the acoustic multiple-mode damping capability by a shunt damping system, the integrated p-version FEM/BEM for the panel with the shunt damping system is modeled and developed by MATLAB. Using the PSOA, the optimization technique for the optimal multiple-mode shunt damper is investigated in order to achieve the optimum damping performance for the well-radiating modes simultaneously. Also, the acoustic damping performance of the shunt damping circuit in the acoustic environment is demonstrated numerically and experimentally with respect to the realistically sized panel. The simulated result shows a good agreement with that of the experimental result

Acoustically sticky topographic metasurfaces for underwater sound absorption.

Science.gov (United States)

Lee, Hunki; Jung, Myungki; Kim, Minsoo; Shin, Ryung; Kang, Shinill; Ohm, Won-Suk; Kim, Yong Tae

2018-03-01

A class of metasurfaces for underwater sound absorption, based on a design principle that maximizes thermoviscous loss, is presented. When a sound meets a solid surface, it leaves a footprint in the form of thermoviscous boundary layers in which energy loss takes place. Considered to be a nuisance, this acoustic to vorticity/entropy mode conversion and the subsequent loss are often ignored in the existing designs of acoustic metamaterials and metasurfaces. The metasurface created is made of a series of topographic meta-atoms, i.e., intaglios and reliefs engraved directly on the solid object to be concealed. The metasurface is acoustically sticky in that it rather facilitates the conversion of the incident sound to vorticity and entropy modes, hence the thermoviscous loss, leading to the desired anechoic property. A prototype metasurface machined on a brass object is tested for its anechoicity, and shows a multitude of absorption peaks as large as unity in the 2-5 MHz range. Computations also indicate that a topographic metasurface is robust to hydrostatic pressure variation, a quality much sought-after in underwater applications.

Evoked acoustic emission

DEFF Research Database (Denmark)

Elberling, C; Parbo, J; Johnsen, N J

1985-01-01

Stimulated acoustic emissions were recorded in response to tonal stimuli at 60 dB p.e. SPL in a small group of normal-hearing adults. Power spectral analysis reveals that the evoked activity from each ear contains energy in preferential frequency bands and the change of stimulus frequency has only...

Polarization dependent behavior of CdS around the first and second LO-phonon modes

International Nuclear Information System (INIS)

Frausto-Reyes, C.; Molina-Contreras, J.R.; Lopez-Alvarez, Y.F.; Medel-Ruiz, C.I.; Perez Ladron de Guevara, H.; Ortiz-Morales, M.

2010-01-01

The present work report studies on resonant Raman experimental line shape for CdS around the first and second LO-phonon modes. The application of our method to the study of LO-phonon modes of CdS suggests that the scattered intensity is dominated by the surface and dependent on polarization. Results showed that the Raman spectra for CdS, roughly fall into three groups: a broad line-wing with apparent maxima around 194 cm -1 in the range of 140 and 240 cm -1 which can be ascribed to overtone scattering from acoustic phonons; a band near the 1LO phonon mode which can be attributed to a combination of one-phonon scattering and peak acoustic phonon and finally, a band near the 2LO phonon mode which can be attributed to a combination of two-phonon scattering and peak acoustic phonon.

Modeling guided wave excitation in plates with surface mounted piezoelectric elements: coupled physics and normal mode expansion

Science.gov (United States)

Ren, Baiyang; Lissenden, Cliff J.

2018-04-01

Guided waves have been extensively studied and widely used for structural health monitoring because of their large volumetric coverage and good sensitivity to defects. Effectively and preferentially exciting a desired wave mode having good sensitivity to a certain defect is of great practical importance. Piezoelectric discs and plates are the most common types of surface-mounted transducers for guided wave excitation and reception. Their geometry strongly influences the proportioning between excited modes as well as the total power of the excited modes. It is highly desirable to predominantly excite the selected mode while the total transduction power is maximized. In this work, a fully coupled multi-physics finite element analysis, which incorporates the driving circuit, the piezoelectric element and the wave guide, is combined with the normal mode expansion method to study both the mode tuning and total wave power. The excitation of circular crested waves in an aluminum plate with circular piezoelectric discs is numerically studied for different disc and adhesive thicknesses. Additionally, the excitation of plane waves in an aluminum plate, using a stripe piezoelectric element is studied both numerically and experimentally. It is difficult to achieve predominant single mode excitation as well as maximum power transmission simultaneously, especially for higher order modes. However, guidelines for designing the geometry of piezoelectric elements for optimal mode excitation are recommended.

Generation of ion-acoustic and magnetoacoustic waves in an RF helicon discharge

International Nuclear Information System (INIS)

Belov, A. S.; Markov, G. A.

2006-01-01

A study is made of the generation of ion-acoustic and magnetoacoustic waves in a discharge excited in an external magnetic field by an electromagnetic wave in the whistler frequency range (ω LH He , where ω LH = √(ω He ω Hi ) and ω He and ω Hi are the electron and ion gyrofrequencies, respectively). The excitation of acoustic waves is attributed to the decay of a high-frequency hybrid mode forming a plasma waveguide into low-frequency acoustic waves and new high-frequency waves that satisfy both the decay conditions and the waveguide dispersion relations. The excitation of acoustic waves is resonant in character because the conditions for the generation of waveguide modes and for the occurrence of the corresponding nonlinear wave processes should be satisfied simultaneously. An unexpected effect is the generation of magnetoacoustic waves by whistlers. A diagnostic technique is proposed that allows one to determine the thermal electron velocity by analyzing decay conditions and dispersion relations for waves in the discharge channel

The effect of dust charge inhomogeneity on low-frequency modes in a strongly coupled plasma

International Nuclear Information System (INIS)

Farid, T.; Mamun, A.A.; Shukla, P.K.

2000-01-01

An analysis of low-frequency modes accounting for dust grain charge fluctuation and equilibrium grain charge inhomogeneity in a strongly coupled dusty plasma is presented. The existence of an extremely low frequency mode, which is due to the inhomogeneity in the equilibrium dust grain charge, is reported. Besides, the equilibrium dust grain charge inhomogeneity makes the dust-acoustic mode unstable. The strong correlations in the dust fluid significantly drive a new mode as well as the existing dust-acoustic mode. The applications of these results to recent experimental and to some space and astrophysical situations are discussed

Helioseismology and asteroseismology: looking for gravitational waves in acoustic oscillations

Energy Technology Data Exchange (ETDEWEB)

Lopes, Ilídio [Centro Multidisciplinar de Astrofísica, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Silk, Joseph, E-mail: ilidio.lopes@tecnico.ulisboa.pt, E-mail: ilopes@uevora.pt, E-mail: silk@astro.ox.ac.uk [Institut d' Astrophysique de Paris, UMR 7095 CNRS, Université Pierre et Marie Curie, 98 bis Boulevard Arago, Paris 75014 (France)

2014-10-10

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

Normal-mode-based analysis of electron plasma waves with second-order Hermitian formalism

Science.gov (United States)

Ramos, J. J.; White, R. L.

2018-03-01

The classic problem of the dynamic evolution and Landau damping of linear Langmuir electron waves in a collisionless plasma with Maxwellian background is cast as a second-order, self-adjoint problem with a continuum spectrum of real and positive squared frequencies. The corresponding complete basis of singular normal modes is obtained, along with their orthogonality relation. This yields easily the general expression of the time-reversal-invariant solution for any initial-value problem. Examples are given for specific initial conditions that illustrate different behaviors of the Landau-damped macroscopic moments of the perturbations.

Gender and vocal production mode discrimination using the high frequencies for speech and singing

Science.gov (United States)

Monson, Brian B.; Lotto, Andrew J.; Story, Brad H.

2014-01-01

Humans routinely produce acoustical energy at frequencies above 6 kHz during vocalization, but this frequency range is often not represented in communication devices and speech perception research. Recent advancements toward high-definition (HD) voice and extended bandwidth hearing aids have increased the interest in the high frequencies. The potential perceptual information provided by high-frequency energy (HFE) is not well characterized. We found that humans can accomplish tasks of gender discrimination and vocal production mode discrimination (speech vs. singing) when presented with acoustic stimuli containing only HFE at both amplified and normal levels. Performance in these tasks was robust in the presence of low-frequency masking noise. No substantial learning effect was observed. Listeners also were able to identify the sung and spoken text (excerpts from “The Star-Spangled Banner”) with very few exposures. These results add to the increasing evidence that the high frequencies provide at least redundant information about the vocal signal, suggesting that its representation in communication devices (e.g., cell phones, hearing aids, and cochlear implants) and speech/voice synthesizers could improve these devices and benefit normal-hearing and hearing-impaired listeners. PMID:25400613

The digital holographic interferometry in resonant acoustic spectroscopy

International Nuclear Information System (INIS)

GAPONOV, V.E.; AZAMATOV, Z.T.; REDKORECHEV, V.I.; ISAEV, A.M.

2014-01-01

The opportunities of application of digital holographic interferometry method for studies of shapes of resonant modes in resonant acoustic spectroscopy are shown. The results of experimental measurements and analytical calculations are submitted. (authors)

Is reverberation time adequate for testing the acoustical quality of unroofed auditoriums?

DEFF Research Database (Denmark)

Paini, Dario; Gade, Anders Christian; Rindel, Jens Holger

2006-01-01

30) and other acoustical parameters normally used to test the acoustical quality of closed auditoria, such as concert halls, theatres, opera houses, are suitable and sufficient for testing the acoustical quality of open performance spaces. Simulations as well as measurements were carried out to study...

Topologically protected one-way edge mode in networks of acoustic resonators with circulating air flow

International Nuclear Information System (INIS)

Ni, Xu; He, Cheng; Sun, Xiao-Chen; Liu, Xiao-ping; Lu, Ming-Hui; Chen, Yan-Feng; Feng, Liang

2015-01-01

Recent explorations of topology in physical systems have led to a new paradigm of condensed matters characterized by topologically protected states and phase transition, for example, topologically protected photonic crystals enabled by magneto-optical effects. However, in other wave systems such as acoustics, topological states cannot be simply reproduced due to the absence of similar magnetics-related sound–matter interactions in naturally available materials. Here, we propose an acoustic topological structure by creating an effective gauge magnetic field for sound using circularly flowing air in the designed acoustic ring resonators. The created gauge magnetic field breaks the time-reversal symmetry, and therefore topological properties can be designed to be nontrivial with non-zero Chern numbers and thus to enable a topological sonic crystal, in which the topologically protected acoustic edge-state transport is observed, featuring robust one-way propagation characteristics against a variety of topological defects and impurities. Our results open a new venue to non-magnetic topological structures and promise a unique approach to effective manipulation of acoustic interfacial transport at will. (paper)

Acoustic levitation and manipulation for space applications

Science.gov (United States)

Wang, T. G.

1979-01-01

A wide spectrum of experiments to be performed in space in a microgravity environment require levitation and manipulation of liquid or molten samples. A novel acoustic method has been developed at JPL for controlling liquid samples without physical contacts. This method utilizes the static pressure generated by three orthogonal acoustic standing waves excited within an enclosure. Furthermore, this method will allow the sample to be rotated and/or oscillated by modifying the phase angles and/or the amplitude of the acoustic field. This technique has been proven both in our laboratory and in a microgravity environment provided by KC-135 flights. Samples placed within our chamber driven at (1,0,0), (0,1,0), and (0,0,1), modes were indeed levitated, rotated, and oscillated.

Predictions and observations of low-shear beta-induced shear Alfven-acoustic eigenmodes in toroidal plasmas

Energy Technology Data Exchange (ETDEWEB)

Gorelenkov, N.N. [Princeton Plasma Physics Laboratory, Princeton University (United States)], E-mail: ngorelen@pppl.gov; Berk, H.L. [IFS, Austin, Texas (United States); Fredrickson, E. [Princeton Plasma Physics Laboratory, Princeton University (United States); Sharapov, S.E. [Euroatom/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire (United States)

2007-10-08

New global MHD eigenmode solutions arising in gaps in the low frequency Alfven-acoustic continuum below the geodesic acoustic mode (GAM) frequency have been found numerically and have been used to explain relatively low frequency experimental signals seen in NSTX and JET tokamaks. These global eigenmodes, referred to here as Beta-induced Alfven-Acoustic Eigenmodes (BAAE), exist in the low magnetic safety factor region near the extrema of the Alfven-acoustic continuum. In accordance to the linear dispersion relations, the frequency of these modes shifts as the safety factor, q, decreases. We show that BAAEs can be responsible for observations in JET plasmas at relatively low beta <2% as well as in NSTX plasmas at relatively high-beta >20%. In contrast to the mostly electrostatic character of GAMs the new global modes also contain an electromagnetic (magnetic field line bending) component due to the Alfven coupling, leading to wave phase velocities along the field line that are large compared to the sonic speed. Qualitative agreement between theoretical predictions and observations are found.

Acoustic modelling in view of a determination of the Boltzmann constant within 1 ppm for the redefinition of the kelvin

International Nuclear Information System (INIS)

Gelat, Pierre; Podesta, Michael de; Sutton, Gavin; Underwood, Robin; Joly, Nicolas

2009-01-01

iMERA/Euromet Project 885 is co-ordinating European effort towards a new determination of the Boltzmann constant k B to within 1 ppm with the aim of redefining the unit of thermodynamic temperature. This project will enable the National Physical Laboratory to perform primary thermometry in the region of -40 0 C (Hg) to 156 0 C (In) with sub-millikelvin uncertainties by 2012. The chosen technique relies on determining the speed of sound in a monatomic gas. Using the radial acoustic modes of a spherical resonator, consisting of a copper shell and filled with argon or helium, the speed of sound can be measured with great precision and from this measurement the Boltzmann constant can be inferred. This project draws on expertise in dimensional, density, microwave and acoustic measurements at the state-of-the-art. In order to gain further understanding of the experimental configuration a vibro-acoustic model has been developed using the finite element method. Initial calculations were carried out to ensure that predictions of the resonant frequency could be made with the required precision by comparing against an analytical model of a spherical shell filled with a gas. A more elaborate model better representing the experimental configuration was then developed. Thermo-viscous effects close to the fluid-structure boundary were accounted for using a linear acoustic formulation, from which a normal incidence admittance boundary condition was derived and imposed on the inner surface of the resonator. Acoustic pressure, particle velocity and temperature variation as a function of position may be obtained within the gas as a function of frequency. It is therefore possible to investigate how changes in the configuration affect the frequency of radial modes. It is hoped that this approach will shed a better understanding of the underlying complex physical phenomena allowing a minimization of the overall uncertainty.

Acoustic modelling in view of a determination of the Boltzmann constant within 1 ppm for the redefinition of the kelvin

Science.gov (United States)

Gélat, Pierre; Joly, Nicolas; de Podesta, Michael; Sutton, Gavin; Underwood, Robin

2009-11-01

iMERA/Euromet Project 885 is co-ordinating European effort towards a new determination of the Boltzmann constant kB to within 1 ppm with the aim of redefining the unit of thermodynamic temperature. This project will enable the National Physical Laboratory to perform primary thermometry in the region of -40 °C (Hg) to 156 °C (In) with sub-millikelvin uncertainties by 2012. The chosen technique relies on determining the speed of sound in a monatomic gas. Using the radial acoustic modes of a spherical resonator, consisting of a copper shell and filled with argon or helium, the speed of sound can be measured with great precision and from this measurement the Boltzmann constant can be inferred. This project draws on expertise in dimensional, density, microwave and acoustic measurements at the state-of-the-art. In order to gain further understanding of the experimental configuration a vibro-acoustic model has been developed using the finite element method. Initial calculations were carried out to ensure that predictions of the resonant frequency could be made with the required precision by comparing against an analytical model of a spherical shell filled with a gas. A more elaborate model better representing the experimental configuration was then developed. Thermo-viscous effects close to the fluid-structure boundary were accounted for using a linear acoustic formulation, from which a normal incidence admittance boundary condition was derived and imposed on the inner surface of the resonator. Acoustic pressure, particle velocity and temperature variation as a function of position may be obtained within the gas as a function of frequency. It is therefore possible to investigate how changes in the configuration affect the frequency of radial modes. It is hoped that this approach will shed a better understanding of the underlying complex physical phenomena allowing a minimization of the overall uncertainty.

Techniques to assess acoustic-structure interaction in liquid rocket engines

Science.gov (United States)

Davis, R. Benjamin

Acoustoelasticity is the study of the dynamic interaction between elastic structures and acoustic enclosures. In this dissertation, acoustoelasticity is considered in the context of liquid rocket engine design. The techniques presented here can be used to determine which forcing frequencies are important in acoustoelastic systems. With a knowledge of these frequencies, an analyst can either find ways to attenuate the excitation at these frequencies or alter the system in such a way that the prescribed excitations do result in a resonant condition. The end result is a structural component that is less susceptible to failure. The research scope is divided into three parts. In the first part, the dynamics of cylindrical shells submerged in liquid hydrogen (LH2) and liquid oxygen (LOX) are considered. The shells are bounded by rigid outer cylinders. This configuration gives rise to two fluid-filled cavities---an inner cylindrical cavity and an outer annular cavity. Such geometries are common in rocket engine design. The natural frequencies and modes of the fluid-structure system are computed by combining the rigid wall acoustic cavity modes and the in vacuo structural modes into a system of coupled ordinary differential equations. Eigenvalue veering is observed near the intersections of the curves representing natural frequencies of the rigid wall acoustic and the in vacuo structural modes. In the case of a shell submerged in LH2, system frequencies near these intersections are as much as 30% lower than the corresponding in vacuo structural frequencies. Due to its high density, the frequency reductions in the presence of LOX are even more dramatic. The forced responses of a shell submerged in LH2 and LOX while subject to a harmonic point excitation are also presented. The responses in the presence of fluid are found to be quite distinct from those of the structure in vacuo. In the second part, coupled mode theory is used to explore the fundamental features of

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

Science.gov (United States)

Zhu, Hongfei; Semperlotti, Fabio

2016-07-15

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

Virtual screening for potential inhibitors of Mcl-1 conformations sampled by normal modes, molecular dynamics, and nuclear magnetic resonance

Directory of Open Access Journals (Sweden)

Glantz-Gashai Y

2017-06-01

Full Text Available Yitav Glantz-Gashai,* Tomer Meirson,* Eli Reuveni, Abraham O Samson Faculty of Medicine in the Galilee, Bar Ilan University, Safed, Israel *These authors contributed equally to this work Abstract: Myeloid cell leukemia-1 (Mcl-1 is often overexpressed in human cancer and is an important target for developing antineoplastic drugs. In this study, a data set containing 2.3 million lead-like molecules and a data set of all the US Food and Drug Administration (FDA-approved drugs are virtually screened for potential Mcl-1 ligands using Protein Data Bank (PDB ID 2MHS. The potential Mcl-1 ligands are evaluated and computationally docked on to three conformation ensembles generated by normal mode analysis (NMA, molecular dynamics (MD, and nuclear magnetic resonance (NMR, respectively. The evaluated potential Mcl-1 ligands are then compared with their clinical use. Remarkably, half of the top 30 potential drugs are used clinically to treat cancer, thus partially validating our virtual screen. The partial validation also favors the idea that the other half of the top 30 potential drugs could be used in the treatment of cancer. The normal mode-, MD-, and NMR-based conformation greatly expand the conformational sampling used herein for in silico identification of potential Mcl-1 inhibitors. Keywords: virtual screening, Mcl-1, molecular dynamics, NMR, normal modes

Underwater Acoustic Target Tracking: A Review

Science.gov (United States)

Han, Ying; Fan, Liying

2018-01-01

Advances in acoustic technology and instrumentation now make it possible to explore marine resources. As a significant component of ocean exploration, underwater acoustic target tracking has aroused wide attention both in military and civil fields. Due to the complexity of the marine environment, numerous techniques have been proposed to obtain better tracking performance. In this paper, we survey over 100 papers ranging from innovative papers to the state-of-the-art in this field to present underwater tracking technologies. Not only the related knowledge of acoustic tracking instrument and tracking progress is clarified in detail, but also a novel taxonomy method is proposed. In this paper, algorithms for underwater acoustic target tracking are classified based on the methods used as: (1) instrument-assisted methods; (2) mode-based methods; (3) tracking optimization methods. These algorithms are compared and analyzed in the aspect of dimensions, numbers, and maneuvering of the tracking target, which is different from other survey papers. Meanwhile, challenges, countermeasures, and lessons learned are illustrated in this paper. PMID:29301318

Modified Acoustic Emission for Prognostic Health Monitoring, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — Prime Photonics proposes to team with Dr. Duke of Virginia Tech to develop a multi-mode, enhanced piezoelectric acoustic emission sensing system to couple large...

Distributed acoustic sensing for pipeline monitoring

Energy Technology Data Exchange (ETDEWEB)

Hill, David; McEwen-King, Magnus [OptaSense, QinetiQ Ltd., London (United Kingdom)

2009-07-01

Optical fibre is deployed widely across the oil and gas industry. As well as being deployed regularly to provide high bandwidth telecommunications and infrastructure for SCADA it is increasingly being used to sense pressure, temperature and strain along buried pipelines, on subsea pipelines and downhole. In this paper we present results from the latest sensing capability using standard optical fibre to detect acoustic signals along the entire length of a pipeline. In Distributed Acoustic Sensing (DAS) an optical fibre is used for both sensing and telemetry. In this paper we present results from the OptaSense{sup TM} system which has been used to detect third party intervention (TPI) along buried pipelines. In a typical deployment the system is connected to an existing standard single-mode fibre, up to 50km in length, and was used to independently listen to the acoustic / seismic activity at every 10 meter interval. We will show that through the use of advanced array processing of the independent, simultaneously sampled channels it is possible to detect and locate activity within the vicinity of the pipeline and through sophisticated acoustic signal processing to obtain the acoustic signature to classify the type of activity. By combining spare fibre capacity in existing buried fibre optic cables; processing and display techniques commonly found in sonar; and state-of-the-art in fibre-optic distributed acoustic sensing, we will describe the new monitoring capabilities that are available to the pipeline operator. Without the expense of retrofitting sensors to the pipeline, this technology can provide a high performance, rapidly deployable and cost effective method of providing gapless and persistent monitoring of a pipeline. We will show how this approach can be used to detect, classify and locate activity such as; third party interference (including activity indicative of illegal hot tapping); real time tracking of pigs; and leak detection. We will also show how an

Evidence for Radial Anisotropy in Earth's Upper Inner Core from Normal Modes

Science.gov (United States)

Lythgoe, K.; Deuss, A. F.

2017-12-01

The structure of the uppermost inner core is related to solidification of outer core material at the inner core boundary. Previous seismic studies using body waves indicate an isotropic upper inner core, although radial anisotropy has not been considered since it cannot be uniquely determined by body waves. Normal modes, however, do constrain radial anisotropy in the inner core. Centre frequency measurements indicate 2-5 % radial anisotropy in the upper 100 km of the inner core, with a fast direction radially outwards and a slow direction along the inner core boundary. This seismic structure provides constraints on solidification processes at the inner core boundary and appears consistent with texture predicted due to anisotropic inner core growth.

Standing wave acoustic levitation on an annular plate

Science.gov (United States)

Kandemir, Mehmet Hakan; Çalışkan, Mehmet

2016-11-01

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

Acoustic cavitation studies

Science.gov (United States)

Crum, L. A.

1981-09-01

The primary thrust of this study was toward a more complete understanding of general aspects of acoustic cavitation. The effect of long-chain polymer additives on the cavitation threshold was investigated to determine if they reduced the acoustic cavitation threshold in a similar manner to the observed reduction in the cavitation index in hydrodynamic cavitation. Measurements were made of the acoustic cavitation threshold as a function of polymer concentration for additives such as guar gum and polyethelene oxide. The measurements were also made as a function of dissolved gas concentration, surface tension and viscosity. It was determined that there was a significant increase in the acoustic cavitation threshold for increased concentrations of the polymer additives (measurable effects could be obtained for concentrations as low as a few parts per million). One would normally expect that an additive that reduces surface tension to decrease the pressure required to cause a cavity to grow and thus these additives, at first thought, should reduce the threshold. However, even in the hydrodynamic case, the threshold was increased. In both of the hydrodynamic cases considered, the explanation for the increased threshold was given in terms of changed fluid dynamics rather than changed physical properties of the fluid.

Impurity modes in the one-dimensional XXZ Heisenberg model

International Nuclear Information System (INIS)

Sousa, J.M.; Leite, R.V.; Landim, R.R.; Costa Filho, R.N.

2014-01-01

A Green's function formalism is used to calculate the energy of impurity modes associated with one and/or two magnetic impurities in the one-dimensional Heisenberg XXZ magnetic chain. The system can be tuned from the Heisenberg to the Ising model varying a parameter λ. A numerical study is performed showing two types of localized modes (s and p). The modes depend on λ and the degeneracy of the acoustic modes is broken.

A linearized dispersion relation for orthorhombic pseudo-acoustic modeling

KAUST Repository

Song, Xiaolei; Alkhalifah, Tariq Ali

2012-01-01

Wavefield extrapolation in acoustic orthorhombic anisotropic media suffers from wave-mode coupling and stability limitations in the parameter range. We introduce a linearized form of the dispersion relation for acoustic orthorhombic media to model acoustic wavefields. We apply the lowrank approximation approach to handle the corresponding space-wavenumber mixed-domain operator. Numerical experiments show that the proposed wavefield extrapolator is accurate and practically free of dispersions. Further, there is no coupling of qSv and qP waves, because we use the analytical dispersion relation. No constraints on Thomsen's parameters are required for stability. The linearized expression may provide useful application for parameter estimation in orthorhombic media.

A linearized dispersion relation for orthorhombic pseudo-acoustic modeling

KAUST Repository

Song, Xiaolei

2012-11-04

Wavefield extrapolation in acoustic orthorhombic anisotropic media suffers from wave-mode coupling and stability limitations in the parameter range. We introduce a linearized form of the dispersion relation for acoustic orthorhombic media to model acoustic wavefields. We apply the lowrank approximation approach to handle the corresponding space-wavenumber mixed-domain operator. Numerical experiments show that the proposed wavefield extrapolator is accurate and practically free of dispersions. Further, there is no coupling of qSv and qP waves, because we use the analytical dispersion relation. No constraints on Thomsen\\'s parameters are required for stability. The linearized expression may provide useful application for parameter estimation in orthorhombic media.

The acoustics of the echo cornet

Science.gov (United States)

Pyle, Robert W., Jr.; Klaus, Sabine K.

2002-11-01

The echo cornet was an instrument produced by a number of makers in several countries from about the middle of the nineteenth to the early twentieth centuries. It consists of an ordinary three-valve cornet to which a fourth valve has been added, downstream of the three normal valves. The extra valve diverts the airstream from the normal bell to an ''echo'' bell that gives a muted tone quality. Although the air column through the echo bell is typically 15 cm longer than the path through the normal bell, there is no appreciable change of playing pitch when the echo bell is in use. Acoustic input impedance and impulse response measurements and consideration of the standing-wave pattern within the echo bell show how this can be so. Acoustically, the echo bell is more closely related to hand-stopping on the French horn than to the mutes commonly used on the trumpet and cornet.

Using acoustic emissions to enhance fracture toughness calculations for CCNBD marble specimens

Directory of Open Access Journals (Sweden)

K. Kaklis

2017-04-01

Full Text Available Rock fracture mechanics has been widely applied to blasting, hydraulic fracturing, mechanical fragmentation, rock slope analysis, geophysics, earthquake mechanics and many other science and technology fields. Development of failure in brittle materials is associated with microcracks, which release energy in the form of elastic waves called acoustic emissions. In the present study, acoustic emission (AE measurements were carried out during cracked chevron notched Brazilian disc (CCNBD tests on Nestos marble specimens. The fracture toughness of different modes of loading (mode-I and –II is calculated and the results are discussed in conjunction with the AE parameters.

Photo-acoustic sensor based on an inexpensive piezoelectric film transducer and an amplitude-stabilized single-mode external cavity diode laser for in vitro measurements of glucose concentration

Science.gov (United States)

Bayrakli, Ismail; Erdogan, Yasar Kemal

2018-06-01

The present paper focuses on development of a compact photo-acoustic sensor using inexpensive components for glucose analysis. An amplitude-stabilized wavelength-tunable single-mode external cavity diode laser operating around 1050 nm was realized and characterized for the use of laser beam as an excitation light source. In the established setup, a fine tuning range of 9 GHz was achieved. The glucose solution was obtained by diluting D-glucose in sterile water. The acoustic signal generated by the optical excitation was detected via a chip piezoelectric film transducer. A detection limit of 50 mM (900 mg/dl) was achieved. The device may be of great interest for its applications in medicine and health monitoring. The sensor is promising for non-invasive in vivo glucose measurements from interstitial fluid.

Predictions and Observations of Low-shear Beta-induced Alfvén-acoustic Eigenmodes in Toroidal Plasmas

Energy Technology Data Exchange (ETDEWEB)

Gorelenkov, N. N.; Berk, H. L.; Fredrickson, E.; Sharapov, S. E.

2007-07-02

New global MHD eigenmode solutions arising in gaps in the low frequency Alfvén -acoustic continuum below the geodesic acoustic mode (GAM) frequency have been found numerically and have been used to explain relatively low frequency experimental signals seen in NSTX and JET tokamaks. These global eigenmodes, referred to here as Beta-induced Alfvén-Acoustic Eigenmodes (BAAE), exist in the low magnetic safety factor region near the extrema of the Alfvén-acoustic continuum. In accordance to the linear dispersion relations, the frequency of these modes shifts as the safety factor, q, decreases. We show that BAAEs can be responsible for observations in JET plasmas at relatively low beta < 2% as well as in NSTX plasmas at relatively high beta > 20%. In contrast to the mostly electrostatic character of GAMs the new global modes also contain an electromagnetic (magnetic field line bending) component due to the Alfvén coupling, leading to wave phase velocities along the field line that are large compared to the sonic speed. Qualitative agreement between theoretical predictions and observations are found.

Observation of low-frequency acoustic surface waves in the nocturnal boundary layer.

Science.gov (United States)

Talmadge, Carrick L; Waxler, Roger; Di, Xiao; Gilbert, Kenneth E; Kulichkov, Sergey

2008-10-01

A natural terrain surface, because of its porosity, can support an acoustic surface wave that is a mechanical analog of the familiar vertically polarized surface wave in AM radio transmission. At frequencies of several hundred hertz, the acoustic surface wave is attenuated over distances of a few hundred meters. At lower frequencies (e.g., below approximately 200 Hz) the attenuation is much less, allowing surface waves to propagate thousands of meters. At night, a low-frequency surface wave is generally present at long ranges even when downward refraction is weak. Thus, surface waves represent a ubiquitous nighttime transmission mode that exists even when other transmission modes are weak or absent. Data from recent nighttime field experiments and theoretical calculations are presented, demonstrating the persistence of the surface wave under different meteorological conditions. The low-frequency surface wave described here is the "quasiharmonical" tail observed previously in nighttime measurements but not identified by S. Kulichkov and his colleagues (Chunchuzov, I. P. et al. 1990. "On acoustical impulse propagation in a moving inhomogeneous atmospheric layer," J. Acoust. Soc. Am. 88, 455-461).

Plasma Modes

Science.gov (United States)

Dubin, D. H. E.

This chapter explores several aspects of the linear electrostatic normal modes of oscillation for a single-species non-neutral plasma in a Penning trap. Linearized fluid equations of motion are developed, assuming the plasma is cold but collisionless, which allow derivation of the cold plasma dielectric tensor and the electrostatic wave equation. Upper hybrid and magnetized plasma waves in an infinite uniform plasma are described. The effect of the plasma surface in a bounded plasma system is considered, and the properties of surface plasma waves are characterized. The normal modes of a cylindrical plasma column are discussed, and finally, modes of spheroidal plasmas, and finite temperature effects on the modes, are briefly described.

Acoustic communication in insect disease vectors

Directory of Open Access Journals (Sweden)

Felipe de Mello Vigoder

2013-01-01

Full Text Available Acoustic signalling has been extensively studied in insect species, which has led to a better understanding of sexual communication, sexual selection and modes of speciation. The significance of acoustic signals for a blood-sucking insect was first reported in the XIX century by Christopher Johnston, studying the hearing organs of mosquitoes, but has received relatively little attention in other disease vectors until recently. Acoustic signals are often associated with mating behaviour and sexual selection and changes in signalling can lead to rapid evolutionary divergence and may ultimately contribute to the process of speciation. Songs can also have implications for the success of novel methods of disease control such as determining the mating competitiveness of modified insects used for mass-release control programs. Species-specific sound “signatures” may help identify incipient species within species complexes that may be of epidemiological significance, e.g. of higher vectorial capacity, thereby enabling the application of more focussed control measures to optimise the reduction of pathogen transmission. Although the study of acoustic communication in insect vectors has been relatively limited, this review of research demonstrates their value as models for understanding both the functional and evolutionary significance of acoustic communication in insects.

Noncontacting acoustics-based temperature measurement techniques in rapid thermal processing

Science.gov (United States)

Lee, Yong J.; Chou, Ching-Hua; Khuri-Yakub, Butrus T.; Saraswat, Krishna C.

1991-04-01

Temperature measurement of silicon wafers based on the temperature dependence of acoustic waves is studied. The change in the temperature-dependent dispersion relations of the plate modes through the wafer can be exploited to provide a viable temperature monitoring scheme with advantages over both thermocouples and pyrometers. Velocity measurements of acoustic waves through a thin layer of ambient directly above the wafer provides the temperature of the wafer-ambient interface. 1.

Negative refraction imaging of solid acoustic waves by two-dimensional three-component phononic crystal

International Nuclear Information System (INIS)

Li Jing; Liu Zhengyou; Qiu Chunyin

2008-01-01

By using of the multiple scattering methods, we study the negative refraction imaging effect of solid acoustic waves by two-dimensional three-component phononic crystals composed of coated solid inclusions placed in solid matrix. We show that localized resonance mechanism brings on a group of flat single-mode bands in low-frequency region, which provides two equivalent frequency surfaces (EFS) close to circular. The two constant frequency surfaces correspond to two Bloch modes, a right-handed and a left-handed, whose leading mode are respectively transverse (T) and longitudinal (L) modes. The negative refraction behaviors of the two kinds of modes have been demonstrated by simulation of a Gaussian beam through a finite system. High-quality far-field imaging by a planar lens for transverse or longitudinal waves has been realized separately. This three-component phononic crystal may thus serve as a mode selector in negative refraction imaging of solid acoustic waves

"Good Vibrations": A workshop on oscillations and normal modes

Science.gov (United States)

Barbieri, Sara; Carpineti, Marina; Giliberti, Marco; Rigon, Enrico; Stellato, Marco; Tamborini, Marina

2016-05-01

We describe some theatrical strategies adopted in a two hour workshop in order to show some meaningful experiments and the underlying useful ideas to describe a secondary school path on oscillations, that develops from harmonic motion to normal modes of oscillations, and makes extensive use of video analysis, data logging, slow motions and applet simulations. Theatre is an extremely useful tool to stimulate motivation starting from positive emotions. That is the reason why the theatrical approach to the presentation of physical themes has been explored by the group "Lo spettacolo della Fisica" (http://spettacolo.fisica.unimi.it) of the Physics Department of University of Milano for the last ten years (Carpineti et al., JCOM, 10 (2011) 1; Nuovo Cimento B, 121 (2006) 901) and has been inserted also in the European FP7 Project TEMI (Teaching Enquiry with Mysteries Incorporated, see http://teachingmysteries.eu/en) which involves 13 different partners coming from 11 European countries, among which the Italian (Milan) group. According to the TEMI guidelines, this workshop has a written script based on emotionally engaging activities of presenting mysteries to be solved while participants have been involved in nice experiments following the developed path.

Testicular microlithiasis and preliminary experience of acoustic radiation force impulse imaging

International Nuclear Information System (INIS)

Pedersen, Malene Roland; Osther, Palle Jørn Sloth; Rafaelsen, Søren Rafael

2016-01-01

Elastography of the testis can be used as a part of multiparametric examination of the scrotum. To determine the testicular stiffness using acoustic radiation force impulse imaging (ARFI) technique in men with testicular microlithiasis (TML). 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. 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). Elastography velocity of testis with TML seems to be in the same velocity range as in men with normal testis tissue

Terahertz plasmon and surface-plasmon modes in cylindrical metallic nanowires

International Nuclear Information System (INIS)

Wu Ping; Xu Wen; Li Long-Long; Lu Tie-Cheng; Wu Wei-Dong

2014-01-01

We present a theoretical study on collective excitation modes associated with plasmon and surface-plasmon oscillations in cylindrical metallic nanowires. Based on a two-subband model, the dynamical dielectric function matrix is derived under the random-phase approximation. An optic-like branch and an acoustic-like branch, which are free of Landau damping, are observed for both plasmon and surface-plasmon modes. Interestingly, for surface-plasmon modes, we find that two branches of the dispersion relation curves converge at a wavevector q z = q max beyond which no surface-plasmon mode exists. Moreover, we examine the dependence of these excitation modes on sample parameters such as the radius of the nanowires. It is found that in metallic nanowires realized by state-of-the-art nanotechnology the intra- and inter-subband plasmon and surface-plasmon frequencies are in the terahertz bandwidth. The frequency of the optic-like modes decreases with increasing radius of the nanowires, whereas that of the acoustic-like modes is not sensitive to the variation of the radius. This study is pertinent to the application of metallic nanowires as frequency-tunable terahertz plasmonic devices. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

STATISTICAL ANALYSIS OF ACOUSTIC WAVE PARAMETERS NEAR SOLAR ACTIVE REGIONS

International Nuclear Information System (INIS)

Rabello-Soares, M. Cristina; Bogart, Richard S.; Scherrer, Philip H.

2016-01-01

In order to quantify the influence of magnetic fields on acoustic mode parameters and flows in and around active regions, we analyze the differences in the parameters in magnetically quiet regions nearby an active region (which we call “nearby regions”), compared with those of quiet regions at the same disk locations for which there are no neighboring active regions. We also compare the mode parameters in active regions with those in comparably located quiet regions. Our analysis is based on ring-diagram analysis of all active regions observed by the Helioseismic and Magnetic Imager (HMI) during almost five years. We find that the frequency at which the mode amplitude changes from attenuation to amplification in the quiet nearby regions is around 4.2 mHz, in contrast to the active regions, for which it is about 5.1 mHz. This amplitude enhacement (the “acoustic halo effect”) is as large as that observed in the active regions, and has a very weak dependence on the wave propagation direction. The mode energy difference in nearby regions also changes from a deficit to an excess at around 4.2 mHz, but averages to zero over all modes. The frequency difference in nearby regions increases with increasing frequency until a point at which the frequency shifts turn over sharply, as in active regions. However, this turnover occurs around 4.9 mHz, which is significantly below the acoustic cutoff frequency. Inverting the horizontal flow parameters in the direction of the neigboring active regions, we find flows that are consistent with a model of the thermal energy flow being blocked directly below the active region.

Acoustic Tomography in the Canary Basin: Meddies and Tides

Science.gov (United States)

Dushaw, Brian D.; Gaillard, Fabienne; Terre, Thierry

2017-11-01

An acoustic propagation experiment over 308 km range conducted in the Canary Basin in 1997-1998 was used to assess the ability of ocean acoustic tomography to measure the flux of Mediterranean water and Meddies. Instruments on a mooring adjacent to the acoustic path measured the southwestward passage of a strong Meddy in temperature, salinity, and current. Over 9 months of transmissions, the acoustic arrival pattern was an initial broad stochastic pulse varying in duration by 250-500 ms, followed eight stable, identified-ray arrivals. Small-scale sound speed fluctuations from Mediterranean water parcels littered around the sound channel axis caused acoustic scattering. Internal waves contributed more modest acoustic scattering. Based on simulations, the main effect of a Meddy passing across the acoustic path is the formation of many early-arriving, near-axis rays, but these rays are thoroughly scattered by the small-scale Mediterranean-water fluctuations. A Meddy decreases the deep-turning ray travel times by 10-30 ms. The dominant acoustic signature of a Meddy is therefore the expansion of the width of the initial stochastic pulse. While this signature appears inseparable from the other effects of Mediterranean water in this region, the acoustic time series indicates the steady passage of Mediterranean water across the acoustic path. Tidal variations caused by the mode-1 internal tides were measured by the acoustic travel times. The observed internal tides were partly predicted using a recent global model for such tides derived from satellite altimetry.

Sediment Types Determination Using Acoustic Techniques in the Northeastern Gulf of Mexico

National Research Council Canada - National Science Library

Kim, Gil

2004-01-01

... those (acoustic impedance and grain size) in the northeastern Gulf of Mexico. The acoustic data were acquired using a 11 kHz normal incident echo sounder over approximately 2000 km of track line...

The acoustic reflex threshold in aging ears.

Science.gov (United States)

Silverman, C A; Silman, S; Miller, M H

1983-01-01

This study investigates the controversy regarding the influence of age on the acoustic reflex threshold for broadband noise, 500-, 1000-, 2000-, and 4000-Hz activators between Jerger et al. [Mono. Contemp. Audiol. 1 (1978)] and Jerger [J. Acoust. Soc. Am. 66 (1979)] on the one hand and Silman [J. Acoust. Soc. Am. 66 (1979)] and others on the other. The acoustic reflex thresholds for broadband noise, 500-, 1000-, 2000-, and 4000-Hz activators were evaluated under two measurement conditions. Seventy-two normal-hearing ears were drawn from 72 subjects ranging in age from 20-69 years. The results revealed that age was correlated with the acoustic reflex threshold for BBN activator but not for any of the tonal activators; the correlation was stronger under the 1-dB than under the 5-dB measurement condition. Also, the mean acoustic reflex thresholds for broadband noise activator were essentially similar to those reported by Jerger et al. (1978) but differed from those obtained in this study under the 1-dB measurement condition.

Asymmetric acoustic transmission in multiple frequency bands

Energy Technology Data Exchange (ETDEWEB)

Sun, Hong-xiang, E-mail: jsdxshx@ujs.edu.cn [Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013 (China); Laboratory of Modern Acoustics, Institute of Acoustics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190 (China); Yuan, Shou-qi, E-mail: Shouqiy@ujs.edu.cn [Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013 (China); Zhang, Shu-yi [Laboratory of Modern Acoustics, Institute of Acoustics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

2015-11-23

We report both experimentally and numerically that the multi-band device of the asymmetric acoustic transmission is realized by placing two periodic gratings with different periods on both sides of two brass plates immersed in water. The asymmetric acoustic transmission can exist in four frequency bands below 1500 kHz, which arises from the interaction between various diffractions from the two gratings and Lamb modes in the brass plates immersed in water. The results indicate that the device has the advantages of multiple band, broader bandwidth, and simpler structure. Our finding should have great potential applications in ultrasonic devices.

Asymmetric acoustic transmission in multiple frequency bands

International Nuclear Information System (INIS)

Sun, Hong-xiang; Yuan, Shou-qi; Zhang, Shu-yi

2015-01-01

We report both experimentally and numerically that the multi-band device of the asymmetric acoustic transmission is realized by placing two periodic gratings with different periods on both sides of two brass plates immersed in water. The asymmetric acoustic transmission can exist in four frequency bands below 1500 kHz, which arises from the interaction between various diffractions from the two gratings and Lamb modes in the brass plates immersed in water. The results indicate that the device has the advantages of multiple band, broader bandwidth, and simpler structure. Our finding should have great potential applications in ultrasonic devices

Low-Frequency Acoustic Noise Mitigation Characteristics of Metamaterials-Inspired Vibro-Impact Structures

Science.gov (United States)

Rekhy, Anuj

Acoustic absorbers like foams, fiberglass or liners have been used commonly in structures for infrastructural, industrial, automotive and aerospace applications to mitigate noise. However, these conventional materials have limited effectiveness to mitigate low-frequency (LF) acoustic waves with frequency less than 400 Hz owing to the need for impractically large mass or volume. LF acoustic waves contribute significantly towards environmental noise pollution as well as unwanted structural responses. Therefore, there is a need to develop lightweight, compact, structurally-integrated solutions to mitigate LF noise in several applications. Inspired by metamaterials, which are man-made structural materials that derive their unique dynamic behavior not just from material constituents but more so from engineered configurations, tuned mass-loaded membranes as vibro-impact attachments on a baseline structure are investigated to determine their performance as a LF acoustic barrier. The hypothesis is that the LF incident waves are up-converted via impact to higher modes in the baseline structure which are far more evanescent and may then be effectively mitigated using conventional means. Such Metamaterials-Inspired Vibro-Impact Structures (MIVIS) could be tuned to match the dominant frequency content of LF acoustic sources in specific applications. Prototype MIVIS unit cells were designed and tested to study the energy transfer mechanism via impact-induced frequency up-conversion, and the consequent sound transmission loss. Structural acoustic simulations were done to predict responses using models based on normal incidence transmission loss tests. Experimental proof-of-concept was achieved and further correlations to simulations were utilized to optimize the energy up-conversion mechanism using parametric studies. Up to 36 dB of sound transmission loss increase is obtained at the anti-resonance frequency (326 Hz) within a tunable LF bandwidth of about 200 Hz while impact

Resonant Absorption in GaAs-Based Nanowires by Means of Photo-Acoustic Spectroscopy

Science.gov (United States)

Petronijevic, E.; Leahu, G.; Belardini, A.; Centini, M.; Li Voti, R.; Hakkarainen, T.; Koivusalo, E.; Guina, M.; Sibilia, C.

2018-03-01

Semiconductor nanowires made of high refractive index materials can couple the incoming light to specific waveguide modes that offer resonant absorption enhancement under the bandgap wavelength, essential for light harvesting, lasing and detection applications. Moreover, the non-trivial ellipticity of such modes can offer near field interactions with chiral molecules, governed by near chiral field. These modes are therefore very important to detect. Here, we present the photo-acoustic spectroscopy as a low-cost, reliable, sensitive and scattering-free tool to measure the spectral position and absorption efficiency of these modes. The investigated samples are hexagonal nanowires with GaAs core; the fabrication by means of lithography-free molecular beam epitaxy provides controllable and uniform dimensions that allow for the excitation of the fundamental resonant mode around 800 nm. We show that the modulation frequency increase leads to the discrimination of the resonant mode absorption from the overall absorption of the substrate. As the experimental data are in great agreement with numerical simulations, the design can be optimized and followed by photo-acoustic characterization for a specific application.

Formation of Hydro-acoustic Waves in Dissipative Coupled Weakly Compressible Fluids

Science.gov (United States)

Abdolali, A.; Kirby, J. T., Jr.; Bellotti, G.

2014-12-01

Recent advances in deep sea measurement technology provide an increasing opportunity to detect and interpret hydro-acoustic waves as a component in improved Tsunami Early Warning Systems (TEWS). For the idealized case of a homogeneous water column above a moving but otherwise rigid bottom (in terms of assessing acoustic wave interaction), the description of the infinite family of acoustic modes is characterized by local water depth at source area; i.e. the period of the first acoustic mode is given by four times the required time for sound to travel from the seabed to the surface. Spreading off from earthquake zone, the dominant spectrum is filtered and enriched by seamounts and barriers. This study focuses on the characteristics of hydro-acoustic waves generated by sudden sea bottom motion in a weakly compressible fluid coupled with an underlying sedimentary layer, where the added complexity of the sediment layer rheology leads to both the lowering of dominant spectral peaks and wave attenuation across the full spectrum. To overcome the computational difficulties of three-dimensional models, we derive a depth integrated equation valid for varying water depth and sediment thickness. Damping behavior of the two layered system is initially taken into account by introducing the viscosity of fluid-like sedimentary layer. We show that low frequency pressure waves which are precursor components of tsunamis contain information of seafloor motion.

Perturbation measurement of waveguides for acoustic thermometry

Science.gov (United States)

Lin, H.; Feng, X. J.; Zhang, J. T.

2013-09-01

Acoustic thermometers normally embed small acoustic transducers in the wall bounding a gas-filled cavity resonator. At high temperature, insulators of transducers loss electrical insulation and degrade the signal-to-noise ratio. One essential solution to this technical trouble is to couple sound by acoustic waveguides between resonator and transducers. But waveguide will break the ideal acoustic surface and bring perturbations(Δf+ig) to the ideal resonance frequency. The perturbation model for waveguides was developed based on the first-order acoustic theory in this paper. The frequency shift Δf and half-width change g caused by the position, length and radius of waveguides were analyzed using this model. Six different length of waveguides (52˜1763 mm) were settled on the cylinder resonator and the perturbation (Δf+ig) were measured at T=332 K and p=250˜500 kPa. The experiment results agreed with the theoretical prediction very well.

Nano-optomechanical system based on microwave frequency surface acoustic waves

Science.gov (United States)

Tadesse, Semere Ayalew

Cavity optomechnics studies the interaction of cavity confined photons with mechanical motion. The emergence of sophisticated nanofabrication technology has led to experimental demonstrations of a wide range of novel optomechanical systems that exhibit strong optomechanical coupling and allow exploration of interesting physical phenomena. Many of the studies reported so far are focused on interaction of photons with localized mechanical modes. For my doctoral research, I did experimental investigations to extend this study to propagating phonons. I used surface travelling acoustic waves as the mechanical element of my optomechanical system. The optical cavities constitute an optical racetrack resonator and photonic crystal nanocavity. This dissertation discusses implementation of this surface acoustic wave based optomechanical system and experimental demonstrations of important consequences of the optomechanical coupling. The discussion focuses on three important achievements of the research. First, microwave frequency surface acoustic wave transducers were co-integrated with an optical racetrack resonator on a piezoelectric aluminum nitride film deposited on an oxidized silicon substrate. Acousto-optic modulation of the resonance modes at above 10 GHz with the acoustic wavelength significantly below the optical wavelength was achieved. The phase and modal matching conditions in this paradigm were investigated for efficient optmechanical coupling. Second, the optomechanical coupling was pushed further into the sideband resolved regime by integrating the high frequency surface acoustic wave transducers with a photonic crystal nanocavity. This device was used to demonstrate optomecahnically induced transparency and absorption, one of the interesting consequences of cavity optomechanics. Phase coherent interaction of the acoustic wave with multiple nanocavities was also explored. In a related experiment, the photonic crystal nanoscavity was placed inside an acoustic

Accretion onto magnetized neutron stars: Normal mode analysis of the interchange instability at the magnetopause

International Nuclear Information System (INIS)

Arons, J.; Lea, S.M.

1976-01-01

We describe the results of a linearized hydromagnetic stability analysis of the magnetopause of an accreting neutron star. The magnetosphere is assumed to be slowly rotating, and the plasma just outside of the magnetopause is assumed to be weakly magnetized. The plasma layer is assumed to be bounded above by a shock wave, and to be thin compared with the radius of the magnetosphere. Under these circumstances, the growing modes are shown to be localized in the direction parallel to the zero-order magnetic field. The structure of the modes is still similar to the flute mode, however. The growth rate at each magnetic latitude is lambda given by γ 2 =g/sub n/kα/sub eff/(lambda) tanh [kz/sub s/(lambda)] where g/sub n/ is the magnitude of the gravitational acceleration normal to the surface, kapprox. =vertical-barmvertical-bar/R (lambda)cos lambda, vertical-barmvertical-bar is the azimuthal mode number, R (lambda) is the radius of the magnetosphere, z/sub s/ is the height of the shock above the magnetopause, and α/sub eff/(lambda) <1 is the effective Atwood number which embodies the stabilizing effects of favorable curvature and magnetic tension. We calculate α/sub eff/(lambda), and also discuss the stabilizing effects of viscosity and of aligned flow parallel to the magnetopause

Probabilistic estimation of splitting coefficients of normal modes of the Earth, and their uncertainties, using an autoregressive technique

Science.gov (United States)

Pachhai, S.; Masters, G.; Laske, G.

2017-12-01

Earth's normal-mode spectra are crucial to studying the long wavelength structure of the Earth. Such observations have been used extensively to estimate "splitting coefficients" which, in turn, can be used to determine the three-dimensional velocity and density structure. Most past studies apply a non-linear iterative inversion to estimate the splitting coefficients which requires that the earthquake source is known. However, it is challenging to know the source details, particularly for big events as used in normal-mode analyses. Additionally, the final solution of the non-linear inversion can depend on the choice of damping parameter and starting model. To circumvent the need to know the source, a two-step linear inversion has been developed and successfully applied to many mantle and core sensitive modes. The first step takes combinations of the data from a single event to produce spectra known as "receiver strips". The autoregressive nature of the receiver strips can then be used to estimate the structure coefficients without the need to know the source. Based on this approach, we recently employed a neighborhood algorithm to measure the splitting coefficients for an isolated inner-core sensitive mode (13S2). This approach explores the parameter space efficiently without any need of regularization and finds the structure coefficients which best fit the observed strips. Here, we implement a Bayesian approach to data collected for earthquakes from early 2000 and more recent. This approach combines the data (through likelihood) and prior information to provide rigorous parameter values and their uncertainties for both isolated and coupled modes. The likelihood function is derived from the inferred errors of the receiver strips which allows us to retrieve proper uncertainties. Finally, we apply model selection criteria that balance the trade-offs between fit (likelihood) and model complexity to investigate the degree and type of structure (elastic and anelastic

ECHOCARDIOGRAPHIC FINDINGS OF BIDIMENSIONAL MODE, M-MODE, AND DOPPLER OF CLINICALLY NORMAL BLACK-RUMPED AGOUTI (DASYPROCTA PRYMNOLOPHA, WAGLER 1831).

Science.gov (United States)

Diniz, Anaemilia das Neves; Pessoa, Gerson Tavares; da Silva Moura, Laecio; de Sousa, André Braga; Sousa, Francisco das Chagas Araújo; de Sá Rodrigues, Renan Paraguassu; da Silva Barbosa, Maria Angélica Parente; de Almeida, Hatawa Melo; Freire, Larisse Danielle Silva; Sanches, Marina Pinto; Júnior, Antônio Augusto Nascimento Machado; Guerra, Porfírio Candanedo; Neves, Willams Costa; de Sousa, João Macedo; Bolfer, Luiz; Giglio, Robson Fortes; Alves, Flávio Ribeiro

2017-06-01

The black-rumped agouti ( Dasyprocta prymnolopha , Wagler 1831) is currently under intense ecologic pressure, which has resulted in its disappearance from some regions of Brazil. Echocardiography is widely used in veterinary medicine but it is not yet part of the clinical routine for wild animals. The objective of the present study was to assess the applicability of the echocardiographic exam in nonanesthetized agouti and to establish normal reference values for echocardiographic measurements in bidimensional mode (2D), M-mode, and Doppler for this species, and a lead II electrocardiogram was simultaneously recorded. Twenty agouti were used in this study. All the echocardiographic measurements were positively correlated with weight (P 0.05). Blood flow velocities in the pulmonary and aortic artery ranged from 67.32-71.28 cm/sec and 79.22-101.84 cm/sec, respectively. The isovolumic relaxation time was assessed in all the animals and ranged from 38.5 to 56.6 ms. The maximum value for the nonfused E and A waves and the Et and At waves was 158 beats/min for both. The results obtained for the morphologic and heart hemodynamic measurements can guide future studies and help in the clinical management of these animals in captivity.

All-optical in-depth detection of the acoustic wave emitted by a single gold nanorod

Science.gov (United States)

Xu, Feng; Guillet, Yannick; Ravaine, Serge; Audoin, Bertrand

2018-04-01

A single gold nanorod dropped on the surface of a silica substrate is used as a transient optoacoustic source of gigahertz hypersounds. We demonstrate the all-optical detection of the as-generated acoustic wave front propagating in the silica substrate. For this purpose, time-resolved femtosecond pump-probe experiments are performed in a reflection configuration. The fundamental breathing mode of the nanorod is detected at 23 GHz by interferometry, and the longitudinal acoustic wave radiated in the silica substrate is detected by time-resolved Brillouin scattering. By tuning the optical probe wavelength from 750 to 900 nm, hypersounds with wavelengths of 260-315 nm are detected in the silica substrate, with corresponding acoustic frequencies in the range of 19-23 GHz. To confirm the origin of these hypersounds, we theoretically analyze the influence of the acoustic excitation spectrum on the temporal envelope of the transient reflectivity. This analysis proves that the acoustic wave detected in the silica substrate results from the excitation of the breathing mode of the nanorod. These results pave the way for performing local in-depth elastic nanoscopy.

Characterization of human breast cancer by scanning acoustic microscopy

Science.gov (United States)

Chen, Di; Malyarenko, Eugene; Seviaryn, Fedar; Yuan, Ye; Sherman, Mark; Bandyopadhyay, Sudeshna; Gierach, Gretchen; Greenway, Christopher W.; Maeva, Elena; Strumban, Emil; Duric, Neb; Maev, Roman

2013-03-01

Objectives: The purpose of this study was to characterize human breast cancer tissues by the measurement of microacoustic properties. Methods: We investigated eight breast cancer patients using acoustic microscopy. For each patient, seven blocks of tumor tissue were collected from seven different positions around a tumor mass. Frozen sections (10 micrometer, μm) of human breast cancer tissues without staining and fixation were examined in a scanning acoustic microscope with focused transducers at 80 and 200 MHz. Hematoxylin and Eosin (H and E) stained sections from the same frozen breast cancer tissues were imaged by optical microscopy for comparison. Results: The results of acoustic imaging showed that acoustic attenuation and sound speed in cancer cell-rich tissue regions were significantly decreased compared with the surrounding tissue regions, where most components are normal cells/tissues, such as fibroblasts, connective tissue and lymphocytes. Our observation also showed that the ultrasonic properties were influenced by arrangements of cells and tissue patterns. Conclusions: Our data demonstrate that attenuation and sound speed imaging can provide biomechanical information of the tumor and normal tissues. The results also demonstrate the potential of acoustic microscopy as an auxiliary method for operative detection and localization of cancer affected regions.

Vibrational normal modes of diazo-dimedone: A comparative study by Fourier infrared/Raman spectroscopies and conformational analysis by MM/QM

Science.gov (United States)

Téllez Soto, C. A.; Ramos, J. M.; Rianelli, R. S.; de Souza, M. C. B. V.; Ferreira, V. F.

2007-07-01

The 2-diazo-5,5-dimethyl-cyclohexane-1,3-dione ( 3) was synthesized and the FT-IR/Raman spectra were measured with the purpose of obtain a full assignment of the vibrational modes. Singular aspects concerning the -C dbnd N dbnd N oscillator are discussed in view of two strong bands observed in the region of 2300-2100 cm -1 in both, Infrared and Raman spectra. The density functional theory (DFT) was used to obtain the geometrical structure and for assisting in the vibrational assignment joint to the traditional normal coordinate analysis (NCA). The observed wavenumbers at 2145 (IR), 2144(R) are assigned as the coupled ν(N dbnd N) + ν(C dbnd N) vibrational mode with higher participation of the N dbnd N stretching. A 2188 cm -1 (IR) and at 2186 cm -1 (R) can be assigned as a overtone of one of ν(CC) normal mode or to a combination band of the fundamentals δ(CCH) found at 1169 cm -1 and the δ (CC dbnd N) found at 1017 cm -1 enhanced by Fermi resonance.

Acoustic cloaking and transformation acoustics

International Nuclear Information System (INIS)

Chen Huanyang; Chan, C T

2010-01-01

In this review, we give a brief introduction to the application of the new technique of transformation acoustics, which draws on a correspondence between coordinate transformation and material properties. The technique is formulated for both acoustic waves and linear liquid surface waves. Some interesting conceptual devices can be designed for manipulating acoustic waves. For example, we can design acoustic cloaks that make an object invisible to acoustic waves, and the cloak can either encompass or lie outside the object to be concealed. Transformation acoustics, as an analog of transformation optics, can go beyond invisibility cloaking. As an illustration for manipulating linear liquid surface waves, we show that a liquid wave rotator can be designed and fabricated to rotate the wave front. The acoustic transformation media require acoustic materials which are anisotropic and inhomogeneous. Such materials are difficult to find in nature. However, composite materials with embedded sub-wavelength resonators can in principle be made and such 'acoustic metamaterials' can exhibit nearly arbitrary values of effective density and modulus tensors to satisfy the demanding material requirements in transformation acoustics. We introduce resonant sonic materials and Helmholtz resonators as examples of acoustic metamaterials that exhibit resonant behaviour in effective density and effective modulus. (topical review)

Perception of acoustic scale and size in musical instrument sounds.

Science.gov (United States)

van Dinther, Ralph; Patterson, Roy D

2006-10-01

There is size information in natural sounds. For example, as humans grow in height, their vocal tracts increase in length, producing a predictable decrease in the formant frequencies of speech sounds. Recent studies have shown that listeners can make fine discriminations about which of two speakers has the longer vocal tract, supporting the view that the auditory system discriminates changes on the acoustic-scale dimension. Listeners can also recognize vowels scaled well beyond the range of vocal tracts normally experienced, indicating that perception is robust to changes in acoustic scale. This paper reports two perceptual experiments designed to extend research on acoustic scale and size perception to the domain of musical sounds: The first study shows that listeners can discriminate the scale of musical instrument sounds reliably, although not quite as well as for voices. The second experiment shows that listeners can recognize the family of an instrument sound which has been modified in pitch and scale beyond the range of normal experience. We conclude that processing of acoustic scale in music perception is very similar to processing of acoustic scale in speech perception.

Acoustic waves in unbounded shear flows

International Nuclear Information System (INIS)

Chagelishvili, G.D.; Khujadze, G.R.; Lominadze, J.G.; Rogava, A.D.

1996-05-01

The linear evolution of acoustic waves in fluid flow with constant density and uniform shear of velocity is investigated. The process of the mean flow energy extraction by the three-dimensional acoustic waves which is due to the non-normality of linear dynamics in shear flows is analyzed. The thorough examination of the dynamics of different physical quantities, specifying the wave evolution, is outlined. The revealing of the behaviour becomes possible owing to the nonmodal approach that has been extensively used in the study of the perturbations evolution in shear flows since the beginning of the nineties. In addition, a detailed analyses of the physics of shear energy gain by vortex and acoustic perturbations is presented. (author). 28 refs, 7 figs

Classifying Particles By Acoustic Levitation

Science.gov (United States)

Barmatz, Martin B.; Stoneburner, James D.

1983-01-01

Separation technique well suited to material processing. Apparatus with rectangular-cross-section chamber used to measure equilibrium positions of low-density spheres in gravitational field. Vertical acoustic forces generated by two opposing compression drivers exciting fundamental plane-wave mode at 1.2 kHz. Additional horizontal drivers centered samples along vertical axis. Applications in fusion-target separation, biological separation, and manufacturing processes in liquid or gas media.

Reverberation chambers a la carte: an overview of the different mode-stirring techniques

NARCIS (Netherlands)

Serra, R.; Marvin, A.C.; Moglie, F.; Mariani Primiani, V.; Cozza, A.; Arnaut, L.R.; Huang, Y.; Hatfield, M.O.; Klingler, M.; Leferink, F.

2017-01-01

Reverberation chambers (RC), a name inspired in room acoustics, are also known in literature as reverberating, reverb, mode-stirred or mode-tuned chambers. In their basic form, they consist of a shielded metallic enclosure, forming a cavity resonator, together with some mode-stirring mechanism. The

Reverberation Chambers à La Carte : An Overview of the Different Mode-Stirring Techniques

NARCIS (Netherlands)

Serra, Ramiro; Marvin, Andy C.; Moglie, Franco; Mariani Primiani, Valter; Cozza, Andrea; Arnaut, Luk R.; Huang, Yi; Hatfield, Michael O.; Klingler, Marco; Leferink, Frank

2017-01-01

Reverberation chambers (RC), a name inspired in room acoustics, are also known in literature as reverberating, reverb, mode-stirred or mode-tuned chambers. In their basic form, they consist of a shielded metallic enclosure, forming a cavity resonator, together with some mode-stirring mechanism. The

Non-Axisymmetric Oscillation of Acoustically Levitated Water Drops at Specific Frequencies

International Nuclear Information System (INIS)

Chang-Le, Shen; Wen-Jun, Xie; Bing-Bo, Wei

2010-01-01

A category of non-axisymmetric oscillations of acoustically levitated water drops was observed. These oscillations can be qualitatively described by superposing a sectorial oscillating term upon the initial oblate shape resulting from the effect of acoustic radiation pressure. The oscillation frequencies are around 25 Hz for the 2-lobed mode and exactly 50 Hz for the 3- and 4-lobed modes. These oscillations were excited by the disturbance from the power supply. For the same water drop, higher mode oscillations were observed with more oblate initial shape, indicating that the eigenfrequencies of these non-axisymmetric oscillations decrease with increasing initial distortion. The maximum velocity and acceleration within the oscillating drop can attain 0.3m·s −1 and 98.7m·s −2 respectively, resulting in strong fluid convection and enhanced heat and mass transfer. (condensed matter: structure, mechanical and thermal properties)

Acoustic manipulation: Bessel beams and active carriers

Science.gov (United States)

Rajabi, Majid; Mojahed, Alireza

2017-10-01

In this paper, we address the interaction of zero-order acoustic Bessel beams as an acoustic manipulation tool, with an active spherical shell, as a carrier in drug, agent, or material delivery systems, in order to investigate the controllability of exerted acoustic radiation force as the driver. The active body is comprised of a spherical elastic shell stimulated in its monopole mode of vibrations with the same frequency as the incident wave field via an internally bonded and spatially uniformly excited piezoelectric actuator. The main aim of this work is to examine the performance of a nondiffracting and self-reconstructing zero-order Bessel beam to obtain the full manipulability condition of active carriers in comparison with the case of a plane wave field. The results unveil some unique potentials of the Bessel beams in the company of active carriers, with emphasis on the consumed power of the actuation system. This paper will widen the path toward the single-beam robust acoustic manipulation techniques and may lead to the prospect of combined tweezers and fields, with applications in delivery systems, microswimmers, and trapper designs.

Acoustic Imaging Frequency Dynamics of Ferroelectric Domains by Atomic Force Microscopy

International Nuclear Information System (INIS)

Kun-Yu, Zhao; Hua-Rong, Zeng; Hong-Zhang, Song; Sen-Xing, Hui; Guo-Rong, Li; Qing-Rui, Yin; Shimamura, Kiyoshi; Kannan, Chinna Venkadasamy; Villora, Encarnacion Antonia Garcia; Takekawa, Shunji; Kitamura, Kenji

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 0.5 kHz by AFM-based acoustic microscopy The frequency-dependent acoustic signal revealed a strong acoustic response in the frequency range from 7kHz to 10kHz, and reached maximum at 8.1kHz. 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. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

On-line surveillance of lubricants in bearings by means of surface acoustic waves.

Science.gov (United States)

Lindner, Gerhard; Schmitt, Martin; Schubert, Josephine; Krempel, Sandro; Faustmann, Hendrik

2010-01-01

The acoustic wave propagation in bearings filled with lubricants and driven by pulsed excitation of surface acoustic waves has been investigated with respect to the presence and the distribution of different lubricants. Experimental setups, which are based on the mode conversion between surface acoustic waves and compression waves at the interface between a solid substrate of the bearing and a lubricant are described. The results of preliminary measurements at linear friction bearings, rotation ball bearings and axial cylinder roller bearings are presented.

Horizontal-Longitudinal Correlations of Acoustic Field in Deep Water

International Nuclear Information System (INIS)

Li Jun; Li Zheng-Lin; Ren Yun; Li Wen; Zhang Ren-He

2015-01-01

The horizontal-longitudinal correlations of the acoustic field in deep water are investigated based on the experimental data obtained in the South China Sea. It is shown that the horizontal-longitudinal correlation coefficients in the convergence zone are high, and the correlation length is consistent with the convergence zone width, which depends on the receiver depth and range. The horizontal-longitudinal correlation coefficients in the convergence zone also have a division structure for the deeper receiver. The signals from the second part of the convergence zone are still correlated with the reference signal in the first part. The horizontal-longitudinal correlation coefficients in the shadow zone are lower than that in the convergence zone, and the correlation length in the shadow zone is also much shorter than that in the convergence zone. The numerical simulation results by using the normal modes theory are qualitatively consistent with the experimental results. (paper)

A monitoring of superconducting magnets by acoustic emission

International Nuclear Information System (INIS)

Nomura, Harehiko; Tateishi, Hiroshi; Onishi, Toshitada

1990-01-01

Since superconducting magnets (SCM) are going to be indispensable to magnetic levitated train, nuclear fusion, magnetic resonating imaging, rotational machines, etc., they must be placed great reliance on its repetitional operations. But without appropriate evaluating methods, these promising techniques must remain still in science levels and hard to be transferable to real human technologies. SCM, being used under dynamical operation with linking other electro-magnetic systems as said above, induce high voltage from which monitoring superconducting to normal transitional voltage is difficult to distinguish. To solve this problem, monitoring SCM by Acoustic Emission (AE) from themselves, have been found effective, in particular, during the dynamical energizing of them. As for a demonstration, this paper will report mainly how to monitor 3 MJ-SCM and a few results of the experiments aquired both by counting and locational mode of AE in pulsed and repeated operations of the magnet. Some discussions on the AE monitorings are also made along the main issues to be solved in future. (author)

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

Science.gov (United States)

Mei, Chuh; Shi, Yacheng

1997-01-01

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

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.

Generation of broadband electrostatic noise by electron acoustic solitons

International Nuclear Information System (INIS)

Dubouloz, N.; Pottelette, R.; Malingre, M.; Treumann, R.A.

1991-01-01

Broadband electrostatic noise (BEN) bursts whose amplitude sometimes reaches about 100 mV m -1 have been observed by the Viking satellite in the dayside auroral zone. These emissions have been shown to be greatly influenced by nonlinear effects and to occur simultaneously with the observation of particle distributions favouring the destabilization of the electron acoustic mode. It is shown that electron acoustic solitons passing by the satellite would generate spectra that can explain the high-frequency part of BEN, above the electron plasma frequency

Picosecond ultrasonic study of surface acoustic waves on periodically patterned layered nanostructures.

Science.gov (United States)

Colletta, Michael; Gachuhi, Wanjiru; Gartenstein, Samuel A; James, Molly M; Szwed, Erik A; Daly, Brian C; Cui, Weili; Antonelli, George A

2018-07-01

We have used the ultrafast pump-probe technique known as picosecond ultrasonics to generate and detect surface acoustic waves on a structure consisting of nanoscale Al lines on SiO 2 on Si. We report results from ten samples with varying pitch (1000-140 nm) and SiO 2 film thickness (112 nm or 60 nm), and compare our results to an isotropic elastic calculation and a coarse-grained molecular dynamics simulation. In all cases we are able to detect and identify a Rayleigh-like surface acoustic wave with wavelength equal to the pitch of the lines and frequency in the range of 5-24 GHz. In some samples, we are able to detect additional, higher frequency surface acoustic waves or independent modes of the Al lines with frequencies close to 50 GHz. We also describe the effects of probe beam polarization on the measurement's sensitivity to the different surface modes. Copyright © 2018 Elsevier B.V. All rights reserved.

Detecting and identifying damage in sandwich polymer composite by using acoustic emission

Energy Technology Data Exchange (ETDEWEB)

McGugan, M.; Soerensen, Bent F.; Oestergaard, R.; Bech, T.

2006-12-15

Acoustic emission is a useful monitoring tool for extracting extra information during mechanical testing of polymer composite sandwich materials. The study of fracture mechanics within test specimens extracted from wind turbine blade material is presented. The contribution of the acoustic emission monitoring technique in defining different failure modes identified during the testing is discussed. The development of in-situ structural monitoring and control systems is considered. (au)

Vibro-acoustics of porous materials - waveguide modeling approach

DEFF Research Database (Denmark)

Darula, Radoslav; Sorokin, Sergey V.

2016-01-01

The porous material is considered as a compound multi-layered waveguide (i.e. a fluid layer surrounded with elastic layers) with traction free boundary conditions. The attenuation of the vibro-acoustic waves in such a material is assessed. This approach is compared with a conventional Biot's mode...

On the plasma confinement by acoustic resonance. An innovation for electrodeless high-pressure discharge lamps

Science.gov (United States)

Courret, Gilles; Nikkola, Petri; Wasterlain, Sébastien; Gudozhnik, Olexandr; Girardin, Michel; Braun, Jonathan; Gavin, Serge; Croci, Mirko; Egolf, Peter W.

2017-08-01

In an applied research project on the development of a pulsed microwave sulfur lamp prototype of 1 kW, we have discovered an amazing phenomenon in which the plasma forms a ball staying at the center of the bulb despite gravity, thus protecting the glass from melting. In this paper, it is shown that this results from an acoustic resonance in a spherical mode. Measurements of the plasma response to short pulses are presented showing beats at the spherical resonance. It is demonstrated that the beats could result from the simultaneous excitation of two normal modes with a frequency difference of approximately 1%. One of the two frequencies matches precisely the microwave pulses repetition, a little below 30 kHz. Thus this one is due to a forced oscillation, whereas the other one is due to a free oscillation. The phase velocity of sound was calculated as a function of temperature in order to find the series of temperatures at which a resonance would occur if the bulb were an isothermal solid sphere. The mean temperature inside the actual bulb was determined from the only doublet of this series, that has characteristic frequencies close enough to cause the observed beats. In addition, one of these two modes has a spherical symmetry that can explain the plasma ball formation. The obtained mean temperature is consistent with the direct measurements on the bulb surface as well as with the temperature in the core of a similar plasma found in the literature. We have also proposed a model of the resonance onset based on the acoustic dispersion and the sound amplification due to electromagnetic coupling.

Tunneling effects in resonant acoustic scattering of an air bubble in unbounded water

Directory of Open Access Journals (Sweden)

ANDRÉ G. SIMÃO

2016-06-01

Full Text Available Abstract The problem of acoustic scattering of a gaseous spherical bubble immersed within unbounded liquid surrounding is considered in this work. The theory of partial wave expansion related to this problem is revisited. A physical model based on the analogy between acoustic scattering and potential scattering in quantum mechanics is proposed to describe and interpret the acoustical natural oscillation modes of the bubble, namely, the resonances. In this context, a physical model is devised in order to describe the air water interface and the implications of the high density contrast on the various regimes of the scattering resonances. The main results are presented in terms of resonance lifetime periods and quality factors. The explicit numerical calculations are undertaken through an asymptotic analysis considering typical bubble dimensions and underwater sound wavelengths. It is shown that the resonance periods are scaled according to the Minnaert’s period, which is the short lived resonance mode, called breathing mode of the bubble. As expected, resonances with longer lifetimes lead to impressive cavity quality Q-factor ranging from 1010 to 105. The present theoretical findings lead to a better understanding of the energy storage mechanism in a bubbly medium.

Acoustic analog of monolayer graphene and edge states

International Nuclear Information System (INIS)

Zhong, Wei; Zhang, Xiangdong

2011-01-01

Acoustic analog of monolayer graphene has been designed by using silicone rubber spheres of honeycomb lattices embedded in water. The dispersion of the structure has been studied theoretically using the rigorous multiple-scattering method. The energy spectra with the Dirac point have been verified and zigzag edge states have been found in ribbons of the structure, which are analogous to the electronic ones in graphene nanoribbons. The guided modes along the zigzag edge excited by a point source have been numerically demonstrated. The open cavity and 'Z' type edge waveguide with 60 o corners have also been realized by using such edge states. -- Highlights: → Acoustic analog of monolayer graphene has been designed. → The energy spectra with the Dirac point have been verified. → The zigzag edge states have been found in ribbons of the structure. → The guided modes excited by a point source have been demonstrated. → The open cavity and 'Z' type edge waveguide have been realized.

Mach-Zehnder interferometric photonic crystal fiber for low acoustic frequency detections

Energy Technology Data Exchange (ETDEWEB)

Pawar, Dnyandeo; Rao, Ch. N.; Kale, S. N., E-mail: sangeetakale2004@gmail.com [Department of Applied Physics, Defence Institute of Advanced Technology (DU), Girinagar, Pune 411 025, Maharashtra (India); Choubey, Ravi Kant [Department of Applied Physics, Amity Institute of Applied Sciences, Amity University, Noida 201 313 (India)

2016-01-25

Low frequency under-water acoustic signal detections are challenging, especially for marine applications. A Mach-Zehnder interferometric hydrophone is demonstrated using polarization-maintaining photonic-crystal-fiber (PM-PCF), spliced between two single-mode-fibers, operated at 1550 nm source. These data are compared with standard hydrophone, single-mode and multimode fiber. The PM-PCF sensor shows the highest response with a power shift (2.32 dBm) and a wavelength shift (392.8 pm) at 200 Hz. High birefringence values and the effect of the imparted acoustic pressure on this fiber, introducing the difference between the fast and slow axis changes, owing to the phase change in the propagation waves, demonstrate the strain-optic properties of the sensor.

Computer based ultrasonic system for mechanical and acoustical characterization of materials

International Nuclear Information System (INIS)

Rosly Jaafar; Mohd Rozni Mohd Yusof; Khaidzir Hamzah; Md Supar Rohani; Rashdi Shah Ahmad; Amiruddin Shaari

2001-01-01

Propagation of both modes of ultrasonic waves velocity i.e. longitudinal (compressional) and transverse (shear), propagating in a material are closely linked with the material's physical and mechanical properties. By measuring both velocity modes, materials' properties such as Young's, bulk and shear moduli, compressibility, Poisson ratio and acoustic impedance can be determined. This paper describes the development of a system that is able to perform the above tasks and is known as Computer Based Ultrasonic for Mechanical and Acoustical Characterisation of Materials (UMC). The system was developed in the NDT Instrumentation and Signal Processing (NDTSP) laboratory of the Physics Department, Universiti Teknologi Malaysia. Measurements were made on four solid samples, namely, glass, copper, mild steel and aluminium. The results of measurements obtained were found to be in good agreement with the values of measurements made using standard methods. The main advantage of using this system over other methods is that single measurement of two ultrasonic velocity modes yields six material's properties. (Author)

Receptivity of Hypersonic Boundary Layers to Acoustic and Vortical Disturbances (Invited)

Science.gov (United States)

Balakumar, P.

2015-01-01

Boundary-layer receptivity to two-dimensional acoustic and vortical disturbances for hypersonic flows over two-dimensional and axi-symmetric geometries were numerically investigated. The role of bluntness, wall cooling, and pressure gradients on the receptivity and stability were analyzed and compared with the sharp nose cases. It was found that for flows over sharp nose geometries in adiabatic wall conditions the instability waves are generated in the leading-edge region and that the boundary layer is much more receptive to slow acoustic waves as compared to the fast waves. The computations confirmed the stabilizing effect of nose bluntness and the role of the entropy layer in the delay of boundary layer transition. The receptivity coefficients in flows over blunt bodies are orders of magnitude smaller than that for the sharp cone cases. Wall cooling stabilizes the first mode strongly and destabilizes the second mode. However, the receptivity coefficients are also much smaller compared to the adiabatic case. The adverse pressure gradients increased the unstable second mode regions.

Dual-temperature acoustic levitation and sample transport apparatus

Science.gov (United States)

Trinh, E.; Robey, J.; Jacobi, N.; Wang, T.

1986-01-01

The properties of a dual-temperature resonant chamber to be used for acoustical levitation and positioning have been theoretically and experimentally studied. The predictions of a first-order dissipationless treatment of the generalized wave equation for an inhomogeneous medium are in close agreement with experimental results for the temperature dependence of the resonant mode spectrum and the acoustic pressure distribution, although the measured magnitude of the pressure variations does not correlate well with the calculated one. Ground-based levitation of low-density samples has been demonstrated at 800 C, where steady-state forces up to 700 dyn were generated.

Dust-acoustic solitary modes in plasmas with isothermal and nonthermal ions: Polarity switches and coexistence domains

International Nuclear Information System (INIS)

Verheest, Frank

2011-01-01

Large dust-acoustic waves are investigated in a multispecies plasma model consisting of cold negative dust in the presence of cooler Boltzmann and hotter nonthermal Cairns positive ions, in a Sagdeev pseudopotential formalism. Use of the pseudopotential at the acoustic speed itself yields in a systematic way compositional parameter values where negative/positive solitons interchange polarities and also where both polarities coexist. The latter requires that solitons at the acoustic speed exist, with finite amplitudes, compared to superacoustic solitons of the opposite polarity. The coexistence region starts when the pseudopotential at the acoustic speed has a negative root at the limit of infinite dust compression and ends when a positive double root is encountered. Outside the coexistence domain, only negative or positive superacoustic solitons can exist. Thus, the discussion and numerical evaluations are guided by precise physical and analytic arguments rather than mere numerical experimentation. Graphs of relevant Sagdeev pseudopotentials illustrate the link with the analytical constraints.

Dust-acoustic solitary modes in plasmas with isothermal and nonthermal ions: Polarity switches and coexistence domains

Energy Technology Data Exchange (ETDEWEB)

Verheest, Frank [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, B-9000 Gent, Belgium and School of Physics, University of KwaZulu-Natal, Private Bag X54001, Durban 4000 (South Africa)

2011-08-15

Large dust-acoustic waves are investigated in a multispecies plasma model consisting of cold negative dust in the presence of cooler Boltzmann and hotter nonthermal Cairns positive ions, in a Sagdeev pseudopotential formalism. Use of the pseudopotential at the acoustic speed itself yields in a systematic way compositional parameter values where negative/positive solitons interchange polarities and also where both polarities coexist. The latter requires that solitons at the acoustic speed exist, with finite amplitudes, compared to superacoustic solitons of the opposite polarity. The coexistence region starts when the pseudopotential at the acoustic speed has a negative root at the limit of infinite dust compression and ends when a positive double root is encountered. Outside the coexistence domain, only negative or positive superacoustic solitons can exist. Thus, the discussion and numerical evaluations are guided by precise physical and analytic arguments rather than mere numerical experimentation. Graphs of relevant Sagdeev pseudopotentials illustrate the link with the analytical constraints.

Kepler detected gravity-mode period spacings in a red giant star

NARCIS (Netherlands)

Beck, P.G.; Bedding, T.R.; Mosser, B.; Stello, D.; Garcia, R.A.; Kallinger, T.; Hekker, S.; Elsworth, Y.; Frandsen, S.; Carrier, F.; de Ridder, J.; Aerts, C.; White, T.R.; Huber, D.; Dupret, M. A.; Montalban, J.; Miglio, A.; Noels, A.; Chaplin, W.J.; Kjeldsen, H.; Christensen-Dalsgaard, J.; Gilliland, R.L.; Brown, T.M.; Kawaler, S.D.; Mathur, S.; Jenkins, J.M.

2011-01-01

Stellar interiors are inaccessible through direct observations. For this reason, helioseismologists made use of the Sun’s acoustic oscillation modes to tune models of its structure. The quest to detect modes that probe the solar core has been ongoing for decades. We report the detection of mixed

NASA Engineering and Safety Center (NESC) Enhanced Melamine (ML) Foam Acoustic Test (NEMFAT)

Science.gov (United States)

McNelis, Anne M.; Hughes, William O.; McNelis, Mark E.

2014-01-01

The NASA Engineering and Safety Center (NESC) funded a proposal to achieve initial basic acoustic characterization of ML (melamine) foam, which could serve as a starting point for a future, more comprehensive acoustic test program for ML foam. A project plan was developed and implemented to obtain acoustic test data for both normal and enhanced ML foam. This project became known as the NESC Enhanced Melamine Foam Acoustic Test (NEMFAT). This document contains the outcome of the NEMFAT project.

Detection of geodesic acoustic mode oscillations, using multiple signal classification analysis of Doppler backscattering signal on Tore Supra

International Nuclear Information System (INIS)

Vermare, L.; Hennequin, P.; Gürcan, Ö.D.

2012-01-01

This paper presents the first observation of geodesic acoustic modes (GAMs) on Tore Supra plasmas. Using the Doppler backscattering system, the oscillations of the plasma flow velocity, localized between r/a = 0.85 and r/a = 0.95, and with a frequency, typically around 10 kHz, have been observed at the plasma edge in numerous discharges. When the additional heating power is varied, the frequency is found to scale with C s /R. The MUltiple SIgnal Classification (MUSIC) algorithm is employed to access the temporal evolution of the perpendicular velocity of density fluctuations. The method is presented in some detail, and is validated and compared against standard methods, such as the conventional fast Fourier transform method, using a synthetic signal. It stands out as a powerful data analysis method to follow the Doppler frequency with a high temporal resolution, which is important in order to extract the dynamics of GAMs. (paper)

Optimizing acoustical conditions for speech intelligibility in classrooms

Science.gov (United States)

Yang, Wonyoung

High speech intelligibility is imperative in classrooms where verbal communication is critical. However, the optimal acoustical conditions to achieve a high degree of speech intelligibility have previously been investigated with inconsistent results, and practical room-acoustical solutions to optimize the acoustical conditions for speech intelligibility have not been developed. This experimental study validated auralization for speech-intelligibility testing, investigated the optimal reverberation for speech intelligibility for both normal and hearing-impaired listeners using more realistic room-acoustical models, and proposed an optimal sound-control design for speech intelligibility based on the findings. The auralization technique was used to perform subjective speech-intelligibility tests. The validation study, comparing auralization results with those of real classroom speech-intelligibility tests, found that if the room to be auralized is not very absorptive or noisy, speech-intelligibility tests using auralization are valid. The speech-intelligibility tests were done in two different auralized sound fields---approximately diffuse and non-diffuse---using the Modified Rhyme Test and both normal and hearing-impaired listeners. A hybrid room-acoustical prediction program was used throughout the work, and it and a 1/8 scale-model classroom were used to evaluate the effects of ceiling barriers and reflectors. For both subject groups, in approximately diffuse sound fields, when the speech source was closer to the listener than the noise source, the optimal reverberation time was zero. When the noise source was closer to the listener than the speech source, the optimal reverberation time was 0.4 s (with another peak at 0.0 s) with relative output power levels of the speech and noise sources SNS = 5 dB, and 0.8 s with SNS = 0 dB. In non-diffuse sound fields, when the noise source was between the speaker and the listener, the optimal reverberation time was 0.6 s with

Shear wave velocity measurements using acoustic radiation force impulse in young children with normal kidneys versus hydronephrotic kidneys

International Nuclear Information System (INIS)

Shon, Beom Seok; Kim, Myung Joon; Han, Sang Won; Im, Young Jae; Lee, Mi Jung

2014-01-01

To measure shear wave velocities (SWVs) by acoustic radiation force impulse (ARFI) ultrasound elastography in normal kidneys and in hydronephrotic kidneys in young children and to compare SWVs between the hydronephrosis grades. This study was approved by an institutional review board, and informed consent was obtained from the parents of all the children included. Children under the age of 24 months were prospectively enrolled. Hydronephrosis grade was evaluated on ultrasonography, and three valid ARFI measurements were attempted using a high-frequency transducer for both kidneys. Hydronephrosis was graded from 0 to 4, and high-grade hydronephrosis was defined as grades 3 and 4. Fifty-one children underwent ARFI measurements, and three valid measurements for both kidneys were obtained in 96% (49/51) of the patients. Nineteen children (38.8%) had no hydronephrosis. Twenty-three children (46.9%) had unilateral hydronephrosis, and seven children (14.3%) had bilateral hydronephrosis. Seven children had ureteropelvic junction obstruction (UPJO). Median SWVs in kidneys with high-grade hydronephrosis (2.02 m/sec) were higher than those in normal kidneys (1.75 m/sec; P=0.027). However, the presence of UPJO did not influence the median SWVs in hydronephrotic kidneys (P=0.362). Obtaining ARFI measurements of the kidney is feasible in young children with median SWVs of 1.75 m/sec in normal kidneys. Median SWVs increased in high-grade hydronephrotic kidneys but were not different between hydronephrotic kidneys with and without UPJO.

Shear wave velocity measurements using acoustic radiation force impulse in young children with normal kidneys versus hydronephrotic kidneys

Energy Technology Data Exchange (ETDEWEB)

Shon, Beom Seok; Kim, Myung Joon; Han, Sang Won; Im, Young Jae; Lee, Mi Jung [Severance Children' s Hospital, Yonsei University College of Medicine, Seoul (Korea, Republic of)

2014-04-15

To measure shear wave velocities (SWVs) by acoustic radiation force impulse (ARFI) ultrasound elastography in normal kidneys and in hydronephrotic kidneys in young children and to compare SWVs between the hydronephrosis grades. This study was approved by an institutional review board, and informed consent was obtained from the parents of all the children included. Children under the age of 24 months were prospectively enrolled. Hydronephrosis grade was evaluated on ultrasonography, and three valid ARFI measurements were attempted using a high-frequency transducer for both kidneys. Hydronephrosis was graded from 0 to 4, and high-grade hydronephrosis was defined as grades 3 and 4. Fifty-one children underwent ARFI measurements, and three valid measurements for both kidneys were obtained in 96% (49/51) of the patients. Nineteen children (38.8%) had no hydronephrosis. Twenty-three children (46.9%) had unilateral hydronephrosis, and seven children (14.3%) had bilateral hydronephrosis. Seven children had ureteropelvic junction obstruction (UPJO). Median SWVs in kidneys with high-grade hydronephrosis (2.02 m/sec) were higher than those in normal kidneys (1.75 m/sec; P=0.027). However, the presence of UPJO did not influence the median SWVs in hydronephrotic kidneys (P=0.362). Obtaining ARFI measurements of the kidney is feasible in young children with median SWVs of 1.75 m/sec in normal kidneys. Median SWVs increased in high-grade hydronephrotic kidneys but were not different between hydronephrotic kidneys with and without UPJO.

Deciphering acoustic emission signals in drought stressed branches: the missing link between source and sensor

Directory of Open Access Journals (Sweden)

Lidewei L Vergeynst

2015-07-01

Full Text Available When drought occurs in plants, acoustic emission signals can be detected, but the actual causes of these signals are still unknown. By analyzing the waveforms of the measured signals, it should however be possible to trace the characteristics of the acoustic emission source and get information about the underlying physiological processes. A problem encountered during this analysis is that the waveform changes significantly from source to sensor and lack of knowledge on wave propagation impedes research progress made in this field. We used finite element modeling and the well-known pencil lead break source to investigate wave propagation in a branch. A cylindrical rod of polyvinyl chloride was first used to identify the theoretical propagation modes. Two wave propagation modes could be distinguished and we used the finite element model to interpret their behavior in terms of source position for both the PVC rod and a wooden rod. Both wave propagation modes were also identified in drying-induced signals from woody branches, and we used the obtained insights to provide recommendations for further acoustic emission research in plant science.

Electron-acoustic solitary waves in the Earth's inner magnetosphere

Science.gov (United States)

Dillard, C. S.; Vasko, I. Y.; Mozer, F. S.; Agapitov, O. V.; Bonnell, J. W.

2018-02-01

The broadband electrostatic turbulence observed in the inner magnetosphere is produced by large-amplitude electrostatic solitary waves of generally two types. The solitary waves with symmetric bipolar parallel (magnetic field-aligned) electric field are electron phase space holes. The solitary waves with highly asymmetric bipolar parallel electric field have been recently shown to correspond to the electron-acoustic plasma mode (existing due to two-temperature electron population). Through theoretical and numerical analysis of hydrodynamic and modified Korteweg-de Vries equations, we demonstrate that the asymmetric solitary waves appear due to the steepening of initially quasi-monochromatic electron-acoustic perturbation arrested at some moment by collisionless dissipation (Landau damping). The typical steepening time is found to be from a few to tens of milliseconds. The steepening of the electron-acoustic waves has not been reproduced in self-consistent kinetic simulations yet, and factors controlling the formation of steepened electron-acoustic waves, rather than electron phase space holes, remain unclear.

Effect of Forcing Function on Nonlinear Acoustic Standing Waves

Science.gov (United States)

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

2003-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

Rahim, Z.; Qamar, A. [Institute of Physics and Electronics, University of Peshawar, Peshawar 25000 (Pakistan); National Center for Physics (NCP) at QAU Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Ali, S. [National Center for Physics (NCP) at QAU Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan)

2014-07-15

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

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

International Nuclear Information System (INIS)

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

2014-01-01

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

Ion-ion dynamic structure factor, acoustic modes, and equation of state of two-temperature warm dense aluminum

Science.gov (United States)

Harbour, L.; Förster, G. D.; Dharma-wardana, M. W. C.; Lewis, Laurent J.

2018-04-01

The ion-ion dynamical structure factor and the equation of state of warm dense aluminum in a two-temperature quasiequilibrium state, with the electron temperature higher than the ion temperature, are investigated using molecular-dynamics simulations based on ion-ion pair potentials constructed from a neutral pseudoatom model. Such pair potentials based on density functional theory are parameter-free and depend directly on the electron temperature and indirectly on the ion temperature, enabling efficient computation of two-temperature properties. Comparison with ab initio simulations and with other average-atom calculations for equilibrium aluminum shows good agreement, justifying a study of quasiequilibrium situations. Analyzing the van Hove function, we find that ion-ion correlations vanish in a time significantly smaller than the electron-ion relaxation time so that dynamical properties have a physical meaning for the quasiequilibrium state. A significant increase in the speed of sound is predicted from the modification of the dispersion relation of the ion acoustic mode as the electron temperature is increased. The two-temperature equation of state including the free energy, internal energy, and pressure is also presented.

Quality Assessment of Scarf Joints Considering the Acoustic Parameters: A Nondestructive Approach

Directory of Open Access Journals (Sweden)

Ali Yavari

2015-07-01

Full Text Available The present research studied the acoustic properties of 40 oak timber samples (Quercus castaneifolia: the acoustic coefficient (K and acoustic conversion efficiency (ACE in free vibration mode, using the free-free bar method with different planes of vibration, i.e., tangential (LT and radial (LR. These acoustic parameters were considered for both primary virgin wooden beams and modified beams carrying a single scarf joint in four different bonding angles (60°, 65°, 70°, and 75°, individually glued with two different adhesives (isocyanate and polyvinyl acetate. Comparing the acoustic properties of primary solid beams with scarf jointed beams of oak wood in LT and LR planes, the steeper joint angles of 70° and 75° did not result in any serious changes with polyvinyl acetate adhesive. Scarf-jointed beams with smaller joint angles (60° and 65° had significant effect on the acoustic properties relative to larger angles. Thus, beams having larger joint angles and beams glued using polyvinyl acetate may have enhanced acoustic properties.

Three-mode coupling interference patterns in the dynamic structure factor of a relaxor ferroelectric

Science.gov (United States)

Manley, M. E.; Abernathy, D. L.; Sahul, R.; Stonaha, P. J.; Budai, J. D.

2016-09-01

A longstanding controversy for relaxor ferroelectrics has been the origin of the "waterfall" effect in the phonon dispersion curves, in which low-energy transverse phonons cascade into vertical columns. Originally interpreted as phonons interacting with polar nanoregions (PNRs), it was later explained as an interference effect of coupling damped optic and acoustic phonons. In light of a recently discovered PNR vibrational mode near the "waterfall" wave vector [M. E. Manley, J. W. Lynn, D. L. Abernathy, E. D. Specht, O. Delaire, A. R. Bishop, R. Sahul, and J. D. Budai, Nat. Commun. 5, 3683 (2014), 10.1038/ncomms4683], we have reexamined this feature using neutron scattering on [100]-poled PMN-30%PT [0.6 Pb (M g1 /3N b2 /3 ) O3-0.3 PbTi O3] . We find that the PNR mode couples to both optic and acoustic phonons and that this results in complex patterns in the dynamic structure factor, including intensity pockets and peaks localized in momentum-energy space. These features are fully explained by extending the mode-coupling model to include three coupled damped harmonic oscillators representing the transverse optic, acoustic, and PNR modes.

Low-emittance tuning of storage rings using normal mode beam position monitor calibration

Science.gov (United States)

Wolski, A.; Rubin, D.; Sagan, D.; Shanks, J.

2011-07-01

We describe a new technique for low-emittance tuning of electron and positron storage rings. This technique is based on calibration of the beam position monitors (BPMs) using excitation of the normal modes of the beam motion, and has benefits over conventional methods. It is relatively fast and straightforward to apply, it can be as easily applied to a large ring as to a small ring, and the tuning for low emittance becomes completely insensitive to BPM gain and alignment errors that can be difficult to determine accurately. We discuss the theory behind the technique, present some simulation results illustrating that it is highly effective and robust for low-emittance tuning, and describe the results of some initial experimental tests on the CesrTA storage ring.

The statistical mechanics of vortex-acoustic ion wave turbulence

International Nuclear Information System (INIS)

Giles, M.J.

1980-01-01

The equilibrium statistical mechanics of electrostatic ion wave turbulence is studied within the framework of a continuum ion flow with adiabatic electrons. The wave field consists in general of two components, namely ion-acoustic and ion vortex modes. It is shown that the latter can significantly affect the equilibria on account of their ability both to emit and to scatter ion sound. Exact equilibria for the vortex-acoustic wave field are given in terms of a canonical distribution and the correlation functions are expressed in terms of a generating functional. Detailed calculations are carried out for the case in which the dominant coupling is an indirect interaction of the vortex modes mediated by the sound field. An equation for the spectrum of the vortex modes is obtained for this case, which is shown to possess a simple exact solution. This solution shows that the spectrum of fluctuations changes considerably as the total energy increases. Condensed vortex states could occur in the plasma sheet of the earth's magnetosphere and it is shown that the predicted ratio of the mean ion energy to the mean electron energy is consistent with the trend of observed values. (author)

On the phase between pressure and heat release fluctuations for propane/hydrogen flames and its role in mode transitions